Forest Dynamics in a Natural Area of the Southern Ridge and Valley, Tennessee University of Tennessee
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Forest Dynamics in a Natural Area of the Southern Ridge and Valley, Tennessee University of Tennessee RES EAR C H ART Ie ABSTRACT: This study was initiated to document forest development in the oldest natural area in the Ridge and Valley of east Tennessee. The ljams Nature Reserve was established in 1910 and provided the opportunity to document secondary succession of the oldest upland forest reserve in the region. We established forest inventory plots in the original land holding of the Ijams family to quantify species composition, stand structure, and successional dynamics. We also analyzed the radial growth patterns of trees to document stand age, recruitment, and the disturbance regime of the reserve. The forest was • dominated by Quercus alba and Liriodendron tulipifera while AceI' saccharum and Fagus grandifolia had high densities in the understory. Liriodendron tulipifera was the most important species in the stand because it colonized the site following agricultural abandonment and subsequently established in Forest Dynamics in a small canopy gaps. The stand had a reverse J-shaped diameter structure typical of regenerating forests. The forest experienced one stand-wide disturbance event likely attributed to the decline of Castanea Natu ral Area of the dentata in the 1920s. The return interval of stand-wide disturbances was much longer than what has been reported in other eastern hardwood forests. With the exception of this one stand-wide release, the disturbance regime was characterized by localized, asynchronous events that influenced only neighbor Southern Ridge and ing trees. Under the current disturbance regime; composition of the stand is projected to change as shade-tolerant mesophytes in the understory (A. saccharum and F. grandifolia) !ll'e recruited to larger .. ... Valley, Tennessee size classes. This phenomenon has been widely reported throughout the eastern United States and is most commonly linked to active fire suppression. However, the forest of the Ijams Nature Reserve has not burned during development and still shows a marked change in species composition even with no change in the fire disturbance regime. We propose the composition shift is related to understory facilita Justin L. Hartl tion by disturbance oriented canopy species that have created conditions favorable for the establishment of mesophytes and by the loss of C. dentata that resulted in canopy gaps. Index terms: dendroecology, disturbance, Liriodendron tulipifera, Quercus, Ridge and Valley, succes sion INTRODUCTION harvesting and grazing. The southern section of the Ridge and While many reserves in the region were Valley physiographic province extends not established until the 1930s, the Ijams from northeast Tennessee through northern Nature Reserve (INR) was established in Georgia to the terminus of the Appalachian 1910 to create a natural area for conserva Highlands in central Alabama. The natu tion and recreation and is the oldest upland ral vegetation of the southern Ridge and forest reserve in the region. Reserve status Valley was originally described as Quere has allowed the forest to mature with cus-Castanea (Braun 1950), but is now minimal anthropogenic disturbance; and dominated by mixed Quercus and Carya because the property was owned and man species (Keever 1953; DeSelm et al. 1969; aged by two naturalists, records of forest McCormick and Platt 1980; Stephenson history have been maintained. The INR et al. 1993). The contemporary forests of provides a unique opportunity to study the the region have been heavily impacted by growth and development of one of the old anthropogenic disturbances. The majority est secondary upland forests in the region of forested land in the southern Ridge that has been in reserve management for and Valley was cleared for settlement, almost one century. timber, row cropping, and grazing during the nineteenth and twentieth centuries. Throughout the Eastern Deciduous Forest Some lands have remained in non-forest Region, the documentation of successional uses while others have been allowed to processes is important because the major develop into mature forests via secondary ity of the land~cape consists of secondary succession. The majority of forest stands forests that have developed following in this region are relatively young « 100 widespread timber removal and intense y) and few old-growth remnants remain. human impacts during the eighteenth, nine Many of these forests are even-aged and teenth, and twentieth centuries. Land use have experienced considerable anthropo practices have been important controls on Natural Areas Journal 28:275-289 genic disturbances during their growth forest vegetation patterns