基于主成分分析的大渡河中游干暖河谷草地土壤质量评价

草地在大渡河干暖河谷植被恢复及植物群落演替中具有重要作用,而植被恢复的关键在于土壤质量。将大渡河干暖河谷泸定至汉源段,依据坡向划分为8个方位（北、东北、东、东南、南、西南、西、西北）,分析了不同坡向和植被盖度草地的土壤理化性质,采用主成分分析法（Principal component analysis,PCA）对河谷区草地土壤质量进行了评价。结果表明：（1）影响河谷草地土壤质量的最小数据集（Minimum data set,MDS）指标包括非毛管孔隙度、土壤容重、有机质和碳氮比;（2）河谷从东北坡过渡到西南坡土壤质量逐渐降低,与南坡热而干旱的微气候使土壤矿化作用剧烈,而北坡适宜的光热和水热条件更有利于土壤中钾和磷的释放有关;（3）植被盖度与土壤质量呈正相关关系,随着草地植被盖度减少土壤质量逐渐降低。高植被盖度（>70%）土壤质量主要受非毛管空隙度影响,而低高盖度草地（<30%）主要受土壤容重影响;（4）河谷区草地土壤质量指数中间值分布较多,土壤肥力属于2-4级中等水平。大渡河干暖河谷区草地土壤质量较好,潜在肥力水平较高,有利于植物生长和植物群落正向演替,是植被人工恢复的重点区域。

Soil quality assessment of grassland in dry and warm valley of Dadu River based on principal component analysis

Grassland in the dry and warm valley of Dadu River plays an important role in vegetation coverage restoration and natural succession of plant communities, while soil quality plays a key part in vegetation restoration. In this study, we divided the slop direction into 8 types (North, Northeast, East, Southeast, South, Southwest, and Northwest) in the Luding-Hanyuan section of the dry warm valley of the Dadu River. The soil physical properties as well as the soil chemical properties of the grassland with different slope directions was analyzed, and the grass coverages with different slope directions of grassland was also investigated, furthermore, the soil quality of dry and warm valley of Dadu River was assessed by principal component analysis. The results show that the minimum data set affecting soil quality of dry and warm valley grassland are non-capillary porosity, soil bulk density, organic content and C/N ratio. In the dry warm valley of Dadu River, the soil quality gradually decreases from the northeast slope to the southwest slope due to the hot and dry microclimate, which leads to more intense soil mineralization. The stable sunshine time and appropriate water conditions on the north slope are advantageous to potassium and phosphorus release in the soil. There was a positive correlation between vegetation coverage and soil quality and soil quality decreased with the decreasing of vegetation coverage. The soil quality of high vegetation coverage (> 70%) is mainly affected by noncapillary porosity, while that of low and high coverage grassland (< 30%) is mainly affected by soil bulk density. The middle value of grassland soil quality index is more distributed in the dry and warm valley of Dadu River, and the soil fertility is in the middle level of 2-4. The soil quality of the grassland is better as a whole in the dry and warm valley of Dadu River, and potential in fertility of grassland is high, which is conducive to plant growth and positive succession of plant community.