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Enrichment Planting for Forest Restoration
What is the difference between reforestation, enrichment planting, and forest restoration?
Reforestation is the process of planting trees where they do not exist. Enrichment planting is planting trees and other plants in areas with woody vegetation with the objective of increasing the species diversity of the site. Forest restoration is the process of planting trees and other vegetation in order to try to recreate the forest ecosystem and the interactions that maintain it. Forest restoration can also include the re-introduction of animals and other organisms and/or creating the conditions so that these organisms can re-colonize the site without the need for re-introduction. Enrichment planting is often a principal component of forest restoration so the two are not mutually exclusive.
Why bother with forest restoration?
Forest restoration is expensive and time consuming, so why bother planting trees instead of just letting the forest regenerate on its own? In tropical rainforests, cleared land left abandoned quickly regenerates with a dense cloak of vegetation, with some trees growing as much as 5 m in the first year. In the reserve landscape we know that within 10 years, cleared land will support a forest with vine covered trees reaching 8+ m. We also know that in regenerating areas far from mature forest stands, that the species that occupy these sites are mostly pioneer species. In the reserve landscape, we have observed that even 70 years after a clearing is abandoned the plant community remains dominated by pioneer species in state sometimes referred to as "arrested succession". Approximately 600 ha of the reserve support rubber groves overgrown with pioneer forest in a state of arrested succession. What is wrong with a forest dominated by pioneer species and why don't these forests develop into the mature forests of high conservation value?
While pioneer species play an important role in the ecosystem, when a forest supports only pioneer species it will be of limited conservation value. Pioneer species tend to grow quickly and produce abundant fruit crops, but the fruits that they produce are mostly of limited nutritional quality for highly frugivorous animals. The fruits tend to contain high sugar content but few other benefits for wildlife, so animals that depend mostly on a fruit diet suffer for lack of adequate nutrition. This means that a forest dominated by pioneer species is unlikely to support the full complement of forest wildlife. In addition, pioneer species are widespread and super-abundant, especially in hyper-disturbed biomes like the Atlantic Forest, which means that they are of lesser conservation concern than trees of the mature forest community and thus less desirable than mature forest trees from the perspective of reserve managers.
In order to understand why these pioneer forests do not develop into mature forests as they would if located adjacent to mature forest patches, it is necessary to understand several important aspects of tree recruitment ecology and the distribution of the mature forests in the reserve. Studies of tree recruitment ecology indicate that most seeds are dispersed short distances from the mother tree (mostly <100 m), especially in forests such as the Michelin Ecological Reserve where frugivores that disperse seeds further, such as the tapir (Tapirus terrestris) and howler monkeys (Alouatta guariba), were extirpated. Less than 2% of sunlight reaches the forest floor in tropical evergreen rainforests, which means that trees in the understory tend to grow slowly, and that canopy tree inter-generation times tend to be long. It may take decades before a tree grows sufficiently to produce fruit and this, coupled with the short dispersal distances, suggests that trees migrate very slowly across the landscape. Since most of the reserve rubber groves are not located near mature forest patches, it will take centuries for plants of high value for frugivorous wildlife and conservation objectives to colonize these areas. If the pioneer forests do not develop into mature forests, the reserve will not attain its full potential to sustain viable populations of species of high conservation value.
Our restoration sites are open to scientific visits scheduled in advance.
The goals of our program are: