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United States Department of Agriculture

Agricultural Research Service

Science Results (Winter 2013)
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Rainfall Erosivity in Brazil:  A Review

Sanches Oliveira, P.                University of Sao Paulo

Endland, E.                             University of Sao Paulo

Nearing, M.A.                         Southwest Watershed Research Center


Rainfall erosivity is the term used to describe the power of rainfall to cause soil erosion.  Rainfall erosivity varies a lot from place to place.  For example, in the United States erosivity values range from around 10 in parts of the western US to more than 700 in southern Louisiana to more than 2000 in a small part of Hawaii.  This means that potential for erosion to occur also varies dramatically depending on the rainfall of a given location.  While a great deal of information is available in the United States on erosivity, much less is known in other parts of the world.  This study was an attempt to review all of the available information known about rainfall erosivity in Brazil.  Various types of information on rainfall were accumulated and equations developed by multiple researchers were used to evaluate that information.  The product of the research will allow us or others to develop a map of erosivity for the entire country of Brazil so that better conservation planning and assessment may be made in that country.


Loss of ecosystem resilience under large-scale altered hydroclimatic condition


Ponce Campos, G.                  University of Arizona

 Zhang, Y.                               University of Arizona

Huxman, T.E.                          University of Arizona

McClaran, M.                          University of Arizona

Moran, M.S.                            Southwest Watershed Research Center

Bresloff C.                              University of Arizona

Huete, A.                                University of Technology, Sydney

Eamus, D.                               University of Technology, Sydney

Bosch, D.                                USDA-ARS

Buda, A.R.                              USDA-ARS

Gunter, S..                               USDA-ARS

Kitchen, S.G.                          USFS

McNab, W.H.                         USFS

Morgan, J.A.                           USDA-ARS

Peters, D.C.                             USDA-ARS

Salder, E.J.                              USDA-ARS

Seyfried, M.S.                         USDA-ARS

Starks, P.J.                              USDA-ARS

Montoya, D.                            USFS

Scalley, T.H.                           USFS


Large-scale, warm droughts have recently impacted North America, Africa, Europe, Amazonia, and Australia resulting in major impacts on terrestrial resources that have threatened life support systems. Yet, food producers, resource managers and policy makers worldwide continue to make important decisions on livelihood and food security with little understanding about how vegetation production will respond to the altered hydroclimatic conditions predicted with climate change. Here we describe the response of plant communities to the altered hydroclimatic conditions that are projected for large international regions in the 21st century.  We found that plant communities exhibited a robust tolerance to low precipitation, but that efficiency constrained the capacity for response to high precipitation.  This continental lack of ecosystem resilience during altered hydroclimatic conditions will result in significant reductions in carbon uptake and food security as parts of the world become more arid.


Estimating crop biophysical properties from remote sensing data by inverting linked radiative transfer and ecophysiological models


Thorp, K.R.                 USDA-ARS

Wang, g.                      University of Arizona

West, A.L.                  University of Arizona

Moran, M.S.                Southwest Watershed Research Center

Bronson, K.F.             USDA-ARS

White, J.W.                 USDA-ARS

Mon, J.                        USDA-ARS


Remote sensing can rapidly map crop growth status over large areas based on reflectance of radiation from the crop canopy.  However, this information must be linked with simulation models in order to quantify crop properties, forecast crop yield, understand the impacts of drought or global climate change, and guide agricultural resource management for water and nitrogen fertilizer.  In this study, we developed techniques for using simulation models to increase the amount of useful information gleaned from remote sensing data.  By implementing inverse modeling techniques (using remote sensing data to automatically parameterize the simulation model), we were able to improve estimates of several crop properties as compared to field-measured values.  We also showed that data from newer 'hyperspectral' instruments, which collect reflectance information in many narrow wavebands, offered several advantages as compared to older instruments that collect information in only a few broad wavebands.  These advantages included better estimation of crop traits and fewer required remote sensing observations.  The results of the study will be useful to agricultural and remote sensing scientists who are using remote sensing solve agricultural problems related to crop yield forecasting and cycling of water and nutrients.


