Abstract: Decomposition of plant debris is an important but incompletely understood process. This is especially true for fine woody debris (i.e. material less than
10cm in diameter) which has been largely neglected in decay research relative to leaf litter and coarse woody debris (Harmon et al. 1995, Müller-Using and
Bartsch 2009). The decay process relies heavily on microbial activity and environmental conditions, but the influence of arthropods remains relatively unclear
(Harmon et al. 1986, Rayner and Boddy 1988). In this ongoing study, mesh bags are being used to exclude arthropods from small diameter Chinese tallow
(Triadica sebifera (L.) Small) twigs in a mature mixed pine/hardwood forest in northeastern Mississippi, USA. The study consists of two mesh sizes (300µm and
1000µm) and a no-mesh treatment, with three size classes of Chinese tallow twigs collected every 4 months over a 2-yr period. Preliminary findings show
significant decreases in mass loss and strong evidence of termite activity and fungal presence. Our preliminary findings also indicate a significant difference in
moisture content between mesh treatments signifying the presence of a mesh effect. Past studies employing the use of mesh bags have rarely addressed the
potential for mesh to affect decay beyond the exclusion of insects, i.e., by affecting substrate moisture or other physical conditions likely to impact microbial
activity (Kampichler and Bruckner 2009). We are testing a novel method aimed at addressing this concern.
Arthropod Results
Methods
 Chinese tallow branches were collected and cut into 15cm dowels of three diameter size
classes (0.2-0.4cm, 0.8-1.1cm, 1.5-2.5cm)
 To measure mesh effects, untreated yellow poplar dowels were used as controls
 Twigs and dowels were then randomly assigned to one of three mesh treatments (Fine
(300µm), Coarse (1000µm), and None)
 Treatments were placed in the field in February 2013 at five locations within the Noxubee
National Wildlife Refuge in northern Mississippi, USA
 Treatments are collected once every four months for a total of 20 months. At this point, we are
12 months into the study
 Mass Loss is measured as: (InitialDryWeight-FinalDryWeight)/InitialDryWeight
 Moisture Content is measured as: (FinalWetWeight-FinalDryWeight)/FinalWetWeight
 Both mass loss and moisture content were analyzed in SAS with ANCOVA
F
Pr > F
There is a significant (p<.0001)
decrease in mass overtime
with a significant difference in
mass lost between the no
mesh treatment and the fine
mesh treatment (p< .05)
106.71
<.0001
Contrast
Mean Square
F Value
Pr > F
Fine vs. Coarse
1
0.05100500
0.05100500
0.95
0.33
Fine vs. None
1
0.19623235
0.19623235
3.64
0.05
Coarse vs. None
1
0.04742381
0.04742381
0.88
0.34
Mean mass loss by month for all twigs
F
Pr > F
DF Contrast SS
1.82
0.1637
DF
Contrast SS
Mean Square
F Value
Pr > F
1 vs 2
1
0.05205661
0.05205661
0.97
0.32
1 vs 3
1
0.25168575
0.25168575
4.69
0.03
2 vs 3
1
0.07523556
0.07523556
1.40
0.23
Total count of twigs with arthropods discovered to date,
arranged by treatment interactions
Pr > F
Pr > F
0.1803
0.0207
0.4201
Mean mass loss by mesh treatment for all twigs
19.52
<.0001
Cerambycidae larva
Subterranean termites (Reticulitermes sp.)
Species of arthropods found include:
Reticulitermes spp., Cerambycidae,
Ichneumonoidae, Temnothorax pergandei,
Elateridae, Tenebrionoidae, Annelida, & Diptera
There was a significant trend observed at the 8
month collection between moisture content of mesh
treatments (p<.02 ), however, these trends were not
apparent in the 4 or 12 month collections
The 8 month collection depicts the expected trend for
moisture content; the fine mesh holds in the most
moisture, while the no mesh treatment was the driest
Moisture content of dowels by mesh and month
Mud covered twigs
after 12 month
collection
Treatments covered in water at
one site at the 12 month
collection
To account for differences in site moisture, soil
moisture content was used as a covariate and a trend
becomes apparent, however statistical significance is
still not observed
Mean mass loss between all twigs with termite
damage and all twigs without
Mean mass loss by diameter class for all twigs
There is also a significant difference between the
smallest and largest diameter classes in terms of
mass lost (p<.03 )
Subterranean termites (Reticulitermes sp.)
Pr > F
Twig with significant termite damage
Contrast
Temnothorax pergandei
Moisture Content Results
F
Pr > F
2.35
0.0971
12 Month
Arthropod, and specifically termite, damage was
observed most frequently in the larger diameter
classes and in the no mesh and coarse mesh
treatments
Mass Loss Results
F
Pr > F
8 Month
In addition, twigs with termite damage
lost significantly more mass (P<.0001)
Moisture content of 12 month dowels by mesh using soil
moisture as a covariate
Conclusions
Our initial findings show arthropod contributions to be significant in the decay of fine woody debris in northern Mississippi and mesh having an effect on substrate moisture
and other physical conditions likely to affect microbial activity.
Moisture content is important to determine the effect of the mesh bags on the decomposition process, however, moisture content is heavily dependent on site characteristics,
weather conditions, and month of collection.
Our final decay models will have to include all of these factors, plus many more, to confidently isolate the contributions of arthropods to the decomposition process.
Acknowledgements
•US Forest Service Southern Research Station Joint Adventure agreement (10-JV-113301234-048)
•Mississippi State University Forest and Wildlife Research Center
•Sam D. Hamilton Noxubee National Wildlife Refuge
•Dr. Zhaofei Fan, Dr. Michael Ulyshen, and Dr. Morgan Varner
•Mary Frances Nieminen, Nana Tian, Zhen Sui, and Darcy Hammond
•And Neville Clokey at Normesh (UK)
References
Harmon, M.E., Anderson, N.H., Franklin, J.F., Cline, S.P., Swanson, F.J, Aumen, N.G., Sollings, P. Sedell, J.R., Gregory, S.V., Lienkaemper, G.W., Lattin, J.D., Cromack Jr., K., and
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Kampichler, C. and Bruckner, A. 2009. The role of microarthropods in terrestrial decomposition: a meta-analysis of 40 years of litterbag studies. Biological Reviews 84:375-389
Müller-Using, S. and Bartsch, N. 2009. Decay dynamic of coarse and fine woody debris of a beech (Fagus sylvatica l.) forest in central Germany. European Journal of Forest Resources
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Rayner, Alan DM, and Lynne Boddy. Fungal decomposition of wood. Its biology and ecology. John Wiley & Sons Ltd., 1988.