Effects of Different Land Use Types on Soil Organic Carbon and Carbon Management Index in Karst Area

[Objective] The aim was to reveal changes of soil organic matter fraction and their corresponding carbon management indexes as affected by different land use types.[Method]Soil organic carbon,active soil organic carbon and soil carbon management index（CMI）of different land use types in Guilin Maocun karst area were studied.Sampling with field investigation and laboratory testing was carried out.Heavy potassium chromate method was adopted to determine soil organic matter.333 mmol/L KMnO4 oxidation method was used to determine active organic carbon.[Result]With active soil organic matter increasing,the differences of CMI between different land use types were bigger.The CMI value of different land uses was shrubforest paddy fielddry farmland.The statistical analysis showed that labile organic matter was related with major soil properties at a significant level.[Conclusion]Labile organic matter could be used to reveal the influence of different land use types on soil organic matter and carbon management index in karst area.

Study on Influences of Different Land Use Types on Soil Qualities in Plateau Karst Depression

[Objective] The aim was to study influences of different land use ways on soil qualities in plateau karst depression.[Method] Different land use types were divided by topographic map of 1∶10 000 scales and soil properties of physics and chemistry were analyzed.[Result] The results showed that the variation trend of soil depth(A+B stratum)was slope plough(include returning farm to forest)land>natural forest land>planted forest land>shrub forest land,and relative indexes changing regularities of soil...

Soil Moisture Characteristics in Karst Area with Different Land Use Types

Ecological efficiency changes of soil moisture were researched in karst areas with different land type uses, including farmland, abandoned farmland （1 y） and shrub land （1 y）, sparse wood land （15 y）, secondary forest （25 y） and the re- sults showed that physical property of soil was not a simple ＂improvement＂ process during land type evolution. Specifically, from farmland to secondary forest, the con- tent of topsoils changed from being washed away to accumulation and soil bulk density changed from increasing to decreasing. For example, soil bulk densities of abandoned farmland and shrub land increased by 6.6% and 11.57% compared with farmland, and of sparse wood land and forest land decreased by 5.0% and 10.0%. The change trend of soil bulk density was just in contrary to total porosity. Available water capacity was the lowest of shrub land, but increased in rest land types. The increase tended to be volatile in 5.1%-12.5% of different land types and water-sta- ble aggregate content （〉0.25 mm） reached the highest of sparse wood land. The destruction rate, however, was declining in the process of land type evolution and the increase was in the range of 34.0%-64.7% compared with farmland. The de- struction rate of aggregate was of negative correlation with organic matter. Water- holding capacity was the best of forest land and abandoned farmland and the poor- est of shrub land, close to sparse wood land. Water-supplying capacity from high to low was as follows： farmland〉sparse wood land〉secondary forest〉shrub land〉a- bandoned farmland. It is obvious that water-holding capacity and water-supplying capacity are not consistent, but both are closely related to the content of soil clays, porosity, and aggregate stability.

Soil Erosion under Different Land Use Types and Zones of Jinsha River Basin in Yunnan Province,China

Severe soil erosion in the middle and upper reaches of Yangtze River has been regarded as a major environmental problem. The on-site impact of soil erosion on agricultural production and the off-site impact on floods and sedimentation in Yangtze Rive are well known. A quantitative assessment of soil erosion intensity is still scanty for developing appropriate soil erosion control measures for different land use types and zones in this region. This article constructs a localized USLE and estimates the average soil loss in the Jinsha River Region in Yunnan Province, one of the priority areas for soil erosion control in the middle and upper reaches of Yangtze River. The estimation is done under different land uses and zones in this basin. The estimation shows that while soil erosion in the cultivated land is the most severe, 36～40% of the garden and forest land suffers from soil erosion of various degrees due to lack of ground cover and other factors. Soil erosion in the pasture is modest when the ground cover is well maintained. It also confirmed that terracing can reduce soil erosion intensity significantly on the cultivated land. Research findings suggest that sufficient attention must be paid to regeneration of the ground cover in reforestation programs. In addition to mass reforestation efforts, restoration of grassland and terracing of the cultivated land should also play an important role in erosion control.

