phillip g. demaynadier and jeffrey e....

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13

Conserving Vernal Pool Amphibians in Managed Forests

Phillip G. deMaynadier and Jeffrey E. Houlahan

CONTENTS

Introduction............................................................................................................254Natural History ......................................................................................................255

A Complex Mosaic....................................................................................255Philopatry and Movement Ecology...........................................................256

Vernal Pool–Forestry Relationships ......................................................................257Vernal Pool Basin Relationships ...............................................................257

Physical Integrity .............................................................................257Hydrology.........................................................................................258Water Quality ...................................................................................259

Forest Canopy Relationships.....................................................................260Clearcutting ......................................................................................260Partial Harvesting and the Canopy Continuum...............................261

Forest Floor Relationships.........................................................................263Forest Litter......................................................................................264Coarse Woody Debris (CWD) .........................................................265

Conservation Recommendations ...........................................................................265Habitat Management Guidelines for Preharvest Planning........................268Habitat Management Guidelines for Harvest Operations.........................269

Vernal Pool Depression....................................................................269Vernal Pool Protection Zone............................................................271Vernal Pool Life Zone .....................................................................272

Summary ................................................................................................................273Acknowledgments..................................................................................................274References..............................................................................................................275

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Science and Conservation of Vernal Pools in Northeastern North America

INTRODUCTION

Arguably the most conspicuous of natural elements in the Northeast are trees andfor good reason, as the region ranks among the most forested in North America. Allnortheastern states and provinces are more than half forested, with forests in northernportions of the region dominating as much as 85% (New Brunswick) to 89% (Maine)of the landscape (Smith et al. 1994; Natural Resources Canada 2006). And yet ithas not always been this way, with the region among the few in the world that isactually more forested today than it was 100 years ago (Foster 1995). Paradoxically,while northeastern landscapes today contain much of their natural forests they alsohost some of the densest, longest-settled human populations in North America.

Starting in the early 1700s Europeans cleared much of the region’s forests foragriculture. However, beginning in the mid-1800s, farming declined across theNortheast with the result that abandoned pastures and fields were again reclaimedby forests whose legacy persists to this day (Irland 1982). The ebb, recovery, andpresent dominance of forestland profoundly influenced the historic distribution andstatus of the region’s wildlife (Litvaitis 1993; Wilcove 1999). Species requiringexpanses of mature, mast-producing forest declined to a level of near-extinction(e.g., wild turkey,

Meleagris gallopavo

) or total extinction (e.g., passenger pigeon,

Ectopistes migratorius

). Other wide-ranging animals (e.g., timber wolf,

Canis lupus

,and woodland caribou,

Rangifer tarandus caribou

) were exposed to unsustainablelevels of hunting and persecution, aggravated by the decline and fragmentation ofpreviously remote forestlands. Fortunately, the region’s forest-dwelling frogs, toads,and salamanders neither required exceptionally large blocks of continuous forest norattracted much hunting pressure or exploitation, with the result that our amphibianfauna remains mostly intact.

More so perhaps than any other region in North America, the Northeast’s forestsand the fate of the wildlife found here lie in private hands, by ownership or lease(i.e., Crown lands, Canada). As much as 90% of the commercial forest land in NewEngland, for example, is privately owned (Irland 1982; Smith et al. 1994). Further-more, most of the region’s private woodlands are subject to varying levels of forestmanagement intensity, ranging from light firewood harvesting to large-scale com-mercial pulp and saw log production. Indeed, with private forestlands dominatingthe natural landscape, timber management is by definition the region’s most wide-spread land-use practice. Understanding forestry–wildlife relationships and, for ourpurposes, forestry–amphibian relationships, in particular, is thus critical if biologists,foresters, and landowners are to make informed decisions when affecting the qualityand extent of managed forest habitat in the Northeast.

Although still lagging behind that of other vertebrate groups, an impressive bodyof knowledge is accumulating on the effects of forest management practices onamphibians, mostly in North America (see reviews by deMaynadier and Hunter 1995and Welsh and Droege 2001). Still, research on the specific effects of timber man-agement on vernal pools and their fauna remains limited. This is of special concernin the Northeast where a high proportion (27 spp. or ~56%) of the salamander, frog,and toad fauna frequent vernal pool ecosystems for breeding, development, foraging,and hibernation (Chapter 7, Semlitsch and Skelly). Furthermore, vernal pools are

3675_C013.fm 54 Friday, June 22, 2007 1:53 PM


255

nearly ubiquitous in northeastern forest landscapes where densities range as high as13.5 pools/km

2

(35 pools/mi

2

; Calhoun et al. 2003). As such, we suggest that it isnearly impossible to avoid at least incidental impacts, positive or negative, on habitatfor vernal pool breeding wildlife during the course of most timber harvesting oper-ations in northeastern forests.

The purpose of this chapter is to introduce readers to specific aspects of thebiology of pool-breeding amphibians relevant to forest management and to providea review of the limited, but growing body of research concerning vernal poolamphibian responses to common forest harvesting practices. Additionally, we usethe literature on forestry–vernal pool relationships to inform the development ofspecific Habitat Management Guidelines for conserving pool-breeding amphibiansin managed landscapes. Our premise is that forest management, if practiced in anecologically sensitive manner, is among the most compatible consumptive land usesfor conserving important elements of vernal pool habitat.

NATURAL HISTORY

Although amphibians are probably the most abundant vertebrate group in northeast-ern forests (Burton and Likens 1975; Hairston 1987), their small size, nocturnalactivity, and often fossorial habits make them relatively inconspicuous and difficultto study. Consequently, most forest and wildlife managers are more familiar withthe ecology of birds, mammals, and fish that has dominated investigations of forestwildlife relationships to date (Gibbons 1988). We provide a brief introduction to theecology of vernal pool-breeding amphibians, focusing on aspects of their naturalhistory relevant to forest ecosystems and their management.

A C

OMPLEX

M

OSAIC

Most pool-breeding amphibians have complex life cycles (Wilbur 1980), beginningas aquatic eggs, hatching to gilled larvae, and metamorphosing into terrestrial, lungedadults within a few weeks (e.g., eastern spadefoot toad,

Scaphiopus holbrookii

) toa few months (e.g., mole salamanders,

Ambystoma

spp.) of hatching. The habitatmosaic required to host self-sustaining populations of pool-breeding amphibians isalso complex and generally comprised of (1) temporary to semipermanent poolslacking fish (for adult breeding and larval development), (2) terrestrial foraging,resting, and overwintering sites, often spatially removed from breeding pools, and(3) a mostly forested matrix permeable to migrating adults and dispersing juveniles.

