Climate-tree Growth Relationships Research Articles

Variable climate-growth relationships of quaking aspen (Populus tremuloides) among Sky Island mountain ranges in the Great Basin, Nevada, USA

The Great Basin is an arid province located in the interior western United States. The region encompasses millions of hectares and quaking aspen (Populus tremuloides Michx.) forests comprise a minor portion of the total area. However, montane aspen forests play a disproportionately large role in providing ecosystem services in the region, including water retention, biodiversity, wildlife habitat, livestock forage, and recreational uses. With warming temperatures, increasing evaporative demand, and heightened precipitation variability, the future of aspen has become a critical concern. Using dendroecological approaches, we assessed growth patterns of 20 aspen stands across three geographically isolated “sky island” mountain ranges spanning portions of the north-central Great Basin. We anticipated that the growth of Great Basin aspen would be strongly influenced by regional climatic patterns and largely in synchrony. Results revealed a more complex growth dynamic that varied among mountain ranges and across environmental gradients. In particular, aspen climate-growth relationships in the slightly dryer Ruby Mountains were strongly and positively correlated (r > 0.5) with previous fall to winter moisture availability. The Jarbidge Mountains had a positive but modest relationship with previous fall to winter moisture availability (r > 0.3). Climate-growth response in the Santa Rosa Mountains, the wettest range, showed no significant response to moisture availability during any time period examined but had greater tree-ring growth with warmer May temperatures. Although tree-ring centennial (1910 – 2010) growth trends were positive for all three mountain ranges, only the Santa Rosa Mountains maintained a positive recent growth trend (1970 – 2010). Moreover, distinct temporal shifts in tree growth-climate relationships in each mountain range suggest potentially unique aspen population adaptations to climate variability. For instance, in two of the mountain ranges, there was a shift from positive/neutral to negative growth relationships with temperature starting around the 1963 – 1987 time period, while tree growth also began simultaneously responding more positively to moisture availability. These growth shifts and observed enhanced sensitivities to monthly and seasonal climate variables over time may reflect dynamic tree growth responses caused by ongoing global climate change, but that may be tempered by local or regional factors, such as the relative availability and timing of soil moisture provided by spring snowmelt. A better understanding of biogeographic variation and causality in aspen growth could provide multiple management pathways governed by resilience characteristics in the face of future anthropogenic and climatic threats.

Analyses of intra-annual density fluctuation signals in Himalayan cedar trees from Himachal Pradesh, western Himalaya, India, and its relationship with apple production

Intra-annual density fluctuation (IADF) refers to anatomical changes in the tree ring caused by a sudden change in wood density triggered by a combination of climate variations and various biotic and abiotic influences. To reveal the occurrence of IADFs, we analyze the growth rings of Himalayan cedar (Cedrus deodara) growing over the Kullu region, Himachal Pradesh, western Himalaya. Using 30 increment cores, we precisely dated and developed a 214-year-long tree-ring chronology extending back to AD 1808. The tree–growth–climate relationship using ring-width chronology and observed climate data revealed that cool and moist condition provides favorable condition for Himalayan cedar tree growth. Delving deeper into wood anatomy of growth rings, we revealed the frequent occurrences of IADFs in both earlywood (IADFe) and latewood (IADFl). The formation of IADFs in earlywood (IADFe) is related to the reduced precipitation from April to July, causing moisture stress in the soil and surrounding climate. However, wetter conditions in the late growing season, mainly August–October, activated the formation of IADFs in latewood (IADFl). The study revealed several IADF years in earlywood and latewood, such as 1901, 1902, 1903, 1914, 1915, 1919, 1920, 1923, 1925, 1943, 1958, 1959 and 1937, 1955, 1956, 1988, respectively. These IADF years corresponded with unusual climatic fluctuations that severely affected apple production, the major cash crop in the region. The analyses demonstrated that the IADF chronology of Himalayan cedar would be a valuable proxy to understand abrupt and unusual climatic fluctuations from a long-term perspective for the data-scarce western Himalayan region.

