Variation, relationship, and trade-offs of leaf traits in large and small deciduous broadleaf tree species

Leaf traits serve as indicators of plant responses to environmental changes and play a pivotal role in shaping ecosystem functions. Deciduous broadleaf trees, widely planted in temperate urban forests, contribute significantly to carbon cycling, water regulation, and biodiversity. Their sensitivity to shifts in temperature and precipitation makes them useful indicators of ecological change. Leaf traits such as nutrient content, specific leaf area, and water-use efficiency are especially informative, as they reflect physiological responses and adaptive strategies under changing conditions. We hypothesized that large and small deciduous broadleaf tree species would exhibit significant differences in variation, relationships, and trade-offs between leaf traits. By examining 12 key structural, chemical, and photosynthetic leaf traits across 10 representative tree species in Zhengzhou, China, we aimed to uncover the patterns and interconnections underlying these traits. The results showed significant differences in key leaf functional traits between large and small tree species. Specifically, large trees had greater leaf area, equivalent water thickness, and leaf phosphorus content than small species, suggesting an emphasis on resource conservation. In contrast, small trees exhibited higher specific leaf area, leaf nitrogen-to-phosphorus ratio, and photosynthetic rates than big species, reflecting a fast-growth strategy. For small trees, leaf dry matter content was positively related to photosynthetic parameters, further suggesting their rapid resource acquisition, while large trees favored traits supporting resource retention and stress tolerance. This study highlights the heterogeneity and adaptive mechanisms of leaf functional traits in different tree species, offering valuable insights into plant configuration and climate adaptation management strategies.