The Scope for Using the Volatile Profiles of Pinus caribaea var. bahamensis as Indicators of Susceptibility to Pine Tortoise Scale and as Predictors of Environmental Stresses

Climate change, unseasonal fire and urbanization are contributing to the decline of Pinus caribaea var. bahamensis populations in the Turks and Caicos Islands (TCI). Infestation of pines with the invasive pine tortoise scale (PTS, Toumeyella parvicornis) is accelerating this decline. Pine trees in the Bahamas are larger and healthier and are not infested with PTS although they are subject to some of the same environmental pressures as the trees in TCI. Volatile compounds were collected from wild and nursery‐reared P. caribaea var. bahamensis from TCI and the Bahamas and characterized using GC/MS analysis, to look for differences between the compounds detected in insect‐infested pines of TCI and the healthy pines of the Bahamas. Ten compounds contributing at least 1% of the total detected peak areas in any one of the samples were selected for further study. Eight of these compounds were identified using authentic standards and mass spectral libraries. The main constituents in the samples were α‐ and β‐pinene as well as β‐phellandrene, and, together with β‐myrcene, their contents varied the most between samples collected at different locations. Principal‐component analysis showed that the two structural isomers of pinene, together with β‐myrcene and β‐phellandrene, contributed 98.4% of the variance between samples. There was a positive relationship between the concentrations of the two structural isomers of pinene and between levels of β‐myrcene and β‐phellandrene. The results are discussed in relation to the biology and adaptations of invasive scale insects, the importance of monoterpenes in pine as a defense against insect predation, whether these compounds can be used as indicators of tree health, and future directions for research into conserving the Caicos pine.     

Common environmental factors explain both ectomycorrhizal species diversity and pine regeneration variability in a post-fire Mediterranean forest

Natural seedling regeneration and establishment after stand replacing wildfires is influenced by a series of environmental and biological constraints. In this study, we characterized the diversity and structure of the ectomycorrhizal (ECM) fungal community associated with post-fire naturally regenerated maritime pine saplings, and individuate the environmental factors responsible for fungal species distribution. We also identify the main environmental factors responsible for maritime pine regeneration variability and assessed the relation between saplings performance and ECM fungal diversity indices. Fungal species were identified by direct sequencing of internal transcribed spacer regions. Five years after the disturbance event, a total of 30 taxa colonized the pine saplings. The ECM fungal community was dominated by ruderal species of the genus Rhizopogon (present in almost half of the samples). Almost one third of the identified ECM fungal species belonged to the family Thelephoraceae. Typical k-selected species like Amanita pantherina, Boletus aestivalis, Lactarius chrysorrheus, and Russula densifolia were found on pine saplings collected in proximity of unburnt pine trees, in correspondence with low erosion extents. Pine regeneration varied throughout the study areas and was enhanced at higher elevations, in correspondence with moderate slopes, shallower soils, and a reduced cover of ericaceous shrubs and bare ground. These conditions were found in close proximity to patches of pine trees that survived the disturbance event and were previously characterized by a higher pre-fire pine biomass. Even though no correlations were found between saplings performance and ECM fungal diversity indices, common environmental factors (i.e., ericaceous shrub cover, extent of erosion, slope, and soil depth) were responsible for shaping the ECM fungal distribution and for describing most of the explained regeneration variability.     

松材线虫与伴生微生物的生态关系

松材线虫是重要的外来有害生物,造成松树大量死亡,带来严重的经济损失和生态破坏.松材线虫与伴生微生物存在密切的生态关系.本文综述了松材线虫伴生微生物的种类及其在松材线虫繁殖和致病过程中的重要生态作用,从微生态系统角度对松材线虫病进行探讨.伴生真菌能为松材线虫提供食物,维持松材线虫次生侵染循环,提高分散型第三龄幼虫在种群中的比例,利于松材线虫侵染扩散;伴生细菌能够提高松材线虫致病性,促进其繁殖,并菌有助于松材线虫降解松萜类物质,从而提高松材线虫的适应性.     

