TY - JOUR
T1 - Impacts of herbivorous insects on decomposer communities during the early stages of primary succession in a semi-arid woodland
AU - Classen, Aimée T.
AU - DeMarco, Jennie
AU - Hart, Stephen C.
AU - Whitham, Thomas G.
AU - Cobb, Neil S.
AU - Koch, George W.
N1 - Funding Information:
M. Dickerson, S. Boyle, and D. Guido assisted with data collection, processing, analysis, and organization. M. Loeser, M. Kearsly, and M. Cammon assisted with NMDS. S. Overby graciously allowed us to use his laboratory. Comments from two anonymous reviewers, C. Gehring, K. Haskins, S. Chapman, and N. Sanders greatly improved this paper. A grant from NSF, a NAU Hooper fellowship awarded to J. Demarco and M. Dickerson, and fellowships awarded to A. Classen from the Merriam-Powel Center for Environmental Research and the American Association of University Women funded this research. This paper was prepared at Oak Ridge National Laboratory (ORNL) with support from the U.S. Department of Energy, Office of Science, Biological, and Environmental Research Program. ORNL is managed by UT-Battelle, LLC, for the US Department of Energy under contract DE-AC05-00OR22725.
PY - 2006/5
Y1 - 2006/5
N2 - Changes in nutrient inputs due to aboveground herbivory may influence the litter and soil microbial community responsible for processes such as decomposition. The mesophyll-feeding scale insect (Matsucoccus acalyptus) found near Sunset Crater National Monument in northern Arizona, USA significantly increases piñon (Pinus edulis) needle litter nitrogen (N) and phosphorus (P) concentrations by 50%, as well as litter inputs to soil by 21%. Because increases in needle litter quality and quantity of this magnitude should affect the microbial communities responsible for decomposition, we tested the hypothesis that insect herbivory causes a shift in soil microbial and litter microarthropod function. Four major findings result from this research: (1) Despite increases in needle inputs due to herbivory, soil carbon (C) was 56% lower beneath scale-susceptible trees than beneath resistant trees; however, soil moisture, N, and pH were similar among treatments. (2) Microbial biomass was 80% lower in soils beneath scale-susceptible trees when compared to resistant trees in the dry season, while microbial enzyme activities were lower beneath susceptible trees in the wet season. (3) Bacterial community-level physiological profiles differed significantly between susceptible and resistant trees during the dry season but not during the wet season. (4) There was a 40% increase in Oribatida and 23% increase in Prostigmata in susceptible needle litter relative to resistant litter. Despite these changes, the magnitude of microbial biomass, activity, and community structure response to herbivory was lower than expected and appears to take a long time to develop. These results suggest that herbivores impact soils in subtle, but important ways; we suggest that while litter chemistry may strongly mediate soil fertility and microbial communities in mesic ecosystems, the influence is lower than expected in this primary succession xeric ecosystem where season mediates differences in microbial populations. Understanding how insect herbivores alter the distribution of susceptible and resistant trees and their associated decomposer communities in arid environments may lead to better prediction of how these ecosystems respond to climatic change.
AB - Changes in nutrient inputs due to aboveground herbivory may influence the litter and soil microbial community responsible for processes such as decomposition. The mesophyll-feeding scale insect (Matsucoccus acalyptus) found near Sunset Crater National Monument in northern Arizona, USA significantly increases piñon (Pinus edulis) needle litter nitrogen (N) and phosphorus (P) concentrations by 50%, as well as litter inputs to soil by 21%. Because increases in needle litter quality and quantity of this magnitude should affect the microbial communities responsible for decomposition, we tested the hypothesis that insect herbivory causes a shift in soil microbial and litter microarthropod function. Four major findings result from this research: (1) Despite increases in needle inputs due to herbivory, soil carbon (C) was 56% lower beneath scale-susceptible trees than beneath resistant trees; however, soil moisture, N, and pH were similar among treatments. (2) Microbial biomass was 80% lower in soils beneath scale-susceptible trees when compared to resistant trees in the dry season, while microbial enzyme activities were lower beneath susceptible trees in the wet season. (3) Bacterial community-level physiological profiles differed significantly between susceptible and resistant trees during the dry season but not during the wet season. (4) There was a 40% increase in Oribatida and 23% increase in Prostigmata in susceptible needle litter relative to resistant litter. Despite these changes, the magnitude of microbial biomass, activity, and community structure response to herbivory was lower than expected and appears to take a long time to develop. These results suggest that herbivores impact soils in subtle, but important ways; we suggest that while litter chemistry may strongly mediate soil fertility and microbial communities in mesic ecosystems, the influence is lower than expected in this primary succession xeric ecosystem where season mediates differences in microbial populations. Understanding how insect herbivores alter the distribution of susceptible and resistant trees and their associated decomposer communities in arid environments may lead to better prediction of how these ecosystems respond to climatic change.
KW - Community-level physiological profiles
KW - Enzyme activity
KW - Insect herbivory
KW - Insect-susceptible and resistant trees
KW - Litter microarthropods
KW - Microbial biomass
KW - Piñon-juniper woodlands
KW - Semi-arid
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U2 - 10.1016/j.soilbio.2005.08.009
DO - 10.1016/j.soilbio.2005.08.009
M3 - Article
AN - SCOPUS:33646076219
SN - 0038-0717
VL - 38
SP - 972
EP - 982
JO - Soil Biology and Biochemistry
JF - Soil Biology and Biochemistry
IS - 5
ER -