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981.
Rita JC Gama-Rodrigues EF Gama-Rodrigues AC Polidoro JC Machado RC Baligar VC 《Environmental management》2011,48(1):134-141
Agroforestry systems (AFSs) have an important role in capturing above and below ground soil carbon and play a dominant role
in mitigation of atmospheric CO2. Attempts has been made here to identify soil organic matter fractions in the cacao-AFSs that have different susceptibility
to microbial decomposition and further represent the basis of understanding soil C dynamics. The objective of this study was
to characterize the organic matter density fractions and soil size fractions in soils of two types of cacao agroforestry systems
and to compare with an adjacent natural forest in Bahia, Brazil. The land-use systems studied were: (1) a 30-year-old stand
of natural forest with cacao (cacao cabruca), (2) a 30-year-old stand of cacao with Erythrina glauca as shade trees (cacao + erythrina), and (3) an adjacent natural forest without cacao. Soil samples were collected from 0-10 cm
depth layer in reddish-yellow Oxisols. Soil samples was separated by wet sieving into five fraction-size classes (>2000 μm,
1000–2000 μm, 250–1000 μm, 53–250 μm, and <53 μm). C and N accumulated in to the light (free- and intra-aggregate density
fractions) and heavy fractions of whole soil and soil size fraction were determined. Soil size fraction obtained in cacao
AFS soils consisted mainly (65 %) of mega-aggregates (>2000 μm) mixed with macroaggregates (32–34%), and microaggregates (1–1.3%).
Soil organic carbon (SOC) and total N content increased with increasing soil size fraction in all land-use systems. Organic
C-to-total N ratio was higher in the macroaggregate than in the microaggregate. In general, in natural forest and cacao cabruca
the contribution of C and N in the light and heavy fractions was similar. However, in cacao + erythrina the heavy fraction
was the most common and contributed 67% of C and 63% of N. Finding of this study shows that the majority of C and N in all
three systems studied are found in macroaggregates, particularly in the 250–1000 μm size aggregate class. The heavy fraction
was the most common organic matter fraction in these soils. Thus, in mature cacao AFS on highly weathered soils the main mechanisms
of C stabilization could be the physical protection within macroaggregate structures thereby minimizing the impact of conversion
of forest to cacao AFS. 相似文献
982.
Increasingly government agencies are seeking to quantify the outcomes of proposed policy options in terms of ecosystem service
benefits, yet conflicting definitions and ad hoc approaches to measuring ecosystem services have created confusion regarding
how to rigorously link ecological change to changes in human well-being. Here, we describe a step-by-step framework for producing
ecological models and metrics that can effectively serve an economic-benefits assessment of a proposed change in policy or
management. A focus of the framework is developing comparable units of ecosystem goods and services to support decision-making,
even if outcomes cannot be monetized. Because the challenges to translating ecological changes to outcomes appropriate for
economic analyses are many, we discuss examples that demonstrate practical methods and approaches to overcoming data limitations.
The numerous difficult decisions that government agencies must make to fairly use and allocate natural resources provides
ample opportunity for interdisciplinary teams of natural and social scientists to improve methods for quantifying changes
in ecosystem services and their effects on human well-being. This framework is offered with the intent of promoting the success
of such teams as they support managers in evaluating the equivalency of ecosystem service offsets and trades, establishing
restoration and preservation priorities, and more generally, in developing environmental policy that effectively balances
multiple perspectives. 相似文献
983.
Generalized additive models were used to synthesize the data from 52 publications on the gonad growth and spawning seasonality
of Paracentrotus lividus and identify spatial and temporal patterns in the reproductive processes. According to our results, Atlantic populations
spawn in spring and develop large gonads (6.4 ± 0.2% of fresh body weight (mean ± SE)), which increase in size toward higher
latitudes. While in the Mediterranean, the gonads are smaller (3.1 ± 0.1%), possibly as the result of successive spawnings
which impede nutrients accumulating in the gonads. Differences were also observed between habitats: gonad production was higher
in seagrass meadows in the Mediterranean and in subtidal rocky substrates in the Atlantic. Food availability might cause these
variations as well as the negative correlation observed between depth and the gonad index for rocky substrates. Sex and body
size do not seem to influence greatly gonad growth. 相似文献
984.
