ArticlePublisher preview available

Increased sensitivity to drought across successional stages in natural Norway spruce (Picea abies (L.) Karst.) forests of the Calimani Mountains, Romania

DOI:10.1007/s00468-019-01862-1
Authors:
Kristýna Svobodová at Czech University of Life Sciences Prague
Kristýna Svobodová
Thomas Langbehn at NABU Sachsen e.V.
Thomas Langbehn
  • NABU Sachsen e.V.
Jesper Bjorklund at Swiss Federal Institute for Forest, Snow and Landscape Research WSL
Jesper Bjorklund
Miloš Rydval at Czech University of Life Sciences Prague
Miloš Rydval
Show all 17 authorsHide
Read publisher preview
Download citation
To read the full-text of this research, you can request a copy directly from the authors.

Abstract and Figures

Key message Winter drought becomes a limiting factor of forest stand growth by the end of the twentieth century. Abstract Disturbances strongly influence the structure of natural forests. The frequency and severity of natural disturbances, as well as drought events, are expected to increase with climate change. Our study investigated if forests with differing forest structures related to disturbance histories also differed in sensitivity to drought. In a natural forest landscape in the Calimani Mountains of the Eastern Carpathians, Romania, we used six forest patches to represent different successional stages, from early- to late-successional stages. We used two temporal resolutions of the Standardized Precipitation-Evapotranspiration Index to describe short and long water resource dynamics within or between hydrological years, respectively. We detected an increase in the importance of winter drought across all successional stages; it was first identified in the oldest patch in the 1970s, and it consecutively affected younger patches. We observed that different forest structures do not lead to substantial differences in trends in drought–growth relationships. A shift in sensitivity to water availability from early spring to winter occurred over the twentieth century. These findings suggest that the impact of climate change on Norway spruce forest ecosystems of the Eastern Carpathians will likely be difficult to mitigate at a local scale using traditional forestry practices.
Locations of the Norway spruce tree-ring chronology network in the Calimani Mountains, Eastern Carpathians of Romania (black points indicate the six patches locations)
Locations of the Norway spruce tree-ring chronology network in the Calimani Mountains, Eastern Carpathians of Romania (black points indicate the six patches locations)
… 
Disturbance histories (a) and diameter distributions of all live and standing dead trees (b) of the six patches grouped along a successional gradient, from early to late succession patches moving downwards. Disturbance histories of single plots and the aggregated patches are indicated by gray and black lines, respectively; the dashed line represents the minimum disturbance threshold of 10% of patch canopy area removed (dashed line). Diameter distributions are expressed as kernel density estimates to allow comparisons of distributions independent of sampling area
Disturbance histories (a) and diameter distributions of all live and standing dead trees (b) of the six patches grouped along a successional gradient, from early to late succession patches moving downwards. Disturbance histories of single plots and the aggregated patches are indicated by gray and black lines, respectively; the dashed line represents the minimum disturbance threshold of 10% of patch canopy area removed (dashed line). Diameter distributions are expressed as kernel density estimates to allow comparisons of distributions independent of sampling area
… 
a Drought index based on a 3-month resolution for May (SPEI3_May) during the study period. Positive and negative SPEI3 values indicate wet and dry periods, respectively. The vertical gray lines denote the years 1947 and 1948 when the water deficit accumulated from March to May. b Mean detrended chronologies for patches with distinct disturbance histories. We used a cubic smoothing spline with 50% frequency response cut-off at 50 years for detrending (Cook and Peters 1981). Mean chronology index was calculated using Tukey’s robust bi-weight mean (Cook and Kairiukstis 2013). The vertical gray lines denote suppressed growth for the years 1947, 1948, and 1949. c drought index based on a 12-month resolution for September (SPEI12_Sep) during the study period. Positive SPEI12 values indicate wet periods and negative SPEI12 values indicate dry periods. The vertical gray line denotes 1946, a year of extreme drought
a Drought index based on a 3-month resolution for May (SPEI3_May) during the study period. Positive and negative SPEI3 values indicate wet and dry periods, respectively. The vertical gray lines denote the years 1947 and 1948 when the water deficit accumulated from March to May. b Mean detrended chronologies for patches with distinct disturbance histories. We used a cubic smoothing spline with 50% frequency response cut-off at 50 years for detrending (Cook and Peters 1981). Mean chronology index was calculated using Tukey’s robust bi-weight mean (Cook and Kairiukstis 2013). The vertical gray lines denote suppressed growth for the years 1947, 1948, and 1949. c drought index based on a 12-month resolution for September (SPEI12_Sep) during the study period. Positive SPEI12 values indicate wet periods and negative SPEI12 values indicate dry periods. The vertical gray line denotes 1946, a year of extreme drought
… 
Running RBAR in a 30-year moving window with 1-year offset for RWI series of all trees that originated before 1900. Patches CAL5 and CAL6 were excluded due to a severe disturbance during the twentieth century. An abrupt increase in RBAR values was evident between 1918 and 1949 due to the drought 1946–1948 (empty symbols). Years 1947, 1948, and 1949 were removed from calculation of running RBAR (black symbols) to identify a linear trend between 1900 and 1981 (starting year of moving window); the linear model with small positive highly significant trend was highly significant (black line)
Running RBAR in a 30-year moving window with 1-year offset for RWI series of all trees that originated before 1900. Patches CAL5 and CAL6 were excluded due to a severe disturbance during the twentieth century. An abrupt increase in RBAR values was evident between 1918 and 1949 due to the drought 1946–1948 (empty symbols). Years 1947, 1948, and 1949 were removed from calculation of running RBAR (black symbols) to identify a linear trend between 1900 and 1981 (starting year of moving window); the linear model with small positive highly significant trend was highly significant (black line)
… 
Static correlations between annual growth and monthly SPEI3 from the previous December to the current September (triangle symbols), and SPEI12 for the September of the growth year (dot symbol). The studied period was divided into two equal periods, 1903–1956 (light gray symbols) and 1957–2010 (dark gray symbols). Significant correlations (p < 0.05) are indicated by large symbols
+1
Static correlations between annual growth and monthly SPEI3 from the previous December to the current September (triangle symbols), and SPEI12 for the September of the growth year (dot symbol). The studied period was divided into two equal periods, 1903–1956 (light gray symbols) and 1957–2010 (dark gray symbols). Significant correlations (p < 0.05) are indicated by large symbols
… 
Figures - available from: Trees
This content is subject to copyright. Terms and conditions apply.
