Brean W. Duncan, Shannon Boyle, Paul A. Schmalzer, and David R. Breininger

Spatial Quantification of Historic Landscape Change Within Two Study Sites on John F. Kennedy Space Center

Abstract

Historical changes in a scrubby flatwoods (Tel-4) and a scrub landscape (Happy Creek) on John F. Kennedy Space Center were measured using aerial images from 1943, 1951, 1958, 1969, 1979, and 1989. Landuse/landcover categories were mapped and digitized into ArcInfo. Coverages were geometrically registered to one another, overlaid, and areas of landcover types were determined. In both study sites, forest cover increased and open scrub decreased. In the Tel-4 study site, forest cover in 1943 was 1.3% of the study area; it increased to a maximum of 30.7% in 1969, and then decreased to 21.8% in 1989. The Happy Creek study site had 5.2% forest cover in 1943, and forest cover steadily increased to a maximum of 18.2% in 1989. Open scrub was at a maximum in Tel-4 during 1943, representing 10.4% of the study area; it decreased to a low of 1.6% in 1969 and increased to 7.7% in 1989. Open scrub in 1943 comprised 7.6% of the Happy Creek study site, increased to 14.0% in 1951, and then decreased to 3.3% in 1989. The study sites had varied land use histories prior to NASA acquisition in the early 1960s. The Tel-4 study site was logged and managed for ranching, while land use at Happy Creek was less uniform with scattered homesteads and farming and extensive soil disturbances in the form of clearings. After acquisition, there was a period of fire suppression until 1981, when prescribed burning was implemented. These management practices have profoundly impacted the landscape and have affected habitat suitability for threatened species such as the Florida Scrub-Jay.

INTRODUCTION

Well-drained scrub communities are under extreme pressure from human disturbance and development in the state of Florida. In northern Brevard County, historic aerial photographs have shown a reduction in well-drained scrub of 68% since the 1940's (Bergen 1994). In the Treasure Coast Region, which stretches from north Indian River to southern Palm Beach counties, loss of xeric scrub has been reported at 64% (Fernald 1989). The remaining scrub in the state is typically heavily fragmented, isolated, or overgrown, making it less suitable for the wildlife species that are dependent on it (Myers 1990).

Scrub communities in Florida are well adapted to fire (Abrahamson 1984a,b; Myers 1990, Schmalzer and Hinkle 1992a,b). In an undisturbed environment, frequent lightning ignitions would maintain natural scrub in a low, open stature. Prior to European settlement, Native Americans used fire and did not decrease the natural fire frequency across the Central Florida landscape (Davison and Bratton 1986). European settlement brought ranching and citrus farming to the central east coast of Florida. Scrub was cleared for citrus groves, and open range management was practiced for ranching. Fires were used annually to encourage herbaceous growth and to improve range for cattle. Open range management continued in Brevard County until 1925 and in Volusia County until 1947, when cattle had to be fenced in and fires restricted to ranchers' property (Davison and Bratton 1986). In the early to mid 1900s a controversy raged between cattle and timber industries. Timber industries wanted to restrict the open range policies because fire was a threat to timber resources. Fire suppression was proposed by the timber industry in the early 1940's. Organized wildland fire suppression in Brevard County began in the 1950's (Larson 1952).

The National Aeronautics and Space Administration (NASA) began acquiring land in early 1962 on north Merritt Island, Brevard County, as a base for launch operations in support of the Manned Lunar Landing Program. Kennedy Space Center (KSC) is now 57,000 ha in size, which is considered extensive enough to provide surrounding communities protection from launch operations. Because KSC was found to include prime habitat for unique and endangered flora and fauna, NASA entered into an agreement with the U.S. Fish and Wildlife Service (USFWS) to establish a wildlife preserve, known as the Merritt Island National Wildlife Refuge (MINWR) within the boundaries of KSC. A similar agreement was reached with the Department of Interior to form the Canaveral National Seashore (CNS) managed by the National Park Service (NPS) within KSC's northernmost boundaries. The majority of KSC land is undeveloped, with only 5% being used for NASA operations and industrial use, while the remaining 95% is managed by the USFWS and NPS.

