Horqin Sandy Land is a fragile,seriously desertified region located in Inner Mongolia of China.Overgrazing is one of the primary drivers of desertification in this region.We investigated whether the establishment of g...Horqin Sandy Land is a fragile,seriously desertified region located in Inner Mongolia of China.Overgrazing is one of the primary drivers of desertification in this region.We investigated whether the establishment of grazing exclosures in areas with active sand dunes enhances soil carbon(C) sequestration and benefits soil recovery.The results showed that soil organic C storage was 1.4,1.9,and 3.5 times,and light fraction C storage was 2.3,3.2,and 4.4 times in the 100-cm topsoil after 7,12,and 25 years of grazing exclusion,respectively,compared to the case in active sand dunes.The light fraction of soil played an important role in soil C sequestration,although it might not change rapidly to provide an early indication of how soil C is increasing in response to grazing exclusion.The results indicated that soils could potentially sequester up to 13.8 Mt C in 25 years if active sand dunes in the study area were to be protected by exclosures.This corresponds to 12.8% of the estimated carbon loss(107.53 Mt) that has been associated with desertification over the past century in the Horqin Sandy Land.Our results suggested that exclosures have the capacity to increase soil C sequestration;however,decades will be required for soil C to recover to historical grassland levels observed prior to desertification.展开更多
Determining an optimal sample size is a key step in designing field surveys,and is particularly important for detecting the spatial pattern of highly variable properties such as soil organic carbon(SOC).Based on 550 s...Determining an optimal sample size is a key step in designing field surveys,and is particularly important for detecting the spatial pattern of highly variable properties such as soil organic carbon(SOC).Based on 550 soil sampling points in the nearsurface layer(0 to 20 cm)in a representative region of northern China's agro-pastoral ecotone,we studied effects of four interpolation methods such as ordinary kriging(OK),universal kriging(UK),inverse distance weighting(IDW)and radial basis function(RBF)and random subsampling(50,100,200,300,400,and 500)on the prediction accuracy of SOC estimation.When the Shannon's Diversity Index(SHDI)and Shannon's Evenness Index(SHEI)was 2.01 and 0.67,the OK method appeared to be a superior method,which had the smallest root mean square error(RMSE)and the mean error(ME)nearest to zero.On the contrary,the UK method performed poorly for the interpolation of SOC in the present study.The sample size of 200 had the most accurate prediction;50 sampling points produced the worst prediction accuracy.Thus,we used 200 samples to estimate the study area's soil organic carbon density(SOCD)by the OK method.The total SOC storage to a depth of 20 cm in the study area was 117.94 Mt,and its mean SOCD was 2.40 kg/m2.The SOCD kg/(C⋅m2)of different land use types were in the following order:woodland(3.29)>grassland(2.35)>cropland(2.19)>sandy land(1.55).展开更多
Periwinkle Littoraria sinensis is a widely distributed gastropod in rocky intertidal zone of the northwestern Pacifi c.To examine genetic diversity and genetic connectivity among coastal populations of L.sinensis in C...Periwinkle Littoraria sinensis is a widely distributed gastropod in rocky intertidal zone of the northwestern Pacifi c.To examine genetic diversity and genetic connectivity among coastal populations of L.sinensis in China,1636 pairs of primers were successfully designed using whole-genome shotgun sequencing,de novo assembly,and a bioinformatics pipeline QDD.Twelve highly variable polymorphic markers were selected to genotype 351 individuals from 15 populations.Data of nine microsatellite loci were retained for population genetic analysis,and weak genetic differentiation among populations were detected,suggesting high gene flow among populations.The long planktonic larval duration of L.sinensis might have played an important role in the high gene flow among populations.A tendency of genetic differentiation between north and south populations of L.sinensis was detected,which might be resulted from isolation due to lowered sea level in the last glacial maximum.Furthermore,the newly founded populations along the coast of Jiangsu Province were closely related to populations to the south of the Changjiang(Yangtze)River estuary,suggesting that the main source of the newly founded populations is from natural rocky populations south of the estuary.展开更多
