Holz als Roh- und Werkstofl51 (1993) 145 155 ,,~? Springer-Verlag 1993

H o l z - " . o . _ . . , Werkstoff

Giant Sequoia (Sequoiadendron giganteum (Lindl.) Buchholz) in Europe'

W. Knigge 2

Institut flit Forstbenutzung dcr Georg August-Universit/it G,Sningen 3, B[isgenweg 4, W-34t)0 G6ttingen

Since 1853 seeds of Sequoia~h,ndrrm gi~,anteum (Lindl.) Buchholz I\mnd Ihcir way to Europe. Planted in botanical gardens, arboreta and parks Gianl Sequoia survived to significant size in lnany countries of Western Europe. Today its growth surpasses that of till olher softwoods known on the continent. The author analyzes its potential as a useful addition to forestry, stressing European experiences with geographic distribution, different climates, soils, genetic variability, increment and yield. Other aspects described tire its wood quality, i.e. knottiness, width of annual rings, heartwood formation, fiberlength, specific gravity, strength properties, durabi- lity and the chance l\~r an adequate utilization by the lk)rest products ir~duslry.

Mammuib/ iume in Europa

Seil 1853 wurde SaatgLit des MamlnutbaLuns (Sequoiadendron ,,..'i- ,,,antcum Lindl. Buchholz) in l.~uropa eingefi]hit. Me,st in botani- schen Giirten. Arborelen oder Parks angepl'lanz! erreichten die B~_iLime in mehrercn L/indern Westeuropas ungew6hnliche I{6hen und Durchmesser. Derzeil /.ibertriffl das Wachstum dieser Solitiirc das aller andercn Nadelb/iume. In der l:olge ~i,d das Potential dieser G;.tstbaunlart ['ill die Forstwirtschaft a tilgruild eigener Unter- suchungen und der anderer Autoren bescllrieben. U.a. werden Erfal~rungen hinsichtlieh geographischer Verbreitung, Anpassungs- I'iihigkcit an unterschiedliclle Standortc, genetischer Variabit{it sowie l l6hen und Durclznaesserzuwachs er6rtert. Wetter werden MeBergebnisse holzbiologischer Weiser wie inhere und ~:iugere Astigkeit, Schwankungen yon Ringbreitc, Verkernung, Faserlfingc, Rohdichte, l=estigkeitseigcnschalken und natOrlicher Dauerhaftig- keit vorgestellt und M6gliclnkei|cn der handwerklichcn und indu- striellen Holzvcrwendung diskutiert.

k n o w n and second o n l y to b r i s t l econe p ine (Pimxs aristata Enge lm. ) in verif ied longev i ty (J. K l e i n s c h m i t 1984, D. L. D e k k e r - R o b e r t s o n a n d J. Svo lba 1992). I r e m e m b e r very well m y first visit to the M a r i p o s a G r o v e in 1959 a n d the awe I felt f ac ing trees exceed ing a he ight o f 80 in, a d i a m e t e r at b r eas the igh t o f 10 m, a n d a v o l u m e o f 1.000 m 3 (Fig. 1).

1 Introduction

It is ce r t a in ly a special pr ivi lege to ta lk here at Visal ia a n d close to the wes te rn s lope of C a l i f o r n i a ' s Sierra N e w t d a a b o u t a species o f tree which is the b o t a n i c a l s a u r i a n of o u r wor ld , the mos t mass ive l iv ing o r g a n i s m

Abbreviated form of the Banquet talk at the Symposium "Giant Sequoias: Their Place in the Ecosystem and Society", held by the U.S. Forest Service, the University of California and other Contributors and Sponsors at Visalia, Calif., USA, June 23 25, 1992.

2 Herrn Professor Dr. Horst Schulz, M/.mchen, aus AnlaB seines Ausscheidens aus dem Dienst gewidmet.

-~ Der Verfasser schuldei Herrn Forstdirektor Dr. J. Kleinschmit Letter der Abt. C der Niedersiichsischen Forstlichen Versuchs- anstalt zu Escherode, herzlichen Dank flit wcrtvolle Hinweise zur Genetik. Anzucht und Verbreitung der G. S.

