伊春地区红松和红皮云杉径向生长对气候变化的响应

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...     

Growth responses to climate and drought at the southernmost European limit of Mediterranean Pinus pinaster forests

Climate warming and increasing aridity may negatively impact forest productivity across southern Europe. A better understanding of growth responses to climate and drought in southernmost populations could provide insight on the vulnerability of those forests to aridification. Here we investigate growth responses to climate and drought in nine Pinus pinaster (maritime pine) stands situated in Andalusia, southern Europe. The effect of climatic variables (temperatures and precipitation) and drought on radial growth was studied using dendrochronology along biogeographic and ecological gradients. We analyzed old native stands with non-tapped and resin-tapped trees mixed, showing their usefulness in dendroclimatic studies. Our results indicate a high plasticity in the growth responses of maritime pine to climate and drought, suggesting that site aridity modulated these responses. The positive growth responses to spring precipitation and the negative responses to summer drought were stronger in the more xeric inland sites than in wet coastal ones, in particular from the 1980s onwards. The characterization of tree species’ responses to climate at the southern or dry limits in relation to site conditions allows improving conservation strategies in drought-prone forest ecosystems.     

Tree-rings to climate relationships in nineteen provenances of four black pines sub-species (Pinus nigra Arn.) growing in a common garden from Northwest Tunisia

In the Mediterranean region, the effects of climate change on tree growth have been more and more noticeable in recent decades. Pinus nigra is one of the most common mid-elevation pine in this region and one of the species most affected by increasing dryness. In Tunisia, in order to guide species selection for future reforestation of the Khroumirie Mountains, research studies are under way to improve knowledge of black pine ecology. The effects of interannual climate variations on radial growth were compared for 19 provenances of black pine in a 51-year-old common garden experiment in Souiniet (NW Tunisia, 492m) in a humid Mediterranean bioclimate. A significant positive correlation with April precipitation and a significant negative correlation with spring temperature were noted. A cool wet spring is beneficial to growth as it affects tree water balance at the onset of the growing season; in contrast, spring drought is responsible for low annual growth. Mild January–February temperatures have a positive influence on ring width as mild winters may foster photosynthesis and promote early resumption of cambial activity. Analysis of the pointer years showed that winter snow and hail are major factors limiting growth of black pine in the studied area. Despite overall similarities in ring width to climate relationships among provenances, differences observed attest to the interaction of the environment and genetic control of black pine diameter growth.     

Growth and response patterns of Picea crassifolia and Pinus tabuliformis to climate factors in the Qilian Mountains,northwest China

Different tree species exhibit different phenological and physiological characteristics, leading to complexity in inter-species comparison of stem radial growth response to climate change. This study explored the climate-growth responses of Qinghai spruce (Picea crassifolia) and Chinese pine (Pinus tabulaeformis) in the Qilian Mountains, Northwest China. Meanwhile, Vaganov-Shashkin model (VS-oscilloscope) was used to simulate the relationships between radial growth rates and phenology. The results showed that 1) in their radial growth patterns, Qinghai spruce showed a significant increasing trend, while Chinese pine showed a decreasing trend, and Qinghai spruce has a longer growing season than Chinese pine. 2) For the radial growth-climate dynamic response, Qinghai spruce was influenced in an unstable manner by the mean temperature in the mid-growing season of the current year and the late growing season of the previous year and by the mean minimum temperature in the mid-growing season of the current year, while Chinese pine was influenced in a stable manner by the mean temperature and mean maximum temperature during the growing season of the current year. 3) The radial growth rates of the two conifer species were limited by temperature at the initiation and cessation of growth and by soil moisture at the peak of growth. But Chinese pine was more severely affected by soil moisture than Qinghai spruce in the middle of growth. Therefore, different management and restoration measures should be taken based on the differences in ecological responses and physical and physiological properties of the two conifer species to climate change in the subalpine forest ecosystems in the semiarid and arid regions of Northwest China.     

