Species interactions may couple the resource dynamics of different primary producers and may enhance productivity by reducing loss from the system. In low‐resource systems, this biotic control may be especially important for maintaining productivity. In drylands, the activities of vascular plants and biological soil crusts can be decoupled in space because biocrusts grow on the soil surface but plant roots are underground, and decoupled in time due to biocrusts activating with smaller precipitation events than plants. Soil fungi are hypothesized to functionally couple the plants and biocrusts by transporting nutrients. We studied whether disrupting fungi between biocrusts and plants reduces nitrogen transfer and retention and decreases primary production as predicted by the fungal loop hypothesis. Additionally, we compared varying precipitation regimes that can drive different timing and depth of biological activities. We used field mesocosms in which the potential for fungal connections between biocrusts and roots remained intact or were impeded by mesh. We imposed a precipitation regime of small, frequent or large, infrequent rain events. We used15N to track fungal‐mediated nitrogen (N) transfer. We quantified microbial carbon use efficiency and plant and biocrust production and N content. Fungal connections with biocrusts benefitted plant biomass and nutrient retention under favourable (large, infrequent) precipitation regimes but not under stressful (small, frequent) regimes, demonstrating context dependency in the fungal loop. Translocation of a15N tracer from biocrusts to roots was marginally lower when fungal connections were impeded than intact. Under large, infrequent rains, when fungal connections were intact, the C:N of leaves converged towards the C:N of biocrusts, suggesting higher N retention in the plant, and plant above‐ground biomass was greater relative to the fungal connections‐impeded treatment. Carbon use efficiency in both biocrust and rooting zone soil was less C‐limited when connections were intact than impeded, again only in the large, infrequent precipitation regime.
The effect of species loss on ecosystem productivity is determined by both the functional contribution of the species lost, and the response of the remaining species in the community. According to the mass ratio hypothesis, the loss of a dominant plant species, which has a larger proportionate contribution to productivity, is expected to exert an overwhelming effect on this important ecosystem function. However, via competitive release, loss of a dominant species can provide the opportunity for other plant species to establish, thrive and become abundant in the community, potentially compensating for the function lost. Furthermore, if resource limitation is removed, then the compensatory response of function to the loss of a dominant species should be greater and more rapid than if resources are more limiting. To evaluate how resources may limit compensation of above‐ground productivity to the loss of a dominant plant species, we experimentally removed the C4perennial tallgrass, Overall, above‐ground biomass production increased in the remaining community with both water and nitrogen addition. However, this increase in biomass production was not sufficient to fully compensate for the loss of Following the removal of the dominant species, there was reordering of species abundances in the community, rather than changes in species richness. The C4grass
- Award ID(s):
- 2025849
- NSF-PAR ID:
- 10446322
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- Journal of Ecology
- Volume:
- 109
- Issue:
- 10
- ISSN:
- 0022-0477
- Format(s):
- Medium: X Size: p. 3617-3633
- Size(s):
- ["p. 3617-3633"]
- Sponsoring Org:
- National Science Foundation
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Abstract Synthesis . Although we did not find evidence of a reciprocal transfer of C and N between plants and biocrusts, plant production was benefited by fungal connections with biocrusts under favourable conditions. -
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Abstract Ecosystem stability is essential to its sustainable functions and services to humanity. Although climate warming is projected to vary from 1 to 5°C by the end of 21st century, how the temporal stability of plant community biomass production responds to different warming scenarios remains unclear.
To fill this knowledge gap, we conducted a 6‐year field experiment with three levels of warming treatments (control, +1.5°C, +2.5°C) by using infrared radiators, in an alpine meadow on the Qinghai–Tibet Plateau.
We found that low‐level warming (+1.5°C), compared to the control, did not significantly change the temporal stability of plant community biomass production and its underlying causes, including species diversity, compensatory dynamics, mean–variance scaling, biomass temporal stability of plant population (the average of temporal stability of species biomass production of all species in the community) or dominant species. However, high‐level warming (+2.5°C) significantly reduced them. Species diversity was not a significant predictor of temporal stability of plant community biomass production in this species‐rich ecosystem, regardless of the magnitude of warming, while co‐existing species compensatory dynamics and the biomass temporal stability of dominant species determined the response of temporal stability of plant community biomass production to warming.
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Our work suggests that plant responses to changes in precipitation result from complex interactions between the direct effect of precipitation and indirect effects through changes in the below‐ground trophic web. Such complex responses challenge current predictions of increasing plant biomass allocation below‐ground in water‐stressed grasslands, and deserve further investigation across ecosystems and in field conditions.
A free
Plain Language Summary can be found within the Supporting Information of this article. -
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