Deciduous Forest Zone Research Articles

Environmental controls of carbon uptake in two woody species with contrasting distributions at the edge of cliffs

Thuja occidentalis L. and Acer saccharum Marsh, show mutually exclusive distribution patterns along forested cliff edges of the Niagara Escarpment; T. occidentalis occurs at the cliff edge and on the cliff face, whereas A. saccharum occurs with increasing frequency away from the cliff edge. To reveal the controls of such patterns, seasonal and diurnal courses of net photosynthesis (Pn), stomatal conductance (gs), and xylem water potential were measured in situ and related to fluctuations in light, temperature, and moisture. For each species, saplings growing in the cedar zone near the cliff edge were compared with saplings growing in the deciduous forest zone farther from the cliff edge on the plateau. The carbon uptake of both species was most often limited by light; limitation by temperature, atmospheric, or soil moisture was rare. Acer saccharum was slightly better adapted than T. occidentalis to growth at the low light levels in both zones because of a greater light-use efficiency. During severe drought, both species showed reductions in Pn and gs when growing near the cliff edge. In the deciduous forest, in contrast, Pn of T. occidentalis, but not A. saccharum, was significantly reduced, suggesting that A. saccharum may outcompete T. occidentalis for water. In the spring and fall, T. occidentalis had higher Pn and gs in the deciduous forest than at the cliff edge. However, all differences in gas exchange rates between trees in the deciduous forest and at the cliff edge were small and relatively rare. During most of the growing season, Pn and gs differed little between saplings in the two zones. This suggests that the pattern of abundance is not controlled to a substantial degree by carbon gain at the sapling stage. Key words: photosynthesis, water potential, Acer saccharum, Thuja occidentalis, plant zonation, cliff–forest ecotone.

The occupation of space and interindividual relations of a nocturnal Madagascan prosimian (Microcebus murinus)

Five male and four female grey lesser mouse lemurs, Microcebus murinus, were trapped with Sherman traps in the Forestry Reserve of Ampijoroa, near Majunga, N.W.-Madagascar and equipped with individual radio-transmitters with a range of 220-300 m. These 9 individuals were then followed and observed (alternatively or simultaneously) for a total of 30 nights spread over a period of 6 weeks (26 September to 11 November 1985). In this dry deciduous forest zone, the subpopulation of 9 M. murinus observed occupied a total area of 7 ha. The home ranges of 4 males were significantly larger than those of 4 females (means: 3.2 +/- 0.2 and 1.8 +/- 0.1 ha, respectively). Nevertheless, because of the larger degree of overlap between home ranges of males, the available mean area per individual did not differ greatly between the sexes (a total of 5.5 ha for 4 males, with 65% overlap, versus a total of 4.2 ha for 4 females, with only 44% overlap). Overlapping of all nine home ranges produced a 'common zone' in the centre of the study area, where meetings between animals of either sex took place. This pattern can be interpreted as representing a pregregarious form of social structure. During nocturnal activity, the animals foraged individually, though an average of 11% of time was spent less than 10 m away from a conspecific. The tendency for dispersion of individuals was most pronounced during foraging for insects, when travel speeds were also relatively high. The most obvious social interactions occurred when females were on their way back to a common nest, calling and following each other. Such behaviour was not exhibited by males, even by those that shared a nest. Away from the nest, physical contacts were rare and brief. During the few days preceding oestrus, females were approached by several males, without agonistic interactions between males being observed at this period. Most observed agonistic interactions were initiated by females and directed against males.

