Savanna tree survey in GLADES (Grid for Landscape Analysis and DEmographic Study)

The GLADES project (Grid for Landscape Analysis and DEmographic Study) is a 16 ha square grid (10x10m cells) covering oak savanna/ woodland and old field habitat at Cedar Creek. All trees greater than 2 cm dbh (more than 11,000) have been measured (dbh), identified, tagged, located (to the nearest m) and monitored (live or dead) since 1995. In addition, tree seedlings have been identified and counted in a circle (1.5 m radius) centered on each of the 1681 rebars (grid nodes) since 1996. A high resolution topographic data set has been constructed for the grid. Since the water table is quite flat at Cedar Creek, distance from water table can be readily calculated from topographic data. In addition, total soil N has been measured for each of the 1600 cells and percent bare soil estimated. Finally, location of current and past tree canopies has been digitized from aerial photographs. All the data is managed with a GIS (Arcinfo). The grid is divided into 3 burn units (115, 116, and 117) with different experimental fire histories. In the absence of fire, this area has been transformed from a predominantly prairie matrix with scattered trees, to a predominantly woodland matrix with scattered prairie openings. I expect future data collection and analysis to help evaluate the applicability of deterministic, stochastic, and neutral models in understanding the spatial and temporal distribution of tree species at this site.