张广才岭北部三大硬阔树木生长-气候关系的时空变异

树木年轮在时空尺度上的比较可以更好地反映环境变化对树木生长的影响,在认识气候变化对森林生态系统的影响上具有重要意义。采用树木年代学方法分析了张广才岭北部地区阔叶红松林中主要阔叶树种-水曲柳(Fraxinus mandshurica)、黄菠萝(Phellodendron amurense)和胡桃楸(Juglans mandshurica)径向生长与气候关系的时空变异。结果表明,在同一地点树种间气候响应差异明显,胡桃楸受降水和最低温度共同作用,而黄菠萝和水曲柳则主要受最低温度限制,这表明树木生长与气候因子的关系具有一定的物种特异性。随着温度和降水格局的改变,三大硬阔年轮与气候关系在空间水平上存在差异,方正和西大圈样点的胡桃楸与6—8月最低温度呈显著正相关(P0.05),而凤凰山样点与5、6月最低温度和降水呈正相关(P0.05);黄菠萝和水曲柳径向生长随着降水空间格局的变化,其生长季末期相关性程度逐渐减弱。1980年后张广才岭北部出现气温显著升高,在升温前三大硬阔的生长趋势相对一致,而在升温后黄菠萝和水曲柳树轮宽度随温度升高呈上升趋势,但胡桃楸却出现随温度升高而生长下降的"分异现象"。如果未来增温趋势持续发生或者加重,可以推断在张广才岭北部胡桃楸可能受干旱胁迫加剧,其可能出现生长衰退,但增温可能更有利于黄菠萝和水曲柳的生长。     

A multi-scale dendroclimatological analysis of four common species in the southern Canadian boreal forest

A comprehensive assessment of the tree growth/climate relationship was undertaken to better understand the potential impacts of climate change on the growth dynamics of four widespread and common boreal tree species, namely jack pine (Pinus banksiana), black spruce (Picea mariana), eastern larch (Larix laricina), and trembling aspen (Populus tremuloides), located at the southern limits of the Canadian boreal forest. Over intra-annual time scales, results show that precipitation is likely the main driver of stem radius change (∆R), with jack pine radius exhibiting the most consistent positive relationship. Precipitation had a stronger relationship with stem radius variation in black spruce and eastern larch during periods when volumetric water content (VWC) in the root zone was below average, pointing to the likelihood that certain species rely more heavily on available moisture in the uppermost layers of the soil column to replenish stem water, especially during extended dry periods. Warm air temperatures had an immediate negative impact on stem water content due to transpiration. This was most marked during periods of reduced moisture availability in the root zone, when trees are more susceptible to net water volume loss. During periods when moisture was not limiting, a positive relationship between lagged air temperature and ∆R was detected. Warm air temperatures may therefore play an important role in stimulating radial growth when moisture requirements are met. At annual temporal resolution, the growth/climate relationship changed over the lifetime of our study species. Over the last several decades, the relationship between precipitation and annual radial tree growth has weakened, while positive relationships between spring and summer air temperature and annual radial tree growth have emerged, likely signaling a decrease in moisture limitations, and a positive response to spring warming. Our findings reveal that boreal forest tree species may benefit from spring and summer warming over the near term, providing there is sufficient moisture to support growth. Over the long term, rates of evapotranspiration are expected to overshadow gains in moisture related to an increase in precipitation. Under these circumstances, we are likely to see reduced growth rates and an increasingly negative response of boreal tree species growth to warm air temperatures.     

Species-specific growth-climate responses of Dahurian larch (Larix gmelinii) and Mongolian pine (Pinus sylvestris var. mongolica) in the Greater Khingan Range,northeast China

