China planted forest data

The dataset is a subset of the large dataset produced by Tang et al. (2018), including 1928 planted forest sites collected from a national field campaign performed in China in the early 2010s. During the field campaign, the mainland China was first divided into three regions in a standardized, sampling protocol. The sampling protocol was enforced to ensure the forest sites sampled are representative of the distribution, composition, and structure of the forests in China. In each of the three regions, the grid sizes of 100, 400, and 900 km² were adopted for tropical/subtropical, temperate, and alpine regions, respectively. Second, 3%–5% of the grids were randomly chosen for the field survey by overlaying the grids and the administrative boundary maps. Third, a 600-1000 m² plot was designed for each forest site (i.e. plot) for data sampling. During the field surveying, each plot was further divided into six to ten 10 × 10 m² subplots, and the geographical information, forest origin, community type, the diameter at breast height (DBH), and stand age were recorded. For each plot, trees with DBH larger than 5 cm were all measured, and the biomass of each tree was estimated with 158 sets of allometric equations (including each dominant tree species in China). The field sampling was conducted from June to September to minimize bias. By excluding planted forests with missing age information and sites established before 1980, 1928 sites were retained. The dataset was used in this study published in One Earth: "<b>China’s forestation on m</b><b>argi</b><b>nal lands was less efficient in carbon sequestration compared to non-marginal lands</b>"

本数据集为Tang等人（2018）构建的大型数据集的子集，数据源自2010年代初期在中国开展的全国性野外调查，共收录1928个人工林样地。本次野外调查首先按照标准化采样方案将中国大陆划分为三大区域，且严格执行该采样方案以确保所选取的林样地能够代表中国森林的分布、组成与结构。其中热带/亚热带区域、温带区域与高寒区域分别采用100、400和900 km²的网格尺度。其次，通过叠加网格图层与行政边界地图，随机选取3%~5%的网格开展野外调查。第三，为每个人工林样地（即样地）设置600~1000 m²的采样样方以开展数据采集。野外调查过程中，每个样方又被进一步划分为6~10个10×10 m²的子样方，并记录了地理信息、森林起源、群落类型、胸径（DBH）以及林分年龄等参数。针对每个样地，胸径大于5 cm的树木均被测量，并采用158组异速生长方程（涵盖中国境内各优势树种）估算单木生物量。为尽可能降低采样偏差，野外调查均于每年6月至9月开展。通过剔除年龄信息缺失以及1980年前营造的人工林样地，最终保留了1928个样地。本数据集被用于发表于《One Earth》的此项研究：《中国边际土地造林的固碳效率低于非边际土地》