Composition, age-structure and dendroecology of high altitude treeline forest in the western Himalaya, India

In the natural treeline ecotones, population structure and tree recruitment dynamics are strong indicators of vegetation responses to global climate change. We dendroecologically investigated age-structure, regeneration and tree-growth climate relationship of Abies spectabilis (D. Don) Mirb. forests along an elevational gradient at high altitude treeline ecotone (3020–3450 m asl) in the Kedarnath wildlife sanctuary, western Himalaya, India. The stand age structure of A. spectabilis was determined by ring counts of tree individuals (n = 95) core and bud scar count in seedlings and saplings. Years taken to reach coring height (CBH-1.37 m) were determined by fitting height-age regression model. Range shift and radial growth-climate relationships were studied to capture the advancement rate and climatic influence on tree growth. The result shows poor regeneration of A. spectabilis and low seedlings and sapling recruitment at the treeline ecotone (∼3340 m), in contrast higher recruitment of Rhododendron campanulatum in meadows zone, forming krummholz line at ∼ 3550 m. The stand age structure shows that older tree individuals were recruited at lower elevations while younger ones were at higher elevations. The treeline migrated upward at ∼10.01 m/decade. A 263-year old ring-width chronology of A. spectabilis shows precipitation of the current year's April month was conducive for radial growth, while the previous year's September and current year's April, May temperature negatively influenced radial growth. The presence of a few A. spectabilis seedlings and saplings within the ecotone limit could be attributed to the combined response of climate change and anthropogenic factors. Despite rapid warming, A. spectabilis treeline in the Tungnath, western Himalaya, has little advanced upslope in contrast with central Himalaya. Positive correlation with winter month’s (DJF) temperature indicated its sensitivity to warming scenario in western Himalaya. It appears that the beneficial effect of warming on tree growth is offset by water stress caused by increased evapotranspiration.

Climate response of Picea schrenkiana based on tree-ring width and maximum density

The effect of global warming on alpine forests is complex. It is crucial, therefore, to investigate the effects of climate change on the radial growth of trees at different altitudes. The tree growth–climate relationship remains poorly understood at large spatial scales in the Tianshan Mountains, China. Schrenk spruce (P. schrenkiana) is a unique tree species to this area. In this study, we collected tree-ring width and maximum density data from nine plots along an altitudinal gradient. Results showed that altitude affected both tree-ring width and maximum density. At high altitudes, tree-ring width was positively correlated with temperature in February of the current year. Tree-ring width was also positively correlated with precipitation in July of the previous year, and January and July of the current year, and negatively correlated with the monthly diurnal temperature range (DTR). At low altitudes, tree-ring width was negatively correlated with temperature in the early growing season and the growing season. Tree-ring width was positively correlated with precipitation in June and September of the previous year, and May of the current year. The tree-ring maximum density was positively correlated with temperature and the DTR of the growing season, and negatively correlated with precipitation in winter and growing season. Moving correlation analysis showed that the positive response of tree-ring width to precipitation in the growing season was enhanced over time at high altitudes. In the low-altitude trees, the negative response of tree-ring width to temperature in the growing season was reduced, while the positive response to precipitation in the growing season was enhanced. The positive response relationship between tree-ring maximum density and the temperature in July weakened over time. At low altitudes, the negative response of tree-ring maximum density to winter precipitation was strengthened, and a stable negative response to July precipitation was observed. As the climate becomes wetter and warmer in the Tianshan Mountains, our results suggest that the radial growth of trees may benefit at elevations above 2400 m a.s.l. There was no obvious elevation limit for the increase in tree-ring maximum density. These findings provide a basis for sustainable forest management under global climate change.

