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Ökophysiologische Bedeutung von Zweigabsprüngen (Kladoptosis) unter besonderer Berücksichtigung der Symptomatologie von Quercus robur L
Abstract
Die Aufrechterhaltung der Trennungszone bewirkt aufgrund ihres histologischen Aufbaus eine Reduzierung der hydraulischen Leitfähigkeit. Die mit einer Trennungzone ausgestatteten Zweige befinden sich in einer indifferenten Phase, in der sie von dem regulären Hydrosystem des Baumes separiert sind. Sie können nachfolgend durch Abgliederung vollständig von ihm getrennt oder durch Eingliederung permanent an das Hydrosystem angeschlossen werden. Bei zusätzlichen negativen Umweltbedingungen steigt der Anteil der nur provisorisch an das Hydrosystem des Baumes angeschlossenen Zweige. In dieser Situation setzt die Eingliederung — Bildung regulären Xylems — nur noch im Abzweigungsbereich der vitalsten Seitenachsen ein. Aufgrund der Reduzierung der hydraulischen Leitfähigkeit wird es dem Baum möglich, das ihm verfügbare Wasser selektiv in der Krone zu verteilen. Eine reduzierte Eingliederungsdynamik der Trennungszone erhöht den hydraulischen Widerstand des daran anschließenden Sprosses. Die in dieser Situation steigende Anzahl der Trennungszonen führt zur Förderung der eingegliederten Leitäste und schützt diese vor unkontrollierter Xylem-Kavitation.
... Rather, the active shedding of twigs from the crowns of mature oaks can be seen as a mechanism of acclimatization to drought stress resulting from conditions such as severe summer drought, preceding frost and ⁄ or insect defoliation, or impairment of root growth that reduce the water flow to the respective twigs (e.g. Klugmann and Roloff 1999). Under those conditions, twigs may be actively shed due to the activation of an anatomically differentiated abscission zone ( Klugmann and Roloff 1999). ...
... Klugmann and Roloff 1999). Under those conditions, twigs may be actively shed due to the activation of an anatomically differentiated abscission zone ( Klugmann and Roloff 1999). If the environmental conditions improve, the loss of twigs may be compensated by a production of new ones in the following vegetation periods, and the crown may completely recover. ...
... If the environmental conditions improve, the loss of twigs may be compensated by a production of new ones in the following vegetation periods, and the crown may completely recover. On the other hand, continuation of adverse environmental conditions or even their aggravation by additional stress factors may prevent both the full integration of the xylem of already produced twigs into the hydraulic system of the tree and the formation of new shoots, and may result in a progressive decline of the crown ( Klugmann and Roloff 1999). ...
Incidences of oak decline have occurred repeatedly during the past three centuries as well as in the most recent decades. On the basis of historical records and dendrochronological measurements, oak decline in Central Europe has been attributed to the single or combined effects of climatic extremes (winter frost, summer drought), defoliating insects, and pathogenic fungi. Starting from a literature review, we discuss the possible roles of various abiotic (air pollution, nitrogen eutrophication, soil chemical stress, climatic extremes, site conditions) and biotic factors (insect defoliation, borer attack, infection by pathogenic fungi, microorganisms) that have been related to oak decline. On the basis of investigations on Quercus petraea and Quercus robur at three different levels (from experiments with young trees to monitoring on a supraregional scale), we suggest a conceptual model of the interaction of abiotic and biotic factors responsible for the onset of oak decline. This model should be valid for Central European oak stands at more acidic sites (soil pH (H2O) ≤ 4.2; on soils with higher pH, pathogenic Phytophthora species may contribute to oak decline). The combination of severe insect defoliation in at least two consecutive years with climatic extremes is the most significant complex of factors in the incidence of oak decline. Combined with defoliation, summer drought or winter/spring frost or both have to occur within the same year or in consecutive years to trigger major outbreaks of decline. Important additional stress factors are the following: (1) hydromorphic site conditions which, particularly in the case of Q. robur, render the trees more susceptible to drought stress as a result of an impairment of root growth in the subsoil; and (2), possibly, excess nitrogen which, in combination with drought stress, results in distinct decreases in the foliar concentrations of allelochemicals in Q. robur, thereby probably making the trees more susceptible to insect defoliation. Air pollution, soil chemical stress (including excess manganese), and nitrogen-induced nutritional imbalance do not seem to be important causal factors in the complex of oak decline. On the basis of the model, the appearance of the most recent oak decline in North-western Germany can be adequately explained.
Facteurs abiotiques et biotiques et leurs interactions, comme causes du dépérissement des chênes dans le centre de l'Europe
Des dépérissements de chênes ont eu lieu périodiquement durant les trois siècles passés comme durant les récentes décades. D'après les mentions historiques et des observations dendrochronologiques, le dépérissement des chênes dans le centre de l'Europe a été attribuéà l'effet simple ou combiné d'extrêmes climatiques (froids hivernaux, sécheresses estivales), de défoliations par les insectes, et de champignons parasites. Dans le présent article, nous discutons du rôle possible de facteurs abiotiques (pollution atmosphérique, eutrophisation azotée, stress chimique du sol, extrêmes climatiques, conditions stationnelles) et de facteurs biotiques (défoliations entomologiques, attaques de xylophages, infection de champignons parasites, et autres microorganismes) qui ont été associés au dépérissement des chênes. Sur la base des recherches réalisées à trois niveaux différents sur Quercus petraea et Q. robur (depuis des expériences sur jeunes plants jusqu'au suivi supra régional), nous proposons un modèle conceptuel d'interactions entre les facteurs abiotiques et biotiques responsables de l'initiation du dépérissement. Ce modèle devrait être valide pour les chênaies du centre de l'Europe sur sols acides (pH(H2O) ≤ 4,2, des Phytophthora ssp. pouvant contribuer au dépérissement sur les sols à pH plus élevé). Les défoliations entomologiques sévères pendant au moins deux années consécutives et les extrêmes climatiques, constituent la combinaison de facteurs la plus significative dans l'apparition du dépérissement. La sécheresse estivale ou les gelées hivernales ou printanières, ou les deux, doivent avoir lieu la même année que la défoliation, ou les années suivantes, pour qu'un dépérissement majeur se développe. D'autres facteurs additionnels de stress sont: (1) les conditions d'hydromorphie qui rendent les arbres (particulièrement Q. robur) plus sensibles au stress hydrique à cause d'une moindre croissance racinaire dans le sol profond; (2) éventuellement l'excès d'azote qui, combiné au stress hydrique, induit une réelle diminution des concentrations foliaires en métabolites secondaires chez Q. robur, ce qui rend probablement les arbres plus sensibles aux défoliations entomologiques. La pollution atmosphérique, le stress chimique du sol (y compris l'excès en manganèse), et les déséquilibres nutritionnels induits par l'azote ne semblent pas intervenir de façon importante dans le processus de dépérissement. Sur la base du modèle, le dépérissement le plus récent apparu dans le nord-ouest de l'Allemagne peut être expliqué de façon satisfaisante.
