藏东南高山松林表层土壤养分含量及其化学计量比特征

Characteristics of topsoil nutrients and their stoichiometry in Pinus densata forest in Southeast Tibet

[目的]探究藏东南高山松林表层土壤养分的分布特征,为高山松林的可持续发展提供理论参考,为西藏生态安全屏障的建立提供指导。[方法]以藏东南林芝市4个地区(巴宜区、波密县、察隅县、米林县)高山松林为研究对象,于2019年9月采集、测定0~10 cm土层土壤的有机质(SOM)、全氮(TN)、全磷(TP)、全钾(TK)、碱解氮(AN)、速效磷(AP)、速效钾(AK)含量,并计算土壤化学计量比(C∶N、C∶P、N∶P),分析不同地区土壤养分含量、化学计量比的差异及土壤养分含量之间及其与土壤化学计量比之间的相关性,并分析土壤养分及其化学计量比与海拔、经度、纬度间的相关性。[结果](1)高山松林表层土壤养分含量均较低,尤以土壤TP、AP含量最低,在全国第二次土壤普查养分分级标准中均处于"极缺"水平。除了土壤AP、AK属于强变异外,其他养分含量均属于中等变异。(2)不同地区土壤养分含量有差异,总体上察隅县、巴宜区较高,米林县、波密县较低。(3)高山松林表层土壤C∶N由大到小表现为米林县>巴宜区>察隅县>波密县。土壤C∶P、N∶P由大到小均表现为察隅县>波密县>巴宜区>米林县。(4)除了土壤TK与其他土壤养分(AP除外)间呈负相关外,其他土壤养分间均呈正相关关系。除了土壤C∶N与土壤TN、TK呈显著负相关以及土壤C∶P、N∶P与土壤TP呈极显著负相关外,土壤C∶N、C∶P、N∶P与其他土壤养分含量之间的相关性均不显著。(5)海拔与土壤AK呈显著正相关,与土壤其他养分含量及化学计量比之间的相关性不显著。经度、纬度与土壤养分含量和化学计量比之间的相关性均不显著。[结论]藏东南高山松林表层土壤养分瘠薄,尤以TP、AP含量较低,且土壤养分含量具有较大的空间变异性;受土壤氮、磷养分含量的影响,表层土壤C∶N、C∶P、N∶P均高于全国森林土壤。

[Objective] The characteristics of soil nutrients in Pinus densata forests in Southeast Tibet were clarified to provide basis for sustainable development of P. densata forests and establishment of ecological security barrier.[Method] P. densata forests in 4 regions(Bayi district, Bomi county, Chayu county and Milin county) in Nyingchi, Southeast Tibet were selected and contents of SOM,TN,TP,TK,AN,AP and AK in the soil layer of 0-10 cm were collected and measured in September 2019.Soil stoichiometric ratios(C∶N,C∶P and N∶P) were then calculated.The differences in soil nutrient contents and stoichiometric ratios in different regions and the correlation between soil nutrient contents and soil stoichiometric ratios were analyzed.The correlations between soil nutrients and stoichiometric ratios with altitude, longitude and latitude were also determined.[Result](1) The nutrient contents of topsoil of P. densata forest were low.Contents of TP and AP were the lowest and were in the "extremely short" level based on the nutrient classification standard of the second soil national soil census.Except for AP and AK,other nutrients were moderately variated.(2) Soil nutrient contents varied in different regions.Chayu county and Bayi district had higher values than Milin county and Bomi county.(3) Topsoil C∶N of P. densata forests was in the order of Milin county>Bayi district>Chayu county>Bomi county, while C∶P and N∶P were in the order of Chayu county>Bomi county>Bayi district>Milin county.(4) Except TK,other soil nutrients showed positive correlations. There were significant negative correlations between C∶N with TN and TK,there were very significant negative correlations between C∶P,N∶P,TP and C∶N,but the correlations of C∶P,N∶P and other soil nutrients were not significant.(5) Altitude had significantly positive correlation with AK,while its correlations with other nutrients and stoichiometric ratios were insignificant.All correlations between longitude and latitude and soil nutrients and stoichiometric ratios all were insignificant.[Conclusion] The topsoil nutrients of the P. densata forest in Southeast Tibet were barren, with lowest TP and AP contents, and topsoil nutrient contents had large spatial variability.Affected by soil nitrogen and phosphorus contents, topsoil C∶N,C∶P and N∶P were higher than national forest soil.