Spatial Patterns Of Soil Carbon And Nitrogen And Their Influencing Mechanisms In Platycladus Orientalis Plantations At Different Ages In The South Of Taihang Mountain

It is of great significance to study the spatial distribution of soil carbon nitrogen and its influencing factors in the exploration of soil carbon sink and to cope with global climate change.There is still great uncertainty about the trend,amplitude and carbon sink function of soil organic carbon sink after artificial afforestation.The experiment was carried out by using time instead of space method,and the study subjects were 5 species of Platycladus orientalis plantations(20a,30a,40a,50a,60a).Set up two kinds of processing methods,for comparison(CK),remove litter handling(M).In this paper,the characteristics of soil properties and the changes of carbon and nitrogen in Platycladus orientalis plantations soil were discussed by using the method of long-term observation and experiment in the field.The influence factors of soil carbon and nitrogen were analyzed,and the scientific basis was provided for the theory of soil organic carbon nitrogen cycle in the soil.Finally,the coordinated development of forest ecological benefit,economic benefit and social benefit is realized.The main results are as follows:(1)There were obvious seasonal changes in soil DOC and DON content in different forest age.The content of soil DOC in the autumn>winter>summer>spring with the change of season,variations in soil DON content with the seasons are summer>spring>>autumn>winter.The combined effect of age and season significantly affects the content of soil DOC and DON.(2)With the increase of soil depth,the contents of soil DOC and DON were significantly decreased(p<0.01).Two kinds of processing the soil DOC and DON content were also decreasing,and the decline in soil DOC content was 49.7%and 33.9%,respectively.Soil DON content decreased by 13.8%and 19.6%respectively.(3)With the increase of the age of the Platycladus orientalis,the contents of the soil DOC and DON were significantly increased and then decreased(p<0.01),soil DOC content increased in 20a-40a,and 40a-60a showed a decreasing trend;Soil DON content increased in 20a-30a,and 30a-60a showed a decreasing trend.Under CK treatment,soil DOC and DON content showed a trend of first increase and then decrease,Among them,there was a trend of increase in 20a-40a,and a decrease in 40a-60a.Under M treatment,the content of soil DOC showed an inverted "N" shape.,and the content of soil DON showed a trend of "N".(4)Soil urease and sucrase activity in different forest age showed significant dynamic characteristics with the change of season.The activity of urease is shown in summer>spring>autumn>winter,the activity of sucrase enzyme was shown as summer>autumn>spring>winter.The combined effect of forest age and season significantly affected the activity of soil urease and sucrase.(5)With the increase of soil depth,the activity of urease and sucrase was significantly decreased(p<0.01),with a decrease of 46.6%and 53.8%respectively.Two kinds of processing both the soil urease and sucrase activity were also decreasing.(6)The activity of urease in soil decreased after significantly increased with the increase in the age of Platycladus orientalis(p<0.01),of which 20a-30a showed an increasing trend,and 30a-60a showed a decreasing trend.The activity of sucrase activity in soil showed an increasing trend,but there was no significant difference.(p>0.05).Under the treatment of CK,the change trend of soil urease activity was the same as that of the annual season,which showed a trend of increasing and then decreasing,and the activity of soil sucrase showed a trend of "M".Under M treatment,soil urease activity showed a trend of "M",and the activity of soil sucrase enzyme showed an inverted "N" trend.(7)To sum up,soil soluble organic carbon nitrogen and soil enzyme activity of different age Platycladus orientalis plantation on southern Taihang Mountains,which were affected by various factors such as season,forest age,return of litter and soil physical and chemical properties,and show significant differences.In general,the physical and chemical indexes of the soil under the Platycladus orientalis plantation of 30a-40a were at a high level.This provides a theoretical basis for the influence of planting and biological activity of Platycladus orientalis plantation on Taihang Mountain.