In drylands,biocrusts play crucial roles in regulating ecosystem functions.The study was conducted in the hilly rangelands of the semi-arid northern Negev of Israel,where we assessed the visual,morphological,spectral,...In drylands,biocrusts play crucial roles in regulating ecosystem functions.The study was conducted in the hilly rangelands of the semi-arid northern Negev of Israel,where we assessed the visual,morphological,spectral,and soil properties of livestock trampling routes and inter-route spaces in northern and southern facing hillslopes.Overall,both hillslope aspects were visually similar,whereas the ground surface of the routes was brighter(74.4%were characterized as having a'light'color)than the inter-route spaces(86.8%were characterized as having a'dark'color).These observations were supported by morphological identification of biocrust composition,which was dominated by cyanobacteria(67%)in the routes,and by mixed cyanobacteria/moss(56%)in the inter-routes.Mean Normalized Difference Vegetation Index(NDVI)was 24%higher in the inter-routes,while the mean Brightness Index(BI)was 12%higher in the routes.At the same time,the mean Crust Index(CI)was identical in the two microhabitats.Soil quality index(SQI),calculated based on the(pedoderm)soil properties of the two microhabitats,was 6%greater in the inter-routes than in the routes.This study suggests that recurrent trampling exacerbates soil compaction and shearing along the routes,thus preventing the successional development of complex biocrust compositions.展开更多
The effects of slope aspects on soil biogeochemical properties and plant communities in forested environments have been studied extensively; however, slope aspect influence on soil microbial communities remains largel...The effects of slope aspects on soil biogeochemical properties and plant communities in forested environments have been studied extensively; however, slope aspect influence on soil microbial communities remains largely unexamined, despite the central role of soil biota in ecosystem functioning. In this study, the communities of both soil bacteria and arbuscular mycorrhizal fungi （AMF） were investigated using tagged pyrosequencing for three types of slope aspects （south-facing aspect, north-facing aspect and flat area） in a boreal forest of the Greater Khingan Mountains, China. The bacterial and AMF community composition differed with slope aspects. Bacterial diversity was the lowest on the north-facing aspect, and AMF diversity was the lowest on the flat area. Aspects also had a significant impact on soil pH and available phosphorus （P） and shrubby biomass. Soil pH and understory shrub biomass were significantly correlated with bacterial communities, and soil available P and shrub biomass showed significant correlations with AMF communities. Our results suggested that slope aspects affected bacterial and AMF communities, mediated by aspect-induced changes in plant community and soil chemical properties （e.g., pH and available P）, which improved the knowledge on the effects of forest slope aspects on aboveground and belowground communities.展开更多
文摘In drylands,biocrusts play crucial roles in regulating ecosystem functions.The study was conducted in the hilly rangelands of the semi-arid northern Negev of Israel,where we assessed the visual,morphological,spectral,and soil properties of livestock trampling routes and inter-route spaces in northern and southern facing hillslopes.Overall,both hillslope aspects were visually similar,whereas the ground surface of the routes was brighter(74.4%were characterized as having a'light'color)than the inter-route spaces(86.8%were characterized as having a'dark'color).These observations were supported by morphological identification of biocrust composition,which was dominated by cyanobacteria(67%)in the routes,and by mixed cyanobacteria/moss(56%)in the inter-routes.Mean Normalized Difference Vegetation Index(NDVI)was 24%higher in the inter-routes,while the mean Brightness Index(BI)was 12%higher in the routes.At the same time,the mean Crust Index(CI)was identical in the two microhabitats.Soil quality index(SQI),calculated based on the(pedoderm)soil properties of the two microhabitats,was 6%greater in the inter-routes than in the routes.This study suggests that recurrent trampling exacerbates soil compaction and shearing along the routes,thus preventing the successional development of complex biocrust compositions.
基金We thank Ms. LIU Weili, Dr. CAI Wenhua, Mr. LIU Bo, and Dr. FANG Lei from the Institute of Ap- plied Ecology, Chinese Academy of Sciences for assis- tance in sampling and Dr. XIONG Jingbo from the Ningbo University of China for assistance in bioinfor- matic analysis. This research was supported by the Strategic Priority Research Program of Chinese Aca- demy of Sciences （No. XDB15010101）, the National Basic Research Program （973 Program） of China （No. 2014CB954002）, and the National Natural Science Foundation of China （No. 41371254）.
文摘The effects of slope aspects on soil biogeochemical properties and plant communities in forested environments have been studied extensively; however, slope aspect influence on soil microbial communities remains largely unexamined, despite the central role of soil biota in ecosystem functioning. In this study, the communities of both soil bacteria and arbuscular mycorrhizal fungi （AMF） were investigated using tagged pyrosequencing for three types of slope aspects （south-facing aspect, north-facing aspect and flat area） in a boreal forest of the Greater Khingan Mountains, China. The bacterial and AMF community composition differed with slope aspects. Bacterial diversity was the lowest on the north-facing aspect, and AMF diversity was the lowest on the flat area. Aspects also had a significant impact on soil pH and available phosphorus （P） and shrubby biomass. Soil pH and understory shrub biomass were significantly correlated with bacterial communities, and soil available P and shrub biomass showed significant correlations with AMF communities. Our results suggested that slope aspects affected bacterial and AMF communities, mediated by aspect-induced changes in plant community and soil chemical properties （e.g., pH and available P）, which improved the knowledge on the effects of forest slope aspects on aboveground and belowground communities.
