气候变化的影响,例如海平面加速上升,会影响应力梯度,然而,对竞争/压力容忍度权衡和分布变化的影响尚不清楚。具有强应力梯度的生态系统,比如河口,允许时空替代压力因素,并可以深入了解未来与气候相关的资源和非资源压力变化。我们测试了胁迫梯度假说,并研究了淹没胁迫和生物相互作用增加对两种同属湿地莎草生长和存活的影响,尖刺和美洲尖刺。我们模拟了现有沼泽海拔的海平面上升,以及目前没有发现的海平面上升反映了两个盐度不同的潮汐湿地的潜在未来海平面上升条件。植物在五个潮汐海拔高度单独和一起生长,最低模拟海平面上升80厘米,并收获以评估一个生长季节后生物量的差异。淹没时间,盐度,硫化物,同时测量氧化还原电位。正如预测的那样,不断增加的淹没减少了通常在较高沼泽海拔地区发现的物种的生物量,对沿通道边缘发现的物种影响很小。邻居的存在减少了两个物种的总生物量,特别是在最高海拔;在任何海拔都没有促进。与预测相反,我们记录了压力耐受剂在增加的淹没下的竞争优势,这不是应力梯度假说所预测的。解决植物对加速气候变化的反应的多因素操纵实验对于创建更现实的,有价值,以及对潜在生态系统响应的必要评估。我们的结果指出了物理压力源之间重要且不可预测的协同作用,预计强度会随着气候变化而增加,随着压力的增加,生物质上的竞争力量也在增加。
Climate change impacts, such as accelerated sea-level rise, will affect stress gradients, yet impacts on competition/stress tolerance trade-offs and shifts in distributions are unclear. Ecosystems with strong stress gradients, such as estuaries, allow for space-for-time substitutions of stress factors and can give insight into future climate-related shifts in both resource and nonresource stresses. We tested the stress gradient hypothesis and examined the effect of increased inundation stress and biotic interactions on growth and survival of two congeneric wetland sedges, Schoenoplectus acutus and Schoenoplectus americanus. We simulated sea-level rise across existing marsh elevations and those not currently found to reflect potential future sea-level rise conditions in two tidal wetlands differing in salinity. Plants were grown individually and together at five tidal elevations, the lowest simulating an 80-cm increase in sea level, and harvested to assess differences in biomass after one growing season. Inundation time, salinity, sulfides, and redox potential were measured concurrently. As predicted, increasing inundation reduced biomass of the species commonly found at higher marsh elevations, with little effect on the species found along channel margins. The presence of neighbors reduced total biomass of both species, particularly at the highest elevation; facilitation did not occur at any elevation. Contrary to predictions, we documented the competitive superiority of the stress tolerator under increased inundation, which was not predicted by the stress gradient hypothesis. Multifactor manipulation experiments addressing plant response to accelerated climate change are integral to creating a more realistic, valuable, and needed assessment of potential ecosystem response. Our results point to the important and unpredicted synergies between physical stressors, which are predicted to increase in intensity with climate change, and competitive forces on biomass as stresses increase.