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News Article

Knock on effects of silviculture for saproxylic beetles


Silvicultural practices can disrupt forest continuity by creating periods without deadwood

Dead wood is the result of natural turnover in forest environments, creating a continuous stock of wood in various stages of decay that supports a whole community of fungi and insects. In managed forests, however, this natural process may be disrupted, creating knock on effects for biodiversity. The level to which these processes are affected is highly dependent on the style of silvicultural management being applied; uneven-aged silviculture maintains a constant turnover of larger trees, creating a continual supply of deadwood however even-aged silviculture leads to periods with no deadwood, disrupting the natural cycle. Even-aged silviculture has already been linked to detrimental ecological effects, including reductions in biodiversity.

In order to better understand the effects of different silvicultural treatments on deadwood volume and decay progress, as well as beetle diversity, researchers in Sweden and Australia have studied five different forest types in Sweden. In boreal forests there has been a sizeable transition from natural woodland to various types of management, making them good study systems for a comparison of impacts. The five boreal forest types compared were each under a different management approach: clearcutting, thinning, selective felling, reference and old growth forests. The first two being even-aged and the latter representing uneven-aged. Deadwood provides a habitat for many insects, namely those that are saproxylic; these beetles can be either dependent on the wood itself or on organisms which are. Tree age and species are known to influence the diversity of these beetles, however, they are also sensitive to dead wood size and decay stage. These characteristics make them highly appropriate to study the influence of various silvicultural management schemes on forest biodiversity.

The most notable result of this work was that the beetle assemblages on clear-cuts were unique irrespective of trapping method or stage of deadwood decay. Early and late successional species showed similar responses to multiple silvicultural practices. Of all the treatments, uneven-aged silviculture showed species assemblages most in line with the reference and old growth forests. Species composition was influenced by the volume of early decay stage wood but only for early and not late successional species.

The uptake of even-aged silviculture has contributed greatly to the decrease in deadwood in managed forests, this has led to a homogenisation of forest environments, to counter this, management programmes should seek to mimic natural processes which diversify the ecosystem. Un-even aged silviculture is more successful in this objective, creating a more consistent environmental structure that reflects natural disturbances.

 

Read the original publication here:

Joelsson, K., Hjältén, J. and Gibb, H., 2018. Forest management strategy affects saproxylic beetle assemblages: A comparison of even and uneven-aged silviculture using direct and indirect sampling. PloS one, 13(4), p.e0194905. https://doi.org/10.1371/journal.pone.0194905

To find over 500 similar papers use the search string below in the Forest Science Database:

"dead wood" AND ("silviculture" OR "forest management" OR "forestry practices" OR "uneven-aged management" OR "even-aged management") AND ("species composition" OR "species diversity" OR "biodiversity")