Brian Tobin

Biomass expansion factors for Sitka spruce ( Picea sitchensis (Bong.) Carr.) in Ireland

The assessment of a forest resource in national inventories provides a firm basis for the calculation of biomass and carbon (C) stocks of forests. Biomass expansion factors (BEFs) and conversion factors provide a robust and simple method of converting from forest tree stem volume to total forest biomass. These factors should be constructed on the basis of nationally specific data in order to take account of regional differences in growth rates, management practices, etc. The objective of this study is to improve the accuracy of biomass estimation by calculating a range of age-dependant BEFs from representative data that more accurately describe the allometry of present forests. The results from this study show that the allocation of biomass to compartments in forest stands and throughout a rotation varies considerably, and that the use of BEFs for the calculation of C stocks in forests of sub-timber dimensions is highly impractical.

Towards developmental modelling of tree root systems

Abstract Knowledge of belowground structures and processes is essential for understanding and predicting ecosystem functioning, and consequently in the development of adaptive strategies to safeguard production from trees and woody plants into the future. In the past, research has mainly been concentrated on growth models for the prediction of agronomic or forest production. Newly emerging scientific challenges, e.g. climate change and sustainable development, call for new integrated predictive methods where root systems development will become a key element for understanding global biological systems. The types of input data available from the various branches of woody root research, including biomass allocation, architecture, biomechanics, water and nutrient supply, are discussed with a view to the possibility of incorporating them into a more generic developmental model. We discuss here the main focus of root system modelling to date, including a description of simple allometric biomass models, and biomechanical stress models, and then build in complexity through static growth models towards architecture models. The next progressive and logical step in developing an inclusive developmental model that integrates these modelling approaches is discussed.

Possible causes of the recent rapid increase in the radial increment of silver fir in the Western Carpathians

Silver fir is one of the most productive and ecologically valuable native European tree species, however, it has been experiencing decline which has periodically occurred over its natural range. This paper aims to investigate the recent climate-growth relationships of silver fir (Abies alba Mill.) and its temporal change along the course of its life. Long-term tree-ring databases, as well as records on climate, atmospheric SO2, NO3 and acid concentrations from four different regions in the Western Carpathians were used. The results provide clear evidence of significant increase of silver firs radial increment over the entire Western Carpathian area since 1970-1980. The results indicated that the most probable factors behind the rapid recovery of tree radial increment were reductions in emissions of NO3 and SO2, alongside a significant increase in mean June, July and April temperatures.

Effects of post‐glacial phylogeny and genetic diversity on the growth variability and climate sensitivity of European silver fir

Summary 1. Growth rates of European silver fi r( Abies alba Mill.) rapidly increased in the last century. At the same time, ring widths declined at the species southern distribution limits in the Mediterranean. Such diverse growth trends and responses have largely been attributed to regional climate conditions, but this was prior to considering the species’ post-glacial phylogeny. 2. A dendrochronological network composed of 1961 tree-ring width series (TRW) from 78 silver fir sites between 365 and 1400 m a.s.l. along the Carpathian Arc was compiled. Spatial differences in the species’ genetic diversity were investigated from genetic data of 69 silver fir populations in the region. Differences in growth variability and climate sensitivity were then related to post-glacial phylogeny and genetic diversity. 3. Significant differences in interannual and longer-term growth trends and climate responses across the Carpathian Arc were found to coincide with the geographical north–south separation of two post-glacial populations from effective refugia originating from the Apennine and Balkan peninsulas. Summer temperature was the main driver of growth in the western (Apennine) lineage, whereas ring widths in the Balkan population from the east were predominantly controlled by summer drought. Fir specimens that originated from the Balkan lineage exhibited higher genetic diversity and more regular growth dynamics and also appeared to be less sensitive to air pollution during the 1970s. 4. Synthesis. Although the phylogeny of forest trees has largely been neglected in most dendroecological studies, results here indicate the importance of different post-glacial histories for the growth sensitivity and adaptability to varying environmental factors. Decision-making under future climate warming scenarios (for building resilience through forest management) should therefore consider different phylogenetic origins.

