蒙古沙冬青伴生植物AM真菌的空间分布

Exploration of the spatial distribution of AM fungi in the rhizospheres of Ammopiptanthus mongolicus-associated plants

进一步探究荒漠植物与AM(arbuscular mycorrhiza)真菌共生关系及其生态适应性,为以蒙古沙冬青为建群种适生区的植被恢复与生态改良提供依据。于2013年6月在内蒙古荒漠带选取以蒙古沙冬青为建群种的3个样地乌海、磴口和阿拉善,从每个样地选择2种主要伴生植物,按0—10、10—20、20—30、30—40、40—50 cm共5个土层采集土样和根样,研究了蒙古沙冬青伴生植物AM真菌空间分布及其与土壤因子的关系。从梭梭(Haloxylon ammodendron)、油蒿(Artemisia ordosica)、柠条锦鸡儿(Caragana korshinskii)和蒙古扁桃(Amygdalus mongolica)4种伴生植物根围土壤共分离鉴定4属25种AM真菌,其中球囊霉属(Glomus)14种,无梗囊霉属(Acaulospora)7种,管柄囊霉属(Funneliformis)3种,盾巨孢囊霉属(Scutellospora)1种,优势菌种为网状球囊霉(Glomus reticulatum),AM真菌属种分布具有不均衡性和地域性。4种伴生植物根系均能与AM真菌形成I-型(intermediate type)丛枝菌根,其共生程度和定殖规律具有明显空间异质性。AM真菌种数随土层深度增加而下降。AM真菌最大定殖率在10—30 cm土层,最大孢子密度在10—20 cm土层。相关性分析表明,AM真菌菌丝与土壤有机C极显著正相关(P<0.01),与易提取球囊霉素(EEG)显著负相关(P<0.05);孢子密度与有机C、碱性磷酸酶极显著负相关(P<0.01),与碱解N极显著正相关(P<0.01)。主成分分析表明,土壤有效P、酸性磷酸酶、碱性磷酸酶和总球囊霉素(TEG)等土壤因子能综合反映内蒙古荒漠带营养状况。TEG和EEG平均含量分别为4.76 mg/g和1.62 mg/g,占土壤有机C平均含量为61.26%和20.8%,说明在贫瘠荒漠环境中球囊霉素是土壤有机碳库重要来源和组成部分。

Ammopiptanthus mongolicus （Leguminosae） is the only endangered broadleaf evergreen shrub endemic to the deserts of northwest China, and plays a number of vital roles. A. mongolicus and its associated plants undergo competition inhibition and cooperative evolution, and are thought to be the ideal plants for use in the improvement of arid desert areas and the prevention of desertification. In this study, the symbiotic relationship between these desert plants and AM fungi was explored, along with their ecological adaptations, in order to establish a basis for vegetative restoration and ecological improvement projects involving the planting of Ammopiptanthus mongolicus. In order to elucidate the activity and ecological distribution of arbuscular mycorrhizal （AM） fungi in the desert ecosystem of northwest China, this study investigated the ecological distribution of AM fungi, and their symbioses with A. mongolicus-associated plants. We collected soil and root samples from three different sites in Dengkou, Wuhai, and Alxa, and selected two dominant A. mongolicus-associated plants from each site in the Inner Mongolian desert, in June 2013. Soil and root samples from under A. mongolicus-associated plants were collected at each site, at five depths in the soil profile：0-10, 10-20, 20-30, 30-40 cm, and 40-50 cm, and two dominant species of A. mongolicus-associated plants were collected at each site. The distribution of the AM fungi was found to be spatially heterogeneous and strongly influenced by soil characteristics. A total of 25 AM fungal species belonging to 4 genera were isolated from the soil under four A. mongolicus-associated plants：Haloxylon ammodendron, Artemisia ordosica, Caragana korshinskii, and Amygdalus mongolica. Of these fungi, 14 species belong to Glomus, 7 to Acaulospora, 3 to Funneliformis, and 1 to Scutellospora. Glomus reticulatum was the dominant fungal species, and its distribution was found to be spatially heterogeneous. Strong, spatially heterogeneous symbiotic relationships were formed between the A. mongolicus-associated plants and the AM fungi. The highest density of fungal hyphae and vesicles was found in the 10-30 cm soil layer, and the highest spore density was found in 10-20 cm soil layer. The number of AM fungal species decreased as soil depth increased. This might be due to the lower organic content and oxygen availability found in deeper soil layers, because fungi are sensitive to oxygen deprivation. Hyphal colonization was positively correlated with organic C （P〈0.01） and negatively correlated with easily extractable glomain （EEG） （P〈0.05）. Spore density was negatively correlated with organic C and alkaline phosphatase （P〈0.01）, and positively correlated with available N （P〈0.01）. Principal component analysis showed that available P, acid phosphatase, alkalin phosphatase, and total extractable glomain （TEG） can be used to determine the nutritional status of the soil of the Inner Mongolian desert. The average TEG and EEG content of the soil was 4.76 and 1.62 mg/g, and accounted for 61.26% and 20.8% of soil organic carbon, respectively. This result indicated that glomalin was the main source of soil organic C in the Inner Mongolian desert. By comparing these results with the results of previous studies, it was determined that the total colonization and spore density of A. mongolicus is higher than that of its associated plants, which demonstrates that the AM symbiont facilitates the adaptation of A. mongolicus to this extreme desert environment. This study provides a basis for the effective use of AM fungal resources to promote the growth of host plants, and thus facilitate the vegetative restoration of desert areas.