Controls on bank in the Frances Crane Management Area

Marta De Giuli1, Chistopher Neill2, Linda Deegan2, Max Black3

1- The University of Chicago, Chicago, IL 60615 2- Hole Research Center, Woods Hole, MA 02543 3- Franklin and Marshall College, Lancaster, PA 17604

Abstract Though coastal sandplain grasslands are located on relatively unproductive and unfavorable , they harbor disproportionately high levels of diversity which are sustained by periodic disturbances. The maintenance of the species richness observed in these areas is potentially aided by recruitment of from the seed bank. As human activity diminishes the frequency of these naturally occurring disturbances, management practices are put into effect which often focus on habitat maintenance with warm season grasses like Schizachyrum scoparium through controlled burns and mowing with the underlying goal of maintaining a diverse community. We examined the effects of burns and S. scoparium cover on seed bank diversity and viability in Crane Area. We took the pH characteristics of the soil profiles of the plots over a gradient of S. scoparium cover, a recently burned plot, and a reference plot. We found that soil pH varies between plots though a clear trend of increased pH in the surface soil compared to deeper soil- likely due to the burning management conducted, is conserved. These changes in acidity may have an effect on which species persist in this environment. We quantified biodiversity through the abundance and species richness found within the germination of seeds from (1) plots of increasing S. scoparium cover, (2) aggregate samples subjected to a gradient of simulated burn temperatures, and (3) the comparison of a recently burned and a reference plot. Burn temperatures had an effect on abundance and richness of the species that germinated, we saw an increase in both with temperatures up to 120 oC followed by no growth in higher temperatures. Inversely, S. scoparium cover did not have a significant impact on species richness but had a similar effect on plant abundance where we observed less abundant growth in the plots with >50% cover. Our results support the current management plan as the steps taken seem to maintain a diverse plant community while also developing more habitat for animals and soil that is more adequate for maintaining grassland species.

Key Words Grassland, sandplain grassland, seed bank, biodiversity, controlled burns, soil pH, seed dispersion, grassland management.

Introduction Increases in the magnitude of human activities over the past century have created more acute global environmental problems including issues related to extensive use changes seen in both developed and developing countries (FAO, 2009). These changes lead to the decline of formerly abundant habitats seen conversion of and grasslands to agricultural areas and the subsequent fractionation of the original habitats. The decline of these habitats as well as more direct anthropogenic impacts on our environments often result in loss of local biological diversity. Decreases in species richness and evenness make ecosystems less stable and thus more susceptible to punctuated changes in non-biotic factors (Tilman and Downing, 1994). These losses are severely impacting the ecosystem services provided by nature, such as fertile land and clean air and (Naeem et al, 2002).