of post-European and development, such as selective timber settlement landscapes as many forest stands Volume 28 (3), 2008 Natural Areas Journal 275 are not returning to their pre-European Land Use History transferal records of the property currently settlement conditions. This phenomenon in the INR were obtained from the Knox is largely attributed to prior land uses Historical inhabitants, such as the Cherokee County Courthouse, Office of the Property (e.g., burning, forest clearing, grazing, row and Creek, traveled through the Tennessee Assessor, and the East Tennessee Histori cropping) and altered disturbance regimes Valley and used resources on an ephemeral, cal Society. The original land grant was that have disrupted vegetation-environ task specific basis (Stueckrath 1859). While provided to William Brown in 1826 by the ment relationships (Fralish et a1. 1991; their influence on the landscape is not state of Tennessee, and the records showed Abrams et al. 1995; Abrams and McCay quantified, the prevalence of disturbance the land was always owned by private in 1996; Cowell 1998; Foster et a1. 1998; oriented vegetation across the region at dividuals (Table 1). Although the records Fuller et a1. 1998; Motzkin et a1. 1999). settlement suggests possible buming and were of limited value because of the lack To comprehensively understand growth and widespread land clearing. The region was of detailed land use information (such as development of modern forest communi known for excellent hunting grounds, number oflivestock), they did provide data ties, researchers must consider the land use and the proximity of the Tennessee River on the original witness trees used to mark and disturbance history of the study site offered additional transportation and com the property boundary. The boundary trees (Raup 1966; Cronon 1983; Foster 1988; mercial advantages (Stueckrath 1859). listed were: Quercus alba L. (three individ Christensen 1989; Foster 1992; Whitney uals), Q. velutina Lam., Castanea dentata 1994; Ruffner and Abrams 1998; Lafon Although anthropogenic disturbances have (Marsh.) Borkh., and one Carya species. et a1. 2000; Foster 2002; Frelich 2002; occurred for millennia in the southern The ownership records indicated the land Foster et a1. 2003). Ridge and Valley, European settlement of was cleared for agriculture sometime after the region intensified human modification 1826 (although it likely experienced prior A widespread pattern of successional of the landscape (DeIcourt and DeIcourt anthropogenic disturbances) and was used change has been reported throughout the 2000). Europeans began to settle the area for subsistence farming until the property eastern United States (Lorimer 1984; and establish land claims soon after the was purchased by Harry P. and Alice Y. Abrams and Downs 1990;. Loftis and Revolutionary War (U.S. Department of Ijams in 1910. The Ijams bought the land McGee 1993; McCarthy and Bailey 1996; Agriculture 1955). Land ownership and for $1000 and converted a resident barn Abrams 2003; Pierce et al. 2006). A lack of Quercus regeneration and increased meso phytic dominance (especially Acer species) Table 1. Land-use history of the Ijams Nature Reserve in the Ridge and Valley of east Tennessee. has been linked to active fire suppression that began in the early 1900s (McCarthy Date Land-Use Practice Forest Impact et al. 1987; Crow 1988; Cho and Boerner Before 1790 Cherokee hunting Hunting pressure and understory 1991; Goebel and Hix 1997). However, some sites undergoing composition shifts grounds burning do not have a history of repeated burns and After 1790 European settlement Timber cut to build homes, roads, and have developed entirely in the absence of railroads in the Knoxville area fire. In these ecosystems, processes other than fire must be examined to explain ob 1794 Knoxville established Log buildings erected, trade center of served successional patterns. Stands at the east Tennessee INR fall under this category and provide an 1826-1910 William Brown and Land granted from Tennessee, opportunity to document relatively long Johnson family subsistence agriculture, forest cutting, term secondary succession of an upland and grazing hardwood forest under reserve manage ment that has developed in the absence of 1910-1964 Harry and Alice Ijams Built home and developed the 8-hectare fire. By quantifying species composition, create reserve property into a nature reserve stand structure, and disturbance history we 1965 Ijams land deeded to Managed by Knoxville Garden Club, can elucidate the processes responsible for Knoxville Knox County Council of Garden Clubs, the documented successional pattern. The and the City of Knoxville specific objectives of our study were to: (1) quantitatively describe species composition 1976-present !jams Nature Center, Formally incorporated