Font Size: a A A

Effects Of Rainfall Change On Soil Physicochemical Properties And Respiration Rate Of Pinus Sylvestris Var. Mongolica Plantation In Sandy Land

Posted on:2020-05-03Degree:MasterType:Thesis
Country:ChinaCandidate:X L H WuFull Text:PDF
GTID:2370330590988671Subject:Forest cultivation
Abstract/Summary:PDF Full Text Request
Soil respiration transports soil carbon to the atmosphere,which is an important way to consume soil carbon pool.Any detailed change in soil respiration changes the concentration of carbon dioxide to affect the global carbon cycle.Soil respiration is the main form of soil organic carbon decomposition.The effect of rainfall on carbon sequestration and soil carbon stability of plantation ecosystem is still uncertain.There are abundant plantation resources in the semi-arid area of Northwest Liaoning Province,which play an important role in windbreak and sand fixation and carbon sequestration of soil,moreover,Northwest Liaoning Province is an important part of the Three-North shelter forest.Hence,scientific analysis of the influence mechanism of rainfall change on soil respiration of Pinus sylvestris var.mongolica plantation is of great significance to forestry development in Northwest Liaoning Province.It also provides a reference for scientific and effective management of plantation under the changing climate in the future.At present,there are few studies on soil respiration and its influence mechanism in this area.In this study,the soil of Pinus sylvestris var.mongolica plantation in sandy land of Northwest Liaoning Province was taken as the research object.Two kinds of rainfall conditions(normal rainfall and rainfall reduced 30%)and different rainfall intensity were set up to explore its effects on soil and its organic carbon decomposition.The main results were as follows:(1)Rainfall reduction treatment increased soil aggregates both of 0.053-0.25 mm and0.25-0.5 mm,with the contents of 34.66% and 31.44% respectively,while the content of macro-aggregates was relatively small.At the same time,the content of organic carbon in the aggregates increased with the treatment of rainfall reduction.The content of organic carbon in the aggregates increased most in 0.5-1 mm,8.91 g搔g-1,and decreased slightly with the treatment of 0.053-0.25 mm,with the content of 4.78 g搔g-1.At the same time,the content of organic carbon and total nitrogen in surface soil(0-10cm)was lower than that in normal rainfall,and with the content of 10.66 g搔g-1 and12.13 g搔g-1,respectively.On the other hand,both the content of organic carbon and total nitrogen in other soil layers was higher in rainfall reduction than that in normal rainfall.The C/N ratio of soil under rainfall reduction treatment was lower than that under normal rainfall,especially in 40-50 cm soil layer.Besides,the correlation between soil organic carbon and total nitrogen after rainfall reduction treatment was slightly higher than that of normal rainfall,and the biodiversity of rainfall reduction plots was lower than that of normal rainfall plots.(2)The diurnal variation of soil total respiration rate under normal rainfall and rainfall reduction was decreased at the beginning and then increased,and the period of higher respiration rate was maintained from 6:00 to 8:00 am,and with the rate of 5.33?mol搶-2新-1and 5.01?mol搶-2新-1,respectively.The changed trends of soil total respiration after rain was similarly under normal rainfall and rainfall reduction.There was no obvious difference between them before rain,but both the total respiration rate increased suddenly after rain,and With the highest respiration rates of 6.76 ?mol搶-2新-1and 7.96 ?mol搶-2新-1 in normal and reduced,respectively.Then the total respiration rate of rainfall reduction in the next two days was significantly higher than that of normal rainfall.The monthly variations of the total respiration rates of normal rainfall and rainfall reduction also were similar.The total respiration rates of normal rainfall and rainfall reductionincreased gradually from May to August,and it reached the highest values in mid-August,which were 5.99 ?mol搶-2新-1 and 7.40 ?mol搶-2新-1,respectively.During this period,the total soil respiration rates of rainfall reduction plots were higher than that of normal rainfall plots.The total soil respiration rate of normal and reduced rainfall decreased rapidly from august to november,and reaching the lowest valuein November.The respiration rates were 0.46?mol搶-2新-1 and 0.29 ?mol搶-2新-1,respectively.At this time,the total soil respiration rate of normal rainfall was higher than that of reduced rainfall.From the annual variation of total respiration,the respiration rate of rainfall reduction is higher than that of normal rainfall for most of the year,especially in July and August.(3)The diurnal variation of soil total respiration rate is less correlated with soil temperature,but positively correlated with soil water content in all soil layers.Moreover,the correlation index of rainfall reduction is higher than that of normal rainfall.The monthly variations of total respiration were positively correlated with soil temperature,but not with soil water content,while the annual variation of total respiration rate was also positively correlated with soil temperature,but only with soil water content of 10 cm and 20 cm.Compared with soil temperature and water content,the correlation between the total respiration and air temperature and humidity is smaller.Only the monthly and annual changes of total respiration are positively correlated with air humidity and temperature,and the spatial correlation between total soil respiration and air temperature will be weakened by rainfall reduction,and the spatial correlation between total soil respiration and air humidity will be weakened.In general,the contents of soil organic carbon and total nitrogen,its macro-aggregates,and the diversity of microorganisms all decreased after rainfall reduction.On the contrary,rainfall reduction increased the total soil respiration rate slightly.It was of great importance for the plantation management scientific of this semi-arid area in the future under climate change scenario.
Keywords/Search Tags:Pinus sylvestris var. mongolica in sandy land, reduced rainfall, soil respiration, soil aggregates
PDF Full Text Request
Related items