Latitudinal patterns and influencing factors of soil humic carbon fractions from tropical to temperate forests

Abstract

Soil humic carbon is an important component of soil organic carbon (SOC) in terrestrial ecosystems. However, no study to date has investigated its geographical patterns and the main factors that influence it at a large scale, despite the fact that it is critical for exploring the influence of climate change on soil C storage and turnover. We measured levels of SOC, humic acid carbon (HAC), fulvic acid carbon (FAC), humin carbon (HUC), and extractable humus carbon (HEC) in the 0-10 cm soil layer in nine typical forests along the 3800-km North-South Transect of Eastern China (NSTEC) to elucidate the latitudinal patterns of soil humic carbon fractions and their main influencing factors. SOC, HAC, FAC, HUC, and HEC increased with increasing latitude (all P<0.001), and exhibited a general trend of tropical < subtropical < temperate. The ratios of humic C fractions to SOC were 9.48%-12.27% (HAC), 20.68%-29.31% (FAC), and 59.37%-61.38% (HUC). Climate, soil texture, and soil microbes jointly explained more than 90% of the latitudinal variation in SOC, HAC, FAC, HEC, and HUC, and interactive effects were important. These findings elucidate latitudinal patterns of soil humic C fractions in forests at a large scale, and may improve models of soil C turnover and storage.

Diversity and Co-Occurrence Patterns of Soil Bacterial and Fungal Communities of Chinese Cordyceps Habitats at Shergyla Mountain, Tibet: Implications for the Occurrence

“…Briefly, SWC was determined by drying at 105 °C for 24 h, soil pH was determined in a soil-water suspension (1:2.5 w/v) by a Corning 610A pH meter (Corning Inc., Corning, NY, USA), NH 4 + -N content, NO 3 − content, TN, APH, and APO were determined by a continuous flow analyzer (SAN++, Skalar, Breda, Holland) by testing the soil filtrates after the soil was extracted with 2 M KCl, 0.5 M NH 4 + OAc (ammonium acetate, pH = 7), and 1 M NaHCO 3 (pH = 8.5), EOC was determined by the KMnO 4 method, SOC was measured by the dichromate method, DOC was determined by analyzing the filtrates of the soil extraction by water, and MBC was determined by the chloroform fumigation-incubation method. The soil humic substance composition, including HEC, FAC, HAC, and HMC, was analyzed according to Xu et al [27]. The content of HEC, FAC, and HAC was determined by a C/N analyzer (Vario-Max CN analyzer, Elementar Analysensysteme, Hanau, Germany), and the FAC was calculated by subtracting HAC from HEC.…”

Carbon and Nitrogen Stocks and Microbiological Activity Under Forest-Pasture System and Traditional Pasture in Pernambuco

“…Humic substances are among the main components of Organic Soil Matter (OSM), playing a central role in the stabilization of Soil Organic Carbon (SOC) reservoirs and can be classified, according to their solubility, into fractions of humic acids (HA), fulvic acids (FA) and humines (HU). Since the distribution of the OSM composition is a deposit of information about the main processes that occur in the soil (Doupoux et al, 2017;Xu et al, 2018;Tadini et al, 2019).…”

Predictability of Functional Diversity Depends on the Number of Traits

“…The study area covered almost all the main types of forest vegetation in the Northern Hemisphere (He et al, 2018). Across the study sites, the annual average temperature and precipitation ranged from -4.4 to 20.9 °C and 481.6 to 2449.0 mm, respectively, with the precipitation mainly concentrating in summer, from June to August (Xu et al, 2018a).…”