Geology topics

Willy Tinner

Publications and source records attributed to Willy Tinner.

10 recordsLinked to original sources

USGS2026

Simulating past and future refugia for temperate trees in northern Italy

During the Quaternary, trees responded to the climatic changes of glacial–interglacial cycles with large-scale range shifts. Over cold glacials, temperate tree species contracted their ranges and survived in areas known as refugia. Several studies point to the Euganean Hills (Colli Euganei), in Veneto, northern Italy, as one of the northernmost European refugia of temperate tree species during the Last Glacial Maximum (LGM, ca 23 000–19 000 calibrated years BP). Using LandClim, a spatially explicit, dynamic forest landscape model, we demonstrate that climate conditions during the LGM likely allowed temperate tree species to persist in the Euganean Hills. The identified refugial locations lie at intermediate to high elevations and in sheltered valleys within the hilly complex. Therefore, the combined palaeoecological and modelling evidence suggests that today's temperate forests of the Euganean Hills have a full glacial legacy. Simulations under future climate conditions suggest a collapse of the sub-mediterranean and oro-mediterranean deciduous forests that are prevalent today and the expansion of thermo-mediterranean evergreen forests (with e.g. Quercus ilex , Q. suber , Olea europaea and Pinus sp.). Specifically, the extrazonal population of oro-mediterranean Fagus sylvatica , which is unique to the Po Plain and likely persisted locally through several glacial–interglacial cycles, is predicted to sharply decline and face local extinction, underscoring a conservation hazard.

Ecography↗

USGS2024

Simulating past and future fire impacts on Mediterranean ecosystems

Worldwide, large wildfires are becoming increasingly common, leading to economic damages and threatening ecosystems and human health. Under future climate change, more frequent fire disturbance may push ecosystems into non-forested alternative stable states. Fire-prone ecosystems such as those in the Mediterranean Basin are expected to be particularly vulnerable, but the position of tipping points is unclear. We compare long-term palaeoecological data from Sardinia with output from a process-based dynamic vegetation model to investigate the mechanisms controlling the complex interactions between fire, climate, and vegetation in the past and the future. Our results show that past vegetation changes from Erica -shrublands to mixed evergreen-broadleaved Quercus ilex -dominated forests were driven by a climate-induced fire regime shift. By simulating vegetation dynamics under varying fire regimes, we could reproduce Holocene vegetation trajectories and mechanistically identify tipping points. Without an immediate reduction of greenhouse gas emissions, we simulate future expansion of fire-prone Mediterranean maquis and increasing fire occurrence. Similarly, high anthropogenic ignition frequencies and plantations of non-native, highly flammable trees could induce a shift to fire-adapted Erica shrublands. However, our simulations indicate that if global warming can be kept below 2°C, Quercus ilex forests will be able to persist and effectively reduce fire occurrences and impacts, making them a valuable restoration target in Mediterranean ecosystems. Synthesis . By combining long-term records of ecosystem change with a dynamic vegetation model, we show that past climate-driven fire regime shifts were the main driver of vegetation change, creating alternative stable states that persisted over centuries. Projected future climate change exceeding Holocene variability leads to pronounced vegetation changes and increased fire risks in our simulations, requiring new fire management strategies to maintain current ecosystem services.

Journal of Ecology↗

USGS2022

A new indicator approach to reconstruct agricultural land use in Europe from sedimentary pollen assemblages

The reconstruction of human impact is pivotal in palaeoecological studies, as humans are among the most important drivers of Holocene vegetation and ecosystem change. Nevertheless, separating the anthropogenic footprint on vegetation dynamics from the impact of climate and other environmental factors (disturbances such as fire, erosion, floods, landslides, avalanches, volcanic eruptions) is a challenging and still largely open issue. For this purpose, palynologists mostly rely on cultural indicator pollen types and related indices that consist of sums or ratios of these pollen types. However, the high environmental and biogeographical specificity of cultural indicator plants hinders the application of the currently available indices to wide geographical settings. Furthermore, the achievable taxonomic resolution of cultural indicator pollen types may hamper their indicative capacity. In this study, we propose the agricultural land use probability (LUP) index, a novel approach to quantify human impact intensity on European ecosystems based on cultural indicator pollen types. From the ‘classic’ cultural indicators, we construct the LUP index by selecting those with the best indicator capacity based on bioindication criteria. We first train the LUP index using twenty palynological sequences along a broad environmental gradient, spanning from treeless alpine to subtropical mediterranean evergreen plant communities. We then validate the LUP index using independent pollen datasets and archaeological proxies. Finally, we discuss the suitability of the selected pollen types and the potential of the LUP index for quantifying Holocene human impact in Europe, concluding that careful application of the LUP index may significantly contribute to refining pollen-based land-use reconstructions.

