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At least 217 records · Page 12Linked to original sources

USGS1987

Regeneration patterns of northern white cedar, an old-growth forest dominant

Regeneration of Thuja occidentalis L. was examined in an old-growth dune forest on South Manitou Island, Michigan. To estimate the current status of cedar regeneration, we determined size structure of seedlings and stems and analyzed present patterns of establishment and persistence relative to substrate type. There has been a shift in the pattern of cedar establishment from soil to log substrates. While 97% of all stems ≥15 cm dbh are associated with a soil substrate, 81% of stems ≥2.5cm-<15 cm dbh, and 98% of all cedar seedlings are confined to log substrates. However, few cedar seedlings survive; only 1% of all seedlings on logs are >25 cm tall. There was no significant relationship between the state of log decay and the density of seedlings >25 cm in height, indicating that long-term survival is not dependent on the degree of log decomposition. However, survival on logs is associated with canopy openings. Seedlings >25 cm tall were associated with gaps, and 78% of cedar stems (≥2.5 cm dbh) on logs were associated with a single windthrow gap. Thus, current cedar regeneration in this old-growth forest depends on logs and the canopy openings associated with them.

American Midland Naturalist↗

USGS2020

Migratory status determines resource selection by American Woodcock at an important fall stopover, Cape May, New Jersey

Migration is a period of high activity and exposure during which risks and energetic demand on individuals may be greater than during nonmigratory periods. Stopover locations can help mitigate these threats by providing supplemental energy en route to the animal’s end destination. Effective conservation of migratory species therefore requires an understanding of use of space that provides resources to migratory animals at stopover sites. We conducted a radio-telemetry study of a short-distance migrant, the American Woodcock ( Scolopax minor ), at an important stopover site, the Cape May Peninsula, New Jersey. Our objectives were to describe land-cover types used by American Woodcock and evaluate home range habitat selection for individuals that stopover during fall migration and those that choose to overwinter. We radio-marked 271 individuals and collected 1,949 locations from these birds (0–21 points individual –1 ) over 4 yr (2010 to 2013) to inform resource selection functions of land-cover types and other landscape characteristics by this species. We evaluated these relationships at multiple spatial extents for (1) birds known to have ultimately left the peninsula (presumed migrants), and (2) birds known to have remained on the peninsula into the winter (presumed winter residents). We found that migrants selected deciduous wetland forest, agriculture, mixed shrub, coniferous wetland forest, and coniferous shrub, while wintering residents selected deciduous wetland forest, coniferous shrub, and deciduous shrub. We used these results to develop predictive models of potential habitat: 7.80% of the peninsula was predicted to be potential stopover habitat for American Woodcock (95% classification accuracy) and 4.96% of the peninsula was predicted to be potential wintering habitat (85% classification accuracy). Our study is the first to report habitat relationships for migratory American Woodcock in the coastal U.S. and provides important spatial tools for local and regional managers to support migratory and winter resident woodcock populations into the future.

New Jersey↗

USGS1998

The seventy-fourth Christmas bird count. 315. Southern Dorchester County, Md

Because limited information is available regarding preferences for nocturnal habitat during winter, we studied use of nocturnal habitats by American woodcock (Scolopax minor) wintering in the Georgia Piedmont (1994-95). During the evening crepuscular period, woodcock on the wintering grounds move from forested to field habitats, presumably to feed, conduct courtship displays, roost, and avoid predators. We conducted crepuscular flight surveys and tracked radio-marked woodcock to compare the use of fields of different sizes (<5.5 ha, 5.540.0 ha, >40.0 ha) and types (seed tree-clearcuts, fallow-old fields, hayfields, pastures). Fields > 5.5 ha were used more frequently than fields <5.5 ha (P < 0.001). Seed tree-clearcuts and fallow-old fields were more frequently used than pastures (P = 0.003). Woodcock also most frequently used fields with greater foliage volume at 0.82.0 m in height and a high percentage of bare soil (P < 0.001). Nocturnal use of fields or forests by radio-marked woodcock did not differ among age or sex classes. However, females moved an average of 230 + 32.1 m between diurnal and nocturnal locations while males moved 525 + 53.1 m ( P = 0.085). Movements differed among moon phases (P < 0.003), ranging from 579 + 79.6 m during the new moon to 213 + 50.5 m during the full moon. To manage habitat on the wintering grounds, seed tree-clearcuts and fallow-old fields should be created or maintained near preferred diurnal habitats.

