A Decade of Research
A Decade of Research and Restoration at Lehigh Gap Wildlife Refuge
| by Diane W. Husic, Ph.D. |
The following article was originally published in the Summer 2013 issue of Wildlife Activist.
Editor’s note: Diane is the vice-president of our Board of Directors and the volunteer research coordinator for LGNC.
This spring, Lehigh Gap Nature Center (LGNC) celebrated the tenth anniversary of the commencement of the restoration process within the 750 acres of property known as Lehigh Gap Wildlife Refuge or “the Refuge.” In fall 2002, Bob Hoopes, an LGNC board member, wrote an article for the Wildlife Activist entitled “A Dream Come True.” In this piece, he talked about the purchase of the land and the vision for what would happen at this site. Interestingly, he referred to the acquisition of the land as a dream come true, even though the organization had just purchased a barren, contaminated piece of land – a moonscape devoid of life. Textbooks used to include images of the destroyed landscape of Lehigh Gap as a case study of just how bad environmental destruction could be. In his article, Bob described the site at the time:
Conditions on the most degraded part of the mountainside are severe. Little soil remains, and the barren mountainside is dry, windswept, suffering severe cold and extreme heat, and periodically subject to fire.
Despite twenty years of attempts at revegetating other parts of the Palmerton Superfund site on the Kittatinny Ridge, those involved with LGNC were incredibly optimistic that they could make a difference. Bob wrote in the 2002 article:
For years, for some a life time, many have dreamed of a day when the Kittatinny Ridge opposite Palmerton, degraded by decades of industrial pollution from zinc smelting, would again be covered in lush green vegetation …We envision working with nature, which is already reclaiming the land on its own, to accelerate the return of native, natural vegetation in the Gap.
And so with this bold statement, board members and friends of LGNC set about performing what seemed to most an impossible task – reclaiming the land.
We will develop a restoration plan that works with natural processes to reclaim the land more rapidly than it would be reclaimed naturally.
In the second edition of the book entitled Ecological Restoration: Principles, Values, and Structure of an Emerging Profession, published in 2013 by the Society of Ecological Restoration, authors Andre Clewell and James Aronson describe restoration as “intentional,” a process that “aims to enhance biodiversity at an impaired site,” and “reinitiates the ecological processes that were interrupted” by some disturbance (like the zinc smelting process that occurred in the Palmerton area for over eight decades). At the Refuge, the process began with 56 test plots in which various grass seeds were planted and in which an assortment of soil amendments to add compost, microorganisms, some fertilizer and adjust the pH were tried. The result has been not only a successful revegetation effort far surpassing initial expectations, but also the development of a unique laboratory for research and education.
It will be a slow process, one measured in years, for sure. But the annual progress will be visible, the community involvement significant, and the public use and enjoyment of this wonderful natural resource will be secured forever.
How prophetic. Ten years later, we have seen the miracle of recovery, the reestablishment of a functioning ecosystem – a thriving grassland – that is home to almost two thousand species of insects, birds, mammals, and plants. And indeed, the community involvement has been significant, forming the critical keystone of the success of the restoration process.
The very first experiments at the Refuge were the test plots in which trials of different grass seeds and soil amendments were conducted in 2003. A mix of eight warm season grasses were used in all of the test plots and 2 annual cool season and 4 perennial cool season grasses were tested in selected plots to see which would grow. Various soil amendments were used to add nutrients, water-retaining organic material, and microorganisms back to the poor mineral soil and to raise the pH of the soil which was low due to decades of sulfur dioxide emissions from the smelters – a chemical that forms acid rain.
All restoration projects should be monitored to see if the desired outcomes are being obtained, but we have learned that this is seldom the case. Yet over 10 years ago, LGNC founders – with not a restoration expert in the bunch – knew the importance of long-term studies. Monitoring is important to follow the progress of the revegetation efforts to learn if the desired ecological outcomes (re-greening the mountain with a thriving grassland habitat) could be achieved. In addition, because the Refuge is within a Superfund site, the EPA requires that monitoring be done as part of risk management. This helps to ensure that remediation actions minimize threats to human health and wildlife. The metal contaminants in the soil (zinc, lead, and cadmium), which are remnants of decades of zinc smelter operations, can be toxic to plants, wildlife, and humans. Thus, revegetation should help prevent erosion of the metal-containing dirt down the mountain, and the plants that grow should not take up metals because the metals may subsequently enter the food chain or be redistributed to the surface of the ground when leaves drop in autumn. It would be fruitless to recreate habitat only to contaminate the wildlife it attracted. Thus, much of the research that was undertaken over the past decade at LGNC has been linked to this notion of monitoring – be it for scientific curiosity, to meet federal regulations, or to ensure a healthy environment for those who visit the Refuge.
