Background: Wild apple (Malus sieversii) is under second-class national protection in China and one of the lineal ancestors of cultivated apples worldwide. In recent decades, the natural habitation area of wild apple trees has been seriously declining, resulting in a lack of saplings and difficulty in population regeneration. Artificial near-natural breeding is crucial for protecting and restoring wild apple populations, and adding nitrogen (N) and phosphorous (P) is one of the important measures to improve the growth performance of saplings. In this study, field experiments using N (CK, N1, N2, and N3: 0, 10, 20, and 40 g m^− 2 yr^− 1, respectively), P (CK, P1, P2, and P3: 0, 2, 4, and 8 g m^− 2 yr^− 1, respectively), N20Px (CK, N2P1, N2P2, and N2P3: N20P2, N20P4 and N20P8 g m^− 2 yr^− 1, respectively), and NxP4 (CK, N1P2, N2P2, and N3P2: N10P4, N20P4, and N40P4 g m^− 2 yr^− 1, respectively) treatments (totaling 12 levels, including one CK) were conducted in four consecutive years. The twig traits (including four current-year stem, 10 leaf, and three ratio traits) and comprehensive growth performance of wild apple saplings were analyzed under different nutrient treatments. Results: N addition had a significantly positive effect on stem length, basal diameter, leaf area, and leaf dry mass, whereas P addition had a significantly positive effect on stem length and basal diameter only. The combination of N and P (NxP4 and N20Px) treatments evidently promoted stem growth at moderate concentrations; however, the N20Px treatment showed a markedly negative effect at low concentrations and a positive effect at moderate and high concentrations. The ratio traits (leaf intensity, leaf area ratio, and leaf to stem mass ratio) decreased with the increase in nutrient concentration under each treatment. In the plant trait network, basal diameter, stem mass, and twig mass were tightly connected to other traits after nutrient treatments, indicating that stem traits play an important role in twig growth. The membership function revealed that the greatest comprehensive growth performance of saplings was achieved after N addition alone, followed by that under the NxP4 treatment (except for N40P4). Conclusions: Consequently, artificial nutrient treatments for four years significantly but differentially altered the growth status of wild apple saplings, and the use of appropriate N fertilizer promoted sapling growth. These results can provide scientific basis for the conservation and management of wild apple populations.

Shrubs play a major role in maintaining ecosystem stability in the arid deserts of Central Asia. During the long-term adaptation to extreme arid environments, shrubs have developed special assimilative branches that replace leaves for photosynthesis. In this study, four dominant shrubs with assimilative branches, namely Haloxylon ammodendron, Haloxylon persicum, Calligonum mongolicum, and Ephedra przewalskii, were selected as the research objects, and the dry mass, total length, node number, and basal diameter of their assimilative branches and the average length of the first three nodes were carefully measured, and the allometric relationships among five traits of four species were systematically compared. The results indicated that: (1) Four desert shrubs have different assimilative branches traits. Compared with H. persicum and H. ammodendron, C. mongolicum and E. przewalskii have longer internodes and fewer nodes. The dry mass of H. ammodendron and the basal diameter of H. persicum were the smallest; (2) Significant allometric scaling relationships were found between dry mass, total length, basal diameter, and each trait of assimilative branches, all of which were significantly less than 1; (3) The scaling exponents of the allometric relationship between four traits and the dry mass of assimilative branches of H. persicum were greater or significantly greater than those of H. ammodendron. The scaling exponents of the relationships between the basal diameter, dry mass, and total length of E. przewalskii were higher than those of the other three shrubs. Therefore, although different species have adapted to drought and high temperatures by convergence, there was great variability in morphological characteristics of assimilative branches, as well as in the scaling exponents of relationships among traits. The results of this study will provide valuable insights into the ecological functions of assimilative branches and survival strategies of these shrubs to cope with aridity and drought in desert environments.

Malus sieversii, commonly known as wild apples, represents a Tertiary relict plant species and serves as the progenitor of globally cultivated apple varieties. Unfortunately, wild apple populations are facing significant degradation in localized areas due to a myriad of factors. To gain a comprehensive understanding of the nutrient status and spatiotemporal variations of M. sieversii, green leaves were collected in May and July, and the fallen leaves were collected in October. The concentrations of leaf nitrogen (N), phosphorus (P), and potassium (K) were measured, and the stoichiometric ratios as well as nutrient resorption efficiencies were calculated. The study also explored the relative contributions of soil, topographic, and biotic factors to the variation in nutrient traits. The results indicate that as the growing period progressed, the concentrations of N and P in the leaves significantly decreased (P < 0.05), and the concentration of K in October was significantly lower than in May and July. Throughout plant growth, leaf N–P and N–K exhibited hyperallometric relationships, while P–K showed an isometric relationship. Resorption efficiency followed the order of N < P < K (P < 0.05), with all three ratios being less than 1; this indicates that the order of nutrient limitation is K > P > N. The resorption efficiencies were mainly regulated by nutrient concentrations in fallen leaves. A robust spatial dependence was observed in leaf nutrient concentrations during all periods (70.1–97.9% for structural variation), highlighting that structural variation, rather than random factors, dominated the spatial variation. Nutrient resorption efficiencies (NRE, PRE, and KRE) displayed moderate structural variation (30.2–66.8%). The spatial patterns of nutrient traits varied across growth periods, indicating they are influenced by multifactorial elements (in which, soil property showed the highest influence). In conclusion, wild apples manifested differentiated spatiotemporal variability and influencing factors across various leaf nutrient traits. These results provide crucial insights into the spatiotemporal patterns and influencing factors of leaf nutrient traits of M. sieversii at the permanent plot scale for the first time. This work is of great significance for the ecosystem restoration and sustainable management of degrading wild fruit forests.

