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Broad‐scale changes in arctic‐alpine vegetation and their global effects have long been recognized and labeled one of the clearest examples of the terrestrial impacts of climate change. Arctic‐alpine dwarf shrubs are a key factor in those processes, responding to accelerated warming in complex and still poorly understood ways. Here, we look closely into such responses of deciduous and evergreen species, and for the first time, we make use of high‐precision dendrometers to monitor the radial growth of dwarf shrubs at unprecedented temporal resolution, bridging the gap between classical dendroecology and the underlying growth physiology of a species. Using statistical methods on a five‐year dataset, including a relative importance analysis based on partial least squares regression, linear mixed modeling, and correlation analysis, we identified distinct growth mechanisms for both evergreen (Empetrum nigrum ssp. hermaphroditum) and deciduous (Betula nana) species. We found those mechanisms in accordance with the species respective physiological requirements and the exclusive micro‐environmental conditions, suggesting high phenotypical plasticity in both focal species. Additionally, growth in both species was negatively affected by unusually warm conditions during summer and both responded to low winter temperatures with radial stem shrinking, which we interpreted as an active mechanism of frost protection related to changes in water availability. However, our analysis revealed contrasting and inter‐annually nuanced response patterns. While B. nana benefited from winter warming and a prolonged growing season, E. hermaphroditum showed high negative sensitivity to spring cold spells after an earlier growth start, relying on additional photosynthetic opportunities during snow‐free winter periods. Thus, we conclude that climate–growth responses of dwarf shrubs in arctic‐alpine environments are highly seasonal and heterogenic, and that deciduous species are overall likely to show a positive growth response to predicted future climate change, possibly dominating over evergreen competitors at the same sites, contributing to the ongoing greening trend. [ABSTRACT FROM AUTHOR]

Dendrometers offer valuable insights into how tree growth responds to climatic variables and physiological processes over the course of a year. Yet, their applicability to extremely slow-growing trees, such as those in peatlands, has been limited due to the intricate and slow nature of growth, therefore rendering interpretation of results complex. In this study, we conducted a comprehensive monitoring of tree wood formation in both peatland and mineral soil ecosystems in southern Sweden (58.37 N, 12.17 E, 75 m asl) in 2021 and 2022, using both band and point dendrometers. To verify and validate the dendrometer data, we also sampled microcores every two weeks during both growing seasons. We find that peatland trees grow at approximately 30 % the rate of their neighbors on mineral soils. The onset of growth among peatland trees typically occurs between mid-May and early June, consistently lagging the start of the growing season in trees on mineral soils by one to three weeks. Notably, growth peaks are synchronized across peatland trees and coincide with the summer solstice. Both types of dendrometers exhibit varying degrees of accuracy depending on the phenological stages measured. They perform well in identifying growth onset and peak but are less effective at detecting growth cessation. Point dendrometers demonstrate superior accuracy as they better capture daily irreversible growth increments. In the case of band dendrometers, growth increments are obscured by greater reversible fluctuations in dead bark tissues. However, they remain valuable for tracking the wood phenology of trees with growth rates exceeding 2 mm/year. Based on our results, for an effective tree monitoring in peatlands, we strongly recommend (1) using point dendrometers and (2) removing the dead bark tissues on monitored trees. [ABSTRACT FROM AUTHOR]

The secondary growth phenology of trees, also known as wood phenology, plays a vital role in assessing the timing of carbon sequestration in forests. However, its spatio-temporal variability and determinants in the Northern Hemisphere remain debated. Here, we presented a meta-analysis using secondary growth phenology data based on dendrometer monitoring of 59 tree species and 84 sites to explore the drivers and temporal connections of phenology across seasonal arid and humid regions in the Northern Hemisphere. We found spring temperatures and precipitation co-regulated the start of secondary growth (SOG) in spring arid regions, and SOG advanced with the increase in spring temperatures and precipitation. However, SOG was only influenced by spring temperatures in spring humid regions. The end of secondary growth (EOG) indicated strong correlations with autumn temperatures only in autumn arid regions but not in humid regions. Interestingly, the earlier SOG promoted advancement of the time of maximum secondary growth rate (MOG) and EOG both in seasonal humid and arid regions, while the end of secondary growth in the previous year (prEOG) negatively affected SOG only in seasonal arid regions. The legacy effects of previous phenological events on subsequent ones should be integrated into phenological prediction models to help accurately assess global carbon, water, and energy cycles. • Spring temperatures and precipitation co-regulate SOG in spring arid regions, but only spring temperatures influence SOG in humid regions. • The end of secondary growth in the previous year (prEOG) negatively affects SOG in seasonal arid regions but not in humid regions. • Earlier SOG promotes the advancement of the time of maximum secondary growth rate (MOG) and the end of secondary growth (EOG) both in seasonal humid and arid regions. [ABSTRACT FROM AUTHOR]

Why this research Matters: The inner bark plays important roles in tree stems, including radial exchange of water with the xylem and translocation of carbohydrates. Both processes affect the water content and the thickness of the inner bark on a diurnal basis. For the first time, we simultaneously measured the diurnal variations in the inner bark thickness of hinoki cypress (Chamaecyparis obtusa) by using point dendrometers and those of local xylem potential by using stem psychrometers located next to the dendrometers to determine how these variations were related to each other, to phloem turgor and carbohydrate transport. We also estimated the axial hydrostatic pressure gradient by measuring the osmolality of the sap extracted from the inner bark. The inner bark shrunk during the day and swelled during the night with an amplitude related to day‐to‐day and seasonal variations in climate. The relationship between changes in xylem water potential and inner bark thickness exhibited a hysteresis loop during the day with a median lag of 2 h. A phloem turgor‐related signal can be retrieved from the diurnal variations in the inner bark thickness, which was higher at the upper than at the lower position along the trunk. However, a downward hydrostatic pressure gradient was only observed at dawn, suggesting diurnal variations in the phloem sap flow velocity. [ABSTRACT FROM AUTHOR]

Drought‐related tree mortality is increasing globally, but the sequence of events leading to it remains poorly understood. To identify this sequence, we used a 2016 tree mortality event in a semi‐arid pine forest where dendrometry and sap flow measurements were carried out in 31 trees, of which seven died. A comparative analysis revealed three stages leading to mortality. First, a decrease in tree diameter in all dying trees, but not in the surviving trees, 8 months "prior to the visual signs of mortality" (PVSM; e.g., near complete canopy browning). Second, a decay to near zero in the diurnal stem swelling/shrinkage dynamics, reflecting the loss of stem radial water flow in the dying trees, 6 months PVSM. Third, cessation of stem sap flow 3 months PVSM. Eventual mortality could therefore be detected long before visual signs were observed, and the three stages identified here demonstrated the differential effects of drought on stem growth, water storage capacity and soil water uptake. The results indicated that breakdown of stem radial water flow and phloem function is a critical element in defining the "point of no return" in the sequence of events leading to mortality of mature trees. The "point of no return" in a mortality sequence of mature Aleppo pine trees in a semi‐arid forest was investigated. Early decline signs started 9 months prior to visual mortality, expressed by stem shrinkage, then cessation of radial water transport and phloem functionality that led to zero sap flow. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate the effects of different crop load levels on apple trees' yield and physiological characteristics, emphasizing the relationship between stem water potential and crop load and the link between trunk diameter growth and crop load. It was conducted in 2014 at Station Expérimentale Fruits et Légumes (SUDEXPE-CEHM) in Southern France. The 'JoyaTM' apple on Pajam-1 rootstock was used as the plant material. Trees were subjected to hand thinning to obtain four final crop load levels as high (100%; 10 fruit/cm2 of branch cross-sectional area (BCSA)), medium-high (75%; 7.5 fruit/cm2 of BCSA), medium-low (50%; 5 fruit/cm2 of BCSA) and low (25%; 2.5 fruit/cm2 of BCSA). The four crop load levels were set up in a randomized block design with four replications, and each plot was formed of five uniform trees. Stem water potential was weakly affected by crop load but was mainly driven by vapor pressure deficit. The maximum daily trunk diameter, by and large, reduced while crop load level increased. The increase in crop load level was negatively related to fruit size, acidity and soluble solids content. Crop load did not affect bitter pit incidence. However, in parallel to the increasing crop load level, cumulative yield, yield efficiency and water productivity increased. [ABSTRACT FROM AUTHOR]

