Changes in plant debris and carbon stocks across a subalpine forest successional series

Abstract

Background As a structurally and functionally important component in forest ecosystems, plant debris plays a crucial role in the global carbon cycle. Although it is well known that plant debris stocks vary greatly with tree species composition, forest type, forest origin, and stand age, simultaneous investigation on the changes in woody and non-woody debris biomass and their carbon stock with forest succession has not been reported. Therefore, woody and non-woody debris and carbon stocks were investigated across a subalpine forest successional gradient in Wanglang National Nature Reserve on the eastern Qinghai-Tibet Plateau. Results Plant debris ranged from 25.19 to 82.89 Mg∙ha− 1 and showed a global increasing tendency across the subalpine forest successional series except for decreasing at the S4 successional stage. Accordingly, the ratios of woody to non-woody debris stocks ranged from 26.58 to 208.89, and the highest and lowest ratios of woody to non-woody debris stocks were respectively observed in mid-successional coniferous forest and shrub forest, implying that woody debris dominates the plant debris. In particular, the ratios of coarse to fine woody debris stocks varied greatly with the successional stage, and the highest and lowest ratios were found in later and earlier successional subalpine forests, respectively. Furthermore, the woody debris stock varied greatly with diameter size, and larger diameter woody debris dominated the plant debris. Correspondingly, the carbon stock of plant debris ranged from 10.30 to 38.87 Mg∙ha− 1 across the successional series, and the highest and lowest values were observed in the mid-coniferous stage and shrub forest stage, respectively. Most importantly, the carbon stored in coarse woody debris in later successional forests was four times higher than in earlier successional forests. Conclusions The stock and role of woody debris, particularly coarse woody debris, varied greatly with the forest successional stage and dominated the carbon cycle in the subalpine forest ecosystem. Thus, preserving coarse woody debris is a critical strategy for sustainable forest management.

The Changes in Soil Microbial Communities across a Subalpine Forest Successional Series

“…In theory, forest succession could influence the shifts in soil microbial communities in at least the following ways. First, the quality and quantity of woody and non-woody debris on the forest floor vary greatly with forest succession [22], and the related changes in substrate quality and quantity alter the composition and diversity of soil microbial communities [23]. Second, soil temperature and moisture can vary greatly with forest succession owing to the changes in canopy structure and understory cover [24,25]; both soil temperature and moisture are key factors in determining the composition and structure of soil microbial communities [15,26].…”

“…As affected by long-term natural disturbances such as earthquakes, debris flows and snowslides, and commercial logging of natural forests, subalpine forest communities of different successional stages have been widely observed in the subalpine forest region [34,35]. To date, changes in woody and non-woody debris stocks across a subalpine forest successional series [22] and changes in soil microbial diversity with gap size [36] and along environmental gradients [37] in the subalpine forest region have been documented. Nevertheless, little information is available on soil microbial community shifts across the subalpine forest successional series.…”

Biomass Carbon and Nitrogen allocation in different tree species: do tree compartments and size affect C:N relationship?

“…Forest type affects the species composition and productivity of the ecosystem, with a significant effect on the forest ecosystem C and N stocks (Liu et al 2018;Wang et al 2021). Previous studies have documented that C and N concentration vary significantly among tree species and plant organs (Yerena Yamallel et al 2012;Yao et al 2015;Liang et al 2018;Ma et al 2018;Jing et al 2020;Zhang et al 2020).…”

“…N-fixers, as some Fabaceae tree species, exhibit higher leaf N concentration than non-fixer species (Taylor and Ostrowsky 2019). Also, many studies reported that the amount and quality of plant woody debris, and non-woody debris, change with forest type and structure, and may affect the biodegradability of soil organic matter (Cools et al 2014;Mendoza et al 2014b;Moreira et al 2019;Wang et al 2021). This is also strongly affected by species composition (Wang et al 2019) and stand age (Schilling et al 2016;Lachowicz et al 2019).…”

“…Some authors founded that, overall, N scaled isometrically with C in different ecosystem components, such as mineral soils, forest floor, foliage and litter (McGroddy et al 2004;Xu et al 2016) but not in plant organs (Liang et al 2018). This stoichiometric scaling relationship can contribute to the comprehension of nutrient cycling across plants and ecosystem (Elser et al 2000;Sardans et al 2012;Wang et al 2021).…”