Tree-ring Growth Response Research Articles

Stress-tolerant trees for resilient cities: Tree-ring analysis reveals species suitable for a future climate

Cities are vulnerable to droughts and heatwaves due to the decline in permeable green spaces and the emergence of heat islands. To tackle these environmental challenges, many cities adopted ambitious tree-planting initiatives. However, tree tolerance to climate extremes is overlooked even though physiological and growth limitations jeopardize ecosystem services provision. We assessed the responses of Tipuana tipu to the 2013/2014 summer drought in São Paulo, Brazil. We sampled trees in a park and streets and assessed how tree-ring δ13C and growth responses to drought differ. The Regression Tree shows that microhabitats exert the strongest control on tree-ring δ13C seconded by drought. δ13C is on average 1.0‰ higher in streets where growth rate is 60% higher than in the park. Similarly, δ13C increased by up to 0.9‰ during the drought when growth increased by up to 45% in both sites. This positive association between δ13C and growth rate (R2 = 0.78) indicates that growth is limited by assimilation rate. Assimilation is up to 15% higher in streets and increased by up to 10% during the drought because of higher incident sunlight and air temperature. Thus, T. tipu is a drought-tolerant species with potential to contribute to (sub)tropical cities, thriving in a warming climate.

Dynamic responses of tree-ring growth to drought over Loess Plateau in the past three decades

Since the 1990s, global warming has substantially affected the dynamic responses of forest ecosystems to drought by altering tree growth and ecosystems carbon cycling. The Loess Plateau is a typical vegetation recovery region with an arid and semiarid climate. However, the responses of the vegetation in this region to drought have not been fully studied. We therefore aimed to characterize these responses in tree-ring samples, which were obtained by drilling tree cores with a growth cone, for establishing the tree-ring width chronologies. In addition, we investigated the main factors controlling the radial growth of Chinese pine (Pinus tabulaeformis) and its dynamic responses to drought in the Loess Plateau using correlation analysis. Our results show that radial growth in Chinese pine had a positive correlation with precipitation during the last growing season, pre-growing season, and entire current growing season. The correlation between the radial growth and temperature was inconsistent between different sampling sites and time periods. These suggest that precipitation was more likely to affect radial vegetation growth than temperature. Moreover, the drought indices calculated using data before the year 2000 more accurately reflected the vegetation drought situation in Loess Plateau than data from the last 20 years. The drier the place, the more accurately the drought indices represented the responses of vegetation to drought. However, these indices cannot satisfactorily capture the drought responses of vegetation in wet regions. Furthermore, the PDSI was more accurate than the SPEI at capturing the effects of drought on radial vegetation growth. Understanding the response mechanism of the radial growth of Chinese pine to drought can provide theoretical support for ecological protection, forest management, and ecological construction under climate change.

Reconstructing mean temperature of April-July in 1809-2018 based on tree-ring of Pinus taiwanensis in the Tianmu Mountain, East China

We established 340-year chronologies of total ring width, early wood width, and late wood width with tree-ring samples of Pinus taiwanensis at high altitude collected from the western Tianmu Mountain in northern Zhejiang Province. According to the criterion that subsample signal strength (SSS) should be larger than 0.8, the reliable period was from 1810 to 2019. Through the correlation analysis between chronologies and climatic factors, we examined the responses of tree ring growth to climate. The results showed that radial growth of P. taiwanensis was more sensitive to temperature than to precipitation. Comprehensively considering the correlation analysis results for the raw and first-order difference series, early wood width was significantly correlated with the early growing season mean and maximum temperatures of the prior year, while late wood width with prior May and current September mean and maximum temperatures. The correlation pattern of total ring width was similar to that of early wood width, although at a low level. The optimal correlation was between early wood width and prior April-July mean temperature. Based on this relationship, April-July mean temperature of the Tianmu Mountain, East China was reconstructed for the period of 1809-2018 with an explained variance of 61.5%. Both the raw and first-order difference series passed the split sample calibration-verification test. The warm periods were 1809-1833 and 1965-2018, with a cold period in 1834-1964. Temperature had risen rapidly since the 1960s. From the standpoint of low frequency, it reached an unprecedented level since the 1980s over the past 210 years. Spatial correlation analysis showed that the reconstructed temperature series could represent temperature variations of East China, which had a good agreement with a reconstructed regional temperature series from East China. Our results showed that P. taiwanensis had a great potential for paleoclimate reconstruction in East China.