Elevation and Land Use Types Have Significant Impacts on Spatial Variability of Soil Organic Matter Content in Hani Terraced Field of Yuanyang County,China

Soil organic matter （SOM） content is one of the most important indicators of the sustainability of soil. To maintain sustainable soil utilization and management in fragile Hani terraced field, it is meaningful to investigate the effects of topography and land use type on SOM content. Descriptive statistics and geostatistics were used to analyze the data and the kriging method was applied to map the spatial patterns of SOM content. The results showed that the mean SOM content was 32.76 g/kg, with a variation coefficient of 40%. The SOM content was affected by elevation and land use type. As the increase of elevation, the SOM content in Hani terraced field also increased obviously. The SOM content in tea garden, which is almost at high elevation, was the highest in all six land use types, and the SOM content decreased in a following sequence： tea garden 〉 paddy field 〉 corn field 〉 banana garden 〉 cassava field 〉 sugarcane field. In addition, at the same elevation, the paddy field had the highest SOM content compared with other land use types. All these results demonstrate that paddy field is the most efficient and suitable land use type for SOM conservation at high, middle or low elevations in the fragile Hani terraced field. In order to protect soil quality and maintain the sustainable agricultural development, it is necessary to maintain or even to enlarge the area of paddy field in Yuanyang county, Yunnan Province, China.

Surface Brightness Temperature Variation of Different Land Use Types

[Objective] The aim of this study is to investigate the surface brightness temperature variation of different land use types.[Method] Based on MODIS data in 2008 and IGBP land classification system,the surface brightness temperature in the Yangtze River Delta area was calculated,and its rules and reasons were also discussed in this study.[Result] Different land use types had its own special brightness temperature variation.During the day,the brightness temperature was as follows：grassland or urban and built-up landcropland,forest land and barrenwetland and water.During the night,the brightness temperature was as follows：water,wetland and barrengrassland or urban and built-up landforest land and cropland.Brightness temperature showed the trend of high in summer and low in winter or increasing in spring and decreasing in fall.The characteristics of surface thermal radiation could be reflected better by brightness temperature at night.Solar radiation,mixed pixel,heat capacity,water content were the main reasons for the difference of brightness temperature in different land types.[Conclusion] The brightness temperature variation of different land use types has significance for water content analysis in soil and dynamic monitoring of land use.

Efficiency Assessment of Land Use Types in Tan Binh Commune,Dak Doa District,Gia Lai Province,Vietnam

Land resource depletion causes a range of consequences,such as threats to food security,increasing poverty,and social unrest.Therefore,reasonable and effective land use has become a crucial issue of the nation and localities nationwide.Research results in Tan Binh commune,Dak Doa district,Gia Lai Province in Vietnam showed that long-term industrial and agricultural land occupies most of the commune's agroforestry land.The study also had shown that there are six common land use types(LUTs)in the commune.In particular,the LUT of pepper cultivation had the highest economic benefit,whereas the LUT of coffee brought the highest social benefit.However,the LUT of chayote was the highest in overall benefits with Ect of 0.93;thus,this LUT should be widely applied throughout Tan Binh commune.The research results were a crucial scientific basis for proposing a group of suitable plants to local natural conditions to bring effective and sustainable efficiency in land-use types.

Soil Physical Properties of Different Land Use Types in Loess Hilly Region

[Objectives]To explore the impact of land use changes on physical properties of soil in loess hilly region.[Methods]The methods of field sampling and indoor analysis were adopted.Farmland in a small watershed in the middle of the Loess Plateau,grassland that had been abandoned for 7 years,grassland that had been abandoned for 30 years,jujube orchard and ditch were sampled,and the particle composition(clay,silt and sand)and moisture changes of the soil in the top 0-100 cm were studied.[Results]In the small watershed,the top 0-100 cm of the soil was composed of 14%clay,70%silt and 16%sand.The contents of clay,silt and sand in the grassland that had been abandoned for 30 years varied greatly,while varied little in the land of other use types.The soil moisture content of grassland that had been abandoned for 30 years,jujube orchard,grassland that had been abandoned for 7 years,farmland and ditch increased with the increase of depth,with means of 10.29%,11.66%,10.08%,11.43%and 11.34%,respectively.[Conclusions]This study provides a theoretical basis for the growth of crops of different land use types in the loess hilly region.

