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 2250m 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 1715m 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.
Plant rooting strongly affects most hydrological, biogeochemical and ecological processes in terrestrial ecosystems, as it presents the main pathway for carbon, water and nutrient transfer from soil ...to the atmosphere and is a key factor in stabilizing the soil layer. Few studies have actually investigated the link between phytosociological and structural vegetation composition and diversity in soil rooting parameters. Our study provides a comprehensive evaluation of plant cover and diversity effects on rooting parameters dependent on different land-use types along a north-south transect in the Eastern Alps. We conducted field studies of root biomass, rooting density and rooting depth for the six main land-use types: intensively and lightly used hay meadows, pastures, arable land, agriculturally unused grasslands and forests. The variation in rooting parameters was explained by different aspects of species and functional richness, species and functional composition, functional traits, abundance of key species and site variables depending on the land-use types. Our results showed that different characteristics of biodiversity explained the variance in root parameters (mass, density and depth) to a high degree (determination coefficient R
values varied between 0.621 and 0.891). All rooting parameters increased with increasing plant species richness, as well as with a higher diversity of plant functional traits. The inclusion of site parameters significantly increased the explained variance, while we could not find evidence for key species and their abundance to provide additional explanatory power. Allowing the effects to vary depending on land-use types turned out to be a necessity supporting the importance of considering land-use types for rooting. The findings indicate that vegetation composition has a clear relationship with rooting parameters across different habitats in the European Alps. As the effect of plant composition differs with respect to the land-use type, rooting can be monitored by land management to achieve the desired benefits. For example, intensified rooting through extensive management decreases erosion risk and increases carbon uptake.
Introduction Climate change affects the vitality of mountain forests through increasing temperatures and decreasing water availability due to changing precipitation patterns, earlier snowmelt, and ...increasing evaporative demand. Depending on species characteristics, tree growth might therefore increase in cold habitats near the forest line but decrease in water-limited conditions at low elevation. Methods We analyzed the tree-ring widths of five conifers ( Picea abies , Larix decidua , Pinus sylvestris , Pinus nigra , and Pinus cembra ) along an elevational gradient from 1,000 m to 2,320 m above sea level (a.s.l.) in Vinschgau/Val Venosta Valley in Northern Italy, one of the driest regions of the Alps (mean annual precipitation of 682 mm at 1,310 m a.s.l.). Results Our aim was to estimate the species-specific growth response to changing climate conditions along an elevational gradient. At low elevations, we observed a significant response to water availability not only during the actual growing season but also throughout the previous autumn for all species present. At mid-elevation, the correlation coefficients to precipitation and drought indices (SPEI) were highest for Picea abies . At high elevations, the positive correlation of growth with temperature was smaller than expected for Pinus cembra. In contrast, Larix decidua responded positively to temperature and grew faster in recent decades. Discussion Considering that a further increase in temperatures will reduce plant water availability during the growing season, our space-for-time approach provides an outlook on future growth conditions of conifers in larger regions of the European Alps. Water limitation will affect tree growth and vitality not only at low elevation in the valleys but also at mid elevation on mountain slopes, potentially impacting timber production and protective and recreative functions of forests. Near the forest line, the different capabilities of tree species to benefit from higher temperatures might lead to changes in species composition.
The global decline of biodiversity has affected European forests, involving many tree species and forest-dwelling threatened animals. An integrated approach linking forest structure and multi-taxon ...diversity is increasingly needed to maintain the multifunctionality of forest ecosystems. We investigated the relationship between forest structure, deadwood elements, canopy attributes, and tree-related microhabitats on bat and bird communities in the north-eastern Italian Alps. We collected forest attributes, bats, and bird data on 40 forest plots encompassing the diversity of forest types. To assess the different contributions of each forest attribute variables we performed a two-step statistical analysis using generalised and linear models, including bat and bird taxonomical and functional diversity indices as response variables. Our findings reveal that bats and birds respond differently to variation in forest structural characteristics. Specifically, bat species richness was higher in forests with both higher standing tree and lying deadwood volume. The Shannon diversity index for bird community was higher in forests with high volumes of coarse lying deadwood and stumps. Moreover, plots with mature trees, gaps, and heterogeneous diameter distribution fostered the presence of generalist species of bats and birds, while the abundance of tree-related microhabitats was not significant for these two taxa. This study demonstrates that the optimal habitat conditions for bats and birds in Alpine forests are multifaceted. Promoting distinctive elements within forest stands and a complex forest structure through adaptations in forest management interventions would enhance the conservation of multi-taxon forest biodiversity.