Tree-Ring Patterns and Growth Response of Abies jaliscana to Climate along Elevational Gradients in the Mountains of Western Jalisco, Mexico

Jalisco fir (Abies jaliscana) is an endemic tree with restricted distribution, and is considered a Pliocene relict inhabiting the cloud montane forests in the humid-temperate upper zone of western Jalisco Mountains. Despite its ecological importance, to date, there are no studies for this taxon aimed to understand its vulnerability to regional climate variability. We used dendrochronological techniques to investigate tree-ring patterns and the effects of climate variability on the radial growth of Jalisco fir through its elevational range in both southern and northern aspects. We developed tree-ring series that ranged in length from 79 to 152 years. High-elevation trees (2400 m.a.s.l.) showed higher annual radial growth compared to those present in low-elevation sites. Over the last 150 years, Abies jaliscana trees have had higher annual radial growth rates compared to those exhibited by other Abies species. Both winter and early spring precipitation are the main factors determining the growth rates at all the elevation sites for both aspects. In the cold season, mean maximum temperature negatively affected ring-width growth at most of the elevation zones except for two study sites. We conclude that the radial growth of A. jaliscana appears to be smaller during lower rainfall periods in the dry seasons (winter and early spring), and A. jaliscana annual radial growth responds differently to regional climate variability along the elevational gradient and mountain aspects.

Fire as a Major Factor in Dynamics of Tree-Growth and Stable δ13C and δ18O Variations in Larch in the Permafrost Zone

Wildfires are one of the most important environmental factors controlling forest ecosystem physiology and the carbon balance in the permafrost zone of North Siberia. We investigated tree-ring width (TRW) and stable isotope chronologies in tree-ring cellulose (δ13CCell, δ18OCell) of Larix Gmelinii (Rupr.) Rupr. from a wet (WS) and a dry (DS) site. These sites are characterized by different fire histories (fire in 1852 at the wet and 1896 at the dry sites, respectively). TRW and δ18OCell are identified to be the most sensitive parameters in the changing tree growth conditions after fire. The differences in the soil seasonal thermal regime of sites after fires are shown in the relationship between the studied parameters. The δ13CCell values in tree rings from the two sites are positively correlated independently of the fire impact. This fact indicates that δ13CCell chronologies might be more adequate for climatic reconstruction in the region due to the climate signal consistency. Relationships of δ18OCell values between the two sites are still significantly positive 60 years after the fire impact. Dendroclimatic analysis indicates significant changes in tree-ring growth and isotopic ratio responses to climate due to the increased demand of water for trees during the post-fire period (deeper seasonal subsidence of permafrost).

Growth ring response of two Atlantic Forest tree species pre- and post-dam operation in Southern Brazil

Hydropower plants are important sources of renewable energy, but the climatic impacts of their constructions remain poorly explored. Considering that tree growth analysis is a useful tool to identify environmental impacts, this study aimed at using climate records and tree-ring chronologies to understand possible local climate changes caused by the construction of a hydropower plant in the 1980s in the State of Paraná, Southern Brazil. Historical climatic data were obtained from the local meteorological station and surrounding municipalities and analyzed using ANOVA and means tests. The Pettitt test was additionally used to identify change-points in the meteorological data. Wood samples from a total of 60 trees from Araucaria angustifolia (Bertol.) Kuntze (Araucariaceae) and Cedrela fissilis Vell. (Meliaceae) were collected, and tree-ring chronologies were built using dendrochronological standard procedures. Chronologies for A. angustifolia and C. fissilis represented time periods from 1800 to 2016 and 1899–2015, respectively. Tree-ring growth responses to climatic variables were evaluated by adjusting generalized mixed linear models and the Spearman correlations. Our results evidenced that the hydropower plant altered the local climate, mostly influencing the hydrological cycle by increasing local rainfall, with monthly rain volumes being statistically higher than in other meteorological stations. Significant responses in the growth of A. angustifolia were found to be associated with the water level increase caused by the dam and of C. fissilis due to the increase in cloud cover.