Spatial patterns of plant species and patchy community are important properties in grasslands.However,research regarding spatial patterns of formed patches with various species has not fully advanced until now.Our pur...Spatial patterns of plant species and patchy community are important properties in grasslands.However,research regarding spatial patterns of formed patches with various species has not fully advanced until now.Our purpose is to clarify differences in spatial pattern formed by species and community constructed under shady and terrace habitats.The three common Kobresia-Carex patches(Size 1,0.6–0.9 m^(2);Size 2,3.0–3.8 m^(2) and Size 3,6.5–8.8 m^(2))were selected in shady and terrace on the Qinghai-Tibetan Plateau,and corresponding quadrats of 1m1m,2m2m and 3m3m were placed for S1,S2 and S3 patches,respectively.The surveyed quadrats were divided into 20cm20cm large cells(L-cells),and further divided into four 10cm10cm small cells(S-cells).We used the binary occurrence system(presence/absence data)to record occurrences of all species in S-cells.The analysis shows that the power law model was well able to determine the spatial distribution pattern of species or patchy community in shady and terrace.All species and patches show aggregated distribution in shady and terrace habitats.In the shady habitat,the relative spatial heterogeneity(ε)of individual plant species was lowest at presence frequency(P)of 0.1–0.3,whereas in the terrace habitatεwas lowest at P<0.1,andεincreased monotonically with increasing P.For most dominant species,P andεvalues were higher in terrace than those in shady.We concluded that the dominant species largely determine spatial heterogeneity of the Kobresia-Carex patches,while companion and rare species have weak influence on the community-level heterogeneity in shady and terrace habitats.展开更多
China's Horqin Sandy Land,a formerly lush grassland,has experienced extensive desertification that caused considerable carbon(C) losses from the plant-soil system.Natural restoration through grazing exclusion is a...China's Horqin Sandy Land,a formerly lush grassland,has experienced extensive desertification that caused considerable carbon(C) losses from the plant-soil system.Natural restoration through grazing exclusion is a widely suggested option to sequester C and to restore degraded land.In a desertified grassland,we investigated the C accumulation in the total and light fractions of the soil organic matter from 2005 to 2013 during natural restoration.To a depth of 20 cm,the light fraction organic carbon(LFOC) storage increased by 221 g C/m2(84%) and the total soil organic carbon(SOC) storage increased by 435 g C/m2(55%).The light fraction dry matter content represented a small proportion of the total soil mass(ranging from 0.74% in 2005 to 1.39% in 2013),but the proportion of total SOC storage accounted for by LFOC was remarkable(ranging from 33% to 40%).The C sequestration averaged 28 g C/(m2·a) for LFOC and 54 g C/(m2·a) for total SOC.The total SOC was strongly and significantly positively linearly related to the light fraction dry matter content and the proportions of fine sand and silt+clay.The light fraction organic matter played a major role in total SOC sequestration.Our results suggest that grazing exclusion can restore desertified grassland and has a high potential for sequestering SOC in the semiarid Horqin Sandy Land.展开更多
The Horqin Sandy Land of northeastern China was originally a grassland with plenty of water and lush vegetation dominated by palatable grass species along with sparsely scattered woody species. However, it has experie...The Horqin Sandy Land of northeastern China was originally a grassland with plenty of water and lush vegetation dominated by palatable grass species along with sparsely scattered woody species. However, it has experienced severe desertification in recent decades due to its fragile ecology together with inappropriate human activities. Currently, the landscape of the Horqin Sandy Land is dominated by irrigated croplands and sand dunes with different degrees of vegetation cover, as the region has become the most important part of the semiarid agro-pastoral ecotone of northern China. In this study, we compared soil physical and chemical properties under different land-use and cover types(irrigated cropland, rainfed cropland, sandy grassland, fixed dunes, and mobile dunes). We found that soil particle size distribution; organic C, total N, and total mineral element, microelement, and available microelement and nutrient contents; p H; CEC; and bulk density differed significantly among the land-use and cover types. In general, soil quality was highest in the cropland, intermediate in the sandy grassland, and lowest in the dunes. The most important soil quality attribute, soil organic carbon(SOC) storage, decreased in the following order: irrigated cropland(5,699 g/m^2) > sandy grassland(3,390 g/m^2) > rainfed cropland(2,411 g/m^2) > fixed dunes(821 g/m^2) > mobile dunes(463 g/m^2). SOC was significantly positively correlated with a large proportion of the other soil physico-chemical parameters. Our results suggest that the key issue in restoration of the degraded soils will be to increase SOC storage, which would also create a high potential for sequestering soil C in desertified areas of the Horqin Sandy Land.展开更多
