forest dieback
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2022 ◽  
Vol 314 ◽  
pp. 108787
Author(s):  
Laura Marqués ◽  
Kiona Ogle ◽  
Drew M.P. Peltier ◽  
J. Julio Camarero
Keyword(s):  

2021 ◽  
Author(s):  
Simon Willcock ◽  
Gregory Cooper ◽  
John Addy ◽  
John Dearing

Abstract The world’s ecosystems are undergoing unprecedented changes due to the impact of climate change and local human activities. A major concern is the possibility of tipping points where ecosystems and landscapes change abruptly to undesirable states. We consider what happens to the timing of tipping points when current stresses strengthen whilst systems experience additional stresses and/or extreme events. We run experiments on four mathematical models that simulate tipping points in lake water quality, the Easter Island community, the Chilika lagoon fishery, and forest dieback. We show that the strongest impacts occur under increasing levels of primary stress, but additional and more extreme stresses in all four models bring the tipping points significantly closer to today. Translating the results to the real world underlines the need for humanity to reduce damaging disturbances and global warming, and to be vigilant for signs that natural systems are degrading more rapidly than previously thought.


2021 ◽  
Author(s):  
Jérémy Cours ◽  
Lucas Sire ◽  
Sylvie Ladet ◽  
Hilaire Martin ◽  
Guillem Parmain ◽  
...  

Abstract Context: Forest ecosystems worldwide are facing increasing drought-induced dieback, causing mortality patches across the landscape at multiple scales. This increases the supply of biological legacies and differentially affects forest insect communities.Objectives: We analysed the relative effects of local- and landscape-level dieback on local saproxylic beetle assemblages. We assessed how classic concepts in spatial ecology (e.g. habitat-amount and habitat-patch hypotheses) are involved in relationships between multi-scale spatial patterns of available resources and local communities.Methods: We sampled saproxylic beetle assemblages in commercial fir forests in the French highlands. Through automatic aerial mapping, we used dead tree crowns to assess dieback levels at several nested spatial scales. We analysed beetle taxonomic, phylogenetic and functional diversity related to differing levels of multi-scale dieback.Results: In line with the habitat-amount hypothesis, taxonomic and functional diversity, but not phylogenetic diversity, of beetle assemblages significantly benefitted from forest dieback, at both local and landscape scales. Very few single or interaction effects were detected in the multiplicative models combining local and landscape variables, though a significant positive effect of landscape-scale dieback on the abundance of cavity- and fungus-dwelling species was consistent with a spill-over effect. Increased landscape-scale dieback also caused a functional specialisation of beetle assemblages, favouring those related to large-diameter, well-decayed deadwood.Conclusions: Increasing tree mortality under benign neglect provides conservation benefits by heterogenising the forest landscape and enhancing deadwood habitats. Legacy retention practices could take advantage of unharvested, declining forest stands to promote species richness and functional diversity within conventionally managed forest landscapes.


Author(s):  
João Filipe ◽  
Paul Rymer ◽  
Margaret Byrne ◽  
Giles Hardy ◽  
Richard Mazanec ◽  
...  

Temperature and precipitation regimes are rapidly changing, resulting in forest dieback and local extinction events, particularly in Mediterranean-type climates. Strategic forest management approaches that enhance forests’ resilience to future climates are urgently required, however adaptation to climates in heterogeneous landscapes with multiple selection pressures may be complex. For widespread trees in Mediterranean-type climates we hypothesized that patterns of local adaptation are associated with climate; precipitation is a stronger factor of adaptation than temperature; functionally related genes show similar signatures of adaptation; and adaptive variants are independently sorting across the landscape. To test our hypotheses, we sampled 28 populations across the geographic and climatic distribution of Eucalyptus marginata (jarrah), in south-west Western Australia, and obtained 13,534 independent single nucleotide polymorphic (SNP) markers across the genome. While overall levels of population differentiation were low (FST=0.04), environmental association analyses found a total of 2,336 unique SNPs potentially associated with five climate variables of temperature and precipitation. Allelic turnover was identified for SNPs associated with temperate seasonality and mean precipitation of the warmest quarter (39.2% and 36.9% deviance explained, respectively), suggesting that both temperature and precipitation are important factors in adaptation. SNPs within similarly function genes, according to gene ontology enrichment analysis, had analogous allelic turnover along climate gradients, while SNPs among temperature and precipitation variables had orthogonal patterns of adaptation. These contrasting patterns of adaptation provide evidence that there may be standing genomic variation adapted to changing climates, providing the substrate needed to promote adaptive management strategies to bolster forest resilience in the future.


Forests ◽  
2021 ◽  
Vol 12 (9) ◽  
pp. 1180
Author(s):  
Ester González de Andrés ◽  
María Laura Suárez ◽  
José Ignacio Querejeta ◽  
J. Julio Camarero

Forest dieback and mortality episodes triggered by droughts are receiving increasing attention due to the projected increases in these extreme climate events. However, the role played by nutrient impairment in dieback is understudied, despite interactions among carbon-water balances and nutrition. Here, we followed a comparative analysis of long-term growth, intrinsic water-use efficiency (iWUE), oxygen isotopes (δ18O) and wood-nutrient composition patterns between living (L) and dead (D) trees of a Nothofagus dombeyi population, showing dieback in Argentina. The onset of the growth decline of D trees occurred ca. 40 years before death. These trees showed higher iWUE, pointing to higher drought stress. Their lower δ18O values, together with the uncoupling between δ18O and leaf-level processes, suggested a deeper source of water uptake for this vigor class. D trees showed a poorer nutritional status than L trees that likely amplified the dieback. This was supported by numerous positive associations of P- and K-concentrations in wood and related ratios with iWUE, δ18O and tree growth. Therefore, drought-related nutrient deterioration can significantly contribute to dieback and be an early warning signal of impending tree death.