Abiotische und biotische Faktoren und ihre Wechselwirkungen als Ursachen für das Eichensterben in Mitteleuropa
Eichensterben-Episoden traten wiederholt in den letzten zweihundertfünfzig Jahren wie auch in den letzten Dekaden auf. Auf der Grundlage historischer Aufzeichnungen und dendrochronologischer Untersuchungen wurde das Eichensterben in Mitteleuropa auf einzelne oder kombinierte Auswirkungen klimatischer Extreme (Winterfrost, sommerliche Trockenheit), Entlaubung durch herbivore Insekten und Befall mit pathogenen Pilzen zurückgeführt. Im vorliegenden Beitrag wird auf der Basis einer Literaturübersicht die Rolle verschiedener abiotischer (Luftverschmutzung, Stickstoff-Eutrophierung, bodenchemischer Stress, Witterungsextreme, Standortsbedingungen) und biotischer Faktoren (fraßbedingte Entlaubung durch Insektenlarven, Borkenkäfer, pathogene Pilze, Mikroorganismen) diskutiert, die mit Eichensterben in Verbindung gebracht wurden. Vor dem Hintergrund von Untersuchungen, die auf drei unterschiedlichen Ebenen (von Experimenten mit Jungbäumen bis zum Monitoring im überregionalen Maßstab) an Quercus petraea und Q. robur durchgeführt wurden, wird ein Modell der Wechselwirkungen abiotischer und biotischer Faktoren bei der Entstehung des Eichensterbens vorgestellt. Dieses Modell gilt für mitteleuropäische Eichenbestände an stärker sauren Standorten (pH (H2O) ≤ 4,2; auf Böden mit höherem pH-Wert können Phytophthora-Arten zum Eichensterben beitragen). Eine Kombination von Kahlfraß in aufeinanderfolgenden Jahren und Witterungsextremen ist bei der Entstehung von Eichenschäden die bedeutendste. Von den drei Faktoren Kahlfraß, sommerliche Trockenheit und Winter- bzw. Spätfrost müssen mindestens zwei zeitgleich oder kurz nacheinander auftreten, um schwerwiegende Episoden von Eichensterben auszulösen. Schadverstärkende Stressfaktoren sind wechselfeuchte Standortsbedingungen, die, insbesondere bei Q. robur, die Anfälligkeit der Bäume für Trockenstress aufgrund der Beeinträchtigung des Wurzelwachstums im Unterboden erhöhen, sowie möglicherweise überschüssiger Stickstoff, der, in Kombination mit Trockenstress, bei Q. robur zu einer drastischen Abnahme der Konzentration sekundärer Pflanzenstoffe in den Blättern führt und somit die Bäume wahrscheinlich anfälliger für fraßbedingte Entlaubung macht. Luftverschmutzung, bodenchemischer Stress (einschließlich überschüssiges Mangan) und Stickstoff-induziertes Nährstoffungleichgewicht scheinen im Ursachenkomplex des Eichensterbens keine wesentliche Rolle zu spielen. Auf der Grundlage des vorgestellten Modells lässt sich die Entstehung der jüngsten Eichenschäden in Nordwestdeutschland angemessen erklären.
... The increase in crown defoliation may not necessarily lead to oak dieback and decrease in its abundance in forest canopies. Although higher crown transparency may be indicative of higher mortality rates in the future (Dobbertin 2005;Dobbertin and Brang 2001), higher degree of crown defoliation and its partial dieback can be a temporal adaptation to minimise water use by the crown during periods with limited water availability (Klugmann and Roloff 1999;Thomas and Hartmann 1996) and may not lead to higher mortality rates (an example of Northern red oak - Demchik and Sharpe 2000). When such periods are over, the crown condition of oak trees appears to recover (Klugmann and Roloff 1999;Osipov and Selochnik 1989). ...
... Although higher crown transparency may be indicative of higher mortality rates in the future (Dobbertin 2005;Dobbertin and Brang 2001), higher degree of crown defoliation and its partial dieback can be a temporal adaptation to minimise water use by the crown during periods with limited water availability (Klugmann and Roloff 1999;Thomas and Hartmann 1996) and may not lead to higher mortality rates (an example of Northern red oak - Demchik and Sharpe 2000). When such periods are over, the crown condition of oak trees appears to recover (Klugmann and Roloff 1999;Osipov and Selochnik 1989). Our study suggests that the pattern of crown defoliation is likely a product of both regional and stand-level factors. ...
Crown defoliation of oak (Quercus robur and Q. petraea) was analysed in 808 trees during three forest condition surveys (1988, 1993, and 1999) in the southern Sweden. From 1988 to 1999 crown defoliation increased by more than 20%. Changes in crown defoliation were related to the pH in the upper 20-30 cm of the mineral soils, which was closely connected to other measures of soil fertility (cation exchange capacity, CEC and C/N ratio). Trees growing on soils with a high pH (> or =4.00, in BaCl2 filtrate), high CEC and low C/N ratio had significantly lower crown defoliation than trees growing on more acid soils (pH <4.00), indicating that less favourable soil conditions may further enhance oak decline. Age did not differentiate trees with respect to crown defoliation, indicating that decline in crown condition was not due to an age-related increase in crown transparency. Considering only trees younger than 100 years, a significant interaction was observed between changes in crown defoliation and soil pH. Trees younger than 100 years old growing on more acidic soils had a greater increase in crown transparency than trees on more basic soils between 1988 and 1999. Trees > or =100 years old had significantly higher defoliation on more acidic than on more basic soils, however defoliation dynamics of these trees over 1988-99 was not related to soil acidity. Two biotic agents (insect and fungal leaf infections) evaluated in this study did not prove to be important drivers of defoliation dynamics.
... Under prolonged water stress, maintenance of transpiration flow in anisohydric plants often requires leaf area control, which reduces water demand (Maseda and Fernández, 2006). Twig abscission is common in oak and enables the trees to avoid runaway embolism (Klugmann and Roloff, 1999). The preventive strategy of isohydric species can reduce stress damage, such as defoliation, loss of fine roots or cavitation of xylem tissue, thereby often resulting in a higher recovery following drought compared with anisohydric species (Leuschner, 1998;Hartmann, 2011). ...
Tree species mixing has been widely promoted as a promising silvicultural tool for reducing drought stress. However, so far only a limited number of species combinations have been studied in detail, revealing inconsistent results. In this study, we analysed the effect of mixing Scots pine and oak (pedunculate oak and sessile oak) trees on their drought response along a comprehensive ecological gradient across Europe. The objective was to improve our knowledge of general drought response patterns of two fundamental European tree species in mixed versus monospecific stands. We focused on three null hypotheses: (HI ) tree drought response does not differ between Scots pine and oak, (HII ) tree drought response of Scots pine and oak is not affected by stand composition (mixture versus monoculture) and (HIII ) tree drought response of Scots pine and oak in mixtures and monocultures is not modified by tree size or site conditions. To test the hypotheses, we analysed increment cores of Scots pine and oak, sampled in mixed and monospecific stands, covering a wide range of site conditions.
... Das gleichbleibend hohe Kronenverlichtungsniveau kann als Indikator für einen verbreitet eingeschränkten Gesundheitszustand und Zuwachseinbußen der Bäume gewertet werden (FÜHRER, 1998). Die Eignung des WZE-Verfahrens zur Abschätzung des Gesundheitszustands der Eiche ist jedoch umstritten (KLUGMANN und ROLOFF, 1999;ZIEGLER, 2004;EISEN HAUER, 2010). Deshalb ist speziell für Alteichen von KÖRVER et al. (1999) ein Verfahren zur Ansprache von Kronenstrukturstufen im Winterzustand entwickelt worden, das jedoch noch nicht flächendeckend eingesetzt wird. ...
