Under changing climatic conditions, plants are simultaneously facing conflicting stresses in nature. Plants can sense different stresses, induce systematic ROS signals, and regulate transcriptomic, hormonal, and stomatal responses. We performed transcriptome analysis to reveal the integrative stress response regulatory mechanism underlying heavy metal stress alone or in combination with heat and drought conditions in pitaya (dragon fruit). A total of 70 genes were identified from 31,130 transcripts with conserved differential expression. Furthermore, weighted gene co-expression network analysis (WGCNA) identified trait-associated modules. By integrating information from three modules and protein-protein interaction (PPI) networks, we identified 10 interconnected genes associated with the multifaceted defense mechanism employed by pitaya against co-occurring stresses. To further confirm the reliability of the results, we performed a comparative analysis of 350 genes identified by three trait modules and 70 conserved genes exhibiting their dynamic expression under all treatments. Differential expression pattern of genes and comparative analysis, have proven instrumental in identifying ten putative structural genes. These ten genes were annotated as PLAT/LH2, CAT, MLP, HSP, PB1, PLA, NAC, HMA, and CER1 transcription factors involved in antioxidant activity, defense response, MAPK signaling, detoxification of metals and regulating the crosstalk between the complex pathways. Predictive analysis of putative candidate genes, potentially governing single, double, and multifactorial stress response, by several signaling systems and molecular patterns. These findings represent a valuable resource for pitaya breeding programs, offering the potential to develop resilient \"super pitaya\" plants.

Caragana sensu lato (s.l.) includes approximately 100 species that are mainly distributed in arid and semi-arid regions. Caragana species are ecologically valuable for their roles in windbreaking and sand fixation. However, the taxonomy and phylogenetic relationships of the genus Caragana are still unclear. In this study, we sequenced and assembled the chloroplast genomes of representative species of Caragana and reconstructed robust phylogenetic relationships at the section level. The Caragana chloroplast genome has lost the inverted repeat region and wascategorized in the inverted repeat loss clade (IRLC). The chloroplast genomes of the eight species ranged from 128,458 bp to 135,401 bp and contained 110 unique genes. All the Caragana chloroplast genomes have a highly conserved structure and gene order. The number of long repeats and simple sequence repeats (SSRs) showed significant variation among the eight species, indicating heterogeneous evolution in Caragana. Selective pressure analysis of the genes revealed that most of the protein-coding genes evolved under purifying selection. The phylogenetic analyses indicated that each section forms a clade, except the section Spinosae, which was divided into two clades. This study elucidated the evolution of the chloroplast genome within the widely distributed genus Caragana. The detailed information obtained from this study can serve as a valuable resource for understanding the molecular dynamics and phylogenetic relationships within Caragana.

Climate change and human activities drive widespread shrub encroachment in global grassland ecosystems, particularly in the Eurasian steppe. Caragana shrubs, the primary contributors to shrub encroachment in this region, play a crucial role in shaping the ecosystem\'s structure and function. Future changes in the suitable distribution range of Caragana species will directly affect the ecological security and sustainable socio-economic development of the Eurasian steppe ecosystem. We used an ensemble modeling approach to predict Caragana shrub-dominated plant communities\' current and future distribution in three major steppe subregions: the Black Sea-Kazakhstan steppe, the Tibetan Plateau steppe, and the Central Asian steppe. We assessed the potential risk of Caragana shrub encroachment by predicting changes in the suitable distribution area of 19 Caragana shrub species under future climate changes. Our research findings suggest that the expansion of Caragana species in different subregions of the Eurasian steppe is influenced by the effects of climate change in various ways. The distribution of Caragana species is primarily influenced by precipitation and temperature, and the global human modification (ghm) has a significant impact on the Central Asian and Tibetan Plateau subregions. Minimal changes are expected in the Black Sea-Kazakhstan subregion, a slight increase on the Tibetan Plateau, and a substantial rise in the Central Asian subregion, which suggests a higher potential risk of Caragana species shrub encroachment in that area. Our research provides valuable insights into the response of Caragana shrub encroachment to changing climates and human activities. It also has implications for the sustainable management of different areas of the vast Eurasian steppe ecosystem.

