河北小五台山不同海拔白桦林土壤有机碳密度分布特征及影响因素

Altitudinal Distribution Rule of Betula platyphylla Forest's Soil Organic Carbon Density And Its Influencing Factors in Xiaowutai Mountain in Hebei

白桦(Betula platyphylla)是中国北方分布广泛的天然林树种。在全球气候变暖的大背景下,对白桦天然林水热梯度上土壤有机碳的垂直分布规律及其影响因素进行研究,对于研究该区域森林土壤有机碳形成机理及该区碳储量合理评测具有重要意义。以冀北山地小五台山山涧口沟白桦天然林单一植被类型为研究对象,沿其海拔分布范围(1 400~2 000 m)以150m为1个海拔梯度设置固定样地,测定每个海拔梯度气候因子、林分生物量、枯落物储量、土壤容重、土壤全氮及土壤有机碳含量等指标,分析土壤有机碳密度沿海拔的分布规律,并采用灰色关联度分析确定8个环境因子对土壤有机碳密度的影响程度。结果表明:(1)随着土层深度增加,土壤有机碳呈逐渐减少的趋势,且近50%的有机碳聚集在0~20 cm土层范围内;(2)随着海拔升高,土壤有机碳呈现显著的先上升后下降的变化趋势,在海拔1 550~1 700 m最大,有机碳密度达到12.03kg·m^(-2);(3)8个环境因子对不同海拔土壤有机碳密度的灰色关联分析表明,植被因子(枯落物储量、林木生物量)和土壤因子(全氮)是小五台山白桦天然次生林土壤有机碳密度沿海拔分布的主要影响因素,且其与土壤有机碳密度的灰色关联度值显著大于气候因子。

The natural forest of Betula platyphylla,which is widely distributed in northern China,is important ecological protection and commercial timber species.In global warming,studying the distributional law of soil organic carbon density(SOCD)along the altitudinal gradient and its influencing factors in Betula platyphylla forest will be very important for illuminating the formation mechanism of forest soil organic carbon and reasonable evaluation of forest carbon storage in this region.The Betula platyphylla forest were located in Xiaowutai Mountain Shanjiankou(lower elevation from 1 400 m above sea level to 2 000 m at its upper limit).The slope,aspect and the stand types were consistent.This study set a series of plots and samples along an altitudinal gradient on Betula platyphylla forest.It tested soil organic carbon content at different attitudes in order to discusse the distributional law of soil organic carbon density(SOCD)along the altitudinal gradient.Based on that,grey relational analysis was used to analyse the impacts of hydrothermal ration,biomass,litter storage,soil bulk density and soil total nitrogen on this law.The results showed that,SOCD presented a decreasing trend with increasing soil depth;at a depth of 0~20 cm SOCD accounted for about 50%of the whole section.From the lower elevation limit to the upper limit,SOCD presented an significant change which increased first and then decreased,the peak appeared at the altitude of 1 550~1 700 m,it was about 12.03 kg·m-2.The grey relational degree values of hydrothermal factors,vegetation factors,soil factors and SOCD showed that biomass,litter storage and soil total nitrogen were main regulating factors of the spatial variability of SOCD along the elevation.The variation of SOCD along the elevation results from the combined action of hydrothermal gradient variation and affected vegetation and soil factors.