XU Lingming, CAO Yun, TANG Siwen, LU Yuanhong, LUO Shanshan, MA Yinshan
Effects of drought stress and rewatering on physiological characteristics of Arundo donax var. versicolor
[Background] Moisture is the main component of plants, affecting the growth, development, metabolism and geographical distribution of plants. Recently, plant physiological ecology research mainly focuses on drought stress, photosynthesis, chlorophyll fluorescence, antioxidant system and osmotic adjustment substances. The effects of drought stress and rewatering on the physiological characteristics of Arundo donax var. versicolor were studied in order to provide reference for the introduction, cultivation and management of wetland gardens and to provide more choices for the use of wetland plants for soil and water conservation in wetland parks.[Methods] Taking the A. donax var. versicolor seedlings as experimental materials, the effects of drought stress and rewatering on the physiological characteristics of A. donax var. versicolor were studied. The indoor pot experiment was conducted to set 9 water gradients[CK:(53±0.5)%(Soil water saturation), C1:(50±0.5)%, C2:(45±0.5)%, C3:(40±0.5)%, C4:(35±0.5)%, C5:(30±0.5)%, C6:(20±0.5)%, C7:(10±0.5)%, C8:(5±0.5)%]. The chlorophyll content, carotenoid content, antioxidant enzyme activity, soluble protein content, malondialdehyde content, and root activity of A. donax var. versicolor were determined, and the effects of different stress treatments on its physiology were analyzed by SPSS 21.0、Microsoft-Excel 2010 and One-wayANOVA.[Results] 1) With the prolongation of stress time, the chlorophyll content of A. donax var. versicolor leaves decreased with the degree of stress deepening, the content of carotenoids decreased first and then increased during the 40%-50% soil moisture content with the prolongation of stress time, while the control and other treatment groups showed a decreased trend. 2) With the prolongation of stress time, the activity of SOD increased first and then decreased, the activity of POD decreased first and then increased, and the activity of CAT increased. With the degree of stress deepening, the activity of SOD increased, while the activities of POD and CAT increased first and then decreased. 3) With the prolongation of stress time, the content of soluble protein and MDA increased first and then decreased, and both increased with the increase of stress degree. 4) After rewatering, the photosynthetic pigments of A. donax var. versicolor leaves increased, and were 40%-50% higher than control groups. The activities of antioxidant enzymes decreased, the activity of SOD was not significantly different from that in the control group, while the activity of POD was significantly different from the control group, and the activities of CAT was extremely different from the control group. The contents of soluble protein and MDA decreased. and the root activity was significantly higher than rewatering before.[Conclusions] Under drought stress, the photosynthetic pigment synthesis of A. donax var. versicolor leaves were inhibited, but it could respond to oxidative damage by coordinating antioxidant enzymes to scavenge free radicals and accumulating soluble proteins. After rewatering, all indicators could be restored to the control level, showing a certain drought tolerance.
Different responses of aggregates-associated organic carbon to tillage and water erosion in the black soil region
[Background] Topsoil in the black soil region of Northeast China has become thinner since cultivation, soil degradation has become more and more serious and been causing soil organic matter content to decrease gradually. Soil erosion is the key contribution to soil degradation. The loss of organic carbon in the black soil region of Northeast China has not only been affected by water erosion, but also by tillage erosion. Further exploring the responses of soil organic carbon within different sizes of aggregates to two types of erosion, and determining the predominant type of erosion driving aggregates-associated organic carbon loss in the black soil region could provide evidences for mechanisms of soil erosion and soil loss and soil quality degradation in the black soil region.[Methods] Based on the surface soil of natural secondary forest which has not been undisturbed by reclamation in the northeastern China, the responses of aggregates-associated organic carbon were studied by simulated tillage erosion (in-situ disruption and tillage migration) and water erosion (raindrop splash and runoff scouring) with different interference intensities. The treatment intensities were 5, 10, 20, 30, 40 times for in-situ disruption; 5, 20, 30, 40 times for tillage migration; 40, 60, 80, 100, 120 mm/h for raindrop splash; as well as 2, 3, 4, 5, 6 L/min for runoff scouring respectively. After simulating, soils from the 0-1 cm surface were collected and incubated for 30 d. Soils after incubation were wet-sieved into >2 mm, 1-2 mm, 0.25-1 mm, 0.053-0.25 mm,<0.053 mm fractions, and then determined the organic carbon content.[Results] After in-situ disruption, soil organic carbon content of >0.25 mm and <0.25 mm aggregates increased and decreased with the increasing interference intensity, respectively. During tillage migration, the organic carbon content of >0.053 mm aggregates increased and <0.053 mm aggregates decreased, respectively. The impact of raindrop splash on organic carbon content of aggregates with different sizes showed a generally increasing trend; however, runoff scouring increased the organic carbon content of >0.25 mm aggregates and decreased the organic carbon content of <0.25 mm aggregates. The change rate of organic carbon content merely in >2 mm, 1-2 mm, 0.053-0.25 mm aggregates was negatively correlated with tillage erosion intensity.[Conclusions] Compared with water erosion, the response of aggregates-associated organic carbon to tillage erosion is more sensitive. Tillage erosion may predominate in the loss of soil organic carbon in the farmland of black soil region of Northeast China. The findings have confirmed the existence and significance of tillage erosion.
