长白山红松年轮细胞尺度参数对气候要素的响应

基于长白山低海拔区的红松年轮样本,建立树轮宽度和细胞尺度参数的7个标准年表;选取部分树轮年表与东岗气象站1959-2007年前一年9月到当年9月的月均气温、月均最高气温、月均最低气温、月降水量进行相关分析;并分析1988年气候突变前后红松年轮指数年表与气候要素的关系,结果表明:所建立的7个标准年表中,细胞个数与轮宽年表的相关性最好;降水和气温都是长白山低海拔区红松树木生长的限制因子,但树轮与降水的相关关系略好于气温,主要表现为与前一年9月和当年5、6月降水的相关达显著水平.细胞大小比轮宽能反映出更多气候信息,主要体现在细胞大小年表与当年3月气温和5月降水呈正相关关系,与当年5月气温呈负相关关系;1988年气温发生升高突变后,树轮对气候要素的响应发生了变化,主要表现为细胞大小对气候要素响应的敏感性降低,与气候要素相关的月份有所提前.     

近40年河北坝上地区杨树人工林径向生长对气候变化的响应差异

运用树木年轮气候学方法,研究近40年河北坝上地区健康和衰退小叶杨人工林径向生长对气候响应敏感性差异,揭示健康和衰退杨树生长与气候关系的时间变异规律。结果表明：（1）衰退杨树径向生长对温度、降水等气候因素响应较健康杨树敏感。衰退杨树年表中的气候信号较强,与当年生长季（4、8-10月）的气温因素呈显著负相关,与上一年休眠期（9月-当年1月）和当年生长季（7月）的降水和相对湿度呈显著正相关。健康杨树年表中气候信号较弱,主要与上一年冬季（12月）和当年生长季（4月）的气温因素呈显著负相关,与上一年生长末期（8-11月）降水和相对湿度呈显著正相关。（2）从各年表与帕默尔干旱指数（PDSI）的响应强度来看,衰退杨树生长更易受夏季干旱胁迫影响。衰退杨树年表与上一年9月-当年3月、6-10月的PDSI呈显著正相关,而健康杨树径向生长与PDSI呈弱的正相关。（3）1975-2017年间,随气温升高,健康和衰退杨树生长对温度的敏感性下降;健康杨树生长对降水和PDSI的敏感性较为稳定,适应能力强,而衰退杨树生长对降水和PDSI的敏感性增强,适应能力变弱。综上所述,干旱胁迫是限制衰退杨树生长的主要因素,而健康杨树生长受气候影响较弱,能适应当地气候条件。衰退杨树对气候变化响应较健康杨树明显,在气候变暖背景下,衰退杨树生长的气候限制因子由温度转变为水分,导致河北坝上地区遭受干旱灾害时发生退化的趋势更加明显。     

黄土高原半干旱区气候变暖对胡麻生育和水分利用效率的影响

利用黄土高原半干旱区胡麻生长发育定位观测资料和同期气象观测资料,分析气候变化对胡麻生长发育的影响,以及胡麻水分利用效率与气象条件的关系.结果表明:研究区年降水量呈下降趋势,其气候倾向率为-15.80 mm·(10 a)-1,年降水量存在3 a、6 a的周期变化;年均气温呈上升趋势,其气候倾向率为0.36℃·(10 a)-1;作物生长季干燥指数呈显著上升趋势,其气候倾向率为0.12· (10a)-1,20世纪90年代初至2009年明显趋于干旱化.研究区胡麻全生育期天数为120～150 d,≥0℃积温为1700～2100℃·d,降水量为200～250mm,日照时数为1000～1300h.影响黄土高原半干旱雨养农业区胡麻生长发育的主导气象因子是气温和降水量.气温增高导致胡麻生育前期的营养生长阶段缩短;而气温增高、降水量减少,则导致生殖生长阶段延长,从而使全生育期延长.除出苗期和成熟期外,气温对其余时期的胡麻产量形成均表现为负效应,现蕾期对气温变化十分敏感;除开花期外,其余时段降水量对胡麻产量形成均为正效应,胡麻出苗期对降水量变化十分敏感.胡麻水分利用率与胡麻出苗期气温、日照时数和现蕾-成熟期干燥度呈显著正相关,与胡麻现蕾-成熟期降水量呈显著负相关.研究区5-7月干燥度是影响胡麻水分利用率的关键因子.     

西昆仑山两种针叶树种径向生长及其对气候变化的响应

利用西昆仑山的雪岭云杉和昆仑圆柏树芯样本,建立其树轮宽度年表。通过分析两种针叶树种树木径向生长特征与气候要素的相关关系,探讨了树种间的树木生长气候响应异同及响应关系的稳定性。结果表明：研究区域内的雪岭云杉和昆仑圆柏年表间存在显著正相关。两种针叶树种在1994年气温突变前树轮宽度年表指数和基部断面生长增量（BAI）呈上升趋势,在气温突变后年表和BAI则呈下降趋势,并且昆仑圆柏的树木径向生长速率高于雪岭云杉。与气候要素的相关性分析结果表明,雪岭云杉径向生长与上年生长季（5—6月和8—10月）和当年生长季（3—6月和10月）气温呈显著负相关,而昆仑圆柏径向生长与上年10月和当年生长季前期（4—6月）气温呈显著负相关;两者均与当年春季降水呈显著正相关。滑动相关分析结果显示,上年和当年生长季气温对两个树种树木径向生长的负响应在增强,特别是在当年生长季前期更为显著。此外,当年生长季前期降水对树木径向生长的促进作用也在增强。在有可能的气候突变年份（1994年）之后,两种针叶树种对气温和降水的响应敏感性均有所增强,并且雪岭云杉对气温的响应敏感性强于昆仑圆柏,而对降水响应敏感性要弱于昆仑圆柏。     

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。     

火干扰后红松生长与气候因子的关系

研究了长白山地区火烧后存活下来的红松(Pinus koraiensis)与气候因子的关系,揭示火干扰后树木生长对气候要素的响应策略,建立生长量与气候要素的模拟方程,定量估算火干扰后温度变化对火烧红松径向生长的影响.结果表明,火烧红松年轮宽度与当年2月份、生长季最高温度显著负相关,与1月、5月、9月份和10月份的月最低温度显著正相关,与上一年6月和8月份的月降水量显著负相关,与平均温度的相关未达到显著,生长季的月最高温度是影响火烧红松径向生长的主要原因,且当温度上升4℃时,火烧红松的年生长量降低14%.推断火干扰后红松生长对温度较敏感,全球变暖有可能导致火烧红松的生长量降低.     

不同纬度阔叶红松林红松径向生长对气候因子的响应

运用树木年轮气候学方法,研究了不同纬度阔叶红松林红松径向生长趋势及其与气候因子的关系,以期揭示不同纬度红松径向生长对气候因子响应的差异以及气候变化影响下红松的动态特征、适应性及敏感性.结果表明: 不同纬度红松径向生长对当地气候因子的响应存在差异,最南部的白石砬子自然保护区红松径向生长与生长季的平均相对湿度呈显著正相关,与平均最高气温呈显著负相关.中部的长白山自然保护区的低海拔区域红松径向生长与生长季的水分因子(降水、相对湿度和帕尔默干旱指数PDSI)呈显著正相关,而与平均最高气温呈显著负相关;凉水自然保护区红松径向生长与生长季的水分因子(相对湿度和PDSI)呈显著正相关,与气温因子(平均气温和平均最高气温)呈显著负相关.而最北部的胜山自然保护区红松径向生长则与大部分月份的气温因子呈显著正相关.当年6月气候因子是影响所有纬度红松径向生长的关键气候因子,4个样地都与当年6月平均最高气温呈显著负相关.在气温不断上升的近40年,最南部的红松径向生长呈显著下降趋势,最北部呈显著上升趋势,中部的变化不显著.如果未来气温升高而降水不变,红松分布区可能缩小.     

