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Friday, 23 August 2013 13:38

Peatland transitions

Peatland transitions

Main Contributors:

Daniel Ospina

Other Contributors:

Helen Moor

Summary

Two alternate regimes in peatland systems are described in this document: bogs, sphagnum-dominated peatlands with long-term carbon storage in peat, and fens, peatland in which vascular plants have a more dominant role, leading to higher-productivity but reduced peat long-term accumulation. The most important variables and mechanisms considered are peat accumulation and height of the surface above the water table, nutrient flux, and competition between plant functional groups. The key drivers of the shift are related with changes in climate (precipitation and temperature) and in nutrient input. The relevance of this shift in terms of ecosystem services and human well-being is the tradeoff between potential gains of nutrient-rich soils for agricultural activities on drained peatlands, versus a loss of long-term carbon accumulation with potentially great implications for global climate change.

Drivers

Key direct drivers

  • External inputs (eg fertilizers)
  • Environmental shocks (eg floods)
  • Global climate change

Land use

  • Small-scale subsistence crop cultivation
  • Large-scale commercial crop cultivation
  • Extensive livestock production (rangelands)
  • Land use impacts are primarily off-site (e.g. dead zones)

Impacts

Ecosystem type

  • Temperate & boreal forests
  • Tropical forests
  • Tundra

Key Ecosystem Processes

  • Soil formation
  • Primary production
  • Nutrient cycling

Biodiversity

  • Biodiversity

Provisioning services

  • Food crops
  • Livestock
  • Fuel and fiber crops

Regulating services

  • Climate regulation

Human Well-being

  • Livelihoods and economic activity

Key Attributes

Typical spatial scale

  • Local/landscape

Typical time scale

  • Years
  • Decades
  • Centuries

Reversibility

  • Hysteretic

Evidence

  • Models
  • Paleo-observation
  • Contemporary observations

Confidence: Existence of RS

  • Speculative – Regime shift has been proposed, but little evidence as yet

Confidence: Mechanism underlying RS

  • Well established – Wide agreement on the underlying mechanism

Alternate regimes

Peatlands are characterized by often deep accumulations of incompletely decomposed organic material (i.e. peat). The accumulation of peat occurs when carbon sequestration exceeds the long-term loss through decomposition or export by hydrological flow. Such rates of decomposition can be very low in acidic and anaerobic conditions. Globally, peatlands occupy about four million km2, of which boreal and subarctic peatlands constitute about 87%, mainly in Russia, Canada, United States, Finland and Sweden. Tropical peatlands also exist, a big percentage of which is in Indonesia (Vitt, 2008). A major distinction within peatlands is between fens (minerotrophic peatlands: plants have access to geogenous water) and bogs (ombrotrophic peatlands: plants are dependent on precipitation). These and other differences in hydrology, acidity and climate produce a great variety of peatlands worldwide. Such variety in genesis and characteristics makes any generalization of peatlands functional values very difficult. A fen to bog transition is often seen as the natural course of peatland succession (Hughes & Barber 2004), whereas a change from bog to fen usually requires external changes in conditions or strong perturbations. Both bogs and fens exhibit internal feedbacks that provide them with some stability, and threshold conditions associated with the transition between each other have been suggested in the literature (Belyea & Malmer 2004). 

 

Bogs (Sphagnum-dominated peatland, with long-term carbon storage)

This regime is characterized by a landscape dominated by sphagnum-mosses, covering low hummocks and lawns, usually exhibiting no conspicuous spatial pattern in vegetation. Under the surface a thick layer of slow-decaying peat is mostly kept in waterlogged and acidic conditions. The concept of ecosystem engineers (Jones et al. 1994) has been used to describe Sphagnum mosses, given their functional capacity to create and maintain an acidic and nutrient-poor environment, harsh for most other plants (references in Ohlson et al. 2001). Additionally, mosses decay at extremely low rates due to their unique tissue chemistry, what strongly limits nutrient fluxes to other types of plants (Pastor et al. 2002). In the absence large external climatic changes or direct human impacts on hydrology or nutrient input, the species composition of these type of peatlands has proven to be very stable (references on Limpens et al. 2008).

 

Fens (Moss and vascular plant coexistence, with reduced peat accumulation)

Vascular plants also alter the environment in ways that negatively affect Sphagnum mosses. So an increase in vascular plant cover beyond critical thresholds inevitably leads to a decrease in Sphagnum (Berendse et al. 2001). Some of the mechanisms involved in this process act by preventing or even reversing ombrotrophication, in favor of minerotropic conditions. While other mechanisms might operate in bogs prompting the development of particular microtopography and associated vegetation spatial patterns. Such microtopography is also believed to be very stable (references in Eppinga et al. 2007 and in Limpens et al. 2008). This regime is characterized by an increasingly dense and connected vascular plants cover, exhibiting spatial patterns (strings-flarks on slopes and maze on flat landscapes) consisting of densely vegetated bands (hummocks forming ridges), alternating with wetter zones that are more sparsely vegetated (hollows forming pools) (Rietkerk et al. 2004).

Drivers and causes of the regime shift

A Sphagnum dominated peatland becomes more susceptible to invasion by vascular plants as the nutrient input increases (Pastors et al. 2002; Eppinga et al. 2007, 2009; Limpens et al. 2008). Ombrotrophic systems are particularly sensitive to nitrogen enrichment, which can prompt the invasion by graminoid species (e.g. Molinia caerulea) and woody species (e.g. Betula pubescens) with a parallel decline of ombrotrophic species (references in Tomassen et al. 2003). Sphagna are negatively affected by high nutrient input due to ammonium toxicity (Fritz et al. 2012). Additionally, related C:N ratio changes could enhance decomposition, further amplifying this nutrient positive relation with vascular plants.

Decreasing wetness during the growing season promotes vascular plant growth and hampers moss development (Eppinga et al. 2007; Limpens et al. 2008), and perhaps more importantly, it weakens the nutrient flux delay of sphagnum peat by increasing aerobic decomposition (Hilbert et al. 2000). Reduced precipitation and droughts in general directly decrease Sphagnum productivity, as photosynthetic rates are strongly dependent on water saturation levels. Additionally, longer dry seasons can potentially increase wild fire frequency, with negative effects on peat depth (references in Limpens et al. 2008). In high latitude peatlands an increase in temperature implies a longer growing season for vascular plants and increases mineralization rates. As vascular plants abundance increases and Sphagnum cover reduces, the temperature feedback in regime 1 weakens, allowing for even warmer conditions in the rooting zone further increasing the growing season of vascular plants (references in Eppinga et al. 2007).

