Seasonal and diurnal trends in progressive isotope enrichment along needles in two pine species

The Craig–Gordon type (C–G) leaf water isotope enrichment models assume a homogeneous distribution of enriched water across the leaf surface, despite observations that Δ¹⁸O can become increasingly enriched from leaf base to tip. Datasets of this ‘progressive isotope enrichment’ are limited, precluding a comprehensive understanding of (a) the magnitude and variability of progressive isotope enrichment, and (b) how progressive enrichment impacts the accuracy of C–G leaf water model predictions. Here, we present observations of progressive enrichment in two conifer species that capture seasonal and diurnal variability in environmental conditions. We further examine which leaf water isotope models best capture the influence of progressive enrichment on bulk needle water Δ¹⁸O. Observed progressive enrichment was large and equal in magnitude across both species. The magnitude of this effect fluctuated seasonally in concert with vapour pressure deficit, but was static in the face of diurnal cycles in meteorological conditions. Despite large progressive enrichment, three variants of the C–G model reasonably successfully predicted bulk needle Δ¹⁸O. Our results thus suggest that the presence of progressive enrichment does not impact the predictive success of C–G models, and instead yields new insight regarding the physiological and anatomical mechanisms that cause progressive isotope enrichment.     

水热耦合对沈阳地区油松木质部生长的影响

利用微树芯技术可以从细胞尺度研究树木形成层物候和径向生长的过程,揭示树木生长与气候的关系。油松是我国北方森林的建群树种之一,也是沈阳地区的优势树种。研究2020年整个生长季(4—11月)油松周尺度的形成层及木质部细胞变化,分析油松在沈阳地区的生长规律。结果表明: 油松形成层分裂活动开始于4月初,结束于9月末。木质部从扩大细胞出现(4月中旬)开始生长,到木质化细胞消失(10月下旬)结束,其生长符合“S”型曲线。2020年生长53个/列木质部细胞,最大生长速率(0.55个/列/d)出现在5月末,早晚材细胞于7月末发生转变。在沈阳地区最低温达到0 ℃以上时树木形成层开始活动,影响木质部生长开始和结束的最低临界温度为2～3 ℃。降水在油松整个生长过程中起到促进作用。沈阳地区7月末的高温和水分供给不足是木质部细胞分化形成早晚材的主要因子。     

Comparison of whole wood and cellulose carbon and oxygen isotope series from Pinus nigra ssp. laricio (Corsica/France)

Stable isotopes in tree rings have widely been used for palaeoclimate reconstructions since tree rings record climatic information at annual resolution. However, various wood components or different parts of an annual tree-ring may differ in their isotopic compositions. Thus, sample preparation and subsequent laboratory analysis are crucial for the isotopic signal retained in the final tree-ring isotope series used for climate reconstruction and must therefore be considered for the interpretation of isotope–climate relationships. This study focuses on wood of Corsican Pine trees (Pinus nigra ssp. laricio) as this tree species allows to reconstruct the long-term climate evolution in the western Mediterranean. In a pilot study, we concentrated on methodological issues of sample preparation techniques in order to evaluate isotope records measured on pooled whole tree-ring cellulose and whole tree-ring bulk wood samples. We analysed 80-year long carbon and oxygen chronologies of Corsican Pine trees growing near the upper tree line on Corsica. Carbon and oxygen isotope records of whole tree-ring bulk wood and whole tree-ring cellulose from a pooled sample of 5 trees were correlated with the climate parameters monthly precipitation, temperature and the self-calibrating Palmer Drought Severity Index (sc-PDSI). Results show that the offsets in carbon and oxygen isotopes of bulk wood and cellulose are not constant over time. Both isotopes correlate with climate parameters from late winter and summer. The carbon and oxygen isotope ratios of cellulose are more sensitive to climatic variables than those of bulk wood. The results of this study imply that extraction of cellulose is a pre-requisite for the reconstruction of high-resolution climate records from stable isotope series of P. nigra ssp. laricio.     

