Figure 1. Model perturbation experiments compared with nitrogen and phosphorus fertilization field experimental data. The blue dots show the difference between control and perturbed simulations, which mean how much newly added nutrient each consumer takes up. The red circles are recovered isotopically labeled nutrient within each consumer. Since plants phosphorus uptake was not measured at Hawaii sites, we didn’t include the plants in the perturbation study.

Validation Test 2

Validation Test 2: 15N fertilization experiments at alpine grassland site

Date last modified: Dec 31 2015

Contributors: Qing Zhu

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Results: 

Figure 2. Observed plant and microbe competition pattern (triangles) compared with (1) Relative Demand competition theory (CT4; red line); (2) “microbes outcompete plant” competition theory (CT2; green line); and (3) the new competition theory based on ECA kinetics (CT5). The blue dashed line is the mean of ECA ensemble predictions using literature-derived parameters from other grassland systems. The shaded area shows 5% - 95% percentiles of those ECA ensembles. The black line shows the best parameter fit ECA model for the observations at this site. Only the ECA competition theory captures the shape and magnitude of the observed competitive environment.

Validation Test 3

Validation Test 2: 15N fertilization experiments at tundra shrub ecosystems

Date last modified: Dec 31 2015

Contributors: Qing Zhu

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Results: 

Figure 3. Comparison between NH4+ uptake profiles observed and predicted by alternative competition hypotheses: (1) N-COM uses ECA; (2) RD-root assumes that the plant NH4+ demand profile is proportional to root biomass density; (3) RD-NH4 assumes that the plant NH4+ demand profile is proportional to soil NH4+ profile; and (4) MIC assumes that microbial decomposers outcompete plants.