Abstract
In karst ecosystems, plants absorbing smaller amounts of nutrients, owing to shallow soil, show limited growth. In addition, fine roots (diameter < 2 mm) contribute to the regulation of nutrient cycles in terrestrial ecosystems. However, the spatial and temporal variations of fine root biomass in different vegetation types of the karst region remains poorly understood. In this study, we investigated the seasonal and vertical variation in biomass, necromass, and total mass of fine roots using sequential soil coring under different stages of vegetation restoration (grassland, shrubland, secondary forest, and primary forest) in Southwest China. The results showed that the fine root biomass and necromass ranged from 136.99 to 216.18 g m−2 and 47.34 to 86.94 g m−2, respectively. The total mass of fine roots and their production ranged from 187.00 to 303.11 g m−2 and 55.74 to 100.84 g m−2 year−1, respectively. They showed a single peak across the vegetation restoration gradient. The fine root biomass and total fine root mass also showed a single peak with seasonal change. In autumn, the fine root biomass was high, whereas the necromass was low. Most of the fine roots were concentrated in the surface soil layer (0–10 cm), which accounted more than 57% root biomass, and decreased with increasing soil depth. In addition, fine root production showed a similar vertical pattern of variation with biomass. Overall, our results suggested that fine roots show clear seasonal and vertical changes with vegetation succession. Moreover, there was a higher seasonal fluctuation and a greater vertical decreasing trend in late-successional stages than in the early-successional stages. The conversion of degraded land to forest could improve the productivity of underground ecosystems and vegetation restoration projects in the fragile karst region should, therefore, continue.
Highlights
The root biomass is an important part of the biosphere and it constitutes approximately 30% of the aboveground biomass (Yuan and Chen, 2010; Zhiyanski, 2014)
They are responsible for water and nutrient uptake, and synthesis of certain growth hormones. They play a vital role in nutrient, water, and elemental cycles (Schmid and Kazda, 2002; McCormack et al, 2017), and in soil carbon sequestration in terrestrial ecosystems, owing to the large carbon input into soil controlled by fine root dynamics (Guo et al, 2007; Wang et al, 2018)
The fine root biomass, necromass, the total fine root mass, and fine root production were estimated along a post-agriculture succession sequence in a karst region Southwest China
Summary
The root biomass is an important part of the biosphere and it constitutes approximately 30% of the aboveground biomass (Yuan and Chen, 2010; Zhiyanski, 2014). They are responsible for water and nutrient uptake, and synthesis of certain growth hormones. They play a vital role in nutrient, water, and elemental cycles (Schmid and Kazda, 2002; McCormack et al, 2017), and in soil carbon sequestration in terrestrial ecosystems, owing to the large carbon input into soil controlled by fine root dynamics (Guo et al, 2007; Wang et al, 2018). Some studies showed that fine root production is an important component of total net primary production (NPP) in forest ecosystems, contributing 40–60% of total NPP (Zhiyanski, 2014; Meng et al, 2018). Accurate estimates of fine root biomass are essential for understanding ecosystem functions
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