Satellite Observations of the Tropical Terrestrial Carbon Balance and Interactions with the Water Cycle During the 21st Century

Forest demographic processes - growth, recruitment and mortality - are being altered by global change. The changing balance between growth and mortality strongly influences forest dynamics and the carbon balance. Elevated atmospheric carbon dioxide (eCO2) has been reported to enhance photosynthesis and tree growth rates by increasing both light-use efficiency (LUE) and water-use efficiency (WUE). Tree growth enhancement could be translated into an increase in biomass stocks or could be associated with a reduction in the longevity of trees, thus reducing the ability of forest ecosystems to act as carbon sinks over long timescales. These links between growth and mortality, and the implications for forest stand density and self-thinning relationships are still debated. Scarce empirical evidence exists for how changing drivers affect tree mortality due to existing data and modelling limitations. Understanding the causes of observed mortality trends and the mechanisms underlying these processes is critical for accurate projections of global terrestrial carbon storage and its feedbacks to anthropogenic climate change.Here, we combine a mechanistic model with empirical forest data to better understand the causes of changes in tree mortality and the implications for past and future trends in forest tree density. Specifically, we test the Grow-Fast-Die-Young hypothesis to investigate if a leaf-level CO2 fertilization effect may lead to an increase in the biomass stock in forest stands. We use a novel vegetation demography model (LM3-PPA) which includes vegetation dynamics with biogeochemical processes allowing for explicit representation of individuals and a mechanistic treatment of tree mortality. The key links between leaf-level assimilation and stand dynamics depend on the carbon turnover time. In this sense, we investigate alternative mortality assumptions about the functional dependence of mortality on tree size, tree carbon balance or growth rate. These formulations represent typical approaches to simulate mortality in mechanistic forest models. Model simulations show that increasing photosynthetic LUE leads to higher biomass stocks, with contrasting behavior among mortality assumptions. Empirical data from Swiss forest inventories support the results from the model simulations showing a shift upwards in the self-thinning relationships, with denser stands and bigger trees. This data-supported mortality-modelling helps to identify links between forest responses and environmental changes at the leaf, tree and stand levels and yields new insight into the causes of currently observed terrestrial carbon sinks and future responses.

Download Full-text

Evaluation of Biases in JRA-25/JCDAS Precipitation and Their Impact on the Global Terrestrial Carbon Balance

Journal of Climate ◽

10.1175/2011jcli3918.1 ◽

2011 ◽

Vol 24 (15) ◽

pp. 4109-4125 ◽

Cited By ~ 21

Author(s):

Makoto Saito ◽

Akihiko Ito ◽

Shamil Maksyutov

Keyword(s):

Carbon Cycle ◽

Carbon Balance ◽

Regional Scale ◽

Precipitation Amount ◽

Temporal Variations ◽

Japan Meteorological Agency ◽

Total Biomass ◽

Monthly Precipitation ◽

Precipitation Data ◽

Terrestrial Carbon

Abstract This study evaluates a modeled precipitation field and examines how its bias affects the modeling of the regional and global terrestrial carbon cycle. Spatial and temporal variations in precipitation produced by the Japanese 25-yr reanalysis (JRA-25)/Japan Meteorological Agency (JMA) Climate Data Assimilation System (JCDAS) were compared with two large-scale observation datasets. JRA-25/JCDAS captures the major distribution patterns of annual precipitation and the features of the seasonal cycle. Notable problems include over- and undersimulated areas of precipitation amount in South America, Africa, and Southeast Asia in the 30°N–30°S domain and a large discrepancy in the number of rainfall days. The latter problem was corrected by using a stochastic model based on the probability of the occurrence of dry and wet day series; the monthly precipitation amount was then scaled by the comparison data. Overall, the corrected precipitation performed well in reproducing the spatial distribution of and temporal variations in total precipitation. Both the corrected and original precipitation data were used to simulate regional and global terrestrial carbon cycles using the prognostic biosphere model Vegetation Integrative Simulator for Trace Gases (VISIT). Following bias correction, the model results showed differences in zonal mean photosynthesis uptake and respiration release ranging from −2.0 to +3.3 Pg C yr−1, compared with the original data. The difference in the global terrestrial net carbon exchange rate was 0.3 Pg C yr−1, reflecting the compensation of coincident increases or decreases in carbon sequestration and respiration loss. At the regional scale, the ecosystem carbon cycle and canopy structure, including seasonal variations in autotrophic and heterotrophic respiration and total biomass, were strongly influenced by the input precipitation data. The results highlight the need for precise precipitation data when estimating the global terrestrial carbon balance.

