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301.
Hai-Hoa Nguyen Clive McAlpine David Pullar Stephen Joseph Leisz Gramotnev Galina 《Environmental management》2015,55(5):1093-1108
Coastal shorelines are naturally dynamic, shifting in response to coastal geomorphological processes. Globally, land use change associated with coastal urban development and growing human population pressures is accelerating coastal shoreline change. In southern Vietnam, coastal erosion currently is posing considerable risks to shoreline land use and coastal inhabitants. The aim of this paper is to quantify historical shoreline changes along the Hon Dat coast between 1995 and 2009, and to document the relationships between coastal mangrove composition, width and density, and rates of shoreline change. The generalized linear mixed-effects models were used to quantify the major biophysical and land-use factors influencing shoreline change rates. Most significant drivers of the rates of change are cutting of mangroves, the dominant mangrove genus, changes in adjacent shoreline land use, changes of shoreline land cover, and width of fringing mangroves. We suggest that a possible and inexpensive strategy for robust mangrove shoreline defense is direct mangrove planting to promote mangrove density with the presence of breakwater structures. In the shorter term, construction of coastal barriers such as fence-structured melaleuca poles in combination with mangrove restoration schemes could help retain coastal sediments and increase the elevation of the accretion zone, thereby helping to stabilize eroding fringe shorelines. It also is recommended that implementation of a system of payments for mangrove ecosystem services and the stronger regulation of mangrove cutting and unsustainable land-use change to strengthen the effectiveness of mangrove conservation programs and coastal land-use management. 相似文献
302.
303.
Summary. Juvenile hormones are sesquiterpenoids that regulate developmental processses such as metamorphosis and reproduction in insects.
Insect juvenile hormone III (JH III), methyl-10R,11-epoxy-3,7,11-trimethyl-2E,6E-dodecadienoate, has also been identified in two sedge species, Cyperus iria and C. aromaticus (Toong et al. 1988). Potential allelopathic activity of this compound and the structurally related sesquiterpenoid farnesol was investigated
using seed germination and seedling growth assays with radish, lettuce and rice. Treatment of seeds with JH III delayed lettuce
seed germination and potently inhibited rice shoot growth. Both farnesol and JH III inhibited the growth of C. iria seedlings. The antimicrobial activity of JH III was also tested on a taxonomic and ecologically diverse range of fungi. Using
the classic cytotoxic disk assay, JH III did not effect growth of the fungal species tested. We believe that JH III may contribute
to the aggressive nature of this invasive weed species.
Received 11 October 1999; accepted 26 February 2000 相似文献
304.
Stephen E. Watts 《Environmental management》1998,22(4):611-616
Artemisia tridentata Nutt.) habitat within the Idaho Army National Guard Orchard Training Area in southwestern Idaho. The purpose of this study
was to determine the short-term (1–2 years) influence of tank tracks on vegetation and microphytic crusts in shrubsteppe habitat.
The two types of tank tracks studied were divots (area where one track has been stopped or slowed to make a sharp turn) and
straight-line tracks. Divots generally had a stronger influence on vegetation and microphytic crusts than did straight-line
tracks. Tank tracks increased cover of bare ground, litter, and exotic annuals, and reduced cover of vegetation, perennial
native grasses, sagebrush, and microphytic crusts. Increased bare ground and reduced cover of vegetation and microphytic crusts
caused by tank tracks increase the potential for soil erosion and may reduce ecosystem productivity. Reduced sagebrush cover
caused by tank tracks may reduce habitat quality for rodents. Tank tracks may also facilitate the invasion of exotic annuals
into sagebrush habitat, increasing the potential for wildfire and subsequent habitat degradation. Thus, creation of divots
and movement through sagebrush habitat by tanks should be minimized. 相似文献
305.
306.
Richard L. Essner Jr. Daniel J. Suffian Phillip J. Bishop Stephen M. Reilly 《Die Naturwissenschaften》2010,97(10):935-939
All frogs are assumed to jump in a similar manner by rapidly extending hindlimbs during the propulsive phase and rotating the limbs forward during flight in order to land forelimbs first. However, studies of jumping behavior are lacking in the most primitive living frogs of the family Leiopelmatidae. These semi-aquatic or terrestrial anurans retain a suite of plesiomorphic morphological features and are unique in using an asynchronous (trot-like) rather than synchronous “frog-kick” swimming gait of other frogs. We compared jumping behavior in leiopelmatids to more derived frogs and found that leiopelmatids maintain extended hindlimbs throughout flight and landing phases and do not land on adducted forelimbs. These “belly-flop” landings limit the ability for repeated jumps and are consistent with a riparian origin of jumping in frogs. The unique behavior of leiopelmatids shows that frogs evolved jumping before they perfected landing. Moreover, an inability to rapidly cycle the limbs may provide a functional explanation for the absence of synchronous swimming in leiopelmatids. 相似文献
307.
