► 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.
Abstract
Questions
Can the model performance of the landscape reconstruction algorithm (
LRA
) for small forest hollows be validated through comparison to inventory‐based vegetation reconstructions ...from the last 150 yrs? Does the application of
LRA
and the comparison to historical data enhance interpretation of the pollen record?
Location
D
enmark. The
G
ribskov‐
O
strup small forest hollow (56°N, 12°20′ E, 44 m a.s.l.) in the forest of
G
ribskov, eastern
D
enmark.
Methods
Pollen analysis was carried out on a small forest hollow, and
LRA
used to derive pollen‐based quantitative estimates of past vegetation. Historical forest inventory data and maps were used to reconstruct the vegetation within three different circles around the hollow (20, 50 and 200 m ring widths) for five time periods during the last 150 yrs. The results of the two approaches were compared in order to evaluate model performance, and the
LRA
‐based reconstruction used to describe how the model changes interpretation of vegetation development during the last ca. 6500 yrs compared to the use of pollen percentages alone.
Results
Distance‐weighted inventory‐based reconstructions within 200 m of the hollow's edge provide the best match with the
LRA
‐modelled vegetation. Precise validation of the model is not possible due to insufficient historical data, but the comparison indicates that the
LRA
reconstruction for
G
ribskov tends to (1) underestimate tree cover and overestimate open areas, (2) give a too high representation of on‐site pollen types, (3) give an underestimation of
F
agus
and (4) a small overestimation of
Q
uercus
and
C
orylus
. Despite these uncertainties, application of the
LRA
model shows a higher degree of openness than would be apparent from the uncorrected pollen diagram, and makes it possible to attempt to distinguish changes at the local scale from regional vegetation changes, thus giving a clearer picture of the vegetation changes at the site.
Conclusions
We demonstrate that the estimates of the
LRA
model applied to pollen data from small forest hollows can be compared with small‐scale historical data to evaluate model performance.
Summary
Ectomycorrhizal plants trade plant‐assimilated carbon for soil nutrients with their fungal partners. The underlying mechanisms, however, are not fully understood. Here we investigate the ...exchange of carbon for nitrogen in the ectomycorrhizal symbiosis of Fagus sylvatica across different spatial scales from the root system to the cellular level.
We provided 15N‐labelled nitrogen to mycorrhizal hyphae associated with one half of the root system of young beech trees, while exposing plants to a 13CO2 atmosphere. We analysed the short‐term distribution of 13C and 15N in the root system with isotope‐ratio mass spectrometry, and at the cellular scale within a mycorrhizal root tip with nanoscale secondary ion mass spectrometry (NanoSIMS).
At the root system scale, plants did not allocate more 13C to root parts that received more 15N. Nanoscale secondary ion mass spectrometry imaging, however, revealed a highly heterogenous, and spatially significantly correlated distribution of 13C and 15N at the cellular scale.
Our results indicate that, on a coarse scale, plants do not allocate a larger proportion of photoassimilated C to root parts associated with N‐delivering ectomycorrhizal fungi. Within the ectomycorrhizal tissue, however, recently plant‐assimilated C and fungus‐delivered N were spatially strongly coupled. Here, NanoSIMS visualisation provides an initial insight into the regulation of ectomycorrhizal C and N exchange at the microscale.
Mixing of complementary tree species may increase stand productivity, mitigate the effects of drought and other risks, and pave the way to forest production systems which may be more resource-use ...efficient and stable in the face of climate change. However, systematic empirical studies on mixing effects are still missing for many commercially important and widespread species combinations. Here we studied the growth of Scots pine (Pinus sylvestris L.) and European beech (Fagus sylvatica L.) in mixed versus pure stands on 32 triplets located along a productivity gradient through Europe, reaching from Sweden to Bulgaria and from Spain to the Ukraine. Stand inventory and taking increment cores on the mainly 60–80 year-old trees and 0.02–1.55 ha sized, fully stocked plots provided insight how species mixing modifies the structure, dynamics and productivity compared with neighbouring pure stands. In mixture standing volume (+12 %), stand density (+20 %), basal area growth (+12 %), and stand volume growth (+8 %) were higher than the weighted mean of the neighbouring pure stands. Scots pine and European beech contributed rather equally to the overyielding and overdensity. In mixed stands mean diameter (+20 %) and height (+6 %) of Scots pine was ahead, while both diameter and height growth of European beech were behind (−8 %). The overyielding and overdensity were independent of the site index, the stand growth and yield, and climatic variables despite the wide variation in precipitation (520–1175 mm year⁻¹), mean annual temperature (6–10.5 °C), and the drought index by de Martonne (28–61 mm °C⁻¹) on the sites. Therefore, this species combination is potentially useful for increasing productivity across a wide range of site and climatic conditions. Given the significant overyielding of stand basal area growth but the absence of any relationship with site index and climatic variables, we hypothesize that the overyielding and overdensity results from several different types of interactions (light-, water-, and nutrient-related) that are all important in different circumstances. We discuss the relevance of the results for ecological theory and for the ongoing silvicultural transition from pure to mixed stands and their adaptation to climate change.
