Abstract
Topography strongly influences the compositional structure of tree communities and plays a fundamental role in classifying habitats. Here, data of topography and 16 dominant tree species abundance were collected in a fully mapped 25-ha forest plot in the Qinling Mountains of north-central China. Multivariate regression trees (MRT) were used to categorize the habitats, and habitat associations were examined using the torus-translation test. The relative contributions of topographic and spatial variables to the total community structure were also examined by variation partitioning. The results showed the inconsistency in association of species with habitats across life stages with a few exceptions. Topographic variables [a + b] explained 11% and 19% of total variance at adult and juvenile stage, respectively. In contrast, spatial factors alone [c] explained more variation than topographic factors, revealing strong seed dispersal limitation in species composition in the 25-ha forest plot. Thus, the inconsistent associations of species and habitats coupled with high portion of variation of species composition explained by topographic and spatial factors might suggest that niche process and dispersal limitation had potential influences on species assemblage in the deciduous broad-leaved forest in north-central China.
Highlights
One of the worldwide hotspots in ecological research is to understand the mechanisms that influence the spatial structure in community assembly
The results of multivariate regression trees (MRT) indicated that habitats in the plot were mainly determined by could be divided into five habitats: (1) high-slope; (2) low-slope; (3) ridge; (4) low-valley; (5) high-valley three topographical variables
The results of MRT indicated that habitats in the plot were mainly determined by three slope for habitats, the second split was determined by elevation
Summary
One of the worldwide hotspots in ecological research is to understand the mechanisms that influence the spatial structure in community assembly. The niche differentiation is an important theory for the maintenance of species diversity in complex forest communities [1,2]. Biotic process stated that multi-species remained in coexistence through interspecies competition for acquiring similar resource, while abiotic rule considered that habitat filtering [3] was a critical process in shaping ecological communities. Forests 2019, 10, 53 ecological drift might play an important role in shaping distribution structure of tree communities and lead to aggregated seedling and adult populations [4]. The relationships between tree species and habitats in forests are essential for understanding the process of species distribution [5]. In order to define the notably different habitat features with similar species composition, De’Ath [8] proposed the multivariate regression trees (MRT) to categorize the area into different habitats
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