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Land cover change caused by humans represents a major threat to the long term viability of natural areas. It is important to accurately classify and map existing natural areas so that this threat can be fully assessed within a given landscape. Availability of free orthorectified Landsat images through the U.S. Geological Survey provides a potentially valuable tool to evaluate human impacts to natural landscapes. We performed a supervised classification of multi-seasonal Landsat images to test the limits of using these images for mapping mixed landscapes at regional to local scales and to assess land cover changes within the Oak Openings region of Northwestern Ohio. Overall accuracy of our 15-class land cover map was 60% and 69% using traditional and fuzzy set analysis respectively. Overall map accuracy improved to 72% and 79% for traditional and fuzzy set analysis respectively using a more broadly defined 7-class land cover map. Accuracy of individual classes varied considerably, although classes made up of larger patches typically achieved greater accuracy. Human-dominated land cover classes currently occupy 73% of the Oak Openings region while < 3% of the region remains covered by native savannas, prairies, and barrens. Currently 10% of the region is permanently protected, including nearly all remnant savannas and wet prairies > 1 ha. Our findings highlight the utility of using Landsat images to evaluate mixed-use landscapes at regional scales but demonstrate the limitations of using these images at local scales.
The sustainability of eastern oak-dominated forests is threatened by high oak mortality rates and widespread oak regeneration failure, and presents a challenge to natural area managers. We tracked the rate and cause of mortality of 287 mature oak trees of five species for 15 years to determine the temporal patterns and sources of mortality. We observed a 15.3% total mortality rate during the study period. Mortality was due to oak decline (7.3% of trees) and high-intensity wind events (6.6% of trees). Decline-related mortality was gradual, averaging 0.5% annually. Windthrow was episodic, occurring during hurricane-related weather events in 1995 and 2004. Within species, total mortality was disproportionately high for scarlet oak (Quercus coccinea Muenchh) (41.2%) compared to other species in the red oak group (13.8% for northern red oak (Q. rubra L.); 12.5% for black oak (Q. velutina Lam.)) or the white oak group (10.4% for white oak (Q. alba L.); 5.7% for chestnut oak (Q. prinus L.)). Decline-related mortality was highest for scarlet oak (15.7%) followed by black oak (8.3%), white oak (7.5%), northern red oak (6.9%), and chestnut oak (2.3%). Within the red oak group, the average age of decline-affected and surviving trees did not differ, but average dbh of decline-affected trees was smaller. Decline-affected trees in the white oak group were on average older, but average dbh did not differ from surviving trees. Wind-related mortality also was higher for scarlet oak (21.6%) than for northern red oak (5.2%), black oak (4.2%), white oak (3.0%) or chestnut oak (2.3%). Windthrown red oaks were smaller than survivors, but windthrown trees in the white oak group did not differ in size from survivors. Average age did not differ between windthrown and surviving trees for either group. Oak mortality rates observed in this study, coupled with oak regeneration failure, could result in a substantial reduction in the proportion of mature canopy oaks and change the relative abundance of oak species in southern Appalachian forests over the long-term.
The vegetation community of the San Joaquin Valley of California has been formally classified as a perennial grassland based largely on assumptions of past climax state. However, historical records suggest that the region might be more accurately classified as a desert. The distinction is important in determining the appropriate management strategies for this ecosystem, particularly for the many rare and endemic taxa that reside there. Abiotic and biotic factors—including low precipitation, arid soils, and desert-adapted plants and vertebrate—are consistent with conditions typical of desert areas. We examined the distributions of these factors to define the extent of the San Joaquin Desert. We conclude that the San Joaquin Desert historically encompassed 28,493 km2 including the western and southern two thirds of the San Joaquin Valley, and the Carrizo Plain and Cuyama Valley to the southwest. However, this ecosystem has been reduced by up to 59% from agricultural, industrial, and urban activities. The conservation of the unique biodiversity of this region is dependent upon this ecosystem being appropriately managed as a desert and not as a perennial or annual grassland.
