Biological soil crusts are essential components of arid ecosystems. We examined the variations in microfungal communities inhabiting different biological crust types in the vicinity of the Shapotou Research Station in...Biological soil crusts are essential components of arid ecosystems. We examined the variations in microfungal communities inhabiting different biological crust types in the vicinity of the Shapotou Research Station in the Tengger Desert, China. A total of 134 species from 66 genera were isolated using the soil dilution plate method. The mycobiota of the crusts from the Tengger Desert, similar to that of the Negev Desert in Israel, was dominated by melanin-containing species with large multicellular spores. Abundance of these xeric species increased spatially with increasing xeric conditions from moss-dominated to cyanobacterial crusts. Density of microfungal isolates displayed the opposite trend and was positively correlated with chlorophyll content, indicating the possible significant influence of organic matter content and wetness duration on fungal biomass. Within a chronosequence of the localities of different periods after sand stabilization with revegetation, little variations were revealed in species composition and isolate density of the crust microfungal communities, while a tendency towards a decrease in the community diversity level with the crust age was noted Microfungal communities from stabilized localities differed from those of the natural localities in abundance of the dominant and some frequent species, and in the fluctuations of diversity characteristics between the cyanobacterial and moss-dominated crusts. The variations in mycobiotie parameters in the soil crusts of the Tengger Desert were apparently associated with the topographically induced variations in abiotic conditions, while the differences in microfungal community of soil crusts between the Tengger and Negev deserts, such as the significantly higher abundance of thermotolerant species in the crusts of the Tengger Deserts, were caused by the principal differences in their precipitation regimes, associated with different rainy seasons, winter and summer in the Negev and Tengger deserts, respectively.展开更多
Leaf wetness duration(LWD)is a critical parameter used to predict plant disease,but its determination under actual field conditions is a major challenge.In this study,a method for determining LWD using thermal infrare...Leaf wetness duration(LWD)is a critical parameter used to predict plant disease,but its determination under actual field conditions is a major challenge.In this study,a method for determining LWD using thermal infrared imaging was developed and applied to cucumber plants grown in a solar greenhouse.Thermal images of the plant leaves were captured using an infrared scanning camera,and a leaf wetness area segmentation method consisting of two procedures was applied.First,a color space conversion was performed automatically by an image-processing algorithm.Then,the K-means clustering algorithm was applied to enable the segmentation of the wetness area on the thermal image.Subsequently,to enable overall thermal image analysis,an initial leaf wetness threshold(LWT)of 5%was defined(where wetness values higher than 5%indicated that the leaf was in a wet state).The results of comparative experiments conducted using thermal images of plant leaves captured using an infrared scanning camera and human visual observation indicated that the estimated LWD values were generally higher than the observed LWD values,because slight leaf wetness condensations were overlooked by the human eye but detected by the infrared scanning camera.While these differences were not found to be statistically significant in this study,the proposed method for determining LWD using thermal infrared imaging may provide a new LWD detection method for cucumber and other plants grown in solar greenhouses.展开更多
Over 100 human thermal indices have been developed to predict the combined thermal impact on the body.In principle,these indices based on energy thermal budget equations should not only be the most complex but also be...Over 100 human thermal indices have been developed to predict the combined thermal impact on the body.In principle,these indices based on energy thermal budget equations should not only be the most complex but also be the most accurate.However,the simple indices based on algebraic or statistical models[e.g.,the wet-bulb globe temperature(WBGT)]continue to be the most popular.A new heat stress index,the enthalpy dry-bulb temperature(EnD)for indoor environments is developed and validated in this study.The EnD index is unique in that it uses the air specific enthalpy,not the wet-bulb temperature,to measure the latent heat transfer from the skin to the surrounding environment.Theoretically,the EnD index can be treated as the equivalent temperature based on the convective heat transfer coefficient h_(c).Comparison is made between the EnD index and the widely used WBGT index based on the experimental data taken from three independent studies available in the scientific literature.The results show that the EnD index can reduce the overestimation of the dry-bulb air temperature and thus reduce heat stress in most cases,especially for hot and humid environments.It can be concluded that the EnD index has the potential to replace the WBGT index as the standard heat stress index in the future.展开更多