Assimilating Remote Sensing Observations of Leaf Area Index and Soil Moisture for Wheat Yield Estimates: An Observing System Simulation Experiment


Nearing, G.S.              University of Arizona

Thorp, K.R.                 USDA-ARS

Crow, W.T.                 USDA-ARS

Moran, M.S.                Southwest Watershed Research Center

Reichle, R.                  NASA

Gu[ta, H.V.                 University of Arizona


Remote sensing technology provides rapid observation of crop growth variability across agricultural regions.  This information can be used to drive crop growth simulation models for temporal and spatial analysis of factors that affect crop production, such as impacts of climate change and drought on agricultural productivity.  Currently, we lack robust techniques for effectively combining remote sensing and crop modeling technologies for crop production assessments.  In this research, we have conducted a simulation study with the CSM-CROPSIM-CERES-Wheat model to understand how to use information from remote sensing images to adjust the crop growth simulation and more accurately estimate crop yield.  The study also tested two statistical approaches for merging remote sensing information into the model.  Results of the study will be useful in the effort to develop information systems that use remote sensing images and crop growth models to monitor regional impacts of drought and climate change on agricultural productivity.  In particular, the study supports the development of NASA's Soil Moisture Active Passive (SMAP) satellite for global soil moisture monitoring.  The study demonstrates how information from such satellite systems can be used for assessing the impact of soil moisture deficits (drought) on agricultural production.


Time-Lapse Very High Resolution Photography in Rangeland Ecosystem Research


Nichols, M.H.             Southwest Watershed Research Center

Steven, J.                     Sweet Briar College

Sargent, R.                  Carnegie Mellon University

Dille, P.                       Carnegie Mellon University

Schapiro, J.                  Carnegie Mellon Univeristy


A robotic camera system was used to create very high resolution, zoomable time-lapse videos of plant growth and movement in a laboratory and monsoon induced vegetation response at a remote site in southern Arizona.  A critical part of the project was the development of a solar powered charging system so that the robotic mount and camera could be operated without plugging in to a wall outlet. Images were taken every two hours at the remote field site during a one month time period and were stitched to create panoramas that were sequenced to produce a time-lapse video that can be zoomed to display high-resolution spatial detail. This type of photography will be useful for both capturing legacy data and for supporting a broad range of hypothesis driven research.

Response of terrestrial ecosystem production to extreme precipitation and temperature regimes across biomass


Zhang, Y.                    University of Arizona

Moran, M.S.                Southwest Watershed Research Center

Nearing, M.A.             Southwest Watershed Research Center

Ponce Campos, G.      University of Arizona

Huete, A.                    University of Technology, Sydney

Buda, A.R.                  USDA-ARS, Pasture & Watershed Management Research Unit

Bosch, D.D.                USDA-ARS Southeast Watershed Research Laboratory

Gunter, S.A.                USDA-ARS Southern Plains Range Research Station

Kitchen, S.G.              USDA-FS

McNab, W.H.             USDA-FS

Morgan, J.A.               Usda-ars  

Mcclaran, M.P.   University of arizona

Montoya, D.S.      usda-fs

Peters, D.C.            usda-ars jornada experimental range

starks, p.j.             usda-ars grazinglands research laboratory


Climates are becoming more and more extreme with higher temperatures and a shift to larger storms and longer dry intervals. There is great interest in how these changes are affecting vegetation production at the continental scale.  In this study, we determined the effects of novel climatic conditions on plant growth by using satellite measurements of greenness during the early 21st century drought in the US (2000-2009).  We found that higher mean annual maximum temperatures greatly reduced grassland production, and yet enhanced forest production.  Meanwhile, increasingly extreme precipitation patterns led to lower plant growth and a decrease in rain-use efficiency across all biomes. The results from this study suggest that extreme precipitation and temperature patterns associated with climate change will have an important and complex effect on vegetation across a range of ecosystems from grasslands and forests.  This, in turn, could impact global carbon balance, US food security and regional livelihood. 


