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991.
Heavy Extinctions of Forest Avifauna in Singapore: Lessons for Biodiversity Conservation in Southeast Asia 总被引:6,自引:0,他引:6
Abstract: The consequences of rapid rainforest clearance on native avifauna are poorly understood. In Southeast Asia, Singapore, a newly developing country, has had 95% of its native lowland rainforest cleared. Most of the rainforest was lost in the mid- to late-nineteenth century. We compared avifauna checklists from 1923, 1949, and 1998 to determine the extent of extinctions between 1923 and 1998 in Singapore. Of 203 diurnal bird species, 65 were extirpated in Singapore in the past 75 years. Four of these species were nonforest- dependent species, whereas 61 (94%) were forest bird species dependent on the primary or old secondary forest to survive. Twenty-six forest bird species became extinct between 1923 and 1949, whereas 35 forest species disappeared after 1949. We compared the body lengths, feeding guilds, and vertical feeding zones between extinct and extant forest bird species to determine whether extinction patterns were dependent on these characteristics. Larger forest bird species went extinct between 1923 and 1949. Body sizes, however, did not affect the loss of forest bird species between 1949 and 1998. We observed high losses of insectivorous birds; the insectivore-carnivore and insectivore-granivore guilds lost> 80% of the species present in 1923. The highest losses were among birds that fed in the canopy. None of the forest bird species are currently common (>100 individuals/species) within Singapore. Our study shows that more than half the forest avifauna became locally extinct after extensive deforestation. Based on this fact, the countries within Southeast Asia should reconsider their heavy deforestation practices. 相似文献
992.
B. Miller # R. Reading J. Hoogland † T. Clark ‡ G. Ceballos § R. List S. Forrest †† L. Hanebury ‡‡ P. Manzano § J. Pacheco § and D. Uresk§§ 《Conservation biology》2000,14(1):318-321
993.
The surface colour and temperature fields of the Mediterranean Sea, as appearing in time series, of basin-wide images available in the CZCS (1979–1985) and AVHRR (1982–1991) historical archives, differentiate between basin interior and continental margins affected by coastal patterns, river plumes, and mesoscale features. The original data were processed to apply calibration factors, to correct for atmospheric contamination, and to estimate chlorophyll-like pigment concentration and surface temperature. Composites were derived, as monthly and annual means, using a fixed equal-area projection with a 1-km2 pixel grid. Enhanced pigment values and lower temperatures along the northern coastal areas (i.e. the Ligurian, Provençal and Balearic basins, as well as the Adriatic, and Aegean Seas) have been associated with the impact of runoff from continental margins (i.e. both a direct impact due to the sediment load and one induced on the planktonic flora by the associated nutrient load) and with vertical mixing due to the prevailing winds (i.e. the Mistral in the northwest, the Bora in the Adriatic, the Etesians in the Aegean). The pattern of increasing pigments and decreasing temperatures in seen to develop in the monthly images from the coastal zone towards the open sea from summer to winter, and then back from winter to summer. The southern coastal areas show different values, namely lower pigments and higher temperatures (except in areas where the data are altered by signal contamination). It is suggested that differences in geomorphology and meteorology of the basin margins have an impact on both water biogeochemistry and dynamics, influencing the biooptical and thermal properties of the various sub-basins, and of the entire Mediterranean region. 相似文献
994.
Lester R.Brown 《生态毒理学报》2000,22(3)
本世纪期间,技术进展已经使农作物生产率发生了革命,但农作物产率的提高已经开始放慢,而世界人口却继续增长.土地退化和水资源的压力是对非常需要的土地生产率提高的严重障碍.满足21世纪全球食品需要将要求一致的人口控制政策,推进可持续消费,和大大提高我们对土地、水及其它自然资源的使用效率.本文提供了对这些问题的前瞻性分析和解决这些问题的建议. 相似文献
995.
