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Improving understanding of the environmental controls of forest biomass and productivity: insights from permanent plot networks

Released: 2015
Stephenson, NL, AJ Das, PJ van Mantgem. 2015. Improving understanding of the environmental controls of forest biomass and productivity:  insights from permanent plot networks. First Biomass Science Workshop, Frascati, Italy. 27-30 January 2015. [presentation]

       A mechanistic understanding of forest biomass and productivity depends, in part, on understanding of the population dynamics of strongly size-structured populations.  While individual tree masses and productivity are functions of growth, at the scale of a forest stand the numbers of trees of different masses and productivities are functions of demographic rates (birth and death rates).  Permanent plot networks, in which the fates of individual trees are tracked through time, can provide unique insights into environmental controls of demographic rates, thus potentially improving key assumptions in dynamic global vegetation models (DGVMs).

            As examples, we offer some findings from plot networks and suggest some implications for modeling.  First, tree mortality rates follow global and regional patterns of site potential for productivity, with the most productive forest sites showing the highest mortality rates.  Second, and contrary to some expectations, this pattern may be driven primarily by plant enemies (mostly insects and pathogens), not competition.  That is, the same warm, moist environments that favor tree growth also favor the plant enemies that kill trees.  Third, the latter finding argues for the importance of considering the effects of environmental changes not just individual tree physiology, but also on the higher trophic levels that influence tree population dynamics.  Environmental effects on plant enemies can explain apparent paradoxes, such as lower forest biomass on sites with higher potential for productivity.

This product is associated with the following project:
Climate and Fire in the Sierra Nevada

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