Positive and Negative Effects of Burning an Environment

Introduction:

Disturbance is a powerful factor in determining the success or failure of different communities of organisms in an environment. The range of disturbance intensities can vary from catastrophic disturbances to something as mild as rain storm. But no matter the intensity of the disturbance it will change and sometimes create lasting impacts on the community and environment (Dornelas 2010). It is easy to think that a disturbance may hinder the environments ability to grow and be successful, but this is not the case for many communities. Many species are adapted to disturbance and occur within dynamic, mosaic landscapes that contain early and late successional microhabitats (Pardini 2015). In many situations’ disturbances are necessary to maintain biological diversity and stability, usually these disturbances need to happen in appropriate time scales for the environment to thrive properly. If the area experiences too much or too little of a disturbance it can negatively impact the community.

The use of fire has noticeably increased and used over the past two decades to manage hardwood and mixed hardwood-pine (Pinus. L.) systems of the central Hardwoods and central and southern Appalachian regions, USA (Harper et al.: Fire Effects on Wildlife in Eastern USA). Controlled burning for these areas has a shown restorative effect for the organisms residing (Johnson and Hale 2002, Van Lear et al. 2005, Masters 2006), since it is a gateway for secondary succession.  But even as fire is used so extensively the methods behind being successful, generally, are not the same for all southeastern hardwood environments, particularly due to the lack of studies done.  However, many types of prescribed burning have developed for pine environments, an example of such is burning before the growing season begins, this is used mostly for longleaf pine (Pinus palustrus.) ((Johnson and Hale 2002, Van Lear et al. 2005)

Florida is subject to extreme weather patterns which makes it a prime candidate for forest fires.  During late summer to mid to late fall, it’s hot and dry, in the winter is it cooler and dry, spring is characterized as humid and warm, summer is hot and wet. During the late summer to fall is when most of Florida’s forest fires occur, considering how dry and hot the forests are. Typically, late August and early September are the start of Florida’s hurricane season. Florida is considered one of the most active places on earth for lightning strikes, especially during its hot and dry periods, which are when most of Florida’s unregulated fires happen. Usually forest fires happen in areas that are fire repressed and create a lot of damage to the area and are dangerous. If an area is regulated with prescribed burning, it has shown to decrease the issue of forest fires by burning the fuel of the fire. Essentially burning off the sub-canopy bushes or shrubs, allowing for safer natural fires. That’s not to say that prescribed burning is safer as it also has calculated risks to the individuals performing the burns and the surrounding area which is usually inhabited by people.  With the information present, I hypothesize that burning an environment like the pine flatwoods will have a positive effect on plants and trees, but it will negatively affect plants that are sub-canopy. I predict that in burned areas will have higher species diversity and biomass will lower and unburned areas will have a higher biomass and less species diversity. The objective of this study is to determine whether controlled burning reflects positively in these southeastern, United States systems.

Methods:

Site description

The University of Central Florida (UCF) Arboretum, 110 Apollo Cir, Orlando, FL 32816. Spans across eighty-two acres and it is nestled east of the UCF campus or to Seminole County’s Econ River Wilderness area east of the campus (Stewart. J, 2018). UCF originally was built on cattle ranches and orange groves. Within the first forty years of growth at UCF only one recorded fire occurred in 1971, in 2005 however, a chance lightning strike started a fire in in an area called unit 7 that was contained. These pine flatwood areas are a fire dependent environment, and until the fire in 2005, UCF didn’t plan or utilize prescribed burning until May of 2005 (unit 11). However, the most recent burn occurred in April of 2016, approximately two years ago (Stewart. J 2018). For this study I will primarily use sections 11A the unburned section and 11B the burned. In Florida, the flatwood pine areas have a fire return interval within the year or ten years, this process is like the natural occurrences of Florida’s fires. Characteristically speaking, the pine flatwoods are composed of various types of pines, Pinus p., Pinus clausa, Pinus elliotti, and Pinus serotina. These are characteristic species because they are normally the dominant species in the environment and are found in the Arboretum.