Relationships of ozone formation sensitivity with precursors emissions,meteorology and land use types,in Guangdong-Hong Kong-Macao Greater Bay Area,China

Due to the influences of precursors emissions,meteorology,geography and other factors,ozone formation sensitivity(OFS)is generally spatially and temporally heterogeneous.This study characterized detailed spatial and temporal variations of OFS in Guangdong-Hong Kong-Macao Greater Bay Area(GBA)from 2012 to 2016 based on OMI satellite data,and analyzed the relationships of OFS with precursors emissions,meteorology and land use types(LUTs).From 2012 to 2016,the OFS tended to be NOx-limited in GBA,with the value of FNR(HCHO/NO 2)increasing from 2.04 to 2.22.According to the total annual emission statistics of precursors,NOx emissions decreased by 33.1%and VOCs emissions increased by 35.2%from 2012 to 2016,directly resulting in OFS tending to be NO x-limited.The Grey Relation Analysis results show that total column water(TCW),surface net solar radiation(SSR),air temperature at 2 m(T2)and surface pressure(SP)are the top four meteorological factors with the greatest influences on OFS.There are significant positive correlations between FNR and T2,SSR,TCW,and significant negative correlations between FNR and SP.In GBA,the OFS tends to be NO x-limited regime in wet season(higher T2,SSR,TCW and lower SP)and VOCs-limited regime in dry season(lower T2,SSR,TCW and higher SP).The FNR displays obvious gradient variations on different LUTs,with the highest in“Rural areas”,second in“Suburban areas”and lowest in“Urban areas”.

Effect of Reclamation Time and Land Use on Soil Properties in Changjiang River Estuary,China

The objective of this study is to analyze soil physical and chemical properties,soil comprehensive functions and impact factors after different years of reclamation.Based on the survey data taken from 216 soil sampling points in the Fengxian Reclamation Area of the Changjiang (Yangtze) River Estuary,China in April 2009 and remotely sensed TM data in 2006,while by virtue of multivariate analysis of variance (MANOVA),geo-statistical analysis (GA),prin-cipal component analysis (PCA) and canonical correspondence analysis (CCA),it was concluded that:1) With the in-crease in reclamation time,soil moisture,soil salinity,soil electric conductivity and soil particle size tended to decline,yet soil organic matter tended to increase.Soil available phosphorous tended to increase in the early reclamation period,yet it tended to decline after about 49 years of reclamation.Soil nitrate nitrogen,soil ammonia nitrogen and pH changed slightly in different reclamation years.Soil physical and chemical properties reached a steady state after about 30 years of reclamation.2) According to the results of PCA analysis,the weighted value (0.97 in total) that represents soil nutrient factors (soil nitrate nitrogen,soil organic matter,soil available phosphorous,soil ammonia nitrogen,pH and soil particle size) were higher than the weighted value (0.48 in total) of soil limiting factors (soil salinity,soil elec-tric conductivity and soil moisture).The higher the F value is,the better the soil quality is.3) Different land use types play different roles in the soil function maturity process,with farmlands providing the best contribution.4) Soil physi-cal and chemical properties in the reclamation area were mainly influenced by reclamation time,and then by land use types.The correlation (0.1905) of the composite index of soil function (F) with reclamation time was greater than that with land use types (-0.1161).

Effects of the Land Use Change on Ecosystem Service Value Based on RS & GIS

Assessing the effect of land use change on ecosystem service value(ESV) can provide reference for sustainable land use and ecological environment protection. The land use information was extracted and analyzed based on Landsat TM images in Shuangliu County, Sichuan Province from 1992 to 2008, following remote sensing(RS) and GIS. The ESV of the land use change in study area was evaluated by adopting the service value method within Chinese terrestrial ecosystem. The results showed that:(1) the area of paddy field and forest land reduced in the 16 years, total area of construction land expanded fast on the basis of occupying paddy field and forest land.(2) The regional ESV increased by 4,508.859×104 RMB, but there is different change trend at different times, such as the ESV fell by 10.59% in 1992–2000, increased by 16.024% in 2000–2008.(3) The conversion from forest land and cultivated land to construction land caused a decline and negative flow in ESV, the total value was 2,197.233×104 RMB and 5,317.460×104 RMB.(4) All land use types showed that change of the ESV coefficient was less elastic, the relative sensitivity: forest land > cultivated land > water area. In terms of variability of ESV, water area change had greater influence on the change of ESV in the study area, and cultivated land and forest land had relatively smaller impact.

