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Recent methodological advancements in determining the nonexchangeable hydrogen isotopic composition (δ2Hne) of plant carbohydrates make it possible to disentangle the drivers of hydrogen isotope (2H) fractionation processes in plants. Here, we investigated the influence of phylogeny on the δ2Hne of twig xylem cellulose and xylem water, as well as leaf sugars and leaf water, across 73 Northern Hemisphere tree and shrub species growing in a common garden. 2H fractionation in plant carbohydrates followed distinct phylogenetic patterns, with phylogeny reflected more in the δ2Hne of leaf sugars than in that of twig xylem cellulose. Phylogeny had no detectable influence on the δ2Hne of twig or leaf water, showing that biochemistry, not isotopic differences in plant water, caused the observed phylogenetic pattern in carbohydrates. Angiosperms were more 2H-enriched than gymnosperms, but substantial δ2Hne variations also occurred at the order, family, and species levels within both clades. Differences in the strength of the phylogenetic signals in δ2Hne of leaf sugars and twig xylem cellulose suggest that the original phylogenetic signal of autotrophic processes was altered by subsequent species-specific metabolism. Our results will help improve 2H fractionation models for plant carbohydrates and have important consequences for dendrochronological and ecophysiological studies., New Phytologist, 239 (2), ISSN:0028-646X, ISSN:1469-8137

Recent methodological achievements in determining the non-exchangeable hydrogen isotopic composition (δ2Hne) of non-structural carbohydrates such as sugars allow to disentangle of so far hidden hydrogen isotope (2H) fractionation processes influencing δ2Hne of plant carbohydrates. We conducted two climate chamber experiments to have a closer look at the basic biochemical drivers of the photosynthetic 2H fractionation between water and sugar and the post-photosynthetic 2H fractionation between sugars and cellulose in leaves: First, we studied the impact of the different biochemical reactions in 10 species with C3, 7 species with C4, and 8 species with CAM carbon fixation pathways, and their response to changes in temperature and vapor pressure deficit (VPD). Second, we investigated the impact of a temperature increase from 10 to 40°C in 5°C steps under a constant VPD on leaf level photosynthesis and metabolic functioning of 7 plant species. The first experiment revealed distinct differences in the photosynthetic 2H fractionation between C3, C4, and CAM plants. In addition, the observed intensity and direction of the shifts in δ2Hne in response to changes in temperature and VPD in C3 plants was species specific, absent in C4 plants, and again species-specific in CAM plants. However, post-photosynthetic 2H fractionation was very similar among the three types of carbon fixation. We demonstrate that, in contrary to widespread believes, the 2H enrichment during post-photosynthetic 2H fractionation is driven by the carbohydrate metabolism, and not by an isotopic exchange with surrounding water. The results of the second experiment identified a plants’ metabolic activity, and its response to changes in temperature, as a major driver of the post-photosynthetic 2H fractionation of leaf sugars in C3 species. Our results clearly demonstrate that δ2Hne of plant carbohydrates are driven by plants metabolism and its response to the environment, which are species-specific. This will help to improve our current ability to interpret δ2Hne chronologies in tree rings and other plant archives, and to use 2H fractionation in carbohydrates as a novel proxy to study a plants’ metabolic properties.