This study investigated the performance of cocoa trees within an irrigated cocoa plantation situated in the semi-arid region of Bahia, Brazil. Two treatments were compared: "full sun," where cocoa trees were not shaded, and "shade," where trees were covered with a shading net absorbing 30 % of the radiation. The number of leaves and the leaf area index (LAI) were assessed using destructive method on 8 trees. In addition, new flushing of leaves, categorized into four flushing stages, were assessed visually on a weekly basis during two years. The variation of the stem diameter was measured using dendrometer sensors (n = 12 trees). Yield parameters like dry bean yield and number of fruits (healthy and aborted) were assessed on 40 trees per treatment. Both treatments, performed well in the semi-arid region. Generative parameters, such as dry bean yield (±2,000 kg/ha), fruit healthy and abortion rate per plot, were unaffected by full sun and shade treatments. The treatments showed high fruit abortion rates of (±60 %), showing that there's still much room for yield optimization. Additionally, stem diameter of the trees showed a significant reduction of the stem growth (daily increase of stem diameter) and maximum daily shrinkage (daily variation of stem diameter) during the flushing of new leaves. This implies that the emergence of new leaves significantly influences stem growth, consequently affecting the fruits which are growing on the stem. This assumption was corroborated by the significantly increased fruit abortion rate during the flushing of new leaves (stages 1 & 2). These findings highlight the potential of dendrometers to quantify this effect what can be used in future to optimize management practices. By doing so, more effective strategies can be developed to enhance cocoa yield and overall productivity in semi-arid regions., Competing Interests: The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Anken, Thomas reports financial support was provided by Innosuisse., (© 2024 The Authors.)

Water deficit, especially during summer, is currently one of the most important stress factors that influence olive oil production in olive orchards. A precision irrigation strategy, based on daily trunk growth, was assessed and compared with one continuous deficit, one full irrigation, and two different regulated deficit irrigation strategies. All of them were tested in a super high-density olive orchard located in northeast Spain, in which oil production, main oil production components, applied irrigation water, and water productivity were assessed. For this purpose, the crop was monitored from budding to harvesting, mainly during the summer months in which the Precision strategy only applied water after two days of negative daily trunk growth. Maximum monthly water savings for the Precision strategy reached 91.8%, compared with full irrigation, while major annual mean water savings reached 50% for the continuous deficit strategy and 31.2% for the Precision strategy, which also reduced irrigation events by up to 19.7%, compared with the full irrigation strategy. Oil production and oil production components varied depending on the irrigation strategies providing the Control, one of the regulated deficit irrigations, and Precision higher values than the other strategies; oil yield results differ, nonetheless. The Precision strategy showed an overall better performance. Despite this, it did not achieve the highest water saving, it achieved higher water productivity.

Abstract Background Stem radial growth in forests is not uniform. Rather, it is characterized by periods of relatively fast or slow growth, or sometimes no growth at all. These fluctuations are generally a function of varying environmental conditions (e.g. water availability) and, importantly, will also be associated with adjustments in properties in the wood formed. Stand level conditions and forest management, particularly thinning and stand density will, however, also have a major influence on patterns of growth variation. We explore how different thinning histories and/or stand densities influence these dynamics of tree growth in the important commercial plantation species Pinus radiata D. Don. Methods Daily stem size change was measured using electronic point dendrometers over two growing seasons on P. radiata trees at two sites, subjected to different thinning regimes. Timing, rates and periodicity of annual growth were calculated from these data. Results Greater overall cross-sectional growth in thinned plots was driven mainly by two dynamics. First, the cessation of seasonal growth occurred at least 3 weeks later in the stands in which thinning had taken place. There was no difference between thinned/unthinned stands, however, in the timing of growth onset. Second, within the longer season, trees in thinned plots had more growth days (as much as 20% more) than unthinned plots. The rates of growth on days when growth occurred were not different, however. In this context, it is notable that in trees in the unthinned plots experiencing the most severe competition there were strong “pulses” of growth following drought-breaking rainfall events. Unthinned plots at high stand densities also maintained a smaller (but consistent) zone of dividing cells throughout the season than thinned plots. Conclusions In Pinus radiata growing under conditions as in our study, conditions late in summer, particularly drought, have an important effect on the timing of cessation of growth. Early season temperature appears to have no effect in determining timing of annual growth. Limiting conditions during the season reduce growing duration, and thus total growth, more in unthinned stands than thinned stands. These findings are valuable in developing new generations of fine-scale growth and wood property models.

The explicit purpose of this study was to characterize climate and vegetation along the western slope of the El Sira Mountains (Peru) and evaluate radial tree growth in response to seasonal rainfall anomalies. From May 2011 until September 2015, we monitored radial stem growth of 67 trees using point dendrometers and measured climate within five sites along an altitudinal gradient. The transect extends from lowland terra firme forests, over submontane forests, late and mid successional montane cloud forests up to exposed elfin forests. Monthly rainfall estimates by the TRMM PR satellite (product 3B42) were highly correlated with our rain gauge observations but underestimate rainfall at high altitudes. Different intra-annual tree growth patterns could be identified within each elevational forest type, showing species with strictly seasonal growth, continuous growth or alternating growth patterns independent of the seasons. Stem growth at each site was generally larger during rainy seasons, except for the elfin forest. The rainy season from October 2013 to March 2014 was extraordinarily dry, with only 73% of long-term mean precipitation received, which resulted in reduced radial growth, again with the exception of the elfin forest. This indicates that montane tropical rain forests may suffer from prolonged droughts, while exposed ridges with elfin forests still receive plenty of precipitation and benefit from receiving more solar radiation for photosynthesis. [ABSTRACT FROM AUTHOR]

Key message: Radial growth in a group ofPinus radiataD. Don. trees varies in magnitude around the circumference and follows synchronous but arrhythmic dynamics. Context: Eccentric and irregular girth growth is typically associated to specific growth responses, but it is generally assumed to be small or absent during normal development. The dynamics by which excess growth is formed are unclear. Aims: The objective of this study is to determine if growth anisotropy is a commonly occurring phenomenon without apparent mechanical imbalance of the tree and to document the temporality of differential radial growth. Methods: Six mature P. radiata trees were equipped with point dendrometers at different circumferential positions. Growth rates and periods of activity were monitored over 4 months. Results: The highest growth differential on a single tree exceeded a factor of two. The direction of the highest growth varied between trees. In one case, that direction switched over time. The amount of anisotropy was explained by differences in the number of growing days and growth rate entropy. Conclusion: Tree stem formation in fast-growing softwoods is a biological process characterized by high spatial heterogeneity and intermittent temporal activity. [ABSTRACT FROM AUTHOR]

