The Vertical Distribution Pattern of Microbial- and Plant-Derived Carbon in the Rhizosphere in Alpine Coniferous Forests

Background and aimsWhile the quantitative assessment of plant- and microbial-derived carbon (C) in the soil organic C (SOC) chemical composition in soil profiles has been initially explored, the vertical distribution pattern of these two C sources and their dominant role in SOC formation based on the insights related to the rhizosphere are still lacking.MethodsWe quantified the divergent accumulation of microbial-derived C (i.e., microbial residues), plant-derived C (i.e., lipids and lignin phenols) and SOC in the rhizosphere at various depths (0-10 cm, 10-20 cm and 20-30 cm) in the upper mineral soil and analyzed its control factors in an alpine coniferous forest (Picea asperata. Mast). We further revealed the relative contribution of plant- or microbial-derived C to rhizosphere SOC in the soil profile.ResultsThe contents of microbial- and plant-derived C and SOC in the rhizosphere decreased with soil depth and were mainly regulated by root and microbial biomass. Moreover, the contribution of microbial-derived C dominated by fungal residues to rhizosphere SOC at each soil depth (more than 62%) was much higher than that of plant-derived C (less than 6%), implying that the soil microbial C pump was intensely stimulated in the rhizosphere.ConclusionsThese results indicated that microbial-derived C was the main contributor of rhizosphere SOC at various depths in the upper mineral soil. Our findings provide direct experimental evidence for assessing the dominant contribution of microbial- or plant-derived C to SOC in the soil profile from the perspective of the rhizosphere.

MACROALGAS ADERIDAS EM RIZÓFOROS DE Rizophora mangle L. EM BOA VIAGEM-SÃO JOSÉ DE RIBAMAR-MARANHÃO

Esta abordagem teve como objetivo analisar as comunidades de macroalgas aderidas em rizóforos de Rizophora mangle L. na praia de Boa Viagem, São José de Ribamar-Maranhão como parâmetro para compreender melhor os diferentes níveis de variação observados no “Bostrychietum” de diferentes áreas de manguezal nas duas baías que compõem o Golfão Maranhense. Foram traçados 12 transectos de linha de novembro de 2018 a maio de 2019. Foram analisados 108 rizóforos englobados pelos transectos ao longo das coletas. Foram registrados os valores de O2 dissolvido, temperatura da água, pH e salinidade, bem como foram considerados os valores de precipitação disponibilizados por órgão oficial. 17 taxa infragenéricos (06 Chlorophyta e 11 Rhodophyta) foram identificados. Observou-se um crescimento tanto na biomassa total quanto na biomassa das espécies ao longo das coletas. Não foi observado nenhum padrão determinante de distribuição vertical das macroalgas. Os valores de precipitação apresentaram uma correlação positiva com os valores de biomassa algácea total. ABSTRACTThis survey aimed to assess macroalgae community attached to rhizophores of Rizophora. mangle L. in Boa Viagem beach, São José de Ribamar, Maranhão, as a parameter to a better understand of the diff erent levels of variation observed inside “Bostrychietum” from diff erent areas of mangroves in the two bays that integrate Golfão Maranhense. 12 line transects were performed from november/2018 to may/2019. 108 rhizophores selected randomly along the transects were analised. Values of dissolved O๗, water temperature, pH and salinity were registered as well as precipitation levels, provided by offi cial department, were also considered. 17 infrageneric taxa were identifi ed (06 Chlorophyta and 11 Rhodophyta). It has been observed an increase in total biomass, as well as individual biomass species along the time of sampling. Vertical distribution pattern were not observed. Precipitation levels correlated positively to total macroalgae biomass.Keywords: Algae; Mangrove; “Bostrychietum”.

Vertical distribution pattern of naidids in granular activated carbon filters and potential technology to control their penetration risk

Aquatic worms propagated in granular activated carbon (GAC) filter has become a troublesome problem for drinking water supply. This study investigated the vertical distribution patterns of naidids in GAC filter beds and assessed the effect of an additional sand bed, located below the GAC bed, in preventing naidids from being present in effluent. The results indicated that the vertical distribution data of naidids in the GAC filter bed were well fitted by a Gaussian distribution, and the location of peak population density was mainly affected by downward flow. Backwashing experiments revealed that additional pressure air scouring shifted the distribution pattern of naidids in the GAC filter bed, resulting in a significant enhancement in naidid removal efficiency. Additionally, the addition of a sand bed exhibited pronounced interception and inactivation effects on naidids, suggesting that it may be a very promising technology for preventing naidids propagated in GAC filters from being present in the effluent.