以荒漠优势植物红砂2年生苗木为试材,采用盆栽试验和开顶式CO2控制气室模拟CO2浓度变化(350μmol/mol和700μ,mol/mol)研究了红砂生物量分配及碳氮特征对降水变化减少30％、减少15％、自然降水、增加15％和增加30％(-30％、-15％、0、15％、30％)的响应.结果表明:(1)CO2浓度上升显著性的促进红砂地上茎叶和地下的根生物量,降雨量增加或减少也显著性的促进或抑制了这一作用;CO2倍增时,红砂的地上生物量在降水增加30％时平均增加了61.28％(P＜0.05),而根生物量在降水增加或减少30％时均分别增加了84％(30％)和3.21％(-30％),这种响应导致红砂根冠比在降水减少时大于降雨量增加时,CO2倍增显著地抑制了这一作用.(2)CO2浓度上升显著性地促进了红砂根、茎、叶中的碳含量,显著性地抑制了红砂根、茎、叶中氮含量,降雨量增加或减少也显著性的促进或抑制了这一作用;这种响应导致红砂根、茎、叶的C/N在降雨减少30％时增加80.22％(根)、103.02％(茎)和199.88％(叶)(P＜0.05),在降雨增加30％时增加24.99％(根)、30.27％(茎0)和104.45％(叶)(P＜0.05),CO2浓度倍增显著性地促进了这一作用.(3)以上结果表明,未来全球CO2浓度升高时,在降雨量增加地区红砂因充足的碳源和水分而得以恢复;在降雨减少的地区,CO2的升高对降雨减少造成的干旱胁迫有一定的补偿作用,红砂则以较高的根冠比来维持其在荒漠生态系统中地位.%Atmospheric CO2 concentrations are predicted to increase from approximately 350μmol/mol today to over 700μmol/mol in the late 21th century.In the future,elevated CO2 levels are likely to have profound effects on precipitation.This change would seriously affect the desert ecosystem,above-and belowground biomass,and carbon and nitrogen allocations of desert plants,leading to changes in ecosystem structure and function.Although many studies have examined the effects of precipitation and CO2,the interactions between changing precipitation and CO2 on desert plants have attracted little attention to date.A pot experiment was conducted to study the interaction of elevated CO2 concentration and changing precipitation with biomass allocation,and carbon and nitrogen content characteristics in roots,stem,and leaf of Reaumuria soongorica,a dominant species of the desert steppe in the arid region of China,in order to assess the possible effect of global climate change on desert ecosystems.The main plot included two CO2 concentrations (350 and 700pmol/mol) and five precipitation conditions(natural precipitationas control [0],precipitation minus 30％ [-30％],precipitation minus 15％ [-15％],precipitation plus 15％ [15％],precipitation plus 30％ [30％]).The results showed that:(1) aboveand belowground biomass of R.soongorica were increased significantly with elevated CO2,and this effect was promoted or inhibited when precipitation increased or decreased,respectively;When the CO2 concentration was increased from 350 to 700μmol/mol,the aboveground biomass increased by 61.28％with precipitation plus 30％ (P＜0.05),whereas root biomass was increased by an average 84％ with precipitation 30％,and 3.21％ with precipitation-30％,respectively (P＜ 0.05);Therefore,the root/shoot ratio (R/S) of R.soongorica with precipitation plus was greater than that with precipitation minus,and this effect was significantly inhibited by elevated CO2(P＜0.05).(2) Elevated CO2 significantly increased the carbon content in the root,stem,and leaf of R.soongorica,and significantly decreased nitrogen content in those organs;this effect was promoted or inhibited with precipitation plus or minus.The C/N ratio of the root,stem,and leaf of R.soongorica increased by 80.22％ (root),103.02％ (stem) and 199.88％ (leaf) with precipitation 30％ (P＜0.05),whereas,the C/N ratio of those organs increased by 24.99％ (root),30.27％ (stem),and 104.45％ (leaf) (P＜0.05) with precipitation-30％,and elevated CO2 significantly promoted the effect (P＜0.05).(3)These results suggested that,under future conditions of elevated CO2,R.soongorica would be restored due to sufficient carbon and water resources in the area where precipitationis increased;Whereas,in areas where precipitation is decreased,R.soongorica would retain its dominant position for the high root/shoot ratio,because there would be compensation of elevated CO2 to drought stress.
展开▼
