Percentage Of Land Research Articles

Efficacy of Natural Grassland Buffers for Removal of Cryptosporidium parvum in Rangeland Runoff

Our goal for this project was to estimate the retention efficiency of natural grassland buffers for Cryptosporidium parvum. Three sets of 16 plots (2.0 by 3.0 m) were established at 5, 20, and 35% slopes. Within each set of 16 plots, residual dry vegetation matter treatments of 225, 560, and 900 kg/ha were implemented, along with a noncut control averaging 4,500 kg/ha. Buffer width treatments were implemented by placing cattle fecal material containing known loads of C. parvum 0.1, 1.1, or 2.1 m up-slope of the runoff collector. Grassland buffers of 1.1 and 2.1 m generated 3.2- to 8.8-log and 3.6- to 8.8-log retention of C. parvum, respectively, across the range of residual dry vegetation matter, land slope, rainfall, and runoff conditions examined during this project. Buffers with an increased percent land slope exhibited improved the retention efficiencies, whereas buffers experiencing larger maximum annual runoff events exhibited reduced retention efficiencies. Water-quality data from the 0.1-m-wide buffer plots (effectively no buffer) demonstrated that the majority of C. parvum oocysts (98 to 99.999%) were retained in the fecal matrix for the duration of the storm season, irrespective of the presence of a vegetated buffer. In conclusion, these results support the assertion that grassland buffers are an effective method for reducing animal agricultural inputs of waterborne C. parvum into drinking and irrigation water supplies.

Macroinvertebrate response to land cover, habitat, and water chemistry in a mining-impacted river ecosystem: A GIS watershed analysis

This study addressed potential land use impacts to macroinvertebrate communities and water quality from past coal mining activities in the watershed of the North Branch of the Susquehanna River (located in northeastern Pennsylvania and southern New York). Landscape tools of GIS and remote sensing (RS) were used to calculate percent land cover (forest, agriculture, barren, urban, and water) from SPOT imagery (for tributaries) and Multi-Resolution Land Characteristics (MRLC) data (for river sites) on 17 subcatchments in the study area. The study design included field sampling at reach locations at four first- and second-order sites with low urban and low barren (mining) land cover, four similar sized sites with high mining and high barren land cover, five sites with intermediate combinations of urban and barren, and four mainstem river sites (60% forest and 35% agriculture). Sites were sampled in early fall for macroinvertebrates (17 parameters, e. g., EPT richness, percent filterers), benthic substrates (including deposits from mine waters), and 10 water chemistry parameters. A principal component analysis (PCA) on the macroinvertebrate parameters provided plot-clustering of subcatchments based generally on the above study design groupings; river sites clustered closer to smaller streams with low mining and urban land cover. Correlations identified six macroinvertebrate parameters (e. g., EPT richness, collector-gatherers) best associated with the three major axes of the PCA; each of these six indicators was analyzed in step-wise multiple regressions as dependent variables against land cover, benthic substrate, and water chemistry parameters. The strongest regressions were for percent barren land cover that explained the greatest amount of variation in both EPT richness and taxa richness. This mining affect was confirmed with dissolved iron and sulfate concentrations and levels of sedimentation and iron deposition explaining variability across several macroinvertebrate parameters. Comparison to the published literature on mining impacts indicated advantages to using a GIS watershed approach in multivariate analyses of stream ecosystem response. Also, this appears to be the first GIS watershed assessment of mining land use affects since most published studies of land use impacts to watersheds and lotic ecosystems have focused on either agriculture or urbanization.

Water quality during winter storm events in Spring Creek, Pennsylvania USA

This study examined the relationship between land cover and three solute (chloride, total organic carbon (TOC), and lead) concentrations during winter rainstorms in 10 subbasins of Spring Creek, Pennsylvania, USA at two spatial scales. Despite similar percent land cover at both scales, correlations between water quality and land cover were stronger at the subbasin scale than at the riparian scale. As basin percent urban land cover increased, mean chloride and lead concentrations increased. Chloride and lead were likely to be a result of roadside sediments and residential housing, as demonstrated by a strong positive relationship between road density and chloride concentration at both spatial scales (r = 0.83, 0.71). Basin percent forested cover at the subbasin scale was weakly positively related to TOC concentrations, suggesting leaf litter as a source. Changes in flow rate related to changes in concentrations of solutes for representative urban and rural subbasins. TOC and lead showed weak positive relationships (flushing effect), while chloride exhibited a strong negative relationship (dilution effect). These different responses to changes in flow rate implied different sources of solutes – soils for TOC and lead and groundwater for chloride. This study underscores some negative effects of increased basin urbanization on stream water quality and potential aquatic ecosystems in small streams during storm events.

Long-term trends and spatial variability in nitrate leaching from alpine catchment–lake ecosystems in the Tatra Mountains (Slovakia–Poland)

Relationships between catchment characteristics of 31 alpine lakes and observed trends in lake water concentrations of nitrate were evaluated in the Tatra Mountains. Nitrate concentrations increased from background levels <4 μeq l −1 in the 1930s to maxima (up to 55 μeq l −1) in the 1980s, after which they declined to 4–44 μeq l −1 by the late 1990s. In-lake nitrate concentrations correlated negatively with parameters characterising catchment-weighted mean pools (CWM; kg m −2) of soil, i.e. with percent land cover with meadow and soil depth, and positively with grade of terrain, annual precipitation, and the highest elevation in the catchment. The CWM pool of soil and annual precipitation explained together 65% of the current spatial variability in nitrate concentrations. Denitrification and direct N deposition on surface area explained 14% of the variability. Increased atmospheric N deposition and declining net N retention in soils were responsible for long-term changes in nitrate concentrations. Long-term decline in %N retention in soils decreased along with the estimated decline in C:N ratios (from 21 to 18 on average during the last 70 years). An empirical model linking nitrate concentrations in different types of alpine Tatra Mountain lakes to four independent variables (CWM soil pool, annual precipitation, increased N deposition, and average trend in soil C:N ratios) explained 80% of the observed spatial and temporal nitrate variability over the period 1937–2000.

Historical Changes in Forest Cover and Land Ownership in a Midwestern U.S. Landscape

Environmental history in the Midwestern Corn Belt includes changes through time in landowners and their consequent effect on agricultural and uncultivated land resources. We examined these changes in Israel Township, southwestern Ohio, using archival accounts from the mid 1800s, land-cover maps compiled from 1935, 1956, and 1984 aerial images, and land-ownership records from 1912, 1940, 1968, 1974, 1983, and 1989 parcel maps. Historical records document the clearing of beech-maple forests for agriculture and show the economic contributions of forests to early settlement. Between 1935 and 1984, agricultural lands declined from 84 percent to 78 percent and forests increased from 10 percent to 19 percent. These are slight changes in comparison with the more than 90 percent of the uncultivated lands that experienced transitions among land uses. We document a decline in land-cover diversity, with losses in successional lands and most forest growth localized to lower stream valleys and Hueston Woods State Park. The amount of land in farms (≥3-ha tracts) declined slightly, from 99 percent to 88 percent, but 79 percent of the land showed two to three changes in landowners and 16 percent showed four to five changes over the study period. Parcels with low turnover had the greatest percent of their land in forest, larger mean forest-patch sizes, and the greatest percent gains in forest area. Our results support coordinated efforts focused on factors that influence stable farm ownership and promote a diversity of environmental and economic gains from forests in the rural landscape.

Impact of sensor's point spread function on land cover characterization: assessment and deconvolution

Measured and modeled point spread functions (PSF) of sensor systems indicate that a significant portion of the recorded signal of each pixel of a satellite image originates from outside the area represented by that pixel. This hinders the ability to derive surface information from satellite images on a per-pixel basis. In this study, the impact of the PSF of the Moderate Resolution Imaging Spectroradiometer (MODIS) 250 m bands was assessed using four images representing different landscapes. Experimental results showed that though differences between pixels derived with and without PSF effects were small on the average, the PSF generally brightened dark objects and darkened bright objects. This impact of the PSF lowered the performance of a support vector machine (SVM) classifier by 5.4% in overall accuracy and increased the overall root mean square error (RMSE) by 2.4% in estimating subpixel percent land cover. An inversion method based on the known PSF model reduced the signals originating from surrounding areas by as much as 53%. This method differs from traditional PSF inversion deconvolution methods in that the PSF was adjusted with lower weighting factors for signals originating from neighboring pixels than those specified by the PSF model. By using this deconvolution method, the lost classification accuracy due to residual impact of PSF effects was reduced to only 1.66% in overall accuracy. The increase in the RMSE of estimated subpixel land cover proportions due to the residual impact of PSF effects was reduced to 0.64%. Spatial aggregation also effectively reduced the errors in estimated land cover proportion images. About 50% of the estimation errors were removed after applying the deconvolution method and aggregating derived proportion images to twice their dimensional pixel size.

