Agricultural Cropland Research Articles

Identification of Land use and Land cover Changes using Remote Sensing and GIS

This study reveals to identify the changes of land use/land cover of rural agricultural watershed of Tamilnadu. The relationship between Land Use and Land Cover Changes (LULCC) has identified using IRS IC LISS III and PAN merged data. Further, the preparation of LULC map using Survey of India (SOI) Toposheet for the year 1972 contain come up to in multipurpose to know the land use pattern. In the same way, the various LULC image classified which has collected from Institute of Remote Sensing (IRS), scanned and digitized using Arc GIS software. The agricultural practices under agriculture land and cropland has most important crash over the hydrological processes of the watershed. Thus, the change detection obtained from LULC serve in most favorable solutions for the selection, planning, implementation and monitoring of development schemes to meet the increasing demands of human needs has lead to land management. The Remote Sensing techniques also cost effective to detect the change in LULC over a large area due to natural and human activities. This study shall be very useful for further development planning.

Effects of Land Use on Soil Properties and Hydrology of Drained Coastal Plain Watersheds

Some of the world's most productive cropland requires artificial or improved drainage for efficient agricultural production. Soil hydraulic properties, such as hydraulic conductivity and drainable porosity, are conventionally used in design of drainage systems. While it is recognized that these soil properties vary over a relatively wide range within a given soil series, it is generally assumed they can be approximated based on soil type, independent of crop or land use. Effects of land use on hydrology of drained soils in the North Carolina lower coastal plain were investigated by comparing hydrologic measurements on drained agricultural cropland, drained forest land (Loblolly pine), and an undrained forested wetland. Higher ET on the drained pine forest site resulted in reduced drainage outflow and deeper water tables compared to the agricultural site. Measurements for the wetland site showed water tables near the surface but annual outflows similar to the drained forest site. Field effective hydraulic conductivity in the top 70 cm of the drained forest site was more than two orders of magnitude greater than that of corresponding layers of the soil on the agricultural site. Drainable porosity, based on measured soil water characteristics, was also much higher for the forested sites. Long term (50-year) DRAINMOD simulations predicted average annual drainage outflow of 51.4 cm for the agricultural field as compared to 37.6 cm for the forested site. The difference resulted primarily from greater ET predicted for the forested site. Because of the high hydraulic conductivity of the surface layers and large surface depressional storage, predicted surface runoff from the forested site was nil, compared to an average annual runoff of 13 cm for the drained cropland site. Results of long-term simulations were used to analyze these effects for the widely variable seasonal and annual weather conditions of eastern North Carolina.

Effect of Minor Drainage on Hydrology of Forested Wetlands

Results of a simulation study to determine the impacts of minor drainage for silviculture on wetland hydrology are presented in this article. Long-term DRAINMOD simulations were conducted to determine the threshold drainage intensity (ditch depth and spacing) that removes wetland hydrology from forested wetlands. Analyses were conducted for 13 soil series and profile combinations at ten locations from Norfolk, Virginia, to Baton Rouge, Louisiana, in the Atlantic and Gulf coastal states. Threshold ditch spacings (LT) were obtained for five ditch depths for all combinations of soil profiles and locations. Analysis of the results showed that LT can be approximated as LT = , where T is the horizontal hydraulic transmissivity of the soil profile, and C is a coefficient dependent on ditch depth and geographic location. The C values for all combinations of ditch depth and location are given in this article. The threshold spacings can be used as benchmarks to directly evaluate the impact of drainage alternatives on wetland hydrology. They were also used herein to determine T25 inputs for previously developed methods to predict the lateral impact of a single ditch on wetland hydrology. Lateral impacts were determined and presented for a 0.9 m (3 ft) deep drainage ditch for all soils and locations considered. The T25 values presented can be used to determine lateral impacts for other ditch depths and soils. The analyses in this study were conducted for a surface depressional storage of 5 cm. More work is needed to define T25 values for smaller surface storages, including those smaller values needed for application to agricultural cropland.

