Taxonomic Monograph of Saxicolella (Podostemaceae), African waterfall plants highly threatened by Hydro-Electric projects, with five new species.

The genus Saxicolella Engl. (Podostemaceae) are African rheophytes, restricted to rapids and waterfalls as are all members of the family. Previously, Saxicolella sensu lato was shown to be polyphyletic with two separate clades in the molecular phylogenetic study of Koi et al. (2012). The name Pohliella Engl. was recently resurrected for one clade that is sister to the American genera Ceratolacis (Tul.)Wedd., Podostemum Michx. and all Old World Podostemoideae (podostemoids) (Cheek 2020). Pohliella has distichous phyllotaxy, bilocular ovaries, filiform roots with paired holdfasts, and rootcaps. The second clade, Saxicolella sensu stricto, including the type of the generic name, has spiral phyllotaxy, unilocular ovaries, ribbon-like or crustose roots that lack both holdfasts and rootcaps. Saxicolella sensu stricto, sampled from the type species, S. nana Engl. of Cameroon, is embedded within and near the base of the major clade of African podostemoids and is sister to all other African genera apart from Inversodicraea R.E.Fr. and Monandriella Engl. Recently reduced to three species in Cameroon and S.E. Nigeria by the resurrection of Pohliella (3 to 4 species in Ghana and Nigeria and Cameroon), Saxicolella sensu stricto is expanded to eight species in this monograph by description of five new taxa. Saxicolella futa Cheek and S. deniseae Cheek are newly described from Guinea, S. ijim Cheek from Cameroon, the informally named S. sp. A from Gabon, and S. angola Cheek from Angola. The known geographic range of the genus is thus expanded c. 2,500 km westwards to Guinea from eastern Nigeria and c.1,500 km southeastwards from Cameroon to Cuanza do Sul, Angola. The greatest concentration of species occurs in the Cross Sanaga interval of western Cameroon and eastern Nigeria, with three species. Cameroon (3 species) followed by Nigeria and Guinea (2 species each) are the countries with highest species diversity. The genus can be expected to be found in Sierra Leone, Liberia, Ivory Coast and Congo Republic. A classification is proposed grouping the species into three subgenera (Saxicolella, Butumia (G.Taylor) Cheek comb. et. stat. nov. and Kinkonia Cheek subgen. nov.) based on root morphology and shoot position and morphology. The discovery, morphology, circumscription, distribution, and ecology of Saxicolella is reviewed, an identification key to the species is presented, together with descriptions, synonymy, links to illustrations, and extinction risk assessments for each of the eight species now recognised. All of the species are provisionally assessed as either Endangered or Critically Endangered using the IUCN 2012 standard, making this genus among the most threatened of its size globally. The major threats, above all, are hydro-electric projects. Saxicolella deniseae may already be globally extinct, and two of the four known locations of S. angola appear lost, S. sp. A of Gabon is threatened at at least one of its three locations, while Saxicolella futa is threatened at all three locations, all due to incipient or active hydro electric projects. Contamination of watercourses by increased turbidity from silt-load due anthropic changes and by eutrophication from pollution are also threats for the majority of the species.

POPULATION KINETICS AND SEASONAL FLUCTUATION OF ZOOPLANKTON OF DAH-REOTI (BALLIA)- AN OX- BOW LAKE

The paper deals with the composition and seasonal variation of different groups of zooplankton as related to physico-chemical variables of water of an ox-bow lake - Dah Reoti, Ballia (U.P.) India. It was observed that Rotifera, copepoda and cladocera encountered in order of abundance (Rotifera>copepoda>cladocera) constituted the major groups of zooplankton. Protozoans and insect larvae were observed in negligible number hence not considered in the present study. Overall winter season provided the most propitious conditions for seasonal abundance (50.80%) probably owing to rich nutrient supply. Period from mid summer to mid monsoon was noticed tough period for zooplankton population owing to high silt load from tributary streamlets, fast wind action and increased pollution load.

The Characteristics of Runoff and Sediment Yield in Different Land Use Types in Southwest Mountains of Henan Province

By indoor artificial rainfall simulator and slope plot test, the regularity of runoff and sediment yield of five types top soil— timber forest, shrubby grassland, terrace, slope cropland and waste-grassland under six kinds of rainfall intensity were studied in Danjiangkou Reservoir on southwest mountains of Henan Province to provide a scientific basis for comprehensive control of regional soil and water loss, to ensure the safety of water quality in the reservoir. The conclusions were that: (1) Land use types had less influence on the runoff comparing to sediment yield. (2) Sediment yield had obvious power function relationship with the runoff amount. (3) Bed load took up majority in the sediment yield of farmland soil while the bed load almost equaled to the value of silt load in woodland soil.

Feasibility Study of Dez Arch Dam Heightening Based on Nonlinear Numerical Analysis of Existing Dam

The Dez dam was commissioned in 1963 and since sediments accumulated in the reservoir up to an elevation of approximately 15m below the intake of the power tunnel. One of the possible measures to improve operation of the reservoir is by heightening of the existing dam. This paper describes the conducted procedure for static and thermal calibration of this 203m dam in Iran based on micro geodesies measurements. Also the nonlinear response of existing dam is investigated under maximum credible earthquake ground motions considering joint behavior and mass concrete cracking and safety of dam is evaluated for possible heightening. For thermal calibration of provided numerical model, transient thermal analysis was conducted and results were compared with thermometers records installed in central block. In addition, for static calibration; thermal distribution within dam body, dam self weight, hydrostatic pressure and silt load applied on the 3D finite element model of dam-reservoir-foundation were considered. Results show that the distribution of stresses will be critical within dam for heightening case under seismic loads in MCL.

