生草栽培对山核桃林地土壤养分及微生物多样性的影响

高强度经营导致山核桃林地土壤性质改变,设置了白三叶、黑麦草、油菜、紫云英、自然杂草和清耕(对照)6个处理,以3次重复,随机排列的2年田间试验,研究了不同生草栽培对山核桃林地土壤养分和微生物多样性的影响。结果表明:与清耕相比,生草栽培均能改善土壤养分状况,除全钾外,白三叶和紫云英处理较其他处理能显著提高土壤养分含量,其余几个处理间差异不明显;生草栽培显著提高了土壤微生物生物量碳(MBC)含量,白三叶、黑麦草、紫云英、油菜和自然杂草处理分别较清耕提高了169.6%、159.7%、144.1%、138.6%和58.6%,差异达显著水平(P0.05)。6种不同处理的土壤微生物活性(AWCD)、微生物Shannon指数和均匀度指数均存在明显差异。不同处理的土壤AWCD为白三叶紫云英油菜自然杂草黑麦草清耕;白三叶处理的土壤微生物Shannon指数高于其他处理;白三叶、紫云英和油菜处理的土壤微生物均匀度指数显著高于其他处理。相关性分析表明,土壤微生物活性、微生物Shannon指数和均匀度指数两两之间均达到极显著差异(P0.01),三者与土壤各养分指标之间未达显著差异,但表现为正相关关系。白三叶、紫云英和油菜对改善土壤微生物特性效果较好。

Effects of sod-cultural practices on soil nutrients and microbial diversity in the Carya cathayensis forest

Rapid development of the hickory (Carya cathayensis Sarg.) industry and excessive use of herbicides as well as other intensive management practices have resulted in serious damage to soil properties and forest vegetation. A decline in soil nutrients and a reduction in soil microbial biodiversity are often observed. To evaluate the potential of sod-culture to improve soil fertility and microbial activities of C. cathayensis forest soil, a 2-year field trial was initiated in 2010. In this study, six treatments (white clover, rye grass, oil rape seed, milk vetch, natural weeds and clean tillage (as CK)) each with three replicates were assessed in a randomized design. The effects of sod-culture treatments on soil nutrients and soil microbial biomass carbon in the C. cathayensis forest soil were measured. Changes in soil microbial diversity were also evaluated using Biolog. The results showed that there are various degrees of change in soil organic matter, available N, available K, available P, total N, total K and total P in C. cathayensis forest soil due to the different sod-culture treatments. Data indicated that except for soil total K, sod-culture treatments enhanced soil nutrient content significantly in the C. cathayensis forest soil as compared with the CK treatment. White clover and milk vetch treatments increased soil nutrient content to a greater extent than the other treatments. There was no significant difference in soil nutrient content between the remaining treatments. Sod-culture treatments increased soil microbial biomass carbon (MBC) in C. cathayensis forest soil as compared with the CK treatment. White clover, rye grass, oil rape seed, milk vetch and natural weed treatments significantly (P < 0.05) increased MBC by 169.6%, 159.7%, 144.1%, 138.6% and 58.6%, respectively. There were differences in soil microbial activity, Shannon diversity and uniformity indices between the six treatments. The Average Well Color Development sequence is as follows: white clover > milk vetch > oil rape seed > natural weeds > rye grass > CK. The Shannon index sequence is as follows: white clover > natural weeds > oil rape seed > milk vetch > rye grass > CK. The uniformity index sequence is as follows: white clover > milk vetch > oil rape seed > natural weeds > rye grass > CK. The Shannon index and uniformity index results were relatively uniform among different treatments. Using the Biolog 96 h absorbance values, principal component analysis was performed using Data Processing System software. The front nine principal components were extracted from the principal component analysis and their cumulative contribution accounted for 86.98% of the total variance. The variance contribution rates of PC1 and PC2 were 33.20% and 11.51%, respectively. The first two principal components (PC1 and PC2) were used for the analysis of soil microbial community functional diversity. The results showed that there is an obvious differentiation in the PC axis of different treatments. The PC1 axis distinguishes the white clover treatment and CK treatment from the other treatments. The white clover treatment sits on the most positive side of the PC1 axis, while the CK treatment sits on the negative side of the PC1 axis. Correlation analysis showed that there were significant differences (P < 0.01) among microbial activity, the Shannon diversity index and the uniformity index in any paired comparison, although there was no significant difference between these three indices and the soil nutrient indices, despite the fact that they were positively correlated. In conclusion, this study showed that planting white clover, milk vetch or oil rape seed will provide the best results for improving soil nutrients and microbial properties under C. cathayensis forest.