外来种湿地松凋落物对土壤微生物群落结构和功能的影响

Effects of exotic species slash pine(Pinus elliottii) litter on the structure and function of the soil microbial community

通过凋落物袋+小盆模拟试验研究,分两个时期(分解5个月和18个月)比较了外来种湿地松与本地种马尾松的凋落物对土壤微生物群落结构(磷脂脂肪酸)和功能(碳代谢)的影响,结果表明:(1)外来种湿地松凋落物的C∶N高于本地种马尾松;(2)两个时期,湿地松凋落物处理土壤细菌和放线菌的磷脂脂肪酸含量均低于马尾松,18个月时湿地松凋落物处理土壤真菌含量和群落真菌/细菌显著高于马尾松处理;(3)湿地松凋落物影响下土壤微生物群落功能多样性显著低于马尾松;(4)土壤微生物群落的结构显著影响微生物的活性和功能多样性:土壤微生物群落碳源代谢的强度、多样性及丰富度与细菌磷脂脂肪酸含量呈极显著正相关,细菌特征脂肪酸14∶0、15∶0、a15∶0、i16∶0、16∶1ω7c、a17∶0和cy19∶0的含量显著影响土壤微生物群落碳代谢功能。上述结果表明:与本地种马尾松相比,引进种湿地松的凋落物显著改变了土壤微生物群落结构,降低了微生物群落的功能。

Litters are the important component of forest ecosystem and play a key role in plant growth and ecosystem nutrient cycle. Soil microbial communities, as one of the driving factors of forest litter decomposition, can significantly influenced by forest litter composition. Understanding the responses of soil microbial communities to litters is of great significance to evaluate the influence of exotic species. We designed a simulation experiment with flowerpots to determine the impacts of exotic slash pine （Pinus elliottii） litter on the structure and function of soil microbial communities in comparison with the native masson pine （Pinus massoniana） litter at the Ecological Benefit Monitoring Station of the Yangtze River Protection Forest, which is located in Hengyang County of southern Hunan Province. The structure and function of soil microbial communities were determined by PLFA （phospholipid fatty acids） and BIOLOG （single carbon metabolism） methods, respectively at two stages （decomposition for 5 months and 18 months）. The results showed that ： （ 1 ） the initial carbon- nitrogen ratio of slash pine litters was significantly higher than that of native species masson pine. （2） Phospholipid fatty acids concentrations of soil bacteria and actinomyces under the slash pine litter treatment was significantly lower than those under masson pine litter treatment at the two stages. And at the latter stage （decomposition for 18 months ）, the phospholipid fatty acids concentration of fungi and the fungi-bacteria ratio of soil microbial community under slash pine litter treatment were significantly higher in comparison with masson pine litter treatment. （3） Microbial function diversity under the slash pine litter treatment was significantly lower than that of masson pine litter treatment： the carbon metabolic intensity, richness and diversity of soil microbial communities under the slash pine litter treatment were significantly lower than those under masson pine litter treatment at the early stages, and the carbon metabolic intensity and richness of soil microbial communities under the slash pine litter treatment also were significantly lower than those under masson pine litter treatment at the latter stages. （4） The structure of soil microbial community significantly affected its activity and functional diversity ： The intensity and diversity of microbial carbon metabolism showed significantly positive correlations with bacterial phospholipid fatty acids. Characteristic phospholipid fatty acids concentrations of bacteria, 14：0, 15：0, a15：0, il6：0, 16 ：lω7c, al7：0 and cyl9：0 significantly correlated with the intensity and diversity of microbial carbon metabolism. Our results suggested that slash pine litter significantly changed the structure and decreased the function of soil microbial communities in comparison with masson pine litter.