基于资源类型和数目的高寒草甸物种丧失机制研究

doi:10.11686/cyxb2024231

摘要/Abstract

摘要：

关于资源添加导致草地物种多样性丧失的模式能够被诸多竞争假说（光竞争假说、生态位维度-多样性假说、氮损害假说、凋落物假说）予以解释。然而，针对不同资源添加类型和数目驱动的物种多样性丧失机制是单独的还是协同的却鲜有研究。为了回答这一问题，以青藏高原甘南高寒草甸为对象，构建不同类型（氮、磷、钾）和数目（0/1/2/3）的资源添加处理，对物种多样性丧失的4种机制进行综合探讨。结果表明：1）相较于对照，氮素添加显著增加了植物地上净初级生产力，减小了物种丰富度，而磷或钾添加则无显著变化；2）氮素添加和资源添加数目都对物种丰富度减小产生直接负效应，这与生态位维度-多样性假说和氮损害假说所蕴含的地下土壤竞争机制有关；3）在氮素添加和资源添加数目处理下，植物地上净初级生产力的增加所引起光照可利用性减小都间接导致物种丰富度的减小，这与地上光竞争假说预测相符。综上，无论在资源类型（氮元素）还是资源添加数目处理下，生态位维度-多样性假说、氮损害假说和光竞争假说所体现的地上和地下多种竞争机制具有驱动草地物种多样性丧失的可能性，研究结果将为高寒草甸物种多样性的维持和保护提供具有可供参考的生态学理论依据。

关键词: 光竞争, 生态位维度, 氮损害, 物种丰富度, 高寒草甸

Abstract:

The patterns of species diversity loss upon resource addition in grassland communities can be explained by several competitive hypotheses， including the light competition hypothesis， the niche dimensionality-diversity hypothesis， the nitrogen detriment hypothesis， and the litter hypothesis. Nevertheless， few studies have explored whether the mechanism of species diversity loss can be attributed to the type and number of added resources. To address this question， we conducted a field experiment with different numbers （0， 1， 2， and 3） and types （nitrogen， phosphorus， and potassium） of added resources， with the aim of exploring the four mechanisms of species diversity loss in an alpine meadow of Gannan on the Qinghai-Tibet Plateau. The results yielded the following findings： 1） Compared with the control， nitrogen addition resulted in a notable increase in aboveground net primary productivity， and a reduction in species richness. However， neither phosphorus addition nor potassium addition significantly affected these variables. 2） Both nitrogen addition and the number of added resources had a direct negative impact on species richness. This was related to belowground soil competition that underlies the niche dimension-diversity hypothesis and the nitrogen detriment hypothesis. 3） As plant aboveground net primary productivity increased， light limitation became more intense， and this indirectly led to the loss of species richness， consistent with the aboveground light competition hypothesis. In conclusion， our results indicate that， with the addition of nitrogen or a number of added resources， aboveground and belowground ecological mechanisms act synergistically to drive losses in grassland species diversity， consistent with the multiple competition hypothesis. The findings of this study can serve as a basis for the formulation of an ecological theory that will contribute to the long-term maintenance and conservation of grassland species diversity in alpine ecosystems.

Key words: light competition, niche dimension, nitrogen detriment, species richness, alpine meadow

王瑞兵, 陈欢, 潘珍珍, 赵维, 蚌绍豪, 周小龙, 任正炜. 基于资源类型和数目的高寒草甸物种丧失机制研究[J]. 草业学报, 2025, 34(5): 1-11.

Rui-bing WANG, Huan CHEN, Zhen-zhen PAN, Wei ZHAO, Shao-hao BANG, Xiao-long ZHOU, Zheng-wei REN. Mechanisms of species diversity loss in an alpine meadow community after adding different types and numbers of resources[J]. Acta Prataculturae Sinica, 2025, 34(5): 1-11.

图/表 5

图1 氮、磷和钾添加对群落特征、群落透光率及土壤pH的影响CK：对照；N：氮添加；P：磷添加；K：钾添加。不同小写字母表示不同处理间差异显著（P<0.05），下同。CK： Control； N： Nitrogen addition； P： Phosphorus addition； K： Potassium addition. Different lowercase letters indicate significant differences （P<0.05） among different treatments， the same below.

Fig.1 Effects of N， P and K addition on community characteristics， community light transmittance and soil pH

图2 氮添加与否对群落特征、群落透光率及土壤pH的影响Ns：涉及氮添加的处理；non-Ns：非氮添加的处理。Ns： Nitrogen addition treatments； non-Ns： Non-nitrogen addition treatments. 下同The same below.

Fig.2 Effects of nitrogen addition or non-nitrogen addition on community characteristics， community light transmittance and soil pH

图3 资源添加数目与群落特征、群落透光率和土壤pH的拟合关系阴影部分为95%的置信区间。The shaded area is a 95% confidence interval.

Fig.3 Fitting relationship between the number of added resources and community characteristics， community light transmittance and soil pH

图4 群落特征与群落透光率、土壤pH之间的拟合关系不同的颜色代表不同的资源添加类型：0代表对照，1~3分别代表不同的资源添加数目。Different colors represent different types of resource addition： 0 represents the control， 1-3 represent different number of added resources.

Fig.4 The fitting relationship between community characteristics， community light transmittance and soil pH

图5 基于资源添加数目和氮添加解释物种丰富度减小的结构方程模型分析方框内的变量为模拟变量，R2表示混合模型中固定效应所解释的方差。带箭头的线条表示模型拟合路径，其中粗线代表显著的关系；细线代表不显著的关系。实线表示正效应；虚线表示负效应。各路径旁的数字表示标准路径系数（λ），*：P<0.05，**：P<0.01，***：P<0.001。Variables in the rectangles are model variables， and R2 represents the variance explained by the fixed effect in the mixed model. The lines with arrows represent the model fitting path， where the thick lines represent significant relationships； The thin line represents an insignificant relationship. The solid line indicates a positive effect； the dotted line represents the negative effect. The numbers next to each path represent the standard path coefficients （λ）， *： P<0.05， **： P<0.01， ***： P<0.001. CFI：比较拟合指数Comparative?fit?index； SRMR：标准化残差均方根Standardized root mean square residual； RMSEA：近似均方根误差Root-mean-square?error?of?approximation.

Fig.5 Structural equation model analysis based on the number of resource addition and nitrogen addition to explain the decrease of species richness

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