•Forest structure and deadwood elements relates to bats and birds in the Italian Alps.•Bat richness was higher with both higher standing tree and lying deadwood volume.•Bird community was more diverse with high volumes of logs and stumps.•Promoting a complex forest structure sustains a multi-taxon forest biodiversity.
•Long-term growth of Larix decidua responded stronger to warming than Pinus cembra.•Precipitation hardly influenced growth of both species at our high elevation sites.•Daily growth was limited by air ...vapor pressure deficit for Pinus but not for Larix.•Sap flow per tree was lower and decreased in dry soils for Pinus but not for Larix.•Short-term moisture limitations of Pinus explain its reduced long-term growth.
High elevation mountain forests in the European Alps are strongly affected by climate change. In this study we aimed to investigate the long- and short-term effects of climate on radial stem growth and tree hydraulics of the two dominant tree species at the forest line of the Eastern central Alps, European larch (Larix decidua Mill. and Swiss stone pine (Pinus cembra L). To this end, we analyzed tree ring widths from stem cores from five sites between 1990 and 2320 m above sea level (a.s.l.) and measured sap flow for three years and radial stem variation for four years at three sites between 1990 and 2100 m a.s.l. in an inner alpine dry valley in Northern Italy. We found that tree ring width of larch responded stronger to temperature and increased more with warming in the last decades than in Swiss stone pine. In the short term, low soil moisture reduced sap flow during the summer in Swiss stone pine but not in larch. Additionally, air vapor pressure deficit clearly reduced the number of days with radial stem growth in Swiss stone pine, leading to lower annual growth than in larch. Consequently, larch at high elevation might actually benefit from climate change at the expense of Swiss stone pine.
To gain a deeper understanding of the water balances of Alpine grassland ecosystems, it is crucial to know the abiotic and biotic drivers of evapotranspiration. The abiotic drivers are very ...heterogeneous in mountain regions because elevation, slope and aspect control incoming Rs, and atmospheric layering affect air temperature, humidity and wind distribution. In a study with 24 lysimeter plots distributed over a study area of approx. 300 km2 in the Eastern Alps, we covered a wide range of topographic conditions. We investigated the effects of abiotic drivers on evapotranspiration by measuring evaporation from a free‐water body (Ew). For the biological modulation of crop evapotranspiration (ETc), we analysed two different grassland types (at peak biomass and at low biomass) and calculated the respective crop coefficients (Kc). Results showed that primarily physical drivers such as the accumulated solar radiation from sunrise to measurement (Rs_acc), followed by atmospheric pressure (P), wind speed (u) and vapour pressure deficit (VPD) influence both Ew and ETc. Moreover, ETc is also significantly influenced by standing biomass and the grassland type (i.e., resource use strategies of the vegetation types) and by the geographic location along the valley (i.e., entrance, middle and head of the valley). We suppose plant stress and/or ground winds to be the underlying factor for the significance of the geographic location, yet further research is needed. The current study helps towards a better understanding of the water balance in alpine grassland ecosystems, but we also show that some spatial drivers cannot yet be adequately addressed.
