Abies - an overview | ScienceDirect Topics (2022)

abies somatic embryogenesis as a model system to study developmental PCD is that it enables the investigator to manipulate cell death by specific agents that either stimulate or inhibit distinct processes of the cell-death pathway (Table II).

From: Current Topics in Developmental Biology, 2005


David J. Magee PhD, BPT, CM, in Orthopedic Physical Assessment, 2021

Feagin Test (Abduction Inferior Stability [ABIS] Test).339

The Feagin test is a modification of the sulcus sign test with the arm abducted to 90° instead of being at the patient’s side (Fig. 5.84). Some authors consider it to bethe second part of the sulcus test.358 The patient stands with the arm abducted to 90° and the elbow extended and resting on the top of the examiner’s shoulder. The examiner’s hands are clasped together over the patient’s humerus, between the upper and middle thirds. The examiner pushes the humerus down and forward (seeFig. 5.84A). The test can also be done with the patient in a sitting position. In this case, the examiner holds the patient’s arm at the elbow (elbow straight) abducted to 90° with one hand and arm holding the arm against the examiner’s body. The other hand is placed just lateral to the acromion over the humeral head. Ensuring the shoulder musculature is relaxed, the examiner pushes the head of the humerus down and forward (seeFig. 5.84B). Doing the test this way often gives the examiner greater control when doing the test. A sulcus may alsobe seen above the coracoid process (Fig. 5.85). A look of apprehension on the patient’s face indicates a positive test and the presence of inferior capsular laxity.359 If both the sulcus sign and Feagin test are positive, it is a greater indication of multidirectional instability rather than just laxity, but it should only be considered positive if the patient is symptomatic (e.g., pain/ache on activity, shoulder does not “feel right” with activity).359 This test position also places more stress on the inferior glenohumeral ligament.

Programmed Cell Death in Plant Embryogenesis

Peter V. Bozhkov, ... Maria F. Suarez, in Current Topics in Developmental Biology, 2005

D The Whole Pathway of Cell Dismantling

In the model system of P. abies somatic embryogenesis, the early embryos establish a gradient of autophagic PCD along their apical–basal axis, thus displaying all the successive stages of cell death, from commitment to PCD in the embryonal tube cells to cell corpses with cleaned protoplasts at the basal end of the embryo suspensor (see Section II.B; Filonova et al., 2000a; Smertenko et al., 2003). Shown in Fig.8 is a schematic representation of the whole cytological process of cell dismantling occurring in an apical-to-basal gradient in early embryos of P. abies. We do not include mitochondrial changes, because mitochondria look morphologically intact till very late in this PCD (Filonova et al., 2000a). Even though mitochondrial permeability transition appears to be involved (Table II; our unpublished data), more extensive studies are required to provide compelling evidence for the role of mitochondria in the activation of autophagic cell death (see also Lemasters et al., 1998).

Abies - an overview | ScienceDirect Topics (1)

Figure8. Cytological characteristics of successive stages of autophagic PCD occurring in apical-to-basal gradient in early embryos of Picea abies. Stage 0 applies to meristematic cells of the embryonal mass (EM), which divides asymmetrically to produce two daughter cells with contrasting developmental fates. One daughter cell retains meristematic identity and remains within EM, whereas its sister cell undergoes terminal differentiation to becomes an embryonal tube (et) cell, which is committed to death (stage I). This cell is added to the suspensor, composed of several layers of dying cells with increased age reflected by increased degree of autodestruction (stages II to V) toward the basal end of the suspensor. The scheme was drawn based on studies of Filonova et al. (2000a,b) and Smertenko et al. (2003). (See Color Insert.)

Stage 0 applies to living meristematic cells of the embryonal mass. These cells are small and have isodiametric shape. They contain dense cytoplasm and a rounded nucleus, which occupies a substantial proportion of the protoplast. F-actin and microtubules in these cells form fine networks; MAP-65 is bound to a subset of microtubules (Fig.8).