Carrying capacity of water resources in Guilin city based on DPSIR framework and water footprint theory
[Background] The evaluation of water resources and its carrying capacity can provide basic support for water resources planning, protection and rational utilization, which is of great significance for the scientific management of regional water resources, the maintenance of regional ecological security and sustainable development. In China, water footprint studies are mostly concentrated in northern areas, especially in areas and cities where water resources are relatively scarce, such as Beijing, Gansu and Liaoning, while that in southern areas got relatively few attentions.[Methods] Based on DPSIR (Driver-pressure-state-impact-response) framework, this study established the evaluation index system and assessed the water resources in the Guilin city, China. At the same time, the water footprint and carrying capacity of water resources in Guilin were evaluated and analyzed using water footprint model.[Results] 1) From 2013 to 2017, the pressure index (e.g. total water consumption, agricultural water consumption, and COD discharge amount) showed a downward trend, while the state and influence index (e.g. total water resources, water consumption in GDP of RMB Yuan 10,000) showed a certain upward trend. All these indicated that water resources of Guilin city were in good condition and were developing in a positive trend. However, the corresponding driving force indicators (e.g. total population, total GDP, value-added of tertiary industry) were increasing, which may cause a certain amount pressure on water resources in the future development process. 2) During 2013-2017, the average carrying capacity of water resources in Guilin city was 9.1624 millionhm2, and the per capita carrying capacity of water resources was 1.75hm2. The average water resources supply was 1.35 times of the demand of water resources. The carrying capacity of water resources was substantially larger than the ecological footprint of water resources and the Guilin city was in the state of ecological surplus. Moreover, the average ecological footprint of water resources of 10,000 RMB Yuan GDP was 0.48hm2, which was at the average level of Guangxi province. However, it was obviously higher than other areas in China.[Conclusions] There are relatively adequate water resources in Guilin city. But the water use efficiency in Guilin is still at a relatively low level in China. The future pressure on water resources should not be ignored with the social-economic development. We suggest that Guilin's government should strengthen the management of environmental protection and water resources protection, such as policy inclination and capital investment, in order to guarantee the regional sustainable development.
Grey relation analysis of soil moisture in different land use in the Loess Plateau of western Shanxi province
[Background] In the loess area, soil moisture (abbreviated as SM below) is a main limiting factor in the process of vegetation restoration and reconstruction. Less grey correlation degree research was conducted on SM change under different land use slopes. This paper studied the dynamic of monthly and vertical profiles and the consumption of SM under different land use slopes in the Loess Plateau of western Shanxi province, and analyzed the relationship of SM in different soil layers, different land uses and different months.[Methods] Three different land use slopes from barren grass field, Pinus tabulaeformis forest and Robinia pseudoacacia forest were selected as research objects, TDR soil moisture meter was used to measure SM to a depth of 0-200 cm at 20 cm intervals at each monitoring point of the land use slopes. SM was measured from April to October in 2018, at least once a month.[Results] 1) Under the condition of the same seasonal precipitation in the year, the grey correlation degrees of SM in the deep layer (120-160 cm) and bottom layer (160-200 cm) of barren grass field and P. tabulaeformis forest was the highest (0.779 4 and 0.749 1), and that of SM in the middle layer (80-120 cm) and deep layer (120-160 cm) of R. pseudoacacia forest was the highest (0.731 3). In addition, under different land use slopes, the grey relational degree of SM in top layer and deep layer, shallow layer and deep layer was lower. 2) The dynamic change trend of SM in barren grass field from April to June was different from July and August, and grey correlation degree of SM between April and July was the least (0.352 0). However, the variation trend of SM from April to June and September to October was highly similar, grey correlation degree of SM between April and October was the largest (0.996 3). The grey correlation degree of SM was small in each month from July to October in P. tabulaeformis. In April to October, the grey correlation degree of SM of R. pseudoacacia forest was close and the change of SM was stable.[Conclusions] The vertical and temporal dynamic change of SM are different under different land use slopes, the monthly dynamic changes of SM are significantly affected by barren grassland, the influence of P. tabulaeformis forest and R. pseudoacacia forest on deep soil moisture in vertical section is significant, and the method of grey relational analysis can be used to identify the dynamic changes of SM.
