The mechanistic pathways connecting ocean-atmosphere variability and terrestrial productivity are well-established theoretically, but remain challenging to quantify empirically. Such quantification ...will greatly improve the assessment and prediction of changes in terrestrial carbon sequestration in response to dynamically induced climatic extremes. The jet stream latitude (JSL) over the North Atlantic-European domain provides a synthetic and robust physical framework that integrates climate variability not accounted for by atmospheric circulation patterns alone. Surface climate impacts of north-south summer JSL displacements are not uniform across Europe, but rather create a northwestern-southeastern dipole in forest productivity and radial-growth anomalies. Summer JSL variability over the eastern North Atlantic-European domain (5-40E) exerts the strongest impact on European beech, inducing anomalies of up to 30% in modelled gross primary productivity and 50% in radial tree growth. The net effects of JSL movements on terrestrial carbon fluxes depend on forest density, carbon stocks, and productivity imbalances across biogeographic regions.
A large part of carbon in forest ecosystems is stored in the soil. Large-scale inventories of soil C stocks in European forests have been published. Nevertheless, detailed site-specific studies are ...still necessary, because C storage is spatially highly variable and depends on site specific soil, ecological and management factors, which cannot be captured by large scale studies.
Here, we assess C stocks in a coastal forest at the Baltic Sea with different tree species, stand ages, management, and soils, to elucidate possible causes for differences in carbon storage. Soil samples were taken down to 1 m depth both from soil profile pits with 250 cm3 cores and by auger cores in the years 2017–2019 in forest treatment plots which varied with respect to forest management, tree species (beech, birch, oak), and tree age. Although the abiotic parameters soil type (mainly gleysol and podsol), soil texture (mainly sandy), pH value, groundwater depth and distance to the coast were not part of the treatment design, these factors were – along with the biotic factors – evaluated to foster our understanding of the importance of possible drivers of carbon storage in forests. Soil carbon stocks were evaluated for 0–1 m soil depth using measured C concentrations in the soil samples and bulk densities. Carbon stocks in the vegetation were determined by detailed stand inventories of the trees on the forest plots.
Total ecosystem carbon stocks were on average 50 kg C m−2, i.e., about threefold higher than the reported average values for forest ecosystems worldwide in temperate climates. Soil C stocks were on average 32 kg C m−2 (0–1 m depth). This is distinctly higher than soil C stocks reported for most other forest sites in similar climatic conditions, and is likely caused by widespread occurrence of anaerobic conditions in the soil, but also by high bioproductivity due to good water availability and low drought stress. Variability of soil carbon stocks at this site is predominantly governed by soil factors (soil type, soil texture, soil pH), whereas tree carbon stocks are mainly determined by tree species and tree age.
•High soil carbon stocks (> 30 kg C m−2) in coastal forest on sandy gley/podsol soils.•Ecosystem C stock (50 kg C m−2), 3 times higher than average of temperate forests.•Soil carbon stocks influenced mainly by soil factors (soil type, soil pH, texture).•Carbon stocks in vegetation predominantly determined by tree species and tree age.
•The uniformitarian principle is the basis for extrapolating into the past.•The dendro-community uses this principle inconsistently and partially incorrect.•We propose a simple, logical and ...straightforward interpretation.
The uniformitarian principle is one of the most important foundations of all dendro- and paleo-sciences. Without it, no inferences about the past can be made. However, the use of this principle in our community is not consistent and partially incorrect, with the main confusion relating to the understanding of the “uniformitarian principle” as somehow implying a stable relationship between climate and tree growth. To solve this, we look briefly at the history of the term, show how we teach this principle in our textbooks, give some examples of incorrect applications of this principle in the recent literature and close with a simple, logical and straightforward interpretation of this principle to the dendro-community. Applying the principle of aggregate tree growth we show that instable climate-growth relationships and the “no-analogue problem” are not a violation of the uniformitarian principle, but rather reflect our incomplete understanding of tree growth processes. Simply stated: The “uniformitarian principle” is an a priori assumption of spatial and temporal invariance of law’s describing nature’s processes. Applied to the dendro-sciences it means that the principle of aggregate tree growth is valid in time and space.
ABSTRACT
Among the many concerns for biodiversity in the Anthropocene, recent reports of flying insect loss are particularly alarming, given their importance as pollinators, pest control agents, and ...as a food source. Few insect monitoring programmes cover the large spatial scales required to provide more generalizable estimates of insect responses to global change drivers.
