养分和水分添加后沙质草地不同功能群植物地上生物量变化对群落生产力的影响

以典型沙质草地为研究区域,通过养分和水分添加控制试验,研究了群落尺度上生产力的变化及其对不同养分和水分处理响应的差异。从不同功能群植物地上生物量对养分和水分响应分异的角度揭示群落尺度初级生产力的变化机理。结果显示:(1)单纯的氮素、磷素、水分添加对群落生产力的影响不明显,只有养分和水分交互作用才能显著增加群落生产力。氮素添加×冬季增雪、氮素添加×夏季增雨、磷素添加×夏季增雨处理使得群落生产力比对照分别提高了85.1%、107.9%、57.2%。(2)氮素添加×冬季增雪处理后群落生产力比磷素×冬季增雪处理高出86.7%,表明虽然水分添加提高了植物对氮素与磷素的利用效率,但水分添加后植物对氮素的利用效率更高。(3)不同功能群植物地上生物量对养分和水分添加的响应程度不一致。总体而言,养分和水分添加对禾本科植物生物量的影响最明显,对杂类草植物生物量的影响不明显。单纯磷素添加明显降低了群落中禾本科植物的生物量,比对照低61.9%;冬季增雪、夏季增雨增加了群落中豆科植物的生物量,与对照相比分别增加了193.3%、220.5%;氮素添加×冬季增雪、氮素×夏季增雨显著增加了禾本科植物的生物量,分别比对照增加了80.4%、91.6%。

Aboveground Biomass Differentiations of Different Functional Group Species after Nitrogen and Snow Addition Altered Community Productivity of Sandy Grassland

Responses of plant community structure and biomass to nutrient addition and increased precipitation were examined in the Horqin Sandy Grassland. We studied the variations of responses to nutrient and water addition of different functional group species biomasses, and discussed how effect of the variations on community productivity. The main conclusions are as follows: (1) Community productivities were not affected by nitrogen, phosphorus and water addition. But the community productivity were significant affected by the interaction of nitrogen and water addition. For example, community productivity were increased 85.1%, 107.9% and 57.2% in nitrogen addition×increase snow in winter, nitrogen addition×increase precipitation in summer and phosphorus addition×increase precipitation in summer treatments. (2) We also found that community productivities were higher in nitrogen addition×increase precipitation in summer than phosphorus addition×increase precipitation in summer, this result may suggested that the plant were more favor nitrogen at high water levels although water increased would enhanced the plant to nitrogen and phosphors use efficiency. (3) The sensitivity of the three plant functional groups was quite different. Grasses were most, forbs were less sensitive to simulated rainfall and available nitrogen in the improved disturbing condition. The biomasses of three functional groups plants were increased as available nitrogen increased. Biomasses of grasses were decreased in phosphorus addition treatments which were 61.9% lower than control treatments. Water addition only affected the biomass of legumes, for example, snow and precipitation decreased 193.3% and 220.5%, respectively, of legumes biomasses. The grasses biomasses were significantly increased in the interaction of nitrogen and water treatment, for example, the biomasses of grasses increase 80.4% in nitrogen×snow treatments and 91.6% in snow×precipitation treatments.