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1.
稻麦轮作生态系统中土壤湿度对N2O产生与排放的影响   总被引:69,自引:7,他引:62  
通过对太湖地区稻麦轮作生态系统的N2O排放及土壤湿度进行系统观测和开展一系列模拟实验,研究了降雨和土壤湿度对N2O排放和产生过程的影响.结果表明,春季和秋季麦田N2O排放与降雨量呈明显正相关,但水稻田和冬季麦田的N2O排放不受降雨影响.稻麦轮作周期内的N2O排放较强烈地受土壤湿度制约,土壤湿度为田间持水量的97~100%或84~86%WFPS(土壤体积含水量与总孔隙度的百分比)时,N2O排放最强,低于此湿度范围时,N2O排放通量与土壤湿度呈正相关,反之,则呈负相关.田间N2O排放随土壤湿度的变化形式与模拟条件下培养土壤样品的N2O产生率变化非常相似,但前者的最佳湿度范围比后者窄,而且偏小.  相似文献
2.
东北典型旱作农田N_2O和CH_4排放通量研究   总被引:46,自引:9,他引:37  
应用封闭式箱法技术测定了玉米、大豆田中N2O和CH4全年的通量变化.指出N2O排放有明显的季节变化和明显的日变化.大量的N2O排放发生在作物生长季节中.在冰雪溶化期和收割作物后也有一定量的N2O从土壤中排放.此外,实验结果也指出,玉米和大豆田作为大气CH4源或汇的作用不明显.  相似文献
3.
景观生态学的核心:生态学系统的时空异质性   总被引:46,自引:8,他引:38  
1 景观生态学与景观异质性景观生态学是研究在一个相当大的区域内 ,由许多不同生态系统所组成的整体 (即景观 )的空间结构、相互作用、协调功能以及动态变化的生态学新分支[1 ] 。它的出现促进了空间关系模型和理论、空间格局与动态的数据类型的获取以及经典生态学很少涉及的空间尺度检测等方面的发展[2 ] 。Risser等认为景观生态学研究就是异质性的研究[3] 。其实 ,“景观”本身就具有“变化的异质性整体”的含义[4] 。景观生态学集中关注于对生态系统空间关系的研究 ,它把景观视为空间上镶嵌出现和紧密联系的生态系统组合 ,景观可…  相似文献
4.
青藏高原高寒草原碳排放及其迁移过程研究   总被引:41,自引:4,他引:37       下载免费PDF全文
采用箱式法通过对青海省五道梁地区高寒草原生态系统表层土壤含碳温室气体的研究发现 ,该地区高寒草原系统表层土壤 CO2 和 CH4 在 7~ 8月份的平均排放通量分别为 0 .46μmol· m- 2 · s- 1和 - 0 .43× 1 0 - 3μmol·m- 2 ·s- 1,此两种气体的排放通量随时间都有明显的变化特征 ,它们的日变化均为明显的单峰型 ,而且其中 CO2 排放通量的变化明显受大气温度变化的影响。地下土壤中 CO2 和 CH4 气体浓度随深度的增加呈递减趋势 ,进一步的分析表明这两种气体浓度在土壤中与相邻层次的气体浓度有很明显的相关关系 ,尤以永久冻土上层边界附近最为显著。  相似文献
5.
几种旱地农作物在农田N2O释放中的作用及环境因素的影响   总被引:34,自引:8,他引:26  
用封闭箱法原位观测几种旱田N2O的排放通量,并与裸地N2O通量比较,评价植物在农田N2O释放中的作用.田间观测与室内模拟实验结合,考察环境因子对N2O通量的影响.结果表明1d内大豆田N2O通量有两个释放高峰,而菠菜田和春小麦田只有1个释放高峰.种植大豆较大地提高了农田N2O的排放通量.农田裸地为一较弱的N2O释放源,且在1年的一定时期内表现为大气N2O的汇.光照变化对植物N2O通量影响很大,在较弱的光照条件下,植物释放N2O的通量较高.  相似文献
6.
生态系统稳定性研究   总被引:31,自引:4,他引:27       下载免费PDF全文
岳天祥  马世骏 《生态学报》1991,11(4):361-366
7.