Controls on the spacing and geometry of rill networks on hillslopes: Rainsplash detachment, initial hillslope roughness, and the competition between fluvial and colluvial transport



McGuire, L.A.             University of Arizona

Pelletier, J.D.               University of Arizona

Gomez, J.                    Instituto de Agricultura Sostenible, Consejo Superior de Investigaciones Científicas

Nearing, M.A.             Southwest Watershed Research Center


Rills are small channels that form on hillslopes during the erosion of topsoil.  Rill networks are the spatial patterns that form from the development of several individual rills.  Rill networks have been studied for a long time but we still lack a complete understanding of what controls the spacing of rills and the geometry of rill networks on hillslopes.  Learning this and understanding the formation of rill networks would be a major advance to the science of soil erosion.  This study was undertaken in order to develop a set of mathematical equations and their solutions that will allow scientists to better understand and compute the formation of rill networks.  The data used were taken from an earlier study conducted by ARS scientists at the ARS National Soil Erosion Research Laboratory.  The results were remarkably good.  The model was able to mimic the fundamental processes of soil erosion by both raindrop splash and surface water flow.  It was able to mimic how the flow of water across the soil surface became concentrated in the experiment and formed rills, and the patterns formed by the model were quite close to those measured in the laboratory. The impact of this work is that it contributes to the greater understanding of soil erosion processes, which leads to better mathematical formulations of soil erosion that are routinely used to design conservation practices and assess soil erosion on America’s agricultural soils.

Using remote sensing and eddy covariance data to determine evapotranspiration across a water-limitation gradient

Bunting, .P.                 University of Arizona

Kurc, S.A.                   University of Arizona

Glenn, E.P.                  University of Arizona

Nagler, P.L.                 University of Arizona

Scott, R.L.                  Southwest Watershed Research Center


A common goal for water resource managers in the southwestern United States, and arid and semiarid regions worldwide, is to ensure long-term water supplies for increasing human populations.  In these regions, evapotranspiration (ET) is an important component of the water budget and has large implications for water resources management. We used satellite data and measured ET from three riparian-influenced and two upland, water-limited sites to develop a computer model that could estimate ET with satellite and rainfall data alone.  We found that two separate models were needed: one for the riparian sites and another for the dry upland sites due to the complete dependency of the upland sites on rainfall.  These models can be used in combination to estimate total annual ET across a watershed provided that each region is classified appropriately.  This approach improves accuracy of ET estimates at large scales while accounting for daily to seasonal fluctuations in ET.


KINEROS2/AGWA: Model Use, Calibration, and Validation

Goodrich, D.C.           Southwest Watershed Research Center

Burns, I.S.                   University of Arizona

Unkrich, C.L.              Southwest Watershed Research Center

Semmens, D.               USGS

Guertin, D.P.               University of Arizona

Hernandez, M.            University of Arizona

Yatheendradas, S.       NASA Goddard Space Flight Center

Kennedy, J.R.             USGS

Levick. L.                    University of Arizona            


When water quantity or water quality is of interest, watersheds are a natural organizing unit in our landscape.  The pathways and processes that affect runoff generation from a watershed result from a complex interaction of the climate, topography, soils, land cover, and land use.  Numerous computer models have been developed to estimate how a watershed produces runoff from rainfall and snowfall.  The KINEROS2 and SWAT models are two common examples. These models often require significant data preparation and input to use them.  To expedite this task we have developed the AGWA (Automated Geospatial Watershed Assessment hydrologic modeling tool which uses nationally available spatial data sets to setup, run, and display the results from KINEROS2 and SWAT.  With these tools, natural resource managers, engineers, and scientists can estimate runoff and places in the watershed that may be prone to flood damage or water quality problems.  These users can also evaluate how conservation measures and changes in land use practices might improve water quality.  This paper provides an overview of the KINEROS2 and AGWA tools and discusses methods that can be used to improve the model’s ability to simulate watershed response and to assess how well the model simulations agree with observations of runoff and erosion.

