ABSTRACT We used dendrochronology ...

ABSTRACT

We used dendrochronology and vegetation sampling to examine climatic rejoinder and stand dynamics at brace slope positions (350 m asl and 520 m asl) upon No Business Mountain in the southwestern Piedmont of Virginia. Modeling plant reply to climate change requires an understanding of the influence of small-scale environmental change. We sampled vegetation and cause to growed pitch pine and Virginia pine tree-ring chronologies from the midslope and the mountaintop. A higher species richness and more hickory and black gum were plant at the mountaintop. Significant correlations existed between tree-ring bourgeoning and temperature in the late fall and precipitation from the prior years' summer months; however, the same dendroclimatological answer existed for both species at one as well as the other slope postions. According to the dendroecological analysis, pitch pine noteed the sites after agricultural abandonment in the early 1900 and Virginia pine noteed the sites following a release affair in the 1940s. Recently, the pine stands forward No Business Mountain have interchangeed to an oak stand at midslope and an oak-hickory stand forward the mountaintop. Microenvironmental differences between the sum of two units slope positions at No Business Mountain influenced vegetation composition still did not result in different dendroclimatological answers These results imply that small scale environmental differences other than climate (soils and land use history, in this case) may be more important to vegetation distribution; therefore, it may not be necessary to include plant reply to small-scale climatic changes in climate change-vegetation answer models.

INTRODUCTION

Recent attempts to pattern vegetation response to climate change elucidate the importance of understanding plant reply to microclimatic changes. Many natural microclimatic gradients exist that could be used to better understand species rejoinder to small changes in climate. one time these relationships are established, this information can be incorportated into climate change-plant reply models to improve their fine-scale predictions. Dendrochronology has proven to be useful for climate change modeler working at regional scales because tree rings rejoin well to regional climate change. In this application of mind we examine the suitability of dendrochronology to lay bare climatic responses in tree rings at small scales in brace species of pine on the Virginia Piedmont.

The Piedmont of Virginia is characterized at relatively level topography with pinehardwood forests (Bailey 1995) The mostly common natural disturbance agents in this region are wind, fire, and climatic circumstances such as drought or ice storms (Orwig and Abrams 1995 Abrams and Copenheaver 1999 Lafon et al. 1999) These disturbances influence species composition and regeneration patterns. common windstorms result in more regeneration occurring in wind-formed gaps, which note carefullys to favor responsive, early successional species so as sassafras [Sassafras albidum (Nutt) Nees] and sweet gum (Liquidambar styraciflua L) (Orwig and Abrams 1995) resort to frequently fire favors species able to invade following fire or species able to tolerate fire, as it is as shortleaf pine (Pinus echinata Miller), table-mountain pine (Pinus pungen Lambert), pitch pine (Pinus rigida Miller), burgoo pine (Pinus taeda L.), situation oak (Quercus stellata Wangenh.), and black oak (Quercus velutina Lam.) (Cowell 1998) strict climatic events favor species adapted to surviving harsh climatic conditions, i.e., periodic dryness s favor pines and oaks.

In the southwestern portion of the Piedmont, occasional small mountains (480-860 m) emanate from the otherwise level landscape (200 m) couple common trees on these Piedmont mountaintops are pitch pine and Virginia pine (Pinus virginiana Miller). Pitch pine and Virginia pine coexist upon many sites because they are early successional and tolerant of xeric, infertile conditions; however, the species have slightly different niches (Carter and Snow 1990 Little and Garrett 1990) Pitch pine is more windfirm than Virginia pine because of its deeper rooting (24-27 m for mature trees) (Carter and Snow 1990 Little and Garrett 1990) Pitch pine tolerates moister soil conditions than Virginia pine (Carter and Snow 1990) and Virginia pine tolerates slightly more shade than pitch pine (Little 1959 Little and Garrett 1990) Virginia pine keeps to invade abandoned agricultural lands, while pitch pine attends to invade post-fire sites (Lafon et al. 2000 Welch et al. 2000) The range of pitch pine go afters the east coast from Maine to Georgia, and Virginia pine ranges from recent York to Alabama. In the Piedmont of Virginia, pitch pine is in the southern portion of its range, and Virginia pine is in the middle of its range.

The objective of this application of mind was to examine the ecology of pitch pine and Virginia pine forward an emergent mountain (No-Business Mountain) in the western portion of the Virginia Piedmont. We were interested in determining whether the species composition, disturbance rate, and dendroclimatic rejoinder differed between a position at the midslope (350 m) versus the mountaintop (520 m) We sampled the vegetation at one as well as the other sites and used dendrochronology to analyze the disturbance rate and the influence of climate at the brace slope positions. Dendrochronology is useful for studying the ecology of species, the dynamics of a forested ecosystem and distinguishes arch disturbance and environmental differences between sites and species (Fritts and Swetnam 1989) individual methodological requirement of dendrochronology is careful species selection (Stokes and Smiley 1996) We chose to do our dendrochronological work with pitch pine and Virginia pine to increase our chances of detecting site differences at the sum of two units slope positions. These species come into one's head at both slope positions and are dendrochronologically responsive to disturbance and climate (Rauscher and Smith 1979 Abrams and Orwig 1995 Orwig and Abrams 1997) These species are also tolerant of the major disturbances of the area; therefore, they are more likely to record the disturbance in their tree-ring record rather than be killed at the disturbance. Additionally, dendrochronology allowed us to further distinguish the ecological niche of each pine species through identifying their unique response to disturbance and climate. Understanding a certain quantity of of the subtle responses of tree to small changes in climate and environmental conditions becomes increasingly important as scientists attempt to understand in what manner plants have responded to historical climate change and to predict to what degree plants will respond to events to come climate changes (Davis and Botkin 1985 Dale and Franklin 1989 He et al. 1999)