A Recent Increase in the Abundance of C4 Vegetation in the High Elevation Meadows of the San Jacinto and San Bernardino Mountains
Abstract
Grasslands and meadows are one of the most prevalent ecosystems in the world and are thus the primary habitat for many biotic communities. For numerous small mammals, grasses also shape species dietary requirements and preferred habitat structure. Today, many grassland ecosystems and the species that inhabit them are experiencing pronounced vegetation change due to climate and land use changes. Stable carbon isotopes can be used to track vegetation changes between C3 and C4 grasses in these ecosystems over historical and paleontological timescales. Soils contain a record of aboveground vegetation in the form of preserved soil carbon, and therefore provide a history of the local flora through time. Additionally, the isotopic composition of herbivorous small mammals can be used to reconstruct vegetation fluctuation because they incorporate the carbon isotopic signature of their diets into their body tissues. In this study, we examine vegetation changes in the high elevation meadows of southern California to understand the impact of direct anthropogenic involvement, such as ranching, restoration projects, and/or climatic changes, over the past century on this presumed C3 ecosystem. We aim to pinpoint if and when changes in the relative abundance of C3 and C4 vegetation of these meadows occurred, discover which C4 grasses are becoming more prevalent, and investigate the underlying causes of this change. We sampled individual plants for isotopic analysis, quantified their relative abundances, and collected soil samples for comparative isotopic analysis along a depth profile from three valleys above 7,000 ft in the San Bernardino and San Jacinto mountains: Holcomb Valley, Bluff Lake and Tahquitz Valley. We also sampled hair from museum specimens of the deer mouse, Peromyscus maniculatus, collected from these localities over the past 100 years. Preliminary results show a significant change from C3-plant sourced soils to C4-plant sourced soils at Holcomb Valley, as well as an increase in the δ13C values of small mammal hair from Bluff Lake and Tahquitz Valley over the last century. A sudden shift in the vegetation of these similar yet separated ecosystems is indicative of a larger scale environmental stress.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.B13F2202P
- Keywords:
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- 0414 Biogeochemical cycles;
- processes;
- and modeling;
- BIOGEOSCIENCESDE: 0428 Carbon cycling;
- BIOGEOSCIENCESDE: 0439 Ecosystems;
- structure and dynamics;
- BIOGEOSCIENCESDE: 1630 Impacts of global change;
- GLOBAL CHANGE