restoration of a severely impacted riparian wetland system — the pen branch project

Ecological Engineering 15 (2000) S3–S15

Guest editorial

Restoration of a severely impacted riparian wetland system— The Pen Branch Project

Christopher Barton a, Eric A. Nelson b, Randall K. Kolka c,Kenneth W. McLeod d, William H. Conner e, Michelle Lakly f,

Douglas Martin b, John Wigginton g, Carl C. Trettin a, Joe Wisniewski h

a Center for Forested Wetlands Research, USDA Forest Ser6ice, SREL – Drawer E, Aiken, SC 29802, USAb Sa6annah Ri6er Technology Center, Westinghouse Sa6annah Ri6er Company, USA

c Department of Forestry, Uni6ersity of Kentucky, USAd Sa6annah Ri6er Ecology Laboratory, Uni6ersity of Georgia, USA

e Baruch Forest Science Institute, Clemson Uni6ersity, USAf Institute of Ecology, Uni6ersity of Georgia, USA

g School of Forestry, Auburn Uni6ersity, USAh Wisniewski and Associates Inc, USA

www.elsevier.com/locate/ecoleng

1. Introduction

The Savannah River Swamp is a 3020 haforested wetland on the floodplain of the Savan-nah River and is located on the Department ofEnergy’s Savannah River Site (SRS) near Aiken,SC (Fig. 1). Historically the swamp consisted ofapproximately 50% baldcypress-water tupelostands, 40% mixed bottomland hardwood stands,and 10% shrub, marsh, and open water. Tributer-ies of the river were typical of Southeastern bot-tomland hardwood forests. The hydrology wascontrolled by flow from four creeks that draininto the swamp and by flooding of the SavannahRiver. Upstream dams on the Savannah Riverhave caused some alteration of the water levelsand timing of flooding within the floodplain(Schneider et al., 1989).

Major impacts to the swamp hydrology oc-curred with the completion of nuclear productionreactors and one coal-fired powerhouse at theSRS in the early 1950s. Water was pumped fromthe Savannah River, through secondary heat ex-changers of the reactors, and discharged intothree of the tributary streams that flow into theswamp. Flow in one of the tributaries, PenBranch, was typically 0.3 m3 s−1 (10–20 cfs) priorto reactor pumping and 11.0 m3 s−1 (400 cfs)during pumping. Elevated flows continued from1954 to 1988 at various levels. The sustainedincreases in water volume resulted in overflow ofthe original stream banks and the creation ofadditional floodplain. Accompanying this wasconsiderable erosion of the original stream corri-dor and deposition of a deep silt layer on thenewly formed delta. Heated water was dischargeddirectly into Pen Branch and water temperature inthe stream often exceeded 65°C. The nearly con-E-mail address: [email protected] (C. Barton).

0925-8574/00/$ - see front matter © 2000 Elsevier Science B.V. All rights reserved.

PII: S 0 9 2 5 -8574 (99 )00084 -1

C. Barton et al. / Ecological Engineering 15 (2000) S3–S15S4

Tab

le1

Tre

atm

ent

zone

desc

ript

ion,

site

prep

arat

ion

and

plan

ting

arra

ngem

ent

for

the

Pen

Bra

nch

syst

em(N

elso

net

al.,

2000

) Pla

ntin

gsc

hem

eT

reat

men

tzo

neA

rea

(ha)

Site

desc

ript

iona

Site

prep

arat

ionb

Aer

ial

herb

icid

eap

plic

atio

n(S

ept.

1993

).U

pper

Cor

rido

r74

7tr

ees

ha−

1(D

ec.

1993

–Jan

.19

94).

24M

esic

bott

omla

ndw

ith

30–8

0cm

ofC

ontr

olle

dB

urn

(Nov

.19

93)

stan

ding

wat

erin

wel

lde

fined

stre

am10

78tr

ees

ha−

1(J

an.

1995

)ch

anne

ls(1

–2)

duri

ngth

egr

owin

gse

ason

.V

eget

atio

ndo

min

ated

byde

nse

will

owth

icke

tsP

oorl

ydr

aine

dbo

ttom

land

wit

hw

ater

16L

ower

Cor

rido

rN

one

747

tree

sha

−1

(Feb

.an

dM

ar.

1993

).54

9tr

ees

ha−

1(J

an.

and

Feb

.19

95)

tabl

e20

–30

cmbe

low

the

soil

surf

ace

duri

ngth

egr

owin

gse

ason

.B

raid

edst

ream

wit

h4–

5flo

wpa

ths.

Veg

etat

ion

dom

inat

edby

will

owth

icke

tsan

dgr

assy

open

ings

Con

tinu

ousl

yflo

oded

swam

pex

cept

on10

78tr

ees

ha−

1(J

an.

and

Feb

.19

95).

AH

erbi

cide

appl

icat

ion

on12

haof

leve

es46

Del

tapo

rtio

n(4

.9ha

)w

aspl

ante

dat

500

tree

san

dal

luvi

alde

posi

tsfo

rw

illow

cont

rol

ridg

esne

arth

em

outh

ofth

est

ream

,(S

ept.

1994

)ha

−1

due

tost

andi

ngw

ater

whe

rew

ater

tabl

eis

foun

d20

cmbe

low

the

soil

surf

ace.

