PARENT SESSION
Organized Oral Session 41: Ecological responses to precipitation: Scaling patterns and processes from the genome to the ecosystem
Organizer(s): ME Loik and SD Smith
Thursday, August 11, 8:00 AM - 11:30 AM, Meeting Room 510b, Level 5, Palais des congrès de Montréal
Effects of altered precipitation on biological soil crusts.
Belnap, Jayne*,1, 2, Smith, Stanley3, Housman, David1, Zimpfer, Jeff4, 1 Southwest Biological Science Center, Moab, UT, USA2 Natural Resource Ecology Laboratory, Ft. Collins, CO, USA3 Department of Biological Sciences, Las Vegas, NV, USA4 Pacific Aquaculture and Coastal Resources Center, Hilo, HI, USA
ABSTRACT- Future climate changes will affect soil moisture regimes through increased temperature and the alteration of precipitation regimes. These effects will be especially pronounced in deserts, as soils are generally young, with low water-holding capacity. Biological soil crusts can be important components in these ecosystems. Because they are only metabolically active when wet, they are at high risk to any changes in soil moisture. We altered precipitation regimes for crusts from winter rainfall deserts. In SE Utah, altered precipitation frequency (but not amount) during summer months resulted in the reduction of fluoresence, pigment production, biomass, and N-fixation in both cyanobacteria and the lichen Collema. However, these negative effects were much more pronounced in the lichen than the cyanobacteria. In a second SE Utah experiment with Collema, altered precipitation frequency again depressed fluoresence, but this time favored N fixation. In a experiment in southern Nevada, increasing summer precipitation decreased lichen cover dominated by Collema and Placidium, while cyanobacterial biomass and fluoresence increased. In addition, adding summer precipitation shifted the microbial composition of the plots. Combined, these results indicate that increased frequency or amount of summer precipitation is likely to favor cyanobacteria over lichens, resulting in biological soil crusts that appear more like those found in deserts whose precipitation regimes are dominated by summer rain than those dominated by winter rain. Such a shift will result in species that contribute less to soil stability and fertility than those species currently present.
Key words: climate change, drylands, photosynthesis, nitrogen fixation