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Ground peak identification in dense shrub areas using large footprint waveform LiDAR and Landsat images

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International Journal of Digital Earth 2015年第10期8卷 805-824页

作者： Wei Zhuang Giorgos Mountrakis Department of Environmental Resources Engineering State University of New York College of Environmental Science and ForestrySyracuseNYUSA

Large footprint waveform LiDAR data have been widely used to extract tree heights.These heights are typically estimated by subtracting the top height from the ground.Compared to the top height detection,the identification of the ground peak in awaveform is more challenging.This is particularly evident in ground detection in shrubareas,where the reflection of the shrub canopy may significantly overlap with theground reflection.To tackle this problem,a novel method based on Partial Curve-Fitting(PCF)of the shrub peak was developed to detect the ground peak.Resultsindicated that the PCF method improves ground identification by 32-42%,comparedto existing methods.To offer further improvement,a Multi-Algorithm IntegrationClassifier(MAIC)was built to fuse multiple ground peak algorithms and selectivelyapply the best method for each waveform plot.The PCF ground peak identificationmethod along with the MAIC-based fusion is expected to significantly improve grounddetection and shrub height estimation,thus assisting biodiversity,forest succession,and carbon sequestration studies,while offering an early example of future multiplealgorithm integration.

关键词： ground identification large footprint waveform LiDAR shrub partial fitting algorithmic fusion

Quantitative estimation of the shrub canopy LAI from atmosphere-corrected HJ-1 CCD data in Mu Us Sandland

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Science China Earth Sciences 2010年第S1期53卷 26-33页

The leaf area index(LAI) is an important ecological parameter that characterizes the interface between vegetation canopy and the atmosphere.In addition,it is used by most process-oriented ecosystem models.This paper investigates the potential of HJ-1 CCD data combined with linear spectral unmixing and an inverted geometric-optical model for the retrieval of the shrub LAI in Wushen Banner of Inner Mongolia in the Mu Us Sandland.MODTRAN(Moderate Resolution Atmospheric Radiance and Transmittance Model) was used for atmospheric correction.shrubland was extracted using the threshold of the normalized difference vegetation index,with which water bodies and farmland were separated,in combination with a vegetation map of the People's Republic of China(1:1000000).Using the geometric-optical model,we derive the per-pixel reflectance as a simple linear combination of two components,namely sunlit background and other.The fraction of sunlit background is related to the shrub LAI.With the support of HJ-1 CCD data,we employ linear spectral unmixing to obtain the fraction of sunlit background in an atmospherically corrected HJ image.In addition,we use the measured shrub canopy structural parameters for shrub communities to invert the geometric-optical model and retrieve the pixel-based shrub LAI.In total,18 sample plots collected in Wushen Banner of Inner Mongolia are used for validation.The results of the shrub LAI show good agreement with R2 of 0.817 and a root-mean-squared error of 0.173.

关键词： shrub leaf area index inversion HJ-1 data geometric-optical model MODTRAN Mu Us Sandland

Patterns of shrub species richness and abundance in relation to environmental factors on the Alxa Plateau:Prerequisites for conserving shrub diversity in extreme arid desert regions

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Science China Earth Sciences 2009年第5期52卷 669-680页

作者： XinRong Li HuiJuan Tan MingZhu He XinPing Wang XiaoJun Li Shapotou Desert Research and Experiment Station Cold and Arid Regions Environmental and Engineering Research Institute Chinese Academy of Sciences Lanzhou 730000 China

shrub species are considered the dominant plants in arid desert ecosystems,unlike in semiarid steppe zones or in grassland ecosystems.On the Alxa Plateau,northern China,sparse vegetation with cover ranging from 15% to 30% is characterized mainly by multifarious shrubs because herbaceous species are strongly restricted by the extreme drought climate,wind erosion,overgrazing and sand burial.Patterns in shrub species richness and species abundance in relation to environmental conditions were examined by DCA(detrended correspondence analysis) and interpreted by a biplot.The rela-tionships between species diversity and environmental factors were examined using regression analyses.Our results show that the distributions of the shrub species in response to environmental conditions can be grouped into four ecological types,corresponding with the biological traits of the shrubs and their responses to the gradients of soil texture and soil water content.Patterns in species richness and species abundance were mainly determined by the deeper soil water content,instead of the soil texture as hypothesized by numerous studies in semiarid grasslands.With exception of the deeper soil water content,soil organic matter and total N content were positively correlated with species abundance,while pH was negatively correlated with it.These findings imply that it is vital for cur-rent shrub diversity conservation to reduce agricultural water use in the middle reaches of the Heihe River,which supplies water for the lower reaches in the western parts of the plateau,and to reduce the amount of groundwater exploitation and urban and oasis water use,to increase the water supply from Helan Mountain to the eastern desert of the Alxa Plateau.

