Main drivers of vertical and seasonal patterns of leaf photosynthetic characteristics of young planted Larix Olgensis trees
2024
Qiang Liu | Zhidong Zhang | Dongzhi Wang | Fengri Li | Longfei Xie
Photosynthetic characteristics of tall trees play important roles in improving the accuracy of ecosystem models, but they are laborious to be accurately measured or estimated owing to the influence of multiple factors. To clarify the main drivers of vertical and seasonal patterns of leaf photosynthetic characteristics of young planted Larix Olgensis trees, we collected data on the photosynthetic, morphological, and meteorological characteristics by a long-term observation throughout the entire growing season. Vertical and seasonal patterns of leaf photosynthetic characteristics and their impact factors were analyzed. Results showed that maximum net CO2 assimilation (Amax), light saturated stomatal conductance (gs-sat), respiration rate (RD), needle mass per area (NMA), and ratio of needle length to needle width (rlw) all significantly and negatively correlated with relative depth into crown (RDINC), that was caused by the adaptive alteration of mesophyll tissue to the differed light intensity and humidity. Amax and gs-sat both showed a similar 'parabolic' seasonal trend, that was not only affected by the variation of environment but also the leaf economic spectrum, such as NMA. Our results suggested that spatiotemporal variations of crown photosynthetic characteristics were directly influenced by leaf economic spectrum but fundamentally affected by the long-term acclimation to surrounding environmental factors. This is helpful to optimize the crown photosynthesis model to assess instantaneous or even long-term photosynthetic production, in order to clarify the balance of supply and demand within crown, and further guide the effective pruning for individual trees.
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