[Objective] To investigate the effect of biochar on the chemical fertility of vegetable soil. [Method] By pot experiments, the effect of biochar the soil pH and the content of organic matter, available nitrogen, readi...[Objective] To investigate the effect of biochar on the chemical fertility of vegetable soil. [Method] By pot experiments, the effect of biochar the soil pH and the content of organic matter, available nitrogen, readily available potassium, avail- able phosphorus, water-soluble phosphorus, exchangeable calcium and magnesium were investigated. The experiment contained five treatments, i.e., CK （no biochar）, T1 （0.10% biochar）, T2 （0.25% biochar）, T3 （0.50% biochar） and T4 （1.00% biochar）. [Result] As the application amount of biochar increases in the treatments, the soil pH, the content of organic matter and readily available potassium ascended significantly, with a trend of T4〉T3 〉T2〉TI〉CK; the contents of available phospho- rus and water-soluble phosphorus first show upward trend then downward trend, with T3 being the highest and CK the lowest; the contents of available nitrogen and exchangeable magnesium did not assume obvious change; compared with control, an appropriate amount of char could significantly increase the content of exchangeable calcium. [Conclusion] Biochar can significantly improve the chemical fertility of vegetable soil, and the application amount in T3 （0.50% biochar） brings the best effects.展开更多
Nutrient limiting factors in acidic soils from vegetable fields of the Chongqing suburbs of China were assessed by employing the systematic approach developed by Agro Services International (ASI) including soil testin...Nutrient limiting factors in acidic soils from vegetable fields of the Chongqing suburbs of China were assessed by employing the systematic approach developed by Agro Services International (ASI) including soil testing, nutrient adsorption study, and pot and field experiments to verify the results of soil testing, with a conventional soil test (CST) used for comparison. The ASI method found the moderately acidic soil (W01) to be N and P deficient; the strongly acidic soil (W04) to be N, K and S deficient; and the slightly acidic soil (W09) to be N, K, S, Cu, Mn, and Zn deficient. The CST method showed that W01 had P, B and Cu deficiencies; W04 had N, P and S deficiencies; and W09 had N, P, S, B, Cu, and Zn deficiencies. There were differences between the two methods. Among the two indicator plants selected, the response of sorghum on the three representative acidic soils was more closely related to the ASI results than that of sweet pepper.展开更多
The influence of nitrification inhibitor(NI) 3,4 dimethylpyrazole phosphate(DMPP) on nitrate accumulation in greengrocery( Brassica campestris L. ssp. chinensis ) and vegetable soil at surface layer were investigated ...The influence of nitrification inhibitor(NI) 3,4 dimethylpyrazole phosphate(DMPP) on nitrate accumulation in greengrocery( Brassica campestris L. ssp. chinensis ) and vegetable soil at surface layer were investigated in field experiments in 2002 and 2003 Results showed that NI DMPP took no significant effect on yields of edible parts of greengrocery, but it could significantly decrease NO - 3 N concentration in greengrocery and in vegetable soil at surface layer. In addition, NI DMPP could reduce the NO - 3 N concentration during the prophase stage of storage.展开更多
The aim of the study was to develop an index to assess the environmental risk of P loss potential in vegetable soils with chronic difference of plantation in the suburbs of Changsha, Hunan Province, China. Chemical me...The aim of the study was to develop an index to assess the environmental risk of P loss potential in vegetable soils with chronic difference of plantation in the suburbs of Changsha, Hunan Province, China. Chemical methodology was used to study soil phosphorus status and the relationships between available P in soil and potential soil leaching P. The results showed that there was a significant linear relationship between Olsen P and CaC12-P or P concentration in soil solution. Olsen P increased sharply when either CaCI2-P or P concentration in soil solution reached a certain level. It was confirmed that 80 mg kg-t of Olsen P was the critical value of soil P leaching in the vegetable soils. P leaching probability over the critical was assessed by GIS and indicator Kriging and four secondary risks of phosphorus leaching loss were defined. In the area with vegetable cropping for over 30 yr （Chenjiadu） and 10-15 planting years （Huangxingzhen）, the indices of phosphorus leaching loss risk were 3 and 2.93, respectively. These two areas belonged to strong secondary of risk of phosphate leaching loss. In the new vegetable planting field less than 2 yr （Ningxiang）, the index was 0.06, which had almost no risk of phosphorus leaching. In vegetable soils in the suburban region of Changsha, the phosphorus leaching peotential is high and the phosphorus leaching loss is related to chronic length of vegetable cropping.展开更多
Reductive soil disinfestation（RSD）, namely amending organic materials and mulching or flooding to create strong reductive status, has been widely applied to improve degraded soils.However, there is little informatio...Reductive soil disinfestation（RSD）, namely amending organic materials and mulching or flooding to create strong reductive status, has been widely applied to improve degraded soils.However, there is little information available about sulfate（SO4^2-） transformation and sulfur（S）gas emissions during RSD treatment to degraded vegetable soils, in which S is generally accumulated. To investigate the effects of liming on SO4^2-transformation and S gas emissions,two SO4^2--accumulated vegetable soils（denoted as S1 and S2） were treated by RSD, and RSD plus lime, denoted as RSD0 and RSD1, respectively. The results showed that RSD0 treatment reduced soil SO4^2-by 51% and 61% in S1 and S2, respectively. The disappeared SO4^2-was mainly transformed into the undissolved form. During RSD treatment, hydrogen sulfide（H2S）,carbonyl sulfide（COS）, and dimethyl sulfide（DMS） were detected, but the total S gas emission accounted for 〈 0.006% of total S in both soils. Compared to RSD0, lime addition stimulated the conversion of SO42-into undissolved form, reduced soil SO4^2-by 81% in S1 and 84% in S2 and reduced total S gas emissions by 32% in S1 and 57% in S2, respectively. In addition to H2S, COS and DMS, the emissions of carbon disulfide, methyl mercaptan, and dimethyl disulfide were also detected in RSD1 treatment. The results indicated that RSD was an effective method to remove SO4^2-, liming stimulates the conversion of dissolved SO4^2-into undissolved form,probably due to the precipitation with calcium.展开更多