Journal of Wildlife Management↗

USGS1998

The seventy-fourth Christmas bird count. 315. Southern Dorchester County, Md

Journal of Wildlife Management↗

USGS1995

Neotropical migrant landbirds and landscape changes in Los Tuxtlas, Veracruz, Mexico

Faced with the problem of habitat loss and with the need to preserve the remaining components of the original avian biodiversity in neotropical regions such as Los Tuxtlas, it is imperative to determine how the neotropical migrant bird species have responded to the anthropogenic alterations of their natural habitats. To provide data in this direction, we censused neotropical migrant birds in undisturbed and in disturbed forest fragments and in regeneratlng forests (young second growths and old second growths). In addition, we conducted censuses in the following man-made habitats: arboreal agricultural habitats (cacao, coffee, mixed, citrus, and allspice), non-arboreal agricultural habitats (corn and jalapeno chili pepper), live fences, and pastures. We censused 4186 neotropical migrant birds representing 71 species. Seven species (Magnolia Warbler, Hooded Warbler, Wilson's Warbler, American Redstart, White-eyed Vireo, Yellow-rumped Warbler, Black-and-white Warbler) accounted for 50% of total records. Isolating distance was an important variable influencing species richness at the non-pasture habitats studied. Disturbed forest fragments had significantly fewer species and individuals than undisturbed forest fragments and than regenerating forests. Pastures were the poorest habitat in neotropical migrant birds. Agricultural habitats, however, were particularly rich in individuals and species (3479 individuals of 59 species). Arboreal agricultural habitats and live fences were richer in species and in birds than non-arboreal man-made habitats and were also the habitats most similar to the undisturbed forest fragments in species assemblage. We discuss the conservation value for neotropical migrant birds of agricultural habitats and of live fences as landscape elements that help reduce physical and biotic isolation among the remaining configurations of forest fragments and compensate, in part, for the loss of vegetation area and habitat heterogeneity that has resulted from anthropogenic activity in Los Tuxtlas.

Book chapter↗

USGS1994

Predators of the Whitetail

white-tailed deer have long been important prey for large predators. Before Europeans colonized North America, deer roaming the forested region east of the Great Plains and areas along the Gulf of Mexico were hunted by wolves and mountain lions, and by Native Americans for food and clothing materials. Today, wolves and mountain lions are largely gone from the white-tailed deer range of the eastern United States. Deer still face the threat of wolves in northern Minnesota, Michigan, and Wisconsin, and of mountain lions, to a limited extent, in Texas and south Florida. Relatively small populations of whitetails have expanded westward, showing up in the Great Plains and several areas west of the Continental Divide such as northwestern Montana, northern Idaho, and eastern Washington. More than half the prey killed by recolonizing wolves in northwestern Montana are white-tailed deer. Although it has not been well documented, these western whitetails undoubtedly also are preyed on by mountain lions. Wolves and mountain lions have evolved as effective killers of deer but with very different physical characteristics and hunting behaviors. Of course, for their part, whitetails have found ways to protect themselves.

Book chapter↗

USGS2021

Phytoplankton and cyanobacteria abundances in mid-21st century lakes depend strongly on future land use and climate projections

Land use and climate change are anticipated to affect phytoplankton of lakes worldwide. The effects will depend on the magnitude of projected land use and climate changes and lake sensitivity to these factors. We used random forests fit with long-term (1971–2016) phytoplankton and cyanobacteria abundance time series, climate observations (1971–2016), and upstream catchment land use (global Clumondo models for the year 2000) data from 14 European and 15 North American lakes basins. We projected future phytoplankton and cyanobacteria abundance in the 29 focal lake basins and 1567 lakes across focal regions based on three land use (sustainability, middle of the road, and regional rivalry) and two climate (RCP 2.6 and 8.5) scenarios to mid-21st century. On average, lakes are expected to have higher phytoplankton and cyanobacteria due to increases in both urban land use and temperature, and decreases in forest habitat. However, the relative importance of land use and climate effects varied substantially among regions and lakes. Accounting for land use and climate changes in a combined way based on extensive data allowed us to identify urbanization as the major driver of phytoplankton development in lakes located in urban areas, and climate as major driver in lakes located in remote areas where past and future land use changes were minimal. For approximately one-third of the studied lakes, both drivers were relatively important. The results of this large scale study suggest the best approaches for mitigating the effects of human activity on lake phytoplankton and cyanobacteria will depend strongly on lake sensitivity to long-term change and the magnitude of projected land use and climate changes at a given location. Our quantitative analyses suggest local management measures should focus on retaining nutrients in urban landscapes to prevent nutrient pollution from exacerbating ongoing changes to lake ecosystems from climate change.

