Bat activity and insect availability in early successional forests: a preliminary analysis

1
Bat activity and insect availability in early
successional forests a preliminary analysis

• Kathryn M. Womack and Alix D. Fink
• Department of Biological and Environmental
  Sciences

Abstract Recent research in the United Kingdom
found significant differences in bat use of
organic and conventional agricultural land. The
elucidated link between vegetation management,
insect communities, and bat foraging activity
also could apply to managed timber lands. We
investigated this potential link in forest stands
managed under various regimes to test the
hypothesis that bat activity is higher in sites
with more plant and, therefore, insect diversity.
We conducted this research in the
Appomattox-Buckingham State Forest in central
Virginia in June-August 2006. We sampled 9 sites
representing a continuum from young (0-1
year-old) released loblolly pine plantations to
oak shelterwood sites.

• Results, continued
• While these preliminary results should be
  interpreted with caution, we look forward to
  exploring in more detail the following trends
• In comparing the three pine habitat types, there
  is a decrease in observed bat activity as
  plantations age (Fig. 9).
• Insect biomass was similar in three habitat
  types, but biomass was much greater in the
  youngest of the habitats (Fig. 10).
• Vegetation density and overall height increased
  with site age (Fig. 11).

Insect Sampling Insect samples were collected
using UBLTs with photoelectric switches running
on 12-V deep-cycle marine batteries (Fig. 5).
Insects were collected in large glass jars that
contained an insect kill strip. We retrieved the
jars each morning, transferred the specimens to
freezer bags, and froze specimens for later
analysis. Prior to processing, each sample was
dried for 24 hours at 60C and transferred to
plastic storage containers along with a
desiccant. Dried insects were separated into 3
groups (Lepidoptera, Coleoptera and other) using
magnifying glasses and a dissecting microscope.
We separated Lepidoptera and Coleoptera because
these orders made up the bulk of our samples and
are known to be important bat prey. We weighed
each group to determine biomass by group and for
the complete sample.
Sampling Arrays In each site, we established an
array with one bat detector and 4 Universal Black
Light Trap (UBLT BioQuip Products, Inc.)
locations (Fig.2).
Bat Sampling Bat detector systems with Anabat II
detector and ZCAIM (Titley Electronics) housed in
a plastic cooler with 4 PVC elbow joint after
S. Amelon recorded data between 1930 and 0630.
Each bat detector system was placed on a stump
for elevation from the ground, and the PVC elbow
was oriented to provide the microphone with a
clear, unobstructed detection cone (Fig. 3). We
used AnaLook to view the data and count number of
passes per hour (Fig. 4).

• Discussion
• In relating our preliminary results to our
  proposed model (Fig. 1), some predictions
  paralleled observed results while others did not.
• We predicted a positive relationship between
  vegetation density and insect abundance (i.e.,
  biomass). However, the sites with the greatest
  insect abundance were those with the lowest
  vegetation density.
• We predicted a positive relationship between
  insect abundance and bat activity. Our
  preliminary results support that relationship.
  However, the mediating factor of vegetation
  clutter on foraging activity is one that we will
  explore in more detail.

Introduction Forests of the southeastern U.S. are
changing rapidly, both in terms of forest
composition and extent of forest cover (Wear and
Greis 2004). Compositional changes are being
driven by increasing conversion to pine (Pinus
sp.) plantations and increasing management
intensity (Siry 2002, Wear and Greis 2004).
Concurrent to changes in composition, forest
cover is decreasing as a result of urbanization
and sprawl associated with human population
growth (Wear 2002). Moreover, the nature and
extent of impacts of global climate change on
Southern forests are largely speculative (Moore
et al. 2002), though further changes in
composition and coverage are expected. Questions
related to the impacts of these changes on
wildlife species are of great conservation
interest and management relevance. Highly mobile
species with large home ranges and complex
habitat requirements, such as bats, may be
especially vulnerable to increasing human
modification of landscapes. However, the impacts
of such modifications on bat species are poorly
understood (e.g., Tibbels and Kurta 2003). These
relationships were recently explored by
researchers in the U.K. who found significant
differences in bat foraging activity in organic
and conventionally managed agricultural land
(Wickramasinghe et al. 2004). The differences
in bat foraging were related to differences in
insect abundance in the sites (Wickramasinghe et
al. 2003), which in turn was directly related to
intensity of vegetation management and/or control
(Wickramasinghe et al. 2004).
Vegetation We quantified vegetation density using
a density board (3 m x 10 cm Fig. 7) at two
vegetation sampling points in each study site
(Fig. 2). We photographed the board from a
distance of 4 m in each of the four cardinal
directions. In the lab we then quantified
percent of vegetation density using photographs.
Fig. 4 Bat calls
Results
8-10 year old pine (released)
3-4 year old pine (not released)
0-1 year old pine
Regenerating oak shelterwood

• Future Directions
• In continuing the analysis of the data collected
  this summer, we will
• Conduct a detailed examination of the full data
  set using the Information Theoretic approach to
  linear modeling.
• Analyze fecal pellets collected at our study
  sites and attempt to relate their contents to
  insects collected in the UBLTs.
• In future field seasons, we will
• Incorporate multiple sampling arrays per site in
  different microhabitats to better understand bat
  activity.
• Include more mature pine sites to extend the
  continuum and assess the trends in insect
  availability and bat use.
• Finally, in the long term we seek to
• Provide information to add to our understanding
  of how wildlife species use intensively managed
  forest systems.
• Relate bat activity in early successional
  habitats to the better understood avian use of
  those habitats to build a more holistic view for
  conservation and management decisions,
  particularly as they relate to management of
  sites within broader landscape contexts.

Overall mean pph SD 7.06 7.96
4.22 3.85
3.13 2.24
3.91 2.46
Mean mass per sample SD (g) 11.6 2.6
3.6 1.3
3.6 1.6
Methods Study Area The Virginia Piedmont region
provides an interesting context for addressing
research questions related to habitat use in
actively managed forests. Virginias Piedmont is
still largely forested (gt80 forest cover in some
counties Wear and Greis 2004), and it includes
large extents of intensively managed pine
forests. Additionally, in the next few decades
the Piedmont region is expected to lose more
forest cover than any other region in the
Southeastern U.S. (Wear and Greis 2004). Our
study area, the Appomattox-Buckingham State
Forest (ABSF), encompasses over 19,000 acres
within a largely forested landscape with
industrial and other private landowners. The
ABSF is managed by the Virginia Department of
Forestry for multiple uses. In the ABSF, we
selected 9 study sites representing a continuum
from young (0-1 year-old) loblolly pine
plantations to oak (Quercus sp.) shelterwood
sites.
Acknowledgements This research was supported by a
Longwood University Faculty Research Grant.
Additional in-kind and indirect support were
provided by Longwoods Department of Biological
and Environmental Sciences and the Geographic
Information Systems Laboratory, the Virginia
Department of Forestry, and the Kennedy Tree
Farm. We also thank the following individuals
for their help and support D. Horchler, T.
Akre, M. Fink, E. Kinman, and S. Amelon.
Overall mean cover (n), max. height (m) 16.7
(16), 1.0
42.6 (15), 1.9
47.7 (6), 2.2
77.3 (6), 2.9
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