Amazon soil charcoal: Pyrogenic carbon stock depends of ignition source distance and forest type in Roraima, Brazil

Pyrogenic carbon stocks and its spatial variability in soils from savanna-forest ecotone in amazon

Forest fragments from Amazon are important long-term carbon (C) reservoirs with an essential role in the global C balance. They are often impacted by understory fires, deforestation, selective logging and livestock. Forest fires convert soil organic matter into pyrogenic carbon (PyC), but little is known about its distribution and accumulation along the soil profile. Thus, the objective of this study is to estimate the refractory carbon stocks derived from PyC accumulated in the soil vertical profile of different seasonal forest fragments in the Amazon. Sixty-nine soil cores (1 m deep) were collected in 12 forest fragments of different sizes considering edge and interior gradients. The mean total organic C (TOC) and PyC contents for the edge and interior gradients were 0.84% and 0.009%, respectively. The PyC/TOC ratio ranged from 0.53% to 1.78%, with an average of 1.32% and increasing in depth, being low when compared with other studies, where the contribution of PyC to TOC ranges from 1 to 9%. PyC stocks on the edge (1.04 ± 0.04 Mg ha^-1) differed significantly from the interior (1.46 ± 0.03 Mg ha^-1). The analyzed forest fragments presented a weighted PyC stock of 1.37 ± 0.65 Mg ha^-1. The vertical distribution of PyC declined in depth with 70% of PyC concentrated in the surface soil layers (0-30 cm). These results indicate that the PyC accumulated in the vertical profile of soils in forest fragments in Amazonia are important, and they need to be considered in Brazilian and global reports on carbon stocks and fluxes.

Recovery patterns of soil bacterial and fungal communities in Chinese boreal forests along a fire chronosequence

Wildfire has profound and pervasive consequences for forest ecosystems via directly altering soil physicochemical properties and modulating microbial community. In this study, we examined the changes in soil properties and microbial community composition and structure at different periods after highly severe wildfire events (44 plots, 113 samples) in the Chinese Great Khingan Mountains. We also separated charcoal from burnt soils to establish the relationship between microbial community structures in soils and charcoal. We found that wildfire only significantly altered bacterial and fungal β-diversity, but had no effect on microbial α-diversity across a 29-year chronosequence. The network analysis revealed that the complexity and connectivity of bacterial and fungal communities were significantly increased from 17 years after fire, compared with either unburnt soils or soils with recent fires (0-4 years after fire). Differential abundance analysis suggested that bacterial and fungal OTUs were enriched or depleted only during 0-4 years after fire compared with the unburnt soils. In addition, soil pH, dissolved organic C and dissolved organic N were key determinants of soil bacterial and fungal communities during 17-29 years after fire. The fire-derived charcoal provided a new niche for microbial colonization, and microbes colonized in the charcoal had a significantly different community structure from those of burnt soils. Our data suggest that soil bacterial and fungal communities changed significantly during the recovery from fire events in terms of the abundance and co-occurrence networks in the boreal forest ecosystems.

Dataset on wood density of trees in ecotone forests in Northern Brazilian Amazonia

Wood density is expressed by the ratio between dry weight and fresh volume of a sample piece. The value of this measure is an important variable for assessing wood functional properties, successional stages and biomass/carbon stock estimates in different terrestrial ecosystems. Wood density data were collected for tree species from ecotone forests of the northern Brazilian Amazonia. We sampled 680 individuals with stem diameter ≥10 cm. For each sampled individual measurements were taken for three stem variables: bark thickness (mm), bark density (g cm⁻³) and wood density (g cm⁻³). This dataset is intended to improve biomass and carbon estimates of forests in the northern ecotone region of Brazilian Amazonia, an area poorly known in terms of ecosystem dynamics.

Floristic composition in ecotone forests in northern Brazilian Amazonia: preliminary data

Background

Ecotone has been defined as "a multi-dimensional environmentally stochastic interaction zone between ecological systems with characteristics defined in space and time, and by the strength of the interaction" (Hufkens et al. 2009). This is a known concept to define transitional zones between two or more ecological communities, ecosystems or biotic regions. Ecotone forests, dispersed in northern Brazilian Amazonia, are natural formations which have been largely affected by anthropogenic impacts, such as deforestation and fire. Maracá Ecological Station, State of Roraima, Brazil, is a protected area with extensive representations of ecotone forests in this region of the Amazonia. Forest inventories and floristic surveys are important as they extend our knowledge (1) of forest structure and tree species composition and (2) of tree and palm species ecology in this region of the Amazonia. Both improve our ability to predict changes in plant diversity, considering the future scenarios of climate change in comparison with previous surveys performed in Maracá.

New information

We present a forest inventory carried out in 129 plots (10 m x 50 m; 6.45 ha in total) dispersed in a grid (5 km x 5 km) located in a forest zone ecotone in the eastern part of Maracá Ecological Station. All stems (tree + palm) with diameter at breast height ≥ 10 cm were recorded, identified and measured. A total of 3040 stems were recorded (tree = 2815; palm = 225), corresponding to 42 botanic families and 140 identified species. Seven families and 20 genera contained unidentified taxa (12.2%). Sapotaceae (735 stems; 10 species), Leguminosae (409; 24) and Rubiaceae (289; 12) were the most abundant families. Peltogyne gracilipes Ducke (Leguminosae), Pradosia surinamensis (Eyma) T.D.Penn. (Sapotaceae) and Ecclinusa guianensis Eyma (Sapotaceae) were the species with the highest importance value index (~ 25%). The dominance (m² ha^-1) of these species corresponds to > 36% of the total value observed in the forest inventory. Our dataset provides complementary floristic and structure information on tree and palm in Maracá, improving our knowledge of this Amazonian ecotone forest.