ABSTRACT Backgrounds: Urban forests can provide citizens with various types and quantities of ecosystem services. However, the contribution of isolated forest fragments to this process and its value are not well understood. Therefore, our main goal was to analyze the patterns of ecosystem service delivery by three forest fragments along an urban-to-rural gradient. Carbon storage was estimated using three different models (general and local), with input variables such as diameter at breast height (DBH), total height, and wood density. Rainfall interception was assessed using water collectors placed inside the forest fragment, at the border, and outside, throughout the four seasons. Data were collected from three forest fragments of different types (urban, periurban, and rural), each covering an area of 1.0 hectare. Results: Isolated forest fragments did not significantly differ (p>0.01) in terms of carbon stocks compared to a protected area. The urban fragment had a carbon stock of 33.70 mg.ha-1, while the rural fragment had a carbon stock of 37.19 mg.ha-1. Regarding rainfall interception, there were no significant differences (p>0.01) among the forest fragments. The highest average rainfall interception percentage (58.65%) was observed during the summer. The capacity for rainfall interception changed from the border (lower) to the center of the fragment (higher) in a similar manner for both isolated and connected forest fragments. Conclusion: Isolated Forest fragments can provide ecosystem services (carbon storage and rainfall interception) in the same way as connected forest fragments in the periurban and rural places, like in protected areas. It highlights the importance of promoting the protection of forests fragments in cities.

O presente estudo objetivou determinar a suficiência amostral para coletas de serapilheira acumulada sobre o solo em povoamentos de Pinus elliottii, Eucalyptus sp., ambos plantados no Campus da Universidade Federal de Santa Maria e em uma área de Floresta Estacional Decidual (FED) localizada no Morro do Elefante, Santa Maria, RS. Para a realização do estudo, foram coletadas 100 amostras de serapilheira por floresta, com o auxílio de uma moldura quadrada de 25 cm de lado, totalizando 300 amostras, as quais foram separadas nas seguintes frações: acículas ou folhas, galhos, estruturas reprodutivas, cascas e resíduos. Com base nos pesos de matéria seca de cada fração, realizou-se a análise estatística dos dados, visando à estabilização dos valores do coeficiente de variação (CV%). Para Pinus elliottii, a maior contribuição na formação da serapilheira foi dada pelas acículas, com 57,2%; em Eucalyptus sp., isso ocorreu com os galhos (38,8%) e na FED, novamente com as folhas, que representaram 49,6% da serapilheira. No Pinus elliottii, o maior CV% se deu nos resíduos, seguido de estruturas reprodutivas. Em Eucalyptus sp., o maior CV% foi encontrado em cascas, seguido de galhos. Na FED, as cascas tiveram o maior CV%. A suficiência amostral necessária para Pinus elliottii foi de 40, sendo esse o povoamento que necessitou de menos amostras para estabilizar o CV%. Em Eucalyptus sp., a suficiência amostral foi de 70, enquanto na FED foram necessárias 80 amostras.

This study determined the sample sufficiency for the collection of litter accumulated on the soil, in Pinus elliottii and Eucalyptus sp. stands, planted in the Campus of the Federal University of Santa Maria and a Seasonal Deciduous Forest, located at the "Morro do Elefante", Santa Maria - RS. To carry out this study, 100 samples were collected per site, using a square frame (25 cm²), totaling 300 samples. The samples were separated in the following fractions: needles or leaves, branches, reproductive structures, barks and wastes. Based on the dry weights of each fraction, a statistical analysis was carried out, aiming the stabilization of the coefficient of variation (CV%). For Pinus elliotti, "needles" was the fraction that contributed the most, 57.2%; for the Eucalyptus sp., the branches contributed with 38.8%; and for the Seasonal Deciduous Forest the leaves contributed with 46.9%. The highest CV% in Pinus elliottii was for the wastes, followed by the reproductive structures. In Eucalyptus sp. the highest CV% was for barks, followed by branches. In the Seasonal Deciduous Forest, the barks had the highest CV%. The sample sufficiency for Pinus elliotti was 40, so this stand needed fewer samples to stabilize the CV%. For Eucalyptus sp. the sample sufficiency was 70, and in the Seasonal Deciduous Forest 80 samples were needed.