Fig. 1. Giant Sequoias of about 700 years in Mariposa Grove within Yosemite National Park (Photograph of 1959) Bild I. Etwa 700jS.hriger Mammutbiiume (Sequoiademlron ,gigan- wum (Lindl.) Buchholz)im Mariposahain innerhalb des Yosemite Nationalparks (photographiert 1959)

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But already in the decade of the Fifties of this century, C. A. Schenck (1953/54), a man who inspired modern forestry in the US as in Europe, finished a broad inventory of ~'exotic" trees investigated by the German Dendrological Society with the remark, that the growth of Giant Sequoia planted in many parks and botanical gardens in Europe surpassed all other species controlled by the society. Looking at the knottiness of the species he asked on the same occasion, what we should do with the wood of a tree, which was shunned for exactly this reason even in California. In 1957/58 E. and I. Marlin, a dentist couple and hobby dendrologists, stressed the potential of Giant Sequoia as an useful addition to forestry and started planting some younger stands in the West of our country, fascinated mainly by the growth rates of stands established at Weinheim (Germany) and Belle Etoile (Belgium).

2 The way to Europe

R. J. Hartesveldt (1969) traced down not only the history of the tree's discovery by the white man about 1833, but also some of the seeds ways to Europe about 1853. He listed 591 locations in 25 European countries, where Sequoiadendron was planted and surviving to significant size. But it was W. J. Libby and L. Fins (1976, 1979 and 1981). who mobilized the interest of Forestry and Forest Product 's research in a species, which was well represent- ed in Europe before the quaternary glacial periods as was Douglas-fir.

Where did we get the first seeds f rom? It seems today that the parties who crossed the Sierras on their way to the west met the giant trees in the most northern areas of a band nearly 4 0 0 k m long distributed along the western slope of California's Sierra Nevada mountains. It is quite sure, that within the 20 years which passed between the first encounters in 1833 and a first report in London 's Gardener ' s Chronicle m 1853. other groves in the Sierras may have been found. Since the seeds were introduced to botanical gardens, arboreta and parks and not to forests, little is known about their origin. On the other hand, these seeds were very expensive (B. J. Hartesveldt 1969). Until the early years of this century, only three true stands according to a forester's un- derstanding were planted in Europe, the first of them in 1862 by Baron Christian v. Berckheim at Weinheim, Germany, the second in line the one in Belle Etoile of the Groenendaal Experiment Station, by now 91 years old, and finally one of the same age at "Tervuren'" at the Donation Royale, both located in Belgium (J. Klein- schmit 1984). All the younger stands were established after World War II in a time, when greater knowledge and experience was available from earlier plantations of stands and solitaires.

3 Climates and soils

What were the lessons learned by Europeans exploring the results o1" more than 100 years of raising Giant

Fig. 2. Locations where Giant Sequoias were st, ccessfully planled ill arboreta, parks and botanical gardens in Western Europe (according to R. H. Hartesveldt (1969), W.J. Libby (1981) and J. Kleinschmit (personal communication)

Bild 2. Verbreitung des Mammutbaunles in Arboreten, Parks und Botanischen Giirten in Westeuropa {nach Anflistungen yon R. H. Hartesveldt (1969), W. J. Libby (1981) und pers6nlicher Mitteilung von J. Kleinschmit

Sequoias between Norway and the Black Sea, and between the Mediterranian and the Baltic Sea (Fig. 2)'?

Sequoiadendron has shown itself to be adaptable to a wide range of climates. While it occurs naturally only between northern latitudes of 35 < 5' and 39: 3', it was successfully planted in Europe between latitudes of about 39 ~ and 61':. In California it occurs between 1370 and 2300 m elevation where annual precipitation averages of more than 1000 mm. Precipitation falls in the form of snow or rain almost entirely in the winter. Most of the European plantations are located further to the north and have a colder and wetter weather. Elevations range from sea level up to 1000 m with rainfall amounts less than 1000 mm scattered all over the year.

M. Guinon, J. B. Larsen and W. Spethmann (1982) found frost resistance to be one of the limiting factors regarding the growth of seedlings, but at the same time significant and substantial differences in winter damage between 22 provenances representing the entire natural range of Giant Sequoia in California. After the period of plantat ion and first thinnings the warmth of the growing season seems to be of some importance (W. Lib- by 1981, Landesanstalt fiN Okologie L61f 1982).

Man}' quite different soils proved to be a healthy basis for the growth of Sequoiadendron. Weak and moderate

147

acidity seems to be a litvourable quality, as are well areated and well drained soils. Loose sediments and sedimentary rocks as graywack and slate showed themsel- ves to be very good as did silicaterich areas. Since the roots of the species keep expanding quickly into the lower horizons of the soil profiles, they are capable of reaching the upper levels of groundwater, developing a somewhat heartlike form of the overall root (Wolford, J. L. and Libby, W. J. 1976). On the other hand stagnating water proved to be the source of many disappointments (L61f 1982).

