施肥对高寒草甸植物群落组分种繁殖分配的影响

FERTILIZATION EFFECTS ON SPECIES REPRODUCTIVE ALLOCATION IN AN ALPINE MEADOW PLANT COMMUNITY

该文以青藏高原东部高寒草甸植物群落的24种主要组分种为材料,研究了施肥对多年生草本植物繁殖分配的影响。结果表明1)对多数群落组分种来说,施肥显著影响生物量和生物量分配;2)随着肥力的增加,大多数物种的植株个体明显增大、繁殖输出减小或不变,进而导致它们的繁殖分配明显减小;3)施肥影响的个体大小和生物量分配变化程度与方向因物种而异,对一些物种的影响不明显,对个别物种的影响方向不同于对多数物种的影响;4)施肥后群落水平的繁殖分配明显减小。

Background and Aims Plant resource allocation strategies are important in determining community structure in variable environments. However, observations of changes in species reproductive allocation under disturbance at the community level are rare. This study addresses the following questions： 1 ） does fertilization alter patterns of species reproductive allocation in natural plant communities, 2） are there interspecific differences for a fertilization effect, and 3） what is the effect of fertilization on assemblage-level reproductive allocation？ Methods The study was conducted at the Alpine Meadow Ecosystem Field Station of Lanzhou University, Maqu （ 101°53′ E, 35°58′N）. The experimental plant communities are typical of alpine meadow of the eastern QingHai-Tibotan Plateau. In mid May of 2002 and 2003, we established a soil nutrient gradient of diammonium phosphate （DAP） in the natural plant communities using a completely randomized design （3 levels of fertilization treatments and 3 repetitions of each level）. From June to September, we sampled above-ground parts of 24 plant species at their fruiting stage, randomly selecting 20 individuals at every treatment level. The samples were dried to constant weight for 10 h at 80 ℃, and each individual was dissected into fruits, stems and leaves, which were weighed by Sartorius balances （to the nearest 10-4 g）. Reproductive, stem, and leaf allocations were calculated as the proportion of total biomass. ANOVA was used to test the effect of fertilization on patterns of species reproductive allocation. Key Results Fertilization significantly affected both the biomass and the biomass allocation of most species. Total biomass, leaf biomass, and stem biomass of most species increased with soil nutrient level, but reproductive biomass remained constant or decreased. Reproductive allocation decreased, stem allocation increased, and leaf allocation was constant in most species. The degree and direction of responses differed among species, indicating the differences of life history. Reproductive allocation at the assemblage-level decreased with fertilization. Conclusions The study suggests that plant individuals tend to become larger, reproductive allocation decreases, and stem allocation and leaf allocation increase as fertility increases. The effect of fertilization on resource allocation strategies is different among species within the same plant community.