Climate response of cork growth in the Mediterranean oak (Quercus suber L.) woodlands of southwestern Portugal

In the Mediterranean climate regions, drought events are expected to affect the growth of forests ecosystems by changing trees growth rates and eventually inducing shifts in their growth patterns. Cork oak (Quercus suber L.) is a strictly western Mediterranean tree species periodically harvested for its bark, the cork. So far, cork oak has received limited attention for dendroclimatological studies due to its typical faint and erratic tree wood rings. Moreover, its distinct cork rings chronologies have been completely neglected. In this study we introduce an approach using cork ring chronologies dated back 9–10 years for climate response. Despite enhancing interannual variability and increasing statistical response to short-term climatic variability, still poorly understood, this study will possibly allow infer long-term climate response. We analyzed the cork ring chronologies of 55 cork samples collected in mature (under exploitation) trees in three distinct locations in southwestern Portugal. Cork growth recorded a high climate signal, with highly significant and coherent responses to the yearly climate-related sources of variation. We successfully assessed trends of cork growth via correlation analysis including selected climate variables among mean monthly temperature, monthly precipitation and, on an annual basis, eight precipitation indices. The high mean sensitivities and inter-series correlations found for cork ring chronologies combined with the significant variance explained by climate variables suggest that climate is likely one dominant signal that affects cork growth, but local environmental stresses can decisively affect this (climate) signal. Assuming cork growth as a proxy for cork oak growth, it seems conceivable that despite the trees being highly resistant to drought stress, cork oak woodlands in southwestern Portugal would have to face lesser growth in a global warming scenario.     

Different responses of Korean pine (Pinus koraiensis) and Mongolia oak (Quercus mongolica) growth to recent climate warming in northeast China

Different tree species growing in the same area may have different, or even contrasting growth responses to climate change. Korean pine (Pinus koraiensis) and Mongolia oak (Quercus mongolica) are two crucial tree species in temperate forest ecosystems. Six tree-ring chronologies for Korean pine and Mongolia oak were developed by using the zero-signal method to explore their growth response to the recent climate warming in northeast China. Results showed that Mongolia oak radial growth was mainly limited by precipitation in the growing season, while Korean pine growth depended on temperature condition, especially monthly minimum temperature. With the latitude decrease, the relationships between Korean pine growth and monthly precipitation changed from negative to positive correlation, while the positive correlation with monthly temperature gradually weakened. In the contrary, Mongolia oak growth at the three sampling sites was significantly and positively correlated with precipitation in the growing season, while it was negatively correlated with temperature and this relationship decreased with the latitude decrease. The radial growth of Korean pine at different sites showed a clearly discrepant responses to the recent warming since 1980. Korean pine growth in the north site increased with the temperature increase, decreased in the midwest site, and almost unchanged in the southeast site. Conversely, Mongolia oak growth was less affected by the recent climate warming. Our finding suggested that tree species trait and sites are both key factors that affect the response of tree growth to climate change. In addition, the suitable distribution area of Korean pine may be moved northward with the continued global warming in the future, but Mongolia oak may not shift in the same way.     

Wood-decay type and fungal guild dominance across a North American log transplant experiment

We incubated 196 large-diameter aspen (Populus tremuloides), birch (Betula papyrifera), and pine (Pinus taeda) logs on the FACE Wood Decomposition Experiment encompassing eight climatically-distinct forest sites in the United States. We sampled dead wood from these large-diameter logs after 2 to 6 y of decomposition and determined wood rot type as a continuous variable using the lignin loss/density loss ratio (L/D) and assessed wood-rotting fungal guilds using high-throughput amplicon sequencing (HTAS) of the ITS-2 marker. We found L/D values in line with a white rot dominance in all three tree species, with pine having lower L/D values than aspen and birch. Based on HTAS data, white rot fungi were the most abundant and diverse wood-rotting fungal guild, and soft rot fungi were more abundant and diverse than brown rot fungi in logs with low L/D values. For aspen and birch logs, decay type was related to the wood density at sampling. For the pine logs, decay type was associated with the balance between white and brown/soft rot fungi abundance and OTU richness. Our results demonstrate that decay type is governed by biotic and abiotic factors, which vary by tree species.     

