scholarly journals Coincidences of climate extremes and anomalous vegetation responses: comparing tree ring patterns to simulated productivity

2015 ◽  
Vol 12 (2) ◽  
pp. 373-385 ◽  
Author(s):  
A. Rammig ◽  
M. Wiedermann ◽  
J. F. Donges ◽  
F. Babst ◽  
W. von Bloh ◽  
...  
Keyword(s):  
Tree Ring ◽  
Tree Growth ◽  
Climate Extremes ◽  
Terrestrial Ecosystems ◽  
Generic Model ◽  
Response Patterns ◽  
Analysis Scheme ◽  
Tree Ring Data ◽  
Vegetation Models

Abstract. Climate extremes can trigger exceptional responses in terrestrial ecosystems, for instance by altering growth or mortality rates. Such effects are often manifested in reductions in net primary productivity (NPP). Investigating a Europe-wide network of annual radial tree growth records confirms this pattern: we find that 28% of tree ring width (TRW) indices are below two standard deviations in years in which extremely low precipitation, high temperatures or the combination of both noticeably affect tree growth. Based on these findings, we investigate possibilities for detecting climate-driven patterns in long-term TRW data to evaluate state-of-the-art dynamic vegetation models such as the Lund-Potsdam-Jena dynamic global vegetation model for managed land (LPJmL). The major problem in this context is that LPJmL simulates NPP but not explicitly the radial tree growth, and we need to develop a generic method to allow for a comparison between simulated and observed response patterns. We propose an analysis scheme that quantifies the coincidence rate of climate extremes with some biotic responses (here TRW or simulated NPP). We find a relative reduction of 34% in simulated NPP during precipitation, temperature and combined extremes. This reduction is comparable to the TRW response patterns, but the model responds much more sensitively to drought stress. We identify 10 extreme years during the 20th century during which both model and measurements indicate high coincidence rates across Europe. However, we detect substantial regional differences in simulated and observed responses to climatic extreme events. One explanation for this discrepancy could be the tendency of tree ring data to originate from climatically stressed sites. The difference between model and observed data is amplified by the fact that dynamic vegetation models are designed to simulate mean ecosystem responses on landscape or regional scales. We find that both simulation results and measurements display carry-over effects from climate anomalies during the previous year. We conclude that radial tree growth chronologies provide a suitable basis for generic model benchmarks. The broad application of coincidence analysis in generic model benchmarks along with an increased availability of representative long-term measurements and improved process-based models will refine projections of the long-term carbon balance in terrestrial ecosystems.

scholarly journals Tree-ring responses to extreme climate events as benchmarks for terrestrial dynamic vegetation models

2014 ◽  
Vol 11 (2) ◽  
pp. 2537-2568 ◽  
Author(s):  
A. Rammig ◽  
M. Wiedermann ◽  
J. F. Donges ◽  
F. Babst ◽  
W. von Bloh ◽  
...  
Keyword(s):  
Tree Ring ◽  
Tree Growth ◽  
Extreme Events ◽  
Ring Width ◽  
Climate Extremes ◽  
Tree Ring Width ◽  
Model Data ◽  
Vegetation Models ◽  
The Impact

Abstract. Climate extremes can trigger exceptional responses in terrestrial ecosystems, for instance by altering growth or mortality rates. Effects of this kind are often manifested in reductions of the local net primary production (NPP). Investigating a set of European long-term data on annual radial tree growth confirms this pattern: we find that 53% of tree ring width (TRW) indices are below one standard deviation, and up to 16% of the TRW values are below two standard deviations in years with extremely high temperatures and low precipitation. Based on these findings we investigate if climate driven patterns in long-term tree growth data may serve as benchmarks for state-of-the-art dynamic vegetation models such as LPJmL. The model simulates NPP but not explicitly the radial tree ring growth, hence requiring a generic method to ensure an objective comparison. Here we propose an analysis scheme that quantifies the coincidence rate of climate extremes with some biotic responses (here TRW or simulated NPP). We find that the reduction in tree-ring width during drought extremes is lower than the corresponding reduction of simulated NPP. We identify ten extreme years during the 20th century in which both, model and measurements indicate high coincidence rates across Europe. However, we detect substantial regional differences in simulated and observed responses to extreme events. One explanation for this discrepancy could be that the tree-ring data have preferentially been sampled at more climatically stressed sites. The model-data difference is amplified by the fact that dynamic vegetation models are designed to simulate mean ecosystem responses at landscape or regional scale. However, we find that both model-data and measurements display carry-over effects from the previous year. We conclude that using radial tree growth is a good basis for generic model-benchmarks if the data are analyzed by scale-free measures such as coincidence analysis. Our study shows strong reductions in carbon sequestration during extreme years. However, for a better understanding of the impact of extreme events on e.g. the long-term fate of the European carbon balance, more long-term measurement data and improved process-based models are needed.

