Other Woody Species (other + woody_species)

Distribution by Scientific Domains

Selected Abstracts

Growth response of woody species to elephant foraging in Mwea National Reserve, Kenya

Robert M. Chira
Abstract The African elephant (Loxodonta africana) is known to greatly affect the structure and dynamics of vegetation. In Mwea National Reserve, elephants foraged mainly on Acacia ataxacantha and Grewia bicolor out of the five most preferred woody species. However, out of the five preferred woody species, only Grewia virosa and G. bicolor showed a positive association between their fresh use and past elephant use. All the five selected woody species showed high coppicing response after foraging, with the highest coppice growth rates recorded for Acacia brevispica and lowest for Grewia tembensis. The mean heights of woody species utilized by elephants were highest for A. brevispica and lowest for G. bicolor. The mean heights of coppices emerging after utilization by elephants were not significantly different for A. ataxacantha but were significantly shorter in the rest of the foraged species. Elephants avoided the coppices of many other woody species notably C. africana, A. tortilis, A. mellifera, Combretum aculeatum among others in the reserve. The objective of this study was to understand the capacity of woody species to recover after utilization by elephants and feeding response of elephants to new woody species re-growth; a cycle that would define the dynamics of food resources and elephant population within the reserve. Résumé On sait que l'éléphant africain Loxodonta africana affecte beaucoup la structure et la dynamique de la végétation. Dans la Réserve Nationale de Mwea, les éléphants consommaient principalement de l'Acacia ataxacantha et du Grewia bicolor parmi les cinq espèces ligneuses préférées. Cependant, parmi ces cinq espèces, seuls Grewia virosa et .G. bicolor présentaient une association positive entre leur utilisation récente et ancienne par les éléphants. Les cinq espèces ligneuses sélectionnées manifestaient une forte repousse en réponse à la consommation des éléphants, et le taux de repousse était le plus élevé a été enregistré chez Acacia brevispica et le plus faible chez Grewia tembensis. La hauteur moyenne des espèces ligneuses consommées par les éléphants était plus grande chez A. brevispica et plus petite chez G. bicolor. La hauteur moyenne des tiges qui avaient repoussé après consommation des éléphants n'était pas significativement différente chez A. ataxacantha, mais elle était significativement plus courte pour les autres espèces consommées. Les éléphants évitaient les taillis de nombreuses autres espèces ligneuses telles que, particulièrement, C. africana, A. tortilis, A. mellifera, Combretum aculeatum, entre autres, dans la réserve. L'objectif de cette étude était de comprendre la capacité des espèces ligneuses de se régénérer après le passage des éléphants, et la réponse alimentaire des éléphants à la nouvelle repousse de différentes espèces ligneuses et d'esquisser ainsi un cycle qui définirait la dynamique des ressources alimentaires et de la population des éléphants de la réserve. [source]

The invasive alien leaf miner Cameraria ohridella and the native tree Acer pseudoplatanus: a fatal attraction?

Christelle Péré
1The horse-chestnut leaf miner Cameraria ohridella is an invasive moth in Europe and a serious pest of horse-chestnut Aesculus hippocastanum. The moth also occasionally attacks sycamore maple Acer pseudoplatanus, when situated beside infested horse-chestnuts. 2The main objective of the present study was to provide an overview of the relationship between C. ohridella and A. pseudoplatanus and to determine whether C. ohridella has the potential to shift to this native tree. 3In the field, females oviposit on different deciduous tree species. Although less frequently attacked than A. hippocastanum, A. pseudoplatanus was clearly preferred for oviposition over 12 other woody species investigated. 4Surveys in Europe demonstrated that the majority of A. pseudoplatanus trees found beside infested A. hippocastanum had mines of C. ohridella, even though more than 70% of the larvae died within the first two instars. Attack rates and development success greatly varied from site to site. Attack levels on A. pseudoplatanus were not always correlated with those on A. hippocastanum, and mines on A. pseudoplatanus were sometimes observed beside weakly-infested A. hippocastanum. 5Field observations, experimental exposure of A. pseudoplatanus saplings and rearing trials in a common garden study showed that individual trees may vary in their susceptibility to C. ohridella, whereas there was no evidence that C. ohridella populations vary in their performance on A. pseudoplatanus. 6To date, there is little evidence that C. ohridella represents a major risk for A. pseudoplatanus. [source]

