Seasonal Changes and Vertical Distribution of Fine Root Biomass During Vegetation Restoration in a Karst Area, Southwest China

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.

Quantifying the Effects of Vegetation Restorations on the Soil Erosion Export and Nutrient Loss on the Loess Plateau

“…Soil erosion, the main process of soil erosion export, occurs naturally but is accelerated by human activities. The physical reservoir of carbon held in soil aggregates could be destroyed by soil erosion (Yue et al, 2016;Deng et al, 2018), resulting in a decrease in effective root depth, nutrient availability and water holding capacity in the root zone (Yang et al, 2003;Du et al, 2019). Soil erosion removes considerable quantities of topsoil, which will greatly influence soil nutrient stocks and will impact soil nutrient redistribution and global biochemistry (Quinton et al, 2010).…”

Stand Structure and Abiotic Factors Modulate Karst Forest Biomass in Southwest China

“…During the past century, a large part of the karst region in southwest China was severely degraded following the destruction of natural vegetation due to human disturbance. Thankfully, most of the degraded land has been undergoing ecological restoration, either through natural regeneration or afforestation, attributed to the implementation of ecological restoration projects (e.g., the "Grain for Green" project, the Karst Rocky Desertification Restoration Project) over the past two decades [8,9]. Therefore, a detailed study on karst forest biomass is important for improving the accuracy of estimating Chinese vegetation carbon storages and sequestration potential.…”

“…Southwest China contains one of the largest karst regions in the world [8]. Previous studies have assessed the biomass in this region on small and large scales.…”

Common Species Maintain a Large Root Radial Extent and a Stable Resource Use Status in Soil-Limited Environments: A Case Study in Subtropical China

“…Not all studies support the viewpoint that deep root penetration is a necessary strategy for plants adapted to shallow soil environments. For example, recent studies suggest that roots of adapted species in typical karst terrains were restricted to shallow soil layers (Heilman et al, 2009;Kukowski et al, 2013;Ni et al, 2015;Dammeyer et al, 2016;Du et al, 2019). Nie et al (2014a) excavated the coarse root systems of two common species in a karst region of southwest China, and showed that common species, from a variety of habitats, exhibited lateral (almost horizontal) rather than vertical root systems.…”

“…shallow soil layer (Heilman et al, 2009;Ni et al, 2015;Nie et al, 2017;Du et al, 2019) where the soil is characterized by higher nutrient content, warmer temperature, and roots require less carbon (Steele et al, 1997). These conflicting viewpoints are due to habitat differences and root plasticity of the plant species (Mulia et al, 2010;Isaac et al, 2014).…”