Evaluating observed versus predicted forest biomass: R-squared, index of agreement or maximal information coefficient?

The accurate prediction of forest above-ground biomass is nowadays key to implementing climate change mitigation policies, such as reducing emissions from deforestation and forest degradation. In this context, the coefficient of determination ($${R^2}$$) is widely used as a means of evaluating the proportion of variance in the dependent variable explained by a model. However, the validity of $${R^2}$$ for comparing observed versus predicted values has been challenged in the presence of bias, for instance in remote sensing predictions of forest biomass. We tested suitable alternatives, e.g. the index of agreement ($$d$$) and the maximal information coefficient ($$MIC$$). Our results show that $$d$$ renders systematically higher values than $${R^2}$$, and may easily lead to regarding as reliable models which included an unrealistic amount of predictors. Results seemed better for $$MIC$$, although $$MIC$$ favoured local clustering of predictions, whether or not they corresponded to the observations. Moreover, $${R^2}$$ was more sensitive to the use of cross-validation than $$d$$ or $$MIC$$, and more robust against overfitted models. Therefore, we discourage the use of statistical measures alternative to $${R^2}$$ for evaluating model predictions versus observed values, at least in the context of assessing the reliability of modelled biomass predictions using remote sensing. For those who consider $$d$$ to be conceptually superior to $${R^2}$$, we suggest using its square $${d^2}$$, in order to be more analogous to $${R^2}$$ and hence facilitate comparison across studies

Recent findings on the pathogenesis of bronchial asthma

In the first part of this series of papers (Székely and Pataki, 102) the pathogenesis of asthma was approached as a pathological antigen-antibody complex induced vago-vagal axon reflex. In the next part (103) the contribution of individual hormonal predisposition, the environmental and the most frequent allergizing factors have been reviewed. In the first section of this last (third) part of the review the genetic factors contributing to the asthma are surveyed. In this field a great progress has been made during the last decade, a lot of genes have been pinpointed which contribute to the heredity of the disease. In the second section of this last paper on the etiology of asthma an attempt is made to summarize the previously reviewed data and some new ones. Actually a new hypothesis is proposed that beyond the multitude of genetic, environmental and hormonal factors the underlying biochemical mechanism is simple: the disequilibrium of two functionally opposing second messenger systems in the airways: the Cai++ liberating PLC-PKC cascade and the Cai++ level reducing cAMP mediated one with preponderance of the former

Recent findings on the pathogenesis of bronchial asthma

In this second part of the review on the pathogenesis of asthma the hormonal factors and adverse external events are shortly reviewed which skew the balance of Th1 vs. Th2 CD4+ lymphocytes towards the latter ones and this way increase the probability of atopic diseases. Among other the role of transplacental priming, insulin, insulin-like and other growth factors, lack of the usual microbial infections in the early childhood (the so-called hygiene hypothesis), gender, diminished testosterone production, gastroesophageal reflux, adverse effects during pregnancy are discussed. A separate chapter deals with the role of central nervous system in the etiology and finally the most common allergizing and airway tissue damaging agents are listed in tabulated form