Site-aspect influence on climate sensitivity over time of a high-altitude Pinus cembra tree-ring network

Abstract. Our understanding of the natural variability of hydroclimate before the instrumental period (ca. 1900 in the United States; US) is largely dependent on tree-ring-based reconstructions. Large-scale soil moisture reconstructions from a network of tree-ring chronologies have greatly improved our understanding of the spatial and temporal variability in hydroclimate conditions, particularly extremes of both drought and pluvial (wet) events. However, certain regions within these large-scale reconstructions in the US have a sparse network of tree-ring chronologies. Further, several chronologies were collected in the 1980s and 1990s, thus our understanding of the sensitivity of radial growth to soil moisture in the US is based on a period that experienced multiple extremely severe droughts and neglects the impacts of recent, rapid global change. In this study, we expanded the tree-ring network of the Ohio River Valley in the US, a region with sparse coverage. We used a total of 72 chronologies across 15 species to examine how increasing the density of the tree-ring network influences the representation of reconstructing the Palmer Meteorological Drought Index (PMDI). Further, we tested how the sampling date influenced the reconstruction models by creating reconstructions that ended in the year 1980 and compared them to reconstructions ending in 2010 from the same chronologies. We found that increasing the density of the tree-ring network resulted in reconstructed values that better matched the spatial variability of instrumentally recorded droughts and to a lesser extent, pluvials. By sampling tree in 2010 compared to 1980, the sensitivity of tree rings to PMDI decreased in the southern portion of our region where severe drought conditions have been absent over recent decades. We emphasize the need of building a high-density tree-ring network to better represent the spatial variability of past droughts and pluvials. Further, chronologies on the International Tree-Ring Data Bank need updating regularly to better understand how the sensitivity of tree rings to climate may vary through time.

Download Full-text

An Overview on Isotopic Divergences – Causes for instability of Tree-Ring Isotopes and Climate Correlations

10.5194/cp-2020-28 ◽

2020 ◽

Author(s):

Martine M. Savard ◽

Valérie Daux

Keyword(s):

Tree Ring ◽

Collaborative Work ◽

Stand Dynamics ◽

Root Functions ◽

Divergence Problem ◽

Climatic Series ◽

Over Time ◽

Process Based Models ◽

Past Conditions

Abstract. Climatic reconstructions based on tree-ring isotopic series convey substantial information about past conditions prevailing in forested regions of the globe. However, in some cases, the relations between isotopic and climatic records appear unstable over time, generating the ‘isotopic divergences’. Former reviews have thoroughly discussed the divergence concept for tree-ring physical properties, but not for isotopes. Here we want to take stock of the isotopic divergence problem, express concerns and stimulate collaborative work for improving paleoclimatic reconstructions. There are five main causes for divergent parts in isotopic and climatic series. (1) Artefacts due to sampling and data treatment, relevant for dealing with long-series using sub-fossil stems. (2) Stand dynamics, including juvenile effects mostly occurring in the early part of tree-ring series. (3) Rise in atmospheric pCO2, which can directly influence the foliar behaviour. (4) Change of climate, which may modify the isotope-climate causal links. Finally (5), atmospheric pollution, which may alter leaf and root functions. Future paleoclimate research would benefit from interdisciplinary efforts designed to develop further process-based models integrating multi-proxy inputs, so to help identify causes of isotopic divergences and circumvent some of them in inverse applications.

Download Full-text

Diseases of high terrestrial altitudes

Oxford Textbook of Medicine ◽

10.1093/med/9780199204854.003.090504 ◽

2010 ◽

pp. 1402-1408

Author(s):

Andrew J. Pollard ◽

Buddha Basnyat ◽

David R. Murdoch

Keyword(s):

High Altitude ◽

Hypobaric Hypoxia ◽

Cell Mass ◽

Red Cell ◽

Physiological Changes ◽

Exposed Individual ◽

Extreme Altitude ◽

First Arrival ◽

The Individual ◽

Over Time

Ascent to altitudes above 2500 m leads to exposure to hypobaric hypoxia. This affects performance on first arrival at high altitude and disturbs sleep, but physiological changes occur over time to defend arterial and tissue oxygenation and allow the individual to adjust. This process of acclimatization includes (1) an increase in the rate and depth of breathing; and (2) an increase in red cell mass, and in red cell 2,3-diphosphoglycerate. Acclimatization is no longer possible at extreme altitude (>5800 m) and the exposed individual will gradually deteriorate....

Download Full-text

Reconstructing drought variability for Mongolia based on a large-scale tree ring network: 1520–1993

Journal of Geophysical Research Atmospheres ◽

10.1029/2010jd013907 ◽

2010 ◽

Vol 115 (D22) ◽

Cited By ~ 42

Author(s):

N. Davi ◽

G. Jacoby ◽

K. Fang ◽

J. Li ◽

R. D'Arrigo ◽

...

