Charbonneau Bianca R, Wnek John P, Langley J Adam, Lee Gina, Balsamo Ronald A
Department of Biology, Villanova University, Villanova, PA 1908, USA; Department of Biology, University of Pennsylvania, Philadelphia, PA 19104, USA.
Marine Academy of Technology and Environmental Science, Manahawkin, NJ 08050, USA.
J Environ Manage. 2016 Nov 1;182:126-133. doi: 10.1016/j.jenvman.2016.06.032. Epub 2016 Jul 25.
Coastal regions are inherently and increasingly vulnerable and geomorphologically unstable, yet are invaluable economic and residential hubs. Dunes are dynamic buffers to erosion and the most natural, economical, and effective defense for coastal communities. Vegetation is integral to dune structure as it facilitates accretion and stabilization. Differences in the vegetation and root density likely translate to variability in coastal erosion prevention, but this notion has been largely unconsidered. We directly compared stabilizing factors, depth and density, of the root systems of two dominant mid-Atlantic dune plant species, native American beach grass (Ammophila breviligulata) and invasive Asiatic sand sedge (Carex kobomugi). Despite high plant density, C. kobomugi is targeted for removal in restoration efforts as its roots are assumed to provide less effective stabilization than A. breviligulata. We collected 30 cores and hand dug 14 A. breviligulata ramets at Island Beach State Park, New Jersey to examine biomass, root:shoot ratios, and root density. C. kobomugi had a more extensive root system with a root:shoot ratio of 11.36:1 compared to 1.62:1 for A. breviligulata. Similarly, cores 60 cm deep and 7.6 cm wide were sufficient to attain fully intact A. breviligulata roots, which did not extend deeper than 40 cm, but insufficient for C. kobomugi roots which extended beyond the sampling system vertically and horizontally. Scaling these findings to m(-2), aboveground biomass is relatively equal, but C. kobomugi had over 700% more root mass m(-2) than A. breviligulata. These results have strong implications for dune management. The root system of C. kobomugi may be better adapted to stabilize dunes and thus protect coastal areas during small and large-scale perturbations than previously supposed. This is a unique situation whereby the creation of monocultures will hyperstabilize dunes and make them more resistant to erosion at the cost of reduced biodiversity within the framework of resiliency.
沿海地区本质上且日益脆弱，地貌不稳定，但却是极其重要的经济和居住中心。沙丘是抵御侵蚀的动态缓冲带，是沿海社区最自然、经济且有效的防御手段。植被对于沙丘结构至关重要，因为它有助于沙丘的堆积和稳定。植被和根系密度的差异可能导致海岸侵蚀预防能力的变化，但这一概念在很大程度上未被考虑。我们直接比较了大西洋中部两种主要沙丘植物物种，即本土的美洲海滩草（Ammophila breviligulata）和入侵的亚洲沙苔草（Carex kobomugi）根系的稳定因素、深度和密度。尽管C. kobomugi植株密度高，但在恢复工作中它仍被列为清除对象，因为人们认为其根系提供的稳定作用不如A. breviligulata有效。我们在新泽西州的海岛海滩州立公园采集了30个土芯，并人工挖掘了14株A. breviligulata分株，以研究生物量、根冠比和根系密度。C. kobomugi的根系更为广泛，根冠比为11.36:1，而A. breviligulata为1.62:1。同样，60厘米深、7.6厘米宽的土芯足以完整获取A. breviligulata的根系，其根系深度不超过40厘米，但对于C. kobomugi的根系来说则不够，因为其根系在垂直和水平方向上超出了采样系统范围。将这些结果按每平方米进行换算，地上生物量相对相当，但C. kobomugi每平方米的根质量比A. breviligulata多700%以上。这些结果对沙丘管理具有重要意义。C. kobomugi的根系可能比之前认为的更能适应稳定沙丘，从而在小规模和大规模扰动期间保护沿海地区。这是一种独特的情况，即在恢复力框架内，营造单一栽培群落将过度稳定沙丘，使其更能抵御侵蚀，但代价是生物多样性降低。