The cells located in the basal part of embryonal mass divide asymmetrically in the plane perpendicular to the apical–basal axis of the embryo and give rise to two daughter cells with fundamentally different developmental fates. One daughter cell retains meristematic identity and remains in the embryonal mass (stage 0), whereas its sister cell elongates and becomes a terminally differentiated tube cell, which is added to the growing suspensor (see Section II.B; Fig.8). The earliest cytological changes in the tube cells are formation of autophagosomes from the Golgi and proplastids, the major hallmark of the commitment phase of the PCD (stage I).

The execution phase of the PCD includes stages II to V, corresponding to the successive layers of cells in the suspensor starting already from the tube cells (Fig.8). During stage II, MAP-65 dissociates from the microtubules and the microtubule network is disrupted, while F-actin forms thick longitudinal bundles. The cells at stage II are much larger than the cells at the previous stages and they expand further as they progress toward stage III. At the same time, autophagosomes increase in size and number, which sometimes leads to the formation of small lytic vacuoles. It is during stage III when the earliest nuclear envelope events, nuclear lobing, and dismantling of nuclear pore complex, occur. By this stage, several large lytic vacuoles occupy most of the cell volume. No microtubules are left by this stage and only microtubule fragments can be seen in the cytoplasm. In contrast to microtubules, the actin is still preserved in the suspensor cells and forms thick longitudinal cables. By stage IV, the nuclear DNA is fragmented and the nuclei are sometimes segmented. The cells at this stage contain a thin layer of the cytoplasm confined between the plasma membrane and the tonoplast of a large lytic vacuole. Once the vacuole collapses, the remaining cytoplasm is degraded, leaving a hollow-walled cell corpse (stage V; Fig.8).

Autophagic PCD in the suspensor is a slow process; it takes approximately 5 days for complete autodestruction of an individual suspensor cell in P. abies. The transition from one stage of the PCD to the next stage takes approximately 24 hours (i.e., the frequency of the addition of the new layers of cells to the suspensor; Filonova et al., 2000b), with the only exception being the transition from the penultimate to the last stage (i.e., rupture of the tonoplast and the clearance of the remaining cytoplasm), which is apparently a very rapid process (see also Obara et al., 2001). The PCD pathway resembling the one shown in Fig.8 for suspensor also operates in the other embryonic cell deaths, including death of the PEM cells (Filonova et al., 2000a) and abortion of the whole subordinate embryos in polyembryonic seeds (Filonova et al., 2002).

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Cynthia C. Chernecky PhD, RN, CNS, AOCN, FAAN, in Laboratory Tests and Diagnostic Procedures, 2013

Ankle-Brachial Index (ABI)—Diagnostic


Pressure IndexInterpretation
0.75-0.85Mild occlusive disease
0.50-0.75Intermittent claudication
0.30-0.50Severe disease: rest pain may occur; pregangrenous state
0.20-0.30Poor probability for tissue healing or limb viability unless compensation by collateral blood flow occurs
<0.20Ischemic or gangrenous extremities


Assessment of arterial blood flow in clients with peripheral vascular disease; monitoring postoperative flow in the lower extremities after vascular surgery such as femoral bypass or after aortofemoral bypass from iliac occlusion; assessment of severity of peripheral vascular disease; predicting carotid artery stenosis. Cilostazol (Pletal) increases ABI at rest.


The ABI is a mathematically calculated ratio of the systolic pressure at a pulse point in a lower extremity with peripheral vascular disease as compared to the systolic pressure of the brachial artery. The index provides a quick, noninvasive assessment of how much arterial blood is perfusing the extremity. Typically an ABI that increases by at least 0.15 (15%) after vascular surgery indicates that the surgery was successful. A baseline in women with an ABI of <0.60 indicates significantly higher probability of developing severe disability for walking specific outcomes (such as walking a quarter of a mile).

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Obtain a dual-frequency Doppler ultrasonograph, a marker, two sphygmomanometers, and ultrasonic gel.


Client is positioned supine.


The femoral, popliteal, dorsalis pedis, and posterior tibial pulse points in both lower extremities are palpated and identified with a marker.


The sphygmomanometer cuff is placed proximally to the marked site. If the flow is being assessed at the knee, the cuff is placed proximally to the popliteal pulse. If the flow is being assessed at the ankle, the cuff is placed proximally to the ankle.