How the regime shift works

Shift from Bogs to Fens

Different mechanisms are responsible for maintaining Bogs, mostly ombrotrophication, which is the ability of Sphagnum mosses to effectively decouple the rooting zone of vascular plants from geogenous mineral-rich water, thereby depriving those plants from key nutrients. This process occurs as a result of peat accumulation, which increases with the slow rates of decay of mosses (Pastor et al. 2002). Once the ombrotrophic conditions are reached, the competitive ability of sphagnum boosts, increasing their dominance. This in turn contributes to more peat accumulation (Granath et al. 2010). Sphagnum out-competes vascular plants, by getting inputs from the atmosphere and releasing decay-resistant and low-nutrient litter, creating a slow nutrient flux. Particularly relevant is nitrogen immobilization, making vascular plants entirely dependent on the slow mineralization of peat (Pastor et al. 2002; Malmer et al. 2003; Tomassen et al. 2003). Additionally, the low-porosity character of sphagnum peat promotes waterlogged conditions that further reduce mineralization rates (references in Eppinga et al. 2007). Other mechanisms include acidification of the environment, competition for light and space, and belowground temperature lowering. Through the organic acids resulting from its humification, bog sphagnum actively promotes acidification of the environment, which limits vascular plant growth (references in Eppinga et al. 2007). In such sphagnum-dominated sites, the establishment and growth of vascular plants is limited by the thick moss carpet that overgrows seedlings (Ohlson et al. 2001; Malmer et al.2003), and its vertical growth engulfing meristemic tissues (references in Pastor et al 2002). Also, the growing season for vascular plants is shortened, given the poor heat conductivity of sphagnum peat, which hampers the functioning of vascular plant roots (references in Eppinga et al. 2007).

Drought or drainage can trigger a shift from Bogs to Fens. A prolonged drought might lower the water table long enough to force moss desiccation and allow for increased mineralization (Tomassen et al. 2003; Eppinga et al. 2009; Granath et al. 2010). This reduces the competitive pressures on vascular plants, increasing the opportunities for colonization. Drainage is a primary shock altering peatland dynamics by lowering the water table (Limpens et al. 2008), and it is done for agricultural and forestry purposes. Also, an influx of water high in nutrients or minerals (e.g. Ca) from surrounding land or from atmosphere could also damage Sphagna and cause vascular plant invasion. Similarly, liming (i.e. spreading Ca- or Mg-rich minerals) is another direct human intervention to eliminate Sphagnum. Basically, as soon as the inorganic nutrient pool that vascular plants require ceases to limited by slow sphagnum peat mineralization rates, this regime shift could occur.

Key mechanisms behind the maintenance of Fens are related to peat accumulation and vascular plants. While vascular plants, which can become highly productive under the influence of geogenous water or some other source of important nutrients, minerotrophic conditions seriously prevent bog sphagnum from settling given its high sensitivity to calcareous water (Granath et al. 2010). Advective transport of nutrients has been proposed by Rietkerk et al. (2004) as a scale-dependent mechanism, having a locally positive and long-range negative effect on nutrient concentration, to explain the spatial patterning of peatlands. This mechanism would be driven by transpiration of vascular plants, enhancing drier microforms (hummocks, ridges) with increased nutrient concentration that vascular plants require to establish and further reinforce their presence. Additionally, transpiration rates are higher in the presence of vascular plants, and this stimulates a lowering of the water table (Rietkerk et al. 2004). While this reduction of water in the surface negatively affects sphagnum productivity by desiccation (references in Tomassen et al 2003), it also leads to an increase of mineralization rates, which reinforces the presence of vascular plants (Tomassen et al. 2003). Another competitive mechanism operates as vascular plants reach above the moss carpet, limiting its development through shading and burial by litter (Berendse et al. 2001; Pastor et al. 2002; Malmer et al. 2003). Under these conditions the limited growth of Sphagnum prevents peat accumulation (Malmer et al. 2003; Limpens et al. 2008). 

 

Shift from Fens to Bogs

Increases in precipitation could lead to a higher water table, potentially causing substantial dieback of vascular plants (references in Eppinga et al. 2007). Moreover, the minerotrophic conditions that are detrimental for bog sphagnum growth are reduced as the relative importance of precipitation water increases over that of geogenous water (Pastor et al. 2002). The height of the peatland surface above the water table is a key determinant of plant species distribution and primary productivity, and consequently the rates of litter production and litter decay losses (Hilbert et al. 2000; Belyea & Malmer 2004). Given the explained mechanism of delayed nutrient flux, it is clear that at a certain height of the surface above the water table, bog sphagnum becomes a superior competitor (Granath et al. 2010), and the reinforcing feedbacks of Bogs are activated.

It is worth mentioning that even though the literature cited here in reference to these alternate stable states relies deeply on modeling (e.g. Hilbert et al 2000; Pastor et a 2002; Rietkerk et al 2004; Eppinga et al 2007, 2009), qualitatively similar shifts have been reported in paleoecological studies as well as present day observations: dominance of deciduous shrubs and graminoids during the early stages of peatland development with little or no presence of moss, followed by landscapes dominated by Sphagnum lawns after the ombrotrophication process, which are later subjected to invasion by shrubs and spruce (references in Pastor et al 2002). The fact that such abrupt shifts between a near-monoculture moss state and a co-existence with vascular plants state have been reported to occur sometimes but not always, suggests that these systems do exhibit alternate stable states.

Impacts on ecosystem services and human well-being

Shift from Bogs to Fens

Since sphagnum litter enhances the formation of collapsible peat (i.e. with low porosity), which easily becomes waterlogged, the conditions for low rates of decomposition, and an overall net carbon sequestration effect are maintained in Bogs. Rates of carbon sequestration and methane emission depend strongly on height of the peatland surface above the water table (references in Belyea & Malmer 2004). Even though the same processes of anaerobic decomposition that increases carbon accumulation, also increases methane production, the overall desirable effect in relation to climate change gets lost in this shift, since the effect of removing long-lived atmospheric carbon dioxide ultimately surpasses that of releasing short-lived methane (Limpens et al. 2008).

Because of the complex relations of acrotelm thickness with vegetation and microtopography, these two are considered to primarily determine carbon sequestration/emission rates (Belyea & Malmer 2004; Belyea & Baird 2006). Peat formation rate is greatest for 'intermediate microforms' (lawns, low hummocks) and lowest for microforms at the extremes of the water table gradient (high hummocks and pools) (Belyea & Malmer 2004). Given this trade-off of decomposability and productivity between elevated and low microforms (reference in Limpens et al 2008), a landscape will exhibit higher short-term sequestration of carbon or long-term storage depending o the microforms by which it is dominated.

Shift from Fens to Bogs

A reduction in species richness and the loss of agriculturally suitable lands are potential impacts of the shift to sphagnum-dominated peatlands.

Management options

Damming or blocking ditches are common management practices aimed at raising the water table.  More direct practices to recover or sustain sphagnum vegetation is to establish rafts of floating brush or clumps of peat for floating mosses settle, as well as the creation of suitable microclimates through techniques such as applying a layer of straw mulch, and carving depressions that promote carpet or lawn level Sphagnum (references in Limpens et al. 2008 and in Rydin & Jeglum 2006).

