Forested wetland community description and analysis. A pre-emerald ash borer study in an era of global change

Trees in 11 900 m2 plots at four headwater wetland sites (Elm Flats, Bonita Swamp, Frog Valley and Bentley) have been identified and measured for 9 years. At Elm Flats trees exhibited a hump-shaped basal area distribution with a high proportion of shade tolerant trees in the larger size classes. This is indicative of a forest that has been subjected to limited anthropomorphic disturbance and possibly retains some old growth characteristics. The older forests also had the richest understory flora. Trees at the other three wetland sites exhibited characteristics indicative of successional swamp forests. Early signs of forest change from the invasive insect, the emerald ash borer, which kills ash (Fraxinus) trees, the most common species in these swamps, are visible in the annual growth increments, tree mortality and canopy cover. This tree census data, in conjunction with the understory species cover data, will be used to assess the impact of non-native species invasions, in particular the emerald ash borer (Agrilus planipennis), and climate change on our forests.

本数据集针对4处源头湿地样地（Elm Flats、Bonita Swamp、Frog Valley与Bentley）内总面积11900平方米的林木样地，完成了为期9年的物种识别与指标监测工作。在Elm Flats样地中，林木的胸高断面积（basal area）分布呈驼峰型，且大径级林木中耐阴树种占比极高。该特征表明此林分受人为干扰程度有限，或保留有部分原始老龄林的特性。老龄林同时拥有最为丰富的林下植物区系（understory flora）。其余三处湿地样地的林木则呈现出演替沼泽林的典型特征。作为该类沼泽最常见树种的白蜡属（Fraxinus）林木，会遭到入侵昆虫翡翠灰螟（Agrilus planipennis）的致死危害；目前已在年生长增量、林木死亡率与冠层盖度（canopy cover）中观测到该虫害引发森林变化的早期迹象。本林木普查数据将与林下物种盖度数据相结合，用于评估外来物种入侵（尤以翡翠灰螟为代表）及气候变化对该区域森林生态系统的影响。