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

Abstract

Global urbanization is a vital process shaping terrestrial ecosystems but its effects on forest soil carbon (C) dynamics are still not well defined. To clarify the effects of urbanization on soil organic carbon (SOC) variation, 306 soil samples were collected and analyzed under two urban-rural gradients, defined according to human disturbance time and ring road development in Changchun, northeast China. Forest SOC showed a linear increase with increasing human disturbance time from year 1900 to 2014 (13.4 g C m −2 year −1 ), and a similar trend was found for the ring road gradient. Old-city regions had the longest SOC turnover time and it increased significantly with increasing urbanization (p = 0.011). Along both urban-rural gradients SOC stability toward temperature variation increased with increasing urbanization, meaning SOC stability in old-city regions was higher than in new regions. However, none of the urban-rural gradients showed marked changes in soil basal respiration rate. Both Pearson correlation and stepwise regression proved that these urbanization-induced SOC patterns were closely associated with landscape forest (LF) proportion and soil electrical conductivity (EC) changes in urban-rural gradients, but marginally related with tree size and compositional changes. Overall, Changchun urbanization-induced SOC accumulation was 60.6-98.08 thousand tons, accounting for 12.8-20.7% of the total forest C biomass sequestration. Thus, China's rapid urbanization-induced SOC sequestration, stability and turnover time, should be fully estimated when evaluating terrestrial C balance.

Peer Review #1 of "Association of urban forest landscape characteristics with biomass and soil carbon stocks in Harbin City, Northeastern China (v0.3)"

“…Harbin (Lv et al, 2016), and the same findings were reported in Changchun, China (Zhai et al, 2017). The aggregation and shape complexity of patches decreased (in terms of LSI increased)…”

“…Specific designs, such as demolition of illegal structures for tree planting, replanting trees in vacant lots that surround by buildings (Bajsanski et al, 2016;Zhao, 2017;Zhao et al, 2017), and implementation of vertical greening on roofs, walls, and bridges, may increase the connectivity of urban forests and have a positive influence on the fragmented landscape (Gao & Yu, 2014). Previous studies have highlighted that urban greening practices should consider the importance of biodiversity conservation (Xiao et al, 2016a), removal of pollutants (Escobedo & Nowak, 2009;Mu et al, 2004), urban microclimate regulations (Wang et al, 2018), urban heat island mitigation (Zhang et al, 2017a), and urban soil improvement (Cui & Mu, 2016;Wang et al, 2017;Zhou et al, 2017). Our findings strongly suggest that urban forest carbon sequestration in both aboveground biomass and belowground soil carbon should be considered for coimprovement of multiple ecological services.…”

“…Currently, China is in a period of rapid urbanization, and there is a general hope for good environmental security from urban green vegetation, such as forests (Mu et al, 2004;Wang, 2009;Liang et al, 2014;He et al, 2017;Zheng et al, 2017;Wang et al, 2018). In China, the urban forests can easily be classified into different types on the basis of their location and functions, such as roadside forest distributed on both sides of roads; affiliation forest in different units of universities, schools, and institutes; landscape and relaxation forest in gardens and parks; and ecological public welfare forest for the prevention of soil erosion, floods, etc.…”

Facial Expressions of Visitors in Forests along the Urbanization Gradient: What Can We Learn from Selfies on Social Networking Services?

“…This methodology enabled us to compare the difference of facial expressions between forests at urban and rural areas. The urban-rural comparison can reflect the environmental and anthropogenic changes caused by urbanization [52,53]. However, in studies on emotional perception in response to nature experience, the urban environment was usually taken as the reference (or the control) to quantify participants' performance in a forest [7,9,19].…”

Glomalin contributed more to carbon, nutrients in deeper soils, and differently associated with climates and soil properties in vertical profiles

“…Structural equation modeling (SEM) is a powerful, multivariate technique found increasingly in scientific investigations to test and evaluate multivariate causal relationships 25 , and powerful in soil ecology from patterns to causalunderstanding 26 . Pearson correlation and stepwise regression are common-used methods for finding complex associations and possible casual relations 27–30 . Canonical ordinations are invaluable tools for modeling communities through environmental predictors, and variation partitioning can then be used to test and determine the likelihood of these sets of predictors in explaining patterns in community structure 31 , is also powerful in identifying co-occurring species on translocation success in Iris atrofusca 32 .…”