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•Total yield production increased by 5–40% compared to simulations.•BAI increased in unmanaged forests and in forests managed by free crown thinning.•BAI was decreasing since 1990 in ...forests managed by heavy thinning from below on less productive sites.•Dominant trees were responsive to climate while the suppressed exhibited no correlation.
Recent studies have revealed that European beech (Fagus sylvatica L.) has significantly increased its growth in Central Europe during the last century but recently started to decline at the edge of its southern distribution. Climate scenarios predict an increased frequency of severe drought events in the future, which is supposed to cause a decline of beech forests even towards the northern edge. Whether the management has the potential to mitigate the negative effects of climate warming has not been fully addressed yet. In order to fill the knowledge gap, we compiled data from 29 long-term research plots (LTRP) at 8 sites across the western Carpathian Mountains (Eastern Europe). The LTRP were established in 1958–84 and measured every 4–5 years till 2015. Development of forest stand attributes including top height (htop), mean quadratic diameter (dq), mean annual tree volume increment (iv̅), periodic annual volume increment (PAIV), mean annual basal area increment (BAI), and total yield production (TY) was compared with the simulations by the Slovakian yield models developed in the 1980s based on data from the period before recent climate change. Results were additionally confronted with the growth of beech forests in a larger Central European region. Results showed an increase of TY since the 1960s compared to the simulated TY, starting from the same value, ranging from 5% to 40% and mainly depending on site quality and average annual temperature. The largest increase was found on less productive sites, which was in line with the previous findings in recent literature. Interestingly, beech TY in the Western Carpathians was found to be lower by −11% on average compared to beech forests in Central Europe (Germany). Moreover, while an increase in the BAI continues in unmanaged forests, it has recently slowed down in forests managed by “free crown thinning” and it even started to decrease in less productive forests where heavy thinning from below was applied. Finally, our results showed that the responses of beech BAI to climate variation significantly depended on tree class.
In this study, different approaches were used to investigate the vulnerability of beech forests, located at the eastern limit of their natural range, to climate change. To accomplish this, six 2500 ...m2 plots were sampled in four European beech forest genetic resources, located in Romania at different altitudinal levels, varying from 230 to 580 m in the Bacau hills and between 650 and 1300 m in the Curvature Carpathian (Brasov region). The analysis of trees phenotypic traits, their radial growth, and the regeneration, did not indicate a vulnerability of the sampled stands to the fluctuations of the environmental factors from the 1950-2014 period. The growth indices of all three populations of Bacau hills are negatively correlated with both June air temperature of current year and September of the previous year. The precipitation amount of September previous year positively influenced the growth indices. The radial growth of plots in Brasov region is slightly linked to the climate. The temperature during the growing season represents a limiting factor for stands that are located outside of the optimal altitudinal species distribution (600-1200 m, in Romania), especially at low altitudes. Our results indicated that a rise of the temperature accompanied by a possible reduction of the precipitations (as is predicted for the coming years) could increase the sensibility of beech forests at lower altitude.
Despite their critical importance for understanding the local effects of global climate change on biodiversity, glacial microrefugia are not well studied because they are difficult to detect by using ...classical palaeoecological or population genetics approaches. We used soil macrofossil charcoal analysis to uncover the presence of cryptic glacial refugia for European beech (Fagus sylvatica) and other tree species in the Landes de Gascogne (southwestern France). Using botanical identification and direct radiocarbon dating (140 ¹⁴C‐dates) of macrofossil charcoal extracted from mineral soils, we reconstructed the glacial and postglacial history of all extant beech stands in the region (n = 11). Soil charcoal macrofossils were found in all sites, allowing the identification of up to at least 14 distinct fire events per site. There was direct evidence of the presence of beech during the last glacial period at three sites. Beech was detected during Heinrich stadial‐1, one of the coldest and driest intervals of the last glacial period in Western Europe. Together with previous results on the genetic structure of the species in the region, these findings suggest that beech persisted in situ in several microrefugia through full glacial and interglacial periods up to the present day.
