DOI: 10.5061/dryad.kkwh70s1m
title: Assessing the Ecological Impacts of Biomass Harvesting along a Disturbance Severity Gradient

description: Disturbance is a central driver of forest development and ecosystem
 processes with variable effects within and across ecosystems. 
 Despite the high levels of variation in disturbance severity often
 observed in forests following natural and anthropogenic disturbance,
 studies quantifying disturbance impacts often rely on categorical
 classifications, thus limiting opportunities to examine potential
 gradients in ecosystem response to a given disturbance or management
 regime.  Given the potential increases in disturbance severity
 associated with global change, as well as shifts in management regimes
 related to procurement of biofuel feedstocks, there is an increasing need
 to quantitatively describe disturbance severity and associated responses
 of forest development, soil processes, and structural conditions. This
 study took advantage of two replicated large-scale studies of forest
 biomass harvesting in Populus tremuloides and Pinus bansksiana forests,
 respectively, to develop and test the utility of a continuous,
 quantitative disturbance severity index (DSI) for describing post-harvest
 response of plant communities and nutrient pools to different levels of
 biomass removal and legacy retention (i.e., live trees and coarse woody
 material). There was a high-degree of variability in DSI within
 categorical treatments associated with different levels of legacy
 retention and regression models using DSI as a predictor explained a
 portion of the variation (&gt;50%) for many of the ecosystem- and
 community-level responses to biomass harvesting examined. Nutrient losses
 associated with biomass harvesting were positively related to disturbance
 severity, particularly in P. tremuloides forests, with post-harvest
 nutrient availability generally declining along the gradient of impacts.
 Consistent with expectations from ecological theory, species richness and
 diversity of woody plant communities were greatest at intermediate
 disturbance severities and regeneration densities of dominant trees
 species were most abundant at highest levels of disturbance. Although
 categorical benchmarks will continue to be the primary way through which
 management guidelines are conveyed to practitioners, evaluation of their
 effectiveness at sustaining ecosystem functioning should be through
 continuous analyses, such as the DSI approach used in this study, to allow
 for the more precise identification of thresholds that ensure a range of
 desirable outcomes exist across managed landscapes.
description: Please consult the "Metadata" table of each spreadsheet
 for variable descriptions, format, units of measurement, and factor codes
 (where applicable). All files are in open document spreadsheet (.ods)
 format. Data are divided by dataset and response
 variable, organized slightly differently between aspen and jack pine
 experiments. Below are descriptions for each file: 
 jack_pine_community.ods: plot-level species richness,
 Bray-Curtis distances, evenness, Shannon's H', and
 Simpson's D for teh jack pine experiment
 jack_pine_lost_nutrients.ods: plot-level aboveground nutrient
 losses (N, Ca, K, P, and C), as well as forest floor biomass change for
 the jack pine experiment. As these data focus on post-harvest changes,
 variables are not repeated across years. jack_pine_
 seedlings.ods: plot-level seedling densities for the jack pine
 experiment. aspen_available_nutrients.ods: availble
 nutrients (total N, NO3, NH4, Ca, Mg,and P) for 2010 and 2011 for the
 aspen experiment. aspen_community.ods: species
 richness, evenness, Simpson's D, and Shannon's H for the
 2009-2013 period for the aspen experiment
 aspen_bray_curtis_distances.ods: Shift of sample plots in
 species space (Bray-Curtis distances) between the preharvest and
 postharvest period for the aspen experiment. As these data represent
 change, they are not repeated across years.
 aspen_lost_nutrients.ods: plot-level aboveground nutrient losses
 (N, Ca, K, P, and C), as well as forest floor biomass change for the aspen
 experiment. As these data focus on post-harvest changes, variables are not
 repeated across years. aspen_litterfall.ods: Annual
 litterfall biomass for 2010 and 2011 at the aspen experiment. This file
 also includes pre-post treatment forest floor biomass change following
 treatment. aspen_seedling_densities.ods: seedling
 densities of all species and <em>Populus tremuloides </em>for
 2009 and 2010.