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51.
Spatial variability of soil gas concentration and methane oxidation capacity in landfill covers 总被引:2,自引:0,他引:2
In order to devise design criteria for biocovers intended to enhance the microbial oxidation of landfill methane it is critical to understand the factors influencing gas migration and methane oxidation in landfill cover soils. On an old municipal solid waste landfill in north-western Germany soil gas concentrations (10, 40, 90 cm depth), topsoil methane oxidation capacity and soil properties were surveyed at 40 locations along a 16 m grid. As soil properties determine gas flow patterns it was hypothesized that the variability in soil gas composition and the subsequent methanotrophic activity would correspond to the variability of soil properties. Methanotrophic activity was found to be subject to high spatial variability, with values ranging between 0.17 and 9.80 g CH4 m−2 h−1. Considering the current gas production rate of 0.03 g CH4 m−2 h−1, the oxidation capacity at all sampled locations clearly exceeded the flux to the cover, and can be regarded as an effective instrument for mitigating methane fluxes. The methane concentration in the cover showed a high spatial heterogeneity with values between 0.01 and 0.32 vol.% (10 cm depth), 22.52 vol.% (40 cm), and 36.85 vol.% (90 cm). The exposure to methane raised the oxidation capacity, suggested by a statistical correlation to an increase in methane concentration at 90 cm depth. Methane oxidation capacity was further affected by the methanotroph bacteria pH optimum and nutrient availability, and increased with decreasing pH towards neutrality, and increased with soluble ion concentration). Soil methane and carbon dioxide concentration increased with lower flow resistance of the cover, as represented by the soil properties of a reduced bulk density, increase in air capacity and in relative ground level. 相似文献
52.
In the Segara Anakan lagoon, Java, 21 tree species and 5 understorey genera have been identified. Average tree density is
0.80 ± 0.99 Ind./m2 with 48.71% seedlings and an average basal area of 9.86 ± 10.54 cm2/m2. Tree density and diversity are
high in the eastern part of the lagoon, located near the city of Cilacap. There, the dominant tree species are Aegiceras corniculatum, Nypa fruticans and Rhizophora apiculata, of which the two latter are characteristic for mature forests. By contrast, understorey species and the pioneer species (Avicennia alba,
Aegiceras corniculatum and Sonneratia caseolaris) dominate the central lagoon where several rivers discharge. Compared to former studies, seedling density and tree diameter
in the central lagoon has declined considerably and tree species dominance has changed. The high sedimentation rates and deforestation
are likely to prevent the formation of a mature forest there. Tree communities are more equilibrated in the eastern lagoon
which points to a more stable and less disturbed mangrove forest. 相似文献
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Stef Bokhorst Stine Højlund Pedersen Ludovic Brucker Oleg Anisimov Jarle W. Bjerke Ross D. Brown Dorothee Ehrich Richard L. H. Essery Achim Heilig Susanne Ingvander Cecilia Johansson Margareta Johansson Ingibjörg Svala Jónsdóttir Niila Inga Kari Luojus Giovanni Macelloni Heather Mariash Donald McLennan Gunhild Ninis Rosqvist Atsushi Sato Hannele Savela Martin Schneebeli Aleksandr Sokolov Sergey A. Sokratov Silvia Terzago Dagrun Vikhamar-Schuler Scott Williamson Yubao Qiu Terry V. Callaghan 《Ambio》2016,45(5):516-537
55.
Glucosinolates (GS) are the main secondary metabolites in brassicaceous plants that play an important role in plant defense
and plant–insect communication. GS biosynthesis in plants and their accumulation may be influenced by biotic and abiotic stressors
from the environment. In the present study, GS levels in broccoli plants, Brassica oleracea var. italica Plenck, grown under different water status conditions of soil—well-watered, drought and waterlogged—were determined after
two aphid species, the specialist Brevicoryne brassicae (L.) and the generalist Myzus persicae (Sulzer), had fed on them for 7 days. High-performance liquid chromatography analysis revealed that GS levels were significantly
induced after B.
brassicae had fed on B. italica plants grown for 2 weeks under the various water status conditions. No significant differences were determined between GS
induction in the three treatments. In contrast, the induction of GS after M. persicae had fed on the plants depended greatly on water stress levels. GS content in well-watered plants increased more significantly
than in plants grown under drought conditions. Feeding by M. persicae did not increase GS levels when plants were grown under waterlogged conditions. The lowest plant growth were found in M. persicae-infested plants for all three water treatments, and measurements of GS showed that the induction of GS by M. persicae decreased in line with the reduction in infested plant growth. GS induction by B. brassicae did not alter remarkably following change in plant growth under water stress. Only one of the five glucosinolates detected,
the aliphatic GS 4-methylsulfinylbutyl, remained unchanged after feeding of both, M. persicae and B. brassicae, on plants under water stress. Variation in GS levels was mainly observed for the induction of indolyl GS due to aphid herbivory,
but changes in indol-3-ylmethyl GS were not always consistent with the induction of other indolyl GS. 相似文献
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Food preferences, consumption rates and dietary assimilation related to food quality were investigated for the large semi-terrestrial
and litter-consuming mangrove crab Ucides cordatus cordatus (Ocypodidae, L. 1763) in northern Brazil. Stomach contents were composed of mangrove leaves (61.2%), unidentified plant material
and detritus (28.0%), roots (4.9%), sediment (3.3%), bark (2.5%), and animal material (0.1%). U. cordatus prefers Rhizophora mangle over Avicennia germinans leaves despite a higher nitrogen content, lower carbon to nitrogen (C/N) ratio and lower tannin content of the latter. Also,
assimilation rates for senescent R. mangle leaves (C: 79.3%, N: 45.4%) were higher than for A. germinans leaves (C: 40.6%, N: 9.1%). Faeces composition indicates that A. germinans leaves were more difficult to masticate and digest mechanically. The leaf-ageing hypothesis, according to which crabs let
leaves age in burrows to gain a more palatable and nutritive food, was rejected for U. cordatus since N content, C/N ratio and the abundance of microorganisms did not differ significantly between senescent leaves and
leaves taken from burrows. The low microbial biomass on leaf surfaces and in the sediment indicates its minor importance for
the nutrition of U. cordatus. It is concluded that high ingestion and assimilation rates of a R. mangle diet together with the consumption of algae allow for a high intake of C, N, and energy. The data suggest that the digestibility
of mangrove leaves by U. cordatus is not hampered by tannins. This may have provided a competitive advantage over other leaf-consuming invertebrates unable
to digest mangrove litter with high tannin concentrations. Due to the large stock biomass of U. cordatus in the study area, a great amount of finely fragmented faeces is produced (about 7.1 ton dry matter ha−1 year−1 in a R. mangle forest) which is enriched in C, N and bacterial biomass compared to the sediment. The decomposition of mangrove litter, and
thus nutrient and energy transfer into the sediment, is greatly enhanced due to litter processing by U. cordatus. 相似文献