Holocene carbon emissions as a result of anthropogenic land cover change

Humans have altered the Earth’s land surface since the Paleolithic mainly by clearing woody vegetation first to improve hunting and gathering opportunities, and later to provide agricultural cropland. In the Holocene, agriculture was established on nearly all continents and led to widespread modification of terrestrial ecosystems. To quantify the role that humans played in the global carbon cycle over the Holocene, we developed a new, annually resolved inventory of anthropogenic land cover change from 8000 years ago to the beginning of large-scale industrialization (ad 1850). This inventory is based on a simple relationship between population and land use observed in several European countries over preindustrial time. Using this data set, and an alternative scenario based on the HYDE 3.1 land use data base, we forced the LPJ dynamic global vegetation model in a series of continuous simulations to evaluate the impacts of humans on terrestrial carbon storage during the preindustrial Holocene. Our model setup allowed us to quantify the importance of land degradation caused by repeated episodes of land use followed by abandonment. By 3 ka BP, cumulative carbon emissions caused by anthropogenic land cover change in our new scenario ranged between 84 and 102 Pg, translating to c. 7 ppm of atmospheric CO2. By ad 1850, emissions were 325–357 Pg in the new scenario, in contrast to 137–189 Pg when driven by HYDE. Regional events that resulted in local emissions or uptake of carbon were often balanced by contrasting patterns in other parts of the world. While we cannot close the carbon budget in the current study, simulated cumulative anthropogenic emissions over the preindustrial Holocene are consistent with the ice core record of atmospheric δ13CO2 and support the hypothesis that anthropogenic activities led to the stabilization of atmospheric CO2 concentrations at a level that made the world substantially warmer than it otherwise would be.

Habitat selection by parturient elk (Cervus elaphus) in agricultural and forested landscapes

I examined the home range and habitat selection of 146 radio-collared female elk ( Cervus elaphus L., 1758) from 2002 to 2005 during the calving period (15 May to 24 June). I determined the proportion of home ranges of parturient cow elk during the calving period and the proportion of birthing sites of elk that were in either forested protected areas or the adjacent fragmented agriculture-dominated matrix in southwestern Manitoba, Canada. Overall, 73% of the minimum convex polygon home ranges were entirely within a protected area, 6% were only on farmland, and 21% included both. Home ranges including farmland and protected area (mean = 17.9 km2) were 3.8 times larger than those entirely inside a protected area (mean = 4.7 km2) or only on farmland (mean = 4.5 km2) (U = –2.79, P = 0.005). Female elk remaining solely in protected areas selected deciduous and mixedwood forest, marsh and fen, and water at the scale of the home range. Elk exclusively on farmland selected forage crops only. At the scale of the birthing site, females on farmland and those in protected areas selected only deciduous forest, and both types avoided agricultural cropland and marsh and fen. Identification of calving habitat will allow resource managers to manage bovine tuberculosis in the population more effectively.

Nitrate removal and greenhouse gas production in a stream-bed denitrifying bioreactor

Denitrifying bioreactors are currently being tested as an option for treating nitrate (NO 3 −) contamination in groundwater and surface waters. However, a possible side effect of this technology is the production of greenhouse gases (GHG) including nitrous oxide (N 2O) and methane (CH 4). This study examines NO 3 − removal and GHG production in a stream-bed denitrifying bioreactor currently operating in Southern Ontario, Canada. The reactor contains organic carbon material (pine woodchips) intended to promote denitrification. Over a 1 year period, monthly averaged removal of influent (stream water) NO 3 − ranged from 18 to 100% (0.3–2.5 mg N L −1). Concomitantly, reactor dissolved N 2O and CH 4 production, averaged 6.4 μg N L −1 (2.4 mg N m −2 d −1), and 974 μg C L −1 (297 mg C m −2 d −1) respectively, where production is calculated as the difference between inflow and effluent concentrations. Gas bubbles entrapped in sediments overlying the reactor had a composition ranging from 19 to 64% CH 4, 1 to 6% CO 2, and 0.5 to 2 ppmv N 2O; however, gas bubble emission rates were not quantified in this study. Dissolved N 2O production rates from the bioreactor were similar to emission rates reported for some agricultural croplands (e.g. 0.1–15 mg N m −2 d −1) and remained less than the highest rates observed in some N-polluted streams and rivers (e.g. 110 mg N m −2 d −1, Grand R., ON). Dissolved N 2O production represented only a small fraction (0.6%) of the observed NO 3 − removal over the monitoring period. Dissolved CH 4 production during summer months (up to 1236 mg C m −2 d −1), was higher than reported for some rivers and reservoirs (e.g. 6–66 mg C m −2 d −1) but remained lower than rates reported for some wastewater treatment facilities (e.g. sewage treatment plants and constructed wetlands, 19,500–38,000 mg C m −2 d −1).

