Landscape Ecology Questions

• Current regulations in Massachusetts and other states tend to leave landscapes rich in wetlands but lacking diverse and extensive terrestrial resources.

• By-laws adopted by many communities seek to increase protection of vernal pools and critical habitat areas by establishing 50 to 100 foot borders around them.

• Efforts by Massachusetts Natural Heritage have greatly increased the knowledge base about the location of vernal pools and may offer assistance to communities seeking to protect breeding habitats and identify priority areas for acquisition.

• This research was carried out to allow for some examination of the effects of this type of landscape management on patterns of persistence and abundance for reptiles and amphibians in eastern Massachusetts.

Natural Heritage Resource Information for the Study Area

Biomap Core Habitat Potential Vernal Pools

Study area showing locations of ponds and pools

Aerial view of selected pools

Culver Street pool and associated land covers

Species Sensitivity to Landscape Change

Spotted Salamander Ambystoma maculatum

Annual migration Importance of upland forest in proximity to suitable

breeding areas Blue-spotted x Jefferson Salamander

Ambystoma laterale x jeffersonianum Annual migration Importance of forest in proximity to suitable breeding

pools Red spotted newt

Notophthalmus viridescens Some populations dependent upon terrestrial resources

for juvenile development Demonstrated metapopulation structure of populations

Green frog Rana clamitans

Possible importance of metapopulation dynamics to population persistence

Bull frog Rana catesbeiana

Evidence of positive response to increased disturbance and fragmentation

Wood frog Rana sylvatica

Evidence of importance of dispersal in some populations

Importance of upland forest in proximity to suitable breeding areas

Gray treefrog Hyla versicolor

Possible importance of metapopulation dynamics to population persistence

Snapping Turtle Chelydra serpentina

Migration for nesting Possible importance of multiple connected pools for

some populations Painted Turtle

Chrysemis picta Migration for nesting

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

0.5

0 50 100 150 200 250 300 350 400 450

Distance to nearest structure (m)

Ab

un

dan

ce o

f A

. mac

ula

tum

(av

era

ge

cap

ture

s

pe

r tr

ap n

igh

t)

Distance of nearest structure in relation to abundance of A. maculatum

Relationship between developed lands in the landscape and abundance of A. maculatum

Effects of the amount of upland forest on the presence and absence of A. maculatum from potential breeding pools.

Occupation of pools by breeding A. maculatum in relation to pond permanence and upland forest coverage within 30 m of pool edge.

0 1000 2000 3000 4000 5000 6000

Coverage of upland forest within 30 m of pool edge (m2)

perm.

long

mod.

short

Pond permanence

Absent Present

Distribution of A. laterale x jeffersonianum hybrids in study area

Present in pools in more developed areas

Abundance greatest in pools with longer hydroperiods with little upland forest in surrounding landscape

Logistic regression analysis of patterns of distribution of A. laterale x jeff.

Occupation patterns of A. laterale hybrids and A. maculatum in relation to significant landscape variables.

0 1000 2000 3000 4000 5000 6000

Upland forest within 30 m of pool (m2)

0

10000

20000

30000

40000

50000

60000

70000

Wooded wetlands within 200m of

pool (m2)

Pool Occupation

Both species A. laterale x only A. maculatum only Neither species

Occurrence of N. viridescens in study area pools

Present in six permanent pools in the less developed southern portion of the study area.

Absent from pools in this area with abundant populations of predatory fish.

Suggestion of large scale landscape effects, consistent with past studies which suggest a high level of importance of successful dispersal

Occurrence of bull frogs and evidence of breeding in study area ponds.

Abundance of R. sylvatica larvae as a function of forested lands within 30 m of pool edge (fish free pools only)

Abundance of R. sylvatica larvae in relation to pond permanence and coverage of forest lands within 30 m of pool edge.

Short Mod Long Perm

Pond Permanence

0

1000

2000

3000

4000

5000

6000

7000

Coverage of forest lands within

30 m of pool edge (m2)

Absent Present Common Abundant

Abundance Category

Abundance of C. picta in relation to developed lands within 30 m of pool edge.

Abundance of C. picta in relation to wooded wetlands within 30 m of pool edge.

Species for which no landscape characteristics emerged as significant predictors of distribution patterns

• C. serpentina – Distribution patterns predicted (poorly) based on pond area and extent of vegetative development. The species occurred in pools throughout the developed portion of the study area, although anecdotal data suggest regular patterns of migration between marginally suitable pools.

• R. clamitans – While wooded wetlands were more extensive around breeding pools, green frogs seemed tolerant of development, although there was no evidence of increased larval densities for the species as there was for bull frogs.

• H. versicolor – Gray treefrogs were collected from 6 fish-free permanent pools characterized by varied intrinsic and extrinsic factors. Repeated observations on windows in densely populated areas suggest some tolerance for development.

Conclusions

• Generally, existing regulations will favor those species that do not have a terrestrial habitat requirement, are characterized by relatively stable population sizes and are able to disperse across developed landscapes.

• This research supported previous studies that have documented the value of small wetlands in the preservation of a diverse herpetofauna.

• Existing wetlands protection legislation may provide the basis for development of more effective regulations, but new regulations must address issues of minimal area, connectivity and buffering if they are to be effective. Such regulations must also address the occasionally conflicting demands of managing for rare species and for overall regional biodiversity.

• Regulations that set de minimus threshold impact levels that allow for the conversion of small systems would allow for the destruction of several small pools in the study area that provide habitat for different species.

• This research suggests that the effectiveness of replacement wetlands would require careful attention to both intrinsic pond characteristics and the ability of the species under consideration to locate and colonize the area. For several species hydrology emerged as a significant predictor of habitat use.