  • A preview of this full-text is provided by Springer Nature.
  • Learn more
Preview content only
Content available from Trees
This content is subject to copyright. Terms and conditions apply.
Vol.:(0123456789)
1 3
Trees (2019) 33:1345–1359
https://doi.org/10.1007/s00468-019-01862-1
ORIGINAL ARTICLE
Increased sensitivity todrought acrosssuccessional stages innatural
Norway spruce (Picea abies (L.) Karst.) forests oftheCalimani
Mountains, Romania
K.Svobodová1,2 · T.Langbehn2· J.Björklund2· M.Rydval2· V.Trotsiuk2· R.C.Morrissey2· V.Čada2· P.Janda2·
K.Begovič2· J.Ágh‑Lábusová2· J.S.Schurman2· M.Nováková2· D.Kozák2· O.Kameniar2· M.Synek2· M.Mikoláš2·
M.Svoboda2
Received: 25 September 2018 / Accepted: 23 April 2019 / Published online: 6 May 2019
© Springer-Verlag GmbH Germany, part of Springer Nature 2019
Abstract
Key message Winter drought becomes a limiting factor of forest stand growth by the end of the twentieth century.
Abstract Disturbances strongly influence the structure of natural forests. The frequency and severity of natural disturbances,
as well as drought events, are expected to increase with climate change. Our study investigated if forests with differing forest
structures related to disturbance histories also differed in sensitivity to drought. In a natural forest landscape in the Calimani
Mountains of the Eastern Carpathians, Romania, we used six forest patches to represent different successional stages, from
early- to late-successional stages. We used two temporal resolutions of the Standardized Precipitation-Evapotranspiration
Index to describe short and long water resource dynamics within or between hydrological years, respectively. We detected
an increase in the importance of winter drought across all successional stages; it was first identified in the oldest patch in the
1970s, and it consecutively affected younger patches. We observed that different forest structures do not lead to substantial
differences in trends in drought–growth relationships. A shift in sensitivity to water availability from early spring to winter
occurred over the twentieth century. These findings suggest that the impact of climate change on Norway spruce forest
ecosystems of the Eastern Carpathians will likely be difficult to mitigate at a local scale using traditional forestry practices.
Keywords Disturbance history· SPEI· Synchronized tree growth· Climate change· Carpathians
Introduction
Droughts are predicted to become more frequent and hotter
(IPCC 2013), and they may become lethal for many plants
under warming conditions (Allen etal. 2015) in European
temperate forests (Lindner etal. 2010). The considerable
influence of climate change on natural disturbance regimes
in forests has been recognized for the past two centuries
(Schelhaas etal. 2003). An increase in natural disturbance
frequency and severity is expected (Dale etal. 2001; Seidl
etal. 2017). To understand the possible consequences of
climate change on future forest growth, it is necessary to
characterize current and past drought–growth relationships.
Ongoing climate change has yielded increasing tempera-
tures and changes in precipitation regimes (IPCC 2013). In
a warmer world, intensification of the hydrologic cycle is
expected (Dore 2005). A simple climatic water balance can
be represented by the Standardized Precipitation-Evapotran-
spiration Index (SPEI; Vicente-Serrano etal. 2010), which
characterizes monthly differences between precipitation
and potential evapotranspiration. Different time resolutions
of SPEI can help us better understand and manage forest
growth–drought interactions (McKee etal. 1993), because
seasonal water deficits may not be restricted only to drier
Communicated by A. Geßler.
Electronic supplementary material The online version of this
article (https ://doi.org/10.1007/s0046 8-019-01862 -1) contains
supplementary material, which is available to authorized users.
* K. Svobodová
kristynaxsvobodova@gmail.com
1 Faculty ofEnvironmental Sciences, Czech University ofLife
Sciences Prague, Kamýcká 129, Suchdol, 16500Prague,
CzechRepublic
2 Faculty ofForestry andWood Sciences, Czech University
ofLife Sciences Prague, Kamýcká 129, Suchdol,
16500Prague, CzechRepublic
Content courtesy of Springer Nature, terms of use apply. Rights reserved.