The ecology of the aquatic phase of pool-breeding amphibians is relatively well-studied (reviewed by Duellman and Trueb 1994, Alford 1999) with important effectson larval fitness and performance documented from both biotic (mainly competitionand predation; Wilbur 1980; Hairston 1987), and abiotic factors (mainly temperature,water chemistry, and hydroperiod; Pechmann et al. 1989; Babbitt et al. 2003; Well-born et al. 1996). Foresters and land managers have the potential to most directlyaffect the latter, through impacts and manipulations to physical basin integrity andmarginal forest vegetation. Tree harvesting decreases pond shading and increaseswater temperature, often accelerating larval amphibian development, of potential


256


benefit for some species (e.g., spring peepers,

Pseudacris crucifer

) and detrimentfor others (e.g., marbled salamanders,

Ambystoma opacum

) (Skelly et al. 2002,2005). The effects of forestry activities on pond hydroperiod are potentially signif-icant but also less predictable (see Vernal Pool Basin Relationships).

Moving to a terrestrial environment places adult amphibians under a differentset of constraints that are complicated by ectothermy, permeable skin, and smallsize. The moist, permeable skin of most adult, pool-breeding species serves as apartial respiratory organ (Stebbins and Cohen 1995), increasing their vulnerabilityto microhabitat drying. This skin also readily absorbs desiccants and toxins fromthe surrounding environment (Frisbie and Wyman 1991). Small size and linearproportions (in salamanders) contribute to a high surface area to volume ratio, furtherincreasing the risk of adult, and especially juvenile, desiccation. In addition, amphib-ians are ectothermic in a region characterized by large intra-annual variation intemperature, including extended periods of subzero winter temperatures and hot,drying summer temperatures. Amphibians must thus respond to two pressing prob-lems: how to prevent or cope with the potential freezing of internal body fluids, andhow to forage, migrate, and otherwise stay active on the forest floor during periodsof high temperatures and low relative humidity. As we will explore further, manypool-breeding amphibians avoid the problem of freezing and desiccation by selectingshaded, forested habitats that contain deep, moisture-trapping litter and woody cover,often with abundant small mammal burrows that provide access below the frostline(Faccio 2003; Regosin et al. 2003). The challenge to foresters is to conserve theintegrity of these and other important elements of forest structure during the courseof timber management.

P

HILOPATRY

AND

M

OVEMENT

E

COLOGY

Investigations of amphibian breeding-site fidelity suggest that most pool-breedingamphibians are highly philopatric (Sinsch 1990; Smith and Green 2005). Bervenand Grudzien (1990) found that all adult wood frogs were faithful to their firstbreeding pond and that 82% of juveniles were faithful to their natal pool. Vasconcelosand Calhoun (2004) documented similar breeding pool fidelity by adult wood frogs(88% female return rates; 98% male), and spotted salamanders (

Ambystoma macu-latum

; 100% female and male). Additionally, nearly 100% breeding pond site fidelityhas been documented for adult eastern newts (

Notophthalmus viridescens

) (Gill1978). Site fidelity of this magnitude underscores the importance of avoiding seem-ingly small-scale disturbances to high value breeding pools that may have lastingimpacts on localized amphibian populations.

Successful upland migrations among breeding pools, summer foraging habitats,and overwintering locales are critical to meet the complex seasonal habitat require-ments of adult pool-breeding amphibians. Both adult migration and juvenile dis-persal through terrestrial ecosystems are complicated by desiccation risk for thereasons outlined above, and evidence is growing that several pool-breeding amphib-ians select for moist, shaded forest conditions during seasonal movements(deMaynadier and Hunter 1998, 1999; Rothermel and Semlitsch 2002; Patrick et al.2006). To develop pool-specific habitat management guidelines we suggest that data



257

on adult migration of pool-breeding amphibians is more informative than juveniledispersal for two reasons. First, natal dispersal occurs over exceptional scales thatoften exceed forest management and ownership boundaries — e.g., over 1 km (0.6mi) for Amystomatids (Funk and Dunlop 1999; Pechmann et al. 2001) and 2.5 km(1.6 mi) for wood frogs (Berven and Grudzien 1990) — complicating efforts todesign management prescriptions around discrete elements (e.g., breeding pools).Secondly, relatively little is known about the habitat preferences of juvenile amphib-ians during their dispersal phase, and it is possible that an intensively managed forestmatrix is more forgiving to short-term dispersal movements than to the more sed-entary home-range and migration movements of adults of the same species (Gibbs1998; deMaynadier and Hunter 2000; Marsh et al. 2004). Although more work isneeded, knowledge of the habitat preferences and adult migration distances of pool-breeding amphibians in the Northeast is growing (Chapter 7, Semlitsch and Skelly;Color Plate 17) and serves as a foundation for our spatial recommendations fortimber management planning around vernal pools.

VERNAL POOL–FORESTRY RELATIONSHIPS

Given the complex life cycle of pool-breeding amphibians, it is important to considerpotential effects that forest harvesting can have on the characteristics of both aquatic(breeding) and terrestrial (nonbreeding) habitat. To inform specific managementrecommendations for the conservation of both these habitats we organized our reviewaround three elements that together define the local quality and extent of pool-breeding amphibian habitat in managed forest landscapes: the vernal pool basin andshoreline, overstory canopy cover in the surrounding forest, and the structure andcondition of the forest floor.

V

ERNAL

P

OOL

B

ASIN

R

ELATIONSHIPS

Land use activities located directly within the vernal pool basin, and its associatedriparian nursery habitat, can have important effects on the breeding success andlong-term population viability of pool-breeding amphibians. Specifically, forestrypractices can affect pool basin habitat characteristics through changes to the physicalintegrity of the depression, pool hydrology, water quality, and riparian tree canopycover and composition.

Physical Integrity

It is well established that disturbance by heavy machinery can have lasting impactson forest ecosystems (Martin 1988; Turcotte et al. 1991). Harvesting operations inthe pool itself, even during winter, can remove basin or riparian vegetation that helpsprovide egg attachment sites, shade, and organic material to the vernal pool’s detritalfoodchain. Furthermore, the basin of many pools is extremely heterogeneous, offer-ing varied moisture and temperature conditions from the development of hummocktopography, hardwood leaf litter wells, sphagnum moss, and accumulations of coarsewoody debris. These moisture-trapping structures provide refuge to the eggs, larvae,


258


metamorphs, and adults of various pool-breeding amphibians, reptiles and inverte-brates at different times of the year and yet are readily compromised by heavymachinery operating in the pool basin.

Hydrology

Precautions should be taken to avoid harvest activities that alter pond hydroperiod— a key driver of amphibian and invertebrate community composition (reviewedby Wellborn et al. 1996 and Semlitsch 2003). Management activities that contributeto shortened hydroperiods can lead to pond-wide desiccation and mortality, or forceamphibian larvae to develop more quickly — generally causing smaller body sizeat metamorphosis, decreased survival, lower female fecundity, and delays in firstreproduction (Howard 1978; Semlitsch et al. 1988; Berven 1990). Alternatively, anartificially extended hydroperiod increases pond habitat suitability for predatory fishand invertebrates (e.g., odonata, coleoptera), and potentially competition and preda-tion by other amphibians more closely associated with permanent waters (e.g., greenfrogs,

Rana clamitans

; bullfrogs,

R. catesbiana

). We briefly review three pool basinforestry activities with potential to affect hydroperiod, including soil disturbance(compaction and rutting), road construction, and local tree removal.

