SE Colorado Inventory Final Report
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Southeastern Colorado Survey of Critical Biological Resources 2007 ii Southeastern Colorado Survey of Critical Biological Resources Prepared for: Colorado Cattleman’s Agricultural Land Trust 8833 Ralston Road Arvada, CO 80002 Great Outdoors Colorado 1600 Broadway, Suite 1650 Denver, CO 80202 Colorado Department of Natural Resources Division of State Board of Land Commissioners 1313 Sherman Street Denver, CO 80203 Colorado Department of Natural Resources Division of Wildlife 6060 Broadway Denver, CO 80216 Prepared by: Joe Stevens, John Sovell, Denise Culver, Karin Decker, Lee Grunau, Amy Lavender, Chris Gaughan Colorado Natural Heritage Program Warner College of Natural Resources Colorado State University 8002 Campus Mail Fort Collins, CO 80523-8002 (970) 491-1309 email: heritage@ colostate.edu http://www.cnhp.colostate.edu May 2008 Copyright © 2008 Colorado State University Colorado Natural Heritage Program All Rights Reserved Cover photograph: Bruno Canyon in morning light, by Renée Rondeau iii EXECUTIVE SUMMARY The biological diversity of the shortgrass prairies and juniper rimmed canyons of Southeast Colorado represent a vast and largely intact ecosystem that is not fully understood or documented. While the ranchers that make up the majority of landowners in the area understand much about the character and capabilities of the area, they too are limited in their knowledge of specifics regarding the full range of biological diversity on their lands. Their desire to better understand the natural heritage maintained on their lands, and in the region as a whole, served as the impetus for this study. It is with that objective in mind that the Southeastern Colorado Survey of Critical Biological Resources 2007 was completed. The Colorado Natural Heritage Program (CNHP) annually works to survey the critical biological resources of Colorado counties and other lands within the state, and this survey serves as a contribution to that effort. This Southeastern Colorado Survey of Critical Biological Resources 2007 used the methods that are employed by Natural Heritage Programs and Conservation Data Centers worldwide. The intent of the project was to: 1) identify the location of high quality examples of plant and animal populations and plant communities on CNHP’s list of rare and imperiled elements of biodiversity existing in the area; 2) to assess the conservation value of those Element Occurrences, and; 3) to systematically define and prioritize Potential Conservation Areas that may be used for effective conservation action. Through a series of stakeholder meetings with private landowners, land managers, and other interested parties, we were able to establish a trust and a strong working relationship with a large number of landowners in the area. The meetings allowed us to meet landowners, discuss and receive permission for access to their lands, collect information from them on the biodiversity of their lands, and identify on maps high priority areas for survey. This and other existing data indicated a number of Target Inventory Areas that served to focus the field survey work completed over the summer of 2007. Results of the survey confirm that there are many areas of high biological significance in Southeast Colorado. While the areas surveyed in summer 2007 represent only a portion of the area and not all the possible taxa, the work completed there yielded a large number of Element Occurrences (EOs). For example, a typical county level field survey will yield approximately 70 to 80 Element Occurrence Records (EORs) for plants, animals, and natural communities. Of those, about one third are typically new and two thirds are typically updates of existing EORs. In contrast, the Southeast Colorado Survey (this project) yielded 150 EORs, 131 of which were new and 19 were updates. The actual number of mapped locations, which represent the number of places we visited and documented a species or community observation, totaled 341, of which 236 were new. Overall, the condition of the biological resources in the study area is excellent, and current management appears compatible with biological diversity in most places. This area harbors the largest intact working landscape remaining not only on Colorado’s eastern plains, but also in the entire Central Shortgrass Prairie ecoregion. The Shortgrass Prairie Partnership (Neely et al. iv 2006) has identified this area as having high landscape integrity and very high conservation value – a testament to the quality of management by the landowners in this area. Potential Conservation Areas (PCAs) were delineated for field surveyed areas found to contain significant elements. There are a total of 34 Potential Conservation Areas within or overlapping the Southeast Colorado project area. Of those 34 PCAs, 21 are either new or have been updated based on the 2007 field work and are highlighted in this report. Of the 21 highlighted here, 13 are new and were based entirely on the 2007 inventory work, while another 8 were preexisting and were updated with data from the 2007 work. While all 34 of the PCAs in the project area are listed in this report, only the 21 that are new or updated have been highlighted. Additional information is needed to evaluate and revise the other PCAs listed. Of the 21 PCAs highlighted in the report: • Nine are of very high biodiversity significance (B2), • Eight are of high biodiversity significance (B3), • One is of moderate biodiversity significance (B4), and • Three are of general biodiversity significance (B5). These PCAs represent the best examples of targeted species and plant communities and their ecological processes observed on the private and public lands visited. The PCA boundaries delineated in this report do not confer any regulatory protection of the site, nor do they automatically recommend exclusion of all activity. All of the PCAs presented in this report represent unique opportunities for Southeast Colorado and its Stakeholders to conserve significant components of the natural heritage of Southeast Colorado, and each is worthy of conservation attention. As the Shortgrass Prairie Partnership (Neely et al. 2006) has identified, this area harbors the largest intact working landscape remaining not only on Colorado’s eastern plains, but also in the entire Central Shortgrass Prairie ecoregion. This is attested to by the excellent condition of the biological resources in the study area, indicating that current management is compatible with biological diversity in most places. The canyon communities are unique in the CSP ecoregion, and are in excellent condition compared to similar canyon systems elsewhere in Colorado. They are generally intact in terms of condition and function, based on the presence of indicators such as the plains leopard frog. Though many of the canyon communities are in excellent condition, there are some areas where altering the management approach could alleviate adverse impacts from current or past land use. Some streams have bullfrogs that compete with, and predate on, native amphibians. Many of the canyons get very little, if any, grazing during growing season, and only light grazing in the winter. Some of the smaller side-tributaries do not get grazed at all due to the difficulty of access for cattle. Side canyons that are not grazed are in very pristine condition. In general, side slopes in the canyons are in excellent condition, due largely to the fact cattle tend to stay in the bottoms of the canyons, and tend to not go upslope. In areas where the predominant land use is cattle grazing, juniper zones are often intensely managed to increase forage production. Within the study area, chaining, bulldozing, herbicides, and burning have been used to reduce juniper density and improve conditions for cattle. The soil v disturbance that results from chaining allows for proliferation of weeds such as cheatgrass, whose seeds germinate earlier and have a competitive advantage over native species. Even so, much of the remaining juniper woodland and savanna systems appear to be in good condition in most areas. In places where control of junipers is unavoidable or desirable (e.g., where junipers are encroaching into adjacent grasslands), controlled burns that mimic the natural fire regime are preferable to use of herbicides or the more destructive methods of chaining or bulldozing. The condition and species composition of grasslands and shrublands is highly variable across the study site. Differences are likely due to variations in soils and grazing management. Areas that have previously been tilled are still showing altered species composition. Many of these areas have significantly reduced cover of blue grama. The grassland and shrubland communities in the study area support many conservation targets, including a suite of declining prairie birds, swift fox, spadefoot toads that inhabit small pools and basins, massasauga rattlesnake, and Texas horned lizard. Though shortgrass prairie is the dominant grassland system, the landscape also supports exemplary patches of midgrass prairie species such as New Mexico feathergrass (Hesperostipa neomexicana). One of the factors that makes this area so phenomenal, and so unique in Colorado, is the fact that the landscape still supports a mosaic of ecological systems, with large, very high quality patches of rare communities such as the New Mexico feathergrass occurring where conditions are suitable. There are many ways to think about conservation of biological diversity. Conservation strategies can include legal