荒漠草原不同植物根际与非根际土壤养分及微生物量分布特征

通过对宁夏荒漠草原6种地带性优势物种长芒草、蒙古冰草、甘草、牛心朴子、黑沙蒿和苦豆子植物根际与非根际土壤养分和微生物量分布特征进行研究,探讨不同植物根际养分的富集的相关性和差异性。研究结果表明:6种植物根际土壤养分和微生物量均表现出明显的富集效应,根际富集率大小依次为菊科(黑沙蒿)豆科(苦豆子、甘草)禾本科(长芒草、蒙古冰草)萝藦科(牛心朴子);全磷(TP)在根际和非根际中无显著差异(P0.05),其它土壤养分及理化指标在根际中均表现出显著富集(P0.05),土壤养分中以有机碳(SOC)的富集作用最为明显;土壤有效态养分较全量养分对植物根际微小的变化响应更为灵敏;不同荒漠植物根际与非根际SOC与全氮(TN)呈极显著线性关系(P0.01),TN与碱解氮之间呈极显著线性关系(P0.01),TP与有效磷(AP)没有显著的相关性(P0.05)。荒漠植物土壤有效养分在根际存在一定的富集,灌木和豆科植物的根际效应的大于禾本科植物,它们通过降低根际pH值可以提高根际养分,有利于在脆弱环境下对土壤养分的有效利用。

Distribution of soil nutrient and microbial biomass in rhizosphere versus non-rhizosphere area of different plant species in desertified steppe

Six plant species, Stipa bungeana, Agropyron mongolicum Keng, Glycyrrhiza uralensis Fisch., Cynanchum komarovii Al., Artemisia ordosica, and Sophora alopecuroides dominate the desertified steppe ecosystems in Ningxia, northern China. However, the distribution of soil nutrients and microbial biomass in the rhizosphere and non-rhizosphere areas of these six plant species in this region has been largely unknown. This study investigated soil nutrients, microbial biomass, and soil physicochemical properties in the rhizosphere and non-rhizosphere areas of these six desert plant species, together with soil physicochemical properties. The results showed that rhizosphere enrichment followed the order shrub (A. ordosica) > Leguminosae (S. alopecuroides, G. uralensis Fisch.) > Gramineae (S. bungeana, A. mongolicum) > Compositae(C. komarovii Al.). In the rhizosphere area, a significant enrichment effect (P < 0.05) was found on the soil nutrients and microbial biomass, but not on the total phosphorus (TP) (P > 0.05). The rhizosphere enrichment effect on soil organic carbon (SOC) was more pronounced than the other indices (i.e., soil nutrients and physicochemical properties), and soil nutrient availability was more sensitive to the changes in the rhizosphere among plant species. In the rhizosphere and non-rhizosphere soil of different desert plant species, a significant linear correlation was observed (P < 0.01) between SOC and total nitrogen (TN) and a significant linear correlation between TN and alkaline hydrolysis nitrogen (P < 0.01), but no significant correlation was observed between TP and available phosphorus (AP) (P > 0.05). The results suggested that the rhizosphere enrichment effect occurred for many desert plant species. Shrubs and leguminous plants had a significantly higher rhizosphere effect than the other herbaceous species. Rhizosphere enrichment effect was found to increase soil nutrients by reducing soil pH, and this was beneficial for the efficient utilization of soil nutrients in the susceptible desertified steppe ecosystems.