三种土壤条件下紫茎泽兰根际的酶活性及细菌群落状况

紫茎泽兰被列为我国危害最严重的外侵植物,为探索其侵入机制,以四川省凉山州的3种主要土壤?红壤、黄壤和紫色土为研究对象,比较了根际和非根际土壤(距离根系约20 cm)的酶活性及细菌群落。结果表明,尽管土壤类型不同,根际酶活性(过氧化氢酶、酸性磷酸酶、脲酶和蔗糖酶)及微生物量碳氮显著高于非根际,说明紫茎泽兰的根系生命活动促进根际微生物生长繁殖,数量增加,活性增强,有益于土壤养分供应,促进紫茎泽兰生长,提高生存竞争优势。在不同类型的土壤中,紫茎泽兰根际细菌的分类单元数和主成分方差比非根际降低或无显著变化,说明紫茎泽兰对土壤细菌群落的影响因土壤而异。3种土壤的优势菌株种类差异极大,根际20种优势细菌中仅链霉菌1(Streptomyces1)为共有菌株,非根际仅有绿弯菌(Chloroflexi KD4-96)为共有菌株,说明紫茎泽兰能在细菌群落不同的土壤上生长,具有极强的适应性。但是,3种土壤的优势细菌均为放线菌门、变形菌门和拟杆菌门,合计占细菌总量的60.69%—78.75%;就同一种土壤而言,根际20种优势细菌中有8—11株与非根际相同。因此,土壤类型是决定细菌群落的主要因素,但因紫茎泽兰入侵而发生一定程度的变化。

Enzyme activities and bacterial community in the rhizosphere of Eupatorium adenophorum under different soil conditions

Eupatorium adenophorum is a harmful invasive plant in China. To understand the invasion mechanisms, three soils widespread in Liangshan Prefecture, Sichuan Province, including red, yellow, and purple soils with prosperous E. adenophorum growth, were collected to study enzyme activities and bacterial communities in the rhizosphere and non-rhizosphere (about 20 cm from the roots). The results showed that enzyme activities such as catalase, acid phosphatase, urease, and sucrase, and microbial biomass carbon and nitrogen in the rhizosphere were significantly higher than that in the non-rhizosphere. Enhanced microbial growth and propagation resulting from E. adenophorum root metabolism activities could increase the numbers of microbes and stimulate their activities, which could benefit soil nutrient supply, resulting in the prosperous growth and strong competition of E. adenophorum in ecosystems. In the three tested soils, bacterial taxon types and principle component variances in the rhizosphere of E. adenophorum decreased or changed more narrowly than that in the non-rhizosphere, indicating that the effects of E. adenophorum on bacterial community structures varied with different soils. There were also huge differences in predominant bacteria among the three tested soils. Only Streptomyces-1 was common in the top 20 predominant bacteria in the rhizosphere of the three studied soils, and Chloroflexi KD4-96 was common in the non-rhizosphere. This suggests that E. adenophorum could grow well in various soils owing to a strong adaptability to environments. However, Actinobacteria, Proteobacteria, and Bacteroidetes were dominant in all studied soils, accounting for 60.69%-78.75% of the total bacteria. In each soil type, 8-11 bacterial strains in top 20 predominant bacteria were commonly present in the rhizosphere or non-rhizosphere of E. adenophorum, suggesting that soil types were the main factor that governed bacterial communities, which could be changed to some extent by E. adenophorum invasion.