Auf einer Versuchsflächenreihe von Sachsen-Anhalt bis Ostpolen wurden 2006–2011 die Beziehungen zwischen der Kronenvitalität und dem Radial- beziehungsweise Kreisflächenzuwachs bei Trauben-Eiche (Quercus petraea [MATT.] LIEBL.) im Alter von 100–150 Jahren auf Ebene des Einzelbaums beobachtet und analysiert (Abb. 1, Tab. 1und 2). Als Vitalitätsweiser dienten jährliche Ansprachen der Kronenstrukturstufen nach dem Schema von KÖRVER et al. (1999; Abb. 2) sowie des Laubverlusts im Sommer nach dem Verfahren der Waldzustandserhebung (WZE). Der Methodenvergleich zeigt nur mäßige Übereinstimmungen zwischen den Aussagen beider Verfahren (Abb. 4). Sie sind deshalb nicht als austauschbare, sondern als komplementäre Ansätze zu betrachten, deren Ergebnisse verschiedene zeitliche Ebenen abdecken. Im Beobachtungszeitraum haben sich der Belaubungsgrad und die Kronenstruktur wesentlich verbessert (Abb. 3, Tab. 3). Für beide Vitalitätskennwerte ergeben sich zwar signifikante, jedoch nur schwache Effekte auf den relativen Durchmesserzuwachs und den relativen Kreisflächenzuwachs (Abb. 5). Der Zuwachs des Einzelbaums wird hauptsächlich von der Ausgangsdimension (BHD bzw. Kreisfläche) und der relativen
Kronenfläche bestimmt (Tab. 4). Die Werte der Vitalitätsansprachen sind für beide Verfahren signifikant mit
der relativen Kronenfläche korreliert: Bei gleichem BHD weisen Bäume mit kleinerer Kronenschirmfläche im
Mittel signifikant schlechtere Kronenstrukturstufen und höhere Laubverlustprozente auf (Abb. 6). Als Schlussfolgerung ist festzuhalten, dass die Kronenstruktur zwar geringe, aber statistisch gesicherte Rückschlüsse auf das Wachstum der Trauben-Eiche erlaubt. Der nach WZE-Methodik geschätzte Laubverlust hingegen war bei Zusammenfassung aller Flächen kein verlässlicher Indikator für das Zuwachsverhalten. Die geografische Lage der Versuchsflächen mit ihrem unterschiedlichen Grad an Kontinentalität hatte keinen wesentlichen Einfluss auf Richtung und Stärke dieser beobachteten Zusammenhänge.
... drought). These adaptations include deep root system or the ability of twigs shedding (cladoptosis) (Klugmann and Roloff, 1999;Rust and Roloff, 2002) or transpiration mechanisms effectively controlled by regulation of the stomatal closure (Maseda and Fernndez, 2006). However, these defensive reactions become less important along with the increase of the drought stress that makes the trees even more vulnerable to the other stress agents (Thomas et al., 2002). ...
... Das gleichbleibend hohe Kronenverlichtungsniveau kann als Indikator für einen verbreitet eingeschränkten Gesundheitszustand und Zuwachseinbußen der Bäume gewertet werden (FÜHRER, 1998). Die Eignung des WZE-Verfahrens zur Abschätzung des Gesundheitszustands der Eiche ist jedoch umstritten (KLUGMANN und ROLOFF, 1999;ZIEGLER, 2004;EISEN HAUER, 2010). Deshalb ist speziell für Alteichen von KÖRVER et al. (1999) ein Verfahren zur Ansprache von Kronenstrukturstufen im Winterzustand entwickelt worden, das jedoch noch nicht flächendeckend eingesetzt wird. ...
The study analyzes the relations between individual crown vitality and basal area increment for sessile oak (Quercus petraea [MArr.] LIEBL.). Investigations were carried out from 2006 to 2011 in five stands of mature sessile oak (table 1) on terrestrial, moderately dry sites with average nutrient supply. The trial stands are located in a geographic sequence with increasingly continental climate from the western border of Brandenburg into Eastern Poland (table 2, fig. 1). To quantify oak vitality, two different approaches were compared: (i) the European standard procedure for annual assessment of crown transparency in summer, and (ii) a method to assess winter crown structure according to KÖRVER et al. (1999; fig. 2). Basal area increment was derived from consecutive diameter measurements at the start and after five years. - A comparison between 2006 and 2011 shows significant improvements in crown condition in all trial stands for both summer and winter assessment (table 3, fig. 3). Spearman rank correlation coefficients between crown transparency and crown structure are relatively small but significant (fig. 4). As a result, the two approaches are seen as complementary methods which allow conclusions on different phenomena and processes: While crown transparency mirrors short-term (mostly annual), volatile influences such as extreme weather periods or insect attacks, crown structure is a measure of environmental changes or vitality problems on a larger time scale of more than one year. Although crown structure is significantly related to basal area increment on four out of five plots (fig. 5), correlations between tree growth and crown vitality are rather weak for both assessment methods and do not follow any spatial trend (table 4). Initial basal area and relative crown size were identified as the most imfluential factors for variation in basal area increment. Low but significant correlations exist between relative crown size and crown vitality: Trees with identical dbh values tend to show less crown transparency and a healthier crown structure with increasing horizontal crown area (fig. 6). All these results show that the investigated crown vitality parameters alone do not completely reflect basal area increment variation and, vice versa, increment values can only partially predict crown development. The geographic gradient covered by the sequence of trial stands does not lead to any detectable spatial trend in the results.
... drought). The morphological adaptations are, among others, a deep-reaching root system or the ability of mature trees to shed twigs (cladoptosis) (Klugmann and Roloff 1999;Rust and Roloff 2004). The physiological mode that contributes to delaying drought mainly concerns transpiration (Maseda and Fernández 2006). ...
Oaks' decline in vitality is attributed to a complex process that involves interactions of several factors leading to increased trees' mortality. This study investigates the structure of trunk wood of oaks with reference to its physiological role in hydraulic conductivity. On the basis of the crown condition, the oaks were classified into three health groups: healthy trees, declining trees and dead trees. Anatomical traits of wood, such as annual ring width, vessel density, vessel diameter of earlywood and theoretical hydraulic conductivity, were measured and calculated. The narrowest annual rings formed by the cambium were observed in dead oaks. These trees were also characterized by the smallest diameter of earlywood vessels, not only in the period of occurrence of dieback symptoms, but also during their whole life. It is suggested that the formation of narrow annual rings and earlywood vessels of small diameter increases susceptibility of a tree to decay. A reduced vessel diameter implies changes in hydraulic conductivity of oak trunks and thus impairs the water transport, which affects the health of trees. The process of oak decline is considered to have characteristics of natural selection and leads to the elimination of the weakest trees.