Palaeogeography, Palaeoclimatology, Palaeoecology↗

USGS2021

Alpine glacier reveals ecosystem impacts of Europe's prosperity and peril over the last millennium

Information about past ecosystem dynamics and human activities is stored in the ice of Colle Gnifetti glacier in the Swiss Alps. Adverse climatic intervals incurred crop failures and famines and triggered reestablishment of forest vegetation but also societal resilience through innovation. Historical documents and lake sediments record these changes at local—regional scales but often struggle to comprehensively document continental-scale impacts on ecosystems. Here, we provide unique multiproxy evidence of broad-scale ecosystem, land use, and climate dynamics over the past millennium from a Colle Gnifetti microfossil and oxygen isotope record. Microfossil data indicate that before 1750 CE forests and fallow land rapidly replaced crop cultivation during historically documented societal crises caused by climate shifts and epidemics. Subsequently, with technology and the introduction of more resilient crops, European societies adapted to the Little Ice Age cold period, but resource overexploitation and industrialization led to new regional to global-scale environmental challenges.

Geophysical Research Letters↗

USGS2021

8,000 years of climate, vegetation, fire and land-use dynamics in the thermo-mediterranean vegetation belt of northern Sardinia (Italy)

Knowledge about the vegetation history of Sardinia, the second largest island of the Mediterranean, is scanty. Here, we present a new sedimentary record covering the past ~ 8,000 years from Lago di Baratz, north-west Sardinia. Vegetation and fire history are reconstructed by pollen, spores, macrofossils and charcoal analyses and environmental dynamics by high-resolution element geochemistry together with pigment analyses. During the period 8,100–7,500 cal BP , when seasonality was high and fire and erosion were frequent, Erica arborea and E. scoparia woodlands dominated the coastal landscape. Subsequently, between 7,500 and 5,500 cal BP , seasonality gradually declined and thermo-mediterranean woodlands with Pistacia and Quercus ilex partially replaced Erica communities under diminished incidence of fire. After 5,500 cal BP , evergreen oak forests expanded markedly, erosion declined and lake levels increased, likely in response to increasing (summer) moisture availability. Increased anthropogenic fire disturbance triggered shrubland expansions (e.g. Tamarix and Pistacia ) around 5,000–4,500 cal BP . Subsequently around 4,000–3,500 cal BP evergreen oak-olive forests expanded massively when fire activity declined and lake productivity and anoxia reached Holocene maxima. Land-use activities during the past 4,000 years (since the Bronze Age) gradually disrupted coastal forests, but relict stands persisted under rather stable environmental conditions until ca. 200 cal BP , when agricultural activities intensified and Pinus and Eucalyptus were planted to stabilize the sand dunes. Pervasive prehistoric land-use activities since at least the Bronze Age Nuraghi period included the cultivation of Prunus , Olea europaea and Juglans regia after 3,500–3,300 cal BP , and Quercus suber after 2,500 cal BP . We conclude that restoring less flammable native Q. ilex and O. europaea forest communities would markedly reduce fire risk and erodibility compared to recent forest plantations with flammable non-native trees (e.g. Pinus , Eucalyptus ) and xerophytic shrubland (e.g. Cistus , Erica ).

Sardinia↗

USGS2020

A critical assessment of human-impact indices based on anthropogenic pollen indicators