Global Change Biology↗

USGS1982

Habitat Suitability Index Models: Fox squirrel

The fox squirrel (Sciurus niger) is the largest of the North American tree squirrels. The species is widely distributed throughout eastern North American and has been introduced in many portions of the West (Wright 1979). Fox squirrels also have expanded their range westward through utilization of gallery forest habitats along major river drainages (Armstrong 1972; Wright 1979).

FWS/OBS↗

USGS2016

Effects of salinity and flooding on post-hurricane regeneration potential in coastal wetland vegetation

PREMISE OF THE STUDY: The nature of regeneration dynamics after hurricane flooding and salinity intrusion may play an important role in shaping coastal vegetation patterns. METHODS: The regeneration potentials of coastal species, types and gradients (wetland types from seaward to landward) were studied on the Delmarva Peninsula after Hurricane Sandy using seed bank assays to examine responses to various water regimes (unflooded and flooded to 8 cm) and salinity levels (0, 1, and 5 ppt). Seed bank responses to treatments were compared using a generalized linear models approach. Species relationships to treatment and geographical variables were explored using nonmetric multidimensional scaling. KEY RESULTS: Flooding and salinity treatments affected species richness even at low salinity levels (1 and 5 ppt). Maritime forest was especially intolerant of salinity intrusion so that species richness was much higher in unflooded and low salinity conditions, despite the proximity of maritime forest to saltmarsh along the coastal gradient. Other vegetation types were also affected, with potential regeneration of these species affected in various ways by flooding and salinity, suggesting relationships to post-hurricane environment and geographic position. CONCLUSIONS: Seed germination and subsequent seedling growth in coastal wetlands may in some cases be affected by salinity intrusion events even at low salinity levels (1 and 5 ppt). These results indicate that the potential is great for hurricanes to shift vegetation type in sensitive wetland types (e.g., maritime forest) if post-hurricane environments do not support the regeneration of extent vegetation.

Delmarva Peninsula↗

USGS1995

Habitat use at night by wintering American woodcock in coastal Georgia and Virginia

Nocturnal habitats used by American woodcock ( Scolopux minor ) were studied using radio telemetry at two coastal wintering sites in Georgia (1982-84) and Virginia (1991-92). In Georgia, use of forested habitats at night was extensive while use of fields at night varied between years but generally was low. We found no difference in the probability of moving to a field at night among the four age-sex classes ( P = 0.23). A significant effect ( P < 0.05) of age-sex class was noted between distances moved from diurnal to nocturnal locations in Georgia. Young females moved farther than any other age-sex class. In Virginia, no effect of age-sex class was found on the probability of being located during the night in either a field or a forest.

Georgia, Virginia↗

USGS1964

Habitat use at night by wintering American woodcock in coastal Georgia and Virginia

Nocturnal habitats used by American woodcock (Scolopux minor) were studied using radio telemetry at two coastal wintering sites in Georgia (1982-84) and Virginia (1991-92). In Georgia, use of forested habitats at night was extensive while use of fields at night varied between years but generally was low. We found no difference in the probability of moving to a field at night among the four age-sex classes (P = 0.23). A significant effect (P < 0.05) of age-sex class was noted between distances moved from diurnal to nocturnal locations in Georgia. Young females moved farther than any other age-sex class. In Virginia, no effect of age-sex class was found on the probability of being located during the night in either a field or a forest.

Audubon Field Notes↗

USGS2007

Reconnaissance study of the hydrology of American Memorial Park, Island of Saipan, Commonwealth of the Northern Mariana Islands