Recent changes in the climate-growth response of European larch (Larix decidua Mill.) in the Polish Sudetes

Key messageRecently observed temporal changes in the climate-growth relationship of larch in the Polish Sudetes suggest growth limitations in the future.Larches in the Sudetes are very sensitive to the currently changing climatic factors, and an extreme negative response to drought is observed. In this study, temporal changes in the climate-growth relationship of European larch were analyzed using moving-window correlation. Change-point detection analysis was performed to determine whether there is a temporal connection between tree-ring growth responses and changes in climatic factors trends. The Random Forest predictor importance determination method was used to establish the set of climatic factors that influence larch tree-ring growth the most and to show how this set changes over time. Additionally, cluster analysis was applied to find spatial growth patterns and to generalize the growth response of larch. The results indicate that the main clustering factor is altitude. Nevertheless, an increasing unification of the larch’s response to dominant climatic factors is observable throughout the whole study area. This unification is expressed in the increasingly positive and recently dominant effect of May temperature. A progressively negative influence of the temperature in the summer and late autumn of the year preceding growth was observed, as was an increasing influence of water availability in the summer months. The study indicates that there is a connection between the observed changes and the recent rapid rise in temperature, which has consequently had a negative influence on water availability. The growth of this tree species in the Sudetes is expected to be very limited in the future due to its sensitivity to drought, the predicted increase in temperatures and thermal extremes, and the decrease of the share of summer precipitation in the annual total.

Greater hydraulic safety contributes to higher growth resilience to drought across seven pine species in a semi-arid environment.

Quantifying inter-specific variations of tree resilience to drought and revealing the underlying mechanisms are of great importance to the understanding of forest functionality, particularly in water-limited regions. So far, comprehensive studies incorporating investigations in inter-specific variations of long-term growth patterns of trees and the underlying physiological mechanisms are very limited. Here, in a semi-arid site of northern China, tree radial growth rate, inter-annual tree-ring growth responses to climate variability, as well as physiological characteristics pertinent to xylem hydraulics, carbon assimilation and drought tolerance were analyzed in seven pine species growing in a common environment. Considerable inter-specific variations in radial growth rate, growth response to drought and physiological characteristics were observed among the studied species. Differently, the studied species exhibited similar degrees of resistance to drought-induced branch xylem embolism, with water potential corresponding to 50% loss hydraulic conductivity ranging from -2.31 to -2.96MPa. We found that higher branch hydraulic efficiency is related to greater leaf photosynthetic capacity, smaller hydraulic safety margin and lower woody density (P<0.05, linear regressions), but not related to higher tree radial growth rate (P>0.05). Rather, species with higher hydraulic conductivity and photosynthetic capacity were more sensitive to drought stress and tended to show weaker growth resistance to extreme drought events as quantified by tree-ring analyses, which is at least partially due to a trade-off between hydraulic efficiency and safety across species. This study thus demonstrates the importance of drought resilience rather than instantaneous water and carbon flux capacity in determining tree growth in water-limited environments.

Response between tree-rings of Pinus kesiya and daily climate data – A study from Manipur, Northeast India

A 39 years (1980–2018 C.E.) long tree–ring width chronology of Khasi Pine (Pinus kesiya) was developed using 36 tree cores collected from Manipur, Northeast India. The significant dendrochronological potential of this tree was achieved from this region, based on tree–ring chronology statistics. A linear response between ring–width chronology of P. kesiya and daily gridded climate (mean temperature and rainfall) records has been established. A significant negative association has been observed between daily mean temperature and tree growth during March 24 to May 27, whereas, rainfall showed positive response from February 24 to March 25. This study is a maiden attempt from India to analyze the response of tree ring growth to the daily climatic records. Further studies with a larger number of samples of P. kesiya are recommended from this region to strengthen the chronology statistics and to extend the chronology time span.

