黄土丘陵区不同种植行距下柳枝稷光合生理日变化研究

以引进禾草柳枝稷为材料,在半干旱黄土丘陵区人工梯田设置20cm(L20)、40cm(L40)和60cm(L60)3种种植行距,比较研究了其光合生理参数日变化、地上部分生物量及土壤水分剖面分布特征,探讨其光合生理和水分利用特征与种植行距的关系。结果表明:(1)不同行距下,柳枝稷叶片净光合速率(Pn)日变化均呈双峰曲线,第一峰值均出现在10:00,第二峰值L40出现在14:00,L20和L60出现在16:00,具有明显的光合"午休"现象,且均由非气孔因素限制引起;柳枝稷叶片Pn日均值大小依次为:L60>L40>L20,且两两间差异显著。(2)柳枝稷叶片水分利用效率(WUE)日变化与Pn相似,分别在10:00和14:00达到峰值,日均值大小依次为:L60>L40>L20。(3)不同行距下,土壤体积含水量均随土层深度增加呈先增加后减少再增加的趋势,除0～50cm土层外,其它各土层土壤储水量均存在较大差异,0～380cm土层总土壤储水量表现为:L20>L40>L60。(4)柳枝稷地上生物量大小依次为:L20>L60>L40。研究发现,20cm行距的柳枝稷个体虽光合速率较低,但群体生物量和土壤储水量较高,所以柳枝稷在黄土丘陵区梯田的较优行距为20cm。

Photosynthetic Dynamic Variation of Switchgrass under Different Row Spacing in Loess Hilly gully Region

In order to offer a scientific base and reference to rational utilization and large-scale planting for introduced switchgrass(Panicum virgatum L.) in the semiarid conditions on the Loess Plateau,we investigated the photosynthetic dynamic variation,aboveground biomass production and soil moisture content profile distribution under three different row spacings,which were 20 cm(L20),40 cm(L40) and 60 cm(L60) on terrace land in loess hilly-gully region.The results indicated that:(1)The curves of diurnal variation in net photosynthetic rate(Pn) had double peaks,showing obvious midday depression.The first peak appeared at 10:00,and the second peak for L40 appeared at 14:00,while for L20 and L60 treatments it appeared at 16:00.The daily mean values order of Pn was as follows:L60>L40 >L20.The midday photosynthesis depression under each row spacing was due to non-stomatal factor limitation.(2)The diurnal variation in WUE was similar to Pn,and the peak values appeared at 10:00 and 14:00 respectively under the three row spacing treatments,and the daily average order was L60>L40>L20.(3)Soil volumetric moisture vertical distribution was similar under each row spacing,showing increased firstly,and decreased,and then increased with soil depth.Except in 0~50 cm soil layer,soil water storage in the other layer was not significant different among the three row spacings.Total soil water storage in 0~380 cm decreased with row spacing,showing that:L20>L40>L60.(4)The aboveground biomass order for the three row spacing was L20>L60>L40.Although the leaf Pn was lower,the biomass production and soil water storage were significantly higher under L20,all these results suggested that the optimum row spacing was 20 cm for switchgrass on terrace land in loess hilly-gully region.