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Tree growth is expected to be responsive to climatic drivers across a spectrum of temporal scales, ranging from yearly growth to daily water use and photosynthesis. Automatic dendrometers offer the potential to provide continuous high-resolution measurements of tree radius changes. The signal recorded contains three components: (1) a long-term seasonal growth component, (2) a mid-term component representing swelling after rainfall and subsequent drying and (3) daily cycles of water-uptake related to tree transpiration. For 91 trees at 4 sites (Picea abies : 58, Pinus cembra : 17, Fagus sylvatica : 14, Pinus sylvestris : 2) monitored in Austria between 2012 and 2015, we simultaneously modelled these three processes using a hierarchical nonlinear mixed-effects model represented by two logistic growth curves. The focus was on the mid-term and daily component, and therefore long-term growth that is typically modelled by including tree size, competition or site variables was represented by random effects only. Both mid-term and short-term components were species-specific. In general, P. cembra and F. sylvatica were less sensitive to climate variables than P. abies. For all species, the mid-term component was best represented using a 14-day moving average difference between rainfall and potential evapotranspiration, a 24-h moving average of precipitation and its 1–3 days lags, a 24-h moving average temperature and its 1–3 days lags. The daily cycles of water uptake were best related to hourly humidity and its 3-h lag, and interactions with the 14-day moving average difference between rainfall and potential evapotranspiration accounted for attenuating cycles after rainy events and increasing cycles in dry periods. [ABSTRACT FROM AUTHOR]

Tree growth depends on tree-intrinsic attributes, synecological interactions, atmospheric conditions and soil properties. While the influence of tree factors and climate are analysed in detail in many studies, the effect of soil properties is less investigated and compensatory soil effects are often not quantified. In this study, we use a comprehensive dataset of 1659 tree increment cores from six common Central European tree species (Abies alba, Fagus sylvatica, Larix decidua, Picea abies, Pinus sylvestris, Quercus spp.) sampled at 1562 locations across large environmental gradients in the Eastern Alps. Soil data was available from an extensive soil survey including soil pits, laboratory analysis and the application of pedotransfer-functions. Up to three main tree species per site were sampled and the tree ring widths were dendrochronologically measured and synchronized. Topographic information from a high-resolution Digital Terrain Model, high-resolution climate data and biometric measures were available at each site. To determine the influence of soil water storage capacity and soil nutrient status, we used generalized additive models to expand standard models of well-known drivers of tree growth, including age, climatic water balance and temperature. For the time span of 38 years from 1981 until 2018, we found species-specific impacts of soil properties on tree ring growth. Specifically, soil water storage acted as a buffer to overcome drought periods, in particular for deep rooting tree species like Quercus spp. and Abies alba. In addition, we found species-specific growth reactions to soil nutrient status for nutrient-demanding species likes Fagus sylvatica but no effects for less demanding tree species like Pinus sylvestris. Our results show the magnitude of the effects of soil properties in relation to other growth factors on radial growth of six Central European tree species. Therefore, we posit that, while age and climate do have a stronger influence on tree growth, it is important to consider soil as a growth factor, particularly at the distribution margins along climatic gradients. • Generalized additive models from 1659 increment cores for six species were developed. • Soil water storage capacity and soil nutrients affect species specific radial growth. • Strong growth decline starts at a still positive climatic water balance of 100 mm. • Soil properties have a higher effect for deep rooting trees. • The interaction of climatic water balance and soil water storage capacity is significant. [ABSTRACT FROM AUTHOR]

