模拟氮沉降和降雨量改变对华西雨屏区常绿阔叶林土壤碳氮特征的影响

发布时间：2018-04-29 22:05

本文选题：氮沉降 + 降雨量改变　；参考：《四川农业大学》2016年博士论文

【摘要】：18世纪后期到20世纪后期,人类实现了氮元素从发现到可以控制全球固氮速率的转变过程。目前,中国已成为三大氮沉降区域之一,仅次于欧洲和北美。就目前来说,氮沉降问题在全球气候变化中是一个非常严重的问题。各种生态系统的特征和过程均由于氮沉降的增加而产生了深刻影响。在全球气候变化的背景下,全球和区域尺度的降水格局产生了巨大的变化,引起降雨量增加或减少的不平衡,且季节变化大,导致北半球中纬度地区降雨量增大,亚热带地区降水量下降,南半球的降水量均增大。降雨是土壤水分最主要的来源,它能改变土壤通气条件,增加土壤湿度,对地表凋落物和土壤有机质分解、土壤酶活性、植物根系、微生物和植被群落结构和功能产生影响,对地下物理生物化学过程具有重要的调控作用。氮沉降的持续增加和降水格局的改变势必会对森林生态系统过程造成影响。本研究以华西雨屏区常绿阔叶林为研究对象,通过定位模拟氮沉降和降雨量改变,研究了华西雨屏区常绿阔叶林生态系统碳氮循环关键过程和特征对模拟氮沉降和降雨的响应,试验设置氮沉降和降雨2个因素,共6种处理,即对照(CK:Comparison)、氮沉降15gNm-2·a-1(N:Nitrogen deposition)、减雨10%(R:Water reduction)增雨10%(A:Water addition)、氮沉降15gNm-2·a-1减雨10%(NR:Nitrogen deposition and water reduction)、氮沉降15gNm-2·a-1+增雨10%(NA:Nitrogen deposition and water addition),每种处理重复3次,共18个处理。主要结果如下：1.华西雨屏区常绿阔叶林土壤各土层有机碳含量表现为夏季较高,春冬季较低,0-10cm土层有机碳含量高于10-20cm土层。从各处理土壤有机碳含量的平均值来看,0-10cm土层土壤有机碳含量高低顺序表现为：RNRCKANNA;10-20cm土层表现为：RNRACKNAN。模拟氮沉降和增雨促进了华西雨屏区常绿阔叶林土壤有机碳的累积,模拟减雨抑制了土壤有机碳的累积。常绿阔叶林0-10cm土层土壤C/N值显著高于10-20cm,土壤C/N值随土层加深而呈现出增加的趋势。降雨使土壤C/N降低,增雨使土壤C/N增高。同一氮沉降条件下,增雨处理增加了土壤TOC的含量,减雨处理减少了土壤TOC的含量；同一降雨条件下,氮沉降增加土壤TOC的含量。氮沉降和降雨对DOC和MBC含量产生显著影响(P0.05),对LC含量影响不显著(P0.05)；其交互作用对TOC、DOC、MBC和LC含量影响不显著(P0.05)。2.华西雨屏区常绿阔叶林土壤无机氮的变化范围介于14.66-18.37 mg·kg-1之间。各处理0-10cm土层的NH4+-N和N03--N含量均高于10-20cm土层。模拟氮沉降促进了华西雨屏区常绿阔叶林土壤无机氮的累积,并使土壤pH值降低；增雨抑制了土壤无机氮的累积。氮沉降处理的土壤NH4+-N与N03-N相关性显著。各处理的土壤硝态氮、铵态氮与全氮、有机质、含水量之间均存在显著相关性。同一氮沉降条件下,增雨处理降低了各土层NH4+-N和N03--N的含量；同一降雨条件下,氮沉降增加了各土层NH4+-N和N03--N的含量。氮沉降和降雨对NH4+-N和N03--N含影响显著(P0.05)。其交互作用对土壤NH4+-N和N03--N含量的影响不显著(P0.05)。3.氮沉降和增雨抑制了华西雨屏区常绿阔叶林土壤呼吸速率,减雨促进了土壤呼吸速率。减雨使华西雨屏区常绿阔叶林土壤呼吸年通量增加了576 g·m-2,而模拟氮沉降和增雨使土壤呼吸年通量分别减少了726和803 g·m-2。CK、N、R、A、NR和NA处理的土壤呼吸速率的Q1o值分别为2.77、2.44、3.18、2.39、2.58和2.22,表明减雨增加了土壤呼吸的温度敏感性,模拟氮沉降和增雨降低了土壤呼吸的温度敏感性。模拟温度和湿度与土壤呼吸速率间回归方程分析表明,土壤水分对土壤呼吸速率的影响较小。模拟氮沉降和增雨处理减少了土壤微生物生物量碳、氮的含量,减雨处理增加了土壤微生物生物量碳、氮的含量。模拟氮沉降和降雨对土壤CO2释放的影响未表现出明显的交互作用。4.华西雨屏区常绿阔叶林各土层微生物总量季节变化明显,表现为秋冬季较高,春夏季较低。0-10cm土层的土壤细菌、真菌、放线菌数量均高于10-20cm土层。各土层中细菌占有绝对优势,放线菌次之,真菌所占微生物数量比例最小。在0-20cm土层,CK、R、A、N、NR和NA处理的土壤微生物总量平均值分别为6.44、7.27、4.98、5.42、5.43和4.81 cfu·g-1-106,表现为：RCKNRNANA,R处理的土壤微生物总量比CK增加了12.89%；而A、N、NR和NA处理比CK减少了22.67%、15.84%、15.68%和25.31%。减水处理增加了土壤微生物总量,模拟氮沉降和增水处理使土壤微生物总量减少。同一降雨处理下,模拟氮沉降使土壤微生物总量减少。同一氮沉降处理下,减雨增加了土壤微生物总量,增雨减少了土壤微生物总量。氮沉降和降雨对表层土壤微生物总量和细菌数量产生显著影响(P0.05),其交互作用对微生物区系的影响不显著(P0.05)。