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Tropical forest tree mortality, recruitment and turnover rates: calculation, interpretation and comparison when census intervals vary 总被引:1,自引:0,他引:1
SIMON L. LEWIS OLIVER L. PHILLIPS DOUGLAS SHEIL BARBARA VINCETI TIMOTHY R. BAKER SANDRA BROWN REW W. GRAHAM NIRO HIGUCHI DAVID W. HILBERT WILLIAM F. LAURANCE JEAN LEJOLY YADVINDER MALHI ABEL MONTEAGUDO PERCY NÚÑEZ VARGAS BONAVENTURE SONKÉ NUR SUPARDI M.N. JOHN W. TERBORGH RODOLFO VÁSQUEZ MARTÍNEZ 《Journal of Ecology》2004,92(6):929-944
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DANIEL SIMBERLOFF MARTIN A. NUÑEZ NICHOLAS J. LEDGARD ANIBAL PAUCHARD DAVID M. RICHARDSON MAURO SARASOLA BRIAN W. VAN WILGEN SERGIO M. ZALBA RAFAEL D. ZENNI RAMIRO BUSTAMANTE EDUARDO PEÑA SILVIA R. ZILLER 《Austral ecology》2010,35(5):489-504
The history of conifers introduced earlier elsewhere in the southern hemisphere suggests that recent invasions in Argentina, Brazil, Chile and Uruguay are likely to increase in number and size. In South Africa, New Zealand and Australia, early ornamental introductions and small forestry plantations did not lead to large‐scale invasions, while subsequent large plantations were followed with a lag of about 20–30 years by troublesome invasions. Large‐scale conifer plantation forestry in South America began about 50–80 years later than in South Africa, Australia and New Zealand, while reports of invasions in South America lagged behind those in the latter nations by a century. Impacts of invading non‐native conifers outside South America are varied and include replacement of grassland and shrubland by conifer forest, alteration of fire and hydrological regimes, modification of soil nutrients, and changes in aboveground and belowground biotic communities. Several of these effects have already been detected in various parts of South America undergoing conifer invasion. The sheer amount of area planted in conifers is already very large in Chile and growing rapidly in Argentina and Brazil. This mass of reproductive trees, in turn, produces an enormous propagule pressure that may accelerate ongoing invasions and spark new ones at an increasing rate. Regulations to control conifer invasions, including measures to mitigate spread, were belatedly implemented in New Zealand and South Africa, as well as in certain Australian states, inspired by observations on invasions in those nations. Regulations in South America are weaker and piecemeal, but the existing research base on conifer invasions elsewhere could be useful in fashioning effective regulations in South America. Pressure from foreign customers in South Africa has led most companies there to seek certification through the Forestry Stewardship Council; a similar programme operates in Australia. Such an approach may be promising in South America. 相似文献
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PAUL W. JOHNSON PERCY L. DONAGHAY EUGENE B. SMALL JOHN MCN. SIEBURTH 《The Journal of eukaryotic microbiology》1995,42(3):323-335
ABSTRACT. High resolution sampling of the stratified water column in a fjord-like ecosystem revealed a green-pigmented planktonic ciliate that was found to be a ravenous predator of Euglena proxima. The vertical distributions of both predator and prey were coincident, and maximum populations occurred across the transition from oxic to anoxic water. This ciliate was identified as Perispira ovum (family Spathidiidae; Order Haptorida). P. ovum was observed by transmission electron microscopy to retain not only the chloroplasts, but also the mitochondria and paramylon reserve of its algal prey. A mechanism of sequestration of algal organelles is demonstrated for the first time. This mechanism includes: recognition, capture, and ingestion of prey; rupture and release of algal cell contents; and enrobing of individual organelles and paramylon by the host vacuolar membrane. The structural integrity, peripheral location, and association with host endoplasmic reticulum suggests the sequestered organelles may be functional within P. ovum. The occurrence and high biomass of this aerobic ciliate in an oxygen-limited environment also suggests that the sequestered chloroplasts are photosynthetically active and may provide additional substrates (such as oxygen) and metabolic capabilities that are crucial for its survival. 相似文献
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The identity of the oomycete causing 'Kikuyu Yellows', with a reclassification of the downy mildews 总被引:3,自引:0,他引:3
MICHAEL W. DICK F.L.S. PERCY T. W. WONG GILLIAN CLARK 《Botanical journal of the Linnean Society. Linnean Society of London》1984,89(2):171-197
Cultures of the causal fungus of Kikuyu Yellows disease of Pennisetum clandestinum isolated from Australia have been examined. The fungus is described. The oospore has three noteworthy features: it is plerotic even into the oogonial neck; the ooplast appears to develop a condensed core; the relative thicknesses of the oospore wall layers appear to differ from those of other Oomycetes. Oogonial characters and parasitism indicate an affinity with the graminicolous downy mildews. However, asexual sporulation is not immediately reconcilable with that of these mildews. A major re-appraisal of the classification of the peronosporalean fungi has been necessary to accommodate this fungus. Attention has been drawn to mycelial morphology. Three new orders and two new families are recognized. The division between the peronosporalean fungi and saprolegnialean fungi is recognized at the sub-class level. 相似文献