Responses of tree growth to climate are usually spatially heterogeneous. Besides regionally varying external environments, species specificity is a crucial factor in determining said spatial heterogeneity. A better understanding of this species specificity would improve our estimations of the warming effects on forests. In this study, we selected two widely-distributed boreal conifers, Dahurian larch (Larix gmelinii) and Mongolian pine (Pinus sylvestris var. mongolica), to compare their growth-climate responses, including long-term growth-climate correlations and short-term growth resilience to drought. We sampled 160 trees and 481 tree-ring cores from the two species in two pure and two mixed forests, located in the Greater Khingan Range, northeast China. We found that Dahurian larch was generally positively correlated with spring temperature and negatively correlated with summer temperature. In contrast, Mongolian pine was more sensitive to summer moisture. Our results suggest that the main climatic limitations were low spring temperatures for Dahurian larch and summer moisture deficits for Mongolian pine. Dahurian larch represented higher growth resistance to drought, while Mongolia pine represented higher recovery. Based on this, we inferred that Dahurian larch was more vulnerable to extreme droughts, while Mongolian pine was more vulnerable to frequent droughts. We also demonstrated the effects of forest type on growth-climate responses. The negative effects of summer temperatures on Mongolian pine seemed to be more significant in mixed forests. As warming continued, Mongolian pine in this area would suffer severer moisture deficits, especially when coexisting with Dahurian larch. Our results suggest that Dahurian larch gained an advantage in the competition with Mongolian pine during high moisture stress. Driven by the warming trends, the species specificity in growth response would ultimately promote the separation of the two species in distribution. This study will help improve our estimations of the warming effects on forests and develop more species-targeted forest management practices.     

Structural attributes,tree-ring growth and climate sensitivity of Pinus nigra Arn. at high altitude: common patterns of a possible treeline shift in the central Apennines (Italy)

European black pine (Pinus nigra ssp. nigra Arnold) encroachment at increasing elevation has been analyzed at four treeline ecotones of the central Apennines (Italy). The study sites are located along a North-South gradient of 170 km across Marche and Abruzzo regions in Central Italy. The aims of this study were: (i) to detect possible common patterns of structural attributes of black pine regeneration at the treeline ecotone; (ii) to date the seedlings germination and (iii) to assess the climate influence on the pine upward encroachment process also using intra-annual density fluctuations (IADFs) in tree-rings. We sampled 658 encroached black pine trees above the current treeline to the mountain top. All individuals were mapped and their basal stem diameter, total height, annual height increments and other structural attributes measured. One increment core was extracted from stem base of most samples for cambial age determination and detection of intra-annual density fluctuations (IADF). At two sites we also extracted cores at DBH from forest trees to assess climate–growth relationships of black pine. We used multivariate analysis (PCA) to explore the correlation structure of the main tree attributes, regression analysis to relate radial and height increment and dendroclimatic analysis to assess the influence of climate on tree growth and IADF formation.Most black pine trees were located at high altitude and their structural attributes were similar at the four sites where the pine encroachment process started between 30 and 40 years ago featuring similar germination peaks and growth patterns. Black pine is particularly sensitive to maximum temperatures and IADF occurred in mid-late summer with highest frequency peaks between 2003 and 2004. The pine encroachment process, besides the differences of environmental features and land use histories of the four study sites, appears synchronic and spatially diffused. Consistent tree-growth dynamics and the species adaptation to a warming climate are signals envisaging a possible treeline upward shift.     

Spatio-temporal growth variability of three Pinus species of Northeast Himalaya with relation to climate

This research aimed to evaluate spatio-temporal growth variability of three Pinus species viz. Pinus kesiya (Khasi pine), Pinus merkusii (Merkus pine) and Pinus wallichiana (Blue pine) along with the existence of species differentiation among the taxa in northeast India. Several statistical analyses were used, namely Pearson correlation and multivariate approaches involving UPGMA Cluster Analysis; ordination methods by Principal Component Analysis (PCA) and Non-metric multidimensional scaling (NMDS) on tree-ring width chronologies from 13 sites. The tree growth-climate relationships were assessed with both correlation and bootstrap response function using regional climate datasets of each sampling site prepared by averaging the nearest grid points of 0.5 × 0.5° of CRU TS-2.1 climate dataset. Pronounced species differentiation in the growth pattern among the three Pinus taxa was inferred. The observed spatio-temporal variability revealed inter-species tree growth variations were not uniform suggesting no common factor influenced the radial tree growth in this region, which may be related to anthropogenic impact or non-climatic factors. The tree growth-climate relationship showed that climatic factors limiting the radial growth of Pine are mostly similar for intra-species but diverse in inter-species. This study is extremely relevant in terms of species and site selection for the long-term climate reconstruction and forest management in the Northeast Himalaya.     