4 Form of the crown

Sequoiadendron is simply a beatttiful tree, a fact, that explains the rapid progress in the many parks and arboreta in Europe. This is true not only for nearly all stages of its life as a solitaire, but also in the companion- ship of its natural neighbors within its Californian environment ( A bh's concolor, Pinu.r.fl~/J)'eri and pondero.~a and Calocedrtts &'currens). The form of the crown is highly variable, partly for genetic reasons (E. J. Martin 1957/58. L. Fins 1979), and partly for the pressure produced from other species within the same stand (Fig. 3)

Since Sequoiadendron suffers badly from all types of shadow, it should be planted in distances of about 4 x 4 m. The other species, in Europe mainly Douglas- fit', European larch, Black pine and European Silver fit-, should be mixed into the spaces left after Sequoiadendron has survived the first tests of its frost hardiness. With increasing age, the yellow-brown colour, the strong textttre of the bark, and the silvery or sometimes yellow- ish-golden shine ot'the leaves, a genetically fixed variabili- ty, will add to this impression (R. J. Hartesveldt 1969, J. Kleinschmit 1984).

Fig. 3. One of the oldest and tallest Giant Sequoias in Germany was planted about 1870 in the country estate of the [\~rmer Grand-Duke of Hessia-Darmstadt at F~rstenlager near Bensheim. Height 1992 about 60 m Bild 3. Ether der iiltesten und h6chsten Mammutbiiumc Deutsch- lands wurde tim 1870 im Park des Landsitzes des GroBherzogs yon Hessen-Darmstadt ,,F{irstenlager" bet Bensheim gepflanzt. H6he 1992 ca. 60 m

5 Genetic architecture

For reasons mentioned before Europeans felt rather disappointed about their restricted knowledge of the differences in growth and quality of Giant Sequoia originating from variations m the genetic architecture of the species within the area of its natural distribution in California. Certainly, R. Kleinschmit, the father of J. Kleinschmit, began a conservation program for Sequoi- dendron specimens older than 60 years, north of the Main river, which had already proven to be frost hardy enough to survive tinder comparably hard conditions in 1955. Seeds of these trees were grafted and planted in an orchard in Escherode. They showed that Sequoiadendron is by far the most productive conifer which can be grown in Europe [J. Kleinschmit 1984). Later it was Lauren Fins, who furnished seeds from 34 different provenances within the Sierras to the Lower Saxony Research Institute in 1976. The seeds constituted the basic material for tests on 3 different sites in North Germany (L. Fins 1979).

Recently, D.L . Dekker-Robertson and J. Svolba (I 992) reported the first results of this experiment (Fig. 4) Leaving aside many of the interesting statistical problems and the uncertainty of inbreeding I should like to mention only that the tallest provenance overall was Whitaker 's Forest, followed by Standard USA and Mountain Home. Mortality did not follow a generally geographic distribu-

148

tion, nor was it influenced by the elevation from which the provenance originated. Certain provenances appear- ed to be poor survivors and performers on most sites. On the other side J. Kleinschmit (1984) mentioned, that he forwarded stecklings from 22 provenances to the French Afocel and received seeds from 11 stands from A. Franclet. Other investigations are under way in Hung- ary and Yugoslavia, all of them cooperating with the University of California.

6 Growth and yield

In our attempt to get more information about the qualities of Sequoiadendron as a forester's tree, its growth and yield required special consideration. We had learned much about the fantastic growth of solitaires in many parts of Europe; but solitary trees don't behave like trees in normal stands, and tile number of real stands is very limited, as mentioned before. The famous stand at Wein- helm, by now 120 years old, still shows a current annual increment per ha of 20 cm 3, the one at Belle Etoilc a mean annual increment of more than 44 m 3.

This is by far more than every European conifer can do in its highest yield classes (European silver-fir, yield class I, after heavy thilming 21) m 3, at age 45). But these "stands" represented a size of only 1,4 resp. 0,25 ha (J. Kleinschmit 1984). Therefore, we decided to analyse growth as weU as yield and wood quality by sampling whole trees from 7 different stands with ages between 11 and 98 years from the same stands. M. Guinon. F. Hapla, S. Lewark and C. Schr6der (1983) collected 2 increment cores per tree from a total of 20 trees in dominant or intermediate positions, representing Kraft 's tree classes l - I l l .

