Study on the Surface Soil Micro-biomass Carbon of Kinds of Vegetation Types in Dagu Estuary Wetland

A field experiment was carried out to explore surface soil mircro-biomass carbon （MBC）. The results showed that the difference of soil MBC was significant among three vegetation types in five sample spots in July. The order of surface soil MBC was： Aquaculture pond reed （sample 2）〉 reed of river bank （sample 5）〉 sea- plant（sample 5）〉 river flat（sample 4）〉 The alkaline（sample 1）. There is a very sig- nificant correlation among the soil MBC, the water content of soil and the content of organic matter. Among wetland plants, reed is kind of plant content of high ground biomass and below-ground biomass,especially the MBC planted in wetland is high- er, which shows that compared with common plants, reed is more conducive to the accumulation of soil MBC and has an important effect to wetland protecting and re- covery of function of ecosystem.

Effect of Different Vegetation Types on the Rhizosphere Soil Microbial Community Structure in the Loess Plateau of China

The Loess Plateau in China is one of the most eroded areas in the world. Accordingly, vegetation restoration has been implemented in this area over the past two decades to remedy the soil degradation problem. Understanding the microbial community structure is essential for the sustainability of ecosystems and for the reclamation of degraded arable land. This study aimed to determine the effect of different vegetation types on microbial processes and community structure in rhizosphere soils in the Loess Plateau. The six vegetation types were as follows：two natural grassland （Artemisia capillaries and Heteropappus altaicus）, two artificial grassland （Astragalus adsurgens and Panicum virgatum）, and two artificial shrubland （Caragana korshinskii and Hippophae rhamnoides） species. The microbial community structure and functional diversity were examined by analyzing the phospholipid fatty acids （PLFAs） and community-level physiological profiles. The results showed that rhizosphere soil sampled from the H. altaicus and A. capillaries plots had the highest values of microbial biomass C, average well color development of carbon resources, Gram-negative （G-） bacterial PLFA, bacterial PLFA, total PLFA, Shannon richness, and Shannon evenness, as well as the lowest metabolic quotient. Soil sampled from the H. rhamnoides plots had the highest metabolic quotient and Gram-positive （G＋） bacterial PLFA, and soil sampled from the A. adsurgens and A. capillaries plots had the highest fungal PLFA and fungal：bacterial PLFA ratio. Correlation analysis indicated a signiifcant positive relationship among the microbial biomass C, G- bacterial PLFA, bacterial PLFA, and total PLFA. In conclusion, plant species under arid climatic conditions signiifcantly affected the microbial community structure in rhizosphere soil. Among the studied plants, natural grassland species generated the most favorable microbial conditions.

Soil Organic Matter Fractions under Different Vegetation Types in Permafrost Regions along the Qinghai-Tibet Highway, North of Kunlun Mountains, China

As a key attribute of soil quality, soil organic matter(SOM) and its different fractions play an important role in regulating soil nutrient cycling and soil properties.This study evaluated the soil carbon(C) and nitrogen(N) concentrations in different SOM fractions(light– and heavy fractions,microbial biomass) under different vegetation types and analyzed their influencing factors in continuous permafrost regions along the Qinghai-Tibet Highway in the North of Kunlun Mountains, China.Soil samples were collected in pits under four vegetation types — Alpine swamp meadow(ASM), Alpine meadow(AM), Alpine steppe(AS) and Alpine desert(AD) — at the depth of 0-50 cm.The vegetation coverage was the highest at ASM and AM, followed byAS and AD.The results indicated that the concentrations of light fraction carbon(LFC) and nitrogen(LFN), and microbial biomass carbon(MBC)and nitrogen(MBN) decreased as follows: ASM > AM >AS > AD, with the relatively stronger decrease of LFC,whereas the heavy fraction carbon(HFC) and nitrogen(HFN) concentrations were lower in AS soils than in the AD soils.The relatively higher proportions of LFC/SOC and MBC/SOC in the 0-10 cm depth under the ASM soils are mainly resulted from its higher substrate input and soil moisture content.Correlation analysis demonstrated that aboveground biomass, soil moisture content, soil organic carbon(SOC) and total nitrogen(TN) positively correlated to LFC, LFN, HFC, HFN, MBC and MBN, while p H negatively correlated to LFC, LFN, HFC, HFN, MBC and MBN.There was no relationship between active layer thickness and SOM fractions, except for the LFC.Results suggested that vegetation cover, soil moisture content, and SOC and TN concentrations were significantly correlated with the amount and availability of SOM fractions, while permafrost had less impact on SOM fractions in permafrost regions of the central Qinghai–Tibet Plateau.

