Populus grandidentata - Michx.
Large-tooth Aspen
Other English Common Names: Bigtooth Aspen
Other Common Names: bigtooth aspen
Taxonomic Status: Accepted
Related ITIS Name(s): Populus grandidentata Michx. (TSN 22463)
French Common Names: peuplier grandes dents
Unique Identifier: ELEMENT_GLOBAL.2.140795
Element Code: PDSAL01060
Informal Taxonomy: Plants, Vascular - Flowering Plants - Willow Family
 
Kingdom Phylum Class Order Family Genus
Plantae Anthophyta Dicotyledoneae Salicales Salicaceae Populus
Check this box to expand all report sections:
Concept Reference
Help
Concept Reference: Kartesz, J.T. 1994. A synonymized checklist of the vascular flora of the United States, Canada, and Greenland. 2nd edition. 2 vols. Timber Press, Portland, OR.
Concept Reference Code: B94KAR01HQUS
Name Used in Concept Reference: Populus grandidentata
Conservation Status
Help

NatureServe Status

Global Status: G5
Global Status Last Reviewed: 28Apr2016
Global Status Last Changed: 25Jun1984
Ranking Methodology Used: Ranked by inspection
Rounded Global Status: G5 - Secure
Reasons: Wide distribution range.
Nation: United States
National Status: N5?
Nation: Canada
National Status: N5 (28Apr2016)

U.S. & Canada State/Province Status
Due to latency between updates made in state, provincial or other NatureServe Network databases and when they appear on NatureServe Explorer, for state or provincial information you may wish to contact the data steward in your jurisdiction to obtain the most current data. Please refer to our Distribution Data Sources to find contact information for your jurisdiction.
United States Connecticut (SNR), Delaware (S5), District of Columbia (SNR), Illinois (S4S5), Indiana (SNR), Iowa (S4), Kentucky (S4?), Maine (SNR), Maryland (SNR), Massachusetts (SNR), Michigan (SNR), Minnesota (SNR), Missouri (S1), New Hampshire (SNR), New Jersey (S5), New York (S5), North Carolina (S2), North Dakota (SNR), Ohio (SNR), Pennsylvania (S5), Rhode Island (SNR), Tennessee (S2), Vermont (SNR), Virginia (S5), West Virginia (S5), Wisconsin (SNR)
Canada British Columbia (SNA), Manitoba (S1S2), New Brunswick (S5), Nova Scotia (S5), Ontario (S5), Prince Edward Island (S5), Quebec (S4)

Other Statuses

NatureServe Global Conservation Status Factors

Range Extent Comments: Nova Scotia to Manitoba, south to northeastern Missouri, east to Virginia, and locally in the eastern United States.

Overall Threat Impact Comments: Aspen invasion of grasslands especially at the prairie-forest border has increased primarily because of fire suppression (Buell 1959, Maini 1960, Blake 1963).

Undisturbed aspen clones expand into adjacent prairie when light, moisture and soil conditions are appropriate especially for vegetative growth (Maini 1966b). Vigorous root suckers emerge in the prairie at the periphery of a clone, where other woody plants also frequently invade the prairie. As these suckers grow, and crowns coalesce, aspen shades out desirable grassland species.

Rate of invasion is related to disturbance, clone phenotype, slope, wind, moisture, drainage, soil texture and climate. P. grandidentata showed an invasion rate of 10 m in 10 years on a hillside in Indiana (Duncan 1935). Aspen persists in prairie regions because of its preference for full sun and its vigorous vegetative reproduction and clonal growth that is well-adapted to top removal (fire, cutting, browsing) and drought.

Short-term Trend: Increase of >10%

Other NatureServe Conservation Status Information

Distribution
Help
Global Range: Nova Scotia to Manitoba, south to northeastern Missouri, east to Virginia, and locally in the eastern United States.