Data Collection

Data collection in the Arboretum’s burned and unburned areas were collected in the morning. When collecting data a few items were necessary, a compass, measuring tape, and DBH tape (diameter tape) along with a quad.  In both the burned and unburned sections, 6 replicates in each unit were selected arbitrarily. The point-quarter method, a plotless technique which aims to estimate density, was used to see species distribution and diversity. This method of data collection is best for counting spaced individuals in an area or for large individuals in tight spaced areas. Data collection for the study began October 15, 2018 and will end October 22, 2018. The compass was used to ensure each transects measures were in the properly selected areas. The quad is a sampling point, the area around each point is divided into four 90° quadrants and the closest organism is recorded.  Measuring and DBH tape were used to assess how far different organisms were from the selected point and how wide the organism was. At each sample the percentages of grasses, woody, open space and flowers present were recorded. Using this method species diversity can be accounted for and used to determine if species diversity is larger or smaller in the comparative sites.

Data Analysis

  All data collected was compiled in Microsoft Office Excel, separating the data into category and in burned or unburned areas. The distance from the sample plot and if necessary the DBH of the organism were also recorded and placed into the data. Using the values from the spreadsheet a F-test and t-test were performed. The F-test testing for equal variances, is used to determine if the populations are equal. The test can be one tailed or two tailed depending on the data. For my data I’ll be using the two-tailed test which tests to see if the variance is unequal. This method was chosen to test if the burned areas are more biodiverse and have less biomass than the unburned. The T-test is quite similar, it needs two sets of data to determine whether there is a statistical difference between them. This test also can be one or two-tailed depending on the data. My data will be employing the two-tailed test, again to assume unequal variance. The MS Excel toolkit will be used to calculate the values of the F-tests and T-tests.

 Results:

Fig.1 Percent Coverage

The data collected shows the burned areas of the arboretum have not yet bounced back to their pre-burned plant densities. In the burned portions of the arboretum wooded coverage was much less in comparison to unburned.  The burned portions also displayed larger areas of open space likely due to burning. Burned areas also showed a greater diversity of plants and more biomass. These areas, granted with smaller numbers, contained species not found in the unburned areas, Opuntia humifusa, Ilex glabra, Baccharius hailmifolia. These areas also had larger open space and more grasses per transect than unburned areas.

Fig.2a Burned species list

Fig.2b Unburned Species Chart

Fig.3 Plot Data

The findings also determined mean canopy DBH values to be significantly larger in the burned areas. Shrub distance was also much shorter for the burned areas.

Discussion: 

 The data findings agree with the hypothesis that the unburned areas had less species diversity, considering burned areas had more plants not found in unburned areas. Sub-canopy species were also negatively affected in burned areas, the amount of open space was considerably larger in burned portions going along with the notion that controlled burning will negatively affect this portion of the property. This is mostly likely because burning limits abundance and decreases the growth and dispersal organisms. The graph data supports this point, the Sabel palmetto and Serenoa repens were observed to be much smaller in burned communities. There is a strong indication that these bushes may have experienced previous disturbances. This example is indicative of how some communities and species thrive with frequent controlled burns but not all are capable of handling them (Wall, 2012). Unburned areas could also suffer from loss of tree fecundity regarding how they’re dispersing in the environment after a disturbance, because, fires may positively or negatively affect the reproductive cycles of plants. The intensity and frequency are concerns as well, along with if the area is previously disturbed. These factors that can be applied to tree fecundity and possible loss. These ideas were previously discussed by Hamyes, who describes that a tree that has experienced several burns may have a different fecundity than one that has not experienced (Haymes, 2012). It is also worth mentioning that scientist have correlated fire with productivity and burn intensity showing heterogeneity characteristics in forest fires (Lyderson, 2012). Which describes that with an increase of trees in the flatwoods with the same type of diversity results in more forest burns. This key point is solidifying the hypothesis that burning increases plant diversity.  By analyzing tree fecundity, biodiversity and observing it in both burned and unburned environments, one could better understand and recognize fire patterns in these kinds of communities. In understanding these patterns, it becomes clear whether controlled burns are suitable for habitat rehabilitation. These findings may also lead to possible inside factors like types of moss, fungi or grasses that may cause certain environments to be more or less prone to forest fires. Giving a possible lead to better understanding wildlife conservation and obtaining for these environments. Moving forward, shrubs may influence the dominance and abundance of other species in unburned plant communities (Hawks, 2004). Though this is primarily substantial in only south eastern ecosystems where shrubs and fires are prevalent. Controlled burns are needed to measure these ecosystems. The consideration arises of natural vs. controlled burning, during repeated growing season burns, the abundance of established shrubs was not increased or reduced. But with long-term shifts in fire regimes, even pyrogenic environments may produce irreversible changes (Drewa, 2002). These studies show the necessity to protect and maintain these ecosystems. Maximizing habitats by means of controlling and maintaining biodiversity and vegetation. While the system I studied is a suitable candidate for using information to analyze southeastern fire patterns there is room for error, since most forest fires are naturally occurring and often highly unpredictable it is easy to disrupt data points and collection. Along with an areas likelihood of natural disasters like hurricanes and flooding. Modifying the experiment is possible but may also lead to tailored outcomes or different results, especially in different areas outside of Florida.