Assessing traveler responsiveness to land and location based accessibility and mobility solutions

In this paper, a joint multinomial logit (MNL) model of residential location and vehicle availability choice is formulated and estimated using a sample of households from the San Francisco, CA area Metropolitan Transportation Commission's 1990 household travel survey. Subsequently, models of travel intensity (number of daily household trips and vehicle-miles traveled) are estimated as a function of household characteristics and of attributes derived from the joint residential location and auto availability choice model (number of vehicles, percent land developed). A policy test shows that reducing the cost of locating in the densest areas of the metropolitan area is likely to have only marginal impact on vehicle availability and household trip making.

Waste minimization program in Shuaiba Industrial Area

The Shuaiba Industrial Area (SIA) is located about 50 km south of Kuwait City. It accommodates most of the large-scale industries in Kuwait. The total area of the SIA (both eastern and western sectors) is about 22.98 million m2. Fifteen plants are located in the eastern sector and 23 in the western sector, including two petrochemical companies, three refineries, two power plants, a melamine company, an industrial gas corporation, a paper products company and, two steam electricity generating stations, in addition to several other industries. Therefore, only 30 percent of the land in the SIA's eastern sector and 70 percent of land in the SIA's western sector is available for future expansion. Presently, industries in the SIA generate approximately 204,000 t of solid waste. With future development in the industries in the SIA, the estimated quantities will reach 240,000 t. The Shuaiba Area Authority (SAA), a governmental regulatory body responsible for planning and development in the SIA, has recognized the problem of solid waste and has developed an industrial waste minimization program. This program would help to reduce the quantity of waste generated within the SIA and thereby reduce the cost of waste management. This paper presents a description of the waste minimization program and how it is to be implemented by major petroleum companies. The protocols employed in the waste minimization program are detailed.

STRUCTURAL CHANGES AND EXPERIENCES WITH LAND REFORM IN GERMAN AGRICULTURE SINCE UNIFICATION / STRUKTURELE VERANDERINGE EN ERVARINGS MET GRONDHERVORMING IN DIE DUITSE LANDBOU SEDERT HERENIGING

Following unification of East and West Germany in 1990, the principal objective of the government was to restore previous property rights in the new federal states and to encourage competitive production structures. Institutions were quickly established to facilitate the required adjustments to a market economy. Privatisation of most firms (farms), which was an intricate and costly procedure, was accomplished within five years and resulted in a completely new farm structure in the new federal states. By 1996 over 80 percent of agricultural enterprises comprised private (individual) operations (cultivating 22 percent of land), 9,1 percent partnerships (22 percent of land), while about 3000 legal entities managed 56 percent of farm land. About 90 percent of farmland in the new states is being rented compared to 47percent in the old states. Significantly, leasing and not selling became the most important method to privatise land in the new federal states. In 1996 the number of farming operations in Germany totalled about 540000. While worker employment in German agriculture is steadily decreasing, worker productivity is increasing—from 17 hectares of farm land per full-time equivalent worker (FTE) in 1991 to 43 hectares per FTE in the new states in 1996.

Butterfly diversity and human land use: Species assemblages along an urban grandient

We examined the distribution and abundance of butterfly species across an urban gradient and concomitant changes in community structure by censusing the butterfly and skipper populations at 48 points within six sites near Palo Alto, California, USA (all former oak woodlands). These sites represent a gradient of urban land use running from relatively undisturbed to highly developed and include a nature preserve, recreational area, golf course, residential neighborhood, office park and business district. The species richness and Shannon diversity of butterflies peaked at moderately disturbed sites while the relative abundance decreased from the natural to the urban areas. Butterfly species thought to be most representative of the original, predevelopment butterfly fauna progressively disappear as the sites become more urban. These patterns are significantly related to shifts in habitat structure that occur along the gradient as determined by canonical correspondence analysis (CCA) using the environmental variables of percent land covered by pavement, buildings, lawn, grasslands, and trees or shrubs. The mechanisms behind these patterns may be related to life history and resource use by the individual butterfly species.

