| Tetraena mongolica Maxim.(Zygophyllaceae), a super-xerophutic shrub with fleshyleaves is a mono-species genus and endemic plant to China. As the constructive species ofdesert communities, T. mongolica plays an irreplaceable role to local ecosystem stability andprotection of the ecological environment. But because of its simple community structure andfragile ecosystems, the natural habitats have been damaged severely, the population hasdropped sharply and the age-class structure has declined under the combined effects of naturaland human factors since the last century.This population is in the seriously endangered status.In order to gather information for promoting its regeneration and rejuvenation and restoring ahealthy T. mongolica community, we conducted stump treatments on aging plants in spring.One transect was set up across the study area and a20×20m sampling plot was marked at ainterval of20m along the transect and a total of6plots were established. The plots includedthe treatments of stubble heights of-3,0,5,10, and15cm and a control. This study wasconducted between March2011and October2012and we found that:(1) Stumping could promote regeneration and rejuvenation of the plant T. mongolicaduring the first two growing seasons after stumping. The stumped plants growthed rapidly afterthe first growing season, and there was a slight slow down in the second. Height annual growthof treatments of-3,0,5,10,15cm improved355%,347%,241%,179%,115%and231%,225%,125%,205%,262%more than control in the first two growing seasons. Crown widthannual growth respectively improved117%,65%,417%,397%,339%and29%,8.5%,156%,83%,97%more than control. The average length of sprouting branches had the following order:15cm of stubble height>10cm>-3cm>0cm>5cm> control; the average basal diameterhad the following order:15cm of stubble height>5cm>10cm>-3cm>0cm> control; andthe number of sprouting branches had the following order:5cm of stubble height>0cm>-3cm>10cm>15cm> control. (2) The diurnal variation of net photosynthesis rate (Pn) and transpiration rate (Tr) ofstumped plants fitted a single-peak curve in first growing season of July after stumping andthen changed to a bimodal curve in the second growing season of July. Water use efficiency(WUE) in first growing season of July was bagger than that in the second growing season ofJuly, and the daily average values of WUE had the same following order:5cm of stubbleheight>10cm>15cm>0cm>-3cm> control.(3) The twig water potential of each stumped plant is higher than control all the daytime inthe first two growing seasons of July after stumping,and stumping treatment increased themoisture content of plants.(4) In the second growing season of July after stumping, we found that both plants at-3cm and0cm of stubble heights were not sufferring drought stress, and drought-stress degreesof other treaments had the following order:5cm of stubble height<10cm<5cm<control. Allof this was based the same natural conditions (Soil moisture content of soil body in0-10cm,10-20cm,20-30cm,30-40cm,40-50cm,50-60cm were0.63%,1.79%,2.61%,2.73%,2.18%,2.47%) by contrast the changes of MDA content and activity in antioxidate systemenzyme before and after irrigation. MDA content of control plants was significant higher thanthat of any other stumped plants, so we thought that accumulation peroxide had producedirreversible injury to the control plants.(5) In the second growing season of July after stumping, the daily mean value oftranspiration transfer coefficient (hat) had the following order: control>5cm of stubble height>10cm>0cm>-3cm>15cm; the not watered plants of all stumped treatments had higherdaily mean value of hatthan the watered plants, the order of the change range was-3cm ofstubble height<0cm <5cm <10cm <15cm. |
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