Vegetation restoration can effectively enhance soil quality and soil organic carbon (SOC) sequestration. In this study, the distribution characteristics of soil nutrients and SOC along soil profile (0-100 cm), and their responses to restoration years (16, 28, 38 years) were studied in Caragana korshinskii plantations in the southern mountainous area of Ningxia, compared with cropland and natural grassland. The results showed that: 1) the contents of SOC, soil total nitrogen (TN), total phosphorus (TP), particulate organic carbon (POC), mineral-associated organic carbon (MAOC) and the proportion of particulate organic carbon to total organic carbon (POC/SOC) all decreased with increasing soil depth. The ratio of mineral-associated organic carbon to total organic carbon (MAOC/SOC) exhibited an opposite trend. 2) The contents of SOC, TN, TP, C:P, N:P, POC and MAOC gra-dually decreased as the restoration years increased. However, the C:N ratio showed no significant change. The POC/SOC ratio initially increased and then decreased, while the MAOC/SOC ratio decreased initially and then increased. 3) In three different types of vegetation, POC, MAOC, and SOC showed a highly significant positive linear correlation, with the increase in SOC mainly depended on the increase in MAOC. The SOC, TN, TP, POC and MAOC contents in natural grassland and C. korshinskii plantations were significantly higher than those in cropland. In conclusion, soil nutrients and POC and MAOC contents of C. korshinskii plantations gradually decreased with the increases in restoration years. However, when compared with cropland, natural grassland and C. korshinskii plantations demonstrated a greater capacity to maintain and enhance soil nutrient and carbon storage.
植被恢复能有效改善土壤质量,促进土壤有机碳(SOC)的固存。本研究以宁南山区0～100 cm土层不同恢复年限(16、28、38年)柠条林为研究对象,以农田和天然草地作为对照,分析了土壤养分及有机碳组分沿剖面分布特征及其对恢复年限的响应。结果表明: 1)SOC、土壤全氮(TN)、全磷(TP)、颗粒态有机碳(POC)和矿物结合态有机碳(MAOC)含量以及颗粒态有机碳占总有机碳的比例(POC/SOC)均随土层深度增加而降低,而矿物结合态有机碳占总有机碳的比例(MAOC/SOC)呈相反趋势; 2)随着柠条恢复年限的增加,SOC、TN、TP、C∶P、N∶P、POC和MAOC含量逐渐降低,C∶N无显著变化,POC/SOC先增后减,MAOC/SOC先减后增;3)在3种土地类型中,POC、MAOC与SOC之间均呈极显著正线性相关关系,且SOC的增加主要依赖于MAOC的增加。天然草地和柠条林地土壤SOC、TN、TP、POC和MAOC含量均显著高于农田。综上,柠条林地土壤养分及POC、MAOC含量随着恢复年限增加逐渐降低;与农田相比,天然草地和柠条林地维持和提高土壤养分及碳储存的能力较高。.

Crown removal revitalises sand-fixing shrubs that show declining vigour with age in drought-prone environments; however, the underlying mechanisms are poorly understood. Here, we addressed this knowledge gap by comparing the growth performance, xylem hydraulics and plant carbon economy across different plant ages (10, 21 and 33 years) and treatments (control and crown removal) using a representative sand-fixing shrub (Caragana microphylla Lam.) in northern China. We found that growth decline with plant age was accompanied by simultaneous decreases in soil moisture, plant hydraulic efficiency and photosynthetic capacity, suggesting that these interconnected changes in plant water relations and carbon economy were responsible for this decline. Following crown removal, quick resprouting, involving remobilisation of root nonstructural carbohydrate reserves, contributed to the reconstruction of an efficient hydraulic system and improved plant carbon status, but this became less effective in older shrubs. These age-dependent effects of carbon economy and hydraulics on plant growth vigour provide a mechanistic explanation for the age-related decline and revitalisation of sand-fixing shrubs. This understanding is crucial for the development of suitable management strategies for shrub plantations constructed with species having the resprouting ability and contributes to the sustainability of ecological restoration projects in water-limited sandy lands.

BACKGROUND: The genus Caragana encompasses multiple plant species that possess medicinal and ecological value. However, some species of Caragana are quite similar in morphology, so identifying species in this genus based on their morphological characteristics is considerably complex. In our research, illumina paired-end sequencing was employed to investigate the genetic organization and structure of Caragana tibetica and Caragana turkestanica, including the previously published chloroplast genome sequence of 7 Caragana plants.
RESULTS: The lengths of C. tibetica and C. turkestanica chloroplast genomes were 128,433 bp and 129,453 bp, respectively. The absence of inverted repeat sequences in these two species categorizes them under the inverted repeat loss clade (IRLC). They encode 110 and 111 genes (4 /4 rRNA genes, 30 /31tRNA genes, and 76 /76 protein-coding genes), respectively. Comparison of the chloroplast genomes of C. tibetica and C. turkestanica with 7 other Caragana species revealed a high overall sequence similarity. However, some divergence was observed between certain intergenic regions (matK-rbcL, psbD-psbM, atpA-psbI, and etc.). Nucleotide diversity (π) analysis revealed the detection of five highly likely variable regions, namely rps2-atpI, accD-psaI-ycf4, cemA-petA, psbN-psbH and rpoA-rps11. Phylogenetic analysis revealed that C. tibetica\'s sister species is Caragana jubata, whereas C. turkestanica\'s closest relative is Caragana arborescens.
CONCLUSIONS: The present study provides worthwhile information about the chloroplast genomes of C. tibetica and C. turkestanica, which aids in the identification and classification of Caragana species.