Organic amendments(OM)can profoundly affect soil nitrous oxide(N_(2)O)emissions via changing nitrogen(N)cycles.However,mechanistic insights into how nitrification inhibitors modulate the responses of soil N_(2)O emiss...Organic amendments(OM)can profoundly affect soil nitrous oxide(N_(2)O)emissions via changing nitrogen(N)cycles.However,mechanistic insights into how nitrification inhibitors modulate the responses of soil N_(2)O emissions to successive applications of OM are currently insufficient.In this study,we performed a laboratory experiment to examine N_(2)O emissions from a tropical vegetable soil subjected to six years of chemical fertilization(CF)and chemical fertilization combined with manure application(CFM)and evaluate the mitigation effectiveness of nitrification inhibitor dicyandiamide(DCD)under each management regime.Isotopocule mapping showed that bacterial nitrification and/or fungal denitrification accounted for 77.4%–88.5%of total N_(2)O production across treatments during the emission peak.The cumulative N_(2)O emissions from the CFM-treated soil were nearly 8-fold of those from the CF-treated soil.The CFM treatment stimulated N_(2)O production from bacterial nitrification and denitrification by increasing the abundance of genes linked to nitrifiers(ammonia-oxidizing bacterial(AOB)amoA and total comammox amoA)and denitrifiers(nirK,nirS,and qnorB),respectively.Importantly,DCD decreased cumulative N_(2)O emissions by an average of 73.3%,with better mitigation performance observed in the CFM-treated soil than in the CF-treated soil due to stronger inhibited nitrification and increased abundance of the nosZ gene,and altered bacterial community composition.The 16S rRNA sequencing further revealed that adding DCD to the CFM-treated soil resulted in declines in the abundances of bacterial phylum Actinobacteria and Chloroflexi that positively affected N_(2)O emissions;the opposite pattern prevailed for Gemmatimonadetes that negatively affected N_(2)O emissions.This study highlights the potential of manure application,when coupled with nitrification inhibitors,to achieve the dual goals of enhancing soil fertility and reducing environmental risk associated with N_(2)O emissions in tropical agricultural soils.展开更多
In recent decades, global climate change and overgrazing have led to severe degradation of alpine meadows. Understanding the changes in soil characteristics and vegetation communities in alpine meadows with different ...In recent decades, global climate change and overgrazing have led to severe degradation of alpine meadows. Understanding the changes in soil characteristics and vegetation communities in alpine meadows with different degrees of degradation is helpful to reveal the mechanism of degradation process and take the remediation measures effectively. This study analyzed the changes in vegetation types and soil characteristics and their interrelationships under three degradation degrees, i.e., non-degradation(ND),moderate degradation(MD), and severe degradation(SD) in the alpine meadows of northeastern Qinghai-Xizang Plateau, China through the long-term observation. Results showed that the aggressive degradation changed the plant species, with the vegetation altering from leguminous and gramineous to forbs and harmful grasses. The Pielou evenness and Simpson index increased by 24.58% and 7.01%,respectively, the Shannon-Wiener index decreased by 17.52%, and the species richness index remained constant. Soil conductivity, soil organic matter, total potassium, available potassium, and porosity declined.However, the number of vegetation species increased in MD. Compared with ND, the plant diversity in MD enhanced by 8.33%, 8.69%, and 7.41% at family, genus, and species levels, respectively. In conclusion,changes in soil properties due to degradation can significantly influence the condition of above-ground vegetation. Plant diversity increases, which improves the structure of belowground network. These findings may contribute to designing better protection measures of alpine meadows against global climate change and overgrazing.展开更多
Nitrification inhibitors, such as dicyandiamide （DCD）, have been shown to decrease leaching from urea- and ammoniumbased fertilizers in agricultural soils. The effect of nitrification inhibitors on nitrifier and den...Nitrification inhibitors, such as dicyandiamide （DCD）, have been shown to decrease leaching from urea- and ammoniumbased fertilizers in agricultural soils. The effect of nitrification inhibitors on nitrifier and denitrifier in short- and long-term intensive vegetable cultivation soils was poorly understood. In this study, the pot trial was conducted to investigate the differential responses of nitrifier （amoA-containing bacteria） and denitrifier （nirK-containing bacteria） to DCD in short-（soil S） and long-term （soil L） intensive vegetable cultivation soils. Quantitative polymerase chain reaction （qPCR） and terminal restriction fragment length polymorphism （T-RFLP） were employed to detect the abundance and composition of amoA- and nirK-containing communities. The results indicated that application of DCD led to a consistently higher NH4＋-N concentration during the whole incubation in soil L, while it was quickly decreased in soil S after 21 days. Furthermore, DCD induced more severe decrease of the abundance of amoA-containing bacteria in soil L than in soil S. However, the abundance of the nirK- containing community was not significantly affected by DCD in both soils. Long-term vegetable cultivation resulted in a super-dominant amoA-containing bacteria group and less divergence in soil L compared with soil S, and DCD did not cause obvious shifts of the composition of ammonia-oxidising bacteria （AOB）. On the contrary, both amoA- and nirK-containing bacterial compositions were influenced by DCD in soil S. The results suggested that long-term intensive vegetable cultivation with heavy nitrogen fertilization resulted in significant shifts of AOB community, and this community was sensitive to DCD, but denitrifiers were not clearly affected by DCD.展开更多
The objective of this study is to explore how different layer thicknesses affect the desiccation cracking behaviour of vegetated soil.During the experiment,an electronic balance was employed to quantify water evaporat...The objective of this study is to explore how different layer thicknesses affect the desiccation cracking behaviour of vegetated soil.During the experiment,an electronic balance was employed to quantify water evaporation,while a digital camera was utilized to capture the initiation and progression of soil surface cracking.Results indicate that in the early drying process,the rate of evapotranspiration in vegetated soil correlates positively with leaf biomass.For soil samples with the same layer thickness,the constant rate stage duration is consistently shorter in vegetated soil samples than in their bare soil counterparts.As the layer thickness increases,both vegetated and bare soil samples crack at higher water content.However,vegetated soil samples crack at lower water content than their bare soil counterparts.Vegetation significantly reduces the soil surface crack ratio and improves the soil crack resistance.The crack reduction ratio is positively correlated with both root weight and length density.In thicker vegetated soil layers,the final surface crack length noticeably declines.展开更多
To evaluate the long-term effects of reforestation types on soil erosion on degraded land, vegetation and soil properties under conventional sloping farmland （CSF） and three different reforestation types including a...To evaluate the long-term effects of reforestation types on soil erosion on degraded land, vegetation and soil properties under conventional sloping farmland （CSF） and three different reforestation types including a Pinus massoniana secondary forest （PSF）, an Eucommia ulmoides artificial economic forest （EEF） and a natural succession type forest （NST）, were investigated at runoff plot scale over a six-year period in a red soil region of southern China. One hundred and thirty erosive rainfall events generating runoff in plots were grouped into four rainfall types by means of K-mean clustering method. Erosive rainfall type I is the dominant rainfall type. The amount of runoff and the soil loss under erosive rainfall type III were the most, followed by rain-fall type II, IV and I. Compared with CSF treatment, reforestation treatments decreased the average annual runoff depth and the soil loss by 25.5%–61.8% and 93.9%– 96.2% during the study period respectively. Meanwhile, runoff depth at PSF and EEF treatments was significantly lower than that in NST treatment, but no significant difference existed in soil erosion modulus among the three reforestation treatments. This is mainly due to the improved vegetation properties （i.e., vegetation coverage, biomass of above- and below-ground and litter-fall mass） and soil properties （i.e., bulk density, total porosity, infiltration rate and organic carbon content） in the three reforestation treatments compared to CSF treatment. The PSF and EEF are recommended as the preferred reforestation types to control runoff and soil erosion in the red soil region of southern China, with the NST potentially being used as an important supplement.展开更多