Assessing Satellite-Based Rainfall Estimates in Semi-Arid Watersheds Using the USDA-ARS Walnut Gulch Gauge Network and TRMM-PR

Amitai, E.                    NASA Goddard, Chapman University

Unkrich, C.L.              Southwest Watershed Research Center

Goodrich, D.C.           Southwest Watershed Research Center

Habib, E.                     University of Louisiana at Lafayette

Thill, B.                       Chapman University


Arid and semi-arid regions account for approximately one-third of the land mass of earth.  These regions are experiencing continued pressure from population growth in many parts of the world.  Water is a critical resource in these regions and is often in short supply.  Detailed study of water resources and the hydrology of semi-arid regions is important if we are to continue to populate and use these regions.  Rainfall estimates from National Weather Service (NWS) radar shown daily on popular news forecasts are now being used for water resource decisions and models.  In addition, satellite based measurement from the Tropical Rainfall Measuring Mission (TRMM) are also being assessed for their ability to estimate rainfall rates. TRMM data has the potential provide estimates over large areas that are not blocked by mountains as is the ground-based NWS Radar in much of the western US. Rainfall observations from the USDA- ARS Walnut Gulch Experimental Watershed (WGEW) were used to assess the ability of  TRMM satellite estimates  for 25 rainy overpasses which occurred during 1999-2010. Preliminary results indicate a very good agreement between the TRMM and WGEW estimates of rainfall rates.  This is an important finding as rainfall is critical in arid and semiarid regions and it not well measured over large parts of the globe.

Uncertainties in the measurement of ecosystem carbon dioxide exchange due to differences in infrared gas analyzer response

Scott, R.L.                  Southwest Watershed Research Center

Measurements of water and carbon exchanges at the land-atmosphere interface are critical for determining local, regional and global hydrological and greenhouse gas budgets.  A widely-used instrument in measuring these exchanges is the fast-response water and carbon dioxide infrared gas analyzer. Here I compare the performance of different gas analyzers for measuring sub-daily to year-long exchanges. Amongst analyzers, differences between measured water exchanges were quite small, but I found significant biases between the estimates of carbon dioxide exchange, even when using analyzers of the same model and manufacturer.  These differences indicate that systematic errors may be present in the measurement of carbon dioxide exchange, and they need to be corrected to improve local to global estimates of this important greenhouse gas exchange.


Antecedent conditions influence soil respiration differences in shrub and grass patches

Cable, J.M.                  University of Alaska

Ogle, K.                       Arizona State University

Barron-Gafford, G.A. University of Arizona

Bentley, L.P.               University of Arizona

Cable, W.L.                 University of Alaska

Scott, R.L.                  Southwest Watershed Research Center

Williams, D.G.             University of Wyoming

Huxman, T.E.              University of Arizona


The response of ecosystem processes to variation in environmental conditions is important to understand in light of recent and future changes in vegetation and climate. This study explored how changes in vegetation associated with recent shrub expansion in grasslands potentially impact soil respiration and its relationship with antecedent environmental conditions.  Continuous measurements of soil respiration, soil temperature, and soil moisture were made over an entire growing season under shrubs, grasses and bare soil in S. Arizona. Data were analyzed within a statistical framework to understand how antecedent conditions influenced soil respiration over time. We found that the antecedent conditions and their effects are more complex than previously understood. Also, the simultaneous estimation of how current and past conditions influence current ecosystem processes will improve our predictive understanding these processes such as soil respiration.

