濒危植物格木天然种群的表型多样性及变异

【目的】通过对濒危植物格木在我国中心分布区种群的果荚和种子表型性状测量分析,研究其表型多样性及变异规律,结合地理气候信息探讨影响表型变异的关键因子,为格木天然种群的遗传多样性保护恢复和引种栽培提供科学依据。【方法】对8个格木天然种群114个单株的13个果荚及种子表型性状进行测量,利用巢式方差分析、多重比较、相关性分析、主成分分析、聚类分析等分析方法,探讨格木天然种群的表型多样性水平、进化和适应性潜力、表型变异规律、表型分化水平、种群聚类特征及其与地理气候因子的相关性。【结果】格木表型多样性水平中等,13个性状的Shannon-Wiener指数在1. 911 1(种形指数)～2. 103 9(果荚周长)之间,平均2. 027 8;8个种群的Shannon-Wiener指数在0. 920 9(P6)～1. 885 6(P8)之间,均值为1. 474 7。格木表型性状离散程度较轻,13个性状的变异系数在7. 544 6%(种子长)～18. 868 5%(果荚面积)之间,均值为12. 410 9%; 8个种群的变异系数在8. 852 9%(P1)～13. 984 8%(P5)之间,均值为12. 410 9%。13个表型性状的极大值为极小值的1. 395 2(种形指数)～2. 805 6(每荚种子数)倍,均值为1. 791 7。巢式方差分析表明,格木13个表型性状在种群间和种群内均存在极显著差异(P<0. 01),说明这些性状在种群间和种群内均存在丰富的变异;种群内的变异(40. 387 1%)远大于种群间(11. 948 9%)。种群平均表型分化系数为21. 857 9%,各性状的分化系数变化幅度在7. 476 5%(种形指数)～38. 674 0%(果荚宽)之间。相关性分析表明,13个表型性状之间大多存在显著或极显著相关,果荚宽度、种子周长等性状和温度指标呈负相关,与纬度呈正相关,格木在气温高、降雨量大的地区往往具有小果荚、小种子的特征,随着温度指标降低和纬度增加,格木果荚及种子有变大的趋势。格木13个表型性状可提炼为4个主成分,累积贡献率为87. 382%。8个天然群体基于欧氏距离可分为3类:第1类2个种群呈现果荚小、种子小的特征,该类表型主要出现在格木分布区的南端;第2类5个种群呈现果荚大、种子大的特征,该类表型主要出现在格木分布区的北部,仅1个种群位于分布区的南部;第3类1个种群呈现果荚小、种子少、种子大而薄的特征,该类表型出现在格木南北分布区的中间衔接部。【结论】格木的表型多样性处于中等水平,在个体上存在较为丰富的变异。在群体及物种水平上,格木表型性状离散程度较轻,各个性状分布相对集中,较为稳定,不易发生群体分化,拥有特殊表型的格木单株具有较高的保存价值。果荚及种子大小进化及适应性潜力相对较大,种形指数最不易产生变异。种群内的变异是格木表型变异的主要来源,格木的种质资源收集保存可减少种群数量,增加种群内个体数量,并优先收集有特殊表型的单株。广西省容县和龙圩区的格木种群是格木遗传多样性保护及种质资源收集保存的重点区域。年均温等温度因子是影响格木表型及分布的最主要因子。果荚及其中种子的大小是格木种群间聚类的主要依据。     

Nucleotide polymorphisms associated with climate,phenology and physiological traits in European beech (<Emphasis Type="Italic">Fagus sylvatica</Emphasis> L.)

