摘要:采用空间与时间序列并用的方法，对贵州茂兰喀斯特森林阳坡和阴坡凋落物的分解特征及土壤微生物进行1年的野外调查和测定，探讨凋落物分解规律及其对土壤微生物群落的影响。凋落物在分解1年后的质量损失率约为72%，在分解过程中的碳、磷元素表现为释放，氮元素表现出富集；土壤微生物各群落磷脂脂肪酸（PLFA）在分解过程中的平均含量表现为：细菌（149.8 nmol/g） > 放线菌（63.9 nmol/g） > 真菌（31.3 nmol/g），阳坡和阴坡的微生物总PLFA在180d（559.2 nmol/g）和360d（513.6 nmol/g）的含量显著高于分解前；随分解时间的增加，阳坡细菌特征磷脂脂肪酸18：1ω7c的含量增加最大，其次是cy19：0和真菌特征磷脂脂肪酸18：1ω9c，阴坡土壤微生物PLFA含量表现出减少的趋势，细菌特征脂肪酸18：1ω7c减少量最大，约9.42 nmol/g，其次是i15：0和真菌特征脂肪酸18：1ω9c，约减少4.29-4.86 nmol/g；凋落物养分释放特征与微生物群落间的Spearman相关分析表明，真菌群落与碳元素释放率呈显著正相关关系，细菌群落与凋落物碳、磷元素的释放呈极显著正相关关系，且阳坡凋落物分解对微生物群落的影响高于阴坡。坡向和凋落物养分释放量对喀斯特森林凋落物的分解及土壤微生物群落的影响较显著，特征磷脂脂肪酸18：1ω7c、cy19：0、i15：0和18：1ω9c对环境变化的响应较为敏感。



Abstract:In this study, spatial and temporal methods were used to conduct field survey sampling and laboratory analysis of litterfall decomposition and soil microbe characteristics in the adret and ubac slopes of the karst forest ecosystem in Maolan, Guizhou. To provide a scientific basis for the monitoring of nutrient cycling and dynamic equilibrium in forest ecosystems, we systematically investigated the characteristics of litter decomposition and soil microbial communities in different slopes, and revealed the relationship between litter decomposition properties and soil microbial communities. We found that the mass loss rate of the litter in the decomposition bag during the 1-year decomposition period was approximately 72%. During the litter decomposition process, the carbon element was released and the total nitrogen content of the litter showed a tendency for enrichment. The total phospholipid fatty acid (PLFA) content in the adret and ubac slopes during litter decomposition was highest at 180 and 360 days, with values of 559.2 and 513.6 nmol/g, respectively. The content of the soil microbial community was in the order of Bacteria (149.8 nmol/g) > Actinomycetes (63.9 nmol/g) > Fungi (31.3 nmol/g). In the adret slope the bacterial characteristics of 18:1ω7c increased mostly after 360-days decomposition, followed by cy19:0, and the characteristic fungal PLFA 18:1ω9c compared to before the decomposition. The PLFA content in the ubac slope showed a decreasing trend. After decomposition of 360-days, the bacterial characteristic fatty acid 18:1ω7c exhibited the greatest decrease of approximately 9.42 nmol/g, followed by i15:0 and the fungal characteristic fatty acid 18:1ω9c, together showing decreases of approximately 4.29-4.86 nmol/g compared to the decomposition of 90-days. Spearman analysis indicated that a positive correlation was found between the fungal community and the carbon release rate. Additionally, there was a significant positive correlation between the bacterial community and litter carbon and phosphorus release, and the effect of litter decomposition on the microbial community was greater in the adret than the ubac slope. Slope and litter nutrient release produced the most significant effects on litter decomposition and on the microbial community in the karst forest; moreover, the characteristic PLFAs 18:1ω7c, cy19:0, i15:0, and 18:1ω9c were observed to be the most sensitive to environmental changes.





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