Soil organic matter (SOM) originates from various sources such as foliar litter, roots and microbial (e.g. fungal) components. The relative sources contribution represents one of the key unknowns in SOM dynamics. Our study aimed to explore whether stable isotope ratios of non-exchangeable hydrogen (Hn) bound to organic matter can be used to differentiate SOM sources, since natural 2Hn abundance can strongly differ between root and foliar tissues. We also investigated if long-term irrigation with 2H-depleted water in a pine forest can be used to track Hn incorporation into organic matter inputs and eventually in the soil pools.In a 17-year-long irrigation experiment in a dry pine forest, we assessed variations in natural abundance of 2Hn, 13C, and 15N in SOM sources (foliar litter, fine roots, fungal mycelia), decomposing litter, soil (organic layers and uppermost 5 cm-mineral soil) and particle-size fractions. We then applied a Bayesian mixing model (including δ2Hn,δ13C, and δ15N) to estimate the relative sources contribution to SOM.Natural 2Hn abundance was significantly higher in roots vs. foliar litter (up to +39‰), and in fungal mycelia vs. roots (up to +41‰). Results from Bayesian mixing model suggest that foliar litter contributed to approximately 68 ± 10% of SOM in organic layers and in coarse particulate organic matter (POM). Foliar litter and roots contributed similarly to upper 2 cm of mineral soil (46 ± 11%), while 2-5 cm of mineral soil were largely derived from roots (61 ± 13%). Fungal mycelia contributed to 18 ± 8% of mineral-associated organic matter (MOM), while only to 1-2% of coarse and fine POM. Bayesian mixing models provided only a general indication of the sources contribution to SOM, also considering that isotopic signatures shifted during decomposition. Measurements of isotope signatures in microbial necromass might allow a more accurate assessment of the different SOM sources contribution.The δ2Hn depletion of soil water under irrigation was paralleled by a comparable decrease in δ2Hn of roots (~12‰). In comparison, the natural 2Hn abundance in fresh needles and foliar litter decreased less strongly (~ 7‰ and 4‰, respectively), likely due to photosynthetic adjustments that may have counterbalanced the irrigation water 2H-depletion. Similar to soil water 2H-depletion, δ2Hn values in coarse POM were 11‰ lower in irrigated vs. dry plots, suggesting that nearly all organic Hn turned over or exchanged with soil water in less than two decades. In contrast, δ2Hn values in fine POM and MOM decreased only by 3‰ under irrigation, which indicate that these fractions comprise slower cycling Hn pools.Our study showed that the natural 2Hn abundance represents a promising tool to differentiate among SOM sources. While 13C and 15N did not clearly separate between roots and foliar litter, Hn isotopic signatures allowed a good discrimination between SOM sources. In addition, long-term irrigation can provide a potential in situ 2H-labelling of SOM, which may help to examine organic Hn turnover rates across SOM pools.

The analysis of a Europe-wide network of tree-ring stable isotopes has shown that the climatic signal of δ2H in tree-ring cellulose (C6H10O5), is far weaker compared to those recorded in carbon (δ13C) and oxygen (δ18O)isotopes. Furthermore, the δ2H and δ18O relationships were shown to be site dependent and significantly deviated from the Global Meteoric Water Line. These results suggest that non-climatic effects are modifying the hydrological signature of δ2H. Recent experiments have underlined the potential of δ2H in tree-ring cellulose as a physiological indicator of shifts in autotrophic versus heterotrophic processes. However, the impact of these processes has not yet been quantified under natural conditions.Defoliating insect outbreaks can disrupt photosynthetic production and carbon allocation, stimulating the remobilization of stored carbohydrates. Such disturbance events, therefore, provide unique opportunities to evaluate the impact of changes in the use of fresh versus stored non-structural carbohydrates, i.e., of non-climatic signals stored in δ2H. By exploring a 700-year tree-ring record from Switzerland, we assess the impact of 79 larch budmoth (LBM, Zeiraphera griseana) outbreaks on the growth of its Larix decidua host trees.LBM outbreaks significantly altered the tree-ring isotopic signature, creating a 2H-enrichment and a depletion in 18O 13C. Changes in tree physiology during outbreak years are shown by the decoupling of δ2H and δ18O (O–H relationship), in contrast to the positive correlation in non-outbreak years. The O–H relationship in outbreak years was not significantly affected by temperature, indicating that non-climatic physiological processes dominate over climate in determining δ2H variations. We conclude that the combination of these isotopic parameters may serve as a metric for assessing changes in physiological mechanisms over time and that hydrogen isotopes can be considered as a proxy for non-climatic disturbance signals in dendrochronological research.

