Pasture Land Cover Research Articles

Land Use/ Cover Change Detection in High-Altitude Mountain Landscapes: A Case of Pangi Valley, Western Himalaya (India).

Recently, mountains are going to widely threatened by developmental activities and global climate change leading to changing shift of land uses/covers across the globe. The present study area has witnessed very significant changes in land use and land cover (LULC) especially after the implementation of Mahatma Gandhi National Rural Employment Guarantee Scheme (MNREGS) in the form of rapid developmental and constructional activities. As a result, rapid local roads and infrastructure construction has lead to increased hazards further putting pressure on the fragile physical landscape. Therefore, the present study is an attempt to evaluate changes and transformation in the LULC patterns in the Pangi valley, Western Himalaya (India). The LULC has been analyzed using remote sensing imagery from LANDSAT for the period 1992-2021. We conduct a supervised classification by using Maximum Likelihood Classifier (MLC) to prepare LULC maps. In short, seven LULC classes have been delineated. The result shows that barren land, built-up land, water bodies and agriculture land have increased by 97.5 per cent, 98.5 per cent, 14.4 per cent and 13.2 per cent, while snow cover pasture land and forest cover have drastically decreased by 68.1 per cent, 21.1 per cent and 20.9 per cent respectively. The LULC transformation result illustrates that the area under snow cover, pasture land and forest cover converted into barren land by 217.8 km2, 175.3 km2 and 47.3 km2 respectively out of the total 1520 km2 area of the Pangi valley. It reflects human influence in terms of developmental activities and impact of global climate change in the transformation of the physical landscape in the study area. The outcome derived from the current research will be helpful for policy makers and spatial planners for sustainable landscape planning and management of the high-altitude mountain landscapes.

Factors associated with returns of snowy owls to airports following translocation

AbstractHuman‐dominated environments often include ecological traps for wildlife, such as airports that may be perceived as suitable habitat by grassland birds but reduce fitness because of collisions with aircraft. Birds of prey are often attracted to airports where collisions with aircraft (i.e., bird strikes) are usually fatal for the birds and are a significant threat to flight safety. The snowy owl (Bubo scandiacus) is known for its nomadism, exhibiting unpredictable and highly variable movements during the nonbreeding season, including being a common visitor to airports, which often have high small‐mammal populations and mimic flat, open habitats used naturally by owls. Since 2009, the Federal Aviation Administration reported an average of 22 snowy owl deaths annually due to aircraft collisions throughout 55 North American airports. To aid in active management of owls at airports, we assessed relocation data of 42 telemetry‐tracked snowy owls from 2000–2020 in the United States and Canada. Owls that returned to the airport after relocation (33%) frequently crisscrossed and perched near runways where they were at risk of strikes. Adult females and immature males were more likely to return than the other sex and age classes, and returns were less likely to occur as the distance between the release site and the airport increased. Owls relocated in open habitats with a greater proportion of wetland and cropland (including grasslands and pasture) land cover classes were also less likely to return. We conclude that inclusion of multiple factors to limit return rates of relocated snowy owls from airport facilities can unspring the ecological trap presented by airports to these owls.

PASTURE LAND COVER CHANGE IN SÃO PAULO STATE, BRAZIL

Abstract. Pastures are complex land covers with a variety of land use systems. This land cover occupies large areas in the globe and is mainly used for livestock production. Brazil is one of the largest livestock producers and has extensive pasture areas. We analyzed the pasture land cover change of the São Paulo State between the years 2000 to 2015. São Paulo was chosen as study case due to its large industrial and agricultural importance and its expressive land cover changes over past decades. It was analyzed land covers databases generated by the Brazilian Annual Land Use and Land Cover Mapping Project (MapBiomas Project) – Collection 4. Transition matrix was generated to analyze the land cover change during the period. Gain, loss, total change, net change and swap were calculated in terms of area. Total pasture area decreased but continues the largest land cover of the São Paulo State; with 79.5% of persistence in the area. Main changes were from losses of pastures and gains in agriculture. Most of the changes to pasture came from other non vegetated areas and grassland categories. These results demonstrated the relevance of pastures areas in land cover change dynamics to address land use policy and plan future land use scenarios.

