DOI: 10.5061/dryad.8h5h762/1
title: pivot points and responses by polygon

description: Data 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)