In order to investigate the effects of afforestation on soil microbial abundance, microbial biomass carbon and enzyme activity in sandy dunes, 20-year-old Pinus sylvestris var. mongolica Litv. (PSM) and Populus simoni...In order to investigate the effects of afforestation on soil microbial abundance, microbial biomass carbon and enzyme activity in sandy dunes, 20-year-old Pinus sylvestris var. mongolica Litv. (PSM) and Populus simonii Carrière (PSC) mature forests were selected in Horqin Sandy Land, and mobile dunes was set as a control (CK). Results show that PSM and PSC plantations can improve soil physicochemical properties and significantly increase microbiological activity in mobile dunes. Soil microbial abundance, microbial biomass carbon and enzyme activity show an order of PS>PSM>CK. Total soil microbial abundance in PSM and PSC was respectively 50.16 and 72.48 times more than that in CK, and the differences were significant among PSM, PSC and CK. Soil microbial biomass carbon in PSM and PSC was respectively 23.67 and 33.34 times more than that in CK, and the difference was insignificant between PSM and PSC. Soil enzyme activity, including dehydrogenase (DEH), peroxidase (PER), protease (PRO), urease (URE) and cellobiohydrolase (CEL) in PSM and PSC were respectively 19.00 and 27.54, 4.78 and 9.89, 4.05 and 8.67, 29.93 and 37.46, and 9.66 and 13.42 times of that in CK. P. sylvestris and P. simonii can effectively improve soil physicochemical and microbiological properties in sandy dunes and fix mobile dunes in Horqin Sandy Land. The C mic :C ratio is an applicable indicator to estimate soil stability and soil water availability, and based on an overall consideration of plantation stability and sustainability, P. sylvestris is better than P. simonii in fixing mobile dunes in sandy land.展开更多
The Horqin Sandy Grassland is one of the most seriously desertified areas in China's agro-pastoral ecotone due to its fragile ecology, combined with improper and unsustainable land management. We investigated orga...The Horqin Sandy Grassland is one of the most seriously desertified areas in China's agro-pastoral ecotone due to its fragile ecology, combined with improper and unsustainable land management. We investigated organic carbon changes in bulk soil(0 to 5 cm), light fraction of soil organic matter, and soil particle-size fractions induced by land-use and cover type changes. The results indicated that total soil organic carbon(SOC) storage decreased by 121 g/m2 with the conversion of grassland into farmland for 30 years, and increased by 261 g/m2 with the conversion of grassland into plantation for 30 years. Total SOC storage decreased by 157 g/m2 as a result of severe grassland desertification due to long-term continuous livestock grazing, whereas total SOC increased by 111 g/m2 following the practice of grazing exclusion(16 years) in desertified areas. Changes in land-use and cover type also show great effects on carbon storage in soil physical fractions.展开更多
The genetic diversity of Artemisia halodendron(Asteraceae), a constructive and dominant species in Horqin Sandy Land,was investigated to examine the genetic relationships with different hydrothermal regions in Horqin ...The genetic diversity of Artemisia halodendron(Asteraceae), a constructive and dominant species in Horqin Sandy Land,was investigated to examine the genetic relationships with different hydrothermal regions in Horqin Sandy Land. We sequenced chloroplast DNA(cp DNA) fragments(trn L–F) of 243 plants from 10 populations across the Horqin Sandy Land.The analyses of cp DNA variation identified seven haplotypes. A low level of haplotype diversity(H_d=0.706) and nucleotide diversity(π=0.0013) was detected. Haplotypes clustered into two tentative clades. Low genetic differentiation among regions was consistently indicated by hierarchical analyses of molecular variance(AMOVA). Across the sampled populations, the haplotype distributions were differentiated with hydrothermal gradients.展开更多
Caragana microphylla is the most dominant and constructive shrub species in the Horqin Sandy Land of northeastern China. We evaluated the level of genetic variation within and among C. microphylla populations sampled ...Caragana microphylla is the most dominant and constructive shrub species in the Horqin Sandy Land of northeastern China. We evaluated the level of genetic variation within and among C. microphylla populations sampled from three different temperature gradients in the Horqin Sandy Land by using inter-simple sequence repeat polymorphism(ISSR) molecular markers. The results show that eight ISSR primers generated 127 bands, of which 123(96.85%) were polymorphic. At the species level, genetic diversity was relatively high(P = 96.85%, h = 0.3143, I = 0.4790). The highest genetic diversity was observed in the Subp6 population from low temperature regions, whereas the lowest diversity was found in the Subp2 population from high temperature regions. Six populations of C. microphylla clustered into two clades. These results have important implications for restoring and managing the degraded ecosystem in arid and semi-arid areas.展开更多