The width of the annual growth rings frequently exceeded 18 nun during the first and second decade of life, leading to diameters at breast height up to 45 cm (including bark)a t an age of only 20 years. Stem analyses of these European trees indicated (Fig. 5) that this period of 11tscinating growth is restricted" and as a result, most plantation trees produce a decidedly tapered form (0~ versus 0,47 for European silver-fir). Only as the crown recedes does the maximunl width of the growth rings shift upwards, resulting in a more cylindrical bole of the mature tree. Using the control data of different stands in Nordrhein-Westlillia and simulating the further devel- opment of height and breast-height diameter, the Forest Experiment Station of Nordrhein-Westlillia designed the future of both parameters to an age of 120 years (L61f 1982). I should like to compare these curves with those of the best site classes of Douglas-Fir, Norway spruce, and Scots pine according to the tables of Bergel 1969, Wiedemann 1936/42 and Wiedemann 1943 to exernpli~* the potentials of Giant Sequoia in Western and Central Europe (Fig. 6 a, 6 b).

Fig. 4. Mortality of provenances fi-om different Calili)rnian G. S.- groves planted by the Lower Saxony Forest Research Institute at Escherode at 3 different areas in Lower Saxony, (D. L. Dekker- Robertson and L. Svolba 11992) Bild 4. Sterblichkeit unterschiedlicher kalifornischer Provenienzen des Mammutbaumes auf 3 unterschiedlichen Versuclasfliichen dcr Nieders. Forstlichen Versuchsanstalt, Abt. C., Escherode. innerhalb Niedersachens (D. L. Dekker-Robertson und L. Svolba 1992)

7 Wood quality

Our drawings lead us to problem No. 1 regarding the use of the wood of our tress: its knottiness. From the lack of natural regeneration and the necessary wide spacing of most plantations we get so many knots within and outside of the trunk, that it appears sometimes difficult even to take increment cores at breast-height fl-om younger or medium aged trees. Due to several l:actors, i. e. the early heartwood formation in stem and branch, the length of time the dead stubs relnain oil the tree exceeds the proport ions known in other species. In addition a two-dimensional drawing of distribution and size of knots on the surface of a younger stem floln Belle Etoile shows that there are practically no internodes between the branch generations (Fig. 7). Giant Sequoia is so slow in shedding its branches that early pruning is a must in order to produce an appreciable vohime of clear lumber within rotation periods of short or

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Fig. 5. Stem analyses of two trees from Belle Etoile, Belgium, showing the typical decrease of diameter growth with age, but also indicating the wmation of the zones of intergrown and loose knots within the trunk of Giant Sequoia

Bild 5. Stammanalysen yon zwei Mammulbiiumcn arts Belle Emile, Belgien, veranschaulichen nicht nt.r den mit dem Baumalter nachlas- sendcn Durchmesscrzuwachs, sondern zugleich die m~ichtigcn und ffir den Mammutbaum typischen weiB- und trockeniistigen Stamm- zonen (M. Guinon, F. Hapla, S. Lewark und C. Schr6der 1983)

medium length. 011 the other side, pruning apparently is the most effective means to achieve a more cylindrical form of the stem within reasonable time.

fungi, phenomena which deserve more exploration and examination.

8 Heartwoodformation

I fhea r twoodformat ion is a prerequisite for early pruning, its wlriation within Sequoiadendron giganteum deserves special attention. In Europe, we were surprised by variations within the different trees collected (W. Knigge, P. Pellinen and T. Schilling 1983). While the transition of sapwood into heartwood starts as early as after the formation of the 5. to 9. growth ring, there is flequently a variety ofcolours within sapwood and heartwood (Fig. 8a, b). Apparently, even the famous heartwood of Giant Sequoia seems to be the object of attacking bacteria and

9 Fiberlength

A significant part of second-growth wood of Seqnoiaden- dron will end up in pulp and board mills. This led us Io the investigation of its tiberlength. As in most softwoods, tracheid length within a stem cross section showed the typical increase from the pith to the bark. From 4.800 measurements in different heights of a 63 year old tree from the Belle Etoile-plantation, the average tracheid length turned out to be 3.09 mm (Fig. 9) compared to 1.1-6.3 in Norway spruce and 1.3 4.5 in Scots pine. As usual the increase was also more distinct within the juvenile wood than within the more mature wood, The

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Fig. 6a, h. Average height a and diameter growth tit breast-height b o[" Giant Sequoias planted in Nordrhein-Westfalia, compared with Site Classes I and 1I of Douglas Fir, White Fir and Scots Pine (Data from L/31f 19821

Bild 6a, h. Vcrlauf des H6hcnzuwachses a und des Durchmesser- zuwachses b des mammutbaun3es, crrechnet yon dcr Nordrhein- Westf:~ilischen Forsllichen Versuchsanstalt im Vergleich zu Fichte. Kiel'er nnd Tanne (L61f 1982)

curves show cont inuous increase in cell length with neither a levelling o f constant cell length nor a decrease after reaching a maximum. Apparent ly the tree in- vestigated had not yet achieved its max imum tracheid length (W. Knigge, B. Wenzel 1992).

