Changing paradigm
Carbon storage is different at different spots in the same soilSOIL has the unique ability to sequester carbon. By doing so, it lowers the amount of carbon released in the atmosphere and plays a significant role in the global carbon cycle. Though the concentration of carbon dioxide in the atmosphere has increased over the years, the rates of carbon sequestration have remained unchanged. Recent scientific developments indicate a shift in our understanding of how sequestration happens in nature, making previous estimates of soil&’s carbon absorption capacity questionable. A paper published in Nature Communications by scientists from the Technische Universität München, Freising-Weihenstephan, Germany, has shown that sequestration of carbon does not happen uniformly across all types of soils. Instead, there is preferential absorption at certain hotspots in the same soil.
   For the study, researchers used soil samples similar to natural top soil and mixed them with litter having labelled carbon and nitrogen isotopes. Carbon and nitrogen were labelled in the litter to distinguish the new sequestration from the existing one. The incubation continued for 42 days, after which the soil was divided into fractions based on particle size and density. Samples were then analysed using ultrasensitive nanoscale secondary iron mass spectrometry technique (Nano-SIMS). This allowed them to get the elemental distribution of the samples at very high resolution.
   Less than 19 per cent of the soil showed evidence of new sequestration. The labels showed that the new sequestration had happened only in organomineral clusters with rough surfaces. In the soil, some mineral particles appeared as individual particles with mostly plain surfaces, whereas others were aggregated in clusters of several small particles. This clustering caused rough surfaces.
   There are no clear answers as to why such a preference occurs. Commenting on the study, S Kundu, principal scientist, division of environmental soil science, Indian Institute of Soil Science, Bhopal, says, “The type of soil taken for this investigation contained 18.5 per cent clay and 18.4 per cent silt and was dominated by chlorite/illite type of minerals. I am sure a distinctly different picture will emerge if the soil were of the vertisol type, containing 40-60 per cent clay, dominated by smectite/ vermiculite type of minerals. More research is needed to interpret the result of this investigation in the context of carbon/nitrogen sequestration in soils of diverse physical, chemical and biological properties.”

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Locust control
Locust swarms destroy crops and threaten the livelihood of millions. The problem is more severe in Asia and Africa because these insects, which belong to grasshopper family Acrididae, breed easily in warm, moist conditions, assemble in massive groups, eat more and cover vast areas.
   According to a new study, the microsporidian gut parasite, Paranosema locustae, can be used to check the swarming behaviour of migratory locusts and control locust plagues. Researchers found that the parasite causes hindgut acidity and controls the locust&’s immune response, which suppresses growth of the hindgut bacteria.
   These bacteria are behind the production of the aggregation pheromone (chemicals released in the locust&’s faecal pellets that encourage swarming behaviour in other locusts). Reduction in hindgut bacteria and the consequent reduction in the aggregation pherom one cause a drop in serotonin and dopamine levels — the neurotransmitters that initiate and maintain swarm behaviour.
   The experiments were conducted by exposing uninfected locusts to glass chambers containing faecal volatile chemicals from both healthy locusts and others infected with Paranosema. The locusts aggregated more and displayed a higher antennal response to uninfected faeces compared to infected faeces.
The research was led by Wangpeng Shi from the department of entomology, China Agricultural University, Beijing, and published in the 14 January issue of Proceedings of the National Academy of Sciences.
Carlos E Lange, research scientist working at the Centre for Parasitological Studies and Vectors in Buenos Aires, Argentina, notes that the parasite has already been introduced to affect outbreaks of locusts in parts of Argentina and China with positive results.
But Gregory A Sword, professor, department of entomology, Texas A&M University, says, “The role of aggregation pheromone in mediating the initial attraction, subsequent phase change and swarm formation is considerably overstated in this article.”

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