Did you know scientists have been digging up dirt on soil for centuries?
From Vasily Dokuchaev the Father of Soil Science in the 19th century, to Hans Jenny in the 20th,
and numerous minds at the frontier of soil science in the 21st century and today,
researchers have been studying how soils form and build up organic matter.
Most recently, they’ve been building big data models that predict how soil carbon,
an essential component of soil organic matter, will respond to Earth’s rising temperatures. With
the introduction of large scale data collection programs like the National Ecological Observatory
Network, scientists are now better prepared to answer long-term questions about soil health,
the fate of soil organic carbon, and CO2 exchange between the atmosphere and soil.
Soil is made up of air, water, minerals, organisms, and organic materials.
Within soil, most concentrated near the surface, lies Soil Organic Matter, or SOM,
which consists of plant, animal, and microbial tissue in various stages of decomposition. Living
organisms like worms, bacteria and fungi are key to turning this dead matter into stable SOM.
SOM plays a key role in many soil functions - it promotes infiltration and increases water
holding capacity and soil fertility, and reduces erosion. Although SOM only makes
up less than 15% of the mass of many soils, at the global scale it contributes a huge volume
of carbon. When added up across all terrestrial ecosystems on Earth, soils are currently storing
an estimated 2500 billion tons of carbon; almost twice the amount that is found in our atmosphere.
Roughly 50% of SOM is actually carbon that, if decomposed, will create Carbon Dioxide.
Along with carbon, Nitrogen, phosphorus and sulfur are also stored in soil organic matter,
and are eventually released to be made available for plants to take up, when SOM is decomposed.
In a healthy, undisturbed, or mature ecosystem there is a general balance of CO2 uptake
by plants and the CO2 created in soils from decomposition - this is called a steady state.
However, the degradation of many ecosystems through climate change, land usage,
agricultural practices, and other human activity and disturbance has led to the decreased
ability of soils to store carbon compared to the increasing CO2 that is released by our ecosystems.
In this case, the steady state is unbalanced. So, why are healthy soils good at storing carbon,
and how does it get locked away in soil organic matter? There are several ways carbon can
be protected from decay; it may be prevented from decomposing in wet and cold environments,
or interactions with soil minerals. It can be stored away inside soil aggregates,
or it might remain because the organisms that typically break down SOM might be absent.
With new, advanced measurement techniques, we are able to get an exciting look into carbon cycling
and storage in soils. Open data and samples from the National Ecological Observatory Network can
contribute to this understanding. In-situ measurements can observe carbon cycling
in place; for instance, eddy covariance systems continuously measure CO2 exchanged between soils,
plants, and the atmosphere. While below ground sensors constantly measure the amount of carbon
dioxide in the spaces between soil particles. In addition to these instrument measurements,
we can make high-resolution molecular measurements of the composition of SOM,
and the organisms that break it down. NEON collects soil samples throughout the US at
regular intervals for scientific research. These samples are collected, processed, and shipped to
the main NEON Biorepository in Arizona for storage where they can be freely requested by researchers.
Methods such as radiocarbon dating can help us understand how long different kinds of organic
matter persist in soils, and advanced spectroscopy techniques reveal the exact chemistry of soil
organic carbon, which helps us understand how it forms. Combining these measurements with
microbial community analyses can give insight into how soil organisms shape SOM dynamics.
Scientists learn more everyday about the fine-scale dynamics of carbon cycling within
soil organic matter, and how stored carbon can have broad implications on overall soil health
and the carbon cycle. Measuring these carbon stores and exchanges is critical in providing data
that better inform scientific models developed to predict future soil carbon concentrations.
It’s important that we, as a society, better understand why,
and how, carbon concentrations in soils are changing, so that we might learn how
to mitigate rising CO2 levels in our atmosphere that contribute to global warming. Can you dig it?
To learn more, visit NEONscience.org