高寒半湿润沙地草本修复期土壤微生物变化研究

Soil microorganism dynamics during grassland restoration in sub-humid sandy land

土壤微生物变化对生态恢复过程中土壤养分循环具有重要作用,但高寒半湿润沙地生态修复过程中土壤微生物及养分变化研究较为缺乏。为明确该环境下沙化生态系统的修复过程中土壤环境的变化,选用燕麦、垂穗披碱草、中华羊茅混播修复高寒半湿润沙地,并以未修复沙地为对照,测定0~10 cm和10~20 cm两土层修复4年过程中土壤微生物及土壤养分含量的变化,分析探讨土壤微生物和养分随植被修复的动态,及微生物与土壤养分变化的相关性。结果表明,随修复年限增加,土壤中主要微生物类群以细菌为主,沙地修复4年后土壤中微生物总量由8.30 nmol·g^-1增加到10.58 nmol·g^-1,但是细菌依然占微生物总量的50%以上,植被恢复并未改变细菌占微生物总量比例。两个土壤层土壤微生物生物量(碳、氮、磷)、多样性(细菌、真菌、放线菌、G^-菌、G^+菌)、土壤养分(有机质、全氮、全磷)含量均呈现先降低后增加趋势,且0~10 cm始终大于10~20 cm土层。草本修复第1年,0~10 cm和10~20 cm土层微生物及养分各组分含量显著降低(P<0.05);修复2年后,0~10 cm土层含量开始增加;到修复第3和4年,土壤微生物与土壤养分中各组分含量均恢复到未治理水平,且有机质、微生物量氮(MBN)含量显著高于未治理沙地(P<0.05)。土壤养分中各组分含量与土壤微生物生物量、微生物总量和细菌含量呈极显著的正相关关系(P<0.01),与G^+、G^-菌、真菌、放线菌均呈不同程度的正相关关系。因此,在沙地进行人工草本种植能够提高土壤养分和微生物含量,对帮助高寒地区生态系统修复和稳定具有重要意义。

Variation in soil microorganism populations has a great influence on soil nutrient cycles during the process of ecological restoration.However,little research has been conducted into variation in soil microorganism populations during the restoration of sub-humid desert land in alpine-cold areas.To investigate this topic,we planted a mixture including Avena sativa,Elymus nutans and Festuca sinensis,among others as an experiment in the restoration of sub-humid desert land.Changes in microbial biomass carbon,nitrogen,phosphorus,microbial biodiversity(phospholipid fatty acids,PLFAs),soil organic carbon,soil total nitrogen and soil total phosphate were checked in the 0-10 cm and 10-20 cm soil layers,annually after re-vegetation,and the changes in soil microorganism populations with time and the correlations between microbial biodiversity,microbial biomass and soil nutrients were analyzed.It was found that re-vegetation increased soil microbial biomass from 8.30 to 10.58 nmol·g^-1 after 4 years and the bacteria still accounted for more than 50%in the total amount of microorganisms.Microbial biomass carbon,nitrogen,and phosphate,microbial biodiversity(i.e.bacteria,fungi,actinomycetes,Gram-negative bacteria,Gram-positive bacteria),soil organic carbon,total nitrogen and total phosphate in the 0-10 cm soil layer were all more than in the 10-20 cm soil layer,throughout the re-vegetation process.Over time,all of these measures showed an initial decrease,and then a tendency to increase.For example,after 1 year’s re-vegetation,soil microbes and nutrients of both soil layers decreased significantly,but soil microbes and nutrients increased in the 0-10 cm soil layer after 2 years re-vegetation.Finally,soil microbe numbers and nutrients increased to values similar to or higher than the controls after 3 or 4 years.In particular,soil organic carbon and microbial biomass nitrogen were significantly(P<0.05)higher in restored grassland than in control plots at the end of the experiment.Soil nutrient levels had extremely positive correlations with soil microbial biomass,and microorganism and bacterial counts(P<0.01),and had positive correlations with counts of soil fungi,actinomycetes,Gram-negative bacteria and Gram-positive bacteria.In summary,artificial re-vegetation with a grass mixture increased soil nutrients and microbes in desert land,thus providing a positive contribution to restoration of a degraded ecosystem in this alpine-cold area where this study was carried out.