Forest soils, particularly when wet, are vulnerable to rutting and compaction byheavy machinery used for harvesting and extraction (Nugent et al. 2003; Horn et al.2004). Deep forest floor ruts that intersect pool basins can alter normal overlanddrainage patterns, artificially increasing or decreasing pool water-holding capacitydepending on local topography (J. Houlahan, personal observation). Machinery-created ruts in the surrounding forest floor proximate to breeding pools can affectthe success of adult breeding migrations by potentially impeding or redirectingsalamander movements (Means et al. 1996) or attracting frogs and salamanders tolay eggs in artificial rut pools that often dry prematurely and constitute ecologicaltraps (DiMauro and Hunter 2002; P. deMaynadier, personal observation).

Roads are often an unavoidable byproduct of timber harvesting and have impor-tant ecological impacts on streams, lakes, and smaller wetlands. In fact, it has beensuggested that harvest roads have potentially larger impacts on hydrology than treeremoval (Lockaby et al. 1997; Cornish 2001), with ditches, culverts, and roadsurfaces able to change the direction and speed of overland sheetflow. Recently,Gomi et al. (2006) reported that forest roads contribute significantly to detritus andsediment accumulation in streams. The effects of roads on vernal pool hydrology isnot well-studied, but it seems reasonable to suggest that, given their generally smallsize and shallow depth, vernal pools may be especially sensitive to sheetflow alter-ation and sedimentation. Indeed, preliminary results suggest a negative correlationbetween forest road density and amphibian species richness in small New Brunswickponds (Jacobs and Houlahan, in preparation).

Finally, there is growing evidence that forest tree removal can influence thewater table dynamics and hydroperiod of local wetlands. Generally, forest harvestingin forested bottomlands results in elevated water tables in the first few years afterclearcutting due to decreased evapotranspiration (Sun et al. 2001; Pothier et al. 2003).More recently evidence suggests that although deforestation tends to increase water



259

table elevation immediately after harvesting, the long-term effects are subtle andtemporally variable, with higher water tables during the nongrowing season andlower water tables during the growing season (Bliss and Comerford 2002). Martinet al. (2000) also showed increases in water yield immediately after strip-cuttingthat lasted for three to six years, but these increases were followed by more than 20years of below-average water yield due to the regeneration of rapid-growing pioneerspecies (e.g.,

Prunus

spp.,

Populus

spp.) with higher transpiration rates. Vernal poolsare particularly vulnerable to changes in water table elevation since water loss (andpresumably water gain) is a function of wetland perimeter to area ratio, a measurethat is relatively high in small wetlands (Millar 1971).

Water Quality

One of the common effects of forest harvesting in or near the pool basin is diminishedcanopy cover over the breeding pool. Recent evidence suggests that amphibianspecies richness, growth, and development are lower in heavily shaded pools (Skellyet al. 2002, 2005), likely due to lower water temperatures and lower food quality(Halverson et al. 2003; Skelly et al. 2005). However, the conservation implicationsare complicated by the fact that several amphibian pool-breeding specialists (e.g.,marbled salamanders; Chapter 7, Semlitsch and Skelly) and invertebrate specialists(e.g., fairy shrimp,

Eubranchipus

spp.; Ossman and Hanson 2002) thrive, or arefound more often, in shaded pool locales.

Perhaps less intuitive, but no less real, are the impacts to vernal pool waterquality that result from watershed-scale forest management practices. Since the earlyexperiments at Hubbard Brook (Bormann et al. 1968), it has become axiomatic thatforest harvesting increases sedimentation and nutrient transport (Lamontagne et al.2000) and lowers surface water quality in clear-cut watersheds (Martin et al. 2000).The evidence indicating that increased nutrient inputs are significant for lakes sug-gests that they are almost certainly significant for small, shallow vernal pools aswell. Additionally, intensive forest management often includes conversion of mixedstands to predominately softwood plantations, and these changes in tree communitycomposition can impact water quality. For example, Ito et al. (2005) found thatwatersheds dominated by coniferous trees exported more dissolved organic carbon(DOC) than those dominated by deciduous trees and that DOC levels were higherin lakes in conifer-dominated watersheds. Conversely, nitrate export to lakes is higherin deciduous forest-dominated watersheds (Ito et al. 2005). This suggests that inten-sive site conversion to softwood-dominated stands may result in higher DOC con-centrations and lower nutrient levels in vernal pools. Interestingly, Waldick et al.(1999) found that amphibian species richness is lower and community compositiondifferent in ponds surrounded by conifer plantations than ponds surrounded bynatural mixedwood forests.

Chemicals are widely used in forestry in the Northeast including insecticidessuch as carbaryl, tebufenozide, and

Bacillus thuringiensis,

and herbicides likeglyphosate and triclopyr (Chapter 11, Boone and Pauli). In most cases, these pesti-cides are applied aerially, making vernal ponds particularly vulnerable to contami-nation because of limited regulatory restrictions on aerial spraying around temporary


260


water bodies and the difficulty of delineating buffer zones around small, widelydistributed pools. Carbaryl is especially persistent under acidic conditions and hasbeen demonstrated to have indirect effects on salamander populations. Tebufenozide,which has recently replaced fenitrothion as the insecticide of choice for controllingspruce budworm (

Choristoneura fumiferana

), has not been shown to have largeeffects on organisms in aquatic systems (Pauli et al. 1999) although there is evidencethat it depresses cladoceran (often called daphnia) species richness (Kreutzweiseret al. 2004), a valuable prey source for pool-breeding fauna. Glyphosate is one ofthe most widely applied herbicides in forestry (Woodburn 2000), and it has, untilrecently, been considered relatively benign because it acts on a metabolic pathwaythat is only found in plants. However, commercial formulations include surfactantsthat prevent glyphosate from “beading up” and rolling off plant leaves, and thesemay be more toxic than glyphosate itself (Giesy et al. 2000). Generally, the use ofsurfactants should be avoided in proximity to high-value vernal pools as they facil-itate absorption through the moist, permeable skin of amphibians and their ecologicaleffects remain largely unknown.

F

OREST

C

ANOPY

R

ELATIONSHIPS

Clearcutting

One of the most defining structural elements in any forest is its canopy, and theresponse of amphibian communities to canopy presence or absence has been rela-tively well-studied. Most North American studies examining the effects of clearcut-ting, for example, report significantly lower overall abundance (deMaynadier andHunter 1995). More interestingly for our purposes, some amphibian groups are moresensitive to intensive canopy removal than others. A detailed review of only thosestudies including data for pool-breeding species native to the Northeast reveals astriking pattern (Figure 13.1). Specifically, the ratio of median abundance for eachof four northeastern seasonal pool-breeding specialists was several times (3.7–5.5)greater in control stands than in clearcut stands, and exceeded the same ratio forNorth American amphibian taxa generally. Mole salamanders as a group (

Ambystoma

spp.), and spotted salamanders in particular, appear to be especially sensitive tolarge-scale canopy removal (Figure 13.1). The ratio for spotted salamanders isnotable in that it exceeds that previously reviewed for Plethodontidae (5.0 times;deMaynadier and Hunter 1995), a family of terrestrial, lungless salamanders gener-ally considered among the most sensitive of amphibian taxa to forest managementand other practices that alter forest floor microclimate (Welsh and Droege 2001).

