Changing temperature response of respiration turns boreal forest from carbon sink into carbon source

2016 ◽  
Vol 223 ◽  
pp. 30-38 ◽  
Author(s):  
David Hadden ◽  
Achim Grelle
Keyword(s):  
Carbon Source ◽  
Boreal Forest ◽  
Carbon Sink ◽  
Temperature Response

A review of exotic earthworm observations in the Canadian boreal forest and taiga zones

2022 ◽  
Author(s):  
Jean-David Moore ◽  
Rock Ouimet ◽  
John W. Reynolds
Keyword(s):  
Carbon Source ◽  
Boreal Forest ◽  
Boreal Forests ◽  
Carbon Sink ◽  
Acid Soils ◽  
Taiga Zone ◽  
Earthworm Species ◽  
Exotic Earthworms ◽  
Harsh Climate ◽  
Canadian Boreal Forest

In the last decades, concerns have emerged that boreal forests could convert from a carbon sink to a carbon source, thus accentuating climate change. Although forest fire is generally mentioned as the main factor that could cause the boreal forest to transition to a carbon source, other factors, such as exotic earthworm activity, could also play an important role. Invasive exotic earthworms can also affect nutrient cycling, biodiversity and forest dynamics. In this context, a better knowledge of the distribution of exotic earthworms can help understand the likely changes in the ecosystems that they have colonized. Here we report the results of an exhaustive literature review of the presence of exotic earthworms in the Canadian boreal forest and taiga zones. We identified 230 sectors containing 14 earthworm species (11 exotic, 2 native and 1 putative native) in 6 provinces and 3 territories across Canada’s boreal forest and taiga zone. We also report 23 as-yet unpublished observations from the province of Quebec. We note the presence of earthworms in environments (acid soils, harsh climate) that were historically considered inadequate for their survival. This suggests that the portion of Canada’s boreal forests suitable for their presence or colonization is larger than what was previously believed. This study represents the first compilation of exotic earthworm presence in this large northern area. Factors that could affect their distribution and potential effects on boreal ecosystems are also discussed. Globally, several earthworm species seem to be overcoming the previously assumed limitation by temperature and pH.

scholarly journals Different climate sensitivity for radial growth, but uniform for tree-ring stable isotopes along an aridity gradient in Polylepis tarapacana, the world’s highest elevation tree-species

2021 ◽  
Author(s):  
Milagros Rodriguez-Caton ◽  
Laia Andreu-Hayles ◽  
Mariano S Morales ◽  
Valérie Daux ◽  
Duncan A Christie ◽  
...  
Keyword(s):  
Stable Isotopes ◽  
Carbon Source ◽  
Tree Ring ◽  
Tree Growth ◽  
Carbon Sink ◽  
Growing Season ◽  
Wood Formation ◽  
Aridity Gradient ◽  
Leaf Level ◽  
Δ13c And Δ18o

Abstract Tree growth is generally considered to be temperature-limited at upper elevation treelines. Yet, climate factors controlling tree growth at semiarid treelines are poorly understood. We explored the influence of climate on stem growth and stable isotopes for Polyepis tarapacana, the world’s highest elevation tree-species found only in the South American Altiplano. We developed tree-ring width index (RWI), oxygen (δ18O) and carbon (δ13C) chronologies for the last 60 years at four P. tarapacana stands located above 4,400 meters in elevation, along a 500-km latitude-aridity gradient. Total annual precipitation decreased from 300 to 200 mm from the northern to the southern sites. We used RWI as a proxy of wood formation (carbon sink) and isotopic tree-ring signatures as proxies of leaf-level gas exchange processes (carbon source). We found distinct climatic conditions regulating carbon-sink processes along the gradient. Current-growing season temperature regulated RWI at wetter-northern sites, while prior-growing season precipitation determined RWI at arid-southern sites. This suggests that the relative importance of temperature to precipitation in regulating tree growth is driven by site-water availability. In contrast, warm and dry growing-seasons resulted in enriched tree-ring δ13C and δ18O at all study sites, suggesting that similar climate conditions control carbon-source processes. Site-level δ13C and δ18O chronologies were significantly and positively related at all sites, with the strongest relationships among the southern-drier stands. This indicates an overall regulation of intercellular carbon dioxide via stomatal conductance for the entire P. tarapacana network, with greater stomatal control when aridity increases. The manuscript also highlights a coupling and decoupling of physiological processes at leaf level versus wood formation depending on their respectively uniform and distinct sensitivity to climate. This study contributes to better understand and predict the response of high-elevation Polylepis woodlands to rapid climate changes and projected drying in the Altiplano.

