模拟氮沉降对杂草生长和氮吸收的影响

以杂草早熟禾、黑麦草、野燕麦、天蓝苜蓿、白车轴草、北美车前、婆婆纳、无芒稗、牛筋草和刺苋为试验材料，以4.0 g·m^-2·yr^-1的N输入为模拟氮沉降浓度，研究了不同杂草功能类群对模拟氮沉降的响应.结果表明，模拟氮沉降处理下，杂草的生物量（总生物量、地上部分生物量、根生物量）呈增加趋势，但不同功能类群对氮增加的响应明显不同，C₄禾本科、C₃豆科及C₃禾本科植物的生物量受到氮沉降的显著促进，但C₃非禾本科和C₄非禾本科植物的生物量则受氮沉降的影响不显著；不同功能类群的根冠比、植株含氮及植株吸收氮的总量对模拟氮沉降的响应无明显规律，但物种间差异显著.氮沉降提高野燕麦和北美车前的生物量的根冠比，但对其他生物种类没有显著影响.没有发现氮沉降对植物体内的含氮量有显著的影响，但氮沉降却显著地提高了除刺苋、早熟禾及婆婆纳之外的所有杂草物种对N的摄收.由于物种对氮沉降的响应不同，未来氮沉降的增加将加速杂草群落组成的变化.

Effects of simulated nitrogen deposition on weeds growth and nitrogen uptake

In this paper, a greenhouse experiment was conducted to study the responses of different functional groups weeds to simulated nitrogen deposition (4.0 g N.m(-2).yr(-1)). Native weed species Poa annua, Lolium perenne, Avena fatua, Medicago lupulina, Trifolium repens, Plantago virginica, Veronica didyma, Echinochloa crusgalli var. mitis, Eleusine indica and Amaranthus spinosus in orchard ecosystem were used test materials, and their above-and underground biomass and nitrogen uptake were measured. The results showed that under simulated N deposition, the total biomass, shoot biomass and root biomass of all weed species tended increase, while the total biomass was differed for different functional groups of weeds. The biomass of C4 grass, legumes and C3 grass was significantly increased under N deposition, while that of C3 and C4 forbs was not significantly impacted. The root/shoot biomass ratio of Avena fatua and Plantago virginica was enhanced by N deposition, but that of Poa annu, Lolium perenne, Medicago lupulina, Trifolium repens and Amarathus spinosus was not impacted significantly. N deposition had no significant effect on plant N concentration, but significantly enhanced the N uptake of all test weed species except Amarathus spinosus, Poa annua and Veronica didyma. was suggested that the further increase of N deposition might speed up the changes of the community structure weed species due to their different responses to N deposition.