Weather fluctuations affect the impact of consumers on vegetation recovery following a catastrophic die‐off

Abstract

Prolonged droughts exacerbated by climate change have been widely documented to interact with consumers to decimate vegetation in many ecosystems. Although climate change is increasing within‐year variation in precipitation and temperature, how weather fluctuations affect the impact of consumers on vegetation processes remains poorly understood. In a salt marsh that has recently experienced drought‐associated vegetation die‐off, we investigated how top‐down control of plant recovery by a prominent salt marsh grazer varies with weather. Our results showed that grazing‐driven plant mortality varied strongly with weather in spring, with intense grazing occurring during cool, wet days immediately following rain. Intense grazing on cool, wet days across the generally dry spring season had a strong impact that eliminated plant seedlings that could otherwise have become tolerant of grazing in the following summer, thereby restricting vegetation recovery and contributing to the persistence of an unvegetated salt barren state. Thus, weather fluctuations can modulate the impact of consumers on vegetation recovery, a fundamental process underlying the fate of ecosystems after disturbances. A multi‐timescale perspective on top‐down control that combines the impact of short‐term fluctuations in weather and that of long‐term variation in mean climate can not only help understand ecosystem dynamics in an increasingly variable climate, but may also inform conservation strategies or recovery plans for ecosystems that are already lost to climate change.

Flood‐stimulated herbivory drives range retraction of a plant ecosystem

“…In salt marshes worldwide, it has been demonstrated that consumers can regulate the resilience of the ecosystem. Die‐off vegetation zones induced by drought–consumer interactions in Chinese (He et al., 2017) and US salt marshes (Angelini et al., 2018; Silliman et al., 2005) have persisted with no signs of recovery for many years, even decades, due to grazing after the consumer front vanishes; while after extreme rainy events, crabs can suppress the recovery of degraded Chinese salt marshes (He et al., 2019). Particularly, in Argentinean salt marshes, it has been demonstrated that even under normal climate conditions, crab herbivory is strong enough to delay for years or even prevent the recovery of disturbed patches (Alberti, Escapa, et al., 2010; Alberti, Méndez Casariego, et al., 2010; Daleo et al., 2011; Kaminsky et al., 2015).…”

“…while after extreme rainy events, crabs can suppress the recovery of degraded Chinese salt marshes (He et al, 2019). Particularly, in…”

System-Specific Complex Interactions Shape Soil Organic Carbon Distribution in Coastal Salt Marshes

“…Our modeling results suggest that the consideration of indirect effects can improve model performance for predicting SOC distribution by up to 16% in terms of explanatory power (for instance, for the 10-30 cm soil layer in the DMNNR site, the multiple regression model had R 2 of 0.22, (Table 1), whereas the structural equation model had R 2 of 0.38 (Figure 4e)). The importance of such indirect effects, particularly those operating through trophic interactions, has been well documented in coastal salt marshes as well as in many other ecosystems [20,21,27,39]. For example, it has been documented that crabs can forage for fallen leaf litter and relocate this source of soil organic carbon to deeper burrow chambers [40].…”

Plant hormesis and Shelford’s tolerance law curve

“…In turn, cyclical changes in the environment never strictly have the same pattern. Their cyclical pattern is always accompanied by non-periodic stochastic fluctuations (He et al 2018). For example, circadian changes of temperature and humidity strongly depend on the weather in the same season.…”