Tropical shelterwood system of forest regeneration its development and application in the Benin Division of Southern Nigeria and a consideration of factors affecting its success

It is the purpose of this paper to give a description of the development of a system of natural regeneration for the Benin forests, to measure the success of the work, and to set out some of the factors which appear to limit or to assist the regeneration. Between the latitudes 6 and 7 degrees north and the longitudes 5 and 6 degrees east in Western Provinces, Kigeria,is situated Benin Division, the most southern and western of the four political Divisions which together form Benin Province. The area of Benin Division is approximately 4,000 square miles, and in 1931 (the latest census figures available) the population was taken to be 111,000, although there is no doubt that during the last two decades this latter figure has greatly increased due to a rising birth -rate and an influx of labour, mainly from the south and east, to the prosperous rubber estates and expanding timber industry. The provincial and divisional capital, Benin City, lies in the centre of the Division. With a population of over 20,000 it is the hub from which radiate the several roads which serve the many small and few large villages of the area and which link the capital with neighbouring Provinces. GEOLOGY: Crystalline rocks (the "undifferentiated basement complex" of gneisses and granites) occur in the extreme north-west of the Division, but the remainder is entirely sedimentary, being part of the extensive Benin Sand Series. In parts this formation consists of a homogeneous layer of quartz sand several hundred feet thick, but the Benin Sands may be part of the Lignite Series, in which unevenly distributed strata of sandstone, shales and clays occur in the red sands. RAINFALL AND DRAINAGE: The average rainfall of the whole Division is probably about 75 inches per annum, distributed in the typical two-peak fashion of the coast of West Africa. The rainfall in the south averages 110 inches per annum (probably higher in the extreme southwest) but that in the extreme north may be as low as 60 inches. The figures for Benin City show that the months of November, Decembers January and February have precipitation below 3 inches per month, but the relative humidity (especially in the forest) remains fairly high throughout the year, and the effect of the dry Harmattan wind from the north is weak and is obvious on only very few, isolated days. The table (t ore p. 3 shows average rainfall, temperature and relative humidity figures for Benin City which is not itself in the forest. Within the forest the mean relative humidity, particularly at 3 p.m., is higher and probably without such large fluctuations between months. The area of the Benin Sands is characterised by a scarcity of streams and the rain water appears to drain to considerable depth, the rivers flowing in deep trenches cut below the general level of the almost flat plain. Except on land which has been completely cleared of vegetation there is little run-off, and the streams, fed by underground drainage, generally hold deep and very clear water. Chukwuogo and other writers have stressed the severe water shortage which exists in the country districts, in the dry season, away from the limited number of streaa. FARMING: The local food farming technique involves the practice of a bush fallow system; the number of years for which a farm is cropped is small, usually two, or possibly three years if the land proves to be of high qw l ity, and this is an index of the rapidity at which the Benin Sands lose their fertility after the removal of the forest vegetation. The farmer cuts, heaps and burns almost every tree on the new farm, and this practice of leaving no high shade has important ecological and economic repercussions. There is a sharp contrast with the practice in other parts of West Africa where the largest trees remain as a high shade, an important reservoir of timber, a source of seed and a skeleton of forest structure. There are practically no cattle in the Division owing to the susceptibility of all but a few strains to trypanosomiasis. The most common domestic animal is the goat, which is here a village or compound animal, living by scavenging and seldom, if, ever, found either it forest or farm. An important plantation crop of the Division is rubber and considerable areas have been planted with Heavea brasil,iensis. During the 1939 - 45 war the plantations prospered, and were largely extended Owing to the inflated price of rubber following the Japanese occupation of Malaya, but the present prices are subject to large fluctuations. TIMBER. By far the most important industry, apart from food farming for local use, is timber working. On this trade, whether for the export market or the Nigerian market, the prosperity of Benin largely depends. A result of the rising standard of living of many Nigerian people, and the growing needs of industry in West Africa and abroad, is that the demand for Nigerian timber has increased. At the same time the area of non reserved forest (forest land not included in Forest Reserves) has been greatly reduced in the last fifteen years owing to the destructive work of farmers and the planting of permanent cash crops. The supply of timber outside the gazetted Reserves dwindled rapidly, particularly because of the clear-felling technique of the farmers, and the Forest Department was faced some years ago with the need to allow the exploitation of Forest Reserves to begin; such exploitation had to be accompanied by regeneration, either artificial or natural. Artificial regeneration, while important in certain limited areas and for special purposes, could not be attempted on the scale necessary to ensure the future of the forests and thus natural regeneration had to be attempted on an enormous scale. The intention in this paper is to describe briefly the technique of natural regeneration adopted and to examine in some detail the success obtained in different forest associations in a single compartment with the object of assessing the suitability of the technique for the maintenance of the forest

