RESUMO
Abstract The production of litterfall is essential for nutrient cycling in terrestrial ecosystems. From November 2009 to October 2011, analyzed the monthly litterfall production in two areas of Caatinga, a type of Seasonally Dry Tropical Forest located in the Cariri Paraibano, in the semiarid region of the Paraíba, Northeastern Brazil. One of the areas, Private Natural Heritage Reserve (RPPN) Fazenda Almas, is legally protected, and the other, Fazenda Moreiras, does not. The aims were to evaluate the effects of precipitation, evapotranspiration and vegetation structure on the temporal and spatial dynamics of litterfall production. Eight sampling points were randomly chosen at each site, and two 1 m2 collectors were installed 50 m apart from each other. The collected material was sorted, dried and weighed. Additionally, the characteristics (density, species richness, height and mean basal area) of the tree-shrub stratum in plots with a 10 m radius surrounding each collector. Total litterfall production was 4,500 kg ha-1 yr-1 for Fazenda Almas and 3,300 kg ha-1 yr-1 for Fazenda Moreiras; these values were within the expected range for Seasonally Dry Tropical Forests. The inter- and intra-annual variation in litterfall production was positively correlated with precipitation and evapotranspiration rates, and four months after the highest precipitation rates, there was a marked decrease in litterfall occurred during the dry season. Furthermore, the contributions of the material fractions were distinct with the leaf fraction representing for more than 60% of the litterfall, and the vegetation structure explained 75% of the variation in litterfall production. Therefore, climatic factors and vegetation structure affect the temporal and spatial dynamics of litterfall production and consequently influence nutrient dynamics in the semiarid region of Brazil.
Resumo A produção de serapilheira é essencial para a ciclagem de nutrientes em ecossistemas terrestres. De Novembro de 2009 a Outubro de 2011, foi analisada a produção de serapilheira em duas áreas de Caatinga, um tipo de Floresta Tropical sazonalmente Seca localizada no Cariri Paraibano, na região do semiárido da Paraíba, Nordeste do Brasil. Uma das áreas, Reserva Particular do Patrimônio Natural - RPPN - Fazenda Almas, é legalmente protegida, ao contrário da outra, Fazenda Moreiras. Os objetivos foram avaliar o efeito da precipitação, evapotranspiração e estrutura da vegetação sobre a dinâmica temporal e espacial da produção de serapilheira. Oito pontos de amostragem foram escolhidos aleatoriamente em cada localidade, e dois coletores de 1 m2 foram instalados a 50 m um do outro. O material coletado foi triado, secado e pesado. Adicionalmente, foram registradas as características (densidade, riqueza de espécies, altura e área basal média) das espécies arbóreo-arbustivas na parcela com um raio (r) de 10 m ao redor de cada coletor. A produção total de serapilheira foi 4,500 Kg ha-1 yr-1 para a Fazenda Almas e 3,300 kg ha-1 yr-1 para a Fazenda Moreiras; estes valores estão dentro da faixa esperada para as Florestas Tropicais sazonalmente secas. A variação inter e intranual na produção de serapilheira foi positivamente correlacionada com as taxas de precipitação e evapotranspiração, e quatro meses depois das maiores taxas de precipitação, houve uma diminuição acentuada na serapilheira coletada durante a estação seca. Além disso, as contribuições das frações de material foram distintas com a fração de folha representando mais que 60% da serapilheira, e a estrutura da vegetação explicou 75% da variação na produção de serapilheira. Portanto, os fatores climáticos e a estrutura da vegetação afetam a dinâmica temporal e espacial da produção de serapilheira e, consequentemente, influenciam a dinâmica de nutrientes na região semiárida do Brasil.
