Revised algorithm of ecosystem water use efficiency for semi-arid steppe in the Loess Plateau of China

Aims We evaluated the applicability of different measures of water use efficiency through analyzing the coupled dynamics of GPP and evapotranspiration in the semi-arid steppe in the Loess Plateau of China. Our objective is to explore the applicability of two quantitative measures of ecosystem water use efficiency—inherent water use efficiency (IWUE) and underlying water use efficiency (uWUE) —for the semi-arid steppe and to endeavor necessary modifications.Methods The consistency and stability of three indices of water use efficiency formulations (i.e. WUE, IWUE, uWUE) were calculated and compared at hourly, daily and annual time scales before proposing an optimal water use efficiency (oWUE). These indices were additionally used to quantify their importances in modeling the diel change of gross primary production (GPP). The yielded-accuracy of the prediction was used for justifying their uses.Important findings IWUE and uWUE appeared suitable for examining the coupled water-carbon characteristics of vegetation at hourly and daily scales, whereas WUE was more plausible on the annual and interannual scales. The optimized water use efficiency index did not improve the prediction of the coupled water-carbon characteristics as compared with uWUE, but it improved the prediction of GPP and its dynamics. oWUE and uWUE improved the predictions of GPP in the peak growing period, while WUE predicted the GPP better at the early and late growing season. Interestingly, we found that IWUE was not suitable for predicting GPP and its dynamics. The results will be of great importance in modeling the effects of climate change on the carbon assimilation and water cycle for the future.     

Use of Photosynthesis and Transpiration for Early Selection of Salt Tolerant Triticales

Three cultivars of winter hexaploid triticales M2A/JAIN, DF 99/Yogu "S5", and Asseret were grown on nutrient solution with or without 75 mM NaCl. Stomatal permeability and transpiration rate decreased in all salt-stressed triticale cultivars. Net photosynthetic rate (P_N) of cv. M2A and Asseret was not affected by NaCl. On the contrary, P_N in cv. DF99 was reduced in relation to control plants. A higher water-use efficiency under saline conditions led to better salt tolerance of cv. M2A compared to cvs. Asseret and DF99. This revised version was published online in June 2006 with corrections to the Cover Date.     

Response of Suaeda aegyptiaca to KCl, NaCl and Na2SO4 treatments

The response of Suaeda aegyptiaca (Hasselq.) Zoh. to various salinity treatments was tested in sand culture. Growth was promoted by NaCl and by Na₂SO₄ at all tested concentrations, but not by KCl. The effect of NaCl on growth was stronger than that of Na₂SO₄ and it increased gradually up to a 125 eq. m⁻³ optimum. Ion uptake was also affected by the different salts. Cl⁻ was taken up in similar quantities from KCl and from NaCl solutions and the content of the respective cations was also similar to one another. The presence of Na⁺ in the medium lowered the content of K⁺ in the plants and at the same time increased growth by as much as 900%. Transpiration was reduced and water use efficiency increased by Na⁺-salts. Highest water use efficiency was exhibited by plants which were treated with 125 eq. m⁻³ NaCl. It is concluded that Na⁺ at the macronutrient level has a specific promotive effect on the physiological processes of S. aegyptiaca. This effect is not due to replacement of K⁺ by Na⁺; neither can it be achieved by increasing the K⁺ concentration. Cl⁻ has an additional positive effect on growth of S. aegyptiaca. This effect is only expressed in the presence of Na⁺.     