基金the Chinese Academy of Sciences Visiting Professorship for Senior International Scientists (No. 2011T1Z16)Israeli Ministry of Absorption for financial support of this research
文摘Biological soil crusts are essential components of arid ecosystems. We examined the variations in microfungal communities inhabiting different biological crust types in the vicinity of the Shapotou Research Station in the Tengger Desert, China. A total of 134 species from 66 genera were isolated using the soil dilution plate method. The mycobiota of the crusts from the Tengger Desert, similar to that of the Negev Desert in Israel, was dominated by melanin-containing species with large multicellular spores. Abundance of these xeric species increased spatially with increasing xeric conditions from moss-dominated to cyanobacterial crusts. Density of microfungal isolates displayed the opposite trend and was positively correlated with chlorophyll content, indicating the possible significant influence of organic matter content and wetness duration on fungal biomass. Within a chronosequence of the localities of different periods after sand stabilization with revegetation, little variations were revealed in species composition and isolate density of the crust microfungal communities, while a tendency towards a decrease in the community diversity level with the crust age was noted Microfungal communities from stabilized localities differed from those of the natural localities in abundance of the dominant and some frequent species, and in the fluctuations of diversity characteristics between the cyanobacterial and moss-dominated crusts. The variations in mycobiotie parameters in the soil crusts of the Tengger Desert were apparently associated with the topographically induced variations in abiotic conditions, while the differences in microfungal community of soil crusts between the Tengger and Negev deserts, such as the significantly higher abundance of thermotolerant species in the crusts of the Tengger Deserts, were caused by the principal differences in their precipitation regimes, associated with different rainy seasons, winter and summer in the Negev and Tengger deserts, respectively.
基金This study was supported by the China National Key R&D Program(2017YFE0122503)National Natural Science Foundation of China(31401683)+1 种基金Beijing Municipal Excellent Talents Project(2016000057592G260)and Postdoctoral Science Foundation of Beijing Academy of Agriculture and Forestry(968).The authors are also grateful to the research centre‘CIMEDES’at University of Almeria,Spain.
文摘Leaf wetness duration(LWD)is a critical parameter used to predict plant disease,but its determination under actual field conditions is a major challenge.In this study,a method for determining LWD using thermal infrared imaging was developed and applied to cucumber plants grown in a solar greenhouse.Thermal images of the plant leaves were captured using an infrared scanning camera,and a leaf wetness area segmentation method consisting of two procedures was applied.First,a color space conversion was performed automatically by an image-processing algorithm.Then,the K-means clustering algorithm was applied to enable the segmentation of the wetness area on the thermal image.Subsequently,to enable overall thermal image analysis,an initial leaf wetness threshold(LWT)of 5%was defined(where wetness values higher than 5%indicated that the leaf was in a wet state).The results of comparative experiments conducted using thermal images of plant leaves captured using an infrared scanning camera and human visual observation indicated that the estimated LWD values were generally higher than the observed LWD values,because slight leaf wetness condensations were overlooked by the human eye but detected by the infrared scanning camera.While these differences were not found to be statistically significant in this study,the proposed method for determining LWD using thermal infrared imaging may provide a new LWD detection method for cucumber and other plants grown in solar greenhouses.
文摘Over 100 human thermal indices have been developed to predict the combined thermal impact on the body.In principle,these indices based on energy thermal budget equations should not only be the most complex but also be the most accurate.However,the simple indices based on algebraic or statistical models[e.g.,the wet-bulb globe temperature(WBGT)]continue to be the most popular.A new heat stress index,the enthalpy dry-bulb temperature(EnD)for indoor environments is developed and validated in this study.The EnD index is unique in that it uses the air specific enthalpy,not the wet-bulb temperature,to measure the latent heat transfer from the skin to the surrounding environment.Theoretically,the EnD index can be treated as the equivalent temperature based on the convective heat transfer coefficient h_(c).Comparison is made between the EnD index and the widely used WBGT index based on the experimental data taken from three independent studies available in the scientific literature.The results show that the EnD index can reduce the overestimation of the dry-bulb air temperature and thus reduce heat stress in most cases,especially for hot and humid environments.It can be concluded that the EnD index has the potential to replace the WBGT index as the standard heat stress index in the future.