Über die Beziehungen zwischen einigen biotischen und abiotischen Faktoren im Latemar-Forst (Bozen)
An investigation has been carried out in the forest of Latemar (the Italian central eastern Alps), dominated byPicea excelsa withAbies alba, Larix europaea andPinus cembra, on the interactions between humus type (tabs 1, 2), litter and understory (including natural regeneration) composition on one hand and tree layer canopy and altitude on the other hand. Starting from ecological profiles, entropy-species (fig. 2, tab. 3) and entropy-factor have been calculated for the factors examined (tab. 4). This way it has been possible to determine the mutual information, the correct ecological profiles and the species groups index for the humus type (tab. 5), height (tab. 6) and canopy (tab. 7), which has allowed to grade species behaviour as regards investigated factors and consequently to single out three groups of species with similar ecological requirements (tab. 8). Moreover litter-humus entropy (tab. 9) and the same cybernetic parameters have been determined for the factor humus. The distribution of each group of species index is characterized by different combination of local factors (tab. 8): Humus type variations depend to a great extent on tree layer canopy and, through this layer, on the resulting litter composition and density: the “correcting” action of grasses with a low C:N on humus evolution is evident (tab. 10). From the silvicultural standpoint, leaving out uniform methods on large areas and chiefly clearcuts, an elastic treatment seems to be recommended, adhering to the actual conditions of forest and soil structure in order to achieve the density with major chances to secure favourable conditions of bioclimate, understory, humus and consequently regeneration. In the “semplified” forest ecosystem, as the investigated one, where natural levels of consumers (herbivores and carnivores) are actually missing, functionality may be secured through proper cuts only and by regularly restoring the nutrients of the litter, here almost entirely vegetal, to the cycle.
Microsite patterns of conifer seedling establishment and growth in a mixed stand in the southern Alps
Abstract In many forests of the Alps, permanent forest cover and, therefore, its continuous renewal is the main silvicultural goal. Regenerating these forests must be based on a sound understanding of the ecology of the tree species in question. The regeneration of silver fir (Abies alba Mill.) and Norway spruce (Picea abies (L.) Karst.) in the upper montane zone of the southern central Alps has so far received little attention. The aim of this study was, therefore, to characterize the ecological niche for the establishment and growth of silver fir and Norway spruce seedlings in this zone. The study was conducted as a case study on a plot of 1.5 ha in the upper montane zone of southern Switzerland, at an altitude of 1380 m. The basal area of the mixed Norway spruce–silver fir stand was 43.7 m2 ha−1. Seedlings were censused on 375 plots of 1.0 m2 area. Seedling density was 1.30 ± 4.25 m−2 (mean ± standard deviation) for Norway spruce and 0.87 ± 1.50 m−2 for silver fir. Logistic regression models were used to test the effect of microsite characteristics on seedling occurrence, and general linear models for effects on seedling height growth and biomass increment. Most seedlings received less than 10% light (photosynthetic photon flux density) as compared to values in the open. Silver fir occurrence was positively related to microsites at the edge of canopy trees, but unrelated to ground cover type, light and micro-relief. Norway spruce occurrence was only, and positively, related to the presence of mosses. Height growth and biomass increment of seedlings of both species were only loosely correlated with microsite conditions. Seedlings without canopy cover grew faster than those under canopy cover, probably as a result of light and moisture limitations under the canopy of adult trees. Diffuse radiation was positively correlated with average annual biomass increment of silver fir, but not of Norway spruce seedlings. In general, the results suggest that silver fir seedlings have less specific microsite requirements than Norway spruce seedlings in terms of ground cover. They are also more shade tolerant, and therefore, grow faster than Norway spruce in low-light environments of the upper montane zone of the southern Alps. While the microsite concept can be helpful in designing silvicultural operations, it has limitations when only patch characteristics that are easy to assess are used, and others neglected. Finally, our study suggests that counting the number of green shoots is a promising method to quickly and non-destructively estimate the biomass of a great number of small seedlings.
Geographic And Environmental Influence On Maya Settlement Patterns Of The Northwest Yucatan: An Explanation For The Sparsely Settled Western Cenote Zone
Most settlement pattern research and GIS analysis of the ancient Maya of the Northern Yucatan have focused on water availability in a dry landscape where cenotes are often the only water source. While water is of paramount importance, permanent settlement secondarily requires farmable soil, a resource often as precious as water in many parts of the Yucatan. The dynamics between these resources reveal areas of ideal settlement and more challenging landscapes for which the Maya developed strategies to overcome environmental conditions. A region of the southwest "Cenote Zone", however, appears to have presented the ancient Maya with insurmountably poor environmental conditions despite abundant water resources. The lack of dense population and stone architecture in this area emphasizes the lack of a simple correlation between cenotes and settlement. This thesis uses GIS analysis to identify and explore such problematic settlement areas to better understand the factors and complexities involved in the more successful settlements of neighboring regions. iv This work is dedicated to my late father, who first introduced me to the Mundo Maya through a visit to the ruins of Tikal at the age of nine, and who instilled in me strength, curiosity, and a love for exploring the world. v ACKLOWLEDGEMENTS I'd like to acknowledge Dr. Arlen Chase and Dr. Diane Chase for providing such outstanding opportunities and instruction, and for leading by example both in the field and in the classroom. Dr. John Walker for his eye-opening perspectives, GIS instruction, inspiring hard-working attitude, and patience in the field. Dr. Clifford Brown and Dr. Walter Witschey for their invaluable correspondence and for their contributions to mapping and GIS data of Maya sites.