U.S. States and Canadian Provinces

Due to latency between updates made in state, provincial or other NatureServe Network databases and when they appear on NatureServe Explorer, for state or provincial information you may wish to contact the data steward in your jurisdiction to obtain the most current data. Please refer to our Distribution Data Sources to find contact information for your jurisdiction.
Color legend for Distribution Map

U.S. & Canada State/Province Distribution
United States CT, DC, DE, IA, IL, IN, KY, MA, MD, ME, MI, MN, MO, NC, ND, NH, NJ, NY, OH, PA, RI, TN, VA, VT, WI, WV
Canada BCexotic, MB, NB, NS, ON, PE, QC

Range Map
No map available.


U.S. Distribution by County Help
State County Name (FIPS Code)
MO Adair (29001), Clark (29045), Phelps (29161), Scotland (29199)
TN Blount (47009), Cannon (47015), Carter (47019), Cumberland (47035), Davidson (47037), Dickson (47043), Greene (47059), Grundy (47061), Montgomery (47125), Morgan (47129), Overton (47133), Putnam (47141), Robertson (47147), Stewart (47161), Unicoi (47171), Washington (47179)*, White (47185)
* Extirpated/possibly extirpated
U.S. Distribution by Watershed Help
Watershed Region Help Watershed Name (Watershed Code)
05 South Fork Cumberland (05130104)+, Upper Cumberland-Cordell Hull (05130106)+, Collins (05130107)+, Caney (05130108)+, Lower Cumberland-Sycamore (05130202)+, Harpeth (05130204)+, Lower Cumberland (05130205)+, Red (05130206)+
06 Watauga (06010103)+, Upper French Broad (06010105)+, Nolichucky (06010108)+, Lower Little Tennessee (06010204)+, Emory (06010208)+, Lower Duck (06040003)+
07 Bear-Wyaconda (07110001)+, North Fabius (07110002)+, Meramec (07140102)+
10 Lower Chariton (10280202)+
+ Natural heritage record(s) exist for this watershed
* Extirpated/possibly extirpated
Ecology & Life History
Help
Basic Description: Shade intolerant tree with smooth gray tan or yellowish-green bark that becomes furrowed and darker with age.
Technical Description: Populus grandidentata is a tree 10-20 m high. Stout twigs are white tomentose becoming reddish brown to greenish-gray with age. The alternate leaves are ovate and coarsely sinuate-toothed. Young leaves are densely white tomentose beneath; older leaves are glabrous, yellow green or dark green. Young suckers often have larger leaves than mature plants. Staminate catkins, 4-7 cm long, are silky pubescent; pistillate catkins are 3-5 cm elongating in fruit to 10-15 cm. Wide spreading lateral root system, sinker roots (vertically penetrating roots) to 3 m. This species forms clones by root-suckering. Suckers are distinguishable from seedlings because they have a thickening that develops on the distal side of the parent root next to the sucker. (Barnes 1981, Rosendahl 1970, Maini 1972)
Duration: PERENNIAL
Reproduction Comments: SEXUAL REPRODUCTION: Flowers appear before leaf expansion, usually in April or May. Phenology varies between clones, with air temperature, and geographic locations (Maini 1972). Following wind pollination, fruits ripen in May or June and are dispersed by wind or water May through July. The light seeds have a silky hair aiding in dispersal.

Most aspens are capable of flowering at ten years (Maini 1972) and 20 year old trees of P. grandidentata produce good seed crops every four or five years (Fowells 1965). Under favorable natural conditions, seeds maintain viability up to two or three weeks.

ASEXUAL REPRODUCTION: In established aspen clones, root suckering accounts for most reproduction, while stump sprouting is less frequent. Suckering sometimes occurs within undisturbed clones, but survival is low. Suckering is most profuse following top removal, and removal of other cover species by cutting, fire, windthrow, and disease. Tens of thousands of suckers per hectare follow clearcutting of P. grandidentata (Perala 1981).

Plants as young as two years old, and both male and female plants are capable of suckering (Fowells 1965). In Michigan, P. grandidentata produces a maximum number of suckers at age 40. (Graham 1963). Number of suckers and length of time required for their initiation varies between clones in P. grandidentata (Garrett 1964).