Although European beech (Fagus sylvatica L.) is one of the most widespread and ecologically and commercially most important deciduous trees in Europe, little is known about its adaptive genetic variation. We explored single-nucleotide polymorphism (SNP) variation in candidate genes for budburst and drought resistance in beech populations sampled across most of the distribution range, represented in an international provenance trial. SNP variation was monitored for six candidate genes, in 114 individuals from 19 natural populations. Population structure was deduced from the analysis of 20 nuclear microsatellite markers. Different methods to detect imprints of natural selection were used (F _ST-outlier, SNP-climate regression, association tests). The F _ST-outlier approach identified the COV gene with unambiguous signal of selection, which is an orthologue of Arabidopsis gene for a membrane protein previously reported as phenology-related. Based on environmental association analysis at the population level, the dehydrin gene was found associated with drought-related climatic variables. At the individual level, dehydrin gene also showed a significant association with chlorophyll fluorescence parameters, which are considered stress markers. The importance of the knowledge of physiological variation and geographical patterns of adaptive genetic variation for guiding reproductive materials transfer under climate change is stressed.     

Plant functional types rather than climate or soil determine leaf traits in the forest biomes of eastern China

Nitrogen (N) has great ecological importance, but the biogeographic pattern across forest biomes in China has only recently been explored. Here we conducted a systematic census of leaf C and N following the same protocol to explore the variations of leaf traits, and their possible responses to plant functional types (PFTs) and environmental factors. Results showed that leaf traits varied substantially across biomes, and the relationships of PFTs to climatic factors were stronger than those of PFTs versus soil nutrient proxies, indicating that plant species composition might be a better predictor of plant species distribution with climate than leaf traits. Soil nutrient proxies explained more variation of leaf traits than climate, which demonstrates that leaf traits reflect important aspects of plant responses to soil nutrients. Importantly, partial general linear models analyses found that PFTs showed the greatest direct influence for leaf traits, and climate and soil affected leaf traits mainly through the change in plant species composition rather than having direct impacts. Hence, we concluded that leaf traits were largely controlled by PFTs rather than climate or soil at the biome scale. The results favored the species composition hypothesis, indicating that leaf nutrient concentration is mainly determined by PFTs.     

林芝云杉天然群体针叶与种实的变异及其地理趋势

在西藏地区11个有代表性的林芝云杉天然群体内分别随机抽取15～30个个体为试材,测量了针叶与种实共9个表型性状,采用统计分析方法研究了在群体内和群体间的变异和分化趋势.结果显示:林芝云杉9个表型性状在群体内和群体间的差异显著.群体间表型分化系数均值为29.55％,与云杉属其他树种相比处于中等水平;群体内的方差分量占70...     

To what extent is altitudinal variation of functional traits driven by genetic adaptation in European oak and beech?

The phenotypic responses of functional traits in natural populations are driven by genetic diversity and phenotypic plasticity. These two mechanisms enable trees to cope with rapid climate change. We studied two European temperate tree species (sessile oak and European beech), focusing on (i) in situ variations of leaf functional traits (morphological and physiological) along two altitudinal gradients and (ii) the extent to which these variations were under environmental and/or genetic control using a common garden experiment. For all traits, altitudinal trends tended to be highly consistent between species and transects. For both species, leaf mass per area displayed a positive linear correlation with altitude, whereas leaf size was negatively correlated with altitude. We also observed a significant increase in leaf physiological performance with increasing altitude: populations at high altitudes had higher maximum rates of assimilation, stomatal conductance and leaf nitrogen content than those at low altitudes. In the common garden experiment, genetic differentiation between populations accounted for 0-28% of total phenotypic variation. However, only two traits (leaf mass per area and nitrogen content) exhibited a significant cline. The combination of in situ and common garden experiments used here made it possible to demonstrate, for both species, a weaker effect of genetic variation than of variations in natural conditions, suggesting a strong effect of the environment on leaf functional traits. Finally, we demonstrated that intrapopulation variability was systematically higher than interpopulation variability, whatever the functional trait considered, indicating a high potential capacity to adapt to climate change.     