黑龙江胜山保护区阔叶红松林不同演替阶段径向生长与气候变化的关系

黑龙江黑河为我国红松(Pinus koraiensis)分布的北界, 在研究红松林的生长、演替、分布, 及其对气候变化的响应上有独特的意义。该文通过研究胜山保护区内阔叶红松林的演替系列(软阔叶林、硬阔叶林、阔叶红松近熟林和成熟林4个阶段), 分析了树木径向生长与气候变化的关系在不同演替阶段的差异。结果表明: 从演替早期的软阔叶林到晚期的红松成熟林, 年表统计特征表明树木径向生长对气候波动的敏感性逐步降低。对年轮-气候关系的分析结果也表明气候对树木径向生长的影响随着演替的进展呈现规律性的变化。上年6月和12月的气温与红松成熟林的径向生长显著正相关, 表现出明显的“滞后效应”。红松成熟林的轮宽指数与当年6月气温显著负相关, 而与当年6月降水量显著正相关, 反映出生长季水分对红松生长的限制。上述这些限制作用均随着演替的进展而增强, 但在演替的早期影响不显著。相反, 上年6月降水量与软阔叶林的生长显著负相关, 但该限制作用在演替的中晚期消失。这些差异反映出随着演替的进展, 优势树种对水分的需求逐步提高。滑动相关分析表明研究区近几十年明显的气候干暖化趋势对各林型的生长兼具有利和不利的影响。不同因素综合作用下, 软、硬阔叶林阶段生长尚未产生清晰的长期变化趋势。但由于水分对红松林生长的限制作用增强, 红松林生长明显下降。今后气候进一步干暖化可能对红松林的生长、恢复演替和分布有不利影响。     

长白山不同海拔树木生长对气候变化的响应差异

以长白落叶松和红松为例,探讨了长白山地区不同海拔树木生长对气候变化的响应。利用长白山北坡不同海拔4个长白落叶松样点和6个红松样点的树轮宽度资料建立差值年表,通过聚类分析、相关分析和响应分析等方法,研究树木生长特征及其气候响应。结果表明:两个树种年表的平均敏感度、树轮宽度指数的年际变率、信噪比等特征值较高,反映年表含有较强的环境信息。随海拔升高,长白落叶松年表特征值呈先下降后增加的趋势,红松年表特征值则呈先增加后下降的趋势。聚类分析将长白落叶松年表分成高、低海拔两类,红松年表分成高、中、低海拔三类。树木生长对气候响应存在海拔差异。高海拔长白落叶松生长受当年气温影响;低海拔长白落叶松生长对气候存在"滞后响应"。高海拔红松不仅受降水限制,且对气温有"滞后响应";中海拔红松不仅受气温限制,且对降水有"滞后响应";低海拔红松生长主要受气温限制。     

气候暖干化对甘肃省谷子产量的影响及对策

基于甘肃省甘州（河西温和干旱绿洲灌溉区）、安定（陇中温和半干旱旱作区）、西峰（陇东温和半湿润旱作区）气温、降水和谷子产量资料,计算出各区域谷子生育期内≥0 ℃、≥5 ℃、≥10 ℃、≥15 ℃、≥20 ℃活动积温以及生育关键期平均气温和降水量,用正交多项式拟合分离出谷子气候产量,并采用线性倾向、累积距平、Mann-Kendall法分析研究区气候和谷子气候产量的变化特征,以及气候变化对谷子产量的影响.结果表明：气候暖干化是甘肃各区域现代气候变化的主要特征,各地气温从20世纪90年代初开始呈显著上升趋势,降水从20世纪80年代后期开始显著减少;该区谷子产量与温度、降水量呈显著相关关系,旱作区谷子产量随生育关键期内气温增高、降水量增多而提高,河西走廊绿洲灌区谷子产量随气温增高而提高;气候暖干化严重影响谷子产量,西峰、安定、甘州谷子产量的气象波动指数分别占实际产量变异系数的73%、72%和54%,变暖后（1993-2008年）较变暖前（1985-1992年）所占百分率明显增大;气候变暖有利于谷子产量增加,与气候变暖前相比,气候变暖后西峰、安定、甘州谷子年均气候产量的增加量分别为30.6、43.1和121.1 kg·hm^-2.针对甘肃省未来气候继续暖干化的趋势,应进一步扩大谷子种植面积、调整谷子种植结构,同时,要根据不同气候类型区域、不同气候年型选种不同特性的品种,采取不同的种植措施.     