At the Harvard Forest, Massachusetts, a long-term effort is under way to study responses in ecosystem biogeochemistry to chronic inputs of N in atmospheric deposition in the region. Since 1988, experimental additions of NH4NO3 (0, 5 and 15 g N m–2 yr–1) have been made in two forest stands:Pinus resinosa (red pine) and mixed hardwood. In the seventh year of the study, we measured solute concentrations and estimated solute fluxes in throughfall and at two soil depths, beneath the forest floors (Oa) and beneath the B horizons.Beneath the Oa, concentrations and fluxes of dissolved organic C and N (DOC and DON) were higher in the coniferous stand than in the hardwood stand. The mineral soil exerted a strong homogenizing effect on concentrations beneath the B horizons. In reference plots (no N additions), DON composed 56% (pine) and 67% (hardwood) of the total dissolved nitrogen (TDN) transported downward from the forest floor to the mineral soil, and 98% of the TDN exported from the solums. Under N amendments, fluxes of DON from the forest floor correlated positively with rates of N addition, but fluxes of inorganic N from the Oa exceeded those of DON. Export of DON from the solums appeared unaffected by 7 years of N amendments, but as in the Oa, DON composed smaller fractions of TDN exports under N amendments. DOC fluxes were not strongly related to N amendment rates, but ratios of DOC:DON often decreased.The hardwood forest floor exhibited a much stronger sink for inorganic N than did the pine forest floor, making the inputs of dissolved N to mineral soil much greater in the pine stand. Under the high-N treatment, exports of inorganic N from the solum of the pine stand were increased >500-fold over reference (5.2 vs. 0.01 g N m–2 yr–1), consistent with other manifestations of nitrogen saturation. Exports of N from the solum in the pine forest decreased in the order NO3-N> NH4-N> DON, with exports of inorganic N 14-fold higher than exports of DON. In the hardwood forest, in contrast, increased sinks for inorganic N under N amendments resulted in exports of inorganic N that remained lower than DON exports in N-amended plots as well as the reference plot.  相似文献
8.
土壤水分状况和氮肥施用及品种对稻田N2O排放的影响   总被引:30,自引:7,他引:23  
土壤水分状况和氮肥施用及品种对稻田N2O排放有明显影响.当稻田持续淹水时,几乎没有N2O排放,而当稻田经历干湿交替循环特别是烤田时,有较高的N2O排放通量.稻田持续淹水、干湿交替及烤田期间5个处理的平均N2O排放通量分别为1.02、23.87和47.99μg·m-2·h-1.化学氮肥的施用增加了稻田N2O的排放量,且硫铵能比尿素排放更多的N2O.施用硫铵氮100和300kg·hm-2引起的N2ON损失率分别为0.04%和0.26%,而施用尿素氮的分别为0.03%和0.15%.  相似文献
9.
Rates of soil respiration (CO2 efflux) were measured for a year in a mature Eucalyptus pauciflora forest in unfertilized and phosphorus-fertilized plots. Soil CO2 efflux showed a distinct seasonal trend, and average daily rates ranged from 124 to 574 mg CO2 m–2 hr–1. Temperature and moisture are the main variables that cause variation in soil CO2 efflux; hence their effects were investigated over a year so as to then differentiate the treatment effect of phosphorus (P) nutrition.Soil temperature had the greatest effect on CO2 efflux and exhibited a highly significant logarithmic relationship (r2 = 0.81). Periods of low soil and litter moisture occurred during summer when temperatures were greater than 10 °C, and this resulted in depression of soil CO2 efflux. During winter, when temperatures were less than 10 °C, soil and litter moisture were consistently high and thus their variation had little effect on soil CO2 efflux. A multiple regression model including soil temperature, and soil and litter moisture accounted for 97% of the variance in rates of CO2 efflux, and thus can be used to predict soil CO2 efflux at this site with high accuracy. Total annual efflux of carbon from soil was estimated to be 7.11 t C ha–1 yr–1. The model was used to predict changes in this annual flux if temperature and moisture conditions were altered. The extent to which coefficients of the model differ among sites and forest types requires testing.Increased soil P availability resulted in a large increase in stem growth of trees but a reduction in the rate of soil CO2 efflux by approximately 8%. This reduction is suggested to be due to lower root activity resulting from reduced allocation of assimilate belowground. Root activity changed when P was added to microsites within plots, and via the whole tree root system at the plot level. These relationships of belowground carbon fluxes with temperature, moisture and nutrient availability provide essential information for understanding and predicting potential changes in forest ecosystems in response to land use management or climate change.  相似文献
10.
Assessing the future global impacts of ozone on vegetation   总被引:29,自引:0,他引:29  
Ozone is a major secondary air pollutant, the current concentrations of which have been shown to have significant adverse effects on crop yields, forest growth and species composition. In North America and Europe, emissions of ozone precursors are decreasing but in other regions of the world, especially Asia, where much less is known about its impacts, they are increasing rapidly. There is also evidence of an increase in global background ozone concentrations, which will lead to significant changes in global ozone exposure over this century, during which direct and indirect effects of other changes in the global atmosphere will also modify plant responses to ozone. This paper considers how far our current understanding of the mechanisms of ozone impacts, and the tools currently used for ozone risk assessment, are capable of evaluating the consequences of these changing global patterns of exposure to ozone. Risk assessment based on relationships between external concentration and plant response is inadequate for these new challenges. New models linking stomatal flux, and detoxification and repair processes, to carbon assimilation and allocation provide a more mechanistic basis for future risk assessments. However, there are a range of more complex secondary effects of ozone that are not considered in current risk assessment, and there is an urgent need to develop more holistic approaches linking the effects of ozone, climate, and nutrient and water availability, on individual plants, species interactions and ecosystem function.  相似文献
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