Patrice Loisel

First-Price Sealed-Bid Auctions with Secret Reservation Prices

In this paper we consider a first-price sealed bid auction with a secret reservation price. Such auctions are used frequently in France to sell timber. Within the independent private values paradigm, we show that the equilibrium strategy of the seller is to choose a reservation price equal to his private value. We characterize the symmetric Bayesian equilibrium strategy for the buyers as the solution of a differential equation. We also show that a strategy of public reservation price is better for the seller than a strategy of secret reservation price. To evaluate the expected gain for the seller from moving from a secret to the optimal public reservation price, we estimate the model using data from an actual auction of timber. First, we solve the problem of identification of the underlying distributions of private values. Then we propose a two-step structural nonparametric estimation method to shed some lights on the shapes of these distributions. This is used to formulate and estimate a parsimonious and structural parametric model that reproduces the salient features of our nonparametric analysis.

Prey synchronize their vigilant behaviour with other group members

It is generally assumed that an individual of a prey species can benefit from an increase in the number of its groups members by reducing its own investment in vigilance. But what behaviour should group members adopt in relation to both the risk of being preyed upon and the individual investment in vigilance? Most models assume that individuals scan independently of one another. It is generally argued that it is more profitable for each group member owing to the cost that coordination of individual scans in non-overlapping bouts of vigilance would require. We studied the relationships between both individual and collective vigilance and group size in Defassa waterbuck, Kobus ellipsiprymnus defassa, in a population living under a predation risk. Our results confirmed that the proportion of time an individual spent in vigilance decreased with group size. However, the time during which at least one individual in the group scanned the environment (collective vigilance) increased. Analyses showed that individuals neither coordinated their scanning in an asynchronous way nor scanned independently of one another. On the contrary, scanning and non-scanning bouts were synchronized between group members, producing waves of collective vigilance. We claim that these waves are triggered by allelomimetic effects i.e. they are a phenomenon produced by an individual copying its neighbours behaviour.

Herd Size in Large Herbivores: Encoded in the Individual or Emergent?

In large mammalian herbivores, the increase of group size with habitat openness was first assumed to be an adaptive response, encoded in the individual. However, it could, alternatively, be an emergent property: if groups were nonpermanent units, often fusing and splitting up, then any increase of the distance at which animals perceive one another could increase the rate of group fusion and thus mean group size. Dynamical models and empirical data support this second hypothesis. This is not to say that adaptive modifications of mean herd size cannot occur. However, this changes the way in which we can envisage the history of gregariousness in large herbivores during the Tertiary.

Impact of storm risk on Faustmann rotation

Global warming may induce in Western Europe an increase in storms. Hence the forest managers will have to take into account the risk increase. We study the impact of storm risk at the stand level. From the analytical expressions of the Faustmann criterion and the Expected Long-Run Average Yield, we deduce in presence of storm risk the influence of criteria and of discount rate in terms of optimal thinnings and cutting age. We discuss the validity of using a risk adjusted discount rate (a rate of storm risk added to the discount rate) without risk to mimic the storm risk case in terms of optimal thinnings.

Faustmann rotation and population dynamics in the presence of a risk of destructive events

The impact of the presence of risk of destructive event on the silvicultural practice of a forest stand is investigated. For that, we consider a model of population dynamics. This model has allowed us to make the comparison without and with risk, and highlight the influence of the presence of risk of destructive event on optimal thinning and optimal rotation period.

A tree-growth model to optimize silviculture

Abstract In this paper, we present the description of a simplified model of the dynamic of a monospecific even-aged forest. The model studied is a tree-growth model based on a system of two ordinary differential equations concerning the tree basal area and the number of trees. The analytical study of this model permits us to predict the behavior of the system solutions. We try to highlight the influence of economic parameters and growth parameters on the system solutions, in the framework of the optimization of silviculture.

Faut-il s’intéresser à la petite et moyenne forêt privée française ?

Given the extent of French forests and of the wood-processing industries in France, management of the interfaces between society, forest and industry is all-important. The management of these interfaces and the difficulties involved are first described. A new management plan for these interfaces devised by the French government is then presented. The draft for regulating the forest-based economy looks at the economic relationships between forestry, industry and government players. This plan would imply vigorous state intervention at the primary wood processing stage aimed at modernisation, sustainability through diversification, integration with secondary manufacturing as well as broadening sources of timber supply. It would strive to diversify and intensify the channels for selling wood to the wood products industry. This aggressive economic interventionism might however be carried out without previously or concomitantly setting up the specific conditions that enable small and medium-sized forested properties of less than 25 ha to develop, unless a separate scheme for regulating the development of private forests is also established.