Short Rotation Forestry and Earthworm Diversity: Impacts and Responses

Abstract

Short Rotation Forestry (SRF) has been introduced to the UK as a method to increase biomass production. However, some SRF species have raised concerns about potential impacts on the environment. A largely unknown aspect of SRF is the quality and quantity of leaf litter, and its impact on soil fauna, of which the earthworm community is a major component. Earthworms have direct impacts on the soil biogeochemistry of SRF systems, and the tree species can impact on the associated earthworm community. The aim of this study was to investigate the effects of SRF species and litter quality on earthworm communities, their diversity and activity. In addition, the effects of earthworms on SRF litter decomposition, carbon-nutrient cycling and tree growth were assessed. Field surveys, laboratory experiments and field experiments were utilised. Survey results suggested that SRF species, tree age, land-used history and soil type exhibited an interactive effect on overall earthworm community development. Further, growth of eucalyptus, as SRF on marginal-arable or reclaimed sites, led to relatively rapid earthworm colonisation and community development. SRF litter quality showed a direct effect on earthworm food selection, growth and reproduction. The native Alnus glutinosa, Betula pendula and Fraxinus excelsior litter supported earthworms and their activities over non-native Acer pseudoplatanus, Castaneas sativa and Eucalyptus nitens. Native British earthworms indicated a significant preference (p < 0.05) for E. nitens litter over A. pseudoplatanus and C. sativa. Earthworms showed a significant contribution (p < 0.05) to SRF litter decomposition, carbon and nutrient release within SRF systems and the degree of contribution varied with SRF species, earthworm density and diversity. Field studies demonstrated that a mixed earthworm community utilised non-native species but favoured particular native trees. Earthworm influence on nutrient uptake, tree growth and biomass production varied with SRF species. A one year field experiment showed that rapidly growing E. nitens benefited more from earthworm activity than relatively slow growing B. pendula. Overall, the current work supports the production of SRF, as with only one exception (C. sativa), results tended to show that SRF-earthworm interactions were positive. It is perhaps most interesting that non-native E. nitens showed a positive interaction with native British earthworms.