Impact Of Land Management Research Articles

Land Degradation and Management within Upper Racova Catchment

Abstract Land degradation has been recognized as an important environmental threat in the Moldavian Plateau of eastern Romania. This study was designed to estimate the magnitude of land degradation and to review land management in a small catchment in the Central Moldavian Plateau. Several methods were deployed to estimate soil erosion losses, gully distribution, landslide inventory and reservoir sedimentation rates. Results obtained in the study area of 7,766 ha, of which 31% is arable and 32% native forest, show that the mean value of soil losses by water erosion on agricultural land is 19.0 t ha−1y−1. By adding the woodland contribution, this value significantly decreases to 12.8 t ha−1y−1. Then, a large proportion of land (58%) is covered by landslides. Most of them are shallow and dormant (stable), and the active ones form only ~2% of the total landslide area. Siltation rates determined using 137Cs reflect the impact of land management on deposition patterns in reservoirs. Proper conservation measures were applied over a 20-year time-span from 1970-1990. Since 1991 the contour farming system collapsed and returned to the traditional ‘up-and-down slope’ farming system on very small plots.

Site occupancy and reproductive dynamics of California spotted owls in a mixed-ownership landscape

Biodiversity conservation in mixed-ownership landscapes often depends on contributions from privately-owned lands, where natural resource development can alter and produce novel habitat conditions for species of conservation concern. A lack of research on private lands stemming from access issues and concerns over regulatory outcomes, however, often limits evaluation of the impact of land management. The California spotted owl (Strix occidentalis occidentalis), for example, often occurs in mixed-ownership landscapes but research on this species has occurred primarily on public lands. Therefore, we conducted the first large-scale private-public cooperative and comparative analyses of California spotted owls inhabiting mixed-ownership landscapes in the Sierra Nevada, California, USA. We surveyed 151 spotted owl sites from 2013 to 2017 within two study systems: one comprised primarily of public lands (national forests) where the owl population has declined over the last ∼20 years and a set of study areas comprised mostly of private lands on which relatively high estimates of site occupancy were recently reported. Multistate occupancy modeling indicated that the probability of occupancy and successful reproduction by owls depended on site status in the previous year, with both probabilities highest at sites where owls successfully reproduced in the previous year, intermediate at occupied sites where owls had not successfully reproduced, and lowest at previously unoccupied sites. Site occupancy probability was higher at low-elevation sites and lower at sites that contained more open area and younger forest. Successful reproduction by owls was also more likely at low-elevation sites and at sites with more north-facing slope and younger forest with high basal area of hardwoods. Study areas with more private lands tended to occur at lower elevations and have greater amounts of younger forest with high basal area of hardwoods, which may have contributed to higher occupancy and reproductive probabilities than the study area with more public land. Thus, differences in occupancy and reproductive probabilities between study areas appeared to be the result of differences in topographic and vegetation conditions that likely promote populations of key spotted owl prey species. Our results suggest that private lands in mixed-ownership landscapes may contribute to spotted owl conservation by conferring different benefits to owls than public lands and, more broadly, highlight the importance of including private lands in conservation research and planning.

Assessing Impacts of Soil Management Measures on Ecosystem Services

Only a few studies have quantified and measured ecosystem services (ES) specifically related to soil. To address this gap, we have developed and applied a methodology to assess changes in ecosystem services, based on measured or estimated soil property changes that were stimulated by soil management measures (e.g., mulching, terracing, no-till). We applied the ES assessment methodology in 16 case study sites across Europe representing a high diversity of soil threats and land use systems. Various prevention and remediation measures were trialled, and the changes in manageable soil and other natural capital properties were measured and quantified. An Excel tool facilitated data collection, calculation of changes in ecosystem services, and visualization of measured short-term changes and estimated long-term changes at plot level and for the wider area. With this methodology, we were able to successfully collect and compare data on the impact of land management on 15 different ecosystem services from 26 different measures. Overall, the results are positive in terms of the impacts of the trialled measures on ecosystem services, with 18 out of 26 measures having no decrease in any service at the plot level. Although methodological challenges remain, the ES assessment was shown to be a comprehensive evaluation of the impacts of the trialled measures, and also served as an input to a stakeholder valuation of ecosystem services at local and sub-national levels.

