DOI: 10.5061/dryad.zkh18936m
title: Data for: The impacts of bioenergy pine plantation management practices on bee communities

description: 1. Cultivation of bioenergy feedstocks is a growing land-use worldwide,
 yet we have a poor understanding of how bioenergy crop management
 practices affect biodiversity. This knowledge gap is particularly acute
 for candidate cellulosic bioenergy feedstocks, such as tree plantations,
 and for organisms that provide important ecosystem services, such as
 pollinators. 2. We examined bee communities in 83 sites across three
 states in the southeastern USA—Alabama, Florida and Georgia. We compared
 bee abundance and diversity in 66 pine plantation sites that reflect
 management with and without potential bioenergy feedstock production. At
 least three bioenergy feedstock production methods have been proposed for
 this region: 1) converting conventional timber stands to short-rotation
 bioenergy plantations; 2) harvesting feedstock by thinning conventional
 plantations; and 3) harvesting of woody debris residues after plantations
 have been clear-cut. 3. We found that bioenergy-associated management
 practices including younger plantations (relative to older) and woody
 debris removal (relative to debris unremoved) in clear-cut plantations
 were associated with reduced bee diversity. Removing ground debris in
 clear-cut plantations also drastically increased bee abundance, though
 this effect was largely driven by strong dominance of just two bee
 species. Clear-cut plantations had lower beta diversity than standing
 plantations. 4. Synthesis and applications. Management practices
 associated with bioenergy feedstock production can have negative effects
 on bee community diversity. In particular, harvesting of debris in
 clear-cut plantations dramatically reduces bee diversity. Large-scale
 bioenergy feedstock production that increases the prevalence of young and
 clear-cut stands may cause landscape-level beta diversity to decline.
 Nevertheless, bioenergy pine plantations likely support higher bee
 diversity than corn fields, an alternative bioenergy feedstock.
description: <em>Study sites and strata</em> We
 sampled bee communities from 83 sites, including 66 pine plantations, 10
 natural reference-condition sites (longleaf pine forest remnants) and 7
 corn production sites, distributed across the U.S. states of Florida,
 Georgia and Alabama, which are expected to be key bioenergy states. The
 sites were the same as those sampled for birds in prior work (Gottlieb et
 al. 2017) and clustered into three geographic ‘strata’ that did not follow
 state lines (Table 1). In pine plantations, we focus on three key
 attributes that reflect potential management changes for bioenergy
 feedstock production: 1) younger plantation age; 2) plantation thinning;
 and 3) harvesting of ground debris after plantations are clear-cut. We
 examined the effect of plantation age on bee communities by comparing
 young, unthinned plantations 8-12 years old (simulating harvest-ready
 bioenergy plantations) to more mature plantations 24-25 years old that
 have already been thinned. We also compared bee communities in plantations
 soon after thinning (simulating harvesting for bioenergy feedstock) to
 unthinned plantations of similar age (12-16 years). Finally, we examined
 the impact of harvesting plantation ground debris by comparing recently
 clear-cut plantations (felled within the last two years) with and without
 debris harvest. Each of the six ‘plantation types’ was represented in 9-12
 sites (Table 1); all sites were &gt;16 ha and spaced at least 2.5 km
 apart. <strong>Table 1</strong> Site
 replications per stratum for the six plantation types with and without
 potential management changes for bioenergy production, as well as natural
 longleaf pine stands and corn fields. Stratum S1 consisted of sites in
 Alabama; S2 in southern Georgia and the Florida panhandle; and S3 in
 north-central Florida. 
 <strong>Plantation Attributes</strong>
 <strong>Resembling bioenergy
 production</strong> <strong>Total
 number</strong> <strong>of
 sites</strong> <strong>Strata</strong>
 <strong>No. of
 sites</strong> <strong>Without Bioenergy
 production</strong> <strong>Total number
 </strong> <strong>of
 sites</strong> <strong>Strata</strong>
 <strong>No. of
 sites</strong> <strong>Younger
 plantations</strong>   Young (8-12
 years), unthinned   11 S1 S2 S3 4 3 4   Mature (24-25
 years), thinned   
 12 
 S1 S2 S3 
 4 6 2 <strong>Harvesting feedstock by
 thinning </strong> Thinned (12-16
 years) 11 S1 S2 S3   4 3 4   Unthinned (12-16
 years) 11 S1 S2 S3   4 3 4   <strong>Harvesting debris after
 clear-cut </strong> Trees
 clear-cut, debris harvested 9 S1 S2 S3 2 3 4 Trees
 clear-cut, debris uncleared 12 S1 S2 S3 5 3 4 <strong>Non-plantation
 land-uses</strong> Corn
 fields 7 S1 S2 S3 2 3 2 Natural
 longleaf pine stands 10 S1 S2 S3 3 4 3 
  
 <em>Measuring local bee and plant
 communities</em> We surveyed bee communities over
 the spring and summer seasons of 2013, 2014 and 2015. Sites were not
 sampled repeatedly across years. In each site, we marked out two 2 x 200 m
 sampling transects at least 50 m from the plantation edge and at least 100
 m away from one another. For each sampling day, we
 collected bees using pan traps and aerial netting, which work effectively
 in tandem (Westphal<em> et al.</em> 2008). Pan traps consisted
 of small, plastic cups (3.25 oz., model P325, SOLO Cup Company, Illinois
 USA) painted with ultraviolet-bright blue, white or yellow paint, and
 filled with a dilute detergent-water solution that drowns the bees (Kearns
 & Inouye 1993; Westphal<em> et al.</em> 2008). Fifteen
 pan traps were held approximately 40 cm above the ground on wire stakes
 (VIGORO plant props, model 611872, Spectrum Brands Holdings Inc.,
 Wisconsin USA, bent to better hold traps) so as to be visible above
 herbaceous vegetation, and positioned in alternating colors evenly along
 the center 100 m of the sampled transect. Pan traps were set up in the
 morning and collected after 24 hours. During each sampling day, we also
 performed targeted aerial netting of bees along the entire length of a
 transect for 30 minutes, excluding handling time for every successful
 capture with a stopwatch. Bee surveys were postponed on cloudy or rainy
 days, and each transect was sampled up to four times on separate days,
 amounting to up to 8 sampling days per site. Due to unforeseen weather and
 logistical difficulties, however, 9 of the 66 sites are represented by
 only one transect or by fewer than 3 samples. These sites were spread
 across two of the three strata and across land use categories. Still, we
 employed statistical methods robust to imbalances in sampling effort
 across our analyses. Collected bees were preserved in ethanol or pinned,
 brought back to the lab and identified to species or occasionally
 genus. We measured available floral resources at each
 site once during the study on a sampling day, within 1 m of the central
 100 m of each transect, by counting and identifying to species all
 understory non-grass plants that were in bloom. We surveyed floral
 resources among sites within a stratum as close together in time as
 possible to maximize comparability. A separate analysis of pollen loads
 present on some of the bee specimens from this work is covered in Bell et
 al. (2017), which describes interactions between bee and plant
 species. <em>Bee specimen preparation and
 identification</em> We usually pinned bee
 specimens on the day of sampling. We keyed out all specimens to genus, and
 92% of taxa to species, using Discover Life online keys
 (https://www.discoverlife.org), in conjunction with Michener (2000) and
 Michener et al. (1994). Our identifications were verified by Ismael
 Hinojosa (Universidad Autonoma de Mexico) and Sam Droege (USGS); Sam
 Droege identified many specimens (particularly
 <em>Lasioglossum</em>) to species.