Ossipee Fuel Mapping Results and Recommended Fuel Models- Summary and 4 reports

Title: Ossipee Fuel Mapping Results and Recommended Fuel Models - Summary

Author: Michael Batcher, Ecologist and Environmental Planner

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Abstract: This report summarizes the results of 1) data collected in 34 plots at Ossipee Pine Barrens in 2013 to describe vegetation and fuels, 2) interviews with several prescribed fire practitioners in the northeast and 3) recommendations on fuel models that could be used at Ossipee based on the above information.

A series of reports (below) including reviews of relevant literature, monitoring protocols and analyses of field data were completed for this study. Full citations are provided in the references sections and copies are available from The Nature Conservancy’s Shawangunk Ridge. 

Title: Analysis of Field Data for the Shawangunks Grassland and Forests Birds Habitat Study- Summary Report

Author: Michael Batcher, Ecologist and Environmental Planner

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Abstract: In early 2008, The Nature Conservancy, in partnership with the Mohonk Preserve and the U.S. Fish and Wildlife Service, initiated a series of coordinated research projects to test the efficacy of several management strategies to achieve specific goals for habitat management for both grassland and forest nesting birds. The studies focused on several species listed as Species of Greatest Conservation Need (SGCN) by the New York State Department of Environmental Conservation (Table 1).

Grassland treatment units were established at the Mohonk Preserve and at Shawangunks Grassland National Wildlife Refuge managed by the U.S. Fish and Wildlife Service. A forest treatment unit was established in the Mohonk Preserve to assess the effects of prescribed fire on bird habitat within the chestnut oak forest, the largest forest type in the northern Shawangunks and one of the largest examples of that community in New York.

In April of 2008, just before initiation of this study, there was a major wildfire in the Overlooks area in Minnewaska State Park Preserve which burned approximately 3,000 acres (1,250 ha) within the Park and some adjacent private lands. This was the largest fire in the Shawangunks since the 1947 wildfire that burned over 7,000 acres (3,000 ha). Given this opportunity, we established both vegetation and bird monitoring plots within the wildfire area and in some unburned areas nearby for comparison. The locations of treatment units and of the wildfire are shown on Maps 1 and 2.

Title: Analysis of Field Data for the Shawangunks Grassland and Forests Birds Habitat Study – Grassland Management

Author: Michael Batcher, Ecologist and Environmental Planner

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Abstract: We established plots and collected data at both the Mohonk Preserve and Shawangunk Grasslands National Wildlife Refuge (SGNWR) to compare management treatments for maintaining open fields at the Mohonk Preserve and grassland bird habitat at SGNWR. We chose a set of variables to measure including shrub cover, grass vs. forb cover, invasive species cover, height density, litter cover and litter depth.

The original, planned treatments included both mid-summer (July) and late summer (September) mow only and mow and burn treatments at SGNWR and the Mohonk Preserve. One field at the Mohonk Preserve was burned in the spring of 2009, but weather and other conditions prevented any other use of prescribed fire. Summer (July) mowing was completed in two of the SGNWR units and September mowing was completed in two of the Mohonk fields. The September mow at SGNWR did not occur. A spring mow was substituted and completed in one field at the Mohonk Preserve.

Total shrub abundance was generally reduced by all treatments. However, in many cases, short shrubs (< 0.5 m) remained stable or increased. Since these will enter taller height classes quickly, the effects of these treatments are temporary. One field that was burned in the spring was mowed in late summer, and the results indicated that multiple treatments in the same year can dramatically reduce shrub cover, which is an important goal both at the Preserve and SGNWR. Invasive species abundance generally increased following all treatments.

Optimal grassland bird habitat includes grass as dominating vegetative cover (70%) with forb cover of 10-30%. Management resulted in mixed changes in grass and forb abundance with most treatments increasing forb abundance. Some treatments resulted in increases in grass in one field and decreases in another at the same site. Litter depth and cover remained relatively unchanged, except for a reduction following the spring burn and increases following mowing. As would be expected, height density decreased following treatments. Annual treatments will likely be needed to reduce height density to levels preferable to most grassland nesting birds.

