亚热带地区不同人工林配置下土壤微生物量碳及微生物墒的年际动态

Interannual Dynamics of Soil Microbial Biomass Carbon under Different Plantations in Subtropical China

以自然恢复的草坡(SH)为对照样地,分析广东鹤山共和样地不同配置人工林——10种树种混交林(10NS)、30种树种混交林(30NS)、厚荚相思纯林(Acacia crassicarpa,AC)、红椎纯林(Castanopsis hystrix,CM)和尾叶桉纯林(Eucalyptus urophylla,EU)在种植后第1年、第6年和第11年的土壤微生物量碳,探讨不同人工林配置下土壤微生物量碳的年际动态。结果表明:除EU外,其他4种林型及对照SH的土壤微生物量碳(MBC)均随着林龄的增加呈先上升后下降趋势,但差异不显著;不同人工林MBC含量在6 a林龄时达到最高,最高值在AC中可达266.078 mg?kg^(-1);相同林龄MBC在不同林型间存在差异,在11 a林龄时该差异达到极显著水平(P=0.001),表现为混交林(10NS和30NS)的MBC含量最高,AC和CM纯林次之,SH和EU最低。不同人工林土壤有机碳(SOC)、全氮(TN)含量在林龄间的变化趋势与不同人工林的MBC(EU除外)在林龄间的变化趋势一致。土壤微生物墒(MBC/SOC)在不同林型间的变化趋势与MBC基本一致,均在11 a林龄时产生显著差异且土壤微生物墒值在混交林达到最高。MBC与SOC(P<0.01)、TN(P=0.01)呈显著正相关,而MBC/SOC与SOC呈显著负相关(P=0.03)。MBC在人工林中的年际变化存在波动,可能与人工林林分和土壤尚未达到成熟水平有关。该研究可为亚热带丘陵荒坡人工林的生态恢复与管理提供科学的基础数据与理论依据。

The interannual dynamics of soil microbial biomass carbon were investigated under five different plantations including Acacia crassicarpa monoculture,Castanopsis hystrix monoculture,Eucalyptus urophylla monoculture,10-species mixed plantation and 30-species mixed plantation at their ages of 1-year,6-year and 11-year-old in subtropical China.The naturally recovered shrub land was used as a reference for the five different plantations.The results showed that the soil microbial biomass carbon(MBC)increased at the early developmental stages of the plantations but decreased at 11-year-old except for Eucalyptus urophylla monoculture and had no siginificant different.The peak value of MBC occurred at the age of 6-year-old with the highest of 255.81 mg.kg-1 for Acacia crassicarpa monoculture.There were differences of MBC among different plantations at the same age,and the most significant differences were detected at the age of 11-year-old(P=0.001).The MBC under both mixed species plantations were the highest,followed by monocultural plantations of Acacia crassicarpa and Castanopsis hystrix,and the lowest MBC occurred at Eucalyptus urophylla monocultural plantation and a naturally recovered shrub land.The temporal change patterns of soil organic carbon(SOC)and total nitrogen(TN)were consistent with that of MBC,i.e.the peak value occurred at 6-year-old.The differences in contributions of MBC to SOC among different plantations showed similar pattern to that of MBC,but this varied with plantation age.Spearman correlations analysis showed positive correlations between MBC and SOC,TN,but negative correlation was detected between the ratio of MBC to SOC and SOC.In conclusion,the interannual change of MBC under different plantations may be related to the instability of early developmental stages of plantations because the vegetation has not yet reached the level of maturity.Our results can provide useful data and theoretical basis for the ecological restoration and management of degraded hilly land in subtropical China.