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Few systemic assessments have evaluated the success of these afforestation programs in alpine semiarid desert ecosystems in the Qinghai-Tibet Plateau. In this study, we investigated the influences of three Salix cupularis plantation age classes (6, 18, and 34 years) on the carbon (C), nitrogen (N), and phosphorus (P) storages and stoichiometry of the soil-plant ecosystem. The consequences of S. cupularis plantation induced soil spatial heterogeneity. The soil-plant ecosystem C storage increased after the plantation. The N storage showed an increasing trend from 6 to 18 years and then slightly decreased. The P storage presented a continuously declining trend. The result indicated that the imbalance in soil N, P, C occurred with plantation age because of the imbalance of their inputs. The N and P uptakes from subsoil and redistribution to topsoil by S. cupularis may contribute to meet N and P demands for the understory plants. Leaf N:P ratios varied from 8.3 to 17.5. These results imply that N and P status are the main factors limiting plant growth in the alpine-cold desert ecosystem. Thus, we recommend adding N and P fertilizers during plant growth. KEYWORDSafforestation, alpine semiarid desert, soil-plant system, stoichiometry, C,N and P storage, salix plantations 1 | INTRODUCTION Arid and semiarid regions are widely distributed in China, accounting for more than 16% of the land area (Wang, Zhang, Hasi, & Dong, 2010). For a long time, these regions have been managed using traditional agricultural and pastoral practices (Liu, Wu, Ding, Tian, & Shi, 2017;Wiesmeier et al., 2016). The land desertification in this region has primarily resulted from an imbalance of between human activities and global climate changes (Wang, Xue, Zhou, & Guo, 2015). Afforestation is an effective method of restoring desert lands, and it has a potentially useful impact on soil quality, vegetation structure, soil nutrient storages, and stoichiometry Therefore, the impact of changes in these nutritive element cycles on soil-plant ecosystems has received widespread attention.Salix cupularis is a shrub that belongs to the Salicaceae family, and it can grow in extremely harsh alpine semiarid environments. In addition, this shrub plays an important role in resisting wind erosion, fixing sand, preserving water, and increasing plant diversity. Since the 1980s, the Qinghai-Tibet Plateau, China, has become one of the key , bulk density (BD), sand content 95.83%, silt 2.04%, and clay 2.13%. | Experimental design and samplingSoil and plant sample collection was conducted in August 2016.Several typical areas along the eastern Qinghai-Tibet Plateau with negligible human disturbance were selected as sample collection sites.Each age class was represented by three plantation ages (6, 18, and 34 yr-old), and each plantation was repeated three times. Three clusters of S. cupularis were randomly selected for each plantation age, and basic information on the S. cupularis samples of each age is shown in Table S1. First, to test the understory plants, ...

Introduction of alkyl groups on azodicarboxylate esters is an important method to prepare alkyl amine derivatives. Herein, we report reactions of 4-alkyl-1,4-dihydropyridines as alkylation reagents with di-tert-butyl azodicarboxylate to prepare alkyl amine derivatives under heating conditions. The alkylation reactions via C–C bond cleavage of the dihydropyridines are achieved in the absence of catalysts and additives.