American Memorial Park, a unit of the National Park Service on the Island of Saipan, includes among its features a 27-acre estuarine system that has become a rarity within the Commonwealth of the Northern Mariana Islands. The estuarine system's mosaic of marshy areas interspersed with emergent wetlands and mixed wet forests provides critical habitat for various migratory and resident waterfowl, including two Federally listed endangered species: the Marianas gallinule ( Gallinula chloropus guami ) and the nightingale reed warbler ( Acrocephalus luscinia ). With sensitivity to the park's ecologic assets and the uncertainty associated with locally rapid urbanization, a need to better understand the hydrology of American Memorial Park was recognized. To address that need, a reconnaissance study of the park was undertaken during August and September 2005. The goals of the study were (1) to describe the occurrence and salinity of surface and ground water within the park; (2) to develop a hydrologic model of the park area of the island, with emphasis on the 27-acre estuarine system; and (3) to identify additional data needed to further develop this model. With regard to surface water, three freshwater inputs to the park's natural wetland are possible: direct rainfall, seaward-flowing ground water, and overland flow. Direct rainfall, which is an important source of freshwater to the wetland, commonly exceeds evapotranspiration both seasonally and per storm. The seaward flow of ground water is likely to be a source of freshwater to the wetland because ground water generally has an upward vertical component in the nearshore environment. Overland flow upgradient of the park could potentially contribute a significant input of freshwater during periods of intense rainfall, but roads that flank the park's perimeter act as a barrier to surficial inflows. During the reconnaissance, four discrete bodies, or zones, of surface water were observed within the park's natural wetland. Conductivity within these surface-water zones typically ranged from 1,540 to 4,370 microsiemens per centimeter (µS/cm) at 25°C although values as low as 829 and as high as 8,750 µ S/cm were measured. As a result of these observations, the American Memorial Park wetland area meets the definition criteria of an estuarine system that is dominantly oligohaline. Conductivity was also measured in a constructed wetland that was built within the park to augment the storm-drainage infrastructure of the village of Garapan. Reverse-osmosis facilities, in operation at hotels adjacent to the park, have historically discharged highly saline wastewater into the storm-drainage system. This collective storm and wastewater flow is routed into the constructed wetland and from there into the ocean. The conductivity of water in the constructed wetland ranged from 45,000 to 62,500 µS/cm , exceeding nominal seawater values by as much as 25 percent, with the highest conductivities recorded near discharging storm drains. With regard to ground water, the reconnaissance included installation of a ground-water-monitoring network. Data collected from this network identified the presence of freshwater underlying the park and indicated that surface water is directly connected to ground water in the natural wetland because the water levels of both surface water and ground water directly varied with the tide. Conductivities of ground-water samples from wells in the monitoring network indicated that ground-water salinity was geographically related: conductivities were lower (801-2,490 (µS/cm) in surficially dry areas, intermediate (6,090-9,180 (µS/cm) in natural-wetland areas, and higher (18,250-27,700 (µS/cm) in areas adjacent to the constructed wetland and its associated ocean-discharge channel. Synoptic water-level surveys were made to enhance understanding of the spatial expression of the water table; they were scheduled to overlap with peak and trough tidal signals to enable limited characteri

Scientific Investigations Report↗

USGS2022

What is a stand? Assessing the variability of composition and structure in floodplain forest ecosystems across spatial scales in the Upper Mississippi River

The forest stand typically represents relatively homogenous forest conditions; the forest stand is generally the unit at which forest attributes are assessed, summarized, and subsequently managed. However, some ecosystems, such as the floodplain forests of the Upper Mississippi River (UMR), can exhibit high variability at fine spatial scales that can confound prescription development, implementation, and ultimate success of stand-level management actions. Here we assess how forest composition and structure vary within and across stand management units on the UMR and test at what spatial scale environmental variables relate to forest characteristics. We found that plot-level measures of composition, structure, and diversity were not well represented by site-level averages of these values. When basal area of all overstory species was combined, this variable was more closely related to “site” than to any of the environmental variables, but when analyzed by species, within-plot topographic variation (“microtopography”) was a significant positive predictor for both importance values of an individual species (swamp white oak ( Quercus bicolor Willd.)) as well as importance value of a specific group of species (oaks (Quercus spp.), bitternut hickory ( Carya cordiformis (Wangenh.) K. Koch), hackberry ( Celtis occidentalis L.), and American basswood ( Tilia americana L.)). This work highlights the challenges of using average stand conditions to summarize complex or heterogeneous systems and the need for flexibility and relaxed assumptions in defining management units in these forests.

Iowa, Minnesota, Wisconsin↗

USGS2021

Floodplain forest tree seedling response to variation in flood timing and duration