After NASA took ownership, fire suppression remained in effect on Kennedy Space Center until 1981, when a wildfire burned out of control killing two fire fighters. The first fire management plan for KSC was developed after this event to reduce dangerous fuel levels and prevent future fuel build up (Lee et al. 1981, Adrian et al. 1983). Scrub communities on KSC in general have become degraded because of fire suppression, fragmentation, and soil disturbance associated with past citrus, ranching, and timbering activities. The realization of this degradation and concern for wildlife species has led to the use of fire as a tool for restoring and maintaining scrub on KSC (Schmalzer et al. 1994). In many cases, fire alone is not adequate to restore degraded scrub (Breininger et al. 1996). Mechanical methods may also be necessary to restore scrub in areas that will no longer carry fire and in areas that have been altered by previous clearing and soil disturbance.

KSC is the largest protected land holding along the east coast of Florida. The Space Center protects approximately 10,000 ha of scrub currently (Breininger et al. 1991), and approximately 2,000 to 3,000 ha of this habitat occurs on well-drained soils (Huckle et al. 1974). There are many species on KSC such as the Gopher Tortoise (Gopherus polyphemus), Eastern Indigo Snake (Drymarchon corias couperi), Florida Mouse (Podomys floridanus), Florida Gopher Frog (Rana capito aesopus), and the Florida Scrub-Jay (Aphelocoma coerulescens) that are directly dependent on suitable scrub habitat. All of these are species of special concern listed either by the state of Florida or federally by the USFWS. The Florida Scrub-Jay is listed as a federally threatened species and is considered an indicator of suitable habitat conditions for many of these other species. Suitable habitat for scrub jays includes areas with sandy openings, sufficient scrub oak cover, little or no tree cover, and shrub heights of 1 to 2 meters (Westcott 1970, Woolfenden 1974, Breininger 1981). Because natural fires occurred so frequently, periodic burning is very important for maintaining suitable habitat conditions.

Kennedy Space Center is one of the three remaining population cores for the Florida Scrub-Jay (Fitzpatrick et al. in press). The scrub habitat contained on KSC is extremely valuable. This resource needs to be managed correctly for survival of the Florida Scrub-Jay and other scrub species of conservation concern. The Florida Scrub-Jay population has been declining for at least the past 10 years and could decline by 40% within the next 10 years. At these rates the Florida Scrub-Jay population on KSC could be endangered with extinction in 50 years (Breininger et al. 1996).

To restore scrub habitat effectively on KSC, land managers need long-term base line information. It is imperative that scrub management decisions are guided by sound scientific data. Our goal is to provide land managers with the necessary information to return KSC scrub to pre fire suppression condition and to stabilize the populations of many scrub species including the Florida Scrub-Jay. This paper documents spatial landscape change within two long-term Florida Scrub-Jay study sites on KSC. The data will play an integral part in the restoration of scrub on KSC and will provide critical understanding of the processes which have led to the Florida Scrub-Jay's current situation.

STUDY SITES

KSC comprises 57,000 ha in Brevard and Volusia counties located along the east coast of central Florida. The Tel-4 study site is a 310-ha area located near the southern boundary of KSC. The vegetation is dominated by pine flatwoods and scrub communities, a combination referred to as scrubby flatwoods. Well-drained upland sites are dominated by scrub oaks (Quercus myrtifolia, Q. geminata, and Q. chapmanii), while mesic shrubs (e.g., Lyonia lucida, Ilex glabra) dominate poorly drained sites (Schmalzer and Hinkle, 1992a,b). A sparse canopy of slash pine (Pinus elliotii) and swale marshes are found interspersed throughout the study site.

The Happy Creek study site is a scrub landscape centrally located within KSC. It is a 536-ha study site dominated by well-drained soils and scrub oaks. Unlike the Tel-4 study site, Happy Creek has very little pine overstory, and forests occur in the form of hardwood hammocks on mesic sites. Swale marshes at Happy Creek also are interspersed but are deeper and larger than the marshes found at Tel-4.

