Potential fecundity of Epirrita autumnata females is strongly correlated with pupal weight. Adult feeding weakly increases fecundity but does not eliminate its ...

Pure forest stands are widely believed to be more prone to pest outbreaks and disease epidemics than mixed stands, leading to recommendations of using stand diversification as a means of controlling forest pests and pathogens. We review the existing evidence concerning the effects of stand tree-species diversity on pests and pathogens in forests of the boreal zone. Experimental data from published studies provide no overall support for the hypothesis that diversification of tree stands can prevent pest outbreaks and disease epidemics. Although beneficial effects of tree-species diversity on stand vulnerability are observed in some cases, in terms of reductions in damage, these effects are not consistent over time and space and seem to depend more on tree-species composition than on tree-species diversity per se. In addition, while mixed stands may reduce the densities of some specialized herbivores, they may be more attractive to generalist herbivores. Given that generalist mammalian herbivores cause considerable tree mortality during the early stages of stand establishment in boreal forests, the net effect of stand diversification on stand damage is unlikely to be positive.

Laser scanning technology has opened new horizons for the research of forest dynamics, because it provides a largely automated and non-destructive method to rapidly capture the structure of individual trees and entire forest stands at multiple spatial scales. The structural data themselves or in combination with additional remotely sensed data also provide information on the local physiological state of structures within trees. The capacity of new methods is facilitated by the ongoing development of automated processing tools that are designed to capture information from the point cloud data provided by the remote measurements. Terrestrial laser scanning (TLS), performed from the ground or from unmanned aerial vehicles, in particular, has potential to become a unifying measurement standard for forest research questions, because the equipment is flexible to use in the field and has the capacity to capture branch-level structural information at the forestplot or even forest scale. This issue of Annals of Botany includes selected papers that exemplify the current and potential uses of TLS, such as for examination of crown interactions between trees, growth dynamics of mixed stands, non-destructive characterization of urban trees, and enhancement of ecological and evolutionary models. The papers also present current challenges in the applicability of TLS methods and report recent developments in methods facilitating the use of TLS data for research purposes, including automatic processing chains and quantifying branch and above-ground biomass. In this article, we provide an overview of the current and anticipated future capacity of TLS and related methods in solving questions that utilize measurements and models of forests. Due to its measurement speed, TLS provides a method to effortlessly capture large amounts of detailed structural forest information, and consequent proxy data for tree and forest processes, at a far wider spatial scale than is feasible with manual measurements. Issues with measurement precision and occlusion of laser beams before they reach their target structures continue to reduce the accuracy of TLS data, but the limitations are counterweighted by the measurement speed that enables large sample sizes. The currently high time-cost of analysing TLS data, in turn, is likely to decrease through progress in automated processing methods. The developments point towards TLS becoming a new and widely accessible standard tool in forest measurement and modelling.