间伐对杉木人工林土壤碳氮及其组分特征的影响

为探究不同间伐强度对杉木人工林土壤碳氮及其组分特征的影响,以福建省三明市官庄国有林场11年生杉木(Cunninghamia lanceolata)人工林为研究对象,采用弱度间伐(LIT)、中度间伐(MIT)、强度间伐(HIT)等3种间伐强度,研究不同间伐强度林分0—10,10—20,20—40,40—60,60—80,80—100 cm土层总有机碳(SOC)、全氮(TN)及易氧化有机碳(ROC)、硝态氮(NO_3~--N)、铵态氮(NH_4~+-N)、微生物量碳(MBC)、微生物量氮(MBN)、微生物熵碳(qMBC)、微生物熵氮(qMBN)的变化特征,以探讨不同间伐强度对杉木人工林土壤碳氮及其组分特征的影响。结果表明:间伐降低了土壤SOC和TN的含量,降低幅度分别为1.4%～36.9%,3.1%～45.7%。间伐增加了土壤MBC、NO_3~--N的含量,而对ROC、NH_4~+-N和MBN的程度在不同土层有差异,qMBC和qMBN随着间伐强度的增加而增大。相关性分析表明,土壤SOC分别与TN、qMBC、ROC、NH_4~+-N、MBC、MBN呈极显著正相关(P0.01);TN与qMBN、ROC、NH_4~+-N、MBC、MBN呈极显著正相关(P0.01)。杉木人工林间伐处理降低了土壤表层SOC和TN含量,增加了土壤SMBC和qMBC、qMBN,同时也增加了土壤表层(0—10 cm)SMBN。抚育间伐导致土壤SOC和TN含量降低主要是由于活性碳、氮含量的增加,提高土壤中有机质分解速率,最终导致土壤SOC和TN含量降低。

Effects of Thinning on Soil Carbon and Nitrogen Fractions in a Cunninghamia lanceolata Plantation

In order to explore the effects of different thinning intensities on soil carbon and nitrogen fractions in Chinese fir plantation, this study was conducted in 11-year-old fir plantations in Guanzhuang state-owned forest in Sanming City, Fujian Province. Three types of thinning, including light intensive thinning (LIT), moderate interval thinning (MIT), and hight intensive thinning (HIT) were adopted. The variations of total organic carbon (SOC), total nitrogen (TN), readily oxidized organic carbon (ROC), nitrate nitrogen (NO₃-N), ammonium nitrogen (NH₄⁺-N), microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), microbial entropy carbon (qMBC) and microbial entropy nitrogen (qMBN) in the 0-10,10-20,20-40,40-60,60-80,80-100 cm soil layers of different thinning intensities were explored. The results showed that thinning reduced soil SOC and TN contents by 1.4%~36.9% and 3.1%~45.7%, respectively. Thinning increased soil MBC and NO₃-N content, while the change degrees on ROC, NH₄⁺-N and MBN showed differences in different soil layers. With the increase of thinning intensity, the values of qMBC and qMBN gradually increased. Correlation analysis showed that soil SOC was significantly positively correlated with TN, qMBC, ROC, NH₄⁺-N, MBC and MBN, respectively (P<0.01). TN was significantly positively correlated with qMBN, ROC, NH₄⁺-N MBC and MBN (P<0.01). The thinning treatment of Cunninghamia lanceolate plantation decreased SOC and TN content in soil surface layer, increased SMBC content and qMBC, qMBN value in soil, and increased SMBN content in soil surface layer (0-10 cm). The results indicate that the decrease of soil SOC and TN content caused by thinning is mainly due to the increase of active carbon and nitrogen content, which improves the decomposition rate of organic matter in soil, and finally leads to the decrease of soil SOC and TN content.