荒漠油蒿（Artemisia ordosica）根围AM真菌分布与土壤酶活性

于2007年10月在油蒿(Artemisia ordosica)集中分布区选取4个典型样地,分别从0～10cm、10～20cm、20～30cm、30～40cm和40～50cm土层采集根围土样,分离其丛枝菌根(arbuscular mycorrhiza,AM)真菌并测定了3种土壤酶活性.结果表明,在各样地0～50cm土层中油蒿根系AM真菌菌丝定殖率均很高,有典型的泡囊与丛枝结构.菌丝定殖率与泡囊定殖率呈显著正相关,但菌丝、泡囊和丛枝定殖率与AM真菌孢子密度和土壤酶活性之间都无相关性;孢子密度在不同样地及采样深度间差异明显,与土壤有机质、速效磷和速效氮含量都呈一定正相关关系.孢子密度与脲酶和酸性磷酸酶活性有显著或极显著相关关系,与碱性磷酸酶活性之间的相关性受到土壤pH的显著影响.孢子密度的峰值出现在0～10cm表层土,并随土壤剖面深度增加而降低.土壤酶活性在土壤垂直剖面显示与孢子密度同样的规律.不同样地间AM真菌分布及油蒿根系定殖率的差异表明,油蒿与AM真菌之间有良好共生性,对维护荒漠生态环境系统结构的完整性具有重要意义.

Distribution of arbuscular mycorrhizal fungi and soil enzyme activities in the rhizosphere of Artemisia ordosica in desert

Soil samples in the rhizosphere of Artemisia ordosica distributed in west and northwest China desert were collected in October 2007 to isolate arbuscular mycorrhizal(AM) fungi, and to determine the soil enzyme activity in 0-10, 10-20, 20-30, 30-40 and 40-50 cm soil layers. The results showed that AM fungi had a relatively high hyphal colonization rate on the roots of A. ordosica, and the hyphal colonization rate was significantly and positively correlated with vesicular colonization rate. However, the colonization of hyphae, vesicles and arbuscules was not correlated to spore density and soil enzyme activities, while spore density was different among sites and soil depths, and was significantly and positively correlated with available P, N, and organic matter contents, urease and acid phosphatase activites. The correlation between the spore density and alkaline phosphatase activity was affected by pH. The maximal value of spore density occurred at the 0-10cm layer, and then gradually decreased with soil depth.The soil enzyme activities showed the same trend as the spore distribution. There was an obviously positive correlation between the activity of the three soil enzymes and soil fertility. This suggests that A. ordosica could establish well symbiosis with AM fungi, which was the main reason for maintaining integrity and stability of the desert ecosystem.