Key References

  1. Belyea LR, Baird AJ. 2006. Beyond u201cthe limits to peat bog growthu201d: cross-scale feedback in peatland development. Ecological Monographs, 76, 299-322.
  2. Belyea LR, Malmer N. 2004. Carbon sequestration in peatland: patterns and mechanisms of response to climate change. Global Change Biology 10: 1043u20131052
  3. Berendse F, Van Breemen N, Rydin H, Buttler A, Heijmans M, Hoosbeek MR, Lee JA, Mitchell E, Saarinen T, Vasander H, Wallen B. 2001. Raised atmospheric CO2 levels and increased N deposition cause shifts in plant species composition and production in Sphagnum bogs. Global Change Biology, 7, 591-598.
  4. Dise, NB. 2009. Peatland Response to Global Change. Science, 326, 810-811.
  5. Dugan PJ. (ed) 1990. Wetland Conservation: a Review of Current Issues and Required Action. IUCN, Gland (Switzerland)
  6. Eppinga MB, Rietkerk M, Wassen, MJ, Ruiter PC. 2007. Linking habitat modification to catastrophic shifts and vegetation patterns in bogs. Plant Ecology, 200, 53-68.
  7. Eppinga, MB, Ruiter, PC de Wassen MJ, Rietkerk M. 2009. Nutrients and hydrology indicate the driving mechanisms of peatland surface patterning. The American Naturalist, 173, 803-18.
  8. Fritz C, van Dijk G, Smolders AJP, Pancotto VA, Elzenga T Volume JTM, Roelofs JGM, Grootjans AP. 2012. Nutrient additions in pristine Patagonian Sphagnum bog vegetation: can phosphorus addition alleviate (the effects of) increased nitrogen loads. Plant Biology 14(3), 491u2013499.
  9. Granath G, Strengbom J, Rydin H. 2010. Rapid ecosystem shifts in peatlands: linking plant physiology and succession. Ecology, 91: 3047-3056.
  10. Hilbert DW, Roulet N, Moore T. 2000. Modelling and analysis of peatlands as dynamical systems. Journal of Ecology, 88: 230-242.
  11. Holmgren M, Lin CY, Murillo JE, Nieuwenhuis A, Penninkhof J, Sanders N, van Bart T, van Veen H, Vasander H, Vollebregt ME & Limpens J. 2015. Positive shrub–tree interactions facilitate woody encroachment in boreal peatlands. Journal of Ecology, 103: 58–66. doi: 10.1111/1365-2745.12331
  12. Hughes PDM, Barber KE. 2004. Contrasting pathways to ombrotrophy in three raised bogs from Ireland and Cumbria, England. The Holocene 14, 65
  13. Malmer N, Albinsson C, Svensson BM, Wallen B. 2003. Interferences between Sphagnum and vascular plants: effects on plant community structure and peat formation. Oikos, 100, 469-482.
  14. Ohlson M, Okland, RH, Nordbakken JF, Dahlberg B. 2001. Fatal interactions between Scots pine and Sphagnum mosses in bog ecosystems. Oikos, 94, 425-432.
  15. Pastor J, Peckham B, Bridgham S, Weltzin J, Chen, J. 2002. Plant community dynamics, nutrient cycling, and alternative stable equilibria in peatland. The American Naturalist, 160, 553-68.
  16. Rietkerk, M, Dekker, SC, Wassen, MJ, Verkroost, AWM, Bierkens, MFP. 2004. A putative mechanism for bog patterning. The American Naturalist, 163, 699-708.
  17. Roulet NT, Lafleur PM, Richard PJH, Moore TR, Humphreys ER, Bubier J. 2007 Contemporary carbon balance and late Holocene carbon accumulation in a northern peatland. Global Change Biology 13(2), 397u2013411.
  18. Rydin H, Jeglum JK. 2006 The Biology of Peatlands. Oxford University Press, New York (USA)
  19. Tomassen HBM, Smolders AJP, Lamers LPM, Roelofs JGM. 2003 Stimulated growth of Betula pubescens and Molinia caerulea on ombrotrophic bogs: role of high levels of atmospheric nitrogen deposition. Journal of Ecology, 91, 357-370.
  20. Vitt DH. 2008 Peatlands. 2656-2664 In: Jurgensen (ed) Encyclopedia of Ecology. Elsevier BV, Amsterdam (Netherlands)

Citation

Daniel Ospina, Helen Moor. Peatland transitions. In: Regime Shifts Database, www.regimeshifts.org. Last revised 2017-08-28 19:52:11 GMT.
Friday, 25 February 2011 09:45

Balinese rice production

Balinese rice production

Main Contributors:

Caroline Schill, Ylva Ran, Daniel Ospina

Other Contributors:

Reinette (Oonsie) Biggs, -1

Summary

As described by Lansing (1991 and others) for roughly a thousand years, rice farming in southern Bali (Indonesia) has operated through a religious and water-irrigation institutional arrangement of Subaks and Water Temples, which coordinate water use and generate landscape-level pest control. During the 1970s, the Indonesian government decided to carry-out a Green Revolution to face the challenge of an increasing internal population demanding more food. Several changes at different levels where introduced: high-yielding varieties of rice were distributed among the farmers, together with a tech-package of pesticides and fertilizers; and the water temples were restricted from regulating water distribution. After a couple of decades of successful increase in production, problems regarding water distribution and pest outbreaks, lead to the recognition of the functional role of Subaks and Water Temples in managing these two factors, so the Indonesian government withdrew the restriction. However, an important percentage of farmers decided to continue using the high-yielding rice varieties, together with pesticides and fertilizers. Given that this agricultural tech-package costs money, the ‘rice production – cash income’ feedback gained strength over ‘rice production – subsistence’, which dominated before the Green Revolution, and was sustained by a variety of agricultural practices that articulated in a more complex form. Cultural and economic dimensions of globalization set the context for this shift, with an increasing importance of money in mediating local social relations, and a slow change in world-views, beliefs and values. Possible negative effects of this farm-level shift in agricultural practices are a fast degradation of soil quality and an increased input of phosphorus to the sea by runoff.

Type of regime shift

  • Unknown

Ecosystem type

  • Tropical Forests

Land uses

  • Small-scale subsistence crop cultivation
  • Tourism

Spatial scale of the case study

  • Local/landscape (e.g. lake, catchment, community)

Continent or Ocean

  • Indian Ocean

Region

  • Southern Bali

Countries

  • Indonesia

Locate with Google Map

Drivers

Key direct drivers

  • Adoption of new technology

Land use

  • Small-scale subsistence crop cultivation
  • Tourism

Impacts

Ecosystem type

  • Tropical forests
  • Agro-ecosystems

Key Ecosystem Processes

  • Nutrient cycling

Biodiversity

  • Biodiversity

Provisioning services

  • Freshwater
  • Food crops

Cultural services

  • Knowledge and educational values

Human Well-being

  • Livelihoods and economic activity

Key Attributes

Spatial scale of RS

  • Local/landscape

Time scale of RS

  • Decades

Evidence

  • Contemporary observations

Confidence: Existence of RS

  • Speculative – Regime shift has been proposed, but little evidence as yet

Confidence: Mechanism underlying RS

  • Speculative – Mechanisms have been proposed, but little evidence as yet

Alternate regimes

Peatlands are characterized by often deep accumulations of incompletely decomposed organic material (i.e. peat). The accumulation of peat occurs when carbon sequestration exceeds the long-term loss through decomposition or export by hydrological flow. Such rates of decomposition can be very low in acidic and anaerobic conditions. Globally, peatlands occupy about four million km2, of which boreal and subarctic peatlands constitute about 87%, mainly in Russia, Canada, United States, Finland and Sweden. Tropical peatlands also exist, a big percentage of which is in Indonesia (Vitt, 2008). A major distinction within peatlands is between fens (minerotrophic peatlands: plants have access to geogenous water) and bogs (ombrotrophic peatlands: plants are dependent on precipitation). These and other differences in hydrology, acidity and climate produce a great variety of peatlands worldwide. Such variety in genesis and characteristics makes any generalization of peatlands functional values very difficult. A fen to bog transition is often seen as the natural course of peatland succession (Hughes & Barber 2004), whereas a change from bog to fen usually requires external changes in conditions or strong perturbations. Both bogs and fens exhibit internal feedbacks that provide them with some stability, and threshold conditions associated with the transition between each other have been suggested in the literature (Belyea & Malmer 2004). 

