A review of the roles of forest canopy gaps

Treefall gap, canopy opening caused by the death of one or more trees, is the dominant form of disturbance in many forest systems worldwide. Gaps play an important role in forest ecology helping to pre- serve bio- and pedo-diversity, influencing nutrient cycles, and maintain- ing the complex structure of the late-successional forests. Over the last 30 years, numerous reviews have been written describing gap dynamics. Here we synthesize current understanding on gap dynamics relating to tree regeneration with particular emphasis on gap characteristics consid- ered critical to develop ecologically sustainable forest management sys- tems and to conserve native biodiversity. Specifically, we addressed the question： how do gaps influence forest structure？ From the literature re- viewed, the size of gaps induces important changes in factors such as light intensity, soil humidity and soil biological properties that influence tree species regeneration and differ in gaps of different sizes. Shade- tolerant species can colonize small gaps; shade-intolerant species need large gaps for successful regeneration. Additionally, gap dynamics differ between temperate, boreal, and tropical forests, showing the importance of climate differences in driving forest regeneration. This review summa- rizes information of use to forest managers who design cutting regimes that mimic natural disturbances and who must consider forest structure, forest climate, and the role of natural disturbance in their designs.

Exploring the silvicultural and economic viability of gap cutting in Mediterranean softwood plantations

Gap cutting consists of the removal of all trees growing on a small surface, varying in size from 200 to 600 m2. In Italy, gap cutting has been successfully tested for introducing the natural regeneration of native species into softwood plantations, thus ac- celerating the transition towards climax hardwood stands. Depending on plantation types and conditions, gap cutting should be start- ed at an age between 70 and 80 years and the system should include at least 12 to 15 gaps, in order to produce enough wood to cover costs. Generally, natural regeneration is firmly established within 5-7 years from treatment. Gap cutting also offers superior results to selection thinning, the latter producing about 35% less value and incurring 25% to 30% more costs. As for all regeneration cuts, the success of gap cutting depends on wildlife control in order to prevent extensive damage to the regeneration.