The environmental consulting group Arcadis (originally known as BBL) has done much risk assessment research for the entire Palmerton Superfund site, carefully monitoring whether the EPA goals are being met. Beside this work, the first major study of the Refuge was Phase 1 of an ecological assessment of the site that began in 2005 and was completed in 2007. This project (the report is available on LGNC’s website under the “Resources” tab, and then under “Reports and Documents”) resulted in the identification and mapping of 23 plant communities, recognized the statewide significance of the ridge top hair grass savanna, documented pond and wetland habitats, identified 374 plant species and 48 lichen species (compared to 5 in 1974), light-trapped 403 different insect species, documented stewardship issues and remaining hazards, and set forth some management priorities. Of the plant species identified, 4 are PA-listed (species that are of special concern, threatened, or endangered) and 110 (29%) are non-native. Four insect species are also PA-listed. This report, along with earlier studies (e.g. Rehn, 1903; Reed, 1984; and Jordan, 1975) provided important baseline information in terms of diversity at Lehigh Gap from over a century of time.
When I first became involved with LGNC in 2005, early successional trees such as gray and sweet birch and various aspen species were already pioneering the site. Black gum (tupelo) and sassafras trees were sending new growth from what appeared to be dead trunks. At that time, the gray birch trees were particularly common along the LNE trail from the end of the parking area to the big bend in the Lehigh River (between the arrows on the map above). They weren’t yet prominent in the grassland area. These trees did not look healthy; the birches were stunted, their leaves yellow, and leaf drop occurred in summer rather than fall. Closer inspection showed that they had what is known as leaf marginal chlorosis, which can be caused by nutrient deficiency (especially nitrogen) or stress. Given that the topsoil that once covered the mountain had long eroded off, nitrogen deficiency was not unexpected. Stress could also be due to insufficient water or the presence of heavy metals in the leaf tissue. It was the latter hypothesis that we decided to check.
Studies conducted by students from Moravian College showed that the birch leaves typically had over 1,000 parts per million (ppm) of zinc in them. Another way of thinking of this is that for every 1,000 grams of leaf tissue, there is about 1 g of zinc present. Aspen leaves were shown to have between 1,000 and 2,200 ppm of zinc, but sassafras had lower levels (100 – 300 ppm). The zinc levels in leaves from black gum trees were even lower. More recent studies done in 2012 showed that the birch trees that are now common in the grassland also take up zinc into the leaves, and the highest levels of uptake observed seem to be where the smoke plumes from the former West Plant blew across the Refuge.
Numerous other plant species at the Refuge have been tested for metal uptake. The warm season grasses take up relatively low levels of zinc (one of the many reasons they were chosen for revegetation). In contrast, sandwort (Minuartia patula), the low-growing plant that blooms profusely in the Palmerton area from the end of May until mid-June, can take up as much as 15,000 ppm. This plant is a known hyperaccumulator of heavy metals and is not native to Pennsylvania. In fact, the Palmerton area is the only place in the state where sandwort is found. The plant seems to serve as a bioindicator of where metal-contaminated soil is present.
If plants take up the metals from the ground, there is a chance that the contaminants can enter the food chain – from insect (or deer) herbivory of the leaves, birds or mammals eating the seeds such as the birch catkins, or insects (or birds and bats) that nectar on or pollinate flowers. Previous studies conducted by Arcadis suggested that the most significant risk was to birds, such as Robins, that eat worms living in the contaminated soil. These studies, however, were conducted prior to the occurrence of succession or habitat enhancement planting at the Refuge. It remains to be determined whether birds or insects at the Refuge have elevated levels of metals in their bodies.
Plants that take up the metals end up redistributing the metals to the ground surface. An important goal of the EPA is to immobilize the metals so that they can’t wash into the river or be mobilized into bioavailable forms. Given the high metal content in birch leaves and the prevalence of this species at the Refuge, the metal uptake studies have been important in helping to develop management plans for the grassland, and contributed to the decision to conduct a test burn (prescribed fire) on 10 acres of the grassland this past spring.
