Experimental data on trait-mediated interactions in temperate forests of northeastern China

The study area was a 30-ha (500  600 m) permanent forest plot (43°57.928′–43°58.214′N; 127°45.287′–127°45.790′E) in Jilin Province, China. Two species, Pinus koraiensis and Ulmus laciniata, were selected as focal trees at the neighborhood scale. In 2010, all healthy adult individuals of P. koraiensis and U. laciniata were selected as focal trees, covering a wide range of DBH (diameter at breast height, 1.3m) classes (10 cm<DBH<80 cm).  We obtained a dataset containing measurements for 74 trees of P. koraiensis and 70 trees of U. laciniata. There were 2,109 neighboring trees sampled for the focal trees of P. koraiensis and 1,400 neighboring trees were neighbors for the focal trees of U. laciniata. We determined soil properties and topographic features as abiotic variables influencing the interactions between trees. The 30-ha plot was divided into 20 ×20 m grid cells. Soils samples were collected from evenly distributed cells at a depth of 10 cm at the four corners of these cells. Four soil properties (soil pH, soil water content, soil organic matter content, and soil nutrients) were measured. The topographic variables, including elevation, convexity, slope steepness, and aspect were calculated for each sample cell