... Among the internal factors, the greatest effects are related to the species of the tree (Magnuszewski et al., 2015;Sitková et al., 2018, Burri et al., 2019, inherited individual variability, age and fruiting (Ding et al., 2017;Latreille et al., 2017;Buras et al., 2018). The most influential external factors are latitudinal, longitudinal and height gradients of the conditions of growth locations of the trees (Magnuszewski et al., 2015;Matskovsky, 2016;Chen, 2017;Gao et al., 2018), air temperature and precipitations (Natalini et al., 2015;Rybníček et al., 2016;Rozas & Olano, 2017), wind (Dinulica et al., 2016), mist (Myskow et al., 2019), soil conditions (Mendivelso et al., 2016), phytocenosis relations (Latreille et al., 2017;Moreau et al., 2019), catastrophes of various origin: fires (Gao et al., 2017), windthrows and windsnaps (Holeska et al., 2016), diseases, attacks of harmful insects (Brygadyrenko, 2016;Faly et al., 2017;Van de Gevel et al., 2017;, summer and winter droughts, emissions of CO 2 (Cavlovic et al., 2015;Svobodova et al., 2019), heavy frosts during snowless periods (Su-vanto et al., 2017), and also agricultural activity by humans (Montoro Girona et al., 2016;Tyukavina et al., 2017;Wang et al., 2018). Forest felling, meso-and macro scale effects on the environment lead to negative tendencies of radial increment and deforestation (Rodriguez-Caton, 2015). ...
... In the Eastern Carpathians, the growth-limiting factor for the tree stands of spruce at all the stages of succession was winter drought. Frequency and scales of the natural disturbances, as well as droughts, are expected to increase with climate changes (Svobodova et al., 2019). In the mountains of the Eastern Tatras (Western Carpathians, Slovakia) during the vegetation period of 2014, at the heights of 810 m to 1,778 m above the sea level, a high phytotoxic potential of О 3 was determined, which increased with height above the sea level and had negative effect on the increment of European spruce (Bicarova et al., 2016). ...
Radial increment in European spruce (Picea abies) as indicator of sanitary condition of spruce forests in the Ukrainian Carpathians
Article
  • Jul 2020
In recent years, there has been an intense desiccation of spruce forests in the Ukrainian Carpathians, where European spruce is the main forest-forming species. Over the recent years, desiccation has spread to the spruce forest stands which grow in the Carpathians at the height of over 1,000 m above the sea level. This process causes large economic losses, significant deterioration of the condition and productivity of the forests in the Carpathians, decrease in the level of provision of ecosystemic services by forests, functions they perform, therefore leading to dangerous exogenic processes (floods, freshets, erosion, mudflows, landslides). To determine the interaction between the radial increment and sanitary condition of the spruce stands and substantiate the measures of the use of drying spruce forests, in the Vysokohirsky forestry reserve district of the Ukrainian Carpathians in anti-erosion forests, in hotbeds of desiccation of spruce in 2018, dendrochronological surveys were undertaken in two monitoring plots in forests in weak and severely weakened condition. We collected cores from the model trees, measured width of the annual rings, and developed individual dendrochronologies according to the absolute values of the radial increments and generalized dendrochronologies according to the absolute values of the radial increments and increment indices of the duration of 97 (1921–2017) and 81 years (1937–2017). We conducted single-factor dispersion analysis, calculated the indices of abnormality of the radial increments and correlation coefficient. The results revealed that the lowest increments occurred in the years 1965–1990 in the weakened stand and in 1997–2017 in the severely weakened stand. The relative indices of the forests ranged 83.8–114.6%. The cycles of increment lasted 7–9 years. Over the last few decades, favourable conditions for the growth of the trees took place in 1991–2010, unfavourable in 2011–2017, very unfavourable in 1981–1990. Synchronicity of annual radial increments in the spruces of two monitoring plots equaled 49 years. Correlation coefficient indicates that the type of the conditions of growth location has a significant effect on its variability in the process of trees’ life cycle. Average radial increment of the weakened stand of trees over the last 10 years decreased by 7.9%, while it declined by 54.9% in the severely weakened stand compared with the average increments of the tree stands for the surveyed periods, suggesting that the forests undergo different stages of succession: the weakened stand undergoes the stage of recovery after disturbance, severely weakened forest – stage of disturbance. The studies revealed the dependence of radial increment of spruce on the sanitary condition of the forests. The results of the studies may be used for the assessment of dynamic processes in forest ecosystems as a result of the impact of various factors and planning of the forestry measures.
View
... The Carpathian Mountains harbor the largest assemblage of primary Norway spruce (Picea abies (L.) Karst) forests in Central-Eastern Europe Sabatini et al., 2018). Extensive studies of Norway spruce growth-climate relationships have shown high sensitivity of Carpathian high-elevation spruce forests to growing season temperature (Bouriaud and Popa, 2009;Büntgen et al., 2007;Nagavciuc et al., 2019;Sedmáková et al., 2019;Svobodová et al., 2019). In addition to climatic drivers, natural disturbances have an important role in regulating forest structure, species composition, and developmental processes across spatial scales (Čada et al., 2020;Pavlin et al., 2021;Schurman et al., 2018;Turner 1987). ...
