As one of the most common natural disaster in the world ,drought had caused serious impact on agricul-tural production in China .However ,one of the key factors that effected the survival rate of trees in arid areas was water use efficiency (WUE) of plant .The net photosynthesis rate ( Pn) ,transpiration rate (Tr) ,stomatal conductance (Gs) , instant water use efficiency (WUEI ) , WUEL ,total biomass and δ13 C were recorded from five economic forest species (Juglans regia ,Ziziphus jujuba ,Lycium chinense ,Hippophae rhamnoides and Zanthoxylum bungeanum ) to analyze the relationship between the comparison of the foliar carbon isotope composition (δ 13 C ) and long-term WUE ( WUEL ) . Seedlings were grown under four soil water regimes which were CK ,light drought (LD ) ,moderate drought (MD ) and se-vere drought (SD ) .Compared with CK , Pn , Tr and Gs significantly decreased with the soil water decreasing for five e-conomic forest species ,except MiD (P<0 .05) .For WUEI ,only Z .bungeanum ,Z .jujuba and L .chinense shown different water effects between SD and CK ( P<0 .05 ) .Under four water treatments ,H .rhamnoides had relatively high-er WUEI and lower Tr than other four economic forest species .The significant differences in WUEL andδ13 C for five e-conomic forest species were only exhibited between SD and CK ( P<0 .05 ) , and the WUEL of L . chinense and H . rhamnoides were higher than other three species . For total biomass , there was only significant variations in Z . bungeanum ,J .regia ,Z .jujuba between SD and CK (P<0 .05) .The relationship between WUEL andδ13C was that L . chinense and H . rhamnoides had higher correlation coefficient than other three species .These results indicated that theδ13 C value could be the reliable evaluation index of WUE to select economic forest species under drought stress .Our results also indicated that L . chinense and H . rhamnoides could be selected in arid areas and other three tree species could be selected in sufficient water area of Gansu .%干旱作为全球最为常见的自然灾害之一,对农林业生产造成了严重的影响.而在干旱地区影响林木成活率的关键因素之一是植物对水分的利用效率的高低.以核桃、枣、枸杞、沙棘和花椒5个甘肃地区的经济林2年生实生苗木为试材,通过盆栽实验,对其在干旱胁迫(对照、轻度胁迫、中度胁迫和重度胁迫)下的光合速率(Pn)、蒸腾速率(Tr)、气孔导度(Gs)、瞬时水分利用效率(WUEI)、长期水分利用效率(WUEL)、生物量以及稳定性碳同位素比率(δ13 C)等进行了测定,分析了5种苗木δ13 C与长期水分利用效率WUEL之间的关系.结果表明:干旱胁迫处理下,5个经济林树种的Pn、Tr、Gs在中度和重度胁迫与对照间差异显著(P<0.05),而WUEI则仅花椒、枣和枸杞在重度胁迫与对照间差异显著(P<0.05).沙棘因较低的Tr而获得了比其它4个树种高的WUEI.5个经济林苗木的WUEL和δ13 C在重度胁迫与对照间差异显著(P<0.05),而生物量则仅花椒、核桃和枣在重度胁迫与对照间差异显著(P<0.05).分析发现,枸杞和沙棘δ13 C与WUEL的相关性较其它3个树种高,而枸杞和沙棘在干旱胁迫下的WUEL也高于其它3个树种,说明干旱条件下高δ13 C是评定经济林高WUE的可靠指标.因此,在甘肃地区进行经济林选择时,枸杞和沙棘可在干旱地区种植,而在水分条件较好的地区则可选择其它3个树种.
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