气温和降水量对东灵山阔叶林凋落物分解特征的影响

EFFECTS OF TEMPERATURE AND PRECIPITATION ON LITTER DECOMPOSITION IN DONGLINGSHAN MOUNTAIN BROAD-LEAVED FOREST

植物凋落物分解是北半球中纬度森林生态系统生物地球化学循环的关键环节,其过程目前尚不甚清楚。北京东灵山暖温带落叶阔叶林凋落物破碎程度、颜色变化和微生物培养的定量化综合研究结果显示:大粒级碎片含量和颜色值L是凋落物早期分解程度的直接量度。可培养微生物菌落数(CFU)自1月起逐渐增加,于9月达到峰值,增幅受控于气温和降水量。微生物菌落数与大粒级凋落物含量和L值具有较强的相关性,显示了微生物的生长繁殖对提高森林凋落物降解速率的作用。本次研究中,气温和降水量两个环境因子能够得以分离。当气温升高而降水量却较低时,凋落物分解减慢;当降水量较高时,即便气温有所下降,分解速率也可能很高,其作用机理可能与微生物生物量有关。升温和降水量的合理分配能够提高凋落物分解速率,促进碳排放。若未来区域升温且降水量也增加,森林土壤碳排放量也将增大。

Donglingshan Mountain(39°48'~40°00'N,115°24'~115°36'E),belonging to Taihang Mountain System,is a branch of the Xiaowutai Mountain and located in Mentougou District of Beijing.The climate of this region is warm temperate continental seasonal climate,with the average temperature of 18~25℃in July,-4~-10℃in January,and 5~11℃in annual.The annual average precipitation in the region is 500~650 mm,74%of which occurs from June to August.The main soil types are brown forest soil,brown soil and subalpine meadow soil.A permanent fixed sample plot of 100 m×100 m was selected in the study area.The sample was located in the eastern slope of the primary growth forest of Donglingshan Mountain,Beijing,with an altitude of 1500~1600 m.The present vegetation in the sampling site is mainly secondary vegetation.Betula platyphylla and Quercus liaotungenisis are the main plants,with a few Acer mono and Juglans mandshurica accompanying plants.The plant litter layer in the area is about 6 cm thick.The results of quantitative comprehensive study on litter fragmentation,color change and microbial culture in a warm temperate deciduous broad-leaved forest in Donglingshan Mountain,Beijing showed that the content of large size debris and color value L were direct measures of early litter decomposition.The number of culturable microbial colonies(CFU)increased gradually from January to September,showing that who was controlled by temperature and precipitation.There was a strong correlation between the number of microbial colonies and the content and L value of large size litter,which indicated that the growth and reproduction of microorganisms could improve the degradation rate of forest litter.In this study,temperature and precipitation can be separated.When the temperature rises and the precipitation is low,the decomposition of litter will slow down;when the precipitation is high,even if the temperature drops,the decomposition rate may be high,and the mechanism of action may be related to the microbial biomass.The reasonable allocation of temperature and precipitation can increase the decomposition rate of litter and promote carbon emissions.If the regional warming and precipitation increase in the future,the forest soil carbon emissions will also increase.