Search

Growth models continue to be of importance in modern multi-functional forestry to provide forecasts. Bayesian calibrations allow both model structure and parameters to be assessed simultaneously in a probabilistic framework, providing a model with which forecasts and their uncertainty can be better understood and quantified using posterior probability distributions. A Bayesian calibration of a stand-level dynamic growth (SLeDG) model is carried out for both Sitka spruce and Scots pine in the UK for the first time. The calibration used the differential evolution Markov-Chain method to reduce the required number of iterations for inference. Two different model structures were considered for estimating local stand productivity: one using the measured height–age relationship, and one using estimated site yield class. The height–age relationship was shown to be more probable for both species in a Bayesian model comparison (total model probability[Math Processing Error]0.64 and 0.58 for Sitka spruce and Scots pine, respectively), although metrics of model performance were similar for both model structures ([Math Processing Error] in all variables). A complete calibration (using all data) of the more probable model structure was then completed, and excellent model fit was observed ([Math Processing Error] for all variables in both species). Example forecasts using the output from the calibration were demonstrated, and are compatible with existing yield tables for both species. This method could be applied to other species or other model structures in the future.

Summary The effects of site preparation practices (drainage, mounding and fertilization) on the fluxes from the soil surface of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) were studied on an organic-rich peaty gley soil at Harwood Forest, north-east England. Drained plots had significantly higher CO 2 fluxes but significantly lower CH4 fluxes compared with undrained plots, while N 2O emissions were not affected by drainage. Mounding caused significantly higher CH 4 emissions, while it significantly reduced N 2O emissions. Fertilization caused significant increases in emissions of CO2, CH4 and N2O. In terms of overall greenhouse warming potential, drainage and fertilization increased CO2-equivalent emissions by ~18−29 and 7−23 per cent, respectively, while mounding reduced CO2-equivalent emissions by ~8 per cent in year 1, but had no effect on emissions in year 2 of study. Soil temperature was the main environmental variable controlling CO2 emissions, while CH4 was controlled primarily by water table depth. Nitrous oxide emissions responded to changes in soil temperature and water table depth. In the short term, drainage and fertilization contributed to accelerating greenhouse gas emissions significantly, although their long-term effects are likely moderated by accelerating carbon accumulation in the tree biomass. Long-term studies are required to assess the cumulative impacts of site preparation practices during the whole rotation cycle.

Summary Continuous cover forestry (CCF) aims at enhancing stand structural diversity and favouring natural regeneration. To give guidance on how to manage a CCF stand to achieve seedling growth below canopy, an estimate of light transmittance is required. So far, in the UK, only stand-level parameters have been used by managers to predict the understorey light in CCF stands. We assessed a UK Sitka spruce stand undergoing transformation to CCF and measured canopy transmittance using hemispherical pictures. Stand-level characteristics were found to be highly stand specific and not appropriate to predict seedling growth in CCF stands. We parameterized a detailed light model (4C-A-RTM) and a simple one-layer turbid medium model (BL). A sensitivity analysis was performed to test the effect of key stand structural parameters on the modelled transmittance. Measured transmittance from hemispherical photographs was used to validate the models. Both models tended to underestimate canopy transmittance but were positively related to current-year growth of the below canopy seedlings (R 2 = 0.92, P < 0.001). Comparison of the two models showed that the 4C-A-RTM provided a better estimation of light transmittance across observed canopy structural differences. Furthermore, the inclusion of stand characteristics in the 4C-A-RTM is likely to confer greater applicability across stands.