Veg

etat

ion

dom

inat

edby

catt

ails

(:66

%)

and

will

ows

(:33

%)

aD

escr

ipti

onpr

ior

tore

stor

atio

n.b

Pre

para

tion

for

plan

ted

sect

ions

only

.

C. Barton et al. / Ecological Engineering 15 (2000) S3–S15 S5

tinuous flooding of the swamp, the thermal loadof the water, and the heavy silting resulted incomplete mortality of the original vegetation inlarge areas of the floodplain (Fig. 2).

In the years since pumping was reduced, earlysuccession has begun in the affected areas. Herbs,

grasses, and shrubs dominate these areas. Fewvolunteer seedlings of heavy-seeded hardwoods orbaldcypress have been found in the corridor areas.Research was conducted to determine methods toreintroduce tree species characteristic of more ma-ture forested wetlands. Three restoration strate-

Fig. 1. Locator map for the Pen Branch study area on the Savannah River Site, SC.


Fig. 2. Aerial view of the Pen Branch corridor prior to restoration (Nelson, 1980).

gies were formulated to address the differing con-ditions of the Upper Corridor, Lower Corridor,and the Delta regions of the impacted area (Fig.1). Site preparation began in 1992 and plantingfollowed in the lower corridor during Feburaryand March of 1993 (Table 1). The upper corridorand the delta were planted in January of 1994 andJanuary and Feburary of 1995, respectively. Por-tions of the upper and lower corridors were re-planted in 1995 to compensate for mortality(Dulohery et al., 1995). Approximately 25% of therestoration area was reserved for nontreated, non-planted control strips (Nelson et al., 2000).

Approximately 8700 seedlings were planted inthe lower corridor (16 ha) at a target density of747 trees ha−1 without any site preparation. Theupper corridor (24 ha) was planted after the appli-cation of a wetland-approved herbicide and aprescribed burn, also at a target density of 747trees ha−1. Herbicide application and prescribedburning were performed to control a dense blackwillow (Salix nigra) overstory and to clear brushand vines from the planting area. The delta (12ha) was planted after the application herbicide,without burning, at a target density of 1078 treesha−1. Replantings in the upper and lower corri-dors were performed at a density of 1078 and 549

trees ha−1, respectively. Tree species included inthe plantings were overcup oak (Quercus lyrata),swamp chestnut oak (Quercus michauxii ), nuttalloak (Quercus nuttallii ), willow oak (Q. phellos),cherrybark oak (Quercus pagodaefolia), waterhickory (Carya aquatica), persimmon (Diospyros6irginiana), green ash (Fraxinus pennsyl6anica),sycamore (Platanus occidentalis), swamp black-gum (Nyssa syl6atica var. biflora), water tupelo(Nyssa aquatica), and baldcypress (Taxodium dis-tichum). Species composition and selection werebased on the hydrological gradient from the uppercorridor to the delta.

Because of the operational design of therestoration project, a research program was devel-oped to document ecosystem response. Informa-tion pertaining to the impact of disturbance andeffects of restoration on Pen Branch were evalu-ated through studies that examined the followingparameters: stream hydrology, seedling survivaland competition, aquatic insect community dy-namics, revegetation techniques, fish ecology andstream habitat, autotroph and macroinvertebratecharacterization, organic matter decompositionand nutrient mineralization, and terrestrial verte-brate distribution. In most of these studies, mea-surements were made in both the restored system


and in one or more minimally disturbed referencesystems (Meyers Branch, Upper Three RunsCreek and Tinker Creek). Some studies also in-cluded control systems (Fourmile Creek and SteelCreek), which experienced a thermal impact simi-lar to that of Pen Branch, but were hydrologicallyrestored at an earlier date. Findings from many ofthese research efforts were presented at the PenBranch workshop. The highlights and key pointsof the workshop are detailed in the followingsections.

2. Hydrology

Water levels in the Savannah River Swamp areinfluenced by the stage height of the SavannahRiver, local drainage, groundwater seepage, andinflows from four tributaries; namely, BeaverDam Creek, Fourmile Creek, Steel Creek, andPen Branch. The ability to predict water levelswithin the swamp was deemed necessary for thedevelopment of a restoration strategy for PenBranch, particularly for the selection of suitablevegetation species. Chen (1999) discussed the useof the TABS-MD modeling system to evaluatewater levels and hydrological influences in theswamp. Based upon boundary conditions fromsediment transport, roughness coefficients, in-channel flow, and groundwater flow, water levelsin the swamp were predicted for a range of flowconditions in the Savannah River and dischargesfrom Pen Branch. Subsequently, the model pro-vided a more precise indicator of flooding suscep-tibility within the restoration area.

Kolka et al. (2000a) examined the hydrologicconditions in a restored section of Pen Branch,two disturbed but recovering systems, and in theMeyers Branch reference site to evaluate the influ-ence of restoration on hydrology. Water tableelevations in the uplands and bottomlands of thereference site were found to be significantly higherthan that of the disturbed sites. Throughfall andevapotranspiration were elevated in the referencesystem over that of the naturally recovering sites,and to an even greater extent over the restoredarea. Enhanced canopy closure across the succes-sional gradient is likely responsible for these dif-

ferences. Results from the study indicated that theindustrial hydrology effect is still impacting PenBranch, but the system appeared to be rebound-ing. Kolka (1999) noted that restoration of thenatural hydrology cannot be fully achieved untillost soil functions and properties are regained.

