戴云山自然保护区森林土壤氮转化特点研究

发布时间：2018-02-09 01:42

  本文关键词： N成对标记 MCMC数值优化模型 氮初级转化速率 保氮机制　出处：《土壤》2017年02期 　论文类型：期刊论文

【摘要】：利用~(15)N稳定同位素成对标记法并结合MCMC数值模型,研究了戴云山国家级自然保护区天然毛竹林(BF)及其邻近黄山松 杉木林(NF)土壤氮素初级转化速率,以评估该地区森林生态系统土壤氮状态,并分析其保氮机制。结果表明:BF土壤NH_4~+-N的总产生速率(以N量计,13.16μg/(g×d))是NF土壤的2倍(6.25μg/(g×d)),其中黏土矿物对NH_4~+-N的解吸作用是BF产生NH_4~+-N的主要过程(55%),而NF主要以有机氮的矿化作用为主(56%)。BF土壤氮素初级矿化速率为5.56μg/(g×d),显著高于NF的3.40μg/(g×d)。土壤氮素初级矿化速率与土壤全氮含量显著正相关(P0.05),而与C/N比表现显著负相关(P0.05)。BF与NF土壤NH_4~+-N总产生量的90%均被土壤微生物的同化作用以及黏土矿物的吸附作用所消耗。两种土壤的硝化作用微弱,BF土壤总硝化速率(以N量计,0.23μg/(g×d))与NF土壤(0.26μg/(g×d))相差不大。两种林地土壤硝化作用均以有机氮的异养硝化为主,自养硝化过程可忽略不计。BF与NF土壤中NO_3~ -N消耗速率均超过了产生速率,表明BF与NF土壤均能有效降低NO_3~ -N的潜在淋失风险,其中BF土壤中NO_3~ -N的消耗以微生物的同化作用为主(58%),而NF土壤以NO_3~ -N异化还原为NH_4~+-N过程为主(68%)。戴云山国家级自然保护区两种亚热带森林土壤的氮转化过程均以NH_4~+-N转化为主,产生的绝大多数NH_4~+-N会迅速通过微生物对NH_4~+-N的同化作用以及黏土矿物对NH_4~+-N的吸附作用固持到有机氮库中;自养硝化过程微弱,使得无机氮主要以NH_4~+-N的形式保存于土壤中,同时酸性土壤环境有效削弱了NH_4~+-N的挥发损失。此外,相对较高的NO_3~ -N微生物同化速率以及异化还原为NH_4~+-N速率,进一步有效降低了NO_3~ -N的淋溶损失以及反硝化作用的气态损失风险,使该地区森林土壤能够在多雨的条件下有效保持氮素,满足植物的生长需求。
[Abstract]:With the method of stable isotope pairwise labeling and MCMC numerical model, the primary nitrogen conversion rate of natural Phyllostachys pubescens forest in Dayunshan National Nature Reserve and its adjacent forest of Pinus tabulaeformis was studied. To assess the soil nitrogen status of forest ecosystems in the region, The results show that the total production rate of NH4- N (measured by N = 13.16 渭 g / g 脳 dU) is 2 times higher than that of NF soil (6.25 渭 g / g / d), and the desorption of NH4- N by clay minerals is the main process of NH4- N production in BF, while NF mainly consists of NH4- N in BF. The primary mineralization rate of nitrogen was 5.56 渭 g / g 脳 d1, which was significantly higher than that of NF 3.40 渭 g / g 脳 d.There was a significant positive correlation between soil nitrogen primary mineralization rate and soil total nitrogen content (P0.05), but a significant negative correlation with C / N ratio (P0.05N). BF was negatively correlated with NF soil NH4- N level. 90% of the total production was consumed by soil microbial assimilation and clay mineral adsorption. The nitrification of the two soils was weak and the total nitrification rate (measured by N = 0.23 渭 g / g / g / d) was similar to that of NF 0.26 渭 g / g / d ~ (-1). Soil nitrification in woodland was dominated by heterotrophic nitrification of organic nitrogen. The autotrophic nitrification process was negligible, and the consumption rate of NO3- N in soil of NF and BF exceeded the production rate, which indicated that both BF and NF soil could effectively reduce the potential leaching risk of NO3 ~ + -N in soil. The consumption of NO3 ~ -N in BF soil was mainly caused by the assimilation of microbes, while in NF soil, no _ 3 ~ + -N was mainly reduced to NH _ 4 ~ -N. The nitrogen transformation process of the two subtropical forest soils in Dayunshan National Nature Reserve was mainly composed of NH _ 4 ~ -N conversion. The vast majority of NH4- N produced will be rapidly consolidated into the organic nitrogen pool through the assimilation of NH4- N by microbes and the adsorption of NH4- N by clay minerals, and the autotrophic nitrification process is weak, so that inorganic nitrogen is mainly stored in the soil in the form of NH4- N. At the same time, the volatilization loss of NH4- N was effectively weakened by acidic soil environment. In addition, the relatively high assimilation rate of NOS3 ~ -N and the rate of alienation reduction to NH4- N were also relatively high. Furthermore, the leaching loss of no _ 3- N and the gas loss risk of denitrification can be reduced effectively, so that the forest soil in this area can effectively maintain nitrogen under the condition of heavy rain, and meet the plant growth needs.
【作者单位】： 南京师范大学地理科学学院;戴云山国家级自然保护区管理局;江苏省地理环境演化国家重点实验室培育建设点;江苏省地理信息资源开发与利用协同创新中心;南京师范大学虚拟地理环境教育部重点实验室;
【基金】：国家重大科学研究计划项目(2014CB953803) 江苏高校优势学科建设工程项目资助
【分类号】：S714
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