荒漠沙蒿根围AM真菌和DSE的空间分布

2009年7月在内蒙古黑城子北、多伦县城东和正蓝旗元上都遗址3个样地分别从0-10 cm、10-20 cm、20-30cm、30-40 cm和40-50 cm 5个土层采集沙蒿(Artemisia sphaerocephala)根围土壤和根样,系统研究了沙蒿根围AM真菌和DSE(Dark septate endophytes)的空间分布及与土壤因子的相关性。结果表明,沙蒿根系能被AM真菌高度侵染形成典型的I-型(Intermediate type)丛枝菌根,并发育形成泡囊和丛枝结构, 并与DSE形成良好的共生关系,样地生态条件和采样深度对AM真菌分布和活动有显著影响。黑城子样地孢子密度最高,元上都样地泡囊定殖率最高,不同样地间丛枝、菌丝、总定殖率和DSE定殖率无显著差异。孢子密度峰值出现在0-10cm表层土,并随土壤剖面深度增加而降低;泡囊定殖率峰值出现在10-20cm土层;AM真菌其他结构定殖率及DSE定殖率在各土层间差异不显著或变化无规律。孢子密度与AM真菌不同结构定殖率无显著相关性,与各土壤因子极显著正相关。泡囊定殖率与脲酶和碱性磷酸酶极显著负相关,与酸性磷酸酶显著负相关。菌丝定殖率、总定殖率及DSE定殖率与各土壤因子均无显著相关性。土壤碱解N和有机C与脲酶、酸性磷酸酶和碱性磷酸酶极显著正相关;土壤速效P与碱性磷酸酶极显著正相关,与脲酶显著正相关。对沙蒿根系AM真菌和DSE真菌分布和定殖规律的研究,可进一步明确AM真菌和DSE的生态功能,为利用菌根生物技术促进荒漠植被恢复和生态重建提供依据。

Spatial distribution of arbuscular mycorrhizal fungi and dark septate endophytes in the rhizosphere of Artemisia sphaerocephala from Inner Mongolia desert

Artemisia sphaerocephala is one of the excellent sand-fixation plants that can not only well stand up to arid desert environment, but also fix sand and promote desert management, so as to maintain the balance and stability of desert ecosystem. To elucidate the spatial distribution of AM fungi and dark septate endophytes (DSE) and the relativity of AM fungi and DSE with environmental factors associated with the common desert plant A. sphaerocephala, we sampled from three different sites in Inner Mongolia in July 2009, which are north of Hei Chengzi, east of Duo Lun and Yuan Shangdu, respectively. Root samples were collected from four robust A. sphaerocephala, and soil samples were taken from the rhizosphere of A. sphaerocephala in three sites and divided into five depth intervals, 0-10 cm, 10-20 cm, 20-30 cm, 30-40 cm and 40-50 cm respectively. The results showed that the roots of A. sphaerocephala could be highly infected by AM fungi and form a typical type of arbuscular mycorrhizal-Intermediate type (I-type). The distribution and activity of AM fungi were significantly affected by ecological conditions and soil depth and DSE established well symbiosis with rhizosphere of host plant as well. There were significant differences in spore density among the three sites. Spores were the densest in Hei Chengzi site and infecting rate reached the peak at the 0-10cm layer, and then gradually decreased with the increasing of soil depth. The colonization of vesicular in Yuan Shangdu site was higher than that in the other two sites and infecting rate reached the peak at the 10-20cm layer. No significant differences were found in the colonization of DSE and other structures of AM fungi, such as arbuscule, hypha and total colonizations, among different soil layers and different sample sites. There were significant positive correlations between spore density and each soil factors, such as available P, available N, organic matter, urease, acid phosphatase and alkaline phosphatase activity. Vesicular colonization had negative correlations with the activity of soil urease, alkaline phosphatase and acid phosphatase. Soil available N and organic matter had extreme positive correlations with the activity of soil urease, alkaline phosphatase and acid phosphatase (P<0.01). Soil available P was extremely positively correlated with the activity of alkaline phosphatase (P<0.01) and significantly positively correlated with soil urease (P<0.05). However, total colonizations and the colonizations of hyphae, and DSE had not significantly correlated to the soil factors (P>0.05). The formation of arbuscular mycorrhizal may be one of the effective countermeasures for A. sphaerocephala adapting barren drought desert environment. The research results provided basis and references for making full use of AM fungi resources and the foundation for further clarifying the ecological functions of DSE, and indicated that the ecological distribution and abundance of AM fungi and DSE might be a useful index to evaluate soil quality and function of desert ecosystem. Further research should concentrate on going into the dynamics of the relationships among AM fungi, DSE and the roots of the host plant.