Assessment of different infiltration equations for cultivated and pasture land

The measure of infiltration of water into the soil is an important indication concerning: the efficiency of irrigation and drainage optimizing the availability of the water for plant improving the yield of the crop and minimizing the erosion. By knowing proper infiltration characteristics and intake capacity of soil, deep percolation losses can be prevented and proper utilization of water may take place. Keeping the importance of infiltration characteristics in mind the study of infiltration was taken. In this study most appropriate methods for determination of infiltration under different land uses were selected among most popular methods. Some of the wellknown equations are Kostiakov equation, Modified Kostiakov equation and Horton equation. These three equations were studied for the assessment infiltration equation. Assessment of these equations was done under different lands covers such as Cultivated land cover, Pasture land cover. From the analysis of the data, it is concluded that for cultivated land cover correlation coefficients for cumulative infiltration were found to be 0.9569, 0.9687 and 0.9724 for Kostiakov, Modified Kostiakov and Horton equation, respectively. As correlation co-efficient for Horton equation is higher, this equation was found best fit for cultivated land cover. Similarly, for pasture land cover the correlation co-efficients for cumulative infiltration were found to be 0.9876, 0.9706 and 0.9891 for Kostiakov, Modified Kostiakov and Horton equation, respectively. As correlation co-efficient for Horton equation is higher, this equation was found best fit for pasture land cover.

Soil organic carbon stabilization changes with an altitude gradient of land cover types in central Himalaya, India

Soil organic carbon (SOC) stabilization in a mountain forest ecosystem is a key component of the global carbon cycle to mitigate the rising level of atmospheric carbon dioxide. We investigated the effects of different types of land cover at different altitudes on SOC stabilization in the Himalayan region, India. We chose four different land covers at different altitudes, viz., pasture land (~2500 m), mixed cover (~2200 m), chirpine (~950 m) and agricultural land (~950 m). Organic carbon (OC), total nitrogen (N), and total microbial activity (MAt) in soils up to depths of 100 cm and under different types of land cover were assessed to study the impact of vegetation cover on the storage of SOC and N. Hydrofluoric acid (HF) soluble carbon, FeDCB/AlDCB oxides and stable carbon isotopes (δ13C) were determined in the soils under different types of land cover to evaluate the amounts of mineral-associated carbon and understand the organic carbon stabilization process. The maximum SOC stock was observed under a mixed land cover (281.86 t ha−1), followed by pasture land cover (229.61 t ha−1), chirpine (182.16 t ha−1) and agricultural land cover (70.20 t ha−1) up to a depth of 100 cm. Higher SOC contents, N contents and MAt were closely linked to the surface layers (0–30 cm), while HF-soluble carbon, FeDCB and AlDCB oxides were linked to sub-surface layers (30–100 cm) of soils under different types of land cover. HF-soluble carbon was more abundant in mixed and pasture land covers compared with chirpine and agricultural land covers. The linear relationship between δ13C values and HF-soluble carbon, FeDCB/OC, δ13C, AlDCB/OC and δ13C in soils under mixed and pasture land covers confirmed that the subsurface soil constituted more decomposed carbon and its associated FeDCB/AlDCB minerals. Nevertheless, this trend was not observed in other types of land cover located at lower altitudes and might be due to the root exudates and/or mixing of young and old carbon. These results suggest that the land cover types at higher altitudes in central Himalaya may be considered as a potential sink for the sequestration of atmospheric carbon and as potential sites for the stabilization of sequestered carbon in soils. However, land cover types at lower altitudes in central Himalaya must be managed by better soil management practices to sequester and stabilize more carbon in soils.

Watershed-Estuary Coupling in Pacific Panama: Isotopic Evidence of Forest and Pasture Land Covers on Watersheds and Marine Contributions to Suspended Particulate Matter in Mangrove Estuaries

