Florida scrub is a xeromorphic shrubland that is maintained by frequent fires.  Historically, scrub occurring on the present day Kennedy Space Center/Merritt Island National Wildlife Refuge (KSC/MINWR) was maintained by growing season fires with a return interval thought to be less than fifteen years.  Today, Florida scrub on KSC/MINWR is managed by the use of prescribed burning to maintain structural characteristics that benefit the threatened Florida Scrub Jay (Aphelocoma coerulescens); this management includes maintaining scrub height below 1.7 meters.  Although much research has been done on understanding the historic fire regime of scrub on KSC/MINWR and the recovery of vegetation after fire, little is known about how growth of the dominant vegetation relates to climatic variables.  The vegetation is dominated by three clonal evergreen oak species; sand live oak (Quercus geminata), myrtle oak (Quercus myrtifolia), and Chapman’s oak (Quercus chapmanii).  Understanding how the growth of these three species responds to climate is important for management decisions and for understanding how climatic changes may impact Florida Scrub-Jay habitat.  Currently on KSC/MINWR, over one hundred long-term monitoring transects 15 m in length are sampled annually in thirteen scrub sites.  Percent cover of each species is designated in two height classes (>0.5 m and <0.5 m) and height growth is measured at four locations along the transect (0, 5, 10, and 15 m).  The four sites with the longest sampling history were chosen for this study.  The height data was averaged for each transect and the annual change in height growth was calculated and used for determining the average annual change in height growth for the site.  Monthly precipitation, total annual precipitation and regional monthly Palmer drought severity index (PDSI) were correlated to annual changes in height growth for each site using simple correlation.

Results/Conclusions

At each site, the average height growth during the first year was 0.9 to 2.2 times greater than the average annual height growth.  Three of four sites had significant correlations between annual height growth and precipitation; whereas, only one site had a significant correlation with PDSI.  Height growth at Shiloh2N was positively correlated with March and July precipitation, and growth at Shiloh 4N was positively correlated with July and total annual precipitation along with September PDSI.  The site near the shuttle landing facility had a significant negative correlation to September precipitation.  Growing season precipitation appears to be most related to scrub height growth.