Water stress is an indicator that plant are suffering from drought. For optimization of the crop production is necessary to indicate physiological changes, those can be represented by stem expansion or shrinkage and sap flow rate. We used the Dynagage SGA5-WS (Dynamax) sensors for the sap flow monitoring and the sensors Diameter Dendrometer Small (Ecomatik) for measuring branches diameter changes in our research. The research was realized during two seasons, in the summer (from 31st July to 14th August 2018) and in the spring (from 27th March to 14th April 2019). The subject in our research were walnut trees (Juglans regia) situated in the private orchard in Nové Zámky area in Slovak Republic. The sap flow values in summer were on average range of 90 g·h-1, with maximum measured values above 160 g·h-1 measured after the precipitation events. After increasing of soil moisture on 1st and 2nd August 2018, it was detected the branches diameter expansion up to 0.05 mm. However, the other spring values were much lower. The sap flow reached less than 35 g·h-1 what was one third values in summer 2018. This phenomenon is a result of the low transpiration intensity of transpiration or a leafless state of trees. Although the changes in diameter were not significant in the early vegetation stage, there were monitored some fluctuation causing the diameter was shrinked by 0.2 mm due to a negative average air temperature. [ABSTRACT FROM AUTHOR]

Growth response of conifers is species- specific and depends on site and climate conditions. Studies on daily radial stem growth use different analytical approaches to determine species reactions to environmental conditions. These results contribute to improve forecasts of tree growth under a changing climate. During 2013 and 2014, radial stem growth of 33 mature Cedrus libani individuals growing under different climatic conditions in Turkey and Germany was monitored hourly using high precision point dendrometers. Stem radius increments (SRI) were extracted from dendrometer readings. The annual course of SRI showed site-specific patterns with mean daily values ranging between 9.9 and 29.3 µm over the growing season. Correlation and principal component analyses indicated that humidity and low temperatures during the growing season favored SRI. Multiple regression analyses demonstrated that precipitation and relative air humidity were the most important factors influencing daily SRI. Climate-growth relationships were further evaluated using the regression tree method. Precipitation was the most significant factor on daily SRI for all sites. The close coupling of SRI to relative air humidity and precipitation underlines the importance of stem water status for radial stem growth of C. libani which is native to regions with summer drought. It further explains the superior growth of C. libani in Germany. [ABSTRACT FROM AUTHOR]

Summary: The pulse of the tree (diurnal cycle of stem radius fluctuations) has been widely studied as a way of analyzing tree responses to the environment, including the phenotypic plasticity of tree–water relationships in particular. However, the genetic basis of this daily phenotype and its interplay with the environment remain largely unexplored. We characterized the genetic and environmental determinants of this response, by monitoring daily stem radius fluctuation (dSRF) on 210 trees from a Eucalyptus urophylla × E. grandis full‐sib family over 2 years. The dSRF signal was broken down into hydraulic capacitance, assessed as the daily amplitude of shrinkage (DA), and net growth, estimated as the change in maximum radius between two consecutive days (ΔR). The environmental determinants of these two traits were clearly different: DA was positively correlated with atmospheric variables relating to water demand, while ΔR was associated with soil water content. The heritability for these two traits ranged from low to moderate over time, revealing a time‐dependent or environment‐dependent complex genetic determinism. We identified 686 and 384 daily quantitative trait loci (QTL) representing 32 and 31 QTL regions for DA and ΔR, respectively. The identification of gene networks underlying the 27 major genomics regions for both traits generated additional hypotheses concerning the biological mechanisms involved in response to water demand and supply. This study highlights that environmentally induced changes in daily stem radius fluctuation are genetically controlled in trees and suggests that these daily responses integrated over time shape the genetic architecture of mature traits. Significance Statement: The 'pulse' of the tree that refers to the environmentally induced changes in daily stem radius fluctuation, is a key trait to understand trees' responses to the environment. This study shows that the 'pulse' is associated with genetic variation in a Eucalyptus hybrid and highlights that the dynamics of its genetic architecture is crucial to investigate the genetic bases of tree responses to changes in water availability. [ABSTRACT FROM AUTHOR]

Copyright of Acta Scientiarum Polonorum. Formatio Circumiectus is the property of Wydawnictwo Uniwersytetu Rolniczego im. Hugona Kollataja w Krakowie and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Revista Brasileira de Agricultura Irrigada - RBAI is the property of Revista Brasileira de Agricultura Irrigada - RBAI and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

• Site-specific soil water supply drives canopy conductance of pine, oak and beech. • Minimum tree water deficit is a valuable proxy for tree water supply. • The operational space of canopy conductance determines tree-water use strategies. • Beech and oak adjust their operational space at a drier site more than pine. Tree-specific canopy conductance (G c) and its adjustment play a critical role in mitigating excess water loss in changing environmental conditions. However, the change of G c sensitivity to environmental conditions due to drought remains unclear for European tree species. Here we quantified the environmental operational space of G c , i.e., the water supply (soil moisture, tree water deficit) and demand conditions (vapor pressure deficit) under which G c ≥ 50% is possible (G c50 OS), at two sites with different soil water availability for three common European tree species. We collected sap flow and dendrometer measurements for co-occurring Pinus sylvestris, Fagus sylvatica and Quercus petraea growing under different soil hydrological conditions (drier/wetter). These measurements were combined with meteorological variables and soil moisture conditions in five depths. Dendrometer measurements were used to confirm soil water availability patterns. For all analyses, the contrasting soil hydrology between sites was the main driver of G c response. At the drier sites, F. sylvatica and P. sylvestris reduced their water consumption in response to decreasing soil water supply earlier in the growing season than Q. petraea. However, our analysis on the G c50 OS revealed that at the drier sites, F. sylvatica and Q. petraea reduced the extent of their G c50 OS to a higher degree than P. sylvestris. This indicates a higher level of G c50 OS adjustment to the drier site conditions for the two broadleaved species. These differences were more pronounced when using the dendrometer-derived tree internal water status as proxy for tree water supply. Our results provide preliminary evidence for diverging short-term G c responses when temperate trees are exposed to prolonged reduction in water availability. These findings suggest that G c50 OS can help to constrain species-specific predictions of water use by mature trees, especially when combined with high-resolution water potential measurements. [ABSTRACT FROM AUTHOR]

