Abstract
Slope aspect plays a critical role in influencing vegetation pattern in semiarid area. The dry valleys of the Hengduan Mountains Region, southwestern China, are striking geographical landscape, suffering from severe ecological degradation. Here, we comprehensively investigated how slope aspect affects vegetation attributes in one of these valleys- the dry valley in the upper reaches of Min River. Three sites were selected along the valley and we quantitively examined the vegetation difference between slope aspects at the whole valley scale and each site level. We found significant vegetation differences between slope aspects in species composition, vegetative structure, and biodiversity pattern, which were in accordance with the observed significant difference in soil nutrient. Generally, north-facing slopes are associated with higher biomass, coverage and height, and species diversity than south-facing slopes. We also found between-aspect differences varied among the study sites, resulting in increased biomass, height, and β diversity differences, decreased density and coverage differences, and opposite trend observed in α diversity at relatively wet site. In conclusion, slope aspect had significant effect on vegetation attributes, which was significantly influenced by local climate (aridity) in terms of both strength and direction depending on the specific attributes investigated.
Highlights
Topographic elements, such as elevation, aspect, and position, significantly influence vegetation distribution and attributes through the modification of local e nvironment[1,2,3,4]
No significant difference in soil moisture (SM) between slope aspects was found at the whole valley (SM.north = 10.28 ± 0.88%, SM.south = 8.73 ± 0.78%, p = 0.124) and at study sites except for Feihong where the SM was significantly higher on north-facing slope (p = 0.006) (Table 1)
Our study demonstrated significant differences in species composition, vegetative structure, and biodiversity pattern between north- and south-facing slopes in the mountainous dry valley of the Min River
Summary
Topographic elements, such as elevation, aspect, and position, significantly influence vegetation distribution and attributes through the modification of local e nvironment[1,2,3,4]. Previous studies have examined the vegetation classification and ordination in environmental space[32], spatial distribution of soil moisture[33], differential response to soil variables between shrub and herb species[34], and vegetation-soil-topography a ssociation[35] Most of these studies focused on vegetation response to spatial variation in soil properties (nutrient and water); studies that precisely examine the topographic effect on vegetation attributes in this mountainous dry valley are lacking. The objectives of this study were to: (1) examine and compare the soil properties between north- and south-facing slopes, (2) examine and compare species composition, vegetation structure, and biodiversity pattern between the opposite slopes, and (3) figure out the potential factors influencing the between-aspect vegetation difference (strength and direction). We hope that the present study findings would assist in better understanding of vegetation distribution, and provide important implication for biodiversity management and ecosystem restoration for contemporary and future climatic conditions, and to inspire future studies on other dry valleys in Hengduan Mountains region
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