5.华西雨屏区常绿阔叶林6种土壤酶活性均为上层土壤(0-10cm)大于下层土壤(10-20cm),且具有明显的季节变化,纤维素酶和酸性磷酸酶活性夏季较高；蔗糖酶和脲酶活性秋季较高；过氧化物酶和多酚氧化酶活性冬季较高。模拟氮沉降和降雨量改变未改变土壤酶活性原有的垂直分布格局。总体上看,模拟氮沉降抑制了蔗糖酶、过氧化物酶、纤维素酶和多酚氧化酶的活性,促进了脲酶、酸性磷酸酶的活性。减雨使土壤多酚氧化酶和过氧化物酶活性降低,减雨使土壤中脲酶、酸性磷酸酶、壤蔗糖酶和纤维素酶活性增加,增雨使土壤中脲酶、酸性磷酸酶、壤蔗糖酶和纤维素酶活性降低。模拟氮沉降对土壤酶产生了显著的影响(P0.05)。模拟氮沉降和降雨量改变对华西雨屏区土壤酶活性的影响未表现出明显的交互作用。6.华西雨屏区常绿阔叶林凋落叶分解较快,凋落枝分解较慢；凋落物夏季分解较快,其他季节分解较慢。经过24个月的分解后,凋落叶和枝的质量残留率分别为38.03%和80.42%,凋落叶分解50%需要的时间为1.48a,比枝短5.58 a。各处理凋落物叶分解系数表现为：k(A)k(CK)k(NA)k(N)k(R)k(NR),凋落枝质量残留率表现为：NNRRNACKA。模拟氮沉降、减雨和增雨处理的凋落叶分解50%分别需要1.86、2.35和1.36 a,凋落枝分解50%分别需要8.97、7.93和6.38 a。各处理凋落叶分解95%需要6.01～11.55 a,凋落枝分解95%需要26.93～38.04a。同一氮沉降条件下,增雨促进凋落叶分解,减雨抑制凋落叶分解；同一降雨条件下,氮沉降抑制凋落叶分解。氮沉降或降雨对凋落物的分解产生显著影响(P0.05),其交互作用影响不显著(P0.05)。可见,在氮沉降持续增加和降雨格局改变的背景下,增雨促进了华西雨屏区常绿阔叶林凋落物的分解,氮沉降和减雨抑制了凋落物的分解,模拟氮沉降和降雨对凋落物的分解交互作用表现不明显。7.试验期间,华西雨屏区常绿阔叶林凋落叶各处理C、N、P浓度分别在345.68-478.53 g·kg-1,5.86-9.56 g·kg-1、0.42-1.15g·kg-1之间波动。模拟氮沉降和减雨处理使常绿阔叶林凋落叶C、N和P浓度增加,增雨使C、N和P浓度减少。华西雨屏区常绿阔叶林凋落叶各养分元素年释放速率大小表现为：NCP。各处理C和N均为直接释放模式,P表现为富集—释放模式。模拟氮沉降和减雨抑制了常绿阔叶林凋落叶C、N和P的释放,增雨促进了常绿阔叶林凋落叶C、N和P的释放。C、N和P元素残留率与干物质残留率相关性显著(P0.5)。经24个月的分解后,各处理C/N值表现为：NANCKRANR;N处理使C/N值减少了4.25%, R和A处理使C/N值分别增加了1.13%和4.02%。氮沉降和降雨对凋落叶C、N和P元素的释放产生显著影响(P0.05);其交互作用对凋落叶N和P元素的释放产生显著影响(P0.05),对C元素的释放影响不显著(P0.05)。
[Abstract]:In the late 18th century to the late 20th century , mankind realized the transformation of nitrogen element from the discovery to the control of global nitrogen fixation rate . At present , China has become one of the three major nitrogen settling regions , which is second only to Europe and North America . 1 . The organic carbon content in the soil layers of the evergreen broad - leaved forest in the Huaxi rain - screen area is higher than that in the 10 - 20cm soil layer . The soil organic carbon content in the 0 - 10cm soil layer is obviously higher than that of the 10 - 20cm soil layer . The soil organic carbon content in the 0 - 10cm soil layer is obviously higher than that of 10 - 20cm . The soil C / N ratio decreases and the soil C / N increases with the deepening of the soil layer .
Under the same rainfall condition , the nitrogen deposition increased the content of TOC in the soil . The effects of nitrogen deposition and rainfall on DOC and MBC content were significantly affected ( P0.05 ) , but the influence on LC content was not significant ( P0.05 ) .