Evaluating the effect of rainfall variability on vegetation establishment in a semidesert grassland

Fehmi, J.                      University of Arizona

Niu, G.Y.                    University of Arizona

Scott, R.L.                  Southwest Watershed Research Center

Mathias, A.                 University of Arizona                                            


Of the operations required for rangeland improvement and reclamation in arid regions, reestablishing vegetation entails the most uncertainty due to unpredictable rainfall for seed germination and seedling establishment. To determine how often grass reseeding operations may be successful in rangelands, we combined a computer simulation model and field data to predict grass establishment success for two sites in southern Arizona.  Vegetation establishment had an annual failure rate of 32%. In the worst 10-year span in the historical rainfall record, six of ten planting years would have failed. In the best 10-year span, only one of ten was projected to fail. To improve future operations, “one-shot” reseeding operations should be discouraged along with a multiyear approach to improve reestablishment success.

Model enhancements for urban runoff predictions in the South-West United States 

Kennedy, J.                 USGS

Goodrich, D.C.           Southwest Watershed Research Center         

Unkrich, C.L.              Southwest Watershed Research Center


Growth and urbanization occurred rapidly in the American Southwest and is projected to exceed the growth of other regions of the United States in the future.  Computer models used to predict the effects of urbanization on runoff typically account for the impervious areas (e.g. roads, roofs, driveways) but not the effect of changes in the soil’s ability to absorb rainfall in the constructed area (e.g. yards, common areas).  In this study detailed hydrologic measurements collected in a residential development and adjacent natural watershed in southeast Arizona were used with a novel ARS watershed model (KINEROS2) to demonstrate that compaction of soils done for construction resulted in roughly a 50% decrease in the amount of water that can infiltrate into the soils. Because of this change, about 17% of the total runoff due to urbanization was caused by soil compaction with the remainder caused by constructed impervious areas.  Overall, the urbanization resulted in a nearly 20-fold increase in runoff over the natural watershed. The study also validated the new KINEROS2 model “urban element” which simplifies how a sub-division can be represented in the watershed computer model.  In recent years, the increase in runoff associated with urbanization in the Southwest has begun to be considered as a potentially renewable water source so it is important to accurately estimate the amount of this extra, manageable water.


Chapter 2: A synthesis framework for runoff predictions in ungauged basins

Wagener, T.                 Pennsylvania State University

Blöschl, G.                  Technical University of Vienna

Goodrich, D.C.           Southwest Watershed Research Center

Gupta, H.V.                University of Arizona

Sivapalan, M.              University of Illinois

Tachikawa, Y.             Kyoto University

Troch, P.A.                  University of Arizona

Weiler, M.                   Freiburg University


The need to estimate runoff from watersheds is essential to properly plan and manage our water resources for agriculture, energy, humans, industry, and ecology.  Yet we cannot directly measure runoff in all the important watersheds in the world. Yet landscapes present amazing patterns that appear to be ubiquitous at any scale one looks. From the pore, to patch, to hillslope, to landscape scale there is a complex interaction between microbes, soils, infiltration, nutrient availability, vegetation, erosive and rill formation and finally the interplay of land uplifting and erosion-deposition processes that generate landforms. It stands to reason that the co-evolution of climate, vegetation and soils at the landscape scale leads to specific patterns reflected in observed runoff records. In this case co-evolution implies a process of reciprocal evolutionary change of soils, vegetation and topography in response to climate dynamics and geologic processes. The patterns that emerge reflect the legacy of past processes, their interconnections over a long period of time leading to the complex spatial patterns that we see in the landscape. This chapter discusses how patterns, primarily at the landscape scale, might in interpreted and analyzed to establish how these patterns could be connected quantitatively to watershed runoff.



