Malus sieversii f. niedzwetzkyan, a wild species capable of growing on saline-alkali soil in Xinjiang, is the most promising horticultural crop for improving the saline-alkali wasteland. However, the tolerance of M. niedzwetzkyan to saline-alkali stress and the underlying molecular mechanisms remains largely unknown. Here, we conducted a hydroponic experiment in which M. niedzwetzkyana and M. domestica “Royal Gala” seedlings were subjected to 150 mM saline-alkali stress. Physiological data showed that M. niedzwetzkyana had a strong ROS scavenging ability and ion transport ability, and its saline-alkali resistance was higher than that of M. “Royal Gala”. Saline-alkali stress also promoted the synthesis of anthocyanins in M. niedzwetzkyana. Transcriptome analysis was conducted on the leaves and roots of M. niedzwetzkyana at different time points under saline-alkali stress (0 h, 6 h, and 12 h). Transcriptome analysis revealed that saline stress down-regulated most genes involved in the anthocyanin flavonoid synthesis pathway. Transcription levels of genes involved in antioxidant enzyme activity and ion transport were altered. We identified hub genes related to superoxide dismutase as well as Na⁺ and K⁺ transport using weighted gene co-expression network analysis. This study elucidated, for the first time at the molecular level, the saline-alkali tolerance of M. niedzwetzkyana, including the complex changes in pathways that regulate reactive oxygen species homeostasis, ion uptake, and anthocyanoside synthesis under saline-alkali stress conditions. This research provides an important genetic resource for identifying genes involved in responses to saline-alkali stress.

Populus euphratica is the only tall tree species that adapts to the desert environment. It has strong drought tolerance and is the subject of extreme concern at home and abroad. After 30 years of development, the scope of research on Populus euphratica is very extensive, but the research content has not yet been crystalized into a mature field, and research directions at home and abroad differ. In this study, we retrieved research references on ‘P. euphratica’ published from 1992 to 2022 in both the China National Knowledge Infrastructure core journals database and the Web of Science core collection database, and CiteSpace software was employed to conduct keyword-centered bibliometric analysis in both the spatial and temporal dimensions. The purpose of this study is to clarify the research areas, developmental changes, differences between domestic and international research priorities in the last 30 years, and future trends in the field of P. euphratica research. The results show that there were 1619 domestic papers published in China related to the field of P. euphratica research, while there were only 656 foreign papers in the same field. The development of domestic P. euphratica research went through three stages initiation (1992–2000), growth (2001–2008) and stability (2009–2021), whereas no significant international trend change was observed. The domestic disciplines focus on biology, while international research focuses on crop science. In terms of content, domestic research focuses on sustainable uses of P. euphratica forests and their response to drought, intending to improve P. euphratica ecosystems. International research, on the other hand, focuses on revealing mechanisms of environmental stresses, including genetic and physiological–morphological characteristics, to exploit the excellent characteristics of P. euphratica to serve agriculture and other fields. The development process of P. euphratica research in the past 30 years has generally evolved from an initial focus on its natural conditions towards the study of the relationship between environmental factors and P. euphratica physiological and morphological characteristics and, finally, the study of stress tolerance mechanisms and gene expression of P. euphratica. There is a trend towards ‘applications of P. euphratica tolerance genes’, which may represent a direction for future growth research.

Impacts of ocean acidification (OA) on noncalcifying organisms and the possibly responsible mechanism have aroused great research interests with the intensification of global warming. The present study focused on a noxious, noncalcifying, bloom-forming dinoflagellate, Karenia mikimotoi (K. mikimotoi), and its variation of growth patterns exposed to different periods of seawater acidification with stressing gradients was discussed. The dinoflagellates under short-time acidifying stress (2d) with different levels of CO₂ presented significant growth inhibition (p < 0.05). The cell cycle was obviously inhibited at S phase, and the photosynthetic carbon fixation was also greatly suppressed (p < 0.05). Apoptosis was observed and the apoptotic rate increased with the increment of pCO₂. Similar tendencies were observed in the key components of mitochondrial apoptotic pathway (the mitochondrial membrane potential (MMP), Caspase-3 and -9, and Bax/Bcl-2 ratio). However, under prolonged stressing time (8 d and 15 d), the growth of dinoflagellates was recovered or even stimulated, the photosynthetic carbon fixation was significantly increased (p < 0.05), the cell cycle of division presented little difference with those in the control, and no apoptosis was observed (p > 0.05). Besides, acidification adjusted by HCl addition and CO₂ enrichment resulted in different growth performances, while the latter had a more negative impact. The results of present study indicated that (1) the short-time exposure to acidified seawater led to reduced growth performance via inducing apoptosis, blocking of cell cycle, and the alteration in photosynthetic carbon fixation. (2) K. mikimotoi had undergone adaptive changes under long-term exposure to CO₂ induced seawater acidification. This further demonstrated that K. mikimotoi has strong adaptability in the face of seawater acidification, and this may be one of the reasons for the frequent outbreak of red tide. (3) Ions that dissociated by the dissolved CO₂, instead of H⁺ itself, were more important for the impacts induced by the acidification. This work thus provides a new perspective and a possible explanation for the dominance of K. mikimotoi during the occurrence of HABs.

