Open AccessBrowsing impacts on the stable isotope composition of chaparral plants
Author(s) -
Koch Paul L.,
Fox Laurel R.
Publication year - 2017
Publication title -
ecosphere
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.255
H-Index - 57
ISSN - 2150-8925
DOI - 10.1002/ecs2.1686
Subject(s) - chaparral , shrub , biology , herbivore , plant community , ecosystem , ecology , botany , abiotic component , frankia , agronomy , nitrogen fixation , ecological succession , root nodule , genetics , bacteria
We assessed the effects of herbivory on competition, water stress, and potentially biological nitrogen fixation on three species of endemic shrubs using variations in the stable isotope ratios ( 13 C/ 12 C and 15 N/ 14 N) in leaves of chaparral shrubs in a long‐term field experiment. While variations in isotopic ratios of plants are often attributed to abiotic stresses, impacts of biotic interactions are rarely evaluated. Our site was a low‐nutrient, chaparral community on the central California coast. In this system, deer browsing on Ceanothus rigidus , which have symbiotic N‐fixing bacteria ( Frankia ), was intense and suppressed growth, while the two non‐fixing shrubs ( Arctostaphylos pumila and Ericameria ericoides ) were not browsed heavily. For Ceanothus , excluding deer increased both plant size and the δ 15 N value to ~0‰; δ 13 C values also increased as the plants increased in mass. In Arctostaphylos and Ericameria , stable isotope values did not change, while plant sizes remained the same or even declined when deer were excluded. We interpret the change in Ceanothus δ 15 N values as due to increased N fixation after evaluating possible alternative explanations. The increase in Ceanothus δ 13 C values may be due to increased water stress with substantial shrub growth. More broadly, herbivore suppression of N fixation may impact ecosystem processes such as productivity and N cycling, as well as an ecosystem's ability to respond to increased CO 2 .