Larch forests are important for species diversity,as well as soil and water conservation in mountain regions.In this study,we determined large-scale patterns of species richness in larch forests and identified the fac...Larch forests are important for species diversity,as well as soil and water conservation in mountain regions.In this study,we determined large-scale patterns of species richness in larch forests and identified the factors that drive these patterns.We found that larch forest species richness was high in southern China and low in northern China,and that patterns of species richness along an elevational gradient depend on larch forest type.In addition,we found that patterns of species richness in larch forests are best explained by contemporary climatic factors.Specifically,mean annual temperature and annual potential evapotranspiration were the most important factors for species richness of tree and shrub layers,while mean temperature of the coldest quarter and anomaly of annual precipitation from the Last Glacial Maximum to the present were the most important for that of herb layer and the whole community.Community structural factors,especially stand density,are also associated with the species richness of larch forests.Our findings that species richness in China's larch forests is mainly affected by energy availability and cold conditions support the ambient energy hypothesis and the freezing tolerance hypothesis.展开更多
we preset the design and rabrication of a novel auai-iunction hign contrast gratings that can De usea as a polarizationselective beam splitter with transverse magnetic polarization,which performs two independent funct...we preset the design and rabrication of a novel auai-iunction hign contrast gratings that can De usea as a polarizationselective beam splitter with transverse magnetic polarization,which performs two independent functions,i.e.,reflection focusing and power equalization at a wavelength of 1550 nm.This dual-function grating profile is optimized by the rigorous coupled-wave analysis and the finite-element method.Simple analytical expressions of phase and modal guideline for the beam splitter design are given.The beam splitter based on the grating structure is experimentally studied at a distance of 160 μm from the reflection plane,the results are consistent with the theoretical results basically.展开更多
基金supported by the National Natural Science Foundation of China(No.31988102)the National Science and Technology Basic Project of China(No.2015FY210200).
文摘Larch forests are important for species diversity,as well as soil and water conservation in mountain regions.In this study,we determined large-scale patterns of species richness in larch forests and identified the factors that drive these patterns.We found that larch forest species richness was high in southern China and low in northern China,and that patterns of species richness along an elevational gradient depend on larch forest type.In addition,we found that patterns of species richness in larch forests are best explained by contemporary climatic factors.Specifically,mean annual temperature and annual potential evapotranspiration were the most important factors for species richness of tree and shrub layers,while mean temperature of the coldest quarter and anomaly of annual precipitation from the Last Glacial Maximum to the present were the most important for that of herb layer and the whole community.Community structural factors,especially stand density,are also associated with the species richness of larch forests.Our findings that species richness in China's larch forests is mainly affected by energy availability and cold conditions support the ambient energy hypothesis and the freezing tolerance hypothesis.
基金Project supported by the Open Fund of the State Key Laboratory of Information Photonics and Optical CommunicationBeijing University of Posts and Telecommunications,China(Grant No.IPOC2019A009)the National Natural Science Foundation of China(Grant Nos.61501214 and 61501213)。
文摘we preset the design and rabrication of a novel auai-iunction hign contrast gratings that can De usea as a polarizationselective beam splitter with transverse magnetic polarization,which performs two independent functions,i.e.,reflection focusing and power equalization at a wavelength of 1550 nm.This dual-function grating profile is optimized by the rigorous coupled-wave analysis and the finite-element method.Simple analytical expressions of phase and modal guideline for the beam splitter design are given.The beam splitter based on the grating structure is experimentally studied at a distance of 160 μm from the reflection plane,the results are consistent with the theoretical results basically.
