Forest understory plant and soil microbial response to an experimentally induced drought and heat‐pulse event: the importance of maintaining the continuum

Abstract

Drought duration and intensity are expected to increase with global climate change. How changes in water availability and temperature affect the combined plant-soil-microorganism response remains uncertain. We excavated soil monoliths from a beech (Fagus sylvatica L.) forest, thus keeping the understory plant-microbe communities intact, imposed an extreme climate event, consisting of drought and/or a single heat-pulse event, and followed microbial community dynamics over a time period of 28 days. During the treatment, we labeled the canopy with (13) CO2 with the goal of (i) determining the strength of plant-microbe carbon linkages under control, drought, heat and heat-drought treatments and (ii) characterizing microbial groups that are tightly linked to the plant-soil carbon continuum based on (13) C-labeled PLFAs. Additionally, we used 16S rRNA sequencing of bacteria from the Ah horizon to determine the short-term changes in the active microbial community. The treatments did not sever within-plant transport over the experiment, and carbon sinks belowground were still active. Based on the relative distribution of labeled carbon to roots and microbial PLFAs, we determined that soil microbes appear to have a stronger carbon sink strength during environmental stress. High-throughput sequencing of the 16S rRNA revealed multiple trajectories in microbial community shifts within the different treatments. Heat in combination with drought had a clear negative effect on microbial diversity and resulted in a distinct shift in the microbial community structure that also corresponded to the lowest level of label found in the PLFAs. Hence, the strongest changes in microbial abundances occurred in the heat-drought treatment where plants were most severely affected. Our study suggests that many of the shifts in the microbial communities that we might expect from extreme environmental stress will result from the plant-soil-microbial dynamics rather than from direct effects of drought and heat on soil microbes alone.

Plant and soil microbe responses to light, warming and nitrogen addition in a temperate forest

“…To date, studies on the effect of global environmental change have involved various drivers, such as N deposition, climate warming, precipitation and CO 2 concentration (Ciais et al, 2005;Hyvonen et al, 2007;Ramirez, Craine, & Fierer, 2012;von Rein et al, 2016).…”

“…Likewise, changes in plant community composition and diversity can also modulate soil microbial activities (Lange et al, 2015). To better understand the mechanisms behind the combined effects of multiple environmental drivers on light-limited ecosystems such as forest understoreys, it is important to not only look at the responses of the understorey plants or the responses of the soil microbes and the understorey plants separately, but to also quantify co-occurring responses (von Rein et al, 2016). Hence, studies should investigate the plant-soil continuum together to make realistic predictions on the effects of global environmental changes (von Rein et al, 2016).…”

“…To better understand the mechanisms behind the combined effects of multiple environmental drivers on light-limited ecosystems such as forest understoreys, it is important to not only look at the responses of the understorey plants or the responses of the soil microbes and the understorey plants separately, but to also quantify co-occurring responses (von Rein et al, 2016). Hence, studies should investigate the plant-soil continuum together to make realistic predictions on the effects of global environmental changes (von Rein et al, 2016). Plants and soil microbes might respond differently to different global environmental change drivers (Farrer and Suding, 2016), and the interaction between the multiple drivers may attenuate or increase the magnitude of the responses of both plants and soil microbes.…”

“…Yet, to which degree the two drivers are synergetic or antagonistic in terms of affecting the soil bacterial community needs further research. vonRein et al (2016), in a warming experiment in an incubator, showed interactive effects of the global change drivers warming and drought on the composition of the soil microbial community, with no effect of warming alone. Hence, when two or more global change drivers are considered simultaneously, the interaction of the drivers may result in additive or attenuated effects and thus cause different responses of the studied community when compared with drivers applied in isolation.…”

Responses of the structure and function of the understory plant communities to precipitation reduction across forest ecosystems in Germany

“…However, we lack information on drought impacts on the understory. It is important to shed more light on drought responses of the understory plant community, as these communities play a central role in ecosystem biogeochemistry, e.g., by influencing water availability, litter decomposition and nutrient cycling (Schulze 2000;von Rein et al 2016), as well as tree recruitment of the future forest. The understory, as understood in the present study, comprises the stratum up to a height of 1 m above ground (Gilliam 2007), including herbaceous vascular plants and seedlings of trees and shrubs, and harbors a great portion of the plant diversity in forests (Gilliam 2007).…”