An Agricultural Monitoring System Based on the Use of Remotely Sensed Imagery and Field Server Web Camera Data

In this study, the authors develop an integrated agricultural monitoring system based on the use of high-spatial-resolution remote sensing imagery and Field Server data for a cabbage field in Tsumagoi, Gunma Prefecture, Japan. The use of the integrated system made it possible to verify the accuracy of cabbage coverage estimated from high-spatial-resolution QuickBird imagery using an unmixing method, because the authors were able to remotely examine cabbages growing in real-time using a Field Server web camera linked to their laboratory via the Internet. Using the developed integrated system, they produced a cabbage coverage map that provided information on cabbage growth that could be used for agricultural land management, particularly with regard to the application of fertilizer and forecasting crop production. The results support the validity of using remote sensing technology in conjunction with a Field Server to manage agricultural crop land.

Satellite-based analysis of the role of land use/land cover and vegetation density on surface temperature regime of Delhi, India

The knowledge of the surface temperature is important to a range of issues and themes in earth sciences central to urban climatology, global environmental change and human-environment interactions. The study analyses land surface temperature (LST) estimation using temporal ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) datasets (day time and night time) over National Capital Territory Delhi using the surface emissivity information at pixel level. The spatial variations of LST over different land use/land cover (LU/LC) at day time and night time were analysed and relationship between the spatial distribution of LU/LC and vegetation density with LST was developed. Minimum noise fraction (MNF) was used for LU/LC classification which gave better accuracy than classification with original bands. The satellite derived emissivity values were found to be in good agreement with literature and field measured values. It was observed that fallow land, waste land/bare soil, commercial/industrial and high dense built-up area have high surface temperature values during day time, compared to those over water bodies, agricultural cropland, and dense vegetation. During night time high surface temperature values are found over high dense built-up, water bodies, commercial/industrial and low dense built-up than over fallow land, dense vegetation and agricultural cropland. It was found that there is a strong negative correlation between surface temperature and NDVI over dense vegetation, sparse vegetation and low dense built-up area while with fraction vegetation cover, it indicates a moderate negative correlation. The results suggest that the methodology is feasible to estimate NDVI, surface emissivity and surface temperature with reasonable accuracy over heterogeneous urban area. The analysis also indicates that the relationship between the spatial distribution of LU/LC and vegetation density is closely related to the development of urban heat islands (UHI).

Breeding and Non‐Breeding Survival of Lesser Prairie‐Chickens Tympanuchus pallidicinctus in Texas, USA

Lesser prairie‐chickens Tympanuchus pallidicinctus have declined throughout their range because of loss or fragmentation of habitat from conversion of native prairie to agricultural cropland, exacerbated by overgrazing and drought. We used data from radio‐marked lesser prairie‐chickens to determine whether differences in survival existed between populations occurring in two areas dominated by different vegetation types (sand sagebrush Artemisia filifolia vs shinnery oak Quercus havardii) in the Texas Panhandle from 2001 through 2005. We used a model‐selection approach to evaluate potential generalities in lesser prairie‐chicken survival. Our results indicated that survival of lesser prairie‐chickens differed between breeding and non‐breeding periods, and between study populations. We estimated annual survival of lesser prairie‐chickens at 0.52 (95% CI: 0.32–0.71) in the sand sagebrush and 0.31 (95% CI: 0.12–0.58) in the shinnery oak vegetation type. Our results suggest that demographic differences in lesser prairie‐chicken within sand sagebrush and shinnery oak vegetation types throughout the Texas Panhandle should be evaluated, especially during the breeding season. Based on our results, higher mortality of birds during the breeding season illustrates the need to manage for vegetation components such as sand sagebrush and residual bunchgrasses as opposed to shinnery oak such that potential breeding season mortality may be lessened.

Past and future phosphorus balances for agricultural cropland in New York State

New York State has a large dairy industry resulting in considerable amounts of manure being applied to cropland. Cropland phosphorus (P) balances (manure and fertilizer P minus crop P removal) combined with soil P assessments are illustrative of both challenges and opportunities for long-term sustainability of cropland management at the farm, county, and state scales. Our objectives were to (1) estimate state, regional, and county-level cropland P balances for NY in 2002, (2) evaluate P-balance trends over time (1987, 1992, 1997, and 2002), and (3) quantify the impact of improved herd nutrition and reduced fertilizer use on cropland P balances. Cropland P balances were derived from animal and cropland data from the Census of Agriculture and New York Agricultural Statistics Annual Bulletins and annual farm-use fertilizer sales data. In 2002, cropland P inputs were estimated at 12.7 and 20.9 million kg (28.1 and 46.1 million lb) of P for fertilizer and manure, respectively. Of the manure P, 69% originated from dairy cows. Crop P removal was 21.1 million kg (46.5 million lb), resulting in an overall P balance of +12.5 million kg (+27.6 million lb) or +8.0 kg P ha-1 (+7.2 lb P ac-1), a considerable improvement over 1987 when the statewide P balance was 24.4 million kg (+53.7 million lb) or 15.4 kg P ha-1 (+13.8 lb P ac-1). Without taking into account recent improvements in dairy herd nutrition (i.e., assuming a P excretion of 28 kg cow-1 [62 lb cow-1] per production period), the ratios of P in manure to P in crops were 1.10, 1.12, 1.00, and 0.99, for 1987, 1992, 1997, and 2002, respectively. Thus, the decrease in P balance from 1987 to 2002 reflected reduced fertilizer P use. When improvements in dairy nutrition were taken into account (a decrease in P excretion of dairy cows from 28 to 18 kg cow-1 [62 to 40 lb cow-1] per production period), the 2002 statewide P balance decreased from +8.0 to +4.8 kg ha-1 (+7.2 to +4.3 lb ac-1). This additional reduction illustrates the impact of precision feeding on overall cropland P balances. With a P excretion of 18 kg cow-1 (40 lb cow-1) per production period, increased yields in 2006 (reflected in crop P removal of 23,255 versus 21,104 Mg [25,639 versus 23,268 tn] in 2002) and reduced P fertilizer sales (10,508 versus 12,725 Mg [11,586 versus 14,030 tn] in 2002), the estimated P balance for 2006 amounted to +1.7 kg ha-1 (+1.5 lb ac-1). These assessments illustrate (1) the importance of precision feeding and cropland fertility management for the long-term sustainability of the dairy sector, and (2) the progress made through enhanced agricultural environmental management in New York.

Surface temperature estimation in Singhbhum Shear Zone of India using Landsat-7 ETM+ thermal infrared data

Land surface temperature (LST) is an important factor in global change studies, heat balance and as control for climate change. A comparative study of LST over parts of the Singhbhum Shear Zone in India was undertaken using various emissivity and temperature retrieval algorithms applied on visible and near infrared (VNIR), and thermal infrared (TIR) bands of high resolution Landsat-7 ETM+ imagery. LST results obtained from satellite data of October 26, 2001 and November 2, 2001 through various algorithms were validated with ground measurements collected during satellite overpass. In addition, LST products of MODIS and ASTER were compared with Landsat-7 ETM+ and ground truth data to explore the possibility of using multi-sensor approach in LST monitoring. An image-based dark object subtraction (DOS3) algorithm, which is yet to be tested for LST retrieval, was applied on VNIR bands to obtain atmospheric corrected surface reflectance images. Normalized difference vegetation index (NDVI) was estimated from VNIR reflectance image. Various surface emissivity retrieval algorithms based on NDVI and vegetation proportion were applied to ascertain emissivities of the various land cover categories in the study area in the spectral range of 10.4–12.5 μm. A minimum emissivity value of about 0.95 was observed over the reflective rock body with a maximum of about 0.99 over dense forest. A strong correlation was established between Landsat ETM+ reflectance band 3 and emissivity. Single channel based algorithms were adopted for surface radiance and brightness temperature. Finally, emissivity correction was applied on ‘brightness temperature’ to obtain LST. Estimated LST values obtained from various algorithms were compared with field ground measurements for different land cover categories. LST values obtained after using Valor’s emissivity and single channel equations were best correlated with ground truth temperature. Minimum LST is observed over dense forest as about 26 °C and maximum LST is observed over rock body of about 38 °C. The estimated LST showed that rock bodies, bare soils and built-up areas exhibit higher surface temperatures, while water bodies, agricultural croplands and dense vegetations have lower surface temperatures during the daytime. The accuracy of the estimated LST was within ±2 °C. LST comparison of ASTER and MODIS with Landsat has a maximum difference of 2 °C. Strong correlation was found between LST and spectral radiance of band 6 of Landsat-7 ETM+. Result corroborates the fact that surface temperatures over land use/land cover types are greatly influenced by the amount of vegetation present.

