民勤沙区胡杨林健康序列及其影响因子分析

运用50个胡杨林样地调查资料对民勤沙区的胡杨林健康状况进行模糊判别分类，并以其中19个样地的土壤取样测定数据，分析胡杨健康指标及伴生植物健康指标与土壤水分、土壤pH值、土壤有机质、土壤全N、土壤速效P以及土壤粒度的关系。模糊判别分类结果表明，健康序列1的胡杨无枯枝枯梢且更新苗相对最多；健康序列2的胡杨植株最高且龄级数最全，更新苗次多；健康序列5的胡杨过熟株、成熟株、中龄株和幼龄株均有枯枝枯梢，且样地上无更新苗。胡杨林健康指标与土壤水分、土壤pH值、土壤养分及土壤粒度的相关分析结果表明，越是靠近农田水分条件好的地块胡杨林的健康状况相对越好；土壤pH值在8.0左右时胡杨林的健康状况相对较好，土壤pH值＞8.5胡杨林健康状况最差；胡杨林的健康状况与土壤有机质和全N及速效P含量正相关；健康状况较好的胡杨林地土壤中细砂、粉粒和粘粒含量较高。在民勤沙区，土壤干旱缺水是导致胡杨林退化的主要原因，土壤pH值在8.0左右的微碱性细沙地上的胡杨林相对较健康。对目前退化的胡杨林应适当补充人工灌溉，使土壤含水率保持在5% 以上。营造人工胡杨林要选择靠近农田边缘水分条件较好的地块。0～60 cm的土壤速效P和0～20 cm的土壤细砂含量较多的土壤胡杨更新苗相对较多，可作为选定胡杨造林地的依据之一。

Health Sequence and Influencing Factors of Populus euphratica Forest in Minqin Desert Area

The objectives of this study were to reveal the health status and influencing factors of Populus euphratica forest occurring in Minqin desert area,and to provide the basis for the restoration of degraded P.euphratica forest at present and for the construction of artificial P.euphratica forest in the future.The health status of P.euphratica forest in Minqin desert area was classified by fuzzy discriminant analysis based on the data of 50 sample plots.The relationship between the health indices of P.euphratica and its associated plants and soil moisture,soil pH,soil organic matter,soil total N,soil available P and soil particle size were analyzed based on the soil sampling data of 19 sample plots.The results of fuzzy discriminant classification showed that in healthy sequence 1,no dead branches were observed and the regenerated seedlings were the most.In healthy sequence 2,the number of the tallest trees was the highest,the number of age classes were the most complete age series,and the number of regenerated seedlings was less than that in sequence 1.In healthy sequence 5,dead branches and tops were found in over mature,mature,middle-aged and young forests of P.euphratica,no regenerated seedlings were found in the sample plots.Correlation analysis between the health index of P.euphratica forest and soil moisture,soil pH,soil nutrient and soil particle size showed that the health status of P.euphratica forest that was close to the farmland with better soil moisture conditions was better,and the health status of P.euphratica forest was relatively good when the pH value of soil was about 8.0.The health status was the worst when the soil pH value was higher than 8.5.The health status was positively correlated with soil organic matter and total N and available P content.The contents of fine sand,silt and clay in soil of P.euphratica forest land with good health condition were higher.In Minqin desert area,soil drought and water shortage were the main reasons for the degradation of P.euphratica forest.The P.euphratica forest on the slightly alkaline fine sand land with pH value of 8.0 was relatively healthy.Artificial irrigation should be supplemented to the existing degraded P.euphratica forest to keep the soil moisture content above 5%.The plantation of P.euphratica should be planted near the edge of farmland with better water conditions.The results showed that there were more regenerated seedlings of P.euphratica in 0-60 cm soil layer with more available P and 0-20 cm soil layer with high fine sand content,which could be used as one of the basis for selecting P.euphratica afforestation sites.