The regeneration process is a sensitive period within life cycles of floodplain tree species and can strongly influence forest community composition. Yet, fundamental information remains limited on the relationship between regeneration processes and the flood disturbances that, together, construct floodplain forest landscapes. In a controlled greenhouse experiment we tested the effects of complete submergence on six temperate floodplain forest species to understand how flood timing and duration influence seedling survival. Groups of overcup oak ( Quercus lyrata ), Nuttall oak ( Quercus texana ), willow oak ( Quercus phellos ), sugarberry ( Celtis laevigata ), green ash ( Fraxinus pennsylvanica ), and American elm ( Ulmus americana ) seedlings were submerged for either 5, 15, 25, or 0 days (control) at the ages of 3-weeks, 6-weeks, and 9-weeks post-emergence. All species demonstrated a higher sensitivity to flooding at age 3-weeks compared to 6- and 9- weeks, indicating substantial changes in seedling resilience within the first months following emergence. Additionally, the heavier-seeded Q. lyrata , Q. texana, and Q. phellos were less or equally vulnerable to flooding compared to the lighter-seeded C. laevigata, F. pennsylvanica, and U. americana across all age groups, especially at 3-weeks post-emergence. The results of this study have implications for understanding woody species regeneration ecology and changes in floodplain forest composition, particularly in the context of hydrologic modifications.

Forest Ecology and Management↗

USGS2003

Vegetation dynamics under fire exclusion and logging in a Rocky Mountain watershed, 1856-1996

How have changes in land management practices affected vegetation patterns in the greater Yellowstone ecosystem? This question led us to develop a deterministic, successional, vegetation model to “turn back the clock” on a study area and assess how patterns in vegetation cover type and structure have changed through different periods of management. Our modeling spanned the closing decades of use by Native Americans, subsequent Euro-American settlement, and associated indirect methods of fire suppression, and more recent practices of fire exclusion and timber harvest. Model results were striking, indicating that the primary forest dynamic in the study area is not fragmentation of conifer forest by logging, but the transition from a fire-driven mosaic of grassland, shrubland, broadleaf forest, and mixed forest communities to a conifer-dominated landscape. Projections for conifer-dominated stands showed an increase in areal coverage from 15% of the study area in the mid-1800s to ∼50% by the mid-1990s. During the same period, projections for aspen-dominated stands showed a decline in coverage from 37% to 8%. Substantial acreage previously occupied by a variety of age classes has given way to extensive tracts of mature forest. Only 4% of the study area is currently covered by young stands, all of which are coniferous. While logging has replaced wildfire as a mechanism for cycling younger stands into the landscape, the locations, species constituents, patch sizes, and ecosystem dynamics associated with logging do not mimic those associated with fire. It is also apparent that the nature of these differences varies among biophysical settings, and that land managers might consider a biophysical class strategy for tailoring management goals and restoration efforts.

Ecological Applications↗

USGS2012

Encroachment of oriental bittersweet into Pitcher’s thistle habitat

Common invasive species and rare endemic species can grow and interact at the ecotone between forested and non-forested dune habitats. To investigate these interactions, a comparison of the proximity and community associates of a sympatric invasive ( Celastrus orbiculatus ; oriental bittersweet) and native ( C. scandens ; American bittersweet) liana species to federally threatened Cirsium pitcheri (Pitcher's thistle) in the dunes habitats of Lake Michigan was conducted. Overall, the density of the invasive liana species was significantly greater in proximity to C. pitcheri than the native species. On the basis of composition, the three focal species occurred in both foredune and blowout habitats. The plant communities associated with the three focal species overlapped in ordination space, but there were significant differences in composition. The ability of C. orbiculatus to rapidly grow and change the ecological dynamics of invasion sites adds an additional threat to the successional habitats of C. pitcheri .

Lake Michigan↗

USGS2024

Comparison of two methods to detect the northwestern pond turtle (Actinemys marmorata) and the invasive American bullfrog (Lithobates catesbeianus) in interior northern California

Knowledge about the distributions of species and the variables influencing their occurrence is important for their management and conservation, but factors affecting occurrence can vary across the range of a species. Northwestern pond turtles ( Actinemys marmorata ) are widespread generalist turtles, but are nonetheless of conservation concern throughout their range. To better understand the distribution of northwestern pond turtles and introduced American bullfrogs ( Lithobates catesbeianus ), we surveyed streams on private timberlands of the interior foothills of northern California using visual encounter surveys and collecting samples of environmental DNA. We found that northwestern pond turtle occurrence was negatively related to elevation in our sampling frame. Detection probabilities with environmental DNA were approximately twice those of visual encounter surveys, but both methods were effective for detecting turtles in streams. American bullfrogs were detected in a single sample at each of 2 sites (one by environmental DNA, one by visual encounter surveys). Management for northwestern pond turtles in forest streams within our sample area will likely have the largest effect at lower elevation sites where turtles are most likely to occur.

