11. The mean individual biomass of carabid beetles in forest ecosystems

Marek Dobrowolski,Andrzej Kolk

   In 2003, the mean individual biomass (MIB) of epigeic carabid beetles was assessed on 40 second-level POPs located in the Regional Directorates of the State Forests in Białystok, Lublin, Łódź and Radom.

The comparison of results obtained from the first and second observation series proved an increase in the MIB values on 19 monitored POPs (73% of all POPs involved in the 2003 study).

The MIB value found for one POP was identical, while on other POPs (6) this value was lower in 2003 when compared to the previous observation series.

It can be stated that an increase in MIB value was found on all monitored POPs which may confirm a general regularity that the mean biomass of carabid assemblages increase with the aging of stands. This statement can account for the undisturbed successional process ongoing in forest ecosystems on the majority of POPs. A decrease in the number of caught beetles and a decrease in the MIB value on a number of POPs can indicate strong disturbances of the process of natural development of the ecosystem structure. However, it has to be remembered that the decrease in the carabid population abundance is a natural phenomenon associated with natural long-term fluctuations in the population abundance of given species in an assemblage.

An increase in the MIB value means that the threat to stands by insect pests outbreaks lowered - Fig. 14.

The greatest threat posed by insects to stands was found only on three monitored POPs, moderate threat was not observed, weak threat - only on two POPs located in the Międzyrzec and Supraśl Forest Districts. On all other plots the lack of a MIB indicator confirmed the lack of threat to stands threat posed by insect pests.