中文摘要：

利用Granier测定系统,对华南丘陵植被恢复先锋树种马占相思和木荷的树干液流分别进行4a（2004—2007年）和5a（2008—2012年）监测,比较不同龄级两树种的蒸腾量及其季节变化.结果表明：马占相思和木荷的年蒸腾量均随树龄增加而增大,木荷蒸腾量的增加速度更快.木荷平均整树年蒸腾量为7014.76kg,比马占相思（3704.97kg）高;马占相思蒸腾量的季节变异（511.46～1802.17kg）比木荷（1346.48～2349.35kg）大.蒸腾速率（Eh）与光合有效辐射（PAR）、水汽压亏缺（VPD）的标准回归系数随土壤湿度的增加而增大,表明土壤水分的增加提高了植物对环境响应的敏感度.偏相关分析表明,土壤湿度的季节变异是导致两树种蒸腾量季节变化的最主要因素.木荷和马占相思的最适土壤湿度分别为0.22～0.40和0.29～0.30（V/V）,表明与外来树种马占相思相比,乡土树种木荷对水分胁迫有更好的适应及调节能力.

英文摘要：

The xylem sap flows of two pioneer tree species, i. e. , Acacia mangium and Schima su- perba, in degraded hill lands of South China, were continually monitored with Granier＇ s thermal dissipation probes during 2004-2007 and 2008 -2012, respectively, and their seasonal transpiration changes at different tree age levels were compared. The results showed that the annual transpiration of both species increased with tree ages, and S. superba demonstrated a higher value than A. man- gium. The average annual whole-tree transpiration of S. superba （7014.76 kg） was higher than that ofA. mangium （3704.97 kg）. A. mangium （511.46-1802.17 kg） had greater seasonal variation than S. superba （ 1346.48 -2349.35 kg）. The standard regression coefficients （~） of transpiration （Eh）, photosynthetically active radiation （PAR） and vapor pressure deficit （VPD） for both species increased with soil moisture, suggesting the increase of soil moisture generated a greater sensitivity of plants to environmental factors. Partial correlation analysis revealed that soil moisture played an important role in the seasonal variation of transpiration of both species. The opti- mum soil moistures of S. superba and A. mangium were 0.22-0.40 and 0.29-0.30 （V/V） , re- spectively, indicating the native pioneer species S. superba better adapted to water deficit compared with exotic pioneer species A. mangium.