Shoot abscission was studied on 20 selected individuals of Common yew (Taxus baccata L.). The study took place at Tharandt Botanic Garden and Arboretum (near Dresden, Saxonia, Germany) from September 2007 to August 2008. Fig. 7 gives an overview of different mechanisms of abscission including abscission of dead shoots, passive abscission caused by animals or wind, and active abscission of living branches with green leaves (cladoptosis). For T. baccata little is known about dynamics, ecology and anatomy of the abscission of vital living shoots, so this study will focus on these mechanisms. On the ground below the studied trees could be found less vigorous, 1-3 year-old shoots without lateral branching (linear-shoots). Far more than 50 % of the shoots were abscised exactly at the shoot-base similar to the cladoptosis process (Fig. 1, 2). This shoot abscission mechanism could be observed during winter, yet also in September to November for female specimen (Fig. 3). An analysis of climate data showed significant correlations between the number of abscised shoots, wind speed, and weekly precipitation, respectively (Fig. 4). The high amount of shoots found below female yew trees in autumn might be caused by seed eating birds. This leads to the conclusion that a mechanic stress is the cause for shoot abscission in T. baccata. In addition an anatomic study of the shoot-base area showed a considerable narrowing of the xylem of the first growth ring. This is evidence for the formation of a predetermined breaking zone because it has a negative effect on mechanic stability in this area (Fig. 5. 6). In vigorous shoots this area is to be integrated in the shoot's tissue by secondary growth within two years. These findings are unique for T baccata and show the plasticity and ability of this species to adapt to a changing environment. We suggest referring to this specialised and unique mechanism of abscission as "separation".
Cladoptosis, the abscission of twigs, is the main mechanism of changes in crown structure in senescing pedunculate oak (Quercus robur L.). We tested the hypotheses that abscission zones in nodes of old pedunculate oak trees reduce leaf-specific hydraulic conductance of shoots and thereby limit the stomatal conductance and assimilation.Hydraulic conductance and leaf-specific hydraulic conductance, measured with a high pressure flowmeter in 0.5–1.5m long shoots, were significantly lower in shoots of low vigour compared to vigorous growing shoots in a 165-years-old stand in the southeast of Germany. Two types of bottlenecks to water transport could be identified in shoots of old oak trees, namely nodes and abscission zones. In young twigs, vessel diameter and vessel density in nodes with abscission zones were significantly reduced compared with internodes. In nodes without abscission zones, vessel density was significantly reduced. The reduction of hydraulic conductance was especially severe in the smallest and youngest shoots with diameters less than 2mm. Internodes of 1–5mm sapwood diameter had an average hydraulic conductance of 7.13×10−6±0.2×10−6kgs−1m−1 MPa−1, compared to 4.54×10−6±0.3×10−6kgs−1m−1 MPa−1 in those with nodes.Maximum stomatal conductance and maximum net assimilation rate increased significantly with hydraulic conductance and leaf-specific hydraulic conductance. Maximum rate of net photosynthesis Amax of the most vigorous shoots (VC0) (7.34±0.55μmolm−2s−1) was significantly higher (P
Crown transparency estimates of Scots pine, Norway spruce, common beech, pedunculate and sessile oak, annually surveyed between
1990 and 2004 within a grid over Germany, provide a suitable response variable to study drought effects on forest trees. Major
climatic factors, available on a monthly basis as plot-specifically interpolated values and parameters of site and stand conditions,
biotic and other relevant factors were used as predictors in different cross- and length-sectional, and longitudinal models.
Stand age is a considerable and most constant driver of crown transparency in all species. Pine, spruce and beech responded—mainly
with a delay of 1year—with some foliar loss in areas where there was a surplus of temperature after the generally hot and
dry summer of 2003. Parallel time-series analyses delivered species-specific geographic large-scale patterns with delayed
or recent precipitation deficits or temperature surpluses. Even if beech is partly responding in current years with leaf loss
towards precipitation surpluses, defoliation is especially high 1year after hot summers, partly a result of high seed sets
after such summers. Crown condition of oak responds in dry and warm areas according to the drought stress hypothesis, however,
in cool and wet mountainous ranges oak responds after wet summers with higher defoliation. Longitudinal approaches revealed
for all 4-tree species significant relationships between crown condition and deviations from the long-term means of temperature,
precipitation but also global radiation and wind speed. Results do not always match the drought stress hypothesis, however,
this is not to expect considering the heterogeneous site, stand and climatic conditions across Germany. Complex interactions
of climatic and biotic factors also impede simple relationships. Soil-related clusters reveal higher sensitivity of spruce
and beech towards climatic drought factors on more acid soils with thin humus layers. Also clusters constructed from plot-specific
courses of defoliation reveal groups with rather closer relationships like a group of pine plots in the Oberpfalz, which seems
to be especially sensitive to summer drought.
La sécheresse exceptionnelle de 2003 a été l'occasion de faire le point de nos connaissances sur les mécanismes écophysiologiques permettant aux arbres de traverser un tel évènement climatique extrême. L'analyse a été conduite à l'échelle de l'arbre et du peuplement, tandis que l'intensité de la sécheresse a été quantifiée à l'aide d'un calcul de bilan hydrique sur neuf sites forestiers européens contrastés du réseau CARBOEUROPE. Le rôle du couvert dans les échanges avec l'atmosphère est rappelé puis intégré dans l'analyse des réductions de bilan d'eau et de carbone en 2003 dus à la régulation stomatique. Les caractéristiques du complexe sol-racine, important à la fois pour l'accès à la ressource et à l'efficience de son absorption, constituent un des premiers traits d'adaptation à la sécheresse. La réponse et les adaptations des espèces ont surtout été analysées en termes de diversité inter-spécifique de fonctionnement hydraulique et du couplage entre propriétés hydrauliques et régulation stomatique. Enfin, nous discutons l'hypothèse selon la quelle les dysfonctionnements hydrauliques ou les déficits de mise en réserve sont impliqués dans les réactions différées de croissance, de développement, d'induction de dépérissement. Par exemple, des mesures de réserves glucidiques dans les troncs de chênes menées en fin d'été 2003 ont permis de prédire l'état des couronnes des arbres au printemps 2004. Les faibles taux d'amidon étaient associés à une forte mortalité de branches et de jeunes pousses.
In “S. Rossore, Migliarino, Massaciuccoli” Natural Park (Pisa, I) six-month-old pedunculate oak seedlings (Quercus robur L.) were transplanted within natural gaps of a mixed oak forest. Micro-environmental variability for radiation and water soil content were measured for 145 seedlings during the year. Irradiation relative to the open field (IR) ranged from 5% to 57%. Seven classes of IR each with 20 seedlings were selected. Leaf mass per area was strongly influenced by IR. In the first 3 years survival was high (95, 76 and 75%, respectively) and seedling reached 14±6 cm, 27±13 cm and 39±19 (sd) cm of height. Even if IR and soil water content (SWC) were negatively associated, indicating a lower SWC at the centre of the gaps, height and its relative growth rate increased with IR (explored range: 8-40%) with a significant interaction with SWC in the 1st year, indicating the positive effect of soil moisture. In the 3rd year dimensional traits were higher in L+W+ (high light and humidity) followed by L-W+ (low light and high humidity), L+W- and finally by L-W-. Summer drought typical of the Mediterranean climate was evaluated by chlorophyll fluorescence of PSII on apical leaves of seedlings and mature trees at the beginning (21 June) and in mid-summer (20 July). While in June physiological traits did not differ between low and high IR, in mid-summer (at the peak of water-stress) seedlings of the two highest light classes showed chronic photoinhibition (Fv/Fm<0.75) and an increase in thermal dissipation (D) by constitutive term (Dc=1-Fv/Fm) and by regulated mechanisms of dissipation through xanthophyll-cycle term (Dx). Moreover, in July seedling leaf physiology largely differed with IR: leaves acclimated to high IR have higher photosynthetic potentialities, as shown by electron transport rate (ETR) and quantum yield (P) at saturating light maintained by an increase of the fraction of open reaction centres (qP), counterbalancing the efficiency decrease of the single reaction centres (Fv’/Fm’) dynamically protected via xanthophyll-cycle (Dx). Tree apical leaf physiology behaved differently from seedling leaves both in June (except Fv/Fm) and in July (except Dx). In June photochemistry was higher in tree apical leaves with higher ETR, P, qP and Fv’/Fm’ with a lower fraction of energy dissipated and in particular through lower loss by photoprotection through Dx as expected for high light conditions without stress; in July no chronic photoinhibition was observed in tree light leaves, the efficiency of single reaction centres (Fv’/Fm’) remained high but a drop in the fraction of open centre (qP) decreased significantly P and thus ETR. Consequently the highest potentialities in photochemistry (P) were observed in large gaps (at 40% IR).
