Experimental warming and its legacy effects on root dynamics following two hurricane disturbances in a wet tropical forest

Abstract

Tropical forests are expected to experience unprecedented warming and increases in hurricane disturbances in the coming decades; yet, our understanding of how these productive systems, especially their belowground component, will respond to the combined effects of varied environmental changes remains empirically limited. Here we evaluated the responses of root dynamics (production, mortality, and biomass) to soil and understory warming (+4°C) and after two consecutive tropical hurricanes in our in situ warming experiment in a tropical forest of Puerto Rico: Tropical Responses to Altered Climate Experiment (TRACE). We collected minirhizotron images from three warmed plots and three control plots of 12 m 2 . Following Hurricanes Irma and María in September 2017, the infrared heater warming treatment was suspended for repairs, which allowed us to explore potential legacy effects of prior warming on forest recovery. We found that warming significantly reduced root production and root biomass over time. Following hurricane disturbance, both root biomass and production increased substantially across all plots; the root biomass increased 2.8-fold in controls but only 1.6-fold in previously warmed plots. This pattern held true for both herbaceous and woody roots, suggesting that the consistent antecedent warming conditions reduced root capacity to recover following hurricane disturbance. Root production and mortality were both related to soil ammonium nitrogen and microbial biomass nitrogen before and after the hurricanes. This experiment has provided an unprecedented look at the complex interactive effects of disturbance and climate change on the root component of a tropical forested ecosystem. A decrease in root production in a warmer world and slower root recovery after a major hurricane disturbance, as observed here, are likely to have longer-term consequences for tropical forest responses to future global change. K E Y W O R D S belowground, climate change, luquillo experimental forest, multiple disturbances, root traits, wet forest This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

The effect of repeated hurricanes on the age of organic carbon in humid tropical forest soil

“…Hurricane inputs were imposed as an additional pulse of litter inputs at each depth interval, declining with depth. The 0–10 cm interval received 100% of the surface input pulse, the 10–35 cm depth received a pulse of root inputs equivalent to 30% of the surface input pulse, and the 35–60 cm depth received root inputs equal to 10% of the surface input pulse, approximating observations following Hurricane Maria (Yaffar et al., 2021). Surface litter pulses under hurricanes were specified according to measured litterfall values and were 42.5 g C m −2 to the surface in 1989 (Hurricane Hugo) and 1998 (Hurricane Georges; Scatena et al., 1993; Silver et al., 1996) and 1611 g C m −2 in 2017 (Hurricanes Irma and Maria; Liu, Zeng, Zou, Gonzalez, et al., 2018).…”

Belowground carbon allocation, root trait plasticity, and productivity during drought and warming in a pasture grass

“…Both drought and warming are known to impair plant physiological processes such as stomatal conductance and leaf cooling, which will potentially lead to heat stress, reducing CO 2 exchange and causing senescence of aboveground plant parts ( Boeck et al , 2011 ). Furthermore, the co-occurrence of drought and heat exacerbates the effects of drought directly by increasing the atmospheric vapour pressure deficit and indirectly by speeding up the process of soil drying due to increased evapotranspiration ( Yuan et al , 2019 ; Grossiord et al , 2020 ; Lian et al , 2021 ; Yaffar et al , 2021 ). Drought and warming treatments each affected soil water content, but responses differed through time, probably owing to changes in both inputs and treatment effects on plant demand ( Supplementary Fig.…”

Global warming changes biomass and C:N:P stoichiometry of different components in terrestrial ecosystems

“…Furthermore, the significant increase in plant and root biomass, but not leaf biomass (Figure 4), suggests that altering growth strategies to adjust biomass allocation is a crucial for mitigating global warming in grassland ecosystems (Chandregowda et al., 2023; Zhou, Terrer, et al., 2022a; Zhou, Zhou, et al., 2022b). Moreover, a recent study concluded that experimental warming reduced root biomass within forest ecosystems characterized by relatively low soil C:N ratios (Yaffar et al., 2021). Overall, tundra ecosystems exhibited the most pronounced response to warming in terms of plant C:N ratios among all studied ecosystems (Figure 4).…”