Abstract
Foliar-level stoichiometry plays an important role in ecosystem elemental cycling. Shifts in foliar ratios of carbon to nitrogen (C:N) and nitrogen to phosphorus (N:P) in response to global change can therefore have a large impact upon ecosystem function. We conducted a meta-analysis with 2,236 paired observations from 123 published studies to investigate the responses of foliar C:N and N:P ratios to experimental global change treatments, i.e. warming, increased precipitation, drought, N addition and elevated carbon dioxide concentration (eCO2), in field conditions. Foliar C:N and N:P ratios were neither affected by warming nor by increased precipitation. Foliar C:N ratio increased with drought and eCO2, and decreased with N addition. Foliar N:P ratios declined with eCO2, and increased under drought and N addition. Our results suggested the responses of the C:N ratio to global change were mainly related to shifts in foliar [N], whereas changes in the N:P ratio were related to the responses of both [N] and [P]. Moreover, the response magnitude of foliar N:P ratio decreased with treatment duration under increased precipitation, N addition and eCO2. Our findings are important for our understanding of plant nutrient dynamic and modeling of nutrient biogeochemistry under global change.
Highlights
Foliar-level stoichiometry plays an important role in ecosystem elemental cycling
We found relationships between the response magnitude of foliar C:N and N:P ratios with latitude, mean annual precipitation (MAP), mean annual temperature (MAT) were weaker under warming and e CO2, but stronger under increased precipitation and N addition (Table 2)
We demonstrate that the response of foliar C:N ratio to global change was largely explained by shifts in foliar [N], whereas the response of foliar N:P ratio was influenced by shifts in both [N] and [P]
Summary
Foliar-level stoichiometry plays an important role in ecosystem elemental cycling. Shifts in foliar ratios of carbon to nitrogen (C:N) and nitrogen to phosphorus (N:P) in response to global change can have a large impact upon ecosystem function. Previous meta-analyses have demonstrated global change impacts on C:N and N:P ratios at the whole-plant level[10,16], by combining the results of experimental field manipulations, natural environmental gradients, and controlled greenhouse or pot experiments These studies have provided important insights into plant responses to change, it is important to evaluate the results from field experiments separately, as these can differ markedly from observations along natural gradients and greenhouse or pot e xperiments[26,27]. To gain a better understanding of the overall responses of foliar-level C:N and N:P ratios to global change, we conducted a metaanalysis with 2,236 observations from 123 reports based on field manipulative experiments, including warming (343 observations), shifts in precipitation (158 observations for increased precipitation and 655 observations for drought), N addition (750 observations) and e CO2 (330 observations).
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