Geostatistical analysis of spatial variations in leaf traits of woody plants in Tiantong, Zhejiang Province

Aims: Exploring spatial variations in leaf traits and their relationships with environmental properties is crucial for understanding plant adaptation strategies and community assembly. This study aimed to reveal how leaf traits varied spatially and the role of environmental factors. Methods: The study was conducted in a 5-hm forest plot in Tiantong, Zhejiang Province. Three leaf traits, including individual leaf area (ILA), specific leaf area (SLA), and leaf dry matter content (LDMC) were measured for 20 253 individual trees with diameter at breast height (DBH) ≥1 cm. Soil properties measured included contents of soil total nitrogen, soil total phosphorus, soil total carbon, soil pH value, soil volumetric water content, bulk density, and humus depth. Topographic variables measured included elevation, slope and convexity. We used geostatistical analysis to reveal spatial variations of the three leaf traits. Relationships between leaf variability and environmental factors were analyzed using principal component analysis (PCA) and Pearson's correlation. Important findings: Spatial variability followed the order of ILA > SLA > IDMC. Spatial autocorrelation of three leaf traits was weak within a distance of 5.16 m. The optimal model of the semi-variogram function was Gaussian model for IIA, and exponential model for SIA and IDMC. IIA showed the largest variability at the direction of northeast-southwest, and smallest variability at the direction of northwest-southeast. In contrast, SIA and IDMC had the highest variability at the direction of northwest-southeast and least variability at the direction of northeast-southwest. There were significantly negative relationships between IIA and topographic factors (r = -0.12, p < 0.000 1), and between SIA and soil nutrients (r = -0.16, p < 0.000 1). In contrast, IDMC was positively correlated with soil nutrients (r = 0.13, p < 0.000 1). Relative to soil nutrients, topographic factors affected much more variations in IIA, SIA and IDMC at the direction of northeast-southwest. Distinctly, at the direction of northwest-southeast, variability of IIA was affected mainly by topographic factors, while soil nutrients resulted in the most variability of SIA and IDMC. In conclusion, leaf traits varied considerably with spatial direction in the studied forest plot. Associations between leaf traits and topographic factors and soil nutrients indirectly indicated effects of environmental filtering on community assembly.