Tree growth-climate relationship in the Azorean holly in a temperate humid forest with low thermal amplitude

Dendroclimatic records in areas with high relative humidity and low thermal amplitude are manifestly scarcer and only a few studies are applied to species that are present in areas with weak seasonality. The Azores archipelago with temperate climate, with low thermal amplitude, has unique biodiversity, including the Azorean holly, Ilex azorica Gand., that is dominant in most extant natural forests. Hence, the importance of understanding its behavior and relation with climate. In this study, we try to understand tree-ring patterns of this species and examine the relationship between radial tree growth and main climatic drivers. For this purpose, we sampled four populations from São Miguel Island and two from Terceira Island. We found a diffuse-ring porous wood with a common layer of vessels associated to the ring boundary, which was critical to identify annual tree-rings. Generalized linear models were used to relate different variations of temperature and precipitation parameters, resulting into a diverse climate-growth relationships of different populations, while the composite population exhibited pronounced effect of temperature. We conclude that, I. azorica forms reliable annual tree-rings, which can be statistically related to climate, mostly temperature. However, there are differences among specific sites, thus the climate sensitivity depends on other site characteristics, such as soil and slope, but probable also to other ecological drivers, such as the competition, water drainage, among others.

Responses of radial growth of Pinus massoniana and Castanopsis eyrei to climate change at different elevations in south China

Rapid warming and increasing drought intensity are exposing forest ecosystems to increasing stress, challenging silvicultural decision-making. Tree growth-climate relationships may provide valuable information on tree species’ adaptive potentials. However, it is not clear how subtropical trees will respond to climate change. Here, we present a dendrochronological study on Pinus massoniana and Castanopsis eyrei growing at two elevations (400 m and 890 m) at the northern Luoxiao Mountain in China to reveal their adaptability to climate change. Results show that long-term drought caused by rapid warming and reduced precipitation after 1997 led to a significant (p < 0.05) decline trend in radial growth of trees at all sites except low elevation P. massoniana. Temperatures in almost all seasons were significantly negatively correlated with the radial growth of C. eyrei. The radial growth of P. massoniana at high elevation was significantly positively correlated with relative humidity and negatively correlated with vapor pressure deficit. The relationship between relative humidity and radial growth of P. massoniana at high elevation showed an increasing trend with time, while P. massoniana at low elevation showed the opposite. At the two elevations, the relationships between the radial growth of C. eyrei and precipitation gradually increased, and the relationships with the temperature gradually weakened. The elevation- or hillslope-related hydrothermal redistribution caused the variations in species-specific growth-climate relationships. Our results suggested that large-scale planting of P. massoniana and C. eyrei in the subtropical area of south China is not effective for wood production or carbon sequestration, and both species- or elevation-related tree growth-climate relationships should be considered in forest management.

Temporal Changes in Growth–Climate Relationship of Pinus taiwanensis Hayata in Subtropical China

Whether the tree growth–climate relationship is consistent in subtropical China has not yet been reported. To fill this gap, we chose Pinus taiwanensis which grow on Lushan Mountain in a subtropical region of China as the target tree species, established a standard tree-ring width chronology, and conducted a moving correlation analysis with climatic factors. The results showed that the relationship between radial growth of P. taiwanensis and climate changed significantly during 1980–1990. From 1955 to 1985, tree rings were negatively affected mainly by precipitation in September of the current growing season. From 1990 to 2014, however, a significant negative correlation appeared between tree rings and sunshine duration from March to April in the growing season. Our results suggest the need to pay attention to this growth–climate inconsistency when conducting dendroclimatology studies in subtropical China. However, the causes of the inconsistency still require further confirmation.

Regional climate moderately influences species-mixing effect on tree growth-climate relationships and drought resistance for beech and pine across Europe

