Showing papers on "Undergrowth published in 1999"

Differences between understorey and canopy in herbivore community composition and leaf quality for two oak species in Missouri

Abstract: Summary 1. From July 1994 to September 1995, at six censuses, the herbivore community associated with understorey (< 2.5 m height) and canopy (15–20 m) leaves of Quercus alba and Q. velutina was sampled in south-eastern Missouri, U.S.A. 2. Across all censuses, herbivore densities were not significantly different between canopy and understorey for Q. alba and Q. velutina, except in August 1994 when herbivore densities were 60% higher in the canopy on Q. alba. Little significant spatial variation in herbivore densities or community composition was found during the study years. 3. The herbivore community was diverse, consisting of 138 species of leaf-chewing insects. Species richness was significantly greater (by 5–20%) in the understorey than in the canopy for both tree species, and the relative abundance of the main families, different feeding guilds, and most common species differed significantly between understorey and canopy. 4. To determine the extent to which leaf quality explained the observed patterns, percentage nitrogen and protein binding capacity were measured in canopy and understorey leaves of Q. alba and Q. velutina. Per cent nitrogen was higher in canopy leaves for Q. velutina while protein binding capacity was higher in canopy leaves for Q. alba. 5. These results suggest that the herbivore community associated with these two species of Quercus comprises species that appear to respond individually to environmental and biological conditions encountered in the understorey and the canopy.

Structural dynamics of a natural mixed deciduous forest in western Thailand

Abstract: . Structural dynamics of a natural tropical seasonal –mixed deciduous – forest were studied over a 4-yr period atMae Klong Watershed Research Station, Kanchanaburi Prov-ince, western Thailand, with particular reference to the role offorest fires and undergrowth bamboos. All trees > 5 cm DBHin a permanent plot of 200 m × 200 m were censused every twoyears from 1992 to 1996. The forest was characterized by alow stem density and basal area and relatively high speciesdiversity. Both the bamboo undergrowth and frequent forestfires could be dominant factors that prevent continuous regen-eration. Recruitment, mortality, gain (growth of survival treeplus ingrowth) and loss in basal area (by tree death) during thefour years were 6.70 %/yr, 2.91 %/yr, 1.22 %/yr and 1.34 %/yr,respectively. Mortality was size dependent; middle size trees(30 - 50 cm) had the lowest mortality, while the smallest (5 - 10cm) had the highest mortality. Tree recruitment was observedparticularly in the first two years, mostly in the area where die-back of undergrowth bamboo occurred. The bias of the spatialdistribution of recruitment to the area of bamboo die-back wassignificant and stronger than that to the forest canopy gaps.Successful regeneration of trees which survive competitionwith other herbs and trees after dieback of bamboo could occurwhen repeated forest fires did not occur in subsequent years. Itis suggested that both the fire disturbance regime and bamboolife-cycle greatly influence the structure and dynamics of thisseasonal tropical forest.Keywords: Bamboo; Canopy gap; Forest fire; Kanchanaburi;Mortality; Recruitment; Spatial pattern.Nomenclature: Smitinand (1980).

High plant diversity of lowland rainforest vestiges in eastern Madagascar

Abstract: Based on cartography, floristic inventory and vegetation analysis in the north and south of the Eastern Domain of Madagascar we identified three original tropical rainforest types which are among the world's most biodiverse known sites for plants: the littoral forest on sand, the lowland forest on gneiss and the lowland forest on basalt. Floristic and structural comparisons were conducted on 37 plots of 50×10m. Multivariate analysis indicates that floristic composition is correlated with abiotic factors of rainfall, latitude, soil composition, and marine influence; the structure of the undergrowth is generally homogeneous and the canopy is more or less open. Many reserves must be created on gneiss, sand and basalt all along the eastern coast to preserve biodiversity from the deforestation process. On basalt, this is especially urgent because about only 10 000 ha of a very ancient forest that shelters numerous botanical novelties remain today.

Eighty-eight years of change in a managed ponderosa pine forest

Abstract: This publication gives an overview of structural and other ecological changes associated with forest management and fire suppression since the early 1900's in a ponderosa pine forest, the most widespread forest type in the Western United States. Three sources of information are presented: (1) changes seen in a series of repeat photographs taken between 1909 and 1997 at 13 camera points; (2) knowledge from 19 authors who have investigated effects of recent ecosystem-based management treatments; integrated with (3) findings of forest changes related to earlier treatments and to succession. The contributing authors discuss effects of historical silviculture and recent ecosystem-based management treatments, including an evaluation of various burning prescriptions in terms of tree response, undergrowth, soils, wildlife habitat, and esthetics and public acceptance.