Biofunctool®: a new framework to assess the impact of land management on soil quality. Part B: investigating the impact of land management of rubber plantations on soil quality with the Biofunctool® index

Biofunctool® is a new framework for assessing the impact of land management on soil quality – defined as the capacity of the soil to function. Biofunctool® uses a set of twelve indicators to monitor changes in three key soil functions: carbon transformation, nutrient cycling and structure maintenance (part A). Information from all the indicators is integrated in a Soil Quality Index using multivariate analysis (PCA) weighting. We used Biofunctool® to assess the impact of land use, land use change and agricultural practices on soil quality. The Biofunctool® index was measured for soils in Thailand within rubber plantations, forests and intensive cash crops (cassava and sugar cane). The results demonstrate that the Biofunctool® index provides an aggregated synthetic soil functioning score that is sensitive to land management and is robust in various pedo-climatic contexts. Firstly, the index revealed the impact on soil of land conversion from annual cropping to rubber plantations and ranked the effect on soil with respect to a natural forest reference. Secondly, it showed the positive effect of legume cover-crops on soil functioning. Thirdly, it highlighted a trend of improving soil quality with increasing age of rubber plantations, in contrasted pedo-climatic contexts. It is concluded that the Biofunctool® index is a reliable and relevant descriptor of integrated soil functioning (i.e. soil quality) that could be useful for environmental impact assessment at regional to global scales.

Biofunctool®: a new framework to assess the impact of land management on soil quality. Part A: concept and validation of the set of indicators

The assessment of soil quality is a scientific issue that has been widely debated in the literature for the last twenty years. We developed the Biofunctool® framework to assess soil quality based on an integrative approach that accounts for the link between the physico-chemical properties and the biological activity of soils. Biofunctool® consists in a set of twelve in-field, time- and cost-effective indicators to assess three main soil functions: carbon transformation, nutrient cycling and structure maintenance. The indicators were applied in a network of mostly rubber plantations compared with three other land uses in Thailand. We collected 1952 indicators values in 180 sampling points over a wide range of pedo-climatic and agronomic contexts in order to assess the validity of the indicators. A reliability, redundancy and sensitivity analysis was performed to validate the capacity of the set of indicators to assess the impact of land management on soil quality. The results showed the relevance and consistence of each of the twelve indicators to assess the soil functioning. Improvements are finally discussed to guide further implementation of the indicators in various contexts and build a soil quality index.

Cultural ecosystem services provision in response to urbanization in Cameroon

In Africa, cities are unable to accommodate population growth within their current administrative limits, putting pressure on ecosystem services (ES) in peripheral areas. Existing ES related studies in the region were conducted in East and South Africa, and rarely focused on cultural ES in peri-urban areas. This study aimed to assess changes in the value of cultural ES in two peripheral areas of Yaoundé, Cameroun. It applied the concept of ES through participatory geographic information systems (PGIS) to understand how the value of cultural ES has changed over time and how residents perceive it. It also considered the impact of land management by relating changes in ecosystem service provisioning areas (SPA), with the current land tenure system. We focused on two study areas, Mbalngong and Nkozoa, which were selected for their high urbanization rates. PGIS activities were conducted during twenty semi-directive interviews and one workshop per site. We found that the provision of ES decreased by more than 90% within an 18-year period, from 2000 to 2018. The lack of randomness in the distribution of ecosystem services showed that SPA had distinct functions for residents, but that this was not taken into consideration in planning decisions. We showed that current land management strategies are influenced by the land tenure system and do not incite landowners to preserve their parcels and associated SPA. While direct subsidies may not be appropriate, other approaches such as community land trusts may be more advisable for the preservation of SPA.

Short Communication: Presence of arbuscular mycorrhiza in maize plantation land cultivated with traditional and improved land management