Increasing species diversity is considered a promising strategy to mitigate the negative impacts of global change on forests. However, the interactions between regional climate conditions and species-mixing effects on climate-growth relationships and drought resistance remain poorly documented.In this study, we investigated the patterns of species-mixing effects over a large gradient of environmental conditions throughout Europe for European beech (Fagus sylvatica L.) and Scots pine (Pinus sylvestris L.), two species with contrasted ecological traits. We hypothesized that across large geographical scales, the difference of climate-growth relationships and drought resistance between pure and mixed stands would be dependent on regional climate. We used tree ring chronologies derived from 1143 beech and 1164 pine trees sampled in 30 study sites, each composed of one mixed stand of beech and pine and of the two corresponding pure stands located in similar site conditions. For each site and stand, we used Bootstrapped Correlation Coefficients (BCCs) on standardized chronologies and growth reduction during drought years on raw chronologies to analyze the difference in climate-tree growth relationships and resistance to drought between pure and mixed stands.We found consistent large-scale spatial patterns of climate-growth relationships. Those patterns were similar for both species. With the exception of the driest climates where pure and mixed beech stands tended to display differences in growth correlation with the main climatic drivers, the mixing effects on the BCCs were highly variable, resulting in the lack of a coherent response to mixing. No consistent species-mixing effect on drought resistance was found within and across climate zones. On average, mixing had no significant effect on drought resistance for neither species, yet it increased pine resistance in sites with higher climatic water balance in autumn. Also, beech and pine most often differed in the timing of their drought response within similar sites, irrespective of the regional climate, which might increase the temporal stability of growth in mixed compared to pure stands.Our results showed that the impact of species mixing on tree response to climate did not strongly differ between groups of sites with distinct climate characteristics and climate-growth relationships, indicating the interacting influences of species identity, stand characteristics, drought events characteristics as well as local site conditions.

December-March temperature reconstruction from tree-ring earlywood width in southeastern China during the period of 1871-2016.

Extremely cold temperatures are a significant threat to agriculture and transportation in winter in southeastern China. However, due to the shortness of instrumental records and the scarcity of long-term temperature reconstructions, more high-quality temperature reconstructions are still needed to fully examine their spatial-temporal variability over the past several centuries. In this study, we built an earlywood width (EWW) chronology, a latewood width (LWW) chronology, and a tree-ring width (TRW) chronology using tree-ring samples of Pinus taiwanensis Hayata from the western Tianmu Mountains and the Xianyu Mountains in southeastern China. The tree growth-climate relationships were analyzed, and we found the strongest correlation between December and March mean temperature and the EWW chronology. The December-March mean temperature history was then reconstructed over the period of 1871-2016 using a linear regression model, which is the first EWW-based temperature reconstruction in southeastern China. With a higher explained variance (47.0%) than that (31.7%) of a previous reconstruction using a TRW chronology, the quality of the model has largely improved. This reconstruction was also comparable with other nearby records, further demonstrating the reliability of our new model. Furthermore, our reconstruction exhibits a significantly negative relationship with the East Asian winter monsoon index (EAWMI) since the 1920s, which may be attributed to the obviously enhanced EAWMI thereafter.

