马尾松林土壤微生群落结构对不同营林处理的响应

以不同营林处理措施(对照、除灌、采伐1(15%)、采伐2(70%)后不同时期(处理后2个月,2013年12月;处理后15个月,2014年12月)三峡库区马尾松飞播林为研究对象,采用磷脂脂肪酸分析法对其土壤微生物生物量、微生物群落结构进行测定,同时比较了不同处理土壤理化性质特征,结果表明:1)处理后1年,除丛枝菌根真菌外,除灌、采伐1和采伐2微生物群落各类群生物量以及总生物量与对照相比均呈现减少的趋势,而在处理后初期并无规律性变化;2)主成分分析表明(PCA)不同处理措施在实施后初期并未对微生物群落结构产生显著影响,而在处理后1年,除灌和采伐1、采伐2的微生物群落结构显著区别于对照,且与土壤微生物群落多样性相关的2个主成分分别解释变量变化的50.40%和26.70%;3)2013年真菌生物标记(20:1 w9c)与主成分1极显著相关,而在2014年与主成分1极显著相关的生物标记物变为革兰氏阴性细菌(16:1w7c);4)冗余度分析表明,土壤湿度、土壤温湿度比值、土壤微生物熵(微生物量碳(MBC)/土壤有机碳(SOC))是影响不同时期微生物群落结构的显著环境因子(P0.05)。

Soil microbial community structure of Pinus massoniana forest under various forest management practices

Soil microorganisms can make up more than 95% of the total soil biomass, and plays important role in decomposition of carbon sources and organic matter. Forest management practices (e.g., harvesting, burning, and thinning) influence the composition of the soil microbial community by affecting habitat and substrate for soil microorganisms directly and indirectly, and hence affect soil carbon process. Quantifying the responses of the soil microbial community to forest management is vital to accurately evaluate forest carbon balance and to reveal the underlying mechanisms of soil carbon process change. Thus, an aerially seeded Pinus massoniana forest was chosen in the Three Gorges reservoir area to evaluate the effects on soil microbial community owing to different forest management practices (i.e., control; shrub-removal:harvesting all shrubs and removing all harvest residues. Harvest strategy 1:15% harvest intensity and removing main harvest residues without leaves and small branches; Harvest strategy 2:70% harvest intensity and the same harvest residue management as that in harvest 1). All experimental treatments were located in similar habitats and consisted of three 20 m×20 m plots. The treatments were conducted in October 2013, and soil samples were collected in December 2013 (2 months post treatments) and December 2014 (12 months post treatments) to analyze soil microbial community by using phospholipid fatty acid (PLFA) methods, and analyze soil chemical properties. The results showed that the total microbial biomass and biomass of all microbial species (except arbuscular mycorrhizal fungi) in shrub-removal, harvest strategy 1 and harvest strategy 2 were lower than those of the control in December 2014. However, there was no consistent rule observed in December 2013. Principal component analysis indicated that all treatments showed no significant change in soil microbial community structure in December 2013; the 2 principal component factors related to microbial community diversity explained 60.90% and 17.40% of the variation respectively. Shrub-removal, harvest strategy 1 and harvest strategy 2 did significantly affect soil microbial community structure in December 2014, and the 2 principal component factors related to microbial community diversity explained 50.40% and 26.70% of the variation respectively. In 2013, 5 PLFAs (Mel 16:0, 16:1w5c, 16:1w7c, al17:0 and 20:1w9c) played a major role in the first principal component, and 7 PLFAs (Mel16:0, 16:1w5c, 14:0, 16:0, cy17:0, 16:1w7c, i14:0) played a major role in the first principal component in 2014. The fungi (20:1w9c) PLFAs played the most significant role in the first principal component in 2013 and was replaced by gram negative bacteria (16:1w7c) PLFAs in 2014. Soil moisture, ratio of soil temperature and soil moisture, and soil microbial quotient (ratio of soil microbial biomass carbon and soil organic carbon) were significant factors regulating soil microbial community structure at different treatment times (P < 0.05), as revealed by redundancy analysis (RDA).