Stable carbon isotope analysis of soil organic matter illustrates vegetation change at the grassland/woodland boundary in southeastern Arizona, USA.
In southeastern Arizona, Prosopis juliflora (Swartz) DC. and Quercus emoryi Torr. are the dominant woody species at grassland/woodland boundaries. The stability of the grassland/woodland boundary in this region has been questioned, although there is no direct evidence to confirm that woodland is encroaching into grassland or vice versa. We used stable carbon isotope analysis of soil organic matter to investigate the direction and magnitude of vegetation change along this ecotone. δ13C values of soil organic matter and roots along the ecotone indicated that both dominant woody species (C3) are recent components of former grasslands (C4), consistent with other reports of recent increases in woody plant abundance in grasslands and savannas throughout the world. Data on root biomass and soil organic matter suggest that this increase in woody plant abundance in grasslands and savannas may increase carbon storage in these ecosystems, with implications for the global carbon cycle.
Forest-Watershed Sciences Program, School of Renewable Natural Resources, University of Arizona, 85721, Tucson, AZ, USA.
G R
GR
McPherson
Department of Rangeland Ecology and Management, Texas A & M University, 77843, College Station, TX, USA.
T W
TW
Boutton
Department of Rangeland Ecology and Management, Texas A & M University, 77843, College Station, TX, USA.
A J
AJ
Midwood
Life-form shifts; Prosopis juliflora; Quercus emoryi; Savanna; δ13C values