Download Full-text

The impact of the 2009/2010 drought on vegetation growth and terrestrial carbon balance in Southwest China

Agricultural and Forest Meteorology ◽

10.1016/j.agrformet.2019.01.036 ◽

2019 ◽

Vol 269-270 ◽

pp. 239-248 ◽

Cited By ~ 27

Author(s):

Xiangyi Li ◽

Yue Li ◽

Anping Chen ◽

Mengdi Gao ◽

Ingrid J. Slette ◽

...

Keyword(s):

Carbon Balance ◽

Southwest China ◽

Terrestrial Carbon ◽

Vegetation Growth ◽

The Impact

Download Full-text

Nitrogen Deposition Maintains a Positive Effect on Terrestrial Carbon Sequestration in the 21st Century Despite Growing Phosphorus Limitation at Regional Scales

Global Biogeochemical Cycles ◽

10.1029/2018gb005952 ◽

2019 ◽

Vol 33 (6) ◽

pp. 810-824 ◽

Cited By ~ 2

Author(s):

Katrin Fleischer ◽

A. J. Dolman ◽

Michiel K. Molen ◽

Karin T. Rebel ◽

Jan Willem Erisman ◽

...

Keyword(s):

Carbon Sequestration ◽

Nitrogen Deposition ◽

21St Century ◽

Phosphorus Limitation ◽

Terrestrial Carbon ◽

Terrestrial Carbon Sequestration ◽

Positive Effect

Download Full-text

Exploring the effects of biodiversity and elemental stoichiometry on terrestrial carbon balance

10.5194/egusphere-egu2020-1589 ◽

2020 ◽

Author(s):

Marcos Fernández-Martínez ◽

Jordi Sardans ◽

Josep Peñuelas ◽

Ivan Janssens

Keyword(s):

Global Change ◽

Elemental Composition ◽

Carbon Balance ◽

Terrestrial Ecosystems ◽

Terrestrial Carbon ◽

Endogenous Factors ◽

Ecosystem Carbon ◽

Elemental Stoichiometry ◽

Ecosystem Carbon Balance

Global change is affecting the capacity of terrestrial ecosystems to sequester carbon. While the effect of climate on ecosystem carbon balance has largely been explored, the role of other potentially important factors that may shift with global change, such as biodiversity and the concentration of nutrients remains elusive. More diverse ecosystems have been shown to be more productive and stable over time and differences in foliar concentrations of N and P are related to large differences in how primary producers function. Here, we used 89 eddy-covariance sites included in the FLUXNET 2015 database, from which we compiled information on climate, species abundance and elemental composition of the main species. With these data, we assessed the relative importance of climate, endogenous factors, biodiversity and community-weighted concentrations of foliar N and P on terrestrial carbon balance. Climate and endogenous factors, such as stand age, are the main determinants of terrestrial C balance and their interannual variability in all types of ecosystems. Elemental stoichiometry, though, played a significant role affecting photosynthesis, an effect that propagates through ecosystem respiration and carbon sequestration. Biodiversity, instead, had a very limited effect on terrestrial carbon balance. We found increased respiration rates and more stable gross primary production with increasing diversity. Our results are the first attempt to investigate the role of biodiversity and the elemental composition of terrestrial ecosystems in ecosystem carbon balance.

Download Full-text