Impact of disturbance signatures on tree-ring width and blue intensity chronology structure and climatic signals in Carpathian Norway spruce
Article
Tree radial growth is influenced by climatic and various non-climatic factors, which can complicate the extraction of climate signals from tree rings. We investigated the influence of disturbance on tree-ring width (RW) and latewood blue intensity (BI) chronologies of Norway spruce from the Carpathian Mountains to explore the extent to which disturbance can affect temperature signals in tree rings. Overall, ∼15000 high-elevation Norway spruce tree cores from 34 sites grouped into four regions (Slovakia, Ukraine, North and South Romania) were analyzed. The curve intervention detection (CID) method was applied to detect and correct identified disturbance trends. RW chronology structural comparisons were performed among disturbance-affected and disturbance-corrected chronologies for various spatial (regional / site) scales and sampling subsets. Structural comparisons were also performed for RW and BI chronologies developed from separate groups of series (i.e., disturbed, and undisturbed) for five sites exhibiting clear disturbance trends. Temperature sensitivity was assessed for all chronology variants of both parameters. We found that disturbance trends only affected RW chronologies at the site/subset scale with relatively small series replication and were not detected at the regional scale. Unlike RW, BI chronologies were generally unaffected by disturbance. BI data also contained much stronger growing season temperature signals, which appeared to be both spatially and temporally more coherent. Whereas highly replicated and spatially extensive datasets can help minimize or eliminate disturbance trends in RW chronologies, this potential influence should be considered when interpreting climatic signals in tree rings and reconstructing historical climate in weakly replicated periods. On the other hand, BI is a promising alternative tree ring parameter with stronger and more stable growing season temperature signals, whose seemingly disturbance-free chronology structure does not appear to suffer from this ecological bias, and therefore represents a more suitable parameter for dendroclimatological research.
View
... We also highlight the importance of accounting for both regional and tree-level drivers when assessing contemporary ecosystem dynamics under climate change. Under the coupled effects of ubiquitous disturbance events and intensifying climate pressures, future forest development will increasingly depend on local site properties (Babst et al., 2013), and novel growth constraints Svobodová et al., 2019), which are harder to predict. Furthermore, it remains unclear whether accelerated growth rates will change the upper limit of forest biomass or translate into an actual increase in carbon sink capacity. ...
Large old trees increase growth under shifting climatic constraints: Aligning tree longevity and individual growth dynamics in primary mountain spruce forests
Article
  • Sep 2022
In a world of accelerating changes in environmental conditions driving tree growth, tradeoffs between tree growth rate and longevity could curtail the abundance of large, old trees (LOTs), with potentially dire consequences for biodiversity and carbon storage. However, the influence of tree‐level tradeoffs on forest structure at landscape scales will also depend on disturbances, which shape tree size and age distribution, and on whether LOTs can benefit from improved growing conditions due to climate warming. We analyzed temporal and spatial variation in radial growth patterns from ~ 5000 Norway spruce (Picea abies (L.) H. Karst) live and dead trees from the Western Carpathian primary spruce forest stands. We applied mixed‐linear modeling to quantify the importance of LOT growth histories and stand dynamics (i.e. competition and disturbance factors) on lifespan. Finally, we assessed regional synchronization in radial growth variability over the 20th century, and modelled the effects of stand dynamics and climate on LOTs recent growth trends. Tree age varied considerably among forest stands, implying an important role of disturbance as an age constraint. Slow juvenile growth and longer period of suppressed growth prolonged tree lifespan, while increasing disturbance severity and shorter time since last disturbance decreased it. The highest age was not achieved only by trees with continuous slow growth, but those with slow juvenile growth followed by subsequent growth releases. Growth trend analysis demonstrated an increase in absolute growth rates in response to climate warming, with late summer temperatures driving the recent growth trend. Contrary to our expectation that LOTs would eventually exhibit declining growth rates, the oldest LOTs (> 400 years) continuously increase growth throughout their lives, indicating a high phenotypic plasticity of LOTs for increasing biomass, and a strong carbon sink role of primary spruce forests under rising temperatures, intensifying droughts, and increasing bark beetle outbreaks.
View
... Drought index may be defined as a tool to quantify the drought nature and used to recognize a drought character (Bhunia et al. 2020). SPEI has recently been used in many drought studies (Ajayi and Ilori 2020;Quenum et al. 2019;Svobodová et al. 2019). Proper understanding of vegetation cover change and drought requires analysis of the relationship between vegetation and drought. ...
A remote sensing study of spatiotemporal variations in drought conditions in northern Asir, Saudi Arabia
Article
Full-text available
Changes in vegetation land cover are influenced by, and therefore an indicator of, climatic conditions. The aim of this study is to investigate the relationship between vegetation cover changes and drought events in a small-scale area. Six Landsat images during 1987–2019 were used to extract information about the vegetation land cover changes using the normalized difference vegetation index (NDVI) and the fractional vegetation cover (FVC) in Balqarn Governorate in the northern mountains of Asir, Saudi Arabia. Two climatic parameters, temperature and precipitation, were used as time series for the same period and were decomposed to investigate the seasonal and trend changes for each parameter. The two parameters were also used to calculate the standardized precipitation evapotranspiration index (SPEI) to conduct an in-depth analysis of the drought events influencing vegetation cover. The results showed that the state of the vegetation coverage of the study area remained at a medium level with an average NDVI value, but the FVC values showed evidence of dynamic variability associated with drought and moisture events. The SPEI showed that the study area has been undergoing a long-duration drought event since 2004, ranging from light to severe drought, which was consistent with the time series decomposition results. This investigation has revealed that drought drives changes in vegetation cover and is expressed on small geographic scales as changes in the vegetation cover structure. The framework described here is simple and can be used to evaluate and manage drought risks.
