Understory Trees 1-20 Cm Dbh in 10-M X 10-M Quadratslocated Within the 30-M X 30-M Plots
Total Page：16
File Type：pdf, Size：1020Kb
RESEARCH ARTICLE ABSTMCT: Previous qualitative surveys have suggestedthe Zoar Valley Canyon of western New York State contains a diverse tract of easternold-growth tbrest. In this first quantitative study of the site, we surveyed canopy trees >20 cm diameter at breast height (dbh) in twenty-three 30-m x 30-m quadrats on five prominent streamside terraces.We also catalogued understory trees 1-20 cm dbh in 10-m x 10-m quadratslocated within the 30-m x 30-m plots. Nineteen broadleafand two coniferous speciesexceeded 20 cm dbh and formed a multi-layered canopy. Four more broadleaf speciesoccuned only in the under- story. Thirteen species reached 80-126 cm dbh. Sugar maple (Acer saccharum Marsh.) accounted for 27.3Vcof canopy basal area and dominated the understory. Size distributions of all trees pooled and. of Canopyand shade-tolerantspecies individually, were uneven and negatively logarithmic. In contrast, shade-intoler- ant species occurred mostly in >40 cm dbh classes and were rare in the understory. Fourteen species reached 35.0-47.5 m in height in this tallest broadleaf forest yet described in the northeastern United Understory States. Increment cores from seven canopy species revealed ages of 170 to 305 years. The study area meets all objective criteria for easternold growth. Compositionof Old- Index terms: broadleaf forest, old growth, riparian forest, Zoar Valley CroMhRiparian INTRODUCTION In this first quantitative study of Zoar Foresttn ZoarValley, Valley's woodlands,we describecanopy Since European settlementbegan, deci- and understorycomposition and structure NewYork,USA mation of the easternUnited States' on five prominentstreamside terraces, and original forest cover has been relentless. assessforest staturein terms of objective It is conservativelyestimated that >99.57o definitionsof easternold growth (e.g., Thomas P.Digginsl of pre-settlementtimber was cleared Martin 1992,Foster et al. 1996,FAO 2002, or heavily logged (Frelich 1995, Davis Frelichand Reich 2003).Subsequent stud- Departmentof Biology 1996, Kershner and Leverett 2003). As ies will quantify herbaceousflora, course YoungstownState University a result, there has emergeda popular as- woodydebris, seedling recruitment, and the One University Plaza sumptionthat easternold growth is gone, role of ripariandynamics in forestdevelop- Youngstown,OH 44555 exceptfor a few well-known "showcase" ment. Futureresearch will alsobe expanded sites.However, field surveysincreasingly to canyonslopes and ridge tops wheread- Bruce Kershner demonstratethat remnantsof old-growth ditional old growth hasbeen qualitatively State Universiw of New York at Buffalo forest, though often critically imperiled, identified (Hunt et al. 2002). York Old Growth ForestAssociation are more numerousand widespreadthan previouslyrecognized (Stahle and Chaney STUDY AREA 1994,Foster et al. 1996,Dunwiddie and Leverett1997, Davis 2003). The ZoarValleyCanyon (N 42'26', W 78' 52') is the seconddeepest vertical-walled A noteworthyrecent discovery is a diverse canyonsystem in NewYork State.encom- tract of broadleafwoodlands in New York passingthe Main and South Branchesof State'sZoar Yalley (Figure 1), a remote CattaraugusCreek (Figure lB), a tributary seriesof canyons60 km southof Buffalo to Lake Erie. The Main Branch Canyon (Kershner 1994,2000:,Hunt et al. 2002). extends I I km from its downstreamend surveyshave identified >300 ha Qualitative to where it abruptly widens into a broad of pre-settlementforest here,of which at agricultural valley upstream.The South least175 ha occurwithin the I I 82-haNew Branch Canyon is approximately 8 km York StateZoarYalley Multiple Use Area in length. The watershedof Cattaraugus (Hunt et al. 2002). Historical aerial pho- Creek totals 1430 km2, >807o of which tographsof this canyon (Fairchild Aerial lies upstreamof Zoar Valley.Typical low- Surveyslnc. 1929)reveal dense stands of flow dischargebelow the confluenceof largetrees blanketing streamside terraces, the two branchesof CattaraugusCreek is slopes(other than cliff faces),and some <5.0 m3/s.but floodscan exceed300 m3/s I Corresponding author: adjacentuplands, corresponding to today's (U.S. GeologicalSurvey 2004). Depth of tpdiggins @ysu.edu suspectedold growth. The conservation the Main Canyon rangesfrom 70 to 130 statusof thispublicly ownedsite has not yet m, while the South Canyon reaches100 been designated,and has beenthe source m. Canyon slopesvary from 60-90' bare Natural Areas Joumal 25:219 227 of debatebetween environmentalists and rock cliffs alone outside bendsto 30-60" stateofficials. Volume25 (3),2005 NaturalAreas Journal 219 d^t vrrsru- ' New York Buffalo State ZoarValley CattaraugusCreek, 500m Canyonrim