Assessing cross-datable distinct annual growth rings in non-native Pinus kesiya Royle ex Gordon in Zambia

Abstract

The response of non-native forest plantation trees to climate change remains poorly understood.We hypothesized that precipitation and temperature modulate tree-ring width chronology at each site and that higher tree growth is exhibited at remote sites than sites near copper mines. This study investigates if the annual tree-ring boundaries in non-native Pinus kesiya Royle ex Gordon in Zambia are distinct, cross-datable, and coherent with climate signal. We collected increment cores from live trees and climate data near and further away from emission sources and developed site tree-ring width chronologies. Based on cross-dating and chronology building statistics (i.e., ESP > 0.85; Glk > 0.6 and series inter-correlation > 0.4), P. kesiya posses cross-datable distinct annual growth ring boundaries that exhibited a high climate signal at both sites. The tree-ring width chronology was positively modulated by precipitation and negatively by solar radiation and temperature. The dry season precipitation was the limiting factor for the growth of P. kesiya. The predicted decrease in dry season precipitation and increase in temperature and solar radiation may reduce tree growth of P. kesiya, reduce productivity, and extend the rotation age. The mean ring width in P. kesiya was not significantly (p = 0.296) different between sites. However, the mean basal area increment at the site near the emission source (Ichimpe) was significantly (p < 0.001) higher than at the remote site (Chati), suggesting site-specific influences that require investigation. We recommend evaluating the causes and consequences of tree growth variation between sites and their relation to environmental variation, including microclimate, soils, and pollution. In this regard, an assessment of site-specific ring-width chronology and tree growth variation in this study directly contributes to an improved understanding of non-native P. kesiya ecology, and it offers the potential to study trees' responses to edaphic and climatic factors. Knowing these responses deepens our understanding of non-native pine tree growth in the face of climate change, given the significant role of tropical forests in the global carbon cycle.