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、植物多样性及土壤性质的影响，相关研究仍较为匮乏。本研究采用惠特克植物多样性调查法（Whittaker's plant diversity technique），在洛斯科普水坝自然保护区（Loskop Dam Nature Reserve, LDNR）内的4个草地群落中，收集了物种组成与植物多样性相关数据。研究结果表明，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了提升。防火隔离带会改变物种组成：4个草地群落中有3个，其防火隔离带样地与未火烧样地的物种组成呈现出清晰分异。多数物种与两类样地之间并无显著生境关联，但Themeda triandra与Tristachya leucothrix除外，二者分别被证实与火烧生境、未火烧生境存在特异性关联。物种组成的变化并未对草场状况产生负面影响。防火隔离带样地的土壤碳、氮浓度略低于未火烧土壤，但该浓度降幅并不足以在防火隔离带区域引发严重的土壤退化。从管理视角来看，防火隔离带似乎是一种可持续的管理手段：在洛斯科普水坝自然保护区的草地群落中，它并未对植物多样性或草场状况产生不利影响。