Restoration of riparian forest cover increases carbon stocks in the Pacific Northwest

Reforestation of degraded riparian areas provides climate mitigation benefits through increased carbon storage. In recent decades, riparian reforestation has accelerated in the Pacific Northwest (PNW) of the United States, primarily aiming to restore ecosystem functions and associated benefits, but few studies have evaluated riparian planting C sequestration and storage, particularly in highly productive wet riparian ecosystems like the PNW. 

Using these plantings as a ‘natural experiment’, we assessed C storage in woody vegetation (trees and shrubs) and soils across a chronosequence of PNW riparian reforestation sites, and non-forested riparian baseline sites, representing the pre-planting condition. These data were used to evaluate changes in C storage with planting age and identify key covariates affecting C storage in plants and soils and their relationship with planting age across a ~430 km latitudinal gradient in western Oregon, USA.   

Sites were distributed across 3 ecoregions, the Willamette Valley, the Pacific Northwest Coast, and the Klamath Mountains. The 43 studies sites were either non-forested or planted 5 -27 years before field data collection. The dataset includes biophysical properties of each site, as well as measurements of trees, shrubs, and soils which were used to calculate C storage at each plot and site. Sites stored between 38.3 – 511.1 Mg C per hectare, and carbon storage generally increased with planting age. The majority of site carbon was stored in soils; however, C storage differed more across planting ages for trees and the understory than for soil.

受损河岸带（riparian areas）的再造林可通过提升碳储量实现气候减缓效益。近数十年来，美国太平洋西北部（Pacific Northwest, PNW）的河岸带再造林活动加速推进，其核心目标多为恢复生态系统功能及其衍生效益，但现有研究中鲜有针对河岸带造林的碳固存与碳储量开展评估的工作，尤其是在太平洋西北部（PNW）这类高生产力的湿润河岸带生态系统中。
本研究将这些造林地块作为"自然实验"，在美国俄勒冈州西部约430公里的纬度梯度范围内，针对一系列太平洋西北部（PNW）河岸带再造林时间序列样地以及代表造林前状态的非造林河岸对照样地，评估了木本植被（乔木与灌木）与土壤的碳储量。通过这些数据，我们分析了碳储量随造林年限的变化规律，识别了影响植物与土壤碳储量的关键协变量，并阐明了其与造林年限之间的关联。
样地分布于3个生态区：威拉米特谷（Willamette Valley）、太平洋西北海岸（Pacific Northwest Coast）以及克拉马斯山脉（Klamath Mountains）。本次研究共纳入43个样地，这些样地要么为非造林状态，要么是在野外数据采集前5至27年完成造林的。本数据集包含各样地的生物物理属性，以及用于计算样地与样点碳储量的乔木、灌木与土壤实测数据。各样地的碳储量介于38.3–511.1兆克碳每公顷（Mg C ha⁻¹），且碳储量总体随造林年限增加而提升。绝大多数样地碳储量储存于土壤中；不过相较于土壤，乔木与林下植被的碳储量随造林年限的变化差异更为显著。