 All in all, the experimental data justified a good portion of the hypothesis, it was able to measure and analyze burned and unburned areas and relate them to abundance, diversity and dispersal. Understanding many factors are in effect during a disturbance and each has its own place in determining ecosystem outcomes. Errors in the results may have stemmed from studying only one ecosystem area that is considered flatlands and had little range. The study was also short in length due to outside circumstances.

Literature Cited

• Craig A. Harper, W. Mark Ford, Marcus A. Lashley, Christopher E. Moorman and Michael C Stambaugh, 2016, Fire effects on wildlife in Central Hardwoods and Appalachian regions, Fire Ecology, Vol. 12, Issue 2, 127-157pgs
• Dornelas, M, 2010, Disturbance and Change in Biodiversity, Philosophical Transaction B, 365
• Drewa et al, “Fire Effects On Resprouting of Shrubs In Headwaters of Southeastern Longleaf Pine Savannas” Ecology. 2002. 83:755–767
• Haymes and Fox, “Variation Among Individuals In Cone Production In Pinus Palustris (Pinaceae)” American Journal of Botany. 2012. 99(4): 1–6.
• Johnson, A.S., and P.E. Hale. 2002. The historical foundations of prescribed burning for wildlife: a southeastern perspective. Pages 11-23 in: W.M. Ford, K.R. Russell, and C.E. Moorman, editors, Northern Research Station, Newtown Square, Pennsylvania, USA.

• Lydersen and North, “Topographic Variation in Structure of Mixed-Conifer Forests Under an Active-Fire Regime” Ecosystems. 2012. 15: 1134–1146
• Masters, R.E. 2006. The importance of shortleaf pine for wildlife and diversity in mixed oakpine  forest and pine-grassland woodlands. Pages 35–46 in: J.M. Kabrick, D.C. Dey, and D. Gwaze, editors. Shortleaf pine restoration and ecology in the Ozarks—proceedings of a symposium. USDA Forest Service General Technical Report NRS-P-15, Northern Research Station, Newtown Square, Pennsylvania, USA
• Pardini, EA; Vickstrom, KE; Knight, TM, 2015, Early Successional Microhabitats Allow the Persistence of Endangered Plants in Coastal Sand Dunes, Plos One, Vol. 10, Issue 4
• Stewart. J, Stahelin. G, Schadegg. P, Biplabendu. D, Department of Biology, 2018, Principles of Ecology Laboratory Manual. University of Central Florida
• Wall et al, “Demographic Effects of Fire On Two Endemic Plant Species In the Longleaf Pine-Wiregrass Ecosystem” Plant Ecol. 2012. 213:1093–1104