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Grasslands have become some of the most endangered ecosystems due to the various anthropogenic pressures they are subjected to, including conversion to cropland, alteration to shrublands due to grazing practices, and edification. It is estimated that only 5% of the natural grasslands in the United States are still in their natural state (National Geographic, 2009). Of the ecosystems in eastern North America that have declined by >98%, 55% are grassland, savanna, and barren communities and 24% are shrubland communities (Noss et al., 1995; Thompson and DeGraaf, 2001). Even open habitats that have not been decimated to this extent have been greatly reduced. For example, >90% of the coastal heathlands of Long Island and New and 69% of the evergreen shrub bogs of the southeastern coastal plain have been destroyed (Noss et al. 1995). The fragmentation and loss of grasslands is placing heavy pressure on many animal species of critical environmental concern and ultimately changing the structure and function of ecosystems we depend on (Joshi et al, 2006). Recovery of grasslands from previous states of anthropogenic use is extremely important for the preservation of animals who rely on this shrinking habitat as well as the many ecosystem services provided by such areas. Management is often needed to preserve these grasslands due to the anthropogenic suppression of natural disturbances that maintain open areas such as fires, , beavers, and windstorms (Askins, 2001). Simulation of these disturbances through mowing, clearing, and controlled burns is necessary to restore these . Management efforts are often focused towards one keystone species like warm season grasses, which provide habitat for grassland animals and maintain open landscapes, but have an end goal to maintain a diverse set of grasses and forbs (Dunwiddie et al, 1996). The ability for grasses to keep out secondary successional species may also extend to other grassland species, so over promotion of these grasses may be at the expense of other species and the overall floral diversity of the ecosystem. Regrowth from soil seed banks as well as seed recruitment from adjacent areas are thought to be important mechanisms for maintaining plant diversity in recovering and stable grasslands. Though burning can encourage growth from seed banks, it may reduce such growth if fires reach temperatures high enough to kill seeds. The alteration of surface soil properties by fire, such as increases in pH as well as in nutrient availability, has been shown to change the ability of certain species to germinate (Certini, 2005; Deska et al, 2011). Dense cover of one species and reduction of species evenness may also reduce seed bank diversity overtime by outcompeting other species and thus lead to a downward spiral - the endpoint of which is an ecosystem with little to no biological diversity. If the long term goal of grassland management is to maintain diversity of native , it is important to know how the combination of all these management effects influence seed banks and seed recruitment. We examined seed banks and seed recruitment along a grassland management gradient from sparse to dense Schizachyrum scoparium (S. scoparium) as well as a recently burned and an unburned site. If S. scoparium cover does negatively impact seed bank diversity, we expect seed bank diversity to be inversely proportional to S. scoparium cover. We tested burn severity on an

3 aggregate seedbank sample, to examine its effect on seedbank viability. Similarly, more severe burns should decrease seed germination.

Methods Description of study site. Crane Wildlife Management Area (Figure 1) is a 200 acre managed sandplain grassland with some pitch pine/scrub oak savannah habitat on recovered agriculture terrains on Cape Cod. The grassland habitat is maintained by the Division of and Wildlife as a grassland through various methods of disturbance such as prescribed fire, mowing, invasive plant control, and tree removal. These anthropogenic disturbances take the place of the natural events such as wildfires which would otherwise maintain the open habitats (Simmons & Mazzei, 2014). Sample Plots. Five areas of S. scoparium cover were identified in the following ranges: 6-15%, 16-25%, 25- 50%, 50-75%, and 76-100% after making 3 replicate cover measurements in 3 m x 3 m quadrats. Circular 10 m radius plots were lain out in each area (Figure 1). Two additional plots of the same size were lain out in a recently burned area and a reference site near the edge of the burn. Soil pH analysis. Five replicate soil cores of 30 cm were taken at each cover site. The cores were subdivided into the following intervals: 0-5 cm, 5-10 cm, 10-20 cm, and 20-30 cm. Five shallow cores (0-5 cm) of the burn and control sites were taken and subdivided into the following intervals: 0-1 cm, 1-2 cm, 2-3 cm, 3-4 cm, and 4-5 cm. A 10 g sample of each depth interval of each core was soaked in 50 mL of pure water for 45 minutes and then a pH meter was used to measure the pH of each soil/water mixture. The probe was rinsed with pure water and dried between each sample. Burn experiment. Twenty soil samples for seed bank analysis were taken from random locations around the larger area of grassland. All samples were combined and homogenized. 65 g subsamples were taken and subjected to one of the following temperature treatments in a muffle furnace for five minutes (5 replicates for each temperature): no-heating, 75 oC, 95 oC, 120 oC, 200 oC, 400 oC. Temperatures were extrapolated from measured surface temperatures during grassland burns conducted by Morgan (1999). Each subsample was potted 0.75 cm thick in 58 cm2 pots on top a 3:2 mix of sterile potting soil and sand. Pots were incubated at 30 oC in a temperature controlled room following a 12 hour light, 12 hour dark cycle and watered twice daily. Extra growing lights were placed over pots once plants began sprouting. Sprouts were counted at 6 day intervals with an extra count at day 21 and identified to the lowest taxonomic category possible. Plants were also classified into the functional groups of graminoids and forbs. Counting ended 21 days after potting.

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Seed bank germination.

