Herbivory and Tree Stand Composition: Moose Patch Use in Winter

• Published in: Ecology
• Main Authors: Danell, Kjell, Edenius, Lars, Lundberg, Per
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 1991
• Subjects: Alces alces
• Online Access: http://dx.doi.org/10.2307/1941107; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.2307%2F1941107; https://esajournals.onlinelibrary.wiley.com/doi/pdf/10.2307/1941107

Foraging decisions by large herbivores in a heterogeneous environment with several available plant species are a scale problem. If, for example, the foraging decisions primarily occur at the stand level, then stands of trees might be regarded as patches within a habitat of several stands over which intake rate is to be maximized. The food consumption within a stand should be in proportion to the availability of different food types. If, on the other hand, food selection occurs at the tree level within a stand, then the individual trees are regarded as "patches"; total stand exploitation should then be the result of foraging decisions made within the stand. We tested these two hypothesis in field experiments in winter with free—ranging moose (Alces alces) having access to artificial stand of trees. In these stands Scots pine (Pinus sylvestris) was mixed with either aspen (Populus tremula) or alder (Alnus incana). In experiment A, where the total available pine biomass per stand was much greater than any of the additional species, total stand consumption did not differ between stand types. In experiment B, where pine biomass did not dominate to the same extent, pine + aspen stands were more heavily used than pine + pine and pine + alder stands. The within—stand consumption of different species appeared to be nonrandom, i.e., the tree biomass was not consumed in proportion to availability. The mean pine biomass consumption per tree did not differ between stand types in either experiment. We conclude that the food selection appears to occur primarily at the tree level within stands. The level of decision might also be important for the performance of the plant species exploited. The results from this study question the general validity of recent hypotheses regarding "associational protection" in plant communities. We suggest that the optimal patch use approach taken in this study might give better insight in these kinds of plant—animal interaction problems.