Ishaq L. 2018. Short Communication: Presence of arbuscular mycorrhiza in maize plantation land cultivated with traditional and improved land management.Trop Drylands 2: 20-24. Arbuscular mycorrhizas (AM) are one of key fungtional soil biota that can greatly contribute to crop productiviy and agricultural sustainability. Their presences could be influenced by soil condition such as land management, and the sporulation of the fungal forming mycorrhiza could be affected by season ie. rainy and dry season. Previously, it was found that the abundance of AM fungi was higher under maize cropping with traditional land management (no tillage, no input of agrochemicals) than that under maize copping system with more modern land management (tillage, agrochemical input), when the soils were sampled at rainy season. As the presence of AM fungi could be influenced by climate factor ie. rain/season, the present study was carried out to examine the abundance and diversity of AM fungi in maize plantation land cultivated with traditional and improved land management in the dry season. At each land management system, three locations of study were purposively selected, and at each location within the cropping system, three soil samples were collected. A total of 9 soil samples representing each land management system were evaluated. The variables observed included AM fungal spore density (expressed as the number of AM fungal spores per 100 g of soil) and biodiversity of AM fungi (expressed as relative abundance of AM fungal spore). It was found that the density of AM fungal spore under maize cropping system with traditional land management was 203.55 per 100g, whereas only 84.91 spores per 100 g soil were found under maize cropping system with improved land management, supporting the previous finding. Despite only six AM fungal spores morphotypes were observed under maize plantation land of both traditional and improved land management, the abundance of the morphotype was different between the two land management systems. The study needs to be extended at a broader location and time to get more representative information on the impact of land management on the abundance of AM fungi in tropical agriculture.

Sediment predictions in Wadi Al-Naft using soil water assessment tool

Sediment production is the amount of sediment in the unit area that is transported through the basin by water transfer over a specified period of time. The main aim of present study is to predict sediment yield of Wadi, Al-Naft watershed with 8820 Km2area, that is located in the North-East of Diyala Governorate in Iraq, using Soil-Water Assessment Tool, (SWAT) and to predict the impact of land management and the input data including the land use, soil type, and soil texture maps which are obtained from Landsat-8 satellite image. Digital Elevation Model,(DEM) with resolution (14 14) meter is used to delineate the watershed with the aid of model. Three Land-sat images were used to cover the study area which were mosaic processed and the study area masked- up from the mosaic, image. The area of study has been registries by Arc-GIS 10.2 and digitized the soil hydrologic group through assistant of Soil Plant Assistant Water Model, (SPAW) which was progressed by USDA, Agricultural, Research Service, using the data of soil textural and organic matter from Food and Agriculture Organization (FAO), the available water content, saturated hydraulic conductivity, and bulk density. The results of average, sediment depth and the maximum upland sediment for simulation period (2010-2020) were predicted to be (1.7 mm), and (12.57 Mg/ha), respectively.

The effects of burning and grazing on soil carbon dynamics in managed Peruvian tropical montane grasslands

Abstract. Montane tropical soils are a large carbon (C) reservoir, acting as both a source and a sink of CO2. Enhanced CO2 emissions originate, in large part, from the decomposition and losses of soil organic matter (SOM) following anthropogenic disturbances. Therefore, quantitative knowledge of the stabilization and decomposition of SOM is necessary in order to understand, assess and predict the impact of land management in the tropics. In particular, labile SOM is an early and sensitive indicator of how SOM responds to changes in land use and management practices, which could have major implications for long-term carbon storage and rising atmospheric CO2 concentrations. The aim of this study was to investigate the impacts of grazing and fire history on soil C dynamics in the Peruvian montane grasslands, an understudied ecosystem, which covers approximately a quarter of the land area in Peru. A density fractionation method was used to quantify the labile and stable organic matter pools, along with soil CO2 flux and decomposition measurements. Grazing and burning together significantly increased soil CO2 fluxes and decomposition rates and reduced temperature as a driver. Although there was no significant effect of land use on total soil C stocks, the combination of burning and grazing decreased the proportion of C in the free light fraction (LF), especially at the lower depths (10–20 and 20–30 cm). In the control soils, 20 % of the material recovered was in the free LF, which contained 30 % of the soil C content. In comparison, the burnt–grazed soil had the smallest recovery of the free LF (10 %) and a significantly lower C content (14 %). The burnt soils had a much higher proportion of C in the occluded LF (12 %) compared to the not-burnt soils (7 %) and there was no significant difference among the treatments in the heavy fraction (F) ( ∼ 70 %). The synergistic effect of burning and grazing caused changes to the soil C dynamics. CO2 fluxes were increased and the dominant temperature driver was obscured by some other process, such as changes in plant C and N allocation. In addition, the free LF was reduced when these two anthropogenic activities took place on the same site – most likely a result of reduced detritus being incorporated into the soil. A positive finding from this study is that the total soil C stocks were not significantly affected and the long-term (+10 years) C storage in the occluded LF and heavy F were not negatively impacted. Possibly this is because of low-intensity fire, fire-resilient grasses and because the grazing pressure is below the threshold necessary to cause severe degradation.

