Continuous availability of food resources, such as pollen, is vital for many insects that provide pollination and pest control services to agriculture. However, there is a lack of knowledge about the ...shared or complementary use of floral resources by such species, which hampers more effective landscape management to simultaneously promote them in agroecosystems.
Here, we simultaneously quantified pollen use by a bumblebee (Bombus terrestris) and a mason bee (Osmia bicornis), two bee species recognized as important crop pollinators, as well as a lacewing (Chrysoperla carnea) and a ladybeetle species (Harmonia axyridis), both common predators of crop aphids, throughout the season in 23 agricultural landscapes in Germany and Switzerland.
Pollen diets were more diverse and similar among C. carnea and H. axyridis compared to the two bee species, but all four species shared key pollen types early in the season such as Acer, Quercus, Salix and Prunus. All species exhibited a pronounced shift in pollen sources from primarily woody plants (mainly trees) in spring to primarily herbaceous plants in summer. The majority of pollen (overall ≥64%) came from non‐agricultural plants even in crop‐dominated landscapes.
Synthesis and applications. Our results highlight the importance of trees as pollen sources for many insect species, particularly early in the season. Our findings support incentives that promote heterogeneous agricultural landscapes including both woody and herbaceous semi‐natural habitats, ensuring phenological complementarity of floral resources for insect species that can provide pollination and pest control services to agriculture. The identified key plant species can help to design and optimize agri‐environment schemes to promote these functionally important insects.
Recent successful Eucalyptus marker-based studies are e.g. Larochelle and others (2018) and Salonen and others (2018). ...there is no need to question the Eucalyptus marker procedure, especially ...given the clear linkage found by the authors that shows that counts of Eucalyptus pollen grains could be used to carefully estimate the mean Lycopodium spore concentrations, if only absolute numbers of Eucalyptus would be known (Maher, 2000). Furthermore, the differences in pollen percentages between the centrifugation-based methods (FESTI, EICHLER) compared to the filtration- and evaporation-based methods indicates a clear variation in pollen composition (pollen percentages), which is independent from marker-based concentration estimates. ...as Festi and others (2019) correctly repeat, the method differences have important implications for the interpretation of pollen records with a preferential loss of vesiculate pollen when using centrifugation-based methods, which is one of the fundamental conclusions in our method comparison (Brugger and others, 2018a). ...Festi and others (2019) arguments do not change that several of the evaluated approaches (e.g. BRUGGER, LIU; Liu and others, 1998; Brugger and others, 2018a) result in more stable ratios between the two markers and group closer to expected values, than others (e.g. FESTI, EICHLER; Eichler and others, 2011; Festi and others, 2015).
The layer B is one of the lower layers of the long stratigraphic sequence of the Kamyana Mohyla 1 site. The layer B received eight new AMS radiocarbon dates that clarified its chronology: 7950–7300 ...calibrated years BC. They are in a reasonable correspondence with the dates for lower and upper layers. The lithic assemblage belongs to Kukrek cultural aspect. It is characterized by pencil-like conical cores, Kukrek inserts, Kukrek burins and Dęby burins, nongeometric microliths (oblique points). The assemblage finds close parallels in the sites of Kukrek, Ihren VIII, Melnychna Krucha SU4 and Domchi-Kaia. They can be united into Kukrek
cultural unit. The overlying layer C yielded somewhat different complex that finds parallels in the materials of the so-called “Kukrek cultural tradition.” Due to clear stratigraphic position of these units in the Kamyana Mohyla 1 sequence, we are able to differentiate Kukrek
and “Kukrek cultural tradition” and suggest their respective chronological positions.
