Two psammophile-dominated Artemisia semi-shrubs （A. wudanica and A. halodendron） and two annual Artemisia forbs （A. sieversiana and A. scoparia） bear significant ecological functions in Horqin Sandy Land, but syst...Two psammophile-dominated Artemisia semi-shrubs （A. wudanica and A. halodendron） and two annual Artemisia forbs （A. sieversiana and A. scoparia） bear significant ecological functions in Horqin Sandy Land, but systematical information on their achenes＇ germination is very limited. A set of studies were conducted to evaluate seed germination responses to storage periods and methods, different temperatures, lights conditions and sand burial depths, in order to determine inter-specific germination variation in the same genus and to explain how the species adapt to its microhabitat. Fresh achenes of A. wudanica, A. halodendron and A. sieversiana showed high germination capacities, but those of A. scoparia had obvious innate dormancy, which could be broken by chilling and dry storage, especially long-term dry storage. Achene germination of the two semi-shrubs preferred lower temperature fluctuation （10 to 22℃） and was not sensitive to light. But the two annuals preferred higher temperature fluctuation （34 to 22℃） and strong light for their achene germination. These four Artemisia species showed similar responses to sand burial, i.e. soil surface was most favorable for seedling emergence, and the deeper the sand burial, the fewer the seedling emergence. For the two semi-shrubs, their microhabitats are sand dunes with high temperature and intense light, which are not favorable for germination and seedling survival. Only rainfall contributes to temporary decrease of temperature and then triggers germination. We deduced that germination is not the main but a supplementary repro- ductive mode for the two semi-shrubs in sand dunes. For the two annuals, achene germination is the only reproductive mode, but different responses have been developed for microhabitat adaptation. For A. sieversiana, high germination capacities in wide temperature ranges and all light conditions could improve its competition and advancement in the wettest microhabitats. For A. scoparia, obvious innate dormancy of fresh achenes and germination inhabitation under unfavorable conditions are important adaptation to environmental disturbances.展开更多
Species richness and abundance are two important species diversity variables that have attracted particular attention because of their significance in determining present and future species composition conditions. Thi...Species richness and abundance are two important species diversity variables that have attracted particular attention because of their significance in determining present and future species composition conditions. This paper aims to explain the qualitative and quantitative relationships between species diversity pattern and grain size （i.e. size of the sampling unit）, and species diversity pattern and sampling area, and to analyze species diversity variability on active sand dunes in the Horqin Sandy Land, northeastern Inner Mongolia, China. A 50 mx50 m sampling plot was selected on the windward slope, where the dominant species was annual herb Agriophyllum squarrosum. Species composition and abundance at five grain sizes were recorded, and the species-area curves were produced for thirteen grain sizes. The range of values for species abundance tended to increase with in- creasing grain size in the study area, whereas, generally, species richness did not follow this rule because of poor species richness on the windward slope of active sand dunes. However, the homogeneity of species richness in- creased significantly. With the increase in sampling area, species abundance increased linearly, but richness in- creased logarithmically. Furthermore, variograms showed that species diversity on the windward slope of active sand dunes was weakly anisotropic and the distribution pattern was random, according to the Moran Coefficient. The results also showed that species richness was low, with a random distribution pattern. This conflicts with the results of previous studies that showed spatial aggregation in lower richness in a sampling area within a community and inferred that the physical processes play a more important role in species diversity than distribution pattern on active sand dunes. Further research into different diversity patterns and mechanisms between active sand dunes and interdune lowlands should be conducted to better understand biodiversity conservation in sand dune fields.展开更多