Management objectives should be developed for each field with a prescription or set of protocols for achieving the desired status. Managing for grassland birds requires avoiding treatments during their breeding seasons which can run from April through July with possible second broods in August. However, individual fields or subareas can be treated in the spring provided sufficient area for breeding is left. To achieve management objectives, multiple treatments within a given growing season will likely be needed to substantially reduce woody species abundance. Once this is reduced, it may be possible to manage less frequently, but annual treatments will likely be necessary.

Mowing multiple times and/or mowing before the seed set of forbs may encourage grass cover and decrease forb cover. However, it may also be necessary to completely replant fields with a high proportion of grasses to achieve the low forb cover preferred by many grassland nesting birds. Fire can also be used if opportunities arise and resources are adequate. Invasive species control will require any of a series of methods including mechanical treatment, the use of fire in the growing season and the use of herbicides. Invasive species control will likely require annual treatments and monitoring of results to keep invasives from expanding.

Monitoring should address the specific management objectives of each field. So, using the shrub cover example, it may only be necessary to monitor shrub cover and not the other variables such as grass or forb cover as we did in this study. This will allow for an adaptive management approach based on solid information on management effectiveness while minimizing resource expenditures for monitoring.

Title: Analysis of Field Data for the Shawangunks Grassland and Forests Birds Habitat Study – Undercliff Oak Forest Management

Author: Michael Batcher, Ecologist and Environmental Planner

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Abstract: As part of a study on the effects of prescribed fire on forest bird habitat, we established 16 plots within a 35.7 acre (14.4 ha) treatment unit in 2009. Target bird species were Black-throated Blue Warbler (Dendroica caerulescens), Scarlet Tanager (Piranga olivacea), Wood Thrush (Hylocichla mustelina) and Worm-eating Warbler (Helmitheros vermivorum), all of which are Species of Greatest Conservation Need (SCGN). We collected data on tree, shrub, sapling and seedling abundance. We also collected data specific to shrub nesting birds by measuring shrub abundance at 0.5 m height increments from zero to three meters. We burned the unit in late April and early May of 2010 and resurveyed all 16 plots.

Live woody stems and leaves were found relatively evenly distributed by height class prior to treatment in 2009. Most mountain laurel stems and leaves were found at a height of between 0.5 and 1.5 meters. Following the burn, shrubs were top killed, so that nearly all live woody material was relegated to less than 0.5 m as plants resprouted.

Tree mortality was negligible, and canopy cover did not change significantly, though there was some increase overall. There were small, but statistically significant reductions in litter cover and increases in duff.

Total seedling density in the 16 plots ranged from 5,333 to 18,416/ha prior to treatment and 7,666 to 31,250 after treatment. Both oaks and red maples showed a significant increase in density between pre and post treatment. Total sapling density ranged from 500 to 2,166/ha, prior to treatment and 0 to 750/ha after treatment. Sapling density decreased significantly for all species, though red maple did increase in one subunit. The proportion of hardwood and/or red maple to oak saplings was higher than for seedlings, both before and after treatment.

Both Black-throated Blue and Canada Warblers nest in the dense shrub layers of 1-3 meters that were reduced in height and cover by the prescribed fire. Clearly the fire was not favorable to those habitat characteristics needed for those species. Increases in seedling densities and regrowth of mountain laurel will likely result in suitable habitat again, though we cannot predict the time frame for that from this study. At the same time, there was negligible change in tree density or canopy cover, so some of the appropriate habitat characteristics for these species remain. Scarlet Tanagers require large, unbroken forests with closed canopy, so their habitat requirements remain unchanged. Litter cover remained relatively unchanged, and new litter will fall to replace what was burned. Therefore, habitat for Worm-eating Warblers should also remain relatively unchanged.

The methods used here could be modified for monitoring site treatments, and recommendations are included for both future research and monitoring.

