IAWA Bulletin n.s., VoI.9(1),1988:24-30 THE ECOLOGICAL WOOD ANATOMY OF THE LILACS (SYRINGA OBLATA VAR. GlRALDll) ON MOUNT TAIBEI IN NORTHWESTERN CHINA by Zhang Xinying, Deng Liang and Pieter Baas Department of Biology, Peking University, Beijing, China and Rijksherbarium, P. O. Box 9514, 2300 RA Leiden, The Netherlands Summary The wood structure of Syringa oblata var. studies of commercially important timber giraldii growing on the northem slope of species,chiefly temperate softwoods and fast Mount Taibei varies with increasing altitude, growing hardwoods such as Euca1ypts. In rainfall and to some extent with plant size between these two extremes, the study of and stern diameter. On Mount Taibei rainfall infraspecific variation in material of pre­ increases with altitude from 1000-1800 m. sumably limited genetical heterogeneity Average growth ring width, vessel member takes its rightfu1 place (e.g., Bissing 1982; length, vessel diameter, fibre-tracheid length Van der Graaff & Baas 1974; Wilkes 1988). and diameter, and ray height increase with The study of wood anatomical variation altitude and rainfall; vessel frequency, ray in the Chinese lilac variety Syringa oblata frequency, and percentage of solitary vessels var. giraldii, growing on the northern slopes decrease along the same ecological gradient. of Mount Taibei in China, was undertaken to These results are discussed against the back­ complement and refine an earlier general ground of general ecological trends: the un­ analysis of ecological trends in the wood usual reversal of the altitudinal trends can be anatomy of Oleaceae in China (Baas & accounted for by the rainfall pattern asso­ Zhang Xinying 1986). ciated with plant size variation on the north­ ern slope of Mount Taibei. Materials and Methods Key words: Ecological wood anatomy, alti­ Wood samples were collected of Syringa tude, rainfall, habit. ob/ata var. giraldii in Young Pe-gou (108° E 34° N) on the northern slopes of Mount Tai­ Introduction bei (3767 m) where it occurs as shrubs or In the study of ecological wood anatomy small trees between 1050 and 1800 m alti­ research of the last decades has mainly fo­ tude. In this region rainfall increases with al­ cussed on structural variation among species titude from 675 mm to 900 mm per year of ecologically diverse genera and families (above 1900 m it decreases again). The ma­ or of entire woody floras (e.g., Carlquist croclimate may be described as temperate, 1966, 1975, 1977; Carlquist & Hoekman with 3-4 fairly cold winter months (average 1985; Baas 1973, 1982, 1986; Baas et al. temperature -2 to -7°C), and mild summers 1983; Baas & Schweingruber 1987; Dicki­ (average day temperature 20-23°C). About son etal.1978; Dickison & Phend 1985; Van two thirds of the annual rainfall occurs in the der Graaff & Baas 1974; Van den Oever et summer months from early July through aI. 1981; Chalk 1983). The results of these September. The lilacs of Mount Taibei grow studies have generally been interpreted as in thick soi!. For full ecological data see Ma genetically fixed ev01utionary adaptations. Naxi (1982); some collecting data are given The study of wood anatomical variation in in Table 1. relation to site factors of genetically homo­ The material was sectioned in the usual geneous material is main1y restricted to way and sections were stained with safranin Downloaded from Brill.com10/02/2021 04:44:30AM via free access Zhang, Deng & Baas - Ecological anatomy of Syringa oblata 25 Figs. 1-6. Wood structure of Syringa ob/ata var. giraldii from Mount Taibei. Figs. 1, 3 and 5 from stern sampled at 1600 m. Figs. 2,4 and 6 from stern sampled at 1200 m. C = crystal, ST = spiral thickenings. Downloaded from Brill.com10/02/2021 04:44:30AM via free access 26 IAWA Bulletin n.s., Vol. 9 (1),1988 Table 1. Collecting data of wood sampies of Syringa oblata var. giraldU, growing on the north slope of Mount Taibei in shrub forest with Ostryopsis and Spiraea as dominant elements. Sampie number Altitude Habit* Plant height Stem diameter Stem age (m) (m) (cm) (years) 8601 1050 S 2 2.5 12 8602 1100 S 2.5 4.1 18 8603 1150 S 3 3.5 13 8604 1200 S 2.5 6.5 23 8605 1250 S 3 5.6 20 8606 1300 S 3 4.9 17 8607 1350 T 2.5 4.4 15 8608 1400 T 3 6.3 21 8609 1450 T 4 4.2 14 8610 1500 T 3 8.0 26 8611 1550 T 3.5 3.7 12 8612 1600 T 4 6.6 21 8613 1650 T 3 6.3 20 8614 1700 T 4 7.0 21 8615 1750 T 3 5.5 16 8616 1800 T 3.5 5.6 16 * S = shrub; T = small tree. and haematoxylin. Macerations were pre­ thick. Vessel member length 314-428 (127- pared using Franklin's method (hydrogen 529) 11m, perforations simple in oblique end peroxide and glacial acetic acid). walls. Intervessel