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Effects Of Exogenous Phosphorus Addition On Soil Organic Carbon Mineralization In Mid-subtropical Forest

Posted on:2018-06-24Degree:MasterType:Thesis
Country:ChinaCandidate:Z ChenFull Text:PDF
GTID:2480305426978019Subject:Physical geography
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Phosphorus plays a critical role in regulating carbon cycle in land ecosystems.However,the mechanism of phosphorus availability on soil organic carbon mineralization and microbial metabolism is unclear.Effect of phosphorus addition on soil organic carbon mineralization and microbial activity would be different due to amount applied,location selected,soil type and other factors.The current research largely focuses on the impact of phosphorus addition on soil microbial metabolic process,while ignoring the interaction between physical and chemical process of soil carbon and phosphorus for example the characteristic of adsorption or desorption and the response of different carbon substrates about phosphorus addition.In addition,the effect of phosphorus addition on soil P availability was also affected by soil parent material,phosphorus forms and soil texture.Therefore,two forest soils,which derive from granite and sandstone,were chosen in this study to investigate thoroughly impact of phosphorus addition on soil-organic carbon mineralization with two different parent materials,attempt to answer a question that whether phosphorus is a limited factor to soil organic carbon mineralization in this area,and provide a theoretical support for sustainable forest management under climate change in the future.The results as following:(1)Phosphorus addition and forest type could lead to significant changes in soil organic carbon mineralization,and there was a significant interaction.In general,phosphorus addition significantly increased four forest soil organic carbon mineralization rate and cumulative amount,and the soil organic carbon mineralization in forest of C.carlesii is greater than the forest of Chinese fir.Based on same parent material,Soil organic carbon mineralization reflect this outcome:natural forest of C.carlesii exceeds Chinese fir.Under the same forest type,soil organic carbon mineralization show result of soil from granite higher than soil from sandstone.Particularly,the average mineralization rate of C.carlesii soil from sandstone under phosphorus addition is higher than control 10.46%and 40.77%,cumulative mineralization amount exceeded control 1.44%and 16.26%.Average mineralization level of C.carlesii soil from granite under phosphorus addition is higher than control 18.89%and 46.92%,cumulative mineralization amount exceed control 9.81%and 21.43%,respectively.Average mineralization rate of Chinese fir soil from sandstone under phosphorus addition is higher than control treatment 5.21%and 32.57%,cumulative mineralization amount exceeded control treatment 0.5%and 8.65%.Average mineralization rate of Chinese fir soil from granite under phosphorus addition is higher than control 28.17%and 82.90%,cumulative mineralization amount exceed control 13.79%and 43.25%.These results show that phosphorus plays a critical role in the process of soil carbon mineralization in the middle subtropical zone.In the unmanured forest system,short-term P addition would significantly stimulate the decomposition of soil organic carbon,resulting in carbon loss,which is bad for the protection of soil carbon.(2)These factors also significantly affected soil DOC and other physical and chemical indicators.Phosphorus input promote the content of soil DOC,MBC and other active carbon of C.carlesii and Chinese fir from two parent materials.These soil active carbon increased provide a richer carbon source for soil microbial activities.For the two forest types,soil DOC and MBC content of C.carlessii is higher than Chinese fir.The stimulation of phosphorus addition on soil DOC was the most highlighted in the early stage.Firest day to phosphorus addition,soil DOC content of C.carlesii from sandstone increased 304%and 1181%,compared with control.Soil DOC of Chinese fir from sandstone is higher than control 322%and 870%.Soil DOC of C.carlesii from granite exceed control 215.1%and 453.56%,soil DOC of Chinese fir from granite is higher than 151.55%and 487%,and the promoting effect of phosphorus addition on soil DOC from two parent materials reached the maximum in fifteenth days.It concluded that short-term phosphorus addition could not only accelerate the soil organic carbon mineralization,but also lead to the change of characteristics with soil organic carbon adsorption or desorption,significantly increasing the content of dissolved organic carbon,and then aggravating soil organic carbon loss.(3)Phosphorus addition and difference of forest type exert obvious influence on soil microbial community structure of C.carlesii and Chinese fir from two parent materials.The microbial community biomass of C.carlesii and Chinese fir are increased with increase of phosphorus fertilizer.In soil microbial community with C.carlesii from sandtone,response of actinomycetes to phosphorus addition is bset,compared with control,it is more than 46.11%.The response of gram positive bacteria to phosphorus addition was the most obvious,it higher than control 28.91%?56.48%in soil of Chinese fir from sandtone.In C.carlesii and Chinese fir from granite,the response of fungal community to phosphorus is best,its exceeded control 61.28%and 35.79%,respectively.The results indicated that the phosphorus addition largely has the most obvious impact on bacterial community in forest soil from sandstone,phosphorus addition mostly exert significant effect on fungal community in forest soil from granite.The reason for this difference may be due to the change of soil available substrate and pH by phosphorus addition.In addition,the effect of forest type on soil microbial community may also be regulated by difference of soil itself parent material.The specific outcome:fungal,bacterial,and total biomass of C.carlesii from sandstone exceeded Chinese fir from sandstone,soil microbial community biomass of C.carlesii from granite was lower than Chinese fir from granite.(4)The response of soil enzyme activity to phosphorus addition and forest type is significantly different in C.carlesii and Chinese fir from two parent matreials.It indicated that changes of soil enzyme activity were influenced by much factors.In addition to limited nutrients,carbon subtrate itself which could meet the microbial metabolism also was important material foundation to regulate soil enzyme activities.Especially two lignin degradation enzymes(PHO?PER)of C.carlesii and Chinese fir from two parent materials were obviously decreased by phosphorus addition,compared with control.The reason for this decline may be owing to the increase of DOC,and the decrease of the utilization efficiency about materials which was difficult to decompose such as lignin.
Keywords/Search Tags:parent material types, forest types, organic carbon mineralization, phosphorus addition, microbial community
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