ObjectiveStand is an important part of forest biodiversity. Due to its complexity or lack of ecological relevance, the typical diversity index cannot be analyzed on a spatial scale and therefore cannot reflect the internal changes of species and spatial structure.

MethodTaking the spruce-fir forest in Jin’gouling Forest Farm in Wangqing County of Jilin Province, northeastern China as an example, two 60 m × 60 m typical sample plots were set by contiguous grid quadrat method, and a new index describing the diversity of spatial structural units-neighbourhood diversity index was evaluated.

Result(1) The diameter structure curve of spruce-fir forest in the study area is multi-peak anti-J-shaped curve. The proportion of forests with small and medium-order diameter was higher, the trees with large diameter were less, and the distribution of diameters was continuous and reasonable. (2) The species diversity and tree diameter of the spruce-fir forest were high, tree species and the diameter distribution were relatively uniform, the degree of mixing was strong, the horizontal structure was highly variable, and the stand structure was complex. (3) Results of the analysis of three neighbourhood diversity indices (species diversity, structural diversity by diameter distribution, and structural diversity by diameter variation) were consistent with the results of the Shannon diversity index, and the close index values were obtained for stand with similar structure.

ConclusionThe neighbourhood diversity index can describe the diversity of forest stands and spatial structure characteristics, and reflect the spatial variation of species and structure diversity, and has obvious ecological significance. It can be applied to the structural adjustment of forest stands and provide a theoretical basis for rational forest management.