There are many intriguing questions related to why some plants take up the metals and others don’t and why some plants can take up high levels of zinc and show few, if any, negative consequences (e.g. the sandwort). Others, like the gray birch, show significant levels of stress. Recent experiments showed that photosynthetic efficiency is diminished in birch leaves that contain elevated levels of zinc. Plant anatomy or biochemical characteristics of a particular species likely determine whether or not plants take up the metals.
A search of the research literature suggests that soil organisms known as mycorrhizae may also be involved. These fungal species have complex and poorly understood relationships with plant roots, sometimes having symbiotic (beneficial) relationships. In other cases, they can be pathogenic. What is known is that they are involved in the uptake of nutrients from the soil and may help confer metal tolerance to a plant. Brenda Casper and her graduate students from the University of Pennsylvania are studying the return of these organisms to the Refuge soil, their relationships with the grasses, birch trees, and other species, and their ability to impact metal uptake.
A group of scientists from Wilkes College have been collecting insects as well as feathers from birds captured in mist nets in order to understand what these organisms are eating on the Refuge. Based on carbon isotope ratios, they can tell if the animals have a preference for C3 or C4 plants. These designations are related to plant physiology; the latter, C4 plants, represent the warm season grasses that have been planted at the site. Much to the surprise of the researchers, it turns out that a large percentage of species were foraging on C4 plants. This demonstrates a rather rapid adaptation to the new conditions at the Refuge (i.e. the grassland on the once denuded land and on a ridge that historically was covered with deciduous forest).
Grasses alone don’t make for a fully functioning ecosystem. Rather, you need a greater diversity of plants to attract pollinators and provide nectar, as well as legume plants that add nitrogen to the soil. In 2006, seeds from eleven species were distributed in the grassland, and by 2009, seven of the eleven were found blooming. In addition, there have been other plantings including trees and 150 plugs each of nine native species with matched sets inside and outside of deer exclosures constructed on the Refuge. Monitoring of succession (how plant cover, size, and diversity changes over time), survival of these plantings, herbivory, and invasions by non-native species are all being monitored by interns, research students from local colleges, and many volunteers.
Back in 2002, when Bob Hoopes wrote his article for the Wildlife Activist, he noted that
We plan to immediately launch a program of monitoring to document and study the ecological succession that takes place as the land reverts to a natural state. This monitoring process holds tremendous long-term educational potential.
I wonder if he had any idea of just how much monitoring would actually take place and how many people would take part in this essential research and the educational opportunities at this site!
A major research initiative at the Refuge included the studies comprising Part II of the Ecological Assessment, completed in 2010. This project involved over 60 students, faculty, and conservation experts, plus students visiting the Refuge with their classes, members of the Naturalists Club, and volunteers (citizen scientists). The report (available at LGNC website) includes three books of material, so obviously, only a few highlights can be provided here.
The report includes updates on plant communities, diversity, and succession from Part I of the assessment. Additionally, extensive surveys of animals of the Refuge were also done to determine what diversity was now being being supported. Mammal surveys were conducted by visual observations, trail cameras, live traps, and netting for bats. In all, 23 species of mammals have been reported for the Refuge. This represents over 40% of the 51 documented species for Carbon and Lehigh counties as determined by the Carnegie Museum of Natural History and also includes porcupines, which are not on the Carnegie list. It is worth reminding readers that, just 10 years ago, this portion of the mountainside was lifeless.
Birds have been an extensively studied group of species on the Refuge, which is not surprising given that the Wildlife Information Center was formed by a group of birding enthusiasts. Since purchasing the property, 169 species of birds have been reported. Year-round surveys led by Corey Husic were conducted between 2006 and 2009 in which locations of 31,000 birds representing 139 species were recorded. The findings were compared to surveys done by Rehn in 1903 (before the peak smelting operation years) and by Reed in 1984 (just after the smelting operations had ceased). There is also data on breeding birds in the range of habitats on the Refuge property. Birds using scrub and grassland habitats are particularly interesting since these habitats are increasingly rare in the eastern U.S.
