Radial growth change of temperate tree species in response to altered regional climate and air quality in the period 1901–2008

Both increasing and decreasing 20th century growth trends have been reported in forests throughout Europe, but only for few species and areas suitable modelling techniques have been used to distinguish individual tree growth (operating on a local scale) from growth change due to exogenous factors (operating on a broad geographical scale). This study relates for the first time observed growth changes, in terms of basal area increment (BAI) of dominant trees of pedunculate oak, common beech and Scots pine, in north-west European temperate lowland forests (Flanders) to climate, atmospheric CO₂ and tropospheric O₃ concentrations, N deposition, site quality and forest structure for more than a century (the period 1901?C2008), applying mixed models. Growth change during the 20th century is observed for oak (increasing growth) and beech (increasing growth until the 1960s, growth decline afterwards), but not for pine. It was possible to relate growth change of oak and beech to climate time series and N deposition trends. Adding time series for CO₂ and O₃ concentration did not significantly improve model results. For oak and beech a switch from positive to negative growth response with increasing nitrogen deposition throughout time is observed. Growth increase for oak is mainly determined by the interaction between growing season temperature and soil water recharge. It is reasonable to assume that the observed growth trend for oak will continue for as long as early season water availability is not compromised. The decreasing trend in summer relative air humidity observed since the 1960s in the study area can be a main cause of recent beech BAI decrease. A further growth decline of beech can be expected, independent of site quality.     

The Effect of Surface Heating on Hill-Induced Flow Separation

A series of two-dimensional mixing length model simulations of boundary-layer flow over idealised ridges of varying steepness are conducted to investigate the effect of surface heating on flow separation. The relatively simple numerical approach used permits characterisation of the influence of heating for a variety of initial conditions and parameter values. For steep terrain, increased surface heating is shown to enhance the strength and extent of hill-induced separation. For more moderate terrain, a critical heating strength is required for a given hill width and background flow speed before separation is initiated. Sensitivity tests show the results to be insensitive to model parameters or the choice of mixing length. The results are accounted for using a scaling analysis in terms of a non-dimensional stability parameter.     

Developing adaptive capacity for responding to environmental change in the Arab Gulf States: Uncertainties to linking ecosystem conservation, sustainable development and society in authoritarian rentier economies

The recent assessment by the Intergovernmental Panel on Climate Change (IPCC) has emphasized that understanding the institutional context in which policies are made and implemented is critical to define sustainable development paths from a climate change perspective. Nevertheless, while the importance of social, political and cultural factors is getting more recognition in some parts of the world, little is known about the human dimensions or the contexts in which they operate in the affluent oil economies of the Arabian Peninsula. Policies that implicitly subsidize or support a wasteful and environmentally destructive use of resources are still pervasive, while noteworthy environmental improvements still face formidable political and institutional constraints to the adaptation of the necessary far reaching and multisectoral approach. The principal aim of this paper is to identify some of the major shortcomings within the special context of the Arab Gulf states' socio-cultural environment in support of appropriate development pathways. Conclusions highlight that past and current policy recommendations for mitigating environmental threats are likely to be ineffective. This is because they are based on the unverified assumption that Western-derived standards of conduct, specifically the normative concept of ”good governance” and ”democracy”, will be adopted in non-Western politico-cultural contexts.     

New cirripedes (Crustacea,Thoracica) from the Jurassic and Cretaceous of the United Kingdom

Extensive new material of scalpelliform cirripedes, including articulated individuals, from the Late Jurassic (Tithonian) Kimmeridge Clay of Dorset, southern England, is described and used as a basis for taxonomic revision of the family Zeugmatolepadidae. Two subfamilies, the Zeugmatolepadinae and Martillepadinae nov., are established and two new genera (Martillepas, Concinnalepas) in the latter subfamily are described from the Upper Jurassic and one (Icenilepas) from the Upper Cretaceous Chalk. Material from the Kimmeridge Clay of Dorset also includes the oldest fossil representative of the family Pollicipedidae for which a new genus and species, Etcheslepas durotrigensis, are erected, and the oldest calanticid, Cretiscalpellum sp. nov. Jurassic taxa established by T.H. Withers in 1928, on the basis of sparse material, are redescribed, and referred to the new genera as Martillepas ovalis, M. costata, M. hollisi, Concinnalepas concinna and Etcheslepas fragilis.     

