The relationship between community species diversity and functional diversity (SFDR) was suggested to reflect the degree of overlap in species functions and highlight the effects of environmental filters on community composition. Using a novel approach, categorizing individual plants into functional groups according to their plant biomass production (function level) and regardless of their taxonomic attribution, we tested the pattern of SFDR (e.g., linear correlation or other type) in a semiarid, annual plant community. Species abundance and biomass were monitored over four years among neighbouring topographic sites representing a range of aridity levels in the Northern Negev, Israel. All sampled plant individuals collected at flowering season were weighted and classified into ten functional groups according to their above-ground biomass. Functional group richness and species richness were calculated for each of the 16 research plots during the four research years. We examined the relationship between species richness and functional richness and the effects of year and topographic site on species richness within each of the functional groups. Species and functional richness varied considerably among years and topographic sites. Functional richness was found to be positively related to species richness throughout the entire studied aridity range. Under relatively humid conditions, species richness was high, and increasing aridity led mainly to loss of functional redundancy. Lost taxa were typically rare, large sized or drought intolerant species with low functional plasticity. Conversely, under relatively dry conditions, species richness was low and further increasing aridity led more to loss of functional richness than to loss of species richness. Typical species that drove this pattern were abundant, medium to low sized and drought tolerant species with high functional plasticity. These species decreased their plant biomass production while guaranteeing their existence under extreme drought.

建议群落物种多样性与功能多样性（SFDR）之间的关系反映物种功能的重叠程度，并突出环境过滤器对群落组成的影响。使用一种新方法，根据植物生物量生产（功能水平）将单个植物分为功能组，无论它们的分类属性如何，我们测试了半干旱一年生植物群落中 SFDR 的模式（例如，线性相关或其他类型） . 对代表以色列内盖夫北部一系列干旱水平的邻近地形地点的物种丰度和生物量进行了四年监测。在开花季节收集的所有采样植物个体根据其地上生物量被加权并分为十个功能组。在四个研究年中，对 16 个研究地块中的每一个都计算了功能群丰富度和物种丰富度。我们研究了物种丰富度和功能丰富度之间的关系，以及年份和地形地点对每个功能组内物种丰富度的影响。物种和功能丰富度因年份和地形地点而异。在整个研究的干旱范围内，功能丰富度与物种丰富度呈正相关。在相对潮湿的条件下，物种丰富度高，干旱增加主要导致功能冗余的丧失。丢失的分类群通常是功能可塑性低的稀有、大型或不耐旱的物种。相反，在相对干燥的条件下，物种丰富度很低，进一步增加的干旱导致功能丰富度的丧失，而不是物种丰富度的丧失。驱动这种模式的典型物种是丰富的、中等至小尺寸且具有高功能可塑性的耐旱物种。这些物种减少了它们的植物生物量产量，同时保证了它们在极端干旱下的生存。