The continuing population decline of Torreya taxifolia Arn

• Published in: Bulletin of the Torrey Botanical Club 1993-07, Vol.120 (3), p.275-286
• Main Authors: Schwartz, M.W, Hermann, S.M
• Format: Article
• Language: English
• Subjects: Agronomy. Soil science and plant productions; Animal and plant ecology; Animal, plant and microbial ecology; ARBOLES; ARBRE; Biological and medical sciences; Censuses; DEAD TREES; Demecology; DEPERISSEMENT TERMINAL; Depopulation; DIEBACK; DISEASES; ENDANGERED SPECIES; ENFERMEDADES FUNGOSAS; ESPECE; ESPECE EN DANGER; ESPECIES; ESPECIES EN PELIGRO DE EXTINCION; FLORIDA; FLORIDE; FOREST INVENTORIES; Fundamental and applied biological sciences. Psychology; FUNGAL DISEASES; GEORGIA (EUA); GEORGIA (USA); GEORGIE (EU); INVENTAIRE FORESTIER; INVENTARIOS FORESTALES; MALADIE FONGIQUE; MARCHITEZ DESCENDENTE; MEASUREMENT; Medical syringes; MEDICION; MESURE; Mortality; Necrosis; Plant diseases; Plant growth; Plants and fungi; Population growth; Ravines; SINTOMAS; SPECIES; SYMPTOME; SYMPTOMS; TAXACEAE; Torreya taxifolia; TREES
• ISSN: 0040-9618; 2325-8055
• DOI: 10.2307/2996992

Torreya taxifolia is a federally endangered dioecious conifer endemic to ravine bluffs along the east side of the Apalachicola River in Gadsden and Liberty Counties, Florida and Decatur County, Georgia (plus one outlying population in Jackson County, Florida). Torreya taxifolia experienced a catastrophic population decline, presumably fungal in origin, in the late 1950's. Within 10 years virtually no adults remained in the wild, a situation that persists to the present. Size measurements of trees indicate that the mean length of the longest stem is less than one meter. In a census population of over 100 trees, 10% died in four years, mostly from small size classes. Extension of terminal buds along the primary stem was infrequent, with only 47% of all trees experiencing any growth in length during the four year census period. With 32% of all trees losing their primary stem during the census interval, the mean size of individuals within the population is decreasing. Most individuals are multi-stemmed and continue to carry symptoms of disease. Although no causative agent for the decline has been identified, the most prevalent symptoms of disease are needle spots, needle necrosis and stem cankers. Growth fate does not appear to be strongly related to habitat or the incidence of disease symptoms, although stem mortality was higher among trees with heavy foliar pathogen loads. With no sexually mature trees and no seed production, this species faces continued decline.