Five soil samples for seed bank analysis were collected at random locations in each cover plot with a cylindrical aluminum corer of diameter 5.2 cm. Two replicates of each sample were separately potted 0.75 cm thick in 58 cm2 pots on top a 3:2 mix of sterile potting soil and sand. Pots were incubated at 30oC in a temperature controlled room following a 12 hour light, 12 hour dark cycle and watered twice daily. Extra growing lights were placed over pots once plants began sprouting. Sprouts were counted at 6 day intervals with an additional count at day 21 after potting and identified to the lowest taxonomic category possible. Plants were also classified into the functional groups. Counting ended on the 21st day after potting. Seed trap germination.

Five replicates collectors for seed were installed at ground level at random locations on each plot and left out for 10 days. Seed rain were two 6-pack seed starter pots with sterile potting soil. Pots were then placed in a freezer for 10 days to simulate stratification and then incubated at 30oC in a growing chamber for germination. Samples were treated with a 12 hour light cycle and watered twice daily. Plants were then counted at 6 day intervals for 18 days and identified.

Results Cover effects on soil pH. No significant correlation was found between S. scoparium cover and soil pH profile though all sites showed a decrease in pH with depth except for the 15-25% and 50-74% cover which saw a spike in the 20-30 cm layer and no change, respectively (Figure 2). There was a significant change in pH with depth with the 0-5cm layer being significantly different from the 5-10 cm, 10- 20 cm, and 20-30 cm layers, p= 0.000168, p=2.2 x 10-6, and p=4.82 x 10-5 respectively.

The change in pH ( pH) of soil from a reference depth (5-10 cm and 10-20 cm layer averaged) to the surface trended around 1 for all cover classes except the 50-74% cover which had a  pH of -0.057 (Figure 3). Burn effects on soil pH. The pH profiles of the burn and control site were significantly different (p=<0.0001), but showed similar trends in decreasing pH value with depth. Similarly to the cover plots, the surface layers of soil (0-1 cm, 1-2 cm, and 2-3 cm layers) were significantly different from the deeper layers, p<0.00163 in all cases, while the deeper layers were not significantly different, p>0.337 in all cases (Figure 4). The  pH of the burn site was significantly larger than that of the reference site, 1.49 vs. 0.73, p=0.00512, with the reference layer of soil being an average of the 3-4 cm and 4-5 cm layers (Figure 3). Fire effects.

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Seed bank samples from the burn site exhibited no growth throughout the 21 day growth period while the samples taken from the reference site had germination in 4 out of the 10 potted samples and seeds of a total of 3 species germinated (Figure 5). In the temperature treatment experiment, both samples exposed to no heat and 75oC had a total species richness of 3 species. The samples treated at 95 oC and 120 oC showed an increase in species richness compared to the lower temperatures with 6 and 7 species each, respectively. No growth was observed in the 200 oC or 400 oC treatments (Figure 6). The species assemblage did not vary between temperatures, with 65% of germinated species being forbs. Though there was a clear trend in higher temperature leading to increased richness, no statistical significance was found, p = 0.199. The abundance showed a similar trend with increased abundance with temperature and no growth at 200 oC and 400 oC (Figure 7), a significant trend with p=8.47 x 10- 5. The abundance assemblage saw a decrease in evenness with temperature, with an increase in forb abundance from 50% to 85% of germinated plants (Figure 8). Cover effects. Though no significant trend was observed in species richness with increased S. scoparium cover (Figure 9, p=0.182), the mean species richness of the plots with <50% cover was higher than that of the denser plots, 2 species vs. 0.8 species per sample. This decrease in richness was followed with a decrease in evenness with forbs increasing in proportion to graminoid species from 55% to 85% (Figure 10). Plant abundance significantly changed with cover (p=5.62 x 10-5), with an increase in abundance with S. scoparium cover below 50% cover and a sharp decrease in denser plots (Figure 11). Plant assemblage showed less of a trend, with the forb proportion increasing rapidly from about 50% to 85% between the least two dense plots then tapering out to about 80% in the plots with cover above 25% (Figure 12). Over the 21 day growing period for the seed trap samples, growth was only observed in the samples obtained from the plot with the lowest S. scoparium cover: 5-14%. Four individuals of a single forb species sprouted. Discussion Many current grasslands are either recovering agricultural lands or newly cut forest (Askins, 2001; Simmons et al, 2014) that began with soil profiles very different from the requirements of grasslands. The addition of lime to agricultural lands increased the pH of the soil while forests developed more acidic organic layers from the decomposition of tree litter (Neill et al, 2007). Grassland species requires less acidic soil pH than forest lands provide and the physical characteristics of varies little between areas in close proximity. With this in mind, the observed positive  pH in the cover plots is in line with the natural requirements of the ecosystem and heavily contrasts the strongly negative (-1.1 and -1.2 in the oak forest and beech