Tree growth across the Nepal Himalaya during the last four centuries

2017 ◽  
Vol 41 (4) ◽  
pp. 478-495 ◽  
Author(s):  
UK Thapa ◽  
S St. George ◽  
DK Kharal ◽  
NP Gaire
Keyword(s):  
Tree Ring ◽  
Tree Growth ◽  
Environmental Changes ◽  
Ring Width ◽  
High Elevation ◽  
Forest Growth ◽  
Tree Ring Width ◽  
Early 19Th Century ◽  
Tree Ring Data ◽  
Instrumental Records

The climate of Nepal has changed rapidly over the recent decades, but most instrumental records of weather and hydrology only extend back to the 1980s. Tree rings can provide a longer perspective on recent environmental changes, and since the early 2000s, a new round of field initiatives by international researchers and Nepali scientists have more than doubled the size of the country’s tree-ring network. In this paper, we present a comprehensive analysis of the current tree-ring width network for Nepal, and use this network to estimate changes in forest growth nation-wide during the last four centuries. Ring-width chronologies in Nepal have been developed from 11 tree species, and half of the records span at least 290 years. The Nepal tree-ring width network provides a robust estimate of annual forest growth over roughly the last four centuries, but prior to this point, our mean ring-width composite fluctuates wildly due to low sample replication. Over the last four centuries, two major events are prominent in the all-Nepal composite: (i) a prolonged and widespread growth suppression during the early 1800s; and (ii) heightened growth during the most recent decade. The early 19th century decline in tree growth coincides with two major Indonesian eruptions, and suggests that short-term disturbances related to climate extremes can exert a lasting influence on the vigor of Nepal’s forests. Growth increases since AD 2000 are mainly apparent in high-elevation fir, which may be a consequence of the observed trend towards warmer temperatures, particularly during winter. This synthesis effort should be useful to establish baselines for tree-ring data in Nepal and provide a broader context to evaluate the sensitivity or behavior of this proxy in the central Himalayas.

scholarly journals Entwicklung klimasensitiver Wachstumsfunktionen für das Szenariomodell «Massimo»

2015 ◽  
Vol 166 (6) ◽  
pp. 389-398 ◽  
Author(s):  
Brigitte Rohner ◽  
Esther Thürig
Keyword(s):  
Tree Ring ◽  
Tree Growth ◽  
Tree Species ◽  
Climatic Factors ◽  
Climate Variables ◽  
Individual Tree ◽  
Climate Effects ◽  
Growth Functions ◽  
Tree Ring Data ◽  
Scenario Model

Development of climate-dependent growth functions for the scenario model “Massimo” Tree growth is substantially influenced by climatic factors. In the face of climate change, climate effects should therefore be included in estimations of Switzerland's future forest productivity. In order to include climate effects in the growth functions of the “Massimo” model, which is typically applied to project forest resources in Switzerland, we statistically modelled climate effects on tree growth representatively for Switzerland by simultaneously considering further growth-influencing factors. First, we used tree ring data to evaluate how climate variables should be defined. This analyses showed that for modelling multi-year tree growth we should use averages of whole-year variables. Second, we fitted nonlinear mixed-effects models separately for the main tree species to individual-tree growth data from the Swiss National Forest Inventory. In these models, we combined climate variables defined according to the results of the tree ring study with various further variables that characterize sites, stands and individual trees. The quantified effects were generally plausible and explained convincingly the physiological differences between the species. The statistical growth models for the main tree species will now be included in the forest scenario model “Massimo”. This will allow for founded analyses of scenarios which assume changing climatic conditions.

scholarly journals The emergent past: past natural and human disturbances of trees can reduce their present resistance to drought stress

2021 ◽  
Author(s):  
Hans Pretzsch
Keyword(s):  
Drought Stress ◽  
Memory Effect ◽  
Tree Ring ◽  
Tree Growth ◽  
Water Retention ◽  
Annual Growth ◽  
Recent Past ◽  
Ecological Memory ◽  
Growth Variation