Characterization of Phytophthora cinnamomi from common walnut in Southern Europe environment

Forty‐eight isolates of Phytophthora cinnamomi obtained from common walnut were analysed according to their variability in growth at different temperatures, virulence, sensitivity to metalaxyl and in genomic DNA. Isolates were obtained from commercial common walnut orchards located in northern Italy and in southern France. Inter‐simple sequence repeat (ISSR) were analysed for the 49 isolates, 43 of which were Italian, 6 French; an isolate of the same species obtained from Viburnum spp. was used as an outgroup. ANOVA on phenotypic characters showed a significant impact of the geographic location of the orchard on isolate variability in terms of reaction to temperatures and aggressiveness. In turn, clustering obtained with UPGMA analysis on genetic data was almost exclusively dependant on isolate variability, nevertheless the 48 isolates seem to share a common variability that differentiates the group from the isolate from Viburnum spp. Correlation between phenotypic and genetic traits was not statistically significant. In conclusion, phenotypic variability like virulence seemed to be conditioned from geographic origin while the genetic variability of P. cinnamomi isolates from walnut was associated to the single genotype.     

Genetic and functional leaf traits variability of Quercus laurina along an oak diversity gradient in Mexico

The ecological literature has documented the effects of plant hybridization on phenotypic variation, and dominant, intermediate, or novel morphological, chemical and physiological traits in hybrids. It is important to understand the ecological consequences of hybridization by evaluating their impact on phenotypic expression of functional traits. We evaluated the relationship between genetic diversity of Quercus laurina and functional foliar traits along an oak diversity gradient. We selected five study sites that represent an oak diversity gradient where Q. laurina is present. Using chloroplast and nuclear microsatellites, we evaluated genetic diversity, measured functional foliar traits of Q. laurina in each site and assessed the effects of local climate variables on the oak community and functional traits. We found a greater abundance of Q. laurina in all study sites. We did not find a relationship between the number of accompanying red oak species and the population genetic diversity in Q. laurina, but higher genetic diversity was found in all study sites in comparison with European oak species. Sites with more oak species had more variation of foliar functional traits. Our results do not support the hypothesis that predicts higher levels of genetic diversity of Q. laurina in communities with greater oak diversity from the same section, but we demonstrated an increase in the foliar functional traits of Q. laurina associated with oak richness and climate variables. We highlight the need to consider environmental and ecological variables linkages as regulatory mechanisms of the phenotypic plasticity expressed in changes of some functional attributes of oaks.

     

油橄榄品种表型和SSR标记的多样性及聚类分析

[目的]利用表型性状和分子标记,对我国油橄榄品种进行鉴定和遗传多样性研究,有利于种质资源保存和利用,对了解油橄榄品种的组成结构及未来的引种和育种工作都具有重要意义。[方法]以甘肃省陇南市17个油橄榄品种为研究材料,利用表型上15个数量性状、18个质量性状和8个SSR荧光标记分别进行多样性和聚类分析。[结果]各性状在品种间存在显著差异,数量性状和质量性状的表型多样性指数分别介于1.579 2.089和0.3621.091,8个SSR位点共检测到51个等位基因变异,平均每个位点等位基因数为6.375个,利用表型性状和SSR标记可以将17个品种完全区分开。[结论]17个油橄榄品种具有较丰富的表型和遗传多样性,基于表型数量性状、质量性状和SSR标记的聚类分析结果,判别品种间遗传关系的结果有一致的,也存在一定差异。对于表型性状相似的品种,需结合SSR标记进行品种鉴定。     

Genotypic variability and phenotypic plasticity of cavitation resistance in Fagus sylvatica L. across Europe

Xylem cavitation resistance is a key physiological trait correlated with species tolerance to extreme drought stresses. Little is known about the genetic variability and phenotypic plasticity of this trait in natural tree populations. Here we measured the cavitation resistance of 17 Fagus sylvatica populations representative of the full range of the species in Europe. The trees were grown in three field trials under contrasting climatic conditions. Our findings suggest that the genotypic variability of cavitation resistance is high between genotypes of a given population. By contrast, no significant differences were found for this trait across populations, the mean population cavitation resistance being remarkably constant in each trial. We found a significant site effect and a significant site?×?population interaction, suggesting that cavitation resistance has a high phenotypic plasticity and that this plasticity is under genetic control. The implications of our findings for beech forest management in a context of climate change are discussed.     