伊春地区红松和红皮云杉径向生长对气候变化的响应

PDF HTML阅读 XML下载 导出引用 引用提醒 伊春地区红松和红皮云杉径向生长对气候变化的响应 DOI: 10.5846/stxb201812292845 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（41877426，31770490）；中央高校基本科研业务费高层次人才发展专项（2572017DG02）；中国气象局东北地区生态气象创新开放实验室基金（stqx2018zd02） Radial growth of Pinus koraiensis and Picea koraiensis response to climate change in Yichun City,Heilongjiang Province 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:树木生长-气候关系对准确评估气候变化对森林生态系统影响、预测森林生产力与植被动态及揭示树木对气候变化的响适应策略至关重要。在全球变暖背景下，升温可能会对树木的生长产生影响，从而改变区域森林生态系统的生产力或碳储量。本研究利用生长-气候响应函数、滑动相关分析等树木年轮学方法，探讨伊春地区阔叶红松林内红松和红皮云杉径向生长的主要限制因子及两者径向生长对快速升温（1980年后）响应的异同。结果表明：1980年前红松径向生长有明显加速的趋势，红皮云杉上升趋势较弱；而1980年后红松径向生长趋势显著下降，红皮云杉则下降不明显。红皮云杉径向生长与上一年9月及当年6月平均气温显著负相关，而红松径向生长与上一年12月及当年1月、4月和6月最低气温显著正相关。1980年快速升温后，高温对两树种生长的抑制作用增强，尤其是红松。生长季末（9月）降水对红松和红皮云杉的限制作用由升温前的负相关转变为升温后的显著正相关。温度是限制红松和红皮云杉径向生长的主要气候因子，降水影响相对较弱；其中红松径向生长对气候变化的响应比红皮云杉更敏感。快速升温后，红松和红皮云杉生长-气候关系的变化可能与升温导致的暖干旱化有关。若气候变暖持续或加剧，二者径向生长的气候限制因子也将由温度转变为水分；红松和红皮云杉会出现生长衰退，尤其是红松。 Abstract:Tree growth-climate relationship is critical for accurately assessing the impact of climate change on forest ecosystems, predicting forest productivity and vegetation dynamics, and revealing tree adaptation strategies to climate change. In the context of global warming, rising temperatures may have an impact on tree growth, thereby changing the productivity or carbon storage in regional forest ecosystems. We investigated the main climatic limiting factors of radial growth of Korean pine (Pinus koraiensis) and Korean spruce (Picea koraiensis) in broad-leaved Korean pine forests in Yichun city, China. We also discussed the similarities and differences of their response to rapid warming (after 1980) by using the growth-climate response function analysis, moving correlation analysis, and other dendroclimatology methods. The results showed that the radial growth of Korean pine was accelerated before 1980, and the upward trend of Korean spruce was weaker than that of Korean pine. However, after 1980, the radial growth trend of Korean pine was significantly decreased, while that of Korean spruce was not. The radial growth of Korean spruce was significantly negatively correlated with the mean temperature in previous September and current June, while the radial growth of Korean pine was significantly positively correlated with the minimum temperatures in previous December and January, April and June of the current year. After rapid warming in 1980, the high temperature significantly increased the growth inhibition of the two species, especially for the Korean pine. The limiting effect of precipitation at the end of growing season (September) on Korean pine and Korean spruce changed from the negative correlation before warming to significant positive correlation after warming. In general, temperature is the main climate factor limiting the radial growth of Korean spruce and Korean, followed by precipitation.The radial growth of Korean pine was more sensitive to climate change than that of Korean spruce. After rapid warming, the change of growth-climate relationship of Korean pine and Korean spruce may be related to the 'Warm-dry Phenomenon' caused by the warming. If climate warming continues or intensifies, the climatic limiting factor of the radial growth of the two species will change from temperature to moisture, and their radial growth will decline, especially for Korean pine. 参考文献 相似文献 引证文献

Fire history and climate-growth response of Abies spectabilis : A case from Langtang National Park, Nepal Himalaya

This study presents the potential of a conifer species (Abies spectabilis D. Don) to reconstruct fire history by using dendro chronological technique along with thedendroclimatic response in Langtang National Park, Central Himalaya of Nepal. For the fire history reconstruction, altogether eight cross-sections samples from fire affected eight trees and another 20 tree-cores from 10 trees with visible fire scars were taken. In the case of dendroclimatic study, 24 healthy cores of A. spectabilis were selected from the 40 cores extracted from 19 trees. The standard dendro chronological methodology was used for sample preparation and analysis. A 199-year long ring-width chronology of A. spectabilis spanning from 1818 to 2016 AD was developed. In spite of visible fire burn in near bark-surface, no potential fire scars are seen in inner parts in the cross-section samples. However, 12 cores showed that three fire burns occurred simultaneously in the forest area in the years 1917−1918, 1969−1970 and 2009−2010, respectively. Tree-ring-based fire event-record is found to be concurrent to the local people's perceptions/experience about the past fire history in the area. Tree growth climate relationship showed sensitive responses to both growing and non-growing season’s temperature and precipitation variability. Summer temperature had positive influence on growth of the species. Precipitation of monsoon and autumn were found to have negative influence on radial growth whereas pre-monsoon precipitation had positive association with tree radial-growth. This preliminary assessment shows that there is a huge potential of tree-ring research for long-term fire history in the region and helps us to better understand the role of fire in the ecology and management in the Himalayan region. The study can also be replicated in other fire-affected areas of the Himalayan region by using fire sensitive species in the sampling.