Twenty-nine species of amphibians and reptiles have been recorded at the Refuge, representing 50% of the species documented by the PA Herpetological Society for the entire Commonwealth. Sean Bankos and Clare Kubik have done much of this work. In fall 2012, Frank Kuserk’s ecology class from Moravian College participated in TurtlePOP, a nation-wide project designed to gather long-term information on turtle populations. Turtles and other reptiles have experienced significant declines in recent years due to road kill, habitat loss from development, and potentially other factors. The ecology class trapped, marked for future identification, and measured over 50 Eastern Painted and Musk turtles at the ponds. The evidence, at least for these two species, is that populations are at healthy levels. In all, six turtle species have been recorded at the Refuge. The only other native turtle species in the region is the endangered Bog Turtle.
Like birds and plants, there has been an incredible amount of research at the Refuge related to insects. Volunteers and students have used a variety of collection methods and devices to gather species, and many experts have contributed their time and expertise to help identify and classify specimens. Anita Collins, a retired honeybee expert from the USDA and president of LGNC board, Sam Droege of the USGS, and John Rawlins of the Carnegie Museum of Natural History have been extremely important contributors to this work. To date, 851 species of insects have been identified at the site.
Insects are important pollinators and food sources and also serve as indicators of different habitats on the Refuge. The 46 butterfly species and the 17 species each of damselflies and dragonflies attract enthusiasts and photographers. The Monarch butterlies that migrate through the Refuge each fall have been of particular interest, and many people have participated in Monarch tagging events. This study contributes to an international project (http://www.monarchwatch.org/) that aims to better understand information about migration routes and survival of these butterflies, which appear to be in decline.
The native bee studies at the Refuge have also captured a lot of attention. With declines in the honeybee population, interest in native pollinators has grown. Inventories at Lehigh Gap are part of a national effort to document which species of native bees are present in different parts of the country. This study also showed the role of non-native plants such as the Spotted Knapweed in attracting non-native insects. Of particular interest was the re-discovery of the Lithurgus chrysurus, a wood-boring bee species from Europe which turned up at Lehigh Gap and that was discovered by members of the Naturalists Club.
Other diversity research has included studies of the soil microbes and soil-borne decomposers, and of aquatic macroinvertebrates (mainly insect larvae and small crustaceans), which serve as indicators of water quality of streams and ponds.
The monitoring of succession, bioavailability of the metals, and effectiveness of the management plans for the Refuge will continue for years to come. We are conducting studies to see if the grassland might become a place to reintroduce the endangered Regal Fritillary butterfly. Along with these studies, data on microclimate will indicate how conditions change with vegetation and geological features. Long-term studies of the impact of climate change and resiliency to environmental change as a result of restoration and creation of a grassland (as opposed to a forest) will also be documented. All of this information will be added to the extensive bibliography of the history and research of Lehigh Gap – a project initiated by Meredith Wright in 2009. Her annotated bibliography consisting of over 500 entries is available on the LGNC website. Given the many contributions to LGNC library and the restoration story that have occurred since Meredith finished her compilation, this will need to be updated.
In the book on ecological restoration mentioned earlier, Clewell and Aronson point out other aspects of restoration that are not typically considered by scientists, but have been essential elements of the story of the restoration and research at Lehigh Gap Wildlife Refuge. The first is that “restoration strengthens our communities.” The obvious example of this is at contaminated sites, like the Palmerton Superfund site, where work is done to decrease the health and safety risks thereby making the community where the site exists, and the people that live and recreate there, safer. But another point these authors make, which is particularly relevant to LGNC, is that the restoration process is a “communal process” – where people join together and through joint participation in a common pursuit help to fix the problem and gain a sense of pride in the results. They note that “participation in community-base restoration develops a strong sense of place and a sense of community”, can lead to “civic celebrations” and that “ecological research can be viewed as a cultural endeavor in the same manner as is education.” The authors note that the restoration process reconnects us, as individuals involved in the project, to the rest of nature, and allows for a form of personal restoration and reinvigoration.
These elements of restoration described by Clewell and Aronson are indeed evident in the sheer numbers of people who work at Lehigh Gap as volunteers in education, research, and other activities. This was all predicted by Bob Hoopes in his “A Dream Come True” article and by others over a decade ago when they not only had the vision to the purchase the property and believe that it could not only be restored, but also to become such an important center for people to gather, learn, do research, and celebrate the resilience of nature.