Factors determining the abundance, distribution and population size–structure of the penshellPinna carnea

Surveys conducted in the south-western Dominican Republic showed that the penshellPinna carneais a consistent component of seagrass beds and is absent in adjacent sandflats. Population densities were low (0.012–0.076·m−2) and the size–structure skewed towards large individuals. Trials with different types of substrata in caged spat collectors, involving a combination of sand, seagrass blades and roots, and an artificial treatment by itself, indicated no settlement preference for any of the substrata tested. Comparison of additional spat collectors (caged and uncaged) indicated high predation losses (84%) for recently settled penshells. Experiments with penshells measuring 10–30, 50–70 and 90–110 mm (anterior to posterior dorsal tip) transplanted to plots in a seagrass bed and sandflat showed that predation losses decreased with increasing size and were much less in seagrass than in the sandflat. In 10-day trials, survival in the three size-groups was 27-fold greater in the seagrass bed than on the sandflat. During 3-day trials in the sandflat, survival increased from 6% for 50–100 mm penshells to 93% for 150–170 mm penshells. At the end of 100-day trials, during which the study area was subjected to Hurricane Dennis, the only surviving penshells were large individuals (90–110 mm) that had been transplanted to the seagrass bed. All individuals transplanted to the sandflat went missing. Growth measurements showed that small penshells grow rapidly (up to 2.2 mm·d−1), but the growth rate drops markedly at ~150 mm. Rapid juvenile growth may be a strategy for reducing the period of high vulnerability to predators. The high proportion of large individuals in the population likely represents the accumulation of successive recruitments as growth slows in older penshells.Pinna carneais mainly restricted to seagrass beds because they provide more protection from predators than adjacent habitats. Moreover, the consolidation of sediments in seagrass beds by roots and algal rhizoids provides a degree of protection from physical disturbances such as hurricanes. The advantages provided by the seagrass habitat come at a cost because we detected a mortality factor in the seagrass bed (possibly related to the ~3-fold higher silt load) that was absent on the sandflat.

Sediment-mass exchange between turbid meltwater streams and proglacial deposits of storglaciären, northern Sweden

Detailed changes in surface elevation of a recently deglaciated area have been mapped using a high-resolution photogrammetric method, with a view to estimating the contribution of debris from the proglacial area to the meltwater streams draining Storglaciären, northern Sweden, over the period 1980-90. The net contribution of sediments originating from the deglaciated area immediately in front of the glacier was of the order of 50% of the suspended silt load transported by meltwater at the flume Rännan downstream from the glacier, but at the same time, a similar amount of sediment accumulated along the streams. Though there is a significant exchange of mass, the net change is close to zero. Moreover, the survey provides detailed information about morphological changes in the landscape. Different processes, such as melting of permafrost, fluvial erosion and sedimentation, have been active.Erosion and sedimentation rates were calculated from the difference between digital terrain models based on aerial photographs taken in 1980 and 1990. The result shows erosion in the central part of the proglacial area and accumulation of coarser sediments along the braided streams. In places, the ground is sinking, possibly due to melting of permafrost.Where the ice is thinner, in the marginal zone, the thermal regime of ice in the tongue of Storglaciären corresponds well with the proglacial geomorphology. At present, the glacier has a 30-40 m thick cold surface layer which at the thinner marginal zone corresponds to a 100-200 m wide frozen rim. The temperature distribution within the ice was mapped using high-resolution radar.

Sediment-mass exchange between turbid meltwater streams and proglacial deposits of storglaciären, northern Sweden

Detailed changes in surface elevation of a recently deglaciated area have been mapped using a high-resolution photogrammetric method, with a view to estimating the contribution of debris from the proglacial area to the meltwater streams draining Storglaciären, northern Sweden, over the period 1980-90. The net contribution of sediments originating from the deglaciated area immediately in front of the glacier was of the order of 50% of the suspended silt load transported by meltwater at the flume Rännan downstream from the glacier, but at the same time, a similar amount of sediment accumulated along the streams. Though there is a significant exchange of mass, the net change is close to zero. Moreover, the survey provides detailed information about morphological changes in the landscape. Different processes, such as melting of permafrost, fluvial erosion and sedimentation, have been active.Erosion and sedimentation rates were calculated from the difference between digital terrain models based on aerial photographs taken in 1980 and 1990. The result shows erosion in the central part of the proglacial area and accumulation of coarser sediments along the braided streams. In places, the ground is sinking, possibly due to melting of permafrost.Where the ice is thinner, in the marginal zone, the thermal regime of ice in the tongue of Storglaciären corresponds well with the proglacial geomorphology. At present, the glacier has a 30-40 m thick cold surface layer which at the thinner marginal zone corresponds to a 100-200 m wide frozen rim. The temperature distribution within the ice was mapped using high-resolution radar.