Ecophysiological Response of Plants to Combined Pollution from Heavy-duty Vehicles and Industrial Emissions in Higher Humidity

Hong-Xia Cui
Abstract Pollution can be aggravated in industrial areas if traffic exhausts are mixed with industrial emissions under high humidity conditions. Plants growing in such environments may suffer from severe stress. The impact of vehicle emissions on urban vegetation in an industrial area in Qingdao, China, was investigated by studying seven plant species at visible, physiological and chemical levels. The traits of plant species in certain environmental conditions were compared between a clear area, Badaguan (BDG), and polluted area, Roadside (RS). We found that foliar sulfur uptake for all species was not significantly high at RS compared with BDG, although the sulfur content of atmosphere and surface soils at RS were much higher than those at BDG. For Ailanthus altissima Swingle, the content of foliar pigment and net photosynthesis rate (PN) decreased by 20%. Meanwhile, leaves became incrassate and no visible leaf damage was noted, suggesting this species could adapt well to pollution. A 50% decrease in PN occurred in Hibiscus syriacus L., but there was no statistical change in content of chlorophyll a and b and water uptake. Also, thickened leaves may prevent the pollutant from permeation. Foliar water content was still at a low level, although a water compensation mechanism was established for Fraxinus chinensis Rosb. reflected by low water potential and high water use efficiency. More adversely, a 65% decrease in PN happened inevitably with the significant decomposition of photosynthetic pigments, which exhibited visible damage. We also noted in one evergreen species (Magnolia grandiflora L.) that water absorption driven by low water potential should be helpful to supply water loss induced by strong stomatal transpiration and maintain normal growth. Furthermore, photosynthetic pigment content did not decline statistically, but supported a stable net assimilation. Two herbaceous species, Poa annua L. and Ophiopogon japonicus Ker-Gawl., were very tolerant to adverse stress compared to other woody species, especially in assimilation through a compensatory increase in leaf area. A more remarkable decline in PN (decrease 80%) was noted in the exotic but widespread species, Platanus orientalis L., with serious etiolation and withering being exhibited on the whole canopy. Our results suggested, special for woody species, that most native species are more tolerant to pollution and therefore should to be broadly used in a humid urban industrial environment with heavy-duty vehicle emissions. (Managing editor: Ya-Qin Han) [source]

Impact of storm-burning on Melaleuca viridiflora invasion of grasslands and grassy woodlands on Cape York Peninsula, Australia

Abstract This paper examines invasion of grasslands on Cape York Peninsula, Australia, by Melaleuca viridiflora and other woody species, and the role of storm-burning (lighting fires after the first wet season rains) in their maintenance. Trends in disturbance features, fuel characteristics, ground layer composition, and woody plants dynamics under combinations of withholding fire and storm-burning over a 3-year period were measured on 19 plots in three landscape settings. Population dynamics of M. viridiflora are described in detail and 20-year population projections based on transition matrices under different fire regimes generated. Numerous M. viridiflora suckers occurred within the grass layer, increasing each year regardless of fire regime, and were rapidly recruited to the canopy in the absence of fire. Storm-burning had little impact on fuel, ground layer or woody plant composition, but maintained open vegetation structure by substantially reducing recruitment of M. viridiflora suckers to the sapling layer, and by reducing the above-grass-layer abundance of several other invasive woody species. Population projections indicated that withholding fire for 20 years could cause a sevenfold increase of M. viridiflora density on Ti-tree flats, and that annual to triennial storm-burning should be effective at maintaining a stable open vegetation structure. These findings argue against vegetation thickening being an inevitable consequence of climate change. We conclude that a fire regime that includes regular storm-burning can be effective for maintaining grasslands and grassy woodlands being invaded by M. viridiflora. [source]