关键词: 林地, 生态需水, 蒸散, 土壤水分, 黄淮海地区

Abstract: In this study,potted C.burmannii saplings were cultured in a top-closed cha mber with elevated CO₂(CO₂，365 μmol·mol-1) and ambient CO₂ (CO₂,365 μmol·mol^-1),and at diurnal temperature(day/night) 25/23 ℃ and 32/25 ℃,respectively.The gas exchange,calculated photosynthesis parameter, Rubisco content,and activated state of Rubisco were examined.The results showed that under +CO₂and at 25/23 ℃,the mean photosynthetic rate(Pnsat) of sapling leaves was 5.1%higher than that under +CO₂and at 32/25 ℃.Temperature enhancement declined Pnsat,while nitrate addition increased it.Under +CO₂,saplings had lower Vcmax and Jmax at 32/25 ℃ than at 25/23 ℃.Temperatureenhancement under +CO₂ also declined Vcmax and Jmax. Under +CO₂,lower photorespiration rate(Rp) occurred in leaves，but temperature enhancement could increase Rp.Under +CO2,Rubisco content(NR) and its active site per unit leaf area(M) decreased as diurnal temperature changed from 25/23 ℃ to 32/25 ℃.Meanwhile,nitrate addition could increase NR and M.It may be suggested that nitrate addition could alleviate the restriction of photosynthesis under elevated CO₂ concentration and enhanced temperature.

Key words: Forestland, Ecological water requirement, Evapotranspiration, Soil moisture content, Huang-Huai-Hai region