The aim of the present study is to investigate the difference between ITS sequences of Artemisia halodendron Turcz. from different habitat gradients in Horqin Sandy Land, with Artemisia depauperata Krasch. selected as...The aim of the present study is to investigate the difference between ITS sequences of Artemisia halodendron Turcz. from different habitat gradients in Horqin Sandy Land, with Artemisia depauperata Krasch. selected as the outgroup. Results indicate that the total length of A. halodendron ITS is 696 bp, the lengths of unaligned ITS-1 and ITS-2 sequences varied from 253 to 256 bp and 264 to 269 bp, respectively, and GC content of ITS-1 and ITS-2 sequences ranged from 54.02% to 54.77% and 56.75% to 58.64%, respectively. This indicates a high difference of length and composition of sequences in ITS-1 than ITS-2. The genetic identity between ITS sequences of A. halodendron from nine populations ranged from 85.7% to 99.7% which indicates some genetic differentiation between sequences. In the maximum parsimony (MP) tree, most ITS sequences from A. halodendron show two major clades: Clade I and Clade II, with Clade II older than Clade I. The order is subp4 → subp1 → subp2 → subp3 → subp8 → subp6 → subp7 → subp9 → subp5, and corresponding habitat order is: inter-dune lowlands → semi-mobile dune → mobile dune → semi-fixed dune → fixed dune. This indicates a close relation between the evolutionary processes of A. halodendron and desertification forming processes and ecological restoration processes of Horqin Sandy Land.展开更多
We developed a highly selective and efficient multicomponent transformation by utilizing alkynes and olefins/(hetero)arenes through photoinduced energy-transfer catalysis.The reaction involves the formation of three d...We developed a highly selective and efficient multicomponent transformation by utilizing alkynes and olefins/(hetero)arenes through photoinduced energy-transfer catalysis.The reaction involves the formation of three distinct chemical bonds,namely C(sp~3)–C(sp~2),C(sp~2)–C(sp~3),and C(sp~3)–N,in a single coordinated manner.The strategy used a vinyl radical-mediated radical relay approach under mild conditions,exhibiting a broad substrate scope(>70 examples),excellent functional-group tolerance,and remarkable regio-and anti-stereoselectivity.Through the utilization of a combination of experimental techniques and density functional theory(DFT),we delved deeper into the mechanistic intricacies of this distinctive system.Results revealed that the selective radical addition to electron-deficient alkynes,rather than olefins,was governed by the inherent reactivity of alkyl radicals.This discovery presented a highly effective approach for the synthesis of stereodefined multisubstituted alkenes.展开更多
本文展示了一种利用超薄导电的Ga_(2)O_(3):Si纳米层获得(AlGa)_(2)O_(3)结晶薄膜的设计策略.受益于Ga_(2)O_(3):Si插层的存在,高质量的(Al_(0.68)Ga_(0.32))_(2)O_(3)倍半氧化物薄膜得以在蓝宝石衬底上外延生长,其中铝组分含量高达~68%...本文展示了一种利用超薄导电的Ga_(2)O_(3):Si纳米层获得(AlGa)_(2)O_(3)结晶薄膜的设计策略.受益于Ga_(2)O_(3):Si插层的存在,高质量的(Al_(0.68)Ga_(0.32))_(2)O_(3)倍半氧化物薄膜得以在蓝宝石衬底上外延生长,其中铝组分含量高达~68%,并被多种技术如HRTEM,XPS和XRD等进行了系统性表征.(Al_(0.68)Ga_(0.32))_(2)O_(3)材料的带隙被成功拓宽至6.14 eV,我们在此基础上制备出了(AlGa)_(2)O_(3)/Ga_(2)O_(3):Si真空紫外光电探测器.该探测器性能优异,开关比高达10^(3),开路电压为1.0 V,0 V偏压下响应度为8.1 m A W-1.以上结果表明,本文提出的生长策略可有效提高(AlGa)_(2)O_(3)倍半氧化物的质量并调节其带隙,有助于推动其在真空紫外探测领域的实际应用.展开更多
基金supported by the National Natural Science Foundation of China(4090104931060060)+1 种基金the Major State Basic Research Development Program of China(2009CB 421303)the 'Qing Lan' Talent Engineering Funds of Lanzhou Jiaotong University(QL-08-14A)
文摘Horqin Sandy Land is a fragile,seriously desertified region located in Inner Mongolia of China.Overgrazing is one of the primary drivers of desertification in this region.We investigated whether the establishment of grazing exclosures in areas with active sand dunes enhances soil carbon(C) sequestration and benefits soil recovery.The results showed that soil organic C storage was 1.4,1.9,and 3.5 times,and light fraction C storage was 2.3,3.2,and 4.4 times in the 100-cm topsoil after 7,12,and 25 years of grazing exclusion,respectively,compared to the case in active sand dunes.The light fraction of soil played an important role in soil C sequestration,although it might not change rapidly to provide an early indication of how soil C is increasing in response to grazing exclusion.The results indicated that soils could potentially sequester up to 13.8 Mt C in 25 years if active sand dunes in the study area were to be protected by exclosures.This corresponds to 12.8% of the estimated carbon loss(107.53 Mt) that has been associated with desertification over the past century in the Horqin Sandy Land.Our results suggested that exclosures have the capacity to increase soil C sequestration;however,decades will be required for soil C to recover to historical grassland levels observed prior to desertification.