川西卧龙国家级自然保护区树木生长对气候响应的时间稳定性评估

根据川西卧龙地区岷江冷杉(Abies faxoniana)的年轮宽度资料, 分析了该地区树木生长特征及对气候响应在最近53年(1956-2008年)的异质性特征。结果表明, 在1956-1976年时段, 树木生长速率较快, 晚冬至早春(1月到4月)温度对树木生长有着明显的促进作用, 而春末5月份的高温对于树木生长有限制性影响, 而与日照时数关系不大; 在1977-2008年时段, 树轮生长主要受冬季(11月到1月)低温的限制, 另外, 日照时数对于树木生长的限制性影响明显增强。秋季到早冬(9-12月)降水在两个时段上对树木生长均有一定的限制性影响。树轮指数在1956-1976年时段与温度序列吻合较好, 而在1977-2008年时段树轮指数明显偏低, 与温度序列出现了明显的分离。1977-2008年时段内云层覆盖量增加导致太阳辐射量显著下降, 进而树木可利用的光合有效辐射也相应地降低, 这可能是树木生长速率在此时期明显较慢的主要原因。     

Relationship between climate and growth of two North African varieties of Pinus pinaster Arn.

Planting tree species that are well adapted to local ecological conditions guarantees the success and sustainability of forest restoration. The aim of this study was to investigate the acclimation of two varieties of Pinus pinaster (var. renoui from Tunisia and var. maghrebiana from Morocco), to the ecological conditions of the Kroumirie Mountains in northwest of Tunisia. Tree growth performance (diameter at 1.30 m [DBH], ring widths and total height) and climate–growth responses over the period 1970–2013 were evaluated for two varieties. The trees used in this study were from pine variety and provenance trials growing in common garden in Souiniet (21 trees per variety). Significant difference in height growth rate, DBH and ring widths was found between the two varieties. The Maghrebiana variety had the highest survival and mean radial growth rates. The mean sensitivity to climate was the same in two varieties. A significant negative correlation between May precipitation and radial growth was found for var. maghrebiana. Both varieties showed a significant negative correlation between May and June temperatures and radial growth. January–February temperatures had a positive influence on ring width. The Maghrebiana variety appears well acclimatised so it is expected to ensure more successful restoration of Kroumirie Mountains.     

Climate response of radial growth and early selection of Larix olgensis at four trials in northeast China

The objective of this study was to evaluate the age trends of genetic variation in radial growth of different provenances and growth-climate relationship in different locations. Tree-ring cores of 10 L. olgensis provenances were sampled from four representative trials with different climatic conditions in 2019. The results of ANOVA show that significant differences for DBH at different ages were detected among provenances within sites, except for 10, 11, 37, and 38 years at LS. The phenotypic and genetic coefficient of variation in different sites were generally decreased with age. Although there were large fluctuations for provenance repeatability at different ages across sites, they all belonged to high repeatability. Age-age correlations show that the early selection for DBH could be made at the age of 10 years at the semi-arid area in Heilongjiang province and the southeast slope of Xiaoxing'an Mountains, while the ages for early selection at the southeastern slope of Daxing'an Mountains and the western slope of Zhangguangcai Mountain were 13 and 12 years old, respectively. The results of growth-climate relationships showed that temperature and precipitation played key roles in the radial growth of larch at each site. In the semi-arid area in Heilongjiang province, radial growth showed significant correlations with August temperature (positive) of the current year, and with previous May temperature (negative) and November temperature (positive), and previous December precipitation (positive). The current June temperature (negative) and precipitation (positive) were important factors affecting the radial growth at the southeastern slope of Daxing'an Mountains. July temperature of the current year had a negative relationship with larch growth at the southeast slope of Xiaoxing'an Mountains, while there were no significant correlations between radial growth and climatic factors at the western slope of Zhangguangcai Mountain. The results reported in this study provide a valuable insight about early selection for different sites and can serve as a reference for future breeding and improvement research.     

