Conifer Branches Research Articles

Relative growth rates of two epiphytic lichens, Lobaria pulmonaria and Hypogymnia occidentalis, transplanted within and outside of Populus dripzones

Overstory Populus has been shown to facilitate establishment by cyano- and cephalolichens on conifer branches within its dripzone; though the mechanisms behind this “dripzone effect” have yet to be elucidated. Here we test the following hypotheses that throughfall from Populus: (i) elevates bark pH; (ii) increases relative growth rate in cephalolichens; and (iii) stimulates their growth through phosphorus (P) fertilization. In southern British Columbia we transplanted the cephalolichen Lobaria pulmonaria (L.) Hoffm. (promoted by dripzones) and the acidophytic chlorolichen Hypogymnia occidentalis L.H. Pike for 14 months to 26 pairs of similar-sized Picea glauca × engelmannii situated within and outside of Populus dripzones. Half of our transplants were fertilized with P. Bark pH was significantly higher on spruce branches within than outside dripzones. Relative growth rate in L. pulmonaria increased with bark pH and was slightly higher within dripzones than outside, consistent with a facilitating effect of Populus on the Lobarion community. By contrast, the addition of P decreased relative thallus area growth in L. pulmonaria and increased relative thallus area growth in H. occidentalis; though a stronger influence on growth could be attributed to variation in canopy cover and tree height. We conclude that cephalolichens in our study area are unlikely to be facilitated by P leached from Populus.

Contributions to the lichen flora of the Hengduan Mountains, China (3). Bryoria divergescens (Parmeliaceae), an overlooked species

Bryoria divergescens, which was previously known only from the 19th century holotype collection, has been rediscovered in various localities in Yunnan and also in Sichuan, southern China. This species should now be considered an endemic to the Hengduan Mountains region. It is characterized by its erect thallus, 3-8 cm tall, main branches 1-2 mm in diam., true lateral spinules, sparse pseudocyphellae, +/- ciliate apothecia, the presence of fumarprotocetraric and lobaric acids. It usually grows on branches of conifers.

Diversity of Shrub-Dwelling Arthropods to Thinning of Young Douglas-Fir Forests in the Pacific Northwest, USA

Abstract We examined an unthinned control stand and three different thinning intensities in 40- to 60-year-old Douglas-fir forests in western Oregon to assess the effects of thinning on the abundance, species richness, and diversity of shrub-dwelling arthropods. Shrub-dwelling arthropods, collected with a bagging technique, decreased significantly as thinning intensity increased in deciduous foliage (vine maple, Acer circinatum Pursh), but arthropods showed no response to thinning on the two types of conifer foliage (Douglas-fir, Pseudotsuga menziesii [Mirb.] Franco and western hemlock, Tsuga heterophylla [Raf.] Sarg.). The species richness and diversity of shrub-dwelling arthropods showed significantly higher values on the coniferous branches than on the deciduous foliage. Functional group composition for the two foliage types revealed consistently different proportions. Deciduous branch supported a higher proportion of sapsuckers and leaf chewers, and conifer branch hosted a higher proportion of predators and detritivores. Nonmetric multidimensional scaling ordination showed a distinct difference between the species assemblages inhabiting the deciduous and conifer branches. The effects of thinning on the arthropods were complex. Seasonal effects on arthropods exceed treatment effects because the species composition in the dry season was very different from that in the wet season. The shrub-dwelling arthropod community reveals little seasonal difference on coniferous branch, but significant differences occur on deciduous branch. In this study, treatment effects were very limited, but our results indicate that as thinning increased, the response of arthropod community on deciduous branch increased more. This large-scale experiment provided an opportunity to assess responses of shrub-dwelling arthropods to levels and patterns of forest management.