基金This research was supported by the National Key R and D Program of China(2016YFC0500901 and 2016YFC0500907)the National Natural Science Foundation of China(Grant Nos.31971466 and 41807525)the One Hundred Person Project of the Chinese Academy of Sciences(Y551821).
文摘Determining an optimal sample size is a key step in designing field surveys,and is particularly important for detecting the spatial pattern of highly variable properties such as soil organic carbon(SOC).Based on 550 soil sampling points in the nearsurface layer(0 to 20 cm)in a representative region of northern China's agro-pastoral ecotone,we studied effects of four interpolation methods such as ordinary kriging(OK),universal kriging(UK),inverse distance weighting(IDW)and radial basis function(RBF)and random subsampling(50,100,200,300,400,and 500)on the prediction accuracy of SOC estimation.When the Shannon's Diversity Index(SHDI)and Shannon's Evenness Index(SHEI)was 2.01 and 0.67,the OK method appeared to be a superior method,which had the smallest root mean square error(RMSE)and the mean error(ME)nearest to zero.On the contrary,the UK method performed poorly for the interpolation of SOC in the present study.The sample size of 200 had the most accurate prediction;50 sampling points produced the worst prediction accuracy.Thus,we used 200 samples to estimate the study area's soil organic carbon density(SOCD)by the OK method.The total SOC storage to a depth of 20 cm in the study area was 117.94 Mt,and its mean SOCD was 2.40 kg/m2.The SOCD kg/(C⋅m2)of different land use types were in the following order:woodland(3.29)>grassland(2.35)>cropland(2.19)>sandy land(1.55).
基金Supported by the National Natural Science Foundation of China(No.31970488)。
文摘Periwinkle Littoraria sinensis is a widely distributed gastropod in rocky intertidal zone of the northwestern Pacifi c.To examine genetic diversity and genetic connectivity among coastal populations of L.sinensis in China,1636 pairs of primers were successfully designed using whole-genome shotgun sequencing,de novo assembly,and a bioinformatics pipeline QDD.Twelve highly variable polymorphic markers were selected to genotype 351 individuals from 15 populations.Data of nine microsatellite loci were retained for population genetic analysis,and weak genetic differentiation among populations were detected,suggesting high gene flow among populations.The long planktonic larval duration of L.sinensis might have played an important role in the high gene flow among populations.A tendency of genetic differentiation between north and south populations of L.sinensis was detected,which might be resulted from isolation due to lowered sea level in the last glacial maximum.Furthermore,the newly founded populations along the coast of Jiangsu Province were closely related to populations to the south of the Changjiang(Yangtze)River estuary,suggesting that the main source of the newly founded populations is from natural rocky populations south of the estuary.
基金funded by The Second Tibetan Plateau Scientific Expedition and Research (STEP)program (Grant No.2019QZKK0305)Youth Science and Technology Fund Program of GanSu (Grant No.22JR5RA083)the National Natural Science Foundation of China (Grant No.31971466).
