The transpiration experiment was done under greenhouse conditions with a C3 plant sweet pepper(Capsicum annuum Linn.) and two C4 plants,sorghum(Sorghum bicolor L.Moench) and maize(Zea mays Linn.).Three species were irrigated with three different water treatment levels of 100%,66% and 33% which gave a comparison of tolerance and adaptation to irrigation and two different levels of water stress.The measurements of transpiration rate and stomatal conductance were done between 8.00 a.m.and 16.00 p.m.with measurements about each 1.5 h with an infrared gas analyzer.The results showed that Z.mays probably due to a higher leaf area had very low values and was signifi cantly different(LSD pairwise comparison) from C.annuum and S.bicolor.The hypotheses that C4 plants and C3 plants have different transpiration rates and stomatal conductance could not be shown with the results.However,the hypotheses that for the same species,the highest values in transpiration rate and stomatal conductance were with the 100% irrigation treatment and the lowest values were with the 33% irrigation treatment could be accepted due to the results of this trial.
Based on the data of 8 analytical trees originated from 3 types tree source collected from Xishan and Dayanshang area of Beijing,the growth process of DBH,height and volume and the relationship between DBH and height were analyzed respectively;4 theoretical equations were applied to fit the growth process.The results showed that the 3 types of sample trees were all in the fast growing stage which was far from quantity mature stage;the comparison of growth process among the 3 types of sample trees showed that the growth of trees originated from seedling sprouts were the fastest,followed by trees originated from natural regeneration and trees originated from planted seedlings,however,the trees originated from seedlings showed larger growth potential than those originated from seedlings sprouts;the results of DBH-height relationship showed a positive correlation trend;but the height growth of trees originated from seedling sprouts became slower when the DBH larger than 7 cm;the results of 4 fitted theoretical equations showed that Richards,Mitscherlich and Gompertz equations well fitted the growth processes of DBH,height and volume of the sample trees,while the fitting precision of Logistic equation was relatively lower.This study can provide reference for the management of Quercus variabilis forest in Beijing.
