Study on paleovegetation is with great significance on understanding the modern vegetation composition, distribution, and its responses to global change. During recent decades, it has been a rapidly developing field in molecular palaeoecology to track the long-term vegetation composition and plant diversity changes by using sedimentary ancient DNA. Meanwhile, the lacustrine sedimentary ancient plant DNA (PsedaDNA) is becoming a popular proxy for palaeovegetation and palaeoecological studies. However, the modern process of PsedaDNA remains unclear compared with pollen analysis, which limits its further application. Here, we reviewed the PsedaDNA researches and tried to elucidate the modern processes of PsedaDNA, including the source, deposition, and preservation processes, and to understand the relationships between the PsedaDNA and modern vegetation. PsedaDNA is mainly derived from the lake surroundings or within the catchment. The abundance and composition of PsedaDNA are influenced by the biomass of terrestrial plants, and factors such as DNA degradation, the adsorption, and dilution of particles in soils and sediments during the transportation and deposition. Moreover, the preservation of PsedaDNA is largely affected by both biotic and abiotic factors, including the microbial activity, chemical properties of lake water (conductivity and pH), and sediment composition. PsedaDNA can be used to reveal the contemporary vegetation and climate information but was incompetent to quantitatively palaeovegetation reconstruction. Considering the complexity of modern processes, the interpretation of PsedaDNA results should be done with extra caution. To sum up, PsedaDNA is still in its infancy, which has been benefiting from the progress of molecular biotechnology, optimization of experimental design, species barcodes, and sophistication of reference databases. The PsedaDNA technique including DNA metabarcoding and metagenomics will certainly promote the development of Chinese palaeophytoecology research.

Aims Revealing occurrence mechanisms of autumn phenology in temperate deciduous trees is of vital importance for improving estimation accuracies of ecosystem carbon sequestration and vegetation productivity. This study aimed to uncover the mechanisms of leaf senescence in response to environmental changes and simulation accuracies of autumn phenology through process-based models, and further investigate impacts of water conditions on leaf senescence mechanisms and simulation accuracy of autumn phenology.

Methods We used the low temperature and photoperiod multiplicative model (TPM) to fit the first leaf coloration dates and leaf fall end dates of six tree species at more than 90 stations across the temperate zone of northern China from 1981 to 2014. The TPM contains two sub-models, i.e., photoperiod-initiated leaf senescence model (TPM_p) and temperature-initiated leaf senescence model. We evaluated simulation accuracies and their spatiotemporal variations of station-species specific optimum models, and analyzed regional differentiation of proportions of two sub-models among optimum models and its spatial dependence on arid-humid gradient.

Important findings (1) Photoperiod shortening plays more important roles in initiating leaf senescence than temperature decrease. The simulated average root mean square errors of optimum models for first leaf coloration and leaf fall end dates are 6.9 d and 6.0 d, respectively. Proportions of significantly positive correlations between simulated and observed time series are 71.4% (first leaf coloration) and 83.6% (leaf fall end), respectively. (2) Simulated regional mean absolute errors and multi-year mean absolute errors of optimum models for first leaf coloration date and leaf fall end date are less than 2.4 d. However, amplitudes of temporal and spatial variations in simulated phenological dates are usually smaller than those in observed phenological dates, which are closely related to the high temporal variability of autumn phenological occurrence date. (3) Water conditions affect the selection of leaf senescence initiation pathways to a certain extent. This is mainly manifested in that proportions of TPM_p among optimum models for first leaf coloration dates in arid and semi-arid regions are higher than those in humid and semi-humid regions, while simulation accuracies of optimum models in humid and semi-humid regions are higher than those in arid and semi-arid regions.

Aims Amygdalus pedunculata is a relict shrub plant, distributed in arid and semi-arid deserts and mountainous areas of northwest China. In order to understand its distribution and evolution under the historical climate change, we performed an analysis on 60 natural distribution points and 8 environmental factors, using GIS spatial analysis and maximum entropy model MaxEnt 3.4.1. We then analyzed the changes in geographical distributions and their environmental drivers of A. pedunculata during the Last Inter Glacial (LIG), the Last Glacial Maximum (LGM) and the present period.

Methods Based on the simulated distribution data of A. pedunculata in different periods and chloroplast gene data of the natural populations, we simulated the possible diffusion path of A. pedunculata since the LIG period by the least cost path method. Principal component analysis (PCA) was used to analyze the historical environmental variables in the suitable areas of A. pedunculata in different periods by “ggbiplot” package of R language. By doing so, we then determined the key climatic factors affecting the historical distribution pattern of A. pedunculata.