pits nonvestured, alternate The 6-8 peripheral growth rings were se­ or altemate to opposite or diffuse, round to lected for wood anatomical study. Measure­ oval, 5-7 (4-12) 11m in diameter, with slit­ ments of length of vessel members and fibre­ like apertures. Vessel-ray and vessel-paren­ tracheids and of fibre-tracheid diameter were chyma pits with much reduced borders to al­ made using macerations. Vessel member most simple, smaller than the intervessel length was measured including the tails, and pits,4 (3-8) 11m in diameter. Spiral thicken­ fibre-tracheid diameter was measured at the ings weIl developed, usuaIly most pro­ widest part. The other quantitative data were nounced near pit apertures. Thin-waIled measured or counted in sections. For vessels tyloses often present. the outside diameter is given. Each average Fibre-tracheids 612-744 (360-2200) 11m value is based on 50 measurements or long, 14-17 (11-22) Ilill wide, thin- to thick­ counts. walled, with distinctly bordered pits in the radial and tangential walls, sometimes with Results spiral thickenings. Libriform fibres absent. Parenchyma very sparse to absent, re­ Wood anatomy 01 Syringa oblata var. gi­ stricted to some paratracheal or diffuse raldU (Figs. 1-6) strands of 2-4 cells. Growth rings distinct. Wood ring-porous to Rays 89-119/sq.mm in tangential sec­ semi-ring-porous. Vessels 332-471/sq.mm, tions, 1-3(-5) cells wide, 5-11 (2-16) cells 68-94% solitary, remainder in radial, oblique or up to 0.1-0.2 mm high, heterogeneous or tangential multiples of 2-5, mostly an­ II-III. gular, sometimes rounded in cross section, Crystals present in ray cells as small rod­ average tangential diameter 23-35 11m, radial like, cubical, acicular or diamond-shaped diameter up to 46-65 11m, walls 1-3(-4) 11m forms. Usually one crystal per ray cello Downloaded from Brill.com10/02/2021 04:44:30AM via free access Zhang, Deng & Baas - Ecological anatomy of Syringa oblata 27 ARD -ARD SV VF • SV (%) • VF 1.7 . 95 460 1.6 90 440 1.5 85 420 · 1.4 . •· 80 400 • · 1.3 75 380 1.2 70 360 1.1 65 340 1000 1200 1400 J600 1800 Fig. 7. Variation in average annual ring width (ARD,in mm),vessel frequency (VF in number per sq.mm) and percentage of solitary vessels (SV) plotted against altitude (in m). VL VD - VL • VD . 35 33 400 31 .• . 29 350 · · 27 . 25 23 1000 1200 1400 1600 1800 Fig. 8. Average vessel member length (VL, in 11m) and average vessel diameter (VD, in 11m) plotted against altitude (in m). Wood anatomical variation in relation to alti­ frequency, percentages of solitary vessels, tude, rain/all, and plant size vessel member length, vessel diameter, fibre­ In the altitudinal range from which our tracheid length and diameter, ray height and sampies were collected there tends to be ray frequency (per square tangential mm) are a steady increase in plant size and stern plotted against altitude of provenance. There diameter with increasing altitude and rainfall is a strong positive correlation between alti­ (Table 1). tude and ringwidth' percentage of solitary ves­ In Figs. 7-10 average ring width, vessel sels, vessel member length,fibre-tracheid, and Downloaded from Brill.com10/02/2021 04:44:30AM via free access 28 IAWA Bulletin n.s., Vol. 9 (1),1988 FL FW • FL *FW 18 . 17 700 * 16 • l 15 14 650 13 12 1000 1200 1400 1600 1800 Fig. 9. Average fibre-tracheid length and diameter (FL and FW, both in 11m) plotted against altitude (in m). RF RH • RF 120 • • RH 170 110 . 150 : 100 130 90 liD 1000 1200 1400 1600 1800 Fig. 10. Average ray height (RH, in 11m) and ray frequency (RF, in number per square tangen­ tial mm) plotted against altitude (in m). ray dimensions; at the same time vessel fre­ In addition to these correlations of quan­ quency and ray frequency are inversely re­ titative wood characters with rainfall and lated to altitude. Since on the north slope of altitude we found some weak tendencies in Mount Taibei rainfaII increases more or less other anatornical attributes. Sampies from linearly with altitude between 1000 and 1800 low altitudes and with narrow growth rings m above sea level, the above dependencies (Fig. 2) appeared to show a more abrupt would also apply to wood anatornical para­ change in size from earlywood pores to later meters and amount of annual rainfall. formed vessels, Le., were more distinctly Downloaded from Brill.com10/02/2021 04:44:30AM via free access Zhang, Deng & Baas - Ecological anatomy of Syringa oblata 29 ring-porous than sampies collected from The present results are not only indicative more fast growing specimens at higher alti­ of a positive correlation between rainfall and tudes (Fig.