Soil microorganisms are important components of terrestrial ecosystems, affecting soil formation and fertility, plant growth and stress tolerance, nutrient turnover and carbon storage. In this study, we collected soil samples (humus layer, 0-10 cm, 10-20 cm, 20-40 cm, and 40-80 cm) from Caragana jubata shrubland in Shanxi subalpine to explore the composition, diversity, and assembly of soil bacterial communities at different depths across the soil profile. The results showed that Actinomycota (19%-28%), Chloromycota (10%-36%) and Acidobacteria (15%-24%), and Proteobacteria (9%-25%) were the dominant bacterial phyla. α-diversity of soil bacterial community significantly decreased with the increases of soil depth. Soil bacterial β-diversity varied across different soil depths. Soil pH, water content, and enzyme activity were the main ecological factors affecting the distribution of soil bacterial communities. Soil bacterial communities had more complex interactions in humus layer and 0-10 cm layer. On the whole, soil bacterial communities were dominated by coexistence in C. jubata shrubland, and the soil bacterial community assembly was driven by random process.
土壤微生物是陆地生态系统的重要组成部分,影响着土壤形成和肥力、植物生长和胁迫耐受性、养分周转和碳储存等过程。本研究于山西亚高山鬼箭锦鸡儿灌丛采集了腐殖质层、0～10、10～20、20～40、40～80 cm土壤样品,探究不同深度土壤细菌群落组成、多样性以及土壤剖面细菌群落的构建机制。结果表明:芦芽山鬼箭锦鸡儿灌丛优势细菌门为放线菌门(19%～28%)、绿湾菌门(10%～36%)、酸杆菌门(15%～24%)和变形菌门(9%～25%)。芦芽山鬼箭锦鸡儿灌丛土壤细菌群落α-多样性沿土壤深度的增加而显著降低,并且不同深度土壤细菌群落的β-多样性存在显著差异。土壤pH、含水量和酶活性是影响细菌群落分布格局的主要生态因子。腐殖质层和0～10 cm土层土壤细菌群落具有更复杂的相互作用关系,但整体上鬼箭锦鸡儿灌丛土壤细菌群落以共存作用为主。土壤细菌群落的构建主要以随机过程为主。.

Microbial necromass, an important and stable source of soil organic carbon (SOC), is an important index to evaluate the contribution of microorganisms to SOC transformation and accumulation. It is not clear about the accumulation of microbial necromass in deep soil layer and its contribution to SOC during the restoration process of Caragana korshinskii forests. Combined with the biomarker method, we investigated the carbon contents of bacte-rial, fungal, and microbial necromass in the soil profiles (0-100 cm) of C. korshinskii forests in 16, 28, and 38 years of restoration, with natural grassland as control. We further examined the contribution of microbial necromass to soil organic carbon. The results showed that: 1) Along the soil profile (0-100 cm), the contents of fungal necromass carbon (FNC), bacterial necromass carbon (BNC), and microbial necromass carbon (MNC) significantly decreased with increasing soil depth in natural grassland and C. korshinskii forests. Except for the significant decrease in FNC/SOC, BNC/SOC, and MNC/SOC in the soil of C. korshinskii forests in 38 years of restoration, FNC/SOC and MNC/SOC generally showed an increasing trend followed by a decreasing trend in other plots, while BNC/SOC gradually decreased. 2) With the increases of restoration years, the contents of FNC, BNC, and MNC significantly decreased in C. korshinskii forests. FNC/SOC and MNC/SOC showed an overall increasing trend followed by a decreasing trend, while BNC/SOC gradually decreased. 3) The average contribution of microbial necromass carbon to SOC was highest in C. korshinskii forests in 28 years of restoration (35.0%), followed by C. korshinskii forests in 16 years of restoration (33.5%), natural grassland (31.0%), and C. korshinskii forests in 38 years of restoration (28.6%). In conclusion, when the restoration years of C. korshinskii forests are 16, the contents of microbial necromass carbon and their contributions to SOC are higher compared to natural grassland, which are beneficial for SOC sequestration.
微生物残体是土壤有机碳(SOC)重要且稳定的来源,已成为评价微生物对SOC转化和积累贡献的重要指标。目前尚不清楚柠条林恢复过程中深层土壤微生物残体的积累及其对SOC的贡献特征。本研究采用生物标志物方法,以宁南山区天然草地为对照,研究了恢复16年、28年和38年的柠条林地沿0～100 cm剖面土壤细菌、真菌、微生物残体碳含量及其对有机碳的贡献特征。结果表明: 1) 沿0～100 cm土壤剖面,随着土层深度的增加,天然草地和柠条林地土壤中真菌残体碳(FNC)、细菌残体碳(BNC)和微生物残体碳(MNC)含量均显著降低;除恢复38年的柠条林土壤FNC/SOC、BNC/SOC和MNC/SOC显著降低外,其余样地FNC/SOC、MNC/SOC总体上呈现先增加后降低的趋势,BNC/SOC则逐渐降低。2) 随着恢复年限增加,柠条林地土壤中FNC、BNC和MNC含量均显著降低;FNC/SOC和MNC/SOC总体上先增后减,BNC/SOC逐渐降低。3) MNC对SOC的平均贡献表现为恢复28年的柠条(35.0%)>恢复16年的柠条(33.5%)>天然草地(31.0%)>恢复38年的柠条(28.6%)。综上,与天然草地相比,当柠条林恢复年限为16年时,土壤微生物残体碳含量及其对SOC的贡献均较高,有利于SOC的固存。.

