Ecosystem fluxes during drought and recovery in an experimental forest

Abstract

An experimental forest ecosystem drought Drought is affecting many of the world’ s forested ecosystems, but it has proved challenging to develop an ecosystem-level mechanistic understanding of the ways that drought affects carbon and water fluxes through forest ecosystems. Werner et al . used an experimental approach by imposing an artificial drought on an entire enclosed ecosystem: the Biosphere 2 Tropical Rainforest in Arizona (see the Perspective by Eisenhauer and Weigelt). The authors show that ecosystem-scale plant responses to drought depend on distinct plant functional groups, differing in their water-use strategies and their position in the forest canopy. The balance of these plant functional groups drives changes in carbon and water fluxes, as well as the release of volatile organic compounds into the atmosphere. —AMS

Leaf-level metabolic changes in response to drought affect daytime CO2emission and isoprenoid synthesis pathways

“…The mean monoterpene emissions were lower for all species under drought conditions than under pre-drought ( Figure 3 ), but not significantly. In this case, the apparent trends in the leaf fluxes diverge from the observed dynamics of monoterpenes in the atmosphere, which increased between our pre-drought and drought measurements (Werner et al ., 2021). Analysis of cartridge samples by GC-MS (which is able to chromatographically resolve different monoterpenes) indicated that α-pinene, β-pinene, 3-carene, limonene, and trans-β-ocimene were the most abundant monoterpenes emitted by C. fairchildiana ( Table 1 ).…”

“…Isoprene emissions from H. rosa sinensis and P. dioica were one to two orders of magnitude lower than those from P. auritum . Between the pre-drought and drought, isoprene emissions only declined significantly for P. auritum (p < 0.05), but there was declining tendency in emissions for C. fairchildiana and P. dioica as well ( Figure 3 ), coincident with an overall decline in atmospheric isoprene abundance (Werner et al ., 2021).…”

“…During the first four weeks of drought in the Biosphere 2 rainforest, surface soil moisture was almost completely depleted and the atmospheric vapor pressure gradient increased in both the canopy and the understory, but at a higher rate in the canopy (Werner et al ., 2021). Drought responses among individuals of the same species were variable and impacted by microclimate conditions ( Figure 2 ) (Werner et al ., 2021). Nevertheless, clear differences in overall drought responses emerged among the four species ( Figure 7 ).…”

“…Black borders indicate measurements where the mean values were significantly different at the p < 0.05 level. 1 Data from Werner et al ., 2021. 2 Data from Huang et al ., in review.…”

“…This study took place within the context of the broader Biosphere 2 Water Atmosphere and Life Dynamics (B2WALD) campaign, described in detail by Werner et al . (2021).…”