476 research outputs found
Entwicklung eines integrierten multifunktionalen Fluoreszenzdetektors
Fluoreszenzdetektion hat eine groĂe Bedeutung in biologischen und medizinischen Anwendungen fĂŒr die Analyse verschiedener Farbstoffe und Zellkulturen. Durch Kombination von Fluidik, Optik und Elektronik ist die Realisierung eines kompakten und hochempfindlichen Messsystems möglich, welches vorteilhaft bei der Messung von Proben mit kleinen Volumina ist
Permafrost
Permafrost is perennially frozen ground, such as soil, rock, and ice. In permafrost regions, plant and microbial
life persists primarily in the near-surface soil that thaws every summer, called the âactive layerâ (Figure 20). The
cold and wet conditions in many permafrost regions limit decomposition of organic matter. In combination with
soil mixing processes caused by repeated freezing and thawing, this has led to the accumulation of large stocks
of soil organic carbon in the permafrost zone over multi-millennial timescales. As the climate warms, permafrost
carbon could be highly vulnerable to climatic warming.
Permafrost occurs primarily in high latitudes (e.g. Arctic and Antarctic) and at high elevation (e.g. Tibetan
Plateau, Figure 21). The thickness of permafrost varies from less than 1 m (in boreal peatlands) to more than
1 500 m (in Yakutia). The coldest permafrost is found in the Transantarctic Mountains in Antarctica (â36°C)
and in northern Canada for the Northern Hemisphere (-15°C; Obu et al., 2019, 2020). In contrast, some of
the warmest permafrost occurs in peatlands in areas with mean air temperatures above 0°C. Here permafrost
exists because thick peat layers insulate the ground during the summer. Most of the permafrost existing today
formed during cold glacials (e.g. before 12 000 years ago) and has persisted through warmer interglacials. Some
shallow permafrost (max 30â70m depth) formed during the Holocene (past 5000 years) and some even during
the Little Ice Age from 400â150 years ago.
There are few extensive regions suitable for row crop agriculture in the permafrost zone. Additionally, in areas
where large-scale agriculture has been conducted, ground destabilization has been common. Surface
disturbance such as plowing or trampling of vegetation can alter the thermal regime of the soil, potentially
triggering surface subsidence or abrupt collapse. This may influence soil hydrology, nutrient cycling, and
organic matter storage. These changes often have acute and negative consequences for continued agricultural
use of such landscapes. Thus, row-crop agriculture could have a negative impact on permafrost (e.g. GrĂŒnzweig
et al., 2014). Conversely, animal husbandry is widespread in the permafrost zone, including horses, cattle, and
reindeer
Decomposability of soil organic matter over time: the Soil Incubation Database (SIDb, version 1.0) and guidance for incubation procedures
The magnitude of carbon (C) loss to the atmosphere via microbial decomposition is a function of the amount of C stored in soils, the quality of the organic matter, and physical, chemical, and biological factors that comprise the environment for decomposition. The decomposability of C is commonly assessed by laboratory soil incubation studies that measure greenhouse gases mineralized from soils under controlled conditions. Here, we introduce the Soil Incubation Database (SIDb) version 1.0, a compilation of time series data from incubations, structured into a new, publicly available, open-access database of C flux (carbon dioxide, CO2, or methane, CH4). In addition, the SIDb project also provides a platform for the development of tools for reading and analysis of incubation data as well as documentation for future use and development. In addition to introducing SIDb, we provide reporting guidance for database entry and the required variables that incubation studies need at minimum to be included in SIDb. A key application of this synthesis effort is to better characterize soil C processes in Earth system models, which will in turn reduce our uncertainty in predicting the response of soil C decomposition to a changing climate. We demonstrate a framework to fit curves to a number of incubation studies from diverse ecosystems, depths, and organic matter content using a built-in model development module that integrates SIDb with the existing SoilR package to estimate soil C pools from time series data. The database will help bridge the gap between point location measurements, which are commonly used in incubation studies, and global remote-sensed data or data products derived from models aimed at assessing global-scale rates of decomposition and C turnover. The SIDb version 1.0 is archived and publicly available at https://doi.org/10.5281/zenodo.3871263 (Sierra et al., 2020), and the database is managed under a version-controlled system and centrally stored in GitHub (https://github.com/SoilBGC-Datashare/sidb, last access: 26 June 2020)
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