DOI: 10.5061/dryad.fv322
title: Data from: Climate and competition effects on tree growth in Rocky Mountain forests

description: 1. Climate is widely assumed to influence physiological and demographic
 processes in trees, and hence forest composition, biomass and range
 limits. Growth in trees is an important barometer of climate change
 impacts on forests as growth is highly correlated with other demographic
 processes including tree mortality and fecundity. 2. We investigated the
 main drivers of diameter growth for five common tree species occurring in
 the Rocky Mountains of the western United States using non-linear
 regression methods. We quantified growth at the individual tree level from
 tree core samples collected across broad environmental gradients. We
 estimated the effects of both climate variation and biotic interactions on
 growth processes and tested for evidence that disjunct populations of a
 species respond differentially to climate. 3. Relationships between tree
 growth and climate varied by species and location. Growth in all species
 responded positively to increases in annual moisture up to a threshold
 level. Modest linear responses to temperature, both positive and negative,
 were observed at many sites. However, model results also revealed evidence
 for differentiated responses to local site conditions in all species. In
 severe environments in particular, growth responses varied non-linearly
 with temperature. For example, in northerly cold locations pronounced
 positive growth responses to increasing temperatures were observed. In
 warmer southerly climates, growth responses were unimodal, declining
 markedly above a threshold temperature level. 4. Net effects from biotic
 interactions on diameter growth were negative for all study species.
 Evidence for facilitative effects was not detected. For some species,
 competitive effects more strongly influenced growth performance than
 climate. Competitive interactions also modified growth responses to
 climate to some degree. 6. Synthesis. These analyses suggest that climate
 change will have complex, species specific effects on tree growth in the
 Rocky Mountains due to non-linear responses to climate, differentiated
 growth processes that vary by location and complex species interactions
 that impact growth and potentially modify responses to climate. Thus,
 robust model simulations of future growth responses to climate trends may
 need to integrate realistic scenarios of neighborhood effects as well as
 variability in tree performance attributed to differentiated populations.
description: Sample tree growth data
 with locationsThis file provides
 measurements of annual radial growth for randomly distributed adult trees
 in the Rocky Mountains of the United States. Measurements were derived
 from increment cores collected in 2012 and 2013. A total of 5 tree species
 were sampled. Sample trees were distributed across a latitudinal gradient
 from the southern terminus of the Rockies in New Mexico to the Canadian
 border in the north. Target tree species include: Abies lasiocarpa
 (subalpine fir), Picea engelmannii (Engelmann spruce), Pinus contorta
 (lodgepole pine), Pinus ponderosa (ponderosa pine) and Pseudotsuga
 menziesii (Douglas-fir). Annual radial increment over a 20 year period was
 measured in millimeters for each sample tree. File headings include:
 Sample tree ID: Identification code for the sample or target tree Species:
 Species of the sample tree Year: The year of growth Site: General location
 of sample tree Longitude and Latitude: Geographical coordinates of sample
 (based on North American Datum 1983) Elevation: Elevation above sea level
 in meters Aspect: Dominant terrain aspect in degrees from north Terrain
 slope: Average slope of land surface measured in percent Stem diameter:
 Diameter of tree stem at breast height (1.3 meters above root crown) in
 year of growth measured in centimeters Age: Age of sample in year of
 growth Ring width: Measured width of annual radial increment in
 millimeters Date collected: Month, day, and year the sample was
 collectedsample tree growth data with
 locations.csvNeighbor tree location
 and size dataThis file provides data
 describing the density and configuration of sample tree neighborhoods for
 calculation of competition indices. The distance to and diameter at breast
 height (DBH; 1.3 meters above root crown) of all neighboring trees within
 a 15 m radius of the sample or target tree were measured. A total of 10
 sample trees had empty neighborhoods (no neighbor trees within 15 meters).
 File headings include: Sample tree ID: Identification code for the sample
 or target tree Sample tree species: Species of sample tree Neighbor tree
 species: Species of neighbor tree Neighbor tree DBH: Diameter at breast
 height of neighbor tree in centimeters Distance to neighbor tree: Distance
 from sample to neighbor tree in metersneighbor tree location and size
 data.csv