Litter phosphorus （P） return is important to maintain the P cycle and balance in the sandy land of arid areas. In this study, we determined the loss and return of litter P in sand dune areas and elucidated their rel...Litter phosphorus （P） return is important to maintain the P cycle and balance in the sandy land of arid areas. In this study, we determined the loss and return of litter P in sand dune areas and elucidated their relation- ship. We investigated litter production and litter P amount, and simulated leaf litter moving dynamics to understand the relationships between the loss of litter P and the total litter P, and between the return of litter P and the total litter P in active （AD）, semi-stabilized （SSD） and stabilized （SD） dunes in Inner Mongolia, northeastern China. The vegetation litter P was 12.6, 94.5, and 201.6 mg P/m2 in AD, SSD, and SD, respectively. A significant movement and loss of leaf litter P with time occurred on the three types of sand dunes. As a result, the loss of P was 7.4, 46.9, and 69.8 mg P/m2 and the return of P was 5.5, 47.6, and 131.8 mg P/m2 in AD, SSD, and SD, respectively. The rela- tionship between both loss and return of P and total litter P in AD, SSD, and SD was revealed by linear regression. The slope of the regression line indicated the rate of loss or return of litter P. From AD to SD, the loss rate showed a declining slope （0.52, 0.32, and 0.17 for AD, SSD, and SD, respectively）, and the return rate showed a rising slope （0.48, 0.67, and 0.83 for AD, SSD, and SD, respectively）. The loss of litter P should be regarded in the local man- agement of vegetation and land in sand dune areas. Improved vegetation restoration measures are necessary to decrease litter P loss to maintain the stability of ecosystems in sand dune areas.展开更多
An accurate and convenient method is essential for measuring the terminal velocity of seeds dispersed by wind.Systematic and random errors produced by existing methods lower the accuracy and convenience in determining...An accurate and convenient method is essential for measuring the terminal velocity of seeds dispersed by wind.Systematic and random errors produced by existing methods lower the accuracy and convenience in determining seed terminal velocity.In this study,a video camera was used to record the falling process of forty-one species of wind-borne seed with eight appendage structures and seven aerodynamic behaviors in a settling tower at a speed of 50 frames per second(fps).The videos were analyzed by Quick Time Player to determine seed acceleration height,acceleration time,and terminal velocity.The results showed that acceleration height and time,terminal velocity,and the diff erence between terminal velocity and descent velocity(DTD)increased with wing loading.Compared with dropping methods,the camera recording method eliminated the eff ect of acceleration and corrected seed terminal velocity.Based on wing loading,release heights were determined for accurate measurement of terminal velocity of diff erent seeds.This method,due to its inexpensive equipment,high accuracy,easy observation and operation,can be applied to measure the terminal velocity of wind dispersed seeds,and provides a promising method in exploring the dispersal process of seeds.展开更多
Desertification in degraded grasslands is manifested through the development of bare sandy patches,which eventually lead to habitat fragmentation.The ability of these bare sandy patches to regenerate naturally through...Desertification in degraded grasslands is manifested through the development of bare sandy patches,which eventually lead to habitat fragmentation.The ability of these bare sandy patches to regenerate naturally through in-situ soil seed banks is not well understood.To fill this knowledge gap,we randomly selected 24 bare sandy patches with areas ranging from 19 to 898 m^(2) in a desertified grassland of the Horqin sandy land,Northern China to determine whether soil seed bank can be used for natural regeneration of bare sandy patches.Species composition and density of soil seed bank as well as aboveground vegetation composition,abundance and coverage were investigated.We then determined their relationships with in-situ habitat characteristics.Our observations showed that the studied area had low soil seed bank density and species richness,as well as depauperate soil seed bank communities.Consequently,local soil seed bank was not able to provide sufficient seed source for natural regeneration.This was indicated by the relationships between aboveground vegetation,soil seed bank and the in-situ habitat characteristics.For bare patches with an area between 300 m^(2) and 900 m^(2),increase the soil seed bank density and species richness should be the main restoration measures.For bare patches with a small area of less than 50 m^(2),restoration of vegetation density should be the main measure.Our data highlighted that different extents of desertification,indicated by different bare patches,are requiring distinct restoration measures.展开更多