Development of Tree Regeneration in Fern-dominated Forest Understories After Reduction of Deer Browsing

Dennstaedtia punctilobula (hay‐scented fern) can act as a native invasive species in forests in eastern North America where prolonged deer browsing occurs in stands with partially open overstory canopies. Ferns dominate the understory with a 60‐cm tall canopy, with little regeneration of native tree species. It has been hypothesized that, once established, ferns may continue to inhibit tree regeneration after deer browsing has been reduced. To test this hypothesis, we documented the pattern of recovery of the tree seedling understory in plantations of Pinus strobus (white pine) and Pinus resinosa (red pine) on the Quabbin Reservation watershed protection forest in central Massachusetts, where after 40 years of intensive deer browsing the deer herd was rapidly reduced through controlled hunting. Dense fern understories occur on nearly 4,000 ha of the predominantly oak–pine forest. Three years after deer herd reduction, stands with the highest density fern cover (77% of plots with>90% cover) had significantly fewer seedlings at least 30 cm in height, compared with stands with lower fern density, and those seedlings consisted almost entirely of Betula lenta (black birch) and white pine. Height growth analysis showed that black birch and white pine grew above the height of the fern canopy in 3 and 6 years, respectively. In contrast, two common species, Fraxinus americana (white ash) and Quercus rubra (red oak), grew beneath the dense fern cover for 5 years with height growth less than 5 cm/yr after the first year. A study of spring phenology indicated that the ability of black birch to grow through the fern canopy might have been due to its early leaf development in spring before the fern canopy was formed, in contrast to oak and ash with delayed leaf development. Thus, the ferns showed differential interference among species with seedling development after reduction of deer browse.     

Parameter-specific hydroclimatic sensitivity of a low-elevation network of living and historical tree-ring series from north-eastern Austria

Compared to the alpine regions of Austria, the eastern part of the country is overall warmer and drier with some tree species growing at the dry limit within their ecological range. This suggests that tree rings may be a valuable proxy for hydroclimatic variability. In this study, we develop ring-width, earlywood-width and latewood-width chronologies obtained from drought sensitive living trees and historical timber from one of the driest and warmest regions of Austria, the Weinviertel. For this, samples of four different tree species − fir (Abies alba Mill.), spruce (Picea abies (L.) Karst.), oak (Quercus petraea Liebl., Q. robur L., Q. cerris L.), and pine (Pinus sylvestris L., P. nigra Arnold) were collected from 88 sites (23 forest stands and 65 historical constructions). 1589 samples (oak: 592 samples, pine: 577, spruce: 212, fir: 208) were dated. Dendro-provenancing was required to ensure that only regional material has entered the chronologies. According to the analyses, historical pine and oak wood were nearly 100% regional, while spruce and fir wood were imported to a great extent with only 44% spruce and 35% fir confirmed to be regional. Because site conditions of historical wood samples are unknown but can have a significant influence on tree growth, changes to site replication over time were important in the assessment of chronology reliability. We also controlled for potential artificial increases in sample depth when more than one construction element is made from a single trunk.We assessed the pine (1584-2011 AD) and oak (1244-2011 AD) chronologies’ potential for reconstructing past hydroclimatic variability by means of response functions in a 17-months window from previous June to current October with climate data from three weather stations (Vienna, Retz, Brno) from 1897 to 2010 AD. The highest seasonal response coefficients are for oak and pine ring width (∼0.43) with respect to aggregated March to July precipitation totals and Thornthwaite climatic water balance. These chronologies reveal a high potential for estimating past changes in regional-scale moisture availability during the earlier growing season.     