Stable isotope compositions of carbon (δ13C) and oxygen (δ18O) in plant carbohydrates such as photosynthetic assimilates or cellulose are widely applied tools to reconstruct climate and plant physiological responses. In contrast, applications of hydrogen isotope composition (δ2H) in plant carbohydrates are limited because of previous methodological constrains and limited knowledge on processes causing hydrogen isotope fractionations. To better understand the individual climatic drivers of isotopic variations in tree rings, particularly for δ2H, we performed a controlled experiment over one growing season in climate chambers with saplings of broadleaf and conifer tree species. The growing conditions resembled conditions that can be typically found in the field: vapor pressure deficit (VPD; 1.0, 1.6, and 2.2 kPa), air temperature (T; 25 and 30 °C), and soil drought (D, well-watered and extreme dry). After 5 months of treatment, δ13C, δ18O, and δ2H of water, sugars and starch in stems and leaves, as well as in cellulose of the recent year tree rings were measured. For δ2H analyses of plant carbohydrates, we applied a newly developed hot water vapour equilibration method (Schuler et al., 2022, doi.org/10.1111/pce.14193). Across all species, first results show that the three elements in tree-ring cellulose respond differently to the climatic drivers: both δ2H and δ13C values increased with increases in D and VPD, but the VPD responses were more pronounced under high than under low T conditions. In contrast, δ18O values were affected by T and VPD, while the VPD response was more pronounced under wet than under dry soil D conditions. Thus, the combination of δ2H and δ13C values could be used to identify D occurrences independent of VPD conditions, while δ18O value is a better indicator for T and VPD responses. In the following steps, the isotopic variations in tree-ring cellulose will be linked to those in water, sugars, and starch and their concentrations in leaf and stem material, as well as to various other structural and functional traits which have been measured throughout the experiment (Schönbeck et al., 2022, doi.org/10.1111/pce.14425). With this unique experimental design, we aim to provide new knowledge facilitating the interpretation of stable isotope patterns in tree rings under field conditions.

Mixed-species plantations of trees with N-fixing species have the potential of promoting forest productivity and soil fertility. However, few studies in the literature have addressed the advantages of mixed-species plantations of leguminous trees over monocultures of leguminous trees based on in situ inventories over a long time period. Here, we monitored the dynamics of tree community composition, vegetation biomass, soil nutrients, and soil microbial phospholipid fatty acids (PLFAs), in an Acacia mangium monoculture plantation during 33 years of development and compared it with a mixed-species plantation of A. mangium associated with 56 native species which were underplanted 14 years after the initial establishment. Leaf N and phosphorus (P) concentrations of three main species in the overstory and understory of the A. mangium monoculture were measured. Our results showed that the soil organic carbon (SOC), total nitrogen (TN), and available phosphorus (AP) concentrations significantly increased over time during the approximately thirty years of A. mangium monoculture plantation, while the disadvantages were associated with new species regeneration and the increment of vegetation biomass. In the A. mangium monoculture plantation, leaf N concentration of A. mangium, Rhodomyrtus tomentosa, and Dicranopteris dichotoma continuously increased from 21 to 31 years, while the leaf P concentration of A. mangium and R. tomentosa decreased. The mixed-species plantations of A. mangium with native tree species had lower SOC and soil TN concentrations, more new tree species recruitment in the understory, and faster vegetation biomass increment than the A. mangium monoculture. However, the PLFAs of soil microbial groups were slightly different between the two types of plantations. We conclude that improved soil N nutrient condition by A. mangium monoculture benefits N absorption by A. mangium, R. tomentosa, and D. tomentosa, while low soil AP limits P absorption by A. mangium and R. tomentosa. Meanwhile, transforming the A. mangium monoculture into a mixed-species plantation via the introduction of multiple native species into the A. mangium monoculture decreases SOC and TN concentrations but the advantages include improving forest regeneration and maintaining forest growth in a long-term sequence. These findings provide useful and practical suggestions for managing forest monocultures of A. mangium in subtropical regions., Forests, 14 (5), ISSN:1999-4907

Despite the rapidly increasing use of resilience indices to analyze responses of trees and forests to disturbance events, there is so far no common framework to apply and interpret these indices for different purposes. Therefore, this review aims to identify and discuss various shortcomings and pitfalls of commonly used resilience indices and to develop recommendations for a more robust and standardized procedure with a particular emphasis on drought events. Growth-based resilience indices for drought responses of trees are widely used but some important drawbacks and limitations related to their application may lead to spurious results or misinterpretation of observed patterns. The limitations include (a) the inconsistency regarding the selection and characterization of drought events and the climatic conditions in the pre- and post-drought period and (b) the calculation procedure of growth-based resilience indices. We discuss alternative options for metrics, which, when used in concert, can provide a more comprehensive understanding of drought responses in cases where common growth-based resilience indices are likely to fail. In addition, we propose a new analytical framework, the “line of full resilience,” that integrates the three most commonly used resilience indices and show how this framework can be used for comparative drought tolerance assessments such as rankings of different tree species or treatments. The suggested approach could be used to harmonize quantifications of tree growth resilience to drought and it may thus facilitate systematic reviews and development of the urgently needed evidence base to identify suitable management options or tree species and provenances to adapt forests for changing climatic conditions.

