Ecological Study On Arbuscular Mycorrhiza Of Caragana Korshinskii At Loess Gully Region

Arbuscular mycorrhizal fungi (AMF) which have a wide distribution in nature, can form arbuscular mycorrhiza (AM) symbiosis with most of the terrestrial plants. In the past decades, AMF has been full appreciated for its physiological and ecological functions. AMF diversity not only determines the plant diversity, but also it may play an important role in ecosystem variability and productivity. Recent years, investigations of the AMF communities in various ecosystems have been attracting increasing attention. However, study of AMF communities of artificial plantations which frequently used in vegetation rehabilitation programs were often ignored.Caragana korshinski, a leguminous shrub, is the dominant plant species which was widely used in vegetation rehabilitation programs in the Loess Plateau of Northwest China. However, understanding of the AMF community in Caragana korshinski is very poor. For finding out the relationship between AMF and Caragana korshinski plantations, we used microscopic inspection of stained roots and PCR-DGGE technique to investigate the diversity and ecology of AMF in different age (5-, 13-, 20-, 42-years) of Caragana korshinskii plantations in Gully Region of Loess Plateau. The main results showed:1. Caragana korshinskii can form intimate symbiosis with AMF and the AM morphological type is Arum-type. The percent of AM colonization was above 80% in all samples, while it had a down trend with the increase of plant age, the highest colonization rate was the 5-years old Caragana korshinskii. A significant effect of season on AM colonization did occur and was attributable to maximum colonization levels in the beginning growth season (April) and minimum levels in the end of growth (October).2. Spores density and percent of AMF colonization were significantly correlated with some soil properties. Spores density increased with increasing soil moisture but was inversely related to soil available P and total P, percent of AMF colonization was positively correlated with soil organic carbon. 3. We Used PCR-DGGE method to estimate the molecular diversity of AMF in Caragana korshinskii and found the AMF diversity was low in these artifical plantations. Total of eight AMF species which belong to the genus of Glomus were detected in all samples, these AMF species including: Gfasciculatum, Gintraradices, Gcaledomium, Gspl, Gsp2, Gsp3, Gsp4 and Gsp5. Communities composition of AMF in different seasons had some difference. In April, five AMF species including of Gfasciculatum, Gcaledomium, Gspl, Gsp2 and Gsp5 were detected in Caragana korshinskii roots. In July, four AMF species including of Gfasciculatum, Gintraradices, Gsp3, and Gsp5 were detected. Additionaly, AMF species composition in October was similar to July, just only Gsp4 replaced the Gsp3. However, there had no change in the composition of the AMF communities across the Caragana korshinskii plantation chronosequence. Contrarily, AMF communities were quietly steady regardless of the succession dynamic of the plantation. This outcome was probably leaded by the little edaphic variation and the prominently positive feedback interaction between AMF and plant communities during the Caragana korshinskii plantation succession.