Smith Lab News
Mar. 24, 2025: Alissar, Evan, and Jeff led a new paper published in New Phytologist titled “Soil resource acquisition strategy modulates global plant nutrient and water economics”
Plants need resources like nutrients and water to grow, and they adopt different
strategies to acquire these resources from the soil. However, acquiring nutrients
comes at a cost—plants must invest carbon belowground to support root systems and
microbial partnerships. But how do these costs change depending on soil conditions,
water availability, and plant nutrient-acquisition strategies? And how are these
costs coupled with photosynthetic acclimation processes?
In this new study, we tackled these questions using a global dataset of leaf carbon
isotopes, spanning a wide range of plant species and environmental conditions.
By applying an eco-evolutionary optimality framework
(Harrison et al., 2021;
Franklin et al., 2020)
that links soil resources to leaf-level photosynthetic
acclimation, we estimated the carbon costs of acquiring nutrients relative to
water and uncovered key patterns.
The findings reveal that these costs decrease as soil nitrogen availability increases
but increase with increasing moisture—yet this pattern depends on how plants acquire
nutrients (Figure 1; see below).
Specifically, plants associated with arbuscular mycorrhizal
fungi experience lower costs when inorganic soluble nitrogen is abundant, as these
fungi efficiently scavenge soluble inorganic nitrogen. In contrast, plants associated
with ectomycorrhizal and ericoid fungi experience lower costs in nitrogen-poor soils,
where these fungi can break down organic matter using specialized enzymes.
Moisture plays a different role. Our study found that the carbon costs of
acquiring nutrients relative to water increase with higher moisture levels,
but mainly for plants relying on arbuscular mycorrhizal fungi. This suggests
that for these plants, wetter conditions directly influence the cost of maintaining
transpiration, altering their carbon investment strategies. Finally, the modulation
of these costs by phosphorus availability depended on the indirect effects of
moisture on soil phosphorus. Interestingly, the effects vary by biome. In tropical
and subtropical ecosystems, both moisture and nitrogen availability shape these costs.
However, in temperate and boreal regions, where nitrogen is the primary limiting
factor for growth, only soil nitrogen availability plays a key role.
This study highlights that plants minimize resource acquisition costs in a
predictable way, balancing trade-offs between water and nutrients depending
on their environment and strategy. These findings emphasize the need to
refine Earth System Models using optimality theory to better integrate how
plants adjust their carbon investments in response to resource availability.
Cheaib, A*, J Chieppa*, EA Perkowski*, and NG Smith* (In Press).
Soil resource acquisition strategy modulates global plant nutrient and water economics.
New Phytologist.
link.
Jan. 19, 2025: Alissar, Lizz, Evan, and Risa lead paper showing that leaf nitrogen demand helps determine leaf nitrogen responses to soil nitrogen, out now in Ecology Letters
Alissar led a
new study published in Ecology Letters titled “Soil nitrogen supply
exerts largest influence on leaf nitrogen in environments
with the greatest leaf nitrogen demand."
The paper uses leaf chemistry data (Firn et al., 2019) from the Nutrient Network to show that sites that have the greatest leaf nitrogen response to soil nitrogen fertilization are those where we would expect there to be the greatest demand for photosynthetic leaf nitrogen.
From theory (see review by Stocker et al. (2024)) we can predict how climatic factors should drive photosynthetic leaf nitrogen demand. This theory predicts that leaf nitrogen demand should increase with aridity and sunlight, and decrease with temperature. The new paper shows that the responsiveness of leaf nitrogen to soil nitrogen across the network increases with these factors (see figure below).
This study provides a novel confirmation of our theoretical understanding of plant nitrogen dynamics. This can serve as a baseline for developing new models (e.g., Stocker et al. (2024)) for simulating these responses, ultimately improving simulations of terrestrial carbon-nitrogen cycle interactions.
As an aside, it is with pleasure to note that this paper was the result of many years of work by the PhUnFETTy lab and our collaborators within the NutNet. The first four authors are current or former PhUnFETTy lab members, all of whom contributed significant effort towards the analyses in this paper. Although, a huge shout out goes to Alissar for bringing many years of thinking together to craft a cohesive suite of analyses and resulting narrative.
This work was primarily supported by the National Science Foundation.
Cheaib, AC*, EF Waring*, RM McNellis*, EA Perkowski*, JP Martina, EW Seabloom, ET Borer, PA Wilfahrt, N Dong, IC Prentice, IJ Wright, SA Power, EK Hersch-Green, AC Risch, M Caldeira, C Nogueira, QQ Chen, and NG Smith (2025). Soil nitrogen supply exerts largest influence on leaf nitrogen in environments with the greatest leaf nitrogen demand. Ecology Letters 28(1): e70015. link.