A Salinity Risk Index for Soils of the Canadian Prairies

Agricultural land use can impact the sustainability of inherent soil quality by its influence on the extent, severity, and dynamics of soil salinity. To assess this impact, a salinity risk index was developed and applied to the agricultural region of the Canadian prairies, utilizing land-use data sets for 1981 and 1991. The analysis is presented in map form. The total extent of moderate or more severe salinity for the prairie region, as determined from a summation of each provincial map, is 1.4 million hectares. The risk assessment based on 1991 land-use data indicates that 62.2 percent of the farm land has little to no risk of a change in salinity, 27.9 percent has a moderate risk, and 9.9 percent of the land has a high risk. A comparison of the risk index classes for the 1981 and 1991 land-use data indicates that risk of salinity for the majority of the land (92 percent) hat not changed, whereas less than 7 percent of the land had a lower risk class, and approximately 0.5 percent had a higher risk class in 1991. This approach could be utilized periodically to track the impacts of changes in land and thus serve as an indicator of agri-environmental sustainability. This information could be applied by upper levels of government to develop programs and to define agricultural policy.

Development of an eco-tourism strategy for Texas

This paper deals with the development of a nature tourism strategy for Texas. As opposed to many states and countries Texas is unique in terms of private land ownership. In fact 97 percent of land belongs to private sector owners leaving 3 percent to the public domain. Private ownership makes it very difficult to maneuver in developing a strategy. This paper gives the history and methodology that was used in developing a nature tourism strategy. The process involved a number of private and public interests and focused on the obstacles that make it difficult for tourism development.

Land Use and Avian Species Diversity Along an Urban Gradient

I examined the distribution and abundance of bird species across an urban gradient, and concomitant changes in community structure, by censuring summer resident bird populations at six sites in Santa Clara County, California (all former oak woodlands). These sites represented a gradient of urban land use that ranged from relatively undisturbed to highly developed, and included a biological preserve, recreational area, golf course, residential neighborhood, office park, and business district. The composition of the bird community shifted from predominantly native species in the undisturbed area to invasive and exotic species in the business district. Species richness, Shannon diversity, and bird biomass peaked at moderately disturbed sites. One or more species reached maximal densities in each of the sites, and some species were restricted to a given site. The predevelopment bird species (assumed to be those found at the most undisturbed site) dropped out gradually as the sites became more urban. These patterns were significantly related to shifts in habitat structure that occurred along the gradient, as determined by canonical correspondence analysis (CCA) using the environmental variables of percent land covered by pavement, buildings, lawn, grasslands, and trees or shrubs. I compared each formal site to four additional sites with similar levels of development within a two‐country area to verify that the bird communities at the formal study sites were representative of their land use category.

Agricultural Impacts on Bacterial Water Quality in Karst Groundwater

AbstractA 2‐yr study (1991–1992) was conducted in a karst region in southeast West Virginia to determine the impact of agriculture on groundwater quality. The primary agriculture is characterized by seasonal cattle grazing. Fecal coliform densities were measured weekly in the resurgences of three karst basins possessing different degrees of agricultural intensity (79, 51, and 16% land use in agriculture). Fecal coliforms were also measured in a creek at sites upstream and downstream of the known resurgences from the most agriculturally intensive (79%) basin. The fecal coliform densities in the resurgences peaked in the summer and declined in the fall, with a recovery in late winter before the introduction of new cattle. The timing of the recovery indicated that significant storage of fecal material had taken place, which was transported to the groundwater when soil water conditions permitted. For most of each year, soil water effects appeared to have a greater bearing on the fecal coliform densities than did the presence or absence of cattle. The data did not generally support a strong relationship with percent land use in agriculture. This was attributed to the high variability in the data and to low soil moisture during periods of recession that inhibited the transport of fecal material to the groundwater. The karst resurgence springs of the most intensively agricultural basin were contaminated with fecal bacteria. Fecal bacteria concentrations were observed to significantly increase, in the receiving surface stream, from a point upstream of the resurgence springs to a point downstream of the resurgence springs.