 

Bogs (Sphagnum-dominated peatland, with long-term carbon storage)

This regime is characterized by a landscape dominated by sphagnum-mosses, covering low hummocks and lawns, usually exhibiting no conspicuous spatial pattern in vegetation. Under the surface a thick layer of slow-decaying peat is mostly kept in waterlogged and acidic conditions. The concept of ecosystem engineers (Jones et al. 1994) has been used to describe Sphagnum mosses, given their functional capacity to create and maintain an acidic and nutrient-poor environment, harsh for most other plants (references in Ohlson et al. 2001). Additionally, mosses decay at extremely low rates due to their unique tissue chemistry, what strongly limits nutrient fluxes to other types of plants (Pastor et al. 2002). In the absence large external climatic changes or direct human impacts on hydrology or nutrient input, the species composition of these type of peatlands has proven to be very stable (references on Limpens et al. 2008).

 

Fens (Moss and vascular plant coexistence, with reduced peat accumulation)

Vascular plants also alter the environment in ways that negatively affect Sphagnum mosses. So an increase in vascular plant cover beyond critical thresholds inevitably leads to a decrease in Sphagnum (Berendse et al. 2001). Some of the mechanisms involved in this process act by preventing or even reversing ombrotrophication, in favor of minerotropic conditions. While other mechanisms might operate in bogs prompting the development of particular microtopography and associated vegetation spatial patterns. Such microtopography is also believed to be very stable (references in Eppinga et al. 2007 and in Limpens et al. 2008). This regime is characterized by an increasingly dense and connected vascular plants cover, exhibiting spatial patterns (strings-flarks on slopes and maze on flat landscapes) consisting of densely vegetated bands (hummocks forming ridges), alternating with wetter zones that are more sparsely vegetated (hollows forming pools) (Rietkerk et al. 2004).

Drivers and causes of the regime shift

A Sphagnum dominated peatland becomes more susceptible to invasion by vascular plants as the nutrient input increases (Pastors et al. 2002; Eppinga et al. 2007, 2009; Limpens et al. 2008). Ombrotrophic systems are particularly sensitive to nitrogen enrichment, which can prompt the invasion by graminoid species (e.g. Molinia caerulea) and woody species (e.g. Betula pubescens) with a parallel decline of ombrotrophic species (references in Tomassen et al. 2003). Sphagna are negatively affected by high nutrient input due to ammonium toxicity (Fritz et al. 2012). Additionally, related C:N ratio changes could enhance decomposition, further amplifying this nutrient positive relation with vascular plants.

Decreasing wetness during the growing season promotes vascular plant growth and hampers moss development (Eppinga et al. 2007; Limpens et al. 2008), and perhaps more importantly, it weakens the nutrient flux delay of sphagnum peat by increasing aerobic decomposition (Hilbert et al. 2000). Reduced precipitation and droughts in general directly decrease Sphagnum productivity, as photosynthetic rates are strongly dependent on water saturation levels. Additionally, longer dry seasons can potentially increase wild fire frequency, with negative effects on peat depth (references in Limpens et al. 2008). In high latitude peatlands an increase in temperature implies a longer growing season for vascular plants and increases mineralization rates. As vascular plants abundance increases and Sphagnum cover reduces, the temperature feedback in regime 1 weakens, allowing for even warmer conditions in the rooting zone further increasing the growing season of vascular plants (references in Eppinga et al. 2007).

How the regime shift works

Shift from Bogs to Fens

Different mechanisms are responsible for maintaining Bogs, mostly ombrotrophication, which is the ability of Sphagnum mosses to effectively decouple the rooting zone of vascular plants from geogenous mineral-rich water, thereby depriving those plants from key nutrients. This process occurs as a result of peat accumulation, which increases with the slow rates of decay of mosses (Pastor et al. 2002). Once the ombrotrophic conditions are reached, the competitive ability of sphagnum boosts, increasing their dominance. This in turn contributes to more peat accumulation (Granath et al. 2010). Sphagnum out-competes vascular plants, by getting inputs from the atmosphere and releasing decay-resistant and low-nutrient litter, creating a slow nutrient flux. Particularly relevant is nitrogen immobilization, making vascular plants entirely dependent on the slow mineralization of peat (Pastor et al. 2002; Malmer et al. 2003; Tomassen et al. 2003). Additionally, the low-porosity character of sphagnum peat promotes waterlogged conditions that further reduce mineralization rates (references in Eppinga et al. 2007). Other mechanisms include acidification of the environment, competition for light and space, and belowground temperature lowering. Through the organic acids resulting from its humification, bog sphagnum actively promotes acidification of the environment, which limits vascular plant growth (references in Eppinga et al. 2007). In such sphagnum-dominated sites, the establishment and growth of vascular plants is limited by the thick moss carpet that overgrows seedlings (Ohlson et al. 2001; Malmer et al.2003), and its vertical growth engulfing meristemic tissues (references in Pastor et al 2002). Also, the growing season for vascular plants is shortened, given the poor heat conductivity of sphagnum peat, which hampers the functioning of vascular plant roots (references in Eppinga et al. 2007).

Drought or drainage can trigger a shift from Bogs to Fens. A prolonged drought might lower the water table long enough to force moss desiccation and allow for increased mineralization (Tomassen et al. 2003; Eppinga et al. 2009; Granath et al. 2010). This reduces the competitive pressures on vascular plants, increasing the opportunities for colonization. Drainage is a primary shock altering peatland dynamics by lowering the water table (Limpens et al. 2008), and it is done for agricultural and forestry purposes. Also, an influx of water high in nutrients or minerals (e.g. Ca) from surrounding land or from atmosphere could also damage Sphagna and cause vascular plant invasion. Similarly, liming (i.e. spreading Ca- or Mg-rich minerals) is another direct human intervention to eliminate Sphagnum. Basically, as soon as the inorganic nutrient pool that vascular plants require ceases to limited by slow sphagnum peat mineralization rates, this regime shift could occur.

Key mechanisms behind the maintenance of Fens are related to peat accumulation and vascular plants. While vascular plants, which can become highly productive under the influence of geogenous water or some other source of important nutrients, minerotrophic conditions seriously prevent bog sphagnum from settling given its high sensitivity to calcareous water (Granath et al. 2010). Advective transport of nutrients has been proposed by Rietkerk et al. (2004) as a scale-dependent mechanism, having a locally positive and long-range negative effect on nutrient concentration, to explain the spatial patterning of peatlands. This mechanism would be driven by transpiration of vascular plants, enhancing drier microforms (hummocks, ridges) with increased nutrient concentration that vascular plants require to establish and further reinforce their presence. Additionally, transpiration rates are higher in the presence of vascular plants, and this stimulates a lowering of the water table (Rietkerk et al. 2004). While this reduction of water in the surface negatively affects sphagnum productivity by desiccation (references in Tomassen et al 2003), it also leads to an increase of mineralization rates, which reinforces the presence of vascular plants (Tomassen et al. 2003). Another competitive mechanism operates as vascular plants reach above the moss carpet, limiting its development through shading and burial by litter (Berendse et al. 2001; Pastor et al. 2002; Malmer et al. 2003). Under these conditions the limited growth of Sphagnum prevents peat accumulation (Malmer et al. 2003; Limpens et al. 2008). 

