Long-term warming in Alaska enlarges the diazotrophic community in deep soils

Published by Stephanie Mayer on

Tundra ecosystems are typically carbon (C) rich but nitrogen (N) limited. Since biological N2 fixation is the major source of biologically available N, the soil N2-fixing (i.e., diazotrophic) community serves as an essential N supplier to the tundra ecosystem. Recent climate warming has induced deeper permafrost thaw and adversely affected C sequestration, which is modulated by N availability. Therefore, it is crucial to examine the responses of diazotrophic communities to warming across the depths of tundra soils. Herein, we carried out one of the deepest sequencing efforts of nitrogenase gene (nifH) to investigate how 5 years of experimental winter warming affects Alaskan soil diazotrophic community composition and abundance spanning both the organic and mineral layers. Although soil depth had a stronger influence on diazotrophic community composition than warming, warming significantly (P < 0.05) enhanced diazotrophic abundance by 86.3% and aboveground plant biomass by 25.2%. Diazotrophic composition in the middle and lower organic layers, detected by nifH sequencing and a microarray-based tool (GeoChip), was markedly altered, with an increase of α-diversity. Changes in diazotrophic abundance and composition significantly correlated with soil moisture, soil thaw duration, and plant biomass, as shown by structural equation modeling analyses. Therefore, more abundant diazotrophic communities induced by warming may potentially serve as an important mechanism for supplementing biologically available N in this tundra ecosystem.IMPORTANCE With the likelihood that changes in global climate will adversely affect the soil C reservoir in the northern circumpolar permafrost zone, an understanding of the potential role of diazotrophic communities in enhancing biological N2 fixation, which constrains both plant production and microbial decomposition in tundra soils, is important in elucidating the responses of soil microbial communities to global climate change. A recent study showed that the composition of the diazotrophic community in a tundra soil exhibited no change under a short-term (1.5-year) winter warming experiment. However, it remains crucial to examine whether the lack of diazotrophic community responses to warming is persistent over a longer time period as a possibly important mechanism in stabilizing tundra soil C. Through a detailed characterization of the effects of winter warming on diazotrophic communities, we showed that a long-term (5-year) winter warming substantially enhanced diazotrophic abundance and altered community composition, though soil depth had a stronger influence on diazotrophic community composition than warming. These changes were best explained by changes in soil moisture, soil thaw duration, and plant biomass. These results provide crucial insights into the potential factors that may impact future C and N availability in tundra regions.

Categories:

Related Posts

A CIRCUIT SHOWS HOW CLIMATE WARMING MAY ALTER DIFFERENT ECOLOGICAL LEGACIES IN THE ARCTIC BOREAL FOREST, WHICH THEN FEEDBACK INTO CLIMATE WARMING AND CHANGES TO LANDSCAPE PROCESSES.

NAU-led research team receives $9.6M to study how Alaska’s forests change, adapt to warmer future

Ecological memory stored in a landscape can help an ecosystem recover from disturbances like fire and outbreaks of disease. But what happens when climate warming disrupts that process? How long before ecological memories stored in Read more…

A SCATTERPLOT DEPICTS HOW MUCH CARBON OR OXYGEN ISOTOPE DIFFERENT SOIL BACTERIA TOOK INTO THEIR DNA (A PROXY FOR GROWTH) DURING A 7-DAY EXPERIMENT. SMALL POINTS REPRESENT THE GROWTH OF INDIVIDUAL BACTERIAL STRAINS LINKED BY LINES TO THE AVERAGE GROWTH OF THEIR CLOSEST IDENTIFIED GENUS. COLORS WERE ASSIGNED BY A CLUSTERING ALGORITHM TO GROUP GENERA INTO FAST-GROWING OR SLOW-GROWING LIFESTYLES.

Lifestyles of the fast and slow (bacteria): In the wild, most live in the slow lane

A study led by Northern Arizona University offers new evidence that a common framework to sort bacteria into two lifestyles doesn’t easily apply to bacteria living in wild soil. The findings, published in The ISME Journal, show Read more…

A trio of illustrated panels depicts the soil microbial communities in three treatments of a long-term warming experiment north of Flagstaff, Arizona. The panels are labeled in gray text, left to right: control, short-term warming, long-term warming. The control treatment, far left, depicts bacteria, protists, and other microorganisms identified by sequencing the soil’s metagenome in yellow, orange, green, and blue, along with chains of available nutrients. Soil depicted in the center panel, which has undergone short-term warming, shows an increased abundance and diversity of microbes, some of which are growing, incorporating nutrients, and respiring carbon dioxide. The soil that has undergone long-term warming, imagined in the panel on the right, shows fewer microbial species and competitive relationships that are developing for control of the scarcer nutrients.

Does a warmer future favor microbial friend or foe? Ecoss researchers win $3.4M to study interactions in changing soil

In 2002, the Odyssey probe discovered evidence of past ice on Mars. The U.S. Congress authorized the Iraq War resolution. The Anaheim Angels won the World Series. And in a meadow 15 miles north of Read more…