I0 Specilic gravity

Specific gravity resp. density o f European Giant Sequoia was the next proper ty to be examined on European trees.

Scole Height 1:10 Oiemeter 1:5

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0,1-1,0 1,1-2,0 2,1-3,0 3,1-4,0crn

Fig. 7. Distr ibution and size of knots found on the two-dimensional- ly drawn outer surface of a medium-aged Giant Sequoia fiom Weinheim, Gemany (W. Knigge, P. Pellinen and T. Schilling 1982) Bild 7. Verteilung und Durchmesser der ]&ste, zweidimensional dargestellt aufder Stammoberfliiche emes mittelalten Mammutbau- rues aus Weinheim (W. Knigge, P. Pellinen und T. Schilling 1983)

The measurements on 3.149 samples from 14 trees produced data, which put this species on the class o f ultra-light softwoods. We found a medium value o f 0.346 g/cm 3 with a range from 0.180 to 0.600 g/cm 3

This permits the conclusion that Giant Sequoias will provide us with an easily handled and easily utilizied raw-material.

On the other side, it is o[" more than only academic interest that we found Giant sequoia 's specific gravily neither positively not" negatively-correlated with the width o f the annual growth rings~ and that some models o f the variation within the trees investigated showed a decrease between the pith and the bark (Fig. 10). No significant correlat ion could be established between wood density and age, width o f the annual rings and the height o f the samples within the tree. Certainly we do not have to be aft'aid o f relatively wide spacings o f new plantat ions as long as we care for the necessary job o f artificial pruning, another reason for doing so.

1 1 Strength properties

Regarding the Strength properties I am well aware o f the fact that in California Giant sequoias strength is generally considered to be inferior to the Coast Redwood. Our own tests based on the trees ment ioned earlier f rom plots in Belgium and G e r m a n y showed low values for Compress ion strength and Tensile strength parallel to grain (Fig. 11). Also, static Bending strength turned out to be low in compar is ion with nearly all o ther

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Fig. 8a, b. a Formation of multicoloured heartwood and moderate decay in two trees from Weinheim (Germany): b Nearly unicoloured in two trees from Belle Etoile (Belgium) Fig. 8a, b. a Verkernung und m/-il3igc Kernl~iule in zwei Stiimmen aus Weinheim (Deutschland); b Nahezu gleichmiiBige Kernfarbe yon zwei Stiimmcn aus Belle Etoile (Belgien) (W. Kiligge, P. Pellinen und T. Schilling 1983)

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152

Fig. 9. Variation of fiber-length between pith and cambium in a tree of 63 years from Belie Etoile (Belgium) Bild 9. Ver~inderungen der Faserlfinge zwischen Mark und Rinde innerhalb eines 63jiihrigen Mammutbaumes aus Belle Etoile (Bel- glen} (W. Knigge, B. WcnzeI 1982)

Fig. 10. Variation of specific gravity within the same tree in- vestigated for its fiber-lenglh 163 years old from Belle Etoile, Belgium) Bild 10. Veriinderungen der Rohdichte innerhalb des gleichen aus Belie Etoile (Belgien) stammenden Mammutbaumes

softwoods of Europe and North America. On the other band, Shock resistance or Toughness showed a medium of 4.21 J/cm 3. Surprisingly, toughness of the sapwood zones proved to be significantly higher than those of the heartwood area, a phenomenon very likely connected with the unusual variation of specific gravity. Puzzled by this result, we increased the number of samples examined, dividing the total 1600 equally between heart- wood and sapwood. But the result did not change significantly. All the data collected lead us to the still tentative statement, that while the static strength proper- ties of second-growth Giant Sequoia are very modest, its toughness deserves recognition.

12 Durability

Last but not least the durability of Giant Sequoia was largely considered as its most outstanding wood quality. We left this part of our investigation to the Fraunhofer- Society for applied research at the Wilhelm-Klauditz- Institute in Braunschweig. While early growth was ham- pered in many areas of Europe by Armillaria mellea (Honey fungi), Botrytis cinerea (Grey-mould) and seve- ral forms of the genus Stereum accompanied single trees

until the age of maturity. At Braunschweig fl-ont- and backside of sun- and rainexposed samples within a multi-year-durability test did not show signs of fungal or bacterial altack during the first 18 months (Fig. 12). According to Dr. B6ttcher the colour changed slightly from red to a grayish red in the heartwood zones, while the sapwood demonstrated not more resistance than other European softwoods, i.e. Norway spruce and White fir.

