The effects of fire-breaks on plant diversity and species composition in the grasslands of the Loskop Dam Nature Reserve, South Africa

There is a dearth of knowledge on the effects of annual burning of fire-breaks on species composition, plant diversity and soil properties. Whittaker's plant diversity technique was used to gather data on species composition and diversity in four grassland communities on the Loskop Dam Nature Reserve (LDNR). The study demonstrated that fire-beaks did not have a negative effect on plant diversity and an increase was even noted in various diversity parameters in the grassland on abandoned cropland. Fire-breaks were changing the species composition, as three of the four communities illustrated a clear separation in species composition between fire-break and unburnt plots. There was not a strong association between specific species and the fire-break or unburnt plots, except for <i>Themeda triandra</i> and <i>Tristachya leucothrix</i>, known for their association with and without fire, respectively. The change in species composition was not negatively affecting range condition. Carbon and nitrogen concentrations were slightly lower in the fire-break than unburnt soils, but the reduced concentrations were unlikely to cause severe soil degradation in fire-break zones. From a management perspective, fire-breaks appear to be a sustainable management tool as they are not adversely affecting plant diversity or range condition in the grassland association on LDNR.

目前关于年度火烧防火隔离带(fire-breaks)对物种组成、植物多样性及土壤特性的影响，相关研究仍较为匮乏。本研究采用惠特克植物多样性采样法(Whittaker's plant diversity technique)，对洛科普普水坝自然保护区（Loskop Dam Nature Reserve, LDNR）内的4个草地群落的物种组成与多样性数据开展采集工作。研究结果显示，防火隔离带并未对植物多样性产生负面影响，甚至在弃耕地草地的多项多样性参数中观测到多样性水平有所提升。防火隔离带改变了群落的物种组成：4个草地群落中有3个在火烧防火隔离带样地与未火烧样地之间呈现出清晰的物种组成分化。除了分别以与火烧生境、无火烧生境相关而闻名的<i>Themeda triandra</i>和<i>Tristachya leucothrix</i>外，并未观测到特定物种与防火隔离带火烧样地或未火烧样地存在显著关联。物种组成的变化并未对草场健康状况产生负面影响。防火隔离带样地的土壤碳、氮浓度略低于未火烧样地，但该浓度降幅并不会导致防火隔离带区域出现严重的土壤退化。从草地管理视角来看，在洛科普普水坝自然保护区的草地群落中，防火隔离带是一种可持续的管理工具，因其并未对植物多样性或草场健康状况造成不利影响。