Background As a key component of terrestrial ecosystems, forest is of important ecological and social functions, while forest health is the prerequisite of ensuring the playing of these functions. Scientific assessment of the health status of forest stands can provide an important basis for function-oriented protection forest management.

Methods Based on the survey data of forests health and the actual situation of shelterbelts in Dahuofang Reservoir, this study identified 4 aspects of "system vitality-organization-resilience-water conservation" as the criteria layer framework for the health assessment of water conservation forests, and then 17 indicators were selected to form a forest health assessment index system. The forest comprehensive health index (H) of different forest stands were calculated by the comprehensive index method, and according to 5 level of high quality, healthy, sub-healthy, unhealthy and disease, and the forest health for 5 typical shelterbelts (Larix gmelinii, Pinus tabuliformis, Pinus koraiensis, Robinia pseudoacacia and natural secondary forest) were analyzed.

Results 1) The average forest heath comprehensive index of water conservation forest in Dahuofang Reservoir is 5.77, which is sub-healthy. Fifteen plots are in three states of healthy, sub-healthy and unhealthy, respectively, with the values of 7, 5 and 3 respectively. 2) For different forests, the forest health comprehensive index(H) of different forests ranks as natural secondary forest(7.29) > R. pseudoacacia(6.67) > P. koraiensis(5.88) > P. tabuliformis(5.79) > L. gmelin(3.21). Among them, the health status of the natural secondary forest is the best, and their forest structure, forest litter, and soil properties of forest land are obviously superior, with high structural stability and water conservation capacity. R. pseudoacacia is also in a healthy level, especially in terms of system vitality and water conservation. P. tabuliformis and P. koraiensis are in a sub-health state, and they have the conditions of transferring to healthy forests; L. gmelinii is unhealthy, which is significantly worse than other forests and needs to be improved.

Conculsions The forests health of artificial forest is worse than that of natural secondary forest as its incomplete structure, the weak function stability, the weak anti-interference ability and the restoring force, and the weak ability of water conservation; the same is true for overall health values. Therefore, practical forest management measures should be taken to improve the health status of artificial forest, and natural secondary forests are a transformation target.