Wild bumblebees are key pollinators of crops and wild plants that rely on the continuous availability of floral resources. A better understanding of the spatio-temporal availability and use of floral ...food resources may help to promote bumblebees and their pollination services in agricultural landscapes. We placed colonies of Bombus terrestris L. in 24 agricultural landscapes with various degrees of floral resource availability and assessed different parameters of colony growth and fitness. We estimated pollen availability during different periods of colony development based on detailed information of the bumblebee pollen diet and the spatial distribution of the visited plant species. Total pollen availability did not significantly explain colony growth or fitness. However, when using habitat maps, the weight gain of colonies, the number of queen cells, and colony survival decreased with increasing distance from the forest. The better explanation of bumblebee performance by forest proximity than by (plant-inferred) pollen availability indicates that other functions of forests than pollen provision were important. The conservation of forests next to agricultural land might help to sustain high populations of these important wild pollinators and enhance their crop pollination services. Combining different mapping approaches might help to further disentangle complex relationships between B. terrestris and their environment in agricultural landscapes.
Aims: The aim of this study is to explore the migration (colonization of new areas) and subsequent population expansion (within an area) since 15
ka cal BP of
Abies,
Fagus,
Picea, and
Quercus into ...and through the Alps solely on the basis of high-quality pollen data.
Methods: Chronologies of 101 pollen sequences are improved or created. Data from the area delimited by 45.5–48.1°N and 6–14°E are summarized in three ways: (1) in a selection of pollen-percentage threshold maps (thresholds 0.5%, 1%, 2%, 4%, 8%, 16%, and 32% of land pollen); (2) in graphic summaries of 250-year time slices and geographic segments (lengthwise and transverse in relation to the main axis of the Alps) as pollen-percentage curves, pollen-percentage difference curves, and pollen-percentage threshold ages cal BP graphed against both the length and the transverse Alpine axes; and (3) in tables showing statistical relationships of either pollen-percentage threshold ages cal BP or pollen expansion durations (=time lapse between different pollen-percentage threshold ages cal BP) with latitude, longitude, and elevation; to establish these relationships we used both simple linear regression and multiple linear regression after stepwise-forward selection.
Results: The statistical results indicate that (a) the use of pollen-percentage thresholds between 0.5% and 8% yield mostly similar directions of tree migration, so the method is fairly robust, (b)
Abies migrated northward,
Fagus southward,
Picea westward, and
Quercus northward; more detail does not emerge due to an extreme scarcity of high-quality data especially along the southern foothills of the Alps and in the eastern Alps. This scarcity allows the reconstruction of one immigration route only of
Abies into the southern Alps. The speed of population expansion (following arrival) of
Abies increased and of
Picea decreased during the Holocene, of
Fagus it decreased especially during the later Holocene, and of
Quercus it increased especially at the start of the Holocene.
The termination of the Last Ice Age after the Last Glacial maximum (LGM) represents a dynamic period in the history of the circum-north Atlantic region. So far, there are few reliably dated climatic ...reconstructions covering the Lateglacial period prior to 14,700 cal. BP in Central and Northern Europe. We present a new chironomid record for the period 18,000–14,000 cal. BP, from Burgäschisee, Switzerland. Chironomid assemblages immediately following glacier retreat were dominated by taxa indicative of cold, oligotrophic conditions such as Sergentia coracina -type and Micropsectra radialis -type. A gradual transition to assemblages with moderate abundances of taxa indicative of warmer climatic conditions such as Dicrotendipes nevosus -type and Tanytarsus glabrescens -type started after ca. 16,100 cal. BP. This initial and gradual chironomid assemblage shift culminated in a more pronounced and rapid inferred temperature change at the Oldest Dryas/Bølling transition at ca. 14,700 cal. BP, where further types indicative of warm conditions such as Tanytarsus lactescens -type first occurred and replaced chironomids indicative of colder conditions such as Paracladius and Protanypus. We estimated past July air temperature changes from the chironomid assemblages by applying to the record a chironomid-temperature transfer function that is based on chironomid distribution data from 274 lakes in Switzerland and Norway. The resulting reconstruction, which features a sample-specific root mean square error of prediction of 1.36–1.46 °C, indicates temperatures around 9 °C at the beginning of the record. An initial gradual warming phase initiating at ca. 16,100 cal. BP is recorded reaching values around 10 °C for the period 16,100–15,500 cal. BP. Temperatures continue to increase reaching values around 12 °C for the period preceding the Bølling warming, when temperatures rose rapidly to values around 15 °C. The early temperature rise to values of 10–12 °C prior to the Bølling warming agrees with widespread vegetation changes recently reported for this region based on palaeobotanical analyses, which indicate a shift from herbaceous tundra to shrub tundra with low density tree birch stands with open canopies. Together, these results suggest an earlier Lateglacial temperature increase in southwest Central Europe than expected based on earlier palaeobotanical reconstructions, although with a less pronounced warming than has been reported for ca. 16,000 cal. BP from south of the Alps. This early Lateglacial warming agrees with glacier reconstructions which suggest several step-wise reductions of glacier extent in this period as well as with evidence from other palaeotemperature reconstructions and suggests that not only Southern Europe but significant parts of Europe north of the Alps may have been characterized by early Lateglacial warming well before the rapid warming at ca. 14,700 cal. BP.