Existing accounts of Myanmar’s film industry available to English speakers are more than twenty years out of date. Opening with a brief overview of cinema in Myanmar since 2000, this article is based on a recent visit to the Myanmar Motion Picture Development Department and the Yangon Film School, on conversations with staff, students and alumnae of these institutions and of the National University of Arts and Culture, and with local independent filmmakers. The purpose of my visit was to begin the groundwork needed to answer basic questions: Who are the women making films in Myanmar today? Where are they trained? What are the conditions in which they work? What kind of films they make? How do they fund production? How do their films circulate? And finally: Is there a women’s cinema in Myanmar? What follows thus outlines the context in which women in Myanmar make films today and introduces the work of a small number of them. I conclude with reflections on three short films: A Million Threads (2006, by Thu Thu Shein), Now I am 13 (2013, by Shin Daewe), and Seeds of Sadness (2018, by Thae Zar Chi Khaing), two of which can be found online (at http://yangonfilmschool.org/___-free-yfs-film / and https://www.youtube.com/watch?v=vX0LUZQcMCQ ).

While carbon (δ13C) and oxygen (δ18O) isotopes in tree-ring cellulose are widely used as climatic and physiological proxy in dendro sciences, the processes that are affecting the fractionation of non-exchangeable hydrogen (δ2H) isotopes and shaping the tree-ring δ2H profile are barely understood and thus not widely applied yet.To establish a first comprehensive comparison of the photosynthetic and post-photosynthetic 2H-fractionation of northern-hemisphere trees, we sampled leaves and twigs of 152 trees representing 73 species, 48 genus, 19 families and 12 orders containing both evergreen and deciduous angio- and gymnosperms in a common garden, as well as diurnal cycles (6 species from 6 families) of leaf sugar. We extracted leaf water and sugar, as well as twig water and the current year twig xylem cellulose for δ2H analysis. Leaf sugar and twig cellulose were measured with a newly established hot water vapour equilibration method.Our findings show a wide variation in 2H-fractionation between species growing at a common site. The measured δ2H values ranged from -63.5 to –33.4‰ for xylem water, between -22.3 and +28.5‰ for leaf water, between -160.9 and +12.6‰ for leaf sugar and between -79.1 and +6.9‰ for twig cellulose. The biological fractionation between leaf water and leaf sugar ranged between -169.6 and +24.2‰ and between leaf sugar and current year twig cellulose from -34.6 to +116.8‰. In general, sugar and cellulose of gymnosperms were significantly more 2H depleted than those of angiosperm species, with no impact of the leaf shedding behaviour to the measured δ2H values. We observed significant differences in the δ2H values between different orders and families, but not between genus and species within a family or genus, respectively. This pattern indicates that the photosynthetic and post-photosynthetic 2H-fractionation are based on conservative metabolic reactions with a generally low mutation rate.Additionally, the results from our diurnal sampling of leaf sugar are showing first evidence for a dynamic and species-specific nature of the photosynthetic 2H-fractionation, which is in contrast to current models, which are assuming the same constant 2H-fractionation processes for all plant species.We conclude that the here presented results will help to improve our understanding of the mechanisms influencing the δ2H values of leaf sugar and tree-ring cellulose and thus enabling the scientific community to use δ2H in tree-ring cellulose as the third isotope-proxy for dendrochronological studies.