Individual resource allocation to vegetative growth and reproduction in subgenus <Emphasis Type="Italic">Cyclobalanopsis</Emphasis> (<Emphasis Type="Italic">Quercus</Emphasis>, Fagaceae) trees

The resource allocation for vegetative growth and female reproduction in three tree species of subgenus Cyclobalanopsis (Quercus, Fagaceae), i.e., Q. salicina, Q. sessilifolia, and Q. acuta, were examined on a per-individual basis in two consecutive reproductive seasons, in order to test whether these trees fit the predictions of the masting hypotheses about resource matching versus resource switching. Since the three Quercus species have a biennial fruiting habit, it takes 3 years for the observation of two reproductive events. Female flower and acorn production per tree were investigated by using a seed-trap method and a numerical analysis of seed dispersal. The net production of each individual was estimated as the sum of the annual increase in the dry mass of vegetative organs and reproductive investment per tree. In the data analyses, the three species were pooled, since all 12 sample trees of the subgenus apparently showed masting in the same year, with no exceptions. Female flower and acorn production per individual tree changed considerably between years. The net production per tree increased with tree size, but did not differ between years. Therefore, the reproductive allocation (proportion of a plant’s annual assimilated resources which are used for reproduction) differed dramatically between years. On the other hand, within a year, the reproductive allocation increased with increasing net production per tree. These results suggest that the switching of resource allocation between years within an individual are occurring in subgenus Cyclobalanopsis species, and the intensity of the switching increases with increasing tree size.     

Modeling spatial dynamics of episodic and synchronous reproduction by plant populations: the effect of small-scale pollen coupling and large-scale climate

Many plant species show masting, intermittent and synchronized reproduction at population level. In the present paper, we review the resource-based model providing a theoretically plausible physiological mechanism underlying masting. In the model, a non-linear allocation of energy reserves is considered: plants accumulate photosynthate every year, produce flowers when the energy reserve level exceeds a threshold, and set seeds at a rate limited by pollen availability. The model predicted that individual plants alter their reproductive dynamics from annual to intermittent depending on how heavily the plant invests resource in reproduction. When fruit production is limited by the availability of outcross pollen, a plant population showed diverse reproductive behavior such as completely synchronized or desynchronized reproduction. Spatial scale of reproductive synchrony tended to be a few times larger than the range of direct pollen exchange. Impact of climatic fluctuation correlated at a large spatial scale was also investigated as an alternative synchronizing factor. The variation in annual productivity and the reproductive threshold induced from climatic fluctuation was accounted for by incorporating an additional term in the model. When plants show a 2 year reproductive cycle, highly synchronized reproduction at a regional scale was induced due to correlated environmental forcing, but reproductive synchrony with long intermast periods was realized only when pollen coupling and environmental forcing were at work. These results suggest that distance-dependent processes, such as pollen exchange between nearby trees, induce synchrony at a local scale and external environmental forcing correlated at geographically large scales works to strengthen and maintain such a synchrony.     