• Junipers had early growth onset and cessation but short growing season than spruces. • Daily tree stem increments associated with atmospheric water conditions. • Long-term tree growth depends on the soil water availability in dryland. • Site aridity influence temporal tree growth in cold and arid ecosystems. Climate change alters regional aridity and species composition in dryland ecosystems. However, the effect of varying aridity and species-specific responses on tree growth remains unclear. Here, we used high-resolution dendrometers to analyze the climatic factors controlling stem diameter variation in two alpine coniferous species, Qilian juniper (Juniperus przewalskii) and Qinghai spruce (Picea crassifolia), in their eastern- and western-most distributions (two species × two sites) in the Qilian Mountains during the 2018–2021 growing seasons. We observed species-, site-, and year-specific differences in growth phenology and radial growth dynamics. Juniper had early growth onset and cessation, but short growing season compared to spruce. Trees in the eastern sites showed earlier growth onset, later cessation, and a much longer growing season than those in the western sites for both species. Daily stem growth revealed similar responses for both species and site aridity, with daily vapor pressure deficit, maximum temperature, and solar radiation negatively, and relative humidity and precipitation positively affecting stem increments. However, when observation was extended to 7 or 21 days, the effect of precipitation on stem increments became weak or negligible in the wetter eastern sites, while continuing in the arid western sites. Further, soil water content appeared to have an impact on growth in the arid western site for both species. These results were confirmed by linear mixed-effects models, which revealed that site-aridity play an important role on tree stem variation, especially in junipers. Our results suggest that although short-term atmospheric water conditions influence radial stem variation, intra-annual tree growth still depends on soil water availability in drylands. Our findings provide new evidence of potential uses of dendrometers to measure environmental stress on tree growth and reveal that site aridity and species influence tree growth at different time scales in cold and arid ecosystems. [ABSTRACT FROM AUTHOR]

Determining the effect of a changing climate on tree growth will ultimately depend on our understanding of wood formation processes and how they can be affected by environmental conditions. In this context, monitoring intra-annual radial growth with high temporal resolution through point dendrometers has often been used. Another widespread approach is the microcoring method to follow xylem and phloem formation at the cellular level. Although both register the same biological process (secondary growth), given the limitations of each method, each delivers specific insights that can be combined to obtain a better picture of the process as a whole. To explore the potential of visualizing combined dendrometer and histological monitoring data and scrutinize intra-annual growth data on both dimensions (dendrometer → continuous; microcoring → discrete), we developed DevX (Dendrometer vs. Xylogenesis), a visualization application using the “Shiny” package in the R programming language. The interactive visualization allows the display of dendrometer curves and the overlay of commonly used growth model fits (Gompertz and Weibull) as well as the calculation of wood phenology estimates based on these fits (growth onset, growth cessation, and duration). Furthermore, the growth curves have interactive points to show the corresponding histological section, where the amount and development stage of the tissues at that particular time point can be observed. This allows to see the agreement of dendrometer derived phenology and the development status at the cellular level, and by this help disentangle shrinkage and swelling due to water uptake from actual radial growth. We present a case study with monitoring data for Acer pseudoplatanus L., Fagus sylvatica L., and Quercus robur L. trees growing in a mixed stand in northeastern Germany. The presented application is an example of the innovative and easy to access use of programming languages as basis for data visualization, and can be further used as a learning tool in the topic of wood formation and its ecology. Combining continuous dendrometer data with the discrete information from histological-sections provides a tool to identify active periods of wood formation from dendrometer series (calibrate) and explore monitoring datasets.

Under drought conditions, even tropical rainforests might turn from carbon sinks to sources, and tree species composition might be altered by increased mortality. We monitored stem diameter variations of 40 tree individuals with stem diameters above 10 cm belonging to eleven different tree genera and three tree life forms with high-resolution dendrometers from July 2007 to November 2010 and additionally March 2015 to December 2017 in a tropical mountain rainforest in South Ecuador, a biodiversity hotspot with more than 300 different tree species belonging to different functional types. Although our study area receives around 2200 mm of annual rainfall, dry spells occur regularly during so-called “Veranillo del Niño” (VdN) periods in October-November. In climate change scenarios, droughts are expected with higher frequency and intensity as today. We selected dry intervals with a minimum of four consecutive days to examine how different tree species respond to drought stress, raising the question if some species are better adapted to a possible higher frequency and increasing duration of dry periods. We analyzed the averaged species-specific stem shrinkage rates and recovery times during and after dry periods. The two deciduous broadleaved species Cedrela montana and Handroanthus chrysanthus showed the biggest stem shrinkage of up to 2 mm after 10 consecutive dry days. A comparison of daily circumference changes over 600 consecutive days revealed different drought responses between the families concerning the percentage of days with stem shrinkage/increment, ranging from 27.5 to 72.5% for Graffenrieda emarginata to 45–55% for Podocarpus oleifolius under same climate conditions. Moreover, we found great difference of recovery times after longer-lasting (i.e., eight to ten days) VdN drought events between the two evergreen broadleaved species Vismia cavanillesiana and Tapirira guianensis. While Vismia replenished to pre-VdN stem circumference after only 5 days, Tapirira needed 52 days on average to restore its circumference. Hence, a higher frequency of droughts might increase inter-species competition and species-specific mortality and might finally alter the species composition of the ecosystem.

A conspicuous feature of natural communities is that individuals within species exhibit broad variation in their phenotype. While the phenotypic differences among species are prominent and have received considerable attention in earlier studies, recent findings suggest that about 40% of the trait variation is found within species. How this intraspecific variation is related to underlying environmental gradients and ultimately linked to performance is an outstanding question in ecology and evolution. Here, we study six broadly distributed species across an elevational gradient in a subtropical forest. We focused on five functional traits reflecting plant functional differentiation in stem transport, leaf architecture, and leaf resource acquisition. We found that leaf thickness, leaf toughness, and specific leaf area generally varied with elevation, while wood density and leaf area exhibited constrained variation. Results on multivariate trait axes also showed mixed evidence with the PC1 values (positively related to leaf toughness and negatively related to specific leaf area) shifting with elevation, while PC2 values (negatively related to wood density) did not change with elevation. We also found that, despite the important variation in some traits along the gradient, growth performance did not follow this same trend. This suggests that strong directional changes in traits along the gradient may result in similar levels of demographic performance. The results, therefore, challenge the simple expectation that a trait will correlate with a demographic rate. More nuanced approaches and additional mechanisms must be considered to advance understanding of the performance–trait relationships. [ABSTRACT FROM AUTHOR]

• Global pattern of tree DBH growth in non-plantations was affected most by climate. • Stand wood production in non-plantations was correlated with stand mean DBH growth. • Global pattern of tree DBH growth in plantations was affected most by taxon. • Global stand wood production in plantations was affected most by taxon and density. Mangrove forests provide important ecological and economic services including carbon sequestration and storage. The conservation and restoration of mangroves are expected to play an important role in mitigating climate change, and understanding the factors influencing mangrove stem growth and wood production are important in predicting and improving mangrove carbon sequestration and responses to environmental change. In this study, we collected data of individual diameter at breast height (DBH) growth rate and stand level aboveground wood production in both non-plantation (commonly termed as natural) mangroves and mangrove plantations across the world. Climatic factors, proxies of edaphic factors, as well as biological factors (e.g. mangrove species) were included as explanatory variables in the analyses to determine factors influencing the global patterns of tree growth rate and stand wood production of mangroves. Using hierarchical Classification and Regression Tree (CART) analysis we found interactions among environmental and biological factors in controlling mangrove tree growth rate and stand wood production. We also found different global patterns of tree growth rate and stand wood production between non-plantation mangroves and plantations. Climatic conditions (precipitation of driest season, precipitation seasonality) were the most important factors influencing the global pattern of tree DBH growth rate in non-plantation mangroves, with edaphic and biological characteristics also playing a role under specific climatic conditions. The global pattern of stand wood production in non-plantation mangroves was primarily determined by stand mean DBH growth rate of individual trees. However, in mangrove plantations management measures, specifically species selection and planting density, were the most important factors influencing the global patterns of tree growth rate and stand wood production. Our study provides parameters for a global estimation of long-term carbon sequestration in both non-plantation mangroves and mangrove plantations. In addition, our results help us better predict the dynamics of tree growth and carbon sequestration of non-plantation mangroves under changing climate. [ABSTRACT FROM AUTHOR]