The Carpinus caroliniana Complex in North America. II. Systematics

The Carpinus caroliniana complex consists of a series of geographical races ranging north and south through the deciduous forest zone of eastern temperate North America and the mountains of Mexico and northern Central America. All of these races are morphologically variable and difficult to distinguish on the basis of independent characters. Nevertheless, each possesses a broadly distinctive set of features related to a particular ecological situation. Published records of Pleistocene and post-Pleistocene pollen floras suggest that Carpinus survived Wisconsin glaciations throughout much of its present range in unglaciated eastern North America, both east and west of the Appalachian Mountains, and geological and paleobotanical evidence supports the hypothesis of pre-Pleistocene western introduction of the genus into Mexico. The complex is divided to form two species. The northern C. caroliniana consists of subsp. caroliniana of the Atlantic and Gulf Coastal Plains of the southeastern United States and subsp. virginiana of the Appalachian Mountains and northern interior regions to the west. The Latin American C. tropicalis is separated into subsp. tropicalis of the deciduous forest zone of the highlands of southern Mexico and northern Central America and subsp. mexicana of the cool humid zone of mountains in northeastern Mexico and the trans-Mexican volcanic belt. The Carpinus caroliniana complex of eastern North America has been shown by multivariate analyses (Furlow 1987) to consist of four phenetically distinct, though usually variable, geographical races. High intraand inter-population variability in many parts of the complex results in the overlap of character states among races, and it is difficult to find absolute character differences to distinguish them. Although these patterns have been noted in the past, they have not been described precisely, leading to confusion and oversimplification in the taxonomic treatment of the group. The American hornbeam was first described in 1785 as C. betulus var. virginiana by Humphrey Marshall. Three years later, Thomas Walter (1788) named material from South Carolina C. caroliniana, establishing the American taxon, taken as a whole, as a species distinct from the European C. betulus L. From then until 1935, except for Michaux's (1803) description of C. americana (a nomenclatural synonym of C. caroliniana), little taxonomic change was proposed. Winkler's (1904) monograph of the Betulaceae recognizes only the single species in North America. In 1935, Fernald recognized two varieties of C. caroliniana in the eastern United States and adjacent Canada, the southeastern var. caroliniana being distinguished in a number of foliage, bark, and habit characters from the common var. virginiana of the northern deciduous forest region. The Mexican and Central American portion of the complex was recognized as distinct from C. caroliniana by John Donnell Smith (1890) who named Carpinus americana var. tropicalis, and this taxon was later given species status by Lundell (1939). A great deal of taxonomic confusion has centered around the Mexican and Central American populations of Carpinus, perhaps in part as a result of a lack of familiarity with the group by the botanists from temperate regions who have treated it taxonomically, and in part due to an uncritical acceptance of the idea that Latin American amentiferous taxa are necessarily conspecific with their vicariads of the northeastern United States (cf. Graham 1973). Most current Mexican and Central American floras (e.g., Nee 1981) treat their material simply as C. caroliniana, without recognizing infraspecific taxa. However, Standley (1920) and Standley and Steyermark (1952) state that both var. caroliniana and var. tropicalis occur in Mexico, var. caroliniana in central and northern Mexico, and var. tropicalis mostly in southern Mexico and Central America. These workers describe var. tropicalis as differing from var. caroliniana primarily by its dense pubescence, as do the authors of virtually all of the subsequent descriptive literature dealing with the group. In his

The distribution of Dermacentor ticks in Canada in relation to bioclimatic zones.

Dermacentor andersoni has been collected north of Jasper, Alberta, close to 54° N. and near 53° N. in British Columbia. Spread to the north and northwest is probably limited by low summer soil temperatures, which would act principally by slowing egg development, thus disrupting the seasonal cycle of the tick. To the southwest, mild winters may fail to release diapause at the correct time of year. Aspect and slope are important factors. Altitude spread of records is from 1000–7000 ft. The most generally applicable description of its distribution is the ecotone between western grassland and moister regions, including clearings and rocky outcrops m the montane and Columbia forests, and shrubby areas of the prairies. In British Columbia, a series of randomly selected transects indicated a strong association between the tick's presence and several species of shrubs growing without tree shade.Each bioclimatic zone tends to have a characteristic group of rodents as main hosts of the immature stages. The prairie and montane regions differ in the indigenous hosts available to the adult tick.East of 105° D. andersoni is replaced by D. variabilis, which is adapted to the more humid summers of the eastern deciduous forest zones, and differs considerably from D. andersoni in its phenology. There are no reliable records of indigenous D. variabilis north of 52° latitude.D. albipictus occurs from the east to the west coast. Because of the winter activity of its larvae, allowing the whole summer for egg development, it is able to penetrate much farther north than the other two species. There are two records close to 60° latitude.

Pollen Analysis and Dates of the Upper Pleistocene Deposits near Towada Caldera, Akita Prefecture

The Kosaka pumice-flow deposits resulting in the older depression of the Towada caldera, are distributed typically near Kosaka, Akita prefecture. The deposits are divided into three units: lower, middle and upper. Each of these deposits lies on a gravel bed with a thin peat-seam.Dates of the deposits were measured by the carbon of the materials from the pumiceflow and the peatseams, and the floras from the peatseams were palynologically investigated. The present locality is situated in the deciduous forest zone. The result are as follows:Upper: 1) Date, 14C-years B. P. 10, 400±200, 2) Flora, subalpine coniferous elements, 3) Climate, cold (the reduction is 5°-9°C as compared with the annual average of temperature of this district).Middle: 1) 12, 000±250, 2) subalpine coniferous elements, 3) cold (5°-9°C).Lower: 1) >33, 000, 2) subalpine coniferous-deciduous (Fagus) elements, 3) cool (about 4°C).

Palynological studies of moors in the deciduous-forest zone in Iwate Pref.

Palynological studies of moors in the deciduous-forest zone in Iwate Pref.