Synergistic effects of the components of global change: Increased vegetation dynamics in open, forest-steppe grasslands driven by wildfires and year-to-year precipitation differences.

Miklós Kertész,Attila Lengyel,Réka Aszalós,Gábor Ónodi,Mehdi Heydari

doi:10.1371/journal.pone.0188260

Miklós Kertész, Attila Lengyel + Show 3 more

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https://doi.org/10.1371/journal.pone.0188260

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Abstract

Climate change and land use change are two major elements of human-induced global environmental change. In temperate grasslands and woodlands, increasing frequency of extreme weather events like droughts and increasing severity of wildfires has altered the structure and dynamics of vegetation. In this paper, we studied the impact of wildfires and the year-to-year differences in precipitation on species composition changes in semi-arid grasslands of a forest-steppe complex ecosystem which has been partially disturbed by wildfires. Particularly, we investigated both how long-term compositional dissimilarity changes and species richness are affected by year-to-year precipitation differences on burnt and unburnt areas. Study sites were located in central Hungary, in protected areas characterized by partially-burnt, juniper-poplar forest-steppe complexes of high biodiversity. Data were used from two long-term monitoring sites in the Kiskunság National Park, both characterized by the same habitat complex. We investigated the variation in species composition as a function of time using distance decay methodology. In each sampling area, compositional dissimilarity increased with the time elapsed between the sampling events, and species richness differences increased with increasing precipitation differences between consecutive years. We found that both the long-term compositional dissimilarity, and the year-to-year changes in species richness were higher in the burnt areas than in the unburnt ones. The long-term compositional dissimilarities were mostly caused by perennial species, while the year-to-year changes of species richness were driven by annual and biennial species. As the effect of the year-to-year variation in precipitation was more pronounced in the burnt areas, we conclude that canopy removal by wildfires and extreme inter-annual variability of precipitation, two components of global environmental change, act in a synergistic way. They enhance the effect of one another, resulting in greater long-term and year-to-year changes in the composition of grasslands.

Highlights

In recent years, human-induced global change and its effects on ecosystems have been one of the most important research topics in ecology [1,2]
1) Does compositional dissimilarity increase with time, and if so, is this increase different in burnt and unburnt areas? 2) Do year-to-year changes in species richness depend on year-to-year differences in precipitation, and if so, is this dependence different in burnt and unburnt areas? We studied the above questions in relations to all vascular plant species, as well as separately for short-lived and long-lived
We found that the species richness difference between consecutive years significantly increases with the precipitation difference of those years (Fig 2 and Section B of Table 2)

Summary

Introduction

Human-induced global change and its effects on ecosystems have been one of the most important research topics in ecology [1,2]. As an element of global change, climate change has major influence on grasslands and grassland-woodland complexes [3,4], altering their extent, species richness and composition [5,6]. The ecological impacts of climate change components, i.e. the rise of temperature and changes in precipitation, are the subject of intensive research [7,8]. The distribution of precipitation is one of the most important regulating factors of ecosystems, especially in arid and semiarid grasslands [9,10]. The year-to-year variation in precipitation can be a dominant driver of species turnover in arid or semiarid ecosystems [11] because both previous and current year precipitation amounts are important regulating factors of species diversity and composition in these communities [12]. Few studies have investigated the relationship between year-to-year species dynamics and year-to-year differences in precipitation [13]

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