北京东灵山辽东栎林树木生长对气候要素的响应特征

PDF HTML阅读 XML下载 导出引用 引用提醒 北京东灵山辽东栎林树木生长对气候要素的响应特征 DOI: 10.5846/stxb201910212210 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家重点研发计划项目（2016YFC0501602）；国家自然科学家基金（31971481） Tree-ring growth responses of Liaodong Oak (Quercus wutaishanica) to climate in the Beijing Dongling Mountain of China Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:根据北京东灵山辽东栎（Quercus wutaishanica）的年轮宽度资料，分析了该地区树木生长在1951-2010年时段对气候要素的响应特征。相关分析表明，夏季干旱胁迫是限制东灵山辽东栎树木生长的最为重要的气候要素，主要体现在与夏季（7-9月）温度的负相关关系和夏季降雨（7月）的正相关关系，另外春季（5月）温度对树木生长也有一定的限制性影响；年表与生长季节干旱指数普遍呈正相关关系，进一步证实了干旱胁迫对树木生长的限制性作用。滑动相关分析表明，年表与夏季温度负相关关系及与夏季降雨的正相关关系在近期趋于增强，这表明夏季干旱胁迫对树木生长影响作用有不断加强的趋势。辽东栎林是北京东灵山温带落叶阔叶林的优势群落，在暖干化气候不断发展背景下，辽东栎林生长的干旱胁迫效应将更加突出，对北京东灵山地区森林的生产力及固碳能力产生负面影响。 Abstract:Based on tree-ring width data of Quercus wutaishanica forest in Beijing Dongling Mountain, we detected response sensitivity of radial growth to local climate variables during the overlap period (1951-2010) between tree ring and climate data. Correlation analysis indicated that yearly growth was strongly correlated with summer temperature (from July to September) and precipitation (July), indicating summer drought stress was the major constraint for tree growth. Tree radial growth was also positively correlated with growing season (from April to October) Palmer Drought Severity Index (PDSI), further confirming high sensitivity of tree growth to moisture condition. Additionally, climate condition in spring had a partial influence on tree growth, representing the significantly negative correlation with May temperature. Moving correlation analysis revealed that the relationship between tree rings and summer temperature (negative) and precipitation (positive) has become strengthened in the recent years. This predominantly show that the influence of summer drought stress on radial growth becomes more evident recently. Climate change models predict higher temperatures and increasing drought stress in the study area. The elevated dry climate will increasingly threaten Q. wutaishanica forest growth, allowing a downward trend in Net Primary Production (NPP), and the weakened ability of terrestrial carbon sink of local forests should be expected. 参考文献 相似文献 引证文献

Securing timelines in the ancient Mediterranean using multiproxy annual tree-ring data

Calendar-dated tree-ring sequences offer an unparalleled resource for high-resolution paleoenvironmental reconstruction. Where such records exist for a few limited geographic regions over the last 8,000 to 12,000 years, they have proved invaluable for creating precise and accurate timelines for past human and environmental interactions. To expand such records across new geographic territory or extend data for certain regions further backward in time, new applications must be developed to secure "floating" (not yet absolutely dated) tree-ring sequences, which cannot be assigned single-calendar year dates by standard dendrochronological techniques. This study develops two approaches to this problem for a critical floating tree-ring chronology from the East Mediterranean Bronze-Iron Age. The chronology is more closely fixed in time using annually resolved patterns of 14C, modulated by cosmic radiation, between 1700 and 1480 BC. This placement is then tested using an anticorrelation between calendar-dated tree-ring growth responses to climatically effective volcanism in North American bristlecone pine and the Mediterranean trees. Examination of the newly dated Mediterranean tree-ring sequence between 1630 and 1500 BC using X-ray fluorescence revealed an unusual calcium anomaly around 1560 BC. While requiring further replication and analysis, this anomaly merits exploration as a potential marker for the eruption of Thera.

