What Does The Future Hold For Our Arid And Semi-Arid Ecosystems?

Published by Malak Tfaily

Environmental Molecular Sciences Laboratory, Richland, WA

These findings are described in the article entitled Elevated [CO2] changes soil organic matter composition and substrate diversity in an arid ecosystem, recently published in the journal Geoderma (Geoderma 330 (2018) 1-8). This work was conducted by Malak M. Tfaily and Nancy J. Hess from the Environmental Molecular Sciences Laboratory, Akihiro Koyama from Algoma University and Washington State University, and R.D. Evans from Washington State University.

ADVERTISEMENT

Arid (dry) and semi-arid ecosystems occupy more than 30% of the Earth’s surface and are predicted to be among the most responsive ecosystems to climate change. There is considerable uncertainty on how these systems will respond to elevated CO2 and global warming. Understanding how arid ecosystems will respond to elated CO2 will help improve our understanding of climate-ecosystem interactions and, hence, improve our mitigation practices.

Increased CO2 concentrations above ground can have direct and indirect effects on arid ecosystems. For example, enhanced CO2 could enhance photosynthesis rates and plant productivity. Increased plant productivity can then affect the quality and quantity of organic compounds in the soil. Increased carbon (C) input belowground could either prime further decomposition of soil organic matter (SOM) thus releasing back CO2 to the atmosphere or on the contrary could stabilize SOM preventing further C losses into the atmosphere.

Our study aims to examine the cumulative effects of 10 years of elevated [CO2] on SOM molecular composition in an intact Mojave Desert ecosystem at the Nevada Desert Free-Air Carbon Dioxide Enrichment (FACE) Facility (NDFF). Our study specifically addresses the potential mechanisms by which elevated [CO2] impacts SOM composition, substrate diversity and potential microbial activity via changes in organic matter chemical composition and diversity (commonly referred to as organic matter “quality”) in an arid ecosystem.

Our data suggested that arid ecosystems under elevated [CO2] and continued water limitation results in increased microbial biomass stimulated both by rhizodeposition and aboveground litter. We found that plant-derived compounds were primary substrates for microbial activity under elevated [CO2] and microbial necromass were the main constituents of stabilized SOM Coordinated shifts in dominant organic C transformations, dominant organic C compounds, and microbial metabolic pathways suggested significant connections among organic C chemistry and microbial activity in this arid ecosystem. This contrasts with mesic forest ecosystems where increasing plant litter inputs did not increase soil C but instead, enhanced SOM degradation, suggesting that different ecosystems may exhibit varying responses to future environmental changes that lead to increased plant productivity and plant inputs to soils

ADVERTISEMENT

Water-limited ecosystems in arid and semi-arid regions are particularly impacted by enhanced CO2 concentrations, however in a good way. As long as the system continues to be water limited, enhanced CO2 did indeed increase C sequestration belowground suggesting that arid ecosystems are a potential large C sink under elevated [CO2]. These results provide direct evidence that CO2 fertilization substantially increases ecosystem C storage and that arid ecosystems are significant, previously unrecognized, sinks for atmospheric CO2 that must be accounted for in efforts to constrain terrestrial and global C cycles.

Our study suggests that arid ecosystems might present a unique opportunity to study soil organic matter accumulation where microbial necromass represent a significant component of its composition. Under this scenario of climate change (i.e., increased CO2 concentrations with no changes in water availability, arid ecosystems might represent a potential large C sink under elevated [CO2]. Our results suggest that arid ecosystems are a potential large C sink under elevated [CO2], given arid ecosystems constitute 47% of the terrestrial land surface, and that labile compounds are transformed to stable SOM via microbial processes. Arid systems are limited by water, and thus may have a different C storage potential under changing climates than other ecosystems that are limited by nitrogen or phosphorus.

So far arid and semi-arid ecosystems have been the subject of few studies that place their importance in a global context and in terms of their role in society and how will they change with climate change. Our findings indicate that semiarid regions and their ecosystems merit increased attention as a key ecosystem that can sequester C from the atmosphere. Multiple lines of evidence suggest significant C accumulation belowground with elevated CO2, confirming a potential substantial negative global feedback to atmospheric CO2 and climate.

ADVERTISEMENT

Comments

READ THIS NEXT

Table-Top Alternative To Synchrotrons: New Instrumentation To Study Radioactive Materials With Great Precision

The study of materials used in nuclear power plants is rendered difficult due to the high radioactivity of even a […]

On The Shoulders Of Giants, Part 1: Henry K. Beecher And The Placebo Effect

When Robert Merton (1910 – 2003) dissected the allegory that we all are “standing on the shoulders of giants” — […]

Sustainable Coastal Development: Should We Care About Surface Materials?

Today, nearly half of the world’s population lives within 150 km from the coast and, in an increasingly urbanized world, […]

Identifying Cognitive Abilities To Serve As Intervention Targets For Treating Psychiatric Disorders

Psychiatric disorders, such as schizophrenia, bipolar disorder, and major depression, have a devastating impact on a patient’s life and contribute […]

Vanadium In Shallow Groundwaters: A Potentially Dangerous Pollutant?

Among the critical elements (Figure 1), vanadium (V) has been proposed to be a potentially dangerous pollutant, especially in the […]

Calligraphy Letters: Learn To Write Calligraphy

Calligraphy letters are an art form of writing which means “beautiful writing” in Greek and employs large brush strokes and […]

Placebo Personalities: Fact, Fake, Fiction, Or A Bit Of Everything?

“Do placebo responders exist?” This is a question raised by many and answered by few (1). Are those who respond […]

Science Trends is a popular source of science news and education around the world. We cover everything from solar power cell technology to climate change to cancer research. We help hundreds of thousands of people every month learn about the world we live in and the latest scientific breakthroughs. Want to know more?