Department of Biology and Biochemistry, University of Houston, Houston, TX 77204, USA.
Oecologia. 2012 Nov;170(3):789-98. doi: 10.1007/s00442-012-2356-2. Epub 2012 May 29.
Oysters are ecosystem engineers in marine ecosystems, but the functions of oyster shell deposits in intertidal salt marshes are not well understood. The annual plant Suaeda linearis is associated with oyster shell deposits in Georgia salt marshes. We hypothesized that oyster shell deposits promoted the distribution of Suaeda linearis by engineering soil conditions unfavorable to dominant salt marsh plants of the region (the shrub Borrichia frutescens, the rush Juncus roemerianus, and the grass Spartina alterniflora). We tested this hypothesis using common garden pot experiments and field transplant experiments. Suaeda linearis thrived in Borrichia frutescens stands in the absence of neighbors, but was suppressed by Borrichia frutescens in the with-neighbor treatment, suggesting that Suaeda linearis was excluded from Borrichia frutescens stands by interspecific competition. Suaeda linearis plants all died in Juncus roemerianus and Spartina alterniflora stands, regardless of neighbor treatments, indicating that Suaeda linearis is excluded from these habitats by physical stress (likely water-logging). In contrast, Borrichia frutescens, Juncus roemerianus, and Spartina alterniflora all performed poorly in Suaeda linearis stands regardless of neighbor treatments, probably due to physical stresses such as low soil water content and low organic matter content. Thus, oyster shell deposits play an important ecosystem engineering role in influencing salt marsh plant communities by providing a unique niche for Suaeda linearis, which otherwise would be rare or absent in salt marshes in the southeastern US. Since the success of Suaeda linearis is linked to the success of oysters, efforts to protect and restore oyster reefs may also benefit salt marsh plant communities.
牡蛎是海洋生态系统中的生态工程师，但人们对潮间带盐沼中牡蛎壳沉积物的功能了解甚少。一年生植物线叶滨藜与佐治亚盐沼中的牡蛎壳沉积物有关。我们假设牡蛎壳沉积物通过工程化土壤条件，促进了线叶滨藜的分布，这些土壤条件不利于该地区的优势盐沼植物（灌木藜、柳枝稷和互花米草）。我们使用常见的温室盆栽实验和野外移植实验来检验这一假设。在线叶滨藜没有邻居的情况下，它在藜属植物丛中茁壮成长，但在有邻居的处理中，它受到藜属植物的抑制，这表明线叶滨藜受到种间竞争的排斥而无法在藜属植物丛中生长。无论是否有邻居，线叶滨藜在柳枝稷和互花米草的植株中都全部死亡，这表明线叶滨藜受到物理胁迫（可能是水涝）而被排斥出这些栖息地。相比之下，无论是否有邻居，藜属植物、柳枝稷和互花米草在藜属植物丛中都表现不佳，可能是由于物理胁迫，如低土壤含水量和低有机质含量。因此，牡蛎壳沉积物通过为线叶滨藜提供独特的生境，在影响盐沼植物群落方面发挥了重要的生态工程作用，否则，线叶滨藜在东南美国的盐沼中会很少见或不存在。由于线叶滨藜的成功与牡蛎的成功息息相关，因此保护和恢复牡蛎礁的努力也可能有益于盐沼植物群落。
