Row Spacing and Productivity of Russian Wild Rye Pastures in Semiarid Environments

To sustain forage yields in dry years in semiarid climates, row spacings \u3e59cm have been recommended for Russian wild rye [Psathyrostachys juncea (Fisch.) Nevski] (Lawrence & Heinrichs, 1968). However, wide row spacings promote weed invasion, soil erosion, and elevated plant crowns resulting in a rough, washboard ground surface (Kilcher, 1961). Jefferson and Kielly (1998) suggested a 30-cm row spacing for optimum sustainable forage yields in Russian wild rye in the semiarid prairie region of Canada. This study aimed to evaluate the relationship between row spacing and productivity of Russian wild rye at two semiarid sites near Mandan, in the northern Great Plains region of the USA (46º 48\u27 N latitude, 100º 55\u27 W longitude)

Possible climate change impacts on water resources availability in a large semi-arid catchment in Northeast Brazil.

The semiarid region of Northeast Brazil is characterized by water scarcity, vulnerability of natural resources, and pronounced climatic variability. An integrated model has been developed to simulate this complex situation with an emphasis on a large-scale representation of hydrological processes and on the sensitivity to climate change. Regional climate change scenarios were obtained by empirical downscaling with large-scale climate information from different GCMs which differ strongly in their projections for future precipitation. The results show that due to these differences, it is still impossible to give quantitative values of the water availability in a forecast sense, i.e. to assign probabilities to the simulated results. However, it becomes clear that efficient and ecologically sound water management is a key question for further development. The results show that, independent of the climate change, agriculture is more vulnerable to drought impacts in the case of rainfed compared to irrigated farming. However, the capacity of irrigation and water infrastructure to enhance resilience with respect to climatic fluctuations is significantly constrained in the case of a negative precipitation trend

Soil biochemistry and microbial activity in vineyards under conventional and organic management at Northeast Brazil.

The São Francisco Submedium Valley is located at the Brazilian semiarid region and is an important center for irrigated fruit growing. This region is responsible for 97% of the national exportation of table grapes, including seedless grapes. Based on the fact that orgThe São Francisco Submedium Valley is located at the Brazilian semiarid region and is an important center for irrigated fruit growing. This region is responsible for 97% of the national exportation of table grapes, including seedless grapes. Based on the fact that organic fertilization can improve soil quality, we compared the effects of conventional and organic soil management on microbial activity and mycorrhization of seedless grape crops. We measured glomerospores number, most probable number (MPN) of propagules, richness of arbuscular mycorrhizal fungi (AMF) species, AMF root colonization, EE-BRSP production, carbon microbial biomass (C-MB), microbial respiration, fluorescein diacetate hydrolytic activity (FDA) and metabolic coefficient (qCO2). The organic management led to an increase in all variables with the exception of EE-BRSP and qCO2. Mycorrhizal colonization increased from 4.7% in conventional crops to 15.9% in organic crops. Spore number ranged from 4.1 to 12.4 per 50 g-1 soil in both management systems. The most probable number of AMF propagules increased from 79 cm-3 soil in the conventional system to 110 cm-3 soil in the organic system. Microbial carbon, CO2 emission, and FDA activity were increased by 100 to 200% in the organic crop. Thirteen species of AMF were identified, the majority in the organic cultivation system. Acaulospora excavata, Entrophospora infrequens, Glomus sp.3 and Scutellospora sp. were found only in the organically managed crop. S. gregaria was found only in the conventional crop. Organically managed vineyards increased mycorrhization and general soil microbial activity

Phylogenetic structure and formation mechanism of shrub communities in arid and semiarid areas of the Mongolian Plateau

