间伐对侧柏人工林土壤微生物生物量碳、氮的影响

以徐州侧柏人工林为对象,研究了在弱度间伐（LIT,20％）、轻中度间伐（MIT1,40％）、中度间伐（MIT2,60％）和强度间伐（HIT,80％）下,林下土壤微生物生物量碳、氮在土壤表层（0 ～ 10 cm）和亚表层（10～20 cm）的变化.结果表明：不同间伐强度下,微生物生物量碳、氮含量均随着土层加深而减少.随着间伐强度增加,微生物生物量碳、氮总体变化趋势为先增加后降低,其中微生物生物量碳表现为MITl＞ LIT＞ HIT＞ MIT2,均与对照CK有显著差异（P＜0.05）;微生物生物量氮表现为MIT2＞ MITl＞ LIT＞ HIT,各处理间均表现出显著差异（P＜0.05）.间伐也使土壤微生物熵增加,尤以MIT2达到最大（2.63％）.研究表明,侧柏人工林经过2 a间伐,土壤微生物生物量碳、氮含量增加,在一定程度上使土壤碳库和氮库短期内出现不稳定趋势.

Effects of thinning on soil microbial biomass carbon and nitrogen for Platycladus orrientalis plantation

Experiment was conducted to study the effects of thinning （weak 20%, light 40%, mederate 60%, intensity 80%） on surface soil （0 - 10 cm） and subsurface soil （10 - 20 cm） microbial carbon （MBC） and nitrogen （MBN） in Platycladus orrientalis plantation in Xuzhou. The resuh showed that the contents of soil MBC and MBN decreased with soil depth in different thinning intensity. With intensity increase, the soil MBC, MBN content generally had a rise - then - fall trend, thereinto the soil MBC had a perfermance in turn by MIT1 〉 LIT 〉 HIT 〉 MIT2, all having significant difference with CK（ P 〈 0.05 ）. The soil MBN performed the same in the case as MBC, ranging as by MIT2 〉 MIT1 〉 LIT 〉 HIT, all having significant difference with CK （ P 〈 0.05 ）. Soil microbial entropy was increased after thinning, reaching highest （2.63%） by MIT2. This study indicated that the soil microbial carbon and nitrogen contents in Platycladus orrientalis plan- tation were increased after 2 years＇ thining, to some extent, which made the soil carbon pool and nitrogen pool unstable.