Soil carbon fractions and biological activity based indices can be used to study the impact of land management and ecological successions

Soil organic carbon (SOC) is a strong indicator of soil health. Development of efficient soil quality indicators is crucial to better understand the impact of land management strategies on the recovery of degraded ecosystems. We hypothesized that SOC fractions and biological attributes can compose strong soil quality indicators to assess an ecosystem recovery following disturbance. Thus, the objective of this study was to evaluate the use of soil biological activity and SOC fractions to study the impact of different land use systems and ecological successions in ecosystem recovery. We selected six land use systems: tobacco (Nicotiana tabacum) cultivation; pastureland; reforested land with Eucalyptus sp.; and natural ecological successions with 10, 20 and 35 years of vegetation regeneration, respectively. We collected disturbed and undisturbed soil samples in triplicate at 0–5, 5–10, 10–20 and 20–40cm depth intervals. Several fractionation approaches were used to determine SOC pools: hot water extractable organic carbon, permanganate oxidized organic carbon, particulate organic carbon, mineral associated organic carbon and total SOC. The activity of the enzyme arylsulfatase was used to represent soil biological attributes. We calculated three indices to represent the soil quality: carbon management index, soil resilience index and biological activity index. Our results suggest that the SOC fractions and the enzyme activity followed the increase of vegetation complexity of the ecological succession stages. The labile SOC pool, in addition to enzyme activity, was the most sensitive variable to assess land use changes. The biomass-C input was considered to be the main reason of SOC increase, and the gains of labile SOC fractions were directly related to the increase of SOC stocks. Both, biological and carbon management indices were efficient tools to characterize the impact of studied management systems. Also, we found that assessment of deeper soil layers (20–40cm) was extremely important as incomplete inferences might be reached while evaluating only surface soil layers (0–20cm). We conclude that the carbon management and biological indices captured the stage of soil degradation and the influence of vegetation diversity in the soil resilience restoration, providing an advance in monitoring strategies that can be reproducible in any environment.

Short Communication: Abundance of Arbuscular Mycorrhiza asociated with corn planted with traditional and more modern farming systems in Kupang, East Nusa Tenggara, Indonesia

Setyawan. 2017. Short Communication: Abundance of Arbuscular Mycorrhizal Fungal spores associated with corn planted with traditional and more modern farming systems at East Nusa Tenggara, Indonesia. Biodiversitas 18: 887-892. Mycorrhizal fungi play an important role in improving plant productivity and soil conservation. One factor that may have an impact on the population of mycorrhizal fungi in the soil is the land management. The study aimed to investigate the impact of land management on the spore density of arbuscular mycorrhiza (AM) associated with corn, and was undertaken at 6 sites in Kupang District of East Nusa Tenggara Province, Indonesia Two farming systems (traditional and more modern) were chosen for the study, and three locations were selected to represent each farming system practiced. Representative soil samples were taken from each location/farming system for AM observation and soil analysis. The results showed that spore density of AM fungi was higher in soil taken from corn plantation with traditional practice than that found in soil taken from corn plantation with more modern practice, indicating a negative impact of the more modern farming practice on the population of AM fungi. The research should be extended to further investigate the diversity and communities of AM fungi at different time and location.

The impact of agricultural management on selected soil properties in citrus orchards in Eastern Spain: A comparison between conventional and organic citrus orchards with drip and flood irrigation.

The agricultural management of citrus orchards is changing from flood irrigated managed orchards to drip irrigated organic managed orchards. Eastern Spain is the oldest and largest European producer of citrus, and is representative of the environmental changes triggered by innovations in orchard management. In order to determine the impact of land management on different soil quality parameters, twelve citrus orchards sites were selected with different land and irrigation management techniques. Soil samples were taken at two depths, 0-2cm and 5-10cm for studying soil quality parameters under the different treatments. Half of the studied orchards were organically managed and the other six were conventionally managed, and for each of these six study sites three fields were flood irrigated plots and the other three drip irrigated systems. The outcome of the studied parameters was that soil organic matter (SOM) and aggregate stability were higher for organic farms. Bulk density and pH were only significantly different for organic farms when drip irrigation was applied in comparison with flooded plots. C/N ratio did not vary significantly for the four treatments. Although there are some points of discussion, this research shows that a combination of different management decisions leads to improvement of a couple of soil quality parameters. Organic management practices were found to be beneficial for soil quality, compared to conventional management for soils with comparable textures and applied irrigation water.