In order to restore a degraded alkaline grassland, the local government implemented a large restoration project using fences in Changling county, Jilin province, China, in 2000. Grazing was excluded from the protected...In order to restore a degraded alkaline grassland, the local government implemented a large restoration project using fences in Changling county, Jilin province, China, in 2000. Grazing was excluded from the protected area, whereas the grazed area was continuously grazed at 8.5 dry sheep equivalent（DSE）/hm2. In the current research, soil and plant samples were taken from grazed and fenced areas to examine changes in vegetation and soil properties in 2005, 2006 and 2008. Results showed that vegetation characteristics and soil properties improved significantly in the fenced area compared with the grazed area. In the protected area the vegetation cover, height and above- and belowground biomass increased significantly. Soil pH, electrical conductivity and bulk density decreased significantly, but soil organic carbon and total nitrogen concentration increased greatly in the protected area. By comparing the vegetation and soil characteristics with pre-degraded grassland, we found that vegetation can recover 6 years after fencing, and soil pH can be restored 8 years after fencing. However, the restoration of soil organic carbon, total nitrogen and total phosphorus concentrations needed 16, 30 and 19 years, respectively. It is recommended that the stocking rate should be reduced to 1/3 of the current carrying capacity, or that a grazing regime of 1-year of grazing followed by a 2-year rest is adopted to sustain the current status of vegetation and soil resources. However, if N fertilizer is applied, the rest period could be shortened, depending on the rate of application.展开更多
In consideration of the spectral character of MODIS (Moderate Resolution Imaging Spectroradiometer) dataand the reflective spectrum of vegetation and soil, NDVI (Normalized Difference Vegetation Index) and NDWI (Nor-m...In consideration of the spectral character of MODIS (Moderate Resolution Imaging Spectroradiometer) dataand the reflective spectrum of vegetation and soil, NDVI (Normalized Difference Vegetation Index) and NDWI (Nor-malized Difference Water Index) are deduced using one visible band (0.66μm) and two near-infrared bands (0.86μm,1.24 μm). Vegetation canopy temperature is derived using two thermal infrared bands (8.6 μm and 11μm). Then thevegetation/soil synthesis water index (VSWI) is acquired through analyzing the coupling character of three indexeswhich can reflect the water condition of vegetation. Finally, the synthesis index is verified by equivalent water contentof a single leaf. The matching results show that the synthesis index is directly proportional to the modeled data,which means that the vegetation water content can be reflected using the synthesis index effectively.展开更多
Arid zones, which cover approximately 40 percent of the earth’s land surface, support complicated and widely varied ecological systems. As such, arid zones are an important composition of the global terrestrial ecosy...Arid zones, which cover approximately 40 percent of the earth’s land surface, support complicated and widely varied ecological systems. As such, arid zones are an important composition of the global terrestrial ecosystem, and water is the key and abiotic lim-ited factor in ecosystem-driven processes in these areas. Ecohydrology is a new cross discipline that provides, in an objective and comprehensive manner, novel ideas and approaches to the evaluation of the interaction and feedback mechanisms involved in the soil–vegetation systems in arid zones. In addition, ecohydrology provides a theoretical basis of ecological restoration that is cen-tered on vegetation construction. In this paper, long-term monitoring and local observations in the transitional belt between a de-sertified steppe and a steppified desert at the Shapotou Desert Research and Experiment Station, Tengger Desert, in northern China, were evaluated. The primary achievements and related research progress regarding ecohydrology in arid zones were analyzed and summarized, as a keystone, and the response of soil ecohydrological processes to the changes in the species composition, structure, and function of sandland vegetation was discussed. Meanwhile, the long-term ecological effects and mechanism of regulation of vegetation on soil habitat and on water-cycling were considered. As a vital participant in the ecohydrological processes of soil–vegetation systems, the studies on biological soil crusts was also summarized, and related theoretical models of restoration based on the water balance was reviewed.展开更多
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 depende...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-conifermixedforest,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.展开更多
Hyperspectral data are an important source for monitoring soil salt content on a large scale. However, in previous studies, barriers such as interference due to the presence of vegetation restricted the precision of m...Hyperspectral data are an important source for monitoring soil salt content on a large scale. However, in previous studies, barriers such as interference due to the presence of vegetation restricted the precision of mapping soil salt content. This study tested a new method for predicting soil salt content with improved precision by using Chinese hyperspectral data, Huan Jing-Hyper Spectral Imager(HJ-HSI), in the coastal area of Rudong County, Eastern China. The vegetation-covered area and coastal bare flat area were distinguished by using the normalized differential vegetation index at the band length of 705 nm(NDVI705). The soil salt content of each area was predicted by various algorithms. A Normal Soil Salt Content Response Index(NSSRI) was constructed from continuum-removed reflectance(CR-reflectance) at wavelengths of 908.95 nm and 687.41 nm to predict the soil salt content in the coastal bare flat area(NDVI705 < 0.2). The soil adjusted salinity index(SAVI) was applied to predict the soil salt content in the vegetation-covered area(NDVI705 ≥ 0.2). The results demonstrate that 1) the new method significantly improves the accuracy of soil salt content mapping(R2 = 0.6396, RMSE = 0.3591), and 2) HJ-HSI data can be used to map soil salt content precisely and are suitable for monitoring soil salt content on a large scale.展开更多
In acid precipitation area of Chongqing suburb the average of Hg in soil rose from 0.158 mg/kg in 1984to 0.20 mg/kg in 1989, and Hg content of crops grown on these soils increased too. Both soil and vegetableHg came m...In acid precipitation area of Chongqing suburb the average of Hg in soil rose from 0.158 mg/kg in 1984to 0.20 mg/kg in 1989, and Hg content of crops grown on these soils increased too. Both soil and vegetableHg came mainly from power plant emission, which caused Hg and acid precipitation pollution in environmentand the Hg pollution of water, crops and milk in the area.展开更多