The effect of interaction on TOC , DOC , MBC and LC was not significant ( P0.05 ) . The inorganic nitrogen content of evergreen broad - leaved forest in Huaxi rain screen was 14.66 - 18.37 mg 路 kg - 1 . The contents of NH4 + - N and N03 - N in each treated 0 - 10cm soil layer were higher than that of 10 - 20cm soil layer .
The soil NH4 + - N was significantly correlated with N03 - N in the treatment of nitrogen deposition . The soil nitrate nitrogen , ammonium nitrogen and total nitrogen , organic matter and water content of each treated soil had a significant correlation .
The results showed that the soil respiration rate of soil microbial biomass increased by 576 g 路 m - 2 . The results showed that the soil respiration rate increased by 576 g 路 m - 2 . The results showed that the soil respiration rate increased by 576 g 路 m - 2 . The results showed that the soil respiration rate increased by 6.44 , 7.27 , 4.98 , 5.42 , 5.43 and 4.81 cfu 路 g - 1 - 106 respectively .
Under the same rainfall treatment , the total amount of soil microorganisms and the total amount of soil microorganisms were decreased by simulated nitrogen deposition and water increasing treatment ( P0.05 ) .
The activity of sucrose and urease was higher in autumn .
The activity of urease , peroxidase , cellulase and polyphenol oxidase in soil was inhibited by simulated nitrogen deposition . The activity of urease , peroxidase , cellulase and polyphenol oxidase in soil was decreased , and the activity of urease , acid phosphatase , sucrose enzyme and cellulase in soil was decreased .
The decomposition coefficients of litter and litter were 38.03 % and 80.42 % , respectively . The decomposition coefficients of litter and litter were 8.97 , 2.35 and 6.38 a respectively . The decomposition coefficients of litter were 8.97 , 2.35 and 6.38 a .
The effects of nitrogen deposition and precipitation on litter decomposition , N and P release of evergreen broad - leaved forest were studied . The effects of nitrogen deposition and precipitation on the release of C , N and P in evergreen broad - leaved forest decreased by 1.13 % and 4.02 % respectively .

【学位授予单位】：四川农业大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：S714

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