Suckers arise from adventitious buds produced on an extensive lateral root system that rises and falls just below the soil surface. Some suckers arise from dormant buds; most suckers are from buds initiated the same season. These buds form where the parent root is closest to the soil surface; usually in the top 5.1 to 7.6 cm of soil, and often above mineral soil (Sandberg 1951). Parent roots range from .51 to 11.43 cm in P. grandidentata (Maini 1972).

Sucker initiation and growth is influenced by growth regulator levels, carbohydrate levels, light, and temperature. Root suckering of Populus species is inhibited by the auxin effect of apical dominance (Farmer 1962, Eliasson 1971, Schier 1973). Auxin production is highest in apical buds during maximum spring shoot elongation, usually in June, and translocation of auxin to the roots inhibits suckering.

Removal of the above-ground plant portion in June or July after maximum auxin production results in fewer suckers than top-removal during the dormant season. Suckers formed early in the season also exhibit apical dominance by reducing the number and success of suckers formed later in the same season (Schier 1972). Seasonal variation in suckering is probably also influenced by other growth regulators including cytokinins and gibberellins (Schier 1972). Cytokinins produced in the roots stimulate suckering (Schier 1981).

Parental root carbohydrate reserves do not affect the number of suckers initiated, but do influence early sucker success. Following initiation, suckers are dependent on parental root reserves until they emerge above the soil and produce their own photosynthates (Schier 1971). Root carbohydrates are lowest in aspen clones after leaf flush (Tew 1970) and remain low until late July (Schier 1971). Both root carbohydrate reserves and early photosynthates are used during this time, primarily for shoot elongation and cambial activity.

Amount of sucker initiation increases with abundant light (Zehngraff 1949) probably because of increases in soil temperature.

SEEDLING ESTABLISHMENT: Seeds germinate readily within a day or two of dispersal if they reach an exposed moist site. Alluvium or the exposed mineral soils following fire are appropriate sites for establishment (Weigle 1911). P. grandidentata is capable of germinating while submerged in water, and at temperatures between 32 degrees F (0 degrees C) and 95 degrees F (35 degrees C) (Fowells 1965). Under controlled conditions, 80-95% germination is possible, but germination is less under natural conditions. Maini (1972) gives the following reasons for seedling failure:

1. Short seed viability

2. Presence of a water-soluble germination and growth inhibitor in the seed hair

3. Inadequate moisture conditions on upland sites

4. Susceptibility of seedlings to high temperatures possible on soil surfaces blackened by fire

5. Fungal pathogens

6. Diurnal temperature fluctuations hindering early seedling growth

7. Unfavorable chemical composition of substrate (e.g. high pH, high salt concentrations)

SUCKER ESTABLISHMENT: Early sucker growth and survival depends primarily on time of sucker initiation, root connections to parent roots, and ample light. The most numerous, tallest and competitive suckers are produced when above-ground portions are removed during the dormant season. Summer top-removal results in short suckers that compete poorly with shrubs, herbaceous species (e.g. Pteridium aquilinum (L.) Kuhn.) and overstory species (Perala 1972). They are also susceptible to winter injury (Zehngraff 1949). However, top removal in the summer results in continued suckering the next season, so that by the end of the second season, the effects of top-removal are sometimes negligible (Graham 1963).

Suckers depend primarily on parent roots during the first season of growth (De Byle 1964) when adventitious root production by suckers is low. The number of root interconnections between suckers and parents decreases with age. P. grandidentata depends partially on parent root functions for 25 years but relies more heavily on adventitiously produced roots after the first six years of sucker establishment (Barnes 1966, Zahner 1965).

P. grandidentata requires abundant light for early growth. Under full sunlight, dominant suckers can grow 4 feet to 8 feet (1.22 m to 2.43 m) the first season.

Growth rate of suckers is rapid for about five years after clearcutting. Then rates slow as suckers compete for light and moisture (Graham 1963). An aspen stand initially producing 40,000 suckers/A can be reduced to 1,000 to 1,500/A in 30 years (Maini 1972). Asexual reproduction results in a group or clone of suckers that has its origin in a seedling established tree (the ortet). The clone is composed of genetically identical stems (ramets) that often remain interconnected by roots to form a single functional unit (Blake 1963).