不同土壤含水量下侧柏幼树叶片水分利用效率

对植物水分利用效率的研究,可以揭示植物的内在耗水机制,为区域森林生态系统经营与维护提供依据.本研究以侧柏幼树为研究对象,通过室内控制试验设置不同的土壤水分梯度,分别用气体交换法和稳定同位素法对其不同土壤含水量条件下的瞬时水分利用效率(WUE_gs)和短期水分利用效率(WUE_cp)进行研究.结果表明:受气孔导度(g_s)的影响,叶片净光合速率(P_n)和蒸腾速率(T_r)随土壤含水量的增加呈现相同的变化趋势,均在土壤含水量为70%～80%田间持水量(FC)时达到最大值;叶片WUE_gs则在土壤含水量最低(35%～45% FC)时达到最大值(7.26 mmol·m^-2·s^-1).叶片可溶性糖、枝条韧皮部渗出液的δ¹³C都在土壤含水量最低(35%～45% FC)条件下达到最大值,且叶片可溶性糖的δ¹³C明显高于枝条韧皮部渗出液的δ¹³C,未产生明显分馏;而叶片WUE_cp也在土壤含水量最低(35%～45% FC)时达到最大值(7.26 mmol·m^-2·s^-1).相同条件下,叶片WUE_gs和WUE_cp存在一定差异(平均相差0.52 mmol·m^-2·s^-1),WUE_gs时空变异性较大,而WUE_cp更具有代表性.侧柏幼树通过降低生理生态活动和提高水分利用效率来适应干旱的土壤条件.     

北京西山侧柏林冠层不同高度处叶片水分利用效率

以北京西山广泛分布的侧柏林为研究对象,综合考虑冠层不同高度处气象因子、大气CO₂浓度以及大气CO₂中碳同位素组成的差异,对其冠层不同高度处叶片的瞬时水分利用效率和短期水分利用效率分别进行了测定,以期为区域森林生态系统固碳与耗水研究提供理论依据,为区域森林生态系统经营与维护提供技术支撑.结果表明: 侧柏林冠层不同高度处叶片的瞬时水分利用效率随冠层高度的变化规律表现为上层>中层>下层,多种气象因子协同影响气孔运动,使瞬时水分利用效率受气孔限制;侧柏林冠层不同高度处的环境因子、大气CO₂浓度以及大气CO₂的δ13C均存在一定差异,导致了林冠各层叶片的短期水分利用效率的变化.林冠上层叶片通过提高水分利用效率适应环境.     

油蒿资源利用效率在生长季的相对变化及对环境因子的响应

为了探明西北半干旱区典型沙生植物油蒿(Artemisia ordosica)叶水平资源利用效率的相对变化及对环境因子的响应机制, 该研究于2018年5-10月, 使用LI-6400XT便携式光合仪测定了毛乌素沙地油蒿叶片的净光合速率(P_n)、蒸腾速率(E)、叶表面光合有效辐射(PAR_l)、叶表面温度(T_l)、叶表面相对湿度(RH_l), 在实验室计算叶片单位面积氮含量(N_area), 分析了叶片氮利用效率(NUE)、水分利用效率(WUE)、光利用效率(LUE)与环境因子之间的关系及NUE、WUE、LUE之间的相对变化。研究结果表明, 在充足且稳定光强下油蒿的P_n主要受温度的影响, NUE、WUE与VPD_l、T_l之间具有显著负相关关系, NUE、WUE与LUE间为正相关关系, NUE、WUE和LUE最大值分别发生在5、7和9月, 分别为9.43 μmol CO₂·g^-1·s^-1、3.86 mmol·mol^-1、0.04 mol·mol^-1, 资源利用效率的变化主要受P_n的影响。温度通过影响植物N分配来改变P_n, 进而影响着资源利用效率, WUE与LUE显著正相关, 对构建荒漠区生态系统能量交换过程模型有重要意义。     

控制小麦种、属旗叶水分利用效率的染色体背景分析

利用ＬＣＡ－３便携式光合仪对不同染色体背景的材料测定表明,就旗叶水分利用效率（ＷＵＥ）而言,不同染色体组的上排序为ＡＡ＞ＢＢ＞ＤＤ＞ＲＲ,说明Ａ组染色体上载有控制高ＷＵＥ的基因,对中国春双端体系列的研究表明,Ａ组染色体无论在缺失长臂和短臂时,其端体也保持较高的旗叶ＷＵＥ,在１ＡＬ、２ＡＬ、２ＡＳ、７ＡＳ染色体臂上载有控制高ＷＵＥ的基因。对小黑麦附加系的研究表明,４Ｒ染色体上载有控制高ＷＵＥ的基因,     

