Long-term insect herbivory slows soil development in an arid ecosystem

Classen, Aimee T. and Chapman, Samantha K. and Whitham, Thomas G and Hart, Stephen C. and Koch, George W. (2013) Long-term insect herbivory slows soil development in an arid ecosystem. Ecosphere, 4 (5). ISSN 2150-8925

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Abstract

Although herbivores are well known to alter litter inputs and soil nutrient fluxes, their long-term influences on soil development are largely unknown because of the difficulty of detecting and attributing changes in carbon and nutrient pools against large background levels. The early phase of primary succession reduces this signal-to-noise problem, particularly in arid systems where individual plants can form islands of fertility. We used natural variation in tree-resistance to herbivory, and a 15 year herbivore-removal experiment in an Arizona pinon-juniper woodland that was established on cinder soils following a volcanic eruption, to quantify how herbivory shapes the development of soil carbon (C) and nitrogen (N) over 36-54 years (i.e., the ages of the trees used in our study). In this semi-arid ecosystem, trees are widely spaced on the landscape, which allows direct examination of herbivore impacts on the nutrient-poor cinder soils. Although chronic insect herbivory increased annual litterfall N per unit area by 50% in this woodland, it slowed annual tree-level soil C and N accumulation by 111% and 96%, respectively. Despite the reduction in soil C accumulation, short-term litterfall-C inputs and soil C-efflux rates per unit soil surface were not impacted by herbivory. Our results demonstrate that the effects of herbivores on soil C and N fluxes and soil C and N accumulation are not necessarily congruent: herbivores can increase N in litterfall, but over time their impact on plant growth and development can slow soil development. In sum, because herbivores slow tree growth, they slow soil development on the landscape.

Item Type:	Article
Publisher’s Statement:	Copyright 2013 Classen et al.
ID number or DOI:	10.1890/ES12-00411.1
Keywords:	carbon cycling; Phytophagous insects; nitrogen availability; nitrogen cycle; northern Arizona; pinyon pine; juniper; Pinon-juniper woodland; soil ecology; arid regions ecology
Subjects:	S Agriculture > SD Forestry
NAU Depositing Author Academic Status:	Faculty/Staff
Department/Unit:	College of Engineering, Forestry, and Natural Science > Biological Sciences Research Centers > Merriam-Powell Center for Environmental Research
Date Deposited:	08 Oct 2015 20:15
URI:	http://openknowledge.nau.edu/id/eprint/653

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