The tallgrass prairie has become one of the most endangered ecosystems in North America. Thus, attempts to restore and reconstruct native tallgrass prairie have been undertaken. Arthropods, an important and diverse taxonomic group of animals, warrant greater attention on remnant and restored tallgrass prairies. A prairie arthropod survey in Iowa has not been attempted since the 1930s and no comprehensive surveys have been conducted on restorations in this state. A survey of insect and spider families was conducted using sweep net transects on three types of Iowa prairies: (1) remnants; (2) isolated restorations/reconstructions; and (3) landscape-scale integrated reconstructions. Richness and abundance of arthropod families differed slightly, although not significantly, between years and prairie types. The high level of similarity documented among prairies restorations and remnants might suggest restoration efforts have been successful for the establishment of the native arthropod community, or may simply reflect the absence of all but the most broadly adaptable insect and spider species from the heavily disrupted landscape. Both of these explanations may be accurate. Restoration efforts may be successful in maintaining a diverse community of native arthropods; however, prairie endemics may have already been extirpated. As natural and anthropogenic stressors and restoration practices continue to impact these systems, this basic arthropod community survey can serve as a baseline for future change.
Japanese barberry (Berberis thunbergii DC) is a non-native shrub currently found in 31 states and four Canadian provinces. We examined the effectiveness of directed heating using 400,000 BTU backpack propane torches to control Japanese barberry infestations at two study areas in southern Connecticut. Each study area had eight 50-m × 50-m plots. Treatment combinations included a pre-leafout or post-leafout initial treatment with propane torches to reduce the size of established clumps and an early (late June), mid (early July), or late (late July) follow-up treatment to kill sprouts that developed from surviving root crowns. All treatment combinations were equally effective and reduced barberry abundance (a surrogate for cover) from 31% prior to treatment to only 0.5% the following autumn (i.e., a 98% reduction). All treatment combinations were also equally effective in reducing the size of surviving barberry to an average of only 11 cm compared with 74 cm for untreated clumps. Estimated labor costs using propane torches for both initial and follow-up treatment was 2.5 hr/ha for every 1% pretreatment abundance (e.g., 25 hr for a 1-ha stand with 10% abundance). Because timing of initial treatments (pre-leafout vs. post-leafout) and follow-up treatment (early, mid, late) were equally effective in reducing Japanese barberry abundance and height of surviving stems, initial treatments can be completed from March–June and follow-up treatments can be completed from June–August in southern New England. For habitat restoration projects on properties where herbicide use is restricted, directed heating with propane torches provides a non-chemical alternative that can effectively control invasive Japanese barberry.
Vegetation monitoring transects established in calcareous glade habitats in 1993 at Chickamauga and Chattanooga National Military Park were resampled in 2006 and 2008. Data showed an increase in woody cover and a correlated decrease in density of herbaceous plants characteristic of this habitat. The average percent cover of woody species increased from 35.9% in 1993 to 64.3% in 2006/2008 for the 11 glades sampled. Nearly all woody species showed an increase in percent cover with Juniperus virginiana var. virginiana (Eastern red-cedar) increasing the most in percent cover (11% increase in cover, a 57% change). The non-native invasive shrub Ligustrum sinense (Chinese privet) ranked second in increase in cover (4.63%) and is now the third most abundant woody species in the glades. In addition, transects showed a decrease in the density of herbaceous plants characteristic of these calcareous glades ranging from 35% to 100%, including Pediomelum subacaule, Viola egglestonii, Dalea gattingeri, Ruellia humilis, Hypericum dolabriforme, Ratibida pinnata, Scutellaria leonardii, Silphium pinnatifidum, Packera paupercula, Leavenworthia exigua var. exigua, and Delphinium carolinianum ssp. calciphilum. The evidence from this study strongly suggests a decline in the natural integrity of these glade communities over a 15-year period and an increase in the natural rate of ecological succession with the invasion of a non-native species. Our management recommendations focus on two equally important actions: the targeted removal of Ligustrum sinense and the re-introduction of fire into the forest/woodland environment surrounding the glades.