Ethiopian vegetation types,climate and topography

Ethiopia is land of geographical contrasts with elevations that range from 125 m below sea level in the Danakil Depression to 4533 m above sea level in the Semien Mountains,a world heritage site.The diverse climate of various ecological regions of the country has driven the establishment of diverse vegetation,which range from Afroalpine vegetation in the mountains to the arid and semi-arid vegetation type in the lowlands.The formation of Ethiopian vegetation is highly connected to the climate and geological history of the country.Highland uplift and rift formation due to volcanic forces formed novel habitats with different topography and climatic conditions that have ultimately become drivers for vegetation diversification.Due to Ethiopia's connection with the temperate biome in the north and the Arabian Peninsula during the dry glacial period,the biotic assemblage of Ethiopian highlands consists of both Afrotropical and palearctic biota.In general,eight distinct vegetation types have been identified in Ethiopia,based mainly on elevation and climate gradients.These vegetation types host their own unique species,but also share several common species.Some of the vegetation types are identified as centers of endemism and have subsequently been identified globally as the East African Afromontane hotspot.Ethiopia is biologically rich,with more than 6500 vascular plant species.Of these species,12%are endemic mainly due to geographical isolation and unique climatic conditions.However,researchers have yet to extensively investigate the ecology,phenology,as well as the evolutionary,genetics,and conservation status of Ethiopian vegetations at community and species level over space and time.This lack of research is a barrier to achieving the goal of zero global plant extinctions.Taxa extinction risk assessment has not been extensively carried out for majority of Ethiopian species.Detailed research is needed to explore how vegetation and species respond to rapidly growing environmental change.Currently,human-induced climate change and habitat fragmentation are severely threatening the country's biodiversity,and the consequences of these effects have not been studied at large.Furthermore,we still lack scientific evidence on how micro-and macro-ecological and evolutionary processes have been shaping vegetation structures in this climatically,topographically,and geologically diverse country.These gaps in our knowledge represent an opportunity for ecologists,geneticists,evolutionary biologists,conservation biologists,and other experts to investigate the biodiversity status and the complex ecological processes involved in structuring vegetation dynamics so as to help take effective conservation actions.

Soil moisture of different vegetation types on the Loess Plateau

Water stored in deep loess soil is one of the most important resources regulating vegetation growth in the semi-arid area of the Loess Plateau, but planted shrub and forest often disrupt the natural water cycle and in turn influence plant growth. The purpose of this study was to examine the effects of main vegetation types on soil moisture and its inter-annual change. Soil moisture in 0-10 m depth of six vegetation types, i.e., crop, grass, planted shrub of caragana, planted forests of arborvitae, pine and the mixture of pine and arborvitae were measured in 2001,2005 and 2006. Soil moisture in about 0-3 m of cropland and about 0-2 m of other vegetation types varied inter-annually dependent on annual precipitation, but was stable inter-annually below these depths. In 0-2 m, soil moisture of cropland was significantly greater than those of all other vegetation types, and there were no si nificant differences among other vegetation types. In 2-10 m, there was no significant mois- ture difference between cropland and grassland, but the soil moistures under both of them were significantly higher than those of planted shrub and forests. The planted shrub and forests had depleted soil moisture below 2 m to or near permanent wilting point, and there were no significant moisture differences among forest types. The soil moisture of caragana shrub was significantly lower than those of forests, but the absolute difference was very small. The results of this study implicated that the planted shrub and forests had depleted deep soil moisture to the lowest limits to which they could extract and they lived mainly on present year precipitation for transpiration.

Response of soil water dynamics to precipitation years under different vegetation types on the northern Loess Plateau, China

Implementation of the Grain-for-Green project has led to rapid land cover changes and resulted in a significantly increased vegetation cover on the Loess Plateau of China during the past few decades. The main objective of this study was to examine the responses of soil water dynamics under four typical vegetation types against precipitation years. Soil water contents (SWCs) were measured in 0–4.0 m profiles on a hillslope under the four vegetation types of shrub, pasture, natural fallow and crop in a re-vegetated catchment area from April to October in normal (2010), dry (2011), wet (2014) and extremely wet (2013) years. The results indicated that precipitation and vegetation types jointly controlled the soil water temporal dynamics and profile characteristics in the study region. SWCs in 0–4.0 m profiles of the four vegetation types were ranked from high to low as crop>fallow>pasture>shrub and this pattern displayed a temporal stability over the four years. In the extremely wet year, SWC changes occurred in the 0–2.0 m layer under shrub and pasture while the changes further extended to the depth of 4.0-m deep layers under fallow and crop. In the other three years, SWCs changes mainly occurred in the 0–1.0 m layer and kept relatively stable in the layers deeper than 1.0 m for all the four vegetation types. The interannual variation in soil depth of SWCs was about 0–2.0 m for shrub and pasture, about 0–3.4 m for fallow and about 0–4.0 m for crop, respectively. The dried soil layers formed at the depths of 1.0, 0.6, 1.6 and 0.7 m under shrub, and 1.0, 1.0, 2.0 and 0.9 m under pasture, respectively in 2010, 2011, 2013 and 2014. The infiltrated rainwater mostly stayed in the 0–1.0 m layer and hardly supplied to soil depth >1.0 m in normal, dry and wet years. Even in the extremely wet year of 2013, rainwater recharge depth did not exceed 2.0 m under shrub and pasture. This implied that soil desiccation was difficult to remove in normal, dry and wet years, and soil desiccation could be removed in 1.0–2.0 m soil layers even in the extremely wet year under shrub and pasture. The results indicated that the natural fallow was the best vegetation type for achieving sustainable utilization of soil water and preventing soil desiccation.

Soil microbial properties under different vegetation types on Mountain Han

This study investigated the influence of broadleaf and conifer vegetation on soil microbial communities in a distinct vertical distribution belt in Northeast China.Soil samples were taken at 0-5,5-10 and 10-20 cm depths from four vegetation types at different altitudes,which were characterized by poplar(Populus davidiana)(1250-1300 m),poplar(P.davidiana) mixed with birch(Betula platyphylla)(1370-1550 m),birch(B.platyphylla)(1550-1720 m),and larch(Larix principis-rupprechtii)(1840-1890 m).Microbial biomass and community structure were determined using the fumigation-extraction method and phospholipid fatty acid(PLFA) analysis,and soil fungal community level physiological profiles(CLPP) were characterized using Biolog FF Microplates.It was found that soil properties,especially soil organic carbon and water content,contributed significantly to the variations in soil microbes.With increasing soil depth,the soil microbial biomass,fungal biomass,and fungal catabolic ability diminished;however,the ratio of fungi to bacteria increased.The fungal ratio was higher under larch forests compared to that under poplar,birch,and their mixed forests,although the soil microbial biomass was lower.The direct contribution of vegetation types to the soil microbial community variation was 12%.If the indirect contribution through soil organic carbon was included,variations in the vegetation type had substantial influences on soil microbial composition and diversity.

Characteristic of Soil Hydro-Physical Properties and Water Dynamics under Different Vegetation Restoration Types

By combining the observation of the soil profile at field and the chemical and physical analysis in laboratory, a study on the hydro-physical properties of soil in six different vegetation types and the dynamics of water content after rain was conducted in Wanchanggou, Guangyuan City to find out the vegetation types with effective water-conservation functions in order to serve the ecological restoration in the low hill heavy rain area upper the Jialing River. Results showed that., the hydro-physical properties of soil in the mixed Alnus crernastogyne and Cupressua Leyland forest （AcCl） were best. But in the depth of 0-20 cm. The properties of soil in the abandoned cropland （Fm） was better than that in the AcCl. The soil bulk densities varied significantly between the layers of 0-20 cm and 20-40 cm in all the six vegetation types except that in the Robinia pseudoacacia shrub forest （RpII）, and the changes of the maximum and the capillary moisture capacity between layers were significant only in the Fm and in the AcCl. Of these stands, the AcCl had the shortest water-absorbing period and the strongest moisture changes in the upper layer （0-15 cm）. In the same stand, the deeper the soil layer, the slighter the soil moisture varied, and the longer the soil moisture accumulating process lasted.

Flight Behavioural Responses for African Ungulates across Species and Vegetation Covers in a Trophy Hunting Ecosystem: A Case Study from Selous Game Reserve, Tanzania

Trophy hunting has severe consequences on wild animals’ behaviors, which in return has implications for affecting wildlife populations. The Selous Game Reserve is a protected area in Tanzania that has been subjected to commercial trophy hunting for decades, and information about the effects of trophy hunting on animals’ welfare is still scarce. The Flight Initiating Distance (FID) can be a good measure to evaluate the welfare of animals and the level of risk perception towards anthropogenic disturbances, including trophy hunting. The study used linear mixed models to assess the flight responses of twelve commonly hunted species in the Selous game reserve (S.G.R.). The study compared animal vigilance between species, vegetation types, and group size. The FID varied between species, with which more vigilance was observed in zebras, elands, wildebeests, and sable antelopes. The study found a significant influence of vegetation cover on individual species’ FID. Further, the study found a significant influence of group size on animals’ vigilance (L. M. M., 95% CI = 0.590 - 4.762), in which there was a decrease in FID with an increase in group size for wildebeests. At the same time, other species, such as buffaloes, eland, hartebeests, and zebras, had their FIDs increasing with the increase in group size. We conclude that the impact of trophy hunting on savannah ungulates varies between species, vegetation covers, and group size of individual species. Regulatory authorities should consider minimum approach distances by trophy hunters in different vegetation cover to reduce animal biological disturbances.

Energy partitioning and environmental influence factors in different vegetation types in the GEWEX Asian Monsoon Experiment

Environmental influences upon energy balance in areas of different vegetation types （i.e., forest at Kog-Ma in Thailand and at Yakutsk in Russia, grassland at Amdo in Chinese Tibet and at Arvaikheer in Mongolia, and mixed farmland at Tak in Thailand） in the GEWEX Asian Monsoon Experiment were investigated. The sites we investigated are geographically and climatologically different; and consequently had quite large variations in temperature （T）, water vapor pressure deficit （VPD）, soil moisture （SM）, and precipitation （PPT）. During May- October, the net radiation flux （Rn） （in W·m^-2） was 406.21 at Tak, 365.57 at Kog-Ma, 390.97 at Amdo, 316.65 at Arvaikheer, and 287.10 at Yakutsk. During the growing period, the Rn partitioned into latent heat flux （2E/Rn） was greater than that partitioned into sensible heat flux （H/Rn） at Tak and at Kog-Ma. In contrast, 2E/Rn was lower than H/Rn at Arvaikheer, H/Rn was less than 2E/Rn between DOY 149 and DOY 270 at Amdo, and between DOY 165 and DOY 235 at Yakutsk. The R, partitioned into ground heat flux was generally less than 0.15. The short-wave albedo was 0.12, 0.18, and 0.20 at the forest, mixed land, and grass sites, respectively. At an hourly scale, energy partitions had no correlation with environmental factors, based on average summer half- hourly values. At a seasonal scale energy partitions were linearly correlated （usually p 〈 0.05） with T, VPD, and SM. The 2E/Rn increased with increases in SM, T, and VPD at forest areas. At mixed farmlands, ）λE/Rn generally had positive correlations with SM, T, and VPD, but was restrained at extremely high values of VPD and T. At grasslands, λE/Rn was enhanced with increases of SM and T, but was decreased with VPD.

Classification of vegetative types in Changbai Mountain based on optical and microwave remote sensing data

Highly accurate vegetative type distribution information is of great significance for forestry resource monitoring and management.In order to improve the classification accuracy of forest types,Sentinel-1 and 2 data of Changbai Mountain protection development zone were selected,and combined with DEM to construct a multi-featured random forest type classification model incorporating fusing intensity,texture,spectral,vegetation index and topography information and using random forest Gini index(GI)for optimization.The overall accuracy of classification was 94.60%and the Kappa coefficient was 0.933.Comparing the classification results before and after feature optimization,it shows that feature optimization has a greater impact on the classification accuracy.Comparing the classification results of random forest,maximum likelihood method and CART decision tree under the same conditions,it shows that the random forest has a higher performance and can be applied to forestry research work such as forest resource survey and monitoring.

Distribution patterns of vegetation biomass and nutrients bio-cycle in alpine tundra ecosystem on Changbai Mountains,Northeast China

A study was conducted to test the correlation between biomass and elevation and the differences in concentration and storks of nutrients among five vegetation types （Felsenmeer alpine tundra vegetation-FA, Lithic alpine tundra vegetation-LA, Typical alpine tundra vegetation-TA, Meadow alpine tundra vegetation-MA, and Swamp alpine tundra vegetation-SA） on alpine tundra of Changbai Mountains, Jilin Province, China in growing seasons of 2003, 2004 and 2005. The biomass of 43 mono-species and soil nutrients in alpine tundra ecosystem were also investigated. Dominant species from Ericaceae （such as Rhododendron chrysanthum and Vaccinium jliginosum var. alpinum） were taken to analyze organ biomass distribution. Result showed that the biomass and elevation had a significant correlation （Biomass-237.3 in（Elevation） ＋494.36; R^2=0.8092; P〈0.05）. No significant differences were found in phosphorus and sulphur concentrations of roots, stems and leaves among the five vegetation types. There were significant differences in nitrogen and phosphorus stocks of roots, stems and leaves and in sulphur stock of stems and leaves among TA, MA, and SA vegetation types （p〈0.05）. The nutrient stock of five vegetations was averagely 72.46 kg.hm^-2, of which N, P, S were 48.55, 10.33 and 13.61 kg·hm^-2, respectively. Soil N and S concentrations in meadow alpine tundra soil type was significantly higher than those in other four soil types （Cold desert alpine tundra soil, Lithic alpine tundra soil, Peat alpine tundra soil, and Gray alpine tundra soil）. Phosphorous concentration in SA type was higher （p〈0.05） than in other types. Soil nutrient stock （0-20cm） was averagely 39.59 t.hm^-2, of which N, P, S were 23.74, 5.86, 9.99 t·hm^-2, respectively.

IMPACT OF ROAD CONSTRUCTION ON VEGETATION ALONGSIDE QINGHAI-XIZANG HIGHWAY AND RAILWAY

Based on the field investigation in August 2001 and August 2002, digitalChina Vegetation Map in 2001 and Qinghai-Xizang (Tibet) Plateau Vegetation Regionalization Map in1996, vegetation characteristics along two sides of Qinghai-Xizang highway and railway are studiedin this paper. Meanwhile, the impact of Qinghai-Xizang highway and railway constructions on thevegetation types are analyzed using ARCVIEW, ARC/INFO and PATCH ANALYSIS. It was found that: 1)Qinghai-Xizang highway and railway span 9 latitudes, 12 longitudes and 6 physical geographic regions(East Qinghai and Qilian mountain steppe region, Qaidam mountain desert region, SouthQinghai-Xizang alpine meadow steppe region, Qiangtang alpine steppe region, Golog-Nagqu alpine shrubmeadow region and South Xizang mountain shrub steppe region); 2) the construction of Qinghai-Xizanghighway and railway destroyed natural vegetation and landscape, especially in 50m-wide bufferregions along both sides of the roads, it was estimated that the net primary productivity deceasedby about 30 504.62t/a and the gross biomass deceased by 432 919.25-1 436 104.3t. The losing primaryproductivity accounted for 5.70% of the annual primary productivity within Ikm-wide buffer regions(535 005.07-535 740.11t/a), and only 0.80%-0.89% of that within 10km-wide buffer regions (3 408950.45-3 810 480.92t/a). The losing gross biomass was about 9.47%-17.06% of the gross biomass within1km-wide buffer regions (7 502 971.85-25 488 342.71t), and only 1.47%-2.94% of that within10km-wide buffer regions (43 615 065.35-164 150 665.37t).

Distribution Patterns of Soil Microorganisms under Different Vegetation Types along the Riparian Wetland of the Ulson River and Its Influencing Factors

Wetlands are important for maintaining global ecosystem functions,mitigating global climate change,and regulating regional climate change.Ecological problems caused by global climate change have had serious impacts on plant distribution patterns in the wetlands of riparian zones,as well as on microbial community habitats in the soil.This study was based on a field sampling survey of the distribution characteristics of plant communities in the Ulson River,combined with remote sensing to obtain the spatial distribution pattern of vegetation in the riparian wetland.High-throughput sequencing technology combined with the characteristics of soil physicochemical factors were then used to explore the distribution characteristics of the community structures of soil bacteria and fungi under different vegetation types in the Ulson River Basin,in order to reveal the pattern of changes of soil microbial microorganisms under the different vegetation types in the wetlands of the riparian area and the factors driving those changes.The results showed an obvious banding phenomenon of wetland vegetation in the Ulson River Basin.Proteobacteria ranked first in relative abundance in all the sample plots and were the dominant bacteria in the study area.Ascomycota and Basidiomycota were the dominant fungi in the study area.In swamp areas,degenerate swamp soils,soil moisture content,and soil bulk density affected the microbial richness directly or indirectly by controlling soil nutrients.Plant aboveground biomass was the most significant factor influencing microbial diversity in a typical wet meadow sample.In salinized meadows and swamped meadows,electrical conductivity affected microbial richness and soil bulk density was the main factor influencing microbial diversity.The findings of this study can provide a theoretical basis for the ecological restoration of degraded riparian wetlands and further clarification of soil ecosystem functions in riparian wetlands.

Decreasing magnitude of soil erosion along vegetation succession on sloping farmland in the Loess Plateau of China:5 years field monitoring evidence

The impacts of vegetation restoration on the soil erosion have been widely elucidated in the semi-arid regions.However,the magnitude of soil erosion on abandoned sloping farmland still remained unclear and their responses to vegetation succession were rarely addressed.The main objective of this study is to determine the magnitude of soil erosion along vegetation succession and explore the impact of vegetation succession on soil erosion from abandoned sloping farmland.Field observations were employed to monitor the rainfall,runoff,and soil erosion of seven sloping farmland plots with different abandoned ages and bare land from 2015 to 2019.The results indicated that the annual runoff depth and soil erosion modulus of vegetation types were in the range of 0.46 to 5.49 mm·a^(-1)and 1.3 to 24.5 t·km^(-2)·a^(-1),respectively.The vegetation effectively reduced the annual surface runoff and soil erosion with reduction of 73.8% to 97.8%and 98.0% to 99.9% as opposed to bare land.However,there were no significant differences in runoff and soil erosion for different vegetation types along succession.The largest event of vegetation types contributed to 38.7%-44.1% of the annual runoff and 42.5%-66.3% of the annual soil erosion,respectively.Vegetation restoration considerably alleviated the contribution of largest erosive event to annual soil erosion.The relationships between soil erosion,runoff and rainfall factors could be fitted well by linear functions,and the performances of regression models in predicting runoff were more satisfactory compared to predicting soil erosion.The Artemisia gmelinii(Agm)+Stipa bungeana(Sb)optimized the trade-off between sediment reduction and runoff maintenance,which should be selected as the suitable vegetation types to achieve the sustainability of socio-ecological systems.

Vegetation impact on the thermal regimes of the active layer and near-surface permafrost in the Greater Hinggan Mountains, Northeastern China

The ground temperature and active layer are greatly influenced by vegetation in the Greater Hinggan Mountains in Northeastern China.However,vegetation,as a complex system,is difficult to separate the influence of its different components on the ground thermal regime.In this paper,four vegetation types,including a Larix dahurica-Ledum palustre var.dilatatum-Bryum forest（P1）,a L.dahurica-Betula fruticosa forest（P2）,a L.dahurica-Carex tato forest（P3） in the China Forest Ecological Research Network Station in Genhe,and a Carex tato swamp（P4） at the permafrost observation site in Yitulihe,have been selected to study and compare their seasonal and annual influence on the ground thermal regime.Results show that the vegetation insulates the ground resulting in a relatively high ground temperature variability in the Carex tato swamp where there are no tree stands and shrubs when compared with three forested vegetation types present in the area.Vegetation thickness,structure,and coverage are the most important factors that determine the insulating properties of the vegetation.In particular,the growth of ground cover,its water-holding capacity and ability to intercept snow exert a significant effect on the degree of insulation of the soil under the same vegetation.

A Fractal Method of Estimating Soil Structure Changes Under Different Vegetations on Ziwuling Mountains of the Loess Plateau,China

Fractal method is a new method to estimate soil structure. It has been shown to be a useful tool in studies related to physical properties of soil as well as erosion and other hydrological processes. Fractal dimension was used to study the soil structure in soil at different stages of vegetative succession on the Ziwuling Mountains. The land use and vegetation types included cultivated land, abandoned land, grassland, two types of shrub land, and three types of forests. The grassland, shrub land, and forested areas represented a continuum in vegetative succession that had occurred naturally, as the land was abandoned in 1862. Disturbed and undisturbed soil samples were collected from ten vegetation types from depths of 0-10, 10-20, and 20-30 cm on the Ziwuling Mountains, at a site with an elevation of about 1 500 m. Particle size distribution was determined by the pipette method and aggregate size distribution was determined by wet sieving. The results were used to calculate the particle and aggregate fractal dimension. The results showed that particle and aggregate fractal dimensions varied between vegetation types. There was a positive correlation between the particle fractal dimension and the weight of particles with diameter 〈 0.001 mm, but no relationship between particle fractal dimension and the other particle size classes. Particle fractal dimension was lower in vegetated soils compared to cropland and there was no consistent relationship between fractal dimension and vegetation type. Aggregate fractal dimension was positively correlated with the weight of 〉 0.25 mm aggregates. Aggregate fractal dimension was lower in vegetated soils compared with cropland. In contrast to particle fractal dimension, aggregate fractal dimension described changes in soil structure associated with vegetative succession. The results of this study indicate that aggregate fractal dimension is more effective in describing soil structure and function compared with particle fractal dimension.

Dynamic monitoring of soil bulk density and infiltration rate during coal mining in sandy land with different vegetation

To investigate the effects of coal mining on soil physical properties,sandy lands with three major vegetation types(Salix psammophila,Populus simonii,and Artemisia ordosica)were investigated by the ring knife method and double-ring infiltrometer.Specifically,variations in soil bulk density and water infiltration rate and the influences of coal mining and vegetation type on the properties during different subsidence stages were studied at the Shendong Bulianta mine.The results showed that,in the period before mining,soil bulk density occurred in the order A.ordosica>P.simonii>S.psammophila,with a negative correlation between the initial infiltration rate and steady infiltration rate being observed.In the period during mining and 3 months after mining,there were no significant differences in soil bulk density and water infiltration rate among vegetation types.At 1 year after mining,the soil bulk density occurred in the order A.ordosica>S.psammophila>P.simonii,having a negative correlation with the steady infiltration rate.The water infiltration depths of the S.psammophila,P.simonii and A.ordosica were 50,60,and 30 cm,respectively.The infiltration characters were simulated by the Kostiakov equations,and the simulated and experimental results were consistent.Linear regression revealed that vegetation types and soil bulk density had significant effects on soil initial infiltration rate during the four study periods,and the infiltration rate of the period 1 year after mining was mainly influenced by the soil bulk density of the period before mining.The results indicated that vegetation types had significant effects on soil bulk density,and that the tree-shrub-grass mode was better than one single plantation for water conversation and vegetation recovery in sandy land subjected to mining.

Seasonal dynamics of soil water content in the typical vegetation and its response to precipitation in a semi-arid area of Chinese Loess Plateau

Soil water content is a key limiting factor for vegetation growth in the semi-arid area of Chinese Loess Plateau and precipitation is the main source of soil water content in this area.To further understand the impact of vegetation types and environmental factors such as precipitation on soil water content,we continuously monitored the seasonal dynamics in soil water content in four plots(natural grassland,Caragana korshinskii,Armeniaca sibirica and Pinus tabulaeformis)in Chinese Loess Plateau.The results show that the amplitude of soil water content fluctuation decreases with an increase in soil depth,showing obvious seasonal variations.Soil water content of artificial vegetation was found to be significantly lower than that of natural grassland,and most precipitation events have difficulty replenishing soil water content below a depth of 40 cm.Spring and autumn are the key seasons for replenishment of soil water by precipitation.Changes in soil water content are affected by precipitation,vegetation types,soil evaporation and other factors.The interception effect of vegetation on precipitation and the demand for water consumption by transpiration are the key factors affecting the efficiency of soil water replenishment by precipitation in this area.Due to artificial vegetation plantation in this area,soil will face a water deficit crisis in the future.

Effect of vegetation on soil bacteria and their potential functions for ecological restoration in the Hulun Buir Sandy Land,China

To date,much of research on revegetation has focused on soil microorganisms due to their contributions in the formation of soil and soil remediation process.However,little is known about the soil bacteria and their functions respond to the diverse vegetational types in the process of vegetation restoration.Effects of dominated vegetation,i.e.,Artemisia halodendron Turcz Ex Bess,Caragana microphylla Lam.,Hedysarum fruticosum Pall.and Pinus sylvestris L.on bacterial community structures and their potential functions in the Hulun Buir Sandy Land,China were determined using high-throughput 16S rRNA gene sequencing and phylogenetic investigation of communities by reconstruction of unobserved states(PICRUSt)in 2015.Although the dominant phyla of soil bacterial community among different types of vegetation,including Proteobacteria,Actinobacteria,Acidobacteria,Bacteroidetes and Firmicutes,were similar,the relative abundance of these dominant groups significantly differed,indicating that different types of vegetation might result in variations in the composition of soil bacterial community.In addition,functional genes of bacterial populations were similar among different types of vegetation,whereas its relative abundance was significantly differed.Most carbon fixation genes showed a high relative abundance in P.sylvestris,vs.recalcitrant carbon decomposition genes in A.halodendron,suggesting the variations in carbon cycling potential of different types of vegetation.Abundance of assimilatory nitrate reduction genes was the highest in P.sylvestris,vs.dissimilatory nitrate reduction and nitrate reductase genes in A.halodendron,indicating higher nitrogen gasification loss and lower nitrogen utilization gene functions in A.halodendron.The structures and functional genes of soil bacterial community showed marked sensitivities to different plant species,presenting the potentials for regulating soil carbon and nitrogen cycling.