Abstract:

The growth and photosynthesis of I-214 poplar trees (Populus×euramericana cv. 'I-214 ') in the plantations with subterranean drip irrigation(SDI) and normal irrigation(NI) on sandy soil in Beijing were studied in this paper. The results showed that: the growth and yields of the plantations were more increased on SDI than on NI. In 2000 (4 years after planting), the average D_1.3 , H and volume per tree were 21.18cm, 14.23m and 0. 1815m³ on SDI,54.5%、36.9% and 247.6% more than on NI; The yields of the plantations with SDI reached 22.78～25.81m³·hm^-2 a ^-1 which were 3.9～4.6 times as much as that with NI. The physiological mechanism of improving the growth of trees and increasing the productivity of forest land was the subterranean drip irrigation,by which the photosynthesis and water use efficiency of trees grown in the plantation would be promoted. The net photosynthetic rate of leaves for poplar trees irrigated with SDI was still significant higher than that with NI in the different time of a day, ranged from 10.0%～21.4%. During an irrigation cycle, the net photosynthetic rate of leaves with SDI was also significant higher than that with NI, ranged from 9.0%～9.9%. Water use efficiency of trees with SDI was also higher than that with NI. The correlativity study showed that the net photosynthetic rate of poplar trees leaves could contain a high level for a long time when the water content of subsurface soil (15～25cm) was 5%～8%; but it would be decreased when the water content was lower than 4%. At last, extending the subterranean drip irrigation in developing the fast-growing and high-yield plantations in arid, semi-arid area, and season arid area was suggested according to the local economic condition. It could not only accelerate the sustainable usage of water resources, but also could increase the plantation productivity and make it reach the high level of the world.

Key words: Poplar, Fast growing and high-yield plantation, Subsurface drip irrigation, Plantation yield, Photosynthesis