What causes variable response in tree growth to climate change at a single site? A case study of Picea crassifolia at the upper treeline, Qilian Mountains, China

In situ observations indicate that different levels of micro-standing could induce divergent temperature responses in trees at similar elevations but different slope aspects, which is supported by physiological process model simulation of radial incremental growth. The unstable response of tree growth to climate change is a well-documented, yet poorly understood phenomenon. It has been reported that Picea crassifolia exhibits a systematically variable response to climate forcing at a single high-mountain study area located at the upper treeline in the Qilian Mountains, China. This study used in situ meteorological observations to force a simplified but nonlinear mechanistic model of tree-ring width to identify how variable conditions translate into differences in radial growth within this site. The simulations suggest no significant difference in soil moisture between sites, but disparate diurnal micro-site temperature maxima, apparently amplified by a uniform warming, drive the divergent growth trends between subsites. For tree-ring-based reconstructions of surface temperature, such divergent growth trends challenge the validity of the assumption that a linear growth response to environmental conditions within and across study sites. Therefore, we recommend the development of precise, high-resolution data sets for calibrating, validating and reconstructing climatic change, given the potential for emergent non-stable tree growth–climate relationships.

Testing three climate datasets for dendroclimatological studies of oaks in the South Carpathians

Three gridded datasets containing interpolated daily and monthly precipitation and temperature values over the past five decades were tested against four tree-ring chronologies of oak (Quercus robur and Q. petraea). The objective of this research was to investigate the climate-growth relationship and whether the Pearson's product-moment correlation coefficients differ significantly if mean monthly precipitation and temperature data from the different climate databases, CRU, E-OBS and ROCADA are used. To this end, we selected two representative oak ecosystems in the South Carpathians, Romania, and analysed earlywood, latewood and tree-ring widths. Climate time series trends for the South Carpathians coldest, warmest days and wettest days were assessed with datasets from E-OBS and ROCADA, which differed in the density of their meteorological station network and their interpolation methods. The observed climatic parameters showed changes towards wetter conditions after the mid-1980s. For 1961–2013, E-OBS underestimated the mean daily temperature and daily precipitation compared with ROCADA. The results showed that higher extreme temperatures from January–March affected earlywood growth. In the investigated study region, latewood formation seemed to be affected by water availability mainly in May. Periods of drought associated with higher temperatures have limiting effects on tree growth, but these events are captured in different ways by each climate database analysed. Similarly, the results showed the discrepancy among datasets for earlywood and climate relationships. The results emphasize the importance of proper selection of climate data for assessing climate-tree growth relationships. For future dendroclimatological and dendroecological studies of oak in Romania, we recommend the ROCADA database, while E-OBS is recommended if an up-to-date climate dataset is needed.

Species-specific and elevation-differentiated responses of tree growth to rapid warming in a mixed forest lead to a continuous growth enhancement in semi-humid Northeast Asia

Simulation and prediction of forest productivity in the context of climate change is more difficult in mixed forests than that in monocultures, because of spatial and species-specific differences in tree growth-climate relationships. A detailed study on species-specific tree growth-climate relationships and their spatial variability is thus essential. Here, we focus on a mixed forest at Changbai Mountain in semi-humid area bestriding the China-Korea border which has experienced rapid climate warming over the past 50 years. Three dominate tree species, one coniferous (Korean pine) and two broad-leaved species (Mongolian oak and Manchurian ash), were selected to analyze how climate warming has affected and will affect tree growth in 21st century along an elevational gradient. Our results showed enhanced growth after 1960s. This trend is predicted to continue until 2070, although elevation could modify the main patterns of climate responses observed among the different species. Compared with low or medium elevations, the correlation coefficient between tree radial growth and temperature was lower at higher sites, except in the case of Mongolian oak, in which there was a similar pattern at all three elevational levels. Korean pine at medium elevation and Machurian ash at the low elevation grew the fastest. Our work confirmed sensitivities of growth-temperature differ in species and across the elevational distribution. It contributes to the estimation of terrestrial carbon sink dynamics.