We investigated the changes of soil nutrients and plant communities in the artificial sand fixation forests of Caragana korshinskii with different ages. The results showed that soil organic carbon and soil total nitrogen contents increased with the stand ages, and were significantly higher in 40 and 50 year-old than other ages. Soil organic carbon and total nitrogen contents recovered much faster in the surface layer (0-10 cm) than in others. Soil nutrient stoichiometric ratios (C:P, N:P) in the 0-10 cm soil layer differed significantly among different stand ages. With the increases of stand age, C and N contents in C. korshinskii leaves increased significantly, and reached the maximum at 50 year-old. Leaf P content increased first and then decreased, being maximum at 18 year-old. Leaf C:N first increased and then decreased, being maximum at 12 year-old. The contents of photosynthetic pigments and leaf C:P and N:P decreased first and then increased, being minimum at 18 year-old. C. korshinskii was mainly influenced by N availability before 40 year-old, but mainly limited by P after. The species number, density, and vegetation cover of annual and perennial herbaceous plants increased with stand ages, and the community shifted from a simple shrub plant community to a complex shrub-herb community. The biomass of C. korshinskii and herbaceous plants increased significantly with stand age, and had a significant positive correlation with the contents of soil organic carbon, total nitrogen and N:P.
以晋西北丘陵风沙区不同林龄(6、12、18、40和50年)柠条锦鸡儿人工林为研究对象,分析其土壤养分和植物群落变化特征。结果表明: 土壤有机碳和全氮随着林龄的增加而增加,在40和50年时养分含量显著高于其他林龄,且土壤表层(0～10 cm)有机碳和土壤全氮恢复远快于其他土层,表层土壤养分计量比C∶P、N∶P在不同林龄间存在显著差异。随着林龄的增加,柠条锦鸡儿叶片C、N含量显著增加,在50年时达到最大值;叶片P含量先增加后减少,18年时达到最大值;叶片C∶N先增加后减少,12年时达到最大值;而光合色素含量、C∶P、N∶P均先减少后增加,18年时为最小值。林龄小于40年的柠条锦鸡儿主要受土壤N的影响,大于40年主要受P限制。柠条锦鸡儿林下一年生和多年生草本植物种类数量、密度、盖度均随林龄增加而增加,植物群落逐渐由简单的灌木向复杂的灌草群落演变。柠条锦鸡儿与草本植物生物量随着林龄的增加显著增加,且均与土壤有机碳、全氮含量和N∶P呈显著正相关关系。.

Caragana, a xerophytic shrub genus widely distributed in northern China, exhibits distinctive geographical substitution patterns and ecological adaptation diversity. This study employed transcriptome sequencing technology to investigate 12 Caragana species, aiming to explore genic-SSR variations in the Caragana transcriptome and identify their role as a driving force for environmental adaptation within the genus. A total of 3666 polymorphic genic-SSRs were identified across different species. The impact of these variations on the expression of related genes was analyzed, revealing a significant linear correlation (p < 0.05) between the length variation of 264 polymorphic genic-SSRs and the expression of associated genes. Additionally, 2424 polymorphic genic-SSRs were located in differentially expressed genes among Caragana species. Through weighted gene co-expression network analysis, the expressions of these genes were correlated with 19 climatic factors and 16 plant functional traits in various habitats. This approach facilitated the identification of biological processes associated with habitat adaptations in the studied Caragana species. Fifty-five core genes related to functional traits and climatic factors were identified, including various transcription factors such as MYB, TCP, ARF, and structural proteins like HSP90, elongation factor TS, and HECT. The roles of these genes in the ecological adaptation diversity of Caragana were discussed. Our study identified specific genomic components and genes in Caragana plants responsive to heterogeneous habitats. The results contribute to advancements in the molecular understanding of their ecological adaptation, lay a foundation for the conservation and development of Caragana germplasm resources, and provide a scientific basis for plant adaptation to global climate change.