Abstract
Treefall gaps, formed as a result of small-scale disturbances, allow seedling recruitment and growth in late-successional forests. Many factors contribute to gap regime heterogeneity within and among forest stands, including wind and fire patterns, insect preferences, stand age and stand composition. While there is some evidence suggesting that topography can also affect gap formation, most studies have examined gaps in steep terrain, and there has been little research in relatively level terrain such as bottomland hardwood forests. This study examined differences in the treefall gap regime among three microtopographical classes - bowl, ridge, and slope - in a late-successional hardwood stand on the Neches River floodplain near Spurger, Texas. I tested the null hypothesis that the gap regime does not vary among microtopographical positions within a floodplain forest. Using point sampling and a clinometer I estimated the microtopographic variation throughout the site. Line intersect sampling was used to select gaps for sampling. Size of sampled gaps was measured using the Global Positioning Svstem (GPS) and a geographic information system (GIS). Each sampled gap was classified as either on a ridge, slope, or bowl based on clinometer measurements. I then determined the frequency and percent cover (fraction) of treefall gaps within each microtopographical class using the GIS and methods described by Runkle (1992). I found that gap frequency and gap fraction were statistically different between the microtopographical classes. Ridges contained the highest frequency of gaps and the most area under gaps compared to bowls and slopes. However, gap area and shape did not vary with microtopography. Based on these initial findings, I have rejected my null hypothesis and concluded that microtopography affects at least some aspects of the gap regime in this forest.
Almquist, Benjamin Eric (1998). Variation of treefall gap characteristics in an East Texas bottomland hardwood forest: effects of microtopography. Master's thesis, Texas A&M University. Available electronically from
https : / /hdl .handle .net /1969 .1 /ETD -TAMU -1998 -THESIS -A46.