Ultrasonic gel is placed over the marked site (popliteal, posterior tibial, or dorsalis pedis), and the Doppler flow signal is identified.


With the Doppler in place, the sphygmomanometer cuff is inflated until the Doppler flow signal disappears.


The cuff is slowly deflated, and the pressure at which the Doppler tone is again audible is noted and recorded.


The brachial systolic blood pressure in both arms is measured with a Doppler scanner, and the highest pressure is selected for use in the ABI calculation.


The ABI ratio is calculated with the following equation:


Evolution and Diversity of Woody and Seed Plants

Michael G. Simpson, in Plant Systematics (Second Edition), 2010



Pine family (Latin name for pine). 12 genera/ca. 225 species. (Figures 5.18, 5.20, 5.21)

Abies - an overview | ScienceDirect Topics (2)

FIGURE 5.21. CONIFERAE—PINOPSIDA. Pinaceae. A,B. Abies bracteata, bristlecone fir. C. Abies concolor, white fir. D. Abies fabri, Faber's fir, seed cone. E. Abies grandis, grand fir, vegetative shoot. F. Cedrus sp., cedar, with short shoots and erect seed cones. G. Picea orientalis, oriental spruce. H–J. P. sitchensis, sitka spruce. H. Shoot with stiff, pungent leaves. I. Twig with persistent, knob-like, leaf bases (distinctive of spruces). J. Seed cone. K–L. Pinus coulteri, coulter pine, having most massive pine cones. M. Pinus muricata, with serotinous cones, opening only after fire. N. Pinus lambertiana, sugar pine, the tallest pine, with longest cones. O. Pinus sabiniana, gray pine. P,Q. Pseudotsuga menziesii, douglasfir, with bracts elongated from ovuliferous scales. R,S. Hesperopeuce [Tsuga] mertensiana, mountain hemlock, with pendant seed cones.

The Pinaceae consist of resinous, monoecious trees (rarely shrubs). The roots are ectomycorrhizal. The leaves are simple, spiral, sessile or short-petiolate, usually evergreen [deciduous in Larix and Pseudolarix], linear to long-acicular; photosynthetic leaves in specialized, short shoots in some taxa (Cedrus, Larix, and Pseudolarix; modified as indeterminate fascicles in Pinus), with nonphotosynthetic, scale-like leaves sometimes borne on long shoots. The pollen cones are small, solitary or clustered, the microsporophylls spiral, each with two abaxial microsporangia, the pollen usually 2-saccate. The seed cones are lateral or terminal, usually woody, sometimes serotinous (not opening at maturity, seed release sometimes induced by fire), the ovuliferous scales spiral, each with usually two, adaxial ovules, the subtending bracts free from the ovuliferous scale, bracts sometimes elongate (e.g., Pseudotsuga). The seeds are usually two per ovuliferous scale, inverted, usually winged, the embryo with multiple cotyledons; germination is epigeal [rarely hypogeal]. One copy of the inverted repeat of the chloroplast DNA is missing in Pinaceae.

The 12 genera of the Pinaceae are: Abies (fir, 46 sp., N. Temperate, S.E. Asia, C. America), Cathaya [Tsuga] (1 sp., C. argyrophylla, China), Cedrus (cedar, 2–4 spp., N. Africa to Asia), Hesperopeuce [Tsuga] (1 sp., H. mertensiana, W. North America), Keteleeria (3 spp., S. China, Taiwan, S.E. Asia), Larix (larch, 10 spp., cool N. Hemisphere), Nothotsuga [Tsuga] (1 sp., N. longibracteata, China), Picea (spruce, 34 spp., cool N. Hemisphere), Pinus (pine, 110 spp., N. Temperate to South America, Indonesia), Pseudolarix (golden-larch, 1 sp., P. amabilis, China), Pseudotsuga (Douglas-fir, 4 spp., E. Asia and W. North America), and Tsuga (spruce, 9 spp., Temperate North America and E. Asia).