Tropical estuaries are increasingly altered by inputs from watersheds subject to widespread deforestation, as well as by globally driven hydrodynamic changes in adjoining seas. To assess contributions of C4 and C3 plants (from pasture and forest vegetation cover, respectively) to particulates exported from Pacific Panama watersheds, we measured δ13C and δ15N in suspended particulate matter (SPM) within eight mangrove estuaries whose watersheds differed in degree of conversion from forest to pasture land cover. These measurements also allowed evaluation of down-estuary transformations and the relative marine influence on transport and exchanges of particles between land, estuary, and sea. Imprint of watershed mosaic was detectable in δ13C of SPM within upper reaches of estuaries but disappeared down-estuary. Detectably heavier δ13C suggested that C4 plants contributed to SPM in upper reaches of estuaries. δ13C signatures were sufficiently sensitive to reveal presence of a small, but still detectable, contribution by C4 grasses to SPM. Influence of heavier marine-derived sources increased down-estuary, erasing terrestrial imprints. δ13C and δ15N in SPM, and in mangrove species present, became enriched down-estuary, likely from increased inputs of particulates bearing heavier signatures from upwelled waters. In this tropical Pacific region, estuarine particulates are subject to increasing shifts in land cover as deforestation increases, and to global-scale changes in hydrodynamic forcing of upwelled waters.

Spatiotemporal variation of bacterial water quality and the relationship with pasture land cover.

Pathogens are a major cause of water quality impairment and public health concern world-wide. In the United States, each state is tasked with developing water quality standards (WQS) to protect the designated use(s) of waterbodies. Several streams in the Illinois River Watershed in northwest Arkansas are currently listed as impaired due to elevated levels of pathogens. Our objective was to evaluate Escherichia coli (E. coli) numbers at 29 stream sites, compare these numbers to the applicable WQS, and investigate the relationship between E. coli numbers and land cover variables. E. coli numbers in samples collected at most sites were within allowable limits, although there were several instances of violations of the WQS. Violations were variable from year to year at some sites, and elevated levels of E. coli were spatially localized during baseflow. Violations also were positively related to pasture land cover in the drainage area, and particularly within the riparian buffer area. This relationship was non-linear, or threshold based, where there was a significant increase in the mean E. coli exceedances when riparian pasture land cover was greater than approximately 50%. These results can be used to identify specific stream reaches where E. coli numbers might be elevated and the implementation of best management practices can be geographically targeted.

Fragmentation increases wind disturbance impacts on forest structure and carbon stocks in a western Amazonian landscape

Tropical second-growth forests could help mitigate climate change, but the degree to which their carbon potential is achieved will depend on exposure to disturbance. Wind disturbance is common in tropical forests, shaping structure, composition, and function, and influencing successional trajectories. However, little is known about the impacts of extreme winds on second-growth forests in fragmented landscapes, though these ecosystems are often located in mosaics of forest, pasture, cropland, and other land cover types. Indirect evidence suggests that fragmentation increases risk of wind damage in tropical forests, but no studies have found such impacts following severe storms. In this study, we ask whether fragmentation and forest type (old vs. second growth) were associated with variation in wind damage after a severe convective storm in a fragmented production landscape in western Amazonia. We applied linear spectral unmixing to Landsat 8 imagery from before and after the storm, and combined it with field observations of damage to map wind effects on forest structure and biomass. We also used Landsat 8 imagery to map land cover with the goals of identifying old- and second-growth forest and characterizing fragmentation. We used these data to assess variation in wind disturbance across 95,596ha of forest, distributed over 6,110 patches. We find that fragmentation is significantly associated with wind damage, with damage severity higher at forest edges and in edgier, more isolated patches. Damage was also more severe in old-growth than in second-growth forests, but this effect was weaker than that of fragmentation. These results illustrate the importance of considering landscape context in planning tropical forest restoration and natural regeneration projects. Assessments of long-term carbon sequestration potential need to consider spatial variation in disturbance exposure. Where risk of extreme winds is high, minimizing fragmentation and isolation could increase carbon sequestration potential.

Urbanization and agriculture increase exports and differentially alter elemental stoichiometry of dissolved organic matter (DOM) from tropical catchments

