Increased rainfall frequency triggers an increase in litter fall rates of reproductive structures in an arid eucalypt woodland

Abstract

Abstract The diversity of responses to episodic rainfall events among perennial plant species is critical for the maintenance of ecosystem functions in arid systems. We use a litter fall study to capture the responses of three species to shifts in environmental conditions. We examined the effects of landform, rainfall and other meteorological variables (temperature, evaporation, relative humidity, solar exposure, wind speed and cloud cover) on the mass of reproductive structures falling from two shrubs (Senna artemisioides ssp. filifolia, Acacia burkittii) and one tree (Eucalyptus gracilis) species in a eucalypt mallee woodland in semi‐arid eastern Australia. Data were collected over three years. The first year received below‐average rainfall and the following years received about twice the average annual rainfall. We assessed the relative importance of our explanatory variables, for each species separately, comparing the results using two methods: (1) multi‐model inference of a zero‐inflated negative binomial generalized linear model, and (2) structural equation modelling. Multi‐model inference showed rainfall frequency, at species‐specific lag intervals, to be of highest relative importance for all three species. Wind speed was also relatively important for all three species. Structural equation modelling supported these results, with strong, direct path coefficients for the number of days of rainfall in the past 12 months. There was, however, no strong effect of the average rainfall event size. Our analyses demonstrate the strong, direct and positive effect of rainfall, and highlight the importance of rainfall frequency rather than rainfall event size. Furthermore, we found species‐specific responses to environmental variables associated with wind, solar exposure and landform, further driving the litter fall of reproductive structures in perennial plants in semi‐arid environments. Understanding how different species respond to rainfall and other meteorological conditions can give us greater insights into the capacity of these systems to adapt, which will be important in a changing climate.