文摘Spatial patterns of plant species and patchy community are important properties in grasslands.However,research regarding spatial patterns of formed patches with various species has not fully advanced until now.Our purpose is to clarify differences in spatial pattern formed by species and community constructed under shady and terrace habitats.The three common Kobresia-Carex patches(Size 1,0.6–0.9 m^(2);Size 2,3.0–3.8 m^(2) and Size 3,6.5–8.8 m^(2))were selected in shady and terrace on the Qinghai-Tibetan Plateau,and corresponding quadrats of 1m1m,2m2m and 3m3m were placed for S1,S2 and S3 patches,respectively.The surveyed quadrats were divided into 20cm20cm large cells(L-cells),and further divided into four 10cm10cm small cells(S-cells).We used the binary occurrence system(presence/absence data)to record occurrences of all species in S-cells.The analysis shows that the power law model was well able to determine the spatial distribution pattern of species or patchy community in shady and terrace.All species and patches show aggregated distribution in shady and terrace habitats.In the shady habitat,the relative spatial heterogeneity(ε)of individual plant species was lowest at presence frequency(P)of 0.1–0.3,whereas in the terrace habitatεwas lowest at P<0.1,andεincreased monotonically with increasing P.For most dominant species,P andεvalues were higher in terrace than those in shady.We concluded that the dominant species largely determine spatial heterogeneity of the Kobresia-Carex patches,while companion and rare species have weak influence on the community-level heterogeneity in shady and terrace habitats.
基金supported by the National Natural Science Foundation of China (41271007,31170413)the National Science and Technology Support Program of China (2011BAC07B02)
文摘China's Horqin Sandy Land,a formerly lush grassland,has experienced extensive desertification that caused considerable carbon(C) losses from the plant-soil system.Natural restoration through grazing exclusion is a widely suggested option to sequester C and to restore degraded land.In a desertified grassland,we investigated the C accumulation in the total and light fractions of the soil organic matter from 2005 to 2013 during natural restoration.To a depth of 20 cm,the light fraction organic carbon(LFOC) storage increased by 221 g C/m2(84%) and the total soil organic carbon(SOC) storage increased by 435 g C/m2(55%).The light fraction dry matter content represented a small proportion of the total soil mass(ranging from 0.74% in 2005 to 1.39% in 2013),but the proportion of total SOC storage accounted for by LFOC was remarkable(ranging from 33% to 40%).The C sequestration averaged 28 g C/(m2·a) for LFOC and 54 g C/(m2·a) for total SOC.The total SOC was strongly and significantly positively linearly related to the light fraction dry matter content and the proportions of fine sand and silt+clay.The light fraction organic matter played a major role in total SOC sequestration.Our results suggest that grazing exclusion can restore desertified grassland and has a high potential for sequestering SOC in the semiarid Horqin Sandy Land.
基金supported by the National Natural Science Foundation of China (Grant Nos. 41271007, 31260089, and 31560161)the One Hundred Person Project of the Chinese Academy of Sciences (Y551821002)
文摘The Horqin Sandy Land of northeastern China was originally a grassland with plenty of water and lush vegetation dominated by palatable grass species along with sparsely scattered woody species. However, it has experienced severe desertification in recent decades due to its fragile ecology together with inappropriate human activities. Currently, the landscape of the Horqin Sandy Land is dominated by irrigated croplands and sand dunes with different degrees of vegetation cover, as the region has become the most important part of the semiarid agro-pastoral ecotone of northern China. In this study, we compared soil physical and chemical properties under different land-use and cover types(irrigated cropland, rainfed cropland, sandy grassland, fixed dunes, and mobile dunes). We found that soil particle size distribution; organic C, total N, and total mineral element, microelement, and available microelement and nutrient contents; p H; CEC; and bulk density differed significantly among the land-use and cover types. In general, soil quality was highest in the cropland, intermediate in the sandy grassland, and lowest in the dunes. The most important soil quality attribute, soil organic carbon(SOC) storage, decreased in the following order: irrigated cropland(5,699 g/m^2) > sandy grassland(3,390 g/m^2) > rainfed cropland(2,411 g/m^2) > fixed dunes(821 g/m^2) > mobile dunes(463 g/m^2). SOC was significantly positively correlated with a large proportion of the other soil physico-chemical parameters. Our results suggest that the key issue in restoration of the degraded soils will be to increase SOC storage, which would also create a high potential for sequestering soil C in desertified areas of the Horqin Sandy Land.