关键词： biodiversity conservation shrub species richness abundance Alxa Plateau desert ecosystems

Intrastorm stemflow variability of a xerophytic shrub within a water-limited arid desert ecosystem of northern China

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Research in Cold and Arid Regions 2017年第5期9卷 495-502页

作者： YaFeng Zhang XinPing Wang YanXia Pan Rui Hu Shapotou Desert Research and Experiment Station Northwest Institute of Eco-Environment and Resources Chinese Academy of Sciences Lanzhou Gansu 730000 China

An increasing number of studies in recent years has elucidated distinguishable effects of stemflow on hydrology and biogeochemistry within a variety of ecosystems.Nonetheless,no known studies have investigated the temporal variability of stemflow volume within discrete rainfall events for xerophytic shrubs.Here,stemflow was monitored at 5-min intervals using a tipping-bucket rain gage during the 2015 growing season for a xerophytic shrub(Caragana korshinskii)within a water-limited arid desert ecosystem of northern China.We characterized the stemflow temporal variability,along with rainfall,and found the temporal heterogeneity of rainfall clearly affected the timing of stemflow inputs into basal soil within discrete rainfall events.The rainfall threshold value for stemflow generation is not a constant value but a range(0.6~2.1 mm,with an average of 1.1 mm)across rainfall events and is closely associated with the antecedent dry period.Time lags existed between the onset of rainfall and the onset of stemflow,and between rainfall peaks and stemflow peaks.Our findings are expected to be helpful for an improved process-based understanding of the temporal stemflow yield of xerophytic shrubs within water-limited arid desert ecosystems.

关键词： stemflow temporal variability xerophytic shrub antecedent dry period time lag

The effects of the identity of shrub species on the distribution and diversity of ground arthropods in a sandy desert ecosystem of northwestern China

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Research in Cold and Arid Regions 2014年第6期6卷 587-596页

作者： JiLiang Liu WenZhi Zhao FengRui Li Linze Inland River Basin Research Station Cold and Arid Regions Environmental and Engineering Research InstituteChinese Academy of Sciences

shrub is an important factor on structuring ground arthropod communities in desert ecosystems. In this study, in order to determine how shrubs and their species influence ground arthropod distribution patterns in a sandy desert scrubland dominated by two different shrub species, Calligonum mongolicum and Nitraria sphaerocarpa, the ground arthropods were sampled with pitfall traps during spring, summer and autumn. At the community level, total arthropod abundance was shown to be significantly higher under shrubs than in intershrub bare areas in spring; similar patterns occurred in terms of the richness of arthropod groups in the spring and over three seasons, suggesting season-specific shrub presence effects on arthropod activity. In addition, more arthropods were found under N. sphaerocarpa shrubs than under C. rnongolicum shrubs in autumn, suggesting season-specific effects of shrub species of arthropod activity, whereas more arthropods taxa were captured under C. mongoIicum than N. sphaerocarpa. At the trophic group level, the abundances of predator and herbivore arthropods were significantly greater under shrubs than in intershrub bare habitats, whereas herbivore arthropods were more abundant under N. sphaerocarpa than C. rnongolicum, and an opposite rule was detected for predator arthropods At the family level, the mean abundances of Carabidae, Curculionidae, Gnaphosidae and Lycosidae were significantly higher in the shrub microhabitats than in the intershrub bare habitat, there was no significant difference between habitats on the mean abundances of Formicidae and Tenebrionidae. The study results suggested that shrub presence and shrub species variation are important determinants of ground arthropod assemblages in this desert ecosystem, but the responses of ar- thropods differed among trophic and taxonomic groups.

