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Earth's Systems / Biological processes / Terrestrial ecosystem functioning / Primary production / Controls on net primary production / Nutrient-driven carbon allocation belowground

Nutrient-driven carbon allocation belowground

Plants facing nutrient scarcity send a larger share of new carbon to roots and exudates, which raises nutrient uptake and so photosynthesis.

Boundary: where this process starts

Starts with: Nutrient scarcity raises the root mass fraction

Boundary: where it ends

Ends after: Greater nutrient uptake raises leaf nitrogen and photosynthesis

PARTICIPANTSRESOURCESPlantsMycorrhizalfungiPlant rootsNitrogenPhosphorusOrganic carbonWaterImpact +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 +3 of 5. Click for details and evidence.Nutrient scarcity raises the root mass fraction: uses NitrogenNutrient scarcity raises the root mass fraction: uses PhosphorusFine root growth and exudation expand the foraged soil volume: uses up Organic carbonuses upFine root growth and exudation expand the foraged soil volume: uses WaterGreater nutrient uptake raises leaf nitrogen and photosynthesis: uses up Nitrogenuses upGreater nutrient uptake raises leaf nitrogen and photosynthesis: uses up Phosphorususes upscarcity drives roots togrowNitrogen: scarcity drives roots to growdeficit prompts moreroot growthPhosphorus: deficit prompts more root growthspent building new roottissueOrganic carbon: spent building new root tissueextracted from a largersoil volumeWater: extracted from a larger soil volumeincorporated into leafproteinNitrogen: incorporated into leaf proteinbuilds photosyntheticmachineryPhosphorus: builds photosynthetic machineryStart: Nutrient-drivencarbon allocationbelowgroundSTARTStart: Nutrient-driven carbon allocation belowgroundEnd: Nutrient-drivencarbon allocationbelowgroundENDEnd: Nutrient-driven carbon allocation belowgroundNutrient scarcityraises the root massfraction📄1Nutrient scarcity raises the root mass fractionFine root growth andexudation expand theforaged soil volume📄1 ↗1Fine root growth and exudation expand the foraged soil volumeGreater nutrient uptakeraises leaf nitrogenand photosynthesis👍1📄1 ↗1Greater nutrient uptake raises leaf nitrogen and photosynthesis
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)
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Nutrient scarcity raises the root mass fraction
PlantsNitrogenPhosphorus
Evidence (1) · added by Broad
  • Poorter 2012, Biomass allocation to leaves, stems and roots: meta-analyses of interspecific variation and environmental control, New Phytologist, doi:10.1111/j.1469-8137.2011.03952.x: Meta-analysis shows root mass fraction increases under low nutrient availability. (confidence 0.75)
Fine root growth and exudation expand the foraged soil volume
PlantsPlant rootsOrganic carbonWater
Evidence (1) · added by Broad
  • Schenk & Jackson 2002, The global biogeography of roots, Ecological Monographs, doi:10.1890/0012-9615(2002)072[0311:tgbor]2.0.co;2: Root biomass and depth distributions vary systematically with biome and soil resources. (confidence 0.65)
Greater nutrient uptake raises leaf nitrogen and photosynthesis
PlantsMycorrhizal fungiNitrogenPhosphorus
Evidence (1) · added by Broad
  • LeBauer & Treseder 2008, Nitrogen limitation of net primary productivity in terrestrial ecosystems is globally distributed, Ecology, doi:10.1890/06-2057.1: Nitrogen addition raises terrestrial NPP by roughly 29% on average, showing nitrogen supply feeds back to production. (confidence 0.75)