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ARS Home » Pacific West Area » Corvallis, Oregon » Horticultural Crops Research Unit » Research » Publications at this Location » Publication #163899
Title: INTERACTION OF OZONE AND GRASS COMPETITION ON ABOVE-AND BELOWGROUND GAS EXCHANGE IN PONDEROSA PINE

Author
item ANDERSON, CHRISTIAN - US-EPA
item HOGGSETT, WILLIAM - US-EPA
item Scagel, Carolyn
item PLOUCHER, MILTON - DYNAMAC CORPORATION
item COULOMBE, ROBERT - DYNAMAC CORPORATION

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 5/17/2004
Publication Date: 7/1/2004
Citation: Anderson, C.P., Hoggsett, W.E., Scagel, C.F., Ploucher, M., Coulombe, R. 2004. Interaction of ozone and grass competition on above-and belowground gas exchange in ponderosa pine. Meeting Abstract.

Interpretive Summary:

Technical Abstract: A three year study was conducted to examine the effects of plant competition and ozone on below-ground processes in Ponderosa pine (Pinus ponderosa Laws). Seedlings were planted with 3 densities of blue Wildrye grass (Elymus glaucus Buckl.) and exposed to ozone. Soil respiration (SR) and foliar gas exchange were measured monthly during the summer. Seasonal variation in SR was high due to changing soil temperatures. There was a general pattern of higher SR in ozone treated seedlings during the first and second exposure seasons, although differences were not always significant. During the third exposure season, SR was not different between ozone and control treatments. Early in the study, soil organic matter (LOI) increased in ozone treated plots compared to control plots, but there were no significant differences in organic material (OM) between ozone treatments by the end of the study. Foliar gas exchange was not different among treatments during the first and second growing season, but differences were observed in one-year-old foliage by the end of the third season. A significant interaction was observed such that photosynthesis in one-year-old foliage decreased with grass competition in ozone treated seedlings, while controls showed an increase in photosynthesis with grass competition. Photosynthesis patterns were positively related to needle nitrogen, which also showed a significant interaction between ozone and grass competition. The results indicate that root and soil processes may respond rapidly to elevated ozone concentrations, sometimes before above-ground changes become evident.