去除根系和凋落物对滨海沙地3种防护林土壤碳氮库的短期影响

以福建长乐滨海沙地上3种人工林(尾巨桉、纹荚相思、木麻黄)土壤为研究对象,设置去除凋落物、去除根系和对照3种处理,观测1年后分析改变地上、地下有机质输入对沙地土壤碳氮储量、可溶性有机碳(DOC)氮(DON)和微生物量碳(MBC)氮(MBN)的影响。结果表明:不同树种人工林间土壤碳氮储量无显著差异;不同树种人工林间土壤活性碳氮组分差异显著,木麻黄土壤DOC含量显著高于纹荚相思,纹荚相思土壤DON显著高于木麻黄和尾巨桉,尾巨桉土壤MBN显著高于木麻黄和纹荚相思。改变地上地下有机质输入对滨海沙地土壤碳氮库有显著影响且这种影响随树种而异。去除凋落物后纹荚相思、木麻黄土壤碳储量分别下降38.0%、25.1%,氮储量分别下降12.9%、12.5%;去除凋落物后尾巨桉、纹荚相思、木麻黄土壤DOC分别下降37.5%、30.6%、52.9%,MBC分别下降31.0%、56.9%、29.7%,MBN分别下降50.7%、34.9%、42.2%;去除根系后尾巨桉、纹荚相思土壤MBC分别下降57.7%、15.4%。回归分析显示,滨海沙地土壤DOC、MBC与土壤碳储量呈显著正相关,土壤DOC和MBC分别能够解释土壤碳储量变化的47.7%和57.7%。研究表明:树种通过调控地上、地下输入影响可溶性有机碳氮和微生物量碳氮,进而影响土壤碳氮库。

Short-term effects of root exclusion and litter removal on sandy soil carbon and nitrogen pools in three coastal plantation forests

The aim of this study was to investigate the effects of manipulated organic matter input (root exclusion, litter removal, and control) on the soil carbon (C) and nitrogen (N) pools in three plantation forests growing on the coastal sandy soil in Changle City, Fujian Province, China. Three plantations included Eucalyptus urophylla×E. grandis hybrid, Acacia aulacocarpa,and Casuarina equisetifolia. The soil C and N stocks, dissolved organic carbon (DOC) and nitrogen (DON) concentrations, and microbial biomass carbon (MBC) and nitrogen (MBN) concentrations were measured after one year of organic matter treatment. The results showed no significant difference in the soil C and N stocks among the three plantations. However, significant difference was observed in the labile carbon and nitrogen components, C. equisetifolia soil showing significantly higher DOC than A. aulacocarpa soil, A. aulacocarpa soil showing significantly higher DON than E. urophylla×E. grandis hybrid and C. equisetifolia soil, and E. urophylla×E. grandis hybrid soil showing significantly higher MBN than A. aulacocarpa and C. equisetifolia soil. Changes in the above-and below-ground C input significantly affected the soil C and N pools, depending on the tree species. Litter removal decreased soil C stocks of A. aulacocarpa and C. equisetifolia by 38.0 and 25.1%, respectively, and the soil N stocks of A. aulacocarpa and C. equisetifolia by 12.9 and 12.5%, respectively. Furthermore, litter removal significantly decreased the soil DOC by 37.5, 30.6, and 52.9; MBC by 31.0, 56.9, and 29.7; and MBN by 50.7, 34.9, 42.2 of E. urophylla×E. grandis hybrids, A. aulacocarpa, and C. equisetifolia, respectively. However, the root exclusion decreased only the soil MBC of E. urophylla×E. grandis hybrids and A. aulacocarpa by 57.7 and 15.4%, respectively. Regression analysis indicated that the soil DOC and MBC were positively correlated with the soil C stocks, while accounting for 47.7% and 57.7% of the variations in soil C stocks. In conclusion, our study suggested that the tree species regulate their soil C and N pools through the effects of the above-and below-ground inputs on soil DOC, DON, MBC and MBN.