水保所知识产出(1956---)知识库

Soil moisture in root zone is highly heterogeneous in space, while its effect on water transport safety in soil-plant-
atmosphere continuum (SPAC) remains poorly understood. In this study, we conducted vertical spilt-root ex-
periments in R. pseudoacacia using loamy clay and sandy loam soils in greenhouse, and measured the dynamics of
midday transpiration rate, predawn and midday leaf water potential with the lower root zone remaining drought
and the upper root zone undergoing the drought-rewatered-drought process. The plant supply-demand hydraulic
model was calibrated with the measured data, indicating that the model could efficiently simulate SPAC water
transport in R. pseudoacacia under the condition of vertical soil moisture heterogeneity. On this basis, we set
various combinations of soil moisture in the upper and lower root zones under different soil types and atmo-
spheric evaporative demands in the model, and simulated the variations of indicators describing water transport
safety in SPAC, including actual transpiration rate (E), the critical leaf transpiration rate at hydraulic failure
(E crit ), hydraulic safety margin (HSM), and percentage loss of soil-plant hydraulic conductance (PLK). The nu-
merical simulations suggested that the water transport safety in SPAC varied substantially with vertical soil
moisture heterogeneity, and the responses were impacted by soil types and atmospheric evaporative demand.
With decreasing soil moisture in the upper root zone (SMC up ), E crit , E and HSM remained steady at first and then
decreased rapidly when SMC up below a threshold, while PLK exhibited an opposite trend. With decreasing soil
moisture in the lower root-zone (SMC down ), the curves of E crit , E and HSM presented a descending trend, while
the curve of PLK went up. Water transport safety in SPAC declined with decreasing SWC up and SWC down and
became more sensitive to SWC up with a lower SWC down . SWC down had greater impact on water transport safety in
SPAC under coarser-textured soil with higher atmospheric evaporative demand. The results were supplemental to
the traditional analysis of soil water availability to plants under homogeneous condition, and would be helpful
for analyzing functional difference of water storage in different soil depths as well as for optimizing water
resource management.