基于地形因素的高寒草甸土壤温湿度和物种多样性与初级生产力关系研究

山地是高寒草甸的主要分布区,地形变化引起了土壤温湿度和物种的差异性分布,进而影响到草地生态系统生产功能。为明晰高寒草甸山地环境因子(土壤温湿度)和物种多样性(丰富度、多度、均匀度、优势度)与初级生产力的关系,本研究以青藏高原东北缘马牙雪山支脉的高寒草甸山体为研究对象,选择阶地、阴坡、山脊和阳坡与3个海拔梯度段,调查了189个样方的植物群落组成和土壤温湿度。采用线性回归法分析土壤温湿度和物种多样性与初级生产力之间的关系。结果表明:(1)以山地高寒草甸整体为研究单元,初级生产力只随物种多度的增加而显著增加(R~2=0.07 P=0.01)。(2)坡向影响初级生产力的因素不同,阴坡初级生产力与物种丰富度正线性相关;山脊初级生产力与土壤湿度正线性相关,也随物种丰富度增加而显著增加;阳坡初级生产力与物种多度正线性相关;阶地初级生产力随均匀度增加而显著增加,随优势度增加而显著降低。(3)只有低海拔区(2860-2910 m)初级生产力随物种多度和丰富度的增加而显著增加。综上所述,山地高寒草甸土壤温湿度和物种多样性与初级生产力关系受坡向比海拔的影响更大,且物种多样性对初级生产力的影响大于土壤温湿度。建议山地高寒草甸生态系统生产和生态管理过程中要重点考虑坡向对植物多样性和初级生产力的影响。

Relationships between soil moisture and temperature, plant species diversity, and primary productivity in an alpine meadow considering topographic factors

Alpine meadows are mostly distributed in mountains. Changes in the mountain landform cause changes in distribution of soil moisture and temperature as well as plant species, which influence primary production of the ecosystem. To reveal the relationship between non-ecological factors (soil moisture and soil temperature), species diversity (richness, abundance, evenness, and dominance), and primary productivity in an alpine meadow ecosystem, we investigated plant community structure and soil moisture and temperature in 189 sampling sites on lowland (bottom land), shadow aspect, ridge, and sunny aspect along three elevation gradients on a hill in the Qilian Mountains in Tianzhu County in northeastern Tibetan Plateau. Linear regression was used to analyze the relationships between soil moisture, soil temperature, species diversity, and primary productivity. When the hill was treated as a single unit, primary productivity only increased significantly with increasing species abundance (R²=0.07 P=0.01). There were different effects of species diversity on primary productivity based on the hill aspect:On the shadow aspect, primary productivity had a positive linear correlation with species richness; On the ridge, primary productivity had a positive linear correlation with soil moisture that significantly increased with species richness; On the sunny aspect, primary productivity had a positive linear correlation with species abundance; and on bottom land, primary productivity had a positive linear correlation with species evenness. Primary productivity only increased significantly with increasing species abundance and richness in the low-elevation plots. In conclusion, the slope aspect had a greater effect on the relationships between soil moisture, soil temperature, species diversity, and primary productivity than did elevation in the alpine meadow and that the effect of species diversity on primary productivity was greater than that of soil moisture and temperature. We suggest that the hill aspect should be the primary consideration, instead of elevation, in grassland production and ecological management assessments in alpine meadow ecosystems.