Regionalization of climate scenarios impacts on maize production and the role of cultivar and planting date as an adaptation strategy

Understanding climate change and its impacts on crops is crucial to determine adaptation strategies. Simulations of climate change impacts on agricultural systems are often run for individual sites. Nevertheless, the scaling up of crop model results can bring a more complete picture, providing better inputs for the decision-making process. The objective of this paper was to present a procedure to assess the regional impacts of climate scenarios on maize production, as well as the effect of crop cultivars and planting dates as an adaptation strategy. The focus region is Santa Catarina State, Brazil. The identification of agricultural areas cultivated with annual crops was done for the whole state, followed by the coupling of soil and weather information necessary for the crop modeling procedure (using crop model and regional circulation models). The impact on maize yields, so as the effect of adaptation strategies, was calculated for the 2012–2040 period assuming different maize cultivars and planting dates. Results showed that the exclusion of non-agricultural areas allowed the crop model to correctly simulate local and regional production. Simulations run without adaptation strategies for the 2012–2040 period showed reductions of 11.5–13.5 % in total maize production, depending on the cultivar. By using the best cultivar for each agricultural area, total state production was increased by 6 %; when using both adaptation strategies—cultivar and best planting date—total production increased by 15 %. This analysis showed that cultivar and planting date are feasible adaptation strategies to mitigate deleterious effects of climate scenarios, and crop models can be successfully used for regional assessments.     

Evidence of at least two evolutionary lineages in Melipona subnitida (Apidae, Meliponini) suggested by mtDNA variability and geometric morphometrics of forewings

Melipona subnitida, a tropical stingless bee, is an endemic species of the Brazilian northeast and exhibits great potential for honey and pollen production in addition to its role as one of the main pollinators of the Caatinga biome. To understand the genetic structure and better assist in the conservation of this species, we characterized the population variability of M. subnitida using geometric morphometrics of the forewing and cytochrome c oxidase I gene fragment sequencing. We collected workers from six localities in the northernmost distribution. Both methodologies indicated that the variability among the sampled populations is related both to the environment in which samples were collected and the geographical distance between the sampling sites, indicating that differentiation among the populations is due to the existence of at least evolutionary lineages. Molecular clock data suggest that this differentiation may have begun in the middle Pleistocene, approximately 396 kya. The conservation of all evolutionary lineages is important since they can present differential resistance to environmental changes, as resistance to drought and diseases.     

Use of an inert radioactive particle for measuring particle accumulation by filter-feeding bivalve molluscs

Because the rate of microbial degradation differs for the various sources contributing to the detrital pool in marine systems, their availability to detritivores might also vary. Carbon-14 tracer experiments were used to compare differences in the oxidation and net incorporation by the polychaete Capitella capitata of a nitrogenrich, easily-decomposable detritus derived from the red macrophytic algae Gracilaria sp. versus a nitrogen-poor, decay-resistant detritus derived from the eelgrass Zostera marina. The net incorporation of Gracilaria sp. detritus by C. capitata reached a maximum (91 g dry weight of detritus/mg dry weight of worm/day) after only 14 days of decomposition, whereas that of z. marina detritus equaled this level after 30 days of aging, but continued to increase to 375 g at 180 days. The oxidation rate of Gracilaria sp. detritus was consistently higher (peak of 61 mg dry weight of detritus/day at 30 day-aging) than z. marina detritus, which reached this level only after 180 days of aging. The presence or absence of C. capitata did not significantly alter the oxidation rate. The above difference might be attributed to a rapid exploitation and mineralization by bacteria of the more available Gracilaria sp. detritus, but a slow, controlled utilization by the microbes of the less available Z. marina detritus, especially during the early stage of decomposition. This would allow maximum exploitation of the substrate by macroconsumers, resulting in more of the detrital resource being tied up in detritivore biomass rather than being rapidly mineralized to CO₂. Difference in the length of aging at which various detrital sources become available to detritivores could result in a temporal partitioning of food resources and should be considered in attempting to understand the dynamics of detrital-based food chains.     

Evaporites and continental drift

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