| The soil is the core of the terrestrial ecosystem,is connected with the atmosphere,hydrosphere,biosphere and lithosphere ties.Nitrogen is one of the essential nutrients for plant growth and the largest mineral element.Research shows that the external nitrogen source after atmospheric deposition in forest ecosystem,only a part of being absorbed by plants,most of the nitrogen is with inorganic nitrogen(NH4+,NO3-)in soil,the inorganic nitrogen in soil micro-organisms or very easy to combine with organic matter and salt ions,to directly or indirectly.Effect of carbon cycle and accumulation of forest ecosystem.Located in the Chengdu plain and the western Dujiangyan lingyanshan transition zone(103 degrees 36 degrees 34 '?103' E,31 degrees 01 degrees 01 'N?31'),a subtropical climate type.Since the middle of last century,natural evergreen broad-leaved forest lingyanshan almost disappeared,and the formation of a variety of artificial forest ecosystem,and some remnants of forest patches.At the Dujiangyan campus of the Sichuan Agricultural Uniersity on the basis of previous work,the existing main forest types including lingyanshan(Phoebe Zhennan),Zhen Nanlin Liu Shanlin(Cryptomeria fortunei),artificial artificial oak forest(Quercus acutissima)and Michelia wilsonii plantation(Michelia wilsonii Finet et Gagn).Teaching and research base of Dujiangyan lingyanshan is the Forestry College of Sichuan Agricultural Uniersity,is also the city of Forest Park,so regional vegetation preservation is complete.This study intends to Dujiangyan lingyanshan 4 Forest Communities(artificial forest,artificial Machilus Liu Shanlin,artificial oak forest and artificial containing jokes)as the research object,comparative study of different land use aggregate characteristics and dynamic characteristics of nitrogen in forest soil,the results can provide the basic data for the subtropical forest restoration and ecological forest management system.The main results are as follows:(1)the variation trend of the soil temperature of the 4 kinds of artificial forest is consistent with that of the local meteorological station,but the variation range is smaller than the air temperature,which shows the tendency of moderate.From January to late 3 and from November to December,the soil temperature was higher than the air temperature,and the soil temperature was lower than the air temperature in the period from April to November.4 soil temperature plantation is basically the same trend.From January to August,the soil temperature of the overall upward trend,the maximum value appeared in August;and from August to December,the overall downward trend,the lowest temperature in January.The rate of high content of humor and oak forest temperature coincide,soil temperature of two woodland and two to the soil temperature in May to October was slightly higher than the rest of the woodland.The soil temperature in January to April of Cryptomeria fortunei is slightly higher than the rest of forestland,soil temperature of Machilus forest from April to December are lower than the other 3 kinds of plantation.Year-round rainfall in Dujiangyan region,but mainly concentrated in the middle of May to September,precipitation frequency and precipitation during this period are larger,and the single rainfall frequency is high;and the rest of the month precipitation and precipitation frequency is low,and the single small amount of precipitation.Combined with the precipitation and temperature in Dujiangyan area can be obtained,the local precipitation concentration month and higher temperatures are concentrated in the month of May to September,basically concentrated in the growing season,with the same characteristics of rain heat.(2)The aggregate composition of each plantation was 2 mm diameter,the proportion reached 94.00%?67.00%,while the particle size of the aggregates with the size of 0.5?0.25 mm was the smallest,only 1.07%?3.39%.Among them,with only 20?40 jokes cm layer>2 mm diameter aggregate ratio is less than 0?20 cm soil layer,the rest of the plantation was 20?40 cm soil>2 mm diameter ratio greater than 0?20 cm soil aggregates.The same soil layer,Cryptomeria fortunei>2 mm aggregates the largest proportion,and Machilus forest>2 mm diameter aggregate minimum proportion.There was no significant effect of forest type and soil layer on soil aggregates.