6 forest, respectively)  pH found between the mineral and organic layers of forest ecosystems by SES students in the 2017 fall semester (Figure 3). All the cover plots had been sites of controlled burns in the past. The significant difference between the  pH of the reference site and the burn site seems to indicate that a  pH of about 1 is due to a burn. The  pH found in the cover plots could therefore be linked to the burning regime and simply maintained by the less acidic litterfall of the grasses and forbs, supporting controlled burns as an effective and important management method for soil characteristics. In terms of seed bank viability, controlled burns also seem to have a positive effect. Many grassland species are fire adapted (Anderson, 1990) and thusly require high temperatures or other elements provided by fire to mature and germinate. This was supported by my finding of an increase in both species richness and plant abundance in the higher temperature treatments (Figures 6, 7). The lack of growth observed at the higher temperatures, 200 oC and 400 oC could have been due to the excessive heat having killed the seeds. This is likely as typical grassland fires do not exceed 150-200 oC below the top 1 cm of soil (Morgan, 1999), allowing for seeds stored deeper to maintain viability, while surface seeds burn. Since the whole sample was exposed to the higher temperatures, all the seeds may have been killed. As mentioned above, burns affect the soil physical characteristics; the high temperatures experienced by the high temperature treatments may have created an environment unfavorable for seeds to germinate, and thus impeded sprouting. A measure of soil temperature during or after the temperature treatment coupled with a pH analysis of a subsection of the soils treated would have provided more support for this claim.

The lack of growth in the burn plot (Figure 5) compared to the reference plot raises issues with the results obtained by the temperature treatments as the controlled burn that created the habitat we sampled did not burn the tufts of grass present to the ground – indicating a relatively cool burn. With this in mind, we expected to see more growth in the burn plot than the reference plot. This could be explained by changes in soil characteristics we did not measure such as water retention, which is altered by burning regimes (Certini, 2005). The two results are still at odds and need to be further studied. Growth from the seedbank also seems to be impacted by the cover of S. scoparium. Though the species of richness is not severely affected until extremely dense covers are reached, species assemblage is altered and becomes less even with increased cover (Figure 10). The relative absence of graminoid species in the sites with high cover can be due to the preferential spread of those species through rhizomes rather than seed. The extensive rooting of S. scoparium would impede other rhizomes from effectively entering the area, preventing grasses of other species to sprout (and then spread seeds). We observed an inverse correlation between S. scoparium cover and plant abundance (Figure 11). The presence of tall grasses may impede the recruitment of seeds from the vicinity, decreasing the abundance of seeds in the seed bank over time, resulting in fewer individuals

7 sprouting. This seems to be supported by the results found from the seed traps where the only viable seeds found were from site with the lowest cover. The lack of growth in the seed traps may have also been due to factors other than the absence of seeds. Different species require different external, or internal, cues to mature including physical scarring, temperatures, stratification, time as well as specific conditions to germinate. It is likely that the conditions provided in the temperature control room and during stratification were not adequate to support germination of seeds from this year. In all scenarios, the latter statement is very important. The conditions in the growth chamber, though fairly controlled not suitable to induce germination for all the species that may have been present in seed form in the samples. Given more time, , and samples, it would have been possible to incubate the samples in different conditions to provide more species with the correct conditions to germinate.