View
... Second, the crucial limiting factor of natural regeneration density is drought . Drought due to climate change is an increasingly limiting factor of tree growth in mountain spruce forests in Europe, in one of Europe's most wet forest ecosystems (PRIMICIA et al. 2015, SVOBODOVÁ et al. 2019. The meta-analysis of densities of regeneration after intensive large-scale disturbances of temperate and boreal forests shows that the regeneration density increases with the average temperature and annual total precipitation (NOVÁKOVÁ 2018). ...
Mapping of mountain temperate forest recovery after natural disturbance: a large permanent plot established on Czech-German border
Article
Full-text available
  • Jan 2019
Natural regeneration following large-scale disturbance is a basic attribute of forest resilience. However, in the intensively managed forest ecosystems in Europe these processes are not well understood which also limits the options for silvicultural management in these ecosystems. To overcome this shortfall, we have established a large (20 ha) permanent research plot in mountain spruce forest of the Bohemian Forest Ecosystem in 2018, 20 years after one of the largest forest disturbances in Central Europe, left without forestry interventions. The spatial positions of all living trees and dead wood, including low stumps and young regeneration above 50 cm in height were recorded. In total we measured 29 464 positions of 6 species. All live individuals were tagged for permanent monitoring of mortality and growth. As a result of the data analysis the tree spatial structure of the pre-disturbance generation was more heterogeneous compared to a commercial forest. After the disturbance, it became even more heterogeneous, with very pronounced aggregation at all spatial levels, from meters to hundreds of meters. This implies that the spatial pattern of regeneration varies, even over the homogeneous environmental conditions. Explaining this large spatial variability is challenging. Current post-disturbance structure is hardly attainable by any human planting intervention. This shows the high value of non-interventional approach for nature conservation. The further purpose of the research plot is to investigate the development of the abundance and composition of species, biomass and dynamics of spatial distribution of tree individuals. The plot also offers a possibility to add further opportunities for research.
View
... The role of climatic extremes may therefore be underestimated in our results, especially considering global climatic trends. It is likely that the major climatic extreme related to mortality in our stands is drought, as suggested also by an observed increase in disturbance rates with decreasing Palmer Drought Severity Index ( Schurman et al., 2018), an increase in moisture sensitivity Schurman et al., 2019), and an increase in sensitivity to winter drought ( Svobodová et al., 2019) in Norway spruce stands in the Carpathians. However, our approach cannot disentangle all possible climatic extremes, which include drought, frost, and temperature extremes, such that we pooled them into the broad "climatic extremes" category. ...
Contrasting patterns of natural mortality in primary Picea forests of the Carpathian Mountains
Article
Mortality, driven by both climate and disturbance legacies, is a key process shaping forest dynamics. Understanding the mortality patterns in primary forests in the absence of severe disturbances provides information on background natural dynamics of a given forest type under ongoing climate change. This can then be compared to mortality rates in severely-disturbed stands. Using a large number of sample plots along a gradient from low to high disturbance, we examined the mortality rates and composition of mortality agents in primary mountain Norway spruce (Picea abies (L.) Karst.) forests on different spatial scales. We evaluated the mortality rates and causes of mortality in 28 stands across a large geographical gradient spanning over 1000 km. We resampled (five-year period) 371 plots (16,287 living trees) in primary Norway spruce forests along the Carpathian mountain chain. The estimated overall annual mortality rate was within the previously reported range of background (ambient) mortality, however, stand-level and plot-level mortality rates varied substantially. Over 18% of plots displayed more than 2% annual mortality and 6% of plots even exceeded 10% per year. Stands in the Western Carpathians showed the highest variability in the mortality rate, with 30% of the stands in this region showing annual mortality rates over 5%. At the plot level, mixed-severity disturbances increased variability of mortality rates within most localities. Overall mortality was evenly distributed among size classes up to 50 cm diameter at breast height (DBH). However, the distributions differ for individual mortality agents. Mortality modes were classified into six categories (broken crown, broken stem, uprooted, competition, bark beetle/fungi, climatic extremes). Bark beetle (Ips typographus L.) infestation was the most frequent mortality agent in all stands, whereas the influence of competition as a mortality agent varied substantially. Mortality from abiotically-caused physical damage was similar to that from competition, yet the distribution among modes of physical damage (uprooted, crown, or stem breakage) varied. The lack of clear evidence of mortality agents in some locations implies that many tree deaths are caused by a combination of contributing factors. The results suggest the role of bark beetle as a mortality agent does not equate to severe mortality at large scales. Prevalence of different size classes affected by individual mortality agents underline the high complexity of the mortality process in primary forests.
