Spatial distribution of grassland productivity and land use in Europe

Grasslands are an important land use in Europe with essential functions for feed and ecosystem service supply. Impact assessment modelling of European agriculture and the environment needs to consider grasslands and requires spatially explicit information on grassland distribution and productivity, which is not available.     

Simulation of land use impacts on groundwater levels and streamflow in a Virginia watershed

Increase in withdrawal and decrease in recharge of groundwater due to urbanization influences subsurface flow regimes. The overall objective of this study was to determine the impact of land development activities on the subsurface flow regime in the Upper Roanoke River Watershed (URRW). A regional groundwater model of the URRW was constructed using Modular Three-Dimensional Ground-Water Flow Model (MODFLOW) and calibrated for steady-state conditions. Then, eight land use management scenarios were simulated on the Back Creek (BC) subwatershed to assess the impacts of residential density, residential location, and land-cover on hydraulic head of groundwater and streamflow. The average recharge output from the Hydrological Simulation Program, FORTRAN (HSPF) simulation was used as the direct input to MODFLOW to take changes in land use into account in the BC watershed. Development of agriculture and forest areas with low-population density on larger area (low-density scenario), near the middle of the watershed (mid-section scenario), and with changes all open space to lawn (lawn scenario) had greatest overall impact on the BC watershed for both hydraulic head and streamflow among density, location, and land-cover scenarios, respectively. The simulated scenarios indicated that decreases in both hydraulic head and streamflow coincided with the increases in impervious land. The reductions in hydraulic head and streamflow were restricted to the subwatershed where land use changes occurred. The urbanization impacts on both surface and subsurface regimes were very local with 20.8 cm of maximum difference in local hydraulic head and 0.532% of maximum percent difference in local streamflow at lawn scenario while average corresponding values through BC watershed was 4.3 cm and 0.153%, respectively. Use of a fully distributed surface model in a dynamic manner was recommended to solve the inconsistencies in the spatial and temporal scale of surface and groundwater models. However, the proposed approach can be used as a management and planning tool for evaluating the local and overall impacts of land use management on the surface and subsurface flow regimes.     

Evaporative water use of different land uses in the upper-Thukela river basin assessed from satellite imagery

Evaporative water use of various land use classes in the upper-Thukela river basin was estimated using the public domain version of the Surface Energy Balance Algorithm for Land (SEBAL) and Moderate Resolution Imaging Spectroradiometer (MODIS) satellite images. Twenty eight images were analyzed covering the period between June 2005 and September 2006. The South Africa land use map developed in the year 2000 was used to compute the evaporative water use of the various land uses in 13 Quaternary Catchments (QCs) in the upper-Thukela river basin.There was a good correlation between the SEBAL estimates of total evaporation and ground measurements from a Large Aperture Scintillometer installed at a site in one of the QCs in the study area. It was observed that the land uses that generated relatively large volumes of evaporative water were forestry (i.e. Eucalyptus, Pine, mixed species & indigenous), “water bodies” (i.e. water supply reservoirs, farm reservoirs) and wetlands. Total evaporation rates for all land use classes were high during the summer season (wet), with Eucalyptus ranging between 3 mm d⁻¹ during the winter season (dry) and about 5 mm d⁻¹ during the summer season. Bare rocks and eroded soil surface land use class had the least evaporative water use i.e., less than 1 mm d⁻¹. The relatively low evaporation rates over “water bodies” during the dry winter season could be attributed to the averaging of mixed pixels (wet and dry) due to change in areal coverage and which could not be captured in the 1 km × 1 km low resolution MODIS images. Thus, the potential for applying remote sensing techniques, using low resolution satellite images, to quantify water use by various land uses in the Thukela river basin was explored with promising results.     