The Pinaceae is distributed in mostly temperate regions of the Northern Hemisphere (one Pinus spp. entering the S. Hemisphere), including most of North America, West Indies, northern Africa, and much of Eurasia. The family is of great economic importance, including very important lumber/timber trees (uses for electrical/telegraph/telephone poles, many used traditionally in wood ships) and wood pulp trees (used, e.g., in paper production), sources of turpentine, gums, resin (e.g., Abies balsamea, balsam fir), oils (used for scent and medicinally), food (seeds of Pinus spp., piñon/pignolias), and many other products (often used industrially), plus numerous cultivated ornamentals (including Christmas trees). Certain Pinus spp., originally introduced for timber or pulp, have become serious weeds in some areas. Pinus longaeva, the bristlecone pine, includes the oldest, single (nonclonal) organisms on earth, some over 5000 years old. See Page (1990i) for general information, Gernandt et al. 2008 for a phylogenetic analysis, and Gernandt et al. 2005 for a study of the largest genus, Pinus.

The Pinaceae are distinctive in being trees [very rarely shrubs] with simple, linear to acicular, spiral leaves, relatively small pollen cones, with two abaxial microsporangia per microsporophyll, and seed cones with woody, ovuliferous scales, each usually bearing two adaxial, inverted ovules/seeds, the seeds usually winged, embryos with multiple cotyledons.

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Chemical Ecology and Phytochemistry of Forest Ecosystems

Axel Schmidt, ... Jonathan Gershenzon, in Recent Advances in Phytochemistry, 2005


Among the proteinaceous plant defenses are chitinases, a group of enzymes that hydrolyze the 1,4-N-acetyl-d-glucosamine (GlcNAc) linkages of chitin, a component of cell walls of higher fungi. Hydrolysis of chitin results in the swelling and lysis of the hyphal tips,65,66 and the chitinolytic breakdown products generated can act as elicitors of further defense reactions in plants.67 Proof of the role of chitinases in plant defense comes from studies in which chitinases were constitutively overexpressed in transgenic plants leading to increased resistance against pathogens in vivo.68,69 However, chitinases can also hydrolyze other substrates, such as arabinogalactan proteins, rhizobial Nod factors, and other lipochitooligosaccharides,70,71 and so may have roles in plants other than defensive ones. Chitinases have been divided into two families (18,19) of glycosylhydrolases (E.C. on the basis of their hydrolytic mechanisms, and into seven classes (class I-VII) based on their primary structure.67,72 Within an individual plant, chitinases are present as multiple isoforms that differ in their size, isoelectric point, primary structure, cellular localization, and pattern of regulation73-75 and function (e.g.70).

In conifers, chitinases have been reported to be induced by pathogen attack and wounding in both P. abies and Pinus elliottii.75-79 Induction occurs at the level of the transcript, the protein, and the active enzyme. Based on EST sequences from a cDNA library prepared from the bark of methyl jasmonate-sprayed P. abies sapling stems, we cloned genes for class I, II, and IV chitinases whose expression changed after mature trees were infected with Heterobasidion annosum.75 The role of these chitinases in resistance was demonstrated by showing that a P. abies clone resistant to H. annosum had more rapid temporal and spatial accumulation of class II and IV chitinase gene transcripts than a susceptible clone in areas immediately adjacent to inoculation.75 Data for the class IV gene is given in Fig.1.11. Similarly, Pinus elliottii seedlings resistant to the fungal pathogen Fusarium subglutinans f. sp. pini accumulated chitinase class II transcripts faster than susceptible seedlings.78 Resistant plants may perceive the pathogen faster and have more efficient signaling mechanisms than susceptible plants.

Abies - an overview | ScienceDirect Topics (3)

Figure1.11. Relative gene expression profiles of PaChi4, a class IV chitinase, and pathogen colonization levels in bark of two Norway spruce clones following inoculation with Heterobasidion annosum. The bark around the inoculation site was spatially sampled 3 and 14days after inoculation. Clone 409 is highly susceptible and clone 589 is moderately resistant to this pathogen. The transcript levels of the chitinase in clone 409 at the time of inoculation (shown at 0mm distance from inoculation) were used as a reference transcript level and defined as the 1x expression level, and the transcript levels of all the other samples are expressed as the fold change over this reference level. Pathogen colonization (Path. col.) was measured as the ratio of pathogen to host DNA. Each data point represents the mean of two ramets. For further details, see Hietala et al. (2004).

