Severity: Warning
Message: file_get_contents(https://...@gmail.com&api_key=61f08fa0b96a73de8c900d749fcb997acc09): Failed to open stream: HTTP request failed! HTTP/1.1 429 Too Many Requests
Filename: helpers/my_audit_helper.php
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File: /var/www/html/application/helpers/my_audit_helper.php
Line: 143
Function: file_get_contents
File: /var/www/html/application/helpers/my_audit_helper.php
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Function: simplexml_load_file_from_url
File: /var/www/html/application/helpers/my_audit_helper.php
Line: 3098
Function: getPubMedXML
File: /var/www/html/application/controllers/Detail.php
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Function: pubMedSearch_Global
File: /var/www/html/application/controllers/Detail.php
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Function: pubMedGetRelatedKeyword
File: /var/www/html/index.php
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Function: require_once
Severity: Warning
Message: Attempt to read property "Count" on bool
Filename: helpers/my_audit_helper.php
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File: /var/www/html/application/helpers/my_audit_helper.php
Line: 3100
Function: _error_handler
File: /var/www/html/application/controllers/Detail.php
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Function: pubMedSearch_Global
File: /var/www/html/application/controllers/Detail.php
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Function: pubMedGetRelatedKeyword
File: /var/www/html/index.php
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Function: require_once
Biocrusts are common biotic components in dryland ecosystems worldwide, they contain diverse soil organisms and effectively enhance soil stability and perform a series of key ecological functions. However, the geographical pattern of microbial communities in biocrusts is rarely assessed, despite it is closely related to the spatial variation of ecosystem functions in drylands. We assessed soil bacterial communities in biocrusts across four ecosystems (Gobi, desert, desert steppe and grassland) in a precipitation gradient (16-566 mm yr) in northern China. Bacterial OTU number and phylogenetic diversity did not linearly increase with decreasing aridity, they were significantly lower in Gobi and similar among desert, desert steppe and grassland. Soil bacterial community composition in Gobi and desert were different than those in desert steppe and grassland, and they were similar between Gobi and desert, this suggests the key role of habitat in structuring soil bacterial communities. The geographic pattern of soil bacterial communities was strongly influenced by both geographic distance and environmental factors. The first explanatory factor for the geographic variation of bacterial community dissimilarity differed among four ecosystems, being aridity in Gobi and desert, precipitation in desert steppe, and soil inorganic nitrogen in grassland. The geographic pattern of the bacterial functional group profile showed a similar pattern with community composition across four ecosystems, and the groups of containing mobile elements and gram negative bacteria were more abundant in drier habitats of Gobi and desert. Our results reveal the non-linear changes in diversity, composition and functional group of soil bacterial communities in biocrusts across the precipitation gradient from hyper-arid to semi-humid regions, and suggest that the geographic distance and habitat-specific environmental factors determine the distribution of soil bacterial communities in different ecosystems.
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Source |
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http://dx.doi.org/10.1016/j.scitotenv.2020.137479 | DOI Listing |
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