Intermediate coupling between aboveground and belowground biomass maximises the persistence of grasslands

Aboveground and belowground biomass compartments of vegetation fulfil different functions and they are coupled by complex interactions. These compartments exchange water, carbon and nutrients and the belowground biomass compartment has the capacity to buffer vegetation dynamics when aboveground biomass is removed by disturbances such as herbivory or fire. However, despite their importance, root-shoot interactions are often ignored in more heuristic vegetation models. Here, we present a simple two-compartment grassland model that couples aboveground and belowground biomass. In this model, the growth of belowground biomass is influenced by aboveground biomass and the growth of aboveground biomass is influenced by belowground biomass. We used the model to explore how the dynamics of a grassland ecosystem are influenced by fire and grazing. We show that the grassland system is most persistent at intermediate levels of aboveground-belowground coupling. In this situation, the system can sustain more extreme fire or grazing regimes than in the case of strong coupling. In contrast, the productivity of the system is maximised at high levels of coupling. Our analysis suggests that the yield of a grassland ecosystem is maximised when coupling is strong, however, the intensity of disturbance that can be sustained increases dramatically when coupling is intermediate. Hence, the model predicts that intermediate coupling should be selected for as it maximises the chances of persistence in disturbance driven ecosystems

Rainfall or Price Variability: What Determines Rangeland Management Decisions? A Simulation-Optimization Approach to South African Savannas

Savannas cover the greater part of Africa and Australia and almost half of South America and contribute to the livelihoods of more than 350 million people. With the intensification of land use during the second half of the 20th century, savannas have become increasingly degraded through bush encroachment as a consequence of increased grazing pressure. Research on rangeland dynamics, however, provides contradicting answers with regard to the causes and possible remedies of bush encroachment. In this paper we present results from an application of a simulation-optimization model to the case of extensive rangeland management in South Africa. Our model differs from previous approaches in that it explicitly accounts for the influence of stochastic prices and rainfall on economically optimal management decisions. By showing the implications of neglecting price variation and stochasticity in rangeland models we provide new insights with regard to the determinants of bush encroachment and rangeland managers' economic utility. We demonstrate that, in the case of South Africa, optimal rangeland management is likely to lead to bush encroachment that eventually makes livestock holding unprofitable. Yet, we identify the costs of fire management to be a limiting factor for managers to counteract bush encroachment and explore the impact of policy measures to reduce fire control costs on the ecological and economic sustainability of livestock holding.Equilibrium, bio-economic modeling, grassland management, sustainable strategies, stochastic conditions, Livestock Production/Industries, Q57,

Behavior Change Trajectories and Metabolic Syndrome Risk Factor Clustering During the Transition to College: A Feasibility Pilot Study

International Journal of Exercise Science 15(5): 125-141, 2022. Metabolic syndrome (MetS) is typically diagnosed in adults; however, MetS risk factors are growing in prevalence during youth and young adulthood. Though the transition from high school to college is associated with adverse changes in lifestyle behaviors that may contribute to MetS risk factor development, the relationship between pre-college MetS risk status and transition-related behavior change is unknown. This prospective study aimed to describe the relationship between pre-college MetS risk status and transition-related behavior change trajectories in college-bound students. Moreover, it aimed to assess the feasibility of the study design, including acceptability to both participants and investigators, prior to implementation in a larger sample. Participants (n = 21, 18.3 ± 0.3 y/o) were assessed for MetS risk factors during their last semester of high school. Self-report behavioral data on dietary habits, physical activity, sleep, stress, and alcohol consumption were collected at baseline and during the fall and spring semesters of the first year of college. Linear mixed models revealed drastic increases in alcohol consumption (β11 = 0.39, p \u3c 0.001) and apparent decreases in moderate-vigorous physical activity (β11 = -0.15, p = 0.185) during the college transition. Furthermore, 47.6% of students had ≥ 1 MetS risk factor at baseline and those with a greater number of risk factors experienced a more severe alcohol-related behavior change trajectory (β11 = 0.29, p \u3c 0.050). These findings highlight the importance of primordial prevention strategies against early MetS risk development, given the potential relationship with future behavioral trajectories. Future research should aim to further characterize this relationship using comprehensive, longitudinal measures that span the college transition in larger, more diverse samples

The Effect of Particle Strength on the Ballistic Resistance of Shear Thickening Fluids

The response of shear thickening fluids (STFs) under ballistic impact has received considerable attention due to its field-responsive nature. While efforts have primarily focused on the response of traditional ballistic fabrics impregnated with fluids, the response of pure STFs to penetration has received limited attention. In the present study, the ballistic response of pure STFs is investigated and the effect of fluid density and particle strength on ballistic performance is isolated. The loss of ballistic resistance of STFs at higher impact velocities is governed by particle strength, indicating the range of velocities over which they may provide effective armor solutions.Comment: 4 pages, 4 figure

Metastable states of a flux line lattice studied by transport and Small Angle Neutron Scattering

Flux Lines Lattice (FLL) states have been studied using transport measurements and Small Angle Neutron Scattering in low T$_c$ materials. In Pb-In, the bulk dislocations in the FLL do not influence the transport properties. In Fe doped NbSe$_{2}$, transport properties can differ after a Field Cooling (FC) or a Zero Field Cooling (ZFC) procedure, as previously reported. The ZFC FLL is found ordered with narrow Bragg Peaks and is linked to a linear V(I) curve and to a superficial critical current. The FC FLL pattern exhibits two Bragg peaks and the corresponding V(I) curve shows a S-shape. This can be explained by the coexistence of two ordered FLL slightly tilted from the applied field direction by different superficial currents. These currents are wiped out when the transport current is increased.Comment: accepted for publication in Phys. Rev.