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  • 1
    Publication Date: 2022-05-25
    Description: Author Posting. © Ecological Society of America, 2010. This article is posted here by permission of Ecological Society of America for personal use, not for redistribution. The definitive version was published in Ecological Applications 20 (2010): 1569–1582, doi:10.1890/09-0693.1.
    Description: We seek to understand how biophysical factors such as soil temperature (Ts), soil moisture (θ), and gross primary production (GPP) influence CO2 fluxes across terrestrial ecosystems. Recent advancements in automated measurements and remote-sensing approaches have provided time series in which lags and relationships among variables can be explored. The purpose of this study is to present new applications of continuous measurements of soil CO2 efflux (F0) and soil CO2 concentrations measurements. Here we explore how variation in Ts, θ, and GPP (derived from NASA's moderate-resolution imaging spectroradiometer [MODIS]) influence F0 and soil CO2 production (Ps). We focused on seasonal variation and used continuous measurements at a daily timescale across four vegetation types at 13 study sites to quantify: (1) differences in seasonal lags between soil CO2 fluxes and Ts, θ, and GPP and (2) interactions and relationships between CO2 fluxes with Ts, θ, and GPP. Mean annual Ts did not explain annual F0 and Ps among vegetation types, but GPP explained 73% and 30% of the variation, respectively. We found evidence that lags between soil CO2 fluxes and Ts or GPP provide insights into the role of plant phenology and information relevant about possible timing of controls of autotrophic and heterotrophic processes. The influences of biophysical factors that regulate daily F0 and Ps are different among vegetation types, but GPP is a dominant variable for explaining soil CO2 fluxes. The emergence of long-term automated soil CO2 flux measurement networks provides a unique opportunity for extended investigations into F0 and Ps processes in the near future.
    Description: Data collection was possible thanks to NASA, the NSF Center for Embedded Networked Sensing (CCR-0120778), DOE (DE-FG02-03ER63638), CONACyT, UCMEXUS, NSF (EF-0410408), NSF-LTER, KAKENHI (12878089 and 13480150), the Academy of Finland (213093), the Austrian Science Fund (FWF, P18756-B16), the Kearney Foundation, the Canadian Foundation for Climate and Atmospheric Sciences (CFCAS), and the Natural Science and Engineering Research Council of Canada (NSERC). R. Vargas was supported by grant DEB-0639235 during the preparation of this manuscript.
    Keywords: Lags ; Moderate-resolution imaging spectroradiometer (MODIS) ; Photosynthesis ; Soil CO2 efflux ; Soil CO2 production ; Soil CO2 sensors ; Soil respiration
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Format: application/pdf
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  • 2
    Publication Date: 2019-07-13
    Description: Incorporating ecological disturbance into biogeochemical models is critical for estimating current and future carbon stocks and fluxes. In particular, anthropogenic disturbances, such as forest conversion and wood harvest, strongly affect forest carbon dynamics within North America. This paper summarizes recent (2000.2008) rates of extraction, including both conversion and harvest, derived from national forest inventories for North America (the United States, Canada, and Mexico). During the 2000s, 6.1 million ha/yr were affected by harvest, another 1.0 million ha/yr were converted to other land uses through gross deforestation, and 0.4 million ha/yr were degraded. Thus about 1.0% of North America fs forests experienced some form of anthropogenic disturbance each year. However, due to harvest recovery, afforestation, and reforestation, the total forest area on the continent has been roughly stable during the decade. On average, about 110 m3 of roundwood volume was extracted per hectare harvested across the continent. Patterns of extraction vary among the three countries, with U.S. and Canadian activity dominated by partial and clear ]cut harvest, respectively, and activity in Mexico dominated by conversion (deforestation) for agriculture. Temporal trends in harvest and clearing may be affected by economic variables, technology, and forest policy decisions. While overall rates of extraction appear fairly stable in all three countries since the 1980s, harvest within the United States has shifted toward the southern United States and away from the Pacific Northwest.
    Keywords: Geophysics
    Type: GSFC.JA.00336.2012 , Journal of Geophysical Research; 116
    Format: text
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