关键词： Heihe River Basin sandy desert ecosystem ground arthropods shrub shrub species

Soil water depletion depth by planted vegetation on the Loess Plateau

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Science China Earth Sciences 2009年第6期52卷 835-842页

作者： WANG ZhiQiang LIU BaoYuan LIU Gang ZHANG YongXuan State Key Laboratory of Earth Surface Processes and Resource Ecology School of GeographyBeijing Normal UniversityBeijing 100875China

Evapotranspiration of much planted vegetation exceeds precipitation, and this can deplete soil water and cause a deep dry layer in the soil profile, which is a serious obstacle to sustainable land use on the Loess Plateau, China. This study aimed to determine water depletion depth of planted grassland, shrub, and forest in a semiarid area on the Loess Plateau. Soil moisture of five vegetation types was measured to >20 m in depth. The vegetation types were crop, natural grasse, seven-year-old planted alfalfa (Medicago sativa L.), 23-year-old planted caragana (Caragana microphylla Lam.) shrub, and 23-year-old planted pine (Pinus tabulaeformis L) forest land. Through comparing moisture of planted alfalfa grass, caragana shrub, and pine forest to crop and natural grassland, the depth and amount of soil water consumed by grassland, caragana brush and pine forest was determined. The depth of soil water depleted by alfalfa, caragana brush, and pine forest reached 15.5, 22.4 and 21.5 m, respectively.

关键词： Loess Plateau planted alfalfa grass planted caragana shrub planted pine forest soil moisture dry soil layer

Leaf nitrogen and phosphorus resorption of woody species in response to climatic conditions and soil nutrients： a meta-analysis

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Journal of Forestry Research 2018年第4期29卷 904-912页

作者： Tao Yan Jiaojun Zhu Kai Yang CAS Key Laboratory of Forest Ecology and Management Institute of Applied Ecology Shenyang 110016 People' s Republic of China Qingyuan Forest CERN Chinese Academy of Sciences Shenyang 110016 People's Republic of China University of Chinese Academy of Sciences Beijing 100049 People's Republic of China

Nutrient resorption before abscission is an important nutrient conservation mechanism regulated by climatic conditions and soil nutrients. However, our current understanding of leaf nutrient resorption is primarily derived from site-specific studies or from the use of greenleaf nutrient concentrations to represent those in soils. It remains unknown how nutrient resorption responds to natural soil-nutrient concentrations at a global scale. The effects of plant functional groups, climatic conditions, and soil nutrients and their interactions on leaf nutrient resorption are also unknown. In this study, we established a global database derived from 85 published papers, including 547 reports of nitrogen and phosphorus resorption efficiency （NRE and PRE）, climatic factors （LAT, latitude; MAT, mean annual temperature; MAP, mean annual precipitation） and soil-nutrient data （STN, soil total nitrogen; STP, soil total phosphorus） across 111 research sites. The results demonstrated that mean NRE and PRE were 48.4 and 53.3%, respectively. NRE of trees was lower than those of shrubs. NRE and PRE of coniferous species were both higher than those of broad-leaved species. Evergreen species had higher PRE than did deciduous species. NRE was negatively related to STN, but PRE and STP were not related. Both NRE and PRE decreased with increasing MAT and MAP but increased with increasing LAT. Plant functional groups, climate and soil nutrients jointly explained 22 and 32% of the variations in NRE and PRE, respectively. It is important to note that climate （especially MAT） explained 12 and 29% of the variations in NRE and PRE, respectively, implying that continuing global warming will exert an increasingly profound influence on plant nutrient cycles.

关键词： Global Climate change Nutrient resorptionefficiency Tree shrub

Snow resisting capacity of Caragana microphylla and Achnatherum splendens in a typical steppe region of Inner Mongolia,China

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Journal of Arid Land 2020年第2期12卷 294-302页

作者： YAN Min ZUO Hejun WANG Haibing DONG Zhi LI Gangtie Key Laboratory of Aeolian Physics and Desertification Control Engineering Inner Mongolia Autonomous RegionCollege of Desert Control Science and EngineeringInner Mongolia Agricultural UniversityHohhot 010018China Forestry College Shandong Agricultural UniversityTai'an 271018China