Radial tree stem growth of Norway spruce ( Picea abies (L.) H. Karst.), European beech ( Fagus sylvatica L.), Scots pine ( Pinus sylvestris L.), and stone pine ( Pinus cembra L.) was monitored from 2012 to 2015 across sites in Austria with high-resolution dendrometers. Seasonal cumulative diameter increment was modeled using a hierarchical nonlinear mixed-effects model framework based on a logistic growth curve. In the dry and warm year 2015, the average annual diameter increment of 0.30 cm decreased by 50% on lower elevation sites and by 10% on higher elevation sites. In the cool and moist year 2014, Norway spruce achieved a higher annual diameter increment than European beech, whereas the opposite occurred in the dry and warm years 2013 and 2015. In the mixed beech-spruce stand, beech's consumptive water-use strategy has obviously caused intensified stress for spruce in these drought periods. On higher elevation sites, Norway spruce reacted more sensitively to climate fluctuation compared with stone pine, but overall reactions were only weak. Productivity varied strongly depending on the social status of the tree, with dominant and intermediate trees suffering more from drought. As warming and drought lowers increment rates on lower elevation sites and as trees on higher elevation sites react less flexibly, productivity losses are expected for Austrian forests due to climate warming. [ABSTRACT FROM AUTHOR]

We examined the relationship between thinning intensity and volume increment predicted by four commonly used individual-tree growth models in Central Europe (i.e., BWIN, Moses, Prognaus, and Silva). We replicated conditions of older growth and yield experiments by selecting 34 young, dense plots of Norway spruce ( Picea abies (L.) Karst.), Scots pine ( Pinus sylvestris L.), and European beech ( Fagus sylvatica L.). At these plots, we simulated growth, with mortality only, to obtain the maximum basal area. Maximum basal area was then decreased by 5% or 10% steps using thinning from below. Maximum density varied considerably between simulators; it was mostly in a reasonable range but partly exceeded the maximum basal area observed by the Austrian National Forest Inventory or the self-thinning line. In almost all cases, simulated volume increment was highest at maximum basal area and then decreased with decreasing basal area. Critical basal area, at which 95% of maximum volume increment can be achieved, ranged from 0.46 to 0.96. For all simulators, critical basal area was lower for the more shade-tolerant species. It increased with age, except for Norway spruce, when simulated with the BWIN model. Age, where mean annual increment culminated, compared well with yield tables. [ABSTRACT FROM AUTHOR]

• Generalized additive basal area increment models were fit for 22 Austrian species. • Climatic effects were included using the long-term mean and deviations thereof. • This formulation separates climatic site effects from yearly weather conditions. • Positive and adverse mixture effects were included but no interactions could be fit. • The omission of National Inventory specific variables facilitates model application. Forest trees exhibit a large variation in basal area increment, which depends on tree specific factors, inter-tree relations and the environment. Studying the effect of the above factors on tree growth is essential for forest ecology and forest management. In this study, a basal area increment model for 22 tree species of the Austrian National Forest Inventory was parameterized. The model included effects of tree size, competition, harvesting and disturbances, climate, soil, and species mixtures. The models were fitted using generalized additive models. Basal area increment increased with tree size for all species, and competition and density reduced tree growth. Shade-tolerant tree species showed a more pronounced decrease with competition, than light-demanding tree species. Tree growth increased with disturbance intensity, but confidence intervals for high disturbance intensities became larger. Many variants of the model that included climatic effects were tested, but the best variants used long-term-mean temperature and precipitation during the growing season and the positive and negative deviations thereof, which separated climatic site effects from temperature deviations due to yearly weather conditions. Several of the tested dryness indices were not able to explain tree growth from inventory data. Soil type and soil moisture were significant for many tree species, each of them accounting for a maximum of 10% of difference in tree growth. Little growth was observed on calcareous Leptosols, whereas trees grew best on Planosols, on flysch or calcareous Cambisols. Growth was decreased on dry sites, but very moist and wet sites could result in either a decrease or an increase in growth, depending on the tree species. Mixture effects were significant for almost all mixtures with a sufficient number of observations in the data set. Notable exceptions were the mixtures of Pinus sylvestris L. with Picea abies (L.) Karst. and Abies alba Mill. and the mixtures of Quercus spp. with Pinus sylvestris L. and Fagus sylvatica L.. Mixture effects were both favorable and adverse at individual tree level. Picea abies and Fagus sylvatica were two tree species, which were mainly favored by mixture effects. Interactions of mixture with age or site could not be modelled from the data because they were confounded with other effects of the inventory data. The new basal area increment model provided a comprehensive formulation, which can be use part of individual tree growth simulators and is easily transferable to other regions and environments and can be extended in the future. [ABSTRACT FROM AUTHOR]