September 15, 2009

Jessica Veysey

Graduate Student

Author of Vernal Pools

Attachment referred to in email follows:

Draft Unique and Fragile Areas: Vernal Pools

x.x VERNAL POOLS AND THE SURROUNDING FOREST

ISSUE

Vernal pools and the adjacent forest provide critical habitat for numerous wildlife species, but vernal pools are easily overlooked because they are small and dry seasonally.

Vernal pools are unique wetlands that provide critical habitat for several amphibian and reptile species of greatest conservation need in New Hampshire. Vernal pools differ from other wetlands in that they have a seasonal cycle of flooding and drying - this cycle determines what wildlife species will use vernal pools as habitat. Many vernal pools flood then dry each year, though some pools may hold water for several years between drying events. Vernal pools form in shallow depressions or basins, and may appear as simple pools of water in the forest, with little or no vegetation growing in them. To be considered a vernal pool in NH[JSV1], the pool can’t have a permanently-flowing outlet and it must hold water for at least two months after spring ice-out (See NH Administrative Rule Env-Wt 101 for the official state definition).

Fish are major predators in wetlands, but they are unable to maintain viable populations in vernal pools (because they dry). As a result, vernal pools provide critical breeding habitat for amphibians whose tadpoles and larvae are especially vulnerable to fish predation. These species include spotted salamanders, blue-spotted/Jefferson’s salamanders, state-endangered marbled salamanders, and wood frogs. Several other amphibian species and invertebrates also use vernal pools as breeding habitat. Other species besides amphibians use vernal pools. Fairy shrimp are small crustaceans that require vernal pools for breeding. State-endangered Blanding’s turtles and state-threatened spotted turtles feed on amphibian eggs in vernal pools and use them for basking, mating, and overwintering[JSV2]. These turtles also use vernal pools as stop-over habitat when migrating through forests, because pools provide moist refuge and abundant food (Grgurovic and Sievert 2005; Baldwin et al. 2006a). Many mammals, birds and snakes also forage at vernal pools, including song birds, wood ducks, ribbon snakes, bats, and raccoons.

While vernal pools are essential habitat for many wildlife species, the forest surrounding the pools is equally important.For example, wood frogs and the salamanders that breed in vernal pools spend over 11 months of the year in the forest (Semlitsch and Bodie 2003). In fact, spotted, blue-spotted/Jefferson’s, and marbled salamanders are often referred to collectively as “mole salamanders” because they spend most of the year underground, in small mammal burrows in upland forests (Madison 1997; Faccio 2003). Wood frogs spend the summer not only in vernal pools, but also in forested wetlands and moist uplands surrounding the pools, and they overwinter beneath the leaf litter in upland forests (Baldwin et al. 2006b; Freidenfelds and Babbitt unpub. data). Also, Blanding’s and spotted turtles use forests adjacent to vernal pools for basking and aestivating during summer (Joyal et al. 2001; Milam and Melvin 2001).

Most wood frogs and mole salamanders occur within 950 feet of the vernal pool in which they breed (Rittenhouse and Semlitsch 2007; Harper et al. 2008; Veysey et al. 2009). Turtles on the other hand, often migrate several thousand feet between vernal pools and their other seasonal habitats (e.g., Joyal et al. 2001; Milam and Melvin 2001, Innes et al. 2008). When these distances are considered with the fact that vernal pools are widely distributed across the landscape, more forestry operations than not will have the potential to directly influence habitats used by vernal pool-dependant amphibians and reptiles. From a forestry standpo[JSV3]int, Tthese species are most sensitive to disturbances that alter water quality or temperature within the pools, alter the length of time the pools hold water, or alter the air and soil temperature in the forest surrounding vernal pools.