An in-depth study of forest clearcutting and edge effects on a community of 14species of amphibians in Maine yields further support for the premise that pool-breeding amphibians rank among the most sensitive of northeastern amphibian taxato intensive harvest practices (deMaynadier and Hunter 1998). Specifically, in con-structing a “management sensitivity index” composed of the ratio of abundance ofrelative forest interior to clearcut captures, three of the four species identified as mostsensitive to the effects of complete canopy removal — redback salamanders (

Plethodoncinereus

), wood frogs, spotted salamanders, and blue-spotted salamanders (

Ambystoma



261

laterale

) — were northeastern pool-breeding specialists. Furthermore, the effects ofintensive canopy removal extended beyond the boundaries of harvested stands withedge effects reducing pool-breeding amphibian abundance levels at distances of 25–35m (82–115 ft) into adjacent unmanaged forests.

Partial Harvesting and the Canopy Continuum

In contrast to clearcutting, the effects of partial harvesting and uneven-aged forestrypractices are less understood, despite their greater frequency of use in most north-eastern forests (Seymour 1995). Because the shade cast by standing trees in apartially harvested stand can have beneficial effects on forest floor microhabitats(e.g., shaded logs are significantly cooler and moister than unshaded logs; Heatwole1962), it is likely that partial cutting practices have relatively less impact on sedentaryspecies that spend most of their life on the forest floor. However, the questionremains: how much canopy can be removed during partial harvesting before terres-trial pool-breeding populations respond with significant declines? Although there isa growing body of knowledge on the effects of partial canopy disturbance onamphibians generally (Pough et al. 1987; Mitchell et al. 1996; Messere and Ducey1998; Sattler and Reichenbach 1998; Brooks 1999; Grialou et al. 2000; Moore etal. 2002; Knapp et al. 2003; Renken et al. 2004; Karraker and Welsh 2006), specificresults for pool-breeding amphibians of the Northeast are limited (Ross et al. 2000;Patrick et al. 2006).

FIGURE 13.1

The median ratio of abundance from mature vs. clearcut forest for several pool-breeding amphibian taxa characteristic of the Northeast. The horizontal line indicates the sameratio for amphibian taxa generally across North America (n = 18 studies; from deMaynadierand Hunter 1995). Ratios were calculated from all datasets that permitted estimates of the relativemagnitude difference in captures for mature (control) versus clearcut (treatment) stands. Inde-pendent estimates were calculated from mean captures, absolute totals, or frequency data,depending upon the reference consulted. (Contributing sources include: Bennett et al. 1980;deMaynadier and Hunter 1998; Enge et al. 1986; Grant et al. 1994; Mitchell et al. 1997; Patricket al. 2006; Ross et al. 2000; Waldick et al. 1999. With permission.)

0.00

1.00

2.00

3.00

4.00

5.00

6.00

S. holbrooki(n=3)

A. opacum(n=3)

R. sylvatica(n=5)

Ambystoma(n=7)

A. maculatum(n=5)

Med

ian

Ab

un

dan

ceR

atio


262


In our view, the most illuminating investigation to date on the effects of partialharvesting on vernal pool amphibians comes from northern Pennsylvania (Ross etal. 2000) where 47 managed hardwood forest stands were selected to represent acontinuum of canopy closure from a nearly intact overstory (unharvested for over70 years), to a wide range of partially intact canopy stands (selection and diameter-limit harvests), to complete absence of any residual overstory (recent clearcuts). Inthis manner, the investigators were uniquely prepared to document potential thresh-olds in population responses to increasing levels of canopy removal associated withvarying intensities of forest management. We reanalyzed the raw data from Ross etal. (2000) and found just such patterns (Figure 13.2A,B). When examining sala-manders alone (12 spp. total), a clear trend emerges of increasing abundance withincreasing basal area and canopy cover (Figure 13.2A), with a potential thresholdof canopy cover at ~45–50%, beyond which salamander abundance levels increasedramatically. More interestingly for our purposes, a similar pattern and threshold(at ~50–55% canopy cover) persists when only a restricted sample of pool-breedingsalamander specialists is examined (

Ambystoma jeffersonianum

,

A. opacum

,

A. mac-ulatum, Hemidactylium scutatum

; Figure 13.2B). More fieldwork is needed toattempt replication of these results for other pool-breeding taxa and other foresttypes, but it appears that several highly characteristic pool-breeding amphibians ofthe Northeast are sensitive to harvesting practices that remove overstory canopylevels below a level of approximately 50%.

Other studies examining the effects of partial harvesting have yielded resultsconsistent with the patterns above, with few if any significant impacts documentedin the abundance of resident salamander populations following light intensity canopy

FIGURE 13.2A

Relationship between salamander abundance (12 spp) and overstory canopyclosure for 47 forest stands in northeastern Pennsylvania (Pearson’s coefficient of correlation= 0.63; P<0.05). The arrow indicates a potential canopy threshold of ~45–50%, below whichsalamander abundance remains consistently low. (Data reanalyzed from Ross et al. 2000.With permission.)

0

100

200

300

400

500

600

0 20 40 60 80 100

% Overstory Cover

Sal

aman

der

s (n

o./s

tan

d)



263

disturbances, including selection harvests (Pough et al. 1987; Messere and Ducey1998; Moore et al. 2002), thinnings (Brooks 1999; Grialou et al. 2000), and shel-terwood harvests (Sattler and Reichenbach 1998; Mitchell et al. 1996; but see Knappet al. 2003). The focus of most of these investigations has been plethodontid sala-manders, a terrestrial-breeding family common to the Northeast but not characteristicof vernal pools. Nonetheless, to the extent that plethodontid salamanders are con-sidered relatively sensitive to changes in microhabitat and microclimate associatedwith forest management (deMaynadier and Hunter 1995; Welsh and Droege 2001),we suggest that their apparent tolerance to less intensive silvicultural practices thatmaintain moderate levels of canopy cover may be indicative of a similar responseby many of the region’s pool-breeding amphibian taxa (e.g.,

Ambystoma

,

Rana

,

Bufo

,

Hemidactylium

).

