PARENT SESSION
Poster Session # 15: Plant Ecology.
Wednesday, August 6 Presentation from 5:00 PM to 6:30 PM. SITCC Exhibit Hall B.
Variation in carbon isotope ratios in Pinus edulis trees following drought-induced mortality.
Kempes, Christopher*,1, Breshears, David2, Fessenden, Julianna2, Heikoop, Jeffrey2, 1 McCurdy High School, Espanola, NM2 Los Alamos National Laboratory, Los Alamos, NM
ABSTRACT- Droughts of a high severity often cause a period of massive tree mortality that may affect one or several species. In northern New Mexico both a severe drought and a high mortality of Pinus edulis, a co-dominant of pinyon-juniper woodlands, has recently been observed. The stress an individual tree is under in any given year may be reflected in the Carbon 13/Carbon 12 ratios in tissue. When a tree is under stress due to either low precipitation or high temperatures (i.e., drought) then that specific tree is forced to close its stoma during the day and increase respiration rates overnight and in the process abandon the normal selection of Carbon 12 over Carbon 13. The drought of the late 1990's /early 2000's is very similar to that of the 1950's, in that there was massive mortality and pest infestations. Obviously any trees that are over the age of 50 years survived the more dramatic portion of the 1950's drought yet those same individual trees may not have survived this past drought. We evaluated Carbon 13 relationships from cores of recently deceased trees for different 4-year intervals, including tree age during a given period as a factor. We used a Walter index, calculated from monthly temperature and precipitation data, to evaluate relationships between Carbon 13 and periods of water stress. Our results indicate that Carbon 13 ratios are related to the integrated periods of water stress reflected in the Walter index. The results on how trees respond to water stress have implications for reconstructing past climate conditions.
Key words: drought, plant physiological ecology, carbon istope ratios, tree morality