Consequences of cool-season drought induced plant mortality to Chihuahuan Desert grassland ecosystem and soil respiration dynamics

Hamerlynck, E.P.        Southwest Watershed Research Center

Scott, R.L.                  Southwest Watershed Research Center

Barron-Gafford, G.A. University of Arizona


The Southwest US is expected to be increasingly drier and warmer over the next century, in part due to an increase in the severity and frequency of drought, especially during the winter and spring.  Strong droughts can induce wide-spread plant death, which in turn can affect ecosystem carbon dynamics.  At a desert grassland that experienced perennial grass die-off twice in the last six years, we quantified ecosystem net carbon dioxide exchange (NEE), and its constituent fluxes, ecosystem respiration (Reco) and gross ecosystem photosynthesis (GEP) responses to spring and summer rains across these six years.  In addition, we measured soil respiration (Rsoil), the dominant part of Reco, over the summer rainy season in high- and low-mortality plots following the most recent plant mortality event.  We found that springtime GEP was sensitive to precipitation, and that bad springtime conditions limited this grassland’s ability to respond to subsequent summer rainfall.  Reco was not as sensitive to spring or summer rain as GEP across all the years, but within the two years with widespread plant death, Reco responded very strongly to the limited spring rains that fell, much more so than GEP, showing additional soil carbon resulting from plant death was quickly burned off by soil microbial activity.   Overall, total carbon respired by the soil did not depend on overall plant mortality, but rather depended on the health of the surviving plants surrounding the plot.  These findings suggest future cool-season conditions may severely affect the productivity and health of these important rangeland ecosystems. 


Water supply to the arid pastures of Kazakhstan's Balkhash region     


Bazarbaev, A.T.                      Kazakhstan Research Institute of Ecology and Climate

Stepanov, B.S.                        Kazakhstan Research Institute of Ecology and Climate

Lebed, L.V.                            Kazakhstan Research Institute of Ecology and Climate

Cherednichenko, A.V.            Kazakhstan Research Institute of Ecology and Climate

Heilman, P.                             Southwest Watershed Research Center

Qi, J.                                      Michigan State University


Grazing systems are often limited by water. Prior to Kazakhstan's independence, there was significant investment in wells to improve grazing distribution in the area around Lake Balkhash, north of Almaty city. However, after independence, property rights were unclear and much of the water infrastructure installed under the Soviet Union was damaged. We inventoried

water infrastructure in this region to assess the extent of damage, finding that south of Lake Balkhash 74% of the area has wells to provide water for grazing, while north of the lake only 38% of the area has water available. There is a significant opportunity to restore damaged wells in the south. New wind and solar technologies may become power sources for pumping water.

Global warming may exacerbate water supply problems on pasture land in Kazakhstan.


A geomorphic perspective on terrain-modulated organization of vegetation productivity:  Analysis in two semiarid grassland ecosystems in Southwestern United States

Flores Cervantes, J.               University of Washington

Istanbulluoglu, E.                    University of Arizona

Vivoni, E.                               Arizona State University

Holifield Collins, C.                Southwest Watershed Research Center

Bras, R.                                 Georgia Institute of Technology


Differences in ecosystem productivity are caused by the influence of terrain on wetting and drying of the landscape.  Daily relative greenness was used to explore how plant productivity changes with landscape over time.  Two semiarid grasslands with pronounced topography, one located in southeastern Arizona, AZ, with a mean annual precipitation (MAP) of 350 mm; and the other in central New Mexico, NM, with a MAP of 250 mm were analyzed.  Results showed that relative greenness was more uniform after wet conditions where higher biomass was present and productivity was higher in channels.  There was a clear dependence between ecosystem productivity and topography, and relative greenness was more sensitive to changes in topography at the wetter Arizona study site.  The results from this study serve to provide an improved understanding of vegetation-topography dependence.  Such understanding is critical for ecosystem management and testing ecohydrologic models.