California↗

USGS2020

Landscape and climatic influences on actual evapotranspiration and available water using the Operational Simplified Surface Energy Balance (SSEBop) Model in eastern Bernalillo County, New Mexico, 2015

The U.S. Geological Survey, in cooperation with the Bernalillo County Public Works Division, conducted a 1-year study in 2015 to assess the spatial and temporal distribution of evapotranspiration (ET) and available water within the East Mountain area in Bernalillo County, New Mexico. ET and available water vary spatiotemporally because of complex interactions among environmental factors, including vegetation characteristics, soil characteristics, topography, and climate. Precipitation data from the Parameter-Elevation Regressions on Independent Slopes Model (PRISM) ( P ) were used in conjunction with actual ET ( ETa ) data from the Operational Simplified Surface Energy Balance (SSEBop) model to estimate available water ( P – ETa ) at 100-meter (m) resolution in the study area. Maps, descriptive statistics, boxplots, regression analyses (continuous data), and multiple comparison tests (categorical data) were used to characterize P , ETa , and available water and their relations to topographic, soil, and vegetation datasets in the East Mountain area. Five categories of the natural land-cover type (evergreen forest, shrub, herbaceous, deciduous forest, and mixed forest) and four categories of developed land-cover type specific to residential intensity (developed open, developed low, developed medium, and developed high) were analyzed individually and in interaction with multiple elevation, tree canopy, and soil texture classes. Annual mean P in 2015 in the East Mountain area was 608 millimeters (mm), and annual mean ETa was 543 mm (89 percent of annual P in 2015), indicating that in 2015, a spatial mean of about 65 mm of water was available for runoff, soil moisture replenishment, or groundwater recharge. Monthly ETa was greatest in July and smallest in January. The intervening months did not show smooth temporal or consistent spatial changes from month to month. Months with lower ETa (January to March, October to December) also tended to have greater available water, indicating that soil moisture (water supply) and potential ET (water demand) may have been out of phase. Regression analyses showed that monthly ETa data had the highest correlation with annual ETa among the atmospheric, topographic, soil, or vegetation datasets, particularly during the early and late growing season (March, April, May, and September). In contrast, monthly P was highly variable and not as highly correlated with annual ETa . Among landscape variables, correlations with annual ETa were highest for tree canopy cover (coefficient of determination [R 2 ] = 0.46). Correlations between ETa and other landscape variables were lower (R 2 = 0.06–0.19): available soil water in the top 100 centimeters, soil bulk density of layer 1, slope, sand content of soil layer 1, soil depth, available soil water in the top 25 centimeters, leaf area index, aspect eastness, and elevation. Evergreen forest areas had the highest annual median ETa , followed by mixed forest, open residential areas, and deciduous forest. Available water typically was higher in landcover types with lower ETa : herbaceous cover, followed by deciduous forest, high-intensity developed areas, and shrub. Deciduous forest had the second highest median available water, despite having the fourth highest ETa , because deciduous forest had greater P than most other areas. Annual median ETa typically was greatest in the second highest elevation band (2,401–2,800 m above the North American Vertical Datum of 1988 [NAVD 88]), and lower in the highest elevation band (2,801–3,254 m above NAVD 88), despite having greater P , likely because of decreased tree canopy cover or a shift from evergreen to deciduous trees at the highest elevations. Annual median ETa increased with tree canopy cover, regardless of landcover type. ETa correlation was higher with tree canopy than with leaf area index or normalized difference vegetation index. This result indicates that it is important to include the thermal band (from satellite multispectral data) in vegetation indices used to describe ETa , perhaps to account for the influence of energy limitation or water limitation on ET. Of all natural landcover types, finer soils had the most available water, whereas coarser soils had the least available water. Relations of soil type with P – ETa were different than with ETa , indicating ET and available water have a complex response to differences in soil type. Further modeling would be useful in determining soils’ infiltration, storage, conductivity, and plant-water availability relations to individual storms for each position in the landscape, as well as the corresponding effects of these processes on ET and available water. The best multivariate linear model for annual ETa had an R 2 value of 0.62. Monthly ETa models had R 2 values between 0.16 and 0.65. Models usually, but not always, performed best during the growing season. These results indicate that even the best multivariate linear models cannot explain a notable amount of the variability in ET. The monthly ETa models with the highest correlations (August and September) followed a July having almost twice the mean precipitation for July (1981–2010), which indicates that a soil-moisture variable is needed to more accurately model monthly ETa . Further study is needed to better characterize this system, the variables that affect ET and available water, and the partitioning of available water into runoff, soil moisture storage, and groundwater recharge.

New Mexico↗