Baseline vegetation monitoring transects were established in calcareous glade habitats in 1993 at Chickamauga and Chattanooga National Military Park and resampled in 2006 and 2008. The resampling results show an increase in woody cover and a correlated decrease in density of herbaceous plants characteristic of this habitat. In addition to documenting changes in glade habitats, the resampling effort highlighted some of the difficulties associated with successful implementation of long-term monitoring, with important lessons for other repeated measures studies. These include the importance of good data archiving procedures, as well as adequate planning and documentation to facilitate: (1) re-location of sample units, (2) implementation of consistent sampling methods, (3) reliable and repeatable species identification, and (4) sampling at the right season of the year.
Slash pile burning is widely conducted by land managers to dispose of unwanted woody fuels, yet this practice typically has undesirable ecological impacts. Simple rehabilitation treatments may be effective at ameliorating some of the negative impacts of pile burning on plants and soils. Here, we investigated: (1) the impacts of slash pile burning on soil nitrogen and understory plant species richness and cover in Colorado Pinus contorta Douglas ex Louden and P. contorta — Populus tremuloides Michx. stands; (2) the effectiveness of woodchip mulch and soil scarification at reversing pile burning impacts on soil nitrogen; and (3) how mulching and scarifying, alone and in conjunction with native grass seeding, promote native plant establishment and discourage exotic invasion in burn scars. We found that pile burning diminished native richness and cover and increased soil nitrogen, particularly in the interior of burn scars where fire severity was greatest. Rehabilitation treatments appear to be useful tools for reversing pile burning impacts on soil and plants. Mulching dampened the increase in soil nitrogen; and scarifying, scarifying plus seeding, and mulching plus seeding were effective at encouraging native plant development while simultaneously minimizing exotic plant colonization.
We reviewed Miami-Dade County's Environmentally Endangered Lands (EEL) Program, created in 1990 for the purpose of acquiring and managing threatened native forests and wetlands within Miami-Dade County, Florida. Funds for the program were initially raised from a two-year extraordinary property tax millage approved by voters, with additional funding coming from various state, county, and private sources. To date, the program has protected over 9000 ha of natural areas within the urban and agricultural matrix of eastern Miami-Dade. Although many of these reserves are small, all are important for the conservation of numerous rare endemic upland plants and are used frequently by a variety of animal species. Their preservation also offers a series of ecosystem services that directly and indirectly benefit the community, such as flood control and aquifer recharge. Many issues remain concerning the program, however. The County has not yet opened most EEL sites to the public, and all sites are threatened by edge effects—including the introduction of invasive exotic plants—that require continual management. None-the-less, the program is popular with residents, successful for its stated purpose, and arguably important for the conservation of rare endemic flora—especially that found within South Florida's pine rocklands, a globally imperiled ecosystem type.
In the San Joaquin Valley of California, land conversion for agricultural and urban uses has resulted in profound habitat loss and diminished biological diversity. However, the large-scale retirement (i.e., removal from irrigated agricultural production) of farmland in the western San Joaquin Valley presents an opportunity to restore native plant communities and wildlife habitat values. A key objective of the proposed restoration efforts was to utilize local seed sources to the extent possible. However, local genotypes of San Joaquin Valley native plants are largely unavailable from commercial seed suppliers, and the amount of seed that could be collected from areas of native habitat would be insufficient for reseeding large tracts of retired farmland. Accordingly, we initiated a regional search for local native plant populations from which seeds could be collected and planted in a field nursery for the purpose of seed production. We identified 41 areas of remnant native habitat (sites) that supported 158 native plant species. The majority of the populations were restricted to isolated habitat remnants. Many of the species were uncommon: 65% were documented at three or fewer sites. The number of species per site was generally low; over half of the sites supported 10 or fewer species. This investigation illustrates the difficulty of identifying local native seed sources for restoration purposes in a highly fragmented landscape.