Dormouse injuries predispose beech to infection byNeonectria ditissima

SummaryAfter awaking from winter hibernation, the Edible dormouse begins to feed by stripping the bark and the outer part of the xylem from the branches of both broadleaves and conifers. Natural or artificial wounds are essential for the penetration and colonisation of the tissues by the fungal pathogenNeonectria ditissima. This pathogen creates open cankers on beech branches and other broadleaves, which are frequently later infected by wood‐decaying fungi. Because of the high frequencies of both dormouse injuries and branch cankers in a large monospecific beech forest in northern Italy, field and laboratory investigations were conducted to verify whether rodent‐inflicted injuries on beech were a preferred infection point for the pathogen. These studies also examined the susceptibility to infection of the dormouse‐inflicted wounds over time, and the relationships between dormouse damage,Neonectriainfection, and wood decay. The results showed a significant direct correlation between the percentage of infections and their proximity to the wounds, indicating that the parasite localises to sites where there are receptive dormouse injuries. In addition, the susceptibility of the wound was found to diminish with increasing age, disappearing in 120–150 days. The association between dormouse injuries,Neonectriacankers and wood decay was also found to cause approximately half of the frequent beech branch breakages during intense weather events.

A fungal pathogen in time and space: the population dynamics of Beauveria bassiana in a conifer forest

The fungal entomopathogen Beauveria bassiana is ubiquitous in below-ground systems; however, there is a dearth of information on the above-ground diversity, temporal and spatial distribution of this fungus. Therefore, we assessed its occurrence in a conifer forest (Pseudotsuga monziesii and Pinus nigra var. maritima) using selective media to isolate B. bassiana from soil, branch and bark samples collected in October 2005, March and June 2006. Fungal density was the highest at all locations in October, declining in March and June, and absent from conifer branches in June. This above-ground decline most likely resulted from more extreme environmental conditions compared with those below ground. Molecular analyses (ISSR-PCR) indicated that B. bassiana is genetically diverse, comprising both distinct microhabitat-specific and seasonal isolates. The occurrence of dissimilar above- and below-ground isolates suggests that B. bassiana occupies various overlapping niches in these systems.

Hypogymnia recurvaandHypogymnia wilfianaspp. nov., two new lichens from western North AmericaThis paper is one of a selection of papers published as part of the special Schofield Gedenkschrift.

Hypogymnia metaphysodes was first described from Japan and Sakhalin, and later reported from western North America. Here we show that the North American material currently referred to H. metaphysodes differs from that species not only morphologically and chemically, but also in ascospore size and shape. We also show that the North American material is in fact heterogeneous, and can be assigned to two well-defined species here described as new: Hypogymnia recurva sp. nov. and H. wilfiana sp. nov. Both of these lichens contain distinctive secondary metabolites: vittatolic acid in the case of H. recurva, and 2-methylene-3-carboxy-18-hydroxynonadecanoic acid (“apinnatic acid”), reported here for the first time from Hypogymnia , in H. wilfiana. Both of our new species are so far known only from western North America, where they occur primarily as epiphytes on the branches of conifers. Hypogymnia metaphysodes s. str. has not yet been reliably reported from this region and should be excluded from the North American lichen flora.

Cellulose fibrils direct plant organ movements

The secondary plant cell wall is a composite of cellulose and a water-swelling matrix containing hemicelluloses and lignin. Recent experiments showed that this swelling capacity helps generating growth stresses, e.g., in conifer branches or in the stem when subjected to side loads. A similar mechanism also provides motility to wheat seeds. Here we study a simple mechanical model for the cell wall which--in contrast to earlier models--considers extensible cellulose fibrils in an isotropically swelling matrix. Depending on the detailed architecture of the cellulose fibrils, the model predicts that swelling may lead either to significant compressive or tensile stresses or to large movements at low stresses. The model reproduces most of the experimental observations in the wood cells and in the awns of wheat dispersal units. It is also simple enough to provide general guidelines for designing the architecture of fibres in an isotropic swelling medium to generate movements and forces of various kinds and directions.

Foliage influences forced convection heat transfer in conifer branches and buds

Conifer foliage structures affect branch and bud temperature by altering the development and convective resistance of the thermal boundary layer. This paper examines foliage effects on forced convection in branches and buds of Picea glauca (Moench) Voss and Pinus contorta Dougl. Ex. Loud., two species that represent the range of variation in foliage structure among conifers. Forced convection is characterized by a power law relating Nusselt (heat transfer) and Reynolds (boundary layer development) numbers. Data were collected in a laminar flow wind tunnel for free stream velocities of 0.16-6.95 m s(-1). Scaling parameters were compared against literature values for silver cast branch replicas, a bed of real foliage, cylinders, and tube banks. Foliage structures reduced Nusselt numbers (heat transfer) relative to cylinders, which are typically used to approximate leafless branches and buds. Significantly different scaling relationships were observed for all foliage structures considered. Forced convection scaling relationships varied with foliage structure. The scaling relationships reported here account for variation within populations of branches and buds and can be used to characterize forced convection in a forest canopy.