Spatiotemporal variation in the relationship between boreal forest productivity proxies and climate data

The impacts of climate change on high-latitude forest ecosystems are still uncertain. Divergent forest productivity trends have recently been reported both at the local and regional level challenging the projections of boreal tree growth dynamics. The present study investigated (i) the responses of different forest productivity proxies to monthly climate (temperature and precipitation) through space and time; and (ii) the local coherency between these proxies through time at four high-latitude boreal Scots pine sites (coastal and inland) in Norway. Forest productivity proxies consisted of two proxies representing stem growth dynamics (radial and height growth) and one proxy representing canopy dynamics (cumulative May-to-September Normalized Difference Vegetation Index (NDVI)). Between-proxy and climate-proxy correlations were computed over the 1982–2011 period and over two 15-yr sub-periods. Over the entire period, radial growth significantly correlated with current year July temperature, and height growth and cumulative NDVI significantly correlated with previous and current growing season temperatures. Significant climate responses were quite similar across sites, despite some higher sensitivity to non-growing season climate at inland sites. Significant climate-proxy correlations identified over the entire period were temporarily unstable. Local coherency between proxies was generally insignificant. The spatiotemporal instability in climate-proxy correlations observed for all proxies underlines evolving responses to climate and challenges the modelling of forest productivity. The general lack of local coherency between proxies at our four study sites suggests that forest productivity estimations based on a single proxy should be considered with great caution. The combined use of different forest growth metrics may help circumvent uncertainties in capturing responses of forest productivity to climate variability and improve estimations of carbon sequestration by forest ecosystems.     

Effects of radial growth, tree age, climate, and seed origin on wood density of diverse jack pine populations

Several models of the effects of silviculture, radial growth, and tree age on wood density have been developed, but they have rarely considered the roles of diverse seed origins and climate. We developed a model to test the effects of radial growth, tree age, climate, and seed-source origins on wood density in 21 diverse populations of jack pine in a common garden in Petawawa, Ontario, Canada over the last 24 years using a linear mixed-effects model. Although we found significant differences in wood density among diverse seed origins, there were no differences between seed origins having the same ring age and ring width, indicating an indirect effect on wood density of seed-source origin via radial growth. High variation in wood density among trees within the same population and between populations indicated high genetic control of wood density. The climate effect was significant on wood density in all populations, but smaller when radial growth was controlled. Climate effect did not differ significantly among populations. Precipitation in July negatively affected latewood density, whereas precipitation in May in the current year and September of the previous year negatively affected earlywood density. We concluded that a single model of jack pine wood density and radial growth could be used, either controlling for climate effects or not, as the relationship between wood density and radial growth is preserved among the diverse populations, and the climate effect controlling for radial growth in the model was only slight.     

不同林龄樟子松人工林径向生长对气候及地下水位变化的响应

全球气候变化导致森林生态系统的结构与功能发生改变,甚至出现树木死亡与林分衰退的现象,研究林分生长对气候变化尤其是干旱事件的响应有助于预测未来气候变化下生态系统的稳定性。以辽宁章古台5个林龄的樟子松人工林为研究对象,分析了树木径向生长对气候因子与地下水位的响应,结果表明：秋季气温,尤其是最低气温显著影响樟子松林的生长(44年生林分除外);低林龄樟子松林(36、39年)生长与当年夏季及生长季内的降水显著正相关,而高林龄樟子松林(52年)生长则与当年春季尤其是当年2月与5月降水显著正相关;36、39、52年生樟子松人工林年表与当年夏季的Palmer干旱指数(PDSI)显著正相关,44、58年生樟子松人工林年表则与地下水位显著正相关。应对早期干旱(即1997年)时,樟子松人工林表现为随林龄增加,其抵抗力增加而恢复力降低;在随后的两个干旱事件中,高林龄樟子松林的抵抗力不再明显高于低林龄,可能是由于地下水位显著降低影响根系吸水;受累积干旱的影响,所有林龄樟子松人工林对2007—2008干旱事件的弹性力均小于1,径向生长量明显降低。地下水位是影响不同林龄樟子松人工林生长及对干旱抵抗力的重要因子,考虑...     