Featured Series Introduction: SWAT Applications for Emerging Hydrologic and Water Quality Challenges

Many global to local-scale issues such as changing climate, urbanization, intensification of agricultural activities, deforestation, and geopolitical conflicts pose serious challenges to the availability, accessibility, and management of water resources. Researchers, decision makers, and the general public are interested in understanding the impacts of these emerging issues so that water resources can be managed sustainably in the future. Besides availability, decision makers and the general public are also interested in how water quality will be impacted by pesticides, nutrients, pathogens, and emerging contaminants including pharmaceuticals and hormones, which are a serious concern for water security. Simulation models play a critical role in understanding the hydrologic processes of a system, the system's behavior, and how it will change in the future due to natural and anthropogenic factors. A plethora of models exist in the field of hydrology to address hydrologic and water quality issues at various spatial and temporal scales. Among these, the Soil and Water Assessment Tool (SWAT) (Arnold et al., 1998) has been used globally to address issues related to hydrology, water quality, and agricultural management (e.g., Gassman et al., 2014; Abbaspour et al., 2015; Cousino et al., 2015; Basheer et al., 2016). SWAT is a semidistributed, conceptual and continuous time catchment-scale hydrologic model supported and used by a global community of researchers, decision makers, and practitioners. The model is open source, has multiple geographic information system interfaces such as ArcSWAT and QSWAT for creating input files, and user-friendly tools for model calibration. SWAT has been continuously improved and expanded since it was created in the early 1990s. Arnold and Fohrer (2005) describe the most significant improvements of the model between releases from its creation until SWAT2000 (e.g., incorporation of multiple hydrologic response units, instream kinetic routines, and Green-Ampt infiltration). Recent improvements include the incorporation of routing capabilities between landscape units or grids (Arnold et al., 2010). SWAT is ideally suited for addressing a wide array of issues related to climate change, land use change, bioenergy crops, blue and green water availability, sediment transport, nutrient cycle and contaminant loads, and best management practices. In addition, the model is flexible in its spatial discretization for applications ranging from watershed to continental scale. Due to its open source nature and an active development community, SWAT is constantly being improved and augmented with new process representations. The goal of this featured series is to demonstrate the versatility of SWAT in addressing traditional hydrologic problems such as Best Management Practices (BMP) implementation, land use/climate change impacts, model/data uncertainty, and emerging issues such as the impact of natural gas development and bio-cropping scenarios on hydrology. In this issue, the use of SWAT to assess the role of climate and land use changes on hydrology of three South Dakota watersheds is presented (Paul et al., 2016). The study by Radcliffe and Mukundan (2016) demonstrates the role of precipitation data quality on SWAT model calibration and validation. Mittelstet et al. (2016) use modified streambank erosion and instream phosphorus routines to study the relative contribution of phosphorus from streambank erosion compared to overland sources in Barren Fork Creek watershed in Oklahoma. Bieger et al. (2016) introduce SWAT+, the next major release of SWAT code, which includes flow and pollutant routing across the landscape, and apply it to the Little River Experimental Watershed in Georgia. Future articles in this series will report on phosphorus transport at watershed scale, upland and foot slope vegetated buffers in agricultural fields, channel representation and sediment export, and novel model calibration techniques. Overall, this featured series presents a cross section of current research topics from around the world which contribute to improved understanding of water resources management and conservation, whether through improved modeling techniques or analysis of the simulated impact of land management under current or future climate.