Assuntos
Florestas , Ecossistema , Estações do Ano , Árvores , Clima Tropical , BrasilRESUMO
The production of litterfall is essential for nutrient cycling in terrestrial ecosystems. From November 2009 to October 2011, analyzed the monthly litterfall production in two areas of Caatinga, a type of Seasonally Dry Tropical Forest located in the Cariri Paraibano, in the semiarid region of the Paraíba, Northeastern Brazil. One of the areas, Private Natural Heritage Reserve (RPPN) Fazenda Almas, is legally protected, and the other, Fazenda Moreiras, does not. The aims were to evaluate the effects of precipitation, evapotranspiration and vegetation structure on the temporal and spatial dynamics of litterfall production. Eight sampling points were randomly chosen at each site, and two 1 m2 collectors were installed 50 m apart from each other. The collected material was sorted, dried and weighed. Additionally, the characteristics (density, species richness, height and mean basal area) of the tree-shrub stratum in plots with a 10 m radius surrounding each collector. Total litterfall production was 4,500 kg ha-1 yr-1 for Fazenda Almas and 3,300 kg ha-1 yr-1 for Fazenda Moreiras; these values were within the expected range for Seasonally Dry Tropical Forests. The inter- and intra-annual variation in litterfall production was positively correlated with precipitation and evapotranspiration rates, and four months after the highest precipitation rates, there was a marked decrease in litterfall occurred during the dry season. Furthermore, the contributions of the material fractions were distinct with the leaf fraction representing for more than 60% of the litterfall, and the vegetation structure explained 75% of the variation in litterfall production. Therefore, climatic factors and vegetation structure affect the temporal and spatial dynamics of litterfall production and consequently influence nutrient dynamics in the semiarid region of Brazil.
Assuntos
Ecossistema , Florestas , Brasil , Estações do Ano , Árvores , Clima TropicalRESUMO
Abstract The production of litterfall is essential for nutrient cycling in terrestrial ecosystems. From November 2009 to October 2011, analyzed the monthly litterfall production in two areas of Caatinga, a type of Seasonally Dry Tropical Forest located in the Cariri Paraibano, in the semiarid region of the Paraíba, Northeastern Brazil. One of the areas, Private Natural Heritage Reserve (RPPN) Fazenda Almas, is legally protected, and the other, Fazenda Moreiras, does not. The aims were to evaluate the effects of precipitation, evapotranspiration and vegetation structure on the temporal and spatial dynamics of litterfall production. Eight sampling points were randomly chosen at each site, and two 1 m2 collectors were installed 50 m apart from each other. The collected material was sorted, dried and weighed. Additionally, the characteristics (density, species richness, height and mean basal area) of the tree-shrub stratum in plots with a 10 m radius surrounding each collector. Total litterfall production was 4,500 kg ha-1 yr-1 for Fazenda Almas and 3,300 kg ha-1 yr-1 for Fazenda Moreiras; these values were within the expected range for Seasonally Dry Tropical Forests. The inter- and intra-annual variation in litterfall production was positively correlated with precipitation and evapotranspiration rates, and four months after the highest precipitation rates, there was a marked decrease in litterfall occurred during the dry season. Furthermore, the contributions of the material fractions were distinct with the leaf fraction representing for more than 60% of the litterfall, and the vegetation structure explained 75% of the variation in litterfall production. Therefore, climatic factors and vegetation structure affect the temporal and spatial dynamics of litterfall production and consequently influence nutrient dynamics in the semiarid region of Brazil.
Resumo A produção de serapilheira é essencial para a ciclagem de nutrientes em ecossistemas terrestres. De Novembro de 2009 a Outubro de 2011, foi analisada a produção de serapilheira em duas áreas de Caatinga, um tipo de Floresta Tropical sazonalmente Seca localizada no Cariri Paraibano, na região do semiárido da Paraíba, Nordeste do Brasil. Uma das áreas, Reserva Particular do Patrimônio Natural - RPPN - Fazenda Almas, é legalmente protegida, ao contrário da outra, Fazenda Moreiras. Os objetivos foram avaliar o efeito da precipitação, evapotranspiração e estrutura da vegetação sobre a dinâmica temporal e espacial da produção de serapilheira. Oito pontos de amostragem foram escolhidos aleatoriamente em cada localidade, e dois coletores de 1 m2 foram instalados a 50 m um do outro. O material coletado foi triado, secado e pesado. Adicionalmente, foram registradas as características (densidade, riqueza de espécies, altura e área basal média) das espécies arbóreo-arbustivas na parcela com um raio (r) de 10 m ao redor de cada coletor. A produção total de serapilheira foi 4,500 Kg ha-1 yr-1 para a Fazenda Almas e 3,300 kg ha-1 yr-1 para a Fazenda Moreiras; estes valores estão dentro da faixa esperada para as Florestas Tropicais sazonalmente secas. A variação inter e intranual na produção de serapilheira foi positivamente correlacionada com as taxas de precipitação e evapotranspiração, e quatro meses depois das maiores taxas de precipitação, houve uma diminuição acentuada na serapilheira coletada durante a estação seca. Além disso, as contribuições das frações de material foram distintas com a fração de folha representando mais que 60% da serapilheira, e a estrutura da vegetação explicou 75% da variação na produção de serapilheira. Portanto, os fatores climáticos e a estrutura da vegetação afetam a dinâmica temporal e espacial da produção de serapilheira e, consequentemente, influenciam a dinâmica de nutrientes na região semiárida do Brasil.