The presence of local and systemic signaling cascades involved in inducing defenses in P. abies has been suggested based on the systemic expression of peroxidases and chitinases following pathogen infection along with associated anatomical changes.50,80,81 The radial and vertical rates of signal movement in different tissues of conifers as well as the components of signal transduction pathways are not well known. In stems, terpene resin-containing-traumatic ducts are induced by fungal inoculation with a signal that moves away from the inoculation point at 2.5cm per day in the axial direction.49 In needles of seedlings, chitinolytic activity increased within 2 to 4days after inoculation with the root pathogen Rhizoctonia, sp.79 For chitinase expression, as for terpene induction as discussed above, jasmonates are clearly a component of the signal transduction cascade in both pine and spruce, as is ethylene in other Pinaceae.82

Many aspects of the defensive function of conifer chitinases remain to be clarified. For example, the multiple chitinases induced by infection probably are not redundant defense enzymes based on data from angiosperms, but instead are complementary hydrolases with synergistic action on N-acetylglucosamine-containing substrates.70 Of the class IV chitinases, at least one member has been proposed to release chito-oligosaccharides from an endogenous substrate in P. abies, promoting programmed cell death needed for proper embryo development.83 Notably, a practically identical class IV chitinase of P. abies shows differential spatiotemporal expression in bark among clones that display variation in resistance to H. annosum.75 This raises the question of whether certain conifer chitinases might have an indirect role in host defense by eliciting programmed cell death through the release of elicitors from an endogenous substrate. In contrast, the class III chitinases are hypothesized to promote symbiotic interaction with ectomycorrhizal fungi by fragmenting chitin derived elicitors and thereby preventing induction of host defense responses.84 Kinetic studies of chitin hydrolysis by purified conifer chitinases, genetic manipulation of chitinase levels in intact plants, and direct application of purified chitinases to plant tissue should help to elucidate their roles in both defense and developmental processes of conifers.

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PAUL F. CANNON, BRIAN C. SUTTON, in Biodiversity of Fungi, 2004


The large number of fungi that are host- or substratum-specific, combined with the fact that plants frequently occupy well-defined ecological niches, suggests that estimates based on the ratios of plant to fungal species may provide the best working hypotheses of total diversity for planning inventories. Even so, such estimates must be used cautiously, especially when incomplete surveys are being considered. The diversities associated with selected plant species are listed in Table 11.1. Many of the earlier studies were not intended to be comprehensive, focusing primarily on species succession rather than diversity. The number of fungi associated with an individual plant species may be quite high, even with incomplete sampling.

TABLE 11.1. Fungal Diversity Associated with Dead Tissues of Selected Species of Plants

Plant speciesPlant partNo. fungal speciesReference
Abies albaLeaf95Aoki et al. (1992)
Abies firmaLeaf104Aoki et al. (1990)
Acanthus ilicifoliusDecayed tissue130Vrijmoed et al. (1995)
Agropyron pungensDebris98Apinis and Chesters (1964)
Alchornea triplinerviaSubmerged leaves81Schoenlein-Crusius and Milanez (1995)
Atlantia monophyllaLeaf73Subramanian and Vittal (1979a, 1979b)
Carpinus carolinianaLiving and dead bark155Bills and Polishook (1991)
Carex paniculataLeaf litter60Pugh (1958)
Castanea sativaCupule&gt;27*Sutton (1975)
Eucalyptus regnansLeaf litter&gt;24Macauley and Thrower (1966)
Fagus sylvaticaLeaf29Hogg and Hudson (1966)
Gymnosporia emarginataLeaf52Subramanian and Vittal (1980)
Helianthus annuusAchene98Roberts et al. (1986)
Heliconia mariaeDecaying leaves56–98Bills and Polishook (1994)
Heracleum sphondyliumStem51Yadav (1966)
Juncus roemerianusDead leaves86J. Kohlmeyer (personal communication)
Laurus nobilisLeaf137Kirk (1983, personal communication)
Nypa fruticansLeaf63Hyde and Alias (2000)
Pinus sylvestrisLeaf120Hayes (1965)
Pinus sylvestrisLeaf70Kendrick and Burges (1962)
Pinus sp.Leaf73Tokumasu et al. (1994)
Pinus sylvestrisDecaying leaves127Tokumasu et al. (1997)
Pteridium aquilinumPetiole114Frankland (1966)
Shorea robustaLeaf litter38Bettucci and Roquebert (1995)
Quercus germana, Q. sartorrii, Liquidambar styracifluaLeaf46Heredia (1993)