Clones of P. grandidentata are usually small. In the Great Lakes states, clones of .04 to .08 ha are common (Perala 1981, Barnes 1966). Larger clones have been recorded in Utah (10.1 and 43.3 ha) and the southern Rocky Mountains (81 ha) (Perala 1981).

Intraclonal ramets are of the same sex, have similar bark color, leaf forms, branching habits, and disease and insect pest susceptibility (Barnes 1966). Phenological patterns including time of leaf flush and fall coloring are also similar, with slight variations from the center to the edge of a clone (Barnes 1969). This intraclonal similarity of ramets is useful in distinguishing one clone from another where clones intermix.

Interclonal differences include ramet density, ability to sucker, and growth rate (Barnes 1969).

Clone profiles indicate ramet origin or topographical variations. Truncated clone profiles usually indicate simultaneous ramet origin (fire, windthrow, clearcutting). Dome-shaped clones result when suckering occurs at the periphery, especially into open sites such as grasslands. Wavy or notched clones usually indicate specific limits to expansion (severe slope, soil texture changes, fluctuating water levels, blowouts, etc.) (Maini 1960).

Expansion at the clone periphery is encouraged by favorable moisture, abundant light, and lack of competition by other ramets (Barnes 1966). Ramets on the periphery usually lack taproots or "sinker roots". In prairies the superficial aspen roots are mixed in the upper soil layers with grass and forb roots. Clones can function opportunistically by expanding under optimal growing conditions, and contracting under stress.

ALLELOPATHY: There is some evidence of aspen allelopathy.

Ecology Comments: PESTS AND DISEASE: Populus spp. have many natural enemies. The forest tent caterpillar, Malacosoma disstria, is a major insect that attacks P. grandidentata.

The most serious diseases of P. grandidentata are the wood-rotting fungi and cankers. Fomes ignarius is a wood-rotting fungus that attacks this species throughout its range, causing decay of heartwood and sapwood (Fowells 1965). Hypoxylon canker is widely distributed in the Northeast and Lake States and causes heavy losses of aspen in these regions. French (pers. comm.) stated that perhaps 15-20% of all trees in the Lake States are infected with Hypoxylon. The Hypoxylon fungus attacks the phloem, and kills the tree within 2-4 years of initial infection (French pers. comm.). P. grandidentata is less frequently attacked than P. tremuloides, and infection in P. balsamifera has so far been negligible (Fowells 1965). More information on the numerous pests and diseases of aspen is available in forestry literature (e.g. Graham 1963, Fowells 1965, USDA 1972).

Moderate browsing by mammals such as deer causes little permanent damage to suckers. Mice, voles, and rabbits can girdle suckers, and beaver frequently cut larger trees.

Terrestrial Habitat(s): Forest - Mixed, Forest/Woodland, Grassland/herbaceous
Habitat Comments: Climatic conditions vary throughout the ranges, but are often characterized by low seasonal temperature provided by high altitudes or northern latitudes, and short growing seasons. P. grandidentata is usually found on dry sites, at elevations from 500 to 2,000 feet (152 to 660 m). Soil textures include sand, loamy sand, light sandy loams, and, less frequently, heavier textured soils. High water tables closer than 18" (45.7 cm) to the surface reduce aeration, and increase chances of windfall (Fowells 1965). It is most commonly associated with quaking aspen (P. tremuloides), gray birch, paper birch and red maple.
Economic Attributes Not yet assessed
Help
Management Summary Not yet assessed
Help
Population/Occurrence Delineation Not yet assessed
Help
Population/Occurrence Viability
Help
U.S. Invasive Species Impact Rank (I-Rank) Not yet assessed
Help
Authors/Contributors
Help
NatureServe Conservation Status Factors Edition Date: 02Sep1987
NatureServe Conservation Status Factors Author: CARMEN K. CONVERSE, UPDATED BY NANCY ECKARDT (MRO) AND JENNIFER SNYDER (HO)
Element Ecology & Life History Edition Date: 02Sep1987
Element Ecology & Life History Author(s): CARMEN K. CONVERSE, UPDATED BY NANCY ECKARDT (MRO) AND JENNIFER SNYDER (HO)

Botanical data developed by NatureServe and its network of natural heritage programs (see Local Programs), The North Carolina Botanical Garden, and other contributors and cooperators (see Sources).