View
... Such changes have dramatic consequences for tree growth and productivity (Babst et al. 2019). In particular, spatial and temporal growth synchronisms among tree species are considered to be an effect of the warming-induced drought (Fang et al. 2015;Svobodová et al. 2019). The growth dynamics of sympatric tree species in mixed forests are affected by interspecific interactions, mostly competition, as interactions depend on stand structure and composition (Linares et al. 2009;Cavin et al. 2013). ...
Negative growth responses to temperature of sympatric species converge under warming conditions on the southeastern Tibetan Plateau
Article
Full-text available
Key message Warming-induced drought stress leads to convergent and negative growth responses to temperature between sympatric tree species, implying an increasing interspecific competition for soil moisture. Abstract In mixed forests, sympatric tree species avoid competition by partitioning their niches according to available environment resources. We raise the hypothesis that climate warming leads to a convergence in growth responses to climate, thus increasing the competition among sympatric species in drought-prone forests. In this study, we selected a mixed forest located at ca. 3600 m a.s.l in the Baima Snow Mountains, an inner dry valley of the southeastern Tibetan Plateau. We measured width of the tree rings produced during 1910–2016 in 60 trees belonging to three sympatric species: Abies georgei, Picea likiangensis, and Betula delavayi. We analyzed the changes in radial growth and their responses to climate. We detected shifts in the responses to climate after the 1990s. The radial growth of all species was positively correlated with precipitation from 1964 to 1990, but negatively correlated with March–June temperature from 1991 to 2016. Compared to the period 1964–1990, convergent and negative growth responses to warmer temperatures in the period 1991–2016 probably reflect less available soil moisture for growing in this mixed forest. We conclude that climate warming will affect the niches of sympatric species in mixed forests subjected to seasonal drought, thus increasing competition and altering structure and composition of the stands in dry regions.
View
View
A Tree Ring Proxy Evaluation of Declining Causes in Pinus sylvestris L. and Pinus nigra J.F. Arnold in Northeastern Romania
Article
Full-text available
  • Feb 2022
Drought-induced dieback has been extensively studied in various forests habitats. We used a retrospective tree ring width (TRW), basal area increment (BAI), oxygen isotope ratios in tree ring cellulose (δ18OTR) and carbon isotope ratios in tree ring cellulose (δ13CTR) to assess causes in declining Pinus sylvestris L. and Pinus nigra J.F. Arnold. The climate data analysis indicates a significant increased trend occurred after 1980 in minimum, mean and maximum temperature and a reduced amount of precipitation compared to the 1920–1980-time scale. According to the Palmer Drought Severity Index, we found two extreme drought years (1946 and 2000) and three years with severe drought (1990, 2003 and 2012). One-way ANOVA indicated no significant difference between P. nigra and P sylvestris tree ring width, basal area increment, but a considerable difference between δ13CTR and δ18OTR. Basal area increment evaluated the climate-growth relationship most accurately, comparing to δ18OTR and δ13CTR, which explained the influences of environmental factors in tree rings formation. The δ13CTR was mainly negatively correlated with high temperatures from April-August current growing seasons. The negative correlation between δ13CTR and NDVI indices (June, August) shows a decreased carbon uptake induced by drought from summer to early autumn. The low δ18OTR signal was associated with a complex of factors, including the strong influence of heavy precipitation occurring in the growing season and a weak reaction of declined trees to resources. Species-specific responses to drought in 1990, 2003 and 2012 indicated P. sylvestris as more sensitive to drought whit higher demand for water supply in the optimal compared with P. nigra. Weak and unstable correlations in time with increasing/decreasing values in drought periods were obtained more accurately using δ18OTR compared to δ13CTR. The species-specific resilience response to drought years showed a weak resilience and resistance in P. sylvestris occurred more evident after the 2012 event compared to less sensitive P. nigra trees. Decision-makers can use presented results to reinforce specific management plans capable of protecting and changing local compositions where is the case with species more resistant to drouth.
View
Радіальний приріст ялини європейської (Picea abies L.) в осередку її всихання (Горгани, Українські Карпати)
Article
Full-text available
  • Jun 2020
Упродовж останніх років відбувається інтенсивне всихання ялинових лісів в Українських Карпатах. Цей процес завдає економічних збитків, призводить до погіршення життєвого стану ялинників та зниження рівня надання екосистемних послуг лісами. Для встановлення щорічного радіального приросту ялини європейської та його динаміки, а також подальшого обґрунтування лісівничих заходів у гірському масиві Горган у дуже ослаблому за санітарним станом та складним за структурою мішаному деревостані в 2019 р. здійснено дендрохронологічні дослідження. Виявлено стрімке зниження приросту ялини, починаючи із першого класу віку, яке може бути пов'язане (окрім інших факторів) із міжвидовою конкуренцією (ялини і ялиці). Середній приріст деревостану за досліджуваний період становить 1,97 мм/рік. Найменші радіальні прирости ялини (1,05 мм/рік) були в 1980–2000 рр., коли деревостан проходив стадію розладнання. За останні 20 років середній приріст дещо збільшився (1,19 мм/рік), очевидно, внаслідок розрідження деревостану. Коливання відносних індексів приростів знаходяться в межах 84,24–115,52 %. Середня тривалість циклів приростів 8 років. Починаючи із середини ХХ ст., частота коливань приростів збільшилася, а отже, умови середовища стали екстремальнішими для росту ялини. Теперішній склад підросту свідчить про те, що в майбутньому на дослідному об'єкті відбудеться зміна біоценозу. Під час дендрохронологічних досліджень в осередках всихання ялини, необхідна різнобічна інформація про природні й антропогенні фактори, які можуть впливати на радіальний приріст дерев та його мінливість.