3. Vegetation establishment and competition

Vegetation studies were performed in the Sa-vannah River Swamp and adjacent watersheds toassess reforestation efforts and to identifyparameters which may benefit future restorationactivities. McLeod et al. (2000) examined the useof 24 tree species for restoring a bottomlandforest in the thermally impacted Fourmile Creek.Results indicated that only the most flood-toler-ant species, such as baldcypress and water tupelo,were capable of surviving in areas occasionallyinundated with 1–2 m of water. Green ash, waterhickory and overcup were also found to exhibithigh survivability (\90% in one experiment), butonly in sites that were not permanently flooded.Three additional oak species (Q. michauxii, Q.nuttallii, and Q. phellos) were shown to have goodsurvival in areas with a slightly higher elevation.Survival of the least expensive planting stock,bareroot saplings, was nearly equivalent to thatobserved for balled and burlapped trees. How-ever, McLeod warned that the bareroot stockheight must exceed that of the water level duringthe growing season. In addition, operationalproblems associated with excessive root pruningand the mishandling of stock under such un-friendly (mucky) conditions may have resulted insome losses. Tree shelters were recommended inareas with high herbivore pressure, but other silvi-cultural techniques, such as fertilization or herbi-cide application, were not deemed necessary.When asked what was responsible for the lack ofeffect when the herbaceous competition was con-trolled, McLeod (1999) suggested that algae accu-mulation on herbaceous vegetation while floodedwould weigh down the herbs and reduce the dele-terious influence on tree growth.

The use of tree shelters in Pen Branch wasexamined to assess the effect of herbivory on


reforestation and to further identify measures forthe enhancement of seedling survivability.Seedlings of baldcypress, water tupelo, swampblackgum, and green ash were planted in fourareas within the Pen Branch delta. Fifty percentof the seedlings were protected with 1.5-m tall treeshelters. After 5 years, Conner et al. (2000) re-ported survival rates from 67 to 100% forseedlings in tree shelters and 2–90% for thosewithout the shelters. High mortality of theseedlings without tree shelters was attributed tobeaver damage. Resprouting of baldcypressseedlings that were clipped by the beavers wasobserved, and the new shoots often exceededgrowth levels exhibited by undamaged plants.However, seedlings of other species tended to dieonce clipped. Elevated height by shelteredseedlings was detected during the first year, butgrowth differences declined thereafter such thatthe two groups were approximately equal by thefifth year. Although the use of tree shelters willadd to the cost of reforestation (approximately $2per tree), Conner (1999) suggested that the shel-ters not only provided excellent protection fromherbivory, but also aided in reducing competitioneffects from herbaceous plants. Moreover, the useof shelters to increase survivability in sensitive orimportant areas, such as the stream banks, mayjustify the extra expense.

Dulohery et al. (2000) examined the effect of anundisturbed, partially thinned, and completely re-moved black willow canopy on four bottomlandtree species (green ash, baldcypress, swamp chest-nut oak, and water tupelo) that were planted inthe Pen Branch and Fourmile Creek corridors.Seedlings in the control area (willows remaining)exhibited elevated growth during the first year,but treatment differences were not evident in thefollowing 4 years. Alterations to the willowcanopy also had no effect on seedling survival,however, mortality differences between the se-lected species was observed. By age 5, over half ofthe baldcypress and green ash seedlings werealive, while most of the swamp chestnut oak(73%) and water tupelo (83%) had perished. Du-lohery (1999) noted that the high mortality maybe attributable to the use of genotypes that werenot well suited for growth in the study area, or

possibly to herbivory. The influence of an intactwillow canopy on hydrology, soil temperature,and herbaceous competition may have providedsome ‘nurse crop’ growth benefits during the first2 years. As a result, Dulohery suggested thatoverstory competition should not be removed un-til after the second growing season.

The status of canopy coverage and macrophyteabundance in treated (restored) and untreatedsections of Pen Branch, a naturally recoveringsection of Fourmile Creek, and in two relativelyundisturbed reference streams (Upper Three Runsand Meyers Branch) were evaluated by Fletcher etal. (2000). Results indicated that the level ofcanopy cover increased across the successionalgradient. A fully open herbaceous canopy wasobserved in the Pen Branch treatment section,while the post-thermal control systems exhibited amoderately closed canopy of herbaceous plants,shrubs, and willows. The undisturbed systems, onthe other hand, displayed a relatively closed hard-wood tree canopy. The aquatic macrophyte abun-dance in these systems was inversely related to thedegree of canopy closure. For example,macrophyte abundance was highest (82% cover-age) in the Pen Branch treatment system, whichhad the least amount of canopy coverage, andlowest (B2%) in the fully closed reference sites.However, canopy closure in the control section ofPen Branch was higher than that observed inFourmile Creek, which exhibited a lowermacrophyte abundance. This may be explained bythe presence of submergent macrophytes in PenBranch that were absent in Fourmile Creek.Fletcher (1999) also suggested that differences inseed dispersal within the two corridors may reflectmacrophyte abundance. In addition, differences incanopy closure in the controls may be indicativeof a successional change from the dense willowspecies in Pen Branch to the more sparse riverbirch found in Fourmile Creek.