Mapping site indices for five Pacific Northwest conifers using a physiologically based model

Questions: How well can we predict tree growth potential (site index) of five, locally dominant tree species in reference to estimates made with a detailed vegetation classification? Location: The forested region of the Pacific Northwest, USA and Canada. Methods: We employed a physiologically based process model (3‐PG, Physiological Processes to Predict Growth) to generate estimates of site index under averaged climatic conditions (1971–2000) generated from hundreds of weather stations and extrapolated, with adjustments for topography, across the region at 1‐km resolution. The model was parameterized from published information, but we had to assume fixed values of soil water storage capacity at 200 mm and soil fertility at 70% of maximum across the region. Field estimates of site index for the five dominant species were derived from published correlations with detailed mapping of vegetation provided by The British Columbia Ministry of Forests and Range. Results: The site indices projected with the 3‐PG model for the five species combined, when compared with those produced by the Ministry of Forests and Range, produced an r² averaging ～0.5 with a standard error of 2.8 m at 50 yr, equivalent to 10% of the mean. Some of the variation may be attributed to inadequate information on soil properties. Importantly, the relationship between the two estimates was not significantly different from a 1:1 line, with an intercept of zero. Conclusions: The 3‐PG modelling approach offers a means of predicting spatial variation in site indices across the Pacific Northwest and provides a basis for predicting future site indices under a changing climate.     

Interaction between flight,reproductive development and oviposition in the pine weevil Hylobius abietis

• 1 The development of reproductive and flight capacity of pine weevils Hylobius abietis during the spring and their dispersal to, and subsequent development at, new clearfell oviposition sites comprise key phases in their life cycle in managed forests. At an old clearfell site where autumn‐emerging weevils had overwintered, weevils were trapped as they re‐emerged in the spring and tested for their ability to fly and then dissected to determine the degree of wing muscle and egg development.
• 2 Re‐emerging weevils were most abundant in pine growing at the edge of the clearfell and, over most of the trapping period (April to June), their capacity for flight (proportion flying and wing muscle width) was more advanced than in weevils from the clearfell itself, with a similar trend in the degree of reproductive development (proportion with mature eggs and egg volume).
• 3 In weevils from the clearfell, flight capacity and reproductive development increased concurrently to a peak around mid‐May. In weevils from pine, wing muscles were already well developed at the start of trapping, although few of them flew. Their more advanced development was attributed to the increased opportunities for maturation feeding after emergence in the previous autumn.
• 4 In the spring, weevils reached the canopy of trees for maturation feeding by walking and, to a lesser extent, by flight. Weevils dispersed by flight to oviposition sites in mid‐May when most of them were reproductively mature. After arrival, flight ability and wing muscle size declined rapidly but egg production was maintained until most weevils had stopped flying. When wing muscles reached their minimum size, there was a marked decline in egg size, suggesting that wing muscle breakdown is important in maintaining egg production at oviposition sites. Prospects for further wing muscle and reproductive development are discussed.

     

Variability in chemical composition and abundance of the rare tertiary relict Pinus heldreichii in Serbia

The particular significance of the whitebark pine (Pinus heldreichii Christ.) stems from the fact that it is a tertiary relict and Balkanic subendemite covering a very narrow and intermittent area in Serbia. A representative pool of 48 adult trees originating from three populations, one recently discovered natural (Population I) and two planted populations (Populations II and III) was investigated in order to evaluate the intra- and interpopulation variability of the essential oil of the complete fund of P. heldreichii in Serbia. In the pine-needle-terpene profile, 104 compounds were detected, 84 of which could be identified. Among the essential-oil constituents, monoterpenes and sesquiterpenes dominated, comprising ca. 90% of the essential oil. The terpenic profile of Population I was characterized by a predominance of monoterpenes (e.g., limonene (1), α-pinene, and Δ(3) -carene (4)), while sesquiterpenes (e.g., germacrene D (2) and β-caryophyllene (3)) obviously preponderated in the profile of Populations II and III. This study also demonstrated that the abundance of whitebark pines in Serbia had significantly changed over the last few decades. The number of individuals in the natural population had increased, while the number of individuals in the planted populations had decreased. Today, the whitebark pine fund in Serbia comprises less than 250 trees.     

