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Presented at the NABS Annual meeting, Athens, Georgia, 2003
in Changing Land Use Effects on Aquatic Food Webs
Riparian vegetation change and detrital stream systems in a tropical montane landscape
T. Heartsill-Scalley1, T.A. Crowl1, T.M. Aide2, and A.P. Covich3. 1Ecology Center and Dept. of AWER, Utah State University, Logan UT 84322-5210, 2Dept. of Biology, University of Puerto Rico, San Juan PR 00931-3360, 3Institute of Ecology, University of Georgia, Athens, Georgia, USA
Changes in land cover from forest to agriculture alter riparian vegetation, which modifies the physical conditions of streams. To understand the impacts of land cover changes on streams, we sampled riparian vegetation and stream condition in three adjacent watersheds in Puerto Rico. Riparian vegetation and stream characteristics were assessed along first order streams in the wet forest life zone. Understory vegetation in the forest sites was mainly shrubs, herbs and ferns, while the mixed and pasture sites were dominated by grasses, vines and bare soil. Syzygium jambos and Spathodea campanulata, non-natives, and Guarea guidonia, a native, were the most common tree species in the riparian areas. Surrounding land cover explained >60% of the variation among stream sites. There was a positive relationship between tree cover and percent dissolved oxygen, and a negative relationship between tree cover and percent of substrata covered by sediments from eroded soil. Woody debris in the streams tended to increase with forest cover. In addition to changes in chemical/physical characteristics, the changes in litter type and quality likely affect nutrient cycling and detrital food web dynamics. We are currently assessing the role of changing allochthonous input rates and types to these freshwater shrimp-dominated food webs.
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