4. Instream fauna

An assessment of the recovery status of thelower food chain community in Pen Branch wasdiscussed by Lakly and McArthur (2000).


Macroinvertebrate faunal assemblages (using nat-ural substrates), organic matter availability, andinstream structural complexity were examined inPen Branch, both above and below the zone ofthermal impaction, and in Meyers Branch. Thestudy revealed that the abundance and diversityof the lower food chain community has recoveredsubstantially since cessation of the thermaleffluents. However, the resultant communities re-main structurally and functionally distinct due tothe differences in instream structural componentsand energy inputs in each stream. In Pen Branch,the macroinvertebrate community relied on thehigh densities of aquatic macrophytes, while thecommunities in Meyers Branch were associatedwith high concentrations of coarse woody debris.Pen Branch also differed from the referencestreams in morphometry, canopy cover, litter in-puts, and floodplain interaction, which resulted indistinct compositions of macroinvertebrate speciesand instream habitat.

Comparisons between the current conditions atPen Branch and those observed 15 years afterthermal effluents ceased in Steel Creek; however,revealed that the systems are distinct from thereference system in form and function but onsimilar trajectories for recovery (Kondratieff andKondratieff, 1985; Lakly and McArthur, 1999).Notably, Lakly and McArthur (2000) found thatthe functional differences between the systemswere not detected using popular biotic indices;however, the relative distribution of functionalgroups across streams was useful in determiningdifferences in resource utilization and processingby stream biota. When asked whether or notcoarse woody debris should be added to the im-pacted stream as a method to advance the restora-tion process, the speaker replied with anacknowledgment of its potential benefits as a sub-strate material, but warned that it may invokesome deleterious side effects to the stream hydrol-ogy. Moreover, she reiterated that the distinctionbetween macroinvertebrate abundance and diver-sity and their function in the ecosystem should beimportant to establishing relevant mitigationplans and endpoints for future restorations.

Parker et al. (1999) also examined macroinver-tebrate recovery and similarly indicated an in-

creased species abundance and diversity in PenBranch over that observed in Meyers Branch.Parker noted that that the insect communitywithin Pen Branch meets the definition of being‘restored’, but cautioned whether stream commu-nities provide an accurate metric for the measure-ment of restoration success.

Fish assemblages in Pen Branch, FourmileCreek, Upper Three Runs Creek, and MeyersBranch were examined to assess differences be-tween the recovering and undisturbed streams,and to determine if such comparisons could beused as a metric for the evaluation of restorationsuccess. Nonparametric multivariate statisticalmethods and the Index of Biotic Integrity (IBI)were employed to identify potential differences infish assemblage structure. Lesions, malformations,and parasites on individual fish species were alsorecorded as an indicator of ecosystem health.Significant differences in fish assemblage structurebetween the recovering and disturbed streams wasdemonstrated using the multivariate techniques.An elevated species density, a more open canopy,and more aquatic vegetation in Pen Branch andFourmile Creek may have contributed to the dif-ferences. With the exception of one section ofFourmile Creek, however, the IBI did not differbetween the recovering and disturbed sites.Streams that were in early stages of successiondisplayed IBI values that are normally found inintermediate to mature communities. Accordingto Reichert et al. (2000), results indicate that theimpacted systems may be considered ‘healthy’ intheir present state of recovery even though devel-opment is not yet complete. Reichert also indi-cated that a combination of multivariate and IBItechniques may provide a more accurate represen-tation of restoration success than either techniquealone.

5. Terrestrial vertebrates

An assessment of the diversity and abundanceof reptile and amphibian species in unplanted andplanted sections of the Pen Branch corridor, andin adjacent unimpacted riparian zones was evalu-ated. During the period of thermal effluent dis-


charge from the reactors, the Pen branch corridorlikely supported no reptile or amphibian species.However, over 12 000 individuals representing 72species were captured in the 21 month survey thatoccurred approximately 8 years after the thermaldischarges had ceased. Amphibians comprised amajority (:85%) of the captures, and recaptureof all species was limited (12%). Successful repro-duction was documented for 48 species (67%),which indicated that the wetland was functioningas a suitable habitat for these individuals. Resultsalso suggested that the planting regimes and treat-ment design (burning or herbicide application)had little influence on herpetofaunal species as-semblage. However, the unimpacted riparian zonesupported a more diverse population of amphibi-ans and reptiles than the corridor. Hanlin (1999)attributed these differences to the enhancedcanopy cover and litter accumulation foundwithin the riparian zone, and noted that the spe-cies will likely migrate as the plant communitywithin the corridor further develops into a matureforest.

