Above: Shelters that impose the rainfall reduction treatments on the RainDrop climate change experiment, Wytham, University of Oxford.
Clipping, drying and weighing above ground biomass is a relatively quick and easy way to quantify response of ecosystem function to global change. For example, at the RainDrop site, Wytham, a climate change experiment which contributes data to drought-net, a global network of co-ordinated drought experiments, we investigate changes in annual above ground biomass production that result from both a 50% reduction and 50% increase in ambient precipitation. However, above ground biomass is only telling a part of the story. Plants do not only consist of stems and leaves but a large proportion of their tissues exist underground as roots and underground storage organs and it is not known whether patterns that are observed above ground mirror those happening below. The response of roots to environment remain far less well studied than above ground parts and this is in large part due to the difficulties involved in measuring below ground traits. One way to study annual root biomass production is by making root in growth cores. After spending some time on the internet trying to make sense of protocols for measuring roots and finding a distinct lack of detailed information, I decided to make this next blog post a methods one. Here’s how I have installed root in growth cores on the RainDrop plots. Continue reading “Going Back to the Roots: How to Measure Underground?”
It is sometimes difficult to believe that globally there are over over 11,000 species of grass that may form extensive swards of homogeneous, green biomass. Even within the UK there are a bewildering ~160 species belonging to the Poaceae that pretty much all look the same. Or do they? Whilst preparing to harvest biomass on the RainDrop drought experiment at Wytham, Oxford (part of the DroughtNet collaboration) I have been thinking about how to identify grasses. A fundamental requirement of many ecological field experiments is knowing exactly what species are present so that changes in abundance and diversity due to treatments can be quantified and explained. However, at times when surveys need to be undertaken it is unlikely that all species will be in flower, a fundamental requirement of many botanical keys. So here are some questions I have found useful when attempting to identify grass species from vegetative features and some notes on some common UK grass species that I thought I would share. Continue reading “Grasses and how on closer inspection they don’t really all look the same”
The causes of a grassy revolution
Grasslands now cover roughly 20% of the terrestrial Earth’s surface, however about 10 million years ago much of these areas were covered by forest. In the Miocene and Early Pliocene (4–8 Myr ago), grasses began a rapid spread across vast areas of the globe causing closed forests to be replaced by grassland. This was one of the most spectacular biome shifts in the geological record but what sparked this sudden rise to dominance of the grasslands we see today and what can this teach us about the future of these ecosystems?
Continue reading “Grass versus Tree”
The word lawn conjures up images of highly artificial and neatly manicured areas of grass in the grounds of a house or park. However, lawns also exist in natural ecosystems with grazing mammals providing the fertilizer and acting as the lawn mower. Grazing lawns (areas dominated by short, palatable, prostrate grass species) are observed across African savannas. Frequent grazing and high nutrient input from animal dung releases short grasses from competition for light and nutrients where they would otherwise be replaced by taller bunch grasses. Continue reading “What will happen if we lose megaherbivores: Africa’s massive lawnmowers?”
South Africa has suffered from its lowest year of rainfall since records began in 1904, and has been in the grip of drought throughout the past year . The causes are an exceptionally strong el nino (a natural phenomena) but also record high temperatures attributable to global warming. The FAO have warned that the extreme weather conditions are “set to have a devastating impact on harvests and food security” and the UN estimate that 49 million people who live in the drought-affected regions of Southern Africa including Zimbabwe, Mozambique, South Africa, Zambia, Malawi and Swaziland will need food assistance over the next year. Should this be a stark reminder of the problems that regions predicted to suffer aridification in the future due to climate change may encounter and have to adapt to? Continue reading “Drought and Food in a Future Climate”
In savanna and grassland ecosystems, globally, the density and cover of woody species has been increasing at unprecedented rates causing large decreases in grassy biomass. In South Africa this land cover change is not an invasion, it is the expansion of native communities of trees and shrubs into grassy areas, and is termed woody encroachment. So what is causing this dramatic increase in tree and shrub cover and why should we care? Continue reading “Woody Encroachment – Can’t See The Grass for the Trees”