G. S. Kalacheva E. S. Zadereev V. G. Gubanov I. V. Gribovskaya 《Russian Journal of Ecology》2000,31(2):113-117
The chemical composition of water conditioned by colonies ofMoina macrocopa and involved in the regulation of their life cycle was analyzed in comparison with water samples from natural water bodies.
Dechlorinated tap water was used as the control medium. The results showed that metabolism of crustaceans leads to an increase
in the concentrations of phosphorus and nitrogen in all forms, the appearance of protein and carbohydrate fractions, and changes
in the composition of lipid fractions in the water conditioned by their colonies. The contents of all organic components are
very low, which makes their identification difficult. Concentrations of substances identified in the conditioned water do
not exceed those occurring in nature. 相似文献
996.
Gradients of genetic distances (GGDs) between 26 adjacent cenopopulations of Scotch pine (Pinus sylvestris L.) along the transects through the distinct landscape-ecotopic isolation borders were analyzed graphically. The results
made it possible to reveal and quantitatively estimate gradients and borders of gene-pool structural patterns in populations
of this species in the central part of Northern Eurasia. In lowland areas, the most distinct borders were found between pine
populations growing on dry lands and bogs (Pineta sphagnosa) in the forest zone of the Transural region, as well as between the Arakaragaiskii and Amankaragaiskii island pine forests
in the steppe zone (Northern Turgai). In highland areas (the Urals and the Carpathians), the greatest GGDs were observed between
low-mountain (about 600 m above sea level) and middle-mountain (850–900 m) populations. Analysis of GGDs is a promising gene-geographic
method for determining population borders and studying the chorogenetic structure of species. 相似文献
997.
998.
The interactions of zebra mussels, invertebrates, fish, and microorganisms were studied experimentally. Trends in the distribution
of total bacterial biomass, the abundance of heterotrophic organisms, and their functional activities in water and grounds
were analyzed. The most favorable conditions for development of bacteria developed in June, in the presence of fish and without
zebra mussels. In experimental ecosystems with zebra mussels, a decrease in the abundance and activity of microorganisms and
a change of dominant yeast forms were observed. 相似文献
999.
This study deals with the emission of methane in relation to changing environmental conditions and human impact, in three
mangrove ecosystems of south India. Time-varying fluxes of methane adopting the close chamber technique were used to estimate
CH4 emission from an unpolluted site (Pichavaram mangroves) and two polluted sites viz. (1) Ennore Creek mangroves (affected
by fertilizer effluents and crude oil discharges) and (2) Adyar estuary mangroves (affected by the discharges of organic and
industrial wastes), covering monthly and seasonal variations. The results indicate annual average CH4 emissions of 7.4, 5.02 and 15.4 mg m−2 h−1 from the sediment–water interface of the Pichavaram, Ennore Creek and Adyar estuary respectively. Emission characteristics
obtained at Pichavaram mangroves represent a natural variability with changing physico-chemical factors, whereas the emission
characteristics at Ennore Creek and Adyar estuary mangroves show anthropogenic influence. Several environmental factors such
as oxygen availability, organic matter, soil physical and chemical properties, in addition to human-mediated interventions
have been identified as influencing emission rates in the mangrove ecosystems. Preliminary CH4 emission estimates for the mangrove ecosystems along the Indian sub- continent and the tropical and subtropical coastline
of the world by linear extrapolation based on surface area range from 0.05 to 0.37 and 2.8 to 19.25 Tg CH4 year−1 respectively. Our results also highlight the impact of human activities on future emission of methane from the mangrove ecosystems.
Received: 3 March 1999 / Accepted: 14 September 1999 相似文献
1000.
Makarov M. I. Kadulin M. S. Turchin S. R. Malysheva T. I. Aksenova A. A. Onipchenko V. G. Menyailo O. V. 《Russian Journal of Ecology》2019,50(4):337-342
Russian Journal of Ecology - Abstract—The study of the effect of mycorrhiza symbiosis on the transformation of carbon and nitrogen compounds in soils is important in view of the necessity to... 相似文献