Aims The belowground bud bank plays an important role in vegetation restoration of sand dune ecosystems in semi-arid regions.However,few studies have focused on the temporal-spatial changes of belowground bud banks in...Aims The belowground bud bank plays an important role in vegetation restoration of sand dune ecosystems in semi-arid regions.However,few studies have focused on the temporal-spatial changes of belowground bud banks in interdune lowlands.Methods The size and composition of belowground bud bank in five interdune lowlands with different sizes were investigated for one growing season to determine the temporal and spatial changes in belowground bud bank.Important Findings Total bud bank density was the highest in the medium-sized interdune lowland as was tiller bud density.The density of stem-base buds exhibited an opposite trend while rhizome bud density did not change with interdune lowland size.There was a significant seasonal change in the bud bank size.The total bud density peaked in August and was the lowest in October.A similar trend was found for rhizome bud density,whereas the density of stem-base buds showed an opposite trend,and tiller bud density did not change signifiesntly during the growing season.We conclude that the belowground bud bank density is changed with interdune lowland size and season.These results contribute to the understanding of adaptive strategies of plants growing in active dune ecosystems and provide pointers for adopting effective measures to restore and conserve dune vegetation in semi-arid regions.展开更多
基金financially supported by the National Natural Science Foundation of China (41071187 and 40701097)
文摘Two psammophile-dominated Artemisia semi-shrubs （A. wudanica and A. halodendron） and two annual Artemisia forbs （A. sieversiana and A. scoparia） bear significant ecological functions in Horqin Sandy Land, but systematical information on their achenes＇ germination is very limited. A set of studies were conducted to evaluate seed germination responses to storage periods and methods, different temperatures, lights conditions and sand burial depths, in order to determine inter-specific germination variation in the same genus and to explain how the species adapt to its microhabitat. Fresh achenes of A. wudanica, A. halodendron and A. sieversiana showed high germination capacities, but those of A. scoparia had obvious innate dormancy, which could be broken by chilling and dry storage, especially long-term dry storage. Achene germination of the two semi-shrubs preferred lower temperature fluctuation （10 to 22℃） and was not sensitive to light. But the two annuals preferred higher temperature fluctuation （34 to 22℃） and strong light for their achene germination. These four Artemisia species showed similar responses to sand burial, i.e. soil surface was most favorable for seedling emergence, and the deeper the sand burial, the fewer the seedling emergence. For the two semi-shrubs, their microhabitats are sand dunes with high temperature and intense light, which are not favorable for germination and seedling survival. Only rainfall contributes to temporary decrease of temperature and then triggers germination. We deduced that germination is not the main but a supplementary repro- ductive mode for the two semi-shrubs in sand dunes. For the two annuals, achene germination is the only reproductive mode, but different responses have been developed for microhabitat adaptation. For A. sieversiana, high germination capacities in wide temperature ranges and all light conditions could improve its competition and advancement in the wettest microhabitats. For A. scoparia, obvious innate dormancy of fresh achenes and germination inhabitation under unfavorable conditions are important adaptation to environmental disturbances.
基金funded by the National Natural Science Foundation of China (41071187)the State Forestry Administration Industry Special Project (201004023)
文摘Species richness and abundance are two important species diversity variables that have attracted particular attention because of their significance in determining present and future species composition conditions. This paper aims to explain the qualitative and quantitative relationships between species diversity pattern and grain size （i.e. size of the sampling unit）, and species diversity pattern and sampling area, and to analyze species diversity variability on active sand dunes in the Horqin Sandy Land, northeastern Inner Mongolia, China. A 50 mx50 m sampling plot was selected on the windward slope, where the dominant species was annual herb Agriophyllum squarrosum. Species composition and abundance at five grain sizes were recorded, and the species-area curves were produced for thirteen grain sizes. The range of values for species abundance tended to increase with in- creasing grain size in the study area, whereas, generally, species richness did not follow this rule because of poor species richness on the windward slope of active sand dunes. However, the homogeneity of species richness in- creased significantly. With the increase in sampling area, species abundance increased linearly, but richness in- creased logarithmically. Furthermore, variograms showed that species diversity on the windward slope of active sand dunes was weakly anisotropic and the distribution pattern was random, according to the Moran Coefficient. The results also showed that species richness was low, with a random distribution pattern. This conflicts with the results of previous studies that showed spatial aggregation in lower richness in a sampling area within a community and inferred that the physical processes play a more important role in species diversity than distribution pattern on active sand dunes. Further research into different diversity patterns and mechanisms between active sand dunes and interdune lowlands should be conducted to better understand biodiversity conservation in sand dune fields.