METHODS

Aerial photographs from 1943, 1951, 1958, 1969, 1979, and 1989 were used to map landuse/landcover (lu/lc) for both the Tel-4 and Happy Creek study sites. Clear mylar was overlaid on enlarged photographic prints (1:4,000) for the years 1943 through 1979. Landuse/landcover polygons were drafted directly onto the mylar and labeled by a photointerpreter. The mylars were then put on a digitizer where they were digitized, edited, and registered using ArcInfo software (Esri 1991). Ground control points were collected in the field using a Trimble Navigation Pathfinder Professional XL GPS unit. Field GPS measurements were then differentially corrected using a Trimble Navigation Community Base Station to achieve one-meter accuracy (root mean squared) on all ground control points (Trimble Navigation 1994). Locating stable ground control points that were visible on each photo was difficult, but made possible by the GPS unit. The 1989 maps for both study sites were derived by reclassifying (cross walking) existing habitat maps (Breininger et al. 1995) to match the historical classification system. The historical classification system is based on physical vegetation characteristics due to limits of the 1943 through 1969 black and white aerial photographs. A physiognomic classification system was appropriate for documenting the changes of concern in scrub habitat on KSC.

The historical maps for the years 1943 through 1989 were overlaid using the Union command. Areas for each year mapped by type were transferred from INFO into Microsoft Excel where time series graphs were produced. Areas of transition between years and type were extracted by using the Frequency command for producing frequency distribution tables. Maps of these transitions were also produced in Arcplot for selected transitions of importance as related to scrub health.

RESULTS AND DISCUSSION

Tel-4

Since the 1940's there has been a dramatic decrease in the amount of open scrub and a dramatic increase in the amount of forest cover in the Tel-4 study area (Figure 1). Forest cover in 1943 was 1.3% of the study area; it increased to 30.7% in 1969, and then decreased to 21.8% in 1989. Open scrub was at its maximum in 1943, representing 10.4% of the study area; it decreased to 1.6% in 1969 and increased to 7.7% in 1989.

Figure 1. Historical landscape trends within the Tel-4 study site.

The dominant landuse in the Tel-4 area during 1943 was ranching; other landuse practices such as citrus and a limited amount of crop farming were also present. Ranchers in the Tel-4 area used fire on their property to improve grazing by encouraging herbaceous growth and keeping the habitat open. The habitat remained very open with range management continuing until NASA purchased the land in the early 1960's (Figure 2). After this time, fire suppression went into effect, and the openings in the scrub began to disappear. In 1977, during this period of fire suppression, a wildfire burned through the Tel-4 area. In the early 1980's, prescribed burning was implemented on KSC. After the implementation of prescribed fire management, openings in the scrub have slowly begun to return but have not yet reached the extent of the pre fire suppression period (Figure 2).

There were large areas of soil disturbance in the form of clearings to support the ranch facilities in the Tel-4 area (Figure 3). These cleared areas were abandoned slowly until total abandonment after NASA purchased the land. Slash pine (Pinus elliottii) recolonized the abandoned cleared areas as pioneer species taking advantage of the disturbed, open habitat. With fire suppression in effect and the lack of a flammable understory, these pine forests spread rapidly across the Tel-4 landscape (Figure 4). Prescribed burning has reduced the rate of spread of these forests but is unlikely to return these areas back to their native type without additional mechanical treatment.

The lu/lc dynamics of specific areas mapped in 1943, 1969, and 1989 within Tel-4 show an initial degradation and then improvement in scrub condition (Table 1). During the period between 1943 to 1969, only 12% of the open scrub mapped in 1943 remained open in 1969 and 75% transitioned to closed scrub. From 1969 to 1989, 38% of the openings reestablished, but 47% of the original openings remained closed. Most of the closed scrub mapped in 1943 (63%) remained closed in 1969, while 24% of it transitioned to forest. From 1969 to 1989, some of the forest (8%) transitioned back to closed scrub. Much of what was mapped as marsh in 1943 transitioned to forest (26%) and closed scrub (22%), while only 45% remained marsh in 1969. The marsh that transitioned to forest and closed scrub remained in those types from 1969 to 1989. Areas mapped as cleared in 1943 transitioned to forest (69%) in 1969, while abandoned citrus also transitioned to forest. These areas remained forest between 1969 and 1989. There were only 4 hectares of forest in 1943; they remained forest with 87% retainment in 1989.

Table 1. Spatial frequency distribution of landscape change between 1943, 1969 and 1989 within the Tel-4 study site. Landcover/landuse (lc/lu) for 1943 are recorded in the left column. Those areas (spatial locations) are held constant and lc/lu are recorded for those same areas in 1969 secound and 1989 third column. Not all lc/lu types are represented, so areas do not sum to 100% of study site.