Depositional history of peatland pines (Pinus sylvestris L.) in NW Enontekiö, Finnish Lapland: implications for Middle Holocene drought and temperature fluctuations

High altitude and latitude findings of subfossil peatland pine trees were unearthed from the region of NW Finnish Lapland and dated by ¹⁴C and tree-ring methods. The depositional history of the trees illustrated two distinct peatland pine phases dated to Middle Holocene intervals 4900–4400 and 4100–3400 cal. a BC. It seems evident that both thermal and hydroclimatic fluctuations have played roles of varying importance in the establishment of this pine population and its demise. The presence of these pines, from a site ~60 km north of the coniferous timberline and conditions ~1 °C and 100 degree-days colder than those at the present-day timberline, concurs with previous studies demonstrating the association between the high-latitude summer-temperature cooling and circumpolar timberline retreat since the Middle Holocene due to Milankovitch forcing. On the other hand, the peatland pine recruitment was made possible by drier than present surface conditions during the previously reconstructed Middle Holocene drought anomaly (Hyvärinen-Alhonen event). Our data suggest this event was not continuous but reached its two-phase climax during the peatland pine phases, with an interruption of several centuries with moister surface conditions between 4400 and 4100 cal. a BC. The findings highlight the sensitivity of well-dated peatland tree assemblages in terms of recording past climatic evolution and events and the need for new collections from north and south Fennoscandia and the Baltic region, for more detailed analyses over extended time intervals and regions.     

Spectrophotometric properties of surface water dissolved organic matter in an afforested upland peat catchment

Many upland catchments in the UK have undergone afforestation; their characteristic waterlogged soils require extensive pre‐plantation ground drainage to allow tree establishment. In peatland areas this can result in very highly coloured runoff and enhanced dissolved organic matter (DOM) export in rivers of naturally high concentrations. In 1966, the Coalburn Experimental Catchment, northern England, was established to investigate the impact of afforestation on an upland peat catchment. Here we report the variations in DOM spectrophotometric properties of streamflow in the catchment at canopy closure, especially with respect to potential carbon sources within the artificial drainage ditches. Drainage ditches are characterized by water that has higher absorption coefficients and which is more highly coloured than in the catchment tributaries. Ditched, afforested areas produce more highly‐coloured runoff waters that are more fluorescent and absorbent normalized to carbon concentration compared to ditches in open moorland. Ditches that had been experimentally re‐excavated have organic matter of different spectrophotometric character, with higher dissolved organic carbon concentration and less aromatic or lower molecular weight material. It is hypothesized that this is due to the exposure of bare peat faces within and adjacent to the ditches that are more susceptible to drying compared to vegetated areas. The large extent of this drainage network acts as both a rapid transport network increasing hydrological connectivity and a pool for the storage of DOM, which is of different spectrophotometric character under low flow conditions, depending on management conditions. Copyright © 2007 John Wiley & Sons, Ltd.     

Recent TIMS dating results from British Late Pleistocene vertebrate faunal localities: context and interpretation

New TIMS dates from British sites underpin and extend the growing model of mammalian faunal history during the Late Pleistocene. The sequence of British faunas during the three successive warm phases of MIS 5 presents a challenging model in which the mammal faunas of the first two temperate phases, 5e and 5c is dominated by species of a classically interglacial character, while that of the final phase, sub‐stage 5a, is dominated by bison and reindeer. This we see as the ‘cold fauna’ appearing in Britain during the cool isotope sub‐stage 5b and subsequently isolated by the rising sea level of isotope sub‐stage 5a. All these three faunas are true island faunas. Copyright © 2007 John Wiley & Sons, Ltd.     

The freshwater dissolved organic matter fluorescence–total organic carbon relationship

The fluorescent properties of dissolved organic matter (DOM) enable comparisons of humic‐like (H‐L) and fulvic‐like (F‐L) fluorescence intensities with dissolved organic carbon (DOC) in aquatic systems. The fluorescence‐DOC relationship differed in gradient, i.e. the fluorescence per gram of carbon, and in the strength of the correlation coefficient. We compare the fluorescence intensity of the F‐L and H‐L fractions and DOC of freshwater DOM in north Shropshire, England, featuring a river, wetland, spring, pond and sewage DOM sources. Correlations between fluorescence and DOC varied between sample sites. Wetland water samples for the F‐L peak gave the best correlation, r = 0·756; the lowest correlation was from final treated sewage effluent, r = 0·167. The relationship between fluorescence and DOC of commercially available International Humic Substances Society standards were also examined and they generally showed a lower fluorescence per gram of carbon for the F‐L peak than the natural samples, whereas peat wetland DOM gave a greater fluorescence per gram of carbon than river DOM. Here, we propose the strength of the fluorescence–DOC correlation to be a useful tool when discriminating sources of DOM in fresh water. Copyright © 2007 John Wiley & Sons, Ltd.