Assessing topographic patterns in moisture use and stress using a water balance approach

Through its control on soil moisture patterns, topography’s role in influencing forest composition is widely recognized. This study addresses shortcomings in traditional moisture indices by employing a water balance approach, incorporating topographic and edaphic variability to assess fine-scale moisture demand and moisture availability. Using GIS and readily available data, evapotranspiration and moisture stress are modeled at a fine spatial scale at two study areas in the US (Ohio and North Carolina). Model results are compared to field-based soil moisture measurements throughout the growing season. A strong topographic pattern of moisture utilization and demand is uncovered, with highest rates of evapotranspiration found on south-facing slopes, followed by ridges, valleys, and north-facing slopes. South-facing slopes and ridges also experience highest moisture deficit. Overall higher rates of evapotranspiration are observed at the Ohio site, though deficit is slightly lower. Based on a comparison between modeled and measured soil moisture, utilization and recharge trends were captured well in terms of both magnitude and timing. Topographically controlled drainage patterns appear to have little influence on soil moisture patterns during the growing season. In addition to its ability to accurately capture patterns of soil moisture in both high-relief and moderate-relief environments, a water balance approach offers numerous advantages over traditional moisture indices. It assesses moisture availability and utilization in absolute terms, using readily available data and widely used GIS software. Results are directly comparable across sites, and although output is created at a fine-scale, the method is applicable for larger geographic areas. Since it incorporates topography, available water capacity, and climatic variables, the model is able to directly assess the potential response of vegetation to climate change.

[1]  Frank P. Day,et al.  Vegetation Patterns on a Southern Appalachian Watershed , 1974 .

[2]  Kenneth B. Pierce,et al.  A simple method for estimating potential relative radiation (PRR) for landscape-scale vegetation analysis , 2005, Landscape Ecology.

[3]  Robert H. Whittaker,et al.  Vegetation of the Great Smoky Mountains , 1956 .

[4]  J. Mather,et al.  THE ROLE OF CLIMATE IN THE DISTRIBUTION OF VEGETATION , 1968 .

[5]  Todd R. Lookingbill,et al.  Gradient analysis, the next generation: towards more plant-relevant explanatory variables , 2005 .

[6]  Igor V. Florinsky,et al.  Prediction of soil properties by digital terrain modelling , 2002, Environ. Model. Softw..

[7]  Dylan Keon,et al.  Equations for potential annual direct incident radiation and heat load , 2002 .

[8]  K. Beven,et al.  A physically based, variable contributing area model of basin hydrology , 1979 .

[9]  D. F. Grigal,et al.  Vertical root distributions of northern tree species in relation to successional status , 1987 .

[10]  Björn Berg,et al.  Apparent controls of mass loss rate of leaf litter on a regional scale , 1990 .

[11]  Charles J Vörösmarty,et al.  Potential evaporation functions compared on US watersheds: Possible implications for global-scale water balance and terrestrial ecosystem modeling , 1998 .

[12]  Ming Xu,et al.  Evapotranspiration models compared on a Sierra Nevada forest ecosystem , 2005, Environ. Model. Softw..

[13]  David R. Maidment,et al.  Handbook of Hydrology , 1993 .

[14]  Wayne T. Swank,et al.  Forest Hydrology and Ecology at Coweeta , 1988, Ecological Studies.

[15]  Todd R. Lookingbill,et al.  An empirical approach towards improved spatial estimates of soil moisture for vegetation analysis , 2004, Landscape Ecology.

[16]  R. Pearson.  Climate change and the migration capacity of species. , 2006, Trends in ecology & evolution.

[17]  A. J. Parker,et al.  THE TOPOGRAPHIC RELATIVE MOISTURE INDEX: AN APPROACH TO SOIL-MOISTURE ASSESSMENT IN MOUNTAIN TERRAIN , 1982 .

[18]  Robert A. Muenchen,et al.  Help and Documentation , 2010 .

[19]  Colorado Colorado,et al.  AMERICAN SOCIETY OF CIVIL ENGINEERS , 2010 .

[20]  J. Mather,et al.  Climatology: fundamentals and applications , 1974 .

[21]  Charles J Vörösmarty,et al.  Intercomparison of Methods for Calculating Potential Evaporation in Regional and Global Water Balance Models , 1996 .

[22]  T. R. Wentworth.  Vegetation on Limestone and Granite in the Mule Mountains, Arizona , 1981 .

[23]  Günter Blöschl,et al.  On the spatial scaling of soil moisture , 1999 .