Dynamics of internal carbon resources during masting behavior in trees

Several proximate factors of masting have been provided. Here, I focus on the role of internal factors, especially the relationship between internal carbon resources and modular structures in trees. I summarize various studies of carbon resource allocation for reproduction during masting events in terms of the proximate factors of masting and discuss the modular structure in which trees accumulate and consume carbon resources as well as the timing when internal carbon resources affect masting since trees have complex resource dynamics among organs. The resource budget model, which provides a simple mechanistic explanation of the masting mechanism, is supported by various study lines. This model assumes decreasing levels of stored photosynthate after flowering and fruiting. According to several studies, however, carbon reserves do not decrease after fruiting in species in which the modules autonomously allocate current photosynthate for fruiting. In addition, it is important to elucidate when carbon resources affect masting events because during their long developmental processes, trees pass through various stages until they produce maturing fruits to create successful masting events. To explore the mechanisms of masting in future studies, it would be important to figure out how and when candidate factors (including nutrients other than carbon) may influence the entire reproduction process, for example, using field manipulation experiments.     

Nitrogen storage dynamics are affected by masting events in Fagus crenata

It is generally assumed that the production of a large crop of seeds depletes stores of resources and that these take more than 1 year to replenish; this is accepted, theoretically, as the proximate mechanism of mast seeding (resource budget model). However, direct evidence of resource depletion in masting trees is very rare. Here, we trace seasonal and inter-annual variations in nitrogen (N) concentration and estimate the N storage pool of individuals after full masting of Fagus crenata in two stands. In 2005, a full masting year, the amount of N in fruit litter represented half of the N present in mature leaves in an old stand (age 190–260 years), and was about equivalent to the amount of N in mature leaves in a younger stand (age 83–84 years). Due to this additional burden, both tissue N concentration and individual N storage decreased in 2006; this was followed by significant replenishment in 2007, although a substantial N store remained even after full masting. These results indicate that internal storage may be important and that N may be the limiting factor for fruiting. In the 4 years following full masting, the old stand experienced two moderate masting events separated by 2 years, whilst trees in the younger stand did not fruit. This different fruiting behavior may be related to different “costs of reproduction” in the full masting year 2005, thus providing more evidence that N may limit fruiting. Compared to the non-fruiting stand, individuals in the fruiting stand exhibited an additional increase in N concentrations in roots early in the 2007 growing season, suggesting additional N uptake from the soil to supply resource demand. The enhanced uptake may alleviate the N storage depletion observed in the full masting year. This study suggests that masting affects N cycle dynamics in mature Fagus crenata and N may be one factor limiting fruiting.     

Masting uncoupling: mast seeding does not follow all mast flowering episodes in a dioecious juniper tree

Evolutionary selective forces, like predator satiation and pollination efficiency, are acknowledged to be major causes of masting (the variable, periodic and synchronic production of seeds in a population). However, a number of recent studies indicate that resources might also play an important role on shaping masting patterns. Dioecious masting species offer a privileged framework to study the role of resources on masting variation, since male and female plants often experience different reproductive costs and selective pressures. We followed masting and reproductive investment (RI) of the dioecious tree Juniperus thurifera in two populations along 10 years and studied the different response of males and females to experimentally increased water and nutrient availability in a third population. Juniperus thurifera females invested in reproduction three times more resources than males. Such disparity generated different resource‐use strategies in male and female trees. Tree‐ring growth and water use efficiency (WUE) confirmed that sexes differed in their resource investment temporal pattern, with males using current resources for reproduction and females using resources accumulated during longer periods. Watered and fertilized female trees presented significantly higher flowering reproductive investments than males and experienced an extraordinary mast‐flowering event. However, seeding RI and mast seeding were not affected by the treatment. This suggests that although resource availability affects the reproductive output of this species, there are other major forces regulating masting on J. thurifera. During 10 years, J. thurifera male and female trees presented high and low flowering years more or less synchronously. However, not all mast flowering episodes resulted in mast seeding, leading to masting uncoupling between flowering and seeding. Since flowering costs represent only 1% of females’ total reproductive investments, masting uncoupling could be a beneficial bet‐hedging strategy to maximize reproductive output in spite of unpredictable catastrophic events.     

