Showing papers on "Undergrowth published in 1984"

Carbon relations and competition between woody species in a Central European hedgerow : I. Photosynthetic characteristics.

Abstract: The CO2 uptake capacity of leaves of five competing woody species in an undisturbed developing Central European hedgerow was investigated for possible factors determining competitive ability in the field. Light-saturated maximal CO2 uptake (A max) showed species-specific seasonal variations in Prunus spinosa, a bushlike pioneer on fallow land, in Crataegusxmacrocarpa and Acer campestre, two treelike species dominating the canopy, in Rubus corylifolius, a pioneer liane, and in Ribes uva-crispa, a shrubby undergrowth species. In fully-expanded sun leaves of Prunus, Crataegus and Acer A max ranged from 8 to 12 μmol m-2 s-1 while it ranged from 6 to 15 μmol m-2 s-1 in Rubus and Ribes. The temperature responses showed no difference among species. Neither leaf photosynthetic capacity nor nutrient use of carbon fixation determined competitive ability. Differences between species in the capacity of leaves to adapt to shade resulted in differences in species' establishment in the understory and demonstrated the importance of growth in order to escape light-limiting conditions. A specific sequence of species was found for the range of A max in sun leaves. It was highest in an early pioneer of low competitive ability (Rubus), medium in a later pioneer (Prunus) and in successional plants (Crataegus, Acer), and lowest in the climax species of high competitive ability, Fagus silvatica, (3-4 μmol m-2 s-1; Schulze 1970).

Zoochorie et premiers stades de la régénération naturelle après coupe en forêt guyanaise

Abstract: Processes leading to forest regeneration in a mature rain forest of French Guiana were studied on six plots representing initial stages of regeneration, from 2 to 10 years following clear-cutting. The first woody species to appear in plots after tree felling are light demanding species growing from seeds remaining dormant in the rain forest soil. Such a « seed bank » is very heterogeneous, its composition being strongly influenced by the proximity of forest gaps and tree falls. Burning and increased soil compaction can prevent dormant seeds from germinating. Other seeds are disseminated by frugivorous bats and birds, yet other by wind. A few other regenerating plants are sucker shoots from eut stumps of shade tolerant species of the undergrowth, which grow easily beneath the canopy of pioneers. The pioneer vegetation (Table 1) is characterized by a Iow species richness: no more than 15 species (out of a grand total of 113 found 3.5 years after clear cutting), contribute to 85 % of the woody community. The seeds of these pioneer species are dispersed by bats and birds. Twenty species of frugivorous bats were observed in the study area, out of which only 4 (Table II) were abundant in the regenerating forest. Forty species of birds (Table III) also contribute to seed dispersal, out of which 1 6 species are restricted to second-growth. Sorne of these birds have a Iimited flight range and tend to disperse seeds more or Jess evenly around feeding trees. Other birds, particularly « lek » forming species (Pipridae), tend to defecate mainly around their traditional display grounds and generate a more aggregative dispersal of seeds. Some generalist species with a mixed insectivorous and frugivorous diet (Turdus albicollis and Ramphocelus carbo) are the first birds to colonize newly formed gaps in the forest. The « seed rain » generated by bats during the night and by birds during the day, was measured (Table IV) both in the open and under the trees, using plastic collecting sheets. Only bats defecate in the open in a 50 metre wide belt bordering the forest edge. Seed rain generated by birds was observed only under isolated trees used as perches in the open, and to a lesser extent in the undergrowth of the mature forest

Winter penetration by mammals of different habitats in the Biebrza valley

Abstract: Tracks left in the snow by wild carnivores, ungulates, rodents and lagomorphs (total of 13 species) were counted over the period of 4 consecutive winters 1977-1980, over a total distance of 383 km on a route running through a group of habitats in a peaty river valley (NE Poland). Predators penetrate bog forests, dense undergrowth and the banks of rivers most intensively.

The isopod fauna of some auckland reserves and areas of native vegetation

Abstract: SUMMARY The isopod fauna of a number of reserves and other sites in the Auckland Province is described and compared. The effects of the stage of plant succession, from dense manuka scrub through to climax mixed kauri rain forest, and the openness of the undergrowth on the isopod fauna are discussed.