AbstractForest tree growth is primarily explained, modelled, and predicted depending on current age or size, environmental conditions, and competitive status in the stand. The accumulated size is commonly used as a proxy for a tree's past development. However, recent studies suggest that antecedent conditions may impact present growth by epigenetic, transcriptional, proteomic, or metabolic changes alongside physiological and structural properties. Here, I analysed the ecological memory effect embedded in the xylem as a tree-ring structure. I used 35 mature Norway spruces (Picea abies (L.) H. Karst.) and 36 European beeches (Fagus sylvatica L.) of the Kranzberg Forest water retention experiment KROOF in South Germany to scrutinise how their past development determines the growth of control plots and plots with 5-year water retention. I hypothesised that the current size and growing conditions determine tree growth and drought stress resistance. Metrics quantifying the trees’ recent and past growth, and correlation and linear mixed models with random effects revealed the following ecological memory effects. (1) For both species, the progressive growth course, low inter-annual growth variation in the long term, and low growth deflections in the recent past increased the growth resistance to drought. (2) The correlation between the past growth metrics and current stress reactions revealed that legacy effects could reach back 5–30 years; I found short- and long-term ecological memory. (3) Parameters of model prediction of the basic model with only size as a predictor of tree growth could be improved. The results suggest differences in the internal stem structure and ring pattern cause-specific differences in the trees' functioning and growth. I conclude that a long-term progressive increase and low variation in ring width may improve water conduction and reduce embolism in both species. Annual growth variation and low growth events in the recent past may have primed the morphology and allocation of the Norway spruce to better resist drought. The strong reduction in current growth, drought resistance by irregular growth, and past growth disturbances reveal a memory effect embedded in the tree ring pattern, suggesting further exploration and consideration in tree monitoring, growth modelling, and silvicultural prescriptions.

scholarly journals Last 1100 yr of precipitation variability in western central Asia as revealed by tree-ring data from the Pamir-Alay

2018 ◽  
Vol 91 (1) ◽  
pp. 81-95 ◽  
Author(s):  
Magdalena Opała-Owczarek ◽  
Tadeusz Niedźwiedź
Keyword(s):  
Central Asia ◽  
Tree Ring ◽  
Tree Growth ◽  
Palmer Drought Severity Index ◽  
Ring Width ◽  
Severity Index ◽  
Drought Severity ◽  
Mountainous Area ◽  
Transfer Function Method ◽  
Tree Ring Data

AbstractWe developed a 1108 yr chronology of tree-ring widths, based on 64 Himalayan pencil juniper (Juniperus semiglobosa Regel) trees, for the Pamir-Alay Mountains, central Asia. Dendroclimatological analysis demonstrates that precipitation has significant effects on tree growth in the semiarid mountainous area of northwestern Tajikistan located on the edge of the great midlatitude Karakum and Kyzylkum deserts. The highest level of linear correlation (r=0.67) is observed between tree growth and seasonalised winter (previous December–February) precipitation. Our studies also show that moisture (precipitation/Palmer Drought Severity Index) from the previous June to the current September was the dominant climatic factor accounting for interannual variations in tree-ring width, suggesting that this should be considered in climate reconstruction. Using the transfer function method, we reconstructed the region’s drought history over the period AD 908–2015. The results of this moisture reconstruction showed that the most recent millennium was characterised by series of dry and wet stages. The driest periods occurred before 1000, 1200–1250, and at the end of the eighteenth century and beginning of the nineteenth century. The wettest conditions existed in 1650–1700 and after 1990.

Tree-Ring Research on Tectona Grandis in Northern Thailand

IAWA Journal ◽  
1995 ◽  
Vol 16 (4) ◽  
pp. 385-392 ◽  
Author(s):  
Nathsuda Pumijumnong ◽  
Dieter Eckstein ◽  
Ute Sass
Keyword(s):  
Total Variation ◽  
Tree Ring ◽  
Tree Growth ◽  
Principal Component ◽  
Tectona Grandis ◽  
Northern Thailand ◽  
Climatic Influence ◽  
First Order ◽  
Tree Ring Data ◽  
Mean Sensitivity

From a network of teak chronologies in northern Thailand, 75 trees within one province were evaluated regarding their climatic signal. The raw tree-ring series revealed a high mean sensitivity of 0.50 and a moderate first-order autocorrelation of 0.48. The first principal component of the standardized data explained 44% of the total variation in the tree-ring data, indicating a considerable climatic influence on tree growth. The climate-growth relationship suggested that growth of teak in this study area is mainly controlled by rainfall from April to June. Thus, there is some promise that the whole network of teak chronologies in northern Thailand can contribute to reconstructing climate over at least the last three centuries.

scholarly journals Using Tree Rings to Predict the Response of Tree Growth to Climate Change in the Continental United States during the Twenty-First Century

2010 ◽  
Vol 14 (19) ◽  
pp. 1-20 ◽  
Author(s):  
A. Park Williams ◽  
Joel Michaelsen ◽  
Steven W. Leavitt ◽  
Christopher J. Still
Keyword(s):  
Climate Change ◽  
United States ◽  
Tree Ring ◽  
Tree Growth ◽  
Ring Width ◽  
First Century ◽  
Annual Growth ◽  
Climate Variations ◽  
Tree Ring Data ◽  
Twenty First Century

