Relationships between topographic variation and plant functional trait distribution across different biomes

Abstract

• Terrain factors and plant functional-trait distribution were studied in 14 biomes. • Geographically weighted regression and ordinary least squares were the methods used. • Terrain factors affected the distribution of plant functional traits. • Topography effects on plant functional-trait distribution showed biome dependency. • Topography effects on plant functional trait distributions was scale dependent. Plant functional traits can affect ecosystem functions and services. Although many studies have investigated the driving factors of plant functional-trait distribution, few have explored the relationship between terrain factors and such distribution. Here, we proposed three hypotheses to explain the above-mentioned relationship: 1) terrain factors affect the distribution pattern of plant functional traits; 2) the relationship between terrain factors and plant functional-trait distribution is biome-dependent; 3) the relationship between terrain factors and plant functional-trait distribution is scale-dependent. To test these hypotheses, we used geographically weighted regression and ordinary least squares to study the relationship between functional traits (specific leaf area, height, and wood density) and terrain factors (roughness, terrain ruggedness index, terrain position index, and vector ruggedness measure) in 14 different biomes at scales of 5 and 50 km 2 . We found that terrain factors affected the distribution of plant functional traits. Specifically, there was a significant negative correlation between terrain factors and wood density; further, terrain factors had effects on specific leaf areas but not on plant height; furthermore, roughness was the most significant among the influential terrain factors, followed by the vector ruggedness measure and the terrain ruggedness index. Additionally, the effect of biome type on the relationship between terrain factors and plant functional-trait distribution was widespread. Finally, spatial scale effects on biodiversity may depend on the transition between different biomes. Therefore, considering biome and scale effects is essential to understanding heterogeneity and biodiversity, especially in macroecological studies with important scientific and practical significance.