Effects of site conditions on biomass allocation patterns of Caragana korshinskii in arid aeolian sand regions, middle area of Ningxia of northwestern China

  Objective  This paper aims to recognize the effects of site conditions on the allocation law of Caragana korshinskii biomass in the arid aeolian sand regions, and research the adaptability of Caragana korshinskii in the middle area of Ningxia, northwestern China.

  Method  Based on biomass data obtained from 109 Caragana korshinskii shrubs in Baijitan Sand Prevention and Control Forest Farm, site conditions (slope aspect, altitude (1 218−1 476 m) and slope degree) were standardized to zero dimension. Then, permutational multivariate analysis of variances (PERMANOVA) with Euclidean distance and Bray-Curtis distance was used to study the relative impact of site conditions on the shrub biomass allocation patterns (leaf biomass fraction(LMF), stem biomass fraction (SMF), root biomass fraction (RMF) and root shoot ratio (R/S)) and comprehensive characteristics.

  Result  (1) Slope aspect had the greatest degree of interpretation on LMF and SMF, and the interpretation degree factor (R²) was 0.144 5 and 0.281 0, respectively; altitude had the greatest degree of interpretation on RMF and R/S, and R² was 0.296 7 and 0.295 7, respectively. (2) In the interaction of site factors, the interaction of altitude and slope degree had significant influences on RMF and R/S (P < 0.05), while the interaction of slope aspect, altitude and slope degree had significant influences on SMF and R/S. (3) The multivariate analysis of variance based on Euclidean distance and Bray-Curtis distance showed that, the comprehensive impact of slope aspect, aititude, and slope degree on shrub biomass allocation was significant (P < 0.05), among which, the impact of slope aspect (R² = 0.232 2, 0.235 7) > aititude (R² = 0.221 3, 0.221 1) > slope degree (R² = 0.035 8, 0.029 2). In the influence of multi-factor interaction, the two-way interactions of altitude and slope degree and three-way interactions of slope aspect, altitude and slope degree had significant effects on shrub biomass allocation patterns (P<0.05).

  Conclusion  Different site conditions showed different influences on shrub biomass allocation patterns. This study establishes the influencing degree of site conditions on shrub biomass allocation patterns for Caragana korshinskii, which provides a scientific basis for further study of shrub carbon sink and the ecological significance of shrubs in the arid aeolian sand regions.