Heatwaves exert disproportionately strong and sometimes irreversible impacts on forest ecosystems. These impacts remain poorly understood at the tree and species level and across large spatial ...scales. Here, we investigate the effects of the record-breaking 2018 European heatwave on tree growth and tree water status using a collection of high-temporal resolution dendrometer data from 21 species across 53 sites. Relative to the two preceding years, annual stem growth was not consistently reduced by the 2018 heatwave but stems experienced twice the temporary shrinkage due to depletion of water reserves. Conifer species were less capable of rehydrating overnight than broadleaves across gradients of soil and atmospheric drought, suggesting less resilience toward transient stress. In particular, Norway spruce and Scots pine experienced extensive stem dehydration. Our high-resolution dendrometer network was suitable to disentangle the effects of a severe heatwave on tree growth and desiccation at large-spatial scales in situ, and provided insights on which species may be more vulnerable to climate extremes.
Better understanding of surface runoff quantity for distinct hydrological units becomes increasingly important as many rainfall–runoff models use static surface runoff coefficients and neglect key ...factors affecting ecohydrological dynamics, e.g. land cover and land use. Especially in small-scale alpine catchments, surface runoff and its contribution to mountain torrent runoff is frequently underestimated. In our study, the seasonal variability of surface runoff on abandoned areas and pastures in the alpine catchment ‘Kaserstattalm’ (Stubai Valley, Austria, Eastern Alps) was analyzed using a rain simulator along with soil water content (
SWC) and soil water tension (
SWT) measurements. Additionally, seasonal variability of soil physical and soil hydraulic properties were assessed. Analyzing more than 30 rainfall simulations on 10
m
2 plots at a rate of 90
mm
h
−1 (equivalent to convective precipitation events with 100
years return period) revealed a mean surface runoff coefficient of 0.01 on abandoned areas and 0.18 on pastures. Regarding seasonal variability, relevant surface runoff was limited to pastures in autumn with a maximum runoff coefficient of 0.25. The field capacity (
Fc) of all soils was found to be stable throughout the season. However, for pastures, cattle trampling led to a significant increase of dry bulk density (
BD) of up to +0.33
g
cm
−3 (
p
⩽
0.01) in the top 0.1
m of the soil which is attributed to a compaction of macropores. Although measured infiltration rates decreased by more than 60%,
BD could ‘recover’ during the winter season presumably due to freezing-and-thawing cycles and bioturbation processes decreasing soil compaction. This study highlights that impacts of land-use changes on soil physical properties make surface runoff difficult to model. Moreover, dynamic and interactive behaviour of soil parameters have to be considered in order to make realistic assessments and accurate predictions of surface runoff rates. Finally, land-use effects on runoff formation in general and significance at catchment scale are discussed.
For central Europe in addition to rising temperatures an increasing
variability in precipitation is predicted. This will increase the probability
of drought periods in the Alps, where water supply ...has been sufficient in
most areas so far. For Alpine grasslands, community-specific imprints on
drought responses are poorly analyzed so far due to the sufficient natural
water supply. In a replicated mesocosm experiment we compared
evapotranspiration (ET) and biomass productivity of two differently
drought-adapted Alpine grassland communities during two artificial drought
periods divided by extreme precipitation events using high-precision small
lysimeters. The drought-adapted vegetation type showed a high potential to
utilize even scarce water resources. This is combined with a low potential to
translate atmospheric deficits into higher water conductance and a lower
biomass production as those measured for the non-drought-adapted type. The
non-drought-adapted type, in contrast, showed high water conductance
potential and a strong increase in ET rates when environmental conditions
became less constraining. With high rates even at dry conditions, this
community appears not to be optimized to save water and might experience
drought effects earlier and probably more strongly. As a result, the water
use efficiency of the drought-adapted plant community is with
2.6 gDW kg−1 of water much higher than that of the
non-drought-adapted plant community (0.16 gDW kg−1). In
summary, the vegetation's reaction to two covarying gradients of potential
evapotranspiration and soil water content revealed a clear difference in
vegetation development and between water-saving and water-spending strategies
regarding evapotranspiration.
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