Data for research: "Divergent nutrient resorption strategies in C4 desert shrubs: Stoichiometric evidence from assimilative branches"

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), 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.

沙拐枣属（Calligonum）植物广泛分布于从北非延伸至中亚的干旱荒漠带。其叶片近乎完全退化，光合活动主要由同化枝（assimilative branches, ABs）承担。值得注意的是，沙拐枣属是蓼科（Polygonaceae）中已知唯一具有C4光合途径的类群。迄今为止，区域尺度上不同沙拐枣属植物同化枝的养分再吸收模式仍不明确。我们对中国西北准噶尔沙漠原生的3个不同分类组的代表性物种进行了研究：蒙古沙拐枣（C. mongolicum，CM；美杜莎组，Sect. Medusa）、白皮沙拐枣（C. leucocladum，CL；翼果组，Sect. Pterococcus）和泡果沙拐枣（C. junceum，CJ；美丽沙拐枣组，Sect. Calliphysa）。分别于夏季和秋季采集绿色同化枝和同化枝枯落物，以评估氮（N）、磷（P）、钾（K）的再吸收效率（nitrogen resorption efficiency, NRE；phosphorus resorption efficiency, PRE；potassium resorption efficiency, KRE）的种间差异，并探究其化学计量关系、变化模式及环境影响。所有物种的养分再吸收效率（nutrient resorption efficiencies, NuREs）顺序为：KRE（65.03±0.57%）>PRE（53.57±0.48%）>NRE（23.36±0.70%）。在这三个类群中，蒙古沙拐枣（CM）的NRE（29.20±1.24%）和PRE（62.44±0.45%）最高，而泡果沙拐枣（CJ）的KRE最低（57.41±1.41%）。三个物种的NRE与PRE均呈现斜率大于2的尺度关系，表明氮的再吸收速率快于磷。PRE与KRE的尺度关系存在显著种间差异，其中泡果沙拐枣（CJ）呈现负斜率（-0.492）。NuREs与夏季绿色同化枝中的养分浓度呈正相关，而与同化枝枯落物中的养分浓度呈负相关。在物种内部，三种NuREs在地理、气候和土壤梯度上的变化模式总体相似，但显著的种间差异依然存在。土壤和气候条件被确定为NuRE变异的主要环境决定因素，尽管物种特异性响应表明，不同养分元素受环境因子间不同相互作用的影响。综上，这三种沙拐枣属植物表现出差异化的养分再吸收策略，与其内部养分状态和环境背景密切相关。这些发现为沙拐枣属及其他生长于干旱生态系统的同化枝灌木的养分利用策略和适应机制提供了有价值的见解。