In the Tel-4 study site, forest coverage decreased, while open scrub and closed scrub increased from 1969 to 1989, improving scrub condition (Table 2). In 1969, there were 90 hectares of forest mapped, and in 1989 61% remained forest and 32% transitioned to closed scrub. In 1989, 23.5 hectares of open scrub were mapped, and the majority of that (70%) transitioned from closed scrub, while only 17% was mapped as open in 1969. Thirty hectares transitioned from forest in 1969 to closed scrub in 1989, while 10 hectares of marsh transitioned to closed scrub from 1969 to 1989.

Table 2. Spatial frequency distribution of landscape change between 1969 and 1989 within the Tel-4 study site. This table shows the reduction of forest and the expansion of open and closed scrub from 1969 to 1989. The spatial locations containing forest in 1969 transitioned to the landcover/landuse (lc/lu) types in the right column 1989 and the areas containing open and closed scrub in 1989 (right column) transitioned from areas containing other lc/lu types previously in 1969.

The changes occurring between 1943, 1969, and 1989 correspond directly to the different management periods in the Tel-4 area. These management periods have profoundly influenced the dynamics between lu/lc types. The period between 1943 to 1969 shows the effects of change from ranching to fire suppression, and the period of 1969 to 1989 shows the effects of change from fire suppression to control burning.

Happy Creek

Happy Creek has gained forest cover and lost openings in its scrub (Figure 5). In 1943, 5.2% of the Happy Creek study site was forest cover, and it steadily increased to a maximum of 18.2% in 1989. Open scrub in 1943 comprised 7.7 % of the Happy Creek study site, increased to 14.0% in 1951, decreased to a low of 2.7% in 1969, and increased slightly to 3.3% in 1989.

Figure 5. Historical landscape trends within the Happy Creek study site.

Landuse practices in Happy Creek during the 1940's and 1950's were less uniform than at the Tel-4 study site. The majority of the land in Happy Creek did not appear to be directly managed and only contained a few scattered homesteads and farming fields. The largest disturbance found in Happy Creek was an extensive land clearing that took place in the northwestern corner just prior to 1958. This clearing, complete with road network, looked as if it was designed for a housing subdivision that would have been build if NASA had not purchased the land.

The Happy Creek landscape differs from Tel-4 in many aspects. Happy Creek's sand ridges are much broader and more extensive than Tel-4's. The dominant vegetation type in Happy Creek is xeric oak scrub with interspersed mesic vegetation communities, while Tel-4 is dominated by mesic vegetation communities with interspersed xeric oak scrub vegetation. Another important distinction is that the Tel-4 study site is dominated by pine flatwoods, while Happy Creek is a scrub landscape with a few interspersed pine trees. The result of these differences is that fires carry through this landscape differently. Hot, dry weather is required to carry fire through these large patches of scrub. As a result, fires would occur less frequently and would have profound effects on the landscape when they burn under these conditions.

Extensive openings in the scrub were mapped from the 1951 imagery (Figure 6). Historical climate records document 1950 as a year with above average rainfall, but June, July, August, and September monthly measurements were far below average. The openings mapped in 1951 were likely a result of a dry lightning strike that ignited a fire under extreme conditions in the summer of 1950. Climate records also show 1958 to be a year with rainfall totals for June, July, August, and September that were far below average. However, the 1958 imagery was collected in April before this dry period (with potential for lightning strikes) had occurred. Therefore, we do not know if 1958 also had fires that opened the scrub and canopy closure filled in the openings by 1969, the next date of image collection. There is also the possibility that the fire prior to 1951 was the last extreme fire that burned freely across the Happy Creek landscape.

The imagery does show that 1958 was the start of a dramatic decline in the amount of openings in the Happy Creek scrub. Once fire suppression was implemented in the early 1960's, fires had no chance to burn through the landscape under any conditions. In the early 1980's prescribed burning was implemented, but these fires have only marginally increased openings in the scrub at Happy Creek. Prescribed fires have not reversed trends initiated by fire suppression, and the openings are far below the extent found in 1943 and 1951, when growing season fires swept through the landscape under extreme conditions.

Forest cover gradually increased from 1943 to 1989 (Figure 7). Naturally occurring hardwood hammocks that occurred on poorly drained soils have spread into surrounding swales. The swale grasses and sedges get replaced by the hardwoods and then fire will not carry through these areas. When the occasional fire does burn through the established hardwoods, the trees simply resprout , and the community composition is unchanged. Prescribed burning around these forests has not appeared to slow this process of forest spread into swales.

