中文摘要：

氮素和水分是荒漠生态系统的两个主要限制因子,研究两者对荒漠植物的效应有助于深入了解荒漠生态系统对全球变化的响应。该文选择准噶尔盆地荒漠地区两种常见的一年生植物涩荠（Malcolmia africana）和钩刺雾冰藜（Bassia hyssopi-folia）,设置0、0.18和0.72gN·m–2·week–13个施氮浓度和湿润与干旱两个土壤水分处理,研究模拟氮沉降增加和干旱对其生长和光合生理的影响。结果表明：（1）两种植物的根长、根重、叶片数、叶面积、总生物量和冠根比均随着施氮浓度的增加而增加,干旱能够抑制氮对植物生长的促进作用,但是,氮的增加同时也能部分缓解干旱对植物生长的影响。与钩刺雾冰藜相比,涩荠的根长、生物量和冠根比更易受氮增加和干旱的影响。（2）两种植物的最大净光合速率、叶绿素含量、可溶性蛋白含量随着氮浓度增加而增加,但涩荠和钩刺雾冰藜对氮增加和干旱的生理响应也有所不同,涩荠的响应更加敏感。两种植物对氮沉降和干旱胁迫响应的差异可能是其生活型等生物学特性差异所引起。通过对两种一年生植物的生长和光合生理分析表明,在古尔班通古特沙漠,春季丰富的降水和氮素增加将有利于涩荠和钩刺雾冰藜的生长和生产力的增加,相对地下生长,地上部分增加更显著。当干旱季节来临时,氮的增加又能够在一定程度上降低干旱对这两种植物的负效应,说明其对干旱具有一定的生态补偿作用。

英文摘要：

Aims The two primary limiting factors for biological activities in desert ecosystems are nitrogen and water. Our study, which examined their combined effects, can provide insight into the responses of arid ecosystems to global climate change. We selected two typical annual desert plants, Malcolmia africana and Bassia hyssopifolia to de-termine the combined effects of nitrogen deposition and drought stress on their growth and photosynthetic physiological responses. Methods Three levels of N addition （0, 0.18 and 0.72 g N·m–2·week–1） and two soil watering regimes （60%–70% and 30%–40% of field capacity） were randomly provided in order to simulate nitrogen deposition and drought stress. Changes in plant growth and photosynthetic physiological traits were measured shortly before flowering. Important findings N supply and drought stress significantly affected growth of both species. With the en-hancement of N supply, we found an increase in growth parameters （including root length, root weight, leaf num-ber, leaf area, total biomass and shoot/root （S/R））. At the same N level, increased drought stress could counteract the positive effects of N supply on plant growth. Increased N, however, could also alleviate the negative effects caused by drought stress. With the increasing N addition, we also observed increase of physiological indices （net photosynthetic rate, content of chlorophyll and soluble protein）. Malcolmia africana was more sensitive to N sup-ply and drought stress than B. hyssopifolia. The different responses of the two species may due to their different biological characteristics, such as life form. The results indicated that N and water pulses in spring in this desert would be beneficial to the growth and productivity of M. africana and B. hyssopifolia, especially for aboveground parts. Moreover, N deposition could partially alleviate the negative effects caused by drought stress during the severe dry season.