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The relationship between agricultural intensification and biological control: experimental tests across Europe 总被引:2,自引:0,他引:2
Thies C Haenke S Scherber C Bengtsson J Bommarco R Clement LW Ceryngier P Dennis C Emmerson M Gagic V Hawro V Liira J Weisser WW Winqvist C Tscharntke T 《Ecological applications》2011,21(6):2187-2196
Agricultural intensification can affect biodiversity and related ecosystem services such as biological control, but large-scale experimental evidence is missing. We examined aphid pest populations in cereal fields under experimentally reduced densities of (1) ground-dwelling predators (-G), (2) vegetation-dwelling predators and parasitoids (-V), (3) a combination of (1) and (2) (-G-V), compared with open-fields (control), in contrasting landscapes with low vs. high levels of agricultural intensification (AI), and in five European regions. Aphid populations were 28%, 97%, and 199% higher in -G, -V, and -G-V treatments, respectively, compared to the open fields, indicating synergistic effects of both natural-enemy groups. Enhanced parasitoid: host and predator: prey ratios were related to reduced aphid population density and population growth. The relative importance of parasitoids and vegetation-dwelling predators greatly differed among European regions, and agricultural intensification affected biological control and aphid density only in some regions. This shows a changing role of species group identity in diverse enemy communities and a need to consider region-specific landscape management. 相似文献
146.
Haijun Yang Christoph Kleinn Lutz Fehrmann Shouzheng Tang Steen Magnussen 《Environmental and Ecological Statistics》2011,18(2):223-237
Adaptive cluster sampling (ACS) is a sampling technique for sampling rare and geographically clustered populations. Aiming
to enhance the practicability of ACS while maintaining some of its major characteristics, an adaptive sample plot design is
introduced in this study which facilitates field work compared to “standard” ACS. The plot design is based on a conditional
plot expansion: a larger plot (by a pre-defined plot size factor) is installed at a sample point instead of the smaller initial
plot if a pre-defined condition is fulfilled. This study provides insight to the statistical performance of the proposed adaptive
plot design. A design-unbiased estimator is presented and used on six artificial and one real tree position maps to estimate
density (number of objects per ha). The performance in terms of coefficient of variation is compared to the non-adaptive alternative
without a conditional expansion of plot size. The adaptive plot design was superior in all cases but the improvement depends
on (1) the structure of the sampled population, (2) the plot size factor and (3) the critical value (the minimum number of
objects triggering an expansion). For some spatial arrangements the improvement is relatively small. The adaptive design may
be particularly attractive for sampling in rare and compactly clustered populations with an appropriately chosen plot size
factor. 相似文献
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Stefanie KE Damme Hans-Toni Ratte Henner Hollert Anja Coors Thomas Knacker Klaus Rettinger Christoph Schulte Andreas Schäffer 《Environmental Sciences Europe》2011,23(1):1-4
This article reports on the second Young Environmental Scientists Meeting that was hosted from 28 February to 2 March 2011 by the Institute for Environmental Research at RWTH Aachen University, Germany. This extraordinary meeting was again initiated and organized by the Student Advisory Council under the umbrella of Society of Environmental Toxicology and Chemistry Europe. A movie about the meeting and the abstracts of poster and platform presentations are freely available as supplemental material of this article. 相似文献
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Mucus released by scleractinian corals can act as an important energy and nutrient carrier in coral reef ecosystems, and a
distinct isotopic signature would allow following the fate of this material. This study investigates the natural C and N stable
isotopic signatures of mucus released by four scleractinian coral genera (Acropora, Fungia, Pocillopora and Stylophora) in comparison with those of suspended particulate organic matter (POM) in seawater of a Northern Red Sea fringing coral
reef near Aqaba, Jordan. The natural δ13C and δ15N signatures of coral mucus differed significantly from seawater POM for the majority of seasonal comparisons, but were inappropriate
for explicit tracing of mucus in the coral reef food web. Thus, a labeling technique using stable isotope tracers (13C and 15N) was developed that produced δ13C values of up to 122 ± 5‰ (mean ± SE) and δ15N of up to 2,100 ± 151‰ in mucus exuded by Fungia corals. 13C and 15N-enriched compounds were rapidly (within 3 h) and light-dependently transferred from the endosymbiotic zooxanthellae to the
mucus-producing coral host. The traceability of 15N-labeled mucus was examined by evaluating its uptake and potential utilization by epizoic acoelomorph Waminoa worms naturally occurring on a range of scleractinian coral taxa. This tracer experiment resulted in uptake of coral mucus
by the coral-associated acoelomorphs and further demonstrated the possibility to trace stable isotope-labeled coral mucus
by revealing a new trophic pathway in coral reef ecosystems. 相似文献