• Unsupervised Anomaly-detection pipeline, allowing to identify faulty dendrometers. • Preserving data quality for irrigation decisions, based on dendrometer sensors. • Identification of anomalies, undetectable only with a "massively univariate" approach. • Visualization aids to identify faulty dendrometers in large networks. Ensuring the integrity of data from large sensor networks is a challenging task that is relevant in many domains. Precision agriculture is one instance of this challenge, where dendrometer sensors provide data used for plot-specific irrigation decisions, with critical implications for yields and water savings. To aid the identification of malfunctioning dendrometer sensors, we introduce a pipeline for detecting various types of anomalies and investigating their root causes using visual analytics. Our pipeline is unique not only in that it borrows from web technologies to provide interactivity, but also because it incorporates detection algorithms from several fields, such as robust multivariate statistics, unsupervised machine learning, and social-network analysis. [ABSTRACT FROM AUTHOR]

Highlights • Thinning affected the beginning and end of growth. • Thinning increased the cumulative growth. • Thinning increased the growing season. • Thinned trees showed less vulnerability to drought. Abstract Thinning is a forestry technique that can improve growth in the remaining trees and make them less vulnerable to water stress, buffering the imminent climatic changes. However, thinning effects have not been thoroughly explored using high-resolution measurements of stem-diameter variation in natural ecosystems, which can provide valuable information on secondary tree growth, relations to climatic variables, and possible water-stress events. In this study, a gradient of thinning intensity was applied on a Pinus halepensis Mill. afforestation in the semiarid SE of the Iberian Peninsula to ascertain the effects on the daily, monthly, annual, and total cumulative growth as well as the relationships between climatic variables and tree-growth parameters (climate-growth sensitivity). The thinning treatments, applied in 2005, consisted of reductions of 75% in the mean basal area (T75), 60% (T60), 48% (T48), and an unthinned control (T0). Digital dendrometers were installed in 2010, 5 years after thinning, to characterize secondary tree growth—i.e. daily-stem variation (DSV), cumulative growth (CG), and the maximum daily shrinkage (MDS), but also the number of days of growth over a 3-year period. Thinning treatments affected the onset and end of growth, making the growing season longer after more intense thinning treatments. Also, the total cumulative growth of the stem diameter increased over the study period following the gradient of thinning intensity. From correlations among climatic variables and DSV, MDS, and CG, we conclude that thinned trees showed better climatic sensitivity and efficiency in the resources use and therefore a stronger adaptation to the environment and greater resilience to perturbations, despite that tree monitoring started 5 years after thinning. In view of these results, we recommend thinning as a tool to adapt forest ecosystems to climate change in Mediterranean areas. [ABSTRACT FROM AUTHOR]

Key message: We investigate the intra-annual growth patterns of Chinese pine in Helan Mountains, confirming that regional water status plays a dominated role in stem radial increment. The associations between environmental conditions and stem radial increment (SRI) are useful for assessing a species' growth response to climate change. Intra-annual SRI dynamics of Chinese pine (Pinus tabulaeformis) were monitored half-hourly by automatic point dendrometer during the growing season (May–September) in 2016 and 2017 at two altitudes in the Helan Mountains, northern central China. Here, we compared the seasonal growth patterns between two altitudes and 2 years. Trees at low altitude are characterized by earlier cessation, shorter growing season, and lower growth rate, resulting in less annual growth, which may reflect the greater drought intensified by rising temperature at low altitude. June precipitation significantly affected tree growth rate. The xylem growth was active when daily mean air temperature was 9.9 °C at our study region for P. tabulaeformis in an arid environment. During the growing season, daily stem radial increment showed a significantly positive correlation with precipitation and a negative correlation with daily air temperature at all altitudes. Climatic variables associated with tree water status, namely precipitation, vapor pressure deficit, and relative humidity, played important roles in daily stem radial increment as the same result as a linear mixed model. These factors drive the complex physiological processes of stem radial increment by influencing the moisture available to the tree. [ABSTRACT FROM AUTHOR]

Under drought conditions, even tropical rainforests might turn from carbon sinks to sources, and tree species composition might be altered by increased mortality. We monitored stem diameter variations of 40 tree individuals with stem diameters above 10 cm belonging to eleven different tree genera and three tree life forms with high-resolution dendrometers from July 2007 to November 2010 and additionally March 2015 to December 2017 in a tropical mountain rainforest in South Ecuador, a biodiversity hotspot with more than 300 different tree species belonging to different functional types. Although our study area receives around 2200 mm of annual rainfall, dry spells occur regularly during so-called "Veranillo del Niño" (VdN) periods in October-November. In climate change scenarios, droughts are expected with higher frequency and intensity as today. We selected dry intervals with a minimum of four consecutive days to examine how different tree species respond to drought stress, raising the question if some species are better adapted to a possible higher frequency and increasing duration of dry periods. We analyzed the averaged species-specific stem shrinkage rates and recovery times during and after dry periods. The two deciduous broadleaved species Cedrela montana and Handroanthus chrysanthus showed the biggest stem shrinkage of up to 2 mm after 10 consecutive dry days. A comparison of daily circumference changes over 600 consecutive days revealed different drought responses between the families concerning the percentage of days with stem shrinkage/increment, ranging from 27.5 to 72.5% for Graffenrieda emarginata to 45–55% for Podocarpus oleifolius under same climate conditions. Moreover, we found great difference of recovery times after longer-lasting (i.e., eight to ten days) VdN drought events between the two evergreen broadleaved species Vismia cavanillesiana and Tapirira guianensis. While Vismia replenished to pre-VdN stem circumference after only 5 days, Tapirira needed 52 days on average to restore its circumference. Hence, a higher frequency of droughts might increase inter-species competition and species-specific mortality and might finally alter the species composition of the ecosystem. [ABSTRACT FROM AUTHOR]

Analysis of continuous sap flux and stem growth measurements can help to elucidate how environmental conditions influence water status and stem growth in trees. Stem radius variations and sap flux densities of the drought-tolerant conifer Cedrus libani were measured using automatic point dendrometers and heat dissipation sensors, respectively. The study was conducted at the Elmalı Cedar Research Forest at 1665 m a.s.l. From April to September 2009, stem radius variation was measured hourly for nine C. libani trees. Concurrently, environmental variables (e.g., air temperature, precipitation, relative humidity, soil water content) were monitored within the study site. From the dendrometer records, maximum daily shrinkage (MDS) of the stem radius was calculated. From June to August, a time period of 2 months, four of the nine study trees were selected for hourly measurements of sap flux density (Js). Daily courses of stem radius variation and Js were very uniform and similar for all studied trees. A daily hysteresis effect was observed, reflecting the pattern of water storage and retrieval. Means of MDS and Js varied between 0.09 and 0.15 mm and between 4.3 and 10.6 g m-2 s-1, respectively. Daily maximum Js varied between 8.0 and 33 g m-2 s-1. Correlation and regression analyses between MDS and Js and environmental variables revealed that MDS and Js were most closely related to vapor pressure deficit and photosynthetic active radiation, respectively. We conclude that C. libani is well adapted to the current environmental conditions at the study site (natural habitat) and that atmospheric conditions play a primary role in transpiration and tree growth. [ABSTRACT FROM AUTHOR]

