贡嘎山不同海拔峨眉冷杉根际土壤化学性质及胞外酶活性

Chemical properties and extracellular enzymatic activity in the rhizosphere soil of Abies fabri at different altitudes on Mount Gongga

探究贡嘎山峨眉冷杉根际土壤化学性质、微生物生物量及土壤胞外酶活性的垂直分布格局,可为川西高寒山地植被的保护及生态环境的恢复提供一定的理论基础.以贡嘎山5个海拔2800 m(A1)、3000 m(A2)、3200 m(A3)、3500 m(A4)、3800 m(A5)的峨眉冷杉群落根际土壤为研究对象,测定并分析其土壤化学性质,土壤微生物碳、氮、磷含量(MBC、MBN、MBP)和胞外酶活性[酸性磷酸酶(AP)、多酚氧化酶(PPO)、过氧化物酶(PER)]的变化及其影响因素.结果显示:(1)土壤含水量(SM)、可溶性有机碳(DOC)、全氮(TN)、硝态氮(NO_(3)^(-)-N)含量均随海拔的升高先降后增,在海拔A1处最大,海拔A3处为其转折点.全磷(TP)、速效磷(AVP)含量随海拔的升高而增加,并且N/P值在A1、A2、A3海拔处高于中国陆地生态系统N/P均值,表明此区域内磷元素较为缺乏;(2)MBC/MBN值在1-3范围内,表明本研究区域中土壤腐殖化能力与固碳能力偏弱,MBC/MBP和MBN/MBP值在A1海拔处显著高于其他海拔,表明海拔A1处磷元素限制最为严重;(3)AP、PPO活性随海拔升高而降低,且与TN含量密切相关,PER酶活性受海拔影响不显著,3种酶活性均在A1海拔处最高.综上所述,不同海拔峨眉冷杉根际土壤化学性质、微生物生物量和胞外酶活性差异显著,TN是影响海拔梯度上土壤酶活性变化的关键因子;最低海拔2800 m处土壤养分含量最为丰富,但相对于其他海拔更易受磷元素限制.

This study investigated the vertical distribution pattern of soil chemical properties,microbial biomass(MBC,MBN,and MBP),and extracellular enzyme activities in the rhizosphere of Abies fabri(Mast.)Craib on Gongga Mountain,aiming to provide a theoretical basis for the protection and restoration of the subalpine ecosystem in the western Sichuan region of China.The rhizospheres of Abies fabri at five altitudes,2800 m(A1),3000 m(A2),3200 m(A3),3500 m(A4),and 3800 m(A5),on Gongga Mountain were selected as the research object in this study.They were analyzed in terms of their soil chemical properties,microbial biomass,and the activity of extracellular enzymes(acid phosphatase(AP),polyphenol oxidase(PPO),peroxidase(PER))and their influencing factors.Results showed that(1)the soil water content(SM)and levels of soluble organic carbon(DOC),total nitrogen(TN),and nitrate nitrogen(NO_(3)^(-)-N)first decreased and then increased with increases in altitude;the maximum was at altitude A1 and the turning point was at altitude A3;the total phosphorus(TP)and available phosphorus(AVP)levels increased with increasing altitude.The N/P ratios at A1,A2,and A3 were higher than the mean N/P ratios of terrestrial ecosystems in China,indicating that phosphorus was scarce in the study area.(2)The MBC/MBN ratio ranged from 1–3,indicating that soil humification and carbon sequestration capacities were weak in this study area.The MBC/MBP and MBN/MBP ratios were significantly higher at A1 than at other altitudes,indicating that phosphorus was more deficient at the latter.(3)The activities of AP and PPO decreased with increase in altitude and were closely related to the TN content while the activity of the PER enzyme was not significantly affected by altitude;the activities of all three enzymes were the highest at A1.In summary,the chemical properties,microbial biomass,and extracellular enzyme activities of the rhizosphere of Abies fabri were significantly different at different altitudes.TN is a key factor affecting changes in soil enzyme activity along the altitude gradient.Soil nutrient content was the highest at the lowest altitude,2800 m;however,it was more susceptible limits in phosphorus at this altitude than at others.