Research On Soil Nutrient Characteristics Of Typical Shelterbelt Forests In Black Soil Region

As an important resource for human survival,soil is an important source of nutrients that plants need.With the continuous development and utilization of black soil,soil erosion,land degradation and other soil environmental degradation in black soil area are becoming more and more serious.Farmland shelterbelt construction can effectively improve the quality of arable land in black soil area and is an important measure for soil ecological protection.The soil nutrient of farmland shelterbelt is the main material base of forest growth.In this study,the typical farmland shelterbelt in black soil area such as pure forest of Pinus sylvestris var.mongholica Litv.,pure forest of Larix gmelinii(Rupr.Kuzen.)and a mix of Pinus sylvestris var.mongholica Litv.and Larix gmelinii(Rupr.)Kuzen were taken as the research object.Determination of soil and forest tree carbon,nitrogen,phosphorus nutrient content characteristics in different growth seasons,analysis of nif H,amo A,nir S and other soil microbial functional genes copy numbers,forest soil nutrient characteristics,forest nutrient status and soil microbial functional genes coupling relationship,explore the material cycle characteristics of shelterbelt system.It provides theoretical basis for farm shelter forest management in black soil area.The main results are as follows:(1)The contents of soil organic carbon,total nitrogen,total phosphorus,ammonium nitrogen and available phosphorus in April and November were significantly lower than those in June and September(P < 0.05).The soil nutrient content was different among different shelterbelts,and the non-rhizosphere soil organic carbon content of mixed forest was significantly higher than that of pure forest(P < 0.05).The content of soil organic carbon in rhizosphere was significantly higher than that in non-rhizosphere soil in June(P < 0.05).The content of soil organic carbon in rhizosphere in April,June and September was significantly positively correlated with that in non-rhizosphere soil(P < 0.05).(2)In June,the forest needles organic carbon content had no significant difference,the organic carbon content of mongolica needles in September pure forest > mixed forest mongolica > mixed forest larch > larch pure forest;The fine root organic carbon content of pure larch forest was significantly higher than that of other forest types in April,and significantly lower than that of other forest types in June(P < 0.05).Compared with other forest types,the C/N of needles and fine roots of larch in mixed forest was lower,and the C/N of coarse roots was higher.There was a significant positive correlation between total nitrogen and total phosphorus content in fine roots and non-rhizosphere soil organic carbon content in June(P < 0.05).(3)The copy number of soil microbial functional genes was different in different sampling periods.The copy number of Acidobacteria in June was significantly higher than that in other months(P < 0.05).In June,the copy numbers of nitrogen-fixing genes nif H,nitrifying genes(amo A-AOA and amo A-AOB),denitrifying genes nos Z and phosphate mineralization genes pho D in pure larch rhizosphere soil were significantly higher than those in non-rhizosphere soil(P < 0.05).Redundancy analysis showed that soil physical and chemical indexes in June were mainly affected by amo A-AOB gene,and the explanatory rates of amo A-AOB gene to rhizosphere and non-rhizosphere soil indexes were 29.2%(F = 4.1,P =0.036)and 63.6%(F = 17.5,P = 0.002),respectively.In conclusion,there are differences in soil nutrient content and microbial distribution among different shelterbelts.The same shelterbelt changed with different time,and the soil quality was the highest in June.Baiquan county built these kinds of farmland shelterbelt,mixed forest index index due to pure forest,pure forest Larix gmelinii due to sylvestris mongolicum.Tree species were important factors that caused the change of soil properties and soil nutrient cycling gene copy number,and the change of soil nutrient content was the result of the interaction between tree species and soil microbial community.This study can provide theoretical support for the selection and optimization of tree species for shelterbelt construction,the regulation and control of forest soil and the selection and adjustment of renewal mode for shelterbelt construction in the study area.