Greater risk of hydraulic failure due to increased drought threatens pine plantations in Horqin Sandy Land of northern China

Widespread decline and mortality of shelterbelt forests in water-limited regions of northern China have been occurring over the past few decades and may become more severe under the influence of climate change; however, our understanding on how droughts affect tree performance in a long-term context and the underlying water-related physiological mechanisms are still limited. Here, using a combination of tree-ring analysis and measurement of water-related functional traits, we investigated patterns of long-term radial growth and the underlying physiology in Pinus sylvestris var. mongolica (Mongolian Pine) and Pinus tabuliformis (Chinese Pine) in relation to variation in environmental water availability in Horqin Sandy Land (HSL), i.e. a key area of land desertification control in northern China where the two species are commonly used for afforestation. Particularly, we studied the association between tree-ring growth responses to drought and xylem hydraulics of the two species at the two sites of HSL that differ in climate regimes, examining the potential impacts of climate warming-related aridification on tree performances using a space-for-time substitution approach. Tree-ring analyses revealed greater degrees of recent growth decline, lower resilience to drought, and more severe tree hydraulic limitations in both pine species at the semiarid site compared to the semi-humid site. Tree-ring width indices of both species in the drier site showed significant positive correlations with May-July total precipitation of the current year and negative correlations with mean temperature of the same period, whereas such correlations were not significant at the wetter site. Lower stem hydraulic conductivity and higher degrees of xylem embolism in the drier site suggest that both pine species suffer from stronger hydraulic limitation when the environment gets drier. Moreover, Mongolian pine with a significantly higher hydraulic conductivity consistently showed higher basal area increments than Chinese pine at both sites. Our results suggest that Mongolian pine, the currently most widely used trees to create shelterbelt plantations in desertified areas of northern China, is more susceptible to decline than Chinese pine as the climate becomes hotter and drier, although the former species has a higher growth rate than the latter one. Our investigation provides a mechanistic explanation for the commonly observed decline and dieback of pine trees in water-limited environments of northern China and suggests that Chinese pine may be a better choice to replace Mongolian pine as the main tree species in plantations of the study area with a changed climate regime in the future.

Lodgepole pine tree-ring growth, Δ13C and the inverse texture effect across a soil chronosequence in glacial till

Our goal was to better understand tree growth and photosynthetic responses to variations in plant available water and elucidate the role of the inverse texture effect in snow dominated montane forests. We measured tree ring carbon isotope composition and annual growth over a 31-year record for lodgepole pine (Pinus contorta Douglas ex Loudon) growing on three different-aged glacial till surfaces in Wyoming, USA. Soils of different ages developed on till surfaces from three separate glaciation events were significantly different in clay content and distribution with depth; maximum clay content at depth ranged from 19 to 20% on the two youngest till surfaces, but was as high as 36% on the oldest till surface. Ring growth was lowest at the youngest till sites, and only on these coarse-textured soils was growth positively correlated with annual maximum snow water equivalent (SWEmax). Δ13C was highest for trees at these young till sites, suggesting that hydraulic conductivity and stomatal conductance is comparatively high during growth periods on these coarse-textured soils. Taken together, we found that age of glacial till and related soil texture differences strongly influenced tree-ring growth and Δ13C response of lodgepole pine to interannual variation in precipitation and drought severity, but responses did not support an inverse texture effect in these semi-arid forest systems.

Temporal Variations in Tree-Ring Growth Response to Climate of European Larch (Larix Decidua Mill.): An Example from Sudetes, Poland

The temporal stability of climate-growth relationship is a basic assumption and requirement of climate reconstruction using tree rings. However, many recent studies showed change in tree-ring growth response to climate for the last decades. The temporal stability of relationship mentioned above can depend on the local factors, e.g. slope aspect. In presented study the tree-ring growth response to climate of larch from Polish part of Sudetes was analysed over time. The aim was to investigate its temporal variability, existence of trends and influence of local factors. The relation between tree-ring growth of larches from six sites located at comparable altitudes (about 700-750 m.a.s.l.) and climatic factors that mainly control the tree-ring growth of larches in the study area was analysed over time. The Pearson correlation between tree-ring width site chronologies and climatic data for the study area (the average monthly air temperature and total monthly precipitation series from high-resolution gridded dataset CRU TS v.4.01) was calculated in 40-years moving windows for the period 1901-2010. The results showed variations in the tree-ring growth response to climate over the analysed time period. Although in general, similar trends were observed for all sites, some differences in trends and magnitudes among sites were also spotted. Interesting is, that the response of sites became more consistent and similar for the last decades. The discussion of the received results with respect to currently observed climatic trends in the region and local factors that can explain the differences in response between particular sites is presented.

