Topographic variation as an indicator of plant functional trait distributions across different biomes

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Qian Wang and Ji-Zhong Wan, State Key Laboratory of Plateau Ecology and Agriculture, Qinghai University, Xining, China

Background/Question/Methods
Functional plant traits can affect ecosystem functionality and services while terrain factors are considered to be the main factors affecting the ecosystem. Although there have been many studies on the driving factors of plant functional trait distributions, studies on the relationships between terrain factors and the distributions of plant functional traits are limited. To further study the relationships between the terrain factors and the distributions of plant functional traits, we proposed three hypotheses: 1) terrain factors affect the distributions of plant functional traits; 2) the relationship between terrain factors and plant functional trait distributions is affected by the biome; 3) the relationship between terrain factors and plant functional trait distributions is also influenced by scale effects. To assess these conjectures, 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) of 14 different global biomes at spatial scales of 5 km and 50 km.
Results/Conclusions
We found that terrain factors had an impact on the distributions of plant functional traits; specifically, there was a significant negative correlation between terrain factors and wood density. Terrain factors also had a certain impact on specific leaf area but had no significant impact on plant height. Among the influential terrain factors, roughness was the most significant, followed by vector ruggedness measure and terrain ruggedness index. Additionally, the effect of biomes on the relationship between terrain factors and plant functional trait distributions was widespread. The results also showed that under the same biome conditions, biomes are more stable and balanced on a large scale than that on a small scale. Considering the influence of different biomes and scale effects is important to understand heterogeneity and biodiversity, especially in macroecological studies that have important scientific and practical significance.