title: Quantifying environmental limiting factors on tree cover using geospatial data.
abstract: Environmental limiting factors (ELFs) are the thresholds that determine the maximum or minimum biological response for a given suite of environmental conditions. We asked the following questions: 1) Can we detect ELFs on percent tree cover across the eastern slopes of the Lake Tahoe Basin, NV? 2) How are the ELFs distributed spatially? 3) To what extent are unmeasured environmental factors limiting tree cover? ELFs are difficult to quantify as they require significant sample sizes. We addressed this by using geospatial data over a relatively large spatial extent, where the wall-to-wall sampling ensures the inclusion of rare data points which define the minimum or maximum response to environmental factors. We tested mean temperature, minimum temperature, potential evapotranspiration (PET) and PET minus precipitation (PET-P) as potential limiting factors on percent tree cover. We found that the study area showed system-wide limitations on tree cover, and each of the factors showed evidence of being limiting on tree cover. However, only 1.2% of the total area appeared to be limited by the four (4) environmental factors, suggesting other unmeasured factors are limiting much of the tree cover in the study area. Where sites were near their theoretical maximum, non-forest sites (tree cover < 25%) were primarily limited by cold mean temperatures, open-canopy forest sites (tree cover between 25% and 60%) were primarily limited by evaporative demand, and closed-canopy forests were not limited by any particular environmental factor. The detection of ELFs is necessary in order to fully understand the width of limitations that species experience within their geographic range.
authors.affiliation: Department of Geography and Geographic Information Science, University of Illinois at Urbana-Champaign, Champaign, Illinois, United States of America.
authors.forename: Jonathan A
authors.initials: JA
authors.lastname: Greenberg
authors.affiliation: Department of Innovation, Environmental and Energy Sciences, Utrecht University, Utrecht, The Netherlands.
authors.forename: Maria J
authors.initials: MJ
authors.lastname: Santos
authors.affiliation: Department of Forest Management, College of Forestry and Conservation, University of Montana, Missoula, Montana, United States of America.
authors.forename: Solomon Z
authors.initials: SZ
authors.lastname: Dobrowski
authors.affiliation: NASA Ames Research Center, Mountain View, California, United States of America.
authors.forename: Vern C
authors.initials: VC
authors.lastname: Vanderbilt
authors.affiliation: Center for Spatial Technologies and Remote Sensing (CSTARS), Department of Land, Air and Water Resources, University of California Davis, Davis, California, United States of America.
authors.forename: Susan L
authors.initials: SL
authors.lastname: Ustin
mesh_terms: D002140:California; D017753:Ecosystem; D004784:Environmental Monitoring; D065928:Forests; D005843:Geography; D008962:Models, Theoretical; D009505:Nevada; D014197:Trees