Longitudinal and seasonal variation of stream N uptake in an urbanizing watershed: effect of organic matter, stream size, transient storage and debris dams

Abstract. The Whittard Canyon is a branching submarine canyon on the Celtic continental margin, which may act as a conduit for sediment and organic matter (OM) transport from the European continental slope to the abyssal sea floor. In situ stable-isotope labelling experiments were conducted in the eastern and western branches of the Whittard Canyon, testing short-term (3–7 days) responses of sediment communities to deposition of nitrogen-rich marine (Thalassiosira weissflogii) and nitrogen-poor terrigenous (Triticum aestivum) phytodetritus. 13C and 15N labels were traced into faunal biomass and bulk sediments, and the 13C label traced into bacterial polar lipid fatty acids (PLFAs). Isotopic labels penetrated to 5 cm sediment depth, with no differences between stations or experimental treatments (substrate or time). Macrofaunal assemblage structure differed between the eastern and western canyon branches. Following deposition of marine phytodetritus, no changes in macrofaunal feeding activity were observed between the eastern and western branches, with little change between 3 and 7 days. Macrofaunal C and N uptake was substantially lower following deposition of terrigenous phytodetritus with feeding activity governed by a strong N demand. Bacterial C uptake was greatest in the western branch of the Whittard Canyon, but feeding activity decreased between 3 and 7 days. Bacterial processing of marine and terrigenous OM were similar to the macrofauna in surficial (0–1 cm) sediments. However, in deeper sediments bacteria utilised greater proportions of terrigenous OM. Bacterial biomass decreased following phytodetritus deposition and was negatively correlated to macrofaunal feeding activity. Consequently, this study suggests that macrofaunal–bacterial interactions influence benthic C cycling in the Whittard Canyon, resulting in differential fates for marine and terrigenous OM.

Download Full-text

An analysis of some pilot fertilizer experiments on paddy.

Netherlands Journal of Agricultural Science ◽

10.18174/njas.v5i4.17730 ◽

1957 ◽

Vol 5 (4) ◽

pp. 284-289

Author(s):

C.T. De Wit

Keyword(s):

Organic Matter ◽

N Uptake ◽

N Recovery ◽

P Placement

Data from 25 experiments in Burma in 1954-55 are discussed. The soils contain 5-15% clay, 10-30% silt and 0.5-1.5% organic matter and pH (dry samples) ranges from 5.0 to 7.5. Yields increase only 11.7 kg per kg of N applied. Placement in rows below the aerobic mud layer would probably double N recovery at rates of 20 kg/ha N. The estimated response to P placement (5.4 kg per kg applied P) is uneconomic. With applications of 22.4 kg/ha N, but not with 44.8 kg/ha, N uptake was increased by applying P. (Abstract retrieved from CAB Abstracts by CABI’s permission)

Download Full-text

Seasonal variation and ecological risk assessment of dissolved organic matter in a peri-urban critical zone observatory watershed

The Science of The Total Environment ◽

10.1016/j.scitotenv.2019.136093 ◽

2020 ◽

Vol 707 ◽

pp. 136093 ◽

Cited By ~ 5

Author(s):

Jianfeng Tang ◽

Wendong Wang ◽

Lei Yang ◽

Qianlinglin Qiu ◽

Meixia Lin ◽

...

Keyword(s):

Risk Assessment ◽

Organic Matter ◽

Seasonal Variation ◽

Dissolved Organic Matter ◽

Ecological Risk ◽

Ecological Risk Assessment ◽

Critical Zone ◽

Critical Zone Observatory

Download Full-text

Seasonal Variation in Flocculation Potential of River Water: Roles of the Organic Matter Pool

Water ◽

10.3390/w9050335 ◽

2017 ◽

Vol 9 (5) ◽

pp. 335 ◽

Cited By ~ 6

Author(s):

Byung Lee ◽

Jin Hur ◽

Erik Toorman

Keyword(s):

Organic Matter ◽

Seasonal Variation ◽

River Water ◽

Organic Matter Pool

Download Full-text

Fast response of fungal and prokaryotic communities to climate change manipulation in two contrasting tundra soils

Environmental Microbiome ◽

10.1186/s40793-019-0344-4 ◽

2019 ◽

Vol 14 (1) ◽

Author(s):

Jana Voříšková ◽

Bo Elberling ◽

Anders Priemé

Keyword(s):

Organic Matter ◽

Seasonal Variation ◽

Snow Cover ◽

Bacterial Communities ◽

Winter Precipitation ◽

Fungal Communities ◽

Tundra Soils ◽

Short Term ◽

Fungal Community Composition ◽

Climate Manipulation

Abstract Background Climate models predict substantial changes in temperature and precipitation patterns across Arctic regions, including increased winter precipitation as snow in the near future. Soil microorganisms are considered key players in organic matter decomposition and regulation of biogeochemical cycles. However, current knowledge regarding their response to future climate changes is limited. Here, we explore the short-term effect of increased snow cover on soil fungal, bacterial and archaeal communities in two tundra sites with contrasting water regimes in Greenland. In order to assess seasonal variation of microbial communities, we collected soil samples four times during the plant-growing season. Results The analysis revealed that soil microbial communities from two tundra sites differed from each other due to contrasting soil chemical properties. Fungal communities showed higher richness at the dry site whereas richness of prokaryotes was higher at the wet tundra site. We demonstrated that fungal and bacterial communities at both sites were significantly affected by short-term increased snow cover manipulation. Our results showed that fungal community composition was more affected by deeper snow cover compared to prokaryotes. The fungal communities showed changes in both taxonomic and ecological groups in response to climate manipulation. However, the changes were not pronounced at all sampling times which points to the need of multiple sampling in ecosystems where environmental factors show seasonal variation. Further, we showed that effects of increased snow cover were manifested after snow had melted. Conclusions We demonstrated rapid response of soil fungal and bacterial communities to short-term climate manipulation simulating increased winter precipitation at two tundra sites. In particular, we provide evidence that fungal community composition was more affected by increased snow cover compared to prokaryotes indicating fast adaptability to changing environmental conditions. Since fungi are considered the main decomposers of complex organic matter in terrestrial ecosystems, the stronger response of fungal communities may have implications for organic matter turnover in tundra soils under future climate.

Download Full-text