成都龙泉山不同林龄香樟人工林土壤养分和微生物群落结构

Soil nutrients and microbial community structure of artificial Cinnamomum camphora forests at different stand ages in Chengdu Longquan Mountain

香樟(Cinnamomum camphora)是我国南方地区重要的造林树种之一,对于生态恢复和城市绿化具有重要作用.以成都市龙泉山不同林龄香樟人工林(10年、20年和40年)为研究对象,分析土壤主要养分状况和微生物群落的演变特征,并与该区域的天然常绿阔叶林进行比较.结果表明,养分总体状况为20年香樟人工林下较差.随着林龄的增加,香樟人工林下土壤总碳、总氮呈“V”型变化,总磷、总钾、总钙则出现持续消耗的趋势.磷脂脂肪酸法(phospholipid fattyacid,PLFA)结果显示香樟人工林土壤微生物总PLFAs量为37.00-67.80nmol/g,细菌PLFAs量为25.42-47.60nmol/g,真菌PLFAs量为7.19-10.00nmol/g.土壤中微生物细菌、G^(+)细菌、G^(-)细菌、放线菌及总PLFAs均随着林龄呈现先降后升的变化趋势,并主要受土壤铵态氮和硝态氮的调控.相比于快速生长阶段,40年香樟人工林的主要土壤养分和微生物群落各类群PLFAs量与天然常绿阔叶林较为接近,意味着随生长年限增加,香樟人工林能逐步改善土壤肥力.

Cinnamomum camphora is an important afforestation species in the southern region of China and plays a key role in ecological restoration and urban greening. In this study, the soil nutrient status and microbial community of artificial C. camphora forests and natural broadleaf evergreen forests aged 10, 20, and 40 years in Longquan Mountain, Chengdu City, were determined. The results indicated a deterioration in the overall soil nutrient status in the 20-year-old artificial C. camphora forest. With increasing plantation age, the soil total carbon and nitrogen levels indicated a “V” shape change, while total phosphorus, potassium, and calcium indicated a continuous depletion trend. The results of phospholipid fatty acid(PLFA) indicated that the total microbial PLFAs of artificial C. camphora forests ranged from 37.00 to 67.80 nmol/g, while bacterial and fungal PLFAs ranged from 25.42 to 47.60 nmol/g and 7.19 to 10.00 nmol/g, respectively. Bacterial, Gbacterial, Gbacterial, actinomycete, and total microbial PLFAs in artificial C. camphora forests indicated an increasing trend with stand age and were mainly regulated by soil ammonium and nitrate nitrogen. Compared with the other age groups, the majority of soil nutrients and PLFAs of various microbial communities in the 40-year-old artificial C. camphora forest was similar to those of the natural broadleaf evergreen forest. This study highlights the potential to return to healthy soil conditions as the age of C. camphora plantations increases.