Population status,habitat dependence,and reproductive ecology of Bahama Orioles: a critically endangered synanthropic species

ABSTRACT Recent elevation of critically endangered Bahama Orioles (Icterus northropi) to species status prompted us to evaluate their population status, habitat use, and breeding ecology. From surveys, we estimated that at least 141 to 254 individuals remain globally, with 90 to 162, 24 to 44, and 27 to 48 individuals remaining on North Andros Island, Mangrove Cay, and South Andros Island, The Bahamas, respectively. Orioles were observed nesting exclusively in anthropogenic habitat (residential and agricultural land), but home ranges also included nearby pine forest and coppice (dry broadleaf forest). Most nests (40 of 46, or 87%) were in nonnative coconut palm (Cocos nucifera), with native Sabal palmetto and Thrinax morrisii, and an introduced Brassaia actinophylla also used. Trees selected by orioles for nesting were significantly taller, less likely to have shrubs underneath, further from cover, and had more palm trees nearby than randomly selected palm trees. Three of eight nests with known contents were parasitized by Shiny Cowbirds (Molothrus bonariensis). Lethal yellowing disease recently devastated coconut palms and reduced the number of orioles on North Andros, but palms on Mangrove Cay and South Andros remain healthy. The juxtaposition of anthropogenic habitat to suitable native habitats may be more important than any single factor for Bahama Orioles, especially for breeding adults and fledged young. Conservation of coppice habitat, at high risk for agricultural and residential development, is crucial for survival of this critically endangered synanthropic species.     

Understory development in canopy gaps of pine and pine-hardwood forests of the upper Coastal Plain of Virginia

Canopygaps are important in establishing a pool of natural regeneration in manytemperate forest ecosystems. Information on the role of gaps in loblolly pine(Pinus taeda L.) and pine-hardwood foreststands in the southeastern Coastal Plain of the United States is lacking.Accordingly, 12 small canopy gaps in mature pine and pine-hardwood standsin Petersburg National Battlefield, Virginia, were studied. Loblolly pineregeneration was significantly more abundant in canopy gaps as compared to theadjacent forest in both forest cover types. In four stands dominated by loblollypine, there were 750 saplings/ha in the gaps compared to only 125saplings/ha in the adjacent forest. Pine saplings dominated the regenerationspectrum in the gaps in the pine stands, while red maple (Acerrubrum L.) was more important in the adjacent forest. In fourpine-hardwood stands, regeneration in both the gaps and adjacent forestwas dominated by sweetgum (Liquidambar styracifluaL.) with importance values of 27% and 28%, respectively.There were no loblolly pine seedlings in the adjacent forest, but an average 313per ha in the gaps of the pine-hardwood stands. Within thegaps in both cover types, loblolly pine saplings were lower in stature thancompeting hardwood stems, leading to the conclusion that the gaps may form atemporary pool of pine regeneration. Without further stand disturbance, theprocess of gap closure may reduce the pine component to a secondary status, orperhaps eliminate it altogether.     

Using an evapo-transpiration model (ETpN) to predict the risk and expression of symptoms of pine wilt disease (PWD) across Europe

The pine wood nematode (PWN) Bursaphelenchus xylophilus is the causal agent of pine wilt disease (PWD), a xylem restricting disease of pine trees. PWN, a native of North America where it very rarely kills native pine trees, has spread internationally killing host trees in China, Japan, Korea, Taiwan and Portugal, with isolated incursions into Spain. Based on the locations where tree mortality has been recorded, it appears that pine trees growing in hot, dry conditions are more susceptible to pine wilt disease. This paper describes the ETpN model, an evapo-transpiration model (previously developed by Forest Research), which has been modified to incorporate the presence of PWN inside a tree and which predicts the regions of Europe that are likely to succumb to PWD. ETpN acts independently of the vector beetle (Monochamus spp.), predicting the likelihood of PWD on the assumption that a tree in a particular region has already been infested by the pine wood nematode. Different regions across Europe are included to investigate and demonstrate how different climates affect PWD incidence significantly. Simplified, “lite” and latency models have been developed to allow a non-specialist user to determine respectively the risk of PWD at a particular location and the likelihood of delays (latency) in expression of wilt symptoms.     