The relative importance of environmental factors on the interannual variability of carbon fluxes in the boreal forest

2020 ◽  
Author(s):  
Mariam El-Amine ◽  
Alexandre Roy ◽  
Pierre Legendre ◽  
Oliver Sonnentag
Keyword(s):  
Environmental Factors ◽  
Boreal Forest ◽  
Vegetation Index ◽  
Normalized Difference Vegetation Index ◽  
Carbon Sink ◽  
Growing Season ◽  
Carbon Uptake ◽  
Net Ecosystem Productivity ◽  
Ecosystem Productivity ◽  
Environmental Controls

<p>As climate change will cause a more pronounced rise of air temperature in northern high latitudes than in other parts of the world, it is expected that the strength of the boreal forest carbon sink will be altered. To better understand and quantify these changes, we studied the influence of different environmental controls (e.g., air and soil temperatures, soil water content, photosynthetically active radiation, normalized difference vegetation index) on the timing of the start and end of the boreal forest growing season and the net carbon uptake period in Canada. The influence of these factors on the growing season carbon exchanges between the atmosphere and the boreal forest were also evaluated. There is a need to improve the understanding of the role of the length of the growing season and the net carbon uptake period on the strength of the boreal forest carbon sink, as an extension of these periods might not necessarily result in a stronger carbon sink if other environmental factors are not optimal for carbon sequestration or enhance respiration.</p><p>Here, we used 31 site-years of observation over three Canadian boreal forest stands: Eastern, Northern and Southern Old Black Spruce in Québec, Manitoba and Saskatchewan, respectively. Redundancy analyses were used to highlight the environmental controls that correlate the most with the annual net ecosystem productivity and the start and end of the growing season and the net carbon uptake period. Preliminary results show that the timing at which the air temperature becomes positive correlates the most strongly with the start of the net carbon uptake period (r = 0.70, p < 0.001) and the start of the growing season (r = 0.55, p < 0.01). Although the increase of the normalized difference vegetation index also correlates with the start of these periods, a thorough examination of this result shows that the latter happens well before the former. No dependency between any environmental control and the end of the net carbon uptake period was identified. Also, the annual net ecosystem productivity is highly correlated with the length of the net carbon uptake period (r = 0.54, p < 0.01). Other environmental controls such as annual precipitations, the mean annual soil temperature or the maximum yearly normalized difference vegetation index have a smaller impact on the annual net ecosystem productivity. By extending the dataset to include forest stands that represent a wider climate and permafrost variability, we will examine the generalizability of these results.</p>

Study on Ecological Carbon Sink Regionalization of Land Use in Shenzhen City

2013 ◽  
Vol 726-731 ◽  
pp. 4730-4737
Author(s):  
Kei Mei Hu ◽  
Wei Ling Liu ◽  
Jing Hai Zhu ◽  
Lin Wang ◽  
Lin Bo Zhang ◽  
...  
Keyword(s):  
Land Use ◽  
Carbon Source ◽  
Greenhouse Gas Emission ◽  
Carbon Sink ◽  
Carbon Sources ◽  
Urban Land ◽  
Urban Land Use ◽  
Medium Carbon ◽  
Source Regions ◽  
Shenzhen City