2021 ◽  
Vol 12 ◽  
Author(s):  
Cristina Valeriano ◽  
Antonio Gazol ◽  
Michele Colangelo ◽  
Ester González de Andrés ◽  
J. Julio Camarero

Forest dieback because of drought is a global phenomenon threatening particular tree populations. Particularly vulnerable stands are usually located in climatically stressing locations such as xeric sites subjected to seasonal drought. These tree populations show a pronounced loss of vitality, growth decline, and high mortality in response to extreme climate events such as heat waves and droughts. However, dieback events do not uniformly affect stands, with some trees showing higher symptoms of drought vulnerability than other neighboring conspecifics. In this study, we investigated if trees showing different vulnerabilities to dieback showed lower growth rates (Grs) and higher sensitivities to the climate in the past using dendroecology and the Vaganov-Shashkin (VS) process-based growth model. We studied two Pinus pinaster stands with contrasting Grs showing recent dieback in the Iberian System, north-eastern Spain. We compared coexisting declining (D) and non-declining (ND) trees with crown defoliation values above and below the 50% threshold, respectively. The mean growth rate was lower in D than in ND trees in the two stands. The two vigor classes showed a growth divergence prior to the dieback onset and different responsiveness to climate. The ND trees were more responsive to changes in spring water balance and soil moisture than D trees, indicating a loss of growth responsiveness to the climate in stressed trees. Such an interaction between water availability and vigor was reflected by the VS-model simulations, which provided evidence for the observation that growth was mainly limited by low soil moisture in both sites. Such an interaction between water availability and vigor was reflected by the VS-model simulations, which provided evidence for the observation that growth was mainly limited by low soil moisture in both sites. The presented comparisons indicated different stand vulnerabilities to drought contingent on-site conditions. Further research should investigate the role played by environmental conditions and individual features such as access to soil water or hydraulic traits and implement them in process-based growth models to better forecast dieback.


Forests ◽  
2021 ◽  
Vol 12 (8) ◽  
pp. 1104
Author(s):  
Sabine Rosner ◽  
Sebastian Nöbauer ◽  
Klara Voggeneder

Research Highlights: novel fast and easily assessable proxies for vulnerability to cavitation of conifer sapwood are proposed that allow reliable estimation at the species level. Background and Objectives: global warming calls for fast and easily applicable methods to measure hydraulic vulnerability in conifers since they are one of the most sensitive plant groups regarding drought stress. Classical methods to determine P12, P50 and P88, i.e., the water potentials resulting in 12, 50 and 88% conductivity loss, respectively, are labour intensive, prone to errors and/or restricted to special facilities. Vulnerability proxies were established based on empirical relationships between hydraulic traits, basic density and sapwood anatomy. Materials and Methods: reference values for hydraulic traits were obtained by means of the air injection method on six conifer species. Datasets for potential P50 proxies comprised relative water loss (RWL), basic density, saturated water content as well as anatomical traits such as double wall thickness, tracheid lumen diameter and wall/lumen ratio. Results: our novel proxy P25W, defined as 25% RWL induced by air injection, was the most reliable estimate for P50 (r = 0.95) and P88 (r = 0.96). Basic wood density (r = −0.92), tangential lumen diameters in earlywood (r = 0.88), wall/lumen ratios measured in the tangential direction (r = −0.86) and the number of radial cell files/mm circumference (CF/mm, r = −0.85) were also strongly related to P50. Moreover, CF/mm was a very good predictor for P12 (r = −0.93). Conclusions: the proxy P25W is regarded a strong phenotyping tool for screening conifer species for vulnerability to cavitation assuming that the relationship between RWL and conductivity loss is robust in conifer sapwood. We also see a high potential for the fast and easily applicable proxy CF/mm as a screening tool for drought sensitivity and for application in dendroecological studies that investigate forest dieback.


Author(s):  
Buho Hoshino ◽  
Daishi Matsukawa ◽  
Takashi Sasamura ◽  
Tserendulam Tserenochir ◽  
Uuganbayar Ganbold ◽  
...  

Author(s):  
Anna K. Gdula ◽  
Piotr Skubała ◽  
Bogna Zawieja ◽  
Dariusz J. Gwiazdowicz

AbstractThe fruiting bodies of bracket fungi are a specific microhabitat colonized by various invertebrates of which mites (Acari) are rarely studied, and if they are, the study is usually faunistic. The aim of the research was to determine whether the diversification of mite assemblages (Mesostigmata, Oribatida) inhabiting the fruiting bodies of Fomitopsis pinicola (Sw.) P. Karst. (Polyporales) are connected with the character of the forests and/or the degree of decay (DD) of the fruiting bodies. The research was conducted at Białowieża National Park (BNP), in forests close to natural ones and in Karkonosze National Park (KNP) which was affected by a large-scale forest dieback in the 1980s. Eighty fruiting bodies (40 at each study site) of F. pinicola belonging to four DD categories were collected. In total, 4,345 individuals of 120 mite species were recorded at BNP, and 13,912 individuals of 96 species were recorded at KNP. Analyses revealed that the sample dispersion at each study site was comparable, nevertheless the samples from each study site were clearly grouped into slightly overlapping sets which allow observation of the differences between them. In the less decayed fungi (DD 1 and 2) there were fewer mite species and individual mites than in the more decayed samples (DD 3 and 4). There were also significant differences between the fauna of the fungi in each particular DD: the fauna of DD 1 differed from all others, whereas the fauna of heavily decayed fungi (DD 3 and 4) was more comparable.


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