RESUMO
Litterfall has a strong influence on biodiversity and on the chemical and physical characteristics of the soil. Its production can be quite variable over time and space, and can be influenced by both natural and anthropogenic factors. We evaluated litterfall production and its relationship with rainfall, species richness, and the densities of the arboreal vegetation. Thirty litter traps were constructed with 1.0 m2 nylon mesh (1.0 mm) and randomly installed within a 2000 m × 500 m area of arboreal/shrub Caatinga (dryland) vegetation. Litter samples were collected monthly from November/2010 to June/2012, and the collected material was classified, dried, and weighted. Species richness and tree densities were determined by conducting phytosociological surveys in 20 m × 20 m plots surrounding each of the litter traps. The litterfall accumulation rate was 3.673 Mgha-1yr-1, similar to values from other seasonally dry tropical forests. Litterfall production was continuous, and principally accompanied the rainfall rate, but with a time interval of 2 to 3 months, with the greatest accumulation at the beginning of the dry season and the least during the rainy season. The different fractions of materials demonstrated distinct accumulation rates, with leaves being the principal category. Litterfall production was found to be related to tree density, but no link was found to species richness. The observed temporal heterogeneity of litterfall production demonstrated a strong link between rainfall and the dynamics of nutrient cycling in the semiarid region of Brazil.
Assuntos
Biodiversidade , Florestas , Fenômenos Fisiológicos Vegetais , Chuva , Brasil , Densidade DemográficaRESUMO
In arid and semiarid environments, seasonality usually exerts a strong influence on the composition and dynamics of the soil community. The soil macroarthropods were studied in a Caatinga forest located in the Reserva Particular do Patrimônio Natural (RPPN) Fazenda Almas, São José dos Cordeiros, Paraíba, Brazil. Samples were collected during the dry and rainy seasons following the method proposed by the Tropical Soil Biology and Fertility Program (TSBF), with minor modifications. At each station, 15 soil blocks (20 × 20 × 30 cm: 12 L) were extracted and divided into three layers: A (0-10 cm), B (10-20 cm), and C (20-30 cm). In the rainy and dry seasons 1,306 ± 543(se) and 458 ± 212 ind.m-2 macroarthropods were found, respectively, with 35 and 18 respective taxa recorded. The abundance of individuals and taxa were significantly higher in the rainy season. Isoptera (57.8%) was the most abundant taxon, followed by Hymenoptera: Formicidae (17.2%), Coleoptera larvae (7.3%), and Araneae (3.5%). In the rainy season, abundance in layer A (576 ± 138 ind.m-2) was significantly higher than that of layer C (117 ± 64 ind.m-2), but was not different from layer B (613 ± 480 ind.m-2). There was also no difference between the layer B and C abundances. In the dry season, abundance in layer B (232 ± 120 ind.m-2) was not significantly different compared to layer A (182 ± 129 ind.m-2), but was significantly higher than abundance in layer C (44 ± 35 ind.m-2). During the rainy season, layer A (34 taxa) was significantly richer in taxa than layers B (19 taxa) and C (11 taxa). On the other hand, during the dry season the richness of layers A (12 taxa) and B (12 taxa) was equal, but significantly higher than that of layer C (6 taxa). Richness of taxa and abundance were positively correlated with soil organic matter and negatively correlated with soil temperature. The community of soil macroarthropods in the area of Caatinga studied has taxonomic and functional structures that are relatively complex and is therefore likely to exert an influence on ecosystem productivity due to its physical effects on soil profile and necromass fragmentation, as occurs in other arid and semiarid ecosystems throughout the world.
