不同海拔红松混交林土壤微生物量碳、氮的生长季动态

Seasonal Dynamics of Soil Microbial Biomass Carbon-Nitrogen in the Korean Pine Mixed Forests along Elevation Gradient

[目的]研究红松混交林下土壤微生物生物量碳、氮的生长季动态变化,为更多地了解红松混交林生态系统中土壤微生物群落在碳氮循环中的作用提供科学依据。[方法]以红松林在长白山海拔分布高度上限为准,从最高海拔起按每100 m海拔为1个梯度依次向下选取5个样地作为研究对象。同一海拔设置3个重复样地,面积均为20 m×20 m,间隔20 m。样地内按S型随机布点,共设10个15 cm×15 cm样方,分别于2013年5月21日、7月19日、8月23日、9月20日进行样品采集。分析不同海拔红松林的土壤理化性质及土壤微生物生物量碳和生物量氮生长季的动态变化规律及差异的机制。[结果]土壤微生物生物量碳、氮含量及碳氮比随海拔的升高呈现出先增加后降低的趋势,土壤微生物生物量碳、氮和碳氮比在900 m达到最高(1 287.18 mg·kg^(-1),224.29 mg·kg^(-1),9.29),各海拔间土壤微生物生物量碳、氮含量有显著差异(P<0.01)。土壤微生物生物量碳和氮含量随着土壤深度的增加呈下降趋势,5个海拔0~5 cm土层微生物生物量碳分别是5~10 cm的1.15,1.55,1.29,2.58,1.32倍,微生物生物量氮则分别是1.50,1.23,1.45,2.64,1.09倍。在5—9月的生长季中,土壤微生物生物量碳、氮含量在0~5 cm土层均为先降低后升高再降低的变化规律,呈倒"N"形曲线,在5~10 cm土层则呈现出先升高再降低的单峰曲线形;不同土层、不同海拔间的土壤微生物生物量碳氮比的季节变化规律均存在差异,但除5月较低外,土壤微生物生物量碳氮比均在5~20之间,说明红松混交林土壤微生物群落中真菌相对于细菌更占优势,土壤的腐殖化能力相对较高;8和9月微生物生物量碳氮比最高,这一时期土壤的固碳能力最强。土壤有效氮、有机碳、有效磷、有效钾含量和p H值、含水量在各海拔之间均存在较大的差异,总体上各指标从海拔700 m到900 m逐步升高到最大值,然后开始呈下降趋势。不同海拔土壤微生物生物量碳与土壤总有机碳、有效氮、有效磷、有效钾含量和土壤含水量呈极显著正相关(P<0.01),与土壤p H值呈显著正相关(P<0.05);土壤微生物生物量氮与土壤p H值呈极显著正相关(P<0.01),与土壤有机碳、有效氮、有效磷、有效钾含量和土壤含水量呈显著正相关(P<0.05)。[结论]海拔、土壤深度、季节变化等都能对土壤微生物生物量碳、氮含量产生显著的影响,土壤的理化性质、样地林分组成等是导致土壤微生物生物量碳、氮差异的主要影响因子。

[Objective]In this study,the seasonal variation of carbon and nitrogen of microbial biomass in the Korean pine（ Pinus koraiensis） mixed forests at different altitudes was investigated. This study would provide a scientific basis for comprehending the role of soil microbial communities in carbon and nitrogen cycles. [Method]In this study,we set 5 sites along the altitude gradient of Changbai Mountain,starting from the highest distribution altitude of Korean pine and down in one hundred meters altitude intervals. At the same altitude,3 sample plots were set,and each of sample plot was 20 m ×20 m in size. A total of 10 sampling points in a size of 15 cm × 15 cm were randomly set up in an S type at each plot.We collected the samples in the plots on May 21,July 19,August 23,September 20 of 2013,respectively. We analyzed the dynamic variation and different mechanism of the soil microbial biomass carbon（ SMBC） and microbial biomass nitrogen（ SMBN） in growing season. [Result]The SMBC,SMBN and the SMBC / SMBN had the same variation trend,that is,increased at first and then decreased with the increased altitude. The SMBC,SMBN and the SMBC / SMBN allreached to their maximum at 900 m（ 1287. 18 mg kg^-1; 224. 29 mg kg^-1; 9. 29）. There were significant differences in the SMBC and SMBN among the elevations（ P〈 0. 01）. The microbial biomass carbon and nitrogen decreased with soil depth. The microbial biomass carbon in 0- 5 cm layers of the soil was 1. 15,1. 55,1. 29,2. 58,and 1. 32 times higher than those in the 5- 10 cm layers at the 5 elevations,respectively. The microbial biomass nitrogen was 1. 50,1. 23,1.45,2. 64,and 1. 09 times higher than those in the 5- 10 cm layers,respectively. In the growing season（ from May to September）,the SMBC and SMBN in the 0- 5 cm soil layers decreased at first,then increased and decreased again. The shape of the curve is inverted ＂N＂. However,the SMBC and SMBN first increased and then decreased and presented a unimodal shape of curve in the 5- 10 cm soil layer. The seasonal variation of microbial biomass carbon-nitrogen ratio among different altitudes and different soil layers were different. The microbial biomass carbon-nitrogen ratio was between5 and 20 during the measuring periods except May. The results showed that fungi were more dominant than bacteria in microbial communities in the forests and the capability of soil humification was relative high. In August and September,the microbial biomass carbon-nitrogen ratios were highest,indicating that the capacity of carbon sequestration of soil was strongest. The content of soil available N,soil organic carbon,available P,available K and p H,and soil moisture was obviously different among the 5 elevations. Generally,all indexes increased gradually from 700 m to 900 m and reached to the maximum,and then decreased with the increased elevation. Soil microbial biomass carbon had extremely significant positive correlations with soil organic carbon,soil moisture,available N,available P and available K at different altitudes（ P〈 0. 01）,and had significant positive correlation with p H at different altitudes（ P〈 0. 05）. Soil microbial biomass nitrogen had extremely significant positive correlations with p H at different altitudes（ P 〈0. 01）,and had significant positive correlations with soil organic carbon,soil moisture,soil available N,available P and available K at different altitudes（ P〈 0. 05）. [Conclusion ]The elevation gradient,soil depth and seasonal variation could impact on soil microbial biomass carbon and nitrogen content significantly. The physical and chemical properties of soil,and the difference of forest types were major factors which led to the changes of soil microbial biomass.