Disturbed sites have often been revegetated by forests in Happy Creek (Figure 8). Well-drained sites have generally returned to scrub, oak scrub woodland, or remained open after disturbance with slightly altered composition. Hardwood trees have established themselves on wetter sites after disturbance. Saw palmetto (Serenoa repens), usually found on mesic sites, revegetates poorly after disturbance (Breininger and Schmalzer 1990). Saw palmetto often carries fire up to and through oak scrub. Its loss on these sites created a fuel disruption and altered fire behavior in Happy Creek. The Tel-4 vegetation responded very differently to clearings, perhaps because there is a pine seed source near by.

The dynamics of areas mapped as specific lu/lc types in the Happy Creek study site between 1943 and 1989 show profound degradation (Table 3). In 1989, there was only 11% of the open scrub that was mapped in 1943; 85% of which transitioned to closed scrub. Forty-four hectares of previously closed scrub became forested by 1989. The majority (61%) of marshes did not change, but 24% became forest and 12% became closed scrub. Consistent with the Tel-4 study site, existing forest remained forest from 1943 to 1989.

Table 3. Spatial frequency distribution of landscape change between 1943 and 1989 within the Happy Creek study site. Landcover/landuse (lc/lu) for 1943 are recorded in the left column. Those areas (spatial locations) are held constant and lc/lu are recorded for those same areas in 1989 second column. Areas do not sum to 100% of study site due to missing lc/lu types.

The cleared areas in Happy Creek responded very differently from those in Tel-4. The majority (54%) of the cleared sites became forested, as at Tel-4. Unlike the Tel-4 study site, 30% of the 1943 cleared areas became open scrub. Of the 17.7 hectares of open scrub in 1989, 11.5 hectares (64%) had been cleared at some time during the study prior to 1989. In 1951 the amount of open scrub peaked at 67 hectares and dropped sharply by 1958.

CONCLUSION

The Tel-4 study area differs from many other areas on KSC because it burned during the fire suppression period, and openings in the scrub oak vegetation were not completely lost. As a result, the scrub in the Tel-4 study site has responded well to prescribed burning. Prescribed fire has also reduced the amount of forest cover over areas with a native understory. Fire is able to carry into these areas, penetrating under the canopy, and thinning the overstory. Prescribed fire has not been able to do much for areas that have been cleared and recolonized by slash pines. The lack of a flammable understory makes fire a relatively ineffective tool for reducing forest cover over these areas. Logging and mechanical treatment may be required in addition to fire to restore these areas. The Tel-4 study area clearly shows the implications of different land management practices on slash pine scrub and the implications for the Florida Scrub-Jay which inhabits this dynamic habitat type.

Unlike Tel-4, Happy Creek went through a long period of fire suppression that had profound effects on the vegetation of the study site. Factors such as extreme weather requirements for fire to carry across the landscape, and lack of fire in early management practices compounded the effects of fire suppression. The majority of openings in Happy Creek scrub are due to disturbance and not natural processes such as fire. Prescribed burning, although useful, has shown little ability to reverse trends associated with lack of openings in the scrub and increased forestation in Happy Creek.

The descriptive data presented in this paper are important because the Tel-4 and Happy Creek study sites once contained common historical landuses found throughout KSC, are very representative of the scrub habitat found on KSC, and are important areas for many scrub species of special concern, especially the Florida Scrub-Jay. These data provide both an initial check of existing scrub management practices and base line data that can be used to improve future management of scrub at KSC.

ACKNOWLEDGMENTS

This study was conducted under NASA contract NAS10-12180. We thank Dr. W.M. Knott, III, and Burton Summerfield, Biomedical Operations Office, for their assistance and support. We thank Vickie Larson for her assistance and forethought in getting this project underway. Trade names and commercial enterprises or products are mentioned only for information. No endorsement by NASA is implied.

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Brean W. Duncan, Shannon Boyle, Paul A. Schmalzer, and David R. Breininger , Dynamac Corporation, NASA Biomedical Operations Office, Mail Code: DYN-2, Kennedy Space Center, Florida 32899, Telephone: (407) 853-3281, Fax: (407) 853-2939, E-mail: duncanb@orcinus.ksc.nasa.gov