Effects of Sand Dune Stabilization on the Spatial Pattern of Artemisia ordosica Population in Mu Us Desert, Northwest China

Abstract

Vegetation patterns are strongly influenced by sand mobility in desert ecosystems. However, little is known about the spatial patterns of Artemisia ordosica, a dominant shrub in the Mu Us desert of Northwest China, in relation to sand fixation. The aim of this study was to investigate and contrast the effects of sand dune stabilization on the population and spatial distribution of this desert shrub. Spatial autocorrelation, semi-variance analysis, and point-pattern analysis were used jointly in this study to investigate the spatial patterns of A. ordosica populations on dunes in Yanchi County of Ningxia, China. The results showed that the spatial autocorrelation and spatial heterogeneity declined gradually, and the distance between the clustered individuals shortened following sand dune fixation. Seedlings were more aggregated than adults in all stage of dune stabilization, and both were more aggregated on shifting sand dunes separately. Spatial associations of the seedlings with the adults were mostly positive at distances of 0–5 m in shifting sand dunes, and the spatial association changed from positive to neutral in semi-fixed sand dunes. The seedlings were spaced in an almost random pattern around the adults, and their distances from the adults did not seem to affect their locations in semi-fixed sand dunes. Furthermore, spatial associations of the seedlings with the adults were negative in the fixed sand dune. These findings demonstrate that sand stabilization is an important factor affecting the spatial patterns of A. ordosica populations in the Mu Us desert. These findings suggest that, strong association between individuals may be the mechanism to explain the spatial pattern formation at preliminary stage of dune fixation. Sand dune stabilization can change the spatial pattern of shrub population by weakening the spatial association between native shrub individuals, which may affect the development direction of desert shrubs.

Spatial Pattern and Population Structure of Artemisia ordosica Shrub in a Desert Grassland under Enclosure, Northwest China

“…In this study, crown classes were used to explain the age structures of A. ordosica population [ 65 ]. All A. ordosica individuals were classified into different classes (Class 1: from 0.1 cm to 10 cm; 10 cm were added gradually from Class 2 to 4 age groups (seedling group: average heights and crown were less than 30 cm; adult group: average heights and crown were more than 30 cm, and the dead branches proportion was less than two-thirds; aging group: the dead branches proportion was more than two-thirds; and dead group: individual which was lifeless) which were consistent with previous research [ 15 , 51 , 65 , 66 ]. The relationship between crown and height was fitted by a linear model.…”

“…The spatial pattern of plants is the performance of comprehensive interactions between plants and environmental factors over a long term, which can be used to reveal the succession law of vegetation [ 35 , 36 , 37 , 40 , 86 , 87 ]. The spatial-patterns structure analysis of different growth stages can obtain some essential information of a population under natural or human disturbance, such as recruitment, wilting or mortality of individuals, and intraspecific competition [ 51 , 70 , 88 , 89 ]. In this study, different age A. ordosica groups showed unpredictable spatial patterns in enclosed and grazing grasslands.…”

“…A. ordosica , a subshrub species, does not produce notable annual rings [ 51 ]. Therefore, the morphological characteristics were used to distinguish age structures.…”

“…Therefore, the study on the A. ordosica shrub species is important for understanding the progress of vegetation restoration in this study area. Recent research on A. ordosica population dynamics mostly concentrated on natural recruitment [ 15 , 47 ], effects of habitat changes [ 15 , 48 , 49 ], spatial pattern [ 50 , 51 ], plant morphology and structural characteristics [ 52 ], soil moisture characteristics [ 53 , 54 ], and soil physicochemical properties [ 55 ]. However, the dynamics of the population structure and spatial pattern of the A. ordosica population in a restored desert grassland after removing livestock have not received enough attention.…”

Sand dune stabilization changes the vegetation characteristics and soil seed bank and their correlations with environmental factors

“…Sand dune mobility in desert ecosystems reflects the underlying ecological processes, including biotic interactions, seed dispersal, vegetation succession, and environmental change (Fan et al, 2017;Hao et al, 2017). Population pattern in sand dunes is a result of long term interactions between living vegetation and seed bank as well as their relationships with the environment (Zhang et al, 2015). Previous studies have shown that dune stabilization in semi-arid areas has led to distinct dune habitat types.…”