三种温带树种叶片呼吸的时间动态及其影响因子

为认知叶片呼吸(RL)的季节变化格局及其影响因子,以东北东部山区3个主要树种(红松Pinus koraiensis、樟子松P.sylvestris var.mongolica和白桦Betula platyphylla)为对象,采用红外气体分析法在2011年生长季(常绿树4月至10月;落叶树6月至9月)测定了自然条件下叶片气体交换及其相关生理特征的季节变化,探索了RL与空气温度(Tair)和相关叶片特征之间的关系.结果表明:红松和樟子松基于叶面积的RL(RL-area)表现为生长季初期和末期较大,而白桦RL-area则随生长季进程而逐渐减小.在生长季中,RL-area与叶片总光合之比的时间动态明显.红松、樟子松RL-area与Tair关系显著,而白桦RL-area与Tair关系不显著;但3种树种基于叶质量的RL(RL-mass)与Tair均呈显著的指数函数关系.叶片特征(包括可溶性糖、淀粉、氮、比叶面积等参数)也有明显的季节变化.影响RL的叶片特征参数因树种而异,其中可溶性糖浓度对3种树种的RL均有显著影响.可见,RL的季节变化格局受树木的生长节律、温度和叶片特征的联合控制.     

长白山白桦林中红松种群动态的研究

山地红松、云杉、冷杉林(简称红松云冷杉林),是山地云冷杉林与红松阔叶林相连接带上的垂直地带性植被。在长白山分布于海拔1100—1400m之间,构成窄狭的山地红松云冷杉林亚带(周以良、李景文,1964)。红松云冷杉林受干扰后,白桦林是最为主要的派生森林类型之一。所以,红松云冷杉林演替过程中。白桦林阶段以及林下红松的更新居于重要的位置。本世纪以来,由于东北山地森林的大规模开发,红松云冷杉林面积急剧减小;而作为红松云冷杉林演替先锋阶段的白桦林比重相     

Patterns of daily stem growth in different tree species in a warm-temperate forest in northern China

Radial growth in trees responds to environmental changes in various ways ranging from immediate to hysteretic responses. However, species-specific tree radial growth patterns and their responses to short-term weather changes are not fully understood. Here, the daily stem radial changes (SRCs) in four common tree species, linden (Tilia mongolica), birch (Betula dahurica), oak (Quercus wutaishanica) and larch (Larix principis-rupprechtii), were monitored with high-resolution point dendrometers during the main growing seasons in 2017–2019 on Dongling Mountain, northern China. The SRC was differentiated into tree water deficit-induced stem shrinkage (TWD) and growth-induced irreversible stem expansion (GRO) to evaluate species-specific responses to weather variables and short-term drought events. We found that the TWD and GRO of the four species were significantly different. The TWD was influenced primarily by the vapor pressure deficit (VPD), whereas the GRO was influenced primarily by precipitation (P). In linden and birch, a larger proportion of the GRO occurred at higher air temperature (T_mean) and VPD values; in contrast, the range of these changes was lower in oak and larch. With the increased durations of drought periods, oak and larch experienced large and rapid increases in TWD, whereas birch and linden showed small and slow increases. These results indicate that oak and larch would be sensitive to warmer and drier weather conditions predicted for the future, while linden and birch would have a conservative growth strategy. Our results provide further insights into the physiology of these four tree species and allow us to better predict the growth response of forest dynamics under climate change.     

Identifying signatures of natural selection in cork oak (Quercus suber L.) genes through SNP analysis

Cork oak (Quercus suber L.) is an evergreen tree species endemic to the western Mediterranean Basin with a major economical, social and ecological relevance, associated with cork extraction and exploitation. In the last years, cork oak stands have been facing a significant decline, which may be aggravated by the climate changes that are predicted to occur within cork oak distribution range during this century. Under this scenario, the assessment of adaptive genetic variation is essential to understand how cork oak may cope with these threats and to delineate strategies for the management of its genetic resources. In this study, six candidate genes possibly significant for environmental adaptation were analysed in cork oak populations from its entire distribution range. Signatures of natural selection were investigated using population genetic statistics and environmental association tests under alternative scenarios of population genetic structure. Signals of balancing selection were detected in the putative non-expressor of pathogenesis-related gene 1 (NPR1), involved in plant defence response against pathogens, in auxin response factor 16 (ARF16), a gene implicated in root development, in RAN3, also involved in developmental processes, and in glutamine synthetase nodule isozyme (GS), involved in nitrogen fixation. Furthermore, for ARF16, a class I heat shock protein (sHSP) and GS, associations were found between SNP allele and haplotype frequencies and several spatial and climatic variables, suggesting that these genes may have a role on cork oak local adaptation. In this study, the first steps were taken into gathering information on cork oak adaptation to environmental conditions.     