F

OREST

F

LOOR

R

ELATIONSHIPS

Investigations of impacts to pool-breeding amphibians following intensive canopyremoval typically compare unmanaged or mature control stands with clearcut treat-ments (Figure 13.1). However, it is important to recognize that this does not neces-sarily suggest that forest age

per se

is critical for maintaining populations of sensitivespecies but, rather, emphasizes the importance of specific structural characteristicsthat are often well developed in late successional forests. More simply, forest ageis likely an indirect measure of the actual microhabitat elements that are critical fordetermining habitat suitability for a particular suite of amphibian species (Welsh1990; deMaynadier and Hunter 1995). This distinction is critical for managers ofprivate forestlands that dominate northeastern landscapes because, while forest ageis a relatively intractable variable that is slow to respond to management (or lack

FIGURE 13.2B

Relationship between vernal pool (VP) salamander abundance (4 spp;

Ambystoma

and

Hemidactylium

) and overstory canopy closure for 47 forest stands in north-eastern Pennsylvania (Pearson’s coefficient of correlation = 0.34; P<0.05). The arrow indicatesan approximate canopy threshold of ~50–55%, below which salamander abundance remainsconsistently low. (Data reanalyzed from Ross et al. 2000. With permission.)

0

2

4

6

8

10

12

14

16

0 20 40 60 80 100

% Overstory Cover

VP

Sal

aman

der

s (n

o./s

tan

d)


264


thereof), many of the specific forest structural elements of importance to pool-breeding amphibians (Table 13.1) can be conserved if ecologically sensitive harvestprescriptions are employed.

Whether foraging within a moist litter layer beneath a decaying log or seekingrefuge within a tree cavity or subterranean root channel, amphibians utilize a varietyof microhabitat structures at the stand-level relevant to forest managers. We highlightthe importance to pool-breeding species of two such elements of documented impor-tance: forest litter and woody debris.

Forest Litter

The structure and composition of the forest floor’s organic layer is integral fororganisms such as frogs or salamanders that spend most of their time there. Althoughinvertebrate prey for amphibians is abundant on the forest floor (Gist and Crossley1975), it is thought to be scarce or unavailable to some salamanders during dryperiods that require retreating underground to avoid desiccation (Fraser 1976). Inaddition to providing habitat for a diverse community of prey, a thick and well-distributed litter base offers a protective foraging substrate by retaining moist con-ditions near the soil interface for a short period after rainfall events, thus prolongingthe effective surface foraging time for salamanders (Heatwole 1962; Jaeger 1980).In northern hardwood and mixed wood forests of Vermont (Faccio 2003) and NewBrunswick (Lavoie 2005), for example, the presence of Jefferson and spotted sala-manders, respectively, was positively associated with the depth and extent of leaflitter (Table 13.1). Similarly, while sampling a larger community of 10 amphibianspecies (including wood frogs and other facultative pool-breeders) from standsdominated by northern hardwood and balsam fir (

Abies balsamea

) in the WhiteMountain National Forest, DeGraaf and Rudis (1990) reported that both diversityand evenness were correlated with litter depth (Table 13.1).

The type and quantity of forest litter available to serve as refugia to vernal poolamphibians is indirectly affected by the history and intensity of forest managementlocally. After large-scale canopy removal, for example, reduced inputs combinedwith increased rates of decomposition lead to a decline in forest litter depth, withrecovery to predisturbance levels requiring up to 50–80 years in northern hardwoodforests (Likens et al. 1978; Hughes and Fahey 1994). Similarly, litter compositionis a reflection of the local tree canopy and thus is also under the control of forestmanagers. Dramatic shifts in litter quality can be expected when converting naturalhardwood or mixed wood stands to homogeneous conifer plantations with potentiallynegative effects for local vernal pool amphibians. Conifer litter is generally drier,warmer, and thinner than mixed or deciduous litter (DeGraaf

and Rudis 1990;Waldick et al. 1999), and thus stands with uniform, planted conifer canopies mayincrease the risk of desiccation for amphibians and some forest floor invertebrates.In the black spruce (

Picea mariana

) plantations studied by Waldick et al. (1999) inNew Brunswick, for example, summer forest floor temperatures exceeded the criticalupper threshold (32º C) for spotted salamanders (Pough and Wilson 1977), a factthey suggest contributed to reduced abundance compared to neighboring, naturalmixed species stands. Finally, needle-dominated litter is often more acidic than



265

hardwood litter (Wyman and Jancola 1992) such that conifer-dominated plantationsmay develop soil conditions intolerable to some amphibians and their prey (Wymanand Hawksley-Lescault 1987; Waldick et al. 1999). This is of special concern inregions with soils of poor buffering capacity such as typifies much of the Northeast.

Coarse Woody Debris (CWD)

Although more patchy in distribution than leaf litter, the relatively consistent micro-climate found within and beneath logs in close contact with the organic layerprovides a valuable forest floor retreat for amphibians and their prey. Large logs ofadvanced decay class are particularly effective at buffering salamanders from warmtemperatures and drying conditions on the forest floor (Mathis 1990; Fraver et al.2002). The specific functional importance of CWD has been well-established forterrestrial salamanders (Plethodontidae) that depend on forest floor cover objects,both as breeding substrate and as moist refugia conducive to extended foraging whendry litter conditions otherwise preclude surface activity (Jaeger 1980). The upland,nonbreeding habitat preferences of pool-breeding amphibians are less understood,but significant selection for areas of the forest floor with an increased abundance ofCWD has been reported in northeastern forests for spotted salamanders (Windmiller1996; Waldick et al. 1999; Faccio 2003), Jefferson salamanders (Faccio 2003) andwood frogs (Ross et al. 2000; Baldwin et al. in preparation) (Table 13.1).

Interestingly, while mole salamanders are frequently found beneath large logsor slabs of bark, especially during migration, one of the primary functions of CWDfor

Ambystoma

may be indirect. As their name implies, mole salamanders spend aconsiderable amount of time underground, often occupying burrows created by smallmammals and other animals (Semlitsch 1981; Madison 1997; Faccio 2003). Trackingindividual spotted and blue-spotted salamanders using radio-telemetry, Windmiller(1996) found that most animals were encountered under or within 0.5 m (1.6 ft) offallen tree trunks, tree stumps, and logs. Rather than selecting CWD

per se

as coverthe animals were exploiting existing small mammal burrows (usually short-tailedshrews,

Blarina brevicauda

; personal communication) that were themselves associ-ated with woody debris on the forest floor. A similarly close association betweensmall mammal tunnels occupied by Jefferson and spotted salamanders and theproximity of CWD was recently documented in Vermont (Faccio 2003). The avail-ability of small mammal burrows may in fact be a limiting factor for mole sala-manders, affecting their distribution and abundance in terrestrial habitats by servingas refugia from desiccation, freezing, and predation (Regosin et al. 2003; Rothermeland Luhring 2005). As such, forest harvest practices that degrade forest floor habitatsuitability for shrews and other burrowing small mammals (e.g., soil and littercompaction, reduced recruitment or removal of CWD) are likely to impact the qualityand carrying capacity of nonbreeding habitat for pool-breeding salamanders as well.

