Watching Grass Grow

Watching Grass Grow: Update on the Restoration Process at Lehigh Gap

Watching grass grow is a metaphor for the dull and the boring.  But watching grass grow on the long barren Kittatinny Ridge at Lehigh Gap is exciting indeed!  Eighty years of zinc smelting left the mountainside barren and contaminated with heavy metals.  While some vegetation has returned in the 20 years since the West Plant of the Horsehead Resources facility was shut down, there are still large barren areas visible from Route 248 near Palmerton.

The Wildlife Center’s plan to revegetate the barren mountainside on our Lehigh Gap Wildlife Refuge relies heavily on the use of native warm-season grasses. These are the grasses of the Midwestern prairies, but they are native to Pennsylvania as well and can be found growing naturally on the Refuge, especially along the railroad beds.  They include species such as Big and Little Bluestem, Indian Grass, Switch Grass, and Deer Tongue.

In May, Viacom’s consulting environmental engineer, Chris West began overseeing the planting of 56 one-acre test plots of these remarkable grasses.  The test plots all received the same mix of the warm-season grasses, although some of the test plots also included quick sprouting cool-season grasses to provide erosion control.  The plots also received varying amounts of lime, fertilizer and organic material such as straw or manure.  These test plots will be used to help determine the best mixture of grasses and amendments to use for full-scale planting next year.

Distributing these materials and seed on the mountain’s moderate slopes has been an experiment in itself.  A Caterpillar Challenger tractor that runs on bulldozer-like rubber treads crawls along the rocky mountainside pulling a large manure spreader that contains the mix of seed and materials to be used on the test plot.  One pass with the spreader applies everything to be added to that plot.  In spite of a few breakdowns and some worn-out treads, the method has proven successful.

In less than two months, the mountain is turning green!  But wait – what’s growing? Warm-season grasses are notoriously slow to germinate, and remain small the first two years while they are growing roots that reach deep in to the soil.  (You may wonder “What soil?” but there is a deep layer of mineral soil between and under all those rocks.)  This growing strategy makes these grasses poor competitors with fast growing weeds, but makes them excellent candidates for this barren mountainside with little weed competition.  The deep roots allow these grasses to grow and stay green all summer long, reaching heights of up to eight feet or more at maturity in some species.

So what is all that green on the mountain that can be seen when driving along Route 248? It is mostly the annual cool-season grasses added to the mix, plus grasses that were brought in with the organic compost.  For example, we have oats growing everywhere straw was used – obviously the straw was from an oat crop.  These species are expected to die off, but the tiny warm-season grasses that can be found in all the test plots should remain and take over.  In fact, the amount of germination and growth of the warm-season mix is surprisingly good and very encouraging, but we will not be certain of their long-term survival until spring.

The best news comes from some very rocky and steep areas where we have scattered a warm-season mix with no other amendments – just grass seed.  Bill Mineo and Sherry Acevedo of the D&L National Heritage Corridor led this work with the help of young people from the Lehigh County Juvenile Probation program.  This planting was done in June, and by early July, we were already able to find many germinated seeds among the rocks, showing that we may not need any amendments at all to revegetate the remaining areas.

Warm-season grasses take three years to reach maturity, spending the first two years growing roots deep underground.  These deep roots allow the grass to grow rapidly and stay green even in times of drought.  Because of their deep roots and naturally slow uptake of heavy metals, these grasses will help us accomplish the seemingly conflicting goals of the Superfund plan – revegetate the mountainside without mobilizing the residual zinc, lead, and cadmium into the food chain through the vegetation.

These grasses are also an ecologically sound way to revegetate. Warm-season grasses build rich soil by adding organic material to the mineral soil.  Each year, about a third of the grass root system dies and becomes organic matter in the soil, building fertile soil from the bottom up.  At the same time, on the surface, the profusion of grass that dies back each year adds organic matter to the surface.  Thus, over time, fertile soil will again blanket the mountain and make way for a healthy forest ecosystem to return.

Meanwhile, the prairie grass is excellent wildlife habitat.  Some of the species provide forage for grazers, which is good nutrition to establish a healthy small mammal population that will feed a variety of predators, including migrating raptors.  All the grasses produce seeds in abundance that are relished by birds ranging from sparrows to Wild Turkeys.  The grasses also provide nesting habitat for several species of special concern in the East, including Bobolink, Henslow’s Sparrow, and Upland Sandpiper.

The green that can be seen on the Kittatinny on the Lehigh Gap Wildlife Refuge is the very hopeful beginning of a process that will produce a grassland habitat that will benefit many species of wildlife.  This grassland will build fertile soil and form the basis for natural ecological succession.  We have a long way to go, but the first steps are very encouraging.  Watching grass grow has never been so exciting!