Analysis of coniferous tree growth gradients in relation to regional pollution and climate change in the Miyun Reservoir Basin, China

Abstract

Forests play a crucial role in regulating regional climate and mitigating local air pollution, but little is known about their responding to such changes. This study aimed to examine the potential responses of Pinus tabuliformis, the major coniferous tree species in the Miyun Reservoir Basin (MRB), along an air pollution gradient in Beijing. Tree rings were collected along a transect, and ring width (basal area increment, BAI) and chemical characteristics were determined and related to long-term climatic and environmental records. The results showed that Pinus tabuliformis showed an overall increase in intrinsic water-use efficiency (iWUE) at all sites, but the relationships between iWUE and BAI differed among the sites. The contribution of atmospheric CO2 concentration (ca) to tree growth was significant at the remote sites (> 90%). The study found that air pollution at these sites might have caused further stomatal closure, as evidenced by the higher δ13C levels (0.5 to 1‰ higher) during heavy pollution periods. The analysis of tree ring δ15N also revealed the potential of using δ15N to fingerprint major nitrogen (N) deposition, as shown in the increasing tree ring δ15N, and major nitrogen losses due to denitrification and leaching, as shown in the higher δ15N in tree rings during heavy rainfall events. Overall, the gradient analysis indicated the contributions of increasing ca, increasing water deficit and elevated air pollution to tree growth and forest development. The different BAI trajectories suggested that Pinus tabuliformis has the ability to adapt to the harsh environment in the MRB.

Effects of planting basins and farmyard manure addition on soil carbon and nitrogen pools under on‐farm conditions in Makueni county of Kenya

“…Thus, higher δ 15 N in terrestrial ecosystems indicates active N cycling or N availability because of increased microbial activity (Asadyar et al., 2021; Hosseini‐Bai et al., 2015; Succarie et al., 2022; Wang et al., 2020). On the other hand, soil δ 13 C is a biological indicator of C cycling and could be used to interpret soil organic matter (SOM) mineralization processes and land uses (Wang et al., 2013; Saiz et al., 2016; Succarie et al., 2020; Sun et al., 2021; Liu et al., 2021; Fu et al., 2023). The C cycle is vital because it affects soil respiration and the process of plant photosynthesis (Farooq et al., 2021; Liu et al., 2021; Succarie et al., 2020; Fu et al., 2023).…”

“…On the other hand, soil δ 13 C is a biological indicator of C cycling and could be used to interpret soil organic matter (SOM) mineralization processes and land uses (Wang et al., 2013; Saiz et al., 2016; Succarie et al., 2020; Sun et al., 2021; Liu et al., 2021; Fu et al., 2023). The C cycle is vital because it affects soil respiration and the process of plant photosynthesis (Farooq et al., 2021; Liu et al., 2021; Succarie et al., 2020; Fu et al., 2023). Soil δ 13 C reflects the source of organic matter (C 3 or C 4 vegetation), C turnover and C loss rates from an ecosystem (Han et al., 2020; Jeong et al., 2022).…”