Sap Flow Characteristics of Four Typical Species in Desert Shelter Forest and Their Responses to Environmental Factors
2012-10-24
Soil–plant–atmosphere continuum (SPAC) is a unified, dynamic, reciprocal and continuous system, where water plays a crucial role. In desert areas, the natural environment is so fragile that a small change in water resources will become a major factor impacting the regional eco-hydrological processes and sustainable development. Understanding the botanic water transportation mechanisms and consumption characteristics is important to manage and utilize the limited water resources in desert areas.
The sap flow of plants can accurately reflect the plants’ transpiration and is very sensitive to changes in environmental water conditions. It is an important parameter to study the plants–water relationship. Because of the inherent fragility of the environment in desert areas, plants in a shelter forest can effectively protect, control, stabilize and improve the ecological environment. Studying the relationship between environmental factors and the transpiration features of plants in a shelter forest will help to understand the law of water consumption in shelter forest, select water-saving species, reasonably combine and distribute species, and provide guidance to resolve the contradictions between water supply and demand.
In this study, Prof. CHEN Yaning and his research team monitored the sap flows of four typical species, Populus russkii Jabl., Populus euphratica Olive., Ulmus pumila L., and Elaeagnus angustifolia L. in a desert area. Meanwhile, air temperature (Ta), leaf temperature (Tl), soil temperature (Ts), relative humidity (RH), and wind velocity (Vw) were simultaneously recorded by an automatic weather station.
The results indicate that (1) the diurnal processes of stem sap flows of P. russkii, P. euphratica, and U. pumila, but not E. angustifolia, show an obvious circadian rhythm. Significant differences of stem sap flow rates were found among species, but not genus. The average sap flow rate of P. russkii is 13.8-fold of that of E. angustifolia. The order of sap flux density from the largest to the smallest is P. russkii, P. euphratica, U. pumila and E. angustifolia; (2) compared with 373 mm, 747 mm irrigation can induce microenvironmental changes that result in the suppression of photosynthesis and transpiration and the decline of stem sap flow rates of the above four species, indicating 373 mm irrigation meets the growth needs of the above species during experiment; (3) sap flow rates are different at different stem positions: the flow rates of P. russkii, U. pumila and E. angustifolia, but not P. euphratica, decline gradually from cambium to pith; (4) the correlation analysis indicates that stem sap flow is negatively correlated with RH and Ts and positively correlated with Ta, Tl and saturation vapor pressure deficit. The sap flow rate of P. russkii is significantly affected by Vw due to its large size and height. In addition, a model was established by stepwise regression analysis to estimate the relationship between the environmental factors and stem sap flows of the above four typical species of shelter forest in the desert area.
The result has been published on Environmental Earth Sciences, 2012, 67: 151-160. The paper can be downloaded from http://www.springerlink.com/index/D0023456K78U4T02.pdf.