The effect of restoration on breeding bird com-munities in undisturbed (control), partiallythinned and replanted, and completely removedand replanted sections of the upper and lower PenBranch corridor were examined. During the 2-year study, no significant differences in the aviancommunities were observed among the PenBranch treatments. Dead vegetation, new herba-ceous growth, and some scattered hardwoods,however, provided many singing perches and nest-ing sites in the upper corridor treatment sections.According to Buffington et al. (2000), IndigoBuntings (Passerina cyanea) preferred these sitesover the control plots, while the White-eyedVireos (Vireo griseus) and Red-winged Blackbirds(Agelaius phoeniceus) were found to be moreprevalent in the lower corridor and control areas.Censusing in later successional bottomland areas(Steel Creek and Tinker Creek) was also per-formed to provide an index of species expected tooccur in Pen Branch as the vegetation communitydevelops. From this research, Kilgo (1999) notedthat species richness and diversity increased alongthe successional gradient, but abundance was neg-atively related to forest age. Pen Branch was

dominated by short-distance migratory birds,while Tinker Creek was primarily occupied byneotropical migratory birds. The mid successionalSteel Creek (20 years older than Pen Branch and30 years younger than Tinker Creek) exhibited amixture of both migratory groups. Thus, aviandiversity and abundance is expected to change asthe Pen Branch forest matures.

The influence of wetland restoration activitieson small mammal populations has not beenwidely examined. However, monitoring of mam-mal populations within these systems may proveto be a useful indicator of ecosystem health andrestoration success, since these animals eat plantsand are themselves eaten by larger carnivores.Hence, live trapping of small mammals was con-ducted on six transects at Pen Branch and threetransects at Meyers Branch to evaluate commu-nity dynamics in response to the restoration ef-fort. The rice rat, cotton rat, wood rat, and cottonmouse exemplify species that were frequentlycaught using the employed trapping procedure. Ofthese species, only the rice rat primarily occupieswetland areas, however, both the wood rat andcotton mouse utilize bottomlands and swamps.Even though habitat use and movement differedamong the species, no significant differences werefound in capture rates between treatment typesand among transects of a particular stream. Wikeet al. (2000) indicated that the proximity of tran-sects to each other may have been too small tofully encompass the habitat range of these species.

Fliermans et al. (1999) further examined thebefore-mentioned small mammal population in aneffort to assess microbiological diversity in theimpacted and relatively undisturbed stream sys-tems. Microbiological samples from 296 speci-mens collected at 18 traps in Meyers Branch and46 traps in Pen Branch were analyzed using Bi-olog™ technology for the identification of bacteri-ological isolates. Results indicated that a greaterdiversity of bacterial species were found in thecotton mice, than in rice rats or wood rats. Thedata also indicated that the rodents in MeyersBranch were host to a greater diversity of patho-gens than those from the Pen Branch area. Thedifferences are likely attributable to the vegetativevariation between the systems, which comprise the


rodent’s diet. Diversity differences between thesites could converge if the Pen Branch systemmatures to a state similar to that currently foundin Meyers Branch.

6. Soils and carbon

Organic carbon is considered to be a key energysource for forested ecosystems. Carbon accumula-tion within the soil is derived from litter fall, rootturnover, and microbial organisms. Understand-ing spatial and temporal biotic–abiotic interac-tions within a riparian forest may provide insightinto past disturbance activity and may also beused as an indicator of functional recovery. Gieseet al. (2000) examined carbon storage patterns inPen Branch, Fourmile Creek, and Meyers Branchto evaluate the role of successional status andmicro-topography on riparian ecosystem restora-tion. Results showed that the mean productivitybetween each of the riparian forest and associateduplands were not significantly different. Althoughproductivity did not differ across the successionalgradient, Giese (1999) pointed out that qualitativedifferences between the systems reveal that func-tional recovery has not been fully achieved. Soilcarbon was found to be higher in Meyers Branchthan the restored Pen Branch system, and bot-tomland areas generally contained more soil car-bon than the adjacent uplands in all systemsstudied. As expected, organic carbon concentra-tions in soils increased as soil moisture increased.Although successional processes appear to bemoving slowly in the disturbed areas, above-ground biomass and soil carbon data suggest thatthese systems are advancing toward conditionsexhibited by the later successional forests.

Wigginton et al. (2000) examined the processesresponsible for soil organic matter formation, car-bon sequestration, and soil structure developmentacross a successional gradient. Results indicatedthat forest floor organic matter increases rapidlyduring early succession, but declines thereafter.The composition of forest floor material wasshown to change from a herbaceous dominatedsystem in early succession (Pen Branch) to oneconsisting primarily of woody foliage in later

stages (Meyers Branch). Aggradation of soil car-bon was observed in the thermally impacted sys-tems, however, regressional analysis indicated thatit would require over 30 years before Pen Branchsoils reached carbon levels equivalent to 50% ofthat currently found in Meyers Branch. Soil struc-ture characterization also exhibited differencesacross the successional gradient. Pen Branch wasfound to have a disproportionate percentage ofmicroaggregates than the later successional sites,but Wigginton (1999) pointed out that microbialinfluenced macroaggregate formation is likely toincrease as a result of the high organic matterconcentrations found in Pen Branch.

7. Implications for riparian wetland restoration:attendee perspective

Following the workshop, a questionnaire wasdistributed among the attendees to provide themwith an opportunity to further evaluate therestoration project and to contribute additionalinsight that may not have been captured in thepresentations and/or journal articles. The follow-ing is a synthesis of responses and commonthemes from the questionnaire. Although a con-sensus was not achieved for each question, theresponses reflect the multitude of personal opin-ions and uncertainties associated with a project ofthis magnitude from both a management andecological standpoint.

