Veteran trees are disappearing from the Moravian Amazonia and the associated biodiversity with them
Recently, a team of geographers from Ostrava and entomologists from České Budějovice have worked together to trace back the past changes of floodplain forests along the lower Dyje and Morava rivers, a hot-spot of biodiversity in South Moravia nicknamed "Moravian Amazonia". The researchers have found that the most valuable veteran trees hosting hundreds of associated species, many of them endangered, are mostly remains of former open woodlands. The increase in canopy cover due to an ongoing succession and the lack of efficient conservation management are the main drivers of biodiversity loss in the area and the country.
Open woodlands are biologically highly diverse habitats, and veteran (i.e., old, senescent) trees are key structures supporting their biodiversity. Open canopy structure had been maintained by both natural and human-induced disturbances. In the past two centuries, suppression of such disturbances, together with forestry intensification, has turned most lowland woodlands into closed-canopy forests. We investigated the effect of increased canopy closure on veteran trees and several threatened beetles associated with them.
We used an approach combining the study of aerial photographs with on-ground survey of veteran trees and associated endangered beetles. The aerial images were used to obtain the information on historical (1938) and recent (2009) canopy closure in the area of 146 km2 of floodplain woodlands along the lower Dyje and Morava rivers, Czech Republic, where we mapped large oaks (d.b.h. >70 cm), hollow trees and three associated beetles including the hermit beetle (Osmoderma barnabita), the great capricorn beetle (Cerambyx cerdo) and the jewel beetle Eurythyrea quercus.
The presence of large oaks, hollow trees and their associated beetle species are negatively related to recent high canopy closure, and the historical level of canopy closure matters, as in nowadays closed-canopy stands, the beetles and veteran trees are more common in places that were rather open in 1938 than in the places with closed canopy already in 1938. Moreover, the health state of veteran trees highly depends on the canopy closure.
The negative effect of canopy closure on veteran trees and their endangered inhabitants is several decades delayed and may thus often go undetected. In the forests, however, large and hollow trees and their associated biodiversity are relics of the past, more open conditions. The restoration of open woodlands is therefore vital for preventing their further decline. Conservation management planning needs to take this into account wherever veteran trees and associated biota are concerned.
Miklín J., Šebek P., Hauck D., Konvička O., Čížek L. Past levels of canopy closure affect the occurrence of veteran trees and flagship saproxylic beetles. Divers Distrib. 2017; 00:1–11. http://onlinelibrary.wiley.com/doi/10.1111/ddi.12670/full