Age-related climate sensitivity in Pinus Edulis at Dinosaur National Monument, Colorado, USA

The influence of tree age on climate sensitivity is of central importance in dendrochronology. Recent research has highlighted the disparate nature of age-dependent growth responses across species and geographic locations. We compared growth sensitivity and the influence of climate in Pinus edulis (Piñon) of varying ages at Dinosaur National Monument (DINO, northwestern Colorado, USA. Piñon is a particularly good species for this study because of its long life-span and climate sensitivity, and the DINO site is at the northern extreme of the current distribution. We evaluated changes in climate-growth relationships in piñon using total ring-width measurements and running averages of chronology statistics, mean sensitivity (MS) and coefficient of variation (CV), and we investigated growth response to climate variability as trees age. These measures indicated initial low growth sensitivity, increasing as trees reached mid-life stages, approximately 200–250 years, then relatively constant sensitivity from 250-800+ years. First order partial auto correlation (PAC1) declined throughout the life stages of piñon at DINO. The trend in declining autocorrelation leads to higher MS values in the older age classes. Greater year to year variation indicates less persistence in the study population, hence lower autocorrelation.We investigated the degree to which this relationship could be explained by the summer Palmer Drought Severity Index (PDSI) and whether this relationship varied with tree age. The strength of the tree-ring growth response to PDSI was at a maximum during the first two centuries of growth (R2 = 0.54). between two and six centuries (R2 = 0.48), after which we detected a decline in the sensitivity of tree growth to PDSI with increasing age (R2 = 0.41). This study adds to the literature on age-related climate sensitivity in trees; our findings indicate that age-related changes in climate-tree-ring growth responses should be considered when climate variables are reconstructed from tree-ring width chronologies, and specifically from Pinus edulis.

Dynamic responses of tree-ring growth to multiple dimensions of drought.

Droughts, which are characterized by multiple dimensions including frequency, duration, severity, and onset timing, can impact tree stem radial growth profoundly. Different dimensions of drought influence tree stem radial growth independently or jointly, which makes the development of accurate predictions a formidable challenge. Measurement-based tree-ring data have obvious advantages for studying the drought responses of trees. Here, we explored the use of abundant tree-ring records for quantifying regional response patterns to key dimensions of drought. Specifically, we designed a series of regional-scaled "natural experiments," based on 357 tree-ring chronologies from Southwest USA and location-matched monthly water balance anomalies, to reveal how tree-ring responds to each dimension of drought. Our results showed that tree-ring was affected significantly more by the water balance condition in the current hydrological year than that in the prior hydrological year. Within the current hydrological year, increased drought frequency (number of dry months) and duration (maximum number of consecutive dry months) resulted in "cumulative effects" which amplified the impacts of drought on trees and reduced the drought resistance of trees. Drought events that occurred in the pregrowing seasons strongly affected subsequent tree stem radial growth. Both the onset timing and severity of drought increased "legacy effects" on tree stem radial growth, which reduced the drought resilience of trees. These results indicated that the drought impact on trees is a dynamic process: even when the total water deficits are the same, differences among the drought processes could lead to considerably different responses from trees. This study thus provides a conceptual framework and probabilistic patterns of tree-ring growth response to multiple dimensions of drought regimes, which in turn may have a wide range of implications for predictions, uncertainty assessment, and forest management.

Araucaria growth response to solar and climate variability in South Brazil

Abstract. In this work, the Sun–Earth–climate relationship is studied using tree growth rings of Araucaria angustifolia (Bertol.) O. Kuntze collected in the city of Passo Fundo, located in the state of Rio Grande do Sul (RS), Brazil. These samples were previously studied by Rigozo et al. (2008); however, their main interest was to search for the solar periodicities in the tree-ring width mean time series without interpreting the rest of the periodicities found. The question arises as to what are the drivers related to those periodicities. For this reason, the classical method of spectral analysis by iterative regression and wavelet methods are applied to find periodicities and trends present in each tree-ring growth, in Southern Oscillation Index (SOI), and in annual mean temperature anomaly between the 24 and 44∘ S. In order to address the aforementioned question, this paper discusses the correlation between the growth rate of the tree rings with temperature and SOI. In each tree-ring growth series, periods between 2 and 7 years were found, possibly related to the El Niño/La Niña phenomena, and a ∼ 23-year period was found, which may be related to temperature variation. These novel results might represent the tree-ring growth response to local climate conditions during its lifetime, and to nonlinear coupling between the Sun and the local climate variability responsible to the regional climate variations. Keywords. History of geophysics (solar–planetary relationships) – meteorology and atmospheric dynamics (climatology; palaeoclimatology)

