Effects of Competition, Drought Stress and Photosynthetic Productivity on the Radial Growth of White Spruce in Western Canada

Abstract

Understanding the complex interactions of competition, climate warming-induced drought stress, and photosynthetic productivity on the radial growth of trees is central to linking climate change impacts on tree growth, stand structure and in general, forest productivity. Using a mixed modeling approach, a stand-level photosynthetic production model, climate, stand competition and tree-ring data from mixedwood stands in western Canada, we investigated the radial growth response of white spruce [Picea glauca (Moench.) Voss] to simulated annual photosynthetic production, simulated drought stress, and tree and stand level competition. The long-term (~80-year) radial growth of white spruce was constrained mostly by competition, as measured by total basal area, with minor effects from drought. There was no relation of competition and drought on tree growth but dominant trees increased their growth more strongly to increases in modeled photosynthetic productivity, indicating asymmetric competition. Our results indicate a co-limitation of drought and climatic factors inhibiting photosynthetic productivity for radial growth of white spruce in western Canada. These results illustrate how a modeling approach can separate the complex factors regulating both multi-decadal average radial growth and interannual radial growth variations of white spruce, and contribute to advance our understanding on sustainable management of mixedwood boreal forests in western Canada.

Individual Tree Diameter Growth Models of Larch–Spruce–Fir Mixed Forests Based on Machine Learning Algorithms

“…This finding was consistent with Yu et al [19], which showed climate factors had limited capacity in explaining the variation in diameter growth, while stand factors were the main drivers to diameter growth. Similar results have been found in other research [14,56,57], for example, Jiang et al [14] found for both trembling aspen and white spruce that the climate factors showed less effects on tree growth than that of stand factors. Alam et al [56] found for white spruce that diameter growth of trees was primary constrained by competition with minor effects from climate factors.…”

“…Similar results have been found in other research [14,56,57], for example, Jiang et al [14] found for both trembling aspen and white spruce that the climate factors showed less effects on tree growth than that of stand factors. Alam et al [56] found for white spruce that diameter growth of trees was primary constrained by competition with minor effects from climate factors. Besides, our results noted that the relative importance of site factors was less than that of stand factors and climate factors.…”

“…Voss) was primarily influenced by tree size, followed by competition. Alam et al [56] found for white spruce that diameter growth of trees was primary constrained by competition. Our study showed that both tree size and competition were the main drivers to diameter growth.…”

Visualizing Individual Tree Differences in Tree-Ring Studies

“…Some of the differences in tree-level climate sensitivity can be explained, and should not necessarily be treated as noise. Earlier studies have shown that parameters like competition, nitrogen deposition, and tree-height-related wood anatomical changes affect climate sensitivity [19][20][21]32,59,66]. In this study, we demonstrated how to visually detect potential causes of different climate sensitivities.…”

“…This article addresses the principle of aggregated tree growth and the accumulating evidence that various parameters influence the climate sensitivity of individual trees, such as, competition [21,25,66], age [29,57], and height [56,59]. The methods described here highlight individual tree differences and potential causes.…”