August 14, 2009

Plantation plantation, what’s your function?

Article reviewed: The role of plantations in managing the world’s forests in the Anthropocene

By A. Paquette and C. Messier, published on line in pre-print form in the journal Frontiers in Ecology and the Environment

The plot line: This is a review/commentary on the positive roles that plantations may have for forest conservation efforts in the future. The authors also list the challenges (mostly social/economic) that are obstacles to accepting plantations as a means for conservation. Three primary benefits of plantations are given: 1) by producing high amounts of wood, they can offset and protect unmanaged forests; 2) they can help fight climate change via sequestration; 3) they can provide ecological and restoration services. They conclude that, with more research and novel management designs, plantations can simultaneously provide these services.   

Relevant quote: “In summary, managers should maintain or enhance structural and functional complexity at all scales, both within and between plantations, because complexity is an important determinant of biodiversity and resilience.”

Relevance to landowners:

The future plantations the authors of this review envision are not what most people picture when they think of plantations. While most people think of “corn rows” of one tree species (i.e. “monoculture”) as far as the eye can see, these authors envision multiple species, diverse structures, and a diverse understory of non-tree vegetation. They also envision plantations as part of a mosaic of distinctly different forest types across a landscape. They remind us of the idea of “functional zoning.” This essentially means allocating forests into three basic management styles:

1.     A conservation zone – no management except to maintain or enhance ecosystem processes

2.     An ecosystem-based management zone – harvests are guided by natural disturbance regimes, (see this entry for more information on this).

3.     Intensive management zone – plantations managed for high productivity

This concept was articulated as the "triad approach" by a couple of academics back in the early 1990’s, although it has been in practice for longer at a number of sites, including UC Berkeley’s Blodgett Forest Research Station since the 1960’s.

I think the functional zoning concept is good for forests, because it promotes structural diversity at different scales. As a forest researcher once said, “diversity should be as much our practice as it is our purpose.” At times I have thought this concept to be too idealistic and impractical because of opposing landowner objectives, but the authors of this article give an example of it being applied on public land in Canada. Even where impractical across multiple landowners, the concept is important for landowners or stakeholders focused within a particular landowner type because it encourages diversity at several scales.

Relevance to managers:

The authors suggest multiple ways in which plantations can be managed to provide multiple ecological services:

·        Retain snags and large trees from the previous stand

·        Reduce the intensity of site preparation to reduce soil disturbance (e.g. reduce soil movement by choice of equipment)

·        Tolerate competing vegetation once plantations have established

·        Strategically place plantations on the landscape to retain habitat corridors between similar-structure forests

·        Plant native species, not exotics.

·        Plant mixed species stands

I am a strong advocate of mixed species stands as an “insurance policy” against uncertainty. With more species, a manager’s bets are hedged against uncertainty in economic conditions, pest outbreaks, and climate change. They also result in structural diversity since different species grow at different rates and with different morphologies. I am also in agreement with the authors on the fact that more experiments are needed to guide managers in how to design mixed species plantations.

Critique (I always have one, no matter how good the article is) for the pedants:

Many of the items on the bullet list above do sacrifice some productivity (not necessarily the last one, however). The authors state these practices as ways in which plantations can be managed without sacrificing productivity. While I agree that these are good ways to make plantations more beneficial for multiple uses, performing them will indeed slightly diminish the capacity for plantations to maximize productivity and therefore diminish the capacity of plantations to offset the use of non-managed forests. But this is a minor critique- I agree with the main point that these are small sacrifices in order to make plantations more acceptable as a global role player in forest conservation during the "Anthropocene."