土壤养分循环.ppt

The cycle has a dynamic nature
The addition of CO2 to the atmosphere through fossil fuel burning in:
a) 1900 - 1 billion tons b) 1955 - 2 billion tons c) 1980 - 5 billion tons
Hypotห้องสมุดไป่ตู้esis: bioenergy plantations increase C
•Affected by many factors •amount and type of biomass input •soil microbial community •moisture regime •oxygen supply •temperature •soil texture •supply of other
•Soil organism food and function •Nutrient reserve
•Leaching protection
•Carbon sink
•Largest terrestrial pool
Effects of SOM depletion on environment
•Decreased yields •Increased erosion
• 1.土壤碳存在的形态:
有机碳和无机碳。后者主要为碳酸盐，对环境 影响不大。
有机碳又分为水溶态和难溶态。 水溶态有机碳包括：低分子量有机酸、AA、
糖酸、羟圬酸高铁载体。 难溶态有机碳包括胡敏酸、胡敏素、木质素、
植物落叶等。 土壤中含碳化合物的来源：
最初源于光合作用
2. 土壤中碳的含量
(1960-1980: from about 325 ppm to 345 ppm)
CO2 content of atmosphere in 1988 was 351 ppm and in 1992 was 356 ppm
CO2 content of atmosphere in 1996 was 363 ppm CO2 content of atmosphere in 1999 was 370 ppm
自然界碳库主要有三：（1pg=1015g）
• 海洋中碳：39000pg
• 大气中碳：750pg
• 陆地中碳：2200pg
一般砂质土0-100cm含碳3.1kg/m2，而有机土含碳 77.6kg/m2，
• 土壤碳以有机碳表示，占总碳的58%左右
• 有机质含量分级：
• 一级:>40 g/kg 级:20-30 g/kg
•50%-90% savings for NT vs. CT
•Increased leaching •Increased fertilizer use
Soil carbon equilibrium
•Affected by many factors
• amount and type of biomass input
二级:30-40 g/kg 三
• 四级:10-20 g/kg 级:<6 g/kg
五级:6-10 g/kg 六
Ecological role of SOM
•Aggregation
•slows erosion
•Soil conditioner
• Water holding capacity • Permeability • Bulk density/penetration resistance
a. carbon is diverted into wood or other durable organic material
b. can also be locked up in coal and oil deposits 5. The oceans may act as a buffer that do not allow the carbon dioxide amount in the atmosphere to vary widely 6. carbon dioxide is dissolved in water and is chemically converted to other forms. All told ocean contains 50 times the amount
土壤养分循环
第一节：土壤碳素及循环与生物 效应
• 土壤碳对植物营养的直接作用不大，植 物从大气中吸收CO2，但土壤有机碳的 转化为大气补充CO2 ，是大气碳的源和 库，调节大气中CO2浓度，特别是温室 效应直接与土壤碳的转化有关。因此， 土壤碳对植物营养、土壤肥力及环境都 很重要。
土壤中碳的形态、含量及转化
•Biomass
•has degradation resistant litter •provides good soil microbial habitat •has high water holding capacity •protects from oxidation •cools soil by shading/water •promotes aggregation •tight nutrient budget
3. 土壤碳的循环转化
The Carbon Cycle
1. autotrophs fix carbon dioxide from the atmosphere during photosynthesis 2. carbon dioxide is released back into the atmosphere by respiration 3. the carbon cycle is very fast 4. Other carbon cycles are slow
• soil microbial community • moisture regime • oxygen supply • temperature • soil texture • supply of other nutrients
•SOM declines 20-40% after conversion to cropland