REN Yuzhi, ZHENG Jiangkun, FU Yan, WANG Wenwu, ZENG Qianting, XIANG Minghui, CHEN Xin
Effects of rainfall levels on runoff and sediment yield of slope farmland in purple soil under different tillage and crop patterns
[Background] In order to select better tillage and crop patterns for soil and water conservation of slope farmland in the purple soil, the characteristics of soil and water loss were investigated.[Methods] Based on the data of rainfall, runoff and sediment yield from 1989 to 2016 at Soil and Water Conservation Experimental Station in Suining city, four periods were divided according to different patterns that include ridge and furrow tillage, economic and fruit forest, cross ridge and planting hedgerows. Runoff and sediment yield of different plots under different patterns were analyzed according to rainfall levels.[Results] 1) Light rain and medium rain hardly caused soil erosion. The erosive rainfall was concentrated in June-August, which was mainly represented by rainstorm and heavy rain. 2) The effect of contour ridge and furrow treatment was the most obvious under heavy rain. Compared with downhill ridge in farmland, cross ridge reduced runoff yield by 50%-56% under large rainstorm and reduced sediment yield by 93%-95% under rainstorm significantly (P<0.05). Compared with Zea mays, planting Hemerocallis citrina Baroni in downhill ridge significantly reduced sediment yield by 88%-98% under heavy rain and rainstorm. Runoff and sediment yield of planting hedgerows was bigger than that of the control plots in the initial stage of planting hedgerows,which was significantly different under heavy rain. However, after three years of planting, hedgerows had great effects of reducing runoff and sediment, and the effect of Vetiveria zizanioides was better than that of Leucaena leucocephala. 3) Runoff and sediment yield of ridge and furrow plots during extraordinary rainstorm was significantly different from that during rainstorm and heavy rain. During large rainstorm, runoff yield of planting Hemerocallis citrina Baroni with downhill ridge was 6.4 times of that during heavy rain, and the difference was significant. The sediment yield during large rainstorm was significantly different from that during rainstorm and heavy rain in cross ridge and downhill ridge plots. At the initial stage of planting hedgerow, runoff yield of hedgerow plots was no significantly different from that of no-hedgerow plots during different rainfall levels (P>0.05). While sediment yield of Amygdalus persica hedgerow plots was significantly different from that of no-hedgerow plots during large rainstorm and heavy rain. Three years after planting hedgerow, runoff and sediment yield during large rainstorm was significantly different from that during rainstorm and heavy rain. The runoff yield during large rainstorm was 3.3-6.6 times of that during rainstorm and heavy rain, meanwhile, sediment yield during large rainstorm was 8.8-113.5 times of that during rainstorm and heavy rain.[Conculsions] Overall, sediment reduction effect of various tillage and crop patterns is better than runoff reduction effect. With the increase of rainfall level, the sediment reduction rate was decreasing. Therefore, considering the agricultural management and economic benefits, the appropriate patterns should be selected according to the actual situation of sloping farmland.