 

Shift from Fens to Bogs

Increases in precipitation could lead to a higher water table, potentially causing substantial dieback of vascular plants (references in Eppinga et al. 2007). Moreover, the minerotrophic conditions that are detrimental for bog sphagnum growth are reduced as the relative importance of precipitation water increases over that of geogenous water (Pastor et al. 2002). The height of the peatland surface above the water table is a key determinant of plant species distribution and primary productivity, and consequently the rates of litter production and litter decay losses (Hilbert et al. 2000; Belyea & Malmer 2004). Given the explained mechanism of delayed nutrient flux, it is clear that at a certain height of the surface above the water table, bog sphagnum becomes a superior competitor (Granath et al. 2010), and the reinforcing feedbacks of Bogs are activated.

It is worth mentioning that even though the literature cited here in reference to these alternate stable states relies deeply on modeling (e.g. Hilbert et al 2000; Pastor et a 2002; Rietkerk et al 2004; Eppinga et al 2007, 2009), qualitatively similar shifts have been reported in paleoecological studies as well as present day observations: dominance of deciduous shrubs and graminoids during the early stages of peatland development with little or no presence of moss, followed by landscapes dominated by Sphagnum lawns after the ombrotrophication process, which are later subjected to invasion by shrubs and spruce (references in Pastor et al 2002). The fact that such abrupt shifts between a near-monoculture moss state and a co-existence with vascular plants state have been reported to occur sometimes but not always, suggests that these systems do exhibit alternate stable states.

Impacts on ecosystem services and human well-being

Shift from Bogs to Fens

Since sphagnum litter enhances the formation of collapsible peat (i.e. with low porosity), which easily becomes waterlogged, the conditions for low rates of decomposition, and an overall net carbon sequestration effect are maintained in Bogs. Rates of carbon sequestration and methane emission depend strongly on height of the peatland surface above the water table (references in Belyea & Malmer 2004). Even though the same processes of anaerobic decomposition that increases carbon accumulation, also increases methane production, the overall desirable effect in relation to climate change gets lost in this shift, since the effect of removing long-lived atmospheric carbon dioxide ultimately surpasses that of releasing short-lived methane (Limpens et al. 2008).

Because of the complex relations of acrotelm thickness with vegetation and microtopography, these two are considered to primarily determine carbon sequestration/emission rates (Belyea & Malmer 2004; Belyea & Baird 2006). Peat formation rate is greatest for 'intermediate microforms' (lawns, low hummocks) and lowest for microforms at the extremes of the water table gradient (high hummocks and pools) (Belyea & Malmer 2004). Given this trade-off of decomposability and productivity between elevated and low microforms (reference in Limpens et al 2008), a landscape will exhibit higher short-term sequestration of carbon or long-term storage depending o the microforms by which it is dominated.

Shift from Fens to Bogs

A reduction in species richness and the loss of agriculturally suitable lands are potential impacts of the shift to sphagnum-dominated peatlands.

Management options

Damming or blocking ditches are common management practices aimed at raising the water table.  More direct practices to recover or sustain sphagnum vegetation is to establish rafts of floating brush or clumps of peat for floating mosses settle, as well as the creation of suitable microclimates through techniques such as applying a layer of straw mulch, and carving depressions that promote carpet or lawn level Sphagnum (references in Limpens et al. 2008 and in Rydin & Jeglum 2006).

Alternate regimes

Subsistence-oriented, rice-based livelihood (with organic, self-sufficient farming)

Traditionally, in these Balinese farms rice production based on local rice varieties represents the main economic activity, and it is performed in a 'self-sufficient way' by relying on the articulation of several practices, such as keeping ducks for local pest control and cows for manure (Lansing et al. 2001; Marion et a.l 2005). This articulation of farming activities is time/labour demanding for members of the household, allowing less time for off-farm economic activities.

 

Market-oriented, diversified livelihood (with agrochemical-dependent farming)

The Green Revolution in Indonesia in the 1970s, presented to Balinese farmers a 'technological packet' including high-yielding rice varieties, chemical fertilizers (nitrogen, potassium and phosphorus) and pesticides (Lansing et al. 2001; Marion et al. 2005). Ever since, some households have replaced some of the labour/time intensive activities traditionally used, with these modern capital intensive inputs. Hence, in this regime household members have to devote less time to within-farm activities, but on the other hand, since access to these inputs requires money, it becomes imperative that an increasing part of their labour/time is devoted to monetized labour (i.e. selling more rice in the market, and/or other economic activities in tourism and commerce, for example).

Drivers and causes of the regime shift

An agricultural credit system developed to promote the use of the 'technological packet' was a key aspect of the Green Revolution in Indonesia enabling the farm-level regime shift in Balinese rice production. To boost rice production, these programs focused on the modernization of the country-side, and the breakdown of traditional management practices (Lansing 2006). This provided the conditions for intimately linking the farming practices to the monetized economy, and as a consequence modifying local livelihoods by allowing/forcing the diversification of economic activities.

Parallel to the increased connection with external markets for agriculture, importance of tourism has continually increased, providing a context for more non-agricultural, off-farm activities (Liater & Me 2003). Further, increased monetary incomes are invested in formal education of younger generations; education which tends to detach them more from agricultural activites (Lorentz & Lorentz, 2010).

How the regime shift worked

In the rice production system of subsistence-orientated rice-based livelihood, the household subsists by ensuring a constant cycle of cultivating and harvesting rice, which depends on both on collective behaviours involving other households, and also within-farm practices. For such practices, members of households in this regime devote most of their time on them, keeping rice production as the economic dominating activity. Under conditions in which such time/labour demanding activities are not 'easily' replaceable, this regime persists.

The agriculture credit system linked to the use of technological packet enabled this replacement. This change both enabled the diversification of economic activities by offering more time flexibility, and demanded an increase in the monetized labour activities. The threshold dividing these two regimes is then related with the importance of money to mediate social and economic interactions on Bali. The increased time flexibility also leads to an increasing access to formal educations, which further leaded to a dominance of non-agricultural economic activities by younger generations, strengthening the trajectory away from the subsistence-orientated rice-based livelihood regime.

Impacts on ecosystem services and human well-being

Both regimes provide rice yields, however the (agro)biodiversity is diminished by the shift described, not only by the adoption of few high-yielding varieties, but also by the effect of pesticides on soil and water habitats. Although the aesthetic value of these landscapes has always been 'provided', the development of infrastructure and training related with tourism increase its perception, and hence its worth in the market-orientated diversified regime.

Management options

.