CONSERVATION RECOMMENDATIONS

We have reviewed several elements of breeding and nonbreeding habitat of impor-tance to pool-breeding amphibians, all of which are subject to potential impact by


266


TAB

LE 1

3.1

Sign

ifica

nt P

osit

ive

Ass

ocia

tion

s of

Nor

thea

ster

n Po

ol-B

reed

ing

Am

phib

ians

wit

h Fo

rest

Mic

roha

bita

ts

Spec

ies/

Com

mun

itie

sW

oody

Deb

ris

Litt

erD

epth

/Ext

ent

Und

erst

ory

Vege

tati

on

a

Can

opy

Clo

sure

Moi

stur

e

b

Ref

eren

ce

Spec

ies

Eas

tern

new

t (

Not

opht

halm

us v

irid

esce

ns

)+

1

(

r

2

= 0

.62)

+

2,4

(

r

2

= 0

.43)

2

+

31

Poug

h et

al.

1987

;

2

deM

ayna

dier

an

d H

unte

r 199

8;

3

Wym

an 1

988;

4

Ros

s et

al.

2000

Spot

ted

sala

man

der

(

Am

byst

oma

mac

ulat

um

)+

2,5

+

4

(

r

2

= 0

.59)

+

5

+

3, 6

(r2

= 0

.51)

3

+1,

51 W

yman

198

8; 2 W

indm

iller

199

6;

3 deM

ayna

dier

and

Hun

ter 1

998;

4 L

aVoi

e 20

05;

5 Fac

cio

2003

; 6 R

othe

rmel

and

Sem

litsc

h 20

02Je

ffer

son

sala

man

der

(A

mby

stom

a je

ffers

onia

num

)+

++

Facc

io 2

003

Woo

d fr

og (

Ran

a sy

lvat

ica)

+5,

c+

5, c

+3

(r2

= 0

.33)

+2,

4,

5

(r2

= 0

.65)

2

+1,

41 W

yman

198

8; 2 d

eMay

nadi

er a

nd

Hun

ter 1

998;

3 deM

ayna

dier

and

H

unte

r 19

99;

4 Bal

dwin

et

al.

2006

; 5 B

aldw

in,

et a

l., i

n pr

epar

atio

nA

mer

ican

toa

d (

Buf

o am

eric

anus

)+

d,1,

2

(r2

= 0

.45)

1

+3

1 Pai

s et

al.

1988

; 2 R

oss

et a

l. 20

00; 3 R

othe

rmel

and

Sem

litsc

h 20

02


Conserving Vernal Pool Amphibians in Managed Forests 267

Spec

ies/

Com

mun

itie

sW

oody

Deb

ris

Litt

erD

epth

/Ext

ent

Und

erst

ory

Vege

tati

ona

Can

opy

Clo

sure

Moi

stur

ebR

efer

ence

Com

mun

itie

sR

anid

ae,

Buf

onid

ae,

and

Ple

thod

onti

daee

and

othe

rse

(10

spp

.; N

ew H

amps

hire

)

+ (r2

= 0

.67)

DeG

raaf

and

Rud

is 1

990

Am

byst

omat

idae

and

Ran

idae

f

(7 s

pp.;

Penn

sylv

ania

)+

g

(r2

= 0

.29)

+h

(r2

= 0

.19)

Ros

s et

al.

2000

Not

e:R

esul

ts a

re f

rom

fiel

d st

udie

s of

nat

ural

pop

ulat

ions

and

rep

rese

nt s

igni

fica

nt a

ssoc

iatio

ns a

t p <

0.05

. The

coe

ffici

ent o

f de

term

inat

ion

is p

rovi

ded

as a

vaila

ble.

a R

efer

s to

per

cent

age

of c

over

of

low

er a

nd m

idle

vel

woo

dy s

hrub

str

ata

in a

ll ca

ses

unle

ss o

ther

wis

e no

ted.

b Fo

r m

easu

rem

ents

tak

en a

t m

icro

site

(vs

. st

and)

sca

le.

cSe

lect

ion

by a

dults

and

met

amor

phs

in o

utdo

or m

esoc

osm

exp

erim

ent.

dPe

rcen

t co

ver

by f

erns

and

(or

) he

rbs.

eR

ana

sylv

atic

a, B

ufo

amer

ican

us,

and

Ple

thod

on c

iner

eus

com

pris

ed 9

0% o

f ca

ptur

es;

depe

nden

t va

riab

le =

H a

nd J

.f

Am

byst

oma

mac

ulat

um,

A.

opac

um, A

. je

ffers

onia

num

, R

ana

sylv

atic

a, R

. pa

lust

ris,

R.

clam

itan

s, a

nd R

. ca

tesb

iana

.g

Ran

idae

onl

y (R

ana

sylv

atic

a, R

. ca

tesb

iana

, R

. cl

amit

ans,

and

R.

palu

stri

s).

h A

mby

stom

atid

ae (

3 sp

p.)

only

; tr

ee b

asal

are

a vs

. ca

nopy

clo

sure

.


268 Science and Conservation of Vernal Pools in Northeastern North America

intensive logging practices. Conversely, we also recognize that forest management,if practiced in an ecologically sensitive manner, can conserve, and even enhance,important elements of habitat structure and composition for pool-breeding fauna. Tothis end we offer a suite of Habitat Management Guidelines (HMGs; see alsoCalhoun and deMaynadier 2004) designed to protect high value vernal pools inworking forest landscapes. Like the familiar Best Management Practices (BMPs)that foresters apply for the protection of water quality, soil integrity, and aesthetics,the HMGs for pool-breeding amphibians are designed to be voluntary, science-based,and readily transferable to managed landscapes.

Notably, the recommendations outlined below are designed for use only inworking forest landscapes where long-term timber management is the primary goal.For applications that involve development, roads, and other types of permanenthabitat conversion and fragmentation readers should consult companion guidelinesfor developed landscapes (Chapter 12, Windmiller and Calhoun; Calhoun andKlemens 2002). Finally, we emphasize that the HMGs, although based upon bestavailable science, are nonetheless presented as a working hypothesis of what isneeded to conserve vernal pool habitat values in managed forests. We stronglyencourage further applied research designed to test and refine these and other poten-tial guidelines in the spirit of adaptive management (Walters 1986). This process ofincorporating new knowledge should be informed by controlled and replicatedexperimental designs and, less formally, through case-study observations and doc-umentation by the foresters, loggers, and land managers whose collective decisionsshape the habitat potential of working forests for pool-breeding wildlife and otherelements of biodiversity throughout the Northeast.

HABITAT MANAGEMENT GUIDELINES FOR PREHARVEST PLANNING

Some of the most important steps for conserving forest habitat for pool-breedingamphibians start in the office. Achieving specific forest harvest outcomes aroundvernal pools is easier if long-range planning has preidentified potential pools andtheir associated upland management zones. Consideration of the following planningsteps prior to forest harvest activity will help avoid potential conflicts:

• Develop a strategy for documenting potential vernal pools using aerialphotography (Chapter 4, Burne and Lathrop), National Wetland Inventorymaps (e.g., PUB, PSS, and PFO classification codes; Cowardin et al.1979), active ground reconnaissance, or incidental documentation duringother management activities (e.g., timber cruising, harvest layout).

• Include vernal pools and surrounding upland management zones (detailedbelow) on all forest management maps and/or Geographic InformationSystem layers used to track sensitive natural resources. Use these mapsand associated databases to help design spring field surveys for confirmingthe presence of high value vernal pools hosting abundant indicator species.

