On a bed of moss on a large rock on a high knoll, below the summit of a steep, forested ridge, lies – prostrate and exposed – a slab of wood. Continue reading
Take a close look at the coppicing trees in the old photo above. Notice anything unusual?
Perhaps it looks like any other stand of burnt mallee? Perhaps it does. But most of the trees aren’t resprouting after a fire. They aren’t recovering from drought, insect attack or damage by humans either. What could have caused the damage? Continue reading
In 2010, Craig Allen and colleagues published ‘the first global assessment of recent tree mortality attributed to drought and heat stress’ (Allen et al. 2010). In this fantastic paper, the authors collated examples of tree die-off (or mortality) from around the world and – in a very long sentence – they concluded:
… studies compiled here suggest that at least some of the world’s forested ecosystems already may be responding to climate change, and raise concern that forests may become increasingly vulnerable to higher background tree mortality rates and die-off in response to future warming and drought, even in environments that are not normally considered water-limited.
Given that pessimistic prognosis, it’s worth asking; how are trees faring here, in our own backyard? Continue reading
We all know an old paddock tree when we see one: broad, deep, canopy; sagging, tangled branches; broken boughs full of hollows. The classic woodland tree. But how do you recognize an old tree that grew – not in the open – but in a closed, dense stand? It won’t have a big, wide canopy nor a thick, wide trunk if its growth was suppressed by neighbors. Continue reading
Everyone sees something different in a patch of bush. I usually wonder: were these patterns that we see created by natural forces (such as soils and geology) or by a hidden mosaic of past disturbances?
Most times, I work in ecosystems with a long history of human disturbances, such as clearing and felling, grazing and burning. Their imprints can be both indelible and invisible, but more often, just plain forgotten. Yet we need to know how disturbances have altered natural ecosystems, so we can predict how our activities will alter ecosystems in the future.
The best way to see the imprint of past disturbances is by combining field evidence and archival documents, like old reports and maps. But we often have to rely solely on field skills. Just as the science of geology required the law of superposition – which simply states that sediments were laid down sequentially, so lower strata are older than upper strata – so historical ecology requires the ability to see key juxtapositions. By observing how things are arranged in space, we can develop a chronology of past events and an informed narrative of ecological change. Continue reading
Apologies for the delay in posting another blog, but I’ve been away in the field enjoying old-growth ironbark forests, long-unburnt box forests, grassland grazing exclosures, regrowth mallee and more. All of which have prompted lots of ideas for future posts.
In the interim, here are three ‘must read’ links from two fantastic vegetation bloggers, which you are sure to enjoy. All three posts highlight the importance of the way we think when we talk about ‘grasslands’, ‘restoration’, ‘conservation’ and ‘functionality’. Continue reading
Predicting how ecosystems will change as climate change progresses is a major challenge. A popular view is that species will move from warmer to cooler regions – towards the alps and poles – as global warming intensifies. We can think of this as the ‘President of the USA’ model, in which every newborn child has the potential to ‘lead the free world’. A theory that emphasizes potentiality over probability. The philosophy is great, but just as most of us have zip chance of becoming President, ecologists worry that many species have no chance of dispersing fast enough to keep up with a rapidly changing climate.
Another curious aspect of this ‘waves of migration’ view is that it implies that species will respond to climate change in isolation. Thus, ten different species might all move uphill as the world gets warmer, without interacting with each other or with other species. But in nature, interactions rule. All populations are influenced by many factors other than climate, including other species and ecological disturbances.
We get a different perspective on how global warming will affect natural ecosystems if we change our view point from the regional to the local.
Picture a reserve that you know well, and imagine how the vegetation might change as global warming progresses.