Radial growth of Picea glauca and Picea engelmannii across Canada and USA: monthly climate, decadal oscillations, and climate change

ABSTRACTWe employ a dendrochronological approach to examine spatial variation in radial tree growth-climate relationships and responses to global climate oscillations across the geographic ranges of Picea glauca and Picea engelmannii. Tree-ring chronologies were constructed for 77 sites and analyzed using correlation coefficients for monthly climatic variables. In general, for Picea glauca, stands in the western portion of its range had significant negative correlations with temperature during fall, winter, and spring; only summer temperature was positively correlated with tree growth. In eastern North America, Picea glauca growth was negatively correlated with winter and spring temperature. Across the north-south range of Picea engelmannii, growth of northern populations was positively correlated with temperature in most seasons except spring, which had negative correlations, and response to winter precipitation differed between northern and southern populations. However, some monthly values for both species correlations were altered due to decadal oscillation phase, especially for the Pacific Decadal Oscillation.

Legacies of La Niña: North American monsoon can rescue trees from winter drought.

While we often assume tree growth-climate relationships are time-invariant, impacts of climate phenomena such as the El Niño Southern Oscillation (ENSO) and the North American Monsoon (NAM) may challenge this assumption. To test this assumption, we grouped ring widths (1900-present) in three southwestern US conifers into La Niña periods (LNP) and other years (OY). The 4years following each La Niña year are included in LNP, and despite 1-2year growth declines, compensatory adjustments in tree growth responses result in essentially equal mean growth in LNP and OY, as average growth exceeds OY means 2-4years after La Niña events. We found this arises because growth responses in the two periods are not interchangeable: Due to differences in growth-climate sensitivities and climatic memory, parameters representing LNP growth fail to predict OY growth and vice versa (decreases in R2 up to 0.63; lowest R2 =0.06). Temporal relationships between growth and antecedent climate (memory) show warmer springs and longer growing seasons negatively impact growth following dry La Niña winters, but that NAM moisture can rescue trees after these events. Increased importance of monsoonal precipitation during LNP is key, as the largest La Niña-related precipitation deficits and monsoonal precipitation contributions both occur in the southern part of the region. Decreases in first order autocorrelation during LNP were largest in the heart of the monsoon region, reflecting both the greatest initial growth declines and the largest recovery. Understanding the unique climatic controls on growth in Southwest conifers requires consideration of both the influences and interactions of drought, ENSO, and NAM, each of which is likely to change with continued warming. While plasticity of growth sensitivity and memory has allowed relatively quick recovery in the tree-ring record, recent widespread mortality events suggest conditions may soon exceed the capacity for adjustment in current populations.

Spatiotemporal evidence of tree-growth resilience to climate variations for Yezo spruce (Picea jezoensis var. komarovii) on Changbai Mountain, Northeast China

Global warming-induced changes in tree-growth resilience to climate variations have been widely reported for mid- and high-latitude regions around the world. Most studies have focused on the spatial variability of trees in radial growth–climate relationships on Changbai Mountain in Northeast China, but little is known about temporal changes in tree growth in response to climate. We explored the stability of effect of climate variables on radial growth of Yezo spruce [Picea jezoensis Carr. var. komarovii (V.Vassil.) Cheng et L.K.Fu] at 1200, 1400, and 1600 m above sea level, representing low, middle, and upper ranges of the spruce–fir mixed forest on Changbai Mountain. The results showed that the relation between tree growth and climate did not vary with altitude, but the stability of the tree-growth–climate relationship did vary with altitude as the climate changed. Radial growth of Yezo spruce at all three elevations was influenced primarily by maximum temperature during May (Tmax5) and mean minimum temperature from January to March (Tmin1–3). More specifically, the relationship strengthened significantly at lower elevations, but weakened significantly at higher elevation, and fluctuated at mid elevations since 1980. Increase in Tmin1–3 and decrease in Tmax5 were the main reasons for the decrease in the radial growth at three altitudes. The findings of this study clarified that the decrease in radial growth on Changbai Mountain is not a “divergence problem” of an unexpected decrease in tree growth in response to an increase in mean temperature and provides a reference for using tree-ring data to reconstruct climate patterns and/or predict the growth of trees under various climate change scenarios.