Keyword(s):

Tree Ring ◽

Large Scale ◽

Ring Network ◽

Drought Variability

Download Full-text

Global airborne microbial communities controlled by surrounding landscapes and wind conditions

Scientific Reports ◽

10.1038/s41598-019-51073-4 ◽

2019 ◽

Vol 9 (1) ◽

Cited By ~ 16

Author(s):

Romie Tignat-Perrier ◽

Aurélien Dommergue ◽

Alban Thollot ◽

Christoph Keuschnig ◽

Olivier Magand ◽

...

Keyword(s):

Particulate Matter ◽

High Altitude ◽

Microbial Communities ◽

Atmospheric Chemistry ◽

Sampling Site ◽

Temporal Stability ◽

Fungal Species ◽

The World ◽

Bacteria And Fungi ◽

Over Time

Abstract The atmosphere is an important route for transporting and disseminating microorganisms over short and long distances. Understanding how microorganisms are distributed in the atmosphere is critical due to their role in public health, meteorology and atmospheric chemistry. In order to determine the dominant processes that structure airborne microbial communities, we investigated the diversity and abundance of both bacteria and fungi from the PM10 particle size (particulate matter of 10 micrometers or less in diameter) as well as particulate matter chemistry and local meteorological characteristics over time at nine different meteorological stations around the world. The bacterial genera Bacillus and Sphingomonas as well as the fungal species Pseudotaeniolina globaosa and Cladophialophora proteae were the most abundant taxa of the dataset, although their relative abundances varied greatly based on sampling site. Bacterial and fungal concentration was the highest at the high-altitude and semi-arid plateau of Namco (China; 3.56 × 106 ± 3.01 × 106 cells/m3) and at the high-altitude and vegetated mountain peak Storm-Peak (Colorado, USA; 8.78 × 104 ± 6.49 × 104 cells/m3), respectively. Surrounding ecosystems, especially within a 50 km perimeter of our sampling stations, were the main contributors to the composition of airborne microbial communities. Temporal stability in the composition of airborne microbial communities was mainly explained by the diversity and evenness of the surrounding landscapes and the wind direction variability over time. Airborne microbial communities appear to be the result of large inputs from nearby sources with possible low and diluted inputs from distant sources.

Download Full-text

Dendroecological assessment of climate resilience of the rare and scattered forest tree species Tilia cordata Mill. in northwestern Europe

Forestry An International Journal of Forest Research ◽

10.1093/forestry/cpaa011 ◽

2020 ◽

Vol 93 (5) ◽

pp. 675-684

Author(s):

Nicolas Latte ◽

Philippe Taverniers ◽

Tanguy de Jaegere ◽

Hugues Claessens

Keyword(s):

Climate Change ◽

Climatic Change ◽

Tree Ring ◽

Tree Species ◽

Forest Tree ◽

Tilia Cordata ◽

The Past ◽

Lime Tree ◽

Over Time ◽

Forest Managers

Abstract To increase forest resilience to global change, forest managers are often directing forest stands towards a broader diversity of tree species. The small-leaved lime (Tilia cordata Mill.), a rare and scattered species in northwestern Europe, is a promising candidate for this purpose. Its life traits suggest a high resilience to climate change and a favourable impact on forest ecosystem services. This study used a dendroecological approach to assess how lime tree radial growth had responded to the past climatic change. First, 120 lime trees from nine sites were selected in southern Belgium based on criteria adapted to the rareness of the species. Chronology quality was assessed and resulting tree-ring series were validated at site and region levels. Second, a range of dendrochronological methods was used to analyze the changes over time in the variability and long-term trends of lime tree growth and their relation to climate during the period 1955–2016. Last, behaviour of lime trees was compared with that of beech from the same region and time period. For this purpose, the same methodology was applied to an additional beech tree-ring dataset (149 trees from 13 sites). Beech is the climax tree species of the region, but is known to be drought-sensitive and has shown weaknesses in the current climate. The quality of our tree-ring series attests that dendroecological investigation using rare and scattered species is possible, opening the way to further analysis on other such lesser-known forest tree species. The analysis showed that the small-leaved lime had been resilient to the past climatic change in multiple ways. Lime growth increased during the preceding decades despite an increased frequency and intensity of stressful climatic events. Lime growth quickly recovered in the years following the stresses. The growth–climate relationships were either stable over time or had a positive evolution. The behaviour of lime contrasted strongly with that of beech. Lime performed better than beech in every analysis. Small-leaved lime is thus a serious candidate for addressing climate change challenges in the region. It should be considered by forest managers planning to improve the sustainability and resilience of their forests, in particular in vulnerable beech stands.

Download Full-text