林窗尺度对侧柏人工林土壤微生物生物量碳氮的短期影响

为了明晰林窗尺度对侧柏人工林土壤微生物生物量碳氮的短期影响,以徐州市50年生侧柏人工林为研究对象,探讨了开设林窗2a后3种林窗尺度(半径分别为4m,S林窗;8m,M林窗;12m,L林窗)和位置(林窗内、林缘和林窗外部)对土壤微生物生物量碳氮(MBC,Microbial Biomass Carbon;MBN,Microbial Biomass Nitrogen)的影响。结果表明:(1)与对照样地相比,L林窗显著提高了春季(207.1mg/kg)和夏季(169.5mg/kg)林窗外部的土壤MBN含量;M林窗显著提高了春季林窗内部(2959.3mg/kg)和林缘(3008.8mg/kg)位置土壤MBC含量和林缘位置(207.7mg/kg)土壤MBN含量,且显著提高了夏季林窗内部(144.4mg/kg)土壤MBN含量;S林窗显著降低了春季林窗外部和林缘位置土壤MBC(分别为2159.2mg/kg和1955.1mg/kg)和MBN(分别为153.1mg/kg和131.3mg/kg)含量。(2)土壤MBC含量与土壤全碳和土壤可溶性有机碳(DOC)含量呈极显著(P0.01)正相关,与土壤温度呈极显著负相关(在3—27℃之间);土壤MBN含量与土壤含水量和DOC含量呈极显著正相关,与土壤全碳呈显著正相关;土壤MBC和MBN含量与凋落物量没有显著相关关系。本研究中,相对于S和L林窗,M林窗对土壤微生物生物量的提高作用较为明显,可促进侧柏人工林土壤碳氮循环过程,在徐州侧柏人工林中开设M林窗有利于提高土壤肥力和林木生长。

Short-term effects of forest gap size on soil microbial biomass carbon and nitrogen in the Platycladus orientalis plantation

To investigate the short-term effects of forest gap size on soil microbial biomass carbon and nitrogen in Platycladus orientalis plantations, we conducted a study in a 50-year P. orientalis plantation in Xuzhou. The effects of three levels of forest gap size (S, M, and L, with a radius of 4, 8, and 12m, respectively) and position (inside, edge, and outside the gap) on soil microbial biomass, carbon (MBC), and nitrogen (MBN) were analyzed two years after the creation of gaps. The results showed that (1) L gaps had significantly higher soil MBN content at the outside position in spring (207.1mg/kg) and summer (169.5mg/kg) than that in the control plots. The M gaps had significantly larger soil MBC content at the inside and edge positions (2959.3 and 3008.8mg/kg, respectively), soil MBN content at the edge position in spring (207.7mg/kg), and soil MBN content at the inside position (144.4mg/kg) in summer than those in the control plots. The S gaps had significantly reduced soil MBC (2159.2 and 1955.1mg/kg) and MBN (153.1 and 131.3mg/kg) content at the outside and edge positions in spring, respectively, than those in the control plots. (2) Soil MBC content was positively correlated with soil total organic carbon and dissolved organic carbon (DOC) content, but negatively correlated with soil temperature; soil MBN content was positively correlated with soil water content, DOC content, and soil total carbon. MBC content was not significantly correlated with MBN content in soil and litter. We recommend the M gap size as an efficient management practice for increasing soil microbial biomass, promoting soil carbon and nitrogen cycling, and improving soil fertility and tree growth in P. orientalis plantations.