7.1. What were the lessons learned from the PenBranch Restoration?

7.1.1. Major problems

� The site itself represented one of the majorobstacles encountered by all researchers. Lim-ited accessibility to research plots combinedwith the complications associated with per-forming research in an often uncompromisingarea added significantly to the time required toperform simple tasks. Plot development andsampling strategies often had to be altered orcustomized to overcome these unexpecteddifficulties and likely had a profound effect onthe final results of the study.


� Beaver damage to planted seedlings proved tobe a major factor in seedling survival rates. Thedegree of herbivory observed at Pen Branchwas not anticipated, however, valuable infor-mation pertaining to site preparation tech-niques was gained as a result of thedestruction.

� Inclusion of Steel Creek as a middle successionsite and the use of larger unplanted ‘control’areas may have provided valuable informationto further assess the role of parameters such ascarbon cycling, nutrient availability, and hy-drology on reforestation. Increasing the size oftreatment and control areas may also havebenefited studies on terrestrial vertebrates.With few exceptions, the normal ranges ofmovements of these animals (reptiles, amphibi-ans, mammals, and birds) are such that noindividual would have a territory confined tothe limits of one of the plots. Thus, habitatdifferences between the control and experimen-tal zones were difficult to ascertain.

� The hydrologic characteristics of Pen Branchhave become very unpredictable due to floodcontrol dams on the Savannah River andstreambed disturbances from past reactor oper-ations. Uncertainties associated with the cur-rent hydrology forced a conservative approachto restoration, which may have been restrictiveto the restoration effort.

� The acquisition of appropriate planting stock(genotypes, size, species) was also problematicfor an operation of such magnitude.

7.1.2. Aspects o6erlooked

� Tree shelters should have been used in areasconsidered sensitive or important.

� The role of natural seed dispersal methods toassist colonization of gaps that exist in thestream deltas was not examined.

� Characterization of the soil/litter microbialcommunity may have provided useful informa-tion on decomposition at different successionalstages.

� More detailed hydrology and soils data (pre-and post-restoration) could have aided our de-velopment of planting strategies and provided

insight into the degree of disturbance and postrestoration recovery.

� Although not anticipated, examining the influ-ence of herbivory on seedling survival mayhave resulted in valuable information pertain-ing to the revegetation effort.

� A thorough study examining the effects ofcoarse woody debris (CWD) in bottomlandsand streams, and the influence CWD has onstructural stability, carbon and nutrient cy-cling, and biota could have provided someinsight into community structure at differentstages of succession.

7.2. What do we expect Pen Branch to look likein 50 years?

� From a vegetation standpoint, responses to thisquestion were highly varied and ranged from amarsh-like system with scattered trees to thatof a mature forest. A consensus was apparent,however, that the degree of disturbance to thesoils and unpredictable nature of the hydrologywill likely influence species composition andrecovery rates. The appearance of canopy gapsis anticipated in the Delta where reestablish-ment of species is not fully achieved.

� In respect to overall diversity of terrestrial ver-tebrates, the vegetative species necessary tosupport a fauna similar to that of MeyersBranch is currently existing in the Pen Branchcorridor such that the two systems would likelyfunction similarly in 50 years.

� Studies of soil carbon show that more carbonis being added to the soil in disturbed systemsover that of the reference. Through incorpora-tion and time, soil carbon levels will eventuallyresemble that of the mature forest. Based uponthe studies presented at this workshop, soilcarbon and nitrogen in Pen Branch may reachapproximately 75% of the reference level(Meyers Branch) in 50 years.

� Although a wide diversity of herbaceous spe-cies are present in the Pen Branch delta, treespecies diversity is limited and may remain sodue to the wet conditions and limited topo-graphical variation.


� Assuming that the Pen Branch riparian zonecontinues to develop at a rate similar to thepresent, increased instream shading and subse-quent alterations in instream structure shouldresult in a reduction of aquatic macrophytesand associated macroinvertebrate communities.

7.3. What are our recommendations for the futureof this and other restoration projects?

� Utilize the lessons learned from this experimentand identify the techniques and metrics whichwere vital to the outcome of the restoration.From these parameters a comprehensive pack-age for future restorations and long-term mon-itoring can be established in a much moreefficient and cost effective manner.

� Given the influence of herbivory on seedlingsuccess, planting is a necessity in order torestore the Pen Branch delta to forested condi-tions. The use of tree shelters and vegetativespecies of a genotype suited for the particularenvironment may enhance restoration success.

� Periodic reexaminations of the sites and somescaled-down monitoring will be beneficial inmaximizing the information obtained to date,and as a method of continuously reevaluatingecosystem function in the restored system.

� Other restorations may benefit by applying thespecific techniques and metrics which weredeemed essential in the Pen Branch restoration.On the other hand, parameters that remain amystery, such as the influence of hydrology andwater quality on vegetation reestablishment,will require further examination and should bescrutinized in future restoration projects.

7.4. Are we naı̈6e in our use of Meyers Branch asa reference wetland, and in our expectation toreach an endpoint similar to that of the referencesystem?