This paper is to propose a method of ecological carbon sink regionalization in the view of GHG (greenhouse gas) emission reduction, which could provide scientific theory basis for development and utilization of urban land resources, ecological environment construction, biodiversity conservation, the industry layout and formulation of the regional sustainable development strategy. Based on the existing researches foundation, this study takes Shenzhen as a typical case to put forward a method for carbon sink regionalization of urban land use with further quantitative evaluation of ecosystem carbon storage (density), carbon sources/sinks function and carbon sink potential of Shenzhen city. The results show that: Shenzhen ecological carbon sink is regionalized into six categories 55 regions, including 15 intensive carbon sink regions, 17 medium carbon sink regions, 10 weak carbon sink regions, 4 carbon neutral regions, 5 medium carbon source regions and 4 intensive carbon source regions.

scholarly journals Multi-year CO<sub>2</sub> budgets in South African semi-arid Karoo ecosystems under different grazing intensities

2020 ◽  
Author(s):  
Oksana Rybchak ◽  
Justin du Toit ◽  
Jean-Pierre Delorme ◽  
Jens-Kristian Jüdt ◽  
Kanisios Mukwashi ◽  
...  
Keyword(s):  
Carbon Sequestration ◽  
Carbon Source ◽  
South African ◽  
Water Availability ◽  
Carbon Sink ◽  
Grazing Intensity ◽  
Livestock Grazing ◽  
Carbon Uptake ◽  
The Past ◽  
Semi Arid

Abstract. Climatic and land management factors, such as water availability and grazing intensity, play an important role in seasonal and annual variability of the ecosystem–atmosphere exchange of CO2 in semi-arid ecosystems. However, the semi-arid South African ecosystems have been poorly studied. Four years of measurements (November 2015–October 2019) were collected and analysed from two eddy covariance towers near Middelburg in the Karoo, Eastern Cape, South Africa. We studied the impact of grazing intensity on the CO2 exchange by comparing seasonal and interannual CO2 fluxes for two sites with almost identical climatic conditions but different intensity of current and historical livestock grazing. The first site represents lenient grazing (LG) and the vegetation comprises a diverse balance of dwarf shrubs and grasses, while the second site has been degraded through heavy grazing (HG) in the past but then rested for the past 10 years and mainly consists of unpalatable grasses and ephemeral species. Over the observation period, we found that the LG site was a considerable carbon source (82.11 g C m−2), while the HG site was a slight carbon sink (−36.43 g C m−2). The annual carbon budgets ranged from −90 ± 51 g C m−2 yr−1 to 84 ± 43 g C m−2 yr−1 for the LG site and from −92 ± 66 g C m−2 yr−1 to 59 ± 46 g C m−2 yr−1 for the heavily grazed site over the four years of eddy covariance measurements. The significant variation in carbon sequestration rates between the last two years of measurement was explained by water availability (25 % of the precipitation deficit in 2019 compared to the long-term mean precipitation). This indicates that studied ecosystems can quickly switch from a considerable carbon sink to a considerable carbon source ecosystem. Our study shows that the CO2 dynamics in the Karoo are largely driven by water availability and the current and historical effects of livestock grazing intensity on aboveground biomass (AGB). The higher carbon uptake at the HG site indicates that resting period after overgrazing, together with the transition to unpalatable drought-tolerant grass species, creates conditions that are favourable for carbon sequestration in the Karoo ecosystems, but unproductive as Dorper sheep pasture. Furthermore, we observed a slight decrease in carbon uptake peaks at the HG site in response to resuming continuous grazing (July 2017).