YU Jiangshan, TIAN Jia, DONG Yaning, XU Lingling, WANG Xiaoyan
Performance comparison of two biological sand-fixing materials in desert area of Ningxia
[Background] China has the largest area of desertification (about 27.2% of its land area) and is one of the most severely affected by windblown sand hazards in the world. Ningxia is located in northwest China with a very dry climate and is one of the worst desertification areas in China. In order to prevent desertification in Ningxia, the introduction of ecological and multi-functional sand-fixing materials is of a great significance, because it has been proved to be very effective and a trend towards desertification control in the future. Therefore, two new biological sand-fixing materials developed by Xiamen University will be tested, and the best one will be chosen for desertification control in Ningxia.[Methods] Two biological sand-fixing materials (biological calcium fertilizer and biological ammonium fertilizer) were sprayed on the surface of sand according to different application amount (40 g/m2, 60 g/m2, 100 g/m2, and 140 g/m2), and their effects on water retention, seed growth, crust compressive strength and pH value were tested by a pot incubation method. The obtained data were mainly analyzed by ANOVA and plotted methods. The water retention of the sand-fixing materials was measured by weighing method, the compressive strength of the crust was measured by surcharge loading method, and the pH value of the crust was measured using a pHs-3C precision acidity meter.[Results] 1) Compared with the CK (control), both the sand-fixing materials had significant water retention effect. The water retention effect of the biological ammonium fertilizer was better than the biological calcium fertilizer under the application amount of 140 g/m2, and the process of water loss was in accordance with power function. 2)When the application amount were 100 g/m2 and 140 g/m2, the biological ammonium fertilizer inhibited the germination of Caragana korshinskii seeds, which were 28% and 50% lower than that of the CK, respectively. However, the germination of the seeds of C. korshinskii was promoted by the biological calcium fertilizer, 12% and 16% higher than that of CK. 3) Both the sand-fixing materials formed a fine crust, and when the application amount were 100 g/m2 and 140 g/m2, the compressive strength of the crust of biological calcium fertilizer was significantly higher than that of the biological ammonium fertilizer, 59.14% and 100.68% higher respectively. 4) The crust pH value of the biological ammonium fertilizer was significantly lower than that of the calcium fertilizer (5.63% lower than the calcium fertilizer on average), but all of them were lower than CK (18.58% lower on average) under different application amount.[Conclusions] A comprehensive analysis shows that the performance of the biological calcium fertilizer is better than the biological ammonium fertilizer, and the optimal application dose of the biological calcium fertilizer is 140 g/m2.
Effect of climate factors on purple soil loss tolerance
[Background] Climate change and soil loss tolerance (SLT) are both among the important concerned items in the long term plan of Chinese science and technology. However, little study reports concerning the effect of climate change on soil loss tolerance is available.[Methods] We collected 3 fresh and typical purplish parent rock samples (Penglaizhen group, Shaximiao group, and Suining group) in sub-tropical region (central area of Sichuan Basin) in the beginning of 2015, then moved them to Yanting station in Sichuan of subtropical area, Yuanmou Station (Yunnan dry-hot valley, representing that climate changes into drying and warming), and to Xishuangbanna Station (Yunnan tropical rain forest, representing that climate becomes wetting and warming), respectively, and let them stand these natural climate at earth surface. We measured the soil formation rate (i.e., SLT) of the purplish rock samples by sieving in December of 2015, 2016, 2017, and 2018, respectively.[Results] There is a significant (P<0.01) exponential function relationship between the soil formation rate of the three parent rocks and the temperature difference and rainfall, and a power function relationship between the rate and the temperature for the parent rocks of Penglaizhen group and Shaximiao group, but no obvious relationship for Suining group. Consequently, model of soil formation rate for Penglaizhen group and Shaximiao group determined by the 3 factors of air temperature, air temperature difference and rainfall, while for Suining group only by the 2 factors of air temperature difference and rainfall. Based on these models, we calculated the annual average soil formation rate of different parent rocks under different observation stations:the averaged soil formation rates of three parent rocks increased by 21.8% and 30.7% at Xishuangbanna and Yuanmou, respectively.[Conculsions] Our results documented that both wetting and warming would increase the SLT value. The SLT of the purple soil increased by 21.8% and 30.7% under the climatic background of Xishuangbanna and Yuanmou, respectively. The results of this study provide scientific basis for accurate determination of SLT in different climatic backgrounds.
