Net primary productivity of forest trees: A review of current issue

Forest growth is important both economically and ecologically and it follows a predictable general trend with age. Generally, the growth of all forests accelerates as canopies develop in young forests and declines substantially soon after the maximum leaf area is attained. The causes of this decline trend are multiple. Initially, age- and size-related declines were attributed to photosynthesis-respiration imbalance. Subsequently, several competing hypotheses have been proposed over the years, although nutrient and hydraulic limitation hypotheses appear to be the most likely to have caused it. In this paper, the authors attempt to review these hypotheses and concentrate on one related aspect, as this can set the scene for further examining the issues of age-related versus size-related processes

Eucalyptus in the British Isles

Eucalypts have been planted successfully in Great Britain and Ireland since the mid nineteenth century. While most of the seven hundred species of eucalypts are not suited to the relative cold of the climate of the British Isles, trials in Britain and Ireland have shown that certain species and subspecies can grow successfully. Further, some eucalypts are the fastest growing trees in the British Isles with mean annual increments of between 25 m3/ha/year and 38 m3/ha/year being reported. Rapid development of a wood biomass energy sector has encouraged a reassessment of the potential of eucalypts grown on short rotations as a source of energy. This article describes the history of eucalypts in the British Isles and their potential

Growth and survival of provenances of snow gums (Eucalyptus pauciflora) and other hardy eucalypts at three trials in England

Three trials of snow gums {Eucalyptus pauciflora) and other cold-tolerant eucalypts, planted in 1985, were assessed for height, diameter at breast height and survival. The trial sites were in southern England but differed in their climate, particularly maritime influence, summer moisture deficit, and in their altitude and soils. Patchy survival and windthrow within the trials posed constraints on the identification of trees of different locations (origins) that performed better. There were, however, some origins that showed good growth and survival across two or three trials. E. pauciflora ssp debeuzevillei from Mount Gininl (Australia) showed superior growth and survival at Thetford (East Anglia) and Torridge (Devon), while E. pauciflora ssp niphophila from Mount Bogong (also Australia) exhibited high survival across all three trials. If biomass production is the objective, many of the origins are too slow growing and faster growing species are available, including other eucalypts. The Mount Ginini origin of E. pauciflora ssp debeuzevillei was estimated to produce 7 m³ ha¯¹ y¯¹ at Thetford and 10 m³ ha¯¹ y¯¹ at Torridge at 26 years old, while Sitka spruce is estimated to yield 13m³ ha¯¹ y¯¹ on a similar rotation. A eucalypt species other than snow gum that showed some promise was f.perriniana, origin 'Smiggin Hole' (New South Wales, Australia) which yielded a mean annual increment of 25m³ ha¯¹ y¯¹ over 24 years at Chiddingfold (Sussex). However, survival was poor at Thetford and so it may be suited to only the warmest of sites (above accumulated temperature (AT5) of 1900)

New record on Rushia parreyssi (Mulsant, 1856), Melandrydae Leach, 1815 and other interesting beetles of the Sierra de Prades, Tarragona (Coleoptera)

En el estudio de la mortalidad de Pinus sylvestris por estrés hídrico en el área mediterránea, se ha querido ver la relación existente entre dicha mortalidad y los artrópodos, en concreto con los coleópteros. El área ibérica escogida para realizar el estudio ha sido el Tillar, situado en la sierra de Prades, en el término de Vimbodí i Poblet (Tarragona). La zona es un bosque mixto de P. sylvestris y Quercus sp. (robles y encinas) con árboles viejos y sin manejos recientes. Para conocer la fauna de coleópteros relacionados con P. sylvestris, se ha realizado una prospección exhaustiva con trampas de interceptación de vuelo, de caída y de berlese in situ. Se ha recolectado un grupo de especies de gran interés faunístico que merecen ser comentadas independientemente del proyecto.In a study on drought-induced Pinus sylvestris mortality in the Mediterranean, we explored the relationship between trees’ mortality and arthropods, specifically with beetles. The Iberian area chosen for the study was the Tillar, located in the Sierra de Prades, nearby Vimbodí i Poblet (Tarragona). The area is in a mixed forest of P. sylvestris and Quercus sp. (oaks), including old trees and without any recent management. In order to study the fauna of beetles associated with P. sylvestris, we carried out a comprehensive survey by using flight interception traps, pitfall trap and in situ Berlese traps. We recovered a very interesting group of species which deserve to be discussed independently of the project

Nuevos datos sobre Rushia parreyssi (Mulsant, 1856), Melandrydae Leach, 1815 y otros coleópteros interesantes de la sierra de Prades, Tarragona (Coleoptera)

En el estudio de la mortalidad de Pinus sylvestris por estrés hídrico en el área mediterránea, se ha querido ver la relación existente entre dicha mortalidad y los artrópodos, en concreto con los coleópteros. El área ibérica escogida para realizar el estudio ha sido el Tillar, situado en la sierra de Prades, en el término de Vimbodí i Poblet (Tarragona). La zona es un bosque mixto de P. sylvestris y Quercus sp. (robles y encinas) con árboles viejos y sin manejos recientes. Para conocer la fauna de coleópteros relacionados con P. sylvestris, se ha realizado una prospección exhaustiva con trampas de interceptación de vuelo, de caída y de berlese in situ. Se ha recolectado un grupo de especies de gran interés faunístico que merecen ser comentadas independientemente del proyecto.In a study on drought-induced Pinus sylvestris mortality in the Mediterranean, we explored the relationship between trees' mortality and arthropods, specifically with beetles. The Iberian area chosen for the study was the Tillar, located in the Sierra de Prades, nearby Vimbodí i Poblet (Tarragona). The area is in a mixed forest of P. sylvestris and Quercus sp. (oaks), including old trees and without any recent management. In order to study the fauna of beetles associated with P. sylvestris, we carried out a comprehensive survey by using flight interception traps, pitfall trap and in situ Berlese traps. We recovered a very interesting group of species which deserve to be discussed independently of the project