Drought-induced shift from a carbon sink to a carbon source in the grasslands of Inner Mongolia, China

CATENA ◽  
2020 ◽  
Vol 195 ◽  
pp. 104845
Author(s):  
Rui Zhang ◽  
Xueyong Zhao ◽  
Xiaoan Zuo ◽  
A. Allan Degen ◽  
Yulin Li ◽  
...  
Keyword(s):  
Carbon Source ◽  
Inner Mongolia ◽  
Carbon Sink

A new global Gross Primary Production (GPP) dataset based on microwave Vegetation Optical Depth Climate Archive (VODCA)

2020 ◽  
Author(s):  
Benjamin Wild ◽  
Irene Teubner ◽  
Leander Moesinger ◽  
Wouter Dorigo
Keyword(s):  
Carbon Source ◽  
Primary Production ◽  
Optical Depth ◽  
Carbon Sink ◽  
Gross Primary Production ◽  
Operation Time ◽  
Ecosystem Dynamics ◽  
Single Frequency ◽  
Model Input ◽  
Single Sensor

&lt;p&gt;Gross Primary Production (GPP) describes the uptake of C0&lt;sub&gt;2&lt;/sub&gt; by plants through photosynthesis and is essential to monitor and analyze ecosystem dynamics. Teubner et al.&lt;sup&gt;1&lt;/sup&gt; developed a carbon sink-driven approach to estimate GPP on a global scale using Vegetation Optical Depth (VOD), derived from active and passive microwave observations. This allows to analyze GPP variability, complementing existing optical GPP products which are more affected by weather conditions. The short operation time of the individual microwave sensors and the bias between them prohibit analyzing GPP variability. This issue can potentially be overcome by using the Vegetation Optical Depth Climate Archive (VODCA) developed by Moesinger et al.&lt;sup&gt;2&lt;/sup&gt;, which merges multiple VOD products into a single data record. However, the use of a long-running VOD composite for estimating global GPP is challenging because the implications of the VOD aggregation process on the modelling of GPP are difficult to identify a priori.&lt;/p&gt;&lt;p&gt;Here, we present the results of applying the carbon sink-driven GPP estimation approach on the VODCA datasets. As model input for each pixel we used raw VOD from VODCA as well as changes in VOD and median VOD, the latter serves as proxy for vegetation cover. In order to analyze the performance of the carbon sink-driven approach when using VODCA as input, the model is cross-validated against single-sensor (AMSR-E) VOD estimates and commonly used carbon source-driven estimates (MODIS/FLUXCOM). We assessed the ability to model GPP based on single-frequency VODCA (C-, X- and Ku-band) as well as using multiple frequencies as model input.&lt;/p&gt;&lt;p&gt;Overall, the results show that single-band as well as multi-band VODCA performs slightly better in predicting GPP than single-sensor based VOD. Especially in the tropical regions multi-frequency VODCA GPP outperforms single-sensor based estimates. Compared to source-driven approaches, VOD based GPP estimates are higher than FLUXCOM and MODIS GPP. The spatial patterns, however, show good correspondence with the carbon source-driven GPP products, confirming that VODCA can be used to extend the GPP estimates to the past three decades.&lt;/p&gt;&lt;p&gt;&lt;sup&gt;1&lt;/sup&gt;Teubner, I., Forkel, M., Camps-Valls, G., Jung, M., Miralles, Diego, Tramontana, G., van der Schalie, R., Vreugdenhil, M., Moesinger, L., Dorigo, W.:A carbon sink-driven approach to estimate gross primary production from microwave satellite observations, 2019. Remote Sensing of Environment. 229. 100-113. 10.1016/j.rse.2019.04.022.&lt;/p&gt;&lt;p&gt;&lt;sup&gt;2&lt;/sup&gt;Moesinger, L., Dorigo, W., de Jeu, R., van der Schalie, R., Scanlon, T., Teubner, I., and Forkel, M.: The Global Long-term Microwave Vegetation Optical Depth Climate Archive VODCA, Earth Syst. Sci. Data Discuss., https://doi.org/10.5194/essd-2019-42, in review, 2019.&lt;/p&gt;

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