Drought events may reduce growth and survival of conifer trees. The effects of the intensity and timing of drought on the growth resilience, including growth reductions during drought and recovery of ...growth after drought, remain, however, highly uncertain.
Growth resilience of 20 conifer species to 11 dry years was compared in a common garden experiment. We assessed (a) the relationships among growth resistance, recovery and resilience, (b) the impacts of different drought dimensions (intensity, onset and length) on resistance and (c) the underlying mechanisms in terms of growth potential and hydraulic traits.
Droughts led to 22% reduction in stem growth for 85% of species, but most species (85%) were resilient due to high recovery. Growth resistance decreased with an early onset of drought (significant for 55% of species), and longer‐lasting (35%) and intense droughts (60%). While fast‐growing species and slow‐growing species were similar in resistance and recovery, fast‐growing species were more resilient. Unexpectedly, resilience could not be explained by hydraulic traits, possibly because the species grew on poor sandy soils and were acclimated to drought with large hydraulic safety margins.
Synthesis. Our study shows that in a mild maritime climate almost all conifer species are resilient to drought, and that putative hydraulic traits may be less important here for growth resilience. It also highlights the importance of addressing multiple dimensions of drought, that is, timing, duration and severity, to predict species responses to climate change.
The impact of multiple dimensions of drought on tree growth resilience remains highly uncertain. Droughts led to 22% reduction in stem growth for 85% of conifer species. Growth resistance decreased with tree size (significant for 40% of species), early onset of drought (55%), longer‐lasting (35%) and intense (60%) droughts. It highlights the importance of addressing multiple dimensions of drought to predict growth responses to climate change.
Variability in xylem anatomy is of interest to plant scientists because of the role water transport plays in plant performance and survival. Insights into plant adjustments to changing environmental ...conditions have mainly been obtained through structural and functional comparative studies between taxa or within taxa on contrasting sites or along environmental gradients. Yet, a gap exists regarding the study of hydraulic adjustments in response to environmental changes over the lifetimes of plants. In trees, dated tree-ring series are often exploited to reconstruct dynamics in ecological conditions, and recent work in which wood-anatomical variables have been used in dendrochronology has produced promising results. Environmental signals identified in water-conducting cells carry novel information reflecting changes in regional conditions and are mostly related to short, sub-annual intervals. Although the idea of investigating environmental signals through wood anatomical time series goes back to the 1960s, it is only recently that low-cost computerized image-analysis systems have enabled increased scientific output in this field. We believe that the study of tree-ring anatomy is emerging as a promising approach in tree biology and climate change research, particularly if complemented by physiological and ecological studies. This contribution presents the rationale, the potential, and the methodological challenges of this innovative approach.
In a comparative study of 42 rainforest tree species we examined relationships amongst wood traits, diameter growth and survival of large trees in the field, and shade tolerance and adult stature of ...the species. The species show two orthogonal axes of trait variation: a primary axis related to the vessel size-number trade-off (reflecting investment in hydraulic conductance vs hydraulic safety) and a secondary axis related to investment in parenchyma vs fibres (storage vs strength). Across species, growth rate was positively related to vessel diameter and potential specific hydraulic conductance (Kp), and negatively related to wood density. Survival rate was only positively related to wood density. Light-demanding species were characterized by low wood and vessel density and wide vessels. Tall species were characterized by wide vessels with low density and large Kp. Hydraulic traits were more closely associated with adult stature than with light demand, possibly because tall canopy species experience more drought stress and face a higher cavitation risk. Vessel traits affect growth and wood density affects growth and survival of large trees in the field. Vessel traits and wood density are therefore important components of the performance and life history strategies of tropical tree species.