The branch-base xylem structure of the endangered Wollemia nobilis was anatomically investigated. Wollemia nobilis is probably the only extant tree species that produces only first-order branches and where all branches are cleanly abscised. An investigation was carried out to see if these unusual features might influence branch-base xylem structure and water supply to the foliage.
The xylem was sectioned at various distances along the branch bases of 6-year-old saplings. Huber values and relative theoretical hydraulic conductivities were calculated for various regions of the branch base.
The most proximal branch base featured a pronounced xylem constriction. The constriction had only 14-31 % (average 21 %) of the cross-sectional area and 20-42 % (average 28 %) of the theoretical hydraulic conductivity of the more distal branch xylem. Wollemia nobilis had extremely low Huber values for a conifer.
The branch-base xylem constriction would appear to facilitate branch abscission, while the associated Huber values show that W. nobilis supplies a relatively large leaf area through a relatively small diameter 'pipe'. It is tempting to suggest that the pronounced decline of W. nobilis in the Tertiary is related to its unusual branch-base structure but physiological studies of whole plant conductance are still needed.
Hydraulic conductivities were measured in branch junctions and in the proximal segments of Quercus velutina Lam., Acer saccharum Marsh., and Tsuga canadensis (L.) Carr. In all three species, the basal proximal segment was more conductive than the junction by a factor of 1.1–1.5. There was no consistent pattern for the distal proximal segments, where the conductivities were higher, lower, or the same as the junction. These data are discussed in terms of Martin H. Zimmermann's concept of plant segmentation. It is concluded that junction constrictions to water flow contribute less to plant segmentation than the variation in leaf specific conductivity in the crown of these species.
Studies by light and scanning-electron microscopy in combination with specific isolation techniques revealed the presence of soil-borne Phytophthora - species in declining oak, beech and other forest trees. The sequence of histopathological reactions in infected roots and distinct fungal structures found in necrotic tissues are documented. Specific laboratory procedures used for the detection and identification of Phytophthora are presented. Pathogenicity of the isolated Phytophthora - species is shown by common tests of soil infestation and stem inoculation. The possible role of predisposing and contributing factors leading to this type of decline is discussed with emphasis on climate change and excess nitrogen.
The past 15 years have seen a surge of interest in modularity; that is, in the implications of the fact that plants are composed of repetitive modules that may in some way behave as independent units. Much has been written about the importance of modularity in plant population biology and also about the advantages and disadvantages of independence or interdependence among separate but disconnected modules. The interest in modularity is mainly at two scales. At the smallest scale, interest has focused on the "nutritional unit" or physiologically independent subunit comprising a unit of foliage, the section of stem to which it is attached, and the subtending axillary bud. At the opposite end of the spectrum, research has focused on clonal herbs in which each module (ramet) contains contains all the parts necessary for independent existence. However, this upsurge of interest in modularity has also led to renewed speculation, about other intermediately scaled, functional units that may behave semiautonomously.
For woody plants, considerable interest has focused onthe degree of autonomy of individual branches on a tree or shrub. Although branches appear to be natural subunits
Whole shoot resistance to water flow was measured in 4 species of oak, Quercus robur L, Q petraea Matt Liebl, Q pubescens Willd, and Q rubra L. Shoots were 1.1 to 1.5 m long with 16-19 mm basal wood diameter and were 4-8 yr old. Whole shoot resistances accounted for 20-40% of the total resistance to water flow from soils to leaves based on comparisons with literature values. Leaf blade resistances accounted for 80-90% of total shoot resistances measured in this study. Stem resistances to water flow were ≈ twice as large in Q robur than in the other species which had comparable stem resistances. Differences in shoot resistance between Q robur versus Q petrae are discussed in terms of the differential response of these species to drought in mixed stands. Mesure de la résistance au transfert de l'eau chez différentes espèces de chênes au moyen d'un nouveau fluxmètre haute pression. La résistance au transfert de l'eau de branches a été mesurée chez 4 espèces de chênes : Quercus robur L, Q petraea Matt Liebl, Q pubescens Willd et Q rubra L. Les branches avaient une longueur comprise entre 1,1 et 1,5 m, pour un diamètre de 16 à 19 mm à leur base, et étaient âgées de 4 à 8 ans. La comparaison des mesures avec des données de la littérature a montré que la résistance au transfert de l'eau dans les branches était de l'ordre de 20 à 40% de la résistance hydraulique totale, calculée entre le sol et les feuilles. La résistance au transfert dans les feuilles représentait de 80 à 90% de la résistance totale de la branche. Les résistances dans les parties ligneuses étaient environ deux fois plus élevées chez Q robur que chez les autres espèces, celle-ci montrant des valeurs comparables. Les différences de résistance hydraulique entre Q robur et Q petraea sont discutées en termes de différences de réponse à la sécheresse de ces espèces dans les peuplements mélangés.
Hydraulic properties were studied in Acer saccharinum L., a riparian species that also grows well on a dry soil when transplanted. Hydraulic resistances were measured by two independent techniques: a new high-pressure flowmeter (HPFM) method and a conventional evaporative flux (EF) method. Vulnerability to cavitation was also investigated on petioles, stems and roots using a hydraulic conductivity technique. Vulnerability segmentation was found, i.e., roots, stems and petioles had different vulnerabilities to xylem dysfunction. Petioles were most vulnerable with 50% loss of hydraulic conductivity at -0.5 MPa, roots were least vulnerable (50% loss at -2.2 MPa) and stems were intermediate in vulnerability. The HPFM and the EF methods gave comparable results, except that the EF method gave a significantly higher value for resistance across petioles plus leaves. Native embolism was high enough to explain the discrepancy in resistance across petioles plus leaves between the HPFM and the EF methods, indicating that the HPFM estimates the minimum (potential) hydraulic resistance of plants. Whole-plant hydraulic resistance of A. saccharinum was low compared to resistances of other temperate species. The hydraulic characteristics of A. saccharinum were consistent with adaptation to its typical environment: low whole-plant resistance assures high transpiration rates in the presence of sufficient water, and vulnerability segmentation provides the ability to survive during droughts through shedding of expendable organs.
