Using Vegetative Nutrient Stocks to Compare Restored and Reference Wetlands in the Upper Klamath Basin, Oregon

Abstract

Vegetative diversity metrics are often used to characterize wetland restoration success. Here we examine whether other important vegetative traits (nutrient standing stocks and tissue nutrient concentrations) can improve our understanding of the structure of restored and reference wetlands and aid in the assessment of functional equivalency. We focus on wetlands of the Upper Klamath Basin (UKB), Oregon because this basin supports a mosaic of remnant, restored, and degraded wetlands dominated by a limited number of common emergent plant species. We summarize nutrient standing stocks using 11 growth limiting micro- and macronutrients present in aboveground tissues of three emergent plant species. We show that interspecific variation in nutrient standing stocks and tissue nutrient concentrations was high and greater than inter-site differences. Interspecific variation for nitrogen standing stocks was 3X larger than inter-site variation. Although less common, inter-site differences in nutrient standing stocks and tissue nutrient concentrations were detected and tissue phosphorus concentrations in a recently restored wetland were nearly twice those of a reference wetland; corresponding levels of aboveground biomass in this wetland were not detected. Our detection of elevated phosphorus in the vegetation of a recently restored wetland is consistent with predictions from both experimental and observational work in UKB and demonstrates that nutrient standing stocks provide important clues about the fate and retention of nutrients in restoration wetlands. Importantly, we show that these vegetative attributes also provide a measure of functional equivalency that is rarely used in the assessment of restoration success.