桂林岩溶石山常绿落叶阔叶混交林乔木层优势物种生态位研究

Abstract

采用样方法对不同资源位群落进行调查，通过冗余分析（RDA）结合Monte Carlo随机置换检验筛选出对桂林岩溶石山常绿落叶阔叶混交林乔木层优势物种分布影响显著的土壤资源轴（土壤有机质、土壤水溶钙、土壤速效氮、土壤全氮、土壤pH值和土壤厚度）。利用Levins生态位宽度指数和Pianka生态位重叠指数对桂林岩溶石山常绿落叶阔叶混交林乔木层14个优势物种在土壤有机质、土壤水溶钙、土壤速效氮、土壤全氮、土壤pH值和土壤厚度6个土壤资源轴上的生态位特征进行研究。结果表明：（1）在土壤有机质和土壤水溶钙资源轴上，生态位宽度最大值为常绿物种檵木（0.89、0.94）；在土壤pH值资源轴上，生态位宽度最大值为常绿物种粗糠柴（0.96）；在土壤速效氮、土壤全氮和土壤厚度资源轴上，生态位宽度最大值为落叶物种南酸枣（0.87、0.99、0.97）。（2）14个优势物种在6个土壤资源轴上，生态位重叠均值由大到小依次为土壤厚度 > 土壤全氮 > 土壤水溶钙 > 土壤速效氮 > 土壤pH值 > 土壤有机质，且均表现为常绿物种与常绿物种形成的种对生态位重叠均值（0.84） > 常绿物种与落叶物种（0.74） > 落叶物种与落叶物种（0.66）。（3）综合6个土壤资源轴，生态位重叠值≥0.5的种对高达480对，占总种对数的87.91%，暗示桂林岩溶石山常绿落叶阔叶混交林乔木层优势物种在资源匮乏且资源异质性高的特殊生境中存在激烈竞争，且乔木层种间关系相对不稳定。;The sample method was employed to investigate the communities with different resource positions. The soil resource axes (soil organic matter, soil water-soluble calcium, soil available nitrogen, soil total nitrogen, soil pH value, and soil depth) which have significant influence on the distribution of dominant species in arbor layer of evergreen deciduous broad-leaved mixed forest in karst hills of Guilin were selected by Redundancy analysis (RDA) with Monte Carlo random replacement test. Niche characteristics of 14 dominant species which in the arbor layer of evergreen deciduous broad-leaved mixed forest in karst hills of Guilin along soil organic matter, soil water-soluble calcium, soil available nitrogen, soil total nitrogen, soil pH value and soil depth were analyzed by Levins niche breadth index and Pianka niche overlap index. The results showed that:(1) on the soil organic matter and soil water-soluble calcium resource axis, the maximum niche width was evergreen species, which were Loropetalum chinense (0.89, 0.94); on the soil pH value resource axis, the maximum niche width was the evergreen species Mallotus philippensis (0.96); on the soil available nitrogen, soil total nitrogen and soil depth resource axis, the maximum niche width was deciduous species, which were Choerospondias axillaris (0.87, 0.99, 0.97). (2) The 14 dominant species composed 91 species pairs on 6 soil resource axes, and their niche overlap averages in descending order were as follows:soil depth > soil total nitrogen > soil water-soluble calcium > soil available nitrogen > soil pH value > soil organic matter. And the six soil resource axes were all showed as the mean niche overlap of species pair between evergreen dominant species and evergreen dominant species (0.84) > evergreen dominant species and deciduous dominant species (0.74) > deciduous dominant species and deciduous dominant species (0.66). This showed that the 14 dominant species have the most intense competition on the soil depth resource axis, followed by soil total nitrogen resource axis, and soil organic matter resource was axis relatively small. Furthermore, the competition between evergreen species was the most intense, followed by competition between evergreen and deciduous species, and between deciduous species competition was relatively small. (3) Based on the six soil resource axes, there were 480 species pairs with niche overlap value ≥ 0.5, accounting for 87.91% of the number of total species pairs. It implies that the dominant species in the arbor layer of the evergreen and deciduous broad-leaved mixed forest in the karst hills in Guilin have fierce competition in the special habitats with scarce resources and high resource heterogeneity, and the interspecific relationship of arbor layer is relatively unstable.