Title: Analysis of Field Data for the Shawangunks Grassland and Forests Birds Habitat Study – Overlook Wildfire Study

Author: Michael Batcher, Ecologist and Environmental Planner

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Abstract: The Overlooks Wildfire burned approximately 1,250 ha within Minnewaska State Park Preserve and some adjacent private lands in April of 2008. This was the largest fire in the Shawangunks since the 1947 wildfire that burned over 3,000 ha. To measure the effects of this fire, vegetation and other data were collected from 96 10-m radius circular plots (314 m2) in Minnewaska State Park Preserve from early June to mid- September of 2008. Fifty-five of these were in burned areas mapped as chestnut oak forest and 20 in nearby, unburned chestnut oak forest. Twenty-one plots were located within burned pitch pine-oak-heath rocky summit. In late May and early June of 2008 bird data was collected from 25 points within the boundary of the Overlooks Wildfire and from 15 points in a nearby, unburned chestnut oak forest. These were also included in the above vegetation plots. To provide further comparison of burned vs. unburned areas, data from 1995-96 mapping of the northern Shawangunks by John Thompson (1996), incorporated into New York Natural Heritage Program data (NHP), were also analyzed.

In 2009, bird data was again collected in the two unburned transects and in two of the burned transects. In 2010, we collected vegetation data in 36 plots mapped as chestnut oak forest and 10 plots in the pitch pine-oak-heath rocky summit in the burned area. We also collected bird data from 25 points in the burned area. No data were collected in unburned areas.

The wildfire reduced total canopy cover well below that of unburned plots from this study and NHP data. High intensity fire likely killed many canopy trees, creating open woodland areas distinct from forest types. These open woodland areas were discovered during field work in 2010 and were not observed in 2008. Tree cover substantially recovered in forest plots.

Overall tree density in the chestnut oak forest was 66.2/ha in 2010, compared to 487.7 in 2008. Plots designated as forested had a density of 244.0/ha, compared to 38.9/ha for open woodland plots. Oaks had higher importance value in the burned area in 2010 than in 2008, primarily due to values in open woodland plots where oaks (Quercus montana, Q. rubra) persisted and red maple did not. This supports the theory that the open woodlands were subject to higher intensity fires than the areas that remained as forest. After two years, more trees died, and it would appear that oaks had a higher survival rate than red maple (Acer rubrum) or other species. Pitch pine (Pinus rigida) also had a high importance value in these open woodland plots, which may indicate that those areas that became open woodland differed from other chestnut oak forest areas prior to the fire. Red maple continued to have high importance values in burned forested areas.

In the pitch pine-oak-heath rocky summit, tree density was 732.8 trees/ha in 2008 and 273.7 trees/ha in 2010 compared to 414.3 in unburned plots. Again, this community likely experienced high intensity fire. Red maple density and importance value were significantly lower in 2010 than in 2008.

In chestnut oak forest plots, red maple constituted 61.4% and sassafras 26.1% of seedlings. In open woodland plots, these proportions were 7.3% for red maple and 89.0% for sassafras, while in the pitch pine-oak-heath rocky summit, these proportions were 60.9% for red maple and 32.1% for sassafras. Only 15 pitch pine seedlings, representing 2.5% of total seedlings, were counted. In the chestnut oak forest, the total seedling density for all species ranged from 78,309/ha in chestnut forest plots to 96,833 in open woodlands, while overall density in the pitch pine-oak-heath rocky summit was 29,666/ha. By comparison, in a separate study of prescribed fire effects in the Undercliff treatment unit, densities across plots ranged from 5,333 to 18,416/ha prior to the 2010 burn and 7,666 to 31,250/ha following that burn.

In the chestnut oak forest, red maple constituted 50.0% and sassafras 40.0% of saplings. In open woodlands, these proportions were 22.8% for red maple and 69.3% for sassafras. Sapling densities were 476/ha in forested plots, 1,727/ha in open woodlands, and 233/ha in the pitch pine-oak-heath rocky summit.