基金supported by the National Natural Science Foundation of China(30800163)
文摘Litter phosphorus （P） return is important to maintain the P cycle and balance in the sandy land of arid areas. In this study, we determined the loss and return of litter P in sand dune areas and elucidated their relation- ship. We investigated litter production and litter P amount, and simulated leaf litter moving dynamics to understand the relationships between the loss of litter P and the total litter P, and between the return of litter P and the total litter P in active （AD）, semi-stabilized （SSD） and stabilized （SD） dunes in Inner Mongolia, northeastern China. The vegetation litter P was 12.6, 94.5, and 201.6 mg P/m2 in AD, SSD, and SD, respectively. A significant movement and loss of leaf litter P with time occurred on the three types of sand dunes. As a result, the loss of P was 7.4, 46.9, and 69.8 mg P/m2 and the return of P was 5.5, 47.6, and 131.8 mg P/m2 in AD, SSD, and SD, respectively. The rela- tionship between both loss and return of P and total litter P in AD, SSD, and SD was revealed by linear regression. The slope of the regression line indicated the rate of loss or return of litter P. From AD to SD, the loss rate showed a declining slope （0.52, 0.32, and 0.17 for AD, SSD, and SD, respectively）, and the return rate showed a rising slope （0.48, 0.67, and 0.83 for AD, SSD, and SD, respectively）. The loss of litter P should be regarded in the local man- agement of vegetation and land in sand dune areas. Improved vegetation restoration measures are necessary to decrease litter P loss to maintain the stability of ecosystems in sand dune areas.
基金the National Natural Science Foundation of China(41571270).
文摘An accurate and convenient method is essential for measuring the terminal velocity of seeds dispersed by wind.Systematic and random errors produced by existing methods lower the accuracy and convenience in determining seed terminal velocity.In this study,a video camera was used to record the falling process of forty-one species of wind-borne seed with eight appendage structures and seven aerodynamic behaviors in a settling tower at a speed of 50 frames per second(fps).The videos were analyzed by Quick Time Player to determine seed acceleration height,acceleration time,and terminal velocity.The results showed that acceleration height and time,terminal velocity,and the diff erence between terminal velocity and descent velocity(DTD)increased with wing loading.Compared with dropping methods,the camera recording method eliminated the eff ect of acceleration and corrected seed terminal velocity.Based on wing loading,release heights were determined for accurate measurement of terminal velocity of diff erent seeds.This method,due to its inexpensive equipment,high accuracy,easy observation and operation,can be applied to measure the terminal velocity of wind dispersed seeds,and provides a promising method in exploring the dispersal process of seeds.
基金This study was supported by National Natural Science Foundation of China(41601588)Natural Science Foundation of Liaoning province(2019-MS-340)National Natural Science Foundation of China(31971732,41501573).
文摘Desertification in degraded grasslands is manifested through the development of bare sandy patches,which eventually lead to habitat fragmentation.The ability of these bare sandy patches to regenerate naturally through in-situ soil seed banks is not well understood.To fill this knowledge gap,we randomly selected 24 bare sandy patches with areas ranging from 19 to 898 m^(2) in a desertified grassland of the Horqin sandy land,Northern China to determine whether soil seed bank can be used for natural regeneration of bare sandy patches.Species composition and density of soil seed bank as well as aboveground vegetation composition,abundance and coverage were investigated.We then determined their relationships with in-situ habitat characteristics.Our observations showed that the studied area had low soil seed bank density and species richness,as well as depauperate soil seed bank communities.Consequently,local soil seed bank was not able to provide sufficient seed source for natural regeneration.This was indicated by the relationships between aboveground vegetation,soil seed bank and the in-situ habitat characteristics.For bare patches with an area between 300 m^(2) and 900 m^(2),increase the soil seed bank density and species richness should be the main restoration measures.For bare patches with a small area of less than 50 m^(2),restoration of vegetation density should be the main measure.Our data highlighted that different extents of desertification,indicated by different bare patches,are requiring distinct restoration measures.
基金supported by the National Natural Science Youth Foundation of China(31600443).
文摘Aims The belowground bud bank plays an important role in vegetation restoration of sand dune ecosystems in semi-arid regions.However,few studies have focused on the temporal-spatial changes of belowground bud banks in interdune lowlands.Methods The size and composition of belowground bud bank in five interdune lowlands with different sizes were investigated for one growing season to determine the temporal and spatial changes in belowground bud bank.Important Findings Total bud bank density was the highest in the medium-sized interdune lowland as was tiller bud density.The density of stem-base buds exhibited an opposite trend while rhizome bud density did not change with interdune lowland size.There was a significant seasonal change in the bud bank size.The total bud density peaked in August and was the lowest in October.A similar trend was found for rhizome bud density,whereas the density of stem-base buds showed an opposite trend,and tiller bud density did not change signifiesntly during the growing season.We conclude that the belowground bud bank density is changed with interdune lowland size and season.These results contribute to the understanding of adaptive strategies of plants growing in active dune ecosystems and provide pointers for adopting effective measures to restore and conserve dune vegetation in semi-arid regions.
