Comparisons of Tree Growth Characteristics in Urban and Rural Environments: Impacts of Urbanization on Tree Growth

Abstract:

Urbanization has substantially altered environmental conditions (e.g., elevated temperatures, higher CO₂ concentrations, and enhanced atmospheric N-deposition) compared with their adjacent rural areas, thus cities could be natural laboratory for studying tree growth characteristics under climate change. However, how urbanization affects tree growth characteristics remains poorly understood. Using 31 species and 253520 individuals, we compared the difference of tree growth characteristics between urban and rural, including diameter at breast height [DBH]-H, Biomass-Age, and Growth rate-Age relationships. Further, we used spatial linear models (SLMs) to evaluate the relative importance of climatic and air pollutants variables in determining these relationships between urban and rural. We found that urban significantly affect the tree growth characteristics compared with rural. rural trees were much higher than the urban trees at the same DBH. Similarly, biomass of urban trees was greater than rural trees at the same age regardless of tree species and locations. Urban trees consistently had higher growth rates compared with rural trees at same age. Urban mainly affect tree growth characteristics via the effects of CO₂ and PM_2.5. Additionally, temperature, VPD, and precipitation also had significant effect on the relationships. Our study highlights the faster growth rates of urban trees than rural trees with the field measurement data at large scale, and provided more evidence for predicting the trends of tree growth characteristics under climate change.