Stable carbon (δ13Cc) and oxygen (δ18Oc)isotopes measured in tree-ring cellulose, together with tree-ring width (TRW), have been used extensively to investigate the effects of past climatic conditions on tree growth. By contrast, the information recorded by the third major chemical component of tree-ring cellulose, the non-exchangeable carbon-bound hydrogen, has been explored far less due to methodological drawbacks and lack of understanding of 2H-specific fractionations. In this first Europe-wide assessment we investigate the signals stored in the hydrogen isotope ratios in tree-ring cellulose (δ2Hc), from a unique collection of 100-years records, from two major genera (Pinus and Quercus) across 17 sites (36°N to 68°N).The climate correlation analyses showed weak climate signals in the δ2Hc high-frequency chronologies, compared to those recorded by δ13Cc and δ18Oc, but similar to the TRW ones. The δ2Hc climate signal strength varied across the continent and was stronger and more consistent for Pinus than for Quercus. The δ2Hc inter-annual variability was strongly site-specific. Focusing on the effect of extreme climatic conditions during years with extremely dry summers, we observed a significant 2H-enrichment in tree-ring cellulose for both genera. Our findings clearly indicate that δ2Hc registers information about hydrology and climate, but it also records non-climatic signals such as physiological mechanisms associated with carbohydrates storage remobilization 2H-specific fractionations and growth.To disentangle the climatic and non-climatic signals in δ2Hc, we investigated its relationships with δ18Oc and TRW. We found significant relationships negative between δ2Hc and TRW at 7 sites and positive between δ2Hc and δ18Oc at 10 sites, while the rest of the sites did not show any significant relationships. The agreement with the TRW chronologies confirms the relationship between growth and δ2Hc, while the divergencefrom δ18O suggests a loss of the hydrological signal in δ2Hc. These highlights, once again,a stronger physiological component in the δ2H signature independent from climate. Advancements in the understanding of 2H-fractionations and their relationships with climate, physiology, and species-specific traits are therefore needed to improve the mechanistic modeling and interpretation accuracy of δ2Hc in plant physiology and paleoclimatology. Such advancements could lead to new insights into trees’ carbon allocation mechanisms, and responses to abiotic and biotic stressors.

The analysis of the non-exchangeable hydrogen isotope ratio (δ2Hne) in carbohydrates is mostly limited to the structural component cellulose, while simple high-throughput methods for δ2Hne values of non-structural carbohydrates (NSC) such as sugar and starch do not yet exist. Here, we tested if the hot vapor equilibration method originally developed for cellulose is applicable for NSC, verified by comparison with the traditional nitration method. We set up a detailed analytical protocol and applied the method to plant extracts of leaves from species with different photosynthetic pathways (i.e., C3, C4 and CAM). δ2Hne of commercial sugars and starch from different classes and sources, ranging from −157.8 to +6.4‰, were reproducibly analysed with precision between 0.2‰ and 7.7‰. Mean δ2Hne values of sugar are lowest in C3 (−92.0‰), intermediate in C4 (−32.5‰) and highest in CAM plants (6.0‰), with NSC being 2H-depleted compared to cellulose and sugar being generally more 2H-enriched than starch. Our results suggest that our method can be used in future studies to disentangle 2H-fractionation processes, for improving mechanistic δ2Hne models for leaf and tree-ring cellulose and for further development of δ2Hne in plant carbohydrates as a potential proxy for climate, hydrology, plant metabolism and physiology., Plant, Cell & Environment, 45 (1), ISSN:0140-7791, ISSN:1365-3040

A small library of dinuclear gold(I) complexes with the title ligands has been prepared, encompassing neutral, mono- and dicationic complexes. The luminescence properties of the complexes in the solid state have been evaluated, and it turns out that neutral and monocationic complexes not presenting a rigid metallamacrocyclic structure can exhibit rather strong emissions that extend towards the red region of the visible spectrum. The

Monitoring early tree physiological responses to drought is key to understanding progressive impacts of drought on forests and identifying resilient species. We combined drone-based multispectral remote sensing with measurements of tree physiology and environmental parameters over two growing seasons in a 100-y-old Pinus sylvestris forest subject to 17-y of precipitation manipulation. Our goal was to determine if drone-based photochemical reflectance index (PRI) captures tree drought stress responses and whether responses are affected by long-term acclimation. PRI detects changes in xanthophyll cycle pigment dynamics, which reflect increases in photoprotective non-photochemical quenching activity resulting from drought-induced photosynthesis downregulation. Here, PRI of never-irrigated trees was up to 10 times lower (higher stress) than PRI of irrigated trees. Long-term acclimation to experimental treatment, however, influenced the seasonal relationship between PRI and soil water availability. PRI also captured diurnal decreases in photochemical efficiency, driven by vapour pressure deficit. Interestingly, 5 years after irrigation was stopped for a subset of the irrigated trees, a positive legacy effect persisted, with lower stress responses (higher PRI) compared with never-irrigated trees. This study demonstrates the ability of remotely sensed PRI to scale tree physiological responses to an entire forest and the importance of long-term acclimation in determining current drought stress responses.