Abstract In the early 1900s, tree-ring scientists began analyzing the relative widths of annual growth rings preserved in the cross sections of trees to infer past climate variations. Now, many ring-width index (RWI) chronologies, each representing a specific site and species, are archived online within the International Tree-Ring Data Bank (ITRDB). Comparing annual tree-ring-width data from 1097 sites in the continental United States to climate data, the authors quantitatively evaluated how trees at each site have historically responded to interannual climate variations. For each site, they developed a climate-driven statistical growth equation that uses regional climate variables to model RWI values. The authors applied these growth models to predict how tree growth will respond to twenty-first-century climate change, considering four climate projections. Although caution should be taken when extrapolating past relationships with climate into the future, the authors observed several clear and interesting patterns in the growth projections that seem likely if warming continues. Most notably, the models project that productivity of dominant tree species in the southwestern United States will decrease substantially during this century, especially in warmer and drier areas. In the northwest, nonlinear growth relationships with temperature may lead to warming-induced declines in growth for many trees that historically responded positively to warmer temperatures. This work takes advantage of the unmatched temporal length and spatial breath of annual growth data available within the ITRDB and exemplifies the potential of this ever-growing archive of tree-ring data to serve in meta-analyses of large-scale forest ecology.

scholarly journals Trees do not always act their age: size-deterministic tree ring standardization for long-term trend estimation in shade-tolerant trees

2019 ◽  
Vol 16 (24) ◽  
pp. 4815-4827
Author(s):  
Rachel Dietrich ◽  
Madhur Anand
Keyword(s):  
Tree Ring ◽  
Basal Area ◽  
Ring Formation ◽  
Tree Size ◽  
Growth Trend ◽  
Biological Growth ◽  
Tolerant Species ◽  
Tree Ring Data ◽  
Shade Tolerant Species

Abstract. With increasing awareness of the consequences of climate change for global ecosystems, the focus and application of tree ring research have shifted to reconstruction of long-term climate-related trends in tree growth. Contemporary methods for estimating and removing biological growth trends from tree ring series (standardization) are ill-adapted to shade-tolerant species, leading to biases in the resultant chronologies. Further, many methods, including regional curve standardization (RCS), encounter significant limitations for species in which accurate age estimation is difficult. In this study we present and test two tree ring standardization models that integrate tree size in the year of ring formation into the estimation of the biological growth trend. The first method, dubbed size-deterministic standardization (SDS), uses tree diameter as the sole predictor of the growth trend. The second method includes the combined (COMB) effects of age and diameter. We show that both the SDS and COMB methods reproduce long-term trends in simulated tree ring data better than conventional methods; this result is consistent across multiple species. Further, when applied to real tree ring data, the SDS and COMB models reproduce long-term, time-related trends as reliably as traditional RCS and more reliably than other common standardization methods (i.e. C-method, basal area increments, conservative detrending). We recommend the inclusion of tree size in the year of ring formation in future tree ring standardization models, particularly when dealing with shade-tolerant species, as it does not compromise model accuracy and allows for the inclusion of unaged trees.

scholarly journals When trees don’t act their age: size-deterministic tree-ring standardization for long-tern trend estimation in shade-tolerant trees

2019 ◽  
Author(s):  
Rachel Dietrich ◽  
Madhur Anand
Keyword(s):  
Tree Ring ◽  
Ring Formation ◽  
Tree Size ◽  
Growth Trend ◽  
Biological Growth ◽  
Tolerant Species ◽  
Tree Ring Data ◽  
Shade Tolerant Species ◽  
Multiple Species

Abstract. With increasing awareness of the consequences of climate change for global ecosystems, the focus and application of tree-ring research has shifted to reconstruction of long-term climate-related trends in tree growth. Contemporary methods for removing the biological growth-trend from tree-ring series (standardization) are ill-adapted to shade-tolerant species, leading to biases in the resultant chronology. Further, many methods, including regional curve standardization (RCS), encounter significant limitations for species in which accurate age estimation is difficult. In this study we present and test two tree-ring standardization models that integrate tree size in the year of ring formation into the estimation of the biological growth-trend. The first method, dubbed size deterministic standardization (SDS), uses tree diameter as the sole predictor of the growth-trend. The second method includes the combined (COMB) effects of age and diameter. We show that both the SDS and COMB methods reproduce long-term trends in simulated tree-ring data better than conventional methods – this result is consistent across multiple species. Further, when applied to real tree-ring data, the COMB method is more parsimonious than its than RCS. We recommend the inclusion of tree size in the year of ring formation in future tree-ring standardization models, particularly when dealing with shade-tolerant species, as it does not compromise model parsimony and allows for the inclusion of unaged trees.

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