13 Sequoiadendron's limits

Regarding the limits of frost-hardiness, we should like to leave this problem to further analysis by geneticists. The problems of diseases or decay are probably not greater than in all other species which were extinguished during the ice-ages and which are currently under consideration for partial repatriation. Therefore the possibilities of utilization of the wood of Giant Sequoia seem to hold the key for its propagation.

However if we can handle the problems of fast-growing Monterey pine (Pimls radiata D. Don.) more or less the world over, we should be able to solve those originating from the particulars of Giant Sequoia. From the Wood

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Fig. 1 l. Static and dynamic strength properties of 14 Giant Sequoias from 7 stands in Belgium and Germany. There were not significant differences between sapwood and heartwood. Static strength turned out to be low, dynamic strength as moderate

Bild II. Statische und dynamische Festigkeitseigenschaften von Proben aus 7 Bestfinden und 14 Stiimmen aus Belgien und Deutsch- land. Es pr~igten sich keine signifikamen Unterschiede zwischen den Proben atts Splmt- und Kernholz aus. lnsgesamt erwiesen sich die statischen Festigkeitseigenschaflen als niedrig, (lie dynamischen als damit verglichen mittelhoch

Biologists point of view, plantations of the future should consist of genetically controlled material. As we learned B. Libby and L. Fins with co-workers of the University of California resp. Idaho keep devoting much interest in the genetic pecnlarities of this species. In Europe, several research groups joined them in exploring the variability of different clones. First thinnings could be combined with harvesting Chrislmas trees, which could casily be sold domestically and internationally. Early pruning, which is extremely necessary, should enable us to sell the green parts of the branches during the October- and November-season. By increasing the ratio of the thinnings over the years, the usual decline of diameter growth should be slowed down to a certain extent.

On the other side, we should not expect a yield of 20 m 3 per annuln et hectare under every condition of soil and climate. But quite apparently the average growth of Monterey Pine at the southern half of this world can at least be achieved. Therefore a rotation period of 30 to 40 years according to the different site classes - would

leave enough time for the necessary heartwood formation and diameter growth at breast height to at least 45 cm.

14 Utilization

Regarding its utilization, Europeans understandably lack the experience gained in the U.S. over 150 years. Because of Sequoiadendron's limited strength, beautiful colour and high durability planing-mill products such as doors, sidings and ceilings, and also fences, poles, boxes and crates could be produced like those recommended for Redwood (Panshin, A . J . ; Zeeuw, C. de 1980). The smoothness of its surti~ce and its low shrinkage and swelling recommend its wood for pipes and flumes as well as for garden furniture and boatbuilding. The pruned lower part of the trunk should permit the production of light plywood, which we need for an alternative to the heavy-weight technical plywood manufactured from Eu- ropean hardwoods. But we could use the wood of Giant

Fig. 12. Durability lest of different species including Sequoiadendron gigameum at the Wilhehn Klauditz Institute at Bratmschweig (Courtesy of P. B6ttcher, WKI)

Bild 12. Freilandversuch zur grmittlung der natfirlichen Dauerhaf- ligkeit verschiedcner Nadelbaumarten, darunter Sequoidendron gi- ganteum (Lindl.) Buchholz im Wilhehn Klauditz-lnstitut zu Braun- schweig (Bild P. B6ttcher, WKI)

154

Fig. 13. Bronze-plaque donated by Prof. H. Bruman (UCLA) oil a stump of a Giant Sequoia in the Botanical Garden cominemorating the '~Education-Abroad-Progranl" between the University of Cali- fornia and the Georg August University of G6ttingen inaugurated in 1963

Bild 13. Bronzetafel at, f einem Stock tines Mammutbaumes im Botanischen Garten der Georg August-Universitiit G6ltingen, ge- stiftet von H. Bruman (UCLA), erinncrt an die Inauguration des akademischen Austauschprogramms mit der Universitfit in Kali- fornien im Jahr 1963

sequoia also for shingles and shakes, and, as experience indicated also, as a material for turned and carved articles, if the width of the annua l rings does not exceed 10 mm. Other parts of the harvest of th inn ings may be used by the f iberboard- and par t ic leboard industry. While most of these forms of intelligent ut i l izat ion are still matters of careful p lann ing and in t roduc t ion , we never- theless believe in a future for the big tree in the western parts of Europe.

A final remark: The Georg-Augus t -Univer s i ty of G6t t in - gen is glad to be the G e r m a n par tner of the Educa t ion- Abroad -P rog ram of the Universi ty of California. A bronze-plaque donated by Dr. Henry Brnman, U C L A , co~rm-mmorates the founda t ion of this ins t i tu t ion in the year 1963 (Fig. 13). Located just in the middle of a small grove of G ian t Sequoias within the new Botanical garden it is close to our School of Forestry and very near to our Forest Products Labora tory .