Differential Responses of Postmetamorphic Amphibians to Cattle Grazing in Wetlands

ABSTRACT Global amphibian declines have been linked to various anthropogenic land uses. Recent studies have documented negative impacts of cropland agriculture and deforestation on amphibians; however, few have examined potential impacts of cattle grazing in wetlands on resident amphibians. Therefore, we measured differences in number of captures and body size of postmetamorphic amphibians, egg mass abundance, and shoreline vegetation structure and composition between 4 wetlands with direct cattle access and 4 wetlands from which cattle were excluded on the Cumberland Plateau in Tennessee, USA. We captured amphibians at wetlands from March to August 2005 and 2006 using pitfall traps. Number of green frog (Rana clamitans) metamorphs captured at nonaccess wetlands was 2.5 times and 9.8 times greater than at wetlands with cattle access in 2005 and 2006, respectively. However, number of American toads (Bufo americanus) captured was 68 times and 76 times greater at cattle‐access wetlands in 2005 and 2006, respectively. In general, metamorph body size was negatively correlated with species‐specific capture rate. We detected no differences in egg mass abundance between cattle land‐use types. Height, percent horizontal cover, and percent vertical cover of shoreline vegetation were 74%,25%, and 84% greater, respectively, in nonaccess wetlands in 2005; vegetation trends were similar in 2006. Our results suggest that cattle impact amphibian populations but effects vary by species. Differences in postmetamorphic capture rate may be related to less emergent vegetation at cattle‐access wetlands. Although body size differed between land uses for metamorphs, these trends probably were short‐lived, because we did not detect differences in juvenile and adult body size between land uses for most species. Based on our findings, we suggest that fencing cattle from wetlands may be a prudent conservation strategy for some amphibian species (e.g., ranids), whereas other species (e.g., bufonids) may benefit from controlled grazing.

Range‐wide patterns of greater sage‐grouse persistence

ABSTRACTAim Greater sage‐grouse (Centrocercus urophasianus), a shrub‐steppe obligate species of western North America, currently occupies only half its historical range. Here we examine how broad‐scale, long‐term trends in landscape condition have affected range contraction.Location Sagebrush biome of the western USA.Methods Logistic regression was used to assess persistence and extirpation of greater sage‐grouse range based on landscape conditions measured by human population (density and population change), vegetation (percentage of sagebrush habitat), roads (density of and distance to roads), agriculture (cropland, farmland and cattle density), climate (number of severe and extreme droughts) and range periphery. Model predictions were used to identify areas where future extirpations can be expected, while also explaining possible causes of past extirpations.Results Greater sage‐grouse persistence and extirpation were significantly related to sagebrush habitat, cultivated cropland, human population density in 1950, prevalence of severe droughts and historical range periphery. Extirpation of sage‐grouse was most likely in areas having at least four persons per square kilometre in 1950, 25% cultivated cropland in 2002 or the presence of three or more severe droughts per decade. In contrast, persistence of sage‐grouse was expected when at least 30 km from historical range edge and in habitats containing at least 25% sagebrush cover within 30 km. Extirpation was most often explained (35%) by the combined effects of peripherality (within 30 km of range edge) and lack of sagebrush cover (less than 25% within 30 km). Based on patterns of prior extirpation and model predictions, we predict that 29% of remaining range may be at risk.Main Conclusions Spatial patterns in greater sage‐grouse range contraction can be explained by widely available landscape variables that describe patterns of remaining sagebrush habitat and loss due to cultivation, climatic trends, human population growth and peripherality of populations. However, future range loss may relate less to historical mechanisms and more to recent changes in land use and habitat condition, including energy developments and invasions by non‐native species such as cheatgrass (Bromus tectorum) and West Nile virus. In conjunction with local measures of population performance, landscape‐scale predictions of future range loss may be useful for prioritizing management and protection. Our results suggest that initial conservation efforts should focus on maintaining large expanses of sagebrush habitat, enhancing quality of existing habitats, and increasing habitat connectivity.