Anthropogenic pollen indicators in pollen records are an established tool for reconstructing the history of human impacts on vegetation and landscapes. They are also used to disentangle the influence of human activities and climatic variability on ecosystems. The comprehensive anthropogenic pollen-indicator approach developed by Behre (1981) has been widely used, including beyond its original geographical scope of Central and Western Europe. Uncritical adoption of this approach for other areas is risky because adventives (plants introduced with agriculture) in Central Europe can be apophytes (native plants favoured by human disturbances) in other regions. This problem can be addressed by identifying region-specific, anthropogenic-indicator pollen types and/or developing region-specific, human-impact indices from pollen assemblages. However, understanding of regional variation in the timing and intensity of human impacts is limited by the lack of standardization, validation and intercomparison of such regional approaches. Here we review the most common European anthropogenic pollen-indicator approaches to assess their performance at six sites spanning a continental gradient over the boreal, temperate and Mediterranean biomes. Specifically, we evaluate the human-indicator approaches by using independent archaeological evidence and models. We present new insights into how these methodologies can assist in the interpretation of pollen records as well as into how a careful selection of pollen types and/or indices according to the specific geographical scope of each study is key to obtain meaningful reconstructions of anthropogenic activity through time. The evaluated approaches generally perform better in the regions for which they were developed. However, we find marked differences in their capacity to identify human impact, while some approaches do not perform well even in the regions for which they were developed, others might be used, with due caution, outside their original areas or biomes. We conclude that alongside the increasing wealth of pollen datasets a need to develop novel tools may assist numeric human impact reconstructions.

Quaternary Science Reviews↗

USGS2018

Microclimatic gradients provide evidence for a glacial refugium for temperate trees in a sheltered hilly landscape of Northern Italy

Aim Refugia play a key role in conserving biodiversity during periods of unfavourable and highly variable regional climate. However, refugial populations are often small and fragmented, which makes their identification difficult. In this study, we investigate whether an area of complex topography in the southern foreland of the Alps could have provided a suitable microclimate to serve as a glacial refugium for temperate trees during the last glacial. Location The Euganean Hills in Northern Italy (Veneto). Methods We assessed the current microclimatic variability in the ecologically diverse region on a fine scale by recording half‐hourly near‐surface temperatures over a period of 11 months. After comparing our measurements with today's vegetation distribution, broad‐scale synoptic patterns, and topoclimatic factors, we estimated refugial suitability based on extreme temperatures, climatic stability, and difference from the regional average. Results Present‐day temperature gradients within the Euganean Hills are large enough to explain the presence of the temperate tree species Fagus sylvatica as well as Mediterranean Quercus ilex , two species that are absent elsewhere in the adjacent Po Plain. During winter, anticyclonic weather patterns resulted in strong atmospheric inversions, with temperatures increasing by +1°C/100 m in the hills relative to the surrounding Po Plain. Main conclusions Our high‐resolution climate data support multi‐proxy palaeoecological records identifying the Euganean Hills as a refugium for temperate trees. Temperature anomalies of 2–4°C relative to the surrounding Po Plain are sufficient to allow several temperate tree species to survive the Last Glacial Maximum (LGM) in the Euganean Hills under a harsh continental climate. Specifically, elevations >200 m a.s.l. in the central parts of the hills may have provided suitable conditions for local LGM refugia. Regions of complex topography such as the Euganean Hills conserved past and present biodiversity and provide high‐priority areas for conservation under future climate warming.

Journal of Biogeography↗

USGS2017

An empirical perspective for understanding climate change impacts in Switzerland

Planning for the future requires a detailed understanding of how climate change affects a wide range of systems at spatial scales that are relevant to humans. Understanding of climate change impacts can be gained from observational and reconstruction approaches and from numerical models that apply existing knowledge to climate change scenarios. Although modeling approaches are prominent in climate change assessments, observations and reconstructions provide insights that cannot be derived from simulations alone, especially at local to regional scales where climate adaptation policies are implemented. Here, we review the wealth of understanding that emerged from observations and reconstructions of ongoing and past climate change impacts in Switzerland, with wider applicability in Europe. We draw examples from hydrological, alpine, forest, and agricultural systems, which are of paramount societal importance, and are projected to undergo important changes by the end of this century. For each system, we review existing model-based projections, present what is known from observations, and discuss how empirical evidence may help improve future projections. A particular focus is given to better understanding thresholds, tipping points and feedbacks that may operate on different time scales. Observational approaches provide the grounding in evidence that is needed to develop local to regional climate adaptation strategies. Our review demonstrates that observational approaches should ideally have a synergistic relationship with modeling in identifying inconsistencies in projections as well as avenues for improvement. They are critical for uncovering unexpected relationships between climate and agricultural, natural, and hydrological systems that will be important to society in the future.