Effect of addition of water-retaining agent on the water-retaining properties of coal gangue matrix
[Background] Coal gangue is a solid waste generated in the process of coal production, which has low water-retaining capacity. A large amount of coal gangue accumulation may cause serious environmental pollutions. At present, the main way to treat gangue mountains is to directly cover soil and vegetation reconstruction; however, usually the mining area is short of soil and the site condition is extremely adverse. Therefore, it is necessary to add different proportion of coal gangue and water-retaining agent in soil to make rational use of coal gangue and improve its water-retaining property.[Methods] Yangchangwan dump site of Lingwu in Ningxia Hui Autonomous Region was taken as the research object, and 3 types of gangue matrix were set up:the ratio of coal gangue to soil was 3:1(CGM1), 1:1(CGM2) and 1:3(CGM3). In addition, acrylamide-potassium acrylate crosspolymer type (CLP) and attapulgite composite acrylamide-acrylamide type (WT) water-retaining agent with ratios of 0.1%, 0.2% and 0.5% were added respectively. The porosity, water absorption, water-retaining capacity and infiltration of gangue matrix were determined by soil column simulation.[Results] 1) The porosity, water-holding capacity and cumulative infiltration of CGM2 and CGM3 were higher than those of CGM1. With the increasing of proportion of CLP and WT, the water absorption and water-holding capacity of these treatments showed an increasing trend. The addition of CLP promoted soil water infiltration, and with the increasing of the proportion, its promotion effect became more obvious. However, the addition of WT was inversely proportional to the cumulative infiltration of coal gangue matrix. In CGM2, the adding proportion of 0.5% CLP had the highest cumulative infiltration at 60 min, reaching 48.78 mL. 2) A multi-way ANOVA demonstrated that the type of coal gangue matrix was the main factor affecting the water-holding capacity of the matrix, and the type of water-retaining agent had the greatest influence on the cumulative infiltration of coal gangue matrix. 3) Cluster analysis was performed on 21 treatments, which were divided into 3 groups. Group Ⅲ only included treatment adding 0.5%CLP under CGM2, which had better water retention and infiltration characteristics than those of other treatments.[Conculsions] Adding water-retaining agent can improve the water retention performance of coal gangue matrix. The best water retention effect is obtained when 0.5% acrylamide-potassium acrylate crosspolymer added to the ratio of coal gangue to soil 1:1.
Growth effect of Lespedeza bicolor Turcz. after the quarry slag substrate improved
[Background] With the development of the social economy and the improvement of industrialization, people's demand and development degrees for natural mineral resources have been becoming higher and higher. However, mining has caused severe damage to the landscape and natural ecosystems. In addition, a large amount of solid waste such as biological feces, reed rods, garden waste cause secondary pollution for the environment, thereby affecting the normal life of human beings. How to reduce the cost of ecological restoration of abandoned mines, and scientifically and rationally dispose of these solid wastes are two issues to be solved urgently.[Methods] The slag mixed with cow dung, reed rods and garden waste according to different mass ratio was made into green substrate, and the Lespedeza with salt, alkali and barren resistance was used as experimental object, focusing on the characteristics of pH, organic matter, nitrogen, phosphorus, potassium and seedling rate under the effect of green substrate. The key factors affecting the water-holding of the substrate and plant growth were explored, and the optimal substrate ratio was determined through comprehensive analysis. Data were analyzed according to ANOVA by SPSS statistical software, and the significant differences among means were identified by LSD's multiple range tests at a significance level of P<0.05,and all data were presented as mean±SE.[Results] 1) The improved substrate significantly increased seedling rate, growth height, soil organic matter, total nitrogen (TN), total phosphorus (TP), total kalium (TK) and other contents, and significantly reduced soil pH value. 2) The different treatment methods had different effects on each indicator. The contents of soil organic matter, TN, TP, TK, etc. significantly increased in the S8 group compared with other groups. 3) Under the improved substrate, soil physical properties increased water-holding capacity and porosity and decreased bulk density.[Conculsions] The optimal substrate formula suitable for the growth of Lespedeza is selected ratio of reed rod to garden waste as 150:40. Through data analysis and comparison, the improved substrate could neutralize soil alkalinity,improve soil fertility, and improve soil water permeability and ventilation capacity. The study may provide theoretical support for mine ecological restoration and reconstruction, thereby improving the ecological and economic benefits of the mining area by determining the optimal substrate ratio.
