Variability of soil carbon and nitrogen stocks after conversion of natural forest to plantations in Eastern China

Abstract

Forest plantation, either through afforestation or reforestation, has been suggested to reverse and mitigate the process of deforestation. However, uncertainties remain in the potential of plantation forest (PF) to sequestrate carbon (C) and nitrogen (N) compared to natural forest (NF). Soil C and N stocks require a critical and updated look at what is happening especially in the context of increasing rate of land use change and climate change. The current study was conducted in China’s Eastern forest to estimate soil C and N stocks in six depth layers (0–10, 10–20, 20–40, 40–60, 60–80 and 80–100 cm) and two forest types (NF and PF) at four sites along climate factors gradient. The results showed that the overall mean soil C and N amounts to a depth of 20 cm ranged from 2.6 ± 1.1 Mg ha−1 to 38.6 ± 23.1 Mg ha−1, and soil nitrogen stock ranged from 0.2 ± 0.1 Mg ha−1 to 3.3 ± 1.5 Mg ha−1. Moreover, a loss of C stock was observed at Qingyuan (QY) by −7%, Dinghushan (DH) by −26%, Jianfengling (JF) by −13% while that of N stock was observed at QY (−8%), DH (−19%) and JF (−12%) at both depth layers. These results indicate that NFs have a better capacity to accumulate soil C and N. The soil C and N decreased from the southeast to the northeast and increased from tropical to temperate mixed forests zone in the eastern part of the study area. The C and N stock mainly occurred in the topsoil and decreased significantly with depth. Moreover, soil C and N stocks increased with age of plantation. This study provides an overview of the current spatial distribution and soil stocks of C and N, as well as the effects of environmental factors on soil C and N stocks. It also indicated that, although mean annual temperature and mean annual precipitation are the key factors affecting the variations in soil C and N, their vertical and horizontal distribution differed in various aspects.

Effects of Varying Forest Management on Soil Carbon and Nutrients in Hill and Coastal Homegardens in Bangladesh

“…Investigation pertaining to the soil BD revealed that BD at the coastal homegardens was higher compared to the hill homegardens due to the smaller amount of litter and organic matter, especially in the middle and deepest layers of the soil. This is consistent with Asok and Sobha (2014) and Ngaba et al (2020) indicating that BD increases with increasing soil depth. The lower BD of the topmost soil layer in our samples could be ascribed to the lower accumulation of litter (Biswas et al 2012).…”

“…The soil conditions are affected by local climatic factors such as temperature and rainfall and are usually attributed to the most common properties: bulk density, pH, and carbon (C), nitrogen (N), and nutrient stocks and their concentrations. Land use changes may affect the stock of soil organic C and N (Maia et al, 2010;Pringle et al, 2014;Schulz et al, 2016;Ngaba et al 2020), which are directly affecting native vegetation. For example, C concentrations are higher in natural or planted forests than in degraded natural forest sites (Zaman et al 2010;Akhtaruzzaman et al 2015).…”

“…Boley et al (2009) found that higher concentrations of Ca are positively associated with high soil pH in the teak plantations over undisturbed forests. Generally, soil pH and electrical conductivity (EC) decrease, but soil bulk density (BD) increases with soil depths in tropical forest ecosystems (Naik et al 2020;Ngaba et al 2020). By contrast, soil EC may be regulated by pH and the cation concentrations (do Carmo et al 2016).…”

Miombo conversion to monoculture tree plantations: Changes in soil properties

“…This is in agreement with the finding by Eclesia et al (2012) and Guo & Gifford (2002), who found that SOC changes following the conversion of native vegetation to tree plantations are strongly dependent on characteristics of the new vegetation (e.g., species) and its age. Tree species are reported to modify soil‐C and soil‐N stocks by changing litter quantity and quality, turnover rate of roots and exudates, microbial communities, and soil physicochemical properties (Ngaba et al, 2020; Paul et al, 2002; Wang et al, 2013). This justifies why species planted was found to be the main driver of the changes in SOC and STN stocks following the replacement of miombo woodland by tree plantations.…”

Intensification and diversification of degraded pasture areas in Brazil: potential of soil C accumulation and mitigation of the climate changes

“…In general, soil C and N stocks decreased significantly with depth under each system of pasture management (Table 2). For Ngaba et al (2020), this effect is due to the topsoil being more biologically active and to the greater contributions of roots relative to the subsoil. The same authors report that understanding the effect of depth on soil C and N stocks is important, as it influences mechanisms of soil sequestration.…”