Relating United States Crop Land Use to Natural Resources and Climate Change

Crop production depends not only on the yield but also on the area harvested. The yield response to climate change has been widely examined, but the sensitivity of crop land use to hypothetical climate change has not been examined directly. Crop land-use regression models for estimating crop area indices (CAIs)-the percent of land used for corn, soybean, wheat, and sorghum production-are presented. Inputs to the models include available water-holding capacity of the soil, percent of land available for rain-fed agricultural production, annual precipitation, and annual temperature. The total variance of CAI explained by the models ranged from 78% from wheat to 87% for sorghum, and the root-mean-square errors ranged from 1.74% for sorghum to 4.24% for corn. The introduction of additional climatic variables to the models did not significantly improve their performance. The crop land-use models were used to predict the CAI for every crop reporting district in the United States for the current climatic condition and for possible future climate change scenarios (various combinations of temperature and precipitation changes over a range of -3{degrees} to +6{degrees}C and -20% to +20% respectively). The magnitude of climatic warming suggested by GCMs (GISS and GFDL) is from 3.5{degrees} to 5.9{degrees}C for regionsmore » of the United States. For this magnitude of warming, the model suggests corn and soybean production areas may decline while wheat and sorghum production areas may expand. If the warming is accompanied by a decrease in annual precipitation from 1% to 10%, then the areas used for corn and soybean production could decrease by as much as 20% and 40%, respectively. The area for sorghum and wheat under these conditions would increase by as much as 80% and 70%, respectively; the exact amount depending strongly on the change in precipitation. 15 refs., 6 figs.« less

A model to predict gross sedimentation in small glacial lakes

This study is an attempt to quantify and rank variables of significance to predict gross sedimentation (i.e., net sedimentation plus resuspension) in small glacial lakes. Sediment traps were placed in 25 Swedish lakes and exposed for about 110 days during the summer for four years. Average values of rates of gross sedimentation in bottom traps were compared to catchment and morphometric parameters determined from different types of maps. Various hypotheses concerning the factors regulating gross sedimentation in lakes were formulated and tested. Different statistical tests were used to separate random influences from causal influences. The most important 'map parameters' were: the relative depth, linked to resuspension and the form and size of lakes, the forest and open land percent of the so-called near area (= the proximate area of the lake as determined by the drainage area zonation method), the distribution of mires and lakes in the catchment, the relief of the drainage area and the theoretical lake water retention time. Each of these variables only provides a limited degree of (statistical) explanation of the variability in gross sedimentation among the lakes. The predictability of models for gross sedimentation can be markedly improved by accounting for the zonation problem, i.e., the distribution of the characteristics in the drainage area. The stability of the final model, which gives a r 2-value of 0.78, has been tested with positive results. The model allows mean values of gross sedimentation to be estimated from readily available data of ‘geological’ characteristics of the lake and its drainage area. The variability in gross sedimentation from other factors/variables, such as temperature, precipitation, wind, and load of nutrients, may then be quantitatively differentiated from the impact of these ‘geological’ factors/constants.

A model to predict gross sedimentation in small glacial lakes

This study is an attempt to quantify and rank variables of significance to predict gross sedimentation (i.e., net sedimentation plus resuspension) in small glacial lakes. Sediment traps were placed in 25 Swedish lakes and exposed for about 110 days during the summer for four years. Average values of rates of gross sedimentation in bottom traps were compared to catchment and morphometric parameters determined from different types of maps. Various hypotheses concerning the factors regulating gross sedimentation in lakes were formulated and tested. Different statistical tests were used to separate random influences from causal influences. The most important 'map parameters' were: the relative depth, linked to resuspension and the form and size of lakes, the forest and open land percent of the so-called near area (= the proximate area of the lake as determined by the drainage area zonation method), the distribution of mires and lakes in the catchment, the relief of the drainage area and the theoretical lake water retention time. Each of these variables only provides a limited degree of (statistical) explanation of the variability in gross sedimentation among the lakes. The predictability of models for gross sedimentation can be markedly improved by accounting for the zonation problem, i.e., the distribution of the characteristics in the drainage area. The stability of the final model, which gives a r 2-value of 0.78, has been tested with positive results. The model allows mean values of gross sedimentation to be estimated from readily available data of ‘geological’ characteristics of the lake and its drainage area. The variability in gross sedimentation from other factors/variables, such as temperature, precipitation, wind, and load of nutrients, may then be quantitatively differentiated from the impact of these ‘geological’ factors/constants.