Application of consumer drone in the earthwork estimation of artificial deposit in construction project
[Background] In the monitoring of soil and water conservation in construction projects, there is a need to quickly and accurately measure the amount of earthwork in artificial deposits and to guide the reasonable disposal of earthwork, while the traditional measurement methods are difficult, costly and inefficient. To address these issues and explore the use of consumer drones to construct terrain models for rapid earthwork measurements, the accuracy and applicability of terrain models, which were constructed using conventional vertical down aerial photography and 45° oblique aerial photography to measure earthwork quantities at different schemes of control points, were studied and compared.[Methods] The authors used the consumer drone DJI Phantom 4pro as an aerial photography platform to take aerial photographs of small deposits at the construction site of a construction project using two schemes, one was conventional vertical down looking single "Z" aerial photography and the other was simulated 45° oblique double "Z" cross aerial photography. The two aerial photography schemes were used to construct high-precision terrain models at different number of control points, and to measure the earthwork at the same bottom; meanwhile the RTK technique was used to collect ultra-dense feature points from small deposits and then construct terrain models to measure the earthwork. The amount of earthwork measured at this time can be considered as the accurate value of the earthwork. The difference between the amount of earthwork measured by the aerial photography method and the accurate value was calculated, and the ratio of this difference to the accurate value was used as the accuracy of the amount of earthwork measured by the aerial photography method. The measurement accuracy of earthwork quantities at different control point quantities under different aerial photography methods was analyzed.[Results] When there was no control point overall or at the top of the stack, the earthwork measurement error was <3% for the oblique 45° double "Z" cross aerial photography. And the error was <2% for the conventional vertical down looking single "Z" aerial photography, when there were five control points at the four corners and the deposit top.[Conclusions] The use of consumer drone aerial photography with a small number of control points to build a terrain model for measuring earthwork may meet the application requirements and accuracy requirements, and 45° oblique cross aerial photography is also highly accurate when there is no control point at the top of the deposit and thus can be widely used in the estimation of earthwork.
Construction of carbon trading pattern based on blockchain
[Background] Chinese nine regional carbon emission quota trading markets have been operated since 2011, and Chinese national market was launched at the end of 2017. The existing issues include market information transparency and regulatory difficulty, high operating cost and low management efficiency, the contradiction between confidential business information and environmental information disclosure, the market is inactive especially for forests CCER(Chinese certified emission reduction), and how to achieve financial docking from the regional national and international carbon emission quota trading platform in future. Building blockchain carbon emission quota trading patterns may be conducive to resolving these issues and ultimately in response to climate change, thus which may prevent water loss and soil erosion and achieve the goals of environmental sustainable development.[Methods] Based on the Pareto optimality and stakeholder theory, using information technology in combination with economic means, we analyzed current carbon emission quota trading business process of CCER and CEPA(carbon emission permits allocation), explored its block chain mechanism, major stakeholders, and business scenario, and considered the typical smart contracts, classification information and data interfaces.[Results] 1) Six-layer core blockchain framework:data stored in shared ledger of data layer; network layer includes all blockchain nodes; distributed consistency technology and data validation mechanism are used in consensus layer; incentive layer is realized offline; contract layer could solve the automatic calculation, trading, settlement and offset following designed business rules; information application system of all market trading and major stakeholder put in application layer. 2)Five-step carbon emission quota trading through blockchain:releasing CEPA and CCER project information; recording, automatic calculating and releasing carbon emission and CCER project audit information; releasing subject matters of the transaction; trading and carbon emission quota trade information disclosure; releasing annual CEPA settlement and CCER project offset. 3) In whole process, every involver could get credible information by rules in limited low cost, all information are protected and every stakeholder is treated fairly and efficiently by rules through blockchain and smart contract. Finally the blockchain carbon emission quota trading pattern of "enterprise trade + government supervising + third-party audit + financial risk prevention" is constructed. In addition, the transaction activity of CCER projects including forestry carbon sequestration may be enhanced by analysis based on the scenario and smart contract.[Conclusions] This pattern is suitable for the technical support of national carbon emission quota trading system based on blockchain features, namely decentralization, collective maintenance data, complete transparent information, trading credible and privacy security decentralization, collective maintenance data, complete transparent information, trading credible and privacy security. It facilitates the docking of financial platforms to realize the huge economic value of carbon emission quota trading. In soil and water conservation plan and scheme, carbon sequestration forest should be planted, and carbon sequestration value should be created through timely trading, so as to achieve double benefits of ecology and economy.
