Augmentative Restoration: Repairing Damaged Ecological Processes During Restoration of Heterogeneous Environments

摘要

Heterogeneity in disturbance regimes, propagule pools, and factors affecting plant performance are a ubiquitous feature of wildlands. We tested a conceptual framework, termed augmentative restoration, aimed at identifying and selectively repairing orreplacing damaged processes based on their predicted influence on the three causes of succession: site availability, species availability, and species performance. This framework was tested at three sites each with a different cause of succession naturally occurring in an ephemeral wetland dominated by invasive plants that had varying levels of disturbance (site availability), remnant native plants (species availability), and water availability (species performance). Our hypotheses were (1) seeding combined with watering would augment meadow vole disturbance to increase desired species composition, (2) shallow tilling combined with watering would augment remnant native species, and (3) shallow tilling combined with seeding would augment mesic soils toincrease desired species composition. Shallow tilling, watering, and seeding were applied in a factorial arrangement at all three sites. These eight treatment combinations were applied in a split-plot design with four replications to generate 32 whole plots (2 m~2). The herbicide 2,4-D was applied on half of each whole plot to influence relative species performance. In two of the three sites, using augmentative restoration to guide our management approaches improved our decision as to the treatment combinations that would maximize seedling establishment. Selectively augmenting successional processes that remain intact by repairing or replacing processes occurring at inadequate levels can improve implementation of successional management and provide a refined process-based framework for restoration across heterogeneous landscapes. Besides the clear economic advantages of lower management inputs associated with augmentative restoration, avoiding unnecessary management inputs has the additional advantageof minimizing unintended negative impacts on ecosystem processes.