Arboreal Richness Research Articles

Population dynamics of Pentaclethra macroloba, a hyperdominant tree in the Amazon River estuary

Pentaclethra macroloba is a hyperdominant tree of the Amazon estuary and highly exploited in the region, because the oil of its seeds has medicinal properties. Little is known about the influence of the flood polymodal cycle on the population dynamics of trees in the Amazon estuary. We evaluated the influence of tree diversity, climate, soil properties and flood level on the population dynamics of P. macroloba. During five years of monitoring (from 2011 to 2015), population density and mortality, recruitment and growth rates data were obtained of three populations of P. macroloba (Mazagão Velho, Maracá and Ajuruxi areas). Four transects were used in each area and 20 permanent plots were installed in each transect to study the population dynamics. Linear models were used to evaluate the relationship between biotic/abiotic factors and population density of P. macroloba. The population density of the three populations analyzed showed a significant decrease between the period from 2011 to 2015 (F = 381.3; p < 0.001). The Maracá area had a higher mortality rate (4.50% year−1) compared to Mazagão Velho (3.24% year−1) and Ajuruxi (1.96% year−1). The recruitment rate in Ajuruxi and Mazagão Velho were 1.05% year−1 and 0.32% year−1, respectively, and in Maracá there were no recruits. Annual growth rate of the Maraca area was higher (0.93 cm−1 year−1) compared to Ajuruxi (0.75 cm−1 year−1) and Mazagão Velho (0.65 cm−1 year−1) populations. The flood level had a negative and significant correlation with the population density of P. macroloba in the Maracá (F = 39.7; p < 0.01), Ajuruxi (F = 9.9; p < 0.05) and Mazagão Velho (F = 19.6; p < 0.05) areas. Only the Ajuruxi area had a positive and significant correlation with arboreal richness (β = 0.14; p < 0.05). The flood gradient is an environmental driver that regulates the population growth of P. macroloba. The hyperdominant characteristic of this species is the result of its adaptability and interactions between soil fertility and tree diversity.

Does degradation from selective logging and illegal activities differently impact forest resources? A case study in Ghana

Abstract: Degradation, a reduction of the ecosystem’s capacity to supply goods and services, is widespread in tropical forests and mainly caused by human disturbance. To maintain the full range of forest ecosystem services and support the development of effective conservation policies, we must understand the overall impact of degradation on different forest resources. This research investigates the response to disturbance of forest structure using several indicators: soil carbon content, arboreal richness and biodiversity, functional composition (guild and wood density), and productivity. We drew upon large field and remote sensing datasets from different forest types in Ghana, characterized by varied protection status, to investigate impacts of selective logging, and of illegal land use and resources extraction, which are the main disturbance causes in West Africa. Results indicate that functional composition and the overall number of species are less affected by degradation, while forest structure, soil carbon content and species abundance are seriously impacted, with resources distribution reflecting the protection level of the areas. Remote sensing analysis showed an increase in productivity in the last three decades, with higher resiliency to change in drier forest types, and stronger productivity correlation with solar radiation in the short dry season. The study region is affected by growing anthropogenic pressure on natural resources and by an increased climate variability: possible interactions of disturbance with climate are also discussed, together with the urgency to reduce degradation in order to preserve the full range of ecosystem functions.

Composition, Biomass, and Overstory Spatial Patterns in a Mature Pine-Hardwood Stand in Southeastern Arkansas

A 1.21-ha plot was established in a mature pine–hardwood forest (Hyatt's Woods) along a low stream terrace in southeastern Arkansas. Compositionally, this stand had considerable arboreal richness, with 26 different tree species ≥9 cm in diameter. Loblolly pine (Pinus taeda) contributed 42% of the stand's 37.1 m2/ha of basal area; the remaining fraction included baldcypress (Taxodium distichum) and 24 hardwood species (no other single taxon exceeded 12%). Only a limited volume (15.2 m3/ha) of dead wood was encountered. The large size of the dominant conifers and abundance of high wood density hardwoods at Hyatt's Woods yielded a considerable quantity of biomass—at 317 Mg/ha, few stands in the region have more. With all species combined, tree stem location exhibited a random spatial pattern, but this changed when individual species were considered. For example, loblolly pine tended to be clustered on the higher portions of this relatively flat site, while white oak (Quercus alba) was well distributed across Hyatt's Woods, and baldcypress was associated with two abandoned stream channels. Unmanaged streamside forests in southeastern Arkansas usually contain high levels of arboreal diversity and biomass, and sometimes possess biological legacies that can date back centuries. These stands retain important structural and ecosystem service components in an otherwise increasingly fragmented and intensively managed landscape.