Litter decomposition is important for understanding the effects of habitat on nutrient cycling. In this study, we investigated the decomposition characteristics, decomposition variability, and regulatory factors restricting the decomposition rates of leaf litter in three different habitats: a flood disturbance habitat, an arid habitat, and a high-salinity habitat. The litter decomposition rates of the habitats decreased in the following order: flood disturbance habit > arid habitat > high-salinity habitat. The organic carbon, total nitrogen, and lignin residues of the litter during the decomposition period were highest in the high-salinity habitat. The litter quality was the main regulator of the release of phosphorus and cellulose residues, which exhibited different release processes and patterns in these three habitats. The litter decomposition coefficient was negatively correlated with litter carbon residue in the flood disturbance habitats, the lignocellulose index in the arid habitats, and soil urease in the high-salinity habitats. It was positively correlated with the lignocellulose index in flood disturbance habitats and litter carbon residue in high-salinity habitats. The litter quality in the flood disturbance area played a significant role in litter decomposition, while environmental quality and litter quality were the dominant factors under arid and high-salt conditions. Litter quality in the flood disturbance area played a significant role in litter decomposition, while both environmental quality and litter quality were the dominant factors under arid and salt conditions.

The relationship between the spatial structure of shelter forests and the diversity of understory herbaceous plants in desert–oasis ecotones is important for maintaining biodiversity indices and protecting the oasis ecosystem. In this paper, we explore the coupling relationship between tree layer structure (competition index, angle scale, neighborhood comparison, DBH, etc.) and understory herb diversity in the transition zone of shelter forest plots near oases and near deserts; in addition, we also aim to elucidate the dominant stand structure factors affecting herb biodiversity. The results indicated the following: A total of 13 herbaceous plant species were discovered in the transitional zone, with 11 species found near the oasis area and 4 species near the desert region. The Shannon, Simpson, and Pielou indices of understory herbaceous plants were significantly higher near the oasis area compared to the desert region. The Margalef index mean was higher in the oasis area compared to the desert region. Pearson and canonical correlation analyses revealed significant associations between specific stand structure indicators and diversity in the herbaceous layer. The results of the multiple linear regression analysis revealed that the competition index had a significant impact on the Shannon, Simpson, and Pielou diversity indices of the herbaceous layer in the understory of the shelterbelt forest near the oasis, with corresponding impact coefficients of 0.911, 0.936, and 0.831, respectively. The mingling degree was found to be the primary influencing factor for the Margalef index, with an impact coefficient of 0.825. However, in the understory of the shelterbelt forest near the desert, the neighborhood comparison ratio negatively affected the Shannon and Margalef indices, with impact coefficients of −0.634 and −0.736, respectively. Additionally, tree height negatively impacted the Simpson and Pielou indices, with impact coefficients of −0.645 and −0.677, respectively. In order to enhance the diversity of understory herbaceous species in the transitional zone and preserve the ecological system of the oasis, specific modifications to the forest structure and arrangement are essential. Pruning and thinning are necessary for shelterbelt forests located near desert regions, while shelterbelt forests near oases should use a suitable mix of tree species. These measures can help preserve or enhance the diversity of understory herbaceous plants.

Aims: Land-use types and soil salinization in arid desert–oasis ecotones are associated with differences in soil CO₂ efflux, yet the combined effects of multiple environmental factors remain poorly understood. This study aims to characterise the seasonal patterns, temperature sensitivity, and major correlates of soil respiration across four typical land-use types, thereby supporting regional carbon budget assessments. Methods: We conducted in situ soil respiration monitoring during the 2024 growing season (April–October) in four representative habitats (Populus euphratica forest, jujube orchard, grassland, and wetland) in the Aksu desert–oasis ecotone, Xinjiang. Concurrent measurements of topsoil (0–20 cm) physicochemical properties and extracellular enzyme activities were taken. Pearson correlation, variation partitioning, and the Van’t Hoff temperature-response model were employed. Results: Soil respiration exhibited a unimodal seasonal pattern peaking in July, with growing-season mean fluxes ranked as grassland > wetland > jujube orchard > Populus euphratica forest. Temperature sensitivity (Q₁₀) followed wetland (3.23) > grassland (2.44) > orchard (2.08) > forest (1.57), a pattern consistent with differences in soil moisture and salinity among the sites. Respiration correlated positively with pH, electrical conductivity, total salt, organic matter, urease, and sucrase, and negatively with available N, P, K, and peroxidase (p < 0.05). Physicochemical properties and enzyme activities jointly explained 70.7% of variation, with total soil salt (12.5%), sucrase (12.2%), and available N (11.1%) as the top contributors. Root and heterotrophic respiration accounted for 37.2% and 62.8% of total soil respiration, respectively, with heterotrophic respiration dominating in all seasons. Conclusions: Soil CO₂ emissions differed markedly among the four land-use types, and these differences were associated with water–salt–thermal–nutrient–enzyme conditions. Carbon cycling mechanisms in wetlands and grasslands differ markedly from those in woody habitats, highlighting the need for differentiated land-use planning and salinity-adapted carbon management strategies in arid regions.