Differences of Soil Nutrient Contents under Different Land Use Patterns in Niyang River Basin

[Objectives]This study was conducted to investigate the variation characteristics of soil nutrient contents under different land use patterns in the middle and upper reaches of the Niyang River in Tibet.[Methods]With the cultivated land,grass land and forest land in the middle and upper reaches of the Niyang River as the research objects,216 soil samples were collected in layers(0-10,10-20,20-30 cm)by the standard sampling method,and the soil total nitrogen,alkali-hydrolyzable nitrogen,total potassium,available potassium,total phosphorus,available phosphorus and organic matter were determined.[Results]The contents of soil organic matter,total nitrogen and alkali-hydrolyzable nitrogen in the middle and upper reaches of Niyang River in Tibet ranked as forest land>grass land>cultivated land,and there were significant differences between the three(P<0.05).The total potassium contents of grass land and forest land were not much different,and the contents of available potassium exhibited an order of forest land>grass land>cultivated land.The distribution of soil total nutrients and available nutrients under different land use patterns showed a certain degree of surface aggregation.The contents of total nutrients and available nutrients in the soil at the 0-10 cm depth were significantly higher than those at 10-20 and 20-30 cm,and there were significant differences between the three(P<0.05).The average content of alkali-hydrolyzable nitrogen was the largest in forest soil and the smallest in cultivated land under the three land use patterns in the study area.The average content of soil available phosphorus in cultivated land(19.47 mg/kg)was significantly higher than those in grass land(5.73 mg/kg)and forest land(5.19 mg/kg).The above results indicate that long-term vegetation restoration can improve the soil quality of the middle and upper reaches of the Niyang River.[Conclusions]The results of this study research provide basic support for improving the soil effect in the area.

Response of ecosystem service value to land use/cover change in the northern slope economic belt of the Tianshan Mountains, Xinjiang, China

Land use/cover change(LUCC)is becoming more and more frequent and extensive as a result of human activities,and is expected to have a major impact on human welfare by altering ecosystem service value(ESV).In this study,we utilized remote sensing images and statistical data to explore the spatial-temporal changes of land use/cover types and ESV in the northern slope economic belt of the Tianshan Mountains in Xinjiang Uygur Autonomous Region,China from 1975 to 2018.During the study period,LUCC in the study region varied significantly.Except grassland and unused land,all the other land use/cover types(cultivated land,forestland,waterbody,and construction land)increased in areas.From 1975 to 2018,the spatial-temporal variations in ESV were also pronounced.The total ESV decreased by 4.00×10^(8) CNY,which was primarily due to the reductions in the areas of grassland and unused land.Waterbody had a much higher ESV than the other land use/cover types.Ultimately,understanding the impact of LUCC on ESV and the interactions among ESV of different land use/cover types will help improve existing land use policies and provide scientific basis for developing new conservation strategies for ecologically fragile areas.

Changes in soil carbon stocks and related soil properties along a 50-year grassland-to-cropland conversion chronosequence in an agro-pastoral ecotone of Inner Mongolia,China

Land use change significantly influences soil properties. There is little information available on the long-term effects of post-reclamation from grassland to cropland on soil properties. We compared soil carbon （C） and nitrogen （N） storage and related soil properties in a 50-year cultivation chronosequence of grassland in the agro-pastoral ecotone of Inner Mongolia. Field surveys on land use changes during the period of 1955-2002 were conducted to build a chronosequence of cropland of different ages since the conversion from grassland. The results showed that soil C and N storage, soil texture, and soil nutrient contents varied with land use types and cropland ages （P〈0.01）. In the 0-30 cm soil layer, the soil organic carbon （SOC） density was significantly lower in the crop- lands （3.28 kg C/m2 for C50 soil） than in the grasslands （6.32 kg C/m2）. After 5, 10, 15, 20, 35, and 50 years of crop planting （years since the onset of cultivation）, the SOC losses were 17%, 12%, 19%, 47%, 46%, and 48%, respec- tively, compared with the grasslands. The soil total nitrogen （TN） density of the grasslands was 65 g N/m2, and TN density of the cropland soil was 35 g N/m2 after 50 years of crop planting. Both the SOC and TN densities could be quantitatively determined by a negative exponential function of cropland age （P〈0.0001, R2=0.8528; P〈0.0001, R2=0.9637）. The dissolved organic carbon （DOC） content, pH value were decreased; and the soil bulk density and soil available potassium （AK） content, clay content, and sand content were increased since the conversion of grassland into cropland during the 50-year period. Our results show soil nutrients were higher in grassland than in cropland. The conversion of grasslands to croplands induced a loss of soil C storage and changes of related soil properties. The reclamation time of cultivated soil （cropland age） had significant effects on soil properties in the study area.

Dehydrogenase Activity of Soil Microorganisms and the Total DNA Level in Soil of Different Use

The aim of the study was to find the interrelations between the activity of intracellular dehydrogenases, abundance of microorganisms, and the level of soil DNA in the Mollic Gleysol profile, with notification on the dominant DNA form （extra-or intra-cellular）, depending on the type of land use. Two neighbouring meadows were selected for investigations： one systematically cultivated and fertilized and the other deprived of any effect of anthropogenic activity, used as a control. We have demonstrated that dehydrogenase activity （DHA）, the DNA content and microbial abundance strongly depended on the type of land use. DHA exhibited a significant correlation with the DNA content （r = 0.99^＊＊＊ and r = 0.74^＊, for cultivated and control sites, respectively）. This relationship with such a high r value might suggest domination of the intracellular form of DNA in the cultivated meadow, which is also confirmed by the c.a. 13% increase in microorganism abundance in the cultivated soil. The optimal conditions for microbial activities were defined by the significant positive interrelationships between microbial abundance and the total organic carbon content, and a negative correlation with pH, redox potential and soil bulk density.

The Ecological Importance and Influence of Land Use on Carbonic Anhydrase Activity of Waters in the Upstream Section of the Wujiang River Basin

Thirty-four sampling sites for surface water and twenty-seven sampling sites for ground water in areas of different land use were selected in the Wujiang River Basin, upstream section in Guizhou Province, China. Carbonic anhydrase （CA） activity in surface and ground water was analyzed and compared. The results show that CA activity was detected in all surface and ground water samples. In general, average CA activity in surface and ground water was highest from samples in arbor lands, followed by shrub lands, shrub and grass lands, agricultural lands, and residential areas. The average CA activity in ground water from arbor lands, shrub lands, and shrub and grass lands was higher than that in surface water. Water CA activity was positively correlated with HCO3- concentration in surface water and ground water. These results imply that the contribution of CA in water to the karst carbon sink potential of river basins warrants further extensive and in-depth research.

Impact of Land Use and Soil Fertility on Distributions of Soil Aggregate Fractions and Some Nutrients

The size distribution of water-stable aggregates and the variability of organic C,N and P contents over aggregate size fractions were studied for orchard,upland,paddy,and grassland soils with high,medium,and low fertility levels.The results showed that > 5 mm aggregates in the cultivated upland and paddy soils were 44.0% and 32.0%,respectively,less than those in the un-tilled orchard soil.Organic C and soil N in different size aggregate fractions in orchard soil with high fertility were significantly higher than those of other land uses.However,the contents of soil P in different size aggregates were significantly greater in the paddy soil as compared to the other land uses.Soil organic C,N and P contents were higher in larger aggregates than those in smaller ones.The amount of water-stable aggregates was positively correlated to their contribution to soil organic C,N and P.For orchard and grassland soils,the > 5 mm aggregates made the greatest contribution to soil nutrients,while for upland soil,the 0.25-0.053 mm aggregates contributed the most to soil nutrients.Therefore,the land use with minimum disturbance was beneficial for the formation of a better soil structure.The dominant soil aggregates in different land use types determined the distribution of soil nutrients.Utilization efficiency of soil P could be improved by converting other land uses to the paddy soil.

