**1. Introduction**

Structure and function are two vital aspects to determine and measure the stability of forests community [1]. Population structure, which reflects the distribution of individuals within a population, may provide insights into past and present regeneration [2, 3]. Life table and survival curve are the main methods when analyzing population structure. By using life table analysis, it was discovered that *H. ammodendron* seedling had two rapid drop stages of survival rate and high mortality rate in natural forest [4]. Meanwhile, by using survival curve analysis, *H. ammodendron* population was suggested closing to progressive or stable status in some suitable habitats [5, 6]. This, however, has been unknown in the plantation which had similar inhabits but different growth stage.

Plantation has been applied in ecological restoration worldwide [7]. A key issue for plantation is that population regeneration is often challenged by seedling

establishment in many plantation ecosystems, which is critical to the stability of plantation species as well as to the plantation sustainability [8]. For *H. ammodendron*, failure in regeneration resulted in the population degradation occurred in old stand in the Hexi Corridor Desert [9, 10], suggesting that the regeneration barrier possibly occurs in *H. ammodendron* plantation. This, however, has not been assessed in the biggest *H. ammodendron* plantation developed in the Gurbantunggut Desert edges.

The wind prevention and sand fixation forest ecosystem, which is a kind of relatively heterogeneous open system, and flow of the material, energy and information constantly happens among the subsystems, thereinto, the two major subsystems, vegetation and soil formed an interdependent and mutually restrictive relationship between them [11]. Exploring the relationship between vegetation and soil has significant meaning in understanding the process and effect of sand fixation vegetation, and further putting forward corresponding optimal management measures [12]. In the ecological process of settlement, growth and succession of artificial *H. ammodendron* population, the accumulation and distribution of soil moisture and nutrient will change. In turn, that will affect the characteristics of vegetation. Therefore, such mutual restriction relationship between vegetation and soil will definitely change according to the spatial and temporal scale [13].

The Gurbantunggut Desert in northwestern China, the third largest desert in the world, is sensitive to climate change and human activities [14]. The desert vegetation is dominated by the *H. ammodendron*, which is greatly tolerant to drought, wind erosion, sand burial and other stress factors [15–18]. Therefore, *H. ammodendron* has been widely used in vegetation restoration and sand-fixation engineering [19]. In the edge of the Gurbantunggut Desert, i.e., the desert-oasis ecotone, *H. ammodendron* forest play an important role in preventing dune movement toward oasis. However, large area of *H. ammodendron* forest was suffered deforestation and overgrazing during the 1970s and 1980s, which leads to severe desertification in this area [20]. Since then *H. ammodendron* plantation has been extensively developed along the edge of the Gurbantunggut Desert. In recent decades, these *ammodendron* plantations have gradually developed into the mature stage, but, some of them tend to decline, which directly threatened the stability of the artificial population system and the normal exertion of ecological functions in this area.

This chapter, the change characteristics of the canopy storey and the regeneration storey structures of *H. ammodendron* plantations at different chronosequence stages, as well as the growth and death dynamic development law of populations ware studied. Meanwhile, the feedback relationship between vegetation and soil were analyzed. Further, the current situation of growth and development of *H. ammodendron* population in the edge of the Gurbantunggut Desert was evaluated accurately and comprehensively. Then, we explained why the *H. ammodendron* population is stable, developing or declining, and whether *H. ammodendron* plantation has the ability of sustainable natural regeneration. On this basis, we put forward the scientific suggestion for the vegetation construction and management of the degraded artificial forest ecosystem in this region. We hope this research could provide basic data and scientific evidence for further research on the vegetation restoration and reconstruction of desert ecosystem in arid region.