Many tropical biomes are threatened by rapid land-use change, but its catchment-wide biogeochemical effects are poorly understood. The few previous studies on DOM in tropical catchments suggest that deforestation and subsequent land use increase stream water dissolved organic carbon (DOC) concentrations, but consistent effects on DOM elemental stoichiometry have not yet been reported. Here, we studied stream water DOC concentrations, catchment DOC exports, and DOM elemental stoichiometry in 20 tropical catchments at the Cerrado–Atlantic rainforest transition, dominated by natural vegetation, pasture, intensive agriculture, and urban land cover. Streams draining pasture could be distinguished from those draining natural catchments by their lower DOC concentrations, with lower DOM C:N and C:P ratios. Catchments with intensive agriculture had higher DOC exports and lower DOM C:P ratios than natural catchments. Finally, with the highest DOC concentrations and exports, as well as the highest DOM C:P and N:P ratios, but the lowest C:N ratios among all land-use types, urbanized catchments had the strongest effects on catchment DOM. Thus, urbanization may have alleviated N limitation of heterotrophic DOM decomposition, but increased P limitation. Land use—especially urbanization—also affected the seasonality of catchment biogeochemistry. While natural catchments exhibited high DOC exports and concentrations, with high DOM C:P ratios in the rainy season only, urbanized catchments had high values in these variables throughout the year. Our results suggest that urbanization and pastoral land use exerted the strongest impacts on DOM biogeochemistry in the investigated tropical catchments and should thus be important targets for management and mitigation efforts.

Modelling the Potential of Integrated Vegetation Bands (IVB) to Retain Stormwater Runoff on Steep Hillslopes of Southeast Queensland, Australia

Rainfall intensity is predicted to increase under a changing climate, leading to increased risks of hillslope erosion, downstream sedimentation and flooding. For many catchments used for grazing and agricultural land uses, it will become increasingly important to maintain ecohydrological functioning despite climatic extremes. One means to achieve this is through strategic reforestation using locally endemic species, in spatial configurations that effectively intercept, retain or and redistribute overland flows. This paper adopts a modelling approach for investigating the potential of one such design termed “integrated vegetation bands” (IVB), to increase the retention of runoff across steep hillslopes, particularly in the sub-tropics where rainstorms are becoming increasingly intense. A spatially distributed simulation model (MIKE-SHE) was applied to a steep, grazed catchment (Maronghi Creek catchment, Southeast Queensland, Australia) to compare stormwater runoff characteristics between: (1) the existing pasture land cover; and (2) a series of hypothetical IVB added across this pasture land. The IVB were approximately 20 m wide, and configured at 5% gradient towards ridgelines. Results for estimates of overland flow depth and infiltration (spatial), and accumulative water balance (temporal), confirm that the area of hillslope retaining > 10 mm/day more runoff increased by 22% under IVB compared to the pasture land use. Excluding the IVB themselves, the area of hillslope where runoff retention increased was 11%. During the most intense rainfall, IVB held up to 25% greater water depth and had 10% greater infiltration at the hillslope scale. At the sub-catchment scale, discharge decreased by 7% and infiltration increased by 23%. The findings for sub-tropical landscapes presented here are consistent with studies conducted in temperate regions. Based on the results of this preliminary modelling work, the IVB concept has been established as a paired-catchment field trial in a high rainfall catchment in Southeast Queensland, Australia.

Assessing the influence of afforestation with Eucalyptus globulus on hydrological response from a small catchment in northwestern Spain using the HBV hydrological model

AbstractLand use change as conversion pasture to forest produces several changes on hydrological cycle. In this paper, we analyse the effects on stream discharge of afforestation of a small watershed devoted to pasture using the HBV hydrological model.Streamflow data obtained over the first 10 years after planting were employed to evaluate the capacity of HBV model to simulate hydrological behaviour of catchment after afforestation. Obtained results indicate that the estimation of streamflow was accurate as reflected by statistics (R2 = 0.90, NSC = 0.89 and PBIAS = 0.34).Afterwards, streamflow under pasture land use (if afforestation had not occurred) was simulated using hydrometeorological data collected during the period of study and model parameters optimized previously, together with two parameters, pcorr and cevpfo, that were adjusted for pasture conditions.The HBV model results indicate that afforestation produced a water yield reduction around 2000 mm (22% of total stream discharge) during the first 10 years of planting growth. The differences between forest and pasture land cover are increasing in all seasons year by year. The greatest streamflow reduction was observed in wet period (autumn and winter) with 76% of total reduction. In summer, streamflow reduction represents only 3% of total, however, represents 24.7% of discharge in this season.Streamflow reduction was related to increase of rainfall interception (mainly in wet periods) and the increase of evapotranspiration by plantation in dry periods. Copyright © 2013 John Wiley & Sons, Ltd.

