The protection period of a sand-fixation plantation is an important part of sustainable management theory for artificial forests. This study was conducted in an artificial sand-fixation ecosystem in Huangyangtan sandy land, and 18 representational forest stands (grasslands) were selected and investigated. The characteristics of initial protection maturity and protection period were analyzed by the hierarchical clustering method. The result showed that the protection period of sand-fixation plantations could be divided into four types. The first type was referred to no protection period and extremely short protection period. The species in this type included Populus simonii, Robinia pseudoacacia and Astragalus adsurgens. Forests of P. simonii and R. pseudoacacia were not able to reach protection maturity. A. adsurgens grassland had only 5 years of protection period. The second type had short protection period. This type included four vegetables, including Ulmus pumila, Populus bolleana, Salix gordeivii and Pinus sylvestris var. mongolica, and most of them were arbor trees. The protection period was between 21 to 36 years, with late initial protection maturity. The third type had intermediate protection period, including forests of Pinus sylvestris var. mongolica x Amorpha fruticosa, Elaeagnus angustifolia, Caragana korshinskii, Sabina vulgaris and S. vulgaris x A. fruticosa. This type was mainly composed of shrubs. The protection period was between 53 to 75 years, and the initial protection maturity came earlier than the arbor forests. The last type had long protection period which only included forests of Platycladus orientalis, its protection period was as long as 74 to 80 years, initial protection maturity came the latest but the protection period was the longest.
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