WHAT THE CONSERVANCY IS DOING
How often do you get the chance to protect an intact natural lake in Indiana? One of the state's last remaining undeveloped lakes and fringing wetlands will forever remain a wild, natural place for the future. Houghton Lake was an opportunity of a lifetime and one that the Conservancy could not resist.
Houghton Lake in Marshall County is a wonderful example of a highly alkaline natural lake. It lies at the bottom of a broad valley that likely once carried off massive quantities of glacial meltwater. The lake is primarily fed by groundwater discharges from the surrounding hills of rolling glacial till. As water seeps through the till, it picks up a heavy load of dissolved limestone, which then precipitates out as marl in the valley bottom. The bottom of Houghton Lake and its shoreline are cement-gray, the color of deep marl deposits. The surrounding wetlands reflect this as well. Extensive fens at Houghton Lake are a mixture of alkaline peat and, nearer the lake, pure marl.
But by no means is Houghton Lake a perfect system. As with most of Indiana, the tillable lands that surround the lake are in agricultural production. Many of those agricultural fields were once fens. Ditches and tiles move water out of the fields and away from our wetlands and the lake. And invasive species are as abundant here as they are elsewhere in the state. One of the worst is common buckthorn, which out-competes native plants for nutrients, light, and moisture and degrades wildlife habitat.
The Nature Conservancy's restoration goals for Houghton Lake were deceptively simple. To the maximum extent possible, we want to restore groundwater flow and quality to the lake and wetlands. To accomplish this, we had to remove buried tiles from the agricultural fields and fill in many of the ditches that in the past had intercepted groundwater before it discharged to the lake. This change moves more water through the lake itself, helping to flush out chemicals and nutrients from adjacent farm fields that have accumulated over the decades. Now that the restoration is complete the annual flush of algae the lake experiences should decrease as nutrients leach out of the system over the years. This will improve habitat for native fish, amphibians, and reptiles as the water clears over time.
What remains so remarkable for Indiana, is the fact that an entire site, all 360.63 acres, was purchased as a single unit. Unlike most conservation areas where we and our partners work piecemeal, the lake and surrounding wetlands were located in the heart of a family-owned farm that was on the market. With a decisive stroke, we were able to purchase the half of the farm that included the 100+ acres of high-quality lands that included the lake and all the surrounding wetlands. We also acquired around 90 acres of lower-quality natural lands that include old marl pits, second-growth forests and a very interesting small glacial outwash rise that supports about 5 acres of overgrown oak savanna. Now that the sand and gravel soils on this small rise will have been successfully restored and managed the area provides important nesting and foraging habitat for turtles and snakes that once had limited opportunities to lay their eggs near the wetlands.
But perhaps most importantly for the long-term, we control almost 180 acres of agricultural fields that surround the site. These include a mix of rolling hills that drain agricultural runoff towards the lake, as well as tiled muck fields that were once part of the wetlands themselves. These lands have the most impact on the future of the site and the rich variety of species it supports. The agricultural drainage system is obviously designed to pull water from adjacent muck soils. This decreases the extent of the wetland complex, but also diverts the flow of groundwater away from the lake. Many of the ditches cut deeply into the perimeter of the natural area, creating fens that seem unnaturally dry. The lake itself is much lower than it once was because of this drainage. Much of the fen, including portions that grow on heavy marl soil, is on the recently exposed lake bottom. Lowering the water table has helped problematic species as well, allowing both native and non-native aggressive species to become well-established on ditch spoils and field edges.
Preparing the Land at Houghton Lake
As we mentioned before, preparing the tract for restoration has been a long, arduous task. Eradicating the invasive species from the land has been our first task. In the spring/summer of 2007, stewardship worked to remove reed canary grass from the ditch and field edges. Attention will soon be turned to common buckthorn and the native cottonwood trees lining the ditches. Though a native species, cottonwoods must be downed to reduce the number of seeds that shower the landscape and potentially turning our restoration into a dense thicket.
In the spring of 2009, our invasive species removal efforts shifted towards purple loosestrife. Efforts to fight it and stem its invasion are costly, time-intensive and often unsuccessful. To help battle purple loosestrife at Houghton Lake, we turned to some unlikely partners. European beetles, Galerucella calmariensis and G. pusilla, have been used since the early 1990's in Indiana as biological control agents for purple loosestrife. In Indiana and numerous sites throughout the Great Lakes, bio-control programs have been reported to have significantly reduced dense infestations, generally within five years of the initial release. Extensive research and testing have shown these beetles would not pester other plants. Therefore, once populations of purple loosestrife start to decline, so will the beetles.
A Great Success
Since we started preparing for this restoration in 2006, we've:
• plugged three ditches to restore the hydrology of the site and create 8 acres of wetlands
• installed a water control structure at the south end of the lake to control the water level
• collected 56 pounds of seed to plant with volunteers
• purchased an additional 852 pounds of seed to plant
• planted 135 acres with seed from 140 native species
• planted 4,500 native plant plugs
• treated invasive plants (reed canary grass, cottonwoods, Phragmites, Canada thistle, buckthorn, and cattails) on 402 acres, 22 miles of ditches, and 11 miles of field borders, including many retreatments
• burned 191 acres of habitat with three burns
Volunteers donated a total of 360 hours, getting their hands dirty to help with the restoration. Full-time and seasonal staff, along with AmeriCorps members, spent over 3,800 hours in the field working on the restoration.
This restoration is finished in the sense that all the necessary pieces – restored hydrology and diverse seed mix – are in place to develop into diverse habitats, but we’ll continue to manage the site to control invasive plants and to introduce fire management.