Carey E. Kuhn 《Marine Biology》2011,158(3):649-663
In the heterogeneous marine environment, predators can increase foraging success by targeting physical oceanographic features,
which often aggregate prey. For northern fur seals (Callorhinus ursinus), two prevalent oceanographic features characterize foraging areas during summer in the Bering Sea: a stable thermocline
and a subsurface “cold pool”. The objective of this study was to examine the influence of these features on foraging behavior
by equipping fur seals from St. Paul Island (Alaska, USA) with time-depth recorders that also measured water temperature.
Foraging bout variables (e.g., mean dive depth and percent time diving in a bout) were compared with respect to subsurface
thermal characteristics (thermocline presence and strength and cold pool presence). Over 74% of bouts occurred in association
with strong thermoclines (temperature change > 5°C). Few differences were found for dive behavior in relation to the presence
of a thermocline and the cold pool, but for epipelagic bouts, a strong thermocline resulted in increased bottom times, number
of dive wiggles, and percent time diving when compared to moderate thermoclines. There was also a positive relationship between
mean dive depth and thermocline depth. The combination of increasing foraging effort in areas with strong thermoclines and
diving to depths closely related to the thermocline indicates this feature is important foraging habitat for northern fur
seals and may act to concentrate prey and increase foraging success. By recognizing the environmental features northern fur
seals use to find prey, managers will be better equipped to identify and protect foraging habitat that is important to northern
fur seals, and possibly other marine predators in the Bering Sea. 相似文献
985.
Claudia Hollatz Leonardo Flach C. Scott Baker Fabrício R. Santos 《Marine Biology》2011,158(4):927-933
A large macrogeographic differentiation has been observed among Sotalia guianensis populations along the South American coast. However, no genetic structure has been detected so far in closely distributed
populations of this species, even though it has been observed in other cetaceans. Here, we examined the fine scale population
structure for the largest populations of S. guianensis inhabiting Sepetiba and Paraty embayments at the south-eastern coast of Rio de Janeiro, Brazil. Analysis of mitochondrial
DNA (mtDNA) control region sequences failed to detect variability among sequences. Conversely, evidence of significant male
population structure was found on the basis of ten nuclear microsatellite loci. Surprisingly, the microsatellite markers were
able to distinguish between individuals from the two embayments located 60 km apart. The results suggest that differences
in habitat type and behavioral specializations are likely to explain the patterns of genetic structure. These findings should
provide baselines for the management of communities exposed to increasing human-driven habitat loss. 相似文献
986.
The Maltese top-shell, Gibbula nivosa Adams 1851, is a critically endangered marine trochid gastropod endemic to the Maltese Islands (central Mediterranean). Previously unrecorded
live since 1981, rediscovery of this species in 2006 has enabled the collection of basic biological data for the first time,
based on a population in Sliema Creek. The field distribution and habitat preferences of G. nivosa were investigated via stratified random sampling, while aspects of its behaviour were studied through laboratory experiments.
Gibbula nivosa occurred primarily in near-homogeneous or homogeneous infralittoral cobble/pebble beds, at an overall density of 17.6 ± 25.0 SD individuals m−2; however, large spatial and temporal variations in abundance were recorded. The snails did not exhibit gregarious behaviour
and the slightly clumped dispersion pattern noted in the field appeared to result from patchiness of the habitat. Recruitment
was observed in post-summer months, which, together with data on shell-size distributions, suggests that G. nivosa spawns in early summer and attains adult size (maximum shell width ~9 mm) in less than 1 year. Gibbula nivosa showed a circadian activity pattern with nocturnal foraging involving indiscriminate ingestion of particles browsed off the
substratum; observations on responses to four potential predators suggest that nocturnal activity may have evolved in response
to diurnal predation. Historical records of snail occurrence and the present study suggest that population declines of G. nivosa in the past were probably related to habitat alteration as a result of anthropogenic pressure. 相似文献
987.