Xylem hydraulic adjustment and growth response of Quercus canariensis Willd. to climatic variability

Global change challenges forest adaptability at the distributional limit of species. We studied ring-porous Quercus canariensis Willd. xylem traits to analyze how they adjust to spatio-temporal variability in climate. Trees were sampled along altitudinal transects, and annual time series of radial growth (ring width (RW)) and several earlywood vessel (EV) traits were built to analyze their relationships with climate. The trees responded to increasing water constraints with decreasing altitude and changes in climate in the short term but the analyses showed that xylem did not acclimate in response to long-term temperature increase during the past 30 years. The plants' adjustment to climate variability was expressed in a different but complementary manner by the different xylem traits. At low elevations, trees exhibited higher correlations with water stress indices and trees acclimated to more xeric conditions at low elevations by reducing radial growth and hydraulic diameter (D(H)) but increasing the density of vessels (DV). Average potential conductivity (K(H)) was similar for trees at different altitudes. However, inter-tree differences in xylem traits were higher than those between altitudes, suggesting a strong influence of individual genetic features or micro-site conditions. Trees exhibited higher RW those years with larger D(H) and particularly the linear density of vessels (DV(l)), but partly, climatic signals expressed in RW differed from those in EVs. Trees produced larger D(H) after cold winters and wet years. Ring width responded positively to wet and cool weather in fall and spring, whereas the response to climate of DV and K(H) was generally opposite to that of RW. These relationships likely expressed the negative impact of high respiration rates in winter on the carbon pools used to produce the EVs in the next spring and the overall positive influence of water availability for trees. Our results showed that trees at different sites were able to adjust their hydraulic architecture to climatic variability and temperature increase during recent decades coordinating several complementary traits. Nonetheless, it should be monitored whether they will succeed to acclimate to future climatic scenarios of increasing water stress.     

Using a spatiotemporal climate model to assess population-level Douglas-fir growth sensitivity to climate change across large climatic gradients in British Columbia, Canada

Effective adaptation of forest management practices to climate change will require a good understanding of the ecological and climatic factors influencing tree sensitivities and responses to climate. Using tree-ring data collected from 33 stands of mature interior Douglas-fir (Pseudotsuga menziesii var. glauca) spanning a wide climatic range in British Columbia (BC), Canada, we present an approach combining high-resolution spatiotemporal climate data with traditional dendroecological analyses to quantify relationships between population climate-growth sensitivity and provenance (i.e., seed-source origin) climate. Key results showed that Douglas-fir climate-growth sensitivities were strongly linked to provenance climate and varied in coherent patterns across climatic gradients. Climate-growth sensitivities and responses were sometimes opposite between provenances from disparate climates. Perhaps most importantly, our results showed that Douglas-fir productivity across most of its range was sensitive to moisture limitations, and this sensitivity increased strongly with decreasing provenance mean annual precipitation and increasing heat-moisture index. Using geographic information systems, we visualize the link between provenance mean annual precipitation and climatic sensitivity of Douglas-fir across BC to identify “high risk” populations. By understanding the link between biological responses and climate, forest managers may be able to spatially identify sensitive populations using spatiotemporal climate data.     

