DOI: 10.5061/dryad.9s4mw6mj7
title: The effects of a half century of warming and fire exclusion on montane forests of the Klamath Mountains, California, USA

description: These files are the raw data used in the manuscript "Effects of a
 half century of warming and fire exclusion on montane forests of the
 Klamath Mountains, California, USA" Manuscript authors: Erik S.
 Jules, Melissa H. DeSiervo, Matthew J. Reilly, Drew S. Bost, and Ramona J.
 Butz Climate warming and altered disturbance regimes are changing forest
 composition and structure worldwide. Given that species often exhibit
 individualistic responses to change, making predictions about the
 cumulative effects of multiple stressors across environmental gradients is
 challenging, especially in diverse communities. For example, warming
 temperatures are predicted to drive species upslope, while fire
 exclusion promotes expansion of species at lower elevations where fire was
 historically frequent. We resampled 148 vegetation plots to assess
 46-years (1969 to 2015) of species and community-level response to warming
 and fire exclusion in a topographically complex landscape in the Klamath
 Mountains, California (USA), a diverse region that served as a climate
 refugia throughout the Holocene. We compared cover and assessed change in
 the elevational distributions of 12 conifer species at different life
 stages (i.e., seedlings, saplings, canopy). We observed consistent but
 non-significant shifts upward in elevation for eight species, and a
 significant shift upward for one species, all of which were far less than
 expectations based on recent warming. Six species declined in total cover
 and another five declined in at least one life stage, while the drought-
 and fire-intolerant Abies concolor increased by 30.7%. The largest
 declines were at lower elevations in drought-tolerant, early seral species
 (Pinus lambertiana and Pinus ponderosa) and at higher elevations for the
 shade-tolerant Abies magnifica var. shastensis and the regionally rare
 Abies lasiocarpa. Regionally rare (Picea engelmannii) and endemic (Picea
 breweriana) species had reductions in early life stages, portending future
 declines. Multivariate analyses revealed a high degree of inertia with a
 minor but significant shift in composition and a slight decrease in
 species turnover along the elevation gradient driven by expansion of A.
 concolor. Our results indicate that most species are declining, especially
 at lower- and mid-elevations where fire exclusion increased cover of
 shade-tolerant species and reduced recruitment for fire-adapted species.
 Collectively, declines in most species, insufficient upward movement to
 track warming, reductions in drought- and fire-tolerant early seral
 species, and an increase in a single, shade-tolerant species will leave
 these communities maladapted to projected climate scenarios and questions
 the potential for future climate refugia in this region.
description: The data file (“Klamath Site data.csv”) includes site information
 from 148 plots surveyed in the Russian Wilderness of northern California
 (USA). Data column information:<br>1. Plot number
 column includes the plot number and year (1969 or 2015).<br>2. The
 column labelled Year is either 1969 or 2015, the two years of the
 survey.<br>3. Elev(dem) is the elevation of each plot in
 meters.<br>4. “heatload” is the heatload index, a proxy for solar
 radiation based on aspect, slope, and topographic position in the context
 of surrounding landscape (defined in McCune 2007).
 Literature Cited:<br>McCune, B. 2007. Improved estimates of
 incident radiation and heat load using non- parametric regression against
 topographic variables. Journal of Vegetation Science 18:751–754.
 The data file (“Klamath tree data.csv”) includes the % cover from
 of trees from 148 plots surveyed in the Russian Wilderness of northern
 California (USA). All data were collected in the field by 2-4 observers in
 1969 and 2014/5. 1. Plot number column includes the
 plot number and year (1969 or 2015). 2. Columns = tree
 species cover in three life stages. CAN = Canopy. SAP = sapling. SEED =
 Seedling. Tree species are in four letter codes. EX: ABMA = Abies
 magnifica.  We converted cover class values for these
 12 species to median values for both years as the following: cover class
 (1) 1 %; (2) 3%; (3) 7%; (4) 17.5%; (5) 37.5%; (6) 62.5%; and (7)
 87.5%.