Abstract
The resource-driven concept, which is an important school for investigating ecosystem production, has been applied for decades. However, the regulatory mechanisms of production by multiple resources remain unclear. We formulated a new algorithm model that integrates multiple resource uses to study ecosystem production and tested its applications on a water-availability gradient in semi-arid grassland. The result of our experiment showed that changes in water availability significantly affected the resources of light and nitrogen, and altered the relationships among multiple resource absorption rate (ε), multiple resource use efficiency (mRUE), and available resource (Ravail). The increased water availability suppressed ecosystem mRUE (i.e., “declining marginal returns”); The changes in mRUE had a negative effect on ε (i.e., “inverse feedback”). These two processes jointly regulated that the stimulated single resource availability would promote ecosystem production rather than suppress it, even when mRUE was reduced. This study illustrated the use of the mRUE model in exploring the coherent relationships among the key parameters on regulating the ecosystem production for future modeling, and evaluated the sensitivity of this conceptual model under different dataset properties. However, this model needs extensive validation by the ecological community before it can extrapolate this method to other ecosystems in the future.
Highlights
Biophysical regulations and resource-driven investigations are the two primary approaches for modeling the magnitudes and dynamics of ecosystem production and understanding its mechanisms[1]
The ecosystem production is often regulated by multiple resources, and the single resource use process was generally constrainted by the other resources
From the viewpoint of plant physiology, an increase in water availability in soil would probably enhance the water uptake and soluble materials of the plant through transpiration pull, leading to a higher ε.the multiple resource use efficiency (RUE) (mRUE) may be reduced if the amount of absorbed resources surpasses the demand of plants[24], suggesting that the increased εcombined with the decreased mRUE may still enhance plant production
Summary
To examine the complex interactions among the elements of multiple resources (i.e., ε, mRUE, Ravail), a non-recursive structural equation model (SEM) for our experimental data in the semi-arid grassland (Fig. 4a without coefficients) was constructed to test four specific hypotheses: Ecosystem type Grassland Grassland Grassland Driest years in arid ecosystems Forest Forest Cropland Grassland Terrestrial Forest Cropland Forest
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