Conclusion We observed that controlled burns increased pH in surface soils and moved them away from the pH characteristics typical of forest profiles and allowed for conditions more favorable for healthy grasslands. This, coupled with an increase in species richness and abundance, supports burning as a favorable management strategy for overall diversity in sandplain grasslands. The issue of managing for an overabundance of S. scoparium or other as might be done through burning in one season is raised as increased cover seems to have an impact on diversity that sprouts from seed bank. This loss of diversity could lead to a negative feedback cycle terminating in a complete . Plant diversity is only a fragment of the grassland management issue as management is often done with the diversity of the whole community in mind. The importance of plants is only valid in light of the ecosystem that is thusly supported. In addition to more in depth research about the effects of management on floral diversity, the effect of the floral diversity on the fauna in these environments still needs to be investigated.

Acknowledgements A huge thanks goes out to Mary Heskel for providing guidance for ANOVA analyses in R and the opportunity to spend time doing the computer work for this project in the company of her magnificent cats: Gus and Lilah. Additional thanks to Max Black for going out to Crane in all types of temperatures to sample, to Chris Neill and Linda Deegan for their endless help and guidance, and Michael Whittemore for identifying plants that at first appeared nearly impossible to distinguish. Finally, thanks to Richard McHorney as well as Jordan Stark, Emily Stone, and Alana Thurston for remembering that I existed even though I spent only 12 hours in lab. Literature Cited Anderson, R. C. (1990). The historic role of fire. Fire in North American tallgrass prairies, 8.

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Askins, R. A. (2001). Sustaining biological diversity in early successional communities: the challenge of managing unpopular habitats. Certini, G. (2005). Effects of fire on properties of forest soils: a review. Oecologia, 143(1), 1-10. Deska, J., Jankowski, K., Bombik, A., & Jankowska, J. (2011). Effect of growing medium pH on germination and initial development of some grassland plants. Acta Scientiarum Polonorum. Agricultura, 10(4). Dunwiddie, Peter W.; Zaremba, Robert E.; Harper, Karen A. 1996. A classification of coastal heathlands and sandplain grasslands in Massachusetts. Rhodora. 98(894): 117-145. FAO. 2009. State of the world's forests: Technical Report, and Agriculture Organization of the United Nations, Rome. Joshi, J., Stoll, P., Rusterholz, H. P., Schmid, B., Dolt, C., & Baur, B. (2006). Small-scale experimental habitat fragmentation reduces colonization rates in species-rich grasslands. Oecologia, 148(1), 144-152. Loreau M., Naeem S., Inchausti P., editors. (2002). Biodiversity and ecosystem functioning: synthesis and perspectives. Oxford: Oxford University Press. Morgan, J. W. (1999). Defining grassland fire events and the response of perennial plants to annual fire in temperate grasslands of south-eastern Australia. Plant ecology, 144(1), 127- 144.

National Geographic. (2009, October 09). Grasslands Are Under Threat. Retrieved November 06, 2017, from https://www.nationalgeographic.com/environment/habitats/grassland- threats/. & Endangered Species Program, Division of Fisheries and Wildlife. (2016). Sandplain Grassland. Classification of Natural Communities of Massachusetts, 2. Neill, C., Patterson, W. A., & Crary, D. W. (2007). Responses of soil carbon, nitrogen and cations to the frequency and seasonality of prescribed burning in a Cape Cod oak-pine forest. Forest Ecology and Management, 250(3), 234-243. Noss, R. F, E.T. LaRoe III, & J. M. Scott (1995). Endangered ecosystems of the United States: A preliminary assessment of loss and degradation. Biological Report 28, National Biological Service, Washington, D.C., USA. Price, J. N. et. al. (2010). Comparison of seedling emergence and seed extraction techniques for estimating the composition of soil seed banks. Methods in Ecology and Evolution, 1(2), 151-157. Simmons, T. and Mazzei, B. (2014). Biodiversity Initiative Plan: Sandplain Grassland & Pitch Pine/Scrub Oak Savannah Restoration at Frances Crane Wildlife Management Area North.

