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Abstract: While forest productivity is usually inferred from height growth indices, retrospective analyses of tree rings have been intensively used to assess long-term trends in forest productivity. However, radial growth is sensitive to the degree of competition between trees and influenced by management practices or local disturbances. Whether radial growth is accurate for diagnosing and quantifying productivity changes remains a debated question. In a previous study (), we assessed historical variations in dominant height growth of even-aged stands of common beech in north-eastern France as a proxy for their productivity changes. The analysis was based on a sampling design including 14 pairs of young/old (75/150yr) neighbour stands growing under the same site conditions. Dominant height was reconstructed from stem analyses and was compared between generations using a statistical modelling procedure. In this analysis, we tested whether radial and height growth of dominant trees may provide compatible indications on long-term trends. We therefore measured and analysed the radial growth of dominant trees at breast height for the same sampled trees. The effects of site, developmental stage, and calendar date were separated by applying a similar modelling approach. Consideration of the developmental stage effect led to the formulation of an original growth equation. Analysis of radial growth revealed: (i) a long-term positive increase; (ii) a magnitude of +50% over the last century; and (iii) growth declines in the 1940s and 1990s. These features were remarkably similar to those reported on dominant height, and indicated that radial growth of dominant trees delivered a sound picture of productivity changes. The radial growth chronology also differed by showing a more acute acceleration phase in the early century, and a recent but significant difference between stand generations. [Copyright &y& Elsevier]

Sources: Landsskogtakseringen, 1933/NIBIO; BFW; BMLRT. [Display omitted] • Early wood shortage in European history caused the need to explore and plan the utilisation of wood resources. • Current NFI methods reflect country-specific conditions, inventory traditions and information needs. • Harmonisation of European NFIs provides internationally comparable growing stock estimations. • Ongoing NFI innovations integrate remote sensing for higher spatial and temporal resolution. • Emerging data requirements relate to forest resilience and stability of growing stocks. Wood resources have been essential for human welfare throughout history. Also nowadays, the volume of growing stock (GS) is considered one of the most important forest attributes monitored by National Forest Inventories (NFIs) to inform policy decisions and forest management planning. The origins of forest inventories closely relate to times of early wood shortage in Europe causing the need to explore and plan the utilisation of GS in the catchment areas of mines, saltworks and settlements. Over time, forest surveys became more detailed and their scope turned to larger areas, although they were still conceived as stand-wise inventories. In the 1920s, the first sample-based NFIs were introduced in the northern European countries. Since the earliest beginnings, GS monitoring approaches have considerably evolved. Current NFI methods differ due to country-specific conditions, inventory traditions, and information needs. Consequently, GS estimates were lacking international comparability and were therefore subject to recent harmonisation efforts to meet the increasing demand for consistent forest resource information at European level. As primary large-area monitoring programmes in most European countries, NFIs assess a multitude of variables, describing various aspects of sustainable forest management, including for example wood supply, carbon sequestration, and biodiversity. Many of these contemporary subject matters involve considerations about GS and its changes, at different geographic levels and time frames from past to future developments according to scenario simulations. Due to its historical, continued and currently increasing importance, we provide an up-to-date review focussing on large-area GS monitoring where we i) describe the origins and historical development of European NFIs, ii) address the terminology and present GS definitions of NFIs, iii) summarise the current methods of 23 European NFIs including sampling methods, tree measurements, volume models, estimators, uncertainty components, and the use of air- and space-borne data sources, iv) present the recent progress in NFI harmonisation in Europe, and v) provide an outlook under changing climate and forest-based bioeconomy objectives. [ABSTRACT FROM AUTHOR]

Abstract: In mixed stands, abiotic effects and interspecific interactions on tree height growth remain largely unknown. We investigated the effects of climate, nutrition and stand composition on silver fir (Abies alba Mill.) height growth in the Vosges Mountains (northeastern France). Data were collected from 143 plots established on seven stand types of silver fir (Abies alba Mill.): pure silver fir stands and six mixed stands of silver fir with Fagus sylvatica, Picea abies, Pinus sylvestris, Quercus petraea and Acer pseudoplatanus, along both elevation and nutritional gradients. Silver fir dominant height was characterised by the site index, which was related by multiple-regression analyses with measured nutritional variables, climatic variables and stand composition descriptors. The results showed that silver fir site index was significantly correlated with climate, nutrition and stand composition. Among climatic variables, elevation was responsible for a large portion of the site index variance (R 2 =0.13). Slope aspect showed an important positive effect of eastern oriented plots on silver fir site index, as did mild winter temperature. Variables related to water availability showed a positive effect on site index only at elevations below 600m, where lower precipitations and higher temperatures lead to a water-limiting factor. Nutritional resources were the second factor determining silver fir site index by both nitrogen nutrition and protons and aluminium acidity or toxicity. An environmental model, including climatic and nutritional variables, explained 64% of site index variance with a standard error of 2.7m. For equivalent sites, basal area of the dominant cohort, as well as basal area of conifer species, showed a positive effect on site index, while broadleaved basal area did not show any significant effect in addition to that of conifers. A final model including abiotic variables and conifer basal area explains 71% of site index variance with a standard error of 2.5m in the study area. The search for ecological drivers of tree height that control access to light is of great importance in the context of environmental changes in predicting tree species relationships in mixed stands. [Copyright &y& Elsevier]

Three linear mixed-effect models for wood density were constructed with average ring density data measured by X-ray microdensitometry on 10427 heartwood rings collected from 82 sessile oaks sampled in five French regions (Alsace, Lorraine, Orne et Sarthe, Allier, Loir-et-Cher). Two types of forest management (coppice-with-standards and high forest) and three site qualities were represented in each region. A model (1) between air dry wood density and radial tree growth was established. Model (2), with radial growth and tree environment (region, silviculture, site quality, and their interactions) as fixed effects, tested whether wood density varied with changing region, silviculture, or site quality when tree radial growth was kept constant. Model (3), derived from model (2), consisted of the effects or interactions found to be significant in model (2). The effects specific to a tree were accounted for by a random tree effect in the three models. We calculated that the fixed effects in models (1), (2) and (3) explained, respectively, 48, 50 and 48% of the total variation of wood density and that the random tree effects were responsible for 31, 29, and 31% of the total variation of wood density, respectively. The comparison of the three models indicated that the fixed effects of the region, silviculture, and site quality and the interactions among them, all present in model (2) or partly present in model (3), explain only a small percentage (2% and less than 1%, respectively) of the total wood density variation when tree radial growth is statistically controlled. Consequently, wood density hardly changed with changing environment and type of forest management when ring width and cambial age were kept constant. It implied that compressed trees in high forests and trees with relatively free radial growth from coppice-with-standards follow similar wood density mixed models. Thus, a single wood density model can be used to predict wood density efficiently in oak stems for several situations with contrasting silviculture, site quality, and geographic location. [Copyright &y& Elsevier]