Impact of forest management regimes on ligneous regeneration in the Sudanian savanna of Burkina Faso

Annual early fire, selective tree cutting and grazing exclusion are currently used to manage the State forests of the Sudanian savanna of Burkina Faso, West Africa. Such prescriptions, however, are not based on experimental evidence. The long-term effects of such management on seedlings and saplings and the germination of selected tree species are discussed. Seedling quality attributes are also assessed. Studies over a 10-year period examined the effects of the three management regimes on species richness and population density. Burkea africana Kook, f., Detarium microcarpum Guill. et Perr., Entada africana Guill. et Perr., and Pterocarpus erinaceus Poir. seed germination was tested for different temperatures, light conditions, dry heat treatments and scarification methods. The quality of Acacia macrostachya Reichenb.ex DC. and P. erinaceus planting stock was evaluated in relation to nursery production period; field performance was assessed with and without watering. Fire, grazing, and selective tree cutting acted independently on sapling and seedling population dynamics. Early fire reduced sapling recruitment; moderate grazing had no significant effect. Although the overall seedling population density was not affected by any of the treatments, fire and grazing had strong effects on single-stemmed seedling density. Ordination using Principal Component Analysis of the seedling population data revealed species-specific responses to treatments, in particular an increase of lianas compared to other species. D. microcarpum and E. africana seeds did not exhibit dormancy. Exposing B. africana seeds to 95-97% sulphuric acid for 15–20 minutes broke their physical dormancy. All seeds tested were neutrally photoblastic, with an optimal germination temperature of 25–35 oC. E. africana, however, germinated over a wider temperature range. P. erinaceus seeds did not tolerate heat shock; while D. microcarpum and E. africana seeds responded positively at low intensity. Eighteen months after outplanting, survival and growth of Acacia macrostachya and Pterocarpus erinaceus seedlings were not affected by their initial size. Drought and non-drought factors affected seedling survival. Performance of P. erinaceus seedlings could be predicted from initial root collar diameter; more data will be required to build a reliable model. This thesis recommends the use of annual early fire as a forest management tool to be continued if timing, weather conditions and other factors affecting fire intensity are given due consideration. Moderate level of grazing does not affect seedling and sapling recruitment. The current prohibition on grazing State forests may need revision to allow multiple-use management. The low seedling density of socio-economically valuable species indicates that natural regeneration could be supplemented by planting high quality seedlings

The effect of high-density, short-duration stocking on soils and vegetation of mesic grassland in South Africa.

Doctor of Philosophy in Grassland and Rangeland Science. University of KwaZulu-Natal, Pietermaritzburg, 2018.High-density, short-duration stocking (HDG) is currently gaining popularity amongst farmers in South African mesic grasslands but little is known about its potential impact on soil properties and plant species composition, particularly the forbs (herbaceous dicotyledonous and non-graminoid monocotyledon) which contribute more to plant diversity than grasses. Under HDG, animals are stocked at higher stocking rates and densities than conventional grazing systems and burning is discouraged. This study used a fence-line contrast approach to compare the long-term impact of “real world” HDG systems with rotational grazing systems at a lower stocking density (LDG) on soils and vegetation composition including forb growth habits at two study sites, Kokstad and Cedarville. An experimental trial was set up at Ukulinga Research Farm to determine the short-term effects of HDG compared with no grazing on plant species composition and demography of the selected perennial forbs. Another field experiment was used to determine the response of three mesic grassland perennial forb species (Afroaster hispida, Gerbera ambigua and Hypoxis hemerocallidea) to intense defoliation and interspecific competition with a grass species (Themeda triandra). Soils were more compacted under HDG but soil chemical properties did not differ between HDG and LDG at both Kokstad and Cedarville. There was a low percentage cover of desirable palatable grasses and high forb species turnover under HDG at Kokstad and low grass and forb species responses at Cedarville. There was high litter accumulation under HDG over the long- and short-term period. High litter accumulation reduces irradiance for plants, and may lead to lower basal cover. The intense grazing and trampling due to the higher stocking rate and stocking density under HDG resulted in less erect forb growth habits and more prostrate growth habits at Kokstad. A study of demography revealed that HDG threatened future populations of the grazing-sensitive species Afroaster hispida, Agathisanthemum chlorophyllum and Gerbera ambigua through increased mortality or reduction in the recruitment of large from small individuals. Intense defoliation altered the competitive response of A. hispida, it had a high competitive response when undefoliated but when defoliated its competitive response was reduced. Gerbera ambigua and H. hemerocallidea were not affected by the interaction between defoliation and competition. Findings from this study has shown that HDG potentially has a negative impact on soil health and vegetation composition of South African mesic grassland

Plant evolution and urbanization: quantifying the effects of natural selection in shaping shepherd’s purse (capsella bursa-pastoris) populations in New York City