The Heterogeneity and Its Influencing Factors of Soil Nutrients in Peak-Cluster Depression Areas of Karst Region

By selecting a typical peak-cluster depression area of karst region in Southwest China, we evaluated the effect of land use types and topographic factors on soil nutrients. Grid and line sampling methods were used to sample soil in depression and slope lands respectively, and classical statistical tools were applied to analyze the spatial variability character of soil organic carbon （SOC）, total nitrogen （TN）, total phosphorus （TP）, total potassium （TK）, available nitrogen （AN）, available phosphorus （AP）, available potassium （AK）, pH, and C/N. It was found that land use type was the dominant factor that effected the spatial heterogeneity of SOC, TN, TP, TK, AN, and AP. The content of SOC, TN, and AN decreased with the increase of land use intensity. Due to high fertilizer input, TP and AP in tillage fields were higher than those in the other land use types. TK had no obvious change trend among various land use types. Topographic factors had a significant effect on SOC, TN, TP, AN, AP, AK, and pH. Habitat factor was the dominant factor that effected AK. Altitude factor was the dominant factor for pH. However, all of these factors had no significant effect on C/N. Tillage practice had important effect on soil nutrients loss and soil degradation in the fragile karst ecosystem, and the input of organic manure should be increased in this region.

Impacts of land use and salinization on soil inorganic and organic carbon in the middle-lower Yellow River Delta

Soil inorganic carbon(SIC)is an important reservoir of carbon(C)in arid,semi-arid,and semi-humid regions.However,knowledge is incomplete on the dynamics of SIC and its relationship with soil organic C(SOC)under different land use types in the semi-humid region,particularly in coastal zones impacted by soil salinization.We collected 170 soil samples from 34 profiles across various land use types(maize-wheat,cotton,paddy,and reed)in the middle-lower Yellow River Delta(YRD),China.We measured soil pH,electrical conductivity(EC),water-soluble salts,and SOC and SIC contents.Our results showed significant differences in both SOC and SIC among land use types.The dry cropland(maize-wheat and cotton)soils had significantly higher SOC and SIC densities(4.71 and 15.46 kg C m^(-2),respectively)than the paddy soils(3.28 and 14.09 kg C m^(-2),respectively)in the 0–100 cm layer.Compared with paddy soils,reed soils contained significantly higher SOC(4.68 kg C m^(-2))and similar SIC(15.02 kg C m^(-2))densities.There was a significant positive correlation between SOC and SIC densities over a 0–100 cm soil depth in dry cropland soils,but a negative relationship in the paddy soils.On average,SOC and SIC densities under maize-wheat cropping were 15%and 4%lower,respectively,in the salt-affected soils in the middle-lower YRD than the upper YRD.This study indicated that land use types had great influences on both SOC and SIC and their relationship,and salinization had adverse effect on soil C storage in the YRD.

Mapping essential urban land use categories(EULUC)using geospatial big data:Progress,challenges,and opportunities

Urban land use information that reflects socio-economic functions and human activities is critically essential for urban planning,land-scape design,environmental management,health promotion,and biodiversity conservation.Land-use maps outlining the distribution,pattern,and composition of essential urban land use categories(EULUC)have facilitated a wide spectrum of applications and further triggered new opportunities in urban studies.New and improved Earth observations,algorithms,and advanced products for extracting thematic urban information,in association with emer-ging social sensing big data and auxiliary crowdsourcing datasets,all together offer great potentials to mapping fine-resolution EULUC from regional to global scales.Here we review the advances of EULUC mapping research and practices in terms of their data,methods,and applications.Based on the historical retrospect,we summarize the challenges and limitations of current EULUC studies regarding sample collection,mixed land use problem,data and model generalization,and large-scale mapping efforts.Finally,we propose and discuss future opportunities,including cross-scale mapping,optimal integration of multi-source features,global sam-ple libraries from crowdsourcing approaches,advanced machine learning and ensembled classification strategy,open portals for data visualization and sharing,multi-temporal mapping of EULUC change,and implications in urban environmental studies,to facil-itate multi-scale fine-resolution EULUC mapping research.