Soil and Vegetation Changes across a Restoration Chronosequence: An Evaluation of Wetlands Reserve Program (WRP) sites in West-central New York, USA

Abstract

Wetland restorations in the United States, including those sponsored by the federal Wetlands Reserve Program (WRP), are driven by the prospect of regaining critical ecosystem services lost during centuries of wetland destruction. Yet, service provision is contingent on the recovery of basic wetland functions, such as carbon (C) storage, which is especially tentative (and unverified) in WRP projects in west-central New York (WCNY), USA because those involve installing isolated wetlands on sites directly degraded by agricultural conversion. To assess recovery, I collected soil and vegetation data from 17 of WCNY’s WRP sites restored from tillage or non- tillage agriculture, aged 0-15 years since restoration at the time of sampling (August-October 2010). These were subjected to chronosequence-based analyses designed to detect divergence from a pre-restoration baseline (calculated using data from active agricultural fields paired to each WRP site) and/or convergence towards a “natural” condition (determined using data from four naturally-occurring, depressional, Palustrine Emergent wetlands within the same region). Restored WRP soils remained similar to agricultural soils in terms of organic matter, density, moisture, and belowground plant biomass across the chronosequences, indicating negligible C storage and soil development during the first 15 years. Additionally, soil development is limited in both post-tillage and post-non-tillage restorations and limited throughout the disparate habitat zone types that occur on these sites (upland meadows, emergent-dominated shorelines, and permanent open-water areas). Plant metrics like vascular species richness, cover of certain qualitative groups, and biomass matched natural wetlands within 15 years. Yet, recovery of some metrics was only detected in previously tilled sites, while other metrics only displayed recovery in untilled sites. Additionally, recovery was often detected in only one of the three habitat zones, collectively suggesting that different plant metrics are differentially influenced by the conditions imposed by historical tillage and/or the zone in which they are measured. Vegetation analyses also showed that plant community recovery can be complicated when plant parameters in restoration sites “overshoot” beyond natural conditions. In conclusion, ecological recovery in WRP restorations in WCNY is variable, depending on metric, land-use history, and habitat zone. Although generally, many plant community features recover rapidly and despite limited recovery in soil physicochemical properties.