The aim of this study is to quantify the effects of natural selection in shaping Capsella bursa-pastoris populations along an urban-rural gradient in New York City. A reciprocal transplant experiment with 168 lab-germinated C. bursa-pastoris seedlings from both urban and rural populations are grown in eight paired home and away sites distributed throughout the New York metropolitan area. Sites are visited approximately thirteen times to record plant fitness. There is evidence for local adaptation of urban populations: urban plants have longer reproductive durations and produce more seed pods in urban environments. These findings suggest that urban plants are better adapted to the stressful abiotic conditions found in urban areas. Water stress laboratory trials test if urban populations are shaped by urban water stress regimes. The trials use 392 lab-germinated seedlings representing urban and rural populations from the New York metropolitan area, and include four water-stress treatments: drought, flood, cyclic drought and flood, and a well-watered control. Leaf traits from plants in the drought and control treatments are quantified to examine their role in water stress response. Both plant types appear unaffected by water stress, and demonstrate plasticity in leaf traits in response to drought. Leaf traits predict final plant size in the drought treatment but not in the control. A salt stress trial tests if urban populations are shaped by urban soil salt stress. The trial includes 288 plants representing urban and rural populations from the New York metropolitan area. Plants are grown under different salt treatments (0, 20, 40, 50, 60, 100, and 150 mM NaCl) for five weeks. Both plant types demonstrate salt-sensitivity, having high rates of mortality at high salt concentrations. However, plants that survive high salt treatments are significantly larger than controls, indicating some individuals are salt tolerant. Leaf trait analysis demonstrates that different plastic responses occur in plants grown in salt stress compared to those grown in drought. The reciprocal transplant experiment shows evidence of local adaptation in urban populations, whereas the laboratory trials find that the species is highly plastic in leaf trait responses to drought and salinity

Crop Updates 2009 - Genetically Modified Crops, Nutrition, Soils, & Others

This session covers fifteen papers from different authors: 1. Performance of Canola Breeders Roundup Ready® canola hybrid CHYB-166 in 2008, Wallace Cowling, Canola Breeders Western Australia Pty Ltd 2. The implications of GM glyphosate resistant lupin, Art Diggle, Caroline Peek, Frank D’Emden, Fiona Evans, Bob French, Rob Grima, Sam Harburg, Abul Hashem,, John Holmes, Jeremy Lemon, Peter Newman, Janet Paterson, Steve Penny,Department of Agriculture and Food, Peter Portmann, Agriconnect 3. Nufarm Roundup Ready® Canola Systems Trials— 2008 Mark Slatter, Research and Development Officer, Victoria, Nufarm (0438 064 845) Angus MacLennan, Business Development Manager, New South Wales, Nufarm (0408 358 024) Cooperators: Monsanto, Nuseed, Pacific Seeds, Pioneer Seeds 4. Roundup Ready® canola—2008 Limited Commercial Release. Getting the system right, Andrew Wells and Mark Slatter, Nufarm Australia Limited (Reprint from 2008 GRDC Cropping Updates with Introductory note) NUTRITION 5. Fertilising in a changing price environment, Bill Bowden1, Wayne Pluske2 and Jeremy Lemon1, 1Department of Agriculture and Food, 2Back Paddock Company 6. Making better fertiliser for Western Australian cropping systems, Wen Chen1 2, Geoff Anderson1, Ross Brennan1and Richard Bell2 1Department of Agriculture and Food, 2School of Environmental Science, Murdoch University 7. The nitrogen fertiliser replacement value of biosolids from wastewater treatment, Hannah Rigby1, Deborah Pritchard1, David Collins1, Katrina Walton2, David Allen2 and Nancy Penney31School of Agriculture and Environment,Curtin University of Technology, Muresk Campus, 2Chemistry Centre of Western Australia 3Water Corporation of Western Australia 8. Fertilising to soil type (usually) pays, Michael Robertson, Bill Bowden and Roger Lawes, CSIRO, Floreat and Department of Agriculture and Food SOILS 9. Management of subsoil acidity and compaction using a combination of lime, deep ripping and controlled traffic, Stephen Davies, Chris Gazey, Breanne Best and David Gartner, Department of Agriculture and Food 10. Optimising gypsum applications through remote sensing and Variable Rate Technology, Frank D’Emden, Department of Agriculture and Food and Quenten Knight,Precision Agronomics Australia 11. Case study of a 17 year agricultural lime trial, Chris Gazey1, Joel Andrew2and Ryan Pearce3 1Department of Agriculture and Food; 2Precision SoilTech; 3ConsultAg 12. Soil organic carbon in WA agricultural soils, FC Hoyle and A Bennett, Department of Agriculture and Food OTHER 13. Is the no-till revolution complete in WA? Frank D’Emden1, Rick Llewellyn2 and Ken Flower3 1Department of Agriculture and Food, 2CSIRO Sustainable Ecosystems, 3University of Western Australia 14. Progression Planning (The Concept), Julian Krieg and Owen Catto, Wheatbelt Men’s Health 15. Is the Department of Agriculture and Food still a primary source of cropping information? Cindy Parsons, Department of Agriculture and Foo