Hydraulic and anatomical properties of light bands in Norway spruce compression wood

Compression wood (CW), which is formed on the underside of conifer branches, exhibits a lower specific hydraulic conductivity (k(s)) compared with normal wood. However, the first-formed tracheids of an annual ring on the underside of a conifer branch often share several properties with normal tracheids, e.g., thin cell walls and angular cross sections. These first-formed tracheids appear bright when observed by the naked eye and are therefore called light bands (LB). In this study, hydraulic and related anatomical properties of LBs were characterized and compared with typical CW and opposite wood (OW). Measurements were made on branches of Norway spruce (Picea abies (L.) Karst.). Specific hydraulic conductivity was measured with fine cannulas connected to microlitre syringes. Micro- and ultrastructural analysis were performed on transverse and radial longitudinal sections by light and scanning electron microscopy. Xylem areas containing both typical CW and LBs had a k(s) 51.5% that of OW (7.95 +/- 0.97 m(2) s(-1) MPa(-1) x 10(-4)), whereas k(s) of pure CW was only 26.7% that of OW. The k(s) of LBs (6.38 +/- 0.97 m(2) s(-1) MPa(-1) x 10(-4); 80.3% of OW) was estimated from these k(s) values because the cannulas were too wide to measure the k(s) of LBs directly. Mean lumen area of first-formed tracheids on the underside of branches was 65.7% that of first-formed tracheids in OW and about three times that of CW. Light-band tracheids exhibited a bordered pit frequency of 42.7 +/- 1.3 pits mm(-1), which was three times that in CW and 1.6 times that in OW. Bordered pit apertures in LB tracheids (9.15 +/- 0.60 microm(2)) were 1.7 times wider than those in CW and similar in aperture to those in OW. The high k(s) of LBs was correlated with their wide tracheid lumina, high pit frequency and wide pit apertures. We therefore suggest that LBs have a primarily hydraulic function within the mechanically optimized CW region. This might be important for supplying water to living tissues on the underside of branches, as well as to other distal areas along water transport pathways following the spiral grain of wood.

Adaptation or random change? The evolutionary response of songs to substrate properties in lacewings (Neuroptera: Chrysopidae: Chrysoperla)

Green lacewings of the carnea group of Chrysoperla constitute a large complex of cryptic species that differ principally in their substrate-borne, vibrational mating signals. Sexual selection has very likely contributed to their recent and rapid divergence. Some theoretical models require that evolutionary environmental adaptation assist sexual selection during speciation, whereas others do not. Here, we looked for evidence of adaptation having shaped the song phenotypes of lacewing species that have different habitat preferences. First, we looked for a pattern of convergent song evolution, predicted under a hypothesis of substrate adaptation during speciation. Focusing on species confined to conifers versus those on herbaceous vegetation, we found several examples where song phenotype showed a correlation with substrate that was independent of phylogeny. We also present results of experimental tests of environmental adaptation using C. downesi and C. plorabunda , which are conifer and meadow species, respectively. Experiments addressing purely biomechanical aspects of substrate transmission showed that the songs of C. downesi and C. plorabunda propagated equally well in either grass stems or conifer branches. Behavioural experiments showed, furthermore, that individuals did not discriminate between conspecific songs played through the ‘correct’ versus the ‘incorrect’ substrate. We conclude that the pattern suggestive of environmental adaptation of lacewing songs to their substrates was not supported by experiments that explicitly tested for adaptation. The carnea group of cryptic species may be one of the few examples where sexual selection has acted on arbitrary differences in premating signals, resulting in speciation.

