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Earth's Systems / Biological processes / Terrestrial ecosystem functioning / Organism-environment interactions / Vegetation-water feedback and dryland patchiness

Vegetation-water feedback and dryland patchiness

In dry lands vegetation raises infiltration of the water that falls, which feeds more vegetation; loss of cover breaks the loop and bare crusted soil sheds water, so ecosystems can flip between vegetated and bare states.

Boundary: where this process starts

Starts with: Plant cover and litter protect the surface and keep infiltration high

Boundary: where it ends

Ends after: Bare crusted soil sheds water as runoff and loses organic matter; Run-off collects in remaining patches, so vegetation self-organises into bands or spots

PARTICIPANTSRESOURCESPlantsSoilRainLitter layerPlant rootsWaterPlant litterPore spaceSoilCarbon dioxideImpact +3 of 5. Click for details and evidence.Impact +3 of 5. Click for details and evidence.Impact +3 of 5. Click for details and evidence.Impact +4 of 5. Click for details and evidence.↻ reinforces · strong · 0.5 more cover proteImpact 03 of 5. Click for details and evidence.Impact -3 of 5. Click for details and evidence.Impact -4 of 5. Click for details and evidence.30% collapse to the bare staImpact 03 of 5. Click for details and evidence.25% patchy vegetation persisImpact +3 of 5. Click for details and evidence.45% cover recoversImpact -4 of 5. Click for details and evidence.↻ reinforces · strong · 0.5 bare soil gets dImpact 02 of 5. Click for details and evidence.Impact 02 of 5. Click for details and evidence.Plant cover and litter protect the surface and keep infiltration high: uses WaterPlant cover and litter protect the surface and keep infiltration high: uses Plant litterPlant cover and litter protect the surface and keep infiltration high: uses Pore spaceMore rain enters the soil instead of running off: uses WaterMore rain enters the soil instead of running off: uses Pore spaceSoil water supports plant growth and cover: uses WaterSoil water supports plant growth and cover: uses up Carbon dioxideuses upDisturbance (grazing, drought, clearing) thins the cover: uses WaterDisturbance (grazing, drought, clearing) thins the cover: uses up Plant litteruses upBare crusted soil sheds water as runoff and loses organic matter: uses WaterBare crusted soil sheds water as runoff and loses organic matter: uses SoilRun-off collects in remaining patches, so vegetation self-organises into bands or spots: uses WaterWhich state persists after disturbance: uses WaterWhich state persists after disturbance: uses Soilprotected from surfacelossWater: protected from surface lossprotects surface fromerosionPlant litter: protects surface from erosionkept open forinfiltrationPore space: kept open for infiltrationinfiltrates instead ofrunning offWater: infiltrates instead of running offreceives water throughopen poresPore space: receives water through open poressupports growth andcoverWater: supports growth and coverfixed by growing coverCarbon dioxide: fixed by growing coverretained less by thincoverWater: retained less by thin coverremoved by disturbancePlant litter: removed by disturbancesheds as runoffWater: sheds as runoffcrusted and sheds waterSoil: crusted and sheds watercollects in remainingpatchesWater: collects in remaining patchesredistributed byremaining coverWater: redistributed by remaining coverstate persists afterdisturbanceSoil: state persists after disturbanceStart: Vegetation-waterfeedback and drylandpatchinessSTARTStart: Vegetation-water feedback and dryland patchinessEnd: Vegetation-waterfeedback and drylandpatchinessENDEnd: Vegetation-water feedback and dryland patchinessPlant cover and litterprotect the surface andkeep infiltration high📄1 ↗1Plant cover and litter protect the surface and keep infiltration highMore rain enters thesoil instead of runningoff📄1 ↗1More rain enters the soil instead of running offSoil water supportsplant growth and cover📄1 ↗1Soil water supports plant growth and coverDisturbance (grazing,drought, clearing)thins the cover📄1Disturbance (grazing, drought, clearing) thins the coverBare crusted soil shedswater as runoff andloses organic matter📄1 ↗1Bare crusted soil sheds water as runoff and loses organic matterRun-off collects inremaining patches, sovegetati…📄1Run-off collects in remaining patches, so vegetation self-organises into bands or spotsWhich state persistsafter disturbance📄1Which state persists after disturbance
Line thickness = size of impact (1 to 5)% on a line = chance a fork takes that branch📄 = pieces of evidence on a stepNegative effectLoops backHypothesisResource used up (arrow into the step)Resource used, not used upResource made or released (arrow out of the step)
What am I looking at? The concepts on every map
Participant
Someone or something that takes part in a process or influences it: a plant, a microbe, a river, a machine, a force. Participants are the rows of a map.
Resource
Something a step uses or uses up: water, oxygen, sunlight, a tool. Each step has an arrow down to the resources it uses.
Step
One thing that happens in a process. Every step has at least one participant and carries evidence.
Decision fork
A step where the process can go several ways. Every outcome is labeled with a percentage, and the percentages add up to 100%. It is not limited to yes or no.
Loop
A line that carries the process back to an earlier step. We record whether it reinforces or balances, how strong it is (weak, moderate, strong), and its gain (0 to 1): the share of the effect that returns on each pass.
Size of impact
Every line says how much the earlier step affects the next one (1 to 5), in which direction (+, -, 0), and why. Thicker lines mean bigger impact.
Evidence
The support for a claim: a source and what it shows. Every step, line, change and vote needs it. Click any step or line to read its evidence.
Boundary
Where a process starts and where it ends. Every process, and every subprocess, has a start and an end.
Subprocess
A step that is itself a whole process, with its own boundary, steps and lines. Click a step marked ↘ to open it. Subprocesses nest as deep as the evidence goes.
Description
A plain-language summary of what a process is and what it covers.
Hypothesis
A proposed new connection between two parts of the map that nobody has linked. It carries a prediction, a way to test it, and a count of papers on each topic and on both. It is an unverified idea until someone tests it.

