Populus alba L. var. pyramidalis Bge. (Populus) is a main tree of the farmland shelter-belt system in the arid region of Northwest China. However, soil moisture cannot satisfy the water requirements of normal Populus growth under local natural conditions, thus studying the transpiration characteristics of irrigated Populus and its relationship with the environmental factors and growth parameters is very important to the growth of the trees in this region. In this study, the sap flow of two irrigated Populus trees was measured during May to September from 2005 to 2008 using the heat-pulse technique. The results show that the maximum and minimum daily sap fluxes in Populus were 15.7-24.0 and 3.0-4.0 L day -1 , respectively. And the sum of sap fluxes from June to August accounted for approximately 63-69% of the total sap flux during May to September (almost the whole growing season). The order of the meteorological factors affecting the daily sap flux of Populus was: vapor pressure deficit [ solar radiation [ mean air temperature [ wind speed. Furthermore, a highly linear relationship between the ratio of daily sap flux to the reference evapotranspiration (SF/ET 0 ) and the amount of soil water in the 0-2.0 m layer was found, indicating that the amount of soil water at this layer was quite important to the growth of Populus in this region. Especially, the amount of soil water in the 0.5-1.0 m soil layer contributed to most of the plant transpiration as the highest coefficient of determination at this layer. Based on the environmental factors and leaf area index influencing sap flux, an empirical transpiration model was constructed to estimate daily transpiration.

Irrigation regime and fertilizer nitrogen (N) are considered as the most effective agricultural management systems to mitigate greenhouse gas (GHG) emissions from crop fields, but few studies have involved saline-alkaline paddy soil. Gas emitted from saline-alkaline paddy fields (1-year-old and 57-year-old) was collected during rice growing seasons by the closed chamber method. Compared to continuous flooding irrigation, lower average CH 4 flux (by 22.81% and 23.62%), but higher CO 2 flux (by 24.84% and 32.39%) was observed from intermittent irrigation fields. No significant differences of N 2 O flux were detected. Application rates of N fertilizer were as follows: (1) No N (N0); (2) 60 kg ha −1 (N60); (3) 150 kg ha −1 (N150); and (4) 250 kg ha −1 (N250). The cumulative emissions of GHG and N fertilizer additions have positive correlation, and the largest emission was detected at the rate of 250 kg N ha −1 (N250). Global warming potential (GWP, CH 4 + N 2 O + CO 2 ) of the 57-year-old field under the N250 treatment was up to 4549 ± 296 g CO 2 -eq m −2 , approximately 1.5-fold that of N0 (no N application). In summary, the results suggest that intermittent irrigation would be a better regime to weaken the combined GWP of CH 4 and N 2 O, but N fertilizer contributed positively to the GWP.

Abstract:Tamarix elongata Ledeb is a desert shrub found in the desert region of Northwest China and is commonly cultivated as a sand-holding plant in this region. To understand its water requirement and the effects of climate conditions on its growth, trunk xylem sap flows of irrigated 8-year-old Tamarix elongata Ledeb plants were monitored continuously with heat-pulse sap flow meters for the entire season. Soil moisture contents at 0-300 cm layer depth were also measured with a tube type time domain reflectometry (Tube-TDR). Meteorological factors, i.e. solar radiation, air temperature, relative humidity and wind speed were simultaneously monitored by an automatic weather station at the site. Daily and seasonal variations of the trunk sap fluxes and their correlations with the meteorological factors, reference evapotranspiration and soil moisture contents in the root-zone were analysed. The results indicated that frost influenced the trunk sap flux greatly under irrigated conditions, although the flux generally fluctuated with the variation of environmental factors and showed a mean trunk sap flux of 4Ð18 l d1 . There was a significantly exponential relationship between sap flux and the reference value of crop evapotranspiration, with a correlation coefficient of R 2 D 0Ð7172. The sap flux also had a significant correlation with the soil water contents at a depth of 150-300 cm from soil surface (R 2 D 0Ð5014). The order of the main meteorological factors affecting the sap flux of Tamarix elongata Ledeb trees was solar radiation > air temperature > vapour pressure deficit > relative humidity > wind speed.

Although autograft is a routine procedure in anterior interbody fusion of the cervical spine, donor site morbidity is a significant problem. Many bone grafting materials developed such as allograft bone, demineralized bone matrix (DBM), and synthetic implants were used to repair bony defects; however, each has its specific disadvantage. Therefore, alternative materials for autogenous bone in grafting are needed. Ninety-one patients with symptomatic cervical disc diseases were randomly allocated for either autologous iliac crest bone graft (AIG) or mineralized collagen (MC). Clinical and radiological comparisons were performed for the two groups. Patients were followed-up routinely in the outpatient clinic, where clinical and radiological evaluations were taken. The mean operation time to perform AIG and MC was 194 ± 37 and 121 ± 26 minutes, respectively. The mean volume of blood loss during the operation was 140 ± 41 and 79 ± 25 mL for AIG and MC, respectively. The mean length of hospitalization due to AIG and MC was 9 7 ± 0 7 and 5 9 ± 0 8 days, respectively. The clinical outcomes were identical, and fusion rates were similar between the two groups. This study shows effective results of MC in anterior cervical intersomatic fusion. MC may be a promising substitute for autologous iliac crest bone graft.

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