Assessing site-specific PRISM precipitation and temperature estimates for rangeland management in the Southwest


Heilman, P.                 Southwest Watershed Research Center

Goodrich, D.C.           Southwest Watershed Research Center

Keefer, T.O.               Southwest Watershed Research Center


Potential effects of climate change should be considered by public land managers and ranchers in the Southwest. With the mountainous terrain typical of rangeland, site-specific estimates of recent climate are needed. Unfortunately, site-specific observations are limited. A potential additional source of information is the PRISM (Parameter-elevation Relationships on Independent Slopes Model) dataset available at both 4 km (free) and 800 m (priced) spatial and monthly temporal resolutions. As summer precipitation falls as localized, short-duration, high-intensity convective thunderstorms, it is unclear how managers in the Southwest should interpret the PRISM estimates which cannot reflect the spatial variability inherent in those storms. We compared PRISM estimates of seasonal and annual precipitation to measured values from 1960 to 2011 for the 149 km2 Walnut Gulch Experimental Watershed (WGEW), containing 88 rain gauges.  PRISM could help managers understand precipitation at seasonal and annual time scales. The PRISM annual estimates of precipitation overestimate measured values on average by 33.5 mm (11%) with 25 mm of the overestimate from winter precipitation. The average error of summer (Jul-Aug) precipitation was 11% of the long term mean. These results may represent an upper limit on the ability of PRISM as one of the rain gauges used to make the PRISM estimates is within the watershed, closer than almost all of State Land, Forest Service, and BLM allotments.


Runoff and sediment yield relationships with soil aggregate stability for a State – and- Transition model in Southeastern Arizona

Holifield Collins, C.    Southwest Watershed Research Center

Stone, J.J.                    Southwest Watershed Research Center

Cratic III., L.              University of Arizona


A relatively quick and easy method to evaluation of a rangeland site’s potential to erode is the soil slake test.  The test measures how strong soil aggregates are which is supposed to be indicative of how easily erodible the soil is.  The resulting aggregate stability (AS) value is used within the context of a State and Transition Model which is a description of how a specific soil-vegetation association changes with changing climate and management.  This study uses runoff and erosion data from a series of rainfall simulator experiments on sites of a State and Transition Model to test if AS is related to those hydrologic processes.  The results show that the AS is not related to runoff but that erosion follows the trends suggested by the stability values.  Analysis of relationships between runoff and erosion with canopy cover and bare soil suggest that there are thresholds beyond which both of these factors have the potential of increasing.  The results also suggest that for AS < 4, the potential for a site to become unstable increases.


Application of a rangeland soil erosion model using NRi data in southeastern Arizona

Hernandez, M.             University of Arizona

Nearing, M.A.             Southwest Watershed Research Center

Stone, J.J.                    Southwest Watershed Research Center

Pierson Jr., F.              USDA-ARS Boise

Wei, H.                       University of Arizona

Spaeth, K.                   NRCS

Heilman, P.                 Southwest Watershed Research Center

Weltz., M.A.               USDA-ARS Reno

Goodrich, D.C.           Southwest Watershed Research Center


Rangelands cover a large portion of the western United States, and they are important to the US public because they serve as sources of clean water and air, wildlife habitat, ecosystem biodiversity, recreation, and aesthetics. The National Resources Inventory (NRI) is a government program that periodically all the non-federal land in the United States, including rangelands.  The data collected during an NRI assessment is typical of the type of information collected by rangeland managers. This study outlines a method for using the type of data collected in the NRI to run a rangeland hydrology and erosion model in order to estimate the relative soil erosion rates across ecosystems located in the American Southwest.  The model was run on data from 134 rangeland field locations with data collected between 2003 and 2006 in southeastern Arizona, which is a diverse ecological area located in the transition zone between the Sonoran and Chihuahuan Deserts.  Results of the study showed that the data collected was effectively used with the model to assess the influence of vegetation, soils, and topography on soil erosion rates.  The results suggested that the model could be further improved with the collection of additional experimental data on key ecological sites in order to better reflect ecosystem.  The results of this study are important because they will help the US government, as well as rangeland land managers, better protect and conserve the open spaces of the American West.

Last Modified: 1/31/2013