Spatial patterns and associations of plant species are important for revealing how species interact with each other and with the environment, and hence have important implications for the understanding of species interaction and underlying ecological processes with apparent patterns in temperate desert vegetation. In this paper, the function g (r) was used to characterize the spatial patterns and associations of four dominant woody species in three 1-ha desert plant plots in the desert-oasis ecotone of South Junggar Basin, NW China. The complete spatial randomness null model showed four species exhibited significant aggregations at small scales (<20 m). Anabasis aphylla and Nitraria roborowskii, Haloxylon ammodendron and Reaumuria songarica were spatially positive associations at small scales with the independent null model, while A. aphylla and H. ammodendron, A. aphylla and R. songarica, R. songarica and N. roborowskii species pairs exhibited negative associations at small or moderate scales (20-60 m) in our study. The random labeling null model showed that dead standing plants of A. aphylla were largely determined by the combined effects of intra-and interspecific competition. In addition, the results also indicated that the two main factors of habitat heterogeneity and sandy desertification play important roles in determining spatial distribution patterns and associations of woody species in the desert-oasis ecotone of South Junggar Basin. Thus, the differences of species features in spatial patterns and associations should be paid more attention when planning afforestation and developing conservation strategies.

Cold stress is one of the major environmental factors that affects plant growth, development, and species distributions. In order to study the molecular mechanism of cold-stress responses in Anabasis aphylla seedlings, we used the isobaric tags for relative and absolute quantification (iTRAQ) technique to identify differential protein expression under cold stress. In total, 211 differentially expressed proteins were identified, including 109 up-accumulated proteins and 102 down-accumulated proteins, these cold-stress response proteins were mainly identified as proteins involved in carbohydrate and energy metabolism, protein metabolism and translation, stress response, transcription-related, amino acid metabolism, signal transduction, and membrane and transport. GO and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analyses indicated that most of the proteins related to cold-stress response were involved in carbohydrate and energy metabolism, indicating A. aphylla seedlings adapted to cold conditions mainly through changes in energy metabolism pathways. Additionally, the correspondence between mRNA transcript levels and protein abundance levels for nine accumulated proteins were also tested by qRT-PCR, only one protein did not show consistent trends in mRNA and protein levels. These data clarify our current understandings of stress responses in seedlings of species such as A. aphylla and identify the molecular mechanisms of the cold-stress responses.

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This study aimed to explore differences in the low-temperature tolerance of a desert plant, Anabasis aphylla, at different seed germination stages during the fall using transcriptome sequencing to identify related genes. The survival rate of the seeds decreased with lower temperatures at different germination stages, and the tolerance of the stages in decreasing order was as follows: imbibition (I) ≈ testa rupture (II) > testa removal (III) > elongation (IV). Superoxide dismutase, peroxidase, and catalase activities and the malondialdehyde content showed a downward trend after stage II. Transcriptome sequencing of seeds, including ripe and dry dominant seeds (W1) and seeds during different germination stages [imbibition (W2), testa removal (W3), and elongation (W4)] was performed. Some genes were downregulated during seed germination, which mainly included cytochrome P450, oleosin, ethylene-responsive transcription factor, and low temperature-induced protein. This study suggests that downregulated of some genes may result in a decrease in lowtemperature tolerance.