Responses of tree-ring growth in Schinopsis brasiliensis to climate factors in the dry forests of northeastern Brazil

This paper aims to provide evidences of the influence of physical atmospheric parameters on the growth of the endemic tree Schinopsis brasiliensis, and their consequent teleconnection with large-scale modes of climate variability affecting rainfall in semi-arid region of the Brazilian Northeast. The Brazilian Northeast is a region of low rainfall and high temperatures and evaporation. The surface temperature of the Atlantic Ocean (STA) modulates the rains in the Northeast in association with El Nino and La Nina (ENSO) events. Tree species that grow in this region, forming the tropical Caatinga dry forests, are subjected to long periods of drought. This study investigated the influence of climatic events on the secondary growth of a typical Caatinga tree species. The analysis was based on 39 samples of Schinopsis brasiliensis, from which we derived a chronology of tree-ring growth between 1963 and 2015, with an inter-correlation of 0.56, mean sensitivity of 0.53, and mean growth rate of 3.33 mm per year. Our results indicate that growth ring chronology is related directly to the rainy season, in addition to peaks in humidity associated with isolated downpours occurring during the dry season. On the other hand, air temperature, insolation, and evaporation revealed an inverse relationship with the chronology. Inter-correlations with ENSO events, STA, and precipitation were negative, while those between ENSO events and temperature were positive. Growth in S. brasiliensis is associated with the climatic anomalies of the region. Leaf-fall and cambial shutdown occur during the dry season, while the plant is predisposed for potential growth spurts during the intermittent rains that may occur from December onwards.

Summer solstice marks a seasonal shift in temperature sensitivity of stem growth and nitrogen-use efficiency in cold-limited forests

In boreal forests and alpine treelines, it is debatable how the temperature sensitivity of tree-ring growth should vary with changes in climate over time and the extent to which seasonal stem increments are controlled by leaf physiology. We aim to test the hypothesis that, in cold-limited forests, maximizing stem growth rate around summer solstice is closely related to foliage turnover, which generally results in high sensitivity of stem growth and less sensitivity of nitrogen-use efficiency (NUE) to early-season temperatures. Our analysis was based on repeat-census observations of stem radial increment (2008–2013; made with dendrometers) and monthly litterfall (2007–2015) as well as the measurements of tree-ring width series (1960–2015; made with tree-ring cores) in two Tibetan treeline forests. NUE was estimated as the inverse of leaf-litter nitrogen concentration. We further examined a global dataset of tree-ring chronologies (1931–1990) from 139 sites across temperate and boreal coniferous forests in the northern high-latitude region. Weekly stem increments across species and years synchronously peaked around summer solstice, with more than half of annual increment produced in the first 28–35days of the growing season when air and soil temperatures were still low. Monthly stem increments were positively related to previous-month litterfall, and higher litterfall generally resulted in higher NUE. NUE was insensitive or less sensitive to soil temperature in the early growing season. Among years, pre-peak increments were positively correlated with pre-solstice temperatures while post-peak increments varied little. The annual increment was dominated by and coherent with the pre-peak increment and well correlated with the ring-width measurements of monitored trees during 2008–2013. Variations in tree-ring width chronologies from the two Tibetan treelines and the global 139 forest sites mainly reflected the change of early summer temperatures. The findings suggest a day-length control on the linkage between seasonal stem growth and nitrogen cycling in a cold-limited forest ecosystem, and provide the basic for predicting responses of tree-ring growth and NUE to climatic warming.

Sex-specific responses of tree-ring growth to climate in the dioecious tree Populus cathayana

Sex-specific responses of tree-ring growth to climate in the dioecious tree Populus cathayana