Impacts of Land Management on the Resilience of Mediterranean Dry Forests to Fire

Wildfires have always been a part of the history of Mediterranean forests. However, forests are not always certain to regenerate after a wildfire. Whether they do depends on many factors, some of which may be influenced by land management activities. Failure to regenerate will cause a regime shift in the ecosystem, reducing the provision of ecosystem services and ultimately leading to desertification. How can we increase the resilience of Mediterranean forests to fire? Our approach to answering this question was twofold: first, we reviewed the literature to investigate chains of processes that allowed forests to regenerate (which we label Regeneration Mechanisms, or RMs); and second, we assessed the impact of selected management practices documented in the WOCAT database on these RMs. For the assessment, we evaluated the relation between the benefits and disadvantages of the land management practices on the one hand, and the hindering and supporting factors of the RMs on the other. We identified three distinct RMs that enable Mediterranean forests to recover, as well as the time frame before and after a fire in which they are at work, and factors that can hinder or support resilience. The three RMs enabling a forest to regenerate after a fire consist of regeneration (1) from a seed bank; (2) from resprouting individuals; and (3) from unburned plants that escaped the fire. Management practices were grouped into four categories: (1) fuel breaks; (2) fuel management; (3) afforestation; and (4) mulching. We assessed how and under what conditions land management modifies the ecosystem’s resilience. The results show that land management influences resilience by interacting with resilience mechanisms before and after the fire, and not just by modifying the fire regime. Our analysis demonstrates a need for adaptive—i.e., context- and time-specific—management strategies.

Impacts of land management on ecosystem service delivery in the Baiyangdian river basin

As the largest freshwater lake in northern China, Lake Baiyangdian provides a diversity of ecosystem services: it guarantees water flow to a number of beneficiaries and is an important component of sustainable regional development. However, the flows of sustainable ecosystem services from Lake Baiyangdian mainly depend on upstream hydrological and nutrient retention functions. For sustainable land management, it is important to explore the implications of upstream land-use changes by humans on the ecosystem services supplied by Lake Baiyangdian. In this study, ecological assets and hydrological time series were analysed, and the InVEST model was used to investigate the implications of land management on the delivery of ecosystem services. The results showed that significant changes in ecological assets occurred in the Baiyangdian river basin during the period 1980–2007, characterised particularly by an increase in forested area and a decline in wetland area. A significant decline in the ecological status of the Baiyangdian river basin, expressed as an abrupt change in stream flow time series 1970–2011, was also noted. Water yield and surface run-off functions were mainly influenced by precipitation, but changes in land-cover patterns exacerbate the impacts of these two factors. Nutrient retention was influenced more by altered land cover than by precipitation. Due to data gaps, it was not possible to link upstream ecosystem functions to the ecosystem services contributed by Lake Baiyangdian. It will be necessary to establish a long-term ecological monitoring programme in order to gather the data needed to gain a deeper understanding of the interconnections between ecosystem function and services. The ultimate aim of such a programme must be to incorporate ecosystem services into ecosystem management and policy-making.

