Ecosystems respond in various ways to disturbances. Quantifying ecological stability therefore requires inspecting multiple stability properties, such as resistance, recovery, persistence and invariability. Correlations among these properties can reduce the dimensionality of stability, simplifying the study of environmental effects on ecosystems. A key question is how the kind of disturbance affects these correlations. We here investigated the effect of three disturbance types (random, species‐specific, local) applied at four intensity levels, on the dimensionality of stability at the population and community level. We used previously parameterized models that represent five natural communities, varying in species richness and the number of trophic levels. We found that disturbance type but not intensity affected the dimensionality of stability and only at the population level. The dimensionality of stability also varied greatly among species and communities. Therefore, studying stability cannot be simplified to using a single metric and multi‐dimensional assessments are still to be recommended.

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Literature on the learning organization There have been a number of reviews of the field of organizational learning. Most of these reviews make the point that the existing literature falls readily into two categories: popular works directed to managers and academic works designed to make a more theoretical contribution. The reviews also point to differences in system levels addressed; for example, some authors argue strongly that only individuals can learn, while others (a minority) adopt a more sociological view, arguing that organizations are systems which can also learn[4-9]. However the most obvious point to emerge from reading the literature in the field is that organizational learning is a tag applied to a divergent set of organizational phenomena which have little in common other than that they could be loosely described as "change for the better". The term organizational learning, like the negative pole of a magnet, seems to attract almost anything with a positive charge. Various authors, for example, have described the following phenomena as organizational learning: (1) training and development[6]; (2) the reduction of defensive routines[7]; (3) a "total learning system" where "the activities of the organization as a whole are more or less continuously monitored to provide feedback which is then used as a basis for learning how to improve performance"[10]; (4) management innovation[11]; and (5) increasing an organization's capacity to take effective action[12]. One of the basic requirements for making advances in science is that concepts acquire agreed meanings; on this criterion the concept of the learning organization ranks more on the level of an ideological slogan than a meaningful scientific term. Some critical issues in defining organizational learning Another approach to developing a meaningful definition of organizational learning is to examine the meaning given it by some of the most quoted authorities in the field. It is not difficult to choose-few articles these days fail to mention the contributions of Argyris and Schon[13-15], and of Senge[16-18]. Central to Argyris and Schon's treatment are the concepts of single-and double-loop learning. Single-loop learning is defined as "instrumental learning that changes strategies of action or assumptions underlying strategies in ways that leave the values of a theory of action unchanged"[7, p. 20]. An example given is quality control inspectors who identify a defective product, convey the information to production engineers, who modify production procedures to eliminate the defect. Such feedback loops do not challenge basic system assumptions and lead to minor incremental change.

Combination antiretroviral therapy can have a salutary effect on preserving or improving neurological function. Superior systemic treatments may likewise better preserve neurological function. The significant association of poor neurological performance with mortality, independent of CD4 counts and HIV-1 RNA levels indicates that neurological dysfunction is an important cause or a strong marker of poor prognosis in late HIV-1 infection. This study demonstrates the value of adjunctive neurological measures in large therapeutic trials of late HIV-1 infection.