International interest is growing in biodiversity conservation and sustainable use in drylands. Desert ecosystems across arid Central Asia are severely affected by global change. Understanding the changes in a plant community is an essential prerequisite to revealing the community assembly mechanism, vegetation conservation, and management. The knowledge of large-scale spatial variation in plant community structure in different Central Asian deserts is still limited. In this study, we selected the Taukum (TD, Kazakhstan) and the Gurbantunggut (GD, China) deserts as the research area, with similar latitudes despite being nearly 1000 km apart. Thirteen and 15 sampling plots were set up and thoroughly investigated. The differences in community structure depending on multiple plant attributes (individual level: plant height, canopy diameter, and plant volume, and community level: plant density, total cover, and total volume) were systematically studied. TD had a better overall environmental status than GD. A total of 113 species were found, with 68 and 74 in TD and GD, respectively. The number of species and plant attributes was unequally distributed across different families and functional groups between deserts. The values of several plant attributes, such as ephemerals, annuals, dicotyledons, and shrubs with assimilative branches in GD, were significantly lower than those in TD. The Motyka indices of six plant attributes (26.18–38.61%) were higher between the two deserts than the species similarity index (20.4%), indicating a more robust convergence for plant functional attributes. The community structures in the two deserts represented by different plant attribute matrices demonstrated irregular differentiation patterns in ordination diagrams. The most variance in community structure was attributed to soil and climatic factors, while geographic factors had the smallest proportion. Consequently, the community structures of the two distant deserts were both different and similar to an extent. This resulted from the long-term impacts of heterogeneous environments within the same region. Our knowledge is further deepened by understanding the variation in community structure in different deserts on a large spatial scale. This therefore provides valuable insights into conserving regional biodiversity in Central Asia.

Calligonum species are widely distributed across the arid desert belt stretching from North Africa to Central Asia. Their leaves are nearly fully degraded, and photosynthetic activity is predominantly undertaken by assimilative branches (ABs). Remarkably, Calligonum represents the only known lineage within the family Polygonaceae to exhibit the C4 photosynthetic pathway. To date, on the regional scale, the nutrient resorption patterns of ABs of different Calligonum species are still unclear. We investigated three representative species from distinct taxonomic sections native to the Junggar Desert of northwestern China: C. mongolicum (CM; Sect. Medusa), C. leucocladum (CL; Sect. Pterococcus), and C. junceum (CJ; Sect. Calliphysa). Green ABs and AB litters were collected during the summer and autumn, respectively, to assess interspecific differences in nitrogen (N), phosphorus (P), and potassium (K) resorption efficiencies (NRE, PRE, and KRE, respectively), and explore their stoichiometric relationships, variation patterns, and the environmental influences. Across all species, the nutrient resorption efficiencies (NuREs) followed the order: KRE (65.03% ± 0.57%) > PRE (53.57% ± 0.48%) > NRE (23.36% ± 0.70%). Among the three taxa, CM exhibited the highest NRE (29.20% ± 1.24%) and PRE (62.44% ± 0.45%), whereas KRE was lowest in CJ (57.41% ± 1.41%). All three species exhibited a scaling relationship between NRE and PRE with slope > 2, indicating that N was resorbed more rapidly than P. The scaling relationship of PRE–KRE showed considerable interspecific variation, with CJ exhibiting a negative slope (−0.492). NuREs were positively correlated with nutrient concentrations in summer green ABs but negatively correlated with those in AB litters. Within species, the three NuREs generally exhibited similar patterns of variation across geographic, climatic, and edaphic gradients, yet marked interspecific differences persisted. Soil and climatic conditions were identified as the primary environmental determinants of NuRE variability, although species‐specific responses indicated that different nutrient elements were affected by distinct interactions among environmental factors. In summary, the three Calligonum species demonstrated differentiated nutrient resorption strategies, closely tied to both their internal nutrient status and environmental contexts. These findings provide valuable insights into nutrient use strategies and adaptive mechanisms in Calligonum and other assimilative‐branch shrubs inhabiting arid ecosystems.

Litter nutrient stoichiometry and its drivers are important for understanding nutrient cycling in desert ecosystems, plant adaptation strategies, and the sustainability of ecosystem functions. However, little is known about the spatial variation in litter nutrient stoichiometry and its environmental drivers in desert shrubs. This study focused on two Nitraria species (N. tangutorum Bobrov and N. sphaerocarpa Maxim) in Northwestern China, analyzing leaf litter N, P, and K stoichiometry, their spatial variation, and environmental drivers. Nutrient concentrations and stoichiometric ratios did not differ significantly between the two species. The average N contents in the litters of N. tangutorum and N. sphaerocarpa were 11.363 mg g⁻¹ and 11.295 mg g⁻¹, respectively. The P contents were 0.591 mg g⁻¹ and 0.611 mg g⁻¹, whereas the K contents were 17.482 mg g⁻¹ and 16.255 mg g⁻¹, respectively. With the changes in geographic and climatic factors, the same nutrient elements of the two Nitraria species showed inconsistent variation patterns. Both species showed low P concentration, indicating high P resorption and possible P limitation, reflecting nutrient vulnerability in desert ecosystems according to the scaling exponents among elements. In litter, the residual nutrient contents ranked as K > P > N, suggesting strong N resorption but low K resorption, especially for N. sphaerocarpa. N was mainly influenced by latitude, P by soil properties, and K by mean annual temperature. Moreover, litter stoichiometric ratios of N. tangutorum were relatively stable, whereas those of N. sphaerocarpa were more sensitive to environmental variables. In conclusion, the two Nitraria shrubs exhibited differential nutrient use strategies under nutrient restriction, providing insights into nutrient cycling and supporting sustainable management of desert ecosystems.