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Smaller Trees (smaller + tree)
Selected AbstractsMagnolia bawangensis sp. nov. (Magnoliaceae) from Hainan, ChinaNORDIC JOURNAL OF BOTANY, Issue 1 2009Dong-Ming Liu Magnolia bawangensis Law, R. Z. Zhou & D. M. Liu (Magnoliaceae), a new species from the Mount Bawangling, Hainan Province, China, is described and illustrated. It is closely related to M. paenetalauma Dandy, but differs by being a smaller tree with fewer spathe scars, absence of pedicels, pubescent and more numerous tepals, white pubescent and more numerous stamens. [source] Host tree architecture mediates the effect of predators on herbivore survivalECOLOGICAL ENTOMOLOGY, Issue 3 2006JANNE RIIHIMÄKI Abstract 1.,Vegetation structural complexity is an important factor influencing ecological interactions between different trophic levels. In order to investigate relationships between the architecture of trees, the presence of arthropod predators, and survival and parasitism of the autumnal moth Epirrita autumnata Borkhausen, two sets of experiments were conducted. 2.,In one experiment, the architectural complexity of mountain birch was manipulated to separate the effects of plant structure and age. In the other experiment the trees were left intact, but chosen to represent varying degrees of natural complexity. Young autumnal moth larvae were placed on the trees and their survival was monitored during the larval period. 3.,The larvae survived longer in more complex trees if predation by ants was prevented with a glue ring, whereas in control trees smaller canopy size improved survival times in one experiment. The density of ants observed in the trees was not affected by canopy size but spider density was higher on smaller trees. The effect of canopy structure on larval parasitism was weak; larger canopy size decreased parasitism only in one year. Until the fourth instar the larvae travelled shorter distances in trees with reduced branchiness than in trees with reduced foliage or control treatments. Canopy structure manipulation by pruning did not alter the quality of leaves as food for larvae. 4.,The effect of canopy structure on herbivore survival may depend on natural enemy abundance and foraging strategy. In complex canopies herbivores are probably better able to escape predation by ambushing spiders but not by actively searching ants. [source] Short-term survival and long-term mortality of Acacia drepanolobium after a controlled burnAFRICAN JOURNAL OF ECOLOGY, Issue 3 2008B. D. Okello Abstract We investigated the short- and long-term effects of a controlled burn in Acacia drepanolobium woodland in Laikipia, Kenya in 1998. Fire temperatures averaged 250°C at ground level, with a maximum of over 500°C, but were rarely >100°C at 1.5 m above the ground or more. Nine months after the fire, virtually all A. drepanolobium trees had survived the fire. Some smaller trees were burnt to ground level, but most were only ,top-killed' and had coppiced. Taller trees suffered less damage than smaller trees. However, a 2003 satellite image suggested a dramatic reduction in A. drepanolobium canopy cover at the site. A survey of the site in 2006 revealed that the density of larger A. drepanolobium trees was nearly three times greater in adjacent control areas than in the old burn, with a lesser reduction in the density of smaller trees. These data suggest that short-term measures of postburn survivorship may be deceptive, and that an additional source of tree mortality (perhaps elephants) was concentrated on trees in burned areas, even many months after the burn, with long-term consequences for tree and ecosystem dynamics. Résumé Nous avons étudié les effets à court et à long terme d'un feu contrôlé dans la forêt àAcacia drepanolobium située à Laikipia, au Kenya, en 1998. La température du feu avoisinait les 250°C au niveau du sol, avec un maximum de 500°C, mais elle dépassait rarement les 100°C à 1,5 mètre au-dessus du sol et plus haut. Neuf mois après le feu, pratiquement tous les Acacia drepanolobium avaient survécu. Certains des arbres plus petits avaient brûlé jusqu'au ras du sol, mais chez la plupart, seule la partie aérienne avait brûlé et ils avaient fait des repousses. Les arbres plus grands avaient subi moins de dommages. Pourtant, une image satellite prise en 2003 a suggéré une réduction spectaculaire de la canopée d'A. drepanolobiumà cet endroit. Une étude du site réalisée en 2006 a révélé que la densité des plus grands A. drepanolobiumétait près de trois fois plus forte dans les zones de contrôle adjacentes que sur le site brûlé, où la densité des plus petits arbres était moins réduite. Ces données suggèrent que les mesures de la survie postincendie faites à court terme peuvent être trompeuses, et qu'une source supplémentaire de mortalité des arbres (peut-être des éléphants) s'est concentrée sur les arbres des zones brûlées, même plusieurs mois plus tard, avec des conséquences à long terme pour les arbres et la dynamique de l'écosystème. [source] Variation in litter under individual tree crowns: Implications for scattered tree ecosystemsAUSTRAL ECOLOGY, Issue 1 2010CHRIS MCELHINNY Abstract In forest ecosystems litter is usually assessed in terms of the average amount produced by the canopy. In scattered tree ecosystems this approach is problematic because the canopy is discontinuous and the spatial arrangement of litter highly variable. We addressed this problem by quantifying the spatial variation in litter load and litter composition associated with individual trees in a Eucalyptus melliodora , Eucalyptus blakelyi woodland. Litter was sampled under crowns and in grassland adjacent to 10 E. blakelyi and 10 E. melliodora trees ranging in diameter at breast height (dbh) from 14 to 129 cm. A total of 302 L samples were collected from these trees, at distances ranging from 0 to 42 m from main stem. The sampled litter loads ranged from 0.02 to 109.3 t ha,1 and were significantly higher under tree crowns than in grassland for litter and each component of litter (leaves, bark, fine twigs, coarse twigs). In particular, the mean litter load under tree crowns (12.5 t ha,1) was an order of magnitude higher than the mean litter load in grassland (1.27 t ha,1). There was a significant (P = 0.0103) positive relationship between mean litter load under the tree crown and dbh, indicating larger trees produced more litter per unit area of ground than smaller trees. Generalized Linear Modelling produced highly significant (P < 0.0001) models predicting the spatial variation in litter load and litter composition in terms of distance from main stem and dbh. Our models demonstrate gradients in litter load and composition under tree crowns. These gradients were most pronounced for the large trees in our study. The disproportionate input of litter and variety of litter components associated with large trees in our study supports their keystone role in scattered tree ecosystems and highlights the need to maintain these structures in agricultural landscapes. [source] Influence of canopy tree size on stand basal area may reflect uncoupling of crown expansion and trunk diameter growthAUSTRAL ECOLOGY, Issue 2 2003Christopher H. Lusk Abstract A recent article by Midgley and colleagues suggests that large trees give rise to inordinately high stand basal areas because they pack canopy space more efficiently than smaller trees. We argue that this phenomenon bears more relation to the fact that diameter increment is not necessarily accompanied by significant crown expansion during all stages of a tree's life. Using data from a canopy tree population in an old-growth temperate forest, we found that crown area scaled as roughly the 3/5 power of trunk basal area. Rather than reflecting fixed scaling laws, we suggest that this pattern arises because of limited opportunities for crown expansion in dense stands. Old canopy trees in dense stands can thus accumulate large basal areas without occupying a commensurately large canopy area. [source] | ||||||||||