15 References

Becker, G. : Die Bedeutung des Roh- und Werkstoffes Holz ffir die Zukunfl sichern: Eine Herausforderung fi.ir die Holzforschung. Forstarchiv 63 (11) (1992) 80 84

Blank. R.: Buck-Gramcko, A.: Knigge, W.: Physikalische Holz- eigenschalien des Mammutbaumes (Sequoiadendron giganteum (Lindl.) Buchholz) aus europiiischen Versuchsanbauten. Forst- archly 55 (5) (I984) 199 202

Cockrell, R.A.: Knudson. R.M.; Stangenberger, A.G.: Me- chanical properties of Southern Sierra old- and second-growth Giant Sequoia. Univ. of Calillk~rnia, Agricultural Experiment Station, Berkeley, Bull. 854: (1971) 14 p.

Cockrell, R. A. : K nudson, R. M. : A comparision of static bending. compression and tension parallel to grain and toughness proper- ties of compression wood and normal wood of a Giant Sequoia. Wood Sci. Technol. 7 (4) (1973) 241 250

I)ekker-Robertson, D. I_,. ; Svolba, J. : Results of a Sequoiadendron giganteum (Lindl.) Buchh. provenance experiment in GeNnany. Silvae Geneticae 41. (in press) (1992)

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Guinon, M.: Larsen. J. B.; Spcthmann, W.: Frost Resistance and Early Growth of Sequoiadendron giganteum seedlings of different origins. Silvae Geneticue 31 (5 6) (1982) 173 I78

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: ~ u c h b e s p r e c h u n g e n ........ ::

K6nig, G.; Nowak, S. (Eds.): Bridge rehabiliiaiion. Proceedings of the 3rd International Workshop on Bridge Rehabilitation, orga- nized by the Tecbnical University Darmstadt and the University of Michigan, June 14 17, 1992. 842 S.: 508 Abb. Berlin 1992: Ernst & Sohn. ISBN 3-433-01235-0. DM 118, .

Von alters hat die Br{icke als Sinnbild Dichter und Denker und nicht zuletzt Ingenieure bewegt und herausgefordert, dem Streben nach Verbindung Dauer zu verleihen. Die Gestalt gewordenen Konstruktionen unterliegen gleichwohl dem immer sch/.irfer werden- den Zahn der Zeit. Nicht, dab ibnen nur ibr natfirliches Alter zusetzen wfirde, vieI mehr sind es die nicht bedachten Belastungen, die ihnen das Altwerden erschweren: Gewachsene Verkehrsbela- stungen, steigendc Luftverschmutzung und Korrosion, mangelhafte Wartung, manchmal gewif3 auch zu wenig erprobte Baustoffe und Herstellungsverfahren, gelegentlich auch Unlcrgrundprobleme oder gar Erdbeben. Und schlieBlich sind moderne Konstruktionen mit Hilfe komplexer Berechnungsverfahren inzwischen so ausgereizt (ausgehungert), dal3 sie Tragreserven im Ernstfall kaum noch mobilisieren k6nnen.

Vor diesem Hintergrund haben die Universit/iten yon Darmstadt und Michigan (USA) vom 14. his 17. Juni 1992 in Darmstadt ihr 3. internationales Arbeitstreffen zum Thema Brfickensanierung durchgeffihrt und als Ergebnis ansatzweise so etwas wie cinen Statusbericht fiber den Zusland amerikanischer und europS.ischer Br/icken vorgelegt. Der Sammelband nail 76 Beitriigen yon 144 Au- toren drei viertel der Beitrfige kommt aus Europa, davon allein ein drittel aus der Bundesrepublik, der Rest aus den USA und Kanada bringt in 10Abschnitten einen ()berblick fiber die brennenden Probleme: Einsch[itzungstechniken und -verfabren (54S.), Sanierung und Ertfichtigung (58 S.), Fallstudien (183 S.), Prfifverfahren und praktiscbe Prfifung (114S.), seismische und dynamische Belastungen 140 S.), externe Vorspannung (60 S.), Ver- sagenswahrscbeinlichkeit 176 S.), Forschung 1104 S.), Vorschriflen (46 S.) sowie Korrosion und Dauerhaftigkeit (98 S.). Ein kurzes Stichwort- und Autorenverzeichnis schlie[,h den Sammelband ab. Bet einigen Beitriigen des im fibrigen lesenswerten Bandes w/-iren zu den Brfickenbeispielen etwas genauere Daten-, Zeit- und Ur- sachenangaben fiir die Schfiden wfinscbenswert gewesen, auch mancbe MaBangaben bleiben wegen feh[ender Einheiten unklar: und dab PC "prestressed concrete" bedeutet, entdeckt der Holzwurm eher zuf'allig!

