Degradation of Baldcypress–Water Tupelo Swamp to Marsh and Open Water in Southeastern Louisiana, U.S.A.: An Irreversible Trajectory?
Degradation of Baldcypress–Water Tupelo Swamp to Marsh and Open Water in Southeastern Louisiana, U.S.A.: An Irreversible Trajectory?
复制标题
美国路易斯安那州东南部秃柏-水图珀洛沼泽退化为沼泽和开放水域：不可逆转的轨迹？
DOI：
10.2112/si54-006.1
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发表时间：
2009
影响因子：
4.6
通讯作者：
Demetra Kandalepas
中科院分区：
文献类型：
--
作者：
G. Shaffer;W. B. Wood;S. Hoeppner;Thais E. Perkins;Jason A. Zoller;Demetra Kandalepas
摘要 总体而言，美国路易斯安那州沿海的许多沼泽已经高度退化，其中一些正在转变为沼泽和开放水域。这项研究的最初目的是确定将密西西比河的水重新引入路易斯安那州东南部庞恰特雷恩盆地退化的莫雷帕斯沼泽的可行性和潜在效益。 2000年初，在三种不同的栖息地类型中选择了20个地点，其特征是流动的淡水（吞吐量地点）、停滞的、几乎永久被淹没的（遗迹地点）和容易发生咸水入侵事件的地区（退化地点）。成对的 625 平方米地块配备了枯枝落叶收集器、草本子地块和用于测量间隙土壤盐度的井。从 2000 年到 2006 年，对 2219 棵树的直径生长进行了跟踪，并使用生长季节中后期的剪裁图估算了草本植物的产量。总体而言，在研究早期，初级生产以树木为主，但随着生态系统的一部分从沼泽转变为沼泽，转向草本植被。盐胁迫是低密度地区树木死亡的主要原因，而积水和养分匮乏似乎是内部（遗迹）地点最大的压力源。 2005 年的飓风导致树冠密度低的地区高达 100% 的中层树木被风吹倒，而当落羽杉 (Taxodium distichum) 和水树 (Nyssa Aquatica) 的基础面积大于 30 m2 ha−1 时，风吹的影响可以忽略不计。利用 625 平方米地块的光谱特征，栖息地类型的空中范围显示，莫雷帕斯沼泽的绝大多数要么是残存的，要么是退化的。如果在不久的将来没有重新引入河流，也没有利用其他点和非点的淡水来源，莫雷帕斯沼泽将继续其清晰的轨迹，走向沼泽和开放水域。
Abstract In general, many of the swamps of coastal Louisiana, U.S.A., are highly degraded, and several are converting to marsh and open water. The initial purpose of this study was to determine the feasibility, and potential benefits, of reintroducing waters of the Mississippi River into the degraded Maurepas swamp, located in the Pontchartrain Basin of southeastern Louisiana. Early in the year 2000, 20 sites were selected in three different habitat types characterized by moving fresh water (throughput sites), stagnant, nearly permanently flooded (relict sites), and areas prone to saltwater intrusion events (degraded sites). Paired 625-m2 plots were outfitted with litter-fall traps, herbaceous subplots, and wells for measuring interstitial soil salinity. From 2000–2006, diameter growth was followed for 2219 trees, and herbaceous production was estimated using mid- and late-growing season clip plots. Overall, primary production was dominated by trees early in the study, but switched to herbaceous vegetation as parts of the ecosystem converted from swamp to marsh. Salt stress was the primary cause of tree mortality in areas of low density, whereas stagnant standing water and nutrient deprivation appear to be the largest stressors at interior (relict) sites. The 2005 hurricanes caused wind throw of up to 100% of midstory trees in areas of low canopy density and was negligible when basal areas of baldcypress (Taxodium distichum) and water tupelo (Nyssa aquatica) were greater than 30 m2 ha−1. Using spectral signatures of the 625-m2 plots, the aerial extent of habitat types revealed that the vast majority of the Maurepas swamp is either relict or degraded. Without a river reintroduction in the near future, as well as harnessing other point and nonpoint sources of fresh water, the Maurepas swamp will continue its clear trajectory to marsh and open water.