[24]  George M. Hornberger,et al.  Soil moisture gradients and controls on a southern Appalachian hillslope from drought through recharge , 1998 .

[25]  D. Frank,et al.  Temporal variation in actual evapotranspiration of terrestrial ecosystems: patterns and ecological implications , 1994 .

[26]  James M. Dyer,et al.  Revisiting the Deciduous Forests of Eastern North America , 2006 .

[27]  M. E. Dale,et al.  A Gis-derived integrated moisture index to predict forest composition and productivity of Ohio forests (U.S.A.) , 1997, Landscape Ecology.

[28]  James S. Clark,et al.  MOLECULAR INDICATORS OF TREE MIGRATION CAPACITY UNDER RAPID CLIMATE CHANGE , 2005 .

[29]  N. Stephenson.  Climatic Control of Vegetation Distribution: The Role of the Water Balance , 1990, The American Naturalist.

[30]  Devendra M. Amatya,et al.  Comparison of methods for estimating REF-ET , 1995 .

[31]  J. D. Helvey,et al.  Research on Interception Losses and Soil Moisture Relationships , 1988 .

[32]  R. Peet.  Forest vegetation of the Colorado Front Range , 1981, Vegetatio.

[33]  James M. Dyer.  Assessment of climatic warming using a model of forest species migration , 1995 .

[34]  R. Allen,et al.  Evapotranspiration and Irrigation Water Requirements , 1990 .

[35]  Bruce G. Terrell,et al.  National Oceanic and Atmospheric Administration , 2020, Federal Regulatory Guide.

[36]  B. McCune.  Improved estimates of incident radiation and heat load using non- parametric regression against topographic variables , 2007 .

[37]  Patrick N. Halpin,et al.  Forest gradient response in Sierran landscapes: the physical template , 2000, Landscape Ecology.

[38]  Sang-Min Park,et al.  Soil–landscape delineation to define spatial sampling domains for hillslope hydrology , 2004 .

[39]  R. Moral,et al.  Gradient modeling, Resource and fire management , 2004, Vegetatio.

[40]  J. T. Hack,et al.  Geomorphology and forest ecology of a mountain region in the central Appalachians , 1960 .

[41]  R. Peet,et al.  Gradient analysis of latitudinal variation in southern Rocky Mountain forests , 1991 .

[42]  Ge Sun,et al.  A COMPARISON OF SIX POTENTIAL EVAPOTRANSPIRATION METHODS FOR REGIONAL USE IN THE SOUTHEASTERN UNITED STATES 1 , 2005 .

[43]  Richard J. Pike,et al.  Landforms of the conterminous United States: a digital shaded-relief portrayal , 1991 .

[44]  Paul E. Gessler,et al.  Spatially Explicit Treatment of Soil-Water Dynamics along a Semiarid Catena , 2002 .

[45]  M. Rosenzweig.  Net Primary Productivity of Terrestrial Communities: Prediction from Climatological Data , 1968, The American Naturalist.

[46]  C. Daly,et al.  A knowledge-based approach to the statistical mapping of climate , 2002 .

[47]  Forest/environment relationships in Lassen Volcanic National Park, California, U.S.A. , 1991 .

[48]  D. Currie.  Energy and Large-Scale Patterns of Animal- and Plant-Species Richness , 1991, The American Naturalist.

[49]  R. B. Jackson,et al.  A global analysis of root distributions for terrestrial biomes , 1996, Oecologia.

[50]  D. Zasłavsky,et al.  Surface Hydrology: I—Explanation of Phenomena , 1981 .

[51]  R. Grayson,et al.  Scaling of Soil Moisture: A Hydrologic Perspective , 2002 .

[52]  James M. Dyer.  A water budget approach to predicting tree species growth and abundance, utilizing paleoclimatology sources , 2004 .

[53]  J. Hewlett,et al.  Predicting Soil Moisture in the Southern Appalachians 1 , 1972 .

[54]  James M. Dyer.  A Comparison of Moisture Scalars and Water Budget Methods to Assess Vegetation-Site Relationships , 2002 .

[55]  Ge Sun,et al.  MODELING ACTUAL EVAPOTRANSPIRATION FROM FORESTED WATERSHEDS ACROSS THE SOUTHEASTERN UNITED STATES 1 , 2003 .

[56]  Tom Ross,et al.  The National Climatic Data Center's (NCDC) New Climate Monitoring Group Products, Reports and Analyses Applicable to the Study of Earth Science , 2000 .

[57]  N. Stephenson,et al.  Actual evapotranspiration and deficit: biologically meaningful correlates of vegetation distribution across spatial scales , 1998 .