The Effect of Forest Management Options on Forest Resilience to Pathogens

Abstract

Invasive pathogens threaten the ability of forests globally to produce a range of valuable ecosystem services over time. However, the ability to detect such pathogen invasions-and thus to produce appropriate and timely management responses-is relatively low. We argue that a promising approach is to plan and manage forests in a way that increases their resilience to invasive pathogens not yet present or ubiquitous in the forest. This paper is based on a systematic search and critical review of empirical evidence of the effect of a wide range of forest management options on the primary and secondary infection rates of forest pathogens, and on subsequent forest recovery. Our goals are to inform forest management decision making to increase forest resilience, and to identify the most important evidence gaps for future research. The management options for which there is the strongest evidence that they increase forest resilience to pathogens are: reduced forest connectivity, removal or treatment of inoculum sources such as cut stumps, reduced tree density, removal of diseased trees and increased tree species diversity. In all cases the effect of these options on infection dynamics differs greatly amongst tree and pathogen species and between forest environments. However, the lack of consistent effects of silvicultural systems or of thinning, pruning or coppicing treatments is notable. There is also a lack of evidence of how the effects of treatments are influenced by the scale at which they are applied, e.g., the mixture of tree species. An overall conclusion is that forest managers often need to trade-off increased resilience to tree pathogens against other benefits obtained from forests.

Commercial afforestation can deliver effective climate change mitigation under multiple decarbonisation pathways

“…Although our modelled commercial forestry system is 100% Sitka spruce, single species forests are not the only commercial option, and there is increasing support for mixed-species conifer forests (or coniferbroadleaf mixtures), under sustainable forest management to deliver both a high yield of wood products and other ecosystem services 20,41 . Diversification of commercial forestry could also enhance resilience to pests, diseases and climate change effects [42][43][44] . Nabuurs et al 8 argue for policy changes to encourage such 'climate-smart forestry', claiming it could deliver an extra 441 Mt CO 2 e year −1 mitigation across Europe by 2050.…”

Catalogue of pests and pathogens of trees on the island of Ireland

“…Species diversification and the use of alternative silvicultural systems (e.g. uneven aged silviculture) have been identified as ways to buffer against large scale pest and pathogen epidemics in forests (Ennos 2015;Jactel et al 2017Jactel et al , 2020Roberts et al 2020).…”

Understanding biological resilience, from genes to ecosystems

“…In tree species with long generation times, resilience is likely to depend strongly on phenotypic plasticity and transgenerational transfer of information 101 , as changes to the genome through selection are slow. Better management of forests, therefore, likely requires managers to avoid conversion of forest to monotypic or reduced species plantations 43 , and to consider use of alternate genotypes when seeding new forests 102 . Achieving increased resilience, however, will require understanding which features at each biological level are most important to manage, and whether enhanced diversity at one level (e.g.…”