Frankland's (1966) study of the succession of fungi colonizing dead Pteridium aquilinum rachides remains one of the most influential. She found a total of 114 fungal species. Some recent studies have charted similar or greater levels of diversity. Cornejo and colleagues (1994) reported the recovery of about 500 species of fungi from leaf litter of only six tree species in Panama, although their methodology might not have accurately discriminated litter fungi from soil fungi. Bills and Polishook (1994), using a particle filtration method, recorded between 56 and 98 species of microfungi for samples derived from individual leaves of Heliconia mariae from Costa Rica. Roberts and associates (1986) isolated 98 fungal species from achenes (“seeds”) of cultivated sunflowers (Helianthus annuus). Aoki and co-workers associated more than 90 fungal species with litter from each of two species of Abies in Germany and Japan (Aoki et al. 1990, 1992). Other recent studies have reported relatively low levels of diversity. Bettucci and Roquebert (1995), for example, identified only 38 taxa from leaf litter of Shorea robusta in Malaysia. That number may in part reflect deficiencies in experimental technique; their incubation of dilution plates at 25°C or 35°C and use of high-nutrient media probably resulted in overgrowth by ruderal saprobes. The high proportion of species detected from genera such as Trichoderma, Gliocladium, and Penicillium suggests that this was the case.

There is little evidence that even the more detailed studies of fungal diversity associated with litter of particular plant species have produced a near-complete inventory. Perhaps the most comprehensive survey available is one made by P. M. Kirk who carried out a series of direct observations of fungi on leaf litter of Laurus nobilis (Lauraceae; Kirk 1981, 1982, 1984). He identified 137 species of microfungi from 44 collections of leaf litter made over a period of 12 years in the southern United Kingdom. Because data were obtained by one person, inconsistencies of observations and their interpretations associated with multiple collectors and identifiers are reduced. We produced a rarefaction curve (Fig. 11.1A) for his data by plotting cumulative species number against cumulative number of collections (P. F. Cannon and B. C. Sutton, unpublished data). It suggests that, at least for this host in the southern United Kingdom, the total number of species of associated microfungi is likely to be about 150, although use of a different sampling technique might reveal another suite of fungi. The data also show (Fig. 11.1B) that no species was found in more than 75% of the 44 samples, that 35% of the species were found only once, and that a majority of species (64%) was found in less than 9% of the samples. Those data strongly suggest that many species of microfungi are rare, although lack of knowledge of host specificity and the fact that Laurus nobilis is not native to Britain make such interpretations less reliable.

Abies - an overview | ScienceDirect Topics (4)

FIGURE 11.1. Fungi from Laurus leaf litter in the United Kingdom. A. Rarefaction curve showing cumulative species of fungi against cumulative number of collections. B. Frequency diagram of incidence of fungal species.

The estimates provided earlier in this section and those in Table 11.1 suggest that the number of microfungi associated with the litter for a plant species is likely to range well over 100. In Kirk's study, and in those listed in Table 11.1, a large proportion of the species recovered were wide-spectrum saprobes. Some crude estimates of the diversity of host-specific species might be attained by combining those disparate character sets, but variations in species concepts and sampling techniques and the large number of incompletely identified taxa included in each study would render any estimates obtained of very uncertain value. Studies by Polishook and associates (1996) on the complementarity of fungal species isolated from litter of two plant species growing together in a forest in Puerto Rico addressed the question of specificity and ubiquity of microfungi on different host plants. Additional studies of the variation in complementarity between different host species and the effects that are genuinely host-related versus those that primarily are the result of physical differences in the host tissue are essential. Such an experimental program would be of considerable value in planning future sampling protocols, especially if it were carried out in a speciose site such as a tropical rain forest.

