Biology subjects

Carrillo, Y.

Publications and source records attributed to Carrillo, Y..

3 recordsLinked to original sources

bioRxiv2021

Phosphorus availability and arbuscular mycorrhizal fungi limit soil C cycling and influence plant responses to elevated CO2 conditions.

Enhanced soil organic matter (SOM) decomposition and organic phosphorus (P) cycling may help sustain plant productivity under elevated CO2 (eCO2) and P-limiting conditions. P-acquisition by arbuscular mycorrhizal (AM) fungi and their impacts on SOM decomposition may become even more relevant in these conditions. Yet, experimental evidence of the interactive effect of AM fungi and P availability influencing altered SOM cycling under eCO2 is scarce and the mechanisms of this control are poorly understood. Here, we performed a pot experiment manipulating P availability, AM fungal presence and atmospheric CO2 levels and assessed their impacts on soil C cycling and plant growth. Plants were grown in chambers with a continuous 13C-input that allowed differentiation between plant- and SOM-derived fractions of respired CO2 (R), dissolved organic C (DOC) and microbial biomass (MBC) as relevant C pools in the soil C cycle. We hypothesised that under low P availability, increases in SOM cycling may support sustained plant growth under eCO2 and that AM fungi would intensify this effect. We found the impacts of CO2 enrichment and P availability on soil C cycling were generally independent of each other with higher root biomass and slight increases in soil C cycling under eCO2 occurring regardless of the P treatment. Contrary to our hypotheses, soil C cycling was enhanced with P addition suggesting that low P conditions were limiting soil C cycling. eCO2 conditions increased the fraction of SOM-derived DOC pointing to increased SOM decomposition with eCO2. Finally, AM fungi increased microbial biomass under eCO2 conditions and low-P without enhanced soil C cycling, probably due to competitive interactions with free-living microorganisms over nutrients. Our findings in this plant-soil system suggest that, contrary to what has been reported for N-limited systems, the impacts of eCO2 and P availability on soil C cycling are independent of each other.

ecology↗

bioRxiv2020

Pastures and Climate Extremes: Impacts of warming and drought on the productivity and resilience of key pasture species in a field experiment

Shifts in the timing, intensity and/or frequency of climate extremes, such as severe drought and heatwaves, can generate sustained shifts in ecosystem function with important ecological and economic impacts for rangelands and managed pastures. The Pastures and Climate Extremes experiment (PACE) in Southeast Australia was designed to investigate the impacts of a severe winter/spring drought (60% rainfall reduction) and, for a subset of species, a factorial combination of drought and elevated temperature (ambient +3 {degrees}C) on pasture productivity. The experiment included nine common pasture and Australian rangeland species from three plant functional groups (C3 grasses, C4 grasses and legumes) planted in monoculture. Winter/spring drought resulted in productivity declines of 45% on average and up to 74% for the most affected species (Digitaria eriantha) during the 6-month treatment period, with eight of the nine species exhibiting significant yield reductions. Despite considerable variation in species sensitivity to drought, C4 grasses were more strongly affected by this treatment than C3 grasses or legumes. Warming also had negative effects on cool-season productivity, associated at least partially with exceedance of optimum growth temperatures in spring and indirect effects on soil water content. The combination of winter/spring drought and year-round warming resulted in the greatest yield reductions. We identified responses that were either additive such that there was only as significant warming effect under drought (Festuca), or less-than-additive, where there was no drought effect under warming (Medicago), compared to ambient plots. Results from this study highlight the sensitivity of diverse pasture species to increases in winter and spring drought severity similar to those predicted for this region, and that anticipated benefits of cool-season warming are unlikely to be realised. Overall, the substantial negative impacts on productivity suggest that future, warmer, drier climates will result in shortfalls in cool-season forage availability, with profound implications for the livestock industry and natural grazer communities.

ecology↗

bioRxiv2019

The fate of carbon in a mature forest under carbon dioxide enrichment

Atmospheric carbon dioxide enrichment (eCO2) can enhance plant carbon uptake and growth1,2,3,4,5, thereby providing an important negative feedback to climate change by slowing the rate of increase of the atmospheric CO2 concentration6. While evidence gathered from young aggrading forests has generally indicated a strong CO2 fertilization effect on biomass growth3,4,5, it is unclear whether mature forests respond to eCO2 in a similar way. In mature trees and forest stands7,8,9,10, photosynthetic uptake has been found to increase under eCO2 without any apparent accompanying growth response, leaving an open question about the fate of additional carbon fixed under eCO24, 5, 7,8,9,10,11. Here, using data from the first ecosystem-scale Free-Air CO2 Enrichment (FACE) experiment in a mature forest, we constructed a comprehensive ecosystem carbon budget to track the fate of carbon as the forest responds to four years of eCO2 exposure. We show that, although the eCO2 treatment of ambient +150 ppm (+38%) induced a 12% (+247 gCm-2yr-1) increase in carbon uptake through gross primary production, this additional carbon uptake did not lead to increased carbon sequestration at the ecosystem level. Instead, the majority of the extra carbon was emitted back into the atmosphere via several respiratory fluxes, with increased soil respiration alone contributing [~]50% of the total uptake surplus. Our results call into question the predominant thinking that the capacity of forests to act as carbon sinks will be generally enhanced under eCO2, and challenge the efficacy of climate mitigation strategies that rely on CO2 fertilization as a driver of increased carbon sinks in standing forests and afforestation projects.

ecology↗