Assessment of tree response to drought: validation of a methodology to identify and test proxies for monitoring past environmental changes in trees

A thinning experiment stand at Avoca, Ballinvalley, on the east coast of the Republic of Ireland was used to test a developed methodology aimed at monitoring drought stress, based on the analysis of growth rings obtained by coring. The stand incorporated six plots representing three thinning regimes (light, moderate and heavy) and was planted in the spring of 1943 on a brown earth soil. Radial growth (early- and latewood) was measured for the purpose of this study. A multidisciplinary approach was used to assess historic tree response to climate: specifically, the application of statistical tools such as principal component and canonical correlation analysis to dendrochronology, stable isotopes, ring density proxy, blue reflectance and forest biometrics. Results showed that radial growth was a good proxy for monitoring changes to moisture deficit, while maximum density and blue reflectance were appropriate for assessing changes in accumulated temperature for the growing season. Rainfall also influenced radial growth changes but not significantly, and was a major factor in stable carbon and oxygen discrimination, mostly in the latewood formation phase. Stable oxygen isotope analysis was more accurate than radial growth analysis in drought detection, as it helped detect drought signals in both early- and latewood while radial growth analysis only detected the drought signal in earlywood. Many studies have shown that tree rings provide vital information for marking past climatic events. This work provides a methodology to better identify and understand how commonly measured tree proxies relate to environmental parameters, and can best be used to characterize and pinpoint drought events (variously described using parameters such as like moisture deficit, accumulated temperature, rainfall and potential evaporation).

Sources of errors and uncertainties in the assessment of forest soil carbon stocks at different scales—review and recommendations

Spatially explicit knowledge of recent and past soil organic carbon (SOC) stocks in forests will improve our understanding of the effect of human- and non-human-induced changes on forest C fluxes. For SOC accounting, a minimum detectable difference must be defined in order to adequately determine temporal changes and spatial differences in SOC. This requires sufficiently detailed data to predict SOC stocks at appropriate scales within the required accuracy so that only significant changes are accounted for. When designing sampling campaigns, taking into account factors influencing SOC spatial and temporal distribution (such as soil type, topography, climate and vegetation) are needed to optimise sampling depths and numbers of samples, thereby ensuring that samples accurately reflect the distribution of SOC at a site. Furthermore, the appropriate scales related to the research question need to be defined: profile, plot, forests, catchment, national or wider. Scaling up SOC stocks from point sample to landscape unit is challenging, and thus requires reliable baseline data. Knowledge of the associated uncertainties related to SOC measures at each particular scale and how to reduce them is crucial for assessing SOC stocks with the highest possible accuracy at each scale. This review identifies where potential sources of errors and uncertainties related to forest SOC stock estimation occur at five different scales—sample, profile, plot, landscape/regional and European. Recommendations are also provided on how to reduce forest SOC uncertainties and increase efficiency of SOC assessment at each scale.

Soils and Productivity

This chapter explores the predominant land-based production systems in Ireland, specifically describing grassland, arable and forestry production. Grass is the most important agricultural crop in Ireland representing the main feed source for the livestock sector. Arable production represents a relatively small area, largely due to excess soil moisture conditions that are typical of many Irish soils. Despite favourable conditions for forestry in Ireland, the level of forest cover is low by European standards and has historically been associated with sub-marginal and marginal agricultural land. The importance of soil structure in the provision of nutrients, water and air is emphasised along with best management practices in relation to the management cycle. The role of soil texture is outlined, as is the agroclimate and soil interaction in Irish soils. The agricultural drainage conditions of Irish soils fall into the temperate zone, where the main role of drainage is the removal of excess water in the root zone of crops from surplus rainfall. This follows with a historical account of land drainage schemes in Ireland. Finally, the issues of the main production systems on poorly drained soils and the cultural practices to maintain trafficability are described. Improving the overall trafficability of any soil first requires the identification of factors causing either excessive moisture or poor soil structure. Correctly ascertaining these issues allows implementation of appropriate preventative and remediation measures, and should be the initial step in any management strategy.