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Land-Use Patterns, Historic

Oliver Rackham, in Encyclopedia of Biodiversity (Second Edition), 2013

Forest and Woodland

It is often supposed that wildwood consisted of trees, trees, and nothing but trees, and only shade-bearing ground vegetation; gaps arising through the death of trees would promptly be filled by the growth of new trees. Examples can be seen where the dominant trees are of shade-bearing kinds such as Abies and Fagus species. The argument that wildwood was like this is often based on the general doctrine of climax vegetation, rather than on evidence of the history of specific forests. Pollen analysis can exaggerate the dominance of trees, many of which produce more pollen than herbaceous plants. If this is allowed for, some wildwoods were much more diverse.

Frans Vera has advanced the theory that wildwood was a mosaic of areas of trees and areas of grassland, continually shifting under the influence of deer, wild oxen, and wild horses. Whether this was so is still controversial. It would explain why agricultural technology should have spread into the seemingly hostile environment of north-west Europe, where (in the continuous-forest theory) people would have had to expend immense labor on digging up trees to make fields before they could grow anything. It also explains why wood-pasture is such an important habitat.

In some tropical forests, there is vast biodiversity, owing to the many species of tree and the abundance of vines, epiphytes, and termites, which enable the trees themselves to support complex ecosystems. In other parts of the world, continuous forests, especially of densely shading trees, are relatively poor habitats: many of their plants and animals are concentrated in gaps, cliffs, watercourses, burnt areas, and other breaks in the continuous shade.

Ancient peoples destroyed some areas of forest to create farmland, grassland, and heath; they also affected the remaining forest by various forms of land management. Continuous forest is not very productive for most human purposes. Edible animals and plants occur sparsely, if at all, and the animals are difficult to catch. Tree fruits are out of reach in the high canopy.

Forests were not generally destroyed by people cutting down the trees in order to use them. The author knows of no instance in European history of a forest being destroyed – converted to nonforest – solely by people using up the trees. Normally they would cut the trees suitable for the purpose in hand and leave the other trees. The result would be a depleted forest, unsuitable for that purpose until a new generation of trees had grown. This is not to be confused with a destroyed forest.

Great trees do not easily furnish wood for fuel and timber for construction. A big tree, when cut down, is a very intractable object. Until the coming of sawmills, vehicles, and railroads capable of dealing with giant trees, people preferred to use the smallest log that would serve the purpose and to manage forests to produce a succession of trees small enough to handle.

Coppicing is an important factor. Most European and North American trees, other than conifers, survive being cut down and sprout from the stump. Clonal trees, like European elms and American beech, sucker from the roots. Coppicing is one of the world's most important practices in historic forest management. By cutting down woodland every 5–30 years and allowing it to grow again from the stumps, a permanent succession of small stems can be assured, of sizes that are easily handled and suitable for light construction and fuel. It was often the practice to leave a scatter of trees of selected species to grow on for three or four cycles to yield constructional timber (Figure 5).

Abies - an overview | ScienceDirect Topics (5)

Figure 5. A coppice wood. The foreground has just been felled, leaving the stools from which new growth will arise. In the middle is an area of 2 years' growth since last felling. An older part of the wood forms the background. Bradfield Woods, Suffolk, England.

Coppicing has been the nearly universal woodland management in Britain, well documented for the past thousand years and known on archeological evidence for some 6000 years. It is the basis of historic forest management in many parts of the broad-leaved and Mediterranean zones of Europe and also in Japan. It was apparently not much practiced by Native Americans but was widely introduced by European settlers in America, where there are large areas of ex-coppiced wood-lots.