水分胁迫下春小麦根系吸水功能效率的研究

对水分胁迫下不同根系大小的春小麦籽粒产量与水分利用效率、相对生长速度和根系功能效率之间的关系进行了研究。实验分为3个水分处理和3个根系大小处理,3个水分处理分别是土壤含水量保持在田间持水量的80％-90％(H),50％-60％(M)和30％-40％(L)。根系大小的处理是(1)大根系处理(B),(2)中根系处理(M)和(3)小根系处理(S)。实验结果表明,在中度和重度干旱条件下小根系处理(MS和LS)的作物具有较高的WEUg,WUEdm、相对生长速度、根系功能效率和籽粒产量;在高水分处理中,上述参数的数值在大根系处理中相对较高。根呼吸耗C量在作物的整个生育期中都占有十分重要的地位,尽管根呼吸耗C比例随作物的生长而呈同步增加的趋势,但实际耗C量却呈逐步下降的趋势,同一时期作物的根呼吸速率与土壤含水量之间存在正相关关系,说明适当降低土壤含水量可以有效地减少根呼吸耗C量,有利于提高作物的存活率。在干旱半干旱地区,春小麦的根功能效率尚未达到最高值,作物产量仍有潜力可挖,通过适时补灌和减少同化物向根系分配的比例和根系对同化产物的消耗量来达到提高春小麦籽粒产量的方法是可行的,但不是长久之计。     

农田水氮关系及其协同管理

作物施氮反应及其氮肥利用率不仅取决于氮肥管理,还与水资源管理有关,并且受到地区气候因素的影响。针对中国灌溉农区氮肥环境污染问题日益突出,协调农田水氮管理,如通过改善水资源管理,发挥水氮协同效应,以提高水分利用效率来改善氮肥利用率,实现水氮利用率双赢,是当前农业水氮管理中亟待探讨和回答的问题。通过对农田水氮协同相关研究文献资料的综述,以华北平原集约种植体系水氮管理为例,根据历年统计数据,分析了该区年水热条件下粮食产量与水、氮及水氮利用效率之间的关系。研究表明,水和氮与作物产量在一定范围表现为水氮的协同效应。水分利用效率一般随灌溉水量减少及氮肥用量增加而提高;氮肥利用效率随氮用量增加而下降。适量节水和减氮分别有助水分利用效率和氮肥利用效率的改善。在气候变暖、变干条件下,适量施氮成为改善水氮利用效率的关键对策。     

C_3和C_4植物的水分利用效率

对C3植物黄豆（Glycinemax）和C4植物玉米（Zeamays）的光合、蒸腾以及水分利用效率（WUE）进行了比较研究。结果表明,玉米WUE水平约为黄豆的2倍,这与两种植物的光合速率水平相一致,说明植物叶片的WUE主要决定于其光合速率大小。通过环境条件对两种植物的影响分析可知,玉米WUE在0-1000μmol·m-2·s-1光强范围内与光合有效辐射（PAR）呈线形关系,最适温度为29℃左右;黄豆WUE在0-　1200mol·m-2·s-1光强范围内与PAR呈线形关系,最适温度为32℃左右。     

亏缺灌溉对棉花生长和水分利用效率的影响研究进展

棉花是世界上最主要的农作物之一。随着全球水资源的日益紧张,灌溉用水将成为限制棉花生产的主要因素。亏缺灌溉是一种低于作物正常腾发量的灌溉方式,可以在保证棉花产量和品质的前提下提高水分利用效率,是一种有效的节水灌溉方式。本文综述了亏缺灌溉对棉花生长和水分利用效率的影响。亏缺灌溉可以通过促进棉花由营养生长向生殖生长转化,降低棉花株高、叶面积、总生物量,从而提高收获指数、茎粗和水分利用效率。最后,综合现有的研究,结合棉花生产实际,提出亏缺灌溉应用推广建议,以期为旱区棉花可持续发展提供理论指导。     

