瑞典河漫滩草甸植被的数量分类和排序

本文用目前各国学者广泛使用的一些数量分类和排序方法对瑞典河漫滩草甸样地资料进行了分类和排序。所用的方法包括多元等级聚合分类(TABORD程序),多元等级分划分类(TWINSPAN程序),PCA排序(ORDINA程序),RA和DCA排序(DECORANA程序)。研究结果表明可以把28个样地分为6个群落类型,它们的分布格局是与土壤水分梯度密切相关的。此外本文还对数量分类和排序方法在植物群落学研究中的应用以及所用方法的比较进行了讨论。     

Transformation of15N-labelled urea and its modified forms in tropical wetland rice culture

Summary The fate of 100 kg N ha^–1 applied as¹⁵N-urea and its modified forms was followed in 4 successive field-grown wetland rice crops in a vertisol. The first wet season crop recovered about 27 to 36.6% of the applied N depending upon the N source. In subsequent seasons the average uptake was very small and it gradually decreased from 1.4 to 0.5 kg N ha^–1 although about 18 to 20, 12 to 17 and 14 to 18 kg ha^–1 residual fertilizer N was available in the root zone after harvest of first, second and third crops, respectively. The average uptake of the residual fertilizer N was only 7.6% in the second crop and it decreased to 4.5% in the third and to 3.2% in the fourth crop although all these crops were adequately fertilized with unlabelled urea. The basal application of neem coated urea was more effective in controlling the leaching loss of labelled NH₄+NO₃–N than split application of uncoated urea. In the first 3 seasons in which¹⁵N was detectable, the loss of fertilizer N through leaching as NH₄+NO₃–N amounted to 0.5 kg ha^–1 from neem-coated urea, 1.5 kg from split urea and 4.1 kg from coal tar-coated urea. At the end of 4 crops, most of the labelled fertilizer N (about 69% on average) was located in the upper 0–20 cm soil layer showing very little movement beyond this depth. In the profile sampled upto 60 cm depth, totally about 13.8 kg labelled fertilizer N ha^–1 from neem-coated urea, 12.7 kg from coal-tar coated urea, and 11.8 kg from split urea were recovered. The average recovery of labelled urea-N in crops and soil during the entire experimental period ranged between 42 and 51%. After correcting for leaching losses, the remaining 47 to 56% appeared to have been lost through ammonia volatilization and denitrification.     

The influence of flood regime on fish catch and fish communities of the Cross River floodplain ecosystem,Nigeria

Synopsis The morphology, climate and flood regime of the Cross River floodplain are summarized and related to the catch, species distribution and abundance of the economically important fishes of the floodplain ecosystem. Two flood indices, FI-1 and FI-2, are used to assess, statistically. the relationship between fish catch and flood regime. There are good positive correlations between the catch (C_T) of year T and the flood index 1 of 1 year T-1 and between (C_T) and the sum of the flood indices 1 and 2 of year T-1 (r = 0.6516 and 0.6894, respectively, both at P = 0.05). Cross River is a relatively highly productive system (in terms of fish catch) and this productivity is attributable mainly to the yearly flooding of the plain when fish find allochthonous food materials in the expanded habitat. Changes in hydrometeorological conditions, such as the drought that affected the northern part of the Cross River basin in 1983–1984. if they persist can effectively reduce fish catch from the system.     

Evolution of major pattern models and processes of alluvial forest of the Rhine in the rift valley (France/Germany)

In the rift valley (North-East of France/South-West of Germany), the Rhine runs freely for 300 km from South to North. The absence of natural obstacles allows the development of a very regular profile of the river. We have therefore an opportunity to study very gradual modifications of the alluvial forest communities of the fluvial corridor from upstream to downstream, according to the gradual evolution of the ecological factors, related to slope decrease and hydrological modifications.We describe, from Basel to Mainz:

The simplified methods of evaluating detention storage volume for small catchment

Massive land development reduces the plant-cover area and increases the impervious area of watershed, which induces downstream flooding. A detention pond stores runoff from watershed and releases the stored runoff slowly to reduce the flood threat in the downstream area. While the runoff hydrograph is irregular, several researches verify that the runoff hydrograph can be represented by simple geometrical-shaped (such as triangular or trapezoidal) hydrographs. This study collects and develops simplified detention volume design models. The study also develops a suitable hydrological condition and the calculation method of detention volume for various models. A real world case is used to demonstrate the calculation procedure used in the detention pond design. The case shows that the combination of triangular inflow and triangular outflow produces a maximum detention volume, which implies a large reduction of peak flow needs greater detention volume. The combination of trapezoidal inflow and triangular outflow produces a second large detention volume. It implies a long duration of inflow hydrograph (IH) needs greater detention volume. A combination of triangular inflow and trapezoidal outflow results in a minimum detention volume, which indicates that either the storm water drains completely before the permissible outflow occurs, or storm water is kept from entering the detention pond before the inflow rate reaches the permissible outflow. In either case, the detention pond has more space to accommodate the flood inflow so as to reduce the rate of peak outflow.     

Restoration ecology meets carabidology: effects of floodplain restitution on ground beetles (Coleoptera,Carabidae)

The effects of different restoration activities on floodplain-inhabiting ground beetles were studied at a lowland river in northwestern Germany. In the 6-km² project area the bank reinforcement was stopped, the dikes that bordered the river on both sides were removed and two oxbows (disconnected parts of the main stream course) were reconnected to the river. We investigated the banks at two sites at the main river, at the two reconnected oxbows and at two unconnected oxbows as reference sites. To analyse the effects of the removal of the dikes we chose three floodplain sites in front and two reference sites behind the new dike. As a consequence of the lack of bank reinforcement and the reconnection of the oxbows, the area of open river banks, a rare bank structure at rivers in northwestern Germany, increased by a factor of 4.6 during the 4 years of investigation. Numerous stenotopic ground beetle species colonized the newly developed habitats at the main river and at the reconnected oxbows quickly, during several weeks or months, and established new populations as indicated by newly hatched individuals. The removal of the dikes should lead to a rewetting of the floodplain area that is incorporated in the flood dynamics, an important aspect of the development of typical floodplain habitats such as wet meadows, reeds and alluvial forests, while reference sites on the other side of the removed dike remained uninfluenced. Four years after the removal of the dikes no species turnover at the sites with a potentially changed water regime was recorded that indicated a shift of the carabid assemblages towards hygrophilous species. One reason could be the low frequency of inundations and their short duration during the investigation period. The flood dynamics could be sustained by the elevation and enlargement of the river bed, and periodic floods are the key factor for a development of floodplain habitats.