Long‐term litter removal rather than litter addition enhances ecosystem carbon sequestration in a temperate steppe

Abstract Tree stem CO2 efflux is an important component of ecosystem carbon fluxes and has been the focus of many studies. While CO2 efflux can easily be measured, a growing number of studies have shown that it is not identical with actual in situ respiration. Complementing measurements of CO2 flux with simultaneous measurements of O2 flux provides an additional proxy for respiration, and the combination of both fluxes can potentially help getting closer to actual measures of respiratory fluxes. To date, however, the technical challenge to measure relatively small changes in O2 concentration against its high atmospheric background has prevented routine O2 measurements in field applications. Here we present a new and low-cost field-tested device for autonomous real-time and quasi-continuous long-term measurements of stem respiration by combining CO2 (NDIR based) and O2 (quenching based) sensors in a tree stem chamber. Our device operates as a cyclic closed system and measures changes in both CO2 and O2 concentration within the chamber over time. The device is battery-powered with a > 1 week power independence and data acquisition is conveniently achieved by an internal logger. Results from both field and laboratory tests document that our sensors provide reproducible measurements of CO2 and O2 exchange fluxes under varying environmental conditions.

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The impact of porosity on organic matter cycling in a two-dimensional porous medium

10.5194/egusphere-egu21-9432 ◽

2021 ◽

Author(s):

Hanbang Zou ◽

Pelle Ohlsson ◽

Edith Hammer

Keyword(s):

Porous Medium ◽

Organic Matter ◽

Carbon Sequestration ◽

Soil Carbon ◽

Pore Network ◽

Pore Scale ◽

Decomposition Of Organic Matter ◽

Organic Matter Cycling ◽

The Impact

Carbon sequestration has been a popular research topic in recent years as the rapid elevation of carbon emission has significantly impacted our climate. Apart from carbon capture and storage in e.g. oil reservoirs, soil carbon sequestration offers a long term and safe solution for the environment and human beings. The net soil carbon budget is determined by the balance between terrestrial ecosystem sink and sources of respiration to atmospheric carbon dioxide. Carbon can be long term stored as organic matters in the soil whereas it can be released from the decomposition of organic matter. The complex pore networks in the soil are believed to be able to "protect" microbial-derived organic matter from decomposition. Therefore, it is important to understand how soil structure impacts organic matter cycling at the pore scale. However, there are limited experimental studies on understanding the mechanism of physical stabilization of organic matter. Hence, my project plan is to create a heterogeneous microfluidic porous microenvironment to mimic the complex soil pore network which allows us to investigate the ability of organisms to access spaces starting from an initial ecophysiological precondition to changes of spatial accessibility mediated by interactions with the microbial community.Microfluidics is a powerful tool that enables studies of fundamental physics, rapid measurements and real-time visualisation in a complex spatial microstructure that can be designed and controlled. Many complex processes can now be visualized enabled by the development of microfluidics and photolithography, such as microbial dynamics in pore-scale soil systems and pore network modification mimicking different soil environments &#8211; earlier considered impossible to achieve experimentally. The microfluidic channel used in this project contains a random distribution of cylindrical pillars of different sizes so as to mimic the variations found in real soil. The randomness in the design creates various spatial availability for microbes (preferential flow paths with dead-end or continuous flow) as an invasion of liquids proceeds into the pore with the lowest capillary entry pressure. In order to study the impact of different porosity in isolation of varying heterogeneity of the porous medium, different pore size chips that use the same randomly generated pore network is created. Those chips have the same location of the pillars, but the relative size of each pillar is scaled. The experiments will be carried out using sterile cultures of fluorescent bacteria, fungi and protists, synthetic communities of combinations of these, or a whole soil community inoculum. We will quantify the consumption of organic matter from the different areas via fluorescent substrates, and the bio-/necromass produced. We hypothesise that lower porosity will reduce the net decomposition of organic matter as the narrower pore throat limits the access, and that net decomposition rate at the main preferential path will be higher than inside branches

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Green manure: Alternative to carbon sequestration in a Typic Ustipsamment under semiarid conditions

Spanish Journal of Soil Science ◽

10.3232/sjss.2018.v8.n3.01 ◽

2018 ◽

Vol 8 ◽

Author(s):

Nelson Virgilio Piraneque Gambasica ◽

Sonia Esperanza Aguirre Forero ◽

Adriano Reis Lucheta

Keyword(s):

Carbon Sequestration ◽

Cover Crops ◽

Green Manure ◽

Block Design ◽

Climatic Variability ◽

Plant Cover ◽

Caribbean Region ◽

Full Potential ◽

Semiarid Conditions

Vegetative soil cover mitigates climatic variability and enhances the balance between mineralization and humification processes. Under aerobic conditions, most of the carbon that enters the soil is labile, but a small fraction (1%) is humified and stable, contributing to the soil carbon reserve; therefore, it is important to assess the carbon content captured after green manure cultivation and decomposition. During two consecutive semesters, July to December 2016 and January to June 2017, green manure plots (Zea mays L., Andropogon sorghum subsp. sudanensis and Crotalaria longirostrata) were cultivated individually, in a consortium or amended with palm oil agro-industrial biosolids in a randomized complete block design with 12 treatments. Once decomposed, the different carbon fractions (organic, oxidizable, non-oxidizable, removable and total) were determined. The results showed high total and organic carbon contents under the sorghum treatment, at 30 and 28 Mg ha-1, respectively, followed by those under the fallow + biosolid treatment, at 29.8 Mg ha-1 and 27.5 Mg ha-1, respectively. Despite the short experiment duration and the possible contributions of previous management on recalcitrant carbon soil stocks, these findings suggest the importance of maintaining plant cover and utilizing green manure in the Colombian Caribbean region. Long-term experiments may be conducted to confirm the full potential of cover crops on carbon sequestration under tropical semiarid conditions.

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Additional Benefits of Community Managed Forest: A Case Study of Champadevi Community Forest

Nepal Journal of Science and Technology ◽

10.3126/njst.v12i0.6490 ◽

2012 ◽

Vol 12 ◽

pp. 127-132

Author(s):

Bhanu B Panthi

Keyword(s):

Carbon Sequestration ◽

Significant Contribution ◽

Research Area ◽

Environmental Benefits ◽

Managed Forests ◽

Managed Forest ◽

Community Based

This research attempts to identify the existing condition of the community managed forest based on the assumption that it will serve as a proxy for the condition of other forests in the mid hills region of Nepal. The research area has an atypical variation in altitude and diverse pattern of vegetation. This study mainly focuses on estimating carbon content in the forest and identifying the species that has more carbon storage capacity. The research signifies the role of forests in mitigation of ‘Global warming’ and ‘Climate change’ by storing carbon in tree biomass. These types of community based forest management programs are significant for their additional carbon sequestration through the avoidance of deforestation and degradation. The carbon sequestration have a significant contribution to environmental benefits, any shrinkage of forests have an enormous impact on CO2 emission with long term consequences. Thus, the development and expansion of community managed forests provide many benefits to the adjacent community and globally at large.DOI: http://dx.doi.org/10.3126/njst.v12i0.6490 Nepal Journal of Science and Technology 12 (2011) 127-32

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