华北落叶松人工林土壤碳氮磷生态化学计量特征

Ecological stoichiometry of soil carbon,nitrogen and phosphorus in a Larix principis-rupprechtii plantation

为阐明华北落叶松（Larixprincipis-rupprechtii）人工林地土壤有机碳、全氮和全磷质量分数的时间变化特征和垂直分布特征,以秦岭20年华北落叶松人工林林地为研究对象,对其土壤有机碳、全氮和全磷质量分数及其化学计量比的季节变化和垂直分布特征进行研究分析。结果表明：1）有机碳、全氮和全磷质量分数随着土层深度增加而降低,土壤有机碳和全氮质量分数具有相似的空间分布和时间变化特征。0-20 cm土壤有机碳、全氮和全磷质量分数从5—10月均呈现明显的动态变化,有机碳质量分数的季节波动性最大;20-40 cm和40-60 cm土层的季节变化规律没有0-20 cm土层明显。2）0-20 cm土层的C/N、C/P和N/P显著高于20-40 cm和40-60 cm土层;各个土层C/N季节变异性最小,季节变化规律不明显,N/P变异性最大,C/P次之,且C/P和N/P具有相似的季节变化趋势。3）土壤C、N和P质量分数之间存在极显著的正相关关系（P〈0.01）,土壤有机碳质量分数与C/N和C/P以及土壤全氮质量分数与C/P和N/P均呈极显著正相关;土壤全磷质量分数与C/P存在极显著正相关关系,而与N/P不相关。表明有机碳和全氮质量分数是导致C/N、C/P和N/P变化的主要因素。

Large areas of plantations have been cultivated in China since 1950 s, which provide tremendous ecological and economic services such as soil and water control,wood production,carbon sequestration and environment protection. Many problems such as soil degradation,tree diseases and wood production decline,however,also appeared after several decades of cultivation due to lack of effective management practices,which seriously threatens the stability and sustainability of plantation development and imposes severe influence on ecological and economic achievements. As the main elements circulation and nutrients turnover pool for plant growth,soil is essential in forest management.The soil fertilization maintenance and promotion have been and still are of significant interest for plantation management. A number of studies concerning spatial pattern of soil nutrients have been conducted in woodland,while little is known about the temporal pattern of soil nutrient status and stoichiometric ratios in plantations which has the important implications for dynamic balance of soilnutrients. The objective of this study was to clarify the seasonal pattern of soil stoichiometric characteristics of a 20-year-old Larix principis-rupprechtii plantation in Qinling. The soil organic carbon（ C）,total nitrogen（ N）,total phosphorous（ P） contents and stoichiometric ratios were measured to explore their seasonal variation and vertical distribution. The results show that： 1） The contents of C,N and P decreased with soil depth throughout the entire growing season（ May to October）. The contents of C,N and P have obvious seasonally dynamic changes from May to October. Soil C and N varied greatly in the 0- 20 cm soil layer（ coefficient of variance（ Cv） of C and N was 0. 28 and 0. 22,respectively） compared to 20- 40 cm and 40- 60 cm soil layers（ Cvfor C 0. 11- 0. 18; for N 0. 13-0. 14）,while soil P fluctuated significantly in the 40- 60 cm layer（ 0. 18） in comparison with the other two layers. The contents of C and P in the 0- 20 cm soil layer reached the top value in October.Also,seasonal variations of C（ 0. 11- 0. 28） and N（ 0. 15- 0. 22） were greater than P（ 0. 06-0. 18）. 2） C / N,C / P and N / P ratios in the 0- 20 cm soil layer was significantly higher than those in20- 40 cm and 40- 60 cm layers（ P〈 0. 05）. In these three soil layers,the seasonal variation of C /N was the smallest and not obvious. The seasonal variation of N / P was the biggest. In May,C / P and N / P in both 0- 20 cm and 20- 40 cm soil layers were significantly higher than in other months（ P 〈0. 05）. In May and June,C / P and N / P in 40- 60 cm soil layer were significantly higher than in July and August. 3） The relative analysis implies that the contents of C,N and P have obvious positive correlation（ P 〈0. 01）. Moreover,C content and C / N,C content and C / P,N content and C / N,N content and N / P,P content and C / P all have obvious positive correlations,but P content has no relation with N / P.