In this study,the impact of the training sample selection method on the performance of fuzzy-based Possibilistic c-means(PCM)and Noise Clustering(NC)classifiers were examined and mapped the cumin and fennel rabi crop....In this study,the impact of the training sample selection method on the performance of fuzzy-based Possibilistic c-means(PCM)and Noise Clustering(NC)classifiers were examined and mapped the cumin and fennel rabi crop.Two training sample selection approaches that have been investigated in this study are“mean”and“individual sample as mean”.Both training sample techniques were applied to the PCM and NC classifiers to classify the two indices approach.Both approaches have been studied to decrease spectral information in temporal data processing.The Modified Soil Adjusted Vegetation Index 2(MSAVI-2)and Class-Based Sensor Independent Modified Soil Adjusted Vegetation Index-2(CBSI-MSAVI-2)have been considered to minimize soil background effects,enhancing vegetation detection accuracy,particularly in areas with sparse vegetation cover.The MMD(MeanMembership Difference)and RMSE(RootMean Square Error)approaches were used to measure the study’s accuracy.To illustrate that the classifier successfully describes classes,cluster validity(SSE)was also performed,and the variance parameter was computed to handle heterogeneity within cumin and fennel crop fields.For the calculation of RMSE,Sentinel-2 data was used as classified,whereas PlanetScope satellite data was utilized as the reference data set.The best result was obtained using the NC classifier with“individual sample as mean”using CBSI-MSAVI-2 temporal indices.For Fuzziness Factor(m)=1.1,the RMSE,MMD,Variance,and SSE values for the NC classifier using“individual sample as mean”on the CBSI-MSAVI-2 temporal indices for cumin were 0.00098,0.00162,0.02857,and 0.97143,respectively and for fennel were 0.00025,0.00248,0.10420,and 3.54286,respectively.展开更多
Soil,as the largest terrestrial organic carbon reservoir,contains approximately 1500 petagrams of organic carbon in its top meter.This amount is roughly twice the carbon stored in the atmosphere and three times that i...Soil,as the largest terrestrial organic carbon reservoir,contains approximately 1500 petagrams of organic carbon in its top meter.This amount is roughly twice the carbon stored in the atmosphere and three times that in vegetation[1].Enhancing soil organic carbon(SOC)storage is an effective strategy for mitigating climate change.Moreover,SOC is a key indicator of soil quality and ecological health and plays a central role in the global carbon cycle.Given increasing concerns over global warming,food security,and environmental sustainability,accurately quantifying SOC at large scales with high spatial resolution and precision is essential.展开更多
Ammonia（NH3） volatilization is a major pathway of nitrogen（N） loss from soil-crop systems.As vegetable cultivation is one of the most important agricultural land uses worldwide,a deeper understanding of NH3 volati...Ammonia（NH3） volatilization is a major pathway of nitrogen（N） loss from soil-crop systems.As vegetable cultivation is one of the most important agricultural land uses worldwide,a deeper understanding of NH3 volatilization is necessary in vegetable production systems.We therefore conducted a 3-year（2010-2012） field experiment to characterize NH3 volatilization and evaluate the effect of different N fertilizer treatments on this process during the growth period of Chinese cabbage.Ammonia volatilization rate,rainfall,soil water content,p H,and soil NH4~＋were measured during the growth period.The results showed that NH3 volatilization was significantly and positively correlated to topsoil p H and NH4＋concentration.Climate factors and fertilization method also significantly affected NH3 volatilization.Specifically,organic fertilizer（OF） increased NH3 volatilization by 11.77%-18.46%,compared to conventional fertilizer（CF,urea）,while organic-inorganic compound fertilizer（OIF） reduced NH3 volatilization by 8.82%-12.67% compared to CF.Furthermore,slow-release fertilizers had significantly positive effects on controlling NH3 volatilization,with a 60.73%-68.80% reduction for sulfur-coated urea（SCU）,a 71.85%-78.97% reduction for biological Carbon Power~？ urea（BCU）,and a 77.66%-83.12% reduction for bulk-blend controlled-release fertilizer（BBCRF）relative to CF.This study provides much needed baseline information,which will help in fertilizer choice and management practices to reduce NH3 volatilization and encourage the development of new strategies for vegetable planting.展开更多
Vegetation fractional coverage （VFC） is an important index to describe and evaluate the ecological system. The vegetation index is widely used to monitor vegetation coverage in the field of remote sensing （RS）. In...Vegetation fractional coverage （VFC） is an important index to describe and evaluate the ecological system. The vegetation index is widely used to monitor vegetation coverage in the field of remote sensing （RS）. In this paper, the author conducted a case study of the delta oasis of Weigan and Kuqa rivers, which is a typical saline area in the Tarim River Watershed. The current study was based on the TM/ETM＋ images of 1989, 2001, and 2006, and supported by Geographic Information System （GIS） spatial analysis, vegetation index, and dimidiate pixel model. In addition, VBSl （vegetation, bare soil and shadow indices） suitable for TM/ETM＋ irrlages, constructed with FCD （forest canopy density） model principle and put forward by ITTO （International Tropical Timber Organization）, was used, and it was applied to estimate the VFC. The estimation accuracy was later prow^n to be up to 83.52%. Further, the study analyzed and appraised the changes in vegetation patterns and revealed a pattern of spatial change in the vegetation coverage of the study area by producing the map of VFC levels in the delta oasis. Forest, grassland, and farmland were the three main land-use types with high and extremely-high coverage, and they played an important role in maintaining the vegetation. The forest area determined the changes of the coverage area, whereas the other two land types affected the directions of change. Therefore, planting trees, protecting grasslands, reclaiming farmlands, and controlling unused lands should be included in a long-term program because of their importance in keeping regional vegetation coverage. Finally, the dynamic variation of VFC in the study area was evaluated according to the quantity and spatial distribution rendered by plant cover diigital images to deeply analyze the reason behind the variation.展开更多
基金Supported by Science and Technology Planning Project of Guangdong Province(2012A020100004)~~
文摘[Objective] To investigate the effect of biochar on the chemical fertility of vegetable soil. [Method] By pot experiments, the effect of biochar the soil pH and the content of organic matter, available nitrogen, readily available potassium, avail- able phosphorus, water-soluble phosphorus, exchangeable calcium and magnesium were investigated. The experiment contained five treatments, i.e., CK （no biochar）, T1 （0.10% biochar）, T2 （0.25% biochar）, T3 （0.50% biochar） and T4 （1.00% biochar）. [Result] As the application amount of biochar increases in the treatments, the soil pH, the content of organic matter and readily available potassium ascended significantly, with a trend of T4〉T3 〉T2〉TI〉CK; the contents of available phospho- rus and water-soluble phosphorus first show upward trend then downward trend, with T3 being the highest and CK the lowest; the contents of available nitrogen and exchangeable magnesium did not assume obvious change; compared with control, an appropriate amount of char could significantly increase the content of exchangeable calcium. [Conclusion] Biochar can significantly improve the chemical fertility of vegetable soil, and the application amount in T3 （0.50% biochar） brings the best effects.