This work reports a method to select the optimal working frequency in transversal bulk resonator acoustophoretic devices by electrical impedance measurements. The impedance spectra of acoustophoretic devices are rich in spurious resonance peaks originating from different resonance modes in the system not directly related to the channel resonance, why direct measurement of the piezoelectric transducer impedance spectra is not a viable strategy. This work presents, for the first time, that the resonance modes of microchip integrated acoustophoresis channels can be identified by sequentially measuring the impedance spectra of the acoustophoretic device when the channel is filled with two different fluids and subsequently calculate the Normalized Differential Spectrum (NDS). Seven transversal bulk resonator acoustophoretic devices of different materials and designs were tested with successful results. The developed method enables a rapid, reproducible and precise determination of the optimal working frequency.

A small library of dinuclear gold(I) complexes with the title ligands has been prepared, encompassing neutral, mono- and dicationic complexes. The luminescence properties of the complexes in the solid state have been evaluated, and it turns out that neutral and monocationic complexes not presenting a rigid metallamacrocyclic structure can exhibit rather strong emissions that extend towards the red region of the visible spectrum. The in vitro anticancer activity of the complexes has been also preliminarly evaluated; cytotoxicity seems to correlate with complex lipophilicity, whereas selectivity towards cancer cells can be apparently enhanced upon a judicious choice of the ligands.

Picea abies (L.) Karst. and Fagus sylvatica (L.) are important tree species in Europe, and the foreseen increase in temperature and vapour pressure deficit (VPD) could increase the vulnerability of these species. However, their physiological performance under climate change at temperate and productive sites is not yet fully understood, especially in uneven-aged stands. Therefore, we investigated tree-ring width and stable isotope chronologies (δ13C/δ18O) of these two species at 10 sites along a climate gradient in Central Europe. In these uneven-aged stands, we compared the year-to-year variability of dominant and suppressed trees for the last 80 years in relation to the sites’ spatial distribution and climate. δ18O and δ13C were generally consistent across sites and species, showing high sensitivity to summer VPD, whereas climate correlations with radial growth varied much more and depended on mean local climate. We found no significant differences between dominant and suppressed trees in the response of stable isotope ratios to climate variability, especially within the annual high-frequency signals. In addition, we observed a strikingly high coherence of the high-frequency δ18O variations across long distances with significant correlations above 1500 km, whereas the spatial agreement of δ13C variations was weaker (~700 km). We applied a dual-isotope approach that is based on known theoretical understanding of isotope fractionations to translate the observed changes into physiological components, mainly photosynthetic assimilation rate and stomatal conductance. When separating the chronologies in two time windows and investigating the shifts in isotopes ratios, a significant enrichment of either or both isotope ratios over the last decades can be observed. These results, translated by the dual-isotope approach, indicate a general climate-driven decrease in stomatal conductance. This improved understanding of the physiological mechanisms controlling the short-term variation of the isotopic signature will help to define the performance of these tree species under future climate.

Picea abies and Fagus sylvatica, are two of the most important tree species in Europe, and their responses to climate are being extensively investigated, especially at the limits of their distribution. However, their physiology at temperate sites is not yet fully understood. In a European tree-ring network, 10 sites along a climate gradient were sampled throughout Central Europe, and tree-ring width and stable isotope chronologies (C and O) were measured. The year-to-year variability of the isotopes time series for the last 100 years was analyzed in relation to tree-ring growth, spatial distribution, and seasonal climate.Climate sensitivity of radial growth of both species was rather variable and site-dependent, and was strongest at the driest sites. On the contrary, variability in the isotopic ratios consistently responded to summer climate, particularly to vapor pressure deficit. The high δ18O coherence of the short-term variability between sites and species highlights the strength of the environmental signal in the O chronology also across long distances. On the contrary, δ13C shows lower correlations between sites and species, showing a stronger site-dependency, and a lower intra-annual variability. The generally positive correlation between the year-to-year differences in δ13C and δ18O across most sites demonstrates the strong role of stomatal conductance in controlling leaf gas exchange for these species. However, in the last decades, sites showed a dissimilar shift in the isotopes relationships, with the warmer sites showing an increase of either or both δ13C and δ18O and consequent decrease of photosynthetic rates and stomatal conductance, highlighting their dependency to atmospheric moisture demand and soil water availability.Understanding the underlying physiological mechanisms controlling the short-term variation in tree-ring records will help with defining the performance of these ecologically and economically important tree species under future climate conditions.

