|其他摘要||The forest is a huge water consuming system which stores water through precipita-tion, reduces surface runoff, and increase water use efficiency. Populus euphratica is one of the important trees in arid areas, which has large root system, and mainly relies on groundwater. Water resources are scarce, and water evaporation is large in extremely arid northwestern region. In the process of afforestation and vegetation restoration, estimating water consumption of P. euphratica tree by trunk sap flow is important for saving water and effectively using water resources in the Tarim River. Thermal diffusion technology was used to estimate water use of trees in current researches.
In this study, three different stages P.euphratica in the lower reaches of the Tarim River were chosen, the daily, monthly and seasonal sap flows were measured and ana-lyzed from January to December through continuously observation. The aim of the study is to find out the main factors affecting sap flow variations and to establish the regression equation between sap flow rate and environmental factors. The results will provide theo-retical basis and references for rational use of water resources for P.euphratica in the lower reaches of the Tarim River:
The results showed that:
1) There are similar trend in P.euphratica tree trunk sap in three different ages, but there are some differences in the amounts of sap flow. Plant sap flow rate not only af-fected by their physiological conditions, but also by its surrounding environments.
2) The amount of P.euphratica tree trunk sap flow showed obvious diurnal variation. Compared with the cloudy days, the sap flow rate in the sunny days started earli-er,stopped later and kept much longer during the top period. In the night, sap flow kept moving all the time, and the proportion of sap flow rate in the evening is different in dif-ferent season. For the increases of air temperature and solar net radiation, the proportion of sap flow is much bigger than in other seasons;
3) There is a significant correlation between the sap flow rate and meteorological factors. To some extent, the sap flow rate was positively correlated with solar radiation and air temperature, negatively correlated with relative humidity and less correlated with wind speed; Soil factors also played an important role in the sap flow rage although there is less correlation. The correlation between underground water depth, cross sectional area and daily sap flow was significant, which was positively correlated with cross sectional area and negatively correlated with underground water depth;
4) Results showed that three regression models showed better simulating effect. sim-ulation accuracy of nonlinear regression model is higher than those of other two models. The coefficients of correlation between observed and simulated transpiration of P.euphratica were 0.5306, 0.6760 and 0.6949, respectively. The model is easy to use and measure and has high precision, which provides an effective and feasible way for the evaluation of natural vegetation evapotranspiration and the calculation of ecological wa-ter requirements in arid region.|
赵天宇. 塔里木河下游河岸胡杨耗水模型研究[D]. 北京. 中国科学院大学,2015.