Drought is generally associated with the persistence of low precipitation amount, decreased soil moisture and water availability relative to the normal levels in a designated area. The effects of drought, range from the morphological to molecular levels, and are evident at all phenological stages of the plant growth, at whatever stage the water deficit occurs. Determination of the surface water demands for irrigation purposes comes out from the assumption of hydrologic processes stationarity. This paper shows our research prerequisite that water stress participates in an important part on the volume changes of over ground parts, which is predictive for the irrigation demand. Malus domestica var. Yellow Transparent was chosen for the measurement of volume changes of the surface plant parts. Our measurements were realised by the Diameter dendrometer small (DD-S) from 24.08. to 13.09.2017. One tree was irrigated by the dose of 50 mm. We compared the dendrometric changes to soil moisture and rainfall on both irrigated and non-irrigated trees. The experiment showed the differences between the irrigated apple tree (the diameters of the branches fluctuated between 11.9 and 12.1 mm) and the non-irrigated apple tree (the diameter of the branches increased after three-day rain from 8.35 to 8.61 mm), in order to determine the water stress of plants based on dendrometric changes and optimize irrigation during the drought period. [ABSTRACT FROM AUTHOR]

Almond yields vary between rainfed and intensively irrigated systems, but how to match irrigation to potential productivity is unclear. Hence, we compared almond physiology under deficit (600 mm) and full (1300 mm) irrigation to identify stress indices and determine the production overheads of mismanaged watering. We hypothesized that trees alter their growth to conserve resources during drought and mitigate their hydraulic stress responses. Thus, we monitored stem water potential and stomatal conductance to characterize the hydraulic responses of trees to deficient and hydrated water conditions. Adapting the seasonal relationship between irrigation coefficients and tree water potential was also tested. Finally, soil water status and trunk development were considered physical stress indices for field conditions. Soil water depletion in deficit irrigation reduced stem water potential below − 2 MPa and checked stomatal conductance at 0.15 mol m-2 s-1 for most of the growing season. An empirical productivity model determined that, under deficit irrigation, almond trees suffer from chronic stress that limits their photosynthetic capacity to ∼14 µmol m-2 s-1. Consequently, nominal assimilation limitations (10%) in early summer manifested to 4 kg C tree-1 metabolic losses by autumn. The inter-annual vegetative limitations in deficit irrigation resulted in significant yield reductions (35%) by the second experimental season. Temporal changes in the correlations between stem water potential, stomatal conductance, and trunk contractions made it difficult to use water stress indices to make irrigation decisions. However, normalizing tree performance by phenology indicated a 960 mm irrigation that supported high yields. Further, integrating the variability in soil water with trunk dendrometry illustrated that trees could maintain constant growth between irrigation days under well-watered conditions. Hence, in commercial operations, variable growth rates and trunk contraction measures signal insufficient irrigation and could guide practical irrigation adaptations. • Global yield discrepancies in almond farms relate to water allocations. • Almonds mask stress indices as they exhaust water and energy resources. • Adapting irrigation via transient drought indices saves water without stress. • Productivity losses in deficit irrigation may not be sustainable. [ABSTRACT FROM AUTHOR]

Fagus sylvatica L. is one of the most important commercial tree species in Europe and its natural distribution range is expected to shift northwards due to climatic changes. Detailed information of factors affecting its growth is crucial as a basis for recommendations of wider use of this tree species. Aim of the study was to characterize the changes of radial growth intensity of European beech during a vegetation season. In mature beech stand in northwest Latvia two sample trees (dominant (DT) and suppressed (ST)) were selected in Hylocomiosa forest type. Continuous measurements of changes of stem diameter and xylem sap fl ow as well as meteorological parameters were carried out. Stem cycle approach was applied to distinguish the duration of contraction, expansion and increment of the stem. Onset and cessation of growth of the ST tree was observed several days later compared with DT and mean growth intensity during the entire observation period was considerably lower (0.014 mm/day-1 for ST and 0.022 mm/day-1 for DT, respectively). Most intensive growth increment diurnally was observed in the early morning before sunrise, and seasonally till beginning of July. Positive effect of precipitation and low water pressure deficit (VPD) on growth was observed, while high VPD coincided with stem contraction. Results indicate the sensitivity of radial growth of European beech to water deficit and high atmospheric transpirational demand; therefore, future potential of cultivation of beech in Latvia depends on changes in moisture regime.

Using measurements from high resolution monitoring of radial tree-growth we present new data of the growth reactions of four widespread broadleaved tree-species to the combined European drought years 2018 and 2019. We can show that, in contrast to field crops, trees could make better use of the winter soil moisture storage in 2018 which buffered them from severe drought stress and growth depressions in this year. Nevertheless, legacy effects of the 2018 drought accompanied by sustained low soil moisture conditions (missing recharge in winter) and again higher than average temperatures and low precipitation in spring/summer 2019 have resulted in severe growth reductions for all studied tree-species in this year. This highlights the pivotal role of soil water recharge in winter. Although short term resistance to hot summers can be high if sufficient winter precipitations buffers forest stands from drought damage, legacy effects will strongly impact tree growth in subsequent years if the drought persists. The two years 2018 and 2019 are extreme with regard to historical instrumental data but, according to regional climate models, resemble rather normal conditions of the climate in the second half of the 21st century. Therefore the observed strongly reduced growth rates can provide an outlook on future forest growth potential in northern Central Europe and beyond.

Dendrometers offer a useful tool for long-term, high-resolution monitoring of tree responses to environmental fluctuations and climate change. Here, we analyze a 4-year dendrometer dataset (2014–17) on European beech (Fagus sylvatica L.), common hornbeam (Carpinus betulus L.) and pedunculate oak (Quercus robur L.), co-occuring in a mixed broadleaved forest in northeastern Germany. In our analyses, we focus both on seasonal growth dynamics as well as on the environmental forcing of daily stem-size variations. Over the study period with contrasting weather conditions, we observed species- and year-specific differences in growth phenology (i.e. growth onset, cessation and duration). Oak was characterized by early growth onset and long growth duration in all years as compared with beech and hornbeam. The analysis on the environmental forcing of daily stem dynamics revealed, however, highly similar responses for the studied species, with current-day vapor pressure deficit and sunshine duration negatively, and relative humidity and precipitation positively affecting stem size. When considering lagged effects, environmental conditions often oppositely affected stem-size changes. No consistent seasonality in environmental responses was detected, though specific weather conditions were found to affect temporal patterns in individual years. We suggest that the high similarity in environmental forcing observed between tree species can be explained by daily stem-size changes mainly reflecting tree water status rather than tree growth. Our results stress that correcting dendrometer series for reversible stem hydrological changes is of utmost importance to better quantify tree growth from dendrometers in future. [ABSTRACT FROM AUTHOR]

