Long-term and realistic global change manipulations had low impact on diversity of soil biota in temperate heathland

In a dry heathland ecosystem we manipulated temperature (warming), precipitation (drought) and atmospheric concentration of CO(2) in a full-factorial experiment in order to investigate changes in below-ground biodiversity as a result of future climate change. We investigated the responses in community diversity of nematodes, enchytraeids, collembolans and oribatid mites at two and eight years of manipulations. We used a structural equation modelling (SEM) approach analyzing the three manipulations, soil moisture and temperature, and seven soil biological and chemical variables. The analysis revealed a persistent and positive effect of elevated CO(2) on litter C:N ratio. After two years of treatment, the fungi to bacteria ratio was increased by warming, and the diversities within oribatid mites, collembolans and nematode groups were all affected by elevated CO(2) mediated through increased litter C:N ratio. After eight years of treatment, however, the CO(2)-increased litter C:N ratio did not influence the diversity in any of the four fauna groups. The number of significant correlations between treatments, food source quality, and soil biota diversities was reduced from six to three after two and eight years, respectively. These results suggest a remarkable resilience within the soil biota against global climate change treatments in the long term

Spatially structured environmental filtering of collembolan traits in late successional salt marsh vegetation

Both the environment and the spatial configuration of habitat patches are important factors that shape community composition and affect species diversity patterns. Species have traits that allow them to respond to their environment. Our current knowledge on environment to species traits relationships is limited in spite of its potential importance for understanding community assembly and ecosystem function. The aim of our study was to examine the relative roles of environmental and spatial variables for the small-scale variation in Collembola (springtail) communities in a Dutch salt marsh. We used a trait-based approach in combination with spatial statistics and variance partitioning, between environmental and spatial variables, to examine the important ecological factors that drive community composition. Turnover of trait diversity across space was lower than for species diversity. Most of the variation in community composition was explained by small-scale spatial variation in topography, on a scale of 4-6 m, most likely because it determines the effect of inundation, which restricts where habitat generalists can persist. There were only small pure spatial effects on species and trait diversity, indicating that biotic interactions or dispersal limitation probably were less important for structuring the community at this scale. Our results suggest that for springtails, life form (i.e. whether they live in the soil or litter or on the surface/in vegetation) is an important and useful trait to understand community assembly. Hence, using traits in addition to species identity when analysing environment-organism relationships results in a better understanding of the factors affecting community composition

Aphid parasitoid responses to semiochemicals - Genetic, conditioned or learnt?

Parasitoid foraging behaviour is known to be influenced by interactions of genetic, physiological, environmental and experiential factors. Although the role of genetics, learning and conditioning in determining responses to foraging cues has been studied in lepidopteran parasitoids, aphid parasitoids have been less intensively researched. Using the tritrophic system, Vicia faba - Acyrthosiphon pisum - Aphidius ervi, evidence for the role of genetics and learning in parasitoid foraging is presented, and the difficulty of differentiating between genetic responses and those conditioned during parasitoid development is discussed. Aphidius ervi responds to aphid sex pheromones both in the field and in the laboratory. Since laboratory reared individuals have never experienced sexual aphids, the response must be genetic as it cannot have been conditioned during development. An example of a response conditioned during development is the variable response of A. rhopalosiphi to different wheat cultivars depending upon host feeding. Aphid parasitoids also are adept at learning as shown by their responses to plant-derived cues which are learnt as Conditioned Stimuli (CS). Host products such as honeydew, as well as the host itself, can act as the Unconditioned Stimulus (US) in the learning process. Aphidius ervi offers a good model for investigating the role of these factors in parasitoid foraging behaviour. Finally, the value of such research for biological control programmes involving aphid parasitoids is discussed

PENENTUAN PANJANG GELOMBANG EMISI PADA NANOPARTIKEL CdS DAN ZnS BERDASARKAN VARIASI KONSENTRASI MERCAPTO ETHANOL

melalui Aqueous Phase Synthesis dengan penambahan variasi Mercapto Ethanol untuk memodifikasi ukuran jari-jari nanopartikelnya. Larutan tersebut digunakan untuk membuat lapisan tipis nanopartikel CdS dan ZnS menggunakan teknik Electrostatics Self-Assembly.Larutan nanopartikel dan lapisan tipis nanopartikel CdS dan ZnS dikarakterisasi dengan UV-Vis Spektrometer untuk mengetahui terbentuknya nanopartikel serta terdepositnya nanopartikel pada substrat dan Luminesen Spektrometer untuk menentukan panjang gelombang emisinya.Spektrum UV-Vis dari sampel menunjukkan pergeseran biru sebagai indikator terbentuknya nanopartikel serta terdepositnya lapisan tipis pada substrat.Emisi cahaya untuk nanopartikel CdS dengan penambahan Mercapto ethanol berada pada panjang gelombang 445-453 nm sedangkan untuk nanopartikel ZnS, 309-371 nm dan 442-574 nm.Pada penelitian ini juga diketahui bahwa panjang gelombang emisi nanopartikel CdS dan ZnS cenderung bertambah besar dengan bertambah besarnya penambahan konsentrasi Mercapto ethanol. Kata Kunci : CdS, ZnS, Mercapto Ethanol, Luminese