� According to McLeod (1999) an endpoint willbe reached, the question remains as to whetherthis endpoint is desirable. Any endpoint willprovide some degree of ‘services’. The endpoint

ecosystem will provide some services differentthan the pre-SRS ecosystem, but maybe theseservices will be more beneficial than those pre-viously provided or might have been providedby the undisturbed ecosystem. As such, we arenot even sure what the undisturbed ecosystemwould have looked like if the SRS never ex-isted. The appropriate question may not be‘will it look and function like Meyers Branch?’,but instead ‘does it look and function like wewant it to?’ The reason for rephrasing thequestion differently is that the Meyers Branchmodel may not give us the services we currentlydesire. We do not currently build cars to lookand work like they did in 1950, we build themto provide the features that we currently thinkare important. So we may have to add featuresif the system does not provide the services wewant, but first we must decide what thoseservices are.

� Meyers Branch may not be the perfect refer-ence, according to Kolka (1999), but it was themost representative system onsite or in thevicinity of Pen Branch. A better referencewould have been Fourmile or Steel Creek ifunimpacted, since they reside at a landscapeposition more similar to Pen Branch. All thingsconsidered, however, both were fine controls aspoints on the succession continuum. From ananimal and plant perspective, Meyers Branchwas an excellent reference. From a hydrology,soils, carbon and nutrient cycling perspective, abetter site may have been utilized. Small differ-ences in landscape position can likely have adrastic impact on energy inputs resulting invarying soil development and hydrology. Wig-ginton (1999) suggested that similarities in soilmorphology and taxonomic classifications be-tween the soils in the two systems make MeyersBranch an acceptable reference system. If theforest canopy was removed in Meyers Branch,soil carbon levels would likely change to resem-ble those observed in the disturbed system.

� The choice of Meyers Branch was pragmaticand not naı̈ve, according to Martin (1999), solong as we admit that localized conditions mayhave effects for which we cannot account. If wehad several comparison sites available (not


truly controls but as close as we can get) wemight have been able to pick out the localizedconditions which lead to differences. However,having no experimental replicates, we have noidea about the variance or sources of variancethere which might mask or emphasize differ-ences between the experimental and controlsystems.

� According to Lakly and McArthur (1999) ad-dressing the concepts of the desired endpoint,Meyers Branch as a reference system, and ap-propriate species in our recommendations isvital. Care should be taken not to insinuatethat our only goal is the creation of a carboncopy of Meyers Branch with exactly the samespecies and metrics. A more appropriate goalwould be the re-establishment of an evolving,dynamically stable, self-sustaining, functionallydiverse system that is well adapted to its cur-rent hydrologic regime and inputs. This con-cept allows for successive changes in metricslike macrophyte biomass, riparian develop-ment, bank stability, and biotic function inrelation to current capacities and developmen-tal histories (Ebersole et al., 1997). Addition-ally, by combining this with our other goals ofrestoration, we incorporate our current charac-terization of the ecological effects of thermaleffluent while indicating which response vari-ables may be important indicators of futurerecovery.

8. Conclusion

Information from the above studies will beutilized in developing a quantitative assessmentmethod for evaluating riparian wetland restora-tion success (Kolka et al., 2000b). It is evidentfrom the research that Pen Branch is currentlyfunctioning as a viable wetland. The degree offunction and level of recovery, however, is subjectto debate. By utilizing biotic and abiotic metricsobtained from research in hydrology, soils, vege-tation, carbon and nutrient cycling, and faunalcommunities, predictions of wetland function inresponse to the restoration activity may be ascer-tained. As succession proceeds and research con-

tinues in the restored and relatively unimpactedreference sites, information shall be accumulatedto validate our predictions and further contributeto the development of this assessment procedure.As a consequence, these efforts may serve as atemplate for future wetland restorations.

References

Buffington, J.M., Kilgo, J.C., Sargent, R.A., Miller, K.V.,Chapman, B.R., 2000. Effects of restoration techniques onthe breeding bird communities in a thermally-impactedbottomland hardwood forest. Ecol. Eng. 15, S115–S120.

Chen, K.F., 1999. Pen Branch Delta and SRS Swamp hy-draulic modeling. Paper presented at Pen Branch Restora-tion Workshop. Clemson, SC, 12–14 April.

Conner, W.H., 1999. The use of tree shelters in restoring forestspecies to the Pen Branch delta: 5 year results. Paperpresented at Pen Branch Restoration Workshop. Clemson,SC, 12–14 April.

Conner, W.H., Inabinette, L.W., Brantley, E.F., 2000. The useof tree shelters in restoring forest species to a flood plaindelta: five year results. Ecol. Eng. 15, S47–S56.

Dulohery, C.J., 1999. Effects of willow overstory on plantedseedlings in a bottomland restoration. Paper presented atPen Branch Restoration Workshop. Clemson, SC, 12–14April.

Dulohery, C.J., Bunton, C.S., Trettin, C.C., McKee, W.H.,1995. Reforestation, monitoring and research at PenBranch: Restoring a thermally-impacted wetland forest.Establishment Report. USDA Forest Service; FS-6200-7.

Dulohery, C.J., Kolka, R.K., McKevlin, M.R., 2000. Effectsof willow overstory on planted seedlings in a bottomlandrestoration. Ecol. Eng. 15, S57–S66.

Ebersole, J.L., Liss, W.J., Frissell, C.A., 1997. Restoration ofstream habitiats in the western United States: restorationas reexpression of habitat capacity. Environ. Manage. 21,1–14.

Fletcher, D.E., 1999. Spatial and temporal variation of canopyand macrophyte coverage in response to past thermaldisturbance and recent canopy alteration. Paper presentedat Pen Branch Restoration Workshop. Clemson, SC, 12–14 April.