Snow resisting capacity of vegetation is important for secondary distribution of water resources in seasonal snow areas of grassland because it affects the regeneration,growth and nutrient circulation of vegetation in grassland.This study investigated vegetation characteristics(canopy height,canopy length and crown width)of Caragana microphylla Lam.(shrub)and Achnatherum splendens(Trin.)Nevski.(herb),and snow morphologies(snow depth,snow width and snow braid length)in a typical steppe region of Inner Mongolia,China in 2017.And the influence of vegetation characteristic on snow resisting capacity(the indices of bottom area of snow and snow volume reflect snow resisting capacity)was analyzed.The results showed that snow morphology depends on vegetation characteristics of shrub and herb.The canopy height was found to have the greatest influence on snow depth and the crown width had the greatest influence on snow width.The canopy length was found to have little influence on morphological parameters of snow.When the windward areas of C.microphylla and A.splendens were within the ranges of 0.0-0.5 m2 and 0.0-8.0 m2,respectively,the variation of snow cover was large;however,beyond these areas,the variation of snow cover became gradually stable.The potential area of snow retardation for a single plant was 1.5-2.5 m2 and the amount of snow resistance was 0.15-0.20 m3.The bottom area of snow and snow volume(i.e.,snow resisting capacity)of clumped C.microphylla and A.splendens was found to be 4 and 25 times that of individual plant,respectively.The results could provide a theoretical basis both for the estimation of snow cover and the establishment of a plant-based technical system for the control of windblown snow in the typical steppe region of Inner Mongolia.

关键词： herb shrub snow cover snow resisting capacity field observation steppe

C:N:P stoichiometry of Ericaceae species in shrubland biomes across Southern China:influences of climate,soil and species identity

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Journal of Plant Ecology 2019年第2期12卷 346-357页

作者： Qiang Zhang Qing Liu Huajun Yin Chunzhang Zhao Lin Zhang Guoying Zhou Chunying Yin Zhijun Lu Gaoming Xiong Yuelin Li Jiaxiang Li Wenting Xu Zhiyao Tang Zongqiang Xie State Key Laboratory of Vegetation and Environment Change Institute of BotanyChinese Academy of SciencesBeijing 100093China University of Chinese Academy of Sciences Beijing 100049China Key laboratory of Mountain Ecological Restoration and Bioresource Utilization&Ecological Restoration and Biodiversity Conservation Key Laboratory of Sichuan Province Chengdu Institute of BiologyChinese Academy of SciencesChengdu 610041China Key Laboratory of Alpine Ecology and Biodiversity of Chinese Academy of Sciences Institute of Tibetan Plateau ResearchChinese Academy of SciencesBeijing 100101China Northwest Institute of Plateau Biology Chinese Academy of SciencesXining 810008 Key Laboratory of Aquatic Botany and Watershed Ecology Wuhan Botanical GardenChinese Academy of SciencesWuhan 430074China South China Botanical Garden Chinese Academy of SciencesGuangzhou 510650China College of Forest Central South University of Forestry&TechnologyChangsha 410004China Department of Ecology College of Urban and Environmental Sciences and Key Laboratory for Earth Surface ProcessesPeking UniversityBeijing 100871China

Aims Carbon(C),nitrogen(N)and phosphorus(P)stoichiometry strongly affect functions and nutrient cycling within ecosystems.However,the related researches in shrubs were very limited.In this study,we aimed to inves-tigate leaf stoichiometry and its driving factors in shrubs,and whether stoichiometry significantly differs among closely related species.Methods We analyzed leaf C,N and P concentrations and their ratios in 32 species of Ericaceae from 161 sites across southern China.We examined the relationships of leaf stoichiometry with environmen-tal variables using linear regressions,and quantified the interactive and independent effects of climate,soil and species on foliar stoi-chiometry using general linear models(GLM).Important Findings The foliar C,N and P contents of Ericaceae were 484.66,14.44 and 1.06 mg g−1,respectively.Leaf C,N and P concentrations and their ratios in Ericaceae were significantly related with latitude and altitude,except the N:P insignificantly correlated with latitude.Climate(mean annual temperature and precipitation)and soil properties(soil C,N and P and bulk density)were significantly influenced element stoichiom-etry.The GLM analysis showed that soil exerted a greater direct effect on leaf stoichiometry than climate did,and climate affected leaf traits mainly via indirect ways.Further,soil properties had stronger influ-ences on leaf P than on leaf C and N.Among all independent factors examined,we found species accounted for the largest proportion of the variation in foliar stoichiometry.These results suggest that species can largely influence foliar stoichiometry,even at a lower taxonomic level.

关键词： biogeographic pattern phylogenetic effect closely related species,Ericoid Mycorrhiza shrub