Document: AND-3-75-1

Macrophyte succession in beaver ponds.

RAY, A.M.* ¹ and A.J.REBERTUS ²

Idaho State University, Pocatello, ID 83201, U.S.A. ¹
Northern Michigan University, Marquette, MI, U.S.A. ²

Abstract:
Beavers have been described as keystone species, because their impoundments and cutting activities dramatically alter nutrient cycles and food chains in both aquatic and terrestrial systems. We documented macrophyte succession by sampling 36 beaver ponds ranging from 4 to >40 years. We used impounded peatlands rather than streams, because the former were isolated from other water bodies and were less prone to washouts. Richness and diversity in ponds increased linearly during the first four decades and stabilized thereafter. Pond age and the interaction of pond size and number of neighboring-ponds within a 0.25-km radius explained 64% (P<0.001) of the variation in species richness. Most compositional trends were best explained by propagule dispersal traits. Initial colonists included the most vagile species, like free-floating macrophytes (e.g. Lemnaceae), and desirable food sources for waterfowl, like the narrow-leaved pondweeds (e.g. Potamogeton pusillus ). Ponds of intermediate age (11 to 40 years) had highest diversity, with both floating-leaved and submersed life forms well represented. Two community types were identified in the oldest ponds (>40 years): One characterized by dense lily pad cover with shade-tolerant Ceratophyllum demersum beneath, and the other characterized by a rich assemblage of Potamogeton and lacking significant lily pad cover. Trends in macrophytes succession may impact many aquatic organisms and ecosystem processes within beaver ponds, and our results may contribute to better understanding the dynamics of these regionally abundant habitats.

Keywords: beavers; beaver ponds; macrophyte succession; Minnesota; peatlands

This abstract is being presented at: 8:45 AM in session:
Oral Session #37: Phytoplankton.