期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2015
卷号：112
期号：23
页码：7213-7218
DOI：10.1073/pnas.1506262112
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：SignificanceWith increasing atmospheric CO2 and a changing climate come changes in both plant water use efficiency and rainfall regimes. The effects of these changes on forests, including feedbacks to the carbon cycle, are complex. Through a theoretical analysis combining CO2, soil moisture dynamics, and individual-based competition in forests, we find that (i) carbon storage has a complex and significant dependence on rainfall amount and timing and (ii) the main effect of increasing CO2 in water-limited forests is a decrease in the amount of time trees spend in water limitation. This main effect is predicted to reduce competitive overinvestment in fine roots, drive competitive trees to increase investment in woody biomass, and greatly increase forest carbon storage in live biomass. Increasing atmospheric CO2 concentrations and changing rainfall regimes are creating novel environments for plant communities around the world. The resulting changes in plant productivity and allocation among tissues will have significant impacts on forest carbon storage and the global carbon cycle, yet these effects may depend on mechanisms not included in global models. Here we focus on the role of individual-level competition for water and light in forest carbon allocation and storage across rainfall regimes. We find that the complexity of plant responses to rainfall regimes in experiments can be explained by individual-based competition for water and light within a continuously varying soil moisture environment. Further, we find that elevated CO2 leads to large amplifications of carbon storage when it alleviates competition for water by incentivizing competitive plants to divert carbon from short-lived fine roots to long-lived woody biomass. Overall, we find that plant dependence on rainfall regimes and plant responses to added CO2 are complex, but understandable. The insights developed here will serve as an important foundation as we work to predict the responses of plants to the full, multidimensional reality of climate change, which involves not only changes in rainfall and CO2 but also changes in temperature, nutrient availability, and disturbance rates, among others.
