Volume 15, issue 13 | Copyright
Biogeosciences, 15, 4193-4203, 2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 11 Jul 2018

Research article | 11 Jul 2018

The strategies of water–carbon regulation of plants in a subtropical primary forest on karst soils in China

Jing Wang1,2,3, Xuefa Wen1,2, Xinyu Zhang1,2, and Shenggong Li1,2 Jing Wang et al.
  • 1Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China
  • 2College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100190, China
  • 3School of Life Sciences, Beijing Normal University, Beijing 100875, China

Abstract. Coexisting plant species in a karst ecosystem may use diverse strategies of trade off between carbon gain and water loss to adopt to the low soil nutrient and low water availability conditions. An understanding of the impact of CO2 diffusion and maximum carboxylase activity of Rubisco (Vcmax) on the light-saturated net photosynthesis (A) and intrinsic water use efficiency (iWUE) can provide insight into physiological strategies of the water–carbon regulation of coexisting plant species used in adaptation to karst environments at the leaf scale. We selected 63 dominant species (across 6 life forms) in a subtropical karst primary forest in southwestern China, measured their CO2 response curves, and calculated the corresponding stomatal conductance to CO2 (gs), mesophyll conductance to CO2 (gm), and Vcmax. The results showed that gs and gm varied about 7.6- and 34.5-fold, respectively, and that gs was positively related to gm. The contribution of gm to the leaf CO2 gradient was similar to that of gs. gsA, gmA and gtA was negatively related to VcmaxA. The relative limitations of gs (ls), gm (lm), and Vcmax (lb) to A for the whole group (combined six life forms) were significantly different from each other (P<0.05). lm was the largest (0.38±0.12), followed by lb (0.34±0.14), and ls (0.28±0.07). No significant difference was found between ls, lm, and lb for trees and tree/shrubs, while lm was the largest, followed by lb and ls for shrubs, grasses, vines and ferns (P<0.05). iWUE varied about 3-fold (from 29.52 to 88.92µmolCO2mol−1H2O) across all species, and was significantly correlated with gs, Vcmax, gmgs, and Vcmaxgs. These results indicated that karst plants maintained relatively high A and low iWUE through the covariation of gs, gm, and Vcmax as an adaptation to a karst environment.

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The different contributions of gs, gm, and Vcmax to A indicated that plants utilized diverse trade-offs between CO2 supply and demand to maintain relatively high A. The iWUE was relatively low, but ranged widely, indicating that plants used a "profligate/opportunistic" water use strategy to maintain their survival, growth, and the structure of the community. These findings highlight the importance of covariation of gs, gm, and Vcmax for the adaptation of plants to the harsh karst environment.
The different contributions of gs, gm, and Vcmax to A indicated that plants utilized diverse...