44 research outputs found
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Factors explaining variability in woody above-ground biomass accumulation in restored tropical forest
Secondary forests comprise an increasing area of the tropics and play an important role in global carbon cycling. We compare above-ground biomass accumulation of both planted and naturally regenerating trees, as well as C in the top soil layer, in three restoration treatments replicated at 14, six to eight year old restoration sites in southern Costa Rica. Restoration strategies include: control (no planting), planting tree islands, and conventional, mixed-species tree plantations. We evaluate the importance of past land-use, soil nutrients, understory cover, and surrounding forest cover in explaining variation in above-ground biomass accumulation (ABA) rate across sites. Total ABA and planted tree ABA rate were highest in plantations, intermediate in islands, and lowest in control treatments, whereas ABA rate of naturally regenerating trees did not differ across treatments. Most ABA in plantations (89%) and islands (70%) was due to growth of planted trees. Soil carbon did not change significantly over the time period of the study in any treatment. The majority of across-site variation in both total and planted tree ABA rate was explained by duration of prior pasture use. Tree growth in the first two years after planting explained approximately two-thirds of the variation in ABA rate after 6-8. years. Soil nutrient concentrations explained relatively little of the variation in planted or naturally recruiting ABA rate. Our results show that planting trees substantially increases biomass accumulation during the first several years of forest recovery in former agricultural lands and that past-land use has a strong effect on the rate of biomass accumulation. Planting tree islands is a cost-effective strategy for increasing ABA and creating more heterogeneous habitat conditions than tree plantations. We recommend small scale planting trials to quickly assess potential biomass accumulation and prioritize sites for ecosystem service payments for carbon sequestration. © 2014 Elsevier B.V
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Passive restoration can be an effective strategy: A reply to Prach and del Moral (2015)
We agree with Prach and del Moral that passive recovery is often a desirable and effective restoration strategy. Passive and various active restoration approaches need to be weighed on a case-by-case basis and depend on the goals, relative rates of recovery desired, and various social and financial costs implicit in each option. That said, we stress that passive restoration has a unique set of challenges and costs, which we highlighted in our original article and briefly reiterate here
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Hidden Costs of Passive Restoration
The first few years of tropical forest restoration can be expensive, especially when applied to expansive areas. In light of this, passive restoration has been recommended as a considerably cheaper or even free alternative. There are, however, both direct and indirect costs associated with passive restoration. First, the longer recovery time that is typically required in passive restoration can be perceived as project failure, especially when compared with nearby active restoration efforts. In the worst-case scenario, this can lead to the premature termination of a project by a landowner who would like to see more rapid or visible results. Second, passive restoration may be viewed as land abandonment, and in developing nations where land tenure is not always strictly enforced this may invite unanticipated uses, such as ranchers who may unintentionally or intentionally allow livestock to take advantage of the "unused" forage grass, thus setting back recovery efforts. Lastly, passive restoration does have direct financial costs, including material costs for establishing fences and repairing them, and labor costs for site vigilance. These upfront investments may need to be made repeatedly in passive restoration efforts, and for a longer time period than for an active restoration project. Both the direct and indirect costs should be considered prior to choosing passive restoration as a strategy in a particular restoration project. © 2014 Society for Ecological Restoration