12-001.qxd 12/18/12 6:17 PM Page 25 Spatio-statistical Predictions of Vernal Pool Locations in Massachusetts: Incorporating the Spatial Component into Ecological Modeling Tina A. Cormier, Russell G. Congalton, and Kimberly J. Babbitt Abstract 1998). In addition to biodiversity functions, vernal pools Vernal pools are small, isolated, depressions that experience also promote flood control, improve water quality, and cyclical periods of inundation and drying. Many species stabilize soils by intercepting sediment, nutrient rich run-off, have evolved strategies to utilize the unique characteristics and precipitation (Leibowitz, 2003; Wolfson et al., 2002). of vernal pools; however, their small size, seasonal nature, For most purposes, including protective legislation, and isolation from other, larger water bodies, suggest vernal pools are primarily defined by the wildlife found increased risk of damage or loss by development. The within them, rather than by their physical features (i.e., objectives of this research were to statistically determine obligate and facultative species) (Table 1 and Table 2). Most physical predictors of vernal pool presence, and subse- pools, however, have some basic physical attributes in quently, to represent the output cartographically for use as common: they are small, depressional basins; they are a conservation tool. Logistic regression and Classification geographically isolated from other wetlands; and they and Regression Tree (CART) methods were used to identify exhibit cyclical periods of inundation and drying. Their important predictors of 405 known vernal pools across small size, seasonal nature, and isolation from other, larger northeastern Massachusetts. The CART models performed water bodies, suggest increased risk of degradation or loss most favorably, achieving map accuracies as high as by development, as they are often left unprotected under 97 percent and providing a set of rules for vernal pool wetland legislation (Calhoun and deMaynadier, 2008). prediction. It is important to note that we observed signifi- The vulnerability of vernal pools to development and cant discrepancies between model accuracy and map the fragmentation of adjacent uplands have led to extensive accuracy, illustrating the pitfall of relying on statistical efforts to identify them in the landscape. Massachusetts, in metrics alone (e.g., R2 values) to assess the quality of spatial particular, has been a pioneer in accepting the difficult analyses. issues surrounding vernal pool identification and protection; it was one of the first states in the nation to pass regulations that specifically protect vernal pool habitat (Burne and Introduction Griffin, 2005). While legislation is an important step in the process of Motivation safeguarding vernal pools, a complete inventory of vernal Vernal pools are ephemeral wetlands that are biologically pool locations across the landscape is critical to begin active primarily during the spring and summer months. effective enforcement of these regulations. Until 2001, vernal Many amphibian and invertebrate species have evolved life pool identification in Massachusetts relied almost exclusively history strategies to utilize the distinctive characteristics of upon discovery and certification by interested citizens, vernal pools and the surrounding uplands. These unique resulting in patchy distributions of known pools. Early efforts ecosystems contribute disproportionately to the biodiversity to identify vernal pools on a regional scale included photoint- of the landscape by providing a range of wetland habitat for erpretation of infrared aerial photography in the Quabbin a variety of rare and endangered species. Despite their small Reservoir in central Massachusetts by Brooks et al. (1998). size, the significance of vernal pools in maintaining the An intensive effort was made to more completely identify diversity of the overall landscape is large (Calhoun and potential vernal pools on a statewide scale using photointer- deMaynadier, 2008; Leibowitz, 2003; Semlitsch and Bodie, pretation in 2001 (Burne, 2001). While photointerpretation is considered to be relatively fast and effective for pool detec- tion across the landscape, there are other methods that may prove to be more time and cost efficient. For example, Frohn Tina A. Cormier is with the Woods Hole Research Center, et al. (2009) used object-oriented classification of Landsat-7 149 Woods Hole Rd., Falmouth, MA 02540, and formerly with the Department of Natural Resources & the Environment, 114 James Hall, University of New Hampshire, Durham, NH 03824. Photogrammetric Engineering & Remote Sensing Vol. 79, No. 1, January 2013, pp. 25–35. Russell G. Congalton and Kimberly J. Babbitt are with the Department of Natural Resources & the Environment, 0099-1112/13/7901–25/$3.00/0 114 James Hall, University of New Hampshire, Durham, © 2013 American Society for Photogrammetry NH 03824 ([email protected]). and Remote Sensing PHOTOGRAMMETRIC ENGINEERING & REMOTE SENSING January 2013 25 12-001.qxd 12/18/12 6:17 PM Page 26 TABLE 1. OBLIGATE VERNAL POOL SPECIES; TABLE ADAPTED FROM and location specific (Vogiatzakis, 2003). Therefore, ecologi- COMMONWEALTH OF MASSACHUSETTS DIVISION OF FISHERIES AND WILDLIFE (2001) cal problems lend themselves well to the use of Geographic Information Systems (GIS) and remotely sensed imagery. Most MA Breeding Obligate Species commercial spatial analysis software packages, however, lack Wood Frog (Rana sylvatica) the statistical capabilities necessary to examine complex Spotted Salamander (Ambystoma maculatum) modeling problems, while most statistical software lacks Blue-spotted Salamander (Ambystoma laterale)** important spatial components (Vogiatzakis, 2003). For these Jefferson Salamander (Ambystoma jeffersonianum)** reasons, many studies have been limited to examining only Marbled Salamander (Ambystoma opacum)** one (the spatial or the statistical) part of an ecological Eastern Spadefoot Toad (Scaphiopus holbrookii)** problem. Fairy Shrimp (Eubranchipus spp.) The main objective of this study is to statistically determine the physical predictors of vernal pool occurrence **State Listed Species in Massachusetts, and to use the statistical models to generate maps, or cartographic/spatial models, for use as conservation tools. Logistic regression and Classification And Regression Tree (CART) analyses were chosen as the TABLE 2. FACULTATIVE VERNAL POOL SPECIES; TABLE ADAPTED FROM statistical modeling approaches. Quantitative assessments COMMONWEALTH OF MASSACHUSETTS DIVISION OF FISHERIES AND WILDLIFE (2001) were performed that compared not only the statistical results, but the cartographic results as well. MA Facultative Species Amphibians Methods Breeding Spring Peeper (Pseudacris crucifer) Study Area Breeding Gray Tree Frog (Hyla versicolor) The study area is in the State of Massachusetts. Massachu- Breeding American Toad (Bufo americanus) Breeding Fowler's Toad (Bufo fowleri) setts is the most populous state in New England, although Breeding Green Frog (Rana clamitans melanota) only about 10 percent of the state is developed (MassGIS, Breeding Pickerel Frog (Rana palustris) 2002). The climate in Massachusetts is temperate with mild, Breeding Leopard Frog (Rana pipiens) humid summers and cold, snowy winters (NOAA National Adult or Breeding Red-spotted Newt (Notophthalmus v. viridescens) Climatic Data Center, 2005). Over half of the state is forested Breeding Four-toed Salamander (Hemidactylium scutatum)** (MassGIS, 2002), the land cover type most commonly associated with vernal pools. Forests in Massachusetts are Reptiles generally classified as “Deciduous Forest Land” and/or “Mixed Forest Land” (Anderson et al., 1976). Deciduous Spotted Turtle (Clemmys guttata)** Blandings Turtle (Emydoidea blandingii)** forests in Massachusetts are most often composed of the Wood Turtle (Clemmys insculpta)** following tree species: red maple (Acer rubrum), oak Painted Turtle (Chrysemys picta) (Quercus spp.), birch (Betula, spp.), and American beech Snapping Turtle (Chelydra serpentina) (Fagus grandifolia). The most common evergreens in Massachusetts are eastern hemlock (Tsuga canadensis) and Invertebrates white pine (Pinus strobus). Predaceous Diving Beetle Larvae (Dytiscidae) Training and Validation Study Sites Water Scorpion (Nepidae) Dragonfly Larvae (Odonata: Anisoptera) Training and validation sites were chosen by analyzing the Damselfly Larvae (Odonata: Zygoptera) Certified Vernal Pool (CVP) layer across Massachusetts Dobsonfly Larvae (Corydalidae) (National Heritage and Endangered Species Program, 2002). Whirligig Beetle Larvae (Gyrinidae) This statewide layer was searched for assemblages of pools Caddisfly Larvae (Trichoptera) with similar geography and vernal pool density to represent Leeches (Hirudinea) training and validation groups. Convex hulls were generated Freshwater (fingernail) Clams (Pisidiidae) around each assemblage (Jenness, 2004) to create eight Amphibious, Air-breathing Snails (Basommatophora) representative areas: four training groups and four validation groups for each of the models (Table 3). The training areas **State Listed Species totaled 9,145 ha, and the validation areas totaled 8,911 ha. The sites were generally located in the northeastern part of the state, as the number and density of known pools was higher in these areas. The sites covered parts of Essex imagery to classify individual, isolated wetlands larger than County, eastern Middlesex County, northern Middlesex 0.20 ha. Similarly,