西宁南山4种灌木根际和非根际土壤微生物、酶活性和养分特征

西宁南山区植被退化情况严重,人工造林植被恢复被看作是最有效的恢复手段,其中选择合适造林树种尤为关键。选择人工种植的唐古特白刺Nitraria tangutorum、柠条Caragana korshinskii、西北小蘗Berberis vernae和短叶锦鸡儿Caragana brevifolia共4种灌木树种造林试验区为研究对象,通过测定根际和非根际土壤微生物数量、酶活性及养分含量,综合比较种植4种灌木树种根际和非根际土壤肥力差异,科学评价其对土壤的改善效果。研究表明:(1)土壤微生物数量和酶活性总体呈现出根际高于非根际的规律,仅放线菌数量和脲酶活性出现了根际低于非根际现象。(2)土壤养分方面,4种灌木根际土壤和非根际土壤p H值、全N、全P、全K含量差异不显著,有机质、有效P、速效K含量均呈现出根际非根际,而碱解N则是根际非根际。(3)土壤酶活性与土壤微生物数量相关性不显著,土壤有机质含量与土壤细菌、真菌数量呈极显著正相关,有效P含量与土壤细菌、真菌和放线菌数量呈极显著正相关,速效K含量与过氧化氢酶、酸性磷酸酶活性呈显著正相关,全N、碱解N含量均与脲酶活性呈显著正相关。(4)从土壤肥力综合水平来看,根际非根际,其中根际土壤中西北小蘗柠条短叶锦鸡儿唐古特白刺,研究结果表明西北小蘗和柠条能大幅提高土壤肥力,改良土壤效果较好。

Microbes, enzyme activities and nutrient characteristics of rhizosphere and non-rhizosphere soils under four shrubs in Xining Nanshan, Prefecture, China

Afforestation is the most effective method of revegetation and choosing suitable afforestation tree species is regarded as a key performance criterion. In this study, 4 shrub species (Nitraria tangutorum, Caragana korshinskii, Berberis vernae and Caragana brevifolia, planted in Xining Nanshan, Prefecture, China in 2009) were studied to measure microbial abundance, enzyme activities and nutrient characteristics of rhizosphere and non-rhizosphere soils. The variables measured included abundance of soil bacteria, fungi and actinomycetes, catalase activity, acid phosphatase activity, urease activity, pH, organic matter (OM), total nitrogen (N), total phosphorus (P), total potassium (K), hydrolysis N, available P and available K. The effects of shrubs on soil properties were evaluated by making a comprehensive comparison of the soil fertility of rhizosphere and non-rhizosphere soils. The results showed: 1) Microbial abundance and enzyme activities of rhizosphere soil were generally higher than non-rhizosphere soil except for the abundance of actinomycetes and urease activity. Specifically, only the total microbial abundance of rhizosphere soil under N. tangutorum was less than that of non-rhizosphere soil, and urease activity in rhizosphere soils under all 4 shrubs were lower than their non-rhizosphere soils; 2) Soil pH, N, P and total K contents of rhizosphere and non-rhizosphere soils were not significantly different. OM, P and available K of rhizosphere soils were significantly higher than non-rhizosphere soils, whereas available N was higher in non-rhizosphere than rhizosphere soils. These results showed that the presence of the 4 shrubs could improve soil OM, available P and available K contents through root aggregation; 3) There was no significant correlation between soil enzyme activities and soil microbial abundance, OM was significantly correlated with soil bacterial and fungal abundance, and soil available P content was significantly correlated with abundance of soil bacteria, fungi and actinomycetes. The soil available P content was significantly correlated with soil catalase and acid phosphatase activities and the soil total N and available N were significantly positively correlated with urease activity. From these results, the correlation between soil nutrients and enzyme activities differed from the correlation between soil nutrients and microbial abundance, thus soil enzyme activities and microbial abundance were proven to have a significant influence on soil nutrients; 4) The results of principal component analysis showed that soil bacterial abundance, fungal abundance, catalase activity, acid phosphatase activity, pH, OM, total N, total K and available P contents showed high factor loadings and these indexes could provide important information on soil fertility. In addition, principal component factor scores and synthetic scores of soil fertility levels showed that soil fertility of rhizosphere soils was significantly higher than non-rhizosphere soils. It showed that the soil fertility of rhizosphere soils ranked as follows: B. vernae > C. korshinskii > C. brevifolia > N. tangutorum. These results indicated that the soil improvement effect of B. vernae and C. korshinskii were better than the other 2 species, indicating that they may be suitable for afforestation in Xining Nanshan. B. vernae and C. korshinskii could be selected as afforestation tree species to help improve soil fertility and make contributions to revegetation. N. tangutorum was not suitable for afforestation in Xining Nanshan. Our research could provide important basic data and theoretical support for choosing suitable afforestation tree species for revegetation by artificial afforestation in Xining Nanshan.