[A-V/VISUAL/CD-ROM] DRAWING WITH LINE: Contour and Negative Space; DRAWING BASICS: Composition; DRAWING WITH LINE: The Grid and Proportions; and DRAWING WITH LIGHT AND SHADE. Videos/10–19 min. each/$39 each, $150 for set. Level: Grade 4 through Adult. Double Diamond Carp., P.O. Box 1557, 1480 Panus Ridge Road, New Canaan, CT 06840, (800) 938-2737. In the Composition video, importance is placed on how to compose a balanced still life, as well as how to find compositional elements in a landscape. Shading–often a difficult learning/ teaching task–is clearly presented with viewers observing how reflected light and cast shadows allows may be used to describe objects as well as establish the setting and scene. Students will also observe how to see the world through a grid drawn on plexiglass or acetate, and how to observe lines that define the subject in each grid square as they draw those lines in the corresponding grid square on their paper. A highly recommended series.-B.H. For information about this program, circle No. 396 on the Reader Service Card.
Licht, Schatten, Raum: Architekturvisu-alierung mit Cinema 4D [Light, Shade, Space: Architectural Visualisation using the Computer Program Cinema 4D], by Horst Sondermann. Springer Verlag, PO Box 89, 1201 Wien, Vienna 2006. 238 pp., 1060 ill., index. Price: 45.27 Euro. He has chosen the Cinema 4D program Version 9.5, because it is particularly well documented in German. Readers with a limited knowledge of the language will be greatly aided by the fact that the German computer terminology makes extensive use of English words, although they do not always have exactly the same meaning in German. The first three chapters explain the computer program, and particularly how a three-dimensional object is represented and developed in three dimensions on a two-dimensional screen. The author then discusses the representation of light, shade and space in three dimensions, and how to deal with central illumination, diffuse and indirect light.
Variation in shade tolerance is a key factor underlying forest successional dynamics. Shade-intolerant seedlings of species dominating early successional seres tend to be restricted to open, high-light habitats where they grow rapidly. Conversely, seedlings of shade-tolerant species dominating late successional seres are abundant beneath closed forest overstories where they are presumed to be able to out grow and/or out survive less tolerant species (Spurr and Barnes 1980). Shade-tolerance classifications for tree species have been developed for many regions, but generally these are based on subjective observation and/or assessment of characters thought to be related to growth in low light (Zon and Graves 1911, Baker 1949). Few studies have directly tested the possibility that both seedling growth and survival in forest understories fit these classifications (but for trees see Lorimer 1981 and for saplings see Pacala et al. 1993, Kobe et al. 1995). Several studies have examined growth (but not survival) in low light and most of them report reduced growth rates for all species in low light. However, most of these studies report higher low-light growth rates for shade-intolerant than tolerant species (Loach 1970, McClendon and McMillen 1982, Ramos and Grace 1990, Chazdon 1992, Kitajima 1994), while fewer report the opposite (Pompa and Bongers 1988, Denslow et al. 1990). Previous studies on five species of northern hardwoods that vary widely in shade tolerance are consistent with the former result (Walters et al. 1993a, b). In controlled-environment rooms we grew Betula papyrifera, Betula alleghaniensis, Ostrya virginiana, Acer saccharum, and Quercus rubra in moderately high light (14 h at 610 [[micro]mol][center dot][m.sup.-2][center dot][s.sup.-1], photosynthetic photon flux density (PPFD), [approximately equal to] 75-100% clear-sky total daily flux) and the two Betula and Ostrya in moderately low light (14 h at 125 [[micro]mol][center dot][m.sup.-2][center dot][s.sup.-1] PPFD, [approximately equal to] 15-20% clear-sky daily flux). We found that shade-intolerant B. papyrifera had higher growth rates than the other species in both high and moderately low light. Prima facie, the bulk of these results suggests that maximizing potential low-light growth rates is not an important and general component of shade tolerance. However, there are several potential reasons why higher growth rates for shade-intolerant than tolerant species have often been observed in low light studies: (1) growth rate potential in low light may be generally higher for shade-tolerant than intolerant species but only at very low light levels; (2) belowground resources (e.g., nitrogen, water) can colimit growth (Korstian and Coile 1938, Shirley 1945) and the degree of colimitation may vary with shade tolerance; (3) allocation to defense and storage in low-light plants may occur at a trade-off to growth (e.g., Chapin et al. 1990); and (4) variation in traits with no direct connection to growth potential or biomass conservation (e.g., seed dispersal and seedling establishment) in low light may be responsible for apparent differences in shade tolerance.In this report we explore some of these possibilities for the same five species we studied previously (Walters et al. 1993a, b). In outdoor shade houses over 2 yr we examined growth, survival, and their interrelationships at low and very low light levels (2 and 8% of full light) and at two levels of nitrogen availability (forest soil and forest soil plus nitrogen). We also explored hypothetical physiological bases of shade tolerance by comparing morphological and photosynthetic characteristics among species and examining their relationships with growth rate. High photosynthetic efficiency in low light and allocation to a large leaf area are assumed to be components of shade tolerance (Spurr and Barnes 1980), yet multiple-species tests of these assumptions in low light are rare (Loach 1967, 1970). In our previous work (Walters et al. 1993b) we found that growth rate in high light was correlated with in situ photosynthetic rate and allocation to leaves, whereas in moderately low light growth rate was correlated only with allocation to leaves. Thus leaf allocation could be more important than leaf photosynthetic rate as a source of variation in low light growth rates.In this study, five questions were addressed: (1) Do growth rankings reverse from those reported for high light levels (Walters et al. 1993a) such that shade-tolerant species have the highest growth rates at low and very low light levels? (2) Does variation in nitrogen availability change species growth rankings in low light? (3) Is survival in low light related to reported shade tolerances? (4) Is survival related to growth? and (5) In very low light is growth rate related to in situ photosynthetic rates and/or to allocation to leaves?
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