基金Project supported by the Potash & Phosphate Institute/Potash & Phosphate Institute of Canada (PPI/PPIC) (No. Chongqing-02).
文摘Nutrient limiting factors in acidic soils from vegetable fields of the Chongqing suburbs of China were assessed by employing the systematic approach developed by Agro Services International (ASI) including soil testing, nutrient adsorption study, and pot and field experiments to verify the results of soil testing, with a conventional soil test (CST) used for comparison. The ASI method found the moderately acidic soil (W01) to be N and P deficient; the strongly acidic soil (W04) to be N, K and S deficient; and the slightly acidic soil (W09) to be N, K, S, Cu, Mn, and Zn deficient. The CST method showed that W01 had P, B and Cu deficiencies; W04 had N, P and S deficiencies; and W09 had N, P, S, B, Cu, and Zn deficiencies. There were differences between the two methods. Among the two indicator plants selected, the response of sorghum on the three representative acidic soils was more closely related to the ASI results than that of sweet pepper.
文摘The influence of nitrification inhibitor(NI) 3,4 dimethylpyrazole phosphate(DMPP) on nitrate accumulation in greengrocery( Brassica campestris L. ssp. chinensis ) and vegetable soil at surface layer were investigated in field experiments in 2002 and 2003 Results showed that NI DMPP took no significant effect on yields of edible parts of greengrocery, but it could significantly decrease NO - 3 N concentration in greengrocery and in vegetable soil at surface layer. In addition, NI DMPP could reduce the NO - 3 N concentration during the prophase stage of storage.
基金supported by the National Nature Science Foundation of China (NSFC4077111 andKZCX2-YW-437)
文摘The aim of the study was to develop an index to assess the environmental risk of P loss potential in vegetable soils with chronic difference of plantation in the suburbs of Changsha, Hunan Province, China. Chemical methodology was used to study soil phosphorus status and the relationships between available P in soil and potential soil leaching P. The results showed that there was a significant linear relationship between Olsen P and CaC12-P or P concentration in soil solution. Olsen P increased sharply when either CaCI2-P or P concentration in soil solution reached a certain level. It was confirmed that 80 mg kg-t of Olsen P was the critical value of soil P leaching in the vegetable soils. P leaching probability over the critical was assessed by GIS and indicator Kriging and four secondary risks of phosphorus leaching loss were defined. In the area with vegetable cropping for over 30 yr （Chenjiadu） and 10-15 planting years （Huangxingzhen）, the indices of phosphorus leaching loss risk were 3 and 2.93, respectively. These two areas belonged to strong secondary of risk of phosphate leaching loss. In the new vegetable planting field less than 2 yr （Ningxiang）, the index was 0.06, which had almost no risk of phosphorus leaching. In vegetable soils in the suburban region of Changsha, the phosphorus leaching peotential is high and the phosphorus leaching loss is related to chronic length of vegetable cropping.
基金supported by grants from the National Natural Science Foundation of China(Nos:41301313,41330744)the Natural Science Foundation of Jiangsu Province(No.BK20140062)+1 种基金the Natural Science Foundation of the Jiangsu Higher Education Institutions of China(No.13KJA210002)the Outstanding Innovation Team in Colleges and Universities in Jiangsu Province and the Priority Academic Program Development of Jiangsu Higher Education Institutions(164320H116)
文摘Reductive soil disinfestation（RSD）, namely amending organic materials and mulching or flooding to create strong reductive status, has been widely applied to improve degraded soils.However, there is little information available about sulfate（SO4^2-） transformation and sulfur（S）gas emissions during RSD treatment to degraded vegetable soils, in which S is generally accumulated. To investigate the effects of liming on SO4^2-transformation and S gas emissions,two SO4^2--accumulated vegetable soils（denoted as S1 and S2） were treated by RSD, and RSD plus lime, denoted as RSD0 and RSD1, respectively. The results showed that RSD0 treatment reduced soil SO4^2-by 51% and 61% in S1 and S2, respectively. The disappeared SO4^2-was mainly transformed into the undissolved form. During RSD treatment, hydrogen sulfide（H2S）,carbonyl sulfide（COS）, and dimethyl sulfide（DMS） were detected, but the total S gas emission accounted for 〈 0.006% of total S in both soils. Compared to RSD0, lime addition stimulated the conversion of SO42-into undissolved form, reduced soil SO4^2-by 81% in S1 and 84% in S2 and reduced total S gas emissions by 32% in S1 and 57% in S2, respectively. In addition to H2S, COS and DMS, the emissions of carbon disulfide, methyl mercaptan, and dimethyl disulfide were also detected in RSD1 treatment. The results indicated that RSD was an effective method to remove SO4^2-, liming stimulates the conversion of dissolved SO4^2-into undissolved form,probably due to the precipitation with calcium.