云南松幼苗棉革菌属菌根真菌的物种多样性

以滇中1～2年生云南松幼苗为研究对象,观察鉴定与其共生的棉革菌属真菌外生菌根真菌.通过形态观察发现了6种形态型菌根.文中对这6种形态型菌根的外观和显微特征进行了详细描述.对rDNAITS片段比对分析结果表明,6种形态型对应6种棉革菌属真菌,它们分别是与Tomentella badia、T.coerelea、T.viri...     

水分胁迫对脂松苗木针叶质膜透性和保护酶活性的影响

以2年生盆栽脂松苗木为材料,研究了不同土壤水分处理（含干旱和水渍胁迫）及解除胁迫后对脂松苗木针叶质膜透性和保护酶活性的影响。结果表明,随着干旱与水渍胁迫时间的延长,脯氨酸、可溶性糖和丙二醛(MDA)含量均有所上升;过氧化氢酶(CAT)活性逐渐降低;过氧化物酶(POD)活性逐渐升高;解除胁迫后,各项指标均有不同程度的恢复,其中田间含水量为40%、80%、100%处理（即FC40%、FC80%、FC）恢复较快;干旱处理中FC20%和水渍处理中的水渍胁迫（FL）对苗木的生理影响在解除胁迫后14天尚未完全恢复且表现为水淹处理恢复能力较干旱处理差。综上,FC60%为最适土壤水分含量,综合表现最佳。     

The breeding biology of the Common Crossbill Loxia curvirostra in the Central Pyrenees

The breeding biology of the Common Crossbill Loxia curvirostra was studied over ten consecutive years in forests of Mountain Pine Pinus uncinata in the Pyrenees, France. The breeding season lasts from summer to the next spring following the maturation and the opening of the pine cones. Pairs with dependent young were most common in November and March–May. The greatest number of clutches was observed in December and January (53%, n = 30). Average clutch size was 3.43 eggs (sd = ±0.57; n = 30), the number of fledged young was 1.32 per completed clutch (sd = ±1.7; n = 25) and the proportion of breeding attempts that were successful was 27.8% in the winter/spring period (n = 36). The number of successful pairs was found to be positively correlated to the number of cones, and in the winter/spring period negatively correlated to the mean depth of snow. Breeding only failed completely during the year in which the density of birds was highest. In years with a good cone crop, breeding that starts early and continues over a long period appears to be an adaptation which increases productivity in this sedentary population dependent on fluctuating food resources. An irruption by birds from northern Europe in 1990 did not affect the numbers or breeding success of the Pyrenean crossbills.     

The Evolutionary Genetics of the Genes Underlying Phenotypic Associations for Loblolly Pine (Pinus taeda,Pinaceae)

A primary goal of evolutionary genetics is to discover and explain the genetic basis of fitness-related traits and how this genetic basis evolves within natural populations. Unprecedented technological advances have fueled the discovery of genetic variants associated with ecologically relevant phenotypes in many different life forms, as well as the ability to scan genomes for deviations from selectively neutral models of evolution. Theoretically, the degree of overlap between lists of genomic regions identified using each approach is related to the genetic architecture of fitness-related traits and the strength and type of natural selection molding variation at these traits within natural populations. Here we address for the first time in a plant the degree of overlap between these lists, using patterns of nucleotide diversity and divergence for >7000 unique amplicons described from the extensive expressed sequence tag libraries generated for loblolly pine (Pinus taeda L.) in combination with the >1000 published genetic associations. We show that loci associated with phenotypic traits are distinct with regard to neutral expectations. Phenotypes measured at the whole plant level (e.g., disease resistance) exhibit an approximately twofold increase in the proportion of adaptive nonsynonymous substitutions over the genome-wide average. As expected for polygenic traits, these signals were apparent only when loci were considered at the level of functional sets. The ramifications of this result are discussed in light of the continued efforts to dissect the genetic basis of quantitative traits.