Agent based modeling and simulation of a pastoral-nomadic land use system

Almost half of Africa is covered by arid savannas, which are used as rangelands and are the source of livelihood for a vast population. To sustain pasture quality, degradation has to be avoided and efficient and sustainable land use strategies are needed. This paper describes the development of a simulation model representing the range management strategies of the Himba people in north-western Namibia. The model recognizes spatial factors and the impact of management decisions on ecosystem dynamics. The paper also describes the process of creating and validating a software application, and implementing the model

Agent based modeling and simulation of a pastoral-nomadic land use system

Almost half of Africa is covered by arid savannas, which are used as rangelands and are the source of livelihood for a vast population. To sustain pasture quality, degradation has to be avoided and efficient and sustainable land use strategies are needed. This paper describes the development of a simulation model representing the range management strategies of the Himba people in north-western Namibia. The model recognizes spatial factors and the impact of management decisions on ecosystem dynamics. The paper also describes the process of creating and validating a software application, and implementing the model

Functional Responses of South African Rangelands in Contrasting Tenure Systems

Land degradation in South African rangelands has frequently been studied in the context of tenure systems, because both governmental policy and range management practices were historically implemented in contrasting forms. We compared the functional response of vegetation along grazing gradients between a communal (CU) and commercial (CO) farming areas. One transect was established per farm from the waterpoint to a mid-field position. Six equally spaced plots (5 m × 5 m) were set up along each transect. Using a taxon-free sampling procedure, we recorded the response of 15 community-aggregated plant functional traits (CPFT) in: (1) mature standing biomass; and (2) after four weeks’ regrowth following clipping. Additionally, species identity was recorded. Grazing on CU was continuous and stocking rate not controlled, while CO applied rotational grazing with recommended stocking rates. From the results, CPFT differences were not significant (Student’s t-test, P \u3c 0.01) between tenure systems. A principal component analysis of CPFT showed largely overlapping functional responses in the two tenure systems in the case of mature standing biomass, while the functional response of regrowing vegetation was clearly separated in the ordination space. Communal rangelands had twice the species richness of commercial farms.We concluded that, from a functional perspective, communities under different tenure systems were similar. However, the functional response of vegetation regrowth might be different as well as the ecological services provided (biodiversity)

Temperature and aridity regulate spatial variability of soil multifunctionality in drylands across the globe

The relationship between the spatial variability of soil multifunctionality (i.e. the capacity of soils to conduct multiple functions; SVM) and major climatic drivers, such as temperature and aridity, has never been assessed globally in terrestrial ecosystems. We surveyed 236 dryland ecosystems from six continents to evaluate the relative importance of aridity and mean annual temperature, and of other abiotic (e.g., texture) and biotic (e.g., plant cover) variables as drivers of SVM, calculated as the averaged coefficient of variation for multiple soil variables linked to nutrient stocks and cycling. We found that increases in temperature and aridity were globally correlated to increases in SVM. Some of these climatic effects on SVM were direct, but others were indirectly driven through reductions in the number of vegetation patches and increases in soil sand content. The predictive capacity of our structural equation modelling was clearly higher for the spatial variability of N- than for C- and P- related soil variables. In the case of N cycling, the effects of temperature and aridity were both direct and indirect via changes in soil properties. For C and P, the effect of climate was mainly indirect via changes in plant attributes. These results suggest that future changes in climate may decouple the spatial availability of these elements for plants and microbes in dryland soils. Our findings significantly advance our understanding of the patterns and mechanisms driving SVM in drylands across the globe, which is critical for predicting changes in ecosystem functioning in response to climate change

Soil fungal abundance and plant functional traits drive fertile island formation in global drylands