Decision support model for assessing aquifer pollution hazard and prioritizing groundwater resources management in the wet Pampa plain, Argentina

This paper gives an account of the implementation of a decision support system for assessing aquifer pollution hazard and prioritizing subwatersheds for groundwater resources management in the southeastern Pampa plain of Argentina. The use of this system is demonstrated with an example from Dulce Stream Basin (1,000 km(2) encompassing 27 subwatersheds), which has high level of agricultural activities and extensive available data regarding aquifer geology. In the logic model, aquifer pollution hazard is assessed as a function of two primary topics: groundwater and soil conditions. This logic model shows the state of each evaluated landscape with respect to aquifer pollution hazard based mainly on the parameters of the DRASTIC and GOD models. The decision model allows prioritizing subwatersheds for groundwater resources management according to three main criteria including farming activities, agrochemical application, and irrigation use. Stakeholder participation, through interviews, in combination with expert judgment was used to select and weight each criterion. The resulting subwatershed priority map, by combining the logic and decision models, allowed identifying five subwatersheds in the upper and middle basin as the main aquifer protection areas. The results reasonably fit the natural conditions of the basin, identifying those subwatersheds with shallow water depth, loam-loam silt texture soil media and pasture land cover in the middle basin, and others with intensive agricultural activity, coinciding with the natural recharge area to the aquifer system. Major difficulties and some recommendations of applying this methodology in real-world situations are discussed.

Physical controls of near‐surface soil moisture across varying spatial scales in an agricultural landscape during SMEX02

Understanding of near‐surface soil moisture variability at different spatial scales and associated dominant physical controls is limited. In the past, soil moisture dynamics studies have been conducted extensively at different spatial scales using both in situ and remote sensing (RS) data in the subhumid Southern Great Plains region, which has mostly pasture and range land cover with rolling topography. Compared to the past efforts, we investigated the space‐time characterization of near‐surface soil moisture and associated physical controls at multiple scales (field, watershed, and region) in a humid hydroclimatic region with different topography and agricultural land cover. Soil moisture data from two different measurement support scales (theta probe based (point scale) and airborne RS derived; footprint scale, 800 m × 800 m), obtained during the Soil Moisture Experiment 2002 (SMEX02) in Iowa were used. Geostatistical analysis showed the spatial soil moisture correlation lengths varied between 78 m and 307 m (at the field scale), 2044 m and 11,882 m (at the watershed scale), and 19,500 m and 118,500 m (at the regional scale). The correlation length values were usually smaller on wet days than the relatively dry days at the field and watershed scales. The trend was opposite at the regional scale with correlation lengths being larger on wet days. Furthermore, the soil moisture data sets were decomposed into spatial Empirical Orthogonal Function (EOF) patterns, and their relationship with various geophysical parameters (rainfall, topography, soil texture, and vegetation) was examined to determine the dominant control on the near‐surface soil moisture variability. At the field scale, the first four EOFs together explained about 81% of the total variability. At the watershed scale, the first two EOFs were dominant explaining about 93% of the total variance, whereas at the regional scale, the primary EOF itself explained more than 70% of the variance. In other words, the complicated dynamics of near‐surface soil moisture fields can be described by a few underlying orthogonal spatial structures related to the geophysical attributes of the region. Correlation analysis of the RS soil moisture data showed that rainfall, topography, and soil texture have mixed effects on the variability explained by the dominant EOFs, at both watershed and regional scales, with limited influence of vegetation parameters. The effect of rainfall on the soil moisture variability is higher at the watershed scale compared to the regional scale in Iowa.

Assessing land-use effects on water quality, in-stream habitat, riparian ecosystems and biodiversity in Patagonian northwest streams

Changes in land-use practices have affected the integrity and quality of water resources worldwide. In Patagonia there is a strong concern about the ecological status of surface waters because these changes are rapidly occurring in the region. To test the hypothesis that greater intensity of land-use will have negative effects on water quality, stream habitat and biodiversity we assessed benthic macroinvertebrates, riparian/littoral invertebrates, fish and birds from the riparian corridor and environmental variables of 15 rivers (Patagonia) subjected to a gradient of land-use practices (non-managed native forest, managed native forest, pine plantations, pasture, urbanization). A total of 158 macroinvertebrate taxa, 105 riparian/littoral invertebrate taxa, 5 fish species, 34 bird species, and 15 aquatic plant species, were recorded considering all sites. Urban land-use produced the most significant changes in streams including physical features, conductivity, nutrients, habitat condition, riparian quality and invertebrate metrics. Pasture and managed native forest sites appeared in an intermediate situation. The highest values of fish and bird abundance and diversity were observed at disturbed sites; this might be explained by the opportunistic behavior displayed by these communities which let them take advantage of increased trophic resources in these environments. As expected, non-managed native forest sites showed the highest integrity of ecological conditions and also great biodiversity of benthic communities. Macroinvertebrate metrics that reflected good water quality were positively related to forest land cover and negatively related to urban and pasture land cover. However, by offering stream edge areas, pasture sites still supported rich communities of riparian/littoral invertebrates, increasing overall biodiversity. Macroinvertebrates were good indicators of land-use impact and water quality conditions and resulted useful tools to early alert of disturbances in streams. Fish and birds having a greater ability of dispersion and capacity to move quickly from disturbances would reflect changes at a higher scale.

