Land sparing and sharing patterns in forestry: exploring even-aged and uneven-aged management at the landscape scale

Abstract

Context

Uneven-aged forest management is sometimes seen as offering interesting compromises between timber production and other important ecosystem services, compared to even-aged approaches. However, uncertainties remain concerning its impacts over longer time periods and broader spatial scales, as larger areas and further roads are required to harvest the same amount of wood.

We compared the large-scale and long-term impacts of uneven-aged and even-aged managements on the composition, road density and fragmentation of a landscape composed of northern temperate and boreal forests, and presenting frequent forest fires.

We simulated an 800,000 ha forested landscape in the Mauricie region (Quebec, Canada) over a 150-year planning horizon with the LANDIS-II model and an extension that simulates forest road construction. We compared 30 different management scenarios that varied the proportion of even- and uneven-aged managements, the level of aggregation of the harvested areas, and the presence of pre-existing forest roads.

Compared with even-aged management, uneven-aged management increased (i) the density of forest roads and their operational costs, (ii) the amount of old forests, and (iii) their fragmentation. Aggregating harvested areas did not noticeably reduce road density, and the presence of an initial road network had no long-term effects. Differences in landscape fragmentation between scenarios were reduced in the northern region of the landscape due to the fire regime.

Choosing uneven-aged over even-aged management represents a trade-off between the amount of old forests in the landscape and three variables related to roads: their density, their related cost, and the fragmentation per se that they generate, This trade-off seems to disappear in the presence of stand-replacing disturbances in the landscape and is unlikely to be improved by aggregating the harvested areas.