西北沙区梭梭根系深色有隔内生真菌等微生物时空分布及对根际土壤环境的响应

为揭示西北沙区不同时空尺度梭梭Haloxylon ammodendron根系深色有隔内生真菌（dark septate endophyte,DSE）分布规律及其环境驱动机制,分别于2019年7月、9月和12月在安西极旱荒漠国家级自然保护区和民勤连古城国家级自然保护区采集根系和土壤样品,根据真菌形态学特征、组织化学等方法,研究了梭梭根系DSE真菌定殖规律、定殖特征及其与土壤环境因子间的相互关系。结果表明,DSE真菌在自然生境梭梭根系广泛定殖,形成具有时空异质性的典型暗色有隔菌丝和微菌核结构。梭梭根系DSE真菌定殖受季节和空间分布影响,其中总定殖率在生长旺季7月最高（85.6%）,且菌丝隔间距显著大于9、12月;安西样地菌丝定殖率（71.5%）和总定殖率（85.6%）显著高于民勤样地（40.7%,60.0%）,但民勤样地微菌核直径显著高于安西样地。相关性分析表明,DSE定殖率及形态特征受土壤理化性质影响,温度、有效磷是影响DSE真菌定殖率的主要土壤因子,湿度和碱解氮是影响DSE真菌定殖形态的主要土壤因子。相比空白土壤,梭梭根际革兰氏阳性细菌含量、土壤脲酶活性以及安西样地有效磷含量均更高,预示其对荒漠土壤具有改善作用。本研究对梭梭DSE真菌时空分布和影响因素的系统性调查有助于为荒漠化治理和生态恢复提供依据。

Spatial and temporal distribution and the response to rhizosphere soil environment of dark septate endophyte and other microorganisms in roots of Haloxylon ammodendron in sand area of Northwest China

The distribution pattern and driving factors of dark septate endophyte (DSE) in roots of Haloxylon ammodendron across spatial and temporal scales in Northwest China were investigated. Soil and plant root samples were collected from Anxi Extreme-arid Desert National Nature Reserve and Minqin Liangucheng National Nature Reserve in July, September and December in 2019. Based on morphology and histochemistry assay, the relationship between the colonization characteristics of DSE fungi in the roots of H. ammodendron and soil factors were observed. The investigation showed that DSE fungi colonized extensively in the roots of H. ammodendron in natural desert habitats, forming typical dark and septate hyphae and microsclerotia with spatial and temporal heterogeneity. The DSE colonization pattern of H. ammodendron roots was affected by seasonal and spatial variability, and the total colonization rate was the highest in vigorous growth period in July (85.6%), and the hyphal septum interval was significantly distant in July than in September and December. The hyphal colonization rate (71.5%) and total colonization rate (85.6%) in Anxi were significantly higher than that in Minqin (40.7%, 60.0%), but the microsclerotium diameter was significantly increased in Minqin as compared with that in Anxi. The correlation analysis indicated that DSE colonization rate and morphological characteristics were affected by soil physical and chemical factors. Temperature and available phosphorus of soil were the main factors affecting DSE colonization rate, while humidity and alkali-hydrolyzed nitrogen were the main soil factors affecting DSE colonization characteristics. Compared with the blank soil, the content of Gram positive bacteria, the activity of soil urease and the available phosphorus content (in Anxi sample plots) in the rhizosphere soil of H. ammodendron were significantly higher, indicating that H. ammodendron could improve the desert soil. This study provides helpful reference material for desertification control and ecological restoration in dry areas of Northwest China.