The exhibition Meanings of Failed Action: Insurrection 1946 opened in Mumbai on 17 March 2017 and in New Delhi on 8 February 2018. The second part of Vivan Sundaram’s The History Project,1 this new installation was intended to mark seventy years of Indian independence and partition by exploring an often forgotten moment of Indian history: the uprising of the Royal Indian Navy’s ratings in February 1946, when 10,000 naval ratings took charge of 66 ships across the Indian subcontinent in the name of the ‘Quit India’ movement. R.I.A.F. men, Sepoys, Bombay’s industrial workers and the city’s population joined in, marching in solidarity with the ratings irrespective of caste and religious affiliation. But the Congress and the Muslim League condemned the action and consented to British military intervention, which resulted in the deaths of over two hundred people and the ratings’ imprisonment. The event has since been erased from Indian national history, perhaps because, had the insurrection succeeded, India’s struggle for freedom might have taken a different turn. I worked on the exhibition as a researcher for the artist, with Ashish Rajadhyaksha and David Chapman, for over a year. The question we sought to answer during those months was: what is the significance of that uprising for India today? With this question in mind, in what follows I focus on the documents we unearthed in the process – pamphlets, slogans, the ratings’ statements to the police and Inquiry, their memories and prison letters – and examine the motivations and hopes that defined the strikers’ action. What kind of freedom did the ratings stand for?

Norway spruce is one of the economically most important tree species in Central European forestry. However, its high susceptibility to droughts poses a strong challenge to its cultivation under future conditions with likely more frequent and prolonged droughts and shifts in the seasonal climate. To compensate for expected losses of forest areas suitable for the cultivation of spruce, more drought-tolerant species are required. Silver fir and Douglas fir are two potential candidates, which promise lower drought susceptibility and equal or even higher yield when compared to Norway spruce. Using the Black Forest as a regional case study, we assessed the effects of seasonal climate change, including drought stress, on tree-ring width formation of these three economically relevant conifer species over the last 60 years. In addition, we projected potential species-specific growth changes under different climate change scenarios until 2100. Our results suggest that both silver fir and Douglas fir will possibly experience growth increases in a warmer future climate, as predicted under the 4.5 and 8.5 Representative Concentration Pathway (RCP) climate change scenarios, whereas growth of spruce is expected to decline. Moreover, drought susceptibility in silver fir and Douglas fir is lower than in spruce, as shown for past drought events, and their ability to benefit from milder winters and springs could play a major role in their capacity to compensate for drier summers in the near to mid-term future. This study highlights the need to advance our understanding of the processes that drive drought resistance and resilience in tree species to guide management strategies in the face of climate change.

Norway spruce is a widely cultivated species in Central Europe; however, it is highly susceptible to droughts, which are predicted to become more frequent in the future. A solution to adapt spruce forests to droughts could be the conversion to mixed-species stands containing species which are less sensitive to drought and do not increase the drought stress in spruce. Here we assessed the drought response of spruce and the presumably more drought-tolerant silver fir and Douglas fir in mixed-conifer stands. We measured tree ring widths of 270 target trees, which grew in mixed and mono-specific neighbourhoods in 18 managed stands in the Black Forest, to quantify the complementarity effects caused by species interactions on growth during the extreme drought event of 2003 and for a number of years with “normal” growth and climatic conditions. Mixed-species neighbourhoods did not significantly affect tree ring growth in normal years. However, during the drought, silver fir benefitted from mixing, while Douglas fir was more drought-stressed in the mixture. The drought response of spruce was dependent on the density and species composition of the neighbourhood, showing both positive and negative mixing effects. Mixed stands containing these tree species could improve adaptation to drought because the risks of extreme events are spread across species, and the performance of individual species is improved. Our knowledge about specific species interactions needs to be improved to manage tree mixtures more effectively with regard to the participating species and stand density.

Quantifying the resilience of forest ecosystems in response to droughts is fundamentally important to assess their capacity to function under intensifying climate change with more extreme droughts. The concept proposed by Lloret et al. (2011) to quantify resilience components of tree growth through indices of resistance, recovery, and resilience has become highly popular in dendro-ecological analyses because it allows a simple, yet highly efficient assessment of short-term responses of trees to drought. Until today these Lloret-indices have been used in 82 studies on growth response to drought of 66 trees species in different climatic regions. Despite their widespread use, some important drawbacks and limitations related to the application of these indices may lead to spurious results or misinterpretation of observed patterns. One major reason for this problem is the inconsistency regarding the selection and characterization of drought events as well as the calculation of the indices. Therefore, this review aims at identifying and discussing shortcomings and pitfalls of Lloret’s indices and to develop recommendations for a more robust and standardized procedure. In addition, we propose a new analytical framework that integrates the different Lloret-indices by comparing observed relationships between resistance and recovery of tree species or treatments to a hypothetical ‘line of full resilience’, which describes the relationship between resistance and recovery that leads to full resilience of radial growth at any given value of resistance. The fit of observed relationships between resistance and recovery with the hypothetical ‘line of full resilience’ can be used for comparative drought-tolerance assessments such as rankings of different tree species or treatments. The suggested approach could be used to harmonize quantifications of tree growth resilience to drought and it may thus facilitate systematic reviews and development of the urgently needed evidence base to identify suitable tree species and management options under climatic change.

