Frederico Costa Beber Vieira

In situ methane and nitrous oxide fluxes in soil from a transect in Hennequin Point, King George Island, Antarctic

The study aimed at to determine the magnitude of the methane (CH(4)) and nitrous oxide (N(2)O) flux rates in soils at Hennequin Point, King George Island, Antarctic, under different slope positions, vegetal covers and presence of skuas, as well as to evaluate the main soil and climate factors that are involved with the flux of such gases. In situ gas sampling (closed chamber method) was performed in four sites along a transect involving a skua nesting field in a moraine with 5% and 100% of surface covered by vegetal, and two poor-drained soils in the toeslope (a bare alluvium soil and a poor-drained moss field with 100% soil cover). Flux rates ranged from -0.86±0.45 to 2.75±1.52 μg N(2)O-N m(-2) h(-1) and -12.26±3.05 to 1.42±1.31 μg CH(4)-C m(-2) h(-1). The soil totally covered by vegetal in the skua field had the largest CH(4) influx rates. However, this benefic effect was counterbalanced by the greatest N(2)O efflux rates from this soil, resulting in the largest contribution to the global warming potential among the soils evaluated. Flux rates were closely related to soil temperature, but no significant relation was observed with mineral N contents and water-filled pore space. In turn, accumulated CH(4) and N(2)O emissions were closely related to the total N and total organic C stocks in the soil. Net CH(4) influx predominated even in the poor-drained soils, suggesting that the coarse soil texture avoided critical anaerobic conditions. No significant changes in flux rates were observed for sampling time along the day.

The conversion of grassland to acacia forest as an effective option for net reduction in greenhouse gas emissions.

This study aimed to evaluate the effect of forestation with leguminous Acacia mearnsii De Wild in native grasslands on the soil greenhouse (GHG) fluxes and their main driving factors. The experiment was conducted in the Brazilian Pampa over the period of one year in a six-year-old Acacia plantation, evaluating four treatments: Acacia (AM), Acacia with litter periodically removed (A-l), Acacia after harvest (AH) and native grassland (NG) (reference treatment). Air samples were obtained by the static chamber method, and gas concentrations were evaluated by gas chromatography. Soil and climate factors were monitored. The accumulated fluxes of methane (CH4) and nitrous oxide (N2O) were statistically similar between the soils in the AM and NG treatments, which tended to oxidize CH4 (-1445 andxa0-1752xa0gxa0C-CH4xa0ha(-1)xa0yr(-1), respectively) and had low emission of N2O (242 and 316xa0gxa0N-N2Oxa0ha(-1)xa0yr(-1)), most likely influenced by the low water-filled pore space and the low content of mineral N in the soil. However, the soil in the AH treatment presented higher emissions of both gases, totaling 1889xa0gxa0C-CH4xa0ha(-1)xa0yr(-1) and 1250xa0gxa0N-N2Oxa0ha(-1)xa0yr(-1). Afforestation neither significantly affected the total organic C stocks nor their lability, keeping the C management index for the forested area similar to that in the NG treatment. The conversion from grassland to Acacia forest represents an effective option for mitigating the net reduction in greenhouse gas emissions, which is basically determined by C accumulation in biomass and wood products.

Improving Acid Soil Fertility and Initial Growth of Eucalyptus by Compost of Bovine Ruminal Residues in a Pot Experiment

This study aimed to evaluate the potential of a compost of bovine ruminal residues to improve soil fertility and initial growth of eucalyptus cultivated in acid soil. Eucalyptus was cultivated in pots with a Hapludalf amended with 0 (Control 1), 5, 10, and 15 m3compost ha−1, and with only liming and mineral fertilization (Control 2). The compost enhanced all evaluated parameters of plant growth and soil and plant chemical analysis; overcoming, or at least equalizing to results from the Control 2. The compost can be used as alternative to liming and mineral fertilization in Eucalyptus urograndis plantations in acid soils of the Brazilian Pampa.

Description of plant communities on Half Moon Island, Antarctica

ABSTRACT During February–March of the austral summers of 2013/14 and 2014/2015, fieldwork was performed on Half Moon Island, South Shetland Archipelago, Antarctica, to evaluate the distribution and abundance of mosses and lichens, as well as to describe and map the plant communities there. The quadrat (20 × 20 cm) sampling method was employed in a phytosociological study that aimed to describe these communities. The area was mapped using an Astech Promark II® DGPS, yielding sub-metric precision after post-processing with software. The number of species totalled 38 bryophytes, 59 lichens, only one flowering plant (Deschampsia antarctica Desv.), and two macroscopic terrestrial algae. Five types of plant communities were identified on the island, as follows: (1) fruticose lichen and moss cushion, (2) moss carpet, (3) muscicolous lichen, (4) crustose lichen and (5) moss turf.

Boron fertilization and liming for Eucalyptus urograndis cropped on sandy arenosol of Brazilian pampa

ABSTRACT Boron (B) requirement and its interaction with liming for eucalyptus plantations in sandy soils of Brazilian Pampa are poorly understood. Aiming to diminish this gap, seedlings of Eucalyptus urograndis were grown in pots with Arenosol fertilized with B at rates 0.0, 1.0, 2.5, 5.0 and 10.0 mg B dm−3, with and without liming. Results of shoot and root dry matter and stem diameter did not evidence the necessity of B fertilization. With the exception of the 1.0 mg B dm−3+lime, all other B-fertilized treatments promoted visual symptoms of toxicity, which were partially mitigated by liming. Liming exacerbated the B loss by leaching, but after five months, limed soils had higher content of available B and their plants had higher B concentration in shoots and roots. For our conditions, application of ≥2.5 mg B dm−3 can cause serious toxic injuries to plants and enlarge dramatically the B losses leaching.

Soil Chemical Attributes as Affected by Vegetal Cover and Seabirds in Punta Hennequin, Antarctica

is study had the purpose of evaluating the e ect of soil cover by vegetation on soil chemical attributes in a skua (Catharacta maccormicki) eld at Punta Hennequin, Shetland Island, Antarctica. Four locals along a transect were sampled, involving soils with 5 and 100% of vegetal cover (L1 and L2, respectively) with Deschampsia+Colobanthus; bare alluvium soil (L3); and poor-drained moss (Sanionia uncinata) carpet with 100% soil cover (L4). Soil samples obtained from three layers and three replicates were submitted to chemical and physical analysis. Although both L1 and L2 are in the same nesting eld, the more abundant vegetation at L2 promoted signi cantly larger (P < 0.05) total organic C (TOC) stocks in the soil than at L1 (43.08 and 9.03 Mg C ha–1, respectively, at the 0-40 cm layer). Total N stocks increased from 2.60 to 6.54 Mg ha–1 for L1 and L2, respectively. Although the presence of seabirds represents an important transfer of organic material from marine to the terrestrial environment, the di erences evidence the importance of vegetation in order to raise the soil organic matter levels. Soil pH was consistently lower in L2 than L1 about 1.0 unit for the soil layers herein evaluated, which is probably linked to the soil organic matter accumulation. Contrary to the distribution of TOC and TN contents, exchangeable P and K had no gradient along the soil pro le, evidencing that most of the P and K is native from the parent material and their input by seabirds to the soil is negligible.