March 2022 Presentation by Bill Van Auken

Dynamics of woodland or forest communities have been difficult to understand. In private property states, trying to determine community dynamics is more difficult because with changing ownership, management changes and temporal effects are difficult to follow especially with long-lived species. In addition to recent changing management strategies, long term changes at least over the last 20,000 years was caused by warming temperatures, glacial re-treat, the presence of Native Americans and the arrival of the Europeans and their animal. Populations of Acer grandidentatum Nutt. (Bigtooth maple, Aceraceae=Sapindaceae) a rare species in central Texas are mostly found in isolated, deep, relatively remote, limestone canyons. Acer grandidentatum is found with a few other mostly deciduous species. Recruitment of juveniles has been reported to be lacking. Populations of A. grandidentatum juveniles were found in limestone canyons in a State Natural Area in Central Texas. Enclosures were placed around half and half were left in the open. Plant survival was followed for four years. At the end of that time when survivals were compared there was a significant difference in survival in the treatments (χ2 , P<0.001). Survival in the enclosures was 92% with 52% in the open. When population extinction was compared, for planted plants using linear regression, extinction was 60.5 yrs in exclosures and 11.9 yrs in the open. For native juveniles it was 12.6 yrs in enclosures and 5.9 yrs in the open. The cause of most mortalities in the open seemed to be herbivory by white-tailed deer (Odocoleus virginianus).