•We report Central European warming ca. 1300 years before the Bølling warming.•This Pre-Bølling warming coincided with a shift from tundra to shrub tundra.•This warming agrees with other palaeoclimate records from Central and South Europe.
Natural succession trajectories of Central European forest ecosystems are poorly understood due to the absence of long‐term observations and the pervasive effects of past human impacts on today's ...vegetation communities. This knowledge gap is significant given that currently forest ecosystems are expanding in Europe as a consequence of global change.
Annually laminated sediments were extracted from two small lowland lakes (Moossee 521 m a.s.l.; Burgäschisee 465 m a.s.l.) on the Swiss Plateau. We combine high‐resolution palaeoecological and quantitative analyses to assess changes in vegetation during the Neolithic. We test for regionally synchronous land‐use phases and plant successional patterns that may originate from complex interactions between human and climatic impacts.
Mixed Fagus sylvatica forests dominated the Swiss Plateau vegetation over millennia. During the period 6,500–4,200 cal year bp, pronounced forest disruptions accompanied by increased fire and agricultural activities occurred at c. 6,400–6,000 cal year bp, 5,750–5,550 cal year bp, around 5,400 cal year bp and at 5,100–4,600 cal year bp. Biodiversity increased during these land‐use phases, likely in response to the creation of new open habitats. After decades to centuries of land‐use, arboreal vegetation re‐expanded. In a first succession stage, heliophilous Corylus avellana shrubs were replaced by pioneer Betula trees. These open arboreal communities were out‐competed within 150–200 years by late‐successional F. sylvatica and Abies alba forests. Most strikingly, cross‐correlations show that these successions occurred synchronously (±11 years) and repeatedly over large areas (>1,000 km2) and millennia.
Synthesis. First notable human impact shaped the primeval mixed Fagus sylvatica forests in Central Europe from c. 6,800–6,500 cal year bp on. Agrarian societies were susceptible to climate changes and we hypothesize that climate‐induced, simultaneous agricultural expansion and contraction phases resulted in synchronous regional forest successions. Currently, forests are expanding in Central Europe as a result of land abandonment in marginal areas. Our results imply that mixed Fagus sylvatica forests with Abies alba and Quercus may re‐expand rapidly in these areas, if climate conditions will remain within the range of the mid‐Holocene climatic variability (with summers c. +1–2°C warmer than today).
First notable human impact shaped the primeval mixed Fagus sylvatica forests in Central Europe from c. 6,800–6,500 cal year BP on. Agrarian societies were susceptible to climate changes and we hypothesize that climate‐induced, simultaneous agricultural expansion and contraction phases resulted in synchronous regional forest successions over millennia.
