元江干热河谷土壤温湿度变化及其对干旱的响应

Variation Characteristic of Soil Moisture and Soil Temperature in Yuanjiang Savanna Ecosystem and Its Response to Drought

随着全球变暖,干旱发生的频率和强度不断上升,但生态系统对干旱的响应机理尚不清楚。为把握生态系统整体对干旱的响应,以元江稀树冠草丛生态系统为研究对象,搭建了冠层上方的整体截雨试验平台,共设4个处理:空白(CK),截雨30%(PE3),截雨50%(PE5)和截雨70%(PE7),每个处理3个重复。主要通过土壤水分、土壤温度对不同截雨处理的响应评估该控雨平台的控水效应,为研究稀树冠草丛生态系统整体对干旱的响应提供试验基础。结果表明:元江年均气温逐年升高(P<0.05),降雨逐年降低(P>0.05),年均最高气温上升最快(P<0.05);CK、PE3、PE5和PE7处理下土壤10cm水分含量年均值分别为17.2%、12.9%、10.3%和9.1%,各处理土壤10 cm水分含量在干季、雨季和全年尺度上均差异极显著(P<0.01);10 cm土壤温度在各截雨处理下依次升高分别为25.1℃(CK)、25.2℃(PE3)、25.8℃(PE5)和26.5℃(PE7),且无论在干季、雨季还是全年尺度上PE7处理与PE3和CK处理差异显著(P<0.05),其它处理间无差异(P>0.05);该冠层上方截雨平台对生态系统整体控水的控水效果(EPE,70.0%~84.0%)优于于国内外冠层下方控穿透雨试验平台(EPE≤35.0%)。该平台为研究生态系统整体对干旱响应提供了良好的方法。

Although the frequency and intensity of drought has been increased with global warming,the response mechanism of ecosystem to drought remains unknown. In order to investigate the global responses of the eco-system to drought,the crown canopy ecosystem in Yuanjiang savanna was targeted as a case study. A integrated rainfall interception experiment platform was designed and placed over the crown for performance testing at 4 selected scenarios： blank（ CK）,30% interception（ PE3）,50% interception（ PE5） and 70% interception（ PE7）,each of them with 3 repeated trials. By examinations of the responses of soil moisture and temperature to the given rainfall under each of the four interception conditions,an evaluation was performed on the water control effects of the platform,whereby it provide new insight into the response of canopy ecosystem in savanna to drought. Results found that annual temperature average in Yuanjiang had increased for years（ P〈0. 05） along with a gradual decrease in precipitation（ P〈0. 05） and the annual maximum temperature disclosed the fastest ascending rate（ P〈0. 05）. In the four testing scenarios of CK,PE3,PE5 and PE7,the annual average of soil moisture contents at10 cm were 17. 2%,12. 9%,10. 3% and 9. 1%,respecitively,and they presented significant difference in dry season,rainy season and a year basis（ P〈0. 01）. Soil temperature at 10 cm deep in each of the four scenarios increased accordingly at 25. 1 ℃（ CK）,25. 2 ℃（ PE3）,25. 8 ℃（ PE5） and 26. 5 ℃（ PE7）. Regardless of the dry season,rainy season or a whole year,in PE7 the temperature of soil was found an great difference as compared with values to be observed in PE3,CK（ P〈0. 05）,whereas at other scenarios they exhibited less. The integrated water controlling efficiency achieved by rainfall interception platform installed above the crown（ EPE,70% ~ 84%） was proved to be better than those of the regular platforms to be seated under crown canopy（ EPE ≤35. 0%）. In conclusion,our suggested platform could provide an acceptable approach to investigation of the response of entire ecosystem to drought.