Shelterbelts increased soil inorganic carbon but decreased nitrate nitrogen, total phosphorus, and bulk density relative to neighbor farmlands depending on tree growth, geoclimate, and soil microbes in the Northeast China Plain

Abstract

Black soils constitute the food basket of many countries, and the improvement of their properties has received increasing attention. We collected 750 samples at 0 to 1 m depth from poplar shelterbelts and farmlands of 15 regions within the NE China Plain. We measured soil organic carbon (SOC), inorganic carbon (SIC), nitrate nitrogen (NO3−-N), total N, available N, ammonia N (NH4+-N), total phosphorus (TP), available P, bulk density (BD), porosity, specific gravity, electrical conductivity (EC), water content (WC), pH, total Glomalin-related soil protein (TG) and easily extracted glomalin (EEG), soil microbial characteristics, and forest characteristics.The results showed that: 1) Pooled data collected from poplar shelterbelts decreased BD, TP and NO3−-N by 7%, 11% and 7%, and increased SIC by 16% (p < 0.05), respectively, in the 0–40 cm soil layer, and sharper NO3−-N decreases have been observed in the 40–100 cm soil layer soils. 2) Compared to farmlands, poplar shelterbelts decreased microbial α-diversity, and the undefined saprotroph-fungi abundance and microbial nitrification and denitrification by 9.25% to 11.67%, but increased ectomycorrhizal fungi dominance, complexity, and stability of microbial network compared with farmlands. 3) The partial least squares path model revealed that NO3−-N, TP, and BD changes were achieved by the direct effects of poplar growth and indirectly through soil microbial modification. At the same time, geo-climatic differences contributed to SIC changes. Poplar shelterbelts significantly affected soil properties in moist and warm areas, and the effects of shelterbelts on soil properties were more evident in the 0–40 cm layer than in the 40–100 cm layer.Our results highlight that, besides windbreaking functions, poplar shelterbelt's benefits for crop productivity should also include their effects on multiple soil properties into l m deep soils, soil microbial alteration, and associated with geoclimatic conditions.