秦岭不同龄组巴山冷杉径向生长对气候因子的响应差异

秦岭地区树轮气候学研究已经引起众多学者的重视,但年龄因素对调节树木径向生长-气候响应关系的研究尚未在当地得到广泛关注。运用树轮气候学方法,建立秦岭牛背梁国家级自然保护区低、中、高3个龄组巴山冷杉(Abies fargesii)的树轮宽度差值年表,探究不同龄组巴山冷杉径向生长与覆盖研究区的0.5°×0.5°分辨率格点气候要素之间的响应关系,以期解译年龄差异对巴山冷杉树木径向生长-气候响应特征的潜在影响。结果表明：不同龄组巴山冷杉差值年表统计特征值存在明显差异,平均敏感度和样本总体代表性随年龄增大而递减,但标准差、样本间平均相关系数和第一特征根变异解释量均以中龄组最低,信噪比却以中龄组最高;春季(3—5月)降水的增加以及秋季(9—11月)气温的升高对低龄组巴山冷杉径向生长的促进作用最强,对中龄组树木生长的促进作用明显减弱,而对高龄组树木生长几乎没有影响;气温对巴山冷杉径向生长的促进作用随树龄增高而增强,差值年表与当年2月、8月、上年5月平均温、平均最高温的相关系数均呈现随龄级增大而逐渐递增的趋势。年龄因素对牛背梁国家级自然保护区巴山冷杉径向生长-气候响应关系存在明确影响,随着年龄的增加,巴...     

Contrasting climate-growth relationship between Larix gmelinii and Pinus sylvestris var. mongolica along a latitudinal gradient in Daxing’an Mountains,China

The Daxing’an Mountains is one of the areas with the most serious climate warming in northern China. Dahurian larch (Larix gmelinii) and Mongolian Scots pine (Pinus sylvestris var. mongolica) are two major coniferous species in boreal forests of the region. Their growth-climate relationship is crucial for understanding the effects of climate change on boreal forest ecosystems. To examine and compare the changes of climate-growth relationship between larch and pine, a total of 418 tree-ring cores of the two species were collected at six sites in the Daxing’an Mountains, and the tree-ring chronologies were developed. The results showed that water availability (Palmer Drought Severity Index, PDSI) played a key role in the stable growth of larch and pine. The temperature and precipitation in January, June-August are important factors affecting the radial growth of the two coniferous species along the latitude gradient. The correlation coefficients of growth and the seasonal temperature and precipitation of larch and pine showed a completely opposite trend with the increase of latitude. In summer and autumn, the correlation coefficients between larch growth and seasonal mean temperature decreased first and then increased with the increase of latitude, while that of pine, on the contrary, increased first and then decreased. In winter, spring and autumn, the correlation coefficients between larch growth and seasonal total precipitation decreased first and then increased with the increase of latitude, while that of pine was opposite. However, the correlation coefficients between larch and pine growth and PDSI showed the same trend with the increase of latitude, decreasing at first and then increasing. Before and after rapid warming (around 1980), the correlation coefficients between larch and pine growth and PDSI showed a completely opposite change. Our findings emphasize that the growth-climate relationships of Dahurian larch and Mongolian Scotts pine shows an opposite trend with latitude, which means that the two species may exhibit a completely opposite response with climate change along the latitude gradient.     

Abies spectabilis shows stable growth relations to temperature,but changing response to moisture conditions along an elevation gradient in the central Himalaya

A better understanding of growth-climate responses of high-elevation tree species across their distribution range is essential to devise an appropriate forest management and conservation strategies against adverse impacts of climate change. The present study evaluates how radial growth of Himalayan fir (Abies spectabilis D. Don) and its relation to climate varies with elevation in the Manaslu Mountain range in the central Himalaya. We developed tree-ring width chronologies of Himalayan fir from three elevational belts at the species’upper distribution limit (3750−3900 m), in the middle range (3500−3600 m), and at the lower distribution limit (3200−3300 m), and analyzed their associations with climatic factors. Tree growth of Himalayan fir varied synchronously across elevational belts, with recent growth increases observed at all elevations. Across the elevation gradient, radial growth correlated positively (negatively) with temperature (precipitation and standardized precipitation-evapotranspiration index, SPEI-03) during the summer (July to September) season. However, the importance of summer (July to September) temperatures on radial growth decreased with elevation, whereas correlations with winter (previous November to current January) temperatures increased. Correlations with spring precipitation and SPEI-03 changed from positive to negative from low to high elevations. Moving correlation analysis revealed a persistent response of tree growth to May and August temperatures. However, growth response to spring moisture availability has strongly increased in recent decades, indicating that intensified spring drought may reduce growth rates of Himalayan fir at lower elevations. Under sufficient moisture conditions, increasing summer temperature might be beneficial for fir trees growing at all elevations, while trees growing at the upper treeline will take additional benefit from winter warming.     

