Influence of Soil Properties on the Biogeochemistry of a Beaver Meadow Hydrosequence

Abstract

Previous research about the biogeochemistry of beaver (Castor canadensis Kuhl) impoundments has generally overlooked the influence of soil type on solutes. In this study, soils derived from glacio‐lacustrine and glacio‐fluvial parent materials in northern Minnesota beaver meadows (i.e., former beaver ponds that have drained and revegetated) were studied to: (i) describe soil morphology, (ii) analyze soil and solute chemistry, and (iii) statistically evaluate the relative influence of hydrology and soil type on solute chemistry. With decreasing depth to groundwater, soils in both hydrosequences were increasingly reducing; redox potentials were consistently negative in the Borosaprist. Differences in soil morphology associated with increasing wetness included: (i) increasing thickness of O and A horizons, (ii) decreasing thickness of the Bt horizon (glacio‐lacustrine hydrosequence), (iii) disappearance of E and Bk horizons (glacio‐lacustrine hydrosequence), and (iv) decreasing depth to redoximorphic features. In the glacio‐lacustrine hydrosequence, depth to subsurface concentrations of oxalateextractable Fe (≥800 g m−3) decreased with increasing wetness. Two‐way ANOVA indicated that differences in water chemistry among soils were due to moisture, parent material, and their interaction. Increasing moisture was associated with increased concentrations of Fe2+, Ca2+, and Mg2+ and decreased concentrations of SO4‐S. Glaciolacustrine soils contained higher concentrations of base cations (K+, Ca2+, and Mg2+) than did glacio‐fluvial soils, and so did their soil water. There were pronounced seasonal variations in cation concentrations and significant interannual differences for NH4‐N, total N, and K+. Nitrate concentrations were consistently low and did not differ significantly among any of the groupings.

An ecosystem engineer, the beaver, increases species richness at the landscape scale

“…Given the large changes in a number of physical conditions that occur after a site has been occupied by beaver (Naiman et al 1994;Johnston et al 1995), it is difficult to predict a priori whether these sites should have higher or lower species richness than sites that have never been modified by beaver. We found that patches that had and had not been modified by beaver had similar levels of species richness at the patch scale (alpha diversity, sensu Whittaker 1972).…”

“…Beaver set the stage for the creation of these meadows by building dams that trap nutrient-rich sediment and by both directly and indirectly killing woody vegetation in the riparian zone via herbivory, felling and flooding. In contrast to forested riparian zones, beaver meadows have high light penetration and elevated soil moisture and nitrogen levels (Naiman et al 1994;Johnston et al 1995). Beaver foraging has been shown to have significant effects on forest succession around active ponds by decreasing densities of preferred food species (Barnes and Dibble 1986;Johnston and Naiman 1990b;Donkor and Fryxell 2000).…”

Predicting Effects of Ecosystem Engineers on Patch-Scale Species Richness From Primary Productivity

“…Consequently, porcupine diggings have a predictable positive effect on species richness in this low-productivity environment (Boeken et al 1995). On the other hand, beaver meadows have been shown to differ from forested riparian zones in light, soil moisture, and nitrogen levels (Naiman et al 1994, Johnston et al 1995, and the two patch types are colonized by very different sets of species, reflecting different species pools (Wright et al 2002). In this case, ecosystem engineering modifies numerous resources in complex ways and results in engineered habitats that do not differ in species richness from unmodified habitat in any obviously predictable way.…”

Using assembly rules to measure the resilience of riparian plant communities to beaver invasion in subantarctic forests

“…Generally, former beaver ponds become grass and sedge-dominated meadows (Naiman et al 1988;Johnston et al 1995;Terwilliger and Pastor 1999). Compared to un-impacted sites, these meadows have distinct ecosystem processes, due to changes in nutrient cycles, decomposition dynamics, physical structure (i.e.…”