Dead wood is a source of life as it provides habitat and substrate for a wide range of fungal species. A growing number of studies show an important role of wood quality for fungal diversity, but in ...most cases for a limited number of wood traits or tree species. In this study, we evaluate how abiotic and biotic factors affect the fungal diversity and composition during dead wood decomposition. For ten common European tree species, fresh similar‐sized logs were incubated simultaneously in two Dutch forests. Annual surveys of fungal fruiting bodies were made for an 8‐year period. For each tree species, 20 fresh stem traits were measured that are important for chemical and physical defence and for nutritional quality. Throughout eight years, 4644 fruiting bodies belonging to 255 species and 90 genera were recorded on the logs of ten tree species. Fungal frequency and richness were higher for Angiosperms than for Gymnosperms, both for individual tree species and as a group, and higher for tree species with more acquisitive stem trait strategies (i.e. high nutritional value and low physical defence). Differences in fungal communities were strongly driven by phylogenetic group (Gymnosperms versus Angiosperms), stem traits, decay time and forest sites, together explaining 23% of the variation. Fungal communities in sandy site diverged early in the decay process but converged later because of substrate homogenization. Of the 128 fungal species included in the analyses, 41% showed a preference for specific tree species and 34% for a specific successional year. In conclusion, dead wood quality, determined by tree species and decay stage, is an important driver of fungal diversity. For forest management, promoting a wide array of dead tree species (especially angiosperm species), a range of stem trait values and decay stages will increase fungal and, thereby, forest biodiversity.
Aim
Spatial variations of environmental conditions translate into biogeographical patterns of tree growth. This fact is used to identify the origin of timber by means of dendroprovenancing. Yet, ...dendroprovenancing attempts are commonly only based on ring‐width measurements, and largely neglect additional tree–ring variables. We explore the potential of using wood anatomy as a dendroprovenancing tool, and investigate whether it increases the precision of identifying the origin of oak wood. Since different tree–ring variables hold different information on environmental conditions prevailing at specific times of the growing season—which vary between source regions—we hypothesize that their inclusion allows more precise dendroprovenancing.
Location
Europe, Spain.
Taxon
Quercus robur L., Quercus petraea (Matt.) Liebl., Quercus faginea Lam., Quercus pyrenaica Willd.
Methods
We sampled four oak species across Northern Spain, i.e. from the Basque country and Cantabria and—in the Basque country—from low to high elevation (topographic/latitudinal gradient). We measured multiple tree–ring variables to (a) extract complementary variables; (b) present statistical relations among them; (c) analyse region‐specific variation in their patterns based on time–series of individual trees; and (d) determine underlying climate–growth relationships. Leave‐one‐out analysis was used to test whether a combination of selected variables allowed dendroprovenancing of a randomly selected tree within the area.
Results
A combination of latewood width (LW) and earlywood vessel size was used to pinpoint the origin of oak wood with higher precision than ring width or LW only. Variation in LW pinpointed the wood to east and west areas, whereas variation in vessels assigned wood to locations along a latitudinal/topographic gradient. The climatic triggers behind these gradients are respectively an east–west gradient in June–July temperature and a north–south gradient in winter/spring temperatures. The leave‐one‐out analyses supported the robustness of these results.
Main conclusions
Integration of multiple wood–xylem anatomical variables analysed with multivariate techniques leads to higher precision in the dendroprovenancing of ring‐porous oak species.
Abstract
Shrubs are expanding across a warming Arctic, evident from range expansion and increases in biomass, stature and cover. This influences numerous aspects of Arctic ecosystems. While shrub ...growth is generally positively associated with summer temperature, tundra ecosystems are characterised by abiotic gradients on small spatial scales (metres), and the Arctic climate and its year‐to‐year variability are changing rapidly. Hence, it is often unclear to what extent climate‐growth associations are scalable to future climate scenarios and across environmental gradients within ecosystems. Here, we investigate the stability of climate–growth associations of Arctic dwarf shrubs across small‐scale (metre to kilometre) topographic gradients and decadal timescales.
We constructed ring width series (1974–2018) for a common Arctic dwarf shrub (
Betula nana
) for three representative types of subsites in the Siberian lowland tundra: higher elevation, lower elevation and thermokarst‐affected (thaw ponds) terrain. We quantified decadal variability in climate–growth associations across subsites using partial least squares regression and a moving window approach.
We found consistently positive association of shrub radial growth with summer temperature, but substantial spatial and temporal variability in precipitation response. Association of shrub growth with summer rainfall increased in recent decades. Shrubs on elevated sites showed particularly strong response to rainfall following drier periods, and a negative association with recent snowfall extremes. Shrubs sampled from thaw ponds showed strong positive association with rainfall, followed by high shrub mortality after an extremely wet summer. This likely resulted from waterlogging due to thermokarst.
