Riparian alder fens — source or sink for nutrients and dissolved organic carbon? — 2. Major sources and sinks     

Lilian B. Busse  Günter Gunkel 《Limnologica》2002,32(1)

Natural riparian forest wetlands are known to be effective in their ability to remove nitrate by denitrification and sediments with attached phosphorus via sedimentation. On the other hand, litter input and decomposition is a process of crucial importance in cycling of nitrogen and phosphorus in a forest ecosystem.In this study we investigated the amount of nitrogen and phosphorus entering the alder fen ecosystem through leaf litter and its decomposition and the removal capacity of nitrogen and phosphorus by measuring denitrification and sedimentation in the alder fen.We found an average input of leaf litter during fall 1998 of 226 g m⁻² yr⁻¹ DW with nutrient concentration of 0.17% P and 1.6% N. This means a yearly input of 0.4 g m⁻² yr⁻¹ P and 3.6 g m⁻² yr⁻¹ N. The decomposition of leaf litter using litter bags with small and large mesh size resulted in bags with macroinvertebrates (large mesh size) and without macroinvertebrates (small mesh size). After 57 days the litter bags with macroinvertebrates had a decomposition rate of 79%.Denitrification was measured in May and June of 1997 using the acetylene inhibition technique on intact soil cores and slurry-experiments. The average annual denitrification rate was 0.2 g m⁻² yr⁻¹ N using data from the core experiments. The denitrification rate was higher after addition of nitrate, indicating that denitrification in the riparian alder fen is mainly controlled by nitrate supply.The sedimentation rate in the investigated alder fen ranged from 0.47 kg m⁻² yr⁻¹ DW to 4.46 kg m⁻² yr⁻¹ DW in 1998 depending on the study site and method we used. Sedimentation rates were lower in newly designed plate traps than in cylinder traps. The alder fen also showed lower rates than the adjacent creek Briese. Average phosphorus removal rate was 0.33 g m⁻² yr⁻¹ P.Input sources for the surface water of the alder fen are sediment mineralization and decomposition of leaf litter; output sources are sedimentation and denitrification. This study showed that a nutrient input of 24.58 kg ha⁻¹ yr⁻¹ N, 8.8 kg ha⁻¹ yr⁻¹ P and 419 kg ha⁻¹ yr⁻¹ DOC into the surface water of the alder fen is possible. Alder fens cannot improve water quality of an adjacent river system. This is only true for a nearly pristine alder fen with the hydrology of 10 months flooded conditions and 2 months non-flooding conditions a year.  相似文献   

内蒙甲生盘层控硫铅锌矿床汞的岩石地球化学特征     

Tang Lilian Li Fanglin 《地球科学》1986,(1)

本文以526个岩石样品的Hg、Zn测定及闪锌矿单矿物Hg的热释温度测定为基础,探讨了甲生盘层控硫铅锌矿床Hg的岩石地球化学异常特征,提出了以Hg×100/Zn为指标研究成矿后侵入体的热力对Hg的驱赶作用的可能性。从岩体向外250m的距离内,该比值逐渐从2升高到7。原生Hg异常的研究有利于解释该地壤中汞气异常的形成。已经证实,壤中汞气测量对寻找这类矿床是有效的。  相似文献   

Experiments on superimposed buckle folding     

Lilian Skjernaa 《Tectonophysics》1975,27(3):255-270

The geometry of experimentally developed superimposed buckle folds with internal tangential longitudinal strain in a single competent layer embedded in an incompetent host is analysed.It has been found that the first-generation folds are not refolded in the same way as a lineation. On the contrary, they have a great influence on the development and geometry of the second-generation folds.Outcrop patterns quite similar to those occurring in natural rock complexes were formed in the experiments in a way which is not in agreement with the explanation usually given to such patterns.When the layer developed folds only in a zone, and not throughout the layer, and the bulk of material was only able to expand upward, it was found that the layer became bent in such a way that the folds are situated on the top of a broad antiformal structure. Fold-zone intersections are situated on broad domal structures.Within the upper surface of the competent layer, the finite strain variation is complicated within the fold areas while no strain is taken up by the unfolded parts of the layer.The possibility of finding similar structures in nature is considered.  相似文献   

The precursory earthquake swarm     

F.F. Evison 《Physics of the Earth and Planetary Interiors》1977,15(4):P19-P23

Prior swarms near the sites of eleven moderate to large earthquakes from diverse tectonic settings in the New Zealand and California regions yield regressions for the estimation of magnitude and time of occurrence, and thus offer a possible basis for long-range forecasting.  相似文献   

Long-range earthquake forecasting based on a single predictor     

D. A. Rhoades  F. F. Evison 《Geophysical Journal International》1979,59(1):43-56

Summary. For a long-term predictor from which a joint distribution of earthquake occurrence time and magnitude has been obtained, and also a record of past successes, false alarms and failures, Bayesian statistical methods yield predictive information of the kind needed as a basis for decision-making on precautionary measures. The information is presented in terms of risk refinement, intensity probability and success probability. After the event the relative likelihood that a prediction was a success or failure can be estimated. Comparisons can also be made of the performance of different forecasting models. The application of these methods is illustrated by an example based on the proposed swarm-magnitude predictor.  相似文献   

On the Growth of Continents by Plastic Flow Under Gravity   总被引：1，自引：0，他引：1  

F. F. Evison 《Geophysical Journal International》1960,3(2):155-190

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Long-Term Behaviour of an Aftershock Sequence: The Inangahua, New Zealand, Earthquake of 1968     

Russell Robinson  Walter J. Arabasz  F. F. Evison 《Geophysical Journal International》1975,41(1):37-49

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Evaluation of recent hydro-climatic changes in four tributaries of the Niger River Basin (West Africa)     

Djigbo Félicien Badou  Evison Kapangaziwiri  Bernd Diekkrüger  Jean Hounkpè  Abel Afouda 《水文科学杂志》2017,62(5):715-728

West Africa experienced severe drought during the 1970s and 1980s, posing a threat to water resources. A wetter climate more recently suggests recovery from the drought. The Mann-Kendall trend and Theil-Sen’s slope estimator were applied to detect probable trends in weather elements in four sub-basins of the Niger River Basin between 1970 and 2010. The cross-entropy method was used to detect breakpoints in rainfall and runoff, Spearman’s rank test for correlation between the two, and cross-correlation analysis for possible lags. Results showed an overall increase in rainfall and runoff and a decrease in sunshine duration. Spearman’s coefficients suggest significant (5%) moderate to strong rainfall–runoff correlation for three sub-basins. A significant lower runoff was observed around 1979, with a rainfall break around 1992, indicating possible cessation of the drought. Temperatures increased significantly, at 0.02–0.05°C year^-1, with a negative wind speed trend for most stations. Half of the stations exhibited an increase in potential evapotranspiration.