We ask how climate and surrounding habitat affect flying insect biomass using data from the first year of a new monitoring network at 84 locations across Germany comprising a spatial gradient of land cover types from protected to urban and crop areas.
Flying insect biomass increased linearly with temperature across Germany. However, the effect of temperature on flying insect biomass flipped to negative in the hot months of June and July when local temperatures most exceeded long‐term averages.
Land cover explained little variation in insect biomass, but biomass was lowest in forests. Grasslands, pastures, and orchards harboured the highest insect biomass. The date of peak biomass was primarily driven by surrounding land cover, with grasslands especially having earlier insect biomass phenologies.
Standardised, large‐scale monitoring provides key insights into the underlying processes of insect decline and is pivotal for the development of climate‐adapted strategies to promote insect diversity. In a temperate climate region, we find that the positive effects of temperature on flying insect biomass diminish in a German summer at locations where temperatures most exceeded long‐term averages. Our results highlight the importance of local adaptation in climate change‐driven impacts on insect communities.
We introduce the German Malaise Trap Program, a new Germany‐wide monitoring network of flying insects, and analyse spatial and seasonal variation in insect biomass during the first monitoring year (2019).
Flying insect biomass generally increased with temperature. However, in the hottest months, at the locations where temperatures most exceeded long‐term averages, temperature had a negative effect on flying insect biomass.
Grasslands, compared to forests, urban areas, or cropland, tended to support the greatest insect biomass, and had the earliest phenological peaks of flying insect biomass.
Competition effects and management related disturbances can contribute to strong non-climatic signals in ring-width trends of trees from closed canopy forests. Removing this noise comes at the price ...of losing a considerable amount of (climatic) information on decadal and centennial time scales. Alternatively, open grown solitary trees, which never competed for light or other resources could function as less biased climate proxies. To explore this potential we analysed individual growth trends and climate-growth relationships of solitary oaks, potentially representative of former, open forests, and compared it to those of trees growing in adjacent closed canopy forests. Solitary oaks show differing tree allometry with bigger crowns and lower absolute heights. Their radial growth was significantly higher compared to forest trees. Contrary to our expectations, these solitary oaks show highly individualistic decadal growth trends. Their inter-annual variations are nevertheless in good agreement between individuals and stronger compared to trees from closed canopy forests. Climate –growth analysis revealed a significantly higher drought sensitivity of solitary oaks. Given the typical open medieval forest structure of large trees with extensive crowns growing in a mosaic of grazed woodlands and grasslands, it is likely that these trees contribute to the historical part of tree-ring collections. When trees from today’s denser forests forming the recent parts of the collections are used to calibrate reconstruction models, the differing drought sensitivity might therefore lead to an overestimation of historical droughts.
For the first time, evidence of a submerged pine forest from the early Holocene can be documented in a central European lake. Subaquatic tree stumps were discovered in Lake Giesenschlagsee at a depth ...of between 2 and 5 m using scuba divers, side‐scan sonar and a remotely operated vehicle. Several erect stumps, anchored to the ground by roots, represent an in situ record of this former forest. Botanical determination revealed the stumps to be Scots pine (Pinus sylvestris) with an individual tree age of about 80 years. The trees could not be dated by means of dendrochronology, as they are older than the regional reference chronology for pine. Radiocarbon ages from the wood range from 10 880±210 to 10 370±130 cal. a BP, which is equivalent to the mid‐Preboreal to early Boreal biozones. The trees are rooted in sedge peat, which can be dated to this period as well, using pollen stratigraphical analysis. Tilting of the peat bed by 4 m indicates subsidence of the ground due to local dead ice melting, causing the trees to become submerged and preserved for millennia. Together with recently detected Lateglacial in situ tree occurrences in nearby lakes, the submerged pine forest at Giesenschlagsee represents a new and highly promising type of geo‐bio‐archive for the wider region. Comparable in situ pine remnants occur at some terrestrial (buried setting) and marine (submerged setting) sites in northern central Europe and beyond, but they partly differ in age. In general, the in situ pine finds document shifts of the zonal boreal forest ecosystem during the late Quaternary.
