基于最小数据集的大渡河干暖河谷典型植被土壤质量评价

Soil quality assessment of typical vegetation in dry and warm valley of Dadu River based on minimum data set

土壤质量是植被恢复重建的关键。大渡河干暖河谷区植被退化严重,开展土壤质量评价对于制定适合该区域的植被恢复重建措施尤为重要。本文采用最小数据集法,评价大渡河干暖河谷区灌丛、草本、针叶林、阔叶林和针阔混交林5种典型植被的土壤质量。基于16个土壤理化指标的主成分分析,构建由土壤毛管孔隙度、非毛管孔隙度、有机质、全氮、全磷、有效磷和速效钾7个指标组成的最小数据集(MDS);根据主成分因子载荷计算MDS指标权重,以毛管孔隙度(18.53%)、全磷(17.36%)、有机质(15.88%)3个指标权重为较大。基于MDS的土壤质量指数依次为:灌丛(0.558)>草地(0.482)>阔叶林(0.392)>针阔混交林(0.387)>针叶林(0.357),土壤肥力评分法进一步验证该评价结果。土壤质量指数分级表明,灌丛和草地以土壤质量等级较高的Ⅲ、Ⅳ级样地为主,而其余3个植被类型以等级较低的Ⅰ、Ⅱ级样地为主。大渡河干暖河谷灌丛具有较好的土壤改良效果,是今后大渡河干暖河谷区植被恢复重建的主要方向;草地土壤质量亦较好,具有较大的植被恢复潜力。

[Background]Soil quality is defined as the capacity of soil performing its functions within ecosystem boundaries,including sustaining biological productivity,maintaining environmental quality,and promoting plants and animals'growths.Existing studies suggested that serious land degradation resulted in the reduction of vegetation and productivity in the dry and warm valley of Dadu River,thus it is urgent to restore the soil quality.This study evaluated the soil quality in the dry and warm valley of Dadu River,and the results may provide scientific support for establishing restoration measures in this region.[Methods]Nevertheless,soil quality cannot be evaluated by individual soil properties,because many of these properties are interdependent and their responses to environmental changes are difficult to interpret.Thus,to comprehensively assess soil quality,a soil quality index(SQI)that integrated soil properties into an overall index was established and has been widely used.The minimum data set(MDS)method was chosen to calculate the soil quality indexes of 5 typical vegetation types including shrub,grassland,coniferous forest,broadleaf forest,and mixed broadleaf-conifer forest along the dry and warm valley of the Dadu River.The soil quality indexes were graded from low to high:ⅰ,ⅱ,ⅲandⅳ.[Results]1)Based on correlation analysis and principal component analysis,7 of 16 soil physical and chemical indicators had been confirmed to be the MDS,including capillary porosity,non-capillary porosity,organic matter,total nitrogen,total phosphorus,available phosphorus and available potassium.According to the load of each index factor,the weight of each index was calculated and then the soil quality index was obtained by summing.The top three weighted indicators were capillary porosity(18.53%),total phosphorus(17.36%)and organic matter(15.88%).The soil quality indexes of those 5 vegetation types ranked in the order of shrub(0.558),grassland(0.482),broad-leaved forest(0.392),mixed broadleaf-conifer forest(0.387),and coniferous forest(0.357).Meanwhile,the soil qualities of the 5 typical vegetation types were also assessed by“soil fertility scoring method“referred to the results of the Second National Soil Survey.As expected,the results were coincided with“the minimum data set method”.The classification of soil quality indexes showed that shrub and grassland were dominated by gradeⅲandⅳplots,while the other three vegetation types were dominated by gradeⅰandⅱplots.[Conculsions]In short,this study demonstrates that the effect of shrub on soil quality improvement is better than other vegetation types and should be the direction of vegetation restoration in the dry and warm valley of the Dadu River,and grassland has great potential for vegetation restoration due to its quite good soil quality.