Principal component regression analysis demonstrates the collinearity-free effect of sub estimated climatic variables on tree growth in the central Amazon

Abstract

Introduction: Climatic variables show a seasonal pattern in the central Amazon, but the intra-annual variability effect on tree growth is still unclear. For variables such as relative humidity (RH) and air vapor pressure deficit (VPD), whose individual effects on tree growth can be underestimated, we hypothesize that such influences can be detected by removing the effect of collinearity between regressors. Objective: This study aimed to determine the collinearity-free effect of climatic variability on tree growth in the central Amazon. Methods: Monthly radial growth was measured in 325 trees from January 2013 to December 2017. Irradiance, air temperature, rainfall, RH, and VPD data were also recorded. Principal Component Regression was used to assess the effect of micrometeorological variability on tree growth over time. For comparison, standard Multiple Linear Regression (MLR) was also used for data analysis. Results: Tree growth increased with increasing rainfall and relative humidity, but it decreased with rising maximum VPD, irradiance, and maximum temperature. Therefore, trees grew more slowly during the dry season, when irradiance, temperature and VPD were higher. Micrometeorological variability did not affect tree growth when MLR was applied. These findings indicate that ignoring the correlation between climatic variables can lead to imprecise results. Conclusions: A novelty of this study is to demonstrate the orthogonal effect of maximum VPD and minimum relative humidity on tree growth.

Wood and bark water content and monthly stem growth in Amazonian tree species

“…In a tropical rainforest at La Selva, Costa Rica, Clark et al (2003) reported a negative correlation between stem growth and mean and minimum temperature over a period of 16 years, while, at the same time, no effect of maximum temperature and irradiance variability on the diameter increment of trees was found. In the central Amazon, variation in mean and minimum temperature did not affect stem growth over the 2013-2017 period, while stem growth decreased with increasing irradiance and maximum temperature across a large number of species (Marenco and Antezana-Vera 2021), which highlights the need for further research on this topic.…”

“…Many other factors contribute to tree growth, including site quality (e.g., soil fertility and topography), ontogeny (tree size), and environmental conditions (Bowman et al 2013). Climatic variables such as irradiance, precipitation and air temperature can affect both photosynthesis and tree growth in tropical rainforests (Clark et al 2003;Méndez 2018;Yang et al 2018;Marenco and Antezana-Vera 2021). Air temperature is an important factor in the climate-forest interaction (Kitayama et al 2021) and irradiance plays an essential role in plant functioning, as photosynthesis is highly responsive to changes in light intensity (Marenco et al 2014).…”

Variation in bark water content in three Amazonian species in response to rainfall seasonality

“…Regarding the effects of microclimatic variability on tree growth, Grogan and Schulze (2012) and Marenco and Antezana-Vera (2021) found a positive relationship between growth and rainfall intensity, whereas Elias et al (2020) reported that tree growth can increase in the warmest years, in response to an increase in temperature.…”

Stem growth of multipurpose tree species: net effect of micrometeorological variability assessed by principal component regression

“…Although tree growth or ecosystem photosynthesis seem to decrease in the dry season in most studies (e.g., Méndez 2018;Yang et al 2018;Antezana-Vera and Marenco 2021), others have reported no effect (Silva et al, 2003;Marenco 2016, 2021) or even an increase in ecosystem photosynthesis in the central Amazon (Green et al 2020). However, because climatic factors are intercorrelated, it is difficult to evaluate the individual effect of a given microclimatic variable on tree growth (Marenco and Antezana-Vera 2021).…”

“…Microclimatic factors such as irradiance, precipitation and air temperature affect both photosynthesis and tree growth (e.g., Méndez 2018;Yang et al 2018;Marenco and Antezana-Vera 2021). Rainfall and soil water content seem to affect tree growth in the Amazon region (Méndez 2018;Antezana-Vera and Marenco 2021), but it is still unclear whether trees grow faster in the rainy season than in the dry season.…”