Climate Sensitive Tree Growth Functions and the Role of Transformations

Abstract

The aim of this study is to develop climate-sensitive single-tree growth models, to be used in stand based prediction systems of managed forest in Switzerland. Long-term observations from experimental forest management trials were used, together with retrospective climate information from 1904 up to 2012. A special focus is given to the role of transformation of modelling basal area increment, helping to normalize the random error distribution. A nonlinear model formulation was used to describe the basic relation between basal area increment and diameter at breast height. This formulation was widely expanded by groups of explanatory variables, describing competition, stand development, site, stand density, thinning, mixture, and climate. The models are species-specific and contain different explanatory variables per group, being able to explain a high amount of variance (on the original scale, up to 80% in the case of Quercus spec.). Different transformations of the nonlinear relation where tested and based on the mean squared error, the square root transformation performed best. Although the residuals were homoscedastic, they were still long-tailed and not normal distributed, making robust statistics the preferred method for statistical inference. Climate is included as a nonlinear and interacting effect of temperature, precipitation and moisture, with a biological meaningful interpretation per tree species, e.g., showing better growth for Abies alba in warm and wet climates and good growing conditions for Picea abies in colder and dryer climates, being less sensitive on temperature. Furthermore, a linear increase in growth was found to be present since the 1940s. Potentially this is an effect of the increased atmospheric CO 2 concentration or changed management in terms of reduced nutrient subtractions from forest ground, since industrialization lowered the demand of residue and slash uptake.

An Annual basal area growth model with multiplicative climate modifier fitted to longitudinal data for shortleaf pine

“…Because of this, climate variables that are often expected to be influential including mean temperature, maximum temperature, and total annual precipitation (Subedi and Sharma, 2013;Manso et al, 2015), did not always perform well in climate-based growth models. However, the interacting effects of climate variables on the tree growth are largely influenced by the individual tree status, stand level competition and site quality while interpreting the biological growth (Zell, 2018). In our study also, change in the coefficient magnitudes for individual tree status, stand age, and stand level competition indicates that climate variables also influence the biological growth pattern of this species.…”

“…This might be because most of the studies have been formulated either on tree-ring chronologies or on annual measurement data where climate variables are regressed against annual growth (Biondi, 2000;Jump et al, 2006;Chhin et al, 2008;Duchesne et al, 2012;Foster et al, 2015). However, Zell (2018) has recently investigated the effects of climate on growth from multi-year periodic measurements of forests in Switzerland. Additionally, the growth models in some of these studies are already linear in form of their arguments (Subedi and Sharma, 2013;Manso et al, 2015) and added climate variables performed better than was the case with our nonlinear model.…”

“…Wykoff et al 1982;Pretzsch et al 2002;Weiskittel et al, 2011), individual tree growth models from such data have been rarely fitted with climate variables included. However, recently Zell (2018) used periodic re-measurement data from experimental forest management trials in Switzerland to study the impact of climate variables on individual tree growth. Saud et al (2016) also used this type of data.…”

Drought Effects on Vessel Plasticity of Two Endemic <em>Magnolia</em> Species in the Tropical Montane Cloud Forests of Eastern Mexico

“…Strong vessel plasticity from M. schiedeana, given drought events ( Figure 4), enhances the statement of its need for specific microclimatic. Rodríguez-Ramírez et al [32] found that Mexican beech trees develop similar vessel trait adjustments, which may indicate that this forest type may be very sensitive to drought and thus susceptible to climate change [17,63,64]. On the other hand, M. vovidesii appears to show resilience to climatic variations such as strong DY, this is seen as a response to climatic variations such as strong DY (Figure 4).…”

“…Climate signals such as precipitation (e.g., rain, mist, fog and cloud water), temperature and/or droughts regulate the growth of TMCFs' tree species [15,16]. Dendroecology allows us to identify climatic processes across time and can be used to reconstruct past local and regional climates [9,16,17]. In this context, one of the most important advances in dendrochronological studies has been the additional focus on anatomical features such as vessel traits and/or tree-ring anatomy [13,18,19].…”