香港人工林改造对林分土壤理化性质、土壤微生物生物量及土壤酶活性的季节影响

Impact of Thinning on Physico-chemical properties,Soil Microorganism biomass,and Soil Enzyme Activities on the Season of Hong Kong Plantation

土壤理化性质、土壤微生物及土壤酶活性是土壤生态系统的重要组成部分,研究林分改造对土壤因子的影响,可为人工林改造与林地土壤质量恢复提供科学依据。文章对香港地区20年生尾叶桉(Eucalyptus urophylla)和马占相思(Acacia mangiumin)人工林进行间伐套种处理(套种密度为1 665 plants·hm^(-2),以不间伐林分为对照),采用野外调查与室内试验相结合的方法分析间伐套种3 a后2种林分的土壤理化性质、土壤微生物生物量和土壤酶活性的季节变化。结果表明,(1)间伐套种3 a后,各林分土壤均呈酸性,间伐对林分土壤容重和孔隙度影响不显著,但提高了冬夏季林分土壤电导率。(2)间伐套种对冬季和夏季2种林分土壤理化性质的影响存在差异。与未间伐林分相比,间伐套种减少了冬季尾叶桉林分土壤养分的消耗,但提高了夏季林分土壤养分的含量。间伐套种降低了冬季马占相思林分土壤氮素含量及夏季土壤交换性Ca含量,提高了冬季林分土壤交换性元素和夏季土壤氮素含量。(3)无论是间伐套种林分还是未间伐林分,夏季2种林分的土壤微生物生物量C(226.35~619.44 mg·kg^(-1))和微生物生物量N(21.18~52.44 mg·kg^(-1))均高于冬季。间伐套种处理促进了尾叶桉林分土壤微生物生物量的增加,而马占相思林分则相反。(4)间伐套种处理对2种林分过氧化氢酶活性的季节影响不显著,对尾叶桉的土壤磷酸酶和脲酶的季节影响不一致,但降低了马占相思林分的土壤酶活性。(5)综合分析,间伐套种处理改善了尾叶桉林分的土壤理化性质,提高了土壤微生物生物量和土壤酶活性;但对马占相思林分的土壤肥力改善作用并不明显。

Soil physico-chemical characteristics,soil enzymes and soil microbes are the important components of soil ecosystem.Predicting impacts of soil factors and providing a scientific basis for plantation rehabilitation and soil quality restoration.In this paper,a thinning experiment was conducted 20-year-old Eucalyptus urophylla and Acacia mangiumin plantations in Hong Kong,with interplanting with a density of 1 665 plants-hm＂2,and the un-thinned plantations were served as control.We analyzed the dynamic change in soil physico-chemical characteristics,soil microorganism biomass and soil enzyme activities after thinning three years.The results showed that,（1） After thinning 3 years,all the stands soil was acid.There was no significant difference in soil bulk density and soil porosity,but promoted the increase of soil electrical conductivity in winter and summer.（2） There was significant difference in soil physico-chemical characteristics of two stands in winter and summer by thinning and interplanted species.Compared to un-thinning stand,thinning and interplanted treatment reduced the nutrient consumption of Eucalyptus urophylla in winter and increased soil nutrient content in summer.However,it reduced the N content in winter and the exchangeable Ca content in summer of Acacia mangiumin,while it improved the increase of the exchangeable Ca content in winter and the N content in summer.（3） In summer,the soil microorganism C biomass（226.35-619.44 mg·kg-（-1）） and microorganism N biomass（21.18-52.44 mg·kg-（-1）） of two stands were higher than that of the winter various thinning and un-thinning treatment.Thinning and interplant species treatment promoted the increased of soil microbial biomass of Eucalyptus urophylla,while decreased in Acacia mangiumin stand.（4） There was no significant difference in soil enzyme by thinning and seasonal,which the effects of thinning on the soil catalase and urease activities of two stands in winter and summer,and reduced the soil enzyme of Acacia mangiumin in seasonal variations.（5）Comprehensive analysis showed that thinning could improve the soil physico-chemical characteristics,soil microorganism biomass and soil enzyme activities in Eucalyptus urophylla stand,while was no obvious in Acacia mangium stand.