References
Help
  • Barnes, B. V. 1966. The clonal growth of American aspens. Ecology 47(3):439-447.

  • Barnes, B. V. 1969. Natural variation and delineation of clones of Populus tremuloides and P. grandidentata in northern lower Michigan. Silvae Genetica 18:130-142.

  • Barnes, B. V. and W. H. Wagner, Jr. 1981. Michigan trees: a guide to the trees of Michigan and the Great Lakes region. Ann Arbor: University of Michigan Press. 384 p.

  • Blake, G. M. 1963. Clone identification and delineation of the aspens. St. Paul, MN: University of Minnesota. 107 pp. Ph.D. thesis.

  • Buell, M. F. and H. F. Buell. 1959. Aspen invasion of prairie. Bull. of the Torrey Botanical Club 86(4):264-265.

  • DeByle, N. V. 1964. Detection of functional intraclonal aspen root connections by tracers and excavation. Forest Sci. 10(4):386-396.

  • Deam, C. C. 1940. Flora of Indiana. Division of Forestry, Dept. of Conservation, Indianapolis, Indiana. 1236 pp.

  • Duncan, W. H. 1935. Root systems of woody plants of old fields of Indiana. Ecology 16(4):554-567.

  • Eliasson, L. 1971. Growth regulators in Populus tremula IV Apical dominance and suckering in young plants. Physiol. Plant. 25:263-267.

  • Farmer, R. E. Jr. 1962. Aspen root sucker formation and apical dominanace. Forest Sci. 8(4):403-410.

  • Fowells, H.A. 1965. Silvics of Forest Trees of the United States. Division of Timber Management Research, Forest Service, USDA, Washington, D.C. 762 pages.

  • Garrett, P. W. and R. Zahner. 1964. Clonal variaiton in suckering of aspen obscures effects of various clearcutting treatments. J. of Forestry 62(10):749-750.

  • Graham, S. A., R. P. Harrison Jr., and C.E. Westell Jr. 1963. Aspens: phoenix trees of the Great Lakes region. Ann Arbor, MI: University of Michigan Press. 272 pp.

  • Herbarium, Department of Botany, University of Manitoba, Winnipeg, Manitoba, Canada.

  • Herbarium, Museum of Man and Nature, 190 Rupert Avenue, Winnipeg, Manitoba.

  • Kartesz, J.T. 1994. A synonymized checklist of the vascular flora of the United States, Canada, and Greenland. 2nd edition. 2 vols. Timber Press, Portland, OR.

  • Little, E.L., Jr. 1979. Checklist of United States trees (native and naturalized). Agriculture Handbook No. 541. U.S. Forest Service, Washington, D.C. 375 pp.

  • Maini, J. S. 1972. Silvics and ecology in Canada. Aspen: Symposium Proceedings. U. S. Dept. Agric. Forest Service General Technical Report, North Central For. Exp. Stat. NC-1:67-73.

  • Maini, J. S. and K. W. Horton. 1966. Vegetative propagation of Populus spp. I. Influence of temperature on formation and initial growth of aspen suckers. Can. J. of Botany 44: 1183-1189.

  • Maini, J.S. 1960. Invasion of grassland by Populus tremuloides in the northern great plains. (Saskatoon, Saskatchewan): University of Saskatchewan. 231 pp. Dissertation.

  • Perala, D. A. 1972. Regeneration: biotic and silvicultural factors. Aspen: Symposium proceedings. U. S. Dept. Agric. Forest Service General Technical Report, North Central For. Exp. Stat. NC-1:67-73.

  • Perala, D. A. 1981. Clone expansion and competition between quaking aspen and bigtooth aspen suckers after clearcutting. U. S. Dept. Agric. Forest Service Research Report, North Central For. Exp. Stat. NC-201. 4 p.

