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1,140 results on '"Butterbach-Bahl, Klaus"'

16. Models in country scale carbon accounting of forest soils

Author

Peltoniemi, Mikko, Thürig, Esther, Ogle, Stephen, Palosuo, Taru, Schrumpf, Marion, Wutzler, Thomas, Butterbach-Bahl, Klaus, Chertov, Oleg, Komarov, Alexander, Mikhailov, Aleksey, Gärdenäs, Annemieke, Perry, Charles, Liski, Jari, Smith, Pete, and Mäkipää, Raisa

Subjects
Forestry, SD1-669.5
Abstract

Countries need to assess changes in the carbon stocks of forest soils as a part of national greenhouse gas (GHG) inventories under the United Nations Framework Convention on Climate Change (UNFCCC) and the Kyoto Protocol (KP). Since measuring these changes is expensive, it is likely that many countries will use alternative methods to prepare these estimates. We reviewed seven well-known soil carbon models from the point of view of preparing country-scale soil C change estimates. We first introduced the models and explained how they incorporated the most important input variables. Second, we evaluated their applicability at regional scale considering commonly available data sources. Third, we compiled references to data that exist for evaluation of model performance in forest soils. A range of process-based soil carbon models differing in input data requirements exist, allowing some flexibility to forest soil C accounting. Simple models may be the only reasonable option to estimate soil C changes if available resources are limited. More complex models may be used as integral parts of sophisticated inventories assimilating several data sources. Currently, measurement data for model evaluation are common for agricultural soils, but less data have been collected in forest soils. Definitions of model and measured soil pools often differ, ancillary model inputs require scaling of data, and soil C measurements are uncertain. These issues complicate the preparation of model estimates and their evaluation with empirical data, at large scale. Assessment of uncertainties that accounts for the effect of model choice is important part of inventories estimating large-scale soil C changes. Joint development of models and large-scale soil measurement campaigns could reduce the inconsistencies between models and empirical data, and eventually also the uncertainties of model predictions.

Published
2007
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33. Suppression of Nitrogen Deposition on Global Forest Soil CH4 Uptake Depends on Nitrogen Status.

Author

Cen, Xiaoyu, He, Nianpeng, Li, Mingxu, Xu, Li, Yu, Xueying, Cai, Weixiang, Li, Xin, and Butterbach‐Bahl, Klaus

Subjects
FOREST soils, ATMOSPHERIC nitrogen, TEMPERATE forests, TROPICAL forests, GEOLOGIC hot spots, TAIGAS
Abstract

Methane (CH4) is the second most important atmospheric greenhouse gas (GHG) and forest soils are a significant sink for atmospheric CH4. Uptake of CH4 by global forest soils is affected by nitrogen (N) deposition; clarifying the effect of N deposition helps to reduce uncertainties of the global CH4 budget. However, it remains an unsolved puzzle why N input stimulates soil CH4 uptake in some forests while suppressing it in others. Combining previous findings and data from N addition experiments conducted in global forests, we proposed and tested a "stimulating‐suppressing‐weakened effect" ("three stages") hypothesis on the changing responses of soil CH4 flux (RCH4) to N input. Specifically, we calculated the response factors (f) of RCH4 to N input for N‐limited and N‐saturated forests across biomes; the phased changes in f values supported our hypothesis. We also estimated the global forest soil CH4 uptake budget to be approximately 11.2 Tg yr−1. CH4 uptake hotspots were predominantly located in temperate forests. Furthermore, we quantified that the current level of N deposition reduced global forest soil CH4 uptake by ∼3%. This suppression effect was more pronounced in temperate forests than in tropical or boreal forests, likely due to differences in N status. The proposed "three stages" hypothesis in this study generalizes the diverse effects of N input on RCH4, which could help improve experimental design. Additionally, our findings imply that by regulating N pollution and reducing N deposition, soil CH4 uptake can be significantly increased in the N‐saturated forests in tropical and temperate biomes. Plain Language Summary: Methane is an important greenhouse gas. Forest soils can absorb methane from the atmosphere and mitigate its warming effect. Meanwhile, forests suffer from high atmospheric nitrogen deposition, yet the effect of nitrogen on the methane uptake by forest soils remains unclear. Using data from global nitrogen addition experiments, we validated a "stimulating‐suppressing‐weakened effect" ("three stages") hypothesis, which could explain the diverse responses of soil methane flux to nitrogen input observed in different forests. On this basis, we quantified that nitrogen deposition decreased global forest soil methane uptake by approximately 3%. Our findings also imply that by regulating nitrogen pollution, soil methane uptake can be significantly increased in the nitrogen‐saturated forests in tropical and temperate biomes, potentially mitigate global warming. Key Points: A "three stage hypothesis" was developed to generalize the diverse responses of forest soil CH4 flux to N inputCH4 uptake by global forest soils was estimated to be 11.2 Tg yr−1, with N deposition suppressing ∼3% of this uptakeEffective regulation to reduce N deposition would promote CH4 uptake by N‐saturated forests and mitigate global warming [ABSTRACT FROM AUTHOR]

Published
2024
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50. Alder expansion stimulates nitrogen oxide (NOx) emissions from southern Eurasian permafrost peatlands.

Author

Liu, Chunyan, Yue, Hongyu, Zhang, Wei, Yao, Zhisheng, Pan, Yuepeng, Wang, Xianwei, Song, Changchun, Butterbach‐Bahl, Klaus, and Dannenmann, Michael

Subjects
SOIL mineralogy, PERMAFROST, NITROGEN oxides, ALDER, RADIATIVE forcing
Abstract

Nitrogen oxides (NOx) play an important role for atmospheric chemistry and radiative forcing. However, NOx emissions from the vast northern circumpolar permafrost regions have not been studied in situ due to limitations of measurement techniques. Our goals were to validate the offline analytical technique, and based on this, to widely quantify in situ NOx emissions from peatlands in the southern Eurasian permafrost region. To this end, we conducted a comparison of online and offline flux measurements in 2018 and 2019 using the synthetic air flushing, steady‐state opaque chamber method. With differences in annual average and cumulative fluxes less than 0.1 μg N m−2 h−1 and 0.01 kg N ha−1 year−1, the online and offline fluxes were in good agreement, demonstrating the feasibility of conducting offline measurements in remote regions without power supply. The flux measurements over 2 years showed obvious NOx emissions of 0.05–0.14 and 0.13–0.30 kg N ha−1 year−1 in the hollow and hummock microtopography of permafrost peatlands, respectively. The rapid expansion of alder (Alnus sibirica) in the peatlands induced by permafrost degradation significantly increased soil mineral N contents and NOx emissions depending on the age of alder (0.64–1.74 and 1.44–2.20 kg N ha−1 year−1 from the alder forests with tree ages of 1–10 years and 11–20 years, respectively). Alder expansion also intensively altered the thermal state of permafrost including the sharp increases of soil temperatures during the non‐growing season from October to April and active layer thickness. This study provides the first in situ evidences of NOx emissions from the northern circumpolar permafrost regions and uncovers the well‐documented expansion of alders can substantially stimulate NOx emissions and thus, significantly affect air quality, radiative forcing, and ecosystem productivity in the pristine regions. [ABSTRACT FROM AUTHOR]

Published
2024
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