基金supported by the National Natural Science Foundation of China(Nos.42007098 and 32001209)the Major Science and Technology Plan of Hainan Province,China(No.ZDKJ2021008)+1 种基金the Natural Science Foundation of Hainan Province,China(Nos.320RC687 and 421QN0915)the Central PublicInterest Scientific Institution Basal Research Fund for Chinese Academy of Tropical Agricultural Sciences(Nos.1630042025001,1630042025011,and 1630042025012)。
文摘Organic amendments(OM)can profoundly affect soil nitrous oxide(N_(2)O)emissions via changing nitrogen(N)cycles.However,mechanistic insights into how nitrification inhibitors modulate the responses of soil N_(2)O emissions to successive applications of OM are currently insufficient.In this study,we performed a laboratory experiment to examine N_(2)O emissions from a tropical vegetable soil subjected to six years of chemical fertilization(CF)and chemical fertilization combined with manure application(CFM)and evaluate the mitigation effectiveness of nitrification inhibitor dicyandiamide(DCD)under each management regime.Isotopocule mapping showed that bacterial nitrification and/or fungal denitrification accounted for 77.4%–88.5%of total N_(2)O production across treatments during the emission peak.The cumulative N_(2)O emissions from the CFM-treated soil were nearly 8-fold of those from the CF-treated soil.The CFM treatment stimulated N_(2)O production from bacterial nitrification and denitrification by increasing the abundance of genes linked to nitrifiers(ammonia-oxidizing bacterial(AOB)amoA and total comammox amoA)and denitrifiers(nirK,nirS,and qnorB),respectively.Importantly,DCD decreased cumulative N_(2)O emissions by an average of 73.3%,with better mitigation performance observed in the CFM-treated soil than in the CF-treated soil due to stronger inhibited nitrification and increased abundance of the nosZ gene,and altered bacterial community composition.The 16S rRNA sequencing further revealed that adding DCD to the CFM-treated soil resulted in declines in the abundances of bacterial phylum Actinobacteria and Chloroflexi that positively affected N_(2)O emissions;the opposite pattern prevailed for Gemmatimonadetes that negatively affected N_(2)O emissions.This study highlights the potential of manure application,when coupled with nitrification inhibitors,to achieve the dual goals of enhancing soil fertility and reducing environmental risk associated with N_(2)O emissions in tropical agricultural soils.
基金supported by the National Forage Industry Technology System Program (CARS-34)Grassland Ecological Restoration and Management Science and Technology Support Project of Gansu Forestry and Grassland Bureau (GSAU-TSYF-2021-011)。
文摘In recent decades, global climate change and overgrazing have led to severe degradation of alpine meadows. Understanding the changes in soil characteristics and vegetation communities in alpine meadows with different degrees of degradation is helpful to reveal the mechanism of degradation process and take the remediation measures effectively. This study analyzed the changes in vegetation types and soil characteristics and their interrelationships under three degradation degrees, i.e., non-degradation(ND),moderate degradation(MD), and severe degradation(SD) in the alpine meadows of northeastern Qinghai-Xizang Plateau, China through the long-term observation. Results showed that the aggressive degradation changed the plant species, with the vegetation altering from leguminous and gramineous to forbs and harmful grasses. The Pielou evenness and Simpson index increased by 24.58% and 7.01%,respectively, the Shannon-Wiener index decreased by 17.52%, and the species richness index remained constant. Soil conductivity, soil organic matter, total potassium, available potassium, and porosity declined.However, the number of vegetation species increased in MD. Compared with ND, the plant diversity in MD enhanced by 8.33%, 8.69%, and 7.41% at family, genus, and species levels, respectively. In conclusion,changes in soil properties due to degradation can significantly influence the condition of above-ground vegetation. Plant diversity increases, which improves the structure of belowground network. These findings may contribute to designing better protection measures of alpine meadows against global climate change and overgrazing.
基金financially supported by the National Natural Science Foundation of China (41071181, 41090282)the Chinese Academy of Sciences (KZCX2-YW-T07)
文摘Nitrification inhibitors, such as dicyandiamide （DCD）, have been shown to decrease leaching from urea- and ammoniumbased fertilizers in agricultural soils. The effect of nitrification inhibitors on nitrifier and denitrifier in short- and long-term intensive vegetable cultivation soils was poorly understood. In this study, the pot trial was conducted to investigate the differential responses of nitrifier （amoA-containing bacteria） and denitrifier （nirK-containing bacteria） to DCD in short-（soil S） and long-term （soil L） intensive vegetable cultivation soils. Quantitative polymerase chain reaction （qPCR） and terminal restriction fragment length polymorphism （T-RFLP） were employed to detect the abundance and composition of amoA- and nirK-containing communities. The results indicated that application of DCD led to a consistently higher NH4＋-N concentration during the whole incubation in soil L, while it was quickly decreased in soil S after 21 days. Furthermore, DCD induced more severe decrease of the abundance of amoA-containing bacteria in soil L than in soil S. However, the abundance of the nirK- containing community was not significantly affected by DCD in both soils. Long-term vegetable cultivation resulted in a super-dominant amoA-containing bacteria group and less divergence in soil L compared with soil S, and DCD did not cause obvious shifts of the composition of ammonia-oxidising bacteria （AOB）. On the contrary, both amoA- and nirK-containing bacterial compositions were influenced by DCD in soil S. The results suggested that long-term intensive vegetable cultivation with heavy nitrogen fertilization resulted in significant shifts of AOB community, and this community was sensitive to DCD, but denitrifiers were not clearly affected by DCD.
基金support from the National Natural Science Foundation of China(Grant No.42172290,42230710,41925012)the Natural Science Foundation of Jiangsu Province(Grant No.BK20221250).
文摘The objective of this study is to explore how different layer thicknesses affect the desiccation cracking behaviour of vegetated soil.During the experiment,an electronic balance was employed to quantify water evaporation,while a digital camera was utilized to capture the initiation and progression of soil surface cracking.Results indicate that in the early drying process,the rate of evapotranspiration in vegetated soil correlates positively with leaf biomass.For soil samples with the same layer thickness,the constant rate stage duration is consistently shorter in vegetated soil samples than in their bare soil counterparts.As the layer thickness increases,both vegetated and bare soil samples crack at higher water content.However,vegetated soil samples crack at lower water content than their bare soil counterparts.Vegetation significantly reduces the soil surface crack ratio and improves the soil crack resistance.The crack reduction ratio is positively correlated with both root weight and length density.In thicker vegetated soil layers,the final surface crack length noticeably declines.
