Why are plant–soil feedbacks so unpredictable, and what to do about it?

Abstract

The study of feedbacks between plants and soils (plant–soil feedbacks; PSFs) is receiving increased attention. However, PSFs have been mostly studied in isolation of abiotic and biotic drivers that could affect their strength and direction. This is problematic because it has led to limited predictive power of PSFs in “the real world,” leaving large knowledge gaps in our ability to predict how PSFs contribute to ecosystem processes and functions. Here, we present a synthetic framework to elucidate how abiotic and biotic drivers affect PSFs. We focus on two key abiotic drivers (temperature and soil moisture) and two key biotic drivers (above‐ground plant consumers and below‐ground top‐down control of pathogens and mutualists). We focus on these factors because they are known drivers of plants and soil organisms and the ecosystem processes they control, and hence would be expected to strongly influence PSFs. Our framework describes the proposed mechanisms behind these drivers and explores their effects on PSFs. We demonstrate the impacts of these drivers using the fast‐ to slow‐growing plant economics spectrum. We use this well‐established paradigm because plants on opposite ends of this spectrum differ in their relationships with soil biota and have developed contrasting strategies to cope with abiotic and biotic environmental conditions. Finally, we present suggestions for improved experimental designs and scientific inference that will capture and elucidate the influence of above‐ and belowground drivers on PSFs. By establishing the role of abiotic and biotic drivers of PSFs, we will be able to make more robust predictions of how PSFs impact on ecosystem function. http://onlinelibrary.wiley.com/doi/10.1111/1365-2435.13232/suppinfo is available for this article.

Can root-associated fungi mediate the impact of abiotic conditions on the growth of a High Arctic herb?

“…Our study revealed that among the abiotic factors temperature was the most important for biotic elements, which reflects its immense significance in physical constraints for arctic biota 1 and the general tendency of modifying interactions between organisms 57 . However, our results also suggest that the impact of temperature on an arctic host plant is far more complex than previously thought 58,59 and in general, perhaps unpredictable 60 . The mechanism behind fungal mediation of temperature is not clear.…”

Climate Affects Plant-Soil Feedback of Native and Invasive Grasses: Negative Feedbacks in Stable but Not in Variable Environments

“…These results are in contrast with previous results of van Grunsven et al (2010), in which direction of PSF detected between pairs of European congeners was largely unaffected by variation in testing temperature, though this study did not manipulate temperature in the testing environment. Our results suggest that across year variation in climate may be one reason why plant-soil feedbacks have been observed to be variable (De Long et al, 2019).…”

“…The first mechanism is that the changes in the AM fungal community contributed to the negative PSF observed (Bever, 2002). In the event of elevated temperatures, AM fungi may decrease activity (Mohan et al, 2014), which in turn weakens positive PSF (De Long et al, 2019), which could further explain our observed negative feedbacks. Changes to the fungal community were likely more pronounced due to the greater growth of the non-native grass relative to the native grass in the training phase of the experiment (Duell et al, 2016) under elevated temperatures (Supplementary Tables 4-6; Supplementary Figure 1).…”

Applying the Aboveground-Belowground Interaction Concept in Agriculture: Spatio-Temporal Scales Matter

“…Although above-belowground biotic interactions have a strong potential to aid sustainable agriculture, the ecological context in which they operate varies strongly across the globe and this can alter how they drive crop growth and ecosystem functioning (Agrawal et al, 2007;Pittelkow et al, 2015;Karp et al, 2018; Figure 2). The impact of soil legacies on plants is strongly dependent on climatic conditions (De Long et al, 2018), as well as biotic and abiotic environmental conditions Casper and Castelli, 2007;Ke et al, 2015). For example, the magnitude and direction of plant growth responses to soil legacy effects can be modified by soil texture or chemistry .…”