荒漠土壤因子和DSE定殖对克隆植物入侵的响应

克隆植物,尤其是游击型克隆植物,具有很强的扩展能力,通过克隆扩展可侵入到不同生境斑块。克隆植物入侵可能会影响入侵地土壤营养状况和微生物群落。为了探明克隆植物入侵对DSE(dark septate endophytes)活动和土壤理化性质的影响,于2013年6月在克隆植物羊柴(Hedysarum laeve)和沙鞭(Psammochloa villosa)群落空地沿根状茎延伸方向设置样方,分别于6月、8月和10月在样方内分0—10、10—20、20—30、30—40、40—50 cm土层采集土样和根样,研究了不同采样时间羊柴和沙鞭群落空地DSE和土壤理化性质时空变化。结果表明,从6月到10月,随时间后延,克隆植物逐渐侵入群落空地,沙鞭入侵群落空地数和分株数高于羊柴。羊柴群落空地根系DSE定殖率随采样时间后延,逐渐降低,最大值在6月;沙鞭群落空地根系DSE定殖率随采样时间后延,逐渐升高,最大值在10月。随着克隆植物入侵,入侵地土壤中可利用的营养物质含量显著提高,羊柴入侵提高了入侵群落空地土壤碱解N、有效P和速效K含量,沙鞭入侵提高了入侵群落空地土壤碱解N和有效P含量。相关性分析表明,羊柴群落空地DSE定殖率与土壤p H值和电导率显著正相关,沙鞭群落空地DSE定殖率与土壤p H值极显著负相关,与电导率、碱解N和有效P极显著正相关。克隆植物入侵使得土壤环境更有利于克隆植物自身生长,为荒漠植被恢复提供了前提。

Responses of desert soil factors and dark septate endophytes colonization to clonal plants invasion

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. 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, especially guerilla ones, 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. Psammochloa villosa produces linear monopodially growing rhizomes and it mainly relies on clonal growth to sustain and renew its populations. Hedysarum laeve is one of the 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), a miscellaneous group of ascomycetes, colonize root tissues intracellularly and intercellularly without causing apparent negative effects on the host plant. DSE fungi exhibit a broad range of host plants. DSE may benefit their host plants by facilitating the uptake of water and mineral nutrients from soil, and suppressing infection by plant pathogens. To investigate the effects of the growth of clonal plants on the activities of DSE and soil physical and chemical properties of invaded sites in Inner Mongolia, China, soil samples (0-50 cm depth) were collected under two guerilla-type, rhizomatous clonal plants, H. laeve and P. villosa, in June, August and October in 2013, respectively. The results showed that 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. 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. DSE colonization rate in H. laeve root systems in the bare spaces positively correlated with soil pH and electrical conductivity. Whilst for P. villosa, DSE colonization rate had strong negative correlation with soil pH, but had positive correlation with soil electrical conductivity, available N and available P, respectively. We concluded that the invasion of clonal plants greatly affected DSE colonization and soil nutrition status, although such effects varied between different clonal plants. Our findings showed that 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.