Coppicing affects biodiversity by drastically reducing the shade at the start of each cycle of felling and regrowth. Two or three years of relatively open conditions follow, ending as the new growth closes in. This favors various woodland plants and animals. Low-growing herbs such as species of Viola and Primula flower in abundance in the years of extra light (Figure 6). Others such as Euphorbia species appear from buried seed produced by their parents at the last felling. Many insects feed on the leaves or nectar of these plants. The middle stages of regrowth, when there is a thicket of young stems, favor warblers and similar small birds – a famous English example is the nightingale (Luscinia megarhynchos). The dormouse (Muscardinus avellanarius), an English woodland mammal, favors the later stages.

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Figure 6. Oxlip (Primula elatior) flowering in abundance among hazel (Corylus) shoots of 1 year's growth since coppicing. Hayley Wood, Cambridgeshire, England.

Coppicing is often thought to be artificial, but the ability to coppice is widespread among the world's trees and presumably was an adaptation to some process in wildwood. Sometimes it is a response to fire, but it is not correlated with flammability: few pines (among the world's most flammable trees) will coppice, but fireproof trees such as elms and poplars coppice or sucker. American, European, and Japanese species of Tilia (lime, basswood) are self-coppicing and grow naturally in a multistemmed form; so do American and Japanese species of Magnolia. Possibly coppicing behavior is an adaptation to tree-breaking mammals: the axes of woodcutters are a replacement of the missing elephants, etc. The author has observed something like a coppicing ecosystem developed in eucalyptus forests in New South Wales after only the third or fourth successive logging (Figure 7).

Abies - an overview | ScienceDirect Topics (7)

Figure 7. Eucalyptus forest 2 years after being logged for the third or fourth time. Note the abundant regrowth and ground vegetation. Merimbula State Forest, New South Wales.

Another historic woodland practice is the creation of permanent edges and open areas. In England, wood-lots have permanent edges (many of them are over a thousand years old) defined by banks and ditches, constructed as a conservation measure (Figure 8). They may also have permanent tracks and other open areas in the interior. In a typical wood-lot, well over half the plant species are associated with the boundary, with recently felled areas, or with permanent openings. The species of permanent openings tend to constitute plant communities of their own, distinct from those of temporary clearings and of grassland away from woodland. On pollen evidence, something like these permanent open areas already existed in wildwood.

Abies - an overview | ScienceDirect Topics (8)

Figure 8. Edge of an English wood. The bank with external ditch was constructed about 1000 years ago by the monks of Bury St. Edmunds Abbey to demarcate their wood-lot. The trees on the bank have just been cut; in the interior, they are of 1 year's growth. Bradfield Woods, Suffolk, England.

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Fungal Endophytes

Thomas N. Sieber, in Fungal Biology Reviews, 2007

A further indication for host-endophyte co-evolution is the degree of relatedness of dominant endophytes in needles of Abies, Tsuga and Pinus species. Whereas Abies and Tsuga are closely related, Pinus is only distantly related to Tsuga and Abies. Correspondingly, species of Phyllosticta (anamorphic forms of Guignardia spp.) are dominant only in needles of Abies or Tsuga species, and Cyclaneusma spp. only in pine needles (Table 1). Congeneric tree species are often colonized by the same species or by a “sister” species of the same fungal genus, e.g. Apiognomonia quercina on Quercus spp., Lophodermium pinastri on Pinus spp., or L. piceae on Picea spp. and Abies spp. (Table 1). It is often impossible to differentiate “sister” species on different hosts based on morphology. The species limits between morphologically identical fungi are a subject of constant debate and several methods to define such limits have been proposed (Grünig etal. 2007; Taylor etal. 2000). Reproductive isolation was demonstrated to occur among populations of the same morphological species. These reproductively isolated populations are considered separate cryptic species, e. g. cryptic species of the dark septate endophyte Phialocephala fortinii s. l. can occur sympatrically adjacent to each other in the same root (Sieber and Grünig 2006). Thus, it is advisable to split rather than to lump species in future taxonomic works. An exception to this rule is the genotypic identity (as determined by ITS sequencing) of Guignardia mangiferae isolates from a wide host range all over the world (Baayen etal. 2002; Rodrigues etal. 2004).

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