Food choice from endemic North Carolina tree species by captive prosimians (Lemur fulvus)

Seven captive-born lemurs (Lemur fulvus) at the Duke University Primate Center were presented with leaves of different maturity from five species of North Carolina trees. The animals demonstrated three distinct behaviors toward the novel plant material. They sniffed, tasted, and/or ingested it. New leaves were sniffed, but little tasting and ingestion was observed. Intermediate pine needles were sniffed and ingested but little tasted. Mature leaves were sniffed equally, but the mature leaves of tulip trees and honeysuckle were tasted significantly more than pine, sweetgum, and red maple. Pine, sweetgum, and red maple were ingested significantly more than tulip trees and honeysuckle. Male lemurs ate significantly more mature pine needles and new sweetgum leaves than did the females. Chemical analysis of these plant materials indicated that the new and mature leaves of tulip tree and honeysuckle contained alkaloids. Captive-born lemurs apparently use their sense of smell and taste in choosing what to eat and seem just as capable as free-ranging animals in finding food when faced with the chemical defenses that protect trees from insect predation.     

Hazard ratings of pine forests to a pine wilt disease at two spatial scales (individual trees and stands) using self-organizing map and random forest

Pine wilt disease (PWD) caused by the pine wood nematode is the most serious global threat to pine forests. Hazard ratings of trees and forests to pest attacks provide important information to efficiently identify current or future hazardous conditions. However, in spite of the importance of hazard ratings for managing PWD, there are few studies on hazard ratings in this system. In this study, we evaluated the hazard ratings of pine trees and pine stands to PWD by considering environmental factors at the level of the stand and the individual tree. Our results showed that trees with larger diameter at breast height (DBH) showed a higher risk rate than those with smaller DBH, indicating that large trees have an increased probability of exposure to vector beetles because they are tall and have a large crown volume. We also found that reduced tree vigour could be related to susceptibility to PWD. In pine stands, geographical factors showed a high correlation with the occurrence of PWD. PWD occurrence was rare at high altitudes, but was more common on steep and south-facing slopes. These patterns were consistently observed in the results from 2 computational approaches: self-organizing map (SOM) and random forest models. The combination of SOM and random forest was effective to extract ecological information from the dataset. The SOM efficiently characterized relations among variables, and the random forest model was effective at predicting ecological variables, including the hazard rating of trees to disturbances.     

Insect-induced chemical changes in young lodgepole pine (Pinus contorta): the effect of previous defoliation on oviposition, growth and survival of the pine beauty moth, Panolis flammea

ABSTRACT. 1. Significantly more eggs were laid by adult female pine beauty moths ( Panolis flammea (D&S)) on previously undefoliated lodgepole pine ( Pinus contorta Douglas) saplings than on those which had been partially defoliated the year before.
2. The larval weights, mean relative growth rates and survival rates of P.flammea were lower on defoliated trees than on undefoliated trees.
3. Marked and significant differences between the monoterpene profiles of the shoot cortical oleoresin of defoliated and undefoliated trees were linked to oviposition preferences in P.flammea.
4. Differences occurred between the levels of soluble tannins in previously defoliated and undefoliated trees.
5. The results are discussed in relation to earlier work on insect-induced changes in plants, and the significance of inter-provenance differences in lodgepole pine response is assessed.     