  • Ronald, W.G. L.M. Lenz. 1973. Biosystematics of the genus Populus. Part 1: Distribution and morphology of native Manitoba species and variants. Can. J. Bot. 51(12)2431-2442.

  • Rosendahl, C. O. 1970. Trees and shrubs of the upper midwest. Minneapolis, MN: Univeristy of Minnesota. 172 p. Thesis.

  • Sandberg, D. 1951. The regeneration of quaking aspen by root suckering. St. Paul, MN: University of Minnesota. 172 p. Thesis.

  • Schier, G. A. 1972. Apical dominance in multi-shoot cultures from aspen roots. Forest Sci. 18(20): 147-149.

  • Schier, G. A. 1973. Seasonal variation in sucker production from excised roots of Populus tremuloides and the role of endogenous auxin. Can. J. Forest Research 3:459-461.

  • Schier, G. A. 1981. Aspen regeneration. DeByle, N. V., ed. Symposium proceedings situation management of two intermountain species: aspen and coyotes. Vol. I:Aspen. Utah State Univ. p. 15-21.

  • Schier, G. A. and R. S. Johnston. 1971. Clonal variation in total nonstructural carbohydrates of trembling aspen roots in three Utah areas. Can. J. Forest Research 1:252-255.

  • Scoggan, H.J. 1978. The Flora of Canada. National Museum of Natural Sciences, National Museum of Canada, Publ. in Botany 7(4).

  • Swink, F., and G. Wilhelm. 1994. Plants of the Chicago Region. Morton Arboretum. Lisle, Illinois.

  • Tew, R. K. 1970. Root carbohydrate reserves in vegetative reproduction of aspen. Forest Sci. 16(3):318-320.

  • United States Dept. of Agr. 1972. USDA forest Service Gen-Tech Rep. p. 7. HCl.

  • Weigle, W. G. and E. H. Frothingham. 1911. The aspens: their growth and management. U. S. Dept. Agric. Forest Service Bull. 93.

  • White, D.J. and K.L. Johnson. 1980. The Rare Vascular Plants of Manitoba. National Museums of Canada Syllogeus no. 27.

  • Zahner, R. and N. V. DeByle. 1965. Effect of pruning the parent root on growth of aspen suckers. Ecology 46(3):373-375.

  • Zehngraff, P. J. 1949. Aspen as a forest crop in the lake states. J. Forestry 47:555-565.

Use Guidelines & Citation

Use Guidelines and Citation

The Small Print: Trademark, Copyright, Citation Guidelines, Restrictions on Use, and Information Disclaimer.

Note: All species and ecological community data presented in NatureServe Explorer at http://explorer.natureserve.org were updated to be current with NatureServe's central databases as of March 2019.
Note: This report was printed on

Trademark Notice: "NatureServe", NatureServe Explorer, The NatureServe logo, and all other names of NatureServe programs referenced herein are trademarks of NatureServe. Any other product or company names mentioned herein are the trademarks of their respective owners.

Copyright Notice: Copyright © 2019 NatureServe, 2511 Richmond (Jefferson Davis) Highway, Suite 930, Arlington, VA 22202, U.S.A. All Rights Reserved. Each document delivered from this server or web site may contain other proprietary notices and copyright information relating to that document. The following citation should be used in any published materials which reference the web site.

Citation for data on website including State Distribution, Watershed, and Reptile Range maps:
NatureServe. 2019. NatureServe Explorer: An online encyclopedia of life [web application]. Version 7.1. NatureServe, Arlington, Virginia. Available http://explorer.natureserve.org. (Accessed:

Citation for Bird Range Maps of North America:
Ridgely, R.S., T.F. Allnutt, T. Brooks, D.K. McNicol, D.W. Mehlman, B.E. Young, and J.R. Zook. 2003. Digital Distribution Maps of the Birds of the Western Hemisphere, version 1.0. NatureServe, Arlington, Virginia, USA.

