A significant scientific study by Zhaosheng Fan & Chao Liang Published 4/2/2015
This is of great interest to all of us who practice
permaculture, we may have a way to slow the global warming effects created by humans.
Since the burning of fossil fuels is pretty much our greatest transgression to mother earth.
Soil organic
carbon (SOC) plays an important role in the global carbon cycle. However, it remains largely
unknown how plant litter inputs impact magnitude, composition and source configuration of the SOC
stocks over long term through microbial catabolism and anabolism, mostly due to uncoupled research on
litter decomposition and SOC formation. This limits our ability to predict soil system responses to changes
in land-use and climate. Here, we examine how microbes act as a valve controlling carbon sequestrated from
plant litters versus released to the atmosphere in natural ecosystems amended with plant litters varying in
quantity and quality. We find that litter quality – not quantity – regulates long-term SOC dynamics under
different plausible scenarios. Long-term changes in bulk SOC stock occur only when the quality of carbon
inputs causes asynchronous change in a microbial physiological trait, defined as ‘‘microbial biosynthesis
acceleration’’ (MBA). This is the first theoretical demonstration that the response of the SOC stocks to litter
inputs is critically determined by the microbial physiology. Our work suggests that total SOC at an
equilibrium state may be an intrinsic property of a given ecosystem, which ultimately is controlled by the
asynchronous MBA between microbial functional groups.
Globally, soils hold a large amount of carbon (C); the size of the SOC pool is twice that of the atmosphere
and greater than the atmospheric and terrestrial vegetation C pools combined1,2. Small changes in the
balance between inputs to and outputs from the SOC pool (especially the stable C pool) could have a
significant impact on atmospheric CO2 concentration3–5, which may either reduce or exacerbate the consequences
of burning of fossil fuels. For example, global climate change due to rising atmospheric CO2 concentration
will likely change aboveground vegetation dynamics. Such changes can then impact the quantity of litter C
inputs to soil by altering plant net primary productivity (NPP) and/or affect the quality of litter C inputs by
altering plant community structure (e.g., population sizes and species composition) and/or chemical composition
(e.g., nitrogen and phosphorus concentrations) of plant litter6–9.
Impacts on plant-C inputs to soil are fairly well represented in current climate and Earth system models
(CESMs) that are driven largely by plant productivity responses10,11. However, microbial roles in soil C cycling are
still poorly reflected in these models12, despite that dynamics of SOC is driven ultimately by microbial catabolic
and anabolic activities2,13,14. In practice, microbial models can be both plausible and straightforward (but not easy)
to parameterize; importantly they also show promise for improving overall knowledge and our ability to predict
the effects of global changes12,15.
Calls for the explicit consideration of microorganisms and their activities in models are increasing15–17, the
necessary theoretical supporting research are growing18–21, and results are beginning to emerge14,22–26. For
example, a recent study showed that performance of the Community
Land Model (a global land surface model)
was substantially improved by addition of microbial processes24. While microbial models are not absent in current
studies, unfortunately most of them only target microbial biomass. Inevitably, microbial controls over SOC
formation, transformation, and stabilization are engaged by numerous functional species that constitute the
microbial community. Yet so far, virtually few published models have incorporated dynamics of microbial
community and examine its relevance for SOC cycling27. Therefore, accounting for the responses of the microbial
community and its physiology in CESMs may be necessary to reliably predict SOC dynamics28.
Emerging opinion suggests that soil microbes act as important agents of SOC formation13,29,30, in part, because
of growing evidence that microbial-derived C forms are primary constituents of the stable SOC pool14,31–35. In this
view, microbial activities simultaneously lead to (1) significantCO2 emissions via decomposition of plant residues
Globally, soils hold a large amount of carbon (C); the size of the SOC pool is twice that of the atmosphere
and greater than the atmospheric and terrestrial vegetation C pools combined1,2. Small changes in the
balance between inputs to and outputs from the SOC pool (especially the stable C pool) could have a
significant impact on atmospheric CO2 concentration3–5, which may either reduce or exacerbate the consequences
of burning of fossil fuels. For example, global climate change due to rising atmospheric CO2 concentration
will likely change aboveground vegetation dynamics. Such changes can then impact the quantity of litter C
inputs to soil by altering plant net primary productivity (NPP) and/or affect the quality of litter C inputs by
altering plant community structure (e.g., population sizes and species composition) and/or chemical composition
(e.g., nitrogen and phosphorus concentrations) of plant litter6–9.
Impacts on plant-C inputs to soil are fairly well represented in current climate and Earth system models
(CESMs) that are driven largely by plant productivity responses10,11. However, microbial roles in soil C cycling are
still poorly reflected in these models12, despite that dynamics of SOC is driven ultimately by microbial catabolic
and anabolic activities2,13,14. In practice, microbial models can be both plausible and straightforward (but not easy)
to parameterize; importantly they also show promise for improving overall knowledge and our ability to predict
the effects of global changes12,15.
Calls for the explicit consideration of microorganisms and their activities in models are increasing15–17, the
necessary theoretical supporting research are growing18–21, and results are beginning to emerge14,22–26. For
example, a recent study showed that performance of the Community Land Model (a global land surface model)
was substantially improved by addition of microbial processes24. While microbial models are not absent in current
studies, unfortunately most of them only target microbial biomass. Inevitably, microbial controls over SOC
formation, transformation, and stabilization are engaged by numerous functional species that constitute the
microbial community. Yet so far, virtually few published models have incorporated dynamics of microbial
community and examine its relevance for SOC cycling27. Therefore, accounting for the responses of the microbial
community and its physiology in CESMs may be necessary to reliably predict SOC dynamics28.
Emerging opinion suggests that soil microbes act as important agents of SOC formation13,29,30, in part, because
of growing evidence that microbial-derived C forms are primary constituents of the stable SOC pool14,31–35. In this
view, microbial activities simultaneously lead to (1) significantCO2 emissions via decomposition of plant residues theory and microbial parameters.
We expect our work serve as the first step towards a new generation of models that include key physical
and chemical mechanisms in the SOC cycling.
Since this report has great significance, good charts and is rather long, read it here
The full Published Report in .pdf format
It is always good to have science recognize what we already do is good for the planet. It give sanction to our methodology and can help further our cause and spread the word.