Some potential impacts of timber harvesting on vernal pools are easy to recognize and can be avoided by following established best management practices. For example, depositing slash directly in vernal pools and creating vehicle ruts that cause sediment to enter pools, can affect pool water quality enough to reduce animal growth and survival, as well as alter what wildlife will use the pool (e.g., Babbitt et al. 2003; Brausch and Smith 2007). Vehicle ruts can also reduce the length of time a pool holds water by directing water away from the pool – such an impact may not be immediately obvious even to trained eyes. Ruts at any distance from a pool can create breeding “traps” for amphibians, since wood frogs and salamanders will often deposit eggs in ruts, but most ruts dry too quickly to allow the eggs to develop completely.

Other potential impacts on vernal pool-dependant species are less understood and much harder to quantify. For example, excessive compaction or scarification of the soil during timber harvesting may reduce leaf litter and burrows, and thus reducinge the amount of suitable upland habitat available to wood frogs and mole salamanders. Further, reducing forest canopy cover can increase water temperature in vernal pools and cause hot, dry conditions in uplands; both conditions can lead to lower amphibian survival (Dexter 1946; Rothermel and Luhring 2005) and alter where in the forest amphibians migrate (Veysey et al. 2009) or disperse (Rothermel 2004). These impacts likely increase as forest opening size increases. However, it is unclear how specifically these impacts change as the disturbance increases from a single-tree opening, to a small group opening, to a large clearcut of many acres. In most cases, the negative effects of timber harvesting on vernal pool-dependant species are temporary and decrease with time as the forest regenerates (Russell et al. 2002; Morris and Maret 2007).

OBJECTIVE

Manage vernal pools and the surrounding forest to provide amphibian, invertebrate, and turtle habitat, by maintaining pool hydrology, water quality, forest floor integrity, and sufficient canopy cover.

CONSIDERATIONS

  • Many vernal pools meet the statutory definition of wetland and are subject to state wetlands regulations pertaining to timber harvesting.
  • Marbled salamanders and Blanding’s turtles are listed as endangered, and spotted turtles as threatened species by the state of New Hampshire, and are protected under the NH Endangered Species Conservation Act. The NH Natural Heritage Bureau can tell you if these or other listed species have been documented on or near your property.
  • Vernal pools are most easily identified when they contain water in the spring. It may be necessary to flag or otherwise mark the perimeter of vernal pools so they can be identified during the dry season or during winter, if harvesting is planned for these seasons. The publication Identification and Documentation of Vernal Pools in New Hampshire (available from the NH Fish and Game Department) is a helpful resource. The UNH Cooperative Extension Wildlife Specialist or a NH Fish and Game Biologist can provide assistance identifying vernal pools.
  • The time a vernal pool fills with water, how long it holds water, and the type and abundance of amphibians and invertebrates it supports can all change dramatically from year to year. This is a natural feature of vernal pool systems and the animals that use the pools are adapted to this variation. Though some species may not be present at a particular pool in a given year, that pool and its surrounding forest may still be high-quality habitat for these species.
  • The variability described above combined with a lack of long-term studies in the northeast means that much is still unknown about the specific effects of timber harvesting on the long-term viability of vernal pool-dependent reptiles and amphibians. However, the available research suggests the following which should be considered when planning activities around vernal pools:
  • Typical wetland buffers intended to protect water quality are generally too narrow to allow amphibians to complete all of their life-history processes and may be inadequate for maintaining viable amphibian populations (Rittenhouse and Semlitsch 2007; Harper et al. 2008; Veysey and Babbitt unpub. data).
  • Forest managers should expect that the negative affects of habitat drying and increased soil and air temperature will increase as forest opening size increases. (Cromer et al. 2002; Renken et al. 2004; Patrick et al. 2006; Veysey et al. 2009; Veysey and Babbitt unpub. data).
  • Where canopy cover is reduced below 65%, it will probably have at least a temporary negative affect on vernal pool-dependent amphibians - until the canopy or understory cover fill in - but this effect is likely lower than would occur in a clearcut in which all over story trees are removed (Miller 2001; Rothermel and Luhring 2005; Patrick et al. 2006).
  • Openings such as wildlife food plots, pastures, fields and landings create barriers to reptile and amphibian dispersal because they are often hot, dry, and slow to revert back to closed-canopy forest conditions (e.g., deMaynadier and Hunter 2000; Rothermel 2004; Veysey et al. 2009). These openings are most likely to create barriers when they are located directly between adjacent wetlands.
  • Impacts of existing forest openings and conversion to non-forest openings will likely have a greater negative impact on vernal pool-dependent species when conducted in landscapes that are already fragmented by development than are similar activities conducted in a heavily forested area where displaced wildlife are more likely to find suitable alternative habitats (Herrmann et al. 2005).
  • Although reptiles and amphibians are small they can, and do, travel long distances across the landscape. These movements are critical for maintaining genetic variability within amphibian populations and for recolonizing sites where local amphibian populations have gone extinct from natural or human-influenced reasons. As a result, few timber harvests will be far enough away from a vernal pool for managers to not at least consider the long-term viability of the site to provide habitat for vernal pool-dependent species. To provide some perspective: adult mole salamanders and wood frogs generally migrate 360 and 460 feet, respectively, between their upland habitats and their vernal pool, but some may migrate seasonally as far as 1650 feet.(e.g., Semlitsch and Bodie 2003; Baldwin et al. 2006b; Veysey et al. 2009) and juvenile salamanders and wood frogs may disperse as far as ½ to several miles away from the pool in which they were born (Smith and Green 2005; Zamudio and Wieczorek 2007).
  • Both the vernal pool itself and the surrounding forests are critical for maintaining a functional vernal pool system, but each habitat serves different functions. Managers planning timber harvests that meet the non-vernal pool objectives of the landowner can avoid or minimize impacts to vernal pool-dependent wildlife by considering two habitat management zones and their biological significance:

Breeding Habitat Zone: The vernal pool and the surrounding 200 feet

The breeding habitat zone includes the vernal pool basin and a forested buffer extending 200 feet from the pool edge. This zone is intended to protect the breeding habitat of vernal-pool-dependent amphibians and macro-invertebrates. The pool basin is the physical breeding location for many of these species and is a nursery for their eggs and larvae. The buffer helps protect pool water quality by filtering sediment and pollutants, providing shade, and slowing surface runoff. The buffer also provides leaf litter, which is the foundation of the vernal pool food chain, and shelter for adult and metamorphic amphibians immediately after they emerge from the pool.

Core Habitat Zone: 950 feet surrounding the vernal pool

The core habitat zone extends from the breeding habitat zone out to 950 ft from the vernal pool edge. The core habitat zone provides critical habitat for amphibians of all age classes during the non-breeding season, and provides aestivating and basking habitat for spotted and Blanding’s turtles. During the non-breeding season, about 70% of the wood frog population and nearly all of the spotted salamander population [JSV4]occur within this zone (Rittenhouse and Semlitsch 2007; Harper et al. 2008; Veysey et al. 2009).

RECOMMENDATIONS

General recommendations for any timber harvesting with regard to vernal pools

  • Note the location of known or potential vernal pools within the harvest area and alert equipment operators of their location. Locations could be GPSed or mapped if similar information is collected as part of a forest stewardship plan.
  • Avoid running machinery through vernal pool basins, even during dry periods, to avoid changing the pool's ability to hold water (Roble and Kittredge 1991).
  • Locate openings such as wildlife food plots, pastures, fields, landings, main skidder trails, and haul roads as far as reasonably possible from vernal pools.
  • When constructing landings, woods roads, and permanent non-forest openings, minimize grading. Maintaining natural topography maintains the volume and timing of water reaching vernal pools.
  • Avoid locating permanent, non-forest openings directly between two adjacent vernal pools.
  • After harvesting, smooth out any vehicle ruts greater than 6 inches deep (Roble and Kittredge 1991) to prevent amphibians from depositing eggs in ruts, which are unsuitable habitat. Avoid, or otherwise minimize rutting by following established BMPs.
  • Avoid adding slash (i.e., woody cutting debris) to vernal pools. Where significant amounts of slash fall into the pool, remove it once the pool is dry, by hand or some other low-impact method. If the pool contains water, leave the slash until the dry season. Removing it when the pool holds water can disrupt amphibian egg and larval development.
  • Retain as much existing dead and down woody material as possible within 200 feet of a vernal pool.
  • Avoid removing trees that have crowns immediately overtopping any portion of the pool in order to maintain water temperature and nutrient inputs. If trees must be removed, remove as few trees as possible. Prioritize removing trees that are overtopping advanced regeneration or established shrub cover in an attempt to minimize the effects of reduced canopy cover around the pool.
  • When operating conditions allow, harvest on frozen ground or in dry summer conditions.