红松和紫椴叶片暗呼吸及其光抑制性在幼、成树间的差异

叶片暗呼吸是森林碳循环的重要组分,深入分析幼、成树的叶片暗呼吸及其光抑制性的差异,对生态系统总生产力(GPP)的准确估算具有重要意义.本研究以长白山阔叶红松林主要树种(红松和紫椴)的幼树和成树为研究对象,分别测算不同光照下叶片暗呼吸与无光暗呼吸,比较叶片暗呼吸及其光抑制性在幼、成树间的差异,结合幼、成树叶片生理生态参数的对比,对幼、成树叶片暗呼吸及其光抑制性差异的原因进行探讨.结果表明: 两个树种幼树叶片光下暗呼吸的值高于成树,在生长季(6—9月),幼树的值比成树高6.8%～39.6%;两个树种幼树叶片暗呼吸光抑制程度低于成树,幼树叶片暗呼吸光抑制性的值比成树低2.5%～14.1%;红松幼、成树间叶片暗呼吸光抑制性的差异总体高于紫椴幼、成树间叶片暗呼吸光抑制性的差异,差值最高可达18.6%;幼树中较高的光下暗呼吸值和较低的光抑制程度可能与最大净光合速率、比叶面积、气孔导度的变化有关,与叶片氮含量的变化无关.     

INFLUENCE OF NEIGHBORS ON TREE FORM: EFFECTS OF LATERAL SHADE AND PREVENTION OF SWAY ON THE ALLOMETRY OF LIQUIDAMBAR STYRACIFLUA (SWEET GUM)

Liquidambar styraciflua (sweet gum) saplings were open grown (control), guy-wired to prevent wind-induced sway (constrained), or guy-wired within open-topped shade cloth cylinders to simulate shading by neighboring trees (shaded). Mechanical stability was assessed after 2 years of growth by field measurement of whole-tree flexibility and with the critical buckling height predictions of five allometrical models. Data from this experiment are supplemented with measurements of sweet gum trees growing in a 9-year-old pine plantation; individuals crowded but not overtopped by pines are compared with similar-aged trees growing in openings within the plantation. Changes in aboveground architecture were stimulated by both prevention of sway and lateral shade but the effect of the latter was most pronounced; shaded saplings approached or exceeded their calculated critical height and buckled under their own weight when the shade cloth cylinders were removed. Rates of aboveground biomass acquisition, total leaf area, wood density, and wood elastic moduli did not differ among the three treatments; changes in stem allometry accounted for most of the observed differences in tree stability. Sweet gum trees growing in a pine plantation responded similarly to neighbors; crowded trees had larger height: diameter ratios and more closely approached their calculated critical heights than did trees growing in the open. Sweet gum saplings growing in dense stands of similar-sized plants may surmount their neighbors by allocating relatively more wood to height growth than to girth increment.     

沙地樟子松天然林南缘分布区林木竞争、空间格局及其更新特征

以呼伦贝尔沙地樟子松地理分布南缘天然林为研究对象,采用Hegyi竞争指数与点格局等分析方法,研究了沙地樟子松天然林的种群结构、种内竞争、空间格局及幼树更新等特征。结果表明:1)所调查区域天然沙地樟子松纯林处于中幼龄阶段,属增长型种群;2)其竞争指数与对象木胸径服从幂函数关系CI=242.24D~(-1.12)(R~2=0.91);3)幼树在小尺度上呈聚集分布,中树与大树在中大尺度上呈随机分布;幼树与中树在小尺度上呈正相关性,中树与大树在小尺度呈负相关性;4)竞争指数与更新幼树和存活更新幼树的密度均呈显著正相关性。在林分管理中需要充分考虑林木竞争、空间格局以及种群更新的关系,本研究可为沙地樟子松天然林的经营管理与保护提供重要的科学依据。     

Regeneration of Scots pine Pinus sylvestris at a natural tree-line in the Cairngorm Mountains, Scotland

The age, density, distribution and reproductive capacity of Scots pine Pinus sylvestris L. were investigated along an altitudinal gradient through the only undisturbed tree-line remaining in the Cairngorm Mountains. Saplings at 300–410 m a.s.l. were unlikely to develop to reproductive maturity because of repeated browsing by red deer Cervus elaphus L. By contrast, pines were regenerating successfully in scrub at 531–590 m, where the population included individuals of all ages up to 300 yr. Above 590 m, there grew only saplings aged less than 30 yr and these declined in density with increasing altitude up to 730 m.
The climate at 531–590 m was not so severe as to prevent pines from growing to reproductive maturity. However, it may have been severe enough to restrict the activities of large herbivores and so the pine saplings there escaped the heavy browsing suffered by plants at lower altitude. Presumably zones of successfully regenerating pine scrub might occur more widely in the Cairngorms but for a shortage of seed-bearing trees.     