基金supported by the National Science and Technology Support Program(2011BAC07B02)Young Scientists Foundation of Chinese Academy of Sciences(CAS)(Y251951001)National Natural Science Foundation of China(41171414and31170413) from Coldand Arid Regions Environmental and Engineering Research Institute,CAS
文摘In order to investigate the effects of afforestation on soil microbial abundance, microbial biomass carbon and enzyme activity in sandy dunes, 20-year-old Pinus sylvestris var. mongolica Litv. (PSM) and Populus simonii Carrière (PSC) mature forests were selected in Horqin Sandy Land, and mobile dunes was set as a control (CK). Results show that PSM and PSC plantations can improve soil physicochemical properties and significantly increase microbiological activity in mobile dunes. Soil microbial abundance, microbial biomass carbon and enzyme activity show an order of PS>PSM>CK. Total soil microbial abundance in PSM and PSC was respectively 50.16 and 72.48 times more than that in CK, and the differences were significant among PSM, PSC and CK. Soil microbial biomass carbon in PSM and PSC was respectively 23.67 and 33.34 times more than that in CK, and the difference was insignificant between PSM and PSC. Soil enzyme activity, including dehydrogenase (DEH), peroxidase (PER), protease (PRO), urease (URE) and cellobiohydrolase (CEL) in PSM and PSC were respectively 19.00 and 27.54, 4.78 and 9.89, 4.05 and 8.67, 29.93 and 37.46, and 9.66 and 13.42 times of that in CK. P. sylvestris and P. simonii can effectively improve soil physicochemical and microbiological properties in sandy dunes and fix mobile dunes in Horqin Sandy Land. The C mic :C ratio is an applicable indicator to estimate soil stability and soil water availability, and based on an overall consideration of plantation stability and sustainability, P. sylvestris is better than P. simonii in fixing mobile dunes in sandy land.
基金supported by the National Natural Science Foundation of China (41271007 and 31170413)the National Science and Technology Support Program of China (2011BAC07B02)One Hundred Person Project of the Chinese Academy of Sciences
文摘The Horqin Sandy Grassland is one of the most seriously desertified areas in China's agro-pastoral ecotone due to its fragile ecology, combined with improper and unsustainable land management. We investigated organic carbon changes in bulk soil(0 to 5 cm), light fraction of soil organic matter, and soil particle-size fractions induced by land-use and cover type changes. The results indicated that total soil organic carbon(SOC) storage decreased by 121 g/m2 with the conversion of grassland into farmland for 30 years, and increased by 261 g/m2 with the conversion of grassland into plantation for 30 years. Total SOC storage decreased by 157 g/m2 as a result of severe grassland desertification due to long-term continuous livestock grazing, whereas total SOC increased by 111 g/m2 following the practice of grazing exclusion(16 years) in desertified areas. Changes in land-use and cover type also show great effects on carbon storage in soil physical fractions.
基金supported by research projects 2016YFC0500907,2017FY100205,41201561,Y551821001,and 145RJYA269
文摘The genetic diversity of Artemisia halodendron(Asteraceae), a constructive and dominant species in Horqin Sandy Land,was investigated to examine the genetic relationships with different hydrothermal regions in Horqin Sandy Land. We sequenced chloroplast DNA(cp DNA) fragments(trn L–F) of 243 plants from 10 populations across the Horqin Sandy Land.The analyses of cp DNA variation identified seven haplotypes. A low level of haplotype diversity(H_d=0.706) and nucleotide diversity(π=0.0013) was detected. Haplotypes clustered into two tentative clades. Low genetic differentiation among regions was consistently indicated by hierarchical analyses of molecular variance(AMOVA). Across the sampled populations, the haplotype distributions were differentiated with hydrothermal gradients.
基金financially supported by One Hundred Person Project of the Chinese Academy of Sciences and research projects--41201561,2011BAC07B02,Y351151001 and 145RJYA269
文摘Caragana microphylla is the most dominant and constructive shrub species in the Horqin Sandy Land of northeastern China. We evaluated the level of genetic variation within and among C. microphylla populations sampled from three different temperature gradients in the Horqin Sandy Land by using inter-simple sequence repeat polymorphism(ISSR) molecular markers. The results show that eight ISSR primers generated 127 bands, of which 123(96.85%) were polymorphic. At the species level, genetic diversity was relatively high(P = 96.85%, h = 0.3143, I = 0.4790). The highest genetic diversity was observed in the Subp6 population from low temperature regions, whereas the lowest diversity was found in the Subp2 population from high temperature regions. Six populations of C. microphylla clustered into two clades. These results have important implications for restoring and managing the degraded ecosystem in arid and semi-arid areas.
