Influence of environmental factors and sheep grazing on an Andean grassland
Influence of environmental factors and sheep grazing on an Andean grassland
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DOI：
10.2307/4003774
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发表时间：
1999-09-01
期刊：
影响因子：
--
通讯作者：
Morales, JM
中科院分区：
文献类型：
--
作者：
Adler, PB;Morales, JM
安第斯山脉中部的长期过度放牧改变了植被，可能造成侵蚀和生产力损失，但缺乏定量研究。在阿根廷西北部的一个偏远地区，我们测量了环境因素和放牧对当地植物物种组成、多样性和土壤有机质的相对影响。通过冗余分析，我们发现环境变量解释了站点间物种组成变化的22%，而与放牧相关的变量解释了24%的变化。完整的模型，包括所有重要的变量，解释了33%的变化。坡向、放牧季节（湿、干）、植被覆盖总量和土壤类型构成了前3个排序轴的基础。与相对受保护的地点相比，在重度放牧的地点，难吃或有毒的物种和生长极低的物种明显更丰富。湿季牧草载畜率与总覆盖度、牧草量、土壤有机质和物种丰富度呈负相关。放牧季节对草地总覆盖度、牧草量、物种多样性和土壤有机质的影响更为显著，且湿季牧草显著低于旱季牧草。放牧季节与坡向交互作用较强：北侧湿季草场比南侧湿季草场更容易发生退化和物种组成的变化。研究结果表明，夏季雨季保护草场可能是传统管理措施的重要补充，以降低放畜率。
Chronic overgrazing in the central Andes alters vegetation and may cause erosion and loss of productivity, but quantitative studies are lacking. We measured the relative influence of environmental factors and sheep grazing on local plant species composition, diversity, and soil organic matter in a remote site in northwestern Argentina. Using redundancy analysis, we found that environmental variables explained 22% of variation in species composition between sites, while grazing-related variables explained 24% of variation. The complete model, incorporating all significant variables, explained 33% of variation. Aspect, season of grazing (wet vs, dry) combined with total vegetative cover, and soil type formed the basis for the first 3 ordination axes. Unpalatable or toxic species and very low-growing species were significantly more abundant on heavily grazed sites compared to relatively protected sites. Stocking rate in wet season pastures was negatively correlated with total cover, forage volume, soil organic matter, and species richness. Season of grazing had a more dramatic effect on total cover, forage volume, species diversity and soil organic matter, which were all significantly lower in wet season pastures compared to dry season pastures. Season of grazing and aspect interacted strongly: wet season pastures on north aspects appear more susceptible to degradation and changes in species composition than south-facing sites, Our results suggest that protecting pastures during the summer rainy season may be an important complement to traditional management efforts to reduce stocking rates.