Variability of radiation use efficiency in mixed pastures under varying resource availability, defoliation and time scale

Forage productivity is the product between incident radiation, the fraction of radiation absorbed by the canopy (fAPAR) and radiation use efficiency (RUE). The extent to which forage productivity may be estimated through remote sensing depends on the relative effects of stress and defoliation on fAPAR and RUE. In a mixed pasture, we determined the relative impact of resource availability and defoliation on forage productivity, fAPAR and RUE, and we evaluated the impact of time scale on fAPAR and RUE under stress conditions. We conducted a one-year experiment in a temperate-mixed pasture subjected to different resource availability treatments and defoliation management. We measured RUE and fAPAR with different temporal windows. RUE was less responsive than fAPAR to changes in resource availability and defoliation intensity. However, RUE slightly decreased under water stress and increased under severe defoliation. Additionally, RUE variability during regrowth and among treatments depended on the temporal scale of observation: RUE was more variable for 12-day periods than 45- or 90-day periods. Our results reinforce the value of fAPAR as an explanatory variable of the variations in forage productivity due to changes in resource availability and management. In addition, the temporal scale of observation affects RUE variability. Thus, most variations of forage productivity may be captured by monitoring systems based on remote sensing of fAPAR provided that the time scale is coarse enough. However, the contrasting response of RUE and fAPAR to defoliation indicates a potential weakness of such a system when situations with contrasting defoliation regime are compared.Fil: Grigera, Gonzalo. Universidad de Buenos Aires. Facultad de Agronomía; ArgentinaFil: Oesterheld, Martin. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; Argentin

Extracting money from causal decision theorists

Newcomb’s problem has spawned a debate about which variant of expected utility maximisation (if any) should guide rational choice. In this paper, we provide a new argument against what is probably the most popular variant: causal decision theory (CDT). In particular, we provide two scenarios in which CDT voluntarily loses money. In the first, an agent faces a single choice and following CDT’s recommendation yields a loss of money in expectation. The second scenario extends the first to a diachronic Dutch book against CDT

Computing Optimal Commitments to Strategies and Outcome-Conditional Utility Transfers

Prior work has studied the computational complexity of computing optimal strategies to commit to in Stackelberg or leadership games, where a leader commits to a strategy which is observed by one or more followers. We extend this setting to one where the leader can additionally commit to outcome-conditional utility transfers. We characterize the computational complexity of finding optimal strategies in normal-form and Bayesian games, giving a mix of efficient algorithms and NP-hardness results. Finally, we allow the leader to also commit to a signaling scheme which induces a correlated equilibrium. In this setting, optimal commitments can be found in polynomial time for arbitrarily many players.Comment: AAMAS 202

Seasonality constraints to livestock grazing intensity

Increasing food production is essential to meet the future food demand of a growing world population. In the light of pressing sustainability challenges like climate change and the importance of the global livestock system for food security as well as GHG emissions, finding ways to increasing food production sustainably and without increasing competition for food crops is essential. Yet, many unknowns relate to livestock grazing, in particular grazing intensity, an essential variable to assess the sustainability of livestock systems. Here we explore ecological limits to grazing intensity (GI; i.e., the fraction of Net Primary Production consumed by grazing animals) by analysing the role of seasonality in natural grasslands. We estimate seasonal limitations to GI by combining monthly Net Primary Production data and a map of global livestock distribution with assumptions on the length of non-favourable periods that can be bridged by livestock (e.g., by browsing dead standing biomass, storage systems or biomass conservation). This allows us to derive a seasonality-limited potential GI, which we compare with the GI prevailing in 2000. We find that GI in 2000 lies below its potential on 39% of the total global natural grasslands, which has a potential for increasing biomass extraction of up to 181 MtC/yr. In contrast, on 61% of the area GI exceeds the potential, made possible by management. Mobilizing this potential could increase milk production by 5%, meat production by 4%, or contribute to free up to 2.8 Mio km² of grassland area at the global scale if the numerous socio-ecological constraints can be overcome. We discuss socio-ecological trade-offs, which may reduce the estimated potential considerably and require the establishment of sound monitoring systems and an improved understanding of livestock system’s role in the Earth system

Pastos y pastizales : Ciencia, docencia y desarrollo de tecnología

Esta charla relatará tres breves historias, una para cada uno de los tres elementos del título: la ciencia, la docencia y el desarrollo de tecnología. Pretendo contar lo que hago, lo que hacemos quienes nos dedicamos a la vida académica: a la investigación, la docencia y el desarrollo de tecnología.Academia Nacional de Agronomía y Veterinari

Vom "Sezessionsgespenst" zum Koalitionspartner - Regionale Parteien im politischen System Indiens

Die Bemerkung von Premierminister Atal Behari Vajpayee am 6. Dezember 2000, dem Jahrestag der Zerstörung der Babri Masjid in Ayodhya, es habe sich bei der Attacke auf die Moschee um einen Ausdruck nationaler Empfindung gehandelt, rief wohl den lautstarken Protest der Opposition (Indian National Congress - INC, linke und andere Parteien) hervor, die von der Bharatiya Janata Party (BJP) geführte Regierungskoalition geriet aber deshalb nicht ins Wanken. Diese so genannte Nationaldemokratische Allianz, eine aus 24 Parteien bestehende Koalition, hatte ein Jahr zuvor bei den 13. Wahlen zur Lok Sabha, der politisch gewichtigeren der beiden Kammern des Zentralparlaments in New Delhi, den Sieg über ihre Kontrahenten davongetragen. Das gemeinsame Interesse der beteiligten Parteien an der Fortsetzung der Regierungstätigkeit stand über Befürchtungen, die BJP als die nach Anzahl von Sitz und Stimme führende Kraft der Koalition könnte zur Rhetorik und Politik vergangener Jahre zurückkehren