Key References

  1. Booth, A. 2002. The Changing Role of Non-Farm Activities in Agricultural Households in Indonesia: Some Insights From the Agricultural Censuses. Bulletin of Indonesian Economic Studies 38, 179-200.
  2. Janssen MA. 2007. Coordination in irrigation systems: An analysis of the Lansing–Kremer model of Bali. Agricultural Systems 93(1-3), 170–190.
  3. Lansing JS, Kremer JN, Gerhart V, Kremer P, Arthawiguna A, Surata SKP, Suryawan SIB, Arsana G, Scarborough VL, Schoenfelder J, Mikita K. 2001. Volcanic fertilization of Balinese rice paddies. Ecological Economics 38, 383–390.
  4. Lansing JS, Miller JH. 2005. Cooperation, games, and ecological feedback: Some insights from Bali. Current Anthropology 46(2), 328–334.
  5. Lansing JS. 1987. Lansing Balinese "Water Temples" and the management of irrigation. American Anthropologist 89, 326–341.
  6. Lansing JS. 1991. Priests and programmers: Technologies of power in the engineered landscape of Bali. Princeton University Press, Princeton.
  7. Lansing, JS, Downey SS, Jannsen M, Schoenfelder J. 2009. A Robust Budding Model of Balinese Water Temple Networks. World Archaeology 41(1), 112–133.
  8. Lietaer B, Meulenaere SD. 2003. Sustaining cultural vitality in a globalizing world: the Balinese example. International Journal of Social Economics 30, 967-984.
  9. Lorenzen RP, Lorenzen S. 2010. Changing realities, perspectives on Balinese rice cultivation. Human Ecology [http://dx.doi.org/10.1007/s10745-010-9345-z]
  10. Lorenzen S, Lorenzen RP. 2008. Institutionalizing the Informal: Irrigation and government intervention in Bali. Development 51, 77-82.
  11. Marion GS, Dunbar RB, Mucciarone DA, Kremer JN, Lansing JS, Arthawiguna A. 2005. Coral skeletal delta(15)N reveals isotopic traces of an agricultural revolution. Marine pollution bulletin 50, 931-44.
  12. Pesticide action network, Asia and the Pacific (PANAP). 2010. Rice country profile for Indonesia. http:// www.panap.net/en/r/post/rice/273
  13. Poffenberger M, Zurbuchen MS. 1980. The economics of village Bali: three perspectives. Economic development and cultural change 29(1),91-133.
  14. Roche F. 1994. The Technical and Price Efficiency of Fertiliser use in Irrigated Rice Production. Bulletin of Indonesian Economic Studies 30, 59-83.
  15. Scarborough VL, Schoenfelder JW, Lansing JS. 1999. Early statecraft on Bali: the water temple complex and the decentralization of the political economy. Research in Economic Anthropology 20, 299-330.
  16. Scarborough VL, Schoenfelder JW, Lansing JS. 2000. Ancient water management and landscape transformation at Sebatu, Bali. Bulletin of the Indo-Pacific Prehistory Associaton 20, 79-92.
  17. Schmuki A. 2007. The Role of a Global Organization in Triggering Social Learning - Insights from a Case Study of a World Heritage Cultural Landscape Nomination in Bali. Governance An International Journal Of Policy And Administration.
  18. Schoenfelder JW. 2000. The co-evolution of agricultural and sociopolitical systems in Bali. IndoPacific Prehistory Association Bulletin 4, 35-46.

Citation

Caroline Schill, Ylva Ran, Daniel Ospina, Reinette (Oonsie) Biggs, -1. Balinese rice production. In: Regime Shifts Database, www.regimeshifts.org. Last revised 2017-02-07 11:26:51 GMT.
Wednesday, 23 February 2011 22:19

Tropical lowland forests (economic use), Colombia

Tropical lowland forests (economic use), Colombia

Main Contributors:

Daniel Ospina

Other Contributors:

-1

Summary

This case is a ‘natural resource-use system’ of afro-descendant communities living in a collectively-own tropical forest territory, in the Chocó biogeographic region. This system flipped from a regime characterized by a diversified use of ecosystems, oriented mainly to subsistence and based on cooperative institutions (regime 1), to one centred on timber extraction, oriented mainly to the market and based of remunerated labour (regime 2). Regime 1 was in place for more than two centuries, not just for that population, but for virtually all the afrodescendant groups in de Colombian and Ecuadorian Pacific coast. However, in the last decades a change in the way these communities relate with the environment, as a result from the interventions from the State and big companies, has been documented. In this particular case, the shift seems to have occurred around the 1970s, after a series of biophysical and economic shocks that affected an already stressed system. One key driver was population growth, while two proposed external drivers of change were 1) the many social and production programmes designed by the national government that portrayed the local ways as inefficient and tried to replace them; and 2) the presence of big timber companies influencing a change in way ‘labour’ was viewed. The main feedback loop locking the system in this new regime is the one that links ‘timber extraction’, monetary income’ and ‘satisfaction of basic needs and desires’, and that now dominates over the one that links ‘agriculture’, ‘goods’ and ‘satisfaction of basic needs and desires’. This is further amplified by the almost complete disappearance of cooperative forms of labour, that where replaced by remunerated ones. The impact on the ecosystem is an increasing rate of timber extraction, and related with this, a change in the edapho-hydric conditions, that could in time lead to a change in the composition of these forests. Human well-being has been affected negatively as the current situation is of high dependence on timber prices and reduced food autonomy.

Type of regime shift

  • socio-economic

Ecosystem type

  • Marine & coastal
  • Tropical Forests

Land uses

  • Timber production

Spatial scale of the case study

  • Local/landscape (e.g. lake, catchment, community)

Continent or Ocean

  • South America

Region

  • Chocó biogeographic region

Countries

  • Colombia

Locate with Google Map

Alternate regimes

Peatlands are characterized by often deep accumulations of incompletely decomposed organic material (i.e. peat). The accumulation of peat occurs when carbon sequestration exceeds the long-term loss through decomposition or export by hydrological flow. Such rates of decomposition can be very low in acidic and anaerobic conditions. Globally, peatlands occupy about four million km2, of which boreal and subarctic peatlands constitute about 87%, mainly in Russia, Canada, United States, Finland and Sweden. Tropical peatlands also exist, a big percentage of which is in Indonesia (Vitt, 2008). A major distinction within peatlands is between fens (minerotrophic peatlands: plants have access to geogenous water) and bogs (ombrotrophic peatlands: plants are dependent on precipitation). These and other differences in hydrology, acidity and climate produce a great variety of peatlands worldwide. Such variety in genesis and characteristics makes any generalization of peatlands functional values very difficult. A fen to bog transition is often seen as the natural course of peatland succession (Hughes & Barber 2004), whereas a change from bog to fen usually requires external changes in conditions or strong perturbations. Both bogs and fens exhibit internal feedbacks that provide them with some stability, and threshold conditions associated with the transition between each other have been suggested in the literature (Belyea & Malmer 2004). 

 

Bogs (Sphagnum-dominated peatland, with long-term carbon storage)

This regime is characterized by a landscape dominated by sphagnum-mosses, covering low hummocks and lawns, usually exhibiting no conspicuous spatial pattern in vegetation. Under the surface a thick layer of slow-decaying peat is mostly kept in waterlogged and acidic conditions. The concept of ecosystem engineers (Jones et al. 1994) has been used to describe Sphagnum mosses, given their functional capacity to create and maintain an acidic and nutrient-poor environment, harsh for most other plants (references in Ohlson et al. 2001). Additionally, mosses decay at extremely low rates due to their unique tissue chemistry, what strongly limits nutrient fluxes to other types of plants (Pastor et al. 2002). In the absence large external climatic changes or direct human impacts on hydrology or nutrient input, the species composition of these type of peatlands has proven to be very stable (references on Limpens et al. 2008).