Comparison of growth-climate relationship of sabina przewalskii at different timberlines along a precipitation gradient in the northeast Qinghai-Xizang Plateau,China北大核心CSCD

Aims To test the hypothesis that water is the main limiting factor of tree growth at the arid alpine timberline, and to explore the effects of water on growth-climate relationships of Sabina przewalskii along a precipitation gradient in the northeast Qinghai-Xizang Plateau. Methods Three sides were selected to sample the alpine timberline along a precipitation gradient in the northeast Qinghai-Xizang Plateau: Halihatu National Forest Park in Wulan County (HL, annual precipitation 217 mm), Qushigang in Dulan County (QS, 281 mm) and Hebei Forest Farm in Tongde County (HB, 470 mm). The correlation and response analysis at seasonal and extreme climate year scales were used to examine the spatial variations of the growth-climate relationship of S. przewalskii at different timberlines. Important findings Our results do not support the hypothesis that water is the main limiting factor of tree growth at the arid alpine timberline. The effect of precipitation on the radial growth of S. przewalskii were consistent across all three sampling sites, while the effects of temperature were different across sites. At HL site (low precipitation), the winter and summer minimum temperature were the main limiting factor of S. przewalskii radial growth, and this relationship did not significantly change in different extreme climate years. At QS site (middle precipitation), the radial growth of S. przewalskii was mainly limited by the minimum temperature in spring and summer, but its effect was weaker than that at low precipitation site. At HB site (high precipitation), the spring temperature had a significant negative effect on tree growth, and the positive effect of spring precipitation on tree growth was significantly enhanced in comparison with those at low and middle precipitation sites, especially in extreme high temperature and drought years. Summer precipitation did not significantly affect tree growth at high precipitation site. Our results did not support the hypothesis that the radial growth of trees at alpine timberline in arid/humid area is mainly limited by water/temperature. However, precipitation at timberline will affect the relationship between tree growth and temperature at different seasons. With the warming and humidification of the northeastern Qinghai-Xizang Plateau, the climatic limiting factors of tree growth in different timberline areas may be complicated. © 2018 Editorial Office of Chinese Journal of Plant Ecology. All rights reserved.     

小兴安岭蒙古栎和黄菠萝径向生长对气候变化的响应比较

蒙古栎和黄菠萝是东北温带森林中重要的阔叶树种,探究二者对气候变化的响应关系能够为未来气候变化情境下东北阔叶林的经营、保护及恢复提供科学依据.本文在小兴安岭地区沿经度梯度设置3个采样点--海伦、铁力和伊春,运用树轮年代学方法建立了3个采样点蒙古栎和黄菠萝的标准年表,分析了其与当地气候因子的关系,揭示了蒙古栎和黄菠萝生长-气候关系的时空变异规律.结果表明: 研究区黄菠萝径向生长对生长季温度变化敏感,而蒙古栎径向生长受生长季温度和降水的共同限制作用.蒙古栎和黄菠萝对温度的响应存在差异: 春季均温升高抑制蒙古栎径向生长,而促进黄菠萝径向生长;夏季高温对蒙古栎径向生长的限制作用明显高于黄菠萝.随经度(水分)增加,蒙古栎径向生长与水分因子的关系逐渐减弱,而黄菠萝没有明显变化.树种生理特性是影响树木生长-气候关系的关键因素.1976年升温后,黄菠萝生长随温度升高而升高,但蒙古栎生长却随温度升高而呈下降趋势.升温造成的干旱胁迫可能是两树种生长响应差异及蒙古栎出现响应分异现象的重要原因.如果未来增温趋势持续或者加重,蒙古栎的生长可能会因干旱胁迫加剧而衰退,黄菠萝则不受影响或生长略微加快.