A review of silvopastoral systems in native forests of Nothofagus antarctica in southern Patagonia, Argentina

Silvopastoral systems in Nothofagus antarctica (ñire) forest have become an economical, ecological and productive alternative in Patagonia. Southern Patagonia’s experience over the past 12 years with silvopastoral systems is reviewed. The productivity and nutritive value (crude protein content and dry matter digestibility) of the understorey grassland were dependent on the interaction of environmental (mainly soil water availability and light intensity) and management factors under the trees and in turn determined animal performance. A method developed for carrying capacity estimation at the paddock level was based on the potential aboveground net primary production, and values ranged from 85 to 2200 kg DM ha−1 year−1. Planned thinning in secondary forest stands provides wood production and also improves the undestorey DM production by increasing incoming radiation. Within a management plan, a stand’s water stress conditions as well as the use of Reineke’s stand density index are proposed to assist in determining thinning intensities. Livestock production is the main annual income of silvopastoral systems where cattle and mixed livestock production (cattle + sheep) is the main activity. Animal performance at the whole farm scale is presented by comparing traditional extensive grazing management with an adaptive silvopastoral management that included strategic separation in homogeneous areas (grass steppe, forest and riparian meadows), stocking rate adjustment to grassland net primary production and the protection of regeneration from herbivores browsing. Data from litter decomposition, nutrient cycling and carbon storage studies also are presented. Finally, aspects related to the criteria and indicators to assess ñire forest’s sustainability under silvopastoral use along with biodiversity conservation issues are presented.Fil: Peri, Pablo Luis. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Patagonia Sur; Argentina. Universidad Nacional de la Patagonia Austral. Unidad Académica Río Gallegos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; ArgentinaFil: Bahamonde, Héctor Alejandro. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Patagonia Sur; Argentina. Universidad Nacional de la Patagonia Austral. Unidad Académica Río Gallegos; ArgentinaFil: Lencinas, María Vanessa. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; ArgentinaFil: Gargaglione, Veronica Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentina. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Patagonia Sur; Argentina. Universidad Nacional de la Patagonia Austral. Unidad Académica Río Gallegos; ArgentinaFil: Soler Esteban, Rosina Matilde. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; ArgentinaFil: Ormaechea, Sebastián Gabriel. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Patagonia Sur; ArgentinaFil: Martínez Pastur, Guillermo José. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentin

A Simple System Dynamics Model for the Global Production Rate of Sand, Gravel, Crushed Rock and Stone, Market Prices and Long-Term Supply Embedded into the WORLD6 Model

A model for global supply of sand, gravel and cut stone for construction based on a system dynamics model was developed for inclusion in the WORLD6 model. The Sand-Gravel-Stone model simulates production and market supply, demand and price for natural sand and gravel, sand and gravel from crushed rock and cut stone. The model uses market mechanisms where the demand is depending on population size, maintenance and price. For the period 2000–2050, the WORLD6 model outputs correlate with the GINFORS model outputs (r 2 = 0.98), but they may take different pathways after 2050. The resources of sand and gravel are estimated at 12 trillion ton each, another 125 trillion tons of rock is suitable for crushing to sand and gravel and at least 42 trillion ton of quality stone is available for production of cut stone. The simulation, under assumed business-as-usual conditions, shows that cut stone production will reach a maximum level by about 2020–2030 and stabilize after that. The cause for this is that demand exceeds extraction as well as slow exhaustion of the known reserves of high-quality stone. Sand and gravel show plateau behaviour and reach their maximum production rate in 2060–2070. The reason for the slight peak towards a plateau behaviour is partly driven by an expected population decline and increasing prices for sand and gravel, limiting demand. Assuming business-as-usual conditions rates remain at that level for centuries

A conceptual model for the development of Phytophthora disease in Quercus robur

Here, a conceptual model is presented for the development of Phytophthora disease in pedunculate oak. The model is presented using the causal loop diagram tool and gives an overview of how various abiotic and biotic factors, such as soil moisture, nutrient availability and mycorrhizal colonization, may affect the reproduction and the infective capacity of soil-borne Phytophthora species, the susceptibility of the host and subsequent disease development. It is suggested that the link between the root damage caused by Phytophthora species and overall tree vitality is in the assimilation and allocation of carbon within the plants. The potential impact of environmental factors on these processes is discussed. The model is presented with reference to scenarios related to variation in soil moisture and nutrient availability. The need for species-specific validation of the model and the implications of the model are discussed