Assessing the Change in Cover of Non-Indigenous Dwarf-Pine Using Aerial Photographs, a Case Study from the Hrubý Jeseník Mts., the Sudetes
In addition to ongoing climate change, alpine ecosystems are also threatened by the expansion of non-indigenous species. Expansion of dwarf pine (Pinus mugo Turra) in the Hrubý Jeseník Mts. is an excellent example of the interactions between a planted alpine shrub and alpine ecosystems dominated by grassland species. Based on a comparison of aerial photographs taken in two different periods (1971/73 and 2003) we analyzed spatial changes in the dwarf pine cover. We focused on an evaluation of the current proportion of dwarf pine stands above the upper forest limit, as well as on the effects of stand texture and environmental variables on dwarf pine expansion over this 30 year period. During this time, dwarf pine stands increased their extent by 63%. Small forest-free areas above the upper forest limit in the northern part of the Hrubý Jeseník ridge are currently covered by dwarf pine on more than 30% of their surface. Expansion of dwarf pine was fastest in open, fine-grained stands, often situated in lower altitudes and on north- to east-facing slopes. The dwarf pine expansion was more intense than predicted by simple model of vegetative growth, especially within open stands with short polycormon margins in low altitudes. This might be explained by more intensive growth in less extreme environment and/or by higher generative reproduction on these sites. Finally, we suggest that expanding dwarf pine shrubs and recessing grassland patches negatively affects the abundance of heliophilous alpine plants and insects. We believe that the results of this study could be relevant to ongoing discussions on the management of summit forest-free areas in the Hrubý Jeseník Mts.
The availability of reliable modeling tools and input data required for the prediction of surface removal rate from the lithium fluoride targets irradiated by the intense photon beams is essential for many practical aspects. This study is motivated by the practical implementation of soft X-ray (SXR) or extreme ultraviolet (XUV) lasers for the pulsed ablation and thin film deposition. Specifically, it is focused on quantitative description of XUV laser-induced desorption/ablation from lithium fluoride, which is a reference large band-gap dielectric material with ionic crystalline structure. Computational framework was proposed and employed here for the reconstruction of plume expansion dynamics induced by the irradiation of lithium fluoride targets. The morphology of experimentally observed desorption/ablation craters were reproduced using idealized representation (two-zone approximation) of the laser fluence profile. The calculation of desorption/ablation rate was performed using one-dimensional thermomechanic model (XUV-ABLATOR code) taking into account laser heating and surface evaporation of the lithium fluoride target occurring on a nanosecond timescale. This step was followed by the application of two-dimensional hydrodynamic solver for description of laser-produced plasma plume expansion dynamics. The calculated plume lengths determined by numerical simulations were compared with a simple adiabatic expansion (blast-wave) model.