基金supported by the National Natural Science Foundation of China(No.30428028)the Innovation Group Project of the National Natural Science Foundation of China(No.40621061)
文摘To evaluate the long-term effects of reforestation types on soil erosion on degraded land, vegetation and soil properties under conventional sloping farmland （CSF） and three different reforestation types including a Pinus massoniana secondary forest （PSF）, an Eucommia ulmoides artificial economic forest （EEF） and a natural succession type forest （NST）, were investigated at runoff plot scale over a six-year period in a red soil region of southern China. One hundred and thirty erosive rainfall events generating runoff in plots were grouped into four rainfall types by means of K-mean clustering method. Erosive rainfall type I is the dominant rainfall type. The amount of runoff and the soil loss under erosive rainfall type III were the most, followed by rain-fall type II, IV and I. Compared with CSF treatment, reforestation treatments decreased the average annual runoff depth and the soil loss by 25.5%–61.8% and 93.9%– 96.2% during the study period respectively. Meanwhile, runoff depth at PSF and EEF treatments was significantly lower than that in NST treatment, but no significant difference existed in soil erosion modulus among the three reforestation treatments. This is mainly due to the improved vegetation properties （i.e., vegetation coverage, biomass of above- and below-ground and litter-fall mass） and soil properties （i.e., bulk density, total porosity, infiltration rate and organic carbon content） in the three reforestation treatments compared to CSF treatment. The PSF and EEF are recommended as the preferred reforestation types to control runoff and soil erosion in the red soil region of southern China, with the NST potentially being used as an important supplement.
基金supported by the National Key Basic Research Program of China (2011CB403203)the Strategic Science and Technology Guide Project of Chinese Academy of Sciences (XDA05050401)
文摘In order to restore a degraded alkaline grassland, the local government implemented a large restoration project using fences in Changling county, Jilin province, China, in 2000. Grazing was excluded from the protected area, whereas the grazed area was continuously grazed at 8.5 dry sheep equivalent（DSE）/hm2. In the current research, soil and plant samples were taken from grazed and fenced areas to examine changes in vegetation and soil properties in 2005, 2006 and 2008. Results showed that vegetation characteristics and soil properties improved significantly in the fenced area compared with the grazed area. In the protected area the vegetation cover, height and above- and belowground biomass increased significantly. Soil pH, electrical conductivity and bulk density decreased significantly, but soil organic carbon and total nitrogen concentration increased greatly in the protected area. By comparing the vegetation and soil characteristics with pre-degraded grassland, we found that vegetation can recover 6 years after fencing, and soil pH can be restored 8 years after fencing. However, the restoration of soil organic carbon, total nitrogen and total phosphorus concentrations needed 16, 30 and 19 years, respectively. It is recommended that the stocking rate should be reduced to 1/3 of the current carrying capacity, or that a grazing regime of 1-year of grazing followed by a 2-year rest is adopted to sustain the current status of vegetation and soil resources. However, if N fertilizer is applied, the rest period could be shortened, depending on the rate of application.
基金Project G2000077907 supported by National Key Basic Research Plan Foundation of China
文摘In consideration of the spectral character of MODIS (Moderate Resolution Imaging Spectroradiometer) dataand the reflective spectrum of vegetation and soil, NDVI (Normalized Difference Vegetation Index) and NDWI (Nor-malized Difference Water Index) are deduced using one visible band (0.66μm) and two near-infrared bands (0.86μm,1.24 μm). Vegetation canopy temperature is derived using two thermal infrared bands (8.6 μm and 11μm). Then thevegetation/soil synthesis water index (VSWI) is acquired through analyzing the coupling character of three indexeswhich can reflect the water condition of vegetation. Finally, the synthesis index is verified by equivalent water contentof a single leaf. The matching results show that the synthesis index is directly proportional to the modeled data,which means that the vegetation water content can be reflected using the synthesis index effectively.
基金supported by the National Natural Scientific Foundation of China (40825001)
文摘Arid zones, which cover approximately 40 percent of the earth’s land surface, support complicated and widely varied ecological systems. As such, arid zones are an important composition of the global terrestrial ecosystem, and water is the key and abiotic lim-ited factor in ecosystem-driven processes in these areas. Ecohydrology is a new cross discipline that provides, in an objective and comprehensive manner, novel ideas and approaches to the evaluation of the interaction and feedback mechanisms involved in the soil–vegetation systems in arid zones. In addition, ecohydrology provides a theoretical basis of ecological restoration that is cen-tered on vegetation construction. In this paper, long-term monitoring and local observations in the transitional belt between a de-sertified steppe and a steppified desert at the Shapotou Desert Research and Experiment Station, Tengger Desert, in northern China, were evaluated. The primary achievements and related research progress regarding ecohydrology in arid zones were analyzed and summarized, as a keystone, and the response of soil ecohydrological processes to the changes in the species composition, structure, and function of sandland vegetation was discussed. Meanwhile, the long-term ecological effects and mechanism of regulation of vegetation on soil habitat and on water-cycling were considered. As a vital participant in the ecohydrological processes of soil–vegetation systems, the studies on biological soil crusts was also summarized, and related theoretical models of restoration based on the water balance was reviewed.
基金supported by National Natural Science Foundation of China (31600330)Guangdong Forestry Science and Technology Innovation Project (2015KJCX029)CFERN & BEIJING TECHNO SOLUTIONS Award Funds on excellent academic achievements
文摘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-conifermixedforest,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.
基金Under the auspices of National Natural Science Foundation of China(No.41230751,41101547)Scientific Research Foundation of Graduate School of Nanjing University(No.2012CL14)
文摘Hyperspectral data are an important source for monitoring soil salt content on a large scale. However, in previous studies, barriers such as interference due to the presence of vegetation restricted the precision of mapping soil salt content. This study tested a new method for predicting soil salt content with improved precision by using Chinese hyperspectral data, Huan Jing-Hyper Spectral Imager(HJ-HSI), in the coastal area of Rudong County, Eastern China. The vegetation-covered area and coastal bare flat area were distinguished by using the normalized differential vegetation index at the band length of 705 nm(NDVI705). The soil salt content of each area was predicted by various algorithms. A Normal Soil Salt Content Response Index(NSSRI) was constructed from continuum-removed reflectance(CR-reflectance) at wavelengths of 908.95 nm and 687.41 nm to predict the soil salt content in the coastal bare flat area(NDVI705 < 0.2). The soil adjusted salinity index(SAVI) was applied to predict the soil salt content in the vegetation-covered area(NDVI705 ≥ 0.2). The results demonstrate that 1) the new method significantly improves the accuracy of soil salt content mapping(R2 = 0.6396, RMSE = 0.3591), and 2) HJ-HSI data can be used to map soil salt content precisely and are suitable for monitoring soil salt content on a large scale.