Isolation of functional RNA from plant tissues rich in phenolic compounds.

A method for the isolation of RNA from different tissues of trees (seedlings, saplings, and adult trees) is described. Using this procedure it is possible to remove large amounts of disturbing polyphenolic compounds from nucleic acids. The method involves an acetone treatment of the freeze-dried and powdered plant material, the use of high salt concentrations in the extraction buffer and an aqueous two-phase system. These steps were combined with the conventional phenol/chloroform extraction and CsCl centrifugation. The method has been successfully applied to the isolation and purification of RNA from pine (Pinus sylvestris L. and Pinus mugo Turr.), Norway spruce (Picea abies L.), and beech (Fagus sylvatica L.). The functional quality of RNA extracted by this procedure has been characterized by its uv spectrum, by agarose gel electrophoresis with ethidium bromide staining, Northern blot hybridization, and in vitro translation.     

Stable isotopic observation of water use sources of Pinus sylvestris var. mongolica in Horqin Sandy Land, China

Since the late 1950s, Mongolian pine (Pinus sylvestris var. mongolica) has been widely planted for vegetation restoration in arid and semi-arid areas in North China. We used stable isotope signals from precipitation, soil water, and xylem water of Mongolian pine trees, which were planted in early 1980s on sand dunes in the east-southern margin of Horqin Sandy Land, to identify water uptake sources of this tree. (1) Stable ¹⁸O isotope composition of the xylem water exhibited little seasonality, suggesting that the trees use a relatively stable water source; (2) the water source of the pine trees primarily came from a soil depth of 20–60 cm (sampling depth up to 60 cm in this study) and the trees might use groundwater when soil moisture became extremely low; and (3) there was not much difference in water sources used by the pine trees grown at the top of the fixed dune and in the inter dune lowland, although these two sites had 3–8 m elevation difference. This study suggests that it is critical for Mongolian pine trees to access relatively reliable and stable water sources to grow in sandy land habitats, and timely recharging of rainwater to the trees’ rooting depth is requisite for avoiding and/or reducing their degradation caused by water shortage.     

Individual-based modeling of the spread of pine wilt disease: vector beetle dispersal and the Allee effect

Pine wilt disease is caused by the pinewood nematode Bursaphelenchus xylophilus, which is vectored by the Japanese pine sawyer beetle Monochamus alternatus. Due to their mutualistic relationship, according to which the nematode weakens and makes trees available for beetle reproduction and the beetle in turn carries and transmits the nematode to healthy pine trees, this disease has resulted in severe damage to pine trees in Japan in recent decades. Previous studies have worked on modeling of population dynamics of the vector beetle and the pine tree to explore spatial expansion of the disease using an integro-difference equation with a dispersal kernel that describes beetle mobility over space. In this paper, I revisit these previous models but retaining individuality: by considering mechanistic interactions at the individual level it is shown that the Allee effect, an increasing per-capita growth rate as population abundance increases, can arise in the beetle dynamics because of the necessity for beetles to contact pine trees at least twice to reproduce successfully. The incubation period after which a tree contacted by a first beetle becomes ready for beetle oviposition by later beetles is crucial for the emergence of this Allee effect. It is also shown, however, that the strength of this Allee effect depends strongly on biological mechanistic properties, especially on beetle mobility. Realistic individual-based modeling highlights the importance of how spatial scales are dealt with in mathematical models. The link between mechanistic individual-based modeling and conventional analytical approaches is also discussed.     

