许多有关物种多样性-生态系统功能关系的观察、理论和实验研究都表明, 在局域尺度范围内, 植物种多样性对生态系统生产力存在正效应。 然而, 对于促成这种关系的潜在生态学机制却缺乏足够的了解。 该实验利用9种一年生栽培牧草, 采用各物种单播及混播的方法, 构建不同多样性梯度的实验群落, 对物种多样性与生态系统生产力的关系及资源互补效应对系统生产力的影响进行了研究。 结果表明, 在一年生植物群落内,植物种多样性在一定程度内对系统生产力存在正效应, 物种多样性与生产力呈二次函数关系, 关系式为y = -98.449x² + 1 039.2 x - 42.407, (R² = 0.423 1)。 各物种在资源利用、生长速度和竞争能力等功能特征方面存在较大差异, 最高产物种和最低产物种间产量相差5.8倍。 在同一多样性梯度内, 不同物种组合的群落间生产力和互补效应也存在较大差异, 说明物种的成分对生态系统生产力也有重要影响。 同时,在混播群落中程度不同地存在着资源的互补性利用, 说明物种多样性对系统生产力有增强作用, 但相关分析表明, 互补效应和物种多样性间不存在显著相关关系。互补效应的4种计算方法所反映的资源互补程度有所不同, 每种方法各有利弊, 在对系统的多样性效应作用机制进行评价时, 应根据具体情况, 同时采用几种方法, 以利于对资源互补效应做出恰当的估测。

A number of observational, theoretical and experimental studies have indicated that local plant species diversity can have positive effects on ecosystem productivity; however, little is known about the ecological mechanisms that regulate this relationship. To investigate the relationship between plant species diversity and ecosystem productivity and the effect of resource complementarity on productivity, we established experimental communities containing different levels of diversity using nine cultivated annual plant species. To address questions of complementary resource use, we planted each species in monocultures as well as in different polycultures, which allowed us to evaluate complementary effects. Complementarity was assessed by using four analytical methods. The first two methods were tested for an absolute increase in productivity with increasing diversity. The hypothesis was that a polyculture would outperform the most productive monoculture of a component species, defined as overyielding effect 1 (OV₁), and a polyculture would perform better than the average yield of monocultures of the component species, defined as overyielding effect 2 (OV₂). The third method measured the relative yield of the polyculture, Relative Yield Totals (RYTs), and the last method measured the D value, the proportional deviation of the productivity of a polyculture from its expected value. The results indicated that, to a certain extent, species diversity showed a positive effect on community productivity. The relationship between species richness and community productivity could be represented by a quadratic equation y = -98.449x² + 1 039.2x - 42.407 (R² = 0.423). Large differences in productivity were found among treatments with similar levels of diversity indicating that species composition had an important impact on community productivity. Calculation of a complementarity index indicated that about 40% of the polycultures outperformed its most productive component monoculture, more than 95% of the polycultures performed better than the average yield of its component monocultures, and more than 50% of the polycultures had significant RYTs > 1 and D > 0. These results suggest that resource complementarity was partly responsible for the positive effect of species diversity on productivity. Complementarity, however, was not significantly related to species diversity. Four analytic methods were used for estimating the net outcome of complementary effects and the different levels of ecological interaction in a community. Each method had its advantages and disadvantages. Therefore, in assessing how complementarity influences ecosystem productivity, different methods should be integrated.