A new method is presented for measuring whole-shoot hydraulic conductance, KT (kg s⁻¹ MPa⁻¹). The method was also used to determine other conductance values in maple (Acer saccharum Marsh.) stem segments of differing diameter including: Kh (absolute conductance or conductance per unit pressure gradient, kg s⁻¹ m MPa⁻¹), Ks (specific conductance or Kh per unit wood area, kg s⁻¹ m⁻¹ MPa⁻¹), and LSC (leaf specific conductance or Kh per unit leaf area, kg s⁻¹ m⁻¹ MPa⁻¹). A regression of KT versus stem basal diameter, D (m), gave KT = 5.998 × 10⁻²D1.402 (R² = 0.986 for D from 0.001 to 0.1 m) and a regression for leaf area, AL (m²), gave AL = 4.667 × 10³D2.007 (R² = 0.981 for D from 0.001 to 0.3 m). More than 50% of the resistance to water flow in large shoots (0.1 m in diameter and 8 to 10 m long) was contained in branches less than 0.012 m in diameter, i.e., in the distal 1.5 m of branches.
We used the regressions to predict the steady state difference in pressure potential, P, between the base of a shoot of diameter D and the average pressure potential at the apices of the shoot; the relation is given by P = 7.781 × 10⁴ED0.605, where E is the average evaporative flux density (kg s⁻¹ m⁻²) in the leaves attached to the shoot. After comparing the predictions of this equation to field observations of E and leaf water potential and stomatal conductance, we concluded that the hydraulic conductance of large maple shoots is sufficiently low to prevent maximum stomatal conductance in maple leaves.
A model is presented for the dynamics of water flow in a single eastern white cedar tree (Thuja occidentalis L.). The model takes into account the spatial and temporal dependence of the evaporative flux from leaves in the crown. It also accounts for the quantitative hydraulic architecture of the tree, i.e., the model characterizes the tree as a branched catena of > 4000 stem segments in which account is taken of the segment length, diameter, hydraulic resistance, and the total area of leaves attached to the segment.
Input values needed to run the model are measurements of evaporative flux, hydraulic conductance of stems versus stem diameter, and leaf and stem water storage capacitances. Output parameters are the spatial and temporal characterization of stem and leaf water potentials, stem and leaf water deficits, sap flow rate, and relative sap velocity. The input and output values of the branched catena model are compared and contrasted to that of an unbranched catena model. It is shown that the branched catena model fits independently measured field parameters better than an unbranched catena model. Close correspondence is found between model predictions and field measurements of shoot water potential, pressure gradients in stems, hysteresis in sap velocity between the lower and upper parts of the tree, and diurnal changes in stem and leaf water deficits.
This model is discussed in terms of both the hydraulic architecture of trees and the potential application of the model to questions of tree morphology, ecology, physiology and evolution.
We discuss the relationship between the dynamically changing tension gradients required to move water rapidly through the xylem conduits of plants and the proportion of conduits lost through embolism as a result of water tension. We consider the implications of this relationship to the water relations of trees. We have compiled quantitative data on the water relations, hydraulic architecture and vulnerability of embolism of four widely different species: Rhizophora mangle, Cassipourea elliptica, Acer saccharum, and Thuja occidentalis. Using these data, we modeled the dynamics of water flow and xylem blockage for these species. The model is specifically focused on the conditions required to generate ;runaway embolism,' whereby the blockage of xylem conduits through embolism leads to reduced hydraulic conductance causing increased tension in the remaining vessels and generating more tension in a vicious circle. The model predicted that all species operate near the point of catastrophic xylem failure due to dynamic water stress. The model supports Zimmermann's plant segmentation hypothesis. Zimmermann suggested that plants are designed hydraulically to sacrifice highly vulnerable minor branches and thus improve the water balance of remaining parts. The model results are discussed in terms of the morphology, hydraulic architecture, eco-physiology, and evolution of woody plants.
The water relations and hydraulic architecture of a tropical tree (Schefflera morototoni) and of two temperate species (Acer saccharum and Thuja occidentalis) are reported. Among the water relations parameters measured were leaf and stem water storage capacity, leaf water potential, transpiration, and vulnerability of stems to cavitation and loss of hydraulic conductivity by embolisms. Among the hydraulic architecture parameters measured were hydraulic conductivity per unit pressure gradient, specific conductivity, leaf-specific conductivity, and Huber value. In terms of vulnerability of stems to cavitation, stem and leaf capacitances, and leaf-specific conductivity, all three species followed the same sequence: Schefflera > Acer > Thuja. It is argued here that the high stem capacitance and high leaf-specific conductivity of Schefflera are necessary to compensate for its high vulnerability to cavitation. Extractable water storage per unit leaf area in Schefflera stems is >100 times that of Acer and may permit the species to survive unusually long, dry seasons in Panama. Although Schefflera frequently grows >20 meters, the biggest resistance to water flow in the shoots resides in the leaves.
Wood litter fall was measured during two years in a Danish oak forest. The total wood fall averaged 774.3 kg ha-1 yr-1, constituting 18,5% of the total litter fall. 77% of the total wood fall represent small wood components (diameter ≤ 10 mm). During 1973 the autumn, summer, and winter wood fall amounted to 60.9%, 30.5%, and 8.6% of the total, respectively. Potential environmental factors affecting the seasonal dynamics of wood fall are discussed. Only in the autumn is a relationship between wood fall and wind speed observed. However, wood fall is largely governed and prepared by physiological processes (abscission). During spring 1974 the abscission was initiated by severe injuries to the buds caused by herbivorous insects, water stress, and frost, producing a summer peak of wood fall additional to the autumnal peak. The great seasonal and inter-annual variation of the wood litter fall, and the increased nitrogen content of the wood components of the summer wood fall are discussed in relation to the decomposition cycle of dead wood. /// В течение двух лет измерялн количество опада в дубовом лесу в Дании. Общее количество опада составляет 774,3 кг/га/-1/год-1, т.е 18,5% от общего запаса подстилки. 77% от общего количества опада составляют мелкие куски дребесины (диаметр ≤10 мм). B течение 1973 г. осенний, летний и зимний опад древесины составиял 60,9, 30,5 и 8,6% от общего количества. Обсуж-даются возмежные факторы, среду\r=?\, влияющие на сезонную динамику опада древесины. Лишь осеыю наблюдается зависимость между опадом древесины и силой ветра. Однако, отпад древесины опреАеляется в основном физмологи-ческими процессами (отламывание). Установлено, что в течение весны 1974 г. отламывание вызывалось сильными повреждениями почек, нанесенными фитофарами, осадками и морозом, которые дали летний пик древесного опада дополнительно к осеннему. Обсуждаются большие сезонные и ежегод-ные колебания количества опада и увеличение содержания азота в древесных компонентах опада в связи с циклом разложения гнилой древесины.
Untersuchungen an Populus ‘Robusta’ ergaben, daß am Ende jeder Vegetationsperiode vorwiegend Kurztriebe in großer Zahl abgeworfen werden. Diese Seitenzweige besitzen während ihrer gesamten Entwicklung an der Basis eine besondere Zone, die nach Entfernung der Rinde bereits makroskopisch sichtbar ist. Der Abbruch erfolgt in dieser Zone und ergibt eine charakteristische Bruchfläche.