Mountain Pine Beetles Use Volatile Cues to Locate Host Limber Pine and Avoid Non-Host Great Basin Bristlecone Pine

The tree-killing mountain pine beetle (Dendroctonus ponderosae Hopkins) is an important disturbance agent of western North American forests and recent outbreaks have affected tens of millions of hectares of trees. Most western North American pines (Pinus spp.) are hosts and are successfully attacked by mountain pine beetles whereas a handful of pine species are not suitable hosts and are rarely attacked. How pioneering females locate host trees is not well understood, with prevailing theory involving random landings and/or visual cues. Here we show that female mountain pine beetles orient toward volatile organic compounds (VOCs) from host limber pine (Pinus flexilis James) and away from VOCs of non-host Great Basin bristlecone pine (Pinus longaeva Bailey) in a Y-tube olfactometer. When presented with VOCs of both trees, females overwhelmingly choose limber pine over Great Basin bristlecone pine. Analysis of VOCs collected from co-occurring limber and Great Basin bristlecone pine trees revealed only a few quantitative differences. Noticeable differences included the monoterpenes 3-carene and D-limonene which were produced in greater amounts by host limber pine. We found no evidence that 3-carene is important for beetles when selecting trees, it was not attractive alone and its addition to Great Basin bristlecone pine VOCs did not alter female selection. However, addition of D-limonene to Great Basin bristlecone pine VOCs disrupted the ability of beetles to distinguish between tree species. When presented alone, D-limonene did not affect behavior, suggesting that the response is mediated by multiple compounds. A better understanding of host selection by mountain pine beetles could improve strategies for managing this important forest insect. Moreover, elucidating how Great Basin bristlecone pine escapes attack by mountain pine beetles could provide insight into mechanisms underlying the incredible longevity of this tree species.     

Phylogeography of the white-breasted nuthatch (Sitta carolinensis): diversification in North American pine and oak woodlands

Pine and oak woodlands are common North American floral communities with distinct regional species composition. The white-breasted nuthatch (Aves: Sitta carolinensis) is a common resident bird of North American pine and oak woodlands, and is distributed continentally across the highly disjunct distribution of these woodlands. We propose three historical hypotheses to explain the evolution of the white-breasted nuthatch in its principal habitat. (i) The species evolved in situ in the regional pine-oak communities and the isolation of populations in these regions is captured in cryptic genetic variation. (ii) Migration of individuals between regions is frequent enough to maintain the widespread distributions and prevent regional divergence. (iii) The species have recently expanded to occupy their current distributions and an insufficient amount of time has passed for divergence to occur. Phylogenetic analysis of mitochondrial DNA (ND2 gene) variation (N = 216) in the white-breasted nuthatch reveals four reciprocally monophyletic clades concordant with the distribution of the regional North American pine and oak woodlands, and supports hypothesis 1 of in situ evolution of populations in the regional pine and oak communities. Within-clade population structure and demographic history are also discussed.     

Ageing culturally significant relic trees in southeast Queensland to support bushfire management strategies

Appropriate fire management strategies are needed to protect forests and large old ecologically and culturally significant trees in natural landscapes. The aim of this study was to determine the age of large old and relic trees of cultural significance that included Cypress Pine (Callitris columellaris F. Muell.), a species that is sensitive to crown scorching fires in a fire‐prone landscape, and to calibrate a tree‐growth‐rate method for estimating tree age. Twelve large trees were dated using radiocarbon (¹⁴C) dating. The trees are located on North Stradbroke Island (Indigenous name: Minjerribah), southeast Queensland (Australia) in a fire‐prone landscape where recent wildfires have destroyed many large trees. The median tree ages ranged from 155 to 369 years. These results suggest an important role of past Indigenous land management practices in protecting Cypress Pine from crown scorching fires. The tree‐growth‐rate‐based method for estimating tree age generally overestimated the age derived from radiocarbon dating. Bias correction factors were developed for correcting various measures of periodic growth rates. This study provides evidence that appropriate low‐intensity fire strategies have the potential to contribute to the survival of forests and conserve large old trees.