Genetic diversity and microgeographic differentiation of Yushan cane (Yushania niitakayamensis; Poaceae) in Taiwan

Abstract: Yushan cane (Yushania niitakayamensis) is distributed in southeast Asia. In Taiwan, the species occurs in mountains 1000–3600 m above sea level. The species appears to spread mainly by rhizomes and flowers only rarely. Nine locations across its distribution range in Taiwan were sampled. Locations at higher altitudes generally consist of grassland and forest undergrowth habitats while those of lower altitudes generally consist of forest undergrowth only. Thus two sampling sites (montane grassland and forest undergrowth) were selected from each location at higher altitudes while only one sampling site was selected from each location at lower altitudes, resulting in a total of 13 sampling sites. Within each sampling site, 20 individual plants were sampled. The results of the cluster analysis and the principal coordinate analysis based on random amplified polymorphic DNA (RAPD) indicated that the populations are generally differentiated according to geographical separation and altitudinal differences that interrupt gene flow. The populations at higher altitudes, where the species is distributed somewhat contiguously, were found to be more similar genetically. Analysis of molecular variance (AMOVA) revealed that the among-location, between sampling sites within location, and among individuals within sampling site components accounted for 15.27%, 4.80% and 79.93% of the total variance, respectively. For locations with two sampling sites, two-level AMOVA revealed that the diversities between sampling sites (sun and shade habitats) within locations ranged from 2.91% to 7.99% of the total diversity. Random permutation tests revealed that these diversities were significant, implying that there is microgeographic differentiation due to habitat differences.

Periphyton Architecture and Susceptibility to Grazing by Periwinkles (Littorina littorea, Gastropoda)

Abstract: Periphyton was grown on transparent plastic substrata in the Kiel Fjord and used for short-term laboratory experiments to study the feeding selectivity of the periwinkle Littorina littorea in response to the vertical structure of the periphyton. The susceptibility of algae to periwinkle grazing was assessed by comparing the species-specific biomass within the grazing tracks of the snails to the biomass outside the tracks. After 3 weeks of incubation, the periphyton consisted of a scattered monolayer of algal cells without vertical structure. No apparent grazing could be found. After 6 weeks of incubation, periphyton consisted of a tightly attached undergrowth (mainly Cocconeis scutellum, Bacillariophyceae, and Myrionema sp., Phaeophyceae) and canopy of filamentous (Melosira moniliformis, Bacillariophyceae) and stalked forms (Achnanthes longipes, Bacillariophyceae). The unicellular diatoms Fragilaria tabulata and Stauroneis constricta grew partly on the primary substratum and partly as epiphytes on the canopy species. The canopy species and the epiphytes were decimated inside the grazing tracks, while the tightly attached undergrowth species appeared ungrazed.

Ecological Impacts of Eucalyptus tereticornis-globulus ( Eucalyptus Hybrid) Plantation in a Mining Area

Abstract: Environmental impact of Eucalyptus tereticornis-globulus ( Eucalyptus hybrid) plantation on the undergrowth diversity, soil moisture, soil nutrients and soil organic carbon, and on wildlife has been assessed. Qualitative as well as computer-aided quantitative studies gave clear indication that the ecological impacts of Eucalyptus hybrid plantation in terms of undergrowth diversity easily matches with the performance of Acacia auriculiformis or Leucaena leucocephala monocultures and polycultures. In other aspects as well these are no different from the impacts of mono or polycultures of Leucaena leucocephala , Acacia auriculiformis, Dalbergia sissoo , and so. The authors conclude that most of the adverse environmental impacts generally alleged against Eucalypts have not been seen.

Evergreen broad-leaved vegetation in the Colchis

Abstract: In Colkheti relict (tertiary) evergreen broad-leaved vegetation exists, which used to be widespread all throughout western Eurasia in the past and can nowadays be found as undergrowth in forests. Its representatives seek shelter in the relatively warm and humid climate of the Colkheti. The snow cover plays the crucial role in those species’ survival. These plants have mainly semi-prostrate growth form, although single individuals that reach 10-12m do exist. A number of syntaxons of broad-leaved and coniferous forests, including the Colkheti evergreen undergrowth, have mainly been marked out by Dolukhanov, and partially by Kolakovski.

Landscape Ecological Studies on Structure and Dynamics of Plant Populations on Vegetation-Landscape Patterns in Rural Regions: I. The Effect of Patch Shape on the Initial Population Structure of Pine and Oaks

Abstract: Secondary vegetation. the holistically integrated system of nature and human being, is the complicated ecosystem that is composed of natural and man-created factors. Understanding the ecological function of secondary vegetation supplies us many important informations for sustainable landscape management and ecological restoration planning. In this research, we tried to examine the shape effect of vegetation patch on early structure of populations of pine and oaks. Moreover. we also tried to clarify the ecological functions of patch edge by exploring the patch effect on germination using patch index. In addition, we present the landscape structure of man -made vegetation of our study area, and setting experimental design of research. Vegetation landscape of study area is typical human disturbed landscape mainly composed of disturbance patches. Vegetation types of graveyard and managed pine forest were controlled by periodically repeated management. However, current seedlings of pine occurred well at both vegetation types. Presence of both saplings were more controlled in managed pine forest (PDM) and graveyard (G) than those of undergrowth (PD) and forest edge (FE) with canopy trees. The number of pine seedlings increased with patch size and patch perimeter. That of oak seedlings was, however, not significantly different. Larger graveyards provided higher light availability for germination of pine seedlings. We think, however, most seedlings of both species in the large sized graveyards without shade will die more easily than that of small sized ones before rainy summer. Relationships between patch shape and germination of two woody species cannot be exactly explained enough yet in these results. More informations on spatial interaction of the total species with differently sized patches are necessary to solve the concept of patch effect on species colonization.