The habitat experienced during early life-history stages can determine the number and quality of individuals that recruit
to adult populations. In a field experiment, biogenic habitat complexity was manipulated (presence or absence of foliose macroalgae)
at two depths (2–3 m and 5–6 m) and the habitat-dependent effects on recruitment of the black foot abalone (Haliotis iris) were examined at three field sites along the south coast of Wellington, New Zealand (41°20′S, 174°47′E), between July and
November 2005. Recruit density (<5 weeks post-settlement) was measured on cobbles covered with crustose coralline algae. Habitats
of low complexity (barrens treatments) had consistently greater densities of recruits than habitats of high complexity (algae
treatments). However, recruits in algae habitats were larger, and for deep habitats, there was greater survival in algae habitats
compared with barrens habitats. While depth had no significant effect on early recruit (<2 weeks post-settlement) density,
late recruit (<5 weeks post-settlement) density was greater in shallow habitats, and so it seems recruit survival was greater
in shallow habitats. In this experiment, algal habitat complexity had strong effects on early recruit abundance, but habitat-dependent
variations in recruit growth and survival may modify initial patterns of abundance and determine recruitment to adult abalone
populations. 相似文献
988.
Eva Friis Møller Christian Marc Andersen Borg Sigrún H. Jónasdóttir Suree Satapoomin Cornelia Jaspers Torkel Gissel Nielsen 《Marine Biology》2011,158(3):677-688
The vertical distribution of copepods, fecal pellets and the fecal pellet production of copepods were measured at seven stations
across the Southern Indian Ocean from productive areas off South Africa to oligotrophic waters off Northern Australia during
October/November 2006. We quantified export of copepod fecal pellet from surface waters and how much was retained. Furthermore,
the potential impact of Oncaea spp. and harpacticoid copepods on fecal pellets degradation was evaluated and found to be regional substantial. The highest
copepod abundance and fecal pellet production was found in the western nutrient-rich stations close to South Africa and the
lowest at the central oligotrophic stations. The in situ copepod fecal pellet production varied between 1 and 1,000 μg C m−3 day−1. At all stations, the retention of fecal pellets in the upper 400 m of the water column was more than 99% and the vertical
export of fecal pellets was low (<0.02 mg m−2 day−1). 相似文献
989.
John M. Logan Enrique Rodríguez-Marín Nicolas Goñi Santiago Barreiro Haritz Arrizabalaga Walter Golet Molly Lutcavage 《Marine Biology》2011,158(1):73-85
Atlantic bluefin tuna (Thunnus thynnus) are highly migratory predators whose abundance, distribution, and somatic condition have changed over the past decades.
Prey community composition and abundance have also varied in several foraging grounds. To better understand underlying food
webs and regional energy sources, we performed stomach content and stable isotope analyses on mainly juvenile (60–150 cm curved
fork length) bluefin tuna captured in foraging grounds in the western (Mid-Atlantic Bight) and eastern (Bay of Biscay) Atlantic
Ocean. In the Mid-Atlantic Bight, bluefin tuna diet was mainly sand lance (Ammodytes spp., 29% prey weight), consistent with historic findings. In the Bay of Biscay, krill (Meganyctiphanes norvegica) and anchovy (Engraulis encrasicolus) made up 39% prey weight, with relative consumption of each reflecting annual changes in prey abundance. Consumption of anchovies
apparently declined after the local collapse of this prey resource. In both regions, stable isotope analysis results showed
that juvenile bluefin tuna fed at a lower trophic position than indicated by stomach content analysis. In the Mid-Atlantic
Bight, stable isotope analyses suggested that >30% of the diet was prey from lower trophic levels that composed <10% of the
prey weights based upon traditional stomach content analyses. Trophic position was similar to juvenile fish sampled in the
NW Atlantic but lower than juveniles sampled in the Mediterranean Sea in previous studies. Our findings indicate that juvenile
bluefin tuna targeted a relatively small range of prey species and regional foraging patterns remained consistent over time
in the Mid-Atlantic Bight but changed in relation to local prey availability in the Bay of Biscay. 相似文献
990.
A review of the distribution of particulate trace elements in urban terrestrial environments and its application to considerations of risk 总被引:6,自引:0,他引:6
We review the evolution, state of the art and future lines of research on the sources, transport pathways, and sinks of particulate
trace elements in urban terrestrial environments to include the atmosphere, soils, and street and indoor dusts. Such studies
reveal reductions in the emissions of some elements of historical concern such as Pb, with interest consequently focusing
on other toxic trace elements such as As, Cd, Hg, Zn, and Cu. While establishment of levels of these elements is important
in assessing the potential impacts of human society on the urban environment, it is also necessary to apply this knowledge
in conjunction with information on the toxicity of those trace elements and the degree of exposure of human receptors to an
assessment of whether such contamination represents a real risk to the city’s inhabitants and therefore how this risk can
be addressed. 相似文献