文摘In acid precipitation area of Chongqing suburb the average of Hg in soil rose from 0.158 mg/kg in 1984to 0.20 mg/kg in 1989, and Hg content of crops grown on these soils increased too. Both soil and vegetableHg came mainly from power plant emission, which caused Hg and acid precipitation pollution in environmentand the Hg pollution of water, crops and milk in the area.
文摘In this study,the impact of the training sample selection method on the performance of fuzzy-based Possibilistic c-means(PCM)and Noise Clustering(NC)classifiers were examined and mapped the cumin and fennel rabi crop.Two training sample selection approaches that have been investigated in this study are“mean”and“individual sample as mean”.Both training sample techniques were applied to the PCM and NC classifiers to classify the two indices approach.Both approaches have been studied to decrease spectral information in temporal data processing.The Modified Soil Adjusted Vegetation Index 2(MSAVI-2)and Class-Based Sensor Independent Modified Soil Adjusted Vegetation Index-2(CBSI-MSAVI-2)have been considered to minimize soil background effects,enhancing vegetation detection accuracy,particularly in areas with sparse vegetation cover.The MMD(MeanMembership Difference)and RMSE(RootMean Square Error)approaches were used to measure the study’s accuracy.To illustrate that the classifier successfully describes classes,cluster validity(SSE)was also performed,and the variance parameter was computed to handle heterogeneity within cumin and fennel crop fields.For the calculation of RMSE,Sentinel-2 data was used as classified,whereas PlanetScope satellite data was utilized as the reference data set.The best result was obtained using the NC classifier with“individual sample as mean”using CBSI-MSAVI-2 temporal indices.For Fuzziness Factor(m)=1.1,the RMSE,MMD,Variance,and SSE values for the NC classifier using“individual sample as mean”on the CBSI-MSAVI-2 temporal indices for cumin were 0.00098,0.00162,0.02857,and 0.97143,respectively and for fennel were 0.00025,0.00248,0.10420,and 3.54286,respectively.
基金supported by the National Natural Science Foundation of China(42375116)the Scientific Innovation Projects of Meteorological Bureau in Nei Mongol Autonomous Region(nmqxkjcx202422)the Fundamental Research Funds for the Central Universities.
文摘Soil,as the largest terrestrial organic carbon reservoir,contains approximately 1500 petagrams of organic carbon in its top meter.This amount is roughly twice the carbon stored in the atmosphere and three times that in vegetation[1].Enhancing soil organic carbon(SOC)storage is an effective strategy for mitigating climate change.Moreover,SOC is a key indicator of soil quality and ecological health and plays a central role in the global carbon cycle.Given increasing concerns over global warming,food security,and environmental sustainability,accurately quantifying SOC at large scales with high spatial resolution and precision is essential.
基金supported by the National Key Science and Technology Project on Water Pollution Control and Treatment (Nos.2008ZX07101-006 and 2012ZX07506-006)
文摘Ammonia（NH3） volatilization is a major pathway of nitrogen（N） loss from soil-crop systems.As vegetable cultivation is one of the most important agricultural land uses worldwide,a deeper understanding of NH3 volatilization is necessary in vegetable production systems.We therefore conducted a 3-year（2010-2012） field experiment to characterize NH3 volatilization and evaluate the effect of different N fertilizer treatments on this process during the growth period of Chinese cabbage.Ammonia volatilization rate,rainfall,soil water content,p H,and soil NH4~＋were measured during the growth period.The results showed that NH3 volatilization was significantly and positively correlated to topsoil p H and NH4＋concentration.Climate factors and fertilization method also significantly affected NH3 volatilization.Specifically,organic fertilizer（OF） increased NH3 volatilization by 11.77%-18.46%,compared to conventional fertilizer（CF,urea）,while organic-inorganic compound fertilizer（OIF） reduced NH3 volatilization by 8.82%-12.67% compared to CF.Furthermore,slow-release fertilizers had significantly positive effects on controlling NH3 volatilization,with a 60.73%-68.80% reduction for sulfur-coated urea（SCU）,a 71.85%-78.97% reduction for biological Carbon Power~？ urea（BCU）,and a 77.66%-83.12% reduction for bulk-blend controlled-release fertilizer（BBCRF）relative to CF.This study provides much needed baseline information,which will help in fertilizer choice and management practices to reduce NH3 volatilization and encourage the development of new strategies for vegetable planting.
基金supported by the National Basic Research Program of China (2009CB421302)the Joint Fundsof the National Natural Science Foundation of China(U1138303)+4 种基金the National Natural Science Foundation of China(41261090,41161063)the Open Foundation of State Key Laboratory of Resources and Environment Information Systems (2010KF0003SA)Scientific Research Foundation for Doctor (BS110125)Xinjiang Natural Science Foundation for Young Scholars (2012211B04)Research Fund for Training Young Teachers (XJEDU2012S03)
文摘Vegetation fractional coverage （VFC） is an important index to describe and evaluate the ecological system. The vegetation index is widely used to monitor vegetation coverage in the field of remote sensing （RS）. In this paper, the author conducted a case study of the delta oasis of Weigan and Kuqa rivers, which is a typical saline area in the Tarim River Watershed. The current study was based on the TM/ETM＋ images of 1989, 2001, and 2006, and supported by Geographic Information System （GIS） spatial analysis, vegetation index, and dimidiate pixel model. In addition, VBSl （vegetation, bare soil and shadow indices） suitable for TM/ETM＋ irrlages, constructed with FCD （forest canopy density） model principle and put forward by ITTO （International Tropical Timber Organization）, was used, and it was applied to estimate the VFC. The estimation accuracy was later prow^n to be up to 83.52%. Further, the study analyzed and appraised the changes in vegetation patterns and revealed a pattern of spatial change in the vegetation coverage of the study area by producing the map of VFC levels in the delta oasis. Forest, grassland, and farmland were the three main land-use types with high and extremely-high coverage, and they played an important role in maintaining the vegetation. The forest area determined the changes of the coverage area, whereas the other two land types affected the directions of change. Therefore, planting trees, protecting grasslands, reclaiming farmlands, and controlling unused lands should be included in a long-term program because of their importance in keeping regional vegetation coverage. Finally, the dynamic variation of VFC in the study area was evaluated according to the quantity and spatial distribution rendered by plant cover diigital images to deeply analyze the reason behind the variation.
