HR: 08:30h
AN: B51E-03    [Abstracts]
TI: Temperature and Moisture Constraints for Growth in a California Mediterranean Forest
AU: * Gershenson, A
EM: agersh@ucsc.edu
AF: UC Santa Cruz, UCSC, Department of Environmental Studies 1156 High St, Santa Cruz, CA 95064 United States
AU: Misson, L
EM: lmisson@nature.berkeley.edu
AF: UC Berkeley, Department of Environmental Science, Policy and Management 137 Mulford Hall #3114, Berkeley, CA 94720 United States
AU: Goldstein, A
EM: ahg@nature.berkeley.edu
AF: UC Berkeley, Department of Environmental Science, Policy and Management 137 Mulford Hall #3114, Berkeley, CA 94720 United States
AU: Cheng, W
EM: wxcheng@ucsc.edu
AF: UC Santa Cruz, UCSC, Department of Environmental Studies 1156 High St, Santa Cruz, CA 95064 United States
AB: Globally, belowground carbon (C) fluxes in forest ecosystems constitute a major link between atmospheric C and the soil C pools. However, a gap in our understanding of belowground carbon fluxes in forest ecosystems in general, and specifically the role that roots play in belowground C dynamics, is one of the primary factors limiting our ability to assess the contribution of forests as global C processors. Root turnover is one of the major pathways for terrestrial carbon cycling. Although many investigations have focused on determining how various factors affect fine root dynamics, few have examined the effects of intra-seasonal variability associated with Mediterranean climates on fine root- and related above-ground growth dynamics. Data collected during the 2003 growth season suggest that phenological development of Ponderosa pine-dominated ecosystems of Sierra Nevada may be highly dependent on prevailing climatic conditions. We monitored fine root development, trunk thickening, shoot and needle elongation, and shrub LAI changes throughout the season, as well as soil moisture, and soil and air temperature, as well as canopy level photosynthesis at the UC Berkeley Blodgett Experimental Station AmeriFlux site. The site is characterized by cold, wet winters and extremely hot and dry summers; it is a young ponderosa pine plantation with a shrub understory (Arctostaphylos sp. and Ceanothus sp.) The onset of phenological development in this ecosystem appears to be controlled by the increase of the daily minimum temperatures above 5 degrees C in the middle of May, and the end of the growing season appears to be controlled by the decrease of available soil moisture to below 15% in the middle of July. Root development appears to follow the overall patterns of warming and drying of the soil profile, with surface root growth initiation and mortality occurring earlier than that of subsurface roots. Current available climate modeling projections focused on this area of California predict significant snow accumulation decreases and increases of springtime temperatures by as much as 4 degrees C within the next twenty years. These changes to the temperature and moisture regimes during the critical time period for growth have the potential of radically altering the time available for ecosystem growth and carbon dynamics.
DE: 0428 Carbon cycling (4806)
DE: 0439 Ecosystems, structure and dynamics (4815)
DE: 0476 Plant ecology (1851)
DE: 9350 North America
SC: Biogeosciences [B]
MN: Fall Meeting 2005