Recommendations when vernal pool-dependent amphibians and reptiles are a management priority

Within 200 feet of a vernal pool:

  • Limit tree removal to individual trees or small groups of trees.
  • If trees must be removed in groups, attempt to locate groups where there is established advanced regeneration or shrub cover which can help to maintain shady conditions after the overstory is removed.
  • Avoid removing stumps, stones, or other large cover objects.
  • Maintain as much of the existing understory vegetation (i.e., small trees, shrubs, herbaceous ground cover) as possible.
  • Limit the activity of heavy equipment.
  • Locate main skidder roads outside of this buffer.
  • Don’t apply herbicides or pesticides.

Between 200 and 950 feet of a vernal pool:

  • Maintain at least 65% crown closure.
  • Avoid, or at least limit the size of, permanent non-forest openings such as wildlife food plots, pastures, and landings.
  • Avoid, or at least limit the amount of area that is scarified, stumped, or regraded, to maintain natural ground conditions, coarse woody material, and other cover objects.
  • Minimize soil compaction and disturbance to leaf litter. Harvesting during winter and when soils are frozen is preferred.
  • Maintain as much of the understory vegetation and existing dead and down woody material as possible.

CROSS REFERENCE

Harvesting Systems; Water Quality; Wetlands; Your Land and the Larger Landscape

REFERENCES

Babbitt, K.J., M. Baber, and T.L. Tarr. 2003. Patterns of larval amphibian distribution along a wetland hydroperiod gradient. Canadian Journal of Zoology 81: 1539-1552.

Baldwin, R.F., A.J.K. Calhoun, and P.G. deMaynadier. 2006a. The significance of hydroperiod and stand maturity for pool-breeding amphibians in forested landscapes. Canadian Journal of Zoology 84: 1604-1615.

Baldwin, R.F., A.J.K. Calhoun, and P.G. deMaynadier. 2006b. Conservation planning for amphibian species with complex habitat requirements: a case study using movements and habitat selection of the wood frog (Rana sylvatica). Journal of Herpetology 40(4): 442-453.

Bell, S.L.M., T.B. Herman, and R.J. Wassersug. 2007. Ecology of Thamnophis sauritus (eastern ribbon snake) at the northern limit of its range. Northeastern Naturalist 14(2): 279-292.

Brausch, J.M., and P.N. Smith. 2007. Toxicity of three polyethoxylated tallowamine surfactant formulations to laboratory and field collected fairy shrimp, Thamnocephalus platyurus. Archives of Environmental Contamination and Toxicology 52: 217-221.

Broadmeadow, S., and T.R. Nisbet. 2004. The effects of riparian forest management on the freshwater environment: a literature review of best management practice. Hydrology and Earth System Science 8: 286-305.

Brodman R., and R. Dorton. 2006. The effectiveness of pond-breeding salamanders as agents of larval mosquito control. Journal of Freshwater Ecology 21(3): 467-474.

Costanzo, J.P., R.E. Lee, and M.F. Wright. 1991. Effect of cooling rate on the survival of frozen wood frogs, Rana sylvatica. Journal of Comparative Physiology B - Biochemical Systematic and Environmental Physiology 161: 225-229.

Cromer, R.B., J.D. Lanham, and H.H. Hanlin. 2002. Herpetofaunal response to gap and skidder-rut wetland creation in a southern bottomland hardwood forest. Forest Science 48: 407-413.