Effects of land use on dissolved organic matter biogeochemistry in piedmont headwater streams of the Southeastern United States

We measured dissolved organic carbon (DOC), dissolved organic nitrogen (DON), and dissolved organic phosphorous (DOP) concentrations over the course of a year in 15 headwater streams within a Georgia Piedmont watershed that is a mosaic of areas with intensive animal agriculture, forestry, and residential development. The watershed receives large non-point-source organic waste inputs, mostly from poultry and beef production, with lesser quantities from the rapidly growing human population. The organic wastes from animal agriculture are deposited on nearby pastures and the human wastes are mostly treated with septic systems. We selected the headwater catchments to fall along a gradient of organic waste inputs, and hypothesized that stream dissolved organic matter (DOM) concentrations would increase along this gradient. We used a set of readily obtainable landscape indicators (land use categories, soil carbon content, and soil clay content), factor scores derived from a principal components analysis (PCA) of the landscape indicators, and organic waste input estimates to develop simple empirical models that describe our measured DOM concentrations and elemental ratios (C:N, C:P, and N:P). The models show positive correlations of stream DOC, DON, and DOP concentrations with pasture land cover, and with estimated organic waste inputs, lending support to our hypothesis. Over the entire measurement period, buffer land cover better described mean DOC and DON concentrations [maximum adjusted R 2 (AdjR 2) of 0.86 and 0.90, respectively] whereas the best models for mean DOP concentration and elemental ratios were comprised of both watershed and buffer scale indicators or PCA factor scores (maximum AdjR 2 ranged from 0.54 to 0.64). Organic waste estimates were also useful DOM descriptors (maximum AdjR 2 ranged from 0.23 to 0.55), although they were less effective than the landscape indicators. Landscape indicators and organic waste estimates were useful descriptors of DOC concentration variation (maximum AdjR 2 ranged from 0.22 to 0.77) after grouping the observations by season. Watershed scale indicators were better descriptors during most of the seasons. We conclude that landscape indicators and organic waste input estimates are useful descriptors of DOM concentrations and elemental ratios in watersheds dominated by non-point-source organic matter inputs.

Biofuel production potentials in Europe: Sustainable use of cultivated land and pastures. Part I: Land productivity potentials

IIASA's agro-ecological zones modelling framework has been extended for biofuel productivity assessments distinguishing five main groups of feedstocks covering a wide range of agronomic conditions and energy production pathways, namely: woody lignocellulosic plants, herbaceous lignocellulosic plants, oil crops, starch crops and sugar crops. A uniform Pan-European land resources database was compiled at the spatial resolution of 1 km2. Suitability and productivity assessments were carried out by matching climate characteristics with plant requirements, calculating annual biomass increments or yields including consideration of soil and terrain characteristics of each grid-cell. Potential biomass productivity and associated energy yields were calculated for each grid-cell. Spatial distributions of suitabilities of biofuel feedstocks in Europe were generated for each individual feedstock as well as for the five biofuel feedstock groups. Estimated agronomical attainable yields, both in terms of biomass (kg ha-1) as well as biofuel energy equivalent (GJ ha-1), were mapped and tabulated by agriculture and pasture land cover classes as derived from the CORINE land cover database. Results have been further aggregated by administrative units at NUTS 2 level.

