华西雨屏区区三种退耕还林模式细根呼吸对水热变化的响应

通过离体根系直接测定的方法对四川盆周低山区三种退耕还林模式（光皮桦＋扁穗牛鞭草、光皮桦＋苦竹、光皮桦＋自然草）细根呼吸动态及其与研究立地上大气温度、土壤温度（地下5cm处）、土壤含水量关系进行研究．结果表明：1）三种模式细根呼吸都呈现明显的季节动态，最高值均出现在大气温度和土壤温度最高的8月分别为1．83，2．03，1．88μmol．m^-2＊s^-1，12月细根呼吸均出现最低值分别为（0．39，0．56，O．48μmol．m^-2＊s^-1）；2）相较于大气温度，细根呼吸和土壤温度的相关性更大（Rair=0．643，0．72，0．676，Rsoi1=0．66．0．75，0．722，P〈0．01）；3）不同研究立地土壤含水量同细根呼吸变化没有呈现出线性相关．

Response of Fine roots Respiration at Three Different Models of Complex Ecosystem of Conversion of Farmland to Forest in Rainy Zone of West China

The respiration of excised fine roots were measured with a LI - COR 6400 at three sites of complex ecosystem（ Betula luminifera ＋ Hemarthria compressa, Betula luminifer ＋ Pleioblastus amarus , Betula luminifer ） of converting farmlands to forest in Sichuan basin in Hong -Ya county （29°24 N, 102°49 E） from March to De- cember 2006. The air temperature, soil temperature of upper layer （5 cm）, water content, biomass of the fine - roots and fine - roots N concentration were analyzed at the three sites. Fine - root CO2 efflux were 0.4 - 2.1 umol· m^-2 ＊ s^-1, differed between sites, but fine -root respiration at three study sires showed a clearly seasonal variation. Maximum values were obtained in August （the mean values in three sites were 1.83 ±0. 12, 2.03 ±0. 15, 1.88 ±0.14）, and then decreased in October, the minimum values were measured in December （0.39 ±0. 18, 0.56 ±0.20, 0.48 ±0.17 ）. There were a significant correlation between fine -roots respiration and temper- ature （ R air = 0. 643, 0.72, 0. 676, R soil = 0.66, 0.75, 0. 722）, and the respiration of fine - roots increased exponentially with air and soil temperature respectively. Compared to air temperature, the correlation between soil temperature and respiration was higher. Contrary to our prediction, soil water content did not appear fine -root respiration at three sites; this phenomenon may be caused by the research method errors.