Community-Based Food Systems in Michigan: Cultivating Diverse Collaborations from the Ground Up

This article discusses the results of a Michigan project to forge partnerships between Extension and diverse teams of community members to enhance development of local food systems. The project provided training and resources for teams to utilize food system work as a community problem solving tool. Such efforts have great potential to address a host of public health, economic, and land use issues

Effects of wheat and oat-based whole grain foods on serum lipoprotein size and distribution in overweight middle aged people : a randomised controlled trial

Peer reviewedPublisher PD

Changes in extracellular pH during electrical stimulation of isolated rat vagus nerve

Double-barrelled pH-sensitive micro-electrodes were used to record changes of extracellular pH during repetitive stimulation of isolated rat vagus nerves. It was found that a small initial alkaline shift was followed by a prolonged acidification. The acidification was correlated in time with the poststimulus undershoot of the extracellular K+ activity and with the recovery phase of the nerve conduction velocity. In the presence of ouabain, the acid component of the pH change was completely abolished (indicating a metabolic origin), whereas the alkaline component remained unaltered. These pH changes were too small to make a significant contribution to the activity-related changes in conduction velocity of the vagal C-fibres

Dark-ages reionization and galaxy formation simulation--VII. The sizes of high-redshift galaxies

We investigate high-redshift galaxy sizes using a semi-analytic model constructed for the Dark-ages Reionization And Galaxy-formation Observables from Numerical Simulation project. Our fiducial model, including strong feedback from supernovae and photoionization background, accurately reproduces the evolution of the stellar mass function and UV luminosity function. Using this model, we study the size--luminosity relation of galaxies and find that the effective radius scales with UV luminosity as $R_\mathrm{e}\propto L^{0.25}$ at $z{\sim}5$--$9$. We show that recently discovered very luminous galaxies at $z{\sim}7$ (Bowler et al. 2016) and $z{\sim}11$ (Oesch et al. 2016) lie on our predicted size--luminosity relations. We find that a significant fraction of galaxies at $z>8$ will not be resolved by JWST, but GMT will have the ability to resolve all galaxies in haloes above the atomic cooling limit. We show that our fiducial model successfully reproduces the redshift evolution of average galaxy sizes at $z>5$. We also explore galaxy sizes in models without supernova feedback. The no-supernova feedback models produce galaxy sizes that are smaller than observations. We therefore confirm that supernova feedback plays an important role in determining the size--luminosity relation of galaxies and its redshift evolution during reionization.Comment: 10 pages, 4 figures, Accepted for publication in MNRA

Dark-ages Reionization & Galaxy Formation Simulation VIII. Suppressed growth of dark matter halos during the Epoch of Reionization

We investigate how the hydrostatic suppression of baryonic accretion affects the growth rate of dark matter halos during the Epoch of Reionization. By comparing halo properties in a simplistic hydrodynamic simulation in which gas only cools adiabatically, with its collisionless equivalent, we find that halo growth is slowed as hydrostatic forces prevent gas from collapsing. In our simulations, at the high redshifts relevant for reionization (between ${\sim}6$ and ${\sim}11$), halos that host dwarf galaxies ($\lesssim 10^{9} \mathrm{M_\odot}$) can be reduced by up to a factor of 2 in mass due to the hydrostatic pressure of baryons. Consequently, the inclusion of baryonic effects reduces the amplitude of the low mass tail of the halo mass function by factors of 2 to 4. In addition, we find that the fraction of baryons in dark matter halos hosting dwarf galaxies at high redshift never exceeds ${\sim}90\%$ of the cosmic baryon fraction. When implementing baryonic processes, including cooling, star formation, supernova feedback and reionization, the suppression effects become more significant with further reductions of ${\sim}30\%$ to 60\%. Although convergence tests suggest that the suppression may become weaker in higher resolution simulations, this suppressed growth will be important for semi-analytic models of galaxy formation, in which the halo mass inherited from an underlying N-body simulation directly determines galaxy properties. Based on the adiabatic simulation, we provide tables to account for these effects in N-body simulations, and present a modification of the halo mass function along with explanatory analytic calculations.Comment: 17 pages, 11 figures; Updated to match the published version. Two changes in Figures 1 and 3 in order to 1) correct bin sizes of the 10^8 and 10^8.5 Msol bins for NOSN_NOZCOOL_NoRe (was 0.5, should be 0.25); 2) include stellar mass in baryon fraction (was missed in Fig. 3). Quantitative description of Fig. 3 changed slightly in Section 2.2. All other results and conclusions remain unchange

