Combining environmentally dependent and independent analyses of witness tree data in east-central Alabama

Abstract

We reconstructed pre-European settlement forest composition across 13 000 km 2 of east-central Alabama using 43 610 witness trees recorded in the original Public Land Surveys. First, we interpolated the witness tree data to estimate broad-scale vegetation patterns. Next, we conducted species-site analysis on landforms, an approach that was dependent on underlying environmental variables yet better resolved fine-scale vegetation patterns. East-central Alabama was dominated by three community types: oak-hickory across the Piedmont physiographic province and valleys of the Ridge and Valley province, pine -blackjack oak on the Coastal Plain province and ridges of the Ridge and Valley province, and white oak -mixed mesophytic in stream valleys and floodplains. Witness tree concentration (trees/km 2 ) was highly uniform across much of the study area. However, there was an unusually low concentration of witness trees in the southwestern corner of the study area, and an unusually high concentration in stream valleys. Another irregularity was the inability of surveyors to distinguish black oak and red oak. Overall, the interpolations provided an unbiased, yet broad-scale estimate of forest composition, while the species-landform analysis greatly increased resolution of forest cover despite the subjectivity of defining environmental variables a priori.Résumé : Nous avons reconstitué la composition de la forêt avant la colonisation par les Européens sur une superficie de 13 000 km 2 dans le Centre-Est de l'Alabama à l'aide de 43 610 arbres témoins présents dans les inventaires originaux des terres publiques. Dans un premier temps, nous avons extrapolé les données des arbres témoins pour estimer la répartition de la végétation à grande échelle. Par la suite, nous avons effectué une analyse des relations entre espèces et stations en fonction du relief; une approche qui est dépendante des variables environnementales sous-jacentes et qui permet de déterminer encore mieux la répartition de la végétation à petite échelle. Le Centre-Est de l'Alabama était dominé par trois types de communautés végétales : chêne-caryer dans la province physiographique du Piedmont et les vallées de la province de faîtes et vallées, pin -chêne noir dans la province de la plaine côtière et les sommets de la province de faîtes et vallées et chêne blanc -espèces mélangées adaptées à des conditions moyennes d'humidité dans les vallées des cours d'eau et les plaines inondables. La concentration des arbres témoins (arbres/km 2 ) était très uniforme dans toute l'aire d'étude. Cependant, il y avait une concentration anormalement faible d'arbres témoins dans le coin sud-ouest de l'aire d'étude et une concentration anormalement élevée dans les vallées des cours d'eau. Une autre irrégularité venait de l'incapacité des arpenteurs à distinguer le chêne noir du chêne rouge. Dans l'ensemble, les extrapolations fournissent une estimation non biaisée mais à grande échelle de la composition de la forêt alors que l'analyse des liens entre l'espèce et le relief augmente ...

Reconstructing Vegetation Past: Pre-Euro-American Vegetation for the Midwest Driftless Area, USA

“…Contingency table analysis has been used in several studies to analyze the relationship between PLS data and environmental factors (Whitney 1982, Whitney 1986, Leitner et al 1991, Black et al 2002, while others have used regression models (Iverson et al 1988, Batek et al 1999. We tallied the sections based on cover class and the associated environmental factor category.…”

Landscape patterns as indicators of ecological change at Fort Benning, Georgia, USA

“…Surveyors marked the corners of each section and defined section boundaries by recording witness trees that were in close proximity to the boundary markers. In the 1830s, when the federal government conducted land surveys in the Alabama portion of the area that would become Fort Benning, corner and witness trees were recorded (Foster, 2001;Black et al, 2002). Earlier, when the Georgia portion was surveyed in 1827, the land was divided into roughly equal lots within districts.…”

“…Others held biases in the species and sizes of trees selected as witness trees. It is often assumed that surveyors were biased towards longer living or larger trees when selecting witness trees (Black et al, 2002). In addition, some surveyors may have exaggerated the amounts of valuable timber species so that land values would be elevated.…”

Considerations for ecological reconstruction of historic vegetation: Analysis of the spatial uncertainties in the California Vegetation Type Map dataset

“…Wang (2005) and Mladenoff et al (2002) provide good reviews of the data. These witness tree point data have been used in interpolations and statistical clustering routines to reconstruct pre-European settlement forest species composition and structure across the Midwest, the Southeast and Eastern US, including Wisconsin (He, Mladenoff et al 2000;Radeloff et al 2000;Schulte et al 2002;Bollinger et al 2004); in Alabama (Black et al 2002;Rathbun and Black 2006); Minnesota (Friedman and Reich 2005); Michigan (Leahy and Pregitzer 2003); Pennsylvania (Black and Abrams 2001); West Virginia (Abrams and McCay 1996), and Southern Illinois (Anderson et al 2006). Other researchers have used the PLS data with archeological sites to examine Native American influence on pre-European settlement vegetation patterns (Black et al 2002;Foster et al 2004).…”