 

Fens (Moss and vascular plant coexistence, with reduced peat accumulation)

Vascular plants also alter the environment in ways that negatively affect Sphagnum mosses. So an increase in vascular plant cover beyond critical thresholds inevitably leads to a decrease in Sphagnum (Berendse et al. 2001). Some of the mechanisms involved in this process act by preventing or even reversing ombrotrophication, in favor of minerotropic conditions. While other mechanisms might operate in bogs prompting the development of particular microtopography and associated vegetation spatial patterns. Such microtopography is also believed to be very stable (references in Eppinga et al. 2007 and in Limpens et al. 2008). This regime is characterized by an increasingly dense and connected vascular plants cover, exhibiting spatial patterns (strings-flarks on slopes and maze on flat landscapes) consisting of densely vegetated bands (hummocks forming ridges), alternating with wetter zones that are more sparsely vegetated (hollows forming pools) (Rietkerk et al. 2004).

Drivers and causes of the regime shift

A Sphagnum dominated peatland becomes more susceptible to invasion by vascular plants as the nutrient input increases (Pastors et al. 2002; Eppinga et al. 2007, 2009; Limpens et al. 2008). Ombrotrophic systems are particularly sensitive to nitrogen enrichment, which can prompt the invasion by graminoid species (e.g. Molinia caerulea) and woody species (e.g. Betula pubescens) with a parallel decline of ombrotrophic species (references in Tomassen et al. 2003). Sphagna are negatively affected by high nutrient input due to ammonium toxicity (Fritz et al. 2012). Additionally, related C:N ratio changes could enhance decomposition, further amplifying this nutrient positive relation with vascular plants.

Decreasing wetness during the growing season promotes vascular plant growth and hampers moss development (Eppinga et al. 2007; Limpens et al. 2008), and perhaps more importantly, it weakens the nutrient flux delay of sphagnum peat by increasing aerobic decomposition (Hilbert et al. 2000). Reduced precipitation and droughts in general directly decrease Sphagnum productivity, as photosynthetic rates are strongly dependent on water saturation levels. Additionally, longer dry seasons can potentially increase wild fire frequency, with negative effects on peat depth (references in Limpens et al. 2008). In high latitude peatlands an increase in temperature implies a longer growing season for vascular plants and increases mineralization rates. As vascular plants abundance increases and Sphagnum cover reduces, the temperature feedback in regime 1 weakens, allowing for even warmer conditions in the rooting zone further increasing the growing season of vascular plants (references in Eppinga et al. 2007).

How the regime shift works

Shift from Bogs to Fens

Different mechanisms are responsible for maintaining Bogs, mostly ombrotrophication, which is the ability of Sphagnum mosses to effectively decouple the rooting zone of vascular plants from geogenous mineral-rich water, thereby depriving those plants from key nutrients. This process occurs as a result of peat accumulation, which increases with the slow rates of decay of mosses (Pastor et al. 2002). Once the ombrotrophic conditions are reached, the competitive ability of sphagnum boosts, increasing their dominance. This in turn contributes to more peat accumulation (Granath et al. 2010). Sphagnum out-competes vascular plants, by getting inputs from the atmosphere and releasing decay-resistant and low-nutrient litter, creating a slow nutrient flux. Particularly relevant is nitrogen immobilization, making vascular plants entirely dependent on the slow mineralization of peat (Pastor et al. 2002; Malmer et al. 2003; Tomassen et al. 2003). Additionally, the low-porosity character of sphagnum peat promotes waterlogged conditions that further reduce mineralization rates (references in Eppinga et al. 2007). Other mechanisms include acidification of the environment, competition for light and space, and belowground temperature lowering. Through the organic acids resulting from its humification, bog sphagnum actively promotes acidification of the environment, which limits vascular plant growth (references in Eppinga et al. 2007). In such sphagnum-dominated sites, the establishment and growth of vascular plants is limited by the thick moss carpet that overgrows seedlings (Ohlson et al. 2001; Malmer et al.2003), and its vertical growth engulfing meristemic tissues (references in Pastor et al 2002). Also, the growing season for vascular plants is shortened, given the poor heat conductivity of sphagnum peat, which hampers the functioning of vascular plant roots (references in Eppinga et al. 2007).

Drought or drainage can trigger a shift from Bogs to Fens. A prolonged drought might lower the water table long enough to force moss desiccation and allow for increased mineralization (Tomassen et al. 2003; Eppinga et al. 2009; Granath et al. 2010). This reduces the competitive pressures on vascular plants, increasing the opportunities for colonization. Drainage is a primary shock altering peatland dynamics by lowering the water table (Limpens et al. 2008), and it is done for agricultural and forestry purposes. Also, an influx of water high in nutrients or minerals (e.g. Ca) from surrounding land or from atmosphere could also damage Sphagna and cause vascular plant invasion. Similarly, liming (i.e. spreading Ca- or Mg-rich minerals) is another direct human intervention to eliminate Sphagnum. Basically, as soon as the inorganic nutrient pool that vascular plants require ceases to limited by slow sphagnum peat mineralization rates, this regime shift could occur.

Key mechanisms behind the maintenance of Fens are related to peat accumulation and vascular plants. While vascular plants, which can become highly productive under the influence of geogenous water or some other source of important nutrients, minerotrophic conditions seriously prevent bog sphagnum from settling given its high sensitivity to calcareous water (Granath et al. 2010). Advective transport of nutrients has been proposed by Rietkerk et al. (2004) as a scale-dependent mechanism, having a locally positive and long-range negative effect on nutrient concentration, to explain the spatial patterning of peatlands. This mechanism would be driven by transpiration of vascular plants, enhancing drier microforms (hummocks, ridges) with increased nutrient concentration that vascular plants require to establish and further reinforce their presence. Additionally, transpiration rates are higher in the presence of vascular plants, and this stimulates a lowering of the water table (Rietkerk et al. 2004). While this reduction of water in the surface negatively affects sphagnum productivity by desiccation (references in Tomassen et al 2003), it also leads to an increase of mineralization rates, which reinforces the presence of vascular plants (Tomassen et al. 2003). Another competitive mechanism operates as vascular plants reach above the moss carpet, limiting its development through shading and burial by litter (Berendse et al. 2001; Pastor et al. 2002; Malmer et al. 2003). Under these conditions the limited growth of Sphagnum prevents peat accumulation (Malmer et al. 2003; Limpens et al. 2008). 

 

Shift from Fens to Bogs

Increases in precipitation could lead to a higher water table, potentially causing substantial dieback of vascular plants (references in Eppinga et al. 2007). Moreover, the minerotrophic conditions that are detrimental for bog sphagnum growth are reduced as the relative importance of precipitation water increases over that of geogenous water (Pastor et al. 2002). The height of the peatland surface above the water table is a key determinant of plant species distribution and primary productivity, and consequently the rates of litter production and litter decay losses (Hilbert et al. 2000; Belyea & Malmer 2004). Given the explained mechanism of delayed nutrient flux, it is clear that at a certain height of the surface above the water table, bog sphagnum becomes a superior competitor (Granath et al. 2010), and the reinforcing feedbacks of Bogs are activated.