• Consider treating pool clusters (three or more pools within a quarter mileof one another) as a single management unit, with a goal of maintaining



contiguous forest between the pools. Extend the recommended uplandmanagement zones around the cluster, rather than around individual pools.

• Plan forest road and log landing construction to avoid vernal pools andnearby upland habitat. In addition to the permanent conversion of potentialforaging and overwintering habitat, such areas contribute to polluted run-off and vehicular mortality.

• Plan clearcut harvests, plantations, and chemical applications (includingpesticides, herbicides, and road dust treatments) to avoid vernal pools andtheir associated upland management zones. Some formulations used forthese purposes can cause amphibian malformation or mortality, even atlow concentrations (Chapter 11, Boone and Pauli).

• When possible, time harvest activities around vernal pools for winter,during frozen ground conditions. Adult and juvenile amphibians are oftennear the soil surface during other periods of the year, increasing their riskof mortality by heavy logging equipment.

HABITAT MANAGEMENT GUIDELINES FOR HARVEST OPERATIONS

The HMGs for harvest operations are designed to protect the vernal pool’s physicalbasin and water quality, and the integrity of surrounding forest habitat for criticalcomponents of pool-breeding amphibian life history including breeding, migration,dispersal, foraging, and hibernation. Although harvest strategies outlined in theHMGs generally lend themselves to uneven-aged management, it is not the intentof the guidelines to focus on specific silvicultural systems but rather to enumeratedesired outcomes and structural habitat thresholds needed to conserve pool-breedingamphibians. The vernal pool HMGs for harvest operations are described for threemanagement zones: the vernal pool depression, a vernal pool protection zone (31m; 100 ft), and a vernal pool life zone (31–22 m; 100–400 ft). An abbreviatedsummary of the Management Zones and Guidelines for conserving pool-breedingamphibians during forest harvest operations is provided in Table 13.2.

Vernal Pool Depression

This zone includes the vernal pool depression at spring high water, which may notalways be wet during the period when timber is being harvested. During the dryseason, the high-water mark can often be determined by the presence of blackened,water- or silt-stained leaves, aquatic debris along the edges, or a clear change intopography from the pool depression to the adjacent upland. The primary manage-ment goal in this zone is to maintain the vernal pool’s water quality, physical basintopography, and associated vegetation in an undisturbed state.

Management RationaleThe pool basin is the primary breeding and nursery habitat for pool-dependentamphibians and invertebrates. Rutting or compaction in the pool can alter the pool’swater-holding capacity, disturb eggs or larvae buried in the organic layer, and alterthe amphibian’s aquatic environment. Harvesting operations in the pool, even during



the winter, can disturb woody vegetation that may serve as egg attachment sites,organic inputs, and shade.

Management Guidelines:

1. Mark the pool’s location.a. Identify the spring high water mark (during the wet season or using

dry season indicators) and flag the pool’s perimeter during harvestlayout and prior to cutting.

TABLE 13.2Summarized Habitat Management Guidelines for Conserving Pool-Breeding Amphibians during Forest Harvest Operations

Management Zone(Radial Distance

from Pool)Managed

Area a Primary Habitat Value Management Guidelines

Vernal Pool Depression(0 m/ft)

0.08 ha(0.2 acres)

Breeding and Larval Habitat

• Water quality, hydrology, micro-relief, egg attachment

No Disturbance

Vernal Pool Protection Zone

(31 m/100 ft)

0.6 ha(1.4 acres)

Riparian Buffer and Staging Habitat

• Pool ecosystem: shade, organic inputs, riparian buffer

• Juvenile nursery and staging habitat during natal dispersal

• Adult concentration habitat during breeding migration

Limited Harvest

• >75% canopy cover• Frozen or dry soil operation

• Avoid use of heavy machinery

• No roads or landings• Avoid chemical application• Abundant CWD

Vernal Pool Life Zone(31–122 m/100–400 ft)

5.3 ha(13.0 acres)

Terrestrial Nonbreeding Habitat

• Migration, dispersal, foraging, summer estivation, and hibernation

• Primary adult nonbreeding habitat for 11+ months of the year

Partial Harvest

• >50% canopy cover• Harvest openings <0.3 ha (3/4 acre)

• Frozen or dry soil operation

• Minimize roads and landings

• Minimize chemical application

• Abundant CWD

a Acreage estimates based on a vernal pool with a 100 ft. diameter, or approximately 0.2 acres.



2. Protect the pool basin and its natural vegetation.a. Leave the depression undisturbed. Avoid harvesting, heavy equipment

operation, skidding activity, or landing construction in the vernal pooldepression.

b. Keep the pool free of sediment, slash, and tree-tops from forestryoperations. Leave woody debris that accidentally falls into the poolduring the breeding season (March to June) to avoid damaging eggmasses. Trees and branches that fall naturally into pools provide valu-able organic inputs and can serve as egg attachment sites.

Vernal Pool Protection Zone (31 m [100 ft] around the Pool)

This zone includes a 31 m (100 ft) radius around the pool measured from the springhigh-water mark. The primary management goal for this zone is to protect the vernalpool and surrounding habitat by maintaining or encouraging a mostly closed canopystand in a pole- or greater-size class that will provide shade, deep litter, and woodydebris around the pool.

Management RationaleThe integrity of the forest immediately surrounding the pool depression is criticalfor maintaining water quality, providing shade and litter for the pool ecosystem, andproviding moist, shaded, upland forest floor conditions. Aquatic systems generallyderive most of their organic inputs from a distance of approximately one to two treelengths (reviewed by Palik et al. 2000), underscoring the dual functions of theprotection zone as both a riparian buffer with effects on the structure, temperature,chemistry, and food supply of the aquatic ecosystem, and as primary habitat foramphibians immigrating and emigrating from the pool. In the spring, high densitiesof adult amphibians occupy the habitat immediately surrounding the pool, followedin late summer by large numbers of recently metamorphosed salamanders and frogs.Juvenile mole salamanders are especially vulnerable to desiccation during the firstmonths after metamorphosis (Semlitsch 1981; Rothermel and Semlitsch 2002) anddispersing wood frogs and spotted salamanders select for shaded, forested conditionsimmediately upon metamorphosis (deMaynadier and Hunter 1999; Vasconcelos andCalhoun 2004).


1. Mark the pool protection zone’s location.a. Based on the spring high water mark of the pool, flag the perimeter of

the protection zone during harvest layout and prior to any cutting.2. Maintain a mostly closed forest canopy.

a. Maintain at least 75% canopy cover of trees at least 6.1–9.1 m (20–30ft) tall, uniformly distributed throughout the zone. In understockedstands, delay harvest activity until overstory canopy cover hasincreased beyond 75%.