Summary: Climate change will further constrain water availability in dry inner‐alpine environments and affect water relations and growth conditions in mountain forests, including the widespread larch forests. To estimate the effects of climate conditions on water balance and growth, variation in sap flow and stem radius of European larch was measured for 3 yr along an elevation transect from 1070 to 2250 m above sea level (asl) in an inner‐alpine dry valley in South Tyrol/Italy. Additionally, long‐term climate–growth relations were derived from tree cores. Sap flow and radial growth were reduced in dry periods up to an elevation of 1715 m, leading to maximum annual growth at 2000 m. In a wet year no growth difference between elevations was observed. Long‐term tree ring data showed a positive growth response to precipitation up to 1715 m and to temperature only above 2000 m. Our results demonstrate that reduced water availability and higher atmospheric water demand limit larch at low elevation within dry Alpine regions. This indicates a general upward shift of this species’ elevational amplitude upon climate change, and respective negative effects on future silvicultural use and ecosystem services at lower elevations in the European Alps. [ABSTRACT FROM AUTHOR]

Key message: The increment duration and rate were equally important in controlling annual stem radial increments of Picea meyeri at its upper limit of distribution.Abstract: Stem radial increment rate and duration are the most important parameters in determining the width of annual tree rings. To identify the contributions of rate and duration to annual radial increments and their relationships with environmental factors, we analyzed intra-annual stem increments of five Picea meyeri trees in a sub-alpine habitat of North-Central China over 7 years (2008-2015, except for the year 2012) with point dendrometers in this study. The results showed the following. (1) We estimated that approximately 53% of the variability in the annual radial increments is attributable to the rate of radial increment and approximately 47% to its duration. (2) The contribution of cessation time to the annual increments was more than three times that of the initiation time. (3) The initiation of radial increment was primarily controlled by soil temperature and warmer soil temperature could advance the initiation time. The cessation and rate of radial increment were mainly influenced by thermal and light-related environmental factors. During growing seasons, low temperatures and insufficient light caused by many rainy and cloudy days at the high altitudes of the Luya Mountains may result in earlier cessations and lower rates of radial increment. Overall, our results may have further applications in modeling the responses of tree stem growth to climate change in a sub-alpine habitat of North-Central China. [ABSTRACT FROM AUTHOR]

Mangrove forests depend on a dense structure of sufficiently large trees to fulfil their essential functions as providers of food and wood for animals and people, CO2 sinks and protection from storms. Growth of these forests is known to be dependent on the salinity of soil water, but the influence of foliar uptake of rainwater as a freshwater source, additional to soil water, has hardly been investigated. Under field conditions in Australia, stem diameter variation, sap flow and stem water potential of the grey mangrove (Avicennia marina (Forssk.) Vierh.) were simultaneously measured during alternating dry and rainy periods. We found that sap flow in A. marina was reversed, from canopy to roots, during and shortly after rainfall events. Simultaneously, stem diameters rapidly increased with growth rates up to 70 µmh-1, which is about 25-75 times the normal growth rate reported in temperate trees. A mechanistic tree model was applied to provide evidence that A. marina trees take up water through their leaves, and that this water contributes to turgor-driven stem growth. Our results indicate that direct uptake of freshwater by the canopy during rainfall supports mangrove tree growth and serve as a call to consider this water uptake pathway if we aspire to correctly assess influences of changing rainfall patterns on mangrove tree growth. [ABSTRACT FROM AUTHOR]

Stem water storage is an important water pool in forests. However, we know little about the heartwood water use processes and the water use strategies of trees in semi-arid temperate forests. We investigated Simon poplar ( Populus simonii ), a heartwood water storage tree species. A combination of methods (sap flow, the dendrometer and the soil–plant–atmosphere canopy model were used to trace the water use dynamics of Simon poplar trees. The aim was to understand how this heartwood water storage tree species survives under drought stress. Our field data showed that P. simonii had significantly higher heartwood water content (60%) than other tree species (30%) in the same region. The enhanced tree water deficit (TWD) and continuous stem shrinkage showed that the heartwood water supply was able to maintain sap flow (1.5–4.6 mm/d) during early growing season droughts. The strong water absorption ability of the roots resulted in the quick recovery of TWD, which caused the rain water could hardly reach 50 cm depth in the soil. The weakened link between transpiration and root water assimilation of heartwood water storage trees meant that sap flow was more sensitive to drivers such as air temperature (R  = −0.71, p < 0.01) and vapor pressure deficit (R = 0.69, p < 0.01). These results suggest that heartwood water storage may buffer drought events during the growing season and reduce the wide fluctuation in interannual precipitation. Therefore, heartwood water storage needs to be taken into account when calculating the soil–plant–atmosphere continuum and creating tree survival models. [ABSTRACT FROM AUTHOR]

Radial tree stem growth of Norway spruce ( Picea abies (L.) H. Karst.), European beech ( Fagus sylvatica L.), Scots pine ( Pinus sylvestris L.), and stone pine ( Pinus cembra L.) was monitored from 2012 to 2015 across sites in Austria with high-resolution dendrometers. Seasonal cumulative diameter increment was modeled using a hierarchical nonlinear mixed-effects model framework based on a logistic growth curve. In the dry and warm year 2015, the average annual diameter increment of 0.30 cm decreased by 50% on lower elevation sites and by 10% on higher elevation sites. In the cool and moist year 2014, Norway spruce achieved a higher annual diameter increment than European beech, whereas the opposite occurred in the dry and warm years 2013 and 2015. In the mixed beech-spruce stand, beech's consumptive water-use strategy has obviously caused intensified stress for spruce in these drought periods. On higher elevation sites, Norway spruce reacted more sensitively to climate fluctuation compared with stone pine, but overall reactions were only weak. Productivity varied strongly depending on the social status of the tree, with dominant and intermediate trees suffering more from drought. As warming and drought lowers increment rates on lower elevation sites and as trees on higher elevation sites react less flexibly, productivity losses are expected for Austrian forests due to climate warming. [ABSTRACT FROM AUTHOR]

Understanding forest responses to the current climate change requires to investigate the effects of competition, buffering or enhancing process of forests decline. Here we attempt to place intra-specific competition in a climate change context, using as experimental system the drought-sensitive fir Abies pinsapo . We conducted a decade-long (2004–2015) investigation at four permanent plots (two thinned plots and two controls), where all trees were identified, tagged and mapped. Experimental thinning was performed attempting to enhance stand structure diversity by (1) reducing tree competition, (2) increasing the equitability of size classes (i.e. diversity) and (3) randomizing tree spatial pattern. We focus on tree basal area increment and sap flow density, as regards microclimate and competition, to quantify the extent to that thinning alleviates drought in the remaining trees. The results support that lower competition fosters short- to long-term tree-level physiological responses, specifically, improved growth and water uptake in the remaining trees. Density reduction provides a promising strategy for minimizing climate change effects on drought-sensitive tree species by improving resources availability to the remaining trees. Nevertheless, our results also support a higher air temperature and soil water depletion according to density reduction, suggesting that lower competition might also increase soil and understory evapotranspiration. Adaptive management, as the experimental thinning reported here, may increase tree-level resources availability, but the long-term stand-level effectiveness of this approach at sustaining forest ecosystem functioning remains uncertain. [ABSTRACT FROM AUTHOR]

