Metabolic rates at the thermoneutral zone and at 0°C were measured in bank voles from four localities: Pallasjärvi (Finland, lat. 68°N), Loppi (Finland, 60°45'N), Niepołomice (Poland, 50°N) and ...Vitosha Mts. (Bulgaria, 43°N, elevation 1500 m). The seasonal times of measurement were chosen to secure that animals were in summer or winter pelage, respectively. Seasonal trends were found in body mass, metabolic rates at thermoneutrality and at 0°C, but no clear relation to latitude was revealed. We conclude that the lack of distinct popoulation differences in the metabolic response to cold exposure may be due to similarity in the microclimatic conditions of the habitats of the voles.
Two races of Djungarian hamsters (Phodopus sungorus sungorus and P. s. campbelli) differ in their responses to low ambient temperatures. The lowest temperature tolerated is 6-10 degrees C higher in ...P. s. campbelli than in P. s. sungorus, both in summer and in winter, but the highest (Vo2-max) and lowest (BMR) metabolic rates are similar in both subspecies. Body temperature and overall conductance in the cold appear to be more variable in P. s. campbelli than in nominative sp.
Thirty forest bird communities were studied with regard to the changes in structural indices (number of species, density, biomass, species diversity H′) and in energetics (energy flow A, production ...P, ecological efficiency P/A) in temporal and spatial gradients. All these characteristics increase during temporal succession; in natural deciduous forest there is a two-peak pattern of the increase, with the maximum in 15-20 yr old forest ("time ecotone";${\rm A}=692.9\ \text{Megajoules}\ {\rm ha}^{-1}\ \text{season}^{-1}$, H′ = 4.2 bits). In artificially managed pine forest these indices rise monotonically, reaching a maximum in sub-climax (${\rm A}=426.2\ {\rm MJ}\ {\rm ha}^{-1}\ \text{season}^{-1}$, H′ = 4.2 bits). In a deciduous forest a tendency exists to decrease the ecological efficiency (from 8% to 2%), while in a coniferous stand this variable remains low (2%) and almost constant during succession. In a spatial gradient, the highest values of energy flow and species diversity occur in forest stands with moderate soil/water regime and of ecotonal character (${\rm A}=851.2\ {\rm MJ}\ {\rm ha}^{-1}\ \text{season}^{-1}$, H′ = 4.5 bits). All mature forest bird communities show similar values of diversity (4.2-4.5 bits) and ecological efficiency (appr. 2%), though they differ in the rate of energy flow. The relation of these findings to the current concepts of ecological succession are discussed.
PDF