Soilguide (Soil guide) : a handbook for understanding and managing agricultural soils

This handbook integrates the current knowledge of soils in south-western Australia in a user-friendly form. It describes how to assess which soil properties influence production and land degradation in the agricultural area and summarises management options to remedy or minimise soil limitations. The potential for growing a large range of crops and pastures can be assessed. In particular, the links between soil morphology, soil properties, management and agronomy are emphasised. The manual is designed for use at the paddock scale or for site assessment, but it can also be used at a catchment or regional scale. It is specifically designed for rain fed agriculture in south-western Australia but many sections will be relevant elsewhere as the manual works from first principles and does not require prior knowledge of the nature and distribution of soils.https://researchlibrary.agric.wa.gov.au/bulletins/1001/thumbnail.jp

Floral trait architecture in crop sunflower (\u3ci\u3eHelianthus annuus\u3c/i\u3e) under drought conditions

Longer and more intense droughts are predicted to become more common in the coming century due to anthropogenic climate change. Drought can reduce crop yield and decrease food security. In order to mitigate the negative effects of drought on crop production, it is important to elucidate the underlying mechanisms that promote drought stress resistance in crop plants. Floral traits impact yield, especially in oilseed crops such as sunflower (Helianthus annuus), but their susceptibility to drought stress is understudied. The goal of this study was to describe the floral trait architecture of H. annuus crop lines under drought versus well-watered conditions and examine the relationship between these traits and drought resistance. Forty H. annuus lines from the Sunflower Association Mapping population were assessed for size traits (height, stem diameter, head diameter and mass) and floral traits (floret lengths, nectar volume and concentration) in a field experiment under well-watered and drought conditions. Drought stress resulted in a decrease for most size traits, as well as shorter corollas and styles, and a decrease in average nectar volume. Floral sucrose concentration was unaffected by drought stress; however, line and line by treatment variation was observed for this trait and for average nectar volume. Line effects were highly significant for each trait, indicating that all traits measured have a strong genetic component. Lines differed significantly in their response to drought for head diameter at time of flowering, anther length, and days to flower. Larger size generally increased drought resistance. Nectar sucrose concentration had a significant positive correlation with final height of the plant and seed total in the watered treatment, indicating that larger plants with higher seed totals had higher nectar sucrose concentrations by volume than those in the drought treatment. The results involving shortened corolla and style lengths during drought should be studied further to determine whether there is an advantage for agricultural pollinators. Anther length was the only floral trait correlated with drought resistance. Anther length should be studied further in order to determine if its conservation across treatments can be useful for improving future H. annuus marker assisted selection efforts

Managing south coast sandplain soils to yield potential

This book has been written to help farmers reach their rainfall-limited yield potential. It comes from a need to understand the properties and management options for grain production on sandplain soils. It also seeks to address concerns that crop yields on sandplain soils are not increasing at the rate experienced on soils elsewhere in the south coast region of Western Australia.https://researchlibrary.agric.wa.gov.au/bulletins/1008/thumbnail.jp

The ecological impact of recreation in British temperate woodlands

In recent decades, the ecological impact of recreation in woodlands and forests has been a subject of considerable world-wide interest. However, there are few studies examining the effects of recreation on woodland vegetation, soils and fauna in Britain. This thesis identifies recreational trampling as a major contributor in facilitating ecological change in urban fringe semi-natural ancient temperate woodlands of Warwickshire, England. Relationships with trampling intensity are generally curvi- linear, suggesting that the rates of damage are most rapid at initial stages of trampling. Biotic communities are shaped so that their structure and diversity is related to the type, intensity and frequency of impact. The impact of trampling on vegetation is the most precise indicator of recreational use. Multi-variate analyses indicates that trampling is the primary organisational gradient operating on ground vegetation, with trail centres dominated by secondary plant associations at equilibrium with the trampling pressure. Trail margins are dominated by vegetation that is tolerant of low levels of trampling and high rates of competition. Experimental trampling experiments show that the ecological carrying capacity of woodlands for recreation are lower than previously thought; from below 150 people per year in Rubusfruticosus agg. and Pteridium aquilinum dominated stands to below 75 people per year in coniferous stands with Hyacinthoides non-scripta ground flora. The ability of vegetation to tolerate trampling is related to plant anatomy, morphological adaptations, plant strategies, growth rate, position of the perennating bud, environmental conditions such as canopy density and is more a function of the ability to recover from trampling rather than to resist. By virtue of their delicate morphology, stands dominated by shade tolerant species are the most vulnerable to trampling. Increases in soil compaction and decreases in pore space and oxygen content are recognised as important in shaping woodland vegetation and fauna, and the reduction in soil inhabiting invertebrate and micro-organism populations have consequences for woodland processes. A bioindicator index to assess soil damage is provided using Acari body length. Models summarising the ecological changes associated with trampling and the ecological carrying capacity of woodlands are provided, along with a woodland management checklist and an index of vulnerability for resource managers to assess the potential of woodland stands to withstand recreational use