Returning to its roots: the restoration of grassland savanna
The ecological restoration of Phil Hardberger Park presents a remarkable opportunity to recreate and preserve a representative sample of our natural heritage.
It’s not only that wide open expanse of sky meeting the land and waving seas of grasses that is missing from the overgrazed former dairy farm, but also the many other organisms that co-evolved with and are dependent upon these grasslands. Fox, great-horned owls, red-tailed hawks, quail, armadillo, many butterflies and other insects, and a panoply of wildflowers are some of the organisms that will not exist within Phil Hardberger Park without substantial grasslands to support them.
Prior to European settlement, Central Texas — indeed, most of the state except deep East Texas — was dominated by prairie and grassland savanna. A little over one hundred years later this landscape is much altered. Overgrazing, overpopulation of deer, erosion and absence of periodic fire have drastically changed the vegetational patterns. The great Central Prairie of North America began in Canada; extending southward, it phased into a tree studded savanna in Texas, and reached into northern Mexico. Today it is estimated that as much as 99% of the native American grasslands have vanished.
Phil Hardberger Park is an example of this process. Chosen by Max and Minnie Voelcker for a dairy farm due to its expansive and productive grasslands, the park is now almost entirely dominated by young, second-growth shrubs and trees – mostly persimmon and juniper.
Based on extensive community input, the plan to develop Phil Hardberger Park for public enjoyment is based on three primary principles: 1) recreation, 2) environmental education and 3) ecological restoration of the land. Ecological restoration is essentially the repair of biological communities to maximize their ability to provide “natural services.” Natural services are products and processes provided by nature that sustain the health of our environment, including climate modification, flood control, pollution abatement, biological diversity, ground water recharge, carbon sequestration, creation of soil and erosion control, nutrient cycling, natural pest control, pollination, seed dispersal, maintenance of the composition of the atmosphere and countless other services.
To ensure maximal diversity of plant and animals species and overall ecological health of Phil Hardberger Park we must implement management programs. Nature preserves are not areas to be set aside and left alone. Due to previous and continuing impacts to our ecosystems, we must through management counterbalance negative effects.
Savannah restoration is one of the management goals for Phil Hardberger Park. The natural services at Phil Hardberger Park that will be improved through the restoration of savanna (replacing a portion of the scrub regrowth) include pollution abatement from stormwater runoff, ground water recharge, erosion control and creation of soil, and biological diversity.
Restoring the grasslands of Phil Hardberger Park also increases the amount of “edge.” Edge is an ecological concept signifying the zone where two communities intersect, in this case the forest community and the grassland community. The edge combines species of plants and animals from both communities. In addition there are species that prefer this transition zone. Thus the edge is richer in diversity than either of the two communities it joins.
As the grasslands of Phil Hardberger Park are restored and the edge effect increased, we will see (and are seeing) an overall increase in biotic diversity. The increased grasses and other herbaceous plants will support herbivores such as grasshoppers, field mice and cottontails. These in turn will support predators such as reptiles, hawks and foxes. This is a greatly simplified illustration. The actual changes will range from microscopic bacteria to large mammals.
The Master Plan for Phil Hardberger Park designates thirty acres of the original grasslands to be restored. A three-acre pilot project was undertaken in 2009. The area was cleared of 80% of its woody plants. Fifty-five thousand plugs of native grass and perennial wildflowers species were grown. These plants were installed in one morning on September 28, 2009, by over 500 community volunteers as part of National Public Lands Day and through partnership of the Conservancy with the City of San Antonio and Texas Public Radio. The three acres were also over-seeded with a broader mix of native grasses and wildflowers. A temporary irrigation system had been installed to help ensure against potential drought conditions. The irrigation system was used three times in October and November of 2009 and never since. The three acres was an ocean of color throughout spring of 2010 and had blooming, climax native grasses (some over five feet in height) by autumn of that year. Though less colorful, this restored savanna continued to perform well in the record drought of 2011, with almost 100 percent ground cover of native grassland species.
The restored savanna at Hardberger Park is also a living laboratory. Trinity University, St. Mary’s University, University of Texas at San Antonio and others are involved in various studies to increase our knowledge of the restoration and functioning of native grasslands and their inhabitants. Alamo Area Master Naturalists and Boy Scouts seeking their Hornaday Environmental award are assisting with the project.
Our challenge is now to take the restoration of grassland savanna within Phil Hardberger Park to the next level. We have a goal of restoring six additional acres in 2012. This will triple the current size of restored grassland and put us at one-third of our ultimate goal.
Sunday, 25 March 2012