Relationships between spatial metrics and plant diversity in constructed freshwater wetlands

The diversity of plant species and their distribution in space are both thought to have important effects on the function of wetland ecosystems. However, knowledge of the relationships between plant species and spatial diversity remains incomplete. In this study, we investigated relationships between spatial pattern and plant species diversity over a five year period following the initial restoration of experimental wetland ecosystems. In 2003, six identical and hydrologically-isolated 0.18 ha wetland “cells” were constructed in former farmland in northeast Ohio. The systems were subjected to planting treatments that resulted in different levels of vascular plant species diversity among cells. Plant species diversity was assessed through annual inventories. Plant spatial pattern was assessed by digitizing low-altitude aerial photographs taken at the same time as the inventories. Diversity metrics derived from the inventories were significantly related to certain spatial metrics derived from the photographs, including cover type diversity and contagion. We found that wetlands with high cover type diversity harbor higher plant species diversity than wetlands with fewer types of patches. We also found significant relationships between plant species diversity and spatial patterning of patch types, but the direction of the effect differed depending on the diversity metric used. Links between diversity and spatial pattern observed in this study suggest that high-resolution aerial imagery may provide wetland scientists with a useful tool for assessing plant diversity.

植物物种多样性及其空间分布格局，均被认为对湿地生态系统（wetland ecosystems）功能具有重要调控作用。然而，当前学界关于植物物种与空间多样性之间的关联认知仍存在不足。本研究针对俄亥俄州东北部原农田区域构建的实验湿地生态系统，于其初始修复完成后的五年周期内，探究了空间格局与植物物种多样性之间的关联。2003年，研究人员在此区域构建了6个规格统一、水文隔离的0.18公顷湿地单元。通过差异化种植处理，各单元间的维管植物（vascular plant）物种多样性水平形成梯度差异。研究通过年度野外清查对植物物种多样性进行量化评估；同时，对与清查同期获取的低空航拍照片进行数字化处理，以此分析植物空间格局。清查所得的多样性指标，与航拍影像衍生的多项空间指标（包括覆盖类型多样性与蔓延度）存在显著相关性。研究发现，覆盖类型多样性较高的湿地，其植物物种多样性显著高于斑块类型较少的湿地。此外，植物物种多样性与斑块类型的空间格局间亦存在显著关联，但影响方向因所采用的多样性指标不同而有所差异。本研究揭示的多样性与空间格局之间的关联，表明高分辨率航拍影像可作为湿地科研人员评估植物物种多样性的实用工具。