Leaf trait networks of subtropical woody plants weaken along an elevation gradient.

The leaf economic spectrum (LES) captures key leaf functional trait relationships, defining a conservative-acquisitive axis of plant resource utilization strategies. Examining the leaf trait network (LTN) is useful for understanding resource utilization strategies but also more broadly, the ecological strategies of plants. However, the relationship between the LES conservation-acquisition axis and LTN correlations across environmental gradients is unclear. To address this knowledge gap, we measured physiological, chemical, and structural traits in 52 broad-leaved tree species spanning an elevation gradient (1400 m, 1600 m, 1800 m) in Wuyi Mountain, China. A total of 12 leaf traits were selected, including: photosynthetic rate (A), respiration rate (R), optimum photosynthetic temperature (T), rate of photosynthesis at optimum temperature (A), mean temperature at which 90 % of A is reached (T), temperature sensitivity of respiration (Q), N and P content, N/P, leaf mass per area (LMA), photosynthetic nitrogen use efficiency (PNUE) and photosynthetic phosphorus use efficiency (PPUE). We found that leaf physiological traits exhibited signs of thermal acclimation along the elevation gradient. We also observed significant changes in leaf N and P content, N/P, photosynthetic phosphorus utilization efficiency (PPUE) and LMA with elevation. The resource utilization strategies of plants changed from conservative to acquisitive as elevation increased. The LTN analysis showed that as elevation increased, the links among traits weakened and modularity (modularity is used to describe the degree of separation between networks) increased. Collectively, our results indicate that elevation changes can trigger moderate shifts in the resource utilization and ecological strategies of plants via leaf functional traits.