Every step, with its evidence

The same information as the map, as a list you can search and share. Click a participant or resource to see everywhere it appears.

Plant cover and litter protect the surface and keep infiltration high
PlantsLitter layerWaterPlant litterPore space
Evidence (1) · added by Loopa
  • Rietkerk 2004, Self-organized patchiness and catastrophic shifts in ecosystems, Science, doi:10.1126/science.1101867: Vegetation raises infiltration relative to bare soil. (confidence 0.8)
More rain enters the soil instead of running off
SoilRainWaterPore space
Evidence (1) · added by Loopa
  • Rietkerk & van de Koppel 1997, Alternate stable states and threshold effects in semi-arid grazing systems, Oikos, doi:10.2307/3546091: Infiltration feedback. (confidence 0.8)
Soil water supports plant growth and cover
PlantsPlant rootsWaterCarbon dioxide
Evidence (1) · added by Loopa
  • Rietkerk & van de Koppel 1997, Alternate stable states and threshold effects in semi-arid grazing systems, Oikos, doi:10.2307/3546091: Water is the limiting resource. (confidence 0.8)
Disturbance (grazing, drought, clearing) thins the cover
LivestockDroughtPlantsWaterPlant litter
Evidence (1) · added by Loopa
  • Schlesinger 1990, Biological feedbacks in global desertification, Science, doi:10.1126/science.247.4946.1043: Loss of cover accelerates degradation in drylands. (confidence 0.8)
Bare crusted soil sheds water as runoff and loses organic matter
RaindropsSoilWindWaterSoil organic matterSoil
Evidence (1) · added by Loopa
  • Schlesinger 1990, Biological feedbacks in global desertification, Science, doi:10.1126/science.247.4946.1043: Desertification feedback via erosion and nutrient loss. (confidence 0.8)
Run-off collects in remaining patches, so vegetation self-organises into bands or spots
PlantsRunoffWaterNutrients
Evidence (1) · added by Loopa
  • Rietkerk 2004, Self-organized patchiness and catastrophic shifts in ecosystems, Science, doi:10.1126/science.1101867: Self-organised patchiness appears near thresholds of degradation. (confidence 0.8)
⑂ Which state persists after disturbance
PlantsSoilWaterSoil
Evidence (1) · added by Loopa
  • Rietkerk & van de Koppel 1997, Alternate stable states and threshold effects in semi-arid grazing systems, Oikos, doi:10.2307/3546091: Threshold behaviour: alternative states depend on grazing pressure and rainfall. Shares are illustrative (range recover 55-80 percent). (confidence 0.4)