Impacts of Climate Change on the Biogeography and Ecological Structure of Zelkova schneideriana Hand.-Mazz. in China.

This study utilized the platform for ensemble forecasting of species distributions, biomod2, to predict and quantitatively analyze the distribution changes of Zelkova schneideriana Hand.-Mazz. under different climate scenarios (SSP1-2.6 and SSP5-8.5) based on climate and land-use data. This study evaluated the geographic range changes in future distribution areas and the results indicated that, under both SSP1-2.6 and SSP5-8.5 scenarios, the distribution area of Zelkova schneideriana would be reduced, showing a trend towards migration to higher latitudes and elevations. Particularly, in the more extreme SSP5-8.5 scenario, the contraction of the distribution area was more pronounced, accompanied by more significant migration characteristics. Furthermore, the ecological structure within the distribution area of Zelkova schneideriana also experienced significant changes, with an increasing degree of fragmentation. The variables of Bio6 (minimum temperature of the coldest month), Bio2 (mean diurnal temperature range), Bio15 (precipitation seasonality), and elevation exhibited important influences on the distribution of Zelkova schneideriana, with temperature being particularly significant. Changes in land use, especially the conversion of cropland, had a significant impact on the species' habitat. These research findings highlight the distributional pressures faced by Zelkova schneideriana in the future, emphasizing the crucial need for targeted conservation measures to protect this species and similar organisms.

Regional environmental differences significantly affect the genetic structure and genetic differentiation of Carpinus tientaiensis Cheng, an endemic and extremely endangered species from China.

Differences in topography and environment greatly affect the genetic structure and genetic differentiation of species, and endemic or endangered species with limited geographic ranges seem to be more sensitive to changes in climate and other environmental factors. The complex topography of eastern China is likely to affect genetic differentiation of plants there. Carpinus tientaiensis Cheng is a native and endangered plants from China, and exploring its genetic diversity has profound significance for protection and the collection of germplasm resources. Based on AFLP markers, this study found that C. tientaiensis has low genetic diversity, which mainly came from within populations, while Shangshantou and Tiantai Mountain populations have relatively high genetic diversity. The Nei genetic distance was closely related to geographical distance, and temperature and precipitation notablely affected the genetic variation and genetic differentiation of C. tientaiensis. Based on cpDNA, this study indicated that C. tientaiensis exhibits a moderate level of genetic diversity, and which mainly came from among populations, while Tiantai Mountain population have the highest genetic diversity. It demonstrated that there was genetic differentiation between populations, which can be divided into two independent geographical groups, but there was no significant phylogeographic structure between them. The MaxEnt model showed that climate change significantly affects its distribution, and the suitable distribution areas in Zhejiang were primarily divided into two regions, eastern Zhejiang and southern Zhejiang, and there was niche differentiation in its suitable distribution areas. Therefore, this study speculated that the climate and the terrain of mountains and hills in East China jointly shape the genetic structure of C. tientaiensis, which gived rise to an obvious north-south differentiation trend of these species, and the populations located in the hilly areas of eastern Zhejiang and the mountainous areas of southern Zhejiang formed two genetic branches respectively.

Analysis of Nitrogen Dynamics and Transcriptomic Activity Revealed a Pivotal Role of Some Amino Acid Transporters in Nitrogen Remobilization in Poplar Senescing Leaves.

Leaf senescence is an important developmental process for deciduous trees during which part of leaf nitrogen is remobilized to branches, thus being beneficial for nitrogen conservation. However, the associated regulatory mechanism remains largely unknown in deciduous trees. In this study, nitrogen dynamics and transcriptomic activity in senescing leaves were measured during autumnal senescence in hybrid poplar. Both concentrations of leaf total nitrogen (N) and amine compounds were found to decline from the pre-senescence (PRE) to the middle-senescence (MS) stage. Although the total N concentration decreased further from MS to the late-senescence (LS) and leveled off to abscission (ABS) stage, amine compound concentration increased continuously from MS to ABS, suggesting that translocation of amine compounds underperformed production of amine compounds in leaves during this period. L-glutamate, L-glutamine and α-aminoadipic acid were the top three amine compounds accumulated in senescent leaves. RNA-Seq profiling identified thousands of differentially expressed genes (DEGs) with functional association with a metabolic transition towards disassimilation. Many genes encoding amino acid metabolism enzymes and amino acid transporters (AATs) were up-regulated. Comparison of expression trend with leaf N dynamics and phylogenetic analysis identified several PtAATs which exhibited down-regulation from MS to LS stage and putatively limited leaf N remobilization. This study can serve as a primary basis to further elucidate the molecular mechanisms of nitrogen remobilization in poplar senescing leaves.