The role of tree size in the leafing phenology of a seasonally dry tropical forest in Belize, Central America

Leafing phenology of two dry-forest sites on soils of different depth (S = shallow, D = deep) at Shipstern Reserve, Belize, were compared at the start of the rainy season (April-June 2000). Trees ≥ 2.5 cm dbh were recorded weekly for 8 wk in three 0.04-ha plots per site. Ten species were analysed individually for their phenological patterns, of which the three most common were Bursera simaruba, Metopium brownei and Jatropha gaumeri. Trees were divided into those in the canopy (> 10 cm dbh) and the subcanopy (≤ 10 cm dbh). Site S had larger trees on average than site D. The proportion of trees flushing leaves at any one time was generally higher in site S than in site D, for both canopy and subcanopy trees. Leaf flush started 2 wk earlier in site S than site D for subcanopy trees, but only 0.5 wk earlier for the canopy trees. Leaf flush duration was 1.5 wk longer in site S than site D. Large trees in the subcanopy flushed leaves earlier than small ones at both sites but in the canopy just at site D. Large trees flushed leaves earlier than small ones in three species and small trees flushed leaves more rapidly in two species. Bursera and Jatropha followed the general trends but Metopium, with larger trees in site D than site S, showed the converse with onset of flushing I wk earlier in site D than site S. Differences in response of the canopy and subcanopy trees on each site can be accounted for by the predominance of spring-flushing or stem-succulent species in site S and a tendency for evergreen species to occur in site D. Early flushing of relatively larger trees in site D most likely requires access to deeper soil water reserves but small and large trees utilize stored tree water in site S

The Theory of Commodity Price Stabilization Rules: Welfare Impacts and Supply Responses

It is the aim of this paper to suggest an alternative framework for the analysis of commodity stabilisation schemes, based on more secure micro-economic foundations. We begin with what might be termed the general theory of partial (or incomplete) price stabilisation. This meets objection (vi) above, and shows how the shape of the demand schedule and the source and specification of risk influence the size and distribution of welfare gains. It therefore allows the reader to appreciate the importance of the more detailed model specification which is required to investigate the remaining questions. This new model allows one to distinguish between the short run and long run impact of stabilisation, and to examine the importance of risk aversion and individual supply elasticity on the distribution of gains and losses from partial stabilisation. In particular, we do not discuss the dynamics of price stabilisation in the paper (price expectations, learning, the stochastic nature of buffer stocks, etc.), nor do we model demand uncertainty, the macro-economic impact of risk and stabilisation, market imperfections, interactions with future markets, private speculators, with other commodities, and a host of other important issues. For these, and for a more detailed exposition of some of the key concepts presented here, the interested reader is referred to our forthcoming book (Newbery and Stiglitz, 1980). Finally, we should point out that the buffer stock rules analysed here are not optimal rules, which can only be derived from complete dynamic analysis, as derived and discussed in the book 1 Turnovsky (1978a) examines a simple parameterisation of a partial stabilisation scheme, but restricts the analysis to the linear Waugh-Oi-Massell case

Risk Aversion, Supply Response, and the Optimality of Random Prices: A Diagrammatic Analysis

This paper analyzes the effect of commodity price stabilization on producers and consumers, both in the short run, and in the long run, when producers have adjusted their production decisions to take account of the change in the price distribution. We derive conditions under which (a) both producers and consumers may be better off; and (b) both producers and consumers may be worse off. Moreover, we show that the long-run effects may differ not only quantitatively but also qualitatively from the short-run effects. The anomalous results may occur even with reasonable assumptions concerning production functions and utility functions of producers and consumers

The Choice of Techniques and the Optimality of Market Equilibrium with Rational Expectations

This paper shows that, in the absence of a complete set of risk markets, prices provide incorrect signals for guiding production decisions. Even if all individuals have rational expectations concerning the distribution of prices which will prevail on the market next period, the market allocation is, in general, not a constrained Pareto optimum. Essentially the only conditions under which, for all technologies, the market equilibrium is a constrained Pareto optimum are those in which risk markets are redundant. We derive the necessary and sufficient conditions for redundancy of risk markets, which turn out to be extremely restrictive

Optimal Commodity Stockpiling Rules

Stiglitz and Newbery discuss optimal commodity stockpiling rules

Wage Rigidity, Implicit Contracts, Unemployment, and Economic Efficiency

This article examines the theory of involuntary unemployment and implicit contracts. Furthermore, the article is concerned with identifying the circumstances under which implicit contracts will give rise to unemployment even though involuntary unemployment has been often attributed to wage rigidities generated by implicit contracts by themselves. Moreover, a simple, general equilibrium model and the three sources of restrictions on the set of feasible contracts: (1) information; (2) enforcement; and (3) complexity. Finally, it is concluded that implicit contracts can then provide an explanation of unemployment

Post-materialistic values and entrepreneurial intention-The Case of Saudi Arabia

Purpose: The purpose of this paper is to investigate how cultural values influence the entrepreneurial process. It conceptualises the relationship between post-materialistic values and entrepreneurial intention to explain low entrepreneurial activity. Design/methodology/approach: The study was conducted in Saudi Arabia with non-entrepreneurs. An online survey returned 405 valid questionnaires, representing a 27 per cent response rate. The data were analysed using partial least structural equation modelling. Findings: The paper identifies key factors that explain the influence of changing cultural values on entrepreneurial activity. The results show that post-materialistic values influence entrepreneurial intention by decreasing desirability and entrepreneurial self-efficacy. Research limitations/implications: The study conceptualises the interplay between cultural values and entrepreneurial intention in Saudi Arabia. Further insights can be developed by comparing Saudi Arabia with other countries. The study was conducted as a “snapshot” of the current situation of entrepreneurship in Saudi Arabia with a cross-sectional survey design. Practical implications: The paper holds important implications for entrepreneurship educators when addressing unsupportive cultures for entrepreneurial activity. Cultural and motivational approaches are suggested. While the former focuses on aspects that encourage the desire and confidence to start a business, the latter involves encouraging setting venture creation as a goal. Originality/value: Previous studies indicated that post-materialistic values negatively influence entrepreneurship; this paper contributes further by exploring how this relationship manifests by exploring the intervening factors between post-materialistic values and entrepreneurial intention. It advances entrepreneurship research by investigating deep assumptions underlying the formulation of entrepreneurial intentions. It also responds to the need to understand the difference in the levels of entrepreneurial activity across countries

Haploinsufficiency for Translation Elongation Factor eEF1A2 in Aged Mouse Muscle and Neurons Is Compatible with Normal Function

Translation elongation factor isoform eEF1A2 is expressed in muscle and neurons. Deletion of eEF1A2 in mice gives rise to the neurodegenerative phenotype "wasted" (wst). Mice homozygous for the wasted mutation die of muscle wasting and neurodegeneration at four weeks post-natal. Although the mutation is said to be recessive, aged heterozygous mice have never been examined in detail; a number of other mouse models of motor neuron degeneration have recently been shown to have similar, albeit less severe, phenotypic abnormalities in the heterozygous state. We therefore examined the effects of ageing on a cohort of heterozygous +/wst mice and control mice, in order to establish whether a presumed 50% reduction in eEF1A2 expression was compatible with normal function. We evaluated the grip strength assay as a way of distinguishing between wasted and wild-type mice at 3-4 weeks, and then performed the same assay in older +/wst and wild-type mice. We also used rotarod performance and immunohistochemistry of spinal cord sections to evaluate the phenotype of aged heterozygous mice. Heterozygous mutant mice showed no deficit in neuromuscular function or signs of spinal cord pathology, in spite of the low levels of eEF1A2