Charles H. Peterson Stephen R. Fegley Christine M. Voss Sara R. Marschhauser Beth M. VanDusen 《Marine Biology》2013,160(3):629-640
Protecting eggs from predators is common practice in sea turtle conservation, but routine protection of hatchlings is not. Of 42 loggerhead hatchlings observed emerging from 10 nests on undeveloped Onslow Beach, North Carolina, 24 % were preyed on by ghost crabs. In experimental trials, ghost crabs similarly threatened and captured neonate freshwater sliders, supporting their substitution as proxy for threatened and endangered sea turtle hatchlings in field experiments testing density dependence. Exploiting natural long-shore variation in ghost crab density, we show that a 2.6-fold higher ghost crab density resulted in 5 times more nocturnal threat encounters with sliders and 3.4 times more slider captures. Sliders released in simulated group emergences experienced lower per capita capture risk by ghost crabs than solitary sliders, implying predator dilution. Non-independence of egg and hatchling depredation motivates consideration of merging sea turtle egg and hatchling stages when modeling and managing food web interactions. 相似文献
308.
Changes in forest and agricultural land management practices have the potential to increase carbon (C) storage by terrestrial
systems, thus offsetting C emissions to the atmosphere from energy production. This study assesses that potential for three
terrestrial management practices within the state of Virginia, USA: afforestation of marginal agricultural lands; afforestation
of riparian agricultural lands; and changing tillage practices for row crops; each was evaluated on a statewide basis and
for seven regions within the state. Lands eligible for each practice were identified, and the C storage potential of each
practice on those lands was estimated through a modeling procedure that utilized land-resource characteristics represented
in Geographic Information System databases. Marginal agricultural lands’ afforestation was found to have the greatest potential
(1.4 Tg C yr−1, on average, over the first 20 years) if applied on all eligible lands, followed by riparian afforestation (0.2 Tg C yr−1 over 20 years) and tillage conversion (0.1 Tg C yr−1 over 14 years). The regions with the largest potentials are the Ridge and Valley of western Virginia (due to extensive areas
of steep, shallow soils) and in the Mid-Atlantic Coastal Plain in eastern Virginia (wet soils). Although widespread and rapid
implementation of the three modeled practices could be expected to offset only about 3.4% of Virginia’s energy-related CO2 emissions over the following 20 years (equivalent to about 8.5% of a Kyoto Treaty–based target), they could contribute to
achievement of C-management goals if implemented along with other mitigation measures. 相似文献
309.
An insect parasitoid carrying an ochratoxin producing fungus 总被引:2,自引:0,他引:2
The insect parasitoid Prorops nasuta has been introduced from Africa to many coffee-producing countries in an attempt to control the coffee berry borer. In this
paper, we report on the sequencing of the ITS LSU-rDNA and beta-tubulin loci used to identify a fungus isolated from the cuticle
of a P. nasuta that emerged from coffee berries infected with the coffee berry borer. The sequences were compared with deposits in GenBank
and the fungus was identified as Aspergillus westerdijkiae. The fungus tested positive for ochratoxin A production, with varying levels depending on the media in which it was grown.
These results raise the possibility that an insect parasitoid might be disseminating an ochratoxin-producing fungus in coffee
plantations. 相似文献
310.
Evidence from woodrat middens and tree rings at Dutch John Mountain (DJM) in northeastern Utah reveal spatiotemporal patterns of pinyon pine (Pinus edulis Engelm.) colonization and expansion in the past millennium. The DJM population, a northern outpost of pinyon, was established by long-distance dispersal (approximately 40 km). Growth of this isolate was markedly episodic and tracked multidecadal variability in precipitation. Initial colonization occurred by AD 1246, but expansion was forestalled by catastrophic drought (1250-1288), which we speculate produced extensive mortality of Utah Juniper (Juniperus osteosperma (Torr.) Little), the dominant tree at DJM for the previous approximately 8700 years. Pinyon then quickly replaced juniper across DJM during a few wet decades (1330-1339 and 1368-1377). Such alternating decadal-scale droughts and pluvial events play a key role in structuring plant communities at the landscape to regional level. These decadal-length precipitation anomalies tend to be regionally coherent and can synchronize physical and biological processes across large areas. Vegetation forecast models must incorporate these temporal and geographic aspects of climate variability to accurately predict the effects of future climate change. 相似文献