22 resultados para humification degree
Resumo:
Permafrost dynamics play an important role in high-latitude peatland carbon balance and are key to understanding the future response of soil carbon stocks. Permafrost aggradation can control the magnitude of the carbon feedback in peatlands through effects on peat properties. We compiled peatland plant macrofossil records for the northern permafrost zone (515 cores from 280 sites) and classified samples by vegetation type and environmental class (fen, bog, tundra and boreal permafrost, thawed permafrost). We examined differences in peat properties (bulk density, carbon (C), nitrogen (N) and organic matter content, C/N ratio) and C accumulation rates among vegetation types and environmental classes.
Resumo:
In addition to enhance agricultural productivity, synthetic nitrogen (N) and phosphorous (P) fertilizer application in croplands dramatically altered global nutrient budget, water quality, greenhouse gas balance, and their feedbacks to the climate system. However, due to the lack of geospatial fertilizer input data, current Earth system/land surface modeling studies have to ignore or use over-simplified data (e.g., static, spatially uniform fertilizer use) to characterize agricultural N and P input over decadal or century-long period. We therefore develop a global time-series gridded data of annual synthetic N and P fertilizer use rate in croplands, matched with HYDE 3,2 historical land use maps, at a resolution of 0.5º latitude by longitude during 1900-2013. Our data indicate N and P fertilizer use rates increased by approximately 8 times and 3 times, respectively, since the year 1961, when IFA (International Fertilizer Industry Association) and FAO (Food and Agricultural Organization) survey of country-level fertilizer input were available. Considering cropland expansion, increase of total fertilizer consumption amount is even larger. Hotspots of agricultural N fertilizer use shifted from the U.S. and Western Europe in the 1960s to East Asia in the early 21st century. P fertilizer input show the similar pattern with additional hotspot in Brazil. We find a global increase of fertilizer N/P ratio by 0.8 g N/g P per decade (p< 0.05) during 1961-2013, which may have important global implication of human impacts on agroecosystem functions in the long run. Our data can serve as one of critical input drivers for regional and global assessment on agricultural productivity, crop yield, agriculture-derived greenhouse gas balance, global nutrient budget, land-to-aquatic nutrient loss, and ecosystem feedback to the climate system.
Resumo:
Taxonomic composition and distribution of planktonic foraminifera are studied in section of Core GC-11 penetrated through Upper Quaternary sediments of the Bowers Ridge western slope, south Bering Sea. It is shown that structure of foraminiferal assemblage and productivity varied substantially during the last 32000 calendar years in response to changes in surface water temperatures and water mass circulation in the North Pacific including the Bering Sea. Productivity was maximal during the deglaciation epoch, being notably lower in Holocene and minimal at glaciation time.
Resumo:
This datafile presents chemical and physical as well as age dating information from the Store Mosse peat bog in southern Sweden. This record dates back to 8900 cal yr BP. The aim of the research was to reconstruct mineral dust deposition over time. As such we have only presented the lithogenic element data (Al, Ga, Rb, Sc, Ti, Y, Zr, Th and the REE) as the sample preparation method was tailored to these. This data is supported by parameters describing the deposit including bulk density, humification, ash content and net peat accumulation rates.