Synthesis
. Our findings imply that the response of shrub growth to changes in Arctic precipitation regimes is regulated by (i) macro‐ (kilometre‐scale) and micro‐topographical (metre‐scale) gradients, (ii) colimitation between temperature and moisture and (iii) potentially nonlinear responses to precipitation extremes. This suggests that the scalability of precipitation‐growth relationships for Arctic shrubs across dynamic tundra landscapes and future climate scenarios is limited. We recommend that future climate–growth studies on Arctic tundra shrubs simulate future precipitation changes across spatial gradients and include detailed microsite and shrub physiological monitoring.
Dead trees are vital structural elements in forests playing key roles in the carbon and nutrient cycle. Stem traits and fungal community composition are both important drivers of stem decay, and ...thereby affect ecosystem functioning, but their relative importance for stem decomposition over time remains unclear.
To address this issue, we used a common garden decomposition experiment in a Dutch larch forest hosting fresh logs from 13 common temperate tree species. In total, 25 fresh wood and bark traits were measured as indicators of wood accessibility for decomposers, nutritional quality and chemical or physical defence mechanisms. After 1 and 4 years of decay, we assessed the richness and composition of wood‐inhabiting fungi using amplicon sequencing and determined the proportional wood density loss.
Average proportional wood density loss for the first year was 18.5%, with further decomposition occurring at a rate of 4.3% year−1 for the subsequent 3 years across tree species. Proportional wood density loss varied widely across tree species in the first year (8.7–24.8% year−1) and subsequent years (0–11.3% year−1). The variation was directly driven by initial wood traits during the first decay year, then later directly driven by bark traits and fungal community composition. Moreover, bark traits affected the composition of wood‐inhabiting fungi and thereby indirectly affected decomposition rates. Specifically, traits promoting resource acquisition of the living tree, such as wide conduits that increase accessibility and high nutrient concentration, increased initial wood decomposition rates. Fungal community composition, but not fungal richness explained differences in wood decomposition after 4 years of exposure in the field, where fungal communities dominated by brown‐rot and white‐rot Basidiomycetes were linked to higher wood decomposition rate.
Synthesis: Understanding what drives deadwood decomposition through time is important to understand the dynamics of carbon stocks. Here, using a tailor‐made experimental design in a temperate forest setting, we have shown that stem trait variation is key to understanding the roles of these drivers; initially, wood traits explained decomposition rates while subsequently, bark traits and fungal decomposer composition drove decomposition rates. These findings inform forest management with a view to selecting tree species to promote carbon storage.
Understanding what drives deadwood decomposition through time is important to understand forest carbon dynamics. Using a tailor‐made experimental design in a temperate forest setting, we found that Initially wood traits explained decomposition rates while subsequently, bark traits and fungal decomposer composition drove decomposition rates. These findings inform forest management with a view to selecting tree species to promote carbon storage.
•Ten species growing on a productive site suffered from summer water shortage.•Species’ responses to the groundwater table reflected their shade tolerance.•On productive sites, climate change can ...hamper tree growth and forest productivity.
Studies on climate impacts on tree annual growth are mainly restricted to marginal sites. To date, the climate effects on annual growth of trees in favorable environments remain therefore unclear despite the importance of these sites in terms of forest productivity. Because species respond differently to climate, comparing a multitude of species further enhances our knowledge on climate impacts on tree growth and forest productivity.
We present a first study that reveals to what extent radial growth is limited by climate and the groundwater table across 10 temperate tree species growing on a uniform, productive soil (i.e. high nutrient and water contents) in the Netherlands. We ranked our study species according to their shade tolerance, which is associated with species’ resource requirements and growth rates, and examined their annual growth using tree-ring analysis. This allowed us to investigate how these species with diverse ecological backgrounds differ in their growth response to precipitation, temperature, irradiance, potential evapotranspiration (PET), and the groundwater table, when growing under similar and favorable site conditions.
