| The site of Qinggeletu is located in the middle of Inner Mongolia, north China. Desertification is the most severe problem in grasslands and sandlands in north China. In the desertified grassland, seed germination and seedling growth are affected by many ecological factors, such as drought, high temperature, sand burial, and wind and water erosion. Wind erosion may reduce the content of nutrients, soil fertility and plant community diversity. In Inner Mongolia grassland of north China, sand burial is a common phenomenon caused by moving sand dunes. Plant shoots, seeds, and seedlings of sand dune plants are often buried by sand. Thus, plants must tolerate sand burial to survive and reproduce in sand dune habitats. Clonal plants, can invade open patches through clonal growth, which may greatly affect soil nutrition status and microbial communities of the invaded sites. Previous study indicated that clonal growth and integration play an important role in their clonal expansion, such as in supporting the survival of new ramet on sand dunes. Clonal plants are arid-active and sand-fixation plants which can not only conserve soil, but also block the wind, reduce soil erosion, and thus maintain the balance and stability of arid areas.Dark septate endophytes(DSE) are a class of micro-fungi which exhibit a broad range of host plants. DSE widely present in a variety of environments under stress. DSE may benefit their host plants by facilitating the uptake of water and mineral nutrients from soil, and suppressing infection by plant pathogens.To elucidate the symbiotic relationship between the DSE and clonal plants, ecological distribution and relationship with soil factors, soil samples were collected under clonal plants(Hedysarum laeve, Psammochloa villosa, Artemisia ordosica) at three different sites(foot-slope, mid-slope, top-slope) in Inner Mongolia. This study also elucidated the characteristics and laws of invasion of guerilla clonal plants. Simultaneously, isolated DSE from the three clonal plants and did the morphological and molecular identification. This research provides basis and references for further clarifying the ecological functions of DSE and making full use of DSE to promote vegetation restoration and soil conservation in arid areas.1. Three clonal plants could be infected by DSE, forming typical symbiotic structures, such as septate hyphae, microsclerotia, vesicle and so on. The morphology of DSE in different clonal plants were difference. The colors of hyphae, microsclerotia, vesicle of P. villosa were lighter than H. laeve and A. ordosica. The microsclerotia and vesicle of A. ordosica were densely distributed. The length of every hyphae septate of A. ordosica was shorter than H. laeve and P. villosa.2. Soil sampling sites and depth had a significant effect on colonization levels of DSE. DSE colonization of H. laeve and A. ordosica showed the following trend across sites: foot-slope > top-slope > mid-slope. But the colonization of P. villosa was foot-slope > mid-slope > top-slope. The greatest colonization levels of DSE of clonal plants were found in the first three layers, between 0–30 cm. DSE colonization of clonal plants had a positive correlation with soil factors. Principal component analysis showed that available K, acid and alkaline phosphatase were the key factors of H. laeve affecting soil nutrient status. Available N and acid phosphatase was the main factor of P. villosa. Available N, available K and acid phosphatase was the main factor of A. ordosica.3. With the time delay, DSE colonization rate of clonal plants had the same variation in two years, but the variation between different types of cloning plants are differences. DSE colonization in roots of H. laeve and A. ordosica increased gradually. But the lowest DSE colonization of P. villosa was in August. After the time extent, the content of available P was increased, but the contents of available N and acid phosphatase were decreased.4. The clonal plants gradually invaded the bare spaces of community from June to October. The number of invaded community of P. villosa was higher than that of H. laeve. The number of invaded spaces and ramets were foot-slope < mid-slope < top-slope.5. DSE colonization in roots of H. laeve community declined gradually with the sampling time. The highest colonization rate was found in roots sampled in June. In contrast, DSE colonization of P. villosa increased with the sampling time with the peak colonization rate in October. The invasion of clonal plants significantly increased the content of soil available nutrition, such as available N and P, which became more suitable for the growth of clonal plants. The invasion of clonal plants greatly affected DSE colonization and soil nutrition status, although such effects varied between different clonal plants. Both clonal plant species enhanced the contents of available nutrients. Clonal plants were superior to non-clonal plants in terms of sand fixation, and greatly improved self-healing ability in adverse environments.6. Seven DSE isolates have been obtained from the roots of three clonal plants: Alternaria arborescens, Pleosporales sp., Thielaviopsis basicola, Paraphoma chrysanthemicola, Leptosphaeria sp., Phoma radicina, Paraphoma radicina. H. laeve and P. villosa had two common species of DSE. P. villosa and A. ordosica had one common specie of DSE. The morphology and mycelium structure of seven DSE were difference. |
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