Spatio-temporal evolution and time-stable characteristics of soil moisture within remote sensing footprints with varying soil, slope, and vegetation

Air-borne passive microwave remote sensors measure soil moisture at the footprint scale, a scale of several hundred square meters or kilometers that encompasses different characteristic combinations of soil, topography, vegetation, and climate. Studies of within-footprint variability of soil moisture are needed to determine the factors governing hydrologic processes and their relative importance, as well as to test the efficacy of remote sensors. Gridded ground-based impedance probe water content data and aircraft-mounted Electronically Scanned Thinned Array Radiometer (ESTAR) pixel-average soil moisture data were used to investigate the spatio-temporal evolution and time-stable characteristics of soil moisture in three selected (LW03, LW13, LW21) footprints from the Southern Great Plains 1997 (SGP97) Hydrology Experiment. Better time-stable features were observed within a footprint containing sandy loam soil than within two pixels containing silty loam soil. Additionally, flat topography with split wheat/grass land cover produced the largest spatio-temporal variability and the least time stability in soil moisture patterns. A comparison of ground-based and remote sensing data showed that ESTAR footprint-average soil moisture was well calibrated for the LW03 pixel with sandy loam soil, rolling topography, and pasture land cover, but improved calibration is warranted for the LW13 (silty loam soil, rolling topography, pasture land) and LW21 (silty loam soil, flat topography, split vegetation of wheat and grass land with tillage practice) pixels. Footprint-scale variability and associated nonlinear soil moisture dynamics may prove to be critical in the regional-scale hydroclimatic models.

Pasture Land Cover in Eastern Australia from NOAA-AVHRR NDVI and Classified Landsat TM

A method for constructing a pasture land cover classification for the high rainfall zone of eastern Australia from the U.S. National Oceanic and Atmospheric Administration’s advanced very high resolution radiometer normalized difference vegetation index (NOAA-AVHRR NDVI) data is described. The method uses an established classification of pasture growth potential from single date, springtime, Landsat thematic mapper (TM) data to provide measures of subpixel mixture composition in mosaicked classes in the absence of ground truth or control sites. A sequence of AVHRR data from 1993 was transformed into a vegetation index and then classified to define pasture classes with differing patterns of NDVI. High-resolution classifications of pasture were constructed for ten selected sites within the study area by using Landsat TM scenes. The study area was split into a northern and southern zone on the basis of the temporal pattern of moisture indices. The pasture land cover classes were described in terms of the shape of the NDVI profiles, their geographical location, and the subpixel composition from Landsat TM data. The classified NDVI data were combined with local government area (LGA) boundary data to allow the particular pasture state of each LGA to be estimated. The NDVI–Landsat TM procedure identified 21 and 22 classes in the northern and southern zones, respectively. These classes could be broadly grouped into eight types: sown perennial pastures, sown perennial pastures with woodland, sown annual pastures (southern zone only), mixed pasture and cropping, native pastures, native pastures with woodland, degraded or revegetated areas, and forest. This eight-class classification combining the two zones appeared to represent regional distribution of the major types quite well. The pasture land cover classification was evaluated for selected LGAs by using agricultural statistics and a specialist pasture survey. Local estimates of proportions of major pasture types were sometimes inaccurate owing to difficulties in distinguishing between perennial, annual, and native types where seasonal conditions caused rapid senescence or where open woodland confused profiles between improved and native pastures. The method is nevertheless useful where ground truth or definitive spectral signatures for cover types are unavailable and where description in terms of an average or predominant cover type within a landscape mosaic is acceptable.

Kriging in the shadows: Geostatistical interpolation for remote sensing

It is often useful to estimate obscured or missing remotely sensed data. Traditional interpolation methods, such as nearest-neighbor or bilinear resampling, do not take full advantage of the spatial information in the image. An alternative method, a geostatistical technique known as indicator kriging, is described and demonstrated using a Landsat Thematic Mapper image in southern Chiapas, Mexico. The image was first classified into pasture and nonpasture land cover. For each pixel that was obscured by cloud or cloud shadow, the probability that it was pasture was assigned by the algorithm. An exponential omnidirectional variogram model was used to characterize the spatial continuity of the image for use in the kriging algorithm. Assuming a cutoff probability level of 50%, the error was shown to be 17% with no obvious spatial bias but with some tendency to categorize nonpasture as pasture (overestimation). While this is a promising result, the method's practical application in other missing data problems for remotely sensed images will depend on the amount and spatial pattern of the unobscured pixels and missing pixels and the success of the spatial continuity model used.