Etwa 60% der Beitrfige befasscn sich mit Problcmen bei Stahl- beton- und Spannbetonbrficken, 28% nail solchen bei Stahlbrficken. 8<% mit weitgebend materiahmabhiingigen Vragestellungen. Ge- mauerte Brficken sind mit rund 3%, h61zerne Brficken /.iberhaupt nicht vertreten. Bereits diese Verteilung zeigt, wo die Probleme konzentriert sind. Wic cin roter Faden zieht sich durch die Papiere die Feststellung, dab die meisten Schfiden bei dcn jfingeren Brficken auftreten, was niemanden verwundern kann, der sich vergegenw/:ir-

tigt, dab beispielsweise in den USA mit msgesanlt 577710 Brficken (1991) knapp 50% nach 1940, in Deutschland sogar 80% nach 1960 erbaut wurden. Dabei sind in erster Linie die Stahlbeton- und Spannbetonbriicken mit Korrosions- nnd Vorspannungst~roblemen betroffen, w/ihrend alte i. a. genietete Stahlbrficken. die z. T. nocb aus dem VOligen Jahrhundert stammen, zwar ebcnfalls rail Korro- sionsproblemen kfimpfen, jedoch i.a. noch als ausreichend sicher gelten und oft nur wegen gestiegener Verkehrslasten ertfichtigt wurden.

Der Salnmelband vermittelt allgemein interessante Einblicke in die HilfsmitteL auf die Diagnose- und Sanierungstechniken heute ztli-fickgreifen k6nnem Beschleunigungsaufnehmer zur Erfassung des Sch~ingungsverhaltens, Sensorcn zur Auffindung yon Korro- sionsncslern im Beton, phutogrammetrische Methoden zur CAD- gestfilzten Erzeugung 3-dimensionaler Plots konstruktiver Details odcr Geriite zur laufenden Beobachtung ausgew/ihlter Bauteilpunk- te [monitoring). Angedeutet werden nicht zuletzt auch die viellSlii- gen Verfahrensteclmiken zur Sanierung und Ertfichtigung bereits gesch~idigter Brl]ckenbauteile.

hn einzclnen interessant sind etwa die Feststelhingen zu einer Spannbetonbrficke fiber den Main, bet der die Vorspannung in 25 Jahren um 30% nachlieB gegenfiber 10% wie vorausbereclmet, oder zur Autobahnbr{icke fiber den Inn bet Kufstein, dercn Pfeiler 1990 ausgerechnel zur Urlaubszeit wegsackte und dercn Haupt- trfger nach Stabilisierung des Pfeilerfundamentes dnrch eine Tief- grfindung um bis zu 128 cm wieder angehoben werden konnten. Aus cinem polnischen Beitrag etwa entnehmen wir schlie[?,lich, dab in Wroclaw von insgesamt 134 Brficken 48% aus Beton, 29% aus Stahl und 20% aus Holz gebaut sind, wobei die Holzbrficken fiberwiegend als FuBgiingerbr/.icken oder untergeordnete Stra3en- br0cken dienen; bet 90% wurden allgemeine Miingel, bet 66% leichle Schiiden und bet 2% aller Briicken akute Einsturzgefahr festgestellt: {iber den Zustand der Holzbrficken im besonderen berichtct der Chronist lcider nichts.

Bedenkt man, dab die Herausgeber bis zu 40% des nationalen Brfickenbestandes als sanierungsbediirftig einstufen, so kann man sich lcicht eine Vorstellung yon den gewaltigen Finanzressourcen machen, die ffir eine fliichendeckende Sanierung der Brficken lockergemachl werden mfiBten. Um abet die knapper werdenden Mittel an den Brennpunkten wirtschaftlich und vor allem langfristig erfolgreich einzusetzen, mfissen Diagnose-, Berechnungs- und Sa- nierungsmethoden sowie die Herstellungsverfahren ffir Brficken so weiterentwickelt werden, dab nicht nur die Sicherheit tmserer Brfickenkonsiruktionen erhalten bleibt, sonderu auch die Dauerhaf- tigkeit dieser Verbindungen wieder ein Ideal der Ingenieurskunst wird. Und ein letztes set nocb angeffigt: Auch aus 6kologischen Griinden scheint es unabwendbar, die Philosophic des immer schnelleren VerschleiBes zugunsten einer Philosophie der Nachhal- tigkeit aufzugeben. D. Henrici