Christian Newesely

Effects of land-use changes on snow gliding processes in alpine ecosystems

Summary The reduction of agricultural use of alpine ecosystems went hand in hand with an increase of soil erosion in many areas. A possible reason for this phenomenon is the more frequent snow gliding in winter. In a large research program (part of the ECOMONT project) managed areas, as well as areas that are not used or only used to some extent, were investigated in order to find out their liability to snow gliding. By means of statistical methods, a model was designed that shall explain the influence of terrain parameters (slope inclination, exposition, altitude) as well as the influence of the management. The investigations have shown that the liability of alpine ecosystems to snow gliding increases with the reduction of agricultural use. Especially high gliding rates were observed on low soft dwarf shrubs canopies. Bigger dwarf shrubs or trees are obstacles and stabilize the snow cover so that the gliding rates decrease drastically.

Canopy structure versus physiology effects on net photosynthesis of mountain grasslands differing in land use

The present paper aims at investigating how changes in canopy structure and species physiology associated with the abandonment of mountain meadows and pastures affect their net photosynthesis. For this purpose, a multi-layer vegetation–atmosphere transfer (VAT) model is employed, which explicitly takes into account the structural and functional properties of the various canopy components and species. Three sites differing in land use are investigated, a meadow, a pasture and an abandoned area. Model simulations agree reasonably with measured canopy net photosynthetic rates, the meadow featuring the highest daily net photosynthesis, followed by the pasture and, finally, the abandoned area. A detailed process analysis suggests this ranking to be mainly due to bulk canopy physiology, which decreases from the meadow to the pasture and the abandoned area, reflecting species composition and species-specific photosynthetic capacities. Differences between the canopies with regard to canopy structure are found to be of minor importance. The amounts of green, photosynthetically active plant matter are too similar at the three sites to be a major source of variation in net photosynthesis. Large differences exist between the canopies with regard to the amount of photosynthetically inactive phytoelements. Even though a model analysis showed them to be potentially important, most of them are accumulated close to the ground surface, where they exert little influence on canopy net photosynthesis.

Water stress limits transpiration and growth of European larch up to the lower subalpine belt in an inner‐alpine dry valley

Summary Climate change will further constrain water availability in dry inner‐alpine environments and affect water relations and growth conditions in mountain forests, including the widespread larch forests. To estimate the effects of climate conditions on water balance and growth, variation in sap flow and stem radius of European larch was measured for 3 yr along an elevation transect from 1070 to 2250 m above sea level (asl) in an inner‐alpine dry valley in South Tyrol/Italy. Additionally, long‐term climate–growth relations were derived from tree cores. Sap flow and radial growth were reduced in dry periods up to an elevation of 1715 m, leading to maximum annual growth at 2000 m. In a wet year no growth difference between elevations was observed. Long‐term tree ring data showed a positive growth response to precipitation up to 1715 m and to temperature only above 2000 m. Our results demonstrate that reduced water availability and higher atmospheric water demand limit larch at low elevation within dry Alpine regions. This indicates a general upward shift of this species’ elevational amplitude upon climate change, and respective negative effects on future silvicultural use and ecosystem services at lower elevations in the European Alps.