Advanced terrestrial ecosystem analysis and modelling

Ecosystems are important for human life and human livelihoods are affected when ecosystem functioning is degraded beyond some threshold. Consequently, most quantitative assessments of ecosystem dynamics have been motivated by a mix of academic curiosity and pressing resource or environmental problems. A classic case for this dualism was presented by research into the expected evolution of the impacts of acid rain in Europe during the 1980s: once the wide-spread damages became evident in Central European forests and freshwater ecosystems, stakeholders quickly began to demand a reliable risk assessment for what was perceived as an ecologically complex and dangerous situation. Scientists attempting to respond to this challenge employed a range of different approaches: while some embarked on data-rich, problem-oriented phenomenological assessments (where do the damages occur, how can they be classified, which climatic or atmospheric deposition patterns coincide, etc.), others went for a more fundamental, hypothesis-driven approach (which factors appear to be most limiting for plant performance, how does acidification work in soil and water bodies, etc.). The two approaches were never reconciled, but mitigation strategies (intentional and unintentional) appear to have been successful: with reduced acidity of rainfall, many ecosystems recovered. In addition, useful fundamental understanding of ecosystem dynamics was gathered. During the 1990s, climate and land use change were recognised as important forcings of (European) ecosystem dynamics [notably through the assessment reports of the Intergovernmental Panel on Climate Change, (IPCC)], and public and private stakeholders began to be concerned about the future functioning of forests, agricultural croplands and other ecosystems. Although the term was barely in use, the services provided by ecosystems were considered to be at risk, potentially implying economic losses compared to those experienced during the acid rain era. Funding agencies, such as the Research Directorate of the European Commission, called for a new well-structured research effort into the problem. Importantly, they directly employed IPCC terminology by defining research programmes addressing vulnerability, understood as a quantified estimate of a system’s sensitivity to the changing environment along with society’s ability to cope with the changing system. Critically, the notion of vulnerability differs from that of (expected) damage. Vulnerability assessment is intimately linked to the extrapolation of current understanding into the future, and the consideration of various scenarios to identify conditions of potential damage. Through its fifth Framework Programme on ‘‘Energy, Environment and Sustainable Development’’, the European Commission supported several integrated projects addressing vulnerability issues, one of these being the ATEAM (‘‘Advanced Terrestrial Ecosystem Analysis and Modelling’’, EVK2-2000-00075, http://www.pik-potsdam. de/ateam) project, coordinated at the Potsdam Institute for Climate Impact Research in Potsdam, Germany. ATEAM, along with its associated Concerted Action AVEC (‘‘Integrated Assessment of Vulnerable Ecosystems under Global Change’’, EVK2-2001-00074, http://www.pik-potsdam. This report was written by W. Cramer, while visiting the Centre Europeen de Recherche et d’Enseignement des Geosciences de l’Environnement (CEREGE), Aix en Provence, France—the sequence of co-authors is alphabetical.

Use of landsat ETM+ SLC-off segment-based gap-filled imagery for crop type mapping

Failure of the Scan Line Corrector (SLC) on the Landsat ETM+ sensor has had a major impact on many applications that rely on continuous medium resolution imagery to meet their objectives. The United States Department of Agriculture (USDA) Cropland Data Layer (CDL) program uses Landsat imagery as the primary source of data to produce crop-specific maps for 20 states in the USA. A new method has been developed to fill the image gaps resulting from the SLC failure to support the needs of Landsat users who require coincident spectral data, such as for crop type mapping and monitoring. We tested the new gap-filled method for a CDL crop type mapping project in eastern Nebraska. Scan line gaps were simulated on two Landsat 5 images (spring and late summer 2003) and then gap-filled using landscape boundary models, or segment models, that were derived from 1992 and 2002 Landsat images (used in the gap-fill process). Various date combinations of original and gap-filled images were used to derive crop maps using a supervised classification process. Overall kappa values were slightly higher for crop maps derived from SLC-off gap-filled images compared to crop maps derived from the original imagery (0.3–1.3% higher). Although the age of the segment model used to derive the SLC-off gap-filled product did not negatively impact the overall agreement, differences in individual cover type agreement did increase (−0.8%–1.6% using the 2002 segment model to −5.0–5.1% using the 1992 segment model). Classification agreement also decreased for most of the classes as the size of the segment used in the gap-fill process increased.