Diurnal patterns of canopy photosynthesis,evapotranspiration and water use efficiency in chickpea (Cicer arietinum L.) under field conditions

Diurnal changes in net photosynthetic rate (PN), evapotranspiration rate (ET) and water use efficiency (WUE=PN/ET) of field grown chickpea (Cicer arietinum) L. cv. H-355 were studied from the vegetative phase through maturirty at Haryana Agricultural University Farm, Hissar, India. The maximum photosynthetic rate (PN max) increased from the initial vegetative phase to pod formation and declined at a rapid rate from pod filling to maturity. The response of PN to photosynthetic photon flux density (PPFD) (400–700 nm) was temperature-dependent during the day, i.e. on cool days the PN rates were lower for certain quanta of PPFD during the first half than during the second half of day, and vice versa on warm days. ET was affected both by crop cover and evaporative demand up to flowering, but thereafter it was independent of crop cover and followed the course of evaporative demand. ET was related to air temperature during the day while PN was related to PPFD. There was a lag of two to three hours between PN_max (around noon) and ET_max (around 2 p.m.). WUE increased from the vegetative stage through flowering but decreased thereafter to maturity.Abbreviations DAS days after planting - ET evapotranspiration - LAI leaf area index - PAR photosynthetically active radiation (in figures) is equivalent to PPFD (see below) - PN net photosynthetic rate - PPFD photosynthetic photon flux density - WUE water use efficiency (= PN/ET)     

水平沟耕作对土壤水分动态及水分利用率的调节

分析了水平沟耕作条件下土壤水分动态、水分利用、水分收支平衡,认为水平沟增产的主要作用是减少了坡耕地表径流量而增加了土壤蓄水量。     

Sensitivity of stomata and water use efficiency to high CO2

Abstract The observed responses of stomata to carbon dioxide are reviewed, and the interaction of other known factors on the sensitivity to CO₂ are summarized. The role of stomatal response to CO₂ is discussed, and it is argued that while the effect of the CO₂ response in normal daily stomatal behaviour is presently poorly understood the stomatal response to CO₂ will have major impact in improving water use efficiency in future CO₂ atmospheres. However, the attenuation of this increase is emphasized so that increases at the crop level will probably be much smaller than those observed at the single leaf assimilation level.     

施氮量对小麦/玉米带田土壤水分及硝态氮的影响

通过田间试验研究了河西绿洲灌区典型的小麦/玉米间作群体不同施氮量(0、210、420和630 kg/hm2)对小麦、玉米带田土壤水分和硝态氮(NO3(-)-N)的动态的影响.结果表明:小麦/玉米总籽粒产量随着施氮量的增加而增加,但当施氮量超过420kg/hm2时,总籽粒产量不再随施氮量增加而增加,最高总籽粒产量可达13661-14668 kg/hm2.水分利用效率在施氮420 kg/hm2时最高可达21.25 kg·hm-2·mm-1.小麦收获后,0-120 cm土层内土壤含水量随施氮量增加而减少,NO3(-)-N的累积量随施氮量增加而增加,并且表层土壤(0-60 cm) NO3(-)-N含量明显高于深层土壤(60-200 cm).在小麦/玉米整个生育期,土壤硝态氮的变化呈双峰曲线.施氮0和210 kg/hm2的土壤硝态氮第一峰值和第二峰值均分别出现在小麦三叶期和玉米大喇叭口期;施氮420和630 kg/hm2的土壤硝态氮第一峰值出现在小麦挑旗期,第二峰值分别出现在玉米大喇叭口期和玉米灌浆期.因此,在该地区小麦/玉米间作栽培模式下,施氮水平控制在420 kg/hm2时,使混合产量达到最高,同时可减轻土壤硝态氮的累积和运移,从而达到高效、安全的目的.     