Long-term fluctuations of a caribou population revealed by tree-ring data

We used a dendroecological approach that involved examination of debarking lesions (trampling scars) produced by caribou (Rangifer tarandus) hooves on surficial roots and low branches of conifers to assess caribou activity in the summer range of the Rivière George caribou herd in northeastern Quebec-Labrador over the last 100 years. We deduced changes in caribou activity from the age-frequency distributions of trampling scars in three widely spaced (>100 km) old-growth conifer stands in the Rivière George area. We used the fluctuating patterns in age distributions, described by residuals of the log-linear regression, as an index of the number of trampling scars with time. This index indicated that caribou activity at the three sites followed a general decreasing trend from the turn of the last century to around 1950. There were two stages of rapid decline, around 1905-1915 and 1940, separated by a minor increase in the 1920-1930s. A sustained increase occurred from the 1950s to the 1980s. A comparison with survey and historical data for caribou suggested that these fluctuations in this common signal of activity at the three sites resulted mainly from fluctuations in caribou abundance that occurred throughout the 20th century in northeastern Quebec-Labrador. The increase in caribou activity during the 1920-1930s suggested by the frequency of trampling scars is not reported in the historical record. Caribou trampling scars on conifers may offer a new opportunity to assess large-scale spatial and temporal population trends of caribou in subarctic and boreal zones.

Cyanolichen Distribution in Young Unmanaged Forests: A Dripzone Effect?

Abstract In young forests of humid south-central British Columbia, Lobaria pulmonaria and other epiphytic “cyanolichens” attain optimum development over the lower branches of conifers growing within the dripzone of Populus. To account for this, we propose the existence of a “dripzone effect”, in which nutrient-rich leachates from the upper branches of Populus enhance the pH of nearby conifers to the benefit of cyanolichen colonization. The dripzone effect is presumably most pronounced in stands located over nutrient-rich soils, in which Populus plays a pivotal role in the early establishment of nitrogen-fixing epiphytic cyanolichens. This phenomenon is assumed to be widespread, but it apparently leads to colonization of conifers by cyanolichens only in humid regions not subject to acid rain. Though the presence of cyanolichens on trees belonging to the Pinaceae is probably indicative of allochthonous nutrient enrichment wherever it occurs, we stress that the dripzone effect is only one of many mechanisms ...

Long-term fluctuations of a caribou population revealed by tree-ring data

We used a dendroecological approach that involved examination of debarking lesions (trampling scars) pro- duced by caribou (Rangifer tarandus) hooves on surficial roots and low branches of conifers to assess caribou activity in the summer range of the Riviere George caribou herd in northeastern Quebec-Labrador over the last 100 years. We deduced changes in caribou activity from the age-frequency distributions of trampling scars in three widely spaced (>100 km) old-growth conifer stands in the Riviere George area. We used the fluctuating patterns in age distributions, described by residuals of the log-linear regression, as an index of the number of trampling scars with time. This index indicated that caribou activity at the three sites followed a general decreasing trend from the turn of the last century to around 1950. There were two stages of rapid decline, around 1905-1915 and 1940, separated by a minor increase in the 1920-1930s. A sustained increase occurred from the 1950s to the 1980s. A comparison with survey and historical data for caribou suggested that these fluctuations in this common signal of activity at the three sites resulted mainly from fluctuations in caribou abundance that occurred throughout the 20th century in northeastern Quebec-Labrador. The increase in caribou activity during the 1920-1930s suggested by the frequency of trampling scars is not reported in the historical record. Caribou trampling scars on conifers may offer a new opportunity to assess large-scale spatial and temporal population trends of caribou in subarctic and boreal zones. 1790

Acute necrotizing pneumonia 16 years after aspiration of a conifer branch

Acute necrotizing pneumonia 16 years after aspiration of a conifer branch

Theoretical study of variables affecting the export of assimilates from branches of Picea.

A theoretical analysis was done to identify the features of conifer branch development, based on a model for Picea sitchensis (Bong.) Carr., that affect the ability to export assimilates, assuming (i) a branch's requirement for assimilates is determined by its need for mechanical support, and (ii) the production of assimilates is a simple function of total shoot length. There were three salient findings. First, there is an optimum and maximum shoot length for assimilate export by unbranched shoots. Second, the less a shoot extends itself each year, the more assimilate it may export, all else being equal. Third, there is a larger surplus of assimilates for export when a shoot develops laterals. A combination of lateral branching, deflection and decreased elongation can enable branches to continue growing and exporting assimilates for many years, as occurs at the bases of tree crowns.