基金financially supported by research projects 41201561, 2011BAC07B02, Y351151001, 41071185 and 31170413
文摘The aim of the present study is to investigate the difference between ITS sequences of Artemisia halodendron Turcz. from different habitat gradients in Horqin Sandy Land, with Artemisia depauperata Krasch. selected as the outgroup. Results indicate that the total length of A. halodendron ITS is 696 bp, the lengths of unaligned ITS-1 and ITS-2 sequences varied from 253 to 256 bp and 264 to 269 bp, respectively, and GC content of ITS-1 and ITS-2 sequences ranged from 54.02% to 54.77% and 56.75% to 58.64%, respectively. This indicates a high difference of length and composition of sequences in ITS-1 than ITS-2. The genetic identity between ITS sequences of A. halodendron from nine populations ranged from 85.7% to 99.7% which indicates some genetic differentiation between sequences. In the maximum parsimony (MP) tree, most ITS sequences from A. halodendron show two major clades: Clade I and Clade II, with Clade II older than Clade I. The order is subp4 → subp1 → subp2 → subp3 → subp8 → subp6 → subp7 → subp9 → subp5, and corresponding habitat order is: inter-dune lowlands → semi-mobile dune → mobile dune → semi-fixed dune → fixed dune. This indicates a close relation between the evolutionary processes of A. halodendron and desertification forming processes and ecological restoration processes of Horqin Sandy Land.
基金supported by the National Natural Science Foundation of China (22101059)the Guangxi Natural Science Foundation of China (2023GXNSFBA026275)+2 种基金the Innovation Project of Guangxi Graduate Education (YCSW2023125)partially supported by the National Key R&D Program of China (2022ZD0160100)in part by Shanghai Committee of Science and Technology(21DZ1100100)。
文摘We developed a highly selective and efficient multicomponent transformation by utilizing alkynes and olefins/(hetero)arenes through photoinduced energy-transfer catalysis.The reaction involves the formation of three distinct chemical bonds,namely C(sp~3)–C(sp~2),C(sp~2)–C(sp~3),and C(sp~3)–N,in a single coordinated manner.The strategy used a vinyl radical-mediated radical relay approach under mild conditions,exhibiting a broad substrate scope(>70 examples),excellent functional-group tolerance,and remarkable regio-and anti-stereoselectivity.Through the utilization of a combination of experimental techniques and density functional theory(DFT),we delved deeper into the mechanistic intricacies of this distinctive system.Results revealed that the selective radical addition to electron-deficient alkynes,rather than olefins,was governed by the inherent reactivity of alkyl radicals.This discovery presented a highly effective approach for the synthesis of stereodefined multisubstituted alkenes.
基金Acknowledgements The author thanks Professor Yimin Xiao for stimulating discussion. Thanks are also due to the anonymous referees for their careful reading and useful suggestions. This work was supported in part by the National Natural Science Foundation of China （Grant No. 10901054）.
基金supported by the National Natural Science Foundation of China(91833301 and 61427901)Guangdong Natural Science Funds for Distinguished Young Scholars(2021B1515020105)Guangdong Basic and Applied Basic Research Foundation(2019A1515110916)。
文摘本文展示了一种利用超薄导电的Ga_(2)O_(3):Si纳米层获得(AlGa)_(2)O_(3)结晶薄膜的设计策略.受益于Ga_(2)O_(3):Si插层的存在,高质量的(Al_(0.68)Ga_(0.32))_(2)O_(3)倍半氧化物薄膜得以在蓝宝石衬底上外延生长,其中铝组分含量高达~68%,并被多种技术如HRTEM,XPS和XRD等进行了系统性表征.(Al_(0.68)Ga_(0.32))_(2)O_(3)材料的带隙被成功拓宽至6.14 eV,我们在此基础上制备出了(AlGa)_(2)O_(3)/Ga_(2)O_(3):Si真空紫外光电探测器.该探测器性能优异,开关比高达10^(3),开路电压为1.0 V,0 V偏压下响应度为8.1 m A W-1.以上结果表明,本文提出的生长策略可有效提高(AlGa)_(2)O_(3)倍半氧化物的质量并调节其带隙,有助于推动其在真空紫外探测领域的实际应用.
基金supported by the National Natural Science Foundation of China(21702151,21774029,and 21871211)the Fundamental Research Funds for Central Universities(2042019kf0208)。
