The behaviour of the measure of surround in relation to the diameter and spatial structure of a forest stand

Forestry inventory practices have, in the past, concentrated on obtaining information primarily required for timber management. To assess the ecological impact of exploitation, particularly under continuous cover forest management, diversity measures are required that consider the structural diversity in a forest stand. The measure of surround that was initially developed in Germany may be used to quantify the spatial interspersion of different tree size classes as a measure of spatial diversity. While the measure of surround has been applied to practical problems in the past, little is known about its actual performance in relation to stand compositions. This study investigate the behaviour of the index using a number of simulated age class distributions under various degrees of interspersion to provide a norm against which it may be compared. The measure of surround applied to diameter distributions is closely related to the diameter structure of a stand. When diameter classes are interspersed completely randomly within a stand the relative cumulative frequency of the diameter class provides an estimator of the size specific measure of surround. This provides a baseline from which the index may be interpreted.     

Understanding how built urban form influences biodiversity

This study seeks to contribute to a more complete understanding of how urban form influences biodiversity by investigating the effects of green area distribution and that of built form. We investigated breeding bird diversity in three types of housing development with approximately the same amount of tree cover. No significant differences in terms of bird communities were found between housing types in any of the survey periods. However, detached housing, especially with interspersed trees, had more neotropical insectivores and higher overall diversity of insectivores. Based on our results and theory we suggest a complementary approach to managing biodiversity in urban landscapes – instead of maximising the value and quality of individual patches efforts could go into enhancing over-all landscape quality at the neighbourhood scale by splitting up part of the green infrastructure. The relatively small differences in bird communities also suggest that different stakeholder groups may be engaged in management.