For the chestnut oak forest, the average total cover of the S1 strata (2-5 m) was significantly lower for burned than unburned plots in 2008, likely the result of high intensity fire burning in mountain laurel (Kalmia latifolia). S1 cover for burned plots in 2010 was less than found in burned plots in 2008. There may have been some dieback in this stratum, or the 2010 plots were simply different from the 2008 plots in shrub cover. For the S2 layer (< 2m), total shrub cover in 2008 burned plots was significantly lower than for unburned plots. In addition, S2 cover for burned areas was significantly higher in 2010 than was found in 2008. This is likely the result of recovery of the S2 layer between 2008 and 2010.

For the pitch pine-oak-heath rocky summit the total S1 layer cover in both 2008 and in 2010 vs. NHP data (unburned) was significantly lower. Apparently S2 cover in the burned area was higher than that for the NHP plots. Little recovery in either the S1 or S2 strata seems to have occurred between 2008 and 2010.

Scorch height and the proportion of canopy scorched varied more in the chestnut oak forest than in the pitch pine oak-heath rocky summit. In the chestnut oak forest, the distribution of proportion of canopy scorched was such that most trees recorded either little or no proportion of canopy scorched or over 90% scorched, with a moderate number of trees in between. In the pitch pine-oak-heath rocky summit, most trees had at least 90% of the canopy scorched. This indicates generally high intensity fire in that community, as well as torching of pitch pine whereas the chestnut oak forest was subjected to much greater variation in fire intensity and, hence, effects.

In 2008, there was significantly less leaf litter cover in burned vs. unburned chestnut oak forest plots and significantly more duff in burned plots, indicating that some areas had burned into the upper organic layers of the soil. Litter cover in plots assessed in 2010 was significantly higher, and duff cover significantly lower, than either measurement in 2008 burned plots. However, for data collected in 2010, those plots designated as open woodland had less litter and more duff than those designated as forested. This may have resulted from greater litter deposition from trees in the forested plots, greater decomposition of litter in open areas, or the occurrence of high intensity fires in 2008 that reduced litter cover.

Forty species of birds were recorded in 2008 in burned areas while 31 were recorded in unburned areas. In 2009, 35 species were recorded in burned areas and 30 in unburned areas. In 2010, 52 species were recorded within the burned area. Changes in mean abundance between burned and unburned areas and between years for birds were inconsistent, both for many individual species as well as for bird guilds. The most consistent findings were for several of the species associated with forests. Ovenbirds, Black-throated Blue Warblers and Black and White Warblers all showed declines from

unburned to burned areas. On the other hand, Scarlet Tanagers were also more abundant in burned areas.

For species associated with open habitats, Prairie Warblers were more abundant in burned areas, but also declined in abundance in both burned and unburned areas. Common Yellowthroats, Morning Doves, Chipping Sparrows and Chestnut-sided Warblers increased in both burned and unburned areas.

For cavity nesters, which we would expect would increase with increased abundance of dead trees, Black-capped Chickadees, House Wrens and Eastern Bluebirds increased in abundance in the wildfire area, while the abundance of woodpeckers and Great-crested Flycatchers was more mixed.

Given the open woodland areas where tree mortality was apparently high and the trajectory of the community toward one dominated by sassafras and red maple, I conclude intervention will be needed to restore the chestnut oak forest in the Overlooks Wildfire area. Leaving the area alone will likely lead to the area stabilizing as a shrubland or a woodland dominated by red maple and sassafras. Fire should be introduced as early a possible to reduce seedling numbers for both of these. Mechanical and herbicide treatments will be needed to reduce sassafras and red maple trees and saplings to reduce seed input. It may even be necessary to distribute acorns in areas where oak density is too low to provide sufficient numbers and where rodents and deer reduce acorns and seedlings. These actions can be incorporated into a program of further research and long-term monitoring of fire effects to track changes resulting from the Overlooks Wildfire. This should be integrated into the prescribed fire program contemplated in the recently completed fire management plan for the Shawangunks.