3. Protect the forest floor.



a. Harvest only during completely frozen or completely dry soil condi-tions. Do not create ruts and minimize soil disturbance.

b. Avoid the use of heavy machinery in this zone by employing techniquessuch as motor-manual crews, directional felling, and extended cablewinching and/or booms.

c. Avoid new road or landing construction.4. Maintain coarse-woody debris.

a. Leave a few larger or older legacy trees to serve as recruitment forcoarse woody debris.

b. Avoid disturbing fallen logs. Leave limbs and tops where felled, orreturn slash to the zone during whole-tree removal.

5. Avoid the use of pesticides, herbicides, and other chemicals.

Vernal Pool Life Zone (31 to 122 m [100 to 400 ft] around the Pool)

This zone includes a 31–122 m (100–400 ft) zone around the pool measured fromthe spring high-water mark. The primary management goal for this zone is to providesuitable upland habitat for local pool-breeding amphibian populations by maintain-ing or encouraging a partially closed-canopy stand that offers shade, deep litter, andwoody debris well distributed around the pool.

Management RationaleThe vernal pool life zone is required to support the nonbreeding, upland life-historyneeds of pool-breeding amphibians. The zone’s radius is designed to address aportion of the habitat used by northeastern pool-breeding mole salamanders(Ambystoma spp) — an amphibian group that is among the most sensitive to uplandforest habitat perturbations, and whose movement ecology is relatively well under-stood. The mean adult migration distance for five species of mole salamander (n =17 studies) distributed throughout the glaciated Northeast is 118.3 m (388 ft) (Chap-ter 7, Semlitsch and Skelly; Color Plate 17), with many individuals migrating toeven greater distances.

Forest floor environments suitable for supporting amphibian populations aremost likely to be maintained by light to moderate partial cuts within this managementzone. Juvenile and adult wood frogs and spotted salamanders select mostly closed-canopy forests during emigration and dispersal in managed forest landscapes(deMaynadier and Hunter 1998, 1999; Vasconcelos and Calhoun 2004). Mole sala-manders are often under or closely associated with woody debris on the forest floor(Faccio 2003). Dramatic shifts in forest cover type should be avoided, as amphibiansare sensitive to the resulting changes in litter composition and chemistry(deMaynadier and Hunter 1995; Waldick et al. 1999). Rutting and scarification ofthe forest floor may impede salamanders from traveling to natural breeding poolsby creating barriers along travel routes (Means et al. 1996) or shallow, anthropogenic“decoy pools” that may not hold water long enough to successfully produce juveniles(DiMauro and Hunter 2002).




1. Maintain a partially closed forest canopy.a. Maintain at least 50% canopy cover of trees at least 6.1–9.1 m (20–30

ft) tall, uniformly distributed throughout the zone. In understockedstands, delay harvest activity until overstory canopy cover hasincreased beyond 50%.

b. Avoid canopy harvest openings greater than 0.3 ha (3/4 acre) in size.c. If even-aged management is practiced, extended shelterwood or similar

systems with continuous partial overstory retention helps to maintainsuitable forest floor conditions.

2. Maintain natural litter composition.a. Avoid significant shifts in forest cover type (e.g., hardwood or mixed

wood to softwood) to minimize changes in natural litter composition.b. Avoid plantation silviculture in this zone.

3. Protect the forest floor.a. Harvest only during completely frozen or dry soil conditions. Do not

create ruts.b. Minimize soil compaction and scarification from heavy machinery by

using techniques such as: controlled yarding (i.e., preplanning locationand spacing of trails and limiting the number of passes), minimizingsharp turns, and placement of slash to increase the bearing capacity ofsoils.

c. Minimize the footprint of new roads or log landings by pre-planningtheir layout and construction either outside of the zone or at the outerportions of the zone.

4. Maintain coarse-woody debris.a. Leave a supply of larger or older trees, approximately 3–5/ha

(1–2/acre), to serve as recruitment for larger diameter coarse-woodydebris.

b. Avoid disturbing fallen logs. Leave limbs and tops where felled, orreturn slash to the zone during whole-tree harvest treatments.

5. Minimize the use of pesticides, herbicides, and other chemicals.a. If chemicals must be sprayed in this zone, avoid use in the spring and

late summer/fall when amphibian surface activity is greatest.6. Extend the Vernal Pool Life Zone as far as practical.

a. Where property boundaries and nonforest land-uses (e.g., residentialareas, agricultural land) limit the extent of accessible forest in this zoneto less than 122 m (400 ft), extend the life zone and associated HMGsas far as practical.

SUMMARY

Northeastern North America is one of the few regions on earth with greater naturalforest cover today than 150 years ago. With most of these forest lands in private



ownership, as much as 90% in New England, timber management is by definitionone of the region’s most widespread land practices affecting the quality and quantityof habitat for forest-dwelling wildlife. Furthermore, given the exceptionally highvernal pool densities found throughout much of the region, it is nearly impossibleto avoid potential impacts, positive or negative, to pool-breeding amphibians duringthe course of most timber harvest operations. We review the ecology, movementsand forestry-habitat relationships of several major pool-breeding amphibian taxa asa basis for informing a specific suite of Habitat Management Guidelines for con-serving pool-breeding amphibians in managed forest landscapes. Designed to bevoluntary, science-based, and realistic in application, the HMGs are recommendedfor landowners, loggers, and foresters who are striving to balance commercial timberinterests with the protection of high-value breeding pools and critical elements ofhabitat structure in the surrounding upland forest. Specific guidelines are providedfor both (1) preharvest planning and (2) active field harvest operations, where distinctmanagement recommendations are offered for three zones: the vernal pool depres-sion, a vernal pool protection zone (31 m [100 ft] around pool), and a vernal poollife zone (31–122 m [100–400 ft] around the pool) (Table 13.2). Although thebreeding pool depression should be left completely undisturbed, we conclude thatpartial harvesting of the immediate upland forest surrounding vernal pools is com-patible with the conservation of pool-breeding amphibian habitat if it is done in anecologically sensitive manner that maintains a moderately shaded forest floor withdeep, uncompacted litter and abundant coarse woody debris. We emphasize that theHMGs, although based upon best available science, are nonetheless a workinghypothesis of what is needed to conserve vernal pool habitat values in managedforests, and therefore we encourage further research to help test, refine, and buildupon their tenets. The challenge for those interested in amphibian-forestry relation-ships has evolved from simply documenting impacts, to identifying realistic harvestprescriptions that maintain critical components of the forest’s biological legacycapable of sustaining healthy amphibian populations.

ACKNOWLEDGMENTS

Financial support for this research was provided by contributions to the Endangeredand Nongame Wildlife Fund of the Maine Department of Inland Fisheries andWildlife (Chickadee Checkoff and Conservation License Plate), Natural Sciencesand Engineering Research Council, and The New Brunswick Wildlife Trust. Theauthors are grateful to Malcolm Hunter, Robert Bryan, and Suzanne Nash forvaluable reviews of the manuscript and to Aram Calhoun for permitting inclusionof the Habitat Management Guidelines, which are closely modeled after those firstpresented in Calhoun and deMaynadier (2004). Finally, the first author wishes tothank his family whose support and encouragement made this project possible.



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