Almost all Australian tropical and subtropical regions lack annually-resolved long-term (multi-decadal to centennial scale) instrumental climate records. Reconstructing climate in these regions requires the use of sparse climate proxy records such as tree rings. Tree rings often archive annually-resolved centennial-scale climate information. However, many tropical and subtropical species have short life-spans, the timbers are poorly preserved, and there is a belief that the proxy records of these species are often compromised by ring anomalies. Additionally, for many species the relationship between climate (e.g. temperature and/or rainfall) and tree growth has not been established. These factors have led to tree-ring data being underutilized in the Australian subtropics. Trees in the Araucariaceae family, a common family in northern and eastern Australia, are both longer lived than many species in the Australian subtropics, present growth rings that are annual in nature, and their growth is known to vary with climate. In this study we examine two subtropical Araucariaceae species, Araucaria cunninghamii and Araucaria bidwillii , and quantify the relationship between their radial growth and climate variability. Ring anomalies including false, faint, locally absent, and pinching rings, are found to be present in these species, however, bomb-pulse radiocarbon dating of A. cunninghamii samples together with a whole tree approach helped to identify annual growth patterns despite such anomalous ring boundaries. Additionally, to determine which climate variables most influence growth in these species, dendrometers were installed at two locations in subtropical Southeast Queensland, Australia. We found that rainfall variability drives annual ring growth, while temperature constrains the onset and conclusion of the growth season each year. Our results demonstrate that through the use of A. cunninghamii and A. bidwillii trees which demonstrate annual growth in relation to climate variables there is potential to develop centennial scale climate reconstructions from the Australian subtropics. We provide recommendations on how to best identify ring anomalies in these species to help in the future development of long-term chronologies and climate reconstructions. [ABSTRACT FROM AUTHOR]

In Mediterranean climates, bimodal growth patterns, corresponding to two peaks in radial increment during favorable seasons, have been described in several tree species. However, we lack a better mechanistic understanding of bimodality and its potential responses to the predicted warming and aridification trends. Filling this research gap is important since growth duration affects the capacity of trees to form wood and uptake carbon. Here we used an 11-year (1994–2004) long record of dendrometer data of the Mediterranean Holm oak ( Quercus ilex ) and compared how climate related to radial increment in trees from the south- and the north-facing slopes. We also related climate variables to tree-ring width and the production of intra-annual density fluctuations (IADFs), which reflects bimodality. In this paper, we introduce a model called VS-Lite2 to simulate tree-growth dynamics, which is a modified version of the process-based Vaganov-Shashkin Lite model. The VS-Lite2 model adequately reproduced the bimodal intra‐annual pattern of radial growth, IADFs, and annual tree growth. Trees from the south-oriented slope grew more, produced more IADFs and showed a more marked bimodal pattern than trees from the north-facing slope. These differences agree with the observation that late-summer drought constrained growth. Therefore, radial-growth models should consider plastic bimodality and micro-environmental conditions in areas subjected to seasonal droughts. [ABSTRACT FROM AUTHOR]

Maximum daily trunk shrinkage (MDS) has been suggested as an appropriate indicator of plant water status because it is closely related to stem water potential. Interaction of MDS and fruit quality was studied in plum (Prunus domestica L. ‘Jojo’/Wavit and ‘Tophit plus’/Wavit) in temperate climate. According to the MDS data, trees were grouped as low MDS (LMDS) and high MDS (HMDS). Fruit quality was analysed during fruit development (95, 103, 117 DAFB for ‘Jojo’ and 99, 112, 121 DAFB for ‘Tophit plus’) before commercial harvest. Fruit picked at commercial harvest (137 DAFB and 140 DAFB for ‘Jojo’ and ‘Tophit plus’, respectively) were stored at 2 ± 0.5 °C (90 ± 2% RH) for 28 days, and 2 days shelf life at 20 °C providing 6 measuring dates postharvest. Results confirmed that MDS was positively correlated with water vapour pressure deficit also in the apparent temperate, semi-humid climate. Transpiration of fruit from high crop load and resulting HMDS trees, which can be assessed as physiologically drought, was low compared to that of fruit from LMDS trees. Furthermore, HMDS tree grown plums had enhanced soluble solids and dry matter contents with a tendency of reduced fruit size. [ABSTRACT FROM AUTHOR]

Grapevines are characterized by a period of irreversible stem shrinkage around the onset of ripening of the grape berries. Since this shrinkage is unrelated to meteorological conditions or drought, it is often suggested that it is caused by the increased sink strength of the grape berries during this period. However, no studies so far have experimentally investigated the mechanisms underlying this irreversible stem shrinkage. We therefore combined continuous measurements of stem diameter variations and histology of potted 2-year-old grapevines (Vitis vinifera L. 'Boskoop Glory'). Sink strength was altered by pruning all grape clusters (treatment P), while non-pruned grapevines served as control (treatment C). Unexpectedly, our results showed irreversible post-veraison stem shrinkage in both treatments, suggesting that the shrinkage is not linked to grape berry sink strength. Anatomical analysis indicated that the shrinkage is the result of the formation of successive concentric periderm layers, and the subsequent dehydration and compression of the older bark tissues, an anatomical feature that is characteristic of Vitis stems. Stem shrinkage is hence unrelated to grape berry development, in contrast to what has been previously suggested. [ABSTRACT FROM AUTHOR]

A fast-responding inexpensive dendrometer is needed for measuring daily or hourly plant growth responses to water stress. This study reports on a low-cost microcontroller driven Trunk Diameter Variations (TDV) measurement system that was designed and constructed for automating the measurement and recording of plant stem diameter. The TDV system comprises of an ATmega 328/P microcontroller, which forms the heart of the controlling circuit, a real time clock for time stamping measurements, liquid crystal display for displaying purposes and an external secure digital card and shield for storing measured data. The stem diameter variations are measured by a caliper-type sensor based on a full bridge strain gauge that is attached to a flexible arm of mild steel. When bearing bending strain, the excited full bridge strain gauge outputs a voltage directly proportional to the bending strain, hence linear displacement. The TDV sensor displacement calibration procedure was carried out using an inside micrometer from a calibration kit. The calibration of the sensor indicated a linear relationship between the displacement and the sensor’s output voltage with a high coefficient of determination value of 0.998, calibration multiplier of 0.426 mm V −1 and an offset output voltage of 0.688 V. The TDV sensor was mounted on a smooth cylindrical dried wood away from direct sunlight and rain while air temperature was measured close to the TDV installation. Temperature sensitivity test results show that the accuracy of the sensor above 20 °C is 0.031 mm and for temperatures below 20 °C the accuracy is above 0.050 mm. The TDV system was tested on a tomato plant for 42 days, Fountain tree for three weeks and on a Citrus tree for one week under greenhouse and open-field conditions in order to evaluate its performance and suitability under different plant species and climatic conditions. The TDV system proved to be robust and produced valid results on the plant’s physiological measurements, with a good storage of the measured data over the experimental period. We concluded that the TDV system is suitable for stem diameter variations measurements and water and fertilizer stress monitoring on herbaceous and woody stem plants due to its fast response (hourly or less), ease of construction and installation, and low cost (