Policy reforms,rice production and sustainable land use in China: A macro–micro analysis

This paper presents a macro–micro analysis of the impact of policy reforms in China on agricultural production, input use and soil quality change for a major rice-producing area, namely Jiangxi province. This is done in three steps. First, a quantitative assessment is made of the impact of market liberalization policies on the economic environment of farm households in Jiangxi province. Econometric analyses based on provincial, national and world market data are used to explain changes in rice and fertilizer prices in Jiangxi province over time. Next, the impact of China’s recent income support policy and latest price trends on farm household choices with respect to activity choice (particularly rice and livestock) and input use (fertilizers, pesticides, manure) is assessed for two villages with different degrees of market access in north-east Jiangxi province. Two village-level general equilibrium models are used to analyse household decision-making and interactions between households within these villages. The parameters are estimated and calibrated from an extensive survey held in these villages in the year 2000. Finally, the impact of land tenure policy on farm management decisions (labour, manure and chemical input use), soil quality (available P and K and total N and C) and rice yields is analysed through an econometric analysis of plot-level data for three villages. Two-stage least squares (2SLS) is used to control for interactions with yields and for feedbacks towards input use. The paper ends with a number of suggestions for policy adjustments that would reduce the problem of natural soil compaction in the research area.     

提高土地利用——土地覆盖遥感分类精度方法研究综述

本文总结了国内外提高土地利用-土地覆盖遥感分类精度的若干方法：可提高精度的大气校正方法、多源信息融合方法、人工智能分类方法等。并对其中部分方法进行了优缺点评价。     

LUSE,a decision support system for exploration of rural land use allocation: Application to the Terra Chá district of Galicia (N.W. Spain)

This article describes LUSE, a system for exploration of rural land use allocations (total area devoted to each kind of use) by multiobjective linear programming methods. The objectives pursued are maximization of gross margin, employment in agriculture, land use naturalness and traditional rural landscape, and minimization of production costs and use of agrochemicals. The constraints on the areas devoted to the land uses considered in addition to those imposed by their joint and individual availabilities, are that they must reach levels considered to satisfy existing demand for those uses or their products, and that the areas devoted to maize and fodder must be sufficient for maintenance of dairy farm production. The program generates comprehensive samples of the Pareto-optimal set, and also allows interactive convergence on a solution that is satisfactory to the decision-maker or interactive exploration of the Pareto-optimal set. The system is currently parameterized for use in an area of Galicia (N.W. Spain), but is easily adaptable to other geographic locations.     

Seasonal and land use impacts on the nitrate budget and export of a mesoscale catchment in Southern Portugal

Stream nitrate nitrogen exports are an important indicator of agricultural impacts on aquatic health in catchments. Quantitative assessment of factors and processes affecting stream nitrate loadings is complex because of the large number of causal factors and processes, such as weather and rainfall, catchment hydrological behavior, soils, land use practices and biogeochemical processes. An eco-hydrological catchment modeling approach, using the SWAT model driven by detailed field data, was used to analyze the nitrate export and the components of the nitrogen budget of the 352 km² upper Roxo river catchment in Southern Portugal. A detailed eight-year record (2001–2008) of the monitoring of weather, reservoir inflow, stream biogeochemistry, soils, in-stream and groundwater quality, and fertilizer application was used to calibrate and validate the streamflow and nitrate loadings obtained by the model. Results indicated a strong seasonal variation in nitrate exports, closely related to temperature and rainfall. Monthly nitrate loadings varied from 0.02 to 2.48 kg N ha⁻¹ during summer and between 0.03 and 14 kg N ha⁻¹ during late autumn and winter. Stream nitrate values, ranging from 1.5 to 16.5 mg N L⁻¹, were strongly related to extreme rainfall occurrences and wet periods. Detailed analysis of nitrate budget components at the sub-catchment level enabled evaluation of the impacts of the various processes affecting the nitrate nitrogen pool of the catchment. Besides high fertilizer inputs for annual crops, it was shown that biological nitrogen fixation and wet deposition by rainfall should be accounted for in input balances. Where denitrification naturally reduces nitrate levels in soils, streams and the reservoir, the largest contribution to stream nitrate originates from leached soil nitrate reappearing in groundwater baseflow, compared with less than 2% from direct surface runoff during high rainfall events. A fertilizer reduction scenario was effectively implemented to evaluate remedial nitrate control policies in accordance with the European Nitrate and Water Framework Directives. Agricultural practices and seasonal weather fluctuations were the main reasons for temporal variations in nitrate export via small streams to the main reservoir.     