View
Influence of sampling and disturbance history on climatic sensitivity of temperature-limited conifers
Article
Full-text available
  • Jul 2018
Accurately capturing medium- to low-frequency trends in tree-ring data is vital to assessing climatic response and developing robust reconstructions of past climate. Non-climatic disturbance can affect growth trends in tree-ring-width (RW) series and bias climate information obtained from such records. It is important to develop suitable strategies to ensure the development of chronologies that minimize these medium- to low-frequency biases. By performing high density sampling (760 trees) over a ~40-ha natural high-elevation Norway spruce (Picea abies) stand in the Romanian Carpathians, this study assessed the suitability of several sampling strategies for developing chronologies with an optimal climate signal for dendroclimatic purposes. There was a roughly equal probability for chronologies (40 samples each) to express a reasonable (r = 0.3–0.5) to non-existent climate signal. While showing a strong high-frequency response, older/larger trees expressed the weakest overall temperature signal. Although random sampling yielded the most consistent climate signal in all sub-chronologies, the outcome was still sub-optimal. Alternative strategies to optimize the climate signal, including very high replication and principal components analysis, were also unable to minimize this disturbance bias and produce chronologies adequately representing climatic trends, indicating that larger scale disturbances can produce synchronous pervasive disturbance trends that affect a large part of a sampled population. The Curve Intervention Detection (CID) method, used to identify and reduce the influence of disturbance trends in the RW chronologies, considerably improved climate signal representation (from r = 0.28 before correction to r = 0.41 after correction for the full 760 sample chronology over 1909–2009) and represents a potentially important new approach for assessing disturbance impacts on RW chronologies. Blue intensity (BI) also shows promise as a climatically more sensitive variable which, unlike RW, does not appear significantly affected by disturbance. We recommend that studies utilizing RW chronologies to investigate medium- to long-term climatic trends also assess disturbance impact on those series.
View
Radial growth response to climate change along the latitudinal range of the world's southernmost conifer in southern South America
Article
Full-text available
  • Mar 2018
Aim We examined whether and how tree radial‐growth responses to climate have changed for the world's southernmost conifer species throughout its latitudinal distribution following rapid climate change in the second half of the 20th century. Location Temperate forests in southern South America. Methods New and existing tree‐ring radial growth chronologies representing the entire latitudinal range of Pilgerodendron uviferum were grouped according to latitude and then examined for differences in growth trends and non‐stationarity in growth responses to a drought severity index (scPDSI) over the 1900–1993 AD period and also before and after significant shifts in climate in the 1950s and 1970s. Results The radial‐growth response of P. uviferum climate was highly variable across its full latitudinal distribution. There was a long‐term and positive association between radial growth and higher moisture at the northern and southern edges of the distribution of this species and the opposite relationship for the core of its distribution, especially following the climatic shifts of the 1950s and 1970s. In addition, non‐stationarity in moisture‐radial growth relationships was observed in all three latitudinal groups (southern and northern edges and core) for all seasons during the 20th century. Main conclusions Climate shifts in southern South America in the 1950s and 1970s resulted in different responses in the mean radial growth of P. uviferum at the southern and northern edges and at the core of its range. Dendroclimatic analyses document that during the first half of the 20th century climate‐growth relationships were relatively similar between the southern and northern range edges but diverged after the 1950s. Our findings imply that simulated projections of climate impacts on tree growth, and by implication on forest ecosystem productivity, derived from models of past climate‐growth relationships need to carefully consider different and non‐stationarity responses along the wide latitudinal distribution of this species.
View
Large-scale disturbance legacies and the climate sensitivity of primary Picea abies forests
Article
Full-text available
  • Jan 2018
Determining the drivers of shifting forest disturbance rates remains a pressing global change issue. Large-scale forest dynamics are commonly assumed to be climate driven, but appropriately scaled disturbance histories are rarely available to assess how disturbance legacies alter subsequent disturbance rates and the climate sensitivity of disturbance. We compiled multiple tree-ring based disturbance histories from primary Picea abies forest fragments distributed throughout five European landscapes spanning the Bohemian Forest and the Carpathian Mountains. The regional chronology includes 11 595 tree cores, with ring dates spanning the years 1750 to 2000, collected from 560 inventory plots in 37 stands distributed across a 1000 km geographic gradient, amounting to the largest disturbance chronology yet constructed in Europe. Decadal disturbance rates varied significantly through time and declined after 1920, resulting in widespread increases in canopy tree age. Approximately 75% of current canopy area recruited prior to 1900. Long-term disturbance patterns were compared to an historical drought reconstruction, and further linked to spatial variation in stand structure and contemporary disturbance patterns derived from LANDSAT imagery. Historically, decadal Palmer drought severity index minima corresponded with higher rates of canopy removal. The severity of contemporary disturbances increased with each stand's estimated time since last major disturbance, increased with mean diameter and declined with increasing within-stand structural variability. Reconstructed spatial patterns suggest that high small-scale structural variability has historically acted to reduce large-scale susceptibility and climate sensitivity of disturbance. Reduced disturbance rates since 1920, a potential legacy of high 19th century disturbance rates, have contributed to a recent region-wide increase in disturbance susceptibility. Increasingly common high-severity disturbances throughout primary Picea forests of Central Europe should be reinterpreted in light of both legacy effects (resulting in increased susceptibility) and climate change (resulting in increased exposure to extreme events). This article is protected by copyright. All rights reserved.