Regional Environmental Change↗

USGS2016

Holocene vegetation and fire history of the mountains of northern Sicily (Italy)

Knowledge about vegetation and fire history of the mountains of Northern Sicily is scanty. We analysed five sites to fill this gap and used terrestrial plant macrofossils to establish robust radiocarbon chronologies. Palynological records from Gorgo Tondo, Gorgo Lungo, Marcato Cixé, Urgo Pietra Giordano and Gorgo Pollicino show that under natural or near natural conditions, deciduous forests ( Quercus pubescens , Q. cerris , Fraxinus ornus , Ulmus ), that included a substantial portion of evergreen broadleaved species ( Q. suber , Q. ilex , Hedera helix ), prevailed in the upper meso-mediterranean belt. Mesophilous deciduous and evergreen broadleaved trees ( Fagus sylvatica , Ilex aquifolium ) dominated in the natural or quasi-natural forests of the oro-mediterranean belt. Forests were repeatedly opened for agricultural purposes. Fire activity was closely associated with farming, providing evidence that burning was a primary land use tool since Neolithic times. Land use and fire activity intensified during the Early Neolithic at 5000 bc , at the onset of the Bronze Age at 2500 bc and at the onset of the Iron Age at 800 bc . Our data and previous studies suggest that the large majority of open land communities in Sicily, from the coastal lowlands to the mountain areas below the thorny-cushion Astragalus belt (ca. 1,800 m a.s.l.), would rapidly develop into forests if land use ceased. Mesophilous Fagus - Ilex forests developed under warm mid Holocene conditions and were resilient to the combined impacts of humans and climate. The past ecology suggests a resilience of these summer-drought adapted communities to climate warming of about 2 °C. Hence, they may be particularly suited to provide heat and drought-adapted Fagus sylvatica ecotypes for maintaining drought-sensitive Central European beech forests under global warming conditions.

Sicily↗

USGS2016

Holocene paleoclimate inferred from salinity histories of adjacent lakes in southwestern Sicily (Italy)

Marked uncertainties persist regarding the climatic evolution of the Mediterranean region during the Holocene. For instance, whether moisture availability gradually decreased, remained relatively constant, or increased during the last 7000 years remains a matter of debate. To assess Holocene limnology, hydrology and moisture dynamics, the coastal lakes Lago Preola and Gorgo Basso, located in southwestern Sicily, were investigated through several stratigraphic analyses of ostracodes, including multivariate analyses of assemblages, transfer functions of salinity, and biochemical analyses of valves (Sr/Ca, δ 18 O and δ 13 C). During the early Holocene, the Gorgo Basso and Lago Preola ostracode records are similar. After an initial period of moderate salinity (1690–6100 mg/l from ca. 10,000–8190 cal yr BP), syndepositional or diagenetic dissolution of ostracode valves suggests that salinity declined to <250 mg/L from ca. 8190 to 7000 cal yr BP at both sites. After ca. 6250 cal yr BP, the ostracode records are strikingly different. Lago Preola became much more saline, with paleosalinity values that ranged from 2270 to about 24,420 mg/L. We suggest that Lago Preola's change from a freshwater to mesosaline lake at about 6250 cal yr BP was related to sea level rise and resulting intrusion of seawater-influenced groundwater. In contrast, Gorgo Basso remained a freshwater lake. The salinity of Gorgo Basso declined somewhat after 6250 cal yr BP, in comparison to the early Holocene, ranging from about 550 to 1680 mg/L. Cypria ophtalmica , a species capable of rapid swimming and flourishing in waters with low dissolved oxygen levels, became dominant at approximately the time when Greek civilization took root in Sicily (2600 cal yr BP), and it completely dominates the record during Roman occupation (roughly 2100 to 1700 cal yr BP). These freshwater conditions at Gorgo Basso suggest high effective moisture when evergreen olive-oak forests collapsed in response to increased Greco-Roman land use and fire. Ostracode valve geochemistry (Sr/Ca, δ 18 O) suggests significant changes in early vs. late Holocene hydrochemistry, either as changes in salinity or in the seasonality of precipitation. Harmonizing the autecological and geochemical data from Gorgo Basso suggests the latter was more likely, with relatively more late Holocene precipitation falling during the spring, summer, and fall, than winter compared to the early Holocene. Our ostracode-inferred paleosalinity data indicate that moisture availability did not decline during the late Holocene in the central Mediterranean region. Instead, moisture availability was lowest during the early Holocene, and most abundant during the late Holocene.

Trapani Province↗