Changes in soil properties, X-ray-mineral diffractions and infrared-functional groups in bulk soil and fractions following afforestation of farmland, Northeast China

Abstract

Analysis of soil properties, the compositional traits in bulk soil and different fractions and their responses to afforestation practices may possibly facilitate clarification of the mechanisms underlying soil changes. Soil properties, the compositional functional groups and minerals were determined in the bulk soil and fractions from forests and adjacent farmlands. The afforestation of farmland could induce accumulation of soil organic carbon [SOC] (+18%) and nitrogen [N] (+4%) with pH increase (+4%), and declines in electric conductivity (−15%) and bulk density (−3%). Sand and aggregates [SA] and easily oxidized fraction [EO] mainly contributed to the SOC and N accumulation. Moreover, afforestation-induced changes were observed in O-H & N-H stretching (−26%), feldspar (+52%) and huntite crystallinity (−40%). The changes of soil properties were strongly associated with the changes in functional groups, followed by minerals. Of them, asymmetric COO- & C = O stretching & O-H bending, symmetric COO- stretching, huntite and smectite-vermiculite crystallinity were the key factors responsible for the changes of soil properties. Our findings highlight that degraded farmland afforestation could strongly affect soil properties in the bulk soil, and the changes in fractions (mainly SA and EO) as well as their changes in the compositional traits strongly supported these bulk soil changes.

Variation in glomalin in soil profiles and its association with climatic conditions, shelterbelt characteristics, and soil properties in poplar shelterbelts of Northeast China

“…Similar findings have been found in other studies. For example, farmland in Northeast China had lower levels of GRSP in deep soils than in surface soils, but 34-50% higher GRSP/SOC in deep soils (Wang et al 2017a). Degraded grasslands had 18-35% higher EEG/SOC and TG/SOC levels in the 5-20 cm layer than in the upper 0-5 cm layer (Zhang et al 2015); citrus orchards had low GRSP contents at the soil surface because of low levels of soil b-glucosidase and carbohydrates (accumulated GRSP) and high levels of protease (decomposed GRSP) in the deep soil layer (Wu et al 2012).…”

“…Climatic conditions shown in Table 1. Detailed information can also be found in previous publications (Wang et al 2015(Wang et al , 2017a.…”

“…Many GRSP-related studies have focused on the surface soil due to the assumption that a stable state is reached in deeper soil layers over time (Wu et al 2012;Zhang et al 2015;Yang et al 2017;Wang et al 2018a), despite evidence contradicting this (Harrison et al 2011). Limited information is available regarding GRSP variation in vertical soil profiles in forests (Wang et al 2017a). Vertical soil sampling at both surface and deeper soil layers in a wide range of regions should be carried out to determine the importance of GRSP in deep soil carbon and nutrient cycling (Wang et al 2017a).…”

“…Limited information is available regarding GRSP variation in vertical soil profiles in forests (Wang et al 2017a). Vertical soil sampling at both surface and deeper soil layers in a wide range of regions should be carried out to determine the importance of GRSP in deep soil carbon and nutrient cycling (Wang et al 2017a).…”

“…Poplar is one of the main genera used in farmland shelterbelts in north eastern China (Zhao 2002;Wu et al 2018;Yang et al 2018a, b) to protect soil against wind erosion, improve soil fertility, and protect food products (Deng et al 2009;Wu and Wang 2016;Wang et al 2017b, c;Ge et al 2018;Jha 2018). Because of the importance of GRSP in improving degraded soil Wang et al 2015), a comprehensive understanding of GRSP variation in northeastern China and its relationship with soil properties, shelterbelt characteristics, and climatic conditions could facilitate effective management aimed at improving soil quality (Wang et al 2015(Wang et al , 2017a.…”