Acknowledgement Statement for Bird Range Maps of North America:
"Data provided by NatureServe in collaboration with Robert Ridgely, James Zook, The Nature Conservancy - Migratory Bird Program, Conservation International - CABS, World Wildlife Fund - US, and Environment Canada - WILDSPACE."

Citation for Mammal Range Maps of North America:
Patterson, B.D., G. Ceballos, W. Sechrest, M.F. Tognelli, T. Brooks, L. Luna, P. Ortega, I. Salazar, and B.E. Young. 2003. Digital Distribution Maps of the Mammals of the Western Hemisphere, version 1.0. NatureServe, Arlington, Virginia, USA.

Acknowledgement Statement for Mammal Range Maps of North America:
"Data provided by NatureServe in collaboration with Bruce Patterson, Wes Sechrest, Marcelo Tognelli, Gerardo Ceballos, The Nature Conservancy-Migratory Bird Program, Conservation International-CABS, World Wildlife Fund-US, and Environment Canada-WILDSPACE."

Citation for Amphibian Range Maps of the Western Hemisphere:
IUCN, Conservation International, and NatureServe. 2004. Global Amphibian Assessment. IUCN, Conservation International, and NatureServe, Washington, DC and Arlington, Virginia, USA.

Acknowledgement Statement for Amphibian Range Maps of the Western Hemisphere:
"Data developed as part of the Global Amphibian Assessment and provided by IUCN-World Conservation Union, Conservation International and NatureServe."

NOTE: Full metadata for the Bird Range Maps of North America is available at:
http://www.natureserve.org/library/birdDistributionmapsmetadatav1.pdf.

Full metadata for the Mammal Range Maps of North America is available at:
http://www.natureserve.org/library/mammalsDistributionmetadatav1.pdf.

Restrictions on Use: Permission to use, copy and distribute documents delivered from this server is hereby granted under the following conditions:
  1. The above copyright notice must appear in all copies;
  2. Any use of the documents available from this server must be for informational purposes only and in no instance for commercial purposes;
  3. Some data may be downloaded to files and altered in format for analytical purposes, however the data should still be referenced using the citation above;
  4. No graphics available from this server can be used, copied or distributed separate from the accompanying text. Any rights not expressly granted herein are reserved by NatureServe. Nothing contained herein shall be construed as conferring by implication, estoppel, or otherwise any license or right under any trademark of NatureServe. No trademark owned by NatureServe may be used in advertising or promotion pertaining to the distribution of documents delivered from this server without specific advance permission from NatureServe. Except as expressly provided above, nothing contained herein shall be construed as conferring any license or right under any NatureServe copyright.
Information Warranty Disclaimer: All documents and related graphics provided by this server and any other documents which are referenced by or linked to this server are provided "as is" without warranty as to the currentness, completeness, or accuracy of any specific data. NatureServe hereby disclaims all warranties and conditions with regard to any documents provided by this server or any other documents which are referenced by or linked to this server, including but not limited to all implied warranties and conditions of merchantibility, fitness for a particular purpose, and non-infringement. NatureServe makes no representations about the suitability of the information delivered from this server or any other documents that are referenced to or linked to this server. In no event shall NatureServe be liable for any special, indirect, incidental, consequential damages, or for damages of any kind arising out of or in connection with the use or performance of information contained in any documents provided by this server or in any other documents which are referenced by or linked to this server, under any theory of liability used. NatureServe may update or make changes to the documents provided by this server at any time without notice; however, NatureServe makes no commitment to update the information contained herein. Since the data in the central databases are continually being updated, it is advisable to refresh data retrieved at least once a year after its receipt. The data provided is for planning, assessment, and informational purposes. Site specific projects or activities should be reviewed for potential environmental impacts with appropriate regulatory agencies. If ground-disturbing activities are proposed on a site, the appropriate state natural heritage program(s) or conservation data center can be contacted for a site-specific review of the project area (see Visit Local Programs).

Feedback Request: NatureServe encourages users to let us know of any errors or significant omissions that you find in the data through (see Contact Us). Your comments will be very valuable in improving the overall quality of our databases for the benefit of all users.