Land Cover, Extent, and Properties of Arenosols in Southern Africa

Arenosols cover about 13% in Sub-Saharan Africa and are widely spread in the southern part of the continent. Knowledge about the spatial distribution, properties, and land cover of Arenosols can be used to design programs to alleviate the major constraints for agricultural production. This article reviews the importance of Arenosols in eight countries of Southern Africa (Angola, Botswana, Lesotho, Mozambique, Namibia, South Africa, Swaziland, and Zimbabwe). Estimates of their extent are based on SOTER databases. The total extent of Arenosols in the eight countries is 169 million ha: extensively in Angola and Botswana (> 50% of total land area) but also in Zimbabwe, South Africa, and Mozambique (> 15% of total land area). About 26.3 million ha of Arenosols are under forest; 104.7 million ha under savannah and 3.5 million ha is desert and dunes. In total, 6.5 million ha of Arenosols are under agriculture cropland, most of which is located in Angola, Botswana, and South Africa. Arenosol topsoils in Namibia and South Africa are mostly alkaline but in Angola and Zimbabwe, the average topsoil pH of Arenosols is below 6. Organic carbon is uniformly low in Arenosols of Southern Africa and rarely exceeds 10 g kg−1. Higher C contents are found in soils with slightly higher clay content, whereas higher C levels are also associated with higher cation exchange capacities (CECs). The low CEC and low water-holding capacity necessitates the addition of organic manures to increase agricultural production on Arenosols in Southern Africa.

N<sub>2</sub>O release from agro-biofuel production negates global warming reduction by replacing fossil fuels

Abstract. The relationship, on a global basis, between the amount of N fixed by chemical, biological or atmospheric processes entering the terrestrial biosphere, and the total emission of nitrous oxide (N2O), has been re-examined, using known global atmospheric removal rates and concentration growth of N2O as a proxy for overall emissions. For both the pre-industrial period and in recent times, after taking into account the large-scale changes in synthetic N fertiliser production, we find an overall conversion factor of 3–5% from newly fixed N to N2O-N. We assume the same factor to be valid for biofuel production systems. It is covered only in part by the default conversion factor for "direct" emissions from agricultural crop lands (1%) estimated by IPCC (2006), and the default factors for the "indirect" emissions (following volatilization/deposition and leaching/runoff of N: 0.35–0.45%) cited therein. However, as we show in the paper, when additional emissions included in the IPCC methodology, e.g. those from livestock production, are included, the total may not be inconsistent with that given by our "top-down" method. When the extra N2O emission from biofuel production is calculated in "CO2-equivalent" global warming terms, and compared with the quasi-cooling effect of "saving" emissions of fossil fuel derived CO2, the outcome is that the production of commonly used biofuels, such as biodiesel from rapeseed and bioethanol from corn (maize), depending on N fertilizer uptake efficiency by the plants, can contribute as much or more to global warming by N2O emissions than cooling by fossil fuel savings. Crops with less N demand, such as grasses and woody coppice species, have more favourable climate impacts. This analysis only considers the conversion of biomass to biofuel. It does not take into account the use of fossil fuel on the farms and for fertilizer and pesticide production, but it also neglects the production of useful co-products. Both factors partially compensate each other. This needs to be analyzed in a full life cycle assessment.

Pervasive wetland flooding in the glacial drift prairie of North Dakota (USA)

This article describes a unique flood hazard, produced by the dramatic expansion of wetlands in Nelson County, located within the North American Prairie Pothole Region of North Dakota, USA. There has been an unprecedented increase in the number, average size, and permanence of prairie wetlands, and a significant increase in the size of a closed lake (Stump Lake) due to a decade-long wet spell that began in 1993 following a prolonged drying trend. Base-line land cover information from the 1992 USGS National Land Cover Characterization dataset, and a Landsat TM scene acquired 9 July 2001 are used to assess the growth of the closed lake and wetland pond surface areas, and to analyze the type and area of various land cover classes inundated between 1992 and 2001. The open water profile in Nelson County changed from one marked by relatively comparable coverage of closed lake and wetland pond areas in 1992, to one in which wetland open water accounted for the vast majority of total open water in 2001. The bulk of the wetland pond area expansion occurred by displacing existing wetland vegetation and agricultural cropland. Producers responded to the flood hazard by filing Federal Crop Insurance Corporation (FCIC) claims and enrolling cropland in the Conservation Reserve Program (CRP), a federal land retirement program. Land taken out of agricultural production has had an enormous impact upon the agricultural sector that forms the economic base of the rural economy. In 2001 the land taken out of production due to CRP enrollment and preventive planting claims represented nearly 42% of Nelson County’s 205.2 K ha base agricultural land. The patterns obtained from this detailed study of Nelson County are likely to be the representative of the more publicized flood disaster occurring within the Devils Lake Basin of North Dakota.