Separating water-potential induced swelling and shrinking from measured radial stem variations reveals a cambial growth and osmotic concentration signal

The quantification of cambial growth over short time periods has been hampered by problems to discern between growth and the swelling and shrinking of a tree stem. This paper presents a model, which separates cambial growth and reversible water-potential induced diurnal changes from simultaneously measured whole stem and xylem radial variations, from field-measured Scots pine trees in Finland. The modelled growth, which includes osmotic concentration changes, was compared with (direct) dendrometer measurements and microcore samples. In addition, the relationship of modelled growth and dendrometer measurements to environmental factors was analysed. The results showed that the water-potential induced changes of tree radius were successfully separated from stem growth. Daily growth predicted by the model exhibited a high correlation with the modelled daily changes of osmotic concentration in phloem, and a temperature dependency in early summer. Late-summer growth saw higher dependency on water availability and temperature. Evaluation of the model against dendrometer measurements showed that the latter masked a true environmental signal in stem growth due to water-potential induced changes. The model provides better understanding of radial growth physiology and offers potential to examine growth dynamics and changes due to osmotic concentration, and how the environment affects growth.Peer reviewe

Balancing the risks of hydraulic failure and carbon starvation : a twig scale analysis in declining Scots pine

Understanding physiological processes involved in drought-induced mortality is important for predicting the future of forests and for modelling the carbon and water cycles. Recent research has highlighted the variable risks of carbon starvation and hydraulic failure in drought-exposed trees. However, little is known about the specific responses of leaves and supporting twigs, despite their critical role in balancing carbon acquisition and water loss. Comparing healthy (non-defoliated) and unhealthy (defoliated) Scots pine at the same site, we measured the physiological variables involved in regulating carbon and water resources. Defoliated trees showed different responses to summer drought compared with non-defoliated trees. Defoliated trees maintained gas exchange while non-defoliated trees reduced photosynthesis and transpiration during the drought period. At the branch scale, very few differences were observed in non-structural carbohydrate concentrations between health classes. However, defoliated trees tended to have lower water potentials and smaller hydraulic safety margins. While non-defoliated trees showed a typical response to drought for an isohydric species, the physiology appears to be driven in defoliated trees by the need to maintain carbon resources in twigs. These responses put defoliated trees at higher risk of branch hydraulic failure and help explain the interaction between carbon starvation and hydraulic failure in dying trees.Peer reviewe

Propagating uncertainty to estimates of above-ground biomass for Kenyan mangroves: a scaling procedure from tree to landscape level

Mangroves are globally important carbon stores and as such have potential for inclusion in future forest-based climate change mitigation strategies such as Reduced Emissions from Deforestation and Degradation (REDD+). Participation in REDD+ will require developing countries to produce robust estimates of forest above-ground biomass (AGB) accompanied by an appropriate measure of uncertainty. Final estimates of AGB should account for known sources of uncertainty (measurement and predictive) particularly when estimating AGB at large spatial scales. In this study, mixed-effects models were used to account for variability in the allometric relationship of Kenyan mangroves due to species and site effects. A generic biomass equation for Kenyan mangroves was produced in addition to a set of species-site specific equations. The generic equation has potential for broad application as it can be used to predict the AGB of new trees where there is no pre-existing knowledge of the specific species-site allometric relationship: the most commonly encountered scenario in practical biomass studies. Predictions of AGB using the mixed-effects model showed good correspondence with the original observed values of AGB although displayed a poorer fit at higher AGB values, suggesting caution in extrapolation. A strong relationship was found between the observed and predicted values of AGB using an independent validation dataset from the Zambezi Delta, Mozambique (R2 = 0.96, p = < 0.001). The simulation based approach to uncertainty propagation employed in the current study produced estimates of AGB at different spatial scales (tree – landscape level) accompanied by a realistic measure of the total uncertainty. Estimates of mangrove AGB in Kenya are presented at the plot, regional and landscape level accompanied by 95% prediction intervals. The 95% prediction intervals for landscape level estimates of total AGB stocks suggest that between 5.4 and 7.2 megatonnes of AGB is currently held in Kenyan mangrove forests

An empirical method that separates irreversible stem radial growth from bark water content changes in trees : theory and case studies

Substantial uncertainty surrounds our knowledge of tree stem growth, with some of the most basic questions, such as when stem radial growth occurs through the daily cycle, still unanswered. We employed high-resolution point dendrometers, sap flow sensors, and developed theory and statistical approaches, to devise a novel method separating irreversible radial growth from elastic tension-driven and elastic osmotically driven changes in bark water content. We tested this method using data from five case study species. Experimental manipulations, namely a field irrigation experiment on Scots pine and a stem girdling experiment on red forest gum trees, were used to validate the theory. Time courses of stem radial growth following irrigation and stem girdling were consistent with a-priori predictions. Patterns of stem radial growth varied across case studies, with growth occurring during the day and/or night, consistent with the available literature. Importantly, our approach provides a valuable alternative to existing methods, as it can be approximated by a simple empirical interpolation routine that derives irreversible radial growth using standard regression techniques. Our novel method provides an improved understanding of the relative source-sink carbon dynamics of tree stems at a sub-daily time scale.Peer reviewe