LUO Shuyuan, ZHU Qingke, XIN Yunling, GOU Qingping
Spatio-temporal characteristics of vegetation coverage and its influencing mechanism in Wuqi county, northern Shaanxi province
[Background] The implementation of forestry ecological engineering such as the Three-North Shelterbelt System and Returning Farmland to Forests has an important and positive effect on the construction of forest and grass vegetation on the Loess Plateau. In order to explore the distribution pattern of forest and grass vegetation and its main influencing mechanism during the implementation of semi-arid loess area, Wuqi county, the first county of conducting China's Returning Farmland to Forests in northern Shaanxi province, has implemented Returning Farmland to Forests for over 20 years, and was selected as the typical representative area of this study.[Methods] Based on the Landsat series data, the image binary model was used to extract vegetation coverage data of Wuqi county in 1997, 2005, 2010 and 2016. Then these data were processed by correlation analysis and principal component analysis. The relationship between vegetation coverage and spatio-temporal distribution characteristics and its relationship with climate and forest vegetation location factors were studied.[Results] 1) From 1997 to 2016, the vegetation coverage of Wuqi county was generally on the rise, and the vegetation coverage from the southeast to the northwest gradually increased. 2) The vegetation coverage structure was significantly improved. The land area with low vegetation coverage was mainly transferred out, and the land area with medium and high vegetation coverage was mainly transferred in. 3) In the long-term sequence, the influence of temperature on vegetation coverage was greater than that of precipitation, and both had hysteresis. Precipitation in winter and spring had an important impact on vegetation coverage. 4) The forest and grass vegetation was mainly distributed in the range of 500-2 500 m from the residential area, 0-800 m from the main road and 0-400 m from the main water system, and had the greatest influence on the distribution position of the forest vegetation in the middle level vegetation cover, and no influence in the low level.[Conculsions] Under the background of the implementation of the project of Returning Farmland to Forests, the living environment of vegetation such as temperature and precipitation has gradually become an major factor affecting the coverage of local vegetation.
Advances of the migration of dissolved organic carbon driven by interflow
[Background] Soil carbon (C) pool is regulated by water erosion on slope or watershed scale. Water erosion is a major driver to C redistribution over terrestrial landscapes and export into aquatic systems. Due to the vital function of soil organic carbon (SOC) in sustainable social and environmental development, SOC migration and its loss accompanied by soil erosion (especially water erosion) have attracted continuous and global attentions. At present, the study of soil C dynamics under water erosion mainly focused on the migration driven by surface runoff and sediment. However, dissolved organic carbon (DOC) migration driven by interflow remains largely unknown. For some well-developed interflow soils, DOC migration is not only an important way of soil C loss, but also can affect the water environment and human health.[Methods] In this study, the research progresses of DOC migration and its main driving forces driven by interflow in typical ecosystems were reviewed, based on a brief summary of the overall dynamics of SOC under water erosion.[Results] 1) DOC migration fluxes have been well documented in the world. Foreign studies focused on the loss of DOC in forest ecosystems and grassland ecosystems. The DOC migration fluxes in some agricultural ecosystems were bigger than that in natural ecosystems, which needs more attention. 2) Recently, the study of DOC migration driven by interflow has gradually increased in China, including some agricultural ecosystems in different erosion type areas, such as northeast black soil area, Sichuan purple soil area, Southwest karst area and southern red soil area. Especially the DOC migration driven by interflow in slope land in purple soil area has attracted more attentions. Many studies showed that the vertical migration of DOC accounted for a large proportion in the total SOC loss in sloping land of purple soil. 3) Rainfall was the main natural factor for DOC migration, including rainfall and rainfall intensity. Rainfall was the decisive factor for DOC migration flux; however DOC migration concentration was closely related to rainfall intensity. 4) For agricultural ecosystems, the effects of fertilization and cultivation on DOC migration have also attracted many attentions. Generally, the application of fertilizer, especially the organic fertilizer could increase DOC migration flux.[Conculsions] The main research directions in this field in the future are suggested, including research contents (DOC redistribution and its influencing factors in soil profile and synchronous monitoring of DOC and dissolved organic nitrogen), research objects (sloping cropland in red soil regions) and research methods (in-situ observation under natural rainfall).