Following the publication of the Millennium EcosystemAssessment (MEA, 2005), there has been increasing interest in evaluating the state of different ecosystems, the range and categories of services these systems provide, their effects upon human well-being, and the consequences of direct and indirect anthropogenic impacts. The framework provided by the MEA’s categories of ecosystem services (ES:, i.e. provisioning, regulating, cultural and supporting services) can be used to explore the role of forests in a wider landscape, as well as to examine the effects at a finer scale and the way ES provision from forests is affected by management actions (Eustafor and Patterson, 2011). There are overlaps between this framework and the concepts of sustainable forest management (SFM) that have underpinned forest policy for at least the last two decades. The multifunctional management strategies developed through SFM may be compromised by economic valuations involved with ES (Quine et al., 2013). There is a recognized need for research that examines the links between ecological systems such as forests and social institutions and management practices both over space and through time in order to improve methods of ecosystem governance (Carpenter et al., 2009). This ongoing dialogue around ES and their value to society presents forest managers with the major challenge of describing, assessing and delivering the various benefits that forest ecosystems provide. These benefits will vary with different types of forest ecosystem and the ways in which they are managed. One forest type of major importance in the northern Hemisphere comprises those forests dominated by spruce (Picea) species which occur both as natural forest systems (e.g. in North West America, Europe and North East Asia) and as plantation forests (e.g. the British Isles, Western Europe). These forests provide a wide range of ES such as biodiversity, recreation, timber, water quality, carbon sequestration and landscape. Planning and implementing multifunctional forest management in spruce-dominated forests is challenging because of the trade-offs and synergies between ES. There is a lack of understanding of appropriate silvicultural and funding measures that will enhance or sustain the provision of different services yet maintain forest resilience in the face of projected climate change and allow for the impacts of biotic and abiotic risks. In an attempt to address this range of issues, a conference was held in Edinburgh, Scotland, UK in October 2012 with the aim of providing a forum where researchers and practitioners could present and discuss new findings on the provision of ES in forests given changing societal demands and uncertainty over future climatic conditions. The main aim of the conference was to see how the concepts promulgated by the MEA and national initiatives such as the UK National Ecosystem Assessment (UKNEA, 2011) could be translated into effective strategic, tactical and operational forest management regimes. Spruce-dominated forests were used as a ‘model’ system to evaluate concepts capable of application across a much wider range of forest ecosystems. The meeting was organized by Forest Research (the research Agency of the Forestry Commission) under the auspices of the International Union of Forest Research Organizations (IUFRO) research group on the ‘Silviculture and Ecology of Spruces’ (group 1.01.08). Scotland was chosen as the venue because of the importance of planted forests of introduced spruce species such as Sitka spruce (Picea sitchensis (Bong.) Carr.). The meeting was attended by 92 delegates from 15 countries. The participants included research scientists from different disciplines, practicing forest managers and policy makers, as well as representatives of sector stakeholders. The conference was structured around a number of themes, providing an overview of forests and their management using an ES framework. These themes included consideration of the ecology and silviculture of spruce forests in different parts of the world, an examination of spruce forest management and the delivery of specific ES, and the way abiotic and biotic risks including climate change could affect the management of spruce forests for ES. The papers and posters presented covered a wide range of aspects relevant to ES provision in spruce-dominated forests including: biodiversity in planted forests, biotic and abiotic risks that may influence management practice, the development of mixed species stands in spruce forests, impacts of management upon carbon stocks in spruce forests, and the role of decision support tools in evaluating trade-offs in the provision of different ES. A number of operational case studies were presented to illustrate how forest managers were adapting their silvicultural regimes to sustain or enhance the provision of particular ES. Most of the presentations are available as

We assessed age-related alterations in carbon (C) stocks and sequestration rates of first rotation Sitka spruce (Picea sitchensis (Bong.) Carr) plantations on predominantly surface-water gley soils. Sites were selected to represent a typical Sitka spruce chronosequence following land use transition from grasslands dominated by surface-water gley soils. Based on inventory, eddy covariance, physiological and modelling assessments of net ecosystem productivity (NEP), we show that afforested stands are a C sink at 10 years, and possibly earlier, followed by an increase to a maximum of 9 t C ha−1 year−1 before the first thinning cycle. NEP subsequently declined from 9 t C ha−1 year−1, at closed canopy, to 2 t C ha−1 year−1 in older and thinned stands. Reductions in the C sequestration rate of older stands were coupled with a decrease in gross primary productivity, increases in maintenance/growth respiration and decomposition losses following harvest. We suggest that the high sequestration potential of these forests may be associated with the high net primary productivity of these plantations in Ireland, a high allocation of assimilates and litter into the belowground C pool and accumulation of C in mineral gley soils following afforestation.