In histologischen Untersuchungen konnte gezeigt werden, daß dieses, als Trennungs zone bezeichnete Gewebe, zu über 70% aus nicht lignifizierten Parenchymzellen besteht; der Gefäßanteil ist wesentlich geringer als im Normalgewebe, Holzfasern sind selten und die Holzstrahlen mehrreihig. Kurze Zeit vor dem Zweigabfall wird in der Mitte der Trennungszone durch intensive antiklinale Zellteilungen eine Trennungsschicht gebildet, an deren äußerer Grenze sich der Zweig ablöst. Die überwiegend lignifizierte und basal von einem Periderm begrenzte Trennungsschicht verbleibt am Hauptzweig und bildet ein Schutzgewebe. Das Alter der abgeworfenen Zweige schwankte bei Populus ‘Robusta’ zwischen ein und zehn Jahren mit einem deutlichen Maximum von zwei- und dreijährigen Abwürfen. Das Wachstum der Kurztriebe ist bei dreijährigen Zweigen im wesentlichen abgeschlossen. Der Zweigabwurf kann als eine natürliche Reinigung der Krone angesehen werden.
Measurements of xylem conduit length and width and the distribution of xylem conduit ends were made in inter-nodes (I), nodes (N) and twig junctions (J) of 1-, 2- and 3-year-old twigs of plants of Quercus cerris L. Parallel measurements were also made of the loss of hydraulic conductivity of twigs subjected to pressure differentials across conduit pit membranes, equalling the leaf water potential at the turgor loss point. The loss of theoretical hydraulic conductivity was calculated as the ratio of i esivr4 (where r is the conduit radius) of the non-conducting conduits to that of all the conduits in the outermost wood ring of I, N and J. Stem zones such as 1-year-old nodes and junctions were localized with narrower and shorter xylem conduits and with higher percentages of conduit ends than internodes. Such ‘constricted zonesrsquo; were less vulnerable to embolism than internodes. Latewood conduits were consistently narrower, shorter and less vulnerable to embolism than earlywood ones. A positive relation therefore existed between conduit diameter and length and vulnerability to embolism. The overall vulnerability to embolism of Q. cerris plants is discussed in terms of xylem conduit width and length and of the distribution of conduit ends.
Quantitative geomorphic methods developed within the past few years provide means of measuring size and form properties of drainage basins. Two general classes of descriptive numbers are (1) linear scale measurements, whereby geometrically analogous units of topography can be compared as to size; and (2) dimensionless numbers, usually angles or ratios of length measures, whereby the shapes of analogous units can be compared irrespective of scale.
Linear scale measurements include length of stream channels of given order, drainage density, constant of channel maintenance, basin perimeter, and relief. Surface and crosssectional areas of basins are length products. If two drainage basins are geometrically similar, all corresponding length dimensions will be in a fixed ratio.
Dimensionless properties include stream order numbers, stream length and bifurcation ratios, junction angles, maximum valley-side slopes, mean slopes of watershed surfaces, channel gradients, relief ratios, and hypsometric curve properties and integrals. If geometrical similarity exists in two drainage basins, all corresponding dimensionless numbers will be identical, even though a vast size difference may exist. Dimensionless properties can be correlated with hydrologic and sediment-yield data stated as mass or volume rates of flow per unit area, independent of total area of watershed.
Litter fall from a mature white oak (Quercusalba L.) was sampled weekly from August through December for 4 years. Litter was separated into abscised twigs with attached leaves, abscised twigs without leaves, leaves attached to abscised twigs, individually abscised leaves, and acorns. Two phases of leaf fall were evident. The first occurred in early autumn and was characterized by abscission of twigs with leaves still attached. The second phase occurred later in the season and was characterized by shedding of individually abscised leaves. The peak of abscission of twigs with attached leaves preceded the peak of individual leaf fall by 10 to 14 days. Approximately 25% of leaves shed early in autumn were attached to abscised twigs. However, only about 10% of total, annual, leaf litter consisted of leaves lost from the tree while attached to abscised twigs. A significant acorn crop was produced only once during the 4-year study.
The rate of flow of a dilute KCl solution through sections of stem, branches, and twigs was measured and expressed in microlitres per hour, under conditions of gravity flow, per gram fresh weight of leaves supplied by that section of xylem. This is called leaf-specific conductivity (LSC). It is not uniform throughout the tree, LSC of the stem being higher than that of branches. Furthermore, vascular junctions, such as the path from stem to branch, represent hydraulic constrictions. Distribution of LSC in the tree is primarily based on varying vessel diameters. Vessel diameters increase from top to bottom in the tree stem. They are smaller in branches than in the main stem, and there is a distinct constriction of diameters at the base of each branch. Functionally this means that when transpiration begins the pressure has to drop more rapidly in the xylem of lower lateral leaves than in those at the top of the tree. It also means that under conditions of water stress peripheral parts of the tree are more vulnerable than the trunk.
Trees of Juglans regia L. shed leaves when subjected to drought. Before shedding (when leaves are yellow), the petioles have lost 87% of their maximum hydraulic conductivity, but stems have lost only 14% of their conductivity. This is caused by the higher vulnerability of petioles than stems to water-stress induced cavitation. These data are discussed in the context of the plant segmentation hypothesis.
A comparative study by light and scanning-electron microscopy of fine and coarse roots from healthy and declining oaks demonstrated a progressive deterioration of fine roots and mycorrhizal systems on mature trees in decline. Histopathological events such as infection of cortical and vascular root tissues by parasitic fungal hyphae leading to the impairment of woody roots are described. Distinct disease symptoms such as necrotic lesions on small diameter roots and callussing wounds on coarse roots are documented, supporting the hypothesis that Phytophthora spp. are involved in oak decline.
In this paper, we have reviewed how the hydraulic design of trees influences the movement of water from roots to leaves. The hydraulic architecture of trees can limit their water relations, gas exchange throughout the crown of trees, the distribution of trees over different habitats and, perhaps, even tbe maximum height that a particular species can achieve. Parameters of particular importance include:
(1) tbe vulnerabihty of stems to drought induced cavitation events because cavitation reduces the hydraulic conductance of stems,
(2) the leaf specific conductivity of stems because it determines the pressure gradients and most negative water potentials needed to sustain evaporation from leaves,
(3) the water storage capacity of tissues because this might determine the ability of trees to survive long drought periods.
All of these parameters are determined by the structure and function of anatomical components of trees. Some of the ecological and physiological trade-offs of specific structures are discussed.
Water relations and hydraulic architecture of a tropical tree(Schefflera morototoni)
- M T Tyree
- D A Snydermann
- R W Timothy
- J Machado
Eichensterben in Deutschland
- A Wolf
- H Kehr
Ursachen und Dynamik von Eichen-Zweigabsrüngen
- A Roloff
- K Klugmann
Kronenentwicklung und Vitalitätsbeurteilung ausgewählter Baumarten der gemäßigten Breiten. 2. Aufl. Frankfurt am Main
- A Roloff
Rätselhaftes Eichensterben auch in Österreich
- J F Kirchhoff
Hrsg.) 1991: Oak Decline in Europe The theory, and practice of branch autonomy
- R ' Sir
- W L~es~
- Poznan
- D G Sprugel
- T M Hinckley
- W Sci Iaap
SIr.',vECKI R. & L~ES~, W. (Hrsg.) 1991: Oak Decline in Europe. Poznan. SPRUGEL, D. G. & HINCKLEY, T. M. & SCI iAAP, W. 1991 : The theory, and practice of branch autonomy. Ann. Rev. Ecol. Syst. 22, 309-334.