Climate variation,reproductive frequency and acorn yield in English Oaks

Aims Annually variable but synchronous production of large seed crops (‘masting’) is a widespread phenomenon in temperate trees. Mounting concerns about the impacts of anthropogenic climate change (ACC) on plant reproduction gives urgency to our need to understand better the role of climate on tree reproduction, and in particular, mast events. Unlike our understanding of reproductive phenology however, there is little consensus regarding how climate affects plant reproductive effort or indeed the actual environmental triggers that underpin masting behaviour.     

Parameterisation and validation of a resource budget model for masting using spatiotemporal flowering data of individual trees

Synchronised and fluctuating reproduction by plant populations, called masting, is widespread in diverse taxonomic groups. Here, we propose a new method to explore the proximate mechanism of masting by combining spatiotemporal flowering data, biochemical analysis of resource allocation and mathematical modelling. Flowering data of 170 trees over 13 years showed the emergence of clustering with trees in a given cluster mutually synchronised in reproduction, which was successfully explained by resource budget models. Analysis of resources invested in the development of reproductive organs showed that parametric values used in the model are significantly different between nitrogen and carbon. Using a fully parameterised model, we showed that the observed flowering pattern is explained only when the interplay between nitrogen dynamics and climatic cues was considered. This result indicates that our approach successfully identified resource type‐specific roles on masting and that the method is suitable for a wide range of plant species.     

Density-dependent reproductive success among sympatric dipterocarps during a major mast fruiting event

Although masting in Southeast Asia is characterized by the interspecific synchronization of reproduction, little is known about the variation in regeneration strategies among sympatric tree species during major masting events. Herein, we examined the hypothesis that non-abundant species achieve greater seed survival per seed production at the pre- and post-dispersal stages by synchronizing reproduction with abundant species. During the masting event from May to September 2010, we installed seed traps in a primary forest plot of the Deramakot Forest Reserve, Borneo. To identify the possible causes of post-dispersal seed mortality, we conducted a seed-sowing experiment from September 2010 to July 2011 in a primary forest plot with high community-level dipterocarp seed density and two surrounding secondary forests with low seed densities. An abundant species (Shorea multiflora) produced more seeds than other species and exhibited a lower survival rate during the pre-dispersal stage. The ratio of aborted seeds was greater in species with greater seed production, while the ratio of seeds predated by insects was not, suggesting that resource limitations and/or greater inbreeding frequency may explain inefficient seed production. Interspecific variation was rarely observed for post-dispersal seed survival rates. Our study highlights the density-dependent variation in reproductive success between abundant and non-abundant dipterocarp species at the pre-dispersal stage. Non-abundant species achieved greater reproductive success by synchronizing reproduction with the masting of abundant species, which might be an important mechanism for sustainability of rare species populations.     

Two-year cycles of synchronous acorn and leaf production in biennial-fruiting evergreen oaks of subgenus Cyclobalanopsis (Quercus, Fagaceae)

Many masting species switch resources between vegetative growth and reproduction in mast and non-mast years. Although masting of oak species is well known, there have been few investigations of the relationship between vegetative growth and reproduction based on long-term monitoring data, especially in evergreen oaks of subgenus Cyclobalanopsis. We investigated annual variations over 13?years in acorn and leaf production of three evergreen oak species in subgenus Cyclobalanopsis, genus Quercus (Fagaceae)??Q. acuta, Q. salicina and Q. sessilifolia??in western Japan. In these species, the maturation of acorns occurs in the second autumn after flowering, which is known as a biennial-fruiting habit. We found a pattern of acorn production and masting in alternate years that was synchronized in all three species. Masting was not correlated with temperature and precipitation. Annual leaf-fall also showed 2-year cycle in the three oak species; peak years were synchronized between species and peak leaf-fall alternated with acorn production in all three species. Furthermore, there was a significant negative correlation between acorn and leaf production in all three species. Data showing 2-year cycles of acorn and leaf production and the negative correlation between them supports the hypothesis of resource switching between vegetative growth and reproduction. The 2-year cycle might be the basic, intrinsic rhythm of resource allocation in biennial-fruiting Cyclobalanopsis species.