Urban trees are subjected to numerous biotic and mechanical damage, which can affect their growth rates and health. However, for most species, a systematic analysis of tree above- and below-ground growth reactions to a variety of damages is still lacking. Under a fully factorial experimental setup, using two common urban trees (Celtis occidentalis, Fraxinus pennsylvanica), we tested the effects of various degrees of frequently occurring damage as defoliation, root reduction and stem injuries for a total of 18 treatments. We hypothesized that i) an increasing amount of damage would proportionally negatively affect both root and stem growth, ii) there would be a lag or lasting effect on growth, and iii) both species would react similarly to the treatments. Contrary to our expectation, increasing levels of single or combined damage did not have an incremental effect on either stem or root growth. Although Celtis was significantly less vigorous than Fraxinus, it did not react strongly to damage treatments compared to the control. Interestingly, Celtis that experienced stem damage alone or in combination with other damages showed higher growth rates than the control. For Celtis, root injury was the treatment having the most impact, decreasing both root and stem growth consistently throughout the 5 years following treatments, whereas defoliation decreased growth only in the first two years. All damage treatments negatively affected stem and root growth of Fraxinus trees. Stem growth was affected the most by defoliation in the first year following the treatment, while root injury became the driving factor in subsequent years. For both species, stem injury showed the least influence on growth rates. The control and low-level damage treatments often affected growth rates in a similar way, suggesting that low-intensity stress triggers compensatory reactions stimulating photosynthetic rates and nutrient utilization. The slower-growing tree species, Celtis, showed a less negative reaction to all damage treatments compared to Fraxinus. This study illustrates that various types of above- and below-ground injuries do not have a simple additive effect on tree growth and that trees are capable of compensating for the loss of foliage, roots, or phloem to meet their metabolic demand.

Lack of research on the Women’s Royal Indian Naval Service (W.R.I.N.S.) has led to the misconception that most of the women recruited into the Royal Indian Navy during World War 2 were either British or ‘Anglo-Indian’. In reality, by far the majority of the ‘Wrins’, as they came to be called, were Indian. In this paper I follow two parallel lines of enquiry. The first inspects the material stored in British archives - official navy documents, illustrated promotional pamphlets, photographs, memoirs, oral history and letters - to offer the first comprehensive account of the W.R.I.N.S.’ formation, operation and dismantlement. This provides the context for an examination of the visual material created to promote the service. More specifically, comparing the few surviving photographs of Wrins with Lee Miller’s photos of Wrens, I argue that W.R.I.N.S. material mediated a specific and, for the time, new set of discourses about Indian women, ideas about women’s role in a nation-in-making that may still speak to Indian women today.

The analysis of stable carbon and oxygen isotopes in tree-rings is a widely applied tool which allows to retrieve information about past climatic conditions, as well as tree physiological responses to environmental changes. This is based on well-established mechanistic models and firm statistical relationships with climate variables. In contrast, the hydrogen isotopic signature (δ2H) of tree-rings has been reported to be poorly correlated to climate or difficult to explain, and as a consequence, hydrogen isotopes are far less utilized. However, recent plant-physiological experiments have highlighted the role of autotrophic versus heterotrophic processes affecting δ2H values, i.e. use of fresh assimilates versus stored carbohydrates, and have much improved our understanding of the role of post-photosynthetic 2H-fractionation. Using unpublished and literature δ2H data of tree-ring cellulose (δ2HC) of 5 study sites in Europe and Asia, we systematically investigated the relationships between δ2HC and tree-ring width (TRW), which, in contrast to previous research, could now be explained through post-photosynthetic 2H-fractionation. In most cases, these relationships were found to be negative (r2 = 0.23 to 0.51, all P