It is worth mentioning that even though the literature cited here in reference to these alternate stable states relies deeply on modeling (e.g. Hilbert et al 2000; Pastor et a 2002; Rietkerk et al 2004; Eppinga et al 2007, 2009), qualitatively similar shifts have been reported in paleoecological studies as well as present day observations: dominance of deciduous shrubs and graminoids during the early stages of peatland development with little or no presence of moss, followed by landscapes dominated by Sphagnum lawns after the ombrotrophication process, which are later subjected to invasion by shrubs and spruce (references in Pastor et al 2002). The fact that such abrupt shifts between a near-monoculture moss state and a co-existence with vascular plants state have been reported to occur sometimes but not always, suggests that these systems do exhibit alternate stable states.

Impacts on ecosystem services and human well-being

Shift from Bogs to Fens

Since sphagnum litter enhances the formation of collapsible peat (i.e. with low porosity), which easily becomes waterlogged, the conditions for low rates of decomposition, and an overall net carbon sequestration effect are maintained in Bogs. Rates of carbon sequestration and methane emission depend strongly on height of the peatland surface above the water table (references in Belyea & Malmer 2004). Even though the same processes of anaerobic decomposition that increases carbon accumulation, also increases methane production, the overall desirable effect in relation to climate change gets lost in this shift, since the effect of removing long-lived atmospheric carbon dioxide ultimately surpasses that of releasing short-lived methane (Limpens et al. 2008).

Because of the complex relations of acrotelm thickness with vegetation and microtopography, these two are considered to primarily determine carbon sequestration/emission rates (Belyea & Malmer 2004; Belyea & Baird 2006). Peat formation rate is greatest for 'intermediate microforms' (lawns, low hummocks) and lowest for microforms at the extremes of the water table gradient (high hummocks and pools) (Belyea & Malmer 2004). Given this trade-off of decomposability and productivity between elevated and low microforms (reference in Limpens et al 2008), a landscape will exhibit higher short-term sequestration of carbon or long-term storage depending o the microforms by which it is dominated.

Shift from Fens to Bogs

A reduction in species richness and the loss of agriculturally suitable lands are potential impacts of the shift to sphagnum-dominated peatlands.

Management options

Damming or blocking ditches are common management practices aimed at raising the water table.  More direct practices to recover or sustain sphagnum vegetation is to establish rafts of floating brush or clumps of peat for floating mosses settle, as well as the creation of suitable microclimates through techniques such as applying a layer of straw mulch, and carving depressions that promote carpet or lawn level Sphagnum (references in Limpens et al. 2008 and in Rydin & Jeglum 2006).

Alternate regimes

Subsistence-oriented, rice-based livelihood (with organic, self-sufficient farming)

Traditionally, in these Balinese farms rice production based on local rice varieties represents the main economic activity, and it is performed in a 'self-sufficient way' by relying on the articulation of several practices, such as keeping ducks for local pest control and cows for manure (Lansing et al. 2001; Marion et a.l 2005). This articulation of farming activities is time/labour demanding for members of the household, allowing less time for off-farm economic activities.

 

Market-oriented, diversified livelihood (with agrochemical-dependent farming)

The Green Revolution in Indonesia in the 1970s, presented to Balinese farmers a 'technological packet' including high-yielding rice varieties, chemical fertilizers (nitrogen, potassium and phosphorus) and pesticides (Lansing et al. 2001; Marion et al. 2005). Ever since, some households have replaced some of the labour/time intensive activities traditionally used, with these modern capital intensive inputs. Hence, in this regime household members have to devote less time to within-farm activities, but on the other hand, since access to these inputs requires money, it becomes imperative that an increasing part of their labour/time is devoted to monetized labour (i.e. selling more rice in the market, and/or other economic activities in tourism and commerce, for example).

Drivers and causes of the regime shift

An agricultural credit system developed to promote the use of the 'technological packet' was a key aspect of the Green Revolution in Indonesia enabling the farm-level regime shift in Balinese rice production. To boost rice production, these programs focused on the modernization of the country-side, and the breakdown of traditional management practices (Lansing 2006). This provided the conditions for intimately linking the farming practices to the monetized economy, and as a consequence modifying local livelihoods by allowing/forcing the diversification of economic activities.

Parallel to the increased connection with external markets for agriculture, importance of tourism has continually increased, providing a context for more non-agricultural, off-farm activities (Liater & Me 2003). Further, increased monetary incomes are invested in formal education of younger generations; education which tends to detach them more from agricultural activites (Lorentz & Lorentz, 2010).

How the regime shift worked

In the rice production system of subsistence-orientated rice-based livelihood, the household subsists by ensuring a constant cycle of cultivating and harvesting rice, which depends on both on collective behaviours involving other households, and also within-farm practices. For such practices, members of households in this regime devote most of their time on them, keeping rice production as the economic dominating activity. Under conditions in which such time/labour demanding activities are not 'easily' replaceable, this regime persists.

The agriculture credit system linked to the use of technological packet enabled this replacement. This change both enabled the diversification of economic activities by offering more time flexibility, and demanded an increase in the monetized labour activities. The threshold dividing these two regimes is then related with the importance of money to mediate social and economic interactions on Bali. The increased time flexibility also leads to an increasing access to formal educations, which further leaded to a dominance of non-agricultural economic activities by younger generations, strengthening the trajectory away from the subsistence-orientated rice-based livelihood regime.

Impacts on ecosystem services and human well-being

Both regimes provide rice yields, however the (agro)biodiversity is diminished by the shift described, not only by the adoption of few high-yielding varieties, but also by the effect of pesticides on soil and water habitats. Although the aesthetic value of these landscapes has always been 'provided', the development of infrastructure and training related with tourism increase its perception, and hence its worth in the market-orientated diversified regime.

Management options

.

Key References

  1. Del Valle JI & Restrepo E. (eds) 1996. Renacientes del guandal. “grupos negros” de los ríos Satinga y Sanquianga. UN–PBP, Bogotá DC.
  2. Escobar A & Pedrosa A. (eds) 1996. Pacífico ¿desarrollo o diversidad? Estado, capital y movimientos sociales en el Pacífico colombiano. CEREC-Ecofondo, Bogotá DC.
  3. Leal C & Restrepo E. 2003. Unos bosques sembrados de aserríos: historia de la extracción maderera en el Pacífico colombiano. ICANH–UN–Universidad de Antioquia, Medellín.
  4. Proyecto Biopacífico. 1994. Economías de las comunidades rurales en el Pacífico colombiano (Memorias del foro Las economías rurales indígenas, negras y mestizas en el Pacífico colombiano, Sena-Codechoco-PBP, Octubre 19-21 de 1994, Quibdó). MMA-PNUD-GEF, Bogotá DC.
  5. West RC. 1957. The Pacific lowlands of Colombia: A negroid area of the American tropics. Louisiana State University Press, Baton Rough.
  6. Whitten NE Jr. 1986. Black Frontiersmen: Afro-Hispanic Culture of Ecuador and Colombia. Waveland Press, Prospect Heights.

Citation

Daniel Ospina, -1. Tropical lowland forests (economic use), Colombia. In: Regime Shifts Database, www.regimeshifts.org. Last revised 2013-08-25 21:53:08 GMT.