Northeastern China shelterbelt-farmland glomalin differences depend on geo-climates, soil depth, and microbial interaction: Carbon sequestration, nutrient retention and implication

Abstract

Glomalin-related soil protein (GRSP) is essential for stable carbon and nutrient sequestration. The spatial variation of GRSP characteristics and its influencing factors after farmland-shelterbelt afforestation remain poorly understood. Thus, 750 soil samples were collected from 15 regions in 1-m soil profiles in the Northeastern China Plain. Nine GRSP traits (EEG[easily-extracted], TG[total extracted], EEG/TG, and GRSP's contribution to SOC[soil organic carbon], TN[total nitrogen], and TP[total phosphorus]), twenty environmental parameters, and the soil microbial composition were also investigated. In the whole Northeastern China Plain, TG was 5.03 g/ kg and 11 % was from EEG, within the reported literature range. EEG contributed 1–3 %, while TG contributed 35 %, 26 %, and 17 % to the SOC, TN, and TP. The coefficient of variations from 25 %–54 % manifested considerable inter-region variation. TG/TP in shelterbelts was 4 % (p = 0.02) higher than in farmlands at the 0–20 cm soil layer, and deep soils (40-100 cm) of poplar shelterbelts had 9 %–12 % higher TG, TG/SOC, and TG/TN than in farmlands. Ordination analysis revealed shelterbelts had more prominent GRSP traits than farmlands in cold and moist regions and more compacted soils. Two microbial groups were related to GRSP accumulation; the first group (Geobacillus, Balneimonas, Virgisporangium, Frankia, Candidatus Xiphinematobacter, Microlunatus, Geopora, Inocybe) was negatively correlated with TG, TG/SOC, and TG/TN but positively correlated with TG/TP and EEG/TP; the second group (Mortierella, Leveillula, Otidea Cryptococcus, Rhizophagus, Aleuria, Thelebolus, Candidatus Solibacter, Mesorhizobium, Phenylobacterium, Ralstonia, Anoxybacillus, Euzebya, Azoarcus, Polaromonas, Hyphomicrobium, Nutrosovibrio, Niabella) showed opposite associations. Pathway analysis showed that soil microorganisms enhanced the geo-climatic explaining power on GRSP variations but weakened the roles of soils and trees. Our data highlighted that GRSP-related soil management should fully consider these influencing factors for improving their microbial roles in soil conditioning.