Photosynthetic response to precipitation/rainfall in predominant tree (<Emphasis Type="Italic">Ulmus pumila</Emphasis>) seedlings in Hunshandak Sandland,China

The responses of gas exchange and chlorophyll fluorescence of field-growing Ulmus pumila seedlings to changes in simulated precipitation were studied in Hunshandak Sandland, China. Leaf water potential (Ψ_wp), net photosynthetic rate (P _N), stomatal conductance (g _s), and transpiration rate (E) were significantly increased with enhancement of precipitation from 0 to 20 mm (p<0.01), indicating stomatal limitation of U. pumila seedlings that could be avoided when soil water was abundant. However, P _N changed slightly when precipitation exceeded 20 mm (p>0.05), indicating more precipitation than 20 mm had no significant effects on photosynthesis. Maximum photochemical efficiency of photosystem 2, PS 2 (F_v/F_m) increased from 0.53 to 0.78 when rainfall increased from 0 to 10 mm, and F_v/F_m maintained a steady state level when rainfall was more than 10 mm. Water use efficiency (WUE) decreased significantly (from 78–95 to 23–27 μmol mol⁻¹) with enhancement of rainfalls. P _N showed significant linear correlations with both g _s and Ψ_wp (p<0.0001), which implied that leaf water status influenced gas exchange of U. pumila seedlings. The 20-mm precipitation (soil water content at about 15 %, v/v) might be enough for the growth of elm seedlings. When soil water content (SWC) reached 10 %, down regulation of PS2 photochemical efficiency could be avoided, but stomatal limitation to photosynthesis remained. When SWC exceeded 15 %, stomatal limitation to photosynthesis could be avoided, indicating elm seedlings might tolerate moderate drought.     

The interaction of rising CO2 and temperatures with water use efficiency

Abstract. Recent data concerning the impact of elevated atmospheric CO₂ upon water use efficiency (WUE) and the related measure, instantaneous transpiration efficiency (ITE), are reviewed. It is concluded from both short and long-term studies that, at the scale of the individual leaf or plant, an increase in WUE or ITE is generally observed in response to increased atmospheric CO₂ levels. However, the magnitude of this increase may decline with time. The opinion that elevated CO₂ may substantially decrease transpiration at the regional scale is discussed. The mechanisms by which elevated CO₂ may cause a change in these measures are discussed in terms of stomatal conductance, assimilation and respiration responses to elevated CO₂. Finally, recent experimental data and model outputs concerning the impact of the interaction of increased temperature with elevated CO₂ on WUE, ITE and yield are reviewed. It is concluded that substantially more data is required before reliable predictions about the regional scale response of WUE and catchment hydrology can be made.     

Effects of different Nitrogen forms and osmotic stress on water use efficiency of rice (Oryza sativa)

A hydroponic experiment with simulated water stress induced by polyethylene glycol (PEG) was conducted in greenhouse to study the effects of different nitrogen (N) forms (; and the mixture of and ) on water stress tolerance and water use efficiency (WUE and WUE_T) of different rice cultivars. Two rice cultivars (cv. ‘Shanyou 63’ hybrid indica and ‘Yangdao 6’ indica, China) were grown under non‐water‐ or water‐stressed condition [10% (w/v) PEG, molecular weight 6000] with different N forms for 3 weeks. Under non‐water stress, the biomass of Shanyou 63 was 50.0% and 64.3% and of Yangdao 6 was 6.9% and 87.8% higher under the supply of mixture of and than either under the sole supply of or , respectively; under water stress, the biomass of both rice cultivars decreased in all three nitrogen forms compared with non‐water stress; however, the inhibitory effect of water stress on biomass varied between and nutrition; the reduction of dry matter was significantly higher in than in nutrition. Compared with non‐water stress, under water stressed condition, WUE of both two rice cultivars significantly decreased in supply; WUE did not vary in and the mixture supply. It is concluded that (a) the resistance of water stress of rice seedlings is related to nitrogen form; (b) under water stress, could maintain a higher WUE compared with ; (c) hybrid indica rice seedlings have a higher water stress tolerance than indica rice seedlings.