Combining remote sensing and in situ soil moisture data for the application and validation of a distributed water balance model (HIDROMORE)

An application of the FAO56 approach to calculate actual evapotranspiration (AET) and soil moisture is reported, implemented by means of the HIDROMORE computerized tool, which performs spatially distributed calculations of hydrological parameters at watershed scale. The paper describes the application and validation of the model over 1 year in an area located in the central sector of the Duero Basin (Spain), where there is a network of 23 stations for continuous measurement of soil moisture (REMEDHUS; Soil Moisture Measurement Stations Network) distributed over an area of around 1300 km². The application integrated a series of Landsat 7 ETM+ images of 2002, from which the NDVI series (Normalized Difference Vegetation Index) and the map of land covers/uses were derived. Validation consisted of the use of the REMEDHUS soil moisture series and their comparison with the series resulting from the application. Two simulations were performed, with soil parameters values at the surface (0-5 cm depth) and at the mean of the profile scale (0-100 cm depth). The behaviour of the simulated soil moisture was described by means of its correlation with the measured soil moisture (determination coefficient, R² = 0.67 for the surface values and 0.81 for the mean profile values), and the Root Mean Square Error (RMSE), resulting in a range of it for the 23 stations between 0.010 and 0.061 cm³ cm⁻³. The application afforded an underestimation of the soil moisture content, which suggests the need for a redefinition of the limits of the plant available water used in the calculation. The results showed that HIDROMORE is an efficient tool for the characterization of hydrological parameters at global scale in the study zone. The combination of the FAO56 methodology and remote sensing techniques was efficient in the spatially distributed simulation of soil moisture.     

Tomato yield, biomass accumulation, root distribution and irrigation water use efficiency on a sandy soil, as affected by nitrogen rate and irrigation scheduling

Florida is the largest producer of fresh-market tomatoes in the United States. Production areas are typically intensively managed with high inputs of fertilizer and irrigation. The objectives of this 3-year field study were to evaluate the interaction between N-fertilizer rates and irrigation scheduling on yield, irrigation water use efficiency (iWUE) and root distribution of tomato cultivated in a plastic mulched/drip irrigated production systems. Experimental treatments included three irrigation scheduling regimes and three N-rates (176, 220 and 230 kg ha⁻¹). Irrigation treatments included were: (1) SUR (surface drip irrigation) both irrigation and fertigation line placed right underneath the plastic mulch; (2) SDI (subsurface drip irrigation) where the irrigation line was placed 0.15 m below the fertigation line which was located on top of the bed; and (3) TIME (conventional control) with irrigation and fertigation lines placed as in SUR and irrigation being applied once a day. Except for the “TIME” treatment all irrigation treatments were controlled by soil moisture sensor (SMS)-based irrigation set at 10% volumetric water content which was allotted five irrigation windows daily and bypassed events if the soil water content exceeded the established threshold. Average marketable fruit yields were 28, 56 and 79 Mg ha⁻¹ for years 1-3, respectively. The SUR treatment required 15-51% less irrigation water when compared to TIME treatments, while the reductions in irrigation water use for SDI were 7-29%. Tomato yield was 11-80% higher for the SUR and SDI treatments than TIME where as N-rate did not affect yield. Root concentration was greatest in the vicinity of the irrigation and fertigation drip lines for all irrigation treatments. At the beginning of reproductive phase about 70-75% of the total root length density (RLD) was concentrated in the 0-15 cm soil layer while 15-20% of the roots were found in the 15-30 cm layer. Corresponding RLD distribution values during the reproductive phase were 68% and 22%, respectively. Root distribution in the soil profile thus appears to be mainly driven by development stage, soil moisture and nutrient availability. It is concluded that use of SDI and SMS-based systems consistently increased tomato yields while greatly improving irrigation water use efficiency and thereby reduced both irrigation water use and potential N leaching.