(3)the contents of organic carbon,total nitrogen and total phosphorus in the 0?20 soil layers of CM cm were higher than that of 20?40.In two soil layers,including our aggregates organic carbon content were significantly lower than those of the other 3 types of forest.For topsoil,the maximum value of soil organic carbon content in four kinds of plantations was in different grain size.In the 20?40 cm soil layer,the maximum value of organic carbon in the plantation was mostly in the size of 0.5-0.25 mm.The results of variance analysis showed that forest type,soil layer and the interaction between the two groups had significant effects on the soil organic carbon content.In two soil layers,including our aggregates total nitrogen content was significantly lower than that of the other 3 types of forest.For different soil layers,the maximum content of total nitrogen in the soil aggregates of four kinds of plantations was in different grain sizes.The forest type,soil layer and the interaction of the two factors had significant effects on the total nitrogen content of the aggregates.The highest in the 0-20 cm soil layer of Cryptomeria fortunei aggregates total phosphorus content,while containing jokes were the lowest in the cm soil layer;20?40,oak forest aggregates total phosphorus content was the highest,the other 3 types of forest soil aggregate total phosphorus content is.The forest type,soil layer and the interaction of the two groups had significant effects on the total phosphorus content of the aggregates.(4)the seasonal dynamic changes of soil ammonium nitrogen content were significantly different.The nitrogen content of 0-20cm depth of soil ammonium was first increased and then decreased,the highest in summer,higher in spring and autumn,lowest in winter;the total 20-40cm decreased gradually,in addition to a smile of artificial forest of ammonium nitrogen content was the highest in summer,followed by spring.As for the different plantations,the soil nitrogen content of the 4 kinds of artificial forests showed different changes in different seasons.The season,forest types and soil depth have significant effects on soil nitrate nitrogen content were consistent,the nitrate nitrogen content dynamic trend in 4 Forest Types in two soil layers,two season content is higher in spring and winter,while in summer and autumn were low,the overall decreased first and then increased.Different plantation,4 forest soil nitrate nitrogen in the 4 seasons are Cryptomeria fortunei forest soil nitrate content was the highest.The seasonal variation of soil microbial biomass nitrogen in 4 plantations of the two soil layers was obvious.The variation of the microbial biomass nitrogen was the highest in winter,except for the artificial forest.The other stands were the highest in spring,decreased significantly in summer,and increased in autumn.The soil microbial biomass nitrogen content in 0-20cm depth was higher than that in 20-40cm soil layer,and the seasonal variation of the same plantation in different soil layers was the same.Different plantation,4 forest soil microbial biomass nitrogen in two soil in spring,summer and autumn are Machilus forest was the highest;winter is the highest with jokes.(5)Seasonal,forest type and soil depth had significant effects on soil urease activity.The urease activity in 0-20cm soil layer of 4 kinds of artificial forests was higher than 20-40cm,and the seasonal changes of soil urease in the 4 kinds of plantations were obvious.4 kinds of artificial forests in two soil urease showed the highest activity in spring,and significantly higher than the other 3 seasons,is 2 times more than the rest of the season is summer and autumn activity;urease activity;urease activity and the lowest in winter.Different forest types,the soil urease activity of Nan Lin Ching is higher than that of the rest of the tree species in each season;the remaining 3 is artificial forest soil urease activity,oak forest is slightly lower than Liu Shanlin and with jokes.The nitrate reductase activity in the two soil layers of the 4 kinds of plantations had obvious seasonal variation,which was the highest in autumn,and significantly higher than that in the other 3 seasons.As for the different forest types,4 kinds of artificial forests showed different changes in different seasons.Smile,and the soil Cryptomeria Machilus forest nitrite reductase activity had little seasonal variation in the two soil layers,nitrate reductase activity only oak forest soils in winter was significantly lower than that of the other three seasons.In addition,the overall 0-20cm nitrite reductase activity in soil is higher than that of 20-40cm layer,on the contrary will only contain jokes in different forest types,4 kinds of artificial forest in different seasons shows different variation.In conclusion,the study samples of 4 forest soil temperature and local temperature changes the same trend,rain heat over the same period the climate characteristics of the area has;due to the different characteristics of soil aggregates of different types of artificial forest;in addition,4 forest soil ammonium nitrogen,nitrate nitrogen,microbial biomass nitrogen and related enzyme activity has obvious seasonal dynamics at the same time;4 kinds of artificial forest has significant difference.Therefore,the plantation of different plantations will have a significant impact on the characteristics of soil aggregates and nitrogen pools in the area,and thus provide a basis for the comprehensive management of plantation in the region. |
PDF Full Text Request