Long-Term Development and Soil-Based Ecosystem Functions of Restored Wetlands.

Long-term development and soil-based ecosystem functions of restored wetlands

K. A. Ballantine

Laboratory and field-scale manipulations were used to investigate the impact that soils amended with organic materials of differing lability have on soil and vegetative development and on desirable and undesirable biogeochemical functions in restored wetlands.  Experimental plots were established in four newly restored depressional freshwater wetlands in central New York.  Amendments ranged along a continuum of decreasing carbon lability (straw, topsoil, straw/biochar mix, and biochar).  The addition of soil amendments to wetland plots stimulated the development of a suite of key structural and chemical properties (e.g., soil carbon, soil nitrogen, cation exchange capacity, bulk density) and biological properties (e.g., microbial biomass and activity, nitrogen cycling) indicative of wetland functions.  Straw had minimal influence on key wetland functions, whereas most properties associated with desirable functions were highest in biochar and topsoil-amended plots.  Potential methane emissions were primarily driven by differences in hydrology among sites, and were significantly higher in amended plots than control plots.  Despite improvements, soil properties did not reach levels of comparable natural wetlands within six years of restoration.  In contrast, plant biomass recovered quickly, and had reached levels of comparable natural wetlands within two years.  Results of this research reveal that addition of organic amendments to soil during wetland restoration can improve key properties indicative of wetland functioning and highlight the importance of site selection in restoration design.  More research is required, however, to determine what level of amendment application will be sufficient for meeting functional goals within an acceptable time frame.