Fletcher, D.E., Wilkins, S.D., McArthur, J.V., Meffe, G.K.,2000. Influence of riparian alteration on canopy coverageand macrophyte abundance in southeastern USA blackwa-ter streams. Ecol. Eng. 15, S67–S78.

Fliermans, M.C., Wike, L.D., Fliermans, C.B., 1999. Bacterialloading in small mammals of Pen and Meyers Branchstream corridors. Paper presented at Pen Branch Restora-tion Workshop. Clemson, SC, 12–14 April.

Giese, L.A., 1999. Spatial and temporal patterns of carbonstorage in a Coastal Plain riparian forest. Paper presentedat Pen Branch Restoration Workshop. Clemson, SC, 12–14 April.


Giese, L.A., Aust, W.M., Trettin, C.C., Kolka, R.K., 2000.Spatial and temporal patterns of carbon storage and spe-cies richness in three South Carolina coastal plain riparianforests. Ecol. Eng. 15, S157–S170.

Hanlin, H.G., 1999. Amphibian and reptile characterization ofa thermally-impacted bottomland hardwood forest. Paperpresented at Pen Branch Restoration Workshop. Clemson,SC, 12–14 April.

Kilgo, J.C., 1999. Effects of restoration techniques on thebreeding bird communities in a thermally-impacted bot-tomland hardwood forest. Paper presented at Pen BranchRestoration Workshop. Clemson, SC, 12–14 April.

Kolka, R.K., 1999. Influence of restoration and succession onbottomland hardwood hydrology.Paper presented at PenBranch Restoration Workshop. Clemson, SC, 12–14 April.

Kolka, R.K., Singer, J.H., Coppock, C.R., Casey, W.P., Tret-tin, C.C., 2000a. Influence of restoration and succession onbottomland hardwood hydrology. Ecol. Eng. 15, S131–S140.

Kolka, R.K., Nelson, E.A., Trettin, C.C., 2000b. Conceptualassessment framework for forested wetland restoration:The Pen Branch experience. Ecol. Eng. 15, S17–S21.

Kondratieff, P., Kondratieff, B., 1985. A lower food chaincommunity study: Thermal effects and post-thermal recov-ery in streams and swamps of the Savannah River Plant.Savannah River Plant Report; DPST-85-376, ECS-SR-19.

Lakly, M.B., McArthur, J.V., 2000. Macroinvertebrate recov-ery of a post-thermal stream: habitat structure and bioticfunction. Ecol. Eng. 15, S87–S100.

Lakly, M.B., McArthur, J.V., 1999. Macroinvertebrate post-thermal recovery of a Coastal Plain stream. Paper pre-sented at Pen Branch Restoration Workshop. Clemson,SC, 12–14 April.

Martin, F.D., 1999. Small mammals of Pen Branch andMeyer’s Branch. Paper presented at Pen Branch Restora-tion Workshop. Clemson, SC, 12–14 April.

McLeod, K.W., 1999. Tree species selection trials and silvicul-tural techniques for use in bottomland hardwood and

swamp forest restoration. Paper presented at Pen BranchRestoration Workshop. Clemson, SC, 12–14 April.

McLeod, K.W., Ciravolo, T.G., Reed, M.R., 2000. Speciesselection trials and silvicultural techniques for the restora-tion of bottomland hardwood forests. Ecol. Eng. 15, S35–S46.

Nelson, E.A., Dulohery, N.C., Kolka, R.K., McKee, W.H.,2000. Operational restoration of the Pen Branch bottom-land hardwood and swamp wetlands: the research setting.Ecol. Eng. 15, S23–S33.

Parker, R.B., McCreadie, L.W., Morse, J.C., Nelson, E.A.,1999. The recovery of an aquatic insect community follow-ing three decades of thermal pollution. Paper presented atPen Branch Restoration Workshop. Clemson, SC, 12–14April.

Reichert, M.J.M., Paller, M.H., Dean, J.M., Siegle, J.C.,Hoyt, J., 2000. Use of the index of biotic integrity to assesswetland restoration success. Paper presented at Pen BranchRestoration Workshop. Clemson, SC, 12–14 April.

Schneider, R.L., Martin, N.E., Sharitz, R.R., 1989. Impact ofdam operations on hydrology and associated floodplainforests of southeastern rivers. In: Sharitz, R.R., Gibbons,J.W. (Eds.),. Freshwater Wetlands and Wildlife. CONF-8603101, DOE Symp. Series No. 61, USDOE Office ofScientific and Technical Information, Oak Ridge, TN, pp.1113–1122.

Wigginton, J.D., 1999. Soil organic matter formation andsequestration across a forested floodplain chronosequence.Paper presented at Pen Branch Restoration Workshop.Clemson, SC, 12–14 April.

Wigginton, J.D., Lockaby, B.G., Trettin, C.C., 2000. Soilorganic matter formation and sequestration across aforested floodplain chronosequence. Ecol. Eng. 15, S141–S155.

Wike, L.D., Martin, F.D., Hanlin, H.G., Paddock, L.S., 2000.Small mammal populations in a restored stream corridor.Ecol. Eng. 15, S121–S129.

.

restoration of a severely impacted riparian wetland system — the pen branch project

Documents