Determinação do volume de resíduos lenhosos pelo método das linhas Interseptadoras na Amazônia brasileira.

Abstract

Coarse woody debris is defined as all dead material that has fallen on the forest floor with a diameter equal to or greater than 10 cm. In managed forest areas, this also includes harvested tree parts that have not been removed from the forest, such as branches, forks, stumps, as well as twisted portions of trunks and branches. In this context, utilizing this coarse woody debris for energy purposes, sawmills, charcoal, and furniture production can be an alternative to optimize forest production. The utilization depends on variables like the degree of decomposition and diameter class. Estimating the volume of this material is crucial for decision-making regarding its feasibility and can be performed through various methods. A low-cost and accurate alternative is the method of intercept lines, which can take on different layouts in the field, although determining the most efficient format is necessary. In this regard, the guiding questions of this research were: a) Is there a difference between layouts for estimating the volume of coarse woody debris?; b) Does the length of the sample line influence the determination of coarse woody debris among layouts?; c) Do layouts exhibit the same diameter distribution for the volume of woody debris?; d) Do layouts differ in estimating volume based on decomposition class?; and e) What are the most frequent usage classes among the layouts? Therefore, the objective of this work was to evaluate and define the most appropriate layout for the estimation of the volume of waste generated by the exploration of reduced impact, in the Green Forever Extractive Reserve, municipality of Porto de Moz, state of Pará, Amazon. Lines of 1000 m were sampled in an area of 100 hectares, where all pieces (diameter ≥ 10 cm) touching the sample lines were cataloged. Each tested layout (Cross, L, Line, and Square shapes) was characterized as a treatment, with 18 repetitions in a completely randomized design. Additionally, in each layout, the volume of debris was evaluated by usage category (charcoal/firewood, small furniture/artifacts, sawmill, and no use), decomposition class (no noticeable degradation, slight signs of deterioration, advanced stage of decomposition), and diameter class. A regression between the estimated volume and the length of the sample line was also conducted, showing better sampling with increased line length. The results indicated similarity between layouts for volume estimation (p >0.05), according to Analysis of Variance, with a very high coefficient of variation (>30%). Nonetheless, layouts L and Square showed the smallest standard errors (9.30% and 9.69%, respectively). In all layouts, distance showed a positive and significant regression for volume estimation; furthermore, larger volumes were found in higher diameter classes. Layouts were similar in volume estimation for decomposition classes, and in all of them, the most frequent usage was for coal and firewood, accounting for more than 50% of the volume. Thus, the efficiency of the intercept line method for estimating coarse woody debris was confirmed, and considering the lower sampling error, broader diameter class coverage, and ease of field execution, the use of the square-type layout is recommended.