THE IMPORTANCE OF MICROTOPOGRAPHY IN RESTORED WETLAND ECOSYSTEMS

Cranberry bogs are an iconic part of the southeastern Massachusetts landscape. Historically built where the cranberries grew naturally in wetland areas, cranberry farms incorporated layers of sand to control weeds (other wetland plants) and introduced dams, ditches, straightened channels and berms to control the flow and flooding of water. Cranberry production increased exponentially on highly managed monoculture cranberry farms. In recent decades, due to a decline in the economics of cranberry cultivation and competition from places with new high-yield varietals, many Massachusetts cranberry producers are being forced to retire their lands.

At the same time, more and more wetland ecosystems are destroyed. Since cranberry farms were built on native wetlands, this presents a unique opportunity: rebuilding wetland ecosystems on where they originally established. Wetland restoration is ramping up in Massachusetts and will continue as more cranberry bogs are retired.

Restoration of wetlands relies on a bit of imagination, a bit of creativity and most importantly, lots of science! Natural wetlands are messy, turbulent landscapes littered with holes and bumps in the ground called hummocks and hollows. These form naturally over centuries as trees fall, leaving holes and exposed ground (hollow) where the roots were, and high areas as the raised root ball becomes overgrown (hummock). As part of the restoration process, we attempt to mimic this microtopography disrupting the flat farmed surface by digging hollows and leaving hummocks. In this study, we quantify changes in the meter-scale microclimate provided by these topographic alterations to determine any substantial benefits that may be gained through this practice. Because the precise post-restoration water table height is unknown, microtopography also ensures both biodiversity and at least some pockets of wetland dominance (success) across the restored landscape.

We measure temperature, vegetation function, and soil moisture before and after restoration in a variety of plots where different microtopographic features will be constructed (control, slash, logs, hummocks/hollows) to see the real-time development of each. Preliminary data indicate that recreating hummocks and hollows has a huge effect on the landscape: hollows are much more moist than the land around them, and hummocks are drier. Average moisture is greater where microtopography is present than where no land surface change was made. Ultimately soil moisture is the key to success of the wetland restoration.