Landscape ecosystem classification in the Cherokee National Forest, east Tennessee, U.S.A.

A landscape ecosystem classification is described for the 43 800 ha Foothills section (elevation 305 to 610 m) of the southern unit of the Cherokee National Forest. Vegetative cover, landform, and soils data were obtained from sixty 0.04 ha plots located in stands representing late successional stages. Vegetation data were grouped by dominant cover type utilizing agglomerative, hierarchical clustering and detrended correspondence analysis. Detrended canonical correspondence analysis (DCCA) and stepwise discriminant analysis (SDA) were used to identify patterns in species composition explained by environmental variables.Four community types were identified: (1) Tsuga canadensis-Acer saccharum-Fagus grandifolia-Fraxinus americana, (2) Tsuga canadensis-Rhododendron maximum, (3) Quercus prinus, and (4) Quercus prinus-Quercus coccinea-Acer rubrum. A recently developed "Landform Index" that quantifies slope type and degree of protection by adjacent land masses was identified through DCCA and SDA as the most important predictor of community types. The strength of the correlations between elevation and several soil thickness variables with DCCA axis 1 indicated that vegetation varies along an interpreted moisture gradient. No ecological meaning was attributed to the second axis.

The fate of ME7 scrapie infection in rats, guinea-pigs and rabbits.

The fate of an intracerebral injection of ME7 scrapie has been followed in groups of rats, guinea-pigs and rabbits. Six days after injection scrapie activity in the brain was similar in all three species and low levels of activity were also present in rat and guinea-pig spleen. Thereafter in the rat the pattern of accumulation of scrapie agent in brain and spleen resembled that frequently described in mice, the disease becoming clinically manifest 20 months after injection. In guinea-pig and rabbit attempts to demonstrate scrapie agent at later stages of lifespan were generally unsuccessful. It is tentatively concluded that in these last two species replication of scrapie agent did not occur though in the guinea-pig there was some evidence that infection could persist for several months. An alternative explanation of the results is briefly discussed.

Copper metabolism in experimental Border disease.

The proposal that hypocupraemia and hypocuprosis are characteristic manifestations of Border disease and of aetiological significance has been investigated. Mean plasma copper concentrations in 65 affected and 47 unaffected lambs were similar and in a controlled experiment, plasma and tissue copper concentrations tended to be higher in affected lambs than in controls. It is concluded that hypocupraemia and hypocuprosis are not consistent features of Border disease and thus have no aetiological significance.