20th century eutrophication and global spread of anoxia is a threat for freshwater ecosystems. Little is known about Holocene anoxia and meromixis events when anthropogenic impacts were weaker and ...natural ecosystem variability played the dominant role. In this study, we examine the relationship between lake mixing and lake production, climate variability, vegetation cover, catchment erosion and (pre)historic anthropogenic impacts in Moossee (Switzerland), over the last 15,000 years. We use sub-annually resolved calibrated hyperspectral imaging data (total chlorophyll for paleoproduction, bacteriopheophytin for anoxia and meromixis) combined with X-ray fluorescence and pollen data. Production shows a first increase at 14,500 cal yr BP, a further increase after 7500 cal BP, relative maxima in the late Bronze, Iron and Middle Ages, and the unprecedented peak in the 20th Century. Until 7500 cal BP, the lake was well mixed with only scarce phases of seasonal to multiannual anoxia. Repeated meromixis events occurred between 7500 and 2500 cal BP when temperatures were high, forests closed, and lake production was already enhanced. After the forests were cleared (2500 cal BP) the lake remained mostly holomictic. Holocene meromixis events were systematically terminated by local deforestation related to Neolithic and Bronze Age lakeshore settlements: charcoal peaked, tree pollen dropped below a threshold of 80%, soil erosion and lake production increased and bacteriopheophytin disappeared. Meromixis re-established after the termination of lakeshore settlements and the onset of afforestation with tree pollen exceeding 80%. These repeated cycles unambiguously document how even early human societies affected the mixing regime and biogeochemical cycling in this lake.
•First Late Glacial/Holocene high-resolution paleoproduction and meromixis record.•Sub-varve resolution hyperspectral data provide information about seasonal anoxia.•Early human impact influenced the lake mixing regime.•Closed forest (tree pollen>80%), eutrophication and warm summers prompted meromixis.
Along with the ongoing climate crisis, research efforts increasingly focus on Pleistocene environmental archives. Interglacial periods are of special interest, as they offer crucial information about ...natural interactions (i.e. not influenced by human activities) between climate and ecosystems within a climatic setting comparable to the Holocene and/or climate change projections. The sedimentary infill of the Rodderberg crater, 10 km south of the city of Bonn (Germany), records several glacial-interglacial cycles in superposition, which makes it a rare and promising environmental archive. One of the most challenging targets is to establish a robust chronological framework for the Rodderberg sediment sequence. In the present study we reconstruct the vegetation history of the basal and most prominent interglacial sequence, the lowermost Rodderberg interglacial (LRI), and apply the principles of pollen biostratigraphy to estimate the depositional age. At the base of the sequence steppe tundra conditions prevailed during the cryocratic phase before the onset of the interglacial. Rising temperatures caused afforestation of the landscape with boreal forests during the protocratic phase, which subsequently were replaced by temperate forests in the mesocratic phase. The sequence continues under unstable vegetation conditions characterized by temperate forests dominated by Carpinus and Abies during the oligocratic phase. During the terminal part of the LRI, the telocratic phase, boreal to nemoboreal forests covered the landscape. Due to climatic deterioration these forests collapsed and a steppe tundra evolved again (cryocratic phase). This climate-driven glacial-interglacial cycle is followed by an interstadial with rather closed nemoboreal forest vegetation. Based on the occurrences of characteristic taxa as well as the vegetation assemblages and succession, we refrain from correlating the LRI with any of the warm stages between c. 240 and 180 ka BP, i.e. roughly corresponding to MIS 7. A correlation with the Holsteinian, which was previously physically dated to c. 340–325 ka BP, cannot unambiguously be excluded, however, the absence of Pterocarya during the LRI argues against it. Instead, the LRI has striking similarities with the Kärlich interglacial, which has been previously physically dated to c. 400 ka BP, making it chronologically equivalent to MIS 11.
•We reconstruct the vegetation history of a novel interglacial from Rodderberg, Germany.•An MIS 7 age for the LRI can be excluded with high certainty.•The LRI has striking similarities with the Kärlich interglacial (MIS 11).
PDF