Canopy Light Reflectance and Remote Sensing of Shin Oak (Quercus havardii) and Associated Vegetation

Shin oak is a deciduous shrub that forms dense stands of brush on sandy soils in rangeland areas of the Rolling and High Plains of Texas. Plant canopy reflectance measurements made on shin oak showed that it had both low visible (0.63- to 0.69-μm waveband) and nearinfrared (0.76- to 0.90-μm waveband) reflectance values, a characteristic generally not shared by associated plant species or mixtures of species. The low reflectance values of shin oak caused it to have dark-red, reddish-brown, or brown image tones on color-infrared photographic, videographic, and SPOT satellite images that made it distinguishable from associated vegetation and other land use features. The optimum time to remotely distinguish this noxious shrub is during the mature phenological stage from June to September. Computer-based image analyses of video and satellite images showed that shin oak populations could be quantified. This technique can permit “percent land area” estimates of shin oak on rangelands. The aerial imagery is useful for detecting shin oak on smaller rangeland areas, whereas the satellite imagery is applicable in mapping large areas of shin oak distribution.

Streamflow Nutrient Dynamics on Coastal Plain Watersheds

AbstractStreamflow and water quality parameters were measured on five watersheds (262 ha‐11 487 ha) of the Little River in the coastal plain near Tifton, GA. Concentrations of nitrate, ammonium, chloride, ortho‐P, total P, total N, and electrical conductivity were determined. Loads and flow‐weighted concentrations were calculated for the five watersheds and for six subwatersheds formed by subtraction of smaller watersheds from larger ones. Mean concentrations and total loads calculated from samples taken every 3 h were not significantly different from samples taken every 12 h on two watersheds. In general, nitrate was enriched and chloride diluted relative to baseflow during storm events. This was attributed to reduction of nitrate in soils and aquifers of riparian areas. Both nitrate loads and concentrations were decreased during low flow years, whereas chloride concentrations were significantly higher in a year with abnormally low flows. Ortho‐P concentrations increased during storm events, but total P showed the opposite response. Enrichment of NO3‐N and ortho‐P and dilution of Cl and conductivity were due, in part, to concentrations in rainfall. Nutrient loads on the 11 watersheds and subwatersheds were similar except for one subwatershed that had the lowest percent of cropland but the highest loads. These high loads were due to exceptionally high flow rates in 1983 and 1984 following clear cutting of forest on nearly 25% of the subwatershed in late 1982. Nutrient loads in Streamflow were not correlated with the percent of land in spring‐planted row crops but were correlated with land in winter wheat, which is fertilized in late fall or early winter. Conditions that change hydrologic responses of watersheds may change the nonpoint sources of nutrients by changing water volumes and by altering processes that create nutrient concentrations in Streamflow.

Detecting Huisache (Acacia farnesiana) and Mexican Palo-verde (Parkinsonia aculeata) by Aerial Photography

Huisache [Acacia farnesiana(L.) Willd. # ACAFA] and Mexican palo-verde (Parkinsonia aculeataL. # PAKAC) are native woody legumes that often occur together on rangelands of southern Texas and northern Mexico. Huisache produces a profusion of orange-yellow flowers during February or March giving it a conspicuous golden appearance. Mexican palo-verde produces a heavy bloom of yellow flowers in mid-April or early May giving it a yellow-green coloration. Plant canopy light reflectance measurements of flowering huisache showed that its reflectance at the 0.55- and 0.65-μm visible wavelengths was significantly higher than that of Mexican palo-verde in the vegetative stage and four other associated plant species or mixture of species. Conversely, reflectance measurements of flowering Mexican palo-verde showed that its reflectance at the 0.55-μm visible wavelength was significantly higher than that of huisache in the vegetative stage and the same four associated plant species or mixtures of species. Flowering huisache had a golden color on conventional color (0.40-to 0.70-μm) aerial photos that made it distinguishable from other plant species, whereas flowering Mexican palo-verde had a pink image on color-infrared (0.50- to 0.90-μm) aerial photos. However, immature plants of both species cannot be detected using this technique. Computer-based image analyses of conventional color film positive transparencies showed that huisache infestations could be quantified from associated rangeland species. This technique can permit ‘percent land area infested’ estimates of mature huisache on rangelands. These results show that aerial photography may be a useful tool to detect and monitor the spread of huisache and Mexican palo-verde on rangelands, and to delineate areas needing control.