Search

The interactions between groundwater depth and soil hydrological processes, play an important role in both arid and semi-arid ecosystems. The effect of groundwater depth on soil water variations were neglected or not explicitly treated. In this paper, we combine a simulation experiment and a water flow module of HYDRUS-1D model to study the variation in soil evaporation under different groundwater depth conditions and the relationship between groundwater depth and evaporation efficiency in Horqin Sandy Land, China. The results showed that with an increase in groundwater depth, the evaporation of soil and the recharge of groundwater decrease. In this study, the groundwater recharge did not account for more than 21% of the soil evaporation for the depths of groundwater examined. The soil water content at 60 cm was less affected by the evaporation efficiency when the mean groundwater depth was 61 cm during the experimental period. In addition, the evaporation efficiency (the ratio of actual evaporation to potential evaporation) decreases with the increase in groundwater depth during the experiment. Furthermore, the soil evaporation was not affected by groundwater when the groundwater depth was deeper than 239 cm.

To incorporate canopy vertical structure in a process-based model over a temperate meadow, a multilayered model estimated canopy carbon flux (Fc) and water flux (LE) was applied by comparing with eddy covariance measurements in Inner Mongolia, China. Simulations of diurnal, seasonal CO2and H2O fluxes and model sensitivity to parameters and variables were analyzed. The results showed that the model underestimated Fcand LEby about 0.6% and 5.0%, respectively. It was able to simulate the diurnal and seasonal variation of Fcand LEand performed well during the day and in the growing season, but poorly at night and early in the growing season. Fcwas more sensitive to the leaf nitrogen content distribution coefficient and maximum catalytic activity of Rubisco, whereas LEshowed greater sensitivity to the stomatal conductance parameter a1, empirical coefficient of stomatal response to saturated vapor pressure difference Vpds0, and minimum stomatal conductance of CO2gsc0. The response of Fcto environmental factors was ranked as air CO2concentration (Ca) > air temperature (Ta) > photosynthetically active radiation (PAR) > soil water content (θsm) > vapor pressure deficit (VPD) > wind speed (u0). The response of LEto environmental factors was ranked as Ta> VPD > θsm> PAR> Ca> u0. The response of LEto vegetation characteristic parameters was greater than that of Fc.

Pd(OTf)2(bcope) is shown to react in methanol solution with diphenylacetylene, carbon monoxide and hydrogen to produce the methoxy-carbonylation product methyl 2,3 diphenyl acrylate alongside cis- and trans-stilbene. In situNMR studies harnessing the parahydrogen induced polarization effect reveal substantially enhanced 1H NMR signals in both protic and aprotic solvents for a series of reaction intermediates that play a direct role in this homogeneous transformation. Exchange spectroscopy (EXSY) measurements reveal that the corresponding CO adducts are less reactive than their methanol counterparts.