A preliminary study on the genetic structure of Northern European pinus sylvestris L. by means of neutral nuclear microsatellite markers

This paper aimed to investigate the genetic structure (GS) of Scots pine in the northern area of its distribution range by means of seven neutral nuclear microsatellite markers. In particular, the postglacial recolonization of these areas and possible different adaptation patterns in distinct refugia were studied. The GS and diversity were assessed with seven pairs of neutral nuclear microsatellite primers. A high genetic diversity was found in the Scots pine material tested, along with a shallow GS. This pattern is typical for recolonized areas and species with large population sizes, which are connected by pollen-mediated gene flow. A STRUCTURE analysis found two genetic groups to be the most likely, one south-eastern and one north-western group that meet in Fennoscandia. This indicates that Scots pine recolonization of Fennoscandia might have taken place from two different directions (south-west and north-east). Scots pine that recolonized the area originated in at least two different refugia during the last glacial maximum. The glacial survival in distinct refugia can have led to different adaptation patterns and growth optima in the different groups as reflected in the formation of latewood content, where lineage was a significant influencing factor.     

云杉天然群体表型多样性研究

以系统揭示云杉全分布区天然群体表型变异程度和变异规律为目的 ,以其全分布区 10个有代表性天然群体 ,每个群体 30个个体为试材 ,对针叶、球果、种鳞、种翅和种子等 17个表型性状进行系统比较分析 ,采用方差分析、多重比较、相关分析和聚类分析等统计分析方法 ,讨论了群体间和群体内的表型多样性。结果表明 :云杉种内表型性状在群体间和群体内存在极其丰富的遗传差异。云杉球果、针叶、种鳞、种翅和种子 5个表型性状的变异系数分别为 19 14 %、2 6 4 6 %、13 5 8%、19 78%和 174 0 % ,种鳞性状稳定性较其他性状高。表型分化系数 (VST)的变幅为 2 0 9%～ 4 0 6 2 % ,群体间表型分化系数均值为 30 99%。群体间变异 (30 99% )小于群体内变异 (6 9 0 1% )。 17个表型性状间多数呈极显著或显著的正相关 ,球果长度、球果径、种鳞长度、种鳞宽度和种子千粒重为云杉易测定和重要的表型性状。云杉种内群体表型变异在空间分布上呈现以纬度为主的单向变异模式 ,利用群体间欧氏距离进行UPGMA聚类分析表明 ,云杉群体可以划分为 5类     

Biogeography of neutral genes and recent evolutionary history of pines in the Mediterranean Basin

Context

Mediterranean pines share many common life-history traits. They are found at almost all altitudinal levels around the Mediterranean Basin, from sea level to high-elevation mountains, and from hot and dry to wet and cold bioclimates. Their distribution ranges from widespread to regional and narrow, and from dense extensive populations to small populations of scattered individuals. They have been extensively used by human civilizations for millennia.

Aims

I show which are the main phylogenetic, ecological, and climatic factors explaining the patterns of within and among-population genetic diversity in Mediterranean pines.

Methods

I use a narrative synthesis approach and multiple examples from the literature on pine species from the Mediterranean Basin and California.

Results

While Mediterranean pines have the highest levels of differentiation worldwide, their genetic diversity increases from west to east and is significantly reduced in low-elevation species. Factors such as ancestral adaptation to wildfire, reduction of effective population size during the Last Glacial Maximum, long distance dispersal during the Holocene, and more recent adaptation to patchy environmental conditions could explain these patterns.

Conclusion

Because of contrasted ecological, demographic, historical, and geographical processes, and despite their common biological attributes, pines of the Mediterranean Basin display complex biogeographic patterns at neutral gene level that can help retrace their evolutionary history. Although individual species often represent unique case studies that make generalizations risky, locating habitats of significantly high and low genetic diversity is key for detecting and understanding the major factors affecting gene diversity and may prove useful for profiling areas of high conservation value in the Mediterranean.     

