► Dendrochronological investigations of beech and oak along precipitation gradient. ► Growth strongly depends on water availability especially during June and July. ► Sensitivity of tree growth and ...correlations to climate increase along gradient. ► Numbers of pointer years increase, changes more pronounced for beech. ► oak might gain competitive advantages under the projected drier climate.
For north-eastern Germany regional climate models project rising temperatures in combination with decreasing summer and increasing winter precipitation. The resulting overall drier conditions during the growing season will considerably impact forest growth there. We evaluate the consequences of increasing drought on the growth of the two locally most important broadleaf tree species common beech (
Fagus sylvatica L.) and pedunculate oak (
Quercus robur L.). Three mixed forests of beech and oak were sampled along a west-east gradient of declining precipitation. In total we used 257 ring-width samples from 133 trees to build six species and site specific chronologies. Additionally, we modelled the soil water budget for each site. We performed continuous and discontinuous (pointer year) analysis of climate-tree-growth relationships with particular emphasis on inter-annual-variations and their dependence upon climatic factors (temperature, precipitation, soil moisture) and on the stability of the obtained relationships. Results of climate-growth correlations together with pointer year analysis indicate a strong dependency of growth of both species from water availability, especially during early summer (June and July). General correlation pattern between growth and climate are similar for both species, but climate sensitivity of beech is generally higher. We identified drought as the main driver of negative growth depressions in both species. Increasing drought stress along the gradient is expressed in higher correlations to climatic variables, higher sensitivity (variance) of growth, and a higher number of negative pointer years for both species. For beech we also found a significant trend of decreasing average growth rates along the gradient. Growth superiority of beech compared to oak declines with decreasing precipitation. The relationships were generally stable throughout the 20th century. A rise of sensitivity together with a higher frequency of negative pointer years during the last decades suggests that increasing climatic variability together with rising temperatures might be influencing growth of
Fagus at the more humid sites. If we substitute space by time it seems that already small changes in precipitation regime can have considerable impact, especially on the growth of beech. Other, more drought tolerant species like oak might gain competitive advantages under the projected climatic changes.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Soil water availability determines the vitality of trees and forest stands to a large degree. Over the last decades, an increasing number of drought spells has been observed in several parts of ...Europe. Our study aims to estimate long-term trends of soil drought at Scots pine (
Pinus sylvestris
L.) stands along the prevailing climatic gradient in Mecklenburg-Western Pomerania, northeastern Germany. To this end, soil water balance simulations were carried out at 24 sites over the period from 1951 to 2009 with the physically based model LWF-BROOK90. As a threshold for soil water stress, we used 40% of relative extractable water (REW). The results indicated an increased number of drought days further east, together with declining totals of precipitation. However, specific site conditions had a large influence on the occurrence of soil drought, partly overriding the climatic differences across the study area. Soil drought has distinctly increased in the recent past, both in duration and in intensity, affecting the eastern sites more than the western sites. The increased soil dryness could be attributed to higher atmospheric evaporative demand due to higher temperatures, as well as slightly lower precipitation sums during the summer months. To mitigate the negative effects of future climate change, adaptation measures should preferably be conducted in the eastern parts of northeastern Germany.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The commonly used multiple‐liner‐system of modern top sealings of contaminated sites is expensive and in many cases (minor hazardousness of pollutants), not necessary. As an alternative, we ...investigated the performance of willow stands as the only measure to reduce percolating soil water and therewith pollutant transport to underlying ground water resources. It is well accepted that willows have a high water demand and may considerably reduce percolation. On the basis of experimentally determined soil physical properties of a landfill site, we performed water balance calculations with the physically based HYDRUS‐code and a simple bucket approach. The 20 yr annual leachate rate for bare soil was calculated to vary from 336 (HYDRUS) to 451 mm yr—1 (bucket‐model). Willows were able to reduce the annual leachate to 146 (HYDRUS) and 186 mm yr—1 (bucket‐model), indicating their great performance compared to a grass‐ or beechwood cover. However, legal regulations (TASi) in Germany cannot be met with the proposed method. In minor hazardous cases, official authorities may accept willow stands as an alternative system for protection.
Weidenpflanzung als Alternativverfahren zur Reduzierung der Sickerwasserrate auf kontaminierten Standorten
Die weitverbreiteten mehrschichtigen Oberflächenabdichtungssys‐teme für Altlasten zur Reduktion von Sickerwasser sind teuer und oftmals nicht erforderlich. In dieser Studie wurde die Leistungsfähigkeit von Weidenanpflanzungen als Alternativverfahren zur Sicherung von Altlasten untersucht. Weiden haben einen beträchtlichen Wasserbedarf und können damit zu einer deutlichen Verringerung des perkolierenden Bodenwassers beitragen. Auf Grundlage experimentell erhobener bodenphysikalischer Kennwerte eines Altstandortes wurden Wasserhaushaltsberechnungen mit dem physikalisch basierten HYDRUS‐Ansatz und einem Speicherzellenmodell durchgeführt. Es wurden als derzeitige (unbewachsener Boden) jährliche Sicker‐wasserraten 336 (HYDRUS) bis 451 mm a—1 (Speichermodell) errechnet (20‐Jahresmittel). Weiden sind in der Lage, die jährliche Sickerwasserrate auf bis zu 146 (HYDRUS) bzw. 186 mm a—1 (Speichermodell) zu senken und sind damit leistungsfähiger als Vegetationsdecken aus Gras und Buchen. Trotzdem können die Vorgaben der TA Siedlungsabfall mit der vorgeschlagenen Methode nicht erfüllt werden. Allerdings können bei mindergefährlichen Standorten — wie in diesem Fall — behördliche Ausnahmeregelungen für Weidenanpflanzungen erteilt werden.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
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