Beurteilung des Gesundheitszustandes yon Altelchen in vom ,Eicher~terben" gesch~idigten Bestiinden
- Hartm~ ~nn
- G Kotcrzog
HARTM~' ~NN, G. & KotcrZOG, H.G. 1994: Beurteilung des Gesundheitszustandes yon Altelchen in vom,Eicher~terben" gesch~idigten Bestiinden. Forst u. Holz 49, 216-217.
Alter > 100 Jahre) und an 3 Jung-eichen (je 10 Eingriffe pro Baum) durchgefiihrt. Die behandelten Triebe wurden bis Ende September w6chentlich untersucht und offensichtliche Veriinderungen festgehalten
- Die Manipulationen
- Solit~reichen
Die Manipulationen wurden an drei alten Solit~reichen (Alter > 100 Jahre) und an 3 Jung-eichen (je 10 Eingriffe pro Baum) durchgefiihrt. Die behandelten Triebe wurden bis Ende September w6chentlich untersucht und offensichtliche Veriinderungen festgehalten. Okopbysiologiscbe Bedeutung yon ZweigabsFriingen (Kladopwsis) 275
Farbatlas Wa]dsch~.den. I. Aufl
- G H^atmann
- E Nzenh^us
- H Btmn
H^aTMANN, G. & NZENH^US, E & BtmN, H. 1988: Farbatlas Wa]dsch~.den. I. Aufl. Stuttgart, 148-149.
The structure and life of forest trees Leaf and twig abscission relationships in a mature white oak
- M Bosgen
- E Munch
- W R Ch~ey
BOSGEN, M. & MUNCH, E. 1929: The structure and life of forest trees. London 1929. CH~EY, W. R. 1979: Leaf and twig abscission relationships in a mature white oak. Can. J. For. Res. 9, 345-348.
1879: Weitere Untersuchungen fiber den Ablfsungsvorgang yon verholzten Zwei-gen
- E I Hohnr
HOHNr.I., E R. v. 1879: Weitere Untersuchungen fiber den Ablfsungsvorgang yon verholzten Zwei-gen. Mitt. forstl. Versuchswesen, ~)sterreich 2, 247-256.
Trennungszone vorhandetx/nicht vorhanden) untersucht. Die Manipulatlonen er~olgten Mitte Juli (nach der Johannistriebbildung) und wurden fol-genderma
- F~ihigkeit
f~ihigkeit (Trennungszone vorhandetx/nicht vorhanden) untersucht. Die Manipulatlonen er~olgten Mitte Juli (nach der Johannistriebbildung) und wurden fol-genderma/~en variiert: MI: Alle Knospen und Bl~itter wurden enffernt;
The hydraulic architecture of trees and other woody plants
- M Ew~rs
TYREIT., M. 2". & Ew~Rs, E W. 1991: The hydraulic architecture of trees and other woody plants. New Phytol. 1 I9, 345--360.
Ursachen und Dynamik yon Eichen-Zweigabsprfingen. Forst-wiss
- Aufl
- Main Frankfurt
- Rot
- A Olaf
- Klugm
- K Xnn
Aufl. Frankfurt am Main. ROt.OlaF, A. & KLUGM,-XNN, K. 1997: Ursachen und Dynamik yon Eichen-Zweigabsprfingen. Forst-wiss. Beitr~.ge Tharandt/Contr. For. Sci. 1, 1-97.
Water relations and hydraulic architecture of a tropical tree (.%hefflera morotowni) Plant Physiol. 96, t 105-1 t 13
- M Z Type
- St
- Yde~
- D A ~rn
- R W Timotiw
- ~ O Mach
- J F Wi_Rt
TypE, M.Z & St,/YDE~4.~rN, D.A. & TIMOTIW, R.W. & MACH,~)O, J. 1991: Water relations and hydraulic architecture of a tropical tree (.%hefflera morotowni). Plant Physiol. 96, t 105-1 t 13. WI_rt.F, A. 1995: ~Eichensterben ~ in Deutschland -Situation, Ursachertforschung und Bewertung. Forst u. Holz 51,266-268.
Jahre alte Trennungszone Fig. 2. Cross section of an 8-year-old abscission zone Abb. 3. Querschnitt durch das internodiale Xylem yon Quercus robur L. Fig. 3. Cross section of the hlternode xylem of Quercus robur L. 5 Literatur BL^
- R Abb~k
Abb. 2: Querschnitt durch eine 8 Jahre alte Trennungszone Fig. 2. Cross section of an 8-year-old abscission zone Abb. 3. Querschnitt durch das internodiale Xylem yon Quercus robur L. Fig. 3. Cross section of the hlternode xylem of Quercus robur L. 5 Literatur BL^.~K, R. 1997: Ringporigkeit des Holzes und hiiufige Entlaubung durch [~ekten als spezifische Risikofaktoren der Eichen. Forst und Holz 9, 235-242.
Ver~nderungen dutch Pilzbefall an Wurzeln gesch~digter Stieleichen. Allge-meine Forstz Anatornisch-histologische Unter~uchungen im Bereich der Astabzweigung bei Nadel-und Lanbbiiumen. Ill. Die Abzweigungsverh~.l~isse bei Quercus robur L. und Populus Sekfion Aigeiros
- H Bl~chke
- D ~ Bohlma
BL~CHKE, H. 1994b: Ver~nderungen dutch Pilzbefall an Wurzeln gesch~digter Stieleichen. Allge-meine Forstz. 14, 775-777. BOHLMA.~, D. 1970: Anatornisch-histologische Unter~uchungen im Bereich der Astabzweigung bei Nadel-und Lanbbiiumen. Ill. Die Abzweigungsverh~.l~isse bei Quercus robur L. und Populus Sekfion Aigeiros. Allg. Forst-u. Jagdztg. 141,224-230.
1893: B;iume und Str~iucher des Waldes
- Aufl
- Stuttgart
- G Hempet
- Wilhe
- K Lm
Aufl. Stuttgart. HEMPEt., G. & WILHE.LM, K. 1893: B;iume und Str~iucher des Waldes. Wien. HOHNEL, E R. v. 1878: Uber den Abl6sungsvorgang der Zweige einiger Holzgew~ichse und seine ana-tomischen Ucsachen. Mitt. forstl. Versuchswesen Osterreich I, 255-268.
1878: Über den Ablösungsvorgang der Zweige einiger Holzgewächse und seine anatomischen Ursachen. Mitt. forstl. Versuchswesen Österreich
- F R Höhnel
1860: Über den Ablösungsprocess saftiger Pflanzenorgane
- H V Mohl
- H. Mohl v
1865: Über die „Absprünge“ der Bäume
- A Röse
- A. Röse
1851: Vollständige Naturgeschichte der forstlichen Culturpflanzen Deutschlands
- T Hartig
Eichen-Erkrankungen in Mitteleuropa
- E Führer
- E. Führer
Hrsg.) 1991: Oak Decline in Europe
- R Siewecki
- W Liese
1995: „Eichensterben“ in Deutschland — Situation, Ursachenforschung und Bewertung
- A Wulf