荒漠沙柳根围AM真菌的空间分布

为探明荒漠植物沙柳(Salix psammophila)根围AM真菌空间分布和土壤因子生态作用，2009年5月在内蒙古黑城子、正蓝旗、元上都3个样地分别从0—10、10—20、20—30、30—40、40—50cm 5个土层采集沙柳根围土壤样品，系统研究了AM真菌空间分布及与土壤因子的相关性。结果表明，沙柳根围AM真菌平均孢子密度为108个?100g-1 土，平均定殖率61.7%；沙柳与AM真菌可形成良好的I型丛枝菌根。不同样地和采样深度对AM真菌孢子密度和定殖率有显著影响，最大孢子密度和最高定殖率均出现在0—10cm土层，并随土层深度增加而下降。黑城子样地孢子密度显著高于其它样地。沙柳根围土壤总球囊霉素(TEG)和易提取球囊霉素(EEG)含量在3个样地均随土层加深而降低，平均值分别为0.24mg?g-1和 0.16mg?g-1，占土壤有机C 23.6%—24.6% 和14.9%—17.3%。相关分析表明，土壤速效P、碱解N与孢子密度显著负相关；土壤有机C与菌丝定殖率显著正相关，与泡囊定殖率显著负相关；土壤磷酸酶与孢子密度和侵染强度极显著正相关；土壤脲酶与孢子密度和定殖率极显著正相关；土壤总球囊霉素和易提取球囊霉素与土壤有机C极显著正相关。主成分分析表明，土壤有机C、磷酸酶和碱解N是影响荒漠土壤AM真菌分布和活动的主要因子。上述结果对进一步探明宿主植物、菌根和土壤三者之间的内在联系，充分利用AM真菌资源，促进荒漠植被恢复和生态重建具有重要意义。

Spatial distribution of arbuscular mycorrhizal fungi in Salix psammophila root- zone soil in Inner Mongolia desert

Arbuscular mycorrhizal fungi are important soil microorganisms belonging to the phylum Glomeromycota, and have a ubiquitous distribution in global terrestrial ecosystems. They are a living bridge for the translocation of nutrients from soil to plant roots and of carbon from plant roots to the soil. Glomalin is a recently discovered glypoproteinaceous substance produced by hyphae and spores of AM fungi that play an important role in structuring soil. Salix psammophila is one of the excellent sand-fixation plants that can not only well stand up to arid desert environment, but also maintain the balance and stability of desert ecosystem. To elucidate the spatial distribution of AM fungi and glomalin and explain the relativity of AM fungi and glomalin with soil factors in rhizosphere of S. psammophila, we sampled from three different sites such as Heichengzi, Zhenglanqi and Yuanshangdu in Inner Mongolia in May 2009. Root samples were taken from four robust S. psammophila, and soil samples from five strata, from ground to deeper layers: 0-10 cm, 10-20 cm, 20-30 cm, 30-40 cm, 40-50 cm, respectively. The results showed that a good symbiotic relation, intermediate type of clumping mycorrhizomata, was formed between AM fungi and S. psammophila; the mean density of AM fungi was 108 spores per 100 g of soil, with a mean of total colonization of 61.7%. There was no significant difference on the total colonization of AM fungi among the three sampling sites (P > 0.05); but the spore densities of AM fungi differed significantly (P < 0.05), with the value at Heichengzi ranking the first. All the highest spore densities were found in the layer of 0-10 cm, and the values decreased with layers deepened. The contents of total extractable glomalin (TEG) and easily extractable glomalin (EEG) were affected by ecological conditions, and also decreased with layers deepened. The means of TEG and EEG were 0.24 and 0.16 mg?g-1, accounting for 23.6 - 24.6% and 14.9 - 17.3% of soil organic matter. Both available P and available N in the soil samples showed a negative correlation on spore density (P < 0.05); hyphal colonization was positively correlated with soil organic matter (P < 0.05), but was vesicular colonization negatively done (P < 0.05). Soil phosphatase had a significantly positive correlation with spore density and colonization intensity (P < 0.01). Soil urease was extremely positively correlated with the spore density and colonization (P < 0.01). TEG and EEG were closely related to soil organic matter (P < 0.01). Principal component analysis showed that soil organic matter, phosphatase and available N were the key factors affecting distributions and activities of AM fungi in the desert of Inner Mongolia. The results of the study suggested that glomalin be an appropriate index related to the level of soil fertility, especially in desert areas. Moreover, the paper revealed the relationship among the host plant, AM fungi and the soils, which might be significant to promote vegetative and ecological restoration in deserts.