Using woopeckers to inform sustainable forestry in the Piedmont Forest of Argentina

POLITI NATALIA; ALBANESI SEBASTIAN; RIVERA LUIS

2009-05-01/2009-08-01

1-5

Biológica

Otros campos

Most of the piedmont forest of Northwestern Argentina (estimates range from 50-90%) has already been transformed to agricultural fields. Protected areas are an essential tool for conservation, but because only a small fraction of lands can be set aside as reserves, it is essential to maintain biodiversity in areas subject to economic activities. Forests managed sustainably are likely to maintain their economic and ecological value.Currently, remnants piedmont forests are subject to unsustainable logging operations that do not consider biodiversity and the important role of biodiversity. Therefore, we have been undertaking research to increase our understanding of how to sustainably manage piedmont forests. In previous projects funded by RSG we have shown that current forest practices have a profound negative effect on tree cavity quantity and quality and affect the richness and abundance of cavity-nesting birds. We determined that suitable tree cavities are a rare resource in piedmont forests and we have provided recommendations on how to conduct selective logging that maintain an important component of Yungas biodiversity (e.g., trees species to be retained, unlogged patches with tree with high DBH, excavated cavities, etc.).The management of tree cavities is challenging because of their dynamic nature. Moreover, cavity development is a relatively uncommon process. In our previous work we have established that there is a high rate of cavity loss and that cavities excavated by woodpeckers are preferred by nesting-birds, highlighting the key role of woodpeckers. Trees with softer, rotten wood are often selected over healthier trees for excavation, but probably do not remain available for long. To better refine our guidelines for maintaining cavity trees we need to understand which trees are selected for excavation, the spatial distribution of potential cavity trees, the rate of creation of cavities, and which cavities are likely to persist longer. By delineating management guidelines based on the requirements of woodpeckers, we hope to mitigate the negative effects of selective logging. A capacity-building workshop and booklets will inform natural resources agency staff and local people of our recommendations for implementation in environmental impact assessments and new legislation for sustainable forest management. We also need to make our information available to the forest stewardship council (FSC) to assure that certification processes have the best available information. ResultsWe found a total density of 41 decayed cavities/ha and 6 excavated cavities/ha, while only 0.41 cavities/ha were excavated by Campephilus leucopogon. DBH of excavated cavities trees was significantly greater than the DBH of decayed cavities (Table 1). Excavated cavities were located significantly higher from the ground than decayed cavities (Table 1). Decayed cavities were approximately equally distributed among trunks and branches (44% vs. 56%, respectively). However, excavated cavities were less likely to occur in trunks than in branches (33% vs. 67%, respectively). One fourth of the total excavated cavities occurred in dead trees (snags), but half of the excavated cavities that occurred in branches were located in dead branches. 99% of decayed cavities occurred in live trees and 20% of decayed cavities located in branches were on dead branches. Calycophyllum multiflorum and snags were selected for excavation by woodpeckers. Cavities excavated by Campephilus leucopogon were found in trees with a mean DBH of 63±12 cm and at a height of 15±3 m from the ground. Calycophyllum multiflorum live trees had most of the cavities (39%) with mean DBH of 63±13 cm (Fig. 2) and at 14.99±3.82 m from the ground (Fig. 3). The second most used tree for excavation of cavities by Campephilus leucopogon was Amburana cearensis (17%) with a mean DBH of 69±17 cm (Fig. 2) at 16.63±6.73 m from the ground (Fig. 3). During our year of study 0.05 new cavities/ha were created by woodpeckers, but we did not detect new decayed cavities. None of the cavities marked were lost during the year of study. We found that the home range of a pair of Campephilus leucopogon to be approximately 20 ha. Cavities excavated by woodpeckers have a clumped distribution. Management recommendationsWith the support of RSG we have shown that current forest practices in the piedmont forest of northwestern Argentina have a profound negative effect on tree cavity quantity and quality and affect the richness and abundance of cavity-nesting birds. We determined that suitable tree cavities are a rare resource in piedmont forests. We have established that there is a high rate of cavity loss but there is a high rate of cavity creation by woodpeckers, we still do not have information on the rate of creation by fungus but it seems to be rather slow. Cavities excavated by woodpeckers are preferred by nesting-birds, highlighting the key role of woodpeckers. Therefore we recommend that timber exploitation consider retaining at least 20 large trees (i.e., >60 cm of DBH)/ha especially of Calycophyllum multiflorum and Amburana cearensis. Furthermore, considering the high rate of decomposition of snags they should be retained since they are prone for excavation and also provide a food resource for woodpeckers. Until we can validate our results that assure that this recommendations are suitable to reach a sustainable timber management and because we have only considered only one component of biodiversity we suggest 10% of the area should be retained unlogged in a single block, preferably connecting with other unlogged patches.