我国南方红壤区氮磷湿沉降对森林流域氮磷输出及水质的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 我国南方红壤区氮磷湿沉降对森林流域氮磷输出及水质的影响 DOI: 10.5846/stxb201503030415 作者: 作者单位: 西南林业大学环境科学与工程学院,中国科学院地理科学与资源研究所,西南林业大学环境科学与工程学院,中国科学院地理科学与资源研究所,中国科学院地理科学与资源研究所 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（31570465）；中国科学院青年创新促进会资助项目 Impact of atmospheric nitrogen and phosphorus wet deposition on nitrogen and phosphorus export and associated water quality: a case study of forest watershed in the red soil area, Southern China Author: Affiliation: College of Forestry, Southwest University of environmental science and engineering,Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences,,, Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:持续高通量的氮、磷输入导致水体富营养化的问题已引起广泛关注。通过对江西省千烟洲香溪流域水样（常规水样，降雨后的地表径流以及雨水水样）的季节性监测，研究大气氮、磷湿沉降对森林流域氮、磷输出动态及水质的影响。结果表明：从2013年6月至2014年5月，香溪流域内氮、磷湿沉降通量分别为11.86 kg/hm2和0.38 kg/hm2，其中氮湿沉降主要集中在夏秋两季，占全年输入量的64%，而磷沉降主要集中在夏季，占全年输入量的43%，表现出明显的季节性差异；水体pH值（6.22-8.89）的变化范围较大，而且氮、磷的输出受土地管理（施肥方式）及降雨事件的影响较为明显，尤其在耕作期，总氮的输出量占全年氮输出总量的96.2%，而总磷的输出量占全年磷输出总量的61.4%；对4场不同强度降雨（按降雨强度从大到小）的氮、磷输出动态过程分析，发现不同强度的降雨对水体氮、磷的输出过程影响不同，在径流未形成前以及降雨强度达到暴雨级别时，降雨对流域水体氮、磷的稀释作用明显，而在大雨强度下水体磷的输出量明显高于其他降雨；研究期间，香溪流域内氮湿沉降对水体的贡献量为101.97 kg，磷湿沉降的贡献量为0.60 kg，4场降雨氮对流域水体的贡献量为4.46kg，占流域氮输出负荷的15.22%，磷对水体的贡献量为0.032kg，占流域磷输出负荷的0.85%。同时，根据营养状态指数（EI），发现流域水体全年处于中至富营养状态，而且研究期间水体氮、磷浓度均超过水体富营养化阈值（氮1.5 mg/L，磷0.15 mg/L），存在爆发水体富营养化的威胁。 Abstract:Continuously high flux of nitrogen (N) and phosphorus (P) input into rivers leading to water eutrophication has attracted public concern. The aim of the study was to determine the impact of N and P wet deposition on N and P transport in the forest watershed in Qianyanzhou, Jiangxi Province, China, based on the monitoring data from long-term sample and analysis. The results showed that from June 2013 to May 2014, the N and P wet deposition flux for the monitored watershed reached 11.86 kg/hm2 and 0.38 kg/hm2, respectively. There was a seasonal difference in deposition rates, wherein the N wet deposition mainly focus on the summer and autumn, accounting for 64% of total N wet deposition, whereas the P deposition mainly occurred in summer, accounting for 43% of total P wet deposition input. The pH fluctuation for watershed was large and the impact of land management (e.g., fertilizing) and rainfall events on N and P output were pronounced. The output of N and P mainly focus on the cultivation period, accounting for 96.2% and 61.4% of the total output from June 2013 to May 2014, respectively, which is because exogenous input of N and P from chemical fertilizers was large in this period. By analyzing the dynamic processes of N and P output during four rainfall events, we found that the impact of different intensities of rain events on the output process was different. The dilution effect on N and P output during rainfall process was significant before becoming runoff or rain intensity reached the storm level. Under heavy rain, P output was higher than that under other rainfall intensities. The contribution of N and P wet deposition to water were 101.97 kg and 0.60 kg, respectively. The N and P wet deposition in four rain events reached 4.46 kg and 0.032 kg, respectively, accounting for 15.22% of total N and 0.85% of total P output. According to the Eutrophication Index for the Xiangxi watershed, the water quality of the Xiangxi watershed is at moderate to severe degree of eutrophication state, especially during the cultivation period. We also analyzed that the N and P concentration in water during study period all exceeded the eutrophication threshold (N 1.5 mg/L, P 0.15 mg/L), which have the potential risk of water eutrophication. 参考文献 相似文献 引证文献

Gully development in eastern Romania: a case study from Falciu Hills

The gullied systems from the Falciu Hills within the Chioara catchment (2997 ha) consist of both main types of gullies, discontinuous and large continuous ones along valley bottoms, and lots of ephemeral gullies. Several methods have been used to measure and estimate gully characteristics. Then, the gully development stages, the effect of the natural conditions, and especially the impact of land management on gullying in the Falciu Hills over the last two centuries have been defined. In addition, the role of gully erosion in triggering landslides has also been studied. Two main periods have been distinguished (until 1960 and 1961–2012) for assessing major characteristics of land degradation. The results show that total gully area in the Chioara catchment is 66.4 ha excepting for the ephemeral gullies, and areas occupied by gullies from the five study sub-catchments (2334 ha) account for two-thirds. Total length of the main gully network in the entire catchment is 33.2 km from which the five sub-catchments account for 71 %. The mean gully density of 1.11 km km−2 supports the evidence that here gullying is the major environmental threat. Half of the gully areal growth and three-quarters of the new landslide area occurred over the 1961–2012 period. Delayed deforestation peaking during 1830–1930 and land conversion to arable use resulted in severe soil erosion, high aggradation along the non-gullied valley bottoms, and severe gullying. The average gully head retreat rate over the last two centuries from four trunk continuous gullies is 14 m year−1, and the sediment yield from gullying only accounted for 54–69 % of the sediment mass produced by water erosion. The evolution of gullies is linked to major land-use changes in the study area. Despite a decreasing tendency of gullying and catchment area over the last half century, gullying still remains problematically high in East Romania.

Analysis of Erosion Level Using Map Windows Agricultural Non-point Source Pollution (MWAGNPS) on Jeneberang Sub-watershed South Sulawesi Province

The aims of this study was to obtain information about the level of soil erosion in Jeneberang sub watershed, as well as the impact of land management and information to determine the direction of land management in the watershed. The approach model used is MWAGNPS. MWAGNPS Model is a model of cell-based rainfall events with the main components are topographic maps, land use and soil type. This model is able to determine the source of erosion and the erosion that occurs. Simulation model showed when Jeneberang watershed has 31.66 mm of rain events with 30-minute rainfall intensity (EI30) can caused erosion 44.81 tons / ha and the sedimentation rate is 2,22 tons / ha. The source of erosion in Jeneberang sub watershed from farm/moor caused erosion is 29552.14 tons / ha and a total of 4,562,625.84 tons of sediment. Normal 0 false false false IN X-NONE X-NONE

Development of a time-stepping sediment budget model for assessing land use impacts in large river basins

The use of river basin modelling to guide mitigation of non-point source pollution of wetlands, estuaries and coastal waters has become widespread. To assess and simulate the impacts of alternate land use or climate scenarios on river washload requires modelling techniques that represent sediment sources and transport at the time scales of system response. Building on the mean-annual SedNet model, we propose a new D-SedNet model which constructs daily budgets of fine sediment sources, transport and deposition for each link in a river network. Erosion rates (hillslope, gully and streambank erosion) and fine sediment sinks (floodplains and reservoirs) are disaggregated from mean annual rates based on daily rainfall and runoff. The model is evaluated in the Burdekin basin in tropical Australia, where policy targets have been set for reducing sediment and nutrient loads to the Great Barrier Reef (GBR) lagoon from grazing and cropping land. D-SedNet predicted annual loads with similar performance to that of a sediment rating curve calibrated to monitored suspended sediment concentrations. Relative to a 22-year reference load time series at the basin outlet derived from a dynamic general additive model based on monitoring data, D-SedNet had a median absolute error of 68% compared with 112% for the rating curve. RMS error was slightly higher for D-SedNet than for the rating curve due to large relative errors on small loads in several drought years. This accuracy is similar to existing agricultural system models used in arable or humid environments. Predicted river loads were sensitive to ground vegetation cover. We conclude that the river network sediment budget model provides some capacity for predicting load time-series independent of monitoring data in ungauged basins, and for evaluating the impact of land management on river sediment load time-series, which is challenging across large regions in data-poor environments.

The effect of land management practices on soil erosion and land desertification in an olive grove

AbstractThe need for reliable estimates of soil loss under different land management practices (LMPs) is becoming imperative in the Mediterranean basin to inform decisions on more effective strategies for land management. The effect of LMPs on soil erosion and land degradation has been investigated using experiments from November 2008 to November 2011 in an olive grove in central Crete (Greece). The study area was on sloping land with soils formed on marl deposits which are vulnerable to desertification because of surface runoff and tillage. The experimental design included three treatments with two replicates (3 × 5 m experimental plots) corresponding to the following LMPs: (i) no tillage–no herbicide application, (ii) no tillage–herbicide application and (iii) ploughing to 20 cm perpendicular to the contours. The following variables were monitored: surface water runoff, sediment loss, soil temperature at 10 cm, soil moisture content at depths of 20 and 50 cm, as well as selected climatic variables. The results show that the no tillage–no herbicide management practice gave the lowest sediment loss (1.44–4.78 g/m2/yr), the lowest water runoff (1.8–11.5 mm/yr), the greatest amount of water stored in the soil, the lowest soil temperature and the lowest desertification risk compared with the other treatments. Tillage resulted in the greatest sediment loss (13.6–39.2 g/m2/yr) and surface runoff (16.5–65.0 mm/yr), and an intermediate amount of water stored in the soil. In addition, this treatment led to the loss of soil thickness of 3.7 mm/yr because of ploughing. The results demonstrate the high risk of desertification in the investigated region and the methodology can be used in other Mediterranean areas as an assessment framework for evaluating land degradation and the impact of land management on soil erosion.