Browse biomass production an.regrowth capacity after biomass loss in deciduous and coniferous trees: responses to moose browsing along a productivity gradient

• Published in: Oikos
• Main Authors: Persson, Inga‐Lill, Bergström, Roger, Danell, Kjell
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2007
• Subjects: Alces alces
• Online Access: http://dx.doi.org/10.1111/j.0030-1299.2007.15946.x; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.0030-1299.2007.15946.x; https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.0030-1299.2007.15946.x; https://onlinelibrary.wiley.com/doi/full-xml/10.1111/j.0030-1299.2007.15946.x

To understand how large herbivores interact with their food resources and the ecosystem, it is necessary to understand plant growth responses to biomass loss. Tolerance to biomass loss, and the ability to regrow new photosynthetic tissue after herbivore attack, is one such important mechanism. Here we experimentally studied how year‐round browsing corresponding to four different levels of moose, Alces alces , population density affected total annual browse biomass production, which also serves as a proxy for production of new photosynthetic tissue, in birch ( Betula pubescens and B. pendula ) and Scots pine, Pinus sylvestris , along a habitat productivity gradient. Our results revealed that habitat productivity index was the most important variable determining annual browse biomass production for birch, and that a high moose density and biomass removals of 25–40% annually actually could stimulate birch above‐ground productivity in more productive sites. Contrary to birch, pine was not affected by habitat productivity index, and appeared to have much lower regrowth capacity than birch. For pine, percent biomass removed was the most important factor affecting annual browse biomass production, which decreased with increasing levels of biomass removal. We also tested if birch and pine responded to biomass removal by allocating more resources to browse biomass production at in the lower portion of the stem (0–0.5 m), which was protected from biomass removal in winter. Birch did not allocate more resources to biomass production in the lower portion of the stem, whereas pines subjected to high biomass removal had more biomass in the lower portion of the stem than those protected from losses. Our study thus shows that plant responses can be linear or non‐linear along the range of herbivore densities we studied, and that responses can change from negative to positive along underlying habitat productivity gradients.