I'. (335-408ma.s.1.) / lJ-!l{!rr1;;41\ Riverbed(262-274 m a.s.l.) ,,,,,,,,,'-y' of B) Detail of cattaraugus creek in vicinity of Zoar valley canyon' c) Detail Figure l. Location and detail of zoarvalley study site. A) Regional location. boundaries of closed'canopy forest on the terraces' Numbers denote study area showing terraces, riverbed, and canyon rim. Solid dark lines are approximate locations of survey quadrats. resentingportions of the study area, the forestedslopes on inside bends.Bedrock METHODS 30-m x 30-m quadrats(Figure lC) were is primarily late Devonian shalesof the of 2002, not locatedentirely randomly.Instead, each Canadawaygroup (Hunt et aI.2002). BetweenAugust and Novembet walking all canopytrees >20 cm diameterat breast quadrat was generally sited by identifiedto l0-50 m downstreamfrom the preceding Through much of the canYon system' height (dbh, ar 1.31 m) were twenty- quadrat. Starting point and orientation pronouncedmeanders have producedflat speciesand measuredfor dbh in tbr were then establishedby blindly tossinga terracesdownstream of each inside bend three30-m x 30-m quadratsaccounting -16%o markerflag. This procedureapproximated (FigurelC). This studycentered on thefirst of the total areaofthe five terraces. 2003' understory a stratifiedsampling design,with similar five terracesin the Main Canyonabove the DuringApril andMay of cataloguedin proportionsof each terracesurveyed. confluence(Figure 1C), totaling 12.7 ha. trees 1-20 cm dbh were quadrats,each Previousobservations had suggestedthat twenty-threel0-m x l0-m 30-m x 30-m Descriptivevariables quantifi ed included: here the broadleafforest (Figure 2) is the randomly located within a ( 1) densityof trees>20 cm dbh, (2) mean most diverseand the tallestin the canyon' canopy-treequadrat. dbh of trees >20 cm dbh, (3) total basal exceeding35 m in height(Eastern Native under-rep- area(including understory) at breastheight Tree Societv 2004). To avoid overlapping and/or Volume25 (3),2005 22O NaturalAreas fournal ,ii i; ! .t'rj ,:$r Figure 2. View of eastern edge of Skinny Dip Terrace where stream erosion has exposed canopy architecture. View extends -100 m from eastern tip of terrace to quadrat #2 (Figure 1). Note B. Kershner for scale, adjacent to 43-m tall Liriodendron tulipifura. for eachspecies and tbr the entirequadrat, representingseven canopy species (listed ing the study terraces.All other canopy (.1)species richness, (5) speciesdiversity in Results).Several T. canadensis<40 cm specieswere representedby multiple in- (Shannon-WeinerH') in termsof basalarea, dbh were cored,but all othertrees directly dividuals. and (6) percent shade-tolerantspecies in aged were >60 cm dbh. This preliminary terms of basal area. Shade-tolerantspe- samplingof canopytree ages was not in- Fifteen tree speciesoccurred in the un- cies (definedby Burns and Honkala 1990) tendedto generateage/size relationships. derstory(Table 2). Acer pensylvanicuntL. include Acer rubrum L., Acer saccharum (stripedmaple), Cornusflorida L. (flower- Marsh., Fagus grandifulia Ehrh., Tilia ing dogwood). Hamamelis virginiana L. RESULTS wnericano L., and Tsugacanadensis (L.) (witch hazel), and Carpinus caroliniana Carr. (red maple, sugar maple,American Walt. (American hornbeam)were found beech, American basswood,and eastern Speciesrichness and diversity only in the understoryduring the present hemlock, respectively). study. The woody shrub Lindera benzoin Twenty-onespecies exceeded 20 cm dbh (L.) Blume (spicebush)also occurred with- In addition to the quadrat surveys, we within the study area,and contributedto in the study area,but we did not include it identified all trees >80 cm dbh through- the mid- and overstories (Table l). Of in countsof understoryspecies more often out the five study terraces.Also, heights these,Magnolia acuminataL. (cucumber classifiedas trees. of notable trees were triangulated,with magnolia), Ostrya virginiana (Mill.) K. distanceto apex measuredusing either a Koch (eastern hop hornbeam), Robinia Speciesrichness in quadratsranged from BushnellYardage Pro 250 or a Nikon 400 pseudoacaciaL. (black locust), andPinus threeto 11 species.Richness pooled within laser range finder, and angle of elevation stobus L. (easternwhite pine) were rep- terraces,including speciesencountered measuredusing a Suunto inclinometer resentedby singlecanopy trees within the outsidequadrats. ranged from l6 species (EasternNative Tree Society 2004). area surveyed (Table 1;, although each on Knife Edge Terraceto 22 specieson was either more abundant elsewherein Elm Terrace (Table 3). Within-quadrat We useda 20-inchSuunto increment borer ZoarYalley or occurred in the understory. diversity ranged from 0.93 to 1.92, with to determineages of a non-systematicsam- Robiniapseudoacacia, which is expanding the highestterrace mean values on Hidden pling of 17 living and fallen