Study On Water Consumption Properties And The Relation With Environmental Factors In Plantation Of Poplar

The water consumption patterns of two poplars species, poplar 'Zhonglin-46' andpopular Langfang which are main tree species of plywood forest in Langfang region,from the levels of leaf, single-tree and stand, were studied in terms of thermal dissipationsap flow probe (TDP) and the environment factors in situ that have effect on it testedsynchronously as well, of which the stand of 3-year and 5-year of"zhonglin-46" poplarand 5-year of "lamgfang" poplar were the emphases. To understand the poplars waterconsumption mechanism and its relation with environmental factors would help to providethe base information for forest management, especially in ecological irrigation. The mainconclusions are showed as below.(1) The leaf transpiration rates(LTR) diurnalvariation, no matter in the clear day orcloudy day, presented orderly a unimodal curve, of which there were wide peak curve inclear day and narrow peak curve in cloud day. Before 6:00 in the morning, the LTR wereat the small level either clear day or cloud day with 30.43 and 35.10 g/h.m² respectively,but it increased synchronously with solar radiation enhancement. It would reach the peak atthe time of 12:00-15:00 with the values of 290.40 g/·h.m² in clear day and 212.99 g/h.m²in the cloud day. When the time last to 18:00, the LTR would decrease with solarradiation weakening, and the values were 50.33 and 34.91 g/h.m², respectively. Amongthe crown, the LTR in different positions presented regularly phenomenon excepting 6:00in typical clear day, i.e. upper position＞middle position＞lower position. The LTR indifferent directions, on the other hand, expressed the same models, i.e. sunny-side＞theshady-side. There were no regular rules in cloud day all the time.(2) The poplars sap flow(SF) of 3-year, 5-year of "zhonglin-46"and 5-year of"langfang", from day to night, showed the similar rules, which it started to increasesmoothly at 7:00 or 8:00 in the morning and would got the peak between the time of11:00-15:00 that subjected to solar radiation increasing, circumference temperature risingand air relative humidity reducing. After that time, the SF would decrease steadily till19:00 when it preserved a relative stabilization flat, but it would reach the bottom beforethe time of sunrise. There were also slight SF phenomenon in the night, either 3-year and5-year stand of "zhonglin-46" or 5-year stand of "langfang", which because it was pressed by root activity absorbing.(3) The SF values probed in the stem varied with different directions. In the daytime,the SF of poplars of 3-year, 5-year 'Zhonglin-46' and 5-year "Langfang" displayed theconsistent rule: south side＞north side. But at night both north and south stem SF ratevaried not so much and maintained undulates about 0～2cm/h.(4) Based on the analysis of relationship between SF and differentmicrometeorological factors in situ, the mufti-linearity models were established for thestands of 3-year, 5-year 'Zhonglin-46' and 5-year "Langfang", respectively. They areshowed below.y=21.922-0.223x₁+0.02x₂+0.784x₃-0.641x₄, y=15.119-0.167x₁+0.015x₂+0.585x₃-0.431x₄, y=7.422-0.165x₁+0.021x₂+0.541x₃。(5) According to regression equation between the sapwood width and diameter atbreast height, combined with data of the sample of stand standard wood at breast height,space scales was successfully amplified from singletree consumption to stand consumptionby the thermal dissipation technology. The forecast suggests that the mean diurnal waterconsumption of 3-year,5-year 'Zhonglin-46' and 5-year "Langfang" are respectively 1.52,2.11 and 2.19mm in the growth season and the total water consumption reach 318.5, 442.2and 460.5mm.