Data from: Comparing the responses of bryophytes and short-statured vascular plants to climate shifts and eutrophication

1. Few experimental studies have tested how abundance and diversity of grassland bryophytes respond to global environmental changes such as climate shifts and eutrophication. Because bryophytes in grasslands are low-statured, and because plant height is a key functional trait governing plant responses to resource gradients, their responses to these factors could resemble those of better-studied small vascular plants. Alternatively, traits unique to bryophytes could lead to qualitatively different responses than those of small vascular plants.

2. In a semiarid Californian grassland system, where bryophytes are at relatively low abundance and their ecology has been little studied, we compared changes in cover and species richness of bryophytes and short-statured vascular plants in response to five years of experimental fertilization, springtime watering, and fertilization + watering, which produced strong gradients in vascular plant biomass.

3. Supporting our hypotheses, the cover and richness of both bryophytes and short vascular plants were negatively related to total community biomass and tall vascular plant cover, and declined in response to the fertilization + watering treatment, in which the cover of tall vascular plants most strongly increased.

4. Two divergent responses were also observed: watering alone increased the cover of bryophytes but not short vascular plants, while fertilization alone reduced the cover of short vascular plants but not bryophytes.

5. Bryophytes and short-statured vascular plants in grasslands both may be expected to decline under projected global changes in climate and nutrient deposition that enhance total community biomass and competitive pressure. However, shifts in either precipitation or eutrophication regimes alone may have differential effects on bryophytes and short vascular plants in grasslands, and organism-specific plant functional traits must also be considered.

1. 目前少有实验研究探讨草原苔藓植物（bryophytes）的丰度与多样性如何响应气候变化、富营养化等全球环境变化。由于草原苔藓植物株型低矮，且株高是调控植物响应资源梯度的关键功能性状，因此它们对上述环境因子的响应或与研究较为充分的矮生维管植物（vascular plants）相似。但另一方面，苔藓植物特有的性状可能使其响应模式与小型维管植物存在本质差异。
2. 本研究以苔藓植物丰度相对较低且生态学研究极少的加利福尼亚半干旱草原生态系统为对象，对比了为期5年的实验性施肥、春季补水以及施肥+补水处理下，苔藓植物与矮生维管植物的盖度和物种丰富度变化——上述处理可使维管植物生物量形成显著梯度。
3. 实验结果验证了我们的假说：苔藓植物与矮生维管植物的盖度和丰富度均与群落总生物量及高大维管植物盖度呈负相关关系，并在施肥+补水处理下出现下降——该处理下高大维管植物的盖度增幅最为显著。
4. 研究同时观测到两种差异化响应模式：仅补水处理可提升苔藓植物盖度，但对矮生维管植物无显著影响；而仅施肥处理会降低矮生维管植物盖度，却不会影响苔藓植物。
5. 在未来可提升群落总生物量与竞争压力的全球气候变化与养分沉降情景下，草原苔藓植物与矮生维管植物均可能出现丰度下降。但单独的降水格局变化或富营养化过程，可能对草原苔藓植物与矮生维管植物产生差异化影响，因此需针对性考量植物的功能性状。