Effects of forest type and urbanization on carbon storage of urban forests in Changchun, Northeast China

Abstract

Rapid urbanization has led to dramatic changes in urban forest structures and functions, and consequently affects carbon (C) storage in cities. In this study, field surveys were combined with high resolution images to investigate the variability of C storage of urban forests in Changchun, Northeast China. The main objectives of this study were to quantify the C storage of urban forests in Changchun City, Northeast China and understand the effects of forest type and urbanization on C storage of urban forests. The results showed that the mean C density and the total C storage of urban forests in Changchun were 4.41 kg/m 2 and 4.74 × 10 8 kg, respectively. There were significant differences in C density among urban forest types. Landscape and relaxation forest (LF) had the highest C density with 5.41 kg/m 2 , while production and management forest (PF) had the lowest C density with 1.46 kg/m 2. These differences demonstrate that urban forest type is an important factor needed to be considered when the C storage is accurately estimated. Further findings revealed significant differences in different gradients of urbanization, and the mean C density decreased from the first ring (6.99 kg/m 2) to the fourth ring (2.87 kg/m 2). The total C storage increased from the first ring to the third ring. These results indicate that C storage by urban forests will be significantly changed during the process of urbanization. The results can provide insights for decision-makers and urban planners to better understand the effects of forest type and urbanization on C storage of urban forests in Changchun, and make better management plans for urban forests.

Urbanization Drives SOC Accumulation, Its Temperature Stability and Turnover in Forests, Northeastern China

“…The climate is temperate humid or sub-humid continental monsoon, the mean annual precipitation is 567 mm, and the mean air temperature is 4.8 • C [26]. Dominant soil types are black soil, dark-brown soil, and chernozem [27]. a global urbanization background and especially considering China's fast urbanization in recent years, addressing these questions might allow for evaluating its forests' ecological services.…”

“…The climate is temperate humid or sub-humid continental monsoon, the mean annual precipitation is 567 mm, and the mean air temperature is 4.8 °C [26]. Dominant soil types are black soil, dark-brown soil, and chernozem [27]. The location and samples of the study area.…”

“…Five categories, based on the years at which soil was built-up (the years 1900,1954,1990,2004, and 2014), indicated human disturbance time, i.e., 114, 60, 24, 10, and 0 years, respectively. Moreover, ring road numbers are another symbol to indicate the urbanization degree, which studies have shown can be used as a proxy for the degree of urbanization [29] or urban-rural gradients [21,27]. Accordingly, the urban area was divided into five categories, i.e., 1st, 2nd, 3rd, 4th, and 5th ring road regions ( Figure 1).…”

“…Urbanization-related C sequestration in soil was about 16% of the NEE (Figure 5A). At the city level, urban forest vegetation could fixate around 474,000 tons of C biomass [27], and the urbanization-induced SOC accumulation ranged from 61,000 tons (estimated from human disturbance time gradient) to 98,000 tons (estimated from the ring roads gradient), which is about 12.8-20.7% (16.8%, on average) of that sequestrated in urban forest biomass ( Figure 5B…”

“…Urbanization-related C sequestration in soil was about 16% of the NEE (Figure 5A). At the city level, urban forest vegetation could fixate around 474,000 tons of C biomass [27], and the urbanization-induced SOC accumulation ranged from 61,000 tons (estimated from human disturbance time gradient) to 98,000 tons (estimated from the ring roads gradient), which is about 12.8-20.7% (16.8%, on average) of that sequestrated in urban forest biomass ( Figure 5B). Notes: The NPP C accrual and biomass C were cited from reference 27, NEE was calculated by NPP and annual respiration, and urbanization C accrual value (1-m depth) was calculated as the 2-fold of 20-cm depth SOCD [37,38].…”