The mechanisms of species coexistence within a community have always been the focus in ecological research. Community phylogenetic structure reflects the relationship of historical processes, regional environments, and interactions between species, and studying it is imperative to understand the formation and maintenance mechanisms of community composition and biodiversity. We studied the phylogenetic structure of the shrub communities in arid and semiarid areas of the Mongolian Plateau. First, the phylogenetic signals of four plant traits (height, canopy, leaf length, and leaf width) of shrubs and subshrubs were measured to determine the phylogenetic conservation of these traits. Then, the net relatedness index (NRI) of shrub communities was calculated to characterize their phylogenetic structure. Finally, the relationship between the NRI and current climate and paleoclimate (since the Last Glacial Maximum, LGM) factors was analyzed to understand the formation and maintenance mechanisms of these plant communities. We found that desert shrub communities showed a trend toward phylogenetic overdispersion; that is, limiting similarity was predominant in arid and semiarid areas of the Mongolian Plateau despite the phylogenetic structure and formation mechanisms differing across habitats. The typical desert and sandy shrub communities showed a significant phylogenetic overdispersion, while the steppified desert shrub communities showed a weak phylogenetic clustering. It was found that mean winter temperature (i.e., in the driest quarter) was the major factor limiting steppified desert shrub phylogeny distribution. Both cold and drought (despite having opposite consequences) differentiated the typical desert to steppified desert shrub communities. The increase in temperature since the LGM is conducive to the invasion of shrub plants into steppe grassland, and this process may be intensified by global warming

Agro-Ecological Zoning for Tall Wheatgrass (Thinopyrum Ponticum) as a Potential Energy and Forage Crop in Salt-Affected and Dry Lands of Argentina

Thinopyrum ponticum, is the most disseminated halophyte speciescultivated for forage on hydro-halomorphic soils in the world. Theobjective of the present work was to identify the geographicareas fordevelopment of tall wheatgrass on halomorphic soils in Argentina, for forageand as feedstock for bioenergy. To define the agroclimate in Argentina, we considered the thermal and hydric limits of the species in its place of originand in locations where it is successfully cultivated around the world. The maps corresponding to the bioclimatic indices were drawn using a GIS, andthe map obtained by overlaying them defined the agroclimatic suitability. Thiszoning was finally superimposed on the drylands saline and alkaline soils inthecountry, thus defining the agro-ecological suitability of Argentina forthis species under different moisture regimes: moist-subhumid,dry-subhumid, semiarid to arid climate. The the agro-ecological zoning showsthe potential growing areas for tall wheatgrass in Argentina on soils withhalomorphism processes under dry climates.Fil: Falasca, Silvia Liliana. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación de Recursos Naturales. Instituto de Clima y Agua; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Miranda del Fresno, Ma. Carolina. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Humanas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Pitta-alvarez, Sandra Irene. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Micología y Botánica. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Micología y Botánica; Argentin

INTERNATIONAL DROUGHT MITIGATION AN INTRODUCTION

This special issue of Great Plains Quarterly includes the papers from the international sessions of the symposium, beginning with the keynote address by J. M. Powell, Abideth Forever? Global Use of Semiarid Lands in the Interwar Years. Powell\u27s thesis is that the new nationalisms, old imperial networks, and burgeoning successes and ambitions of scientists combined between the two world wars to create new systems of land use in semiarid regions. In his introduction, Powell poses an interesting question: Were decisions about the management of these fragile ecosystems developed within the region as a result of experience, or outside the region in response to planners\u27 hopes for the society as a whole? His conclusions are revealing and provide challenges for the future management of semiarid lands

INTERNATIONAL DROUGHT MITIGATION AN INTRODUCTION

This special issue of Great Plains Quarterly includes the papers from the international sessions of the symposium, beginning with the keynote address by J. M. Powell, Abideth Forever? Global Use of Semiarid Lands in the Interwar Years. Powell\u27s thesis is that the new nationalisms, old imperial networks, and burgeoning successes and ambitions of scientists combined between the two world wars to create new systems of land use in semiarid regions. In his introduction, Powell poses an interesting question: Were decisions about the management of these fragile ecosystems developed within the region as a result of experience, or outside the region in response to planners\u27 hopes for the society as a whole? His conclusions are revealing and provide challenges for the future management of semiarid lands