Document: KAT-3-76-18

Identifying links between riparian water conditions and diverse terrestrial communities.

WILLIAMS, K.S.*

San Diego State University, San Diego, CA 92182, U.S.A. ¹

Abstract:
This project is part of a multidisciplinary, multi-institutional project that is integrating hydrologic models, a riparian ecosystem integrity index, and economic analyses. In the first year of this 3-yr study, work focused on the San Pedro River watershed in southeastern Arizona. This work will contribute to developing a riparian ecosystem integrity index, which will be based on landscape, community, and population level traits. In addition to studies of insects, field studies of plants and birds are being conducted to refine our understanding of the linkages between groundwater, surface water, and ecological variables, and ultimately enhance our capacity to restore and preserve riparian ecosystems. In summer 1999, we collected insects and related terrestrial arthropods at 3 times to represent pre-, during-, and post- monsoon conditions. Standard sweep-netting techniques were used to collect insects off specific vegetation along river reaches and adjacent grasslands: young/old willow and young/old cottonwood, baccharis, saltcedar, and big sacaton bunch grass. Initial analyses compared insect abundance/diversity to river flow and duration at 9 riparian sites and 10 adjacent grassland sites. Results showed strong differences in insect abundances and diversity among dates with many more insects present after monsoons began. There were differences among sites, and much of that appeared to be related to the local hydrology. For example, before monsoons began, spiders and insects from many orders were most abundant at Perennial and Intermittent flow sites and significantly less abundant at Ephemeral flow sites. No striking differences in abundances of insects among riparian plant types were found. After monsoons began, differences in insects among habitats with different hydrological patterns were not as consistent. However, interesting differences in abundances of insects among plants appeared after rains began. For example, collections from non-native saltcedar produced significantly more Coleoptera, Lepidoptera, and Homoptera than collections from other riparian plants. Some insect types were significantly more abundant on willow. These results appear to illustrate critical linkages between riparian systems and diverse terrestrial communities.

Keywords: insect ecology, riparian ecosystems, biodiversity, restoration ecology

This abstract is being presented at: 10:30 AM in session:
RIPARIAN ECOLOGY