Institute of Ecology and Botany, MTA Centre for Ecological Research, Vácrátót, Hungary.
MTA Centre for Ecological Research, GINOP Sustainable Ecosystems Group, Tihany, Hungary.
PLoS One. 2017 Nov 17;12(11):e0188260. doi: 10.1371/journal.pone.0188260. eCollection 2017.
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.
气候变化和土地利用变化是人类引起的全球环境变化的两个主要因素。在温带草原和林地，干旱等极端天气事件的发生频率增加，野火的严重程度加剧，改变了植被的结构和动态。在本文中，我们研究了野火和年际降水差异对森林草原复合生态系统半干旱草原物种组成变化的影响，该生态系统部分受到野火干扰。特别是，我们研究了长期组成差异变化和物种丰富度如何受到火烧区和未烧区年际降水差异的影响。研究地点位于匈牙利中部，位于受保护的地区，这些地区以部分燃烧的、具有高生物多样性的杜松-杨树林草原复合体为特征。数据来自于 Kiskunság 国家公园的两个长期监测站点，这两个站点的特征都是相同的栖息地复合体。我们使用距离衰减方法研究了物种组成随时间的变化。在每个采样区域，组成差异随采样事件之间时间的流逝而增加，物种丰富度差异随连续几年降水差异的增加而增加。我们发现，无论是长期的组成差异还是物种丰富度的年际变化，在火烧区都高于未烧区。长期组成差异主要由多年生物种引起，而物种丰富度的年际变化则由一年生和二年生物种驱动。由于降水年际变化的影响在火烧区更为明显，我们得出结论，野火去除林冠和降水的极端年际变异性这两个全球环境变化的组成部分以协同方式发挥作用。它们相互增强，导致草原组成在长期和年际上发生更大的变化。