Dark-ages reionization & galaxy formation simulation IV: UV luminosity functions of high-redshift galaxies

In this paper we present calculations of the UV luminosity function from the Dark-ages Reionization And Galaxy-formation Observables from Numerical Simulations (DRAGONS) project, which combines N-body, semi-analytic and semi-numerical modelling designed to study galaxy formation during the Epoch of Reionization. Using galaxy formation physics including supernova feedback, the model naturally reproduces the UV LFs for high-redshift star-forming galaxies from $z{\sim}5$ through to $z{\sim}10$. We investigate the luminosity--star formation rate (SFR) relation, finding that variable SFR histories of galaxies result in a scatter around the median relation of $0.1$--$0.3$ dex depending on UV luminosity. We find close agreement between the model and observationally derived SFR functions. We use our calculated luminosities to investigate the luminosity function below current detection limits, and the ionizing photon budget for reionization. We predict that the slope of the UV LF remains steep below current detection limits and becomes flat at $M_\mathrm{UV}{\gtrsim}{-14}$. We find that $48$ ($17$) per cent of the total UV flux at $z{\sim}6$ ($10$) has been detected above an observational limit of $M_\mathrm{UV}{\sim}{-17}$, and that galaxies fainter than $M_\mathrm{UV}{\sim}{-17}$ are the main source of ionizing photons for reionization. We investigate the luminosity--stellar mass relation, and find a correlation for galaxies with $M_\mathrm{UV}{<}{-14}$ that has the form $M_*{\propto}10^{-0.47M_\mathrm{UV}}$, in good agreement with observations, but which flattens for fainter galaxies. We determine the luminosity--halo mass relation to be $M_\mathrm{vir}{\propto}10^{-0.35M_\mathrm{UV}}$, finding that galaxies with $M_\mathrm{UV}{=}{-20}$ reside in host dark matter haloes of $10^{11.0\pm 0.1}\mathrm{M_\odot}$ at $z{\sim}6$, and that this mass decreases towards high redshift.Comment: 17 pages, 14 figures, Accepted for publication in MNRA

Dark-ages Reionization and Galaxy Formation Simulation - X. The small contribution of quasars to reionization

Motivated by recent measurements of the number density of faint AGN at high redshift, we investigate the contribution of quasars to reionization by tracking the growth of central supermassive black holes in an update of the Meraxes semi-analytic model. The model is calibrated against the observed stellar mass function at $z\sim0.6-7$, the black hole mass function at $z\lesssim0.5$, the global ionizing emissivity at $z\sim2-5$ and the Thomson scattering optical depth. The model reproduces a Magorrian relation in agreement with observations at $z<0.5$ and predicts a decreasing black hole mass towards higher redshifts at fixed total stellar mass. With the implementation of an opening angle of 80 deg for quasar radiation, corresponding to an observable fraction of ${\sim}23.4$ per cent due to obscuration by dust, the model is able to reproduce the observed quasar luminosity function at $z\sim0.6-6$. The stellar light from galaxies hosting faint AGN contributes a significant or dominant fraction of the UV flux. At high redshift, the model is consistent with the bright end quasar luminosity function and suggests that the recent faint $z\sim4$ AGN sample compiled by Giallongo et al. (2015) includes a significant fraction of stellar light. Direct application of this luminosity function to the calculation of AGN ionizing emissivity consequently overestimates the number of ionizing photons produced by quasars by a factor of 3 at $z\sim6$. We conclude that quasars are unlikely to make a significant contribution to reionization.Comment: 21 pages, 12 figures; Updated to match the published version. All results and conclusions remain unchange