Abstract: The diurnal photosynthetic characteristics of Trifolium repens， Festuca elata， Cichorium intybus and Zea mays in karst rock desertification areas were determined by British Lcpro+photosynthetic instrument on sunny days. Daily mean value of net photosynthetic rate of Trifolium repens， Festuca elata， Cichorium intybus and Zea mays was 10.01， 6.23， 6.16 and 7.64 μmol CO2·m-2·s-1， respectively， the average daily transpiration rate was 5.11， 5.44， 4.35 and 3.36 mmol H2O·m-2·s-1 daily， respectively， and the water\|use efficiency was 1.94， 0.98， 1.40 and 2.09 μmol CO2·mmol-1 H2O. The characteristics of Trifolium repens were high in both photosynthetic and transpiration rate， whose Pn value was the highest in these four forage grasses. Festuca elata exhibited low photosynthetic rate and high transpiration rate， of which the water\|use efficiency was the lowest. Net photosynthetic rate of Cichorium intybus was the lowest. Zea mays exhibited the lowest transpiration rate and the highest water\|use efficiency， along with a relatively high Pn value. In order to make full use of scarce light energy and soil moisture content in karst rock desertification areas， it was suggested that Zea mays should be intercropped with Cichorium intybus， Trifolium repens and Festuca elata， and soil nitrogen and ground surface coverage could be increased while the water loss and soil erosion would be reduced consequently.

Key words: karst, rock desertification, artificial forage, photosynthetic characteristics, diurnal change