Bending of a conifer branch at subfreezing temperatures: implications for snow interception

Ice crystals in cells of frozen wood increase the wood's modulus of elasticity so that branches become more rigid at colder temperatures. As temperature increases after a snowstorm, melting of crystals within the cells allows increased bending of branches under intercepted snow loads. Measurements of the force that produced a 10-cm deflection of branch tips of subalpine fir (Abieslasiocarpa (Hook.) Nutt.) and lodgepole pine (Pinuscontorta var. latifolia Engelm.) showed a linear decrease as temperature rose from −12 to 0 °C. Model predictions for the bending of a tapered branch supported the hypothesis that increased bending can explain unloading of intercepted snow under certain conditions when warming occurs after snowstorms.

Branch-cutting behavior by the vole (Microtus pennsylvanicus)

While investigating the preferences of meadow voles (Microtus pennsylvanicus) toward various coniferous species, we noted they often cut the branches of young trees, and then left them lying on the snow for two days or more before eating them completely. We tested whether this "behavioral manipulation" of a potential food resource resulted in a decrease in the level of secondary metabolites in branches. We found that after being cut for more than three days, the branches of young conifers had significantly less phenolics and condensed tannins. These postmanipulation levels of secondary metabolites were similar to those found in preferred summer food resources. Voles were thus capable of transforming a low-quality resource into one that was more compatible with their feeding patterns and detoxification mechanisms.

Entropy budget of conifer branches

From energy budget data for a branch of ponderosa pine given by Gates, Tibbals and Kreith, entropy fluxes into or out of the branch due to solar radiation, infrared radiation, transpiration and convection are calculated. Net entropy flow into the branch is negative. Assuming that the entropy in the branch is at steady state, the entropy production in the branch of ponderosa pine is calculated and shown to be positive. A positive entropy production indicates that the Second Law of Thermodynamics is certainly valid in the branch. Entropy productions in other conifers, blue spruce and white fir, and in a single pine needle in a horizontal position are also calculated. The entropy production (Sprod) increases linearly with the solar energy absorbed by the plant surface (Esolar); Sprod≈(30.6 Esolar)×10−4. The ratio (Sprod/Esolar) does not differ between deciduous leaves reported earlier and conifer branches. The theorem of oscillating entropy production proposed earlier holds also for conifer branches and will be of universal nature, applicable to all plant leaves.

Early Holocene thermal maximum in western North America: New evidence from Castle Peak, British Columbia

Conifer logs and branches of early Holocene age are common on the surface and in sediments above timberline at Castle Peak in the southeastern Coast Mountains of British Columbia. A study of this wood and associated peat and colluvium has shown that local timberline from 9.1 to 8.2 ka was at least 60 m, and perhaps more than 130 m, higher than today. Mean growing-season temperature at Castle Peak during this period thus may have been 0.4-0.8°C warmer than at present. This is consistent with theoretical considerations based on Milankovitch forcing of climatic change and is supported by other paleoecological data from the southern Canadian Cordillera and adjacent northwestern United States. A generally warm climate may have persisted until about 5-6 ka, followed by late Holocene cooling.

A Late Permian flora of Pechora affinity in North Greenland

Late Permian plant impressions comprising six taxa have been obtained from the North Greenland fold belt. Rhipidopsis, a probable ginkgophyte, occurs together with the fems Prynadaeopteris venusta Radczenko and Pecopteris (Asterotheca?) cf. P. (A?) helenaeana Zalessky, the sphenophyte Sphenophyllum cf. S. biarnicum Zalessky the cordaitean Cordaites cf. C. sylovaensis (Neuburg) Meyen and a possibie conifer branch fragment. The assemblage invites comparison with the Pechora flora of the northem Pre-Urals, and also with that of Mongolia and north-eastern China. These may be warm temperate floras on approximately the same palaeolatitude.