Future changes in tree growth, associated with a warmer and drier climate, are predicted for many species and locations across the European Mediterranean Basin. However, quantification of the ...intensity and severity of related consequences for forest ecosystem functioning and productivity remains challenging. Species-specific distribution limits that are particularly sensitive to small changes in the ambient climate may provide an ideal test bed to assess the nature of past growth trends and extremes and their responsible controls. Here, we seek to understand how twentieth century climate change affected the growth of European beech (Fagus sylvatica L.) nearby its south-eastern distribution limit in Albania and Macedonia on the Balkan Peninsula. We sampled 93 living trees from undisturbed mixed forest stands at ~1,450 m a.s.l. and 29 timbers from nearby historical buildings. Application of different tree-ring detrending techniques allowed robust composite chronologies with varying degrees of high- to low-frequency variability to be developed back to 1648 AD. Comparison with local meteorological station measurements and continental grid-box climate indices revealed spatiotemporal instability in growth–climate response patterns. Nevertheless, year-to-year and decadal-long fluctuations in radial beech growth were significantly (P < 0.001) negatively correlated at −0.61 with June–September temperature over the 1951–1995 period. This (inverse) relationship between increased beech growth and decreased summer temperature is somewhat indicative for the importance of plant-available soil moisture, which likely controls ring width formation near the species-specific south-eastern distribution limit. Significant positive correlations between beech growth and drought (scPDSI; r = 0.57) confirm metabolistic drought constraints. However, an unexpected late twentieth century growth increase not only contradicts the previously observed growth dependency to summer soil moisture, but also denies any putative drought-induced forest ecosystem suppression in this part of the Mediterranean Basin.
•Multiple types of evidence yield an overview of the disturbance regime in Dinaric Mountain forests.•Variation in regime components from multiple agents results in a complex disturbance ...regime.•Intermediate severity disturbance events are characteristic of the regime.
Quantitative descriptions of natural disturbance regimes are lacking for temperate forest regions in Europe, primarily because a long history of intensive land-use has been the overriding driver of forest structure and composition across the region. The following contribution is the first attempt to comprehensively describe the natural disturbance regime of the dominant forest communities in the Dinaric Mountain range, with an emphasis on the range of natural variability of regime components for the main disturbance agents. Compared to other forest regions in Europe, the mountain range has a history of less intensive forest exploitation and provides a suitable record of natural disturbance processes. Our synthesis is based on multiple types of evidence, including meteorological information, historical documentation, evidence from old-growth remnants, and salvage logging data from National forest inventories. Taken together, the results show that no single disturbance agent dominates the regime in the dominant forest types (i.e. beech and mixed beech-fir forests), and any given agent exhibits remarkable variation in terms of severity and spatial extent both within and among individual disturbance events. Thunderstorm winds cause the most severe damage (i.e. near stand replacement), but blowdown patches are typically limited to stand-scales (e.g. 10s of ha). Ice storms and heavy snow typically cause intermediate severity damage and affect much larger areas (e.g. 100s of km2). A notable exception was the 2014 ice storm, which was nearly an order of magnitude larger and more severe than any other event recorded in the synthesis. Severe and prolonged periods of drought have occurred several times over the past century, and along with secondary insect damage (e.g. bark beetles), have caused episodes of forest decline. Overall, our synthesis indicates that on top of the background of relatively continuous gap dynamics, stand-scale intermediate severity events are an important part of the regime; these events likely have rotation periods that are less than the lifespan of a tree cohort (e.g. several centuries) and create canopy openings large enough to alter successional trajectories.
Insights from in vivo micro-CT analysis Losso, Adriano; Bär, Andreas; Dämon, Birgit ...
The New phytologist,
March 2019, Letnik:
221, Številka:
4
Journal Article
Recenzirano
Odprti dostop
• The seedling stage is the most susceptible one during a tree′s life. Water relations may be crucial for seedlings due to their small roots, limited water buffers and the effects of drought on water ...transport. Despite obvious relevance, studies on seedling xylem hydraulics are scarce as respective methodical approaches are limited.
• Micro-CT scans of intact Acer pseudoplatanus and Fagus sylvatica seedlings dehydrated to different water potentials (Ψ) allowed the simultaneous observation of gas-filled versus water-filled conduits and the calculation of percentage loss of conductivity (PLC) in stems, roots and leaves (petioles or main veins). Additionally, anatomical analyses were performed and stem PLC measured with hydraulic techniques.
• In A. pseudoplatanus, petioles showed a higher Ψ at 50% PLC (Ψ50 1.13MPa) than stems (–2.51 MPa) and roots (–1.78 MPa). The main leaf veins of F. sylvatica had similar Ψ50 values (–2.26 MPa) to stems (–2.74 MPa) and roots (–2.75 MPa). In both species, no difference between root and stems was observed. Hydraulic measurements on stems closely matched the micro-CT based PLC calculations.
• Micro-CT analyses indicated a species-specific hydraulic architecture. Vulnerability segmentation, enabling a disconnection of the hydraulic pathway upon drought, was observed in A. pseudoplatanus but not in the especially shade-tolerant F. sylvatica. Hydraulic patterns could partly be related to xylem anatomical traits.
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