Abstract: The main aim of this study is to provide a theoretical basis for the optimization and adjustment of the spatial structure of mixed and pure Pinus tabuliformis ecological forest in Beijing Jiulong Mountain by analyzing the spatial structure of P. tabuliformis ecological forest and evaluating its management urgency. Based on empirical data, the spatial structure characteristics of P. tabuliformis ecological forests were analyzed using seven spatial structure parameters including mingling, dominance, uniform angle index, crowding, stand layer index, open degree, and competition index. Ten indices were selected to construct the evaluation index system of management urgency from four aspects of density, pattern, competition and mingling, and their standards were determined. Meanwhile, the management urgency of P. tabuliformisecological forest was evaluated. Results showed that: (1) Trees in both mixed forest and pure forest were close to random distribution. Compared with the mixed forest, the spatial structure of pure forest was relatively simple, tree species composition was simple, dominated by non-mixture and low-mixture and with a trend of single aggregation. (2) Tree size differentiation was insignificant, and P. tabuliformis and Larix principis rupprechtii were dominant species. (3) Trees were in a state of dense, and trees of the very dense had a higher proportion. (4) Most trees were in the middle and upper forest layers, with no obvious forest layer structure. (5) Both stands were under moderate competition. Compared with the pure forest, the open degree of the mixed forest was lower and its growth space was not enough. (6) Management urgency of the pure and mixed forest was 0.6 and 0.5, respectively. The grades of management urgency for those two stands were particularly urgent and very urgent, which illustrated that most of the characteristics of P. tabuliformis ecological forest did not meet the standards. It is necessary to adopt reasonable management strategies to optimize the spatial structure of theP. tabuliformis ecological forests, with the aim to improve forest status and achieve sustainable development.

Key words: climate change, common garden., Larix gmelinii, adaptation, transplant