Nine out of 10 species had strikingly similar radial growth rates (on average 3.9–4.8mmyr−1), which contradicts the widely established trade-off between shade tolerance and growth. Populus trichocarpa, the least shade-tolerant of our species, however grew much faster (on average 6.8mmyr−1). Trees of all species reduced their growth significantly during dry summers, driven by low rainfall and high PET. Yet, the magnitude of their growth responses to climate conditions and especially the groundwater table differed across species. Receding groundwater tables significantly and strongly reduced radial growth of the shade-intolerant species, but not of the shade-tolerant species. The climate impacts on growth were not associated with variation in shade tolerance across our species.
Our study demonstrates that even on a productive forest site, summer droughts reduced radial growth across a multitude of common tree species, whereas lower groundwater tables only affected the shade-intolerant species significantly. Thus, the productivity of forests in favorable environments may be seriously affected when summers in north western Europe become hotter and drier as predicted by climate models.
Previous studies showed that bark cover at early‐decay stage had profound control on the invertebrate assemblages of bark and wood, with possible consequence for the decomposition process. However, ...previous experimental designs could not disentangle how bark versus wood traits affect the invertebrate assemblage process in bark and/or wood separately because wood traits of different tree species may vary independently from bark traits. Furthermore, we do not know whether such tree species‐specific bark trait effects are still influential at mid‐decay stage.
To unravel whether and how bark and wood traits influence invertebrate communities in tree logs at mid‐decay stage, we introduce reciprocal bark transplantation within pairs of different tree species as a new method. We applied this method to two pairs of phylogenetically contrasting species of gymnosperms (pair I: Araucaria araucana and Cryptomeria japonica, pair II: Picea abies and Thuja plicata) and another gymnosperm (Chamaecyparis lawsoniana) set as disturbance control to test for potential bark manipulation artefacts on invertebrate community composition.
Our bark exchange experiment revealed that both bark and wood host abundant and divergent subsets of invertebrates on mid‐decay logs of different tree species. We further documented that the invertebrate community composition was predominantly shaped by the traits of host tissue per se, while also being significantly but less strongly affected by the traits of the other tissue, that is, the adjacent bark or wood. Our results indicated that bark trait effects faded with time and how long bark trait effects persist greatly depends on bark thickness.
Synthesis. Our study suggests that maintaining deadwood heterogeneity related to variation between tree species and bark versus wood, is important for nursing a large biodiversity of invertebrates. Combined with bark removal methodology, our bark exchange method can be further extended to more decay stages and more forest biomes to track bark trait effects and bark induced priority effects on deadwood decomposition, and its associated invertebrate and microbial communities.
To unravel whether and how bark and wood traits influence invertebrate communities in tree logs at mid‐decay stage, we introduce reciprocal bark transplantation within pairs of different tree species as a new method. Combined with bark removal methodology, our bark exchange method can be further extended to more decay stages and more forest biomes to track bark trait effects and bark induced priority effects on deadwood decomposition, and its associated invertebrate and microbial communities.
Oak wood was highly appreciated and widely used for construction in past centuries. As population sizes expanded in some regions of Europe, local forests were depleted of high-quality timber. ...Therefore, regions of soaring economies were importing timber initially from the European market and eventually from other continents. Origin of archaeological or historical timber is usually identified by means of dendroprovenancing, i.e. statistical matching of tree-ring-width (TRW) series of timber of unknown origin with TRW reference datasets. However, this method has pitfalls and limitations and therefore alternative techniques are needed. Here, we used three different DNA analysis methods to investigate the potential of using ancient (a)DNA, extracted from oak timber derived from historical buildings and shipwrecks from a variety of countries. All the material had also been analysed dendrochronologically, so its dating and provenance is demonstrated. We included heartwood samples in this analysis, for which DNA extraction is especially challenging as it contains chemicals that inhibit DNA amplification. We succeeded in amplifying DNA for at least one marker from 56% of samples (including heartwood samples), yielding crucial information that allowed us to identify the potential source area of centuries old timber buildings in Latvia and Denmark and of 750-year-old shipwreck material from Germany. Our results prove the strong potential of DNA analyses for identifying timber origin to the regional scale, but by combining these with the dendrochronological results, we can control the exactitude of the aDNA approach and demonstrate a more nuanced examination of the timber sources for these historic structures.
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