Forest structure as a determinant of grouse brood occurrence – An analysis linking LiDAR data with presence/absence field data

Abstract

Forest-dwelling grouse, and especially their broods, are highly dependent on forest and vegetation structure. In countries with intense forest management, it follows that the quality of their habitats is directly affected by forestry operations. Therefore, we must know which structural features of forests define a good grouse habitat and how the abundance of these features is affected by the forestry operations. Nowadays, airborne lidar (light detection and ranging) is being frequently used for forest inventories and terrain mapping. These data is becoming more and more publicly available and it holds detailed information about the forests and the vegetation structure; a key component of wildlife habitats.In this study, we integrated lidar data with grouse brood presence/absence data. Through GLMM modelling, we aimed (1) to identify the structural features of forests that mostly determine grouse brood occurrence and (2) to assess how they are affected by forest management. The three species assessed were capercaillie, hazel grouse and black grouse. Depending on species, the brood presence was positively (and significantly) affected by denser shrub layer cover, denser canopy cover, higher canopies, or all of these features. The results indicate that grouse broods are highly susceptible to changes in forest structure.In countries like Finland, game management is almost always implemented in managed forests, which in the light of our results creates a need to integrate habitat management into forest management. Our results suggest that when managing grouse brood habitats, attention should be given to maintain both, protective canopy cover and a good understorey cover. It is fair to assume that the removal of these components will significantly decrease brood occurrence. Further, the study showed that a dataset (lidar) collected more for the purposes of forestry can also be used to study wildlife habitats occurring often in the same forests.