View
Silver fir and Douglas fir are more tolerant to extreme droughts than Norway spruce in south‐western Germany
Article
Full-text available
  • May 2017
Improving our understanding of the potential of forest adaptation is an urgent task in the light of predicted climate change. Long-term alternatives for susceptible yet economically important tree species such as Norway spruce (Picea abies) are required if the frequency and intensity of summer droughts will continue to increase. Although Silver fir (Abies alba) and Douglas fir (Pseudotsuga menziesii) have both been described as drought-tolerant species, our understanding of their growth responses to drought extremes is still limited. Here, we use a dendroecological approach to assess the resistance, resilience, and recovery of these important central Europe to conifer species the exceptional droughts in 1976 and 2003. A total of 270 trees per species were sampled in 18 managed mixed-species stands along an altitudinal gradient (400-1200 m a.s.l.) at the western slopes of the southern and central Black Forest in southwest Germany. While radial growth in all species responded similarly to the 1976 drought, Norway spruce was least resistant and resilient to the 2003 summer drought. Silver fir showed the overall highest resistance to drought, similarly to Douglas fir, which exhibited the widest growth rings. Silver fir trees from lower elevations were more drought-prone than trees at higher elevations. Douglas fir and Norway spruce, however, revealed lower drought resilience at higher altitudes. Although the 1976 and 2003 drought extremes were quite different, Douglas fir maintained consistently the highest radial growth. Although our study did not examine population level responses, it clearly indicates that Silver fir and Douglas fir are generally more resistant and resilient to previous drought extremes and are therefore suitable alternatives to Norway spruce; Silver fir more so at higher altitudes. Cultivating these species instead of Norway spruce will contribute to maintaining a high level of productivity across many Central European mountain forests under future climate change.
View
Forest disturbances under climate change
Article
Full-text available
  • Jul 2017
Forest disturbances are sensitive to climate. However, our understanding of disturbance dynamics in response to climatic changes remains incomplete, particularly regarding large-scale patterns, interaction effects and dampening feedbacks. Here we provide a global synthesis of climate change effects on important abiotic ( re, drought, wind, snow and ice) and biotic (insects and pathogens) disturbance agents. Warmer and drier conditions particularly facilitate re, drought and insect disturbances, while warmer and wetter conditions increase disturbances from wind and pathogens. Widespread interactions between agents are likely to amplify disturbances, while indirect climate effects such as vegetation changes can dampen long-term disturbance sensitivities to climate. Future changes in disturbance are likely to be most pronounced in coniferous forests and the boreal biome. We conclude that both ecosystems and society should be prepared for an increasingly disturbed future of forests.
View
Tree-ring widths are good proxies of annual variation in forest productivity in temperate forests
Article
Full-text available
  • May 2017
Tree rings have long been used to calibrate the net primary production (NPP) time-series predicted by process-based models, based on an implicit assumption that ring-width indices (RWI) can well reflect temporal NPP change. However, this assumption has seldom been tested systematically. In this study, 36 plots were set in three forest types from four sites along a latitudinal gradient in northeast China. For each plot, we constructed chronologies and stand NPP of the past 20 years to examine: is RWI a good proxy of inter-annual variation of forest NPP for different forest types under different climate? If it is, why? Our results indicate that RWI was closely related to stand NPP in most cases, and could be used as a good proxy of NPP in temperate forests. Standard and arstan chronologies were better related to NPP series than residual chronology. Stand NPP time-series were mainly determined by large trees, and the correlation between RWI and NPP was also higher for larger trees. We suggest that large trees and dominant species of canopy layer should be sampled for chronology construction. Large trees are major contributors of forest biomass and productivity, and should have priority in forest conservation in a rapid-warming world.
View
View
View
View
Forest disturbances under climate change
Article
  • May 2017
Forest disturbances are sensitive to climate. However, our understanding of disturbance dynamics in response to climatic changes remains incomplete, particularly regarding large-scale patterns, interaction effects and dampening feedbacks. Here we provide a global synthesis of climate change effects on important abiotic (fire, drought, wind, snow and ice) and biotic (insects and pathogens) disturbance agents. Warmer and drier conditions particularly facilitate fire, drought and insect disturbances, while warmer and wetter conditions increase disturbances from wind and pathogens. Widespread interactions between agents are likely to amplify disturbances, while indirect climate effects such as vegetation changes can dampen long-term disturbance sensitivities to climate. Future changes in disturbance are likely to be most pronounced in coniferous forests and the boreal biome. We conclude that both ecosystems and society should be prepared for an increasingly disturbed future of forests.
View