Important findings The historical distribution of A. pedunculata has experienced significant contraction since the LIG period but significant expansion after the LGM. From the LIG to the LGM period, the suitable distribution areas of A. pedunculata significantly contracted in the eastern Hobq Desert, the northern Mau Us Desert, the northern Shaanxi Province, the northern Yinshan Mountain, the southern Ulan Qab Plateau, and the Onqin Daga Desert. In contrast, since the LGM, A. pedunculata has undergone significant expansion in the eastern Hobq Desert, the central Mau Us Desert, east Yinshan Mountain, and the western Onqin Daga Desert. There were highly suitable distribution areas of A. pedunculata in the middle and western parts of Nei Mongol Plateau in three periods, including the northern edge of Mau Us Desert, the eastern edge of Hobq Desert and Daqing Mountain. It is possible that these areas may be the ice age shelter of A. pedunculata. The Yin Shan Mountain in the north and the edge of Mau Us Desert was the important diffusion corridor. From the LIG to the LGM, the temperature, including the min temperature of the coldest month, the annual mean diurnal range and the max temperature of the warmest month, all fluctuantly decreased over time. The distribution of A. pedunculata during the ice age was limited by the cold and dry climate, and the suitable area contracted significantly. The precipitation in wettest month and the precipitation seasonality have increased significantly since the LGM period. Amygdalus pedunculata has expanded significantly in the eastern Hobq Desert, the central part of Mau Us Desert, Yinshan Mountain and the western Part of Onqin Daga Desert. Precipitation was also a key limiting factor affecting the current suitable distribution.

Aims Wetland is a typical ecotone between terrestrial and aquatic ecosystems, with very high levels of habitat heterogeneity and biodiversity. The complex community structure and species interactions may have unusual pollination networks as compared to other ecosystems such as meadows and forests, which will affect species coexistence and community assembly. Our objective was to determine the pollination network and its seasonal dynamics in a tropical wetland.

Methods In this research, we studied pollination networks in four plots of Yangshan Wetland on Hainan Island, in dry seasons (May) and rainy seasons (August) respectively. Two 10-m-long walked line transects were set in each plot to sample pollination events. Both pollinators and their visitation times on each flower (plant) were recorded to determine the pollination networks.

Important findings The results showed that the species of plants and pollinators in the dry season were richer than that in the rainy season. The pollination network structure was not different between two seasons, and the visitation relationship between plant and pollinator species was relatively stable in the two seasons. There was no seasonal difference in connectance, nestedness and network specialization (H′₂) on pollination network. The nestedness and H′₂ of Plot 4 with higher species diversity fluctuated less in seasonal dynamic, and species relationships was stable in the community of 4 plots.

Aims Impatiens davidii, a rare ornamental flower endemic to China, had a small wild population and depended on pollination of Bombus trifasciatus. As I. davidii has a specialized pollination system, pollination resources were one of the important factors limiting its population diffusion.

Methods In this study, the maximum entropy (MaxEnt) model was used to simulate the potential distribution area of the two species based on 63 distribution records of I. davidii, 54 distribution records of B. trifasciatus, and 19 climatic factors. The potential distribution of the two species under three climate representative concentration pathway scenarios RCP2.6, RCP4.5, and RCP8.5 were predicted for the future (2050s, 2070s).

Important findings The results showed that the main environmental factor affecting the distribution of I. davidii was precipitation of warmest quarter. Under the current climate conditions, the range overlap, niche overlap, and niche breadth of two species were higher. Approximately 99.09% of the suitable areas of I. davidiiwas overlapped with B. trifasciatus, which ensured the pollination resources to a large extent. Under the three future climate scenarios, the distribution area of I. davidii will expand to northeast and north China, and the suitable habitat area will increase by 66 000-221 900 km². The suitable habitat area of B. trifasciatus moved northward slightly, and increased by 44 800-155 000 km². The proportion of suitable habitat areas of I. davidii overlapped with B. trifasciatus decreased by 1.40%-9.00%, indicating that the suitable area of I. davidii might be affected by climate change and lack of pollination resources in the future.

Aims The input of exogenous organic matter can affect the mineralization of soil organic carbon (SOC) through positive or negative priming effects. However, few studies have considered the effect of dissolved organic matter (DOM) derived from different plant and tissues on soil priming effect and revealed the underlying mechanisms.

Methods In this study, we investigated the different priming effects of ¹³C-labeled DOM derived from roots and leaves of different plants (i.e., Cyclobalanopsis glauca, Cunninghamia lanceolata, Manglietia fordiana and Acacia confusa) on SOC mineralization and clarifying the underlying mechanisms via an incubation experiment of soils sampled from Wuyi Mountain.

Important findings Inputs of DOM derived from different plant and tissues all accelerated the mineralization of SOC, exhibiting a positive priming effect at the initial stage after DOM input, and then showed a negative priming effect. For the cumulative priming effect during the whole incubation period (90 d), the input of DOM inhibited the mineralization of SOC, with the reduction magnitude ranging from 22% to 49%. Among them, the input of DOM derived from roots of Cyclobalanopsis glauca had the most pronounced effect on the reduction of SOC mineralization, while the input of DOM derived from leaves of M. glauca had the least effect on reduction of SOC mineralization. The intensity of soil priming effect induced by DOM was significantly affected by different plant tissues. DOM derived from plant roots showed more pronounced negative priming effect than DOM derived from plant leaves. In general, DOM input increased soil microbial biomass carbon (MBC) and soil β-glucosidase activities and cellobiohydrolase activities and soil available nitrogen content, but had no significant effect on the composition of soil microbial community. The structural equation model showed that soil priming effect induced by DOM was mainly affected by soil ¹³C-MBC, cellobiohