Influence of vegetation on runoff and sediment in wind-water erosion crisscross region in the upper Yellow River of China

All characteristics of vegetation,runoff and sediment from 1960 to 2010 in the Xiliu Gully Watershed,which is a representative watershed in wind-water erosion crisscross region in the upper reaches of the Yellow River of China,have been analyzed in this study.Based on the remote sensing image data,and used multi-spectral interpretation method,the characteristics of vegetation variation in the Xiliu Gully Watershed have been analyzed.And the rules of precipitation,runoff and sediment's changes have been illuminated by using mathematical statistics method.What′s more,the influence mechanism of vegetation on runoff and sediment has been discussed by using the data obtained from artificial rainfall simulation test.The results showed that the main vegetation type was given priority to low coverage,and the area of the low vegetation coverage type was reducing year by year.On the country,the area of the high vegetation coverage type was gradually increasing.In a word,vegetation conditions had got better improved since 2000 when the watershed management project started.The average annual precipitation of the river basin also got slightly increase in 2000–2010.The average annual runoff reduced by 37.5%,and the average annual sediment reduced by 73.9% in the same period.The results of artificial rainfall simulation tests showed that the improvement of vegetation coverage could increase not only soil infiltration but also vegetation evapotranspiration,and then made the rainfall-induced runoff production decrease.Vegetation root system could increases the resistance ability of soil to erosion,and vegetation aboveground part could reduce raindrop kinetic energy and splash soil erosion.Therefore,with the increase of vegetation coverage,the rainfall-induced sediment could decrease.     

Analyzing forest effects on runoff and sediment production using leaf area index

Quantifying the effects of forests on water and soil conservation helps further understanding of ecological functions and improving vegetation reconstruction in water-eroded areas.Studies on the effects of vegetation on water and soil conservation have generally focused on vegetation types or vegetation horizontal distribution densities.However,only a few studies have used indicators that consider the vegetation vertical distribution.This study used the leaf area index(LAI) to investigate the relationship between forests and water and soil conservation in experimental plots.From 2007 to 2010,rainfall characteristics,LAI,and water and soil loss in 144 natural erosive rainfall events were measured from five pure tree plots(Pinus massoniana).These tree plots were located in Hetian Town,Changting County,Fujian Province,which is a typical water-eroded area in Southern China.Quadratic polynomial regression models for LAI and water/soil conservation effects(RE/SE) were established for each plot.The RE and SE corresponded to the ratios of the runoff depth(RD) and the soil loss(SL) of each pure tree plot to those of the control plot under each rainfall event.The transformation LAIs of the LAI–RE and LAI–SE curves,as well as the rainfall characteristics for the different water/soil conservation effects,were computed.The increasing LAI resulted in descending,descending–ascending,ascending–descending,and ascending trends in the LAI–RE and LAI–SE curves.The rainfall frequencies corresponding to each trend of LAI–RE and LAI–SE were different,and the rainfall distributions were not uniform per year.The effects of soil conservation in the plots were superior to those of water conservation.Most of the RE and SE values presented a positive effect on water and soil conservation.The main factor that caused different effects was rainfall intensity.During heavy rains(e.g.,rainfall erosivity R = 145 MJ mm/ha h and maximum 30 min intensity I30 = 13 mm/h),the main effects were positive,whereas light rains(e.g.,R = 70 MJ mm/ha h and I30 = 8 mm/h) generally led to negative effects.When the rainfall erosivity was lower than that of the positive or the negative effects to a threshold and the tree LAI reached a transformation value,the relationships between LAI and RE or SE notably transformed.Results showed that the plottransformation LAIs for water and soil conservation during rainfall events were both approximately 1.0 in our study.These results could be used to come up with a more efficient way to alleviate water and soil loss in water-eroded areas.     

Changes in vegetation and soil properties during recovery of a subtropical forest in South China

Secondary forests account for a large amount of subtropical forest due to persistent anthropogenic disturbance in China. The interaction between vegetation and soil during recovery process is rather complex and dependent on forest conditions. Understanding how vegetation and soil properties changes and how their relationship develops in secondary forests is key to effective forest restoration and management. Here we explored the patterns of vegetation and soil properties as well as their correlations during forest recovery process in a subtropical forest in south China. Plots of three forest types, i.e., broadleaf-conifer mixed forest, broadleaved forest and old growth stand, were established to represent the recovery stages. The results showed that diversity patterns in the tree, shrub and herb layers were different: in the tree layer the species diversity peaked at the intermediate stage, while in the understory layers it decreased chronologically. Most of the soil factors showed an increasing trend, and different effects of soil factors were found for the three layers as well as for the two spatial scales. Together, our results suggested that vegetation and soil might be interdependent during the recovery course. Further studies are needed on exploring how vegetation interplays with soil at different scales and how nutrient limitations affects the vegetation development in a chronosequence.     

Historical Changes and Characteristics of Rehabilitation, Management and Utilization of Forest Resources in South Korea

This study analyzed the causes of forest devastation, the characteristics of forest rehabilitation process, and the success factors of reforestation. And it reviewed the management of rehabilitated forest resources and identified the income sources of mountain villages in South Korea. The devastation of forest starting from the early twentieth century was continued to the 1950＇s. The main causes of deforestation were the illegal cutting of trees for fuel and the slash-and-burning agriculture in forest. The success factors of reforestation were the decrease in the dependence on forest of fuel source, strict administration system and national participation. Sustainable forest management could be made possible through the practical use of social issues like public work project for prevention of landslide damages caused by the thinned logs left in the forest. Also it could be possible by making people realize that the public benefit was obtained from forest and the income sources of mountain villages were supplemented by non-timber forest products and tourism. Food and Agriculture Organization indicated Korea as the country that forestation was succeeded in a very short period. Korea seems to be not ordinary because economic growth was accomplished with rehabilitating natural environment. Korean forestation can become a good prototype of combining environmental rehabilitation and economic development.     

Metagenomic approach revealed effects of forest thinning on bacterial communities in the forest soil of Mt. Janggunbong,South Korea

The soil microbiome that plays important ecological roles in mountains and forests is influenced by anthropogenic and natural causes. Human activity, particularly harvesting or thinning, affects the soil microbiome in forests by altering environmental conditions, such as vegetation, microclimate, and soil physicochemical properties. The purpose of this study was to investigate the effects on forest thinning on the diversity and composition of the soil bacterial community. From next-generation sequencing results of the 16S rRNA gene, we examined differences in soil bacterial diversity and community composition before and after thinning at Mt. Janggunbong, South Korea. We identified 40 phyla, 103 classes, 192 orders, 412 families, 947 genera, and 3,145 species from the soil samples. Acidobacteria and Proteobacteria were the most dominant bacterial phyla in the forest soil of Mt. Janggunbong. Soil bacterial diversity measures (richness, Shannon diversity index, and evenness) at the phylum level increased after thinning, whereas species-level taxonomic richness decreased after thinning. Thinning provided new opportunities for bacterial species in Chloroflexi, Verrucomicrobia, Nitrospirae, and other nondominant bacterial taxa, especially for those not found in Mt. Janggunbong before thinning, to settle and adapt to the changing environment. Our results suggested that thinning affected the diversity and composition of soil bacterial communities in forests and mountains.     

Estimation of actual carbon dioxide removal in burned forests using satellite data: A case study in South Korea

With the increasing impact of climate change, carbon emissions and removals have become major issues. Forests are major carbon pools, and forest fires are an essential part of the carbon cycle.This study introduces a model for estimating the detailed actual CO₂ removal in burned forests using burn severity and tree survivability. Actual CO₂removal was estimated from empirical yield tables without using the standard carbon removal provided by the national inventory. The prim...     

Impact of natural disturbance,forest management and vegetation cover on topsoil biochemical characteristics of Tatra Mts.(Slovakia)

Perturbations caused by windstorms usually lead to the harvesting and clearcutting of fallen trees and wood debris, especially in the areas of managed forest ecosystems. Induced shifts in soils due to management practices play a crucial role in the restoration and maintaining of key ecosystem services.This paper focuses on topsoil chemical properties in relation to vegetation type(trees, shrubs and herbs)evolving at windstorm damaged(in 2004) areas with former Norway spruce(Picea abies) forests in the Tatra Mts. region(Slovakia). We assessed the content of topsoil organic matter fractions(extractives,holocellulose(HC) and lignin(Lig)), carbon in microbial biomass(C_(mic)), soil organic matter(SOM)and the content of elements N, C, H and S. The study plots represent different types of post-windthrow disturbance history/regime: wooden debris extraction(EXT), wooden debris not extracted(NEX), wooden debris extraction followed by wildfire(FIR), affected by the windstorm in 2014 with the subsequent wooden debris extraction(REX) and unaffected(REF). Our results revealed significant differences among sites in the content of dichloromethane extractives(EXT vs. REX and FIR), acetone extractives(NEX vs. EXT, FIR and REF), ethanol extractives(FIR vs. EXT, NEX and REF), water extractives(FIR vs. REX, NEX) and C_(mic)(EXT vs.NEX, FIR and REF). The topsoil of Vaccinium myrtillus and Picea abies showed a higher ratio of C/N, N/Lig, and Lig/HC compared to Rubus idaeus,Avenella flexuosa, Calamagrostis villosa, and Larix decidua. The content of N, C, H and S varied between topsoil with shrubs(Vaccinium myrtillus, Rubus idaeus) and grasses(Avenella flexuosa,Calamagrostis villosa). A positive correlation between soil organic matter(SOM) and polar extractives(r=0.81) and a negative correlation between SOM and HC(r=-0.83) was revealed. The carbon content in microbial biomass(C_(mic)) is positively correlated with acid soluble lignin(ASL)(r=0.85). We also identified a strong correlation between Klason lignin(KL) and the Lig/HC ratio(r=0.97).     

Impacts of land cover changes on runoff and sediment in the Cedar Creek Watershed,St. Joseph River,Indiana, United States

The relation between runoff and sediment and land cover is investigated in the Cedar Creek Watershed （CCW）, located in Northeastern Indiana, United States. The major land cover types in this watershed are cultivated land, woodland and pasture /Conservation Reserve Program （CRP）, which account for approximate 90 % of the total area in the region. Moreover, land use was changed tremendously from aooo to 9004, even without regarding the effect of the crop rotation system （corn ＆ soybean）. At least 49 % of land cover types were changed into other types in this period. The land cover types, ranking by changing area from high to low series, are rye, soybean, corn, woodland and pasture/CRP. The CCW is divided into 21 subwatersheds, and soil and water loss in each sub-watershed is computed by using Soil and Water Assessment Tool （SWAT）. The results indicate that the variations in runoff and sediment have positive relation to the area of crops （especially corn and soybean）; sediment is more sensitive to land cover changes than runoff; more heavy rainfall does not always mean more runoff because the combination of different land cover types always modify runoff coefficient; and rye, soybean and corn are the key land cover types, which affected the variation in runoff and sediment in the CCW.     

Clay mineral distribution in surface sediments of the South China Sea and its significance for in sediment sources and transport

Clay minerals of surface sediments in the South China Sea (SCS) are analyzed with X-ray diffraction, and their transport is explored with a grain size trend analysis (GSTA) model. Results show that clay mineral types in various sedimentary environments have different sediment sources and transport routes. Sediments in the northern SCS (north of 20°N) between the southwest of Taiwan Island and the outer mouth of the Pearl River have high contents of illite and chlorite, which are derived mainly from sediments on Taiwan Island and/or the Yangtze River. Sediments from the Pearl River are characterized by high kaolinite and low smectite content, and most are distributed in the area between the mouth of the Pearl River and northeast of Hainan Island and transported vertically from the continental shelf to the slope. Characterized by high illite content, sediments from Kalimantan Island are transported toward the Nansha Trough. Sediments from Luzon Island are related with volcanic materials, and are transported westwards according to smectite distribution. On the Sunda Shelf, sediments from the Mekong River are transported southeast in the north while sediments from the Indonesian islands are transported northward in the south. Ascertaining surface sediment sources and their transport routes will not only improve understanding of modern transportation and depositional processes, but also aid paleoenvironmental and paleoclimatic analysis of the SCS.     

Clay mineral distribution in surface sediments of the South China Sea and its significance for in sediment sources and transport

Clay minerals of surface sediments in the South China Sea (SCS) are analyzed with X-ray diffraction, and their transport is explored with a grain size trend analysis (GSTA) model. Results show that clay mineral types in various sedimentary environments have different sediment sources and transport routes. Sediments in the northern SCS (north of 20°N) between the southwest of Taiwan Island and the outer mouth of the Pearl River have high contents of illite and chlorite, which are derived mainly from sediments on Taiwan Island and/or the Yangtze River. Sediments from the Pearl River are characterized by high kaolinite and low smectite content, and most are distributed in the area between the mouth of the Pearl River and northeast of Hainan Island and transported vertically from the continental shelf to the slope. Characterized by high illite content, sediments from Kalimantan Island are transported toward the Nansha Trough. Sediments from Luzon Island are related with volcanic materials, and are transported westwards according to smectite distribution. On the Sunda Shelf, sediments from the Mekong River are transported southeast in the north while sediments from the Indonesian islands are transported northward in the south. Ascertaining surface sediment sources and their transport routes will not only improve understanding of modern transportation and depositional processes, but also aid paleoenvironmental and paleoclimatic analysis of the SCS.     

Crown fuel characteristics and carbon emission from Japanese red pine stands burned by crown fire in Mt. Palgong, South Korea

Carbon emissions from forest fires are considered an important factor of ecosystem carbon balance and global climate change. Carbon emissions from Japanese red pine stands (Pinus densiflora S. et Z.) burned by crown fire were estimated at Mt. Palgong in Daegu Metropolitan City, and crown fuel characteristics, including crown bulk density, crown base height, and fuel moisture content of Japanese red pine, were analyzed. Total biomass combusted was calculated by subtracting the biomass of burned stands from that of unburned stands exhibiting similar stand structures and site environments. Ten trees in the unburned area and five trees in the burned area were cut by using direct harvesting techniques to estimate crown layer biomass. All biomass sampled was oven-dried and weighed. The dry weight ratios of stems, branches, and needles were 70%, 21%, and 9%, respectively. The available fuel load susceptible to combustion during the crown fire spread was equivalent to 55% of the crown layer biomass. The crown bulk density was 0.24 kg/ m 3 on average. The estimated amount of CO 2 was 23,454 kg CO 2 /ha for the crown layer. These results will be useful for calculating the amount of CO 2 emitted from forest fires and for developing a forest carbon model in P. densiflora forests.     

青藏高原植被变化特征及其对气候变化的影响

利用1982-2001年美国国家航天航空局(NASA)的归一化植被指数(NDVI)资料以及55个青藏高原地区气象台站实测的最高气温、最低气温、平均气温和降水资料,初步分析了青藏高原地区各季节植被变化特征及其对气候变化的影响,通过分析发现,各季节青藏高原地区NDVI均以增长为主.特别是高原南部、北部和西部等地区增加明显,高原中东部地区植被有所减少.通过相关分析和台站概率相关分析发现,高原冬季和春季NDVI与后期春季和夏季的最高气温、最低气温、平均气温和降水有较好的正相关关系,但有的表现在相关系数比较显著,有的表现为概率相关较明显.     

Influence of Land Use/Cover Change on Storm Runoff— A Case Study of Xitiaoxi River Basin in Upstream of Taihu Lake Watershed

Land use/cover change (LUCC) is one of the main boundary conditions which influence many hydrologic processes. In view of the importance of Taihu Lake Watershed in China and the urgency of discovering the impacts of LUCC on storm runoff, two flood events under five land cover scenarios in the Xitiaoxi River Basin of the upstream of Taihu Lake watershed were simulated by distributed hydrologic modeling system HEC-HMS. The influences of each land cover on storm runoff were discussed. It was concluded that under the same rainstorm the ascending order of runoff coefficient and peak flow produced by the 5 different land covers were woodland, shrub, grassland, arable land, and built-up land; the descending order of swelling time were woodland, shrub, grassland, arable land, and built-up land. Scenario of built-up land was the first to reach peak flow, then arable land, grassland, shrub, and woodland. There were close relationships between the runoff coefficients produced by the 5 different land covers. The degrees of impacts on runoff coefficient of land cover change modes were sorted by descending: woodland to built-up land, shrub to built-up land, grassland to built-up land, arable land to built-up land, woodland to arable land, shrub to arable land, arable land to grassland, shrub to grassland, grassland to arable land, and woodland to shrub. Urbanization will contribute to flood disaster, while forestation will mitigate flood disaster.     

Seasonal variations in the influence of vegetation cover on soil water on the loess hillslope

Soil water is the key factor that restricts the restoration of the local ecological systems in the Loess Plateau of China. Studying the effects of vegetation types on soil water and its seasonal variation helps to understand hydrological characteristics and provides insights into the sustainable restoration of vegetation. Therefore, the Caijiachuan watershed was chosen as the research object to investigate the water status of a 0-10 m soil layer under different vegetation types including Pinus tabulaeformis, Robinia pseudoacacia, Platycladus orientalis, apple orchard, natural forestland,farmland and grassland. By comparing the difference between soil water of different land use types and that of grassland during the same period, the seasonal changes of soil water status of different types were judged. The results show that(1) in the 0-10 m soil layer, the largest value of soil water content was in the0.3-0.4 m layer, and the lowest was in the 5.6-5.8 m layer. The depths at which the vegetation cover influenced the soil water were up to 10 m;(2) among summer, fall and spring, the soil water storage wasthe highest in the fall. In addition, the lowest value of relative accumulation was in the fall, which was the period in which the soil water recovered;(3) the soil water in the 0-10 m layer was in a relatively deficient state in the artificial forestlands, apple orchards and native forestlands, while the relative accumulation was in the farmland. In addition, the relative deep soil layers(8-10 m) had more serious deficits in the areas in which P. tabulaeformis, R. pseudoacacia and the apple orchard grew;(4) during the study period, the farmland in the summer had the largest relative accumulation(182.71 mm), and the land under R.pseudoacacia in the fall had the lowest relative deficit(512.20 mm). In the Loess Plateau, vegetation cover will affect the change of deep soil moisture and artificial forest will cause soil water loss in different degrees.     

Temporal Change of Runoff and Sediment Load and their Differential Response to Human Activities：A Case Study for a Well-vegetated Mountain Watershed of Southern China

This study examined the temporal trends of runoff and sediment load and their differential response to human activities in the Lishui river,a tributary of the Yangtze river in southern China.The long-term observation data at four gauging stations,generally involving two periods from 1954 to 1985 and from 2007 to 2011,were used.We detected no significant temporal trend for both the annual runoff volume（Q） and the annual suspended Sediment Load（SL） over more than 30 years before 1985.The flow duration curves and the Suspended Sediment Concentration（SSC） also hold constant before 1985.Compared with the period before 1985,SL has decreased by about 80% though Q remains unchanged for the period after 2007.Detailed examination shows that the flow duration curves after 2007 have changed with a significant decrease in the high-flow component,which acts as a major cause for the decreasing SL.In addition,SSC has decreased by several times,which also contributes to the decrease in SL after 2007.Both decreases in high-flow discharges and in SSC can be linked with recent human activities,mainly including vegetation establishment and dam constructions.The constant Q and the decreasing SL are also reported for the main stream of the Yangtze River and other major rivers in southern China,although they are orders of magnitude larger than our study area in drainage area size.The present study highlights the importance of high-flow discharges on SL and suggests that the use of SL is more appropriate to reflect environmental change than Q.     

矾山铜钼矿区重金属与覆盖植被胁迫相关性光谱特征

高光谱遥感在地物精细探测方面具有较高的精度,能够实现弱缓信息的提取。应用高光谱遥感技术研究福建矾山高植被覆盖铜钼矿区重金属铜铅等元素与覆盖植被光谱胁迫相关性。通过对比分析矿区与非矿区典型植被光谱特征,在光谱特征分析结果基础上得出矿区典型植被均不同程度受到了重金属元素胁迫,并造成光谱曲线发生变异。在分析结果基础上,结合植被地球化学数据建立重金属与植被光谱胁迫相关性数学模型,提出矿区重金属与覆盖植被胁迫相关性。依据该模型可获得金属元素的空间分布,最终实现高光谱遥感技术在高植被覆盖区地质找矿中的应用。      

INFLUENCE OF GLOBAL WARMING ON VEGETATION IN NORTHEAST CHINA

GlObalwa-rmingisoneoftheseriousenvironmentproblemswhichattractattentionsofscientistsandgove~entsofvariouscountries.TheglobalatmOSpherecomponentschangebecauseofhtirnanactivitiesandthedevelopmentofindustry.Theincreaseofgreenhouseeffectleadstoglobalw~ng.Basedonthepredictionofgeneralcirculationmodel(GCM),bythemiddleofnextcentury,theconcentrationofopwillbedoubledandtheglobaltemperaturewillinCreasebyZt(Han,1993;She~,1983).WestudiedthelawofvegetationalterationunderthisconditioninnortheastChinain…     

The vertical distributions and sources of PAHs in sediment of Xiamen Bay

INTRODUCTIONTheindustrialdevelopmentandrisingpopulationintheXiamencoastalzonearelikelytoresultinincreasingpollutantsloadingwhichcanaffecttheoceanicecosystemsenvironmentthereandthreatenhumanhealth .PAHs ,asgoodenvironmentpollutionindicators(Aizenshat,1 973 ;Randahl,1 983 ) ,arerela tivelystableinairandwater,andarewidelydistributedintheaquaticenvironmentasaresultofhumanactivities.ProposedprimarysourcesofPAHsincludecombustionofvariousfossilfuels,nat uralfires,roadrunoff streetdustaswellas…     

Spatio-temporal trends and causes of variations in runoff and sediment load of the Jinsha River in China

The Jinsha River Basin is an important basin for hydropower in China and it is also the main runoff and sediment source area for the Yangtze River,which greatly influence the runoff and sediment in the Three Gorges Reservoir.This study aims to characterize the spatial distribution,inter-annual variation of runoff and sediment load in the Jinsha River Basin,and to analyze the contribution of rainfall and human activities to the runoff and sediment load changes.The monitoring data on runoff,sediment load and precipitation were collected from 11hydrological stations in the Jinsha River Basin from1966 to 2016.The data observed at the outlet of the basin showed that 71.4%of the runoff is from the upper reaches of the Jinsha River Basin and the Yalong River,while 63.3%of the sediment is from the lower reaches(excluding the Yalong River).There is no significant increase in runoff on temporal scale in the Jinsha River Basin,while it has an abrupt change in runoff in both upstream and midstream in 1985,and an abrupt change in downstream in 1980 and2013.The sediment load demonstrated a significantincreasing trend in the upstream,no significant reducing trend in the midstream,but significant reducing trend in the downstream.The sediment load in upstream showed abrupt change in 1987,in midstream in 1978 and 2014,in downstream in 2012.Rainfall dominated runoff variation,contributing more than 59.0%of the total variation,while human activity,including reservoirs construction,the implementation of soil and water conservation projects,is the major factor to sediment load variation,contributing more than 87.0%of the total variation.