Climate Change-Induced Shift of Tree Growth Sensitivity at a Central Himalayan Treeline Ecotone

Himalayan treelines are exposed to above average climate change impact, resulting in complex tree growth–climate relationships for Himalayan Silver Fir (Abies spectabilis (D. Don) Spach) at central Himalayan treelines. The majority of recent studies detected current tree growth sensitivity to dry conditions during pre-monsoon seasons. The aim of this study was to analyze growth–climate relationships for more than a century for a treeline ecotone in east-central Nepal and to test for Blue Intensity (BI; used as a surrogate of maximum late wood density) as climate proxy. We determined the relationships of Abies spectabilis radial tree growth and BI to climate by correlating both to temperature, precipitation and drought index data. The results showed a significantly unstable dendroclimatic signal over time. Climate warming-induced moisture deficits during pre-monsoon seasons became a major factor limiting radial tree growth during recent decades. Earlier in time, the dendroclimatic signal was weaker, predominantly reflecting a positive relationship of tree growth and summer temperature. Compared to radial tree growth, BI showed a different but strong climate signal. Temporally unstable correlations may be attributed to increasing effects of above-average rates of climate warming. An extended network of Himalayan tree-ring sites is needed to further analyze cause–effect relationships and to solve this attribution problem.

Extracting coherent tree-ring climatic signals across spatial scales from extensive forest inventory data.

Increasing access to extensively replicated and broadly distributed tree-ring collections has led to a greater use of these large data sets to investigate climate forcing on tree growth. However, the number of chronologies added to large accessible databases is declining and few are updated, while chronologies are often sparsely distributed and are more representative of marginal growing environments. On the other hand, National Forest Inventories (NFI), although poorly replicated at the plot level as compared to classic dendrochronological sampling, contain a large amount of tree-ring data with high spatial density designed to be spatially representative of the forest cover. We propose an a posteriori approach to validating tree-ring measurements and dating, selecting individual tree-ring width time series, and building average chronologies at various spatial scales based on an extensive collection of ring width measurements of nearly 94,000 black spruce trees distributed over a wide area and collected as part of the NFI in the province of Quebec, Canada. Our results show that reliable signals may be derived at various spatial scales (from 37 to 583,000 km2) from NFI increment core samples. Signals from independently built chronologies are spatially coherent with each other and well-correlated with independent reference chronologies built at the stand level. We thus conclude that tree-ring data from NFIs provide an extraordinary opportunity to strengthen the spatial and temporal coverage of tree-ring data and to improve coordination with other contemporary measurements of forest growth to provide a better understanding of tree growth-climate relationships over broad spatial scales.

Climate-growth relationships and pointer year analysis of a Siberian larch (Larix sibirica Ledeb.) chronology from the Mongolian mountain forest steppe compared to white birch (Betula platyphylla Sukaczev)

BackgroundForest area, stand quality and growth of Siberian larch in Mongolia have decreased significantly over recent decades. This forest decline is frequently attributed to factors such as unregulated logging, increased ecological disturbances (primarily fire) and climate change. In this study, we analyzed climate-growth response and pointer years for Siberian larch observed in the Altansumber forest research area in the Mongolian mountain forest steppe zone. We compare our results with previously published results of white birch from the same area.MethodsWe built a reference chronology from wood core samples taken from 30 trees in three neighboring larch stands. Climate-growth relationships were analyzed monthly and seasonally over the period 1962–2009 using climate data from the Eroo weather station. Pointer year analysis covered the same time frame.ResultsOur analysis of the larch chronology showed that precipitation during autumn of the previous year and directly before the growing season of the current year was the most decisive factor determining tree-ring growth. Regional pointer year analysis further indicated that a humid summer and autumn followed by a warm spring support current-year tree-ring growth in these larch stands. Our findings were comparable to a white birch study in the same area. The larch trees, however, showed stronger growth performance and were more tolerant of higher temperatures, notably in spring during peak fire season.ConclusionsWater availability is the decisive factor for larch growth in the mountain forest steppe zone. The chronologies showed no climatic indication of insect infestations. Differences in climate-growth relationships of birch and larch trees during peak fire season may to some degree be explained by their respective means of protecting themselves against low-intensity surface fires (e.g. thick bark of larch). These fire events occur regularly in the region and are influenced by climatic factors. Our analysis and comparison of climate tree-growth relationships may be valuable for developing climate- and disturbance-resilient forestry practices in Mongolian mountain forest ecosystems.