Bubas bison tunneling - photos

From: Date:  05/12/2008

Hi All, As many of you know, over the last few years I've been conducting research on the impact of dung burial (by dung beetles) on soil health. As part of the study I am describing tunneling and dung burial by summer (Onthophagus binodis) and winter-active (Bubas bison) dung beetles, in a clay soil (at Merton, NE Vic.) and have attached an initial summary of some of the info. I'm also measuring changes in soil chemistry, soil biology, compaction and water infiltration. Data analysis is far from complete, but some early conclusions are worth sharing now. The soils at the Merton research site typically have a compacted hard pan just below the surface (~2-5cm; where the clay starts). At ~15cm depth there is a ~10cm thick buckshot layer that overlies a mottled orange-red clay. Typically, pasture root development is concentrated in the top few cm, with only limited root penetration into the layers below. However, all that changes when Bison start digging. And the effect is staggering. Bison not only tunnel into the top of the buckshot layer; they go through it, into the subsoil. This gives plant roots, earthworms and other soil organisms (like Click Beetle larvae) easy and direct access to the sub soil (below the buckshot), which remains moist for much longer than the surface layers of the soil. Of course, the roots and earthworms are also feeding in the tunnels, which are filled with dung/loose soil, so improving pasture productivity significantly (more on this another later). The dung was buried in August 2007 and the photos on the attached pdf were taken in Nov 2008, 15 months later. By burying dung so deeply, Bison bring a lot of less-fertile subsoil, buckshot and all, to the surface, which can actually cause a temporary bare patch on the soil surface. But, over time, and in combination with improved earthworm activity (which follows naturally) the benefits to a soils such as this are massive; breaking up hard pans, mixing soil/nutrients and providing roots and soil biology with access to the top ~30cm of the soil profile - pretty amazing really. The summer active dung beetles don't tunnel nearly as deeply (not surprising, as soil soil can be rock-hard), so their dung burial and soil mixing occurs in the top ~10cm. A consequence of this is that summer dung beetles have a more immediate impact on improving and deepening the topsoil and they don't bring the infertile subsoil to the surface as much as Bison. These differences are clearly reflected in the changes in soil chemistry, when comparing summer dung burial, winter dung burial and controls (more on this another time). So there's a good reason for having different types of dung beetle, that are active at different times of the year. And to get the benefits it's important that farms are dung beetle friendly. In this regard, making informed drenching decisions can be crucial (recent Kondinin Group article attached). Bison is now well established in the Goulburn Broken catchment and over quite a large area (map attached). Hope you find this of interest. Link Posted with this message http://mc2.vicnet.net.au/home/bertraml/files/Images_of_Bubas_bison_tunneling_B.pdf