Leaf characters of Ulmus elongata in fragmented habitats: Implications for conservation

Ulmus elongata is on the verge of extinction due to habitat fragmentation and habitat loss. Identifying the environmental factors affecting the leaf traits of U. elongata is important for understanding its endangerment mechanisms. Specific leaf area (SLA), leaf nitrogen content, and leaf carbon isotope discrimination (δ13C) were determined. Temperature and light were found to be the main environmental factors influencing SLA, indicating that U. elongata is heliophilous. The maximum and minimum δ13C values of the plant species were − 26.33‰ and − 29.64‰, respectively (the mean was − 28.09‰), suggesting that it is of the C3 photosynthetic type. Compared with the altitude, annual sunshine duration, annual precipitation, and mean annual temperature accounted for 36% of the variance in δ13C, which is the main environmental factor affecting 13C fractionation. The foliar δ13C value of U. elongata was significantly more negative than that of Ulmus pumila, a widely distributed elm tree in northern China (P