蒙古栎红松林演替模型FOROAK的研究

Based on forest dynamics theory, gap model FOROAK was developed for simulating long-termdynamics of Mongolian oak (Quercus rnongolica Fisch. )-Korean pine (Pinus koraiensis Sieb. et Zucc. )forest. The model included two parts: biological growth and environmental impacts on growth. Different areapatches were used in simulating forest changes. The results showed that this forest gap was 0.05 hm2. Themodel testing demonstrated that it could reasonably simulate forest dynamic process, and had a very highaccuracy to predict species compositions. The observed species basal areas was similar to the predicted at 60,100 and 270 year forests, the observed species compositions were similar to the predicted at old forest period.Complex changes were found through modeling forest dynamics of bare ground. Mongolian oak and white birch( Betula platyphylla Sukacz. ) dominated at early stage, forest dominated by broad leaved species was formedat middle stage, and then Korean pine dominated at latter stage. The prediction of current primary forestshowed that it was steady during the next 300 year period, the number of trees and the biomass of Korean pine changed very little.     

Effects of subsidy quality on reciprocal subsidies: how leaf litter species changes frog biomass export

Spatial subsidies are resources transferred from one ecosystem to another and which can greatly affect recipient systems. Increased subsidy quantity is known to increase these effects, but subsidy quality is likely also important. We examined the effects of leaf litter quality (varying in nutrient and tannin content) in pond mesocosms on gray treefrog (Hyla versicolor) biomass export, as well as water quality and ecosystem processes. We used litter from three different tree species native to Missouri [white oak (Quercus alba), northern red oak (Quercus rubra), and sugar maple (Acer saccharum)], one non-native tree [white pine (Pinus strobus)], and a common aquatic grass [prairie cordgrass (Spartina pectinata)]. We found that leaf litter species affected almost every variable we measured. Gray treefrog biomass export was greatest in mesocosms with grass litter and lowest with white oak litter. Differences in biomass export were affected by high tannin concentrations (or possibly the correlated variable, dissolved oxygen) via their effects on survival, and by primary production, which altered mean body mass. Effects of litter species could often be traced back to the characteristics of the litter itself: leaf nitrogen, phosphorus, and tannin content, which highlights the importance of plant functional traits in affecting aquatic ecosystems. This work and others stress that changes in forest species composition could greatly influence aquatic systems and aquatic–terrestrial linkages.     

蒙古栎红松林演替模型FOROAK的研究

以森林动态斑块理论为基础建立了蒙古栎（ＱｕｅｒｃｕｓｍｏｎｇｏｌｉｃａＦｉｓｃｈ．）红松（ＰｉｎｕｓｋｏｒａｉｅｎｓｉｓＳｉｅｂ．ｅｔＺｕｃｃ．）林动态变化的林窗模型ＦＯＲＯＡＫ,该模型包括对树木生长的生物学过程和影响树木生长的环境因子模拟两部分。用两种不同面积大小的样地分析森林动态,确定蒙古栎红松林林窗面积为０．０５ｈｍ２。以实际调查数据检验模型,证明所得模型能合理预测森林变化过程,在预测树种组成上精度很高,实际调查和预测的树种断面积组成比在６０、１００和２７０年非常接近,在森林发育后期观测样地的树种组成与预测结果吻合程度良好。对裸地上森林模拟,表明森林的动态过程规律是,蒙古栎和白桦（ＢｅｔｕｌａｐｌａｔｙｐｈｙｌａＳｕｋａｃｚ．）在林分发育开始占优势,中期形成阔叶树和针叶树混交,但以阔叶树为主的森林,后期渐被红松取代。对现实原始林预测显示,森林未来３００年变化稳定,红松株数和生物量变化很小。     

Climate response among growth increments of fish and trees

Significant correlations were found among the annual growth increments of stream fish, trees, and climate variables in the Ozark region of the United States. The variation in annual growth increments of rock bass (Ambloplites rupestris) from the Jacks Fork River was significantly correlated over 22 years with the ring width of four tree species: white oak (Quercus alba), post oak (Quercus stellata), shortleaf pine (Pinus echinata) and eastern red cedar (Juniperus virginiana). Rock bass growth and tree growth were both significantly correlated with July rainfall and stream discharge. Variations in annual growth of smallmouth bass (Micropterus dolomieu) from four streams were significantly correlated over 29 years (1939–1968) with mean May maximum air temperature but not with tree growth. The magnitude and significance of correlations among growth increments from fish and trees imply that conditions such as topography, stream gradient, organism age, and the distribution of a population relative to its geographic range can influence the climatic response of an organism. The timing and intensity of climatic variables may produce different responses among closely related species.     

小兴安岭阔叶红松林不同演替系列森林细根生物量的研究

以小兴安岭地区阔叶红松林旱生演替系列的蒙古栎次生林和蒙古栎红松林、中生演替系列的枫桦次生林和枫桦红松林、湿生演替系列的白桦次生林和云冷杉红松林这6种林型为研究对象,采用土钻取样法对不同演替系列细根生物量的空间变化、垂直分布规律及其影响因子进行系统地研究。结果表明：（1）3种演替系列总细根生物量存在显著差异（P<0.05）。中生演替系列生物量最高,平均达8.56 t·hm^-2,其次是旱生演替系列8.18 t·hm^-2,湿生演替系列生物量最低,为5.79 t·hm^-2;（2）对于不同演替系列细根生物量垂直变化,在阔叶红松林的正向演替过程中,森林细根生物量逐渐增加,且随着土层的增加而降低,拟合效果均达显著水平（P<0.05）,中根和粗根的垂直分布差异较大;（3）在小兴安岭地区,6块林地不同径级细根生物量与土壤有机C和全N、土壤容重、土壤含水率呈显著负相关（P>0.05）,而土壤pH值与细根生物量呈显著正相关性（P>0.05）。     

四个温带树种树干呼吸的时间动态及其影响因子

揭示树干呼吸(RW)的时空变化规律及其影响因子,不但是模拟和估测森林碳收支的重要内容,而且对解释森林生产力的变化有重要意义。采用红外气体分析法于2008年5-9月份测定了自然条件下东北东部山区4个主要树种(红松Pinus koraiensis,兴安落叶松Larix gmelinii,白桦Betula platyphylla,水曲柳Fraxinus mandshurica)的RW日进程,探索其RW及其温度系数(Q10)的时间变化格局及其影响因子。结果表明:树种、径级、月份及其交互作用均显著地影响RW。测定期间RW的总体平均值分别为:落叶松(3.69μmol·m-·2s-1)、水曲柳(3.24μmol·m-·2s-1)、白桦(1.64μmol·m-·2s-1)、红松(1.62μmol·m-·2s-1)。4个树种的RW的日变化(7月除外)大体上与树干温度(TW)变化一致,呈单峰曲线格局,但峰值出现时间因树种和月份而异,RW比TW滞后2-6h。7月份的RW对TW的响应不明显,呈现S型或无峰的日变化格局。RW日平均的季节变化基本与TW和物候节律相符,呈单峰模式。虽然树种之间Q10的差异显著(波动在1.09-2.95之间),但所有树种Q10的季节变化格局一致,均在8月达到最低值,9月份反弹达到最大值。除白桦之外,同一树种不同个体的RW与其胸径之间有显著的正相关关系,但这种关系的形式和相关程度却因树种而异。在构建森林碳循环机理模型时,应考虑RW及其温度敏感性随树种和时间的变化特性。     

Analysis of raw cork production in Portugal and Catalonia using life cycle assessment

Purpose

This study aims to (1) evaluate the environmental impacts associated with the three types of raw cork produced in Portuguese cork oak woodlands (in Alentejo region) considering two alternative practices for stand establishment (plantation and natural regeneration), (2) compare the environmental impacts of raw cork production in Portuguese cork oak woodlands and in Catalonian cork oak forests, and (3) assess the influence of different allocation criteria for partitioning the environmental impacts between the different types of raw cork produced.

Methods

A cradle-to-gate approach was adopted starting with stand establishment up to cork storage in a field yard. The system boundaries include all management operations undertaken during the following stages: stand establishment, stand tending, cork stripping, and field recovery. The allocation of the environmental impacts to reproduction, second, and virgin cork was based on mass and market price criteria. An alternative allocation approach was simulated by allocating environmental impacts also to the wood produced in the cork oak stands. The impact assessment was performed using the characterization factors recommended by the International Reference Life Cycle Data System (ILCD).

Results and discussion

In Portugal, cork produced from naturally regenerated stands has a better environmental performance than cork produced from planted stands, but the differences are smaller than 10 %. Different management models of cork oak stands in Portugal and Catalonia (agro-silvopastoral system and forest system, respectively) originate different impact levels, which tend to be significantly lower in Catalonia. The environmental hot spots in the two regions are also distinct. In Catalonia, they are associated with cleaning, road maintenance, and worker and cork transport. In Portugal, they are fertilization, pruning, and cleaning. The two allocation criteria affect significantly the results obtained for virgin cork in Portugal and for virgin and second cork in Catalonia. Besides, when impacts are also allocated to wood, mass allocation should be avoided as it would not create incentives for a sustainable management of cork oak stands.

Conclusions

The environmental impact from Catalonian cork may be reduced by decreasing mechanized shrub cleaning and road maintenance operations through the introduction of livestock in cork oak forests, and also by a better planning of management operations. For the Portuguese cork, improvements may be achieved by optimizing fertilizer dosage, planting nitrogen-fixing crops and pastures that improve soil quality, avoiding unnecessary operations, improving the efficiency of management operations, and increasing tree density.     

长白山红松年轮碳同位素与净初级生产力的关系

解析树木年轮碳同位素变化是揭示气候与环境变化的有效途径,然而少有研究分析年轮碳同位素对森林净初级生产力(NPP)的指示效应.基于生长季气象因子,分析了长白山红松年轮δ¹³C记录序列与阔叶红松林红松种群NPP变化趋势以及两者之间的相关关系.结果表明: 1970年以前,研究区红松年轮δ¹³C与红松种群NPP变化同步,且两者间呈极显著线性正相关关系,年轮δ¹³C记录了气候变化对红松种群NPP的影响;1970年以后,红松年轮δ¹³C与红松种群NPP变化出现分异,两者呈负相关关系但相关性不显著,表明干旱等其他环境因子的影响使年轮δ¹³C对气候变化的敏感性和对NPP指示性降低.这一相关关系在红松年轮δ¹³C与当年和下一年红松种群NPP之间都存在,表明当年环境状况对来年红松生长的重要意义.说明长白山红松年轮δ¹³C对红松种群NPP有良好的指示性,树木年轮δ¹³C有重建森林历史NPP长期变化的潜力.     

长白山红松林干扰节律研究

以长白山红松林的现存林木年轮资料为基础,３采用辩识从被压中释压和早期生长林冠空隙的分析方法,研究了长白山红松林中红松及其伴生树种的年轮生长方式的变化规律以及长白山红松林中小规模的干扰及干扰的影响。     

长白山三种林型对蛾类群落结构和多样性的影响

选择长白山阔叶红松林、白桦林和落叶松林3种林型,对各林型蛾类的群落结构和多样性进行了比较。结果表明:蛾类各科(亚科)在3种林型中的比例分配明显不同。阔叶红松林中尺蛾科数量占优绝对优势,占47.0%,其次是舟蛾科,为9.3%。优势种为台褥尺蛾,占17.2%;从蛾类总种数和蛾类个体总数上看,白桦林中蛾类物种丰富度、多度和多样性指数明显高于阔叶红松林和落叶松林,优势度指数则最低;白桦林的优势种有尘尺蛾、枞灰尺蛾和双星白枝尺蛾;在落叶松林中,灯蛾科、波纹蛾科和枯叶蛾科的多度都比阔叶红松林和白桦林高,其优势种为阿泊波纹蛾。