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Thompson, F. R. III & R. M. DeGraaf (2001). Conservation approaches for woody-early successional communities in the eastern USA. Wildlife Society Bulletin: in press. Tilman, D., & Downing, J. A. (1994). Biodiversity and stability in grasslands. Nature, 367(6461), 363-365.

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Figures

Figure 1: Map of Frances Crane Wildlife Management Area. Sites 1-5 represent cover plots of 50-74%, 25-49%, 75-100%, 5-14%, and 15-24% cover respectively. Marker B represents the location of the burn site and the green marker, the reference site.

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pH 4 5 6 7 8 0

5

10 50-74% cover

25-49% cover 15 75-100% cover 5-14% cover

Depth (cm) Depth 15-24% cover 20

25

30

Figure 2: Soil pH profiles of S. scoparium cover plots in Crane Wildlife Management Area.

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2

1.5

1

0.5 pH δ 0

-0.5

-1 0 50 100 -1.5 % S. scoparium cover Burn Reference Beech Oak Forest Forest

Figure 3: pH with % S. scoparium cover and in different sites in Crane Wildlife Management Area. The dotted line represents no change between reference (deep) soil pH and surface pH. Beech and Oak forest data collected by SES students in fall of 2017.

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pH 4 5 6 7 8 0

1

2 Burn Reference

3 Depth (cm) Depth 4

5

Figure 4: Soil pH profile of the burn and reference site in Crane Wildlife Management Area.

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Total Species Richness 4

3

2 # species #

1

0 Burn Reference

Figure 5: Total species richness in burn and reference sites in Crane Wildlife Management Area.

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Total Species Richness 8 7 6 5 4

# species # 3 2 1 0 no heat 75 95 120 200 400 Temperature Treatment (oC)

Figure 6: Total species richness in temperature treatments. All samples for a temperature treatment were summed to obtain a total number.

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Mean Sprout Abundace per m2 4000

3000

2000

# individuals # 1000

0 no heat 75 95 120 200 400 Temperature Treatment (oC)

Figure 7: Mean sprout abundance per m2 of grassland for temperature treatments. Counts scaled up from area of core sample.

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Abundace Assemblage

Forbs Graminoids 100%

80%

60%

40%

20%

0% no heat 75 95 120 200 400 Temperature Treatment (oC)

Figure 8: Abundance assemblage for temperature treatments in Crane Wildlife Management Area.

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Total Species Richness 10

8

6

# species # 4

2

0 5-14% 15-24% 25-49% 50-74% 75-100% cover cover cover cover cover

Figure 9: Species richness with S. scoparium cover in Crane Wildlife Management Area.

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Total Species Assemblage

forbs graminoids 100%

80%

60%

40%

20%

0% 5-14% 15-24% 25-49% 50-74% 75-100% cover cover cover cover cover

Figure 10: Species assemblage in terms of proportion of forbs to graminoid species with S. scoparium cover in Crane Wildlife Management Area.

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Mean Sprout Abundance per m2 8000 7000

6000

5000 4000

3000 # individuals # 2000 1000 0 5-14% cover 15-24% 25-49% 50-74% 75-100% cover cover cover cover

Figure 11: Mean sprout abundance per m2 of grassland with S. scoparium cover in Crane Wildlife Management Area.

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Plant Abundance Assemblage

Forbs Graminoids 100%

80%

60%

40%

20%

0% 5-14% cover 15-24% 25-49% 50-74% 75-100% cover cover cover cover

Figure 12: Abundance assemblage for S. scoparium cover plots in Crane Wildlife Management Area.

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Tables Table 1: Coordinates of plots in Frances Crane Wildlife Management Area

Plot Coordinates N 41.63782o 5-14% cover W 070.56102o N 41.63753o 15-24% cover W 070.55738o N 41.63487o 25-49% cover W 070.56361o N 41.63466o 50-74% cover W 070.56292o N 41.63557o 75-100% cover W 070.56072o N 41.63722o Burn W 070.5625o N 41.63778o Reference W 070.56306o

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