Grassroots Grassroots - Vol 18 No 4 | Page 20

NEWS Lightning, biodiversity, global change and Smarties in the mountains – say what? Paul Gordijn and Professor Tim O’Connor Current Address: SAEON Reprinted From: http://bit.ly/2OPhQDg W ith intrigue, researchers have noted the co-occurrence of grasslands and areas with fre- quent lightning storms. Lightning has played a key role in the evolution of these grassland ecosys- tems specifically, by influencing how of- ten and when fires move through land- scape. Fire limits tree growth; without it, grass- lands in tropical and subtropical regions would transform into shrublands and forest. Before humans became domi- nant drivers in the grassland landscape, fire regimes were driven by patterns in lightning ignition. Although we may predict that a lightning-driven fire re- gime may be more variable than a rig- orous anthropogenic or human-driven management regime, the particulars of historic lightning-driven fire regimes re- main elusive. What’s with the fascination in historic fire regimes anyway? Well, the reasoning goes that since grassland flora and fauna have evolved under these ‘natural’ fire regimes, if we were able to reproduce a ‘natural’ re- gime, ecosystems would flourish. Perhaps we may expect optimal func- tioning of ecosystems and maximal di- versity in these grasslands? Maybe un- der these regimes, grasslands would be best suited to the extremes of climate change associated with global change? These are important questions to ask under current global change pressures and also realising that grasslands are one of the most transformed biomes on earth. Drakensberg grasslands Of southern African grasslands, Drak- ensberg grasslands stand out for their high levels of endemism and for being a biodiversity hotspot (that is, the area hosts numerous species and many of them are found nowhere else), plus the important ecosystem services they pro- vide. Also, these grasslands are known as the ‘water tower’ of southern Africa, for from these mountains our great riv- ers such as the Orange and uThugela find their source. In these grasslands, charcoal deposits and palynological (i.e. ‘pollen archaeol- ogy’) evidence from cores suggest that with the arrival of farmers and pasto- ralists, fire has intensified over the last thousand years or so. In particular, fire use may be expected to have become more finely managed or rigorous over the last century as settlement in the re- gion increased. The contrast of the presumed ‘natural’ fire regime versus the recent rigorous fire regimes begs a question of the ef- fect of different fire regimes on these grasslands. If we were able to answer this question we are on track to promot- ing ecosystem functioning and biodi- versity in the face of global change. Cathedral Peak sentinel site The SAEON Cathedral Peak research platform provides a unique opportunity to assess grassland vegetation change over time in response to different fire regimes or treatments. The platform is a world-class research site with a long history of research. Importantly, the fire treatments at the Cathedral Peak research catchments have been running for over half a centu- ry. The fire treatments include both fre- quent (burnt every one to three years) Figure 1: Lightning has played a key role in the evolution of our grassland ecosystems by influencing how often, when and how fires move through the landscape (Photo: Sue Janse van Rensburg) 19 Grassroots Vol 18 No 4 December 2018