DOI: 10.5061/dryad.8h5h762
title: Data from: Landscape pivot points and responses to water balance in national parks of the southwest U.S.

description: 1. A recent drying trend that is expected to continue in the southwestern
 U.S. underscores the need for site-specific and near real-time
 understanding of vegetation vulnerability so that land management actions
 can be implemented at the right time and place. 2. We related the annual
 integrated normalized difference vegetation index (iNDVI), a proxy for
 vegetation production, to water balance across landscapes of the Colorado
 Plateau. We determined how changes in production per unit of water
 (vegetation responses), and the water balance amounts at which production
 shifted from above to below average values (pivot points), varied across
 dominant vegetation and soil types. 3. Precipitation (PRCP), actual
 evapotranspiration (AET), water deficit (D), and soil moisture (SM)
 explained 13 – 82% of variation in vegetation production. Along an
 increasing water availability gradient, vegetation responses to PRCP and
 AET increased, responses to SM decreased, and responses to D became more
 negative. We found tradeoffs between vegetation responses and pivot points
 within and across all vegetation types that were mediated by soil
 properties. 4. Synthesis and applications. The water needed by native
 vegetation to maintain production depends on plant traits. The water
 available to vegetation depends on climate and soil properties that change
 along environmental gradients. Tracking this biologically-relevant water
 availability in relation to water need provides an indicator of vegetation
 growth or stress that can help guide the time and place for management
 actions.
description: pivot points and
 responses by polygonData from: Thoma, D.P.,
 S.M. Munson & D.L. Witwicki 2018. Landscape pivot points and responses
 to water balance in national parks of the southwest U.S. Contact: David
 Thoma Dave_thoma@nps.gov 406-994-7725 These data are the polygon
 attributes and linear regression coefficients of iNDVI and water balance
 relations for years 2000-2014 where we found significant relationships
 (P-val &lt; 0.10). Polygons greater than 6.25 ha (the area of a single
 MODIS pixel) were delineated along ecological site boundaries or, in areas
 where ecological sites have not been mapped, along soil or vegetation map
 unit boundaries (Witwicki et al. 2016). Ecological sites are unique
 combinations of vegetation and soil properties that provide an organizing
 framework for understanding management-relevant patterns in production at
 landscape scales (Herrick et al 2006; Munson et al. 2016b). Data from this
 digital file were used to create figures 3-5 in “Landscape pivot points
 and responses to water balance in national parks of the southwest U.S.”
 Column definitions Park: four letter code that identifies park unit arch =
 Arches National Park blca = Black Canyon of the Gunnison National Park
 cure = Curecanti National Recreation Area cany = Canyonlands National Park
 care = Capitol Reef National Park dino = Dinosaur National Monument zion =
 Zion National Park Polygon: polygon identifier randomly generated Area:
 polygon area (hectares) Latitude: latitude in decimal degrees based on the
 World Geodetic System (WGS) 1984 Longitude: longitude in decimal degrees
 based on the World Geodetic System (WGS) 1984 Waterbalance: a water
 balance variable significantly related to annual production (iNDVI) for
 the polygon D= annual sum water deficit (mm) AET = annual sum actual
 evapotranspiration (mm) PCRP = annual sum precipitation (mm) SM = annual
 average soil moisture (mm) Response: slope of the regression between
 annual production and annual water balance. Units are change in iNDVI per
 1000 mm of water balance term listed in the Waterbalance column Pivot: the
 pivot point, the water balance amounts at which production shifted from
 above to below average values for the polygon and associated water balance
 variable. SE: standard error of the pivot point (mm) Correlation:
 Pearson’s correlation between iNDVI and annual water balance rsq:
 coefficient of determination of the regression between iNDVI and annual
 water balance pval: p value of the regression between iNDVI and annual
 water balance slope: topographic slope of the ground surface (degrees) at
 the center of the target polygon aspect: topographic aspect (degrees) at
 the center of the target polygon whc: spatially weighted polygon average
 of water holding capacity (millimeters) which is water at field capacity
 minus water at wilting point in the top meter of soil. Field capacity is
 water remaining in the soil after excess has drained by gravity (−0.33 bar
 suction pressure). Permanent wilting point is water held too tightly for
 plant use ( −15 bar of suction pressure). Sand: spatially weighted polygon
 average of percent sand in top meter of soil that intersected the target
 polygon Clay: spatially weighted polygon average of percent clay in top
 meter of soil that intersected the target polygon Soil Depth: spatially
 weighted polygon average depth of soil (centimeters) that intersected the
 target polygon Vegetation: dominant vegetation type of the target polygon
 Elevation: elevation (meters) at the center of the target polygon Annual
 PCRP: annual sum of precipitation at center of the target polygon
 (millimeters)