Dryland vegetation is characterized by discrete plant patches that accumulate and capture soil resources under their canopies. These “fertile islands” are major drivers of dryland ecosystem structure and functioning, yet we lack an integrated understanding of the factors controlling their magnitude and variability at the global scale.EEA BarilocheFil: Ochoa-Hueso, Raúl. Universidad Autónoma de Madrid. Department of Ecology; EspañaFil: Eldridge, David J. University of New South Wales. School of Biological, Earth and Environmental Sciences; AustraliaFil: Delgado-Baquerizo, Manuel. University of Colorado. Cooperative Institute for Research in Environmental Sciences; Estados Unidos. Universidad Rey Juan Carlos. Escuela Superior de Ciencias Experimentales y Tecnología. Departamento de Biología y Geología, Física y Química Inorgánica; EspañaFil: Soliveres, Santiago. University of Bern. Institute of Plant Sciences; SuizaFil: Bowker, Matthew A. Northern Arizona University. School of Forestry; Estados UnidosFil: Gross, Nicolás. Universidad Rey Juan Carlos. Escuela Superior de Ciencias Experimentales y Tecnología. Departamento de Biología y Geología, Física y Química Inorgánica; España. Institut Nationale de la Recherche Agronomique; Francia. Université La Rochelle. Centre d’étude biologique de Chizé; FranciaFil: Le Bagousse-Pinguet, Yoann. Universidad Rey Juan Carlos. Escuela Superior de Ciencias Experimentales y Tecnología. Departamento de Biología y Geología, Física y Química Inorgánica; EspañaFil: Quero, José L. Universidad de Córdoba. Escuela Técnica Superior de Ingeniería Agronómica y de Montes. Departamento de Ingeniería Forestal: EspañaFil: García-Gómez, Miguel. Universidad Rey Juan Carlos. Escuela Superior de Ciencias Experimentales y Tecnología. Departamento de Biología y Geología, Física y Química Inorgánica; EspañaFil: Valencia, Enrique. Universidad Rey Juan Carlos. Escuela Superior de Ciencias Experimentales y Tecnología. Departamento de Biología y Geología, Física y Química Inorgánica; EspañaFil: Arredondo, Tulio. Instituto Potosino de Investigación Científica y Tecnológica. División de Ciencias Ambientales; MéxicoFil: Beinticinco, Laura. Universidad Nacional de La Pampa. Facultad de Agronomía; ArgentinaFil: Bran, Donaldo Eduardo. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Bariloche; ArgentinaFil: Cea, Alex. Universidad de La Serena. Departamento de Biología; ChileFil: Coaguila, Daniel. Instituto de Ensino Superior de Rio Verde; BrasilFil: Dougill, Andrew J. University of Leeds. School of Earth and Environment; Gran BretañaFil: Espinosa, Carlos I. Universidad Técnica Particular de Loja. Departamento de Ciencias Naturales; EcuadorFil: Gaitan, Juan Jose. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Suelos; ArgentinaFil: Guuroh, Reginald T. University of Cologne. Botanical Institute. Range Ecology and Range Management Group; Alemania. CSIR-Forestry Research Institute of Ghana; GhanaFil: Guzmán, Elizabeth. Universidad Técnica Particular de Loja. Departamento de Ciencias Naturales; EcuadorFil: Gutiérrez, Julio R.. Universidad de La Serena. Departamento de Biología; Chile. Centro de Estudios Avanzados en Zonas Áridas (CEAZA); Chile. Instituto de Ecología y Biodiversidad; ChileFil: Hernández, Rosa M. Universidad Experimental Simón Rodríguez. Centro de Agroecología Tropical. Laboratorio de Biogeoquímica; VenezuelaFil: Huber-Sannwald, Elisabeth. Instituto Potosino de Investigación Científica y Tecnológica. División de Ciencias Ambientales; MéxicoFil: Jeffries, Thomas. Western Sydney University. Hawkesbury Institute for the Environment; AustraliaFil: Linstädter, Anja. University of Cologne. Botanical Institute. Range Ecology and Range Management Group; AlemaniaFil: Mau, Rebecca L. Northern Arizona University. Center for Ecosystem Science and Society: Estados UnidosFil: Monerris, Jorge. Université du Québec à Montréal. Pavillon des Sciences Biologiques. Département des Sciences Biologiques; CanadáFil: Prina, Anibal. Universidad Nacional de La Pampa. Facultad de Agronomía; ArgentinaFil: Pucheta, Eduardo. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Departamento de Biología; ArgentinaFil: Stavi, Ilan. Dead Sea and Arava Science Center, IsraelFil: Thomas, Andrew. Aberystwyth University. Department of Geography and Earth Sciences; Gran BretañaFil: Zaady, Eli. Agricultural Research Organization. Gilat Research Center. Natural Resources; IsraelFil: Singh, Brajesh K. Western Sydney University. Hawkesbury Institute for the Environment; Australia. Western Sydney University. Global Centre for Land-Based Innovation; AustraliaFil: Maestre, Fernando T. Universidad Rey Juan Carlos. Escuela Superior de Ciencias Experimentales y Tecnología. Departamento de Biología y Geología, Física y Química Inorgánica; Españ

Soil fungal abundance and plant functional traits drive fertile island formation in global drylands

International audience1.Dryland vegetation is characterised by discrete plant patches that accumulate and capture soil resources under their canopies. These “fertile islands” are major drivers of dryland ecosystem structure and functioning, yet we lack an integrated understanding of the factors controlling their magnitude and variability at the global scale.2.We conducted a standardized field survey across two hundred and thirty-six drylands from five continents. At each site, we measured the composition, diversity and cover of perennial plants. Fertile island effects were estimated at each site by comparing composite soil samples obtained under the canopy of the dominant plants and in open areas devoid of perennial vegetation. For each sample, we measured fifteen soil variables (functions) associated with carbon, nitrogen and phosphorus cycling and used the Relative Interaction Index to quantify the magnitude of the fertile island effect for each function. In eighty sites, we also measured fungal and bacterial abundance (quantitative PCR) and diversity (Illumina MiSeq).3.The most fertile islands, i.e. those where a higher number of functions were simultaneously enhanced, were found at lower-elevation sites with greater soil pH values and sand content under semiarid climates, particularly at locations where the presence of tall woody species with a low specific leaf area increased fungal abundance beneath plant canopies, the main direct biotic controller of the fertile island effect in the drylands studied. Positive effects of fungal abundance were particularly associated with greater nutrient contents and microbial activity (soil extracellular enzymes) under plant canopies.4.Synthesis. Our results show that the formation of fertile islands in global drylands largely depends on: (i) local climatic, topographic and edaphic characteristics, (ii) the structure and traits of local plant communities and (iii) soil microbial communities. Our study also has broad implications for the management and restoration of dryland ecosystems worldwide, where woody plants are commonly used as nurse plants to enhance the establishment and survival of beneficiary species. Finally, our results suggest that forecasted increases in aridity may enhance the formation of fertile islands in drylands worldwide