The cool season rainfall at our study site should favour C₃ rather than C₄ grasses. There are, however, several locations where C₄ grasses have become dominant, suggesting that rainfall seasonality is not a constraint on distribution. Here, we explored the limitations on C₄ grass distribution in a fynbos shrubland. Using δ¹³C values of SOM, we determined when these grasses had established. We also looked at the role of roads as conduits for establishment and asked what impact these grasses may have on fynbos species richness. We then conducted a field experiment designed to examine the extent to which soil moisture, nutrient availability, and competition with fynbos for resources influence the establishment and growth of the grasses. Finally using aerial photography, we explored the role of changes in land use on distribution. Our results showed that the establishment is recent, that roads may be acting as conduits, and that with establishment, there is a reduction in fynbos species richness and diversity. Disturbance and removing below-ground competition for resources open the system to establishment in wetter areas. This study is the first to look at the potential for C₄ grasses expanding into cool season rainfall shrublands such as in Western Australia and South Africa. What is interesting about these results is that C₄ grasses can establish and dominate in a cool season rainfall regime. Rather than temperature of the growing season, it is competition for resources from fynbos that prevents these grasses from encroaching.

我们研究地点的凉爽季节降雨应该偏爱C ₃草，而不是C ₄草。但是，在C ₄草占主导地位的几个地方，这表明降雨季节对分布没有限制。在这里，我们探讨了在小灌木丛灌木丛中C ₄草分布的局限性。使用δ ¹³SOM的C值，我们确定这些草何时成立。我们还研究了道路作为建立渠道的作用，并询问这些草可能对Fynbos物种丰富度有何影响。然后，我们进行了一项野外试验，旨在研究土壤水分，养分利用率以及与粉虱争夺资源的程度影响草的生长和发育。最后，通过航拍，我们探讨了土地利用变化对分配的作用。我们的结果表明，该设施是最近才建立的，道路可能起着管道的作用，而随着设施的建立，雌雄同体物种的丰富性和多样性有所降低。干扰和消除地下资源竞争使系统得以在较潮湿的地区建立。₄种草扩展到凉爽的降雨灌木丛，例如在西澳大利亚和南非。这些结果令人感兴趣的是，C ₄草可以在凉爽的降雨条件下建立并占据主导地位。并非是生长期的高温，而是蕨类植物对资源的竞争阻止了这些草类的入侵。