The times they are changing: soil and water conservation in the 21st century

Received 19 June 2007 Accepted 20 June 2007 Our planet is in a never-ending natural state of flux, with perhaps the life-sustaining hydrologic system being the prime example. This system displays a seasonal rhythm, year-to-year variations, and slower changes at time scales of decades, centuries, and even longer periods. Since the dawn of civilization, humans have contributed to and influenced this natural flux. During early human settlement and the beginning of agriculture, impacts were minimal, local, and scattered, mainly in the form of rudimentary field-scale irrigation and limited water withdrawals for human consumption. Over time, as population increased and societies and technologies evolved, humans began to impact hydrology, land use, and microclimate at the watershed, basin, and regional scale. For example, during the time of Greek civilization and the Roman Empire, large portions of the Mediterranean basin were irreversibly deforested for fuel and construction material, trans-basin water diversions were made to supply growing cities with water, and agriculture was expanded to meet the demand for food (Hughes, 1975). All these actions contributed further to uncontrolled erosion and the sedimentation problems already caused by deforestation. In the 20th century such human impacts affected most continents, often at larger scales due to widespread mechanization, rapidly increasing population, and expanding metropolitan area. In addition to impacts on water supply and sedimentation, more recent impacts included emissions from industrialization, energy production, and transportation, as well as agrichemical runoff from agricultural croplands. Towards the end of the 20th century, there was little doubt that the hydrologic system, land use, and climate were changing at continental and global scales, and action was needed to reduce or slow cumulative negative impacts of human activity on our life-sustaining environment. Today, global climate change, society’s unsustainable consumption of energy, increasing greenhouse gases emissions, continued deforestation, and mitigating actions to regain control of these runaway cumulative impacts have become popular topics of discussion. Within this broad framework, specific concerns in the United States that must be recognized and addressed include current and anticipated impacts of changing climate, increased bio-energy demands, and population growth on agricultural landscapes. Climate change, only recently viewed by many as a far-away projection 30, 50 or 100 years from now, is already affecting us. Studies have shown that large regions of the United States are experiencing more frequent and more severe storm events (e.g. Groisman et al., 1999; Kunkel et al., 1999) and corresponding increases in runoff and streamflow (e.g. Lins and Slack, 1999; Miles et al., 2000), leading to higher soil and agricultural chemical movement and transport (e.g. Phillips et al., 1993; Pruski and Nearing, 2002), as well as more stream erosion, stream instability, and gully formation in susceptible areas. At the same time, climbing global energy prices and the push for energy independence and biofuels in the United States are increasing pressures to expand and intensify the production of biofuel feedstocks

Landscape ecology of house mouse outbreaks in south‐eastern Australia

Summary House mouse Mus domesticus outbreaks in the grain‐growing areas of south‐eastern Australia occur irregularly and may be local or widespread, covering thousands of square kilometres. All natural and agricultural habitats are occupied when house mouse numbers are high, and the question we addressed was whether we can distinguish source and sink habitats within these agricultural landscapes so that management practices can be better targeted. Live‐trapping on replicated grids in 15 habitats, including eucalypt woodland, cypress pine woodland, areas of permanent water and crop habitats, was carried out from 1983 to 1988 at 9‐week intervals. Agricultural cropland (including crops, fallow and pastures), farm buildings, seepage areas and natural woodland could be source habitats. Farm buildings, seepage areas and saltbush areas all had high mouse densities entering the 1983–84 outbreak and were refuge habitats for mice. Cropland habitats quickly became the source area in spring 1983, and woodlands were initially sinks that lagged 2–4 months behind the population growth shown in crops. Adult female mice in cropland habitats were more often in breeding condition compared with mice in natural woodland. Mice also had higher indices of residency in cropland than in natural woodland. Synthesis and applications. In non‐irrigated cereal production areas of south‐eastern Australia, house mice move from refuge habitats in seepage areas and farm buildings into crops, build up in numbers in cropland habitats, and then invade woodland habitats, which by themselves cannot generate outbreaks of this pest species. Monitoring for incipient outbreaks should concentrate on refuges in seepage areas and crops and their associated fence lines as source habitat indicators. Population control in these habitats in spring would reduce the likelihood of population outbreaks in autumn, leading to reduced rodenticide use and a concomitant reduction in environmental hazards.