Tree growth depends, among other factors, largely on the prevailing climatic conditions. Therefore, changes to tree growth patterns are to be expected under climate change. Here, we analyze the ...tree-ring growth response of three major European tree species to projected future climate across a climatic (mostly precipitation) gradient in northeastern Germany. We used monthly data for temperature, precipitation, and the standardized precipitation evapotranspiration index (SPEI) over multiple time scales (1, 3, 6, 12, and 24 months) to construct models of tree-ring growth for Scots pine (Pinus sylvestris L.) at three pure stands, and for common beech (Fagus sylvatica L.) and pedunculate oak (Quercus robur L.) at three mature mixed stands. The regression models were derived using a two-step approach based on partial least squares regression (PLSR) to extract potentially well explaining variables followed by ordinary least squares regression (OLSR) to consolidate the models to the least number of variables while retaining high explanatory power. The stability of the models was tested through a comprehensive calibration-verification scheme. All models were successfully verified with R²s ranging from 0.21 for the western pine stand to 0.62 for the beech stand in the east. For growth prediction, climate data forecasted until 2100 by the regional climate model WETTREG2010 based on the A1B Intergovernmental Panel on Climate Change (IPCC) emission scenario was used. For beech and oak, growth rates will likely decrease until the end of the 21st century. For pine, modeled growth trends vary and range from a slight growth increase to a weak decrease in growth rates. The climatic gradient across the study area will possibly affect the future growth of oak with larger growth reductions towards the drier east. For beech, site-specific adaptations seem to override the influence of the climatic gradient. We conclude that Scots pine has great potential to remain resilient to projected climate change without any greater impairment, whereas common beech and pedunculate oak will likely face lesser growth under the expected warmer and dryer climate conditions. The results call for an adaptation of forest management to mitigate the negative effects of climate change for beech and oak.
Scots pine (Pinus sylvestris L.) is a widely used tree species in European dendroclimatology studies due to its common distribution across much of the continent. Almost all studies find radial growth ...strongly related to summer temperature, a result reflecting site selection at high elevation/latitude environments where trees grow at their ecophysiological limits. Due to the amount of attention spent on these sites there is a geographical and seasonal bias in temperature reconstructions based upon tree‐ring proxies in Europe. To overcome the limited availability of tree‐ring data in temperate lowlands, we present a northern Poland ring‐width chronology developed from living and historic Scots pine material with a strong common growth signal going back to AD 1200. Investigations into climate‐growth relationships found year‐to‐year ring‐width variability to be more strongly correlated to cold season temperature (November to April) prior to the growing season than summer temperatures during tree‐ring formation. Based on this relationship it was possible to reconstruct cold season temperature conditions for the last 810 years. Spatial field correlations with gridded instrumental records indicated that the reconstruction provides relevant cold season temperature information across the land regions bordering the North Atlantic Ocean and Baltic Sea, lowlands and uplands of western and central Europe, and the eastern and central interior of Russia. Despite an unsuccessful attempt to find a stationary relationship with the North Atlantic Oscillation, comparisons with several cold season temperature reconstructions confirmed the long‐term connection between our reconstructed temperature series for northern Poland and the wider area.
In this study, we explore the potential to reconstruct lake-level (and groundwater) fluctuations from tree-ring chronologies of black alder (Alnus glutinosa L.) for three study lakes in the ...Mecklenburg Lake District, northeastern Germany. As gauging records for lakes in this region are generally short, long-term reconstructions of lake-level fluctuations could provide valuable information on past hydrological conditions, which, in turn, are useful to assess dynamics of climate and landscape evolution. We selected black alder as our study species as alder typically thrives as riparian vegetation along lakeshores. For the study lakes, we tested whether a regional signal in lake-level fluctuations and in the growth of alder exists that could be used for long-term regional hydrological reconstructions, but found that local (i.e. site-specific) signals in lake level and tree-ring chronologies prevailed. Hence, we built lake/groundwater-level reconstruction models for the three study lakes individually. Two sets of models were considered based on (1) local tree-ring series of black alder, and (2) site-specific Standardized Precipitation Evapotranspiration Indices (SPEI). Although the SPEI-based models performed statistically well, we critically reflect on the reliability of these reconstructions, as SPEI cannot account for human influence. Tree-ring based reconstruction models, on the other hand, performed poor. Combined, our results suggest that, for our study area, long-term regional reconstructions of lake-level fluctuations that consider both recent and ancient (e.g., archaeological) wood of black alder seem extremely challenging, if not impossible.
Provider: - Institution: - Data provided by Europeana Collections- Greifswald, Univ., Diss., 2015- All metadata published by Europeana are available free of restriction under the Creative Commons CC0 ...1.0 Universal Public Domain Dedication. However, Europeana requests that you actively acknowledge and give attribution to all metadata sources including Europeana
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