Contribution of environmental variability and ecosystem functional changes to interannual variability of carbon and water fluxes in a subtropical coniferous plantation

Abstract

Accurate quantification of the contribution of environmental variability and functional changes to the interannual variability of net ecosystem production (NEP) and evapotranspiration (ET) in coniferous forests is needed to understand global carbon and water cycling. This study quantified these contributions to the interannual variability of NEP and ET for a subtropical coniferous plantation in southeastern China, and the effect of drought stress on these contributions was also investigated. NEP and ET were derived from eddy covariance measurements carried out over the period 2003-2012. A homogeneity-of-slopes model was adopted to quantify the contribution to the interannual variability of these fluxes. Environmental variability accounted for 71% and 85.7% of the interannual variability of NEP and ET, respectively; however, functional changes accounted for only 11.3% and 5.9%, respectively. Furthermore, functional changes explained more of the interannual variability of NEP in dry years (16.3%) than in wet years (3.8%), but there was no obvious change in the contribution of functional changes to the interannual variability of ET in dry (4.7%) or wet (5.5%) years. Thus, environmental variability rather than ecosystem functional changes dominated the interannual variability of both ET and NEP. However, different environmental variables controlled the interannual variability of NEP and ET. The results also indicated that, compared with NEP, ET was more resistant to drought stress through the self-regulating mechanisms of this plantation.

Water use strategies for two dominant tree species in pure and mixed plantations of the semiarid Chinese Loess Plateau

“…Species exploit different water use strategies in the trade‐off among water absorption, stomatal adjustment, leaf water potential, and carbon gain to adapt to varied soil moisture (Tang, Wen, Sun, Chen, & Wang, ; West et al, ; Zapater, Breda, Bonal, Pardonnet, & Granier, ). The root architecture system (Swaffer, Holland, Doody, Li, & Hutson, ; Yang, Wen, & Sun, ) and precipitation characteristics (Wu et al, ) are considered to be the essential factors influencing water uptake by plant species.…”

Estimating Forest Carbon Fluxes Using Machine Learning Techniques Based on Eddy Covariance Measurements

“…In addition, the substantial impacts of 2 of 26 climate extreme events (e.g., droughts, precipitation, wind storms, heat waves, frosts and fires) on the terrestrial carbon cycle have been revealed by a few recent studies [3,4]. These effects may alter the growth patterns of pine species and biodiversity as well as the structure and functioning of forest ecosystems [5,6], which will lead to a major impediment in our understanding of the underlying mechanisms causing the ongoing seasonal variation in carbon fluxes, mainly including gross primary production (GPP), ecosystem respiration (R) and net ecosystem exchange (NEE). Therefore, quantification of the carbon exchanges between the forest ecosystems and the atmosphere is challenging for current modeling techniques, due to the complex interactions and feedbacks involved in biological, physical and chemical processes across various spatial and temporal scales.…”