Will all the trees fall? Variable resistance to an introduced forest disease in a highly susceptible host

Although tanoak (Notholithocarpus densiflorus syn. Lithocarpus densiflorus) is the species most affected by the introduced pathogen Phytophthora ramorum, with demonstrable risk of extirpation, little is known about the origin, range or structuring of the tree's susceptibility. We examined variation in resistance to P. ramorum using a wound inoculation assay of detached leaves from trees at five geographically separated sites, and a non-wound inoculation assay on twigs from trees at two sites. The structure of variation in resistance was compared to the structure at nine nuclear microsatellite markers.Resistance varied quantitatively, with 23% and 12% of the variation among individuals and populations, respectively. There was a significant correlation between resistance in detached leaves and lesion size in non-wounding twig inoculations. Among-population genetic diversity at nine microsatellite loci was weakly structured but significantly non-zero, with 9.5% of variation among populations. Within-population neutral genetic diversity was a poor predictor of resistance, and estimates of phenotypic distances for resistance were no greater than neutral genetic distances.The limited phenotypic and genetic structure we found indicates that tanoaks at all study sites are susceptible, and there is no evidence of prior selection for disease resistance. We conclude that tanoak populations across the species’ range are at risk, but local disease dynamics will depend on both host genetics and environmental conditions.     

不同种源樟树果实和种子表型性状对比分析

为探讨不同种源樟树(Cinnamomum camphora)果实和种子的表型性状差异程度、变异规律及其与地理气候因子的关系,以重庆、湖南和广西等7个种源地的樟树果实和种子为试验材料,采用方差分析、相关性分析和主成分分析方法对樟树果实和种子的8个表型性状进行比较研究。结果表明,除果形指数外,其他7个表型性状在种源间均差异极显著。8个表型性状的变异系数为3.671%~18.497%,其中种子千粒重的变异系数最大(18.497%),种形指数的变异系数最小(3.671%),说明樟树的种子形状最稳定。樟树果实及种子的表型性状与年均气温和年均降水量相关性明显,在年均气温高和年均降水量大的分布区,果实和种子较大,并呈现由北向南逐渐增大的趋势。     

QTL detection for growth traits in Pinus elliottii var. elliottii and P. caribaea var. hondurensis

Quantitative trait locus （QTL） detection was carried out for growth traits in 122 F1 progenies of Pinus elliottiivar. elliottii （PEE） x tR caribaea var. hondurensis （PCH） hybrid. The PCH male parent linkage map contained 108 mark- ers in 16 linkage groups, while the PEE female parent contained 93 markers in 19 linkage groups. Sequence-related amplified polymorphism （SRAP）, microsatellite （SSR）, expressed sequence tag polymorphism （ESTP） and inter-simple sequence repeat （ISSR） were selected from an existing linkage map. Growth traits investigated were height at age five （HT05） and six years （HT06）, diameter at breast height at age five （DBH05） and six years （DBH06） and annual growth from age five to six years of height （AGHT） and diameter at breast height （AGDBH）. KruskaI-Wallis and interval mapping approaches were used to estimate levels of significance, the number of QTLs, the percentage of the phenotypic varia- tion explained by each of QTLs and their positions on the genetic linkage maps. Twenty six QTLs with significance levels p 〈 0.05 were detected on the parental maps for the six growth traits, which explained more than 15% of the phenotypic variation, suggesting an existence of major-effect genes. Several QTLs had the pleiotropy controlling more than one sin- gle growth trait. Overall, the proportion of phenotypic variation explained by QTLs ranged from 5.9% to 40.6% for HT05 and HT06, from 6.6% to 42.0% for DBH05 and DBH06 and from 5.8% to 22.3% for AGHT and AGDBH. The results from this study provide a basis for marker-aided selection （MAS） in PEE x PCH hybrids.     

Genetic variation and divergence in Scots pine (Pinus sylvestris L.) within its natural range in Italy

Twenty-one populations of Scots pine sampled over the entire Italian range of the species were analysed for genetic variation scored at nine nuclear SSR markers. The main aim of the work was to find genetic features useful for conservation management, namely allelic composition, gene diversity and differentiation. High levels of intra-population variability were scored. The only population sampled in the Apennines gave the lowest values, confirming the genetic erosion undergone in the Scots pine remnants in this area. A low level of genetic variability was also scored for populations from the Po valley and hills of Piedmont. Most genetic diversity was found within populations, while only a small amount occurred among them (F _ST?=?0.058). Both Bayesian clustering and sPCA analysis showed a East–West subdivision, notwithstanding the unclear position of populations from the Po valley. The population from the Apennines was always clearly separated from the others. The results are discussed in terms of post-glacial recolonisation, as well as for defining genetically homogeneous regions for Scots pine in Italy. The management of genetic resources could benefit from the identification of such ‘gene zones’, thereby avoiding the use of non-local reproductive material for plantations, which can represent one of the most important reasons for failure of reforestation. In addition, the assessment of the biogeographic genetic structure by neutral markers is a prerequisite for disentangling the influence of selectively neutral and non-neutral processes on the distribution of adaptive genetic variability.     

Variability in seed traits and genetic divergence in a clonal seed orchard of Dalbergia sissoo Roxb.

The variations in seed and pod traits, genetic superiority and genetic divergence were evaluated for a Clonal Seed Orchard (CSO) of Dalbergia sissoo Roxb. at Bithmera, India consisting of 20 clones from different agro-climatic conditions of four northern states (Uttar Pradesh, Uttarakhand, Haryana and Rajasthan). The seeds and pods of various clones in the orchard exhibited significant variability in size, weight and other characters. Significant positive correlations were observed between seed length and seed width (p<0.05), seed length and seed thickness (p<0.01), seed length and seed weight (p<0.01), seed thickness and seed weight (p<0.01), seed length and germination value (p<0.05). The genetic parameters for seed and pod traits also showed a wide range of variations in the orchard. Heritability values were found to be over 50 percent for most of the seed and pod traits. Seed weight, seed length and seed thickness showed high heritability values coupled with maximum genetic gain for these characters. Ward’s minimum variance dendrogram of clones of D. sissoo showed three distinct clusters; cluster 1 was the largest with 12 better clones whereas cluster 2 and 3 consisting of seven moderate clones and one poor clone, respectively. Mean cluster values showed sufficient variation among the clusters for seed weight, germination value and seed length. The possible hybridization between best clones of cluster 1 to the disease resistant clone of cluster 2 (resistant against deadly Gandoderma lucidum root rot disease of D. sissoo) is also suggested for further breeding programmes of the species. The deployment of clone 194 (better performed and disease resistant) is also recommended in future plantation programmes of D. sissoo in northern India.     

Regional and annual trends in Douglas-fir foliage retention: Correlations with climatic variables

Swiss needle cast imposes strong geographical patterns in Douglas-fir needle retention throughout the Coast Ranges of Oregon and southwestern Washington. These geographical patterns in foliage retention have been related to the spatial variability in average climatic conditions, with climate presumed a major causal factor in the spread and intensification of the fungus that causes Swiss needle cast. Annual fluctuations in foliage retention have likewise been hypothesized to follow fluctuations in annual climatic conditions. The objective of this analysis was to test a full suite of climatic variables for their ability to predict regional and annual patterns in Douglas-fir foliage retention on 296 permanent sample plots comprising six different Swiss needle cast studies. Foliage retention was estimated annually from 1996 to 2009 and climatic data were generated from the PRISM website through ClimateWNA (Wang et al., 2006). Among the 85 annual, seasonal, and monthly climate variables explored, average foliage retention was predicted most consistently by a temperature-based continentality index, mean annual precipitation, winter temperature, summer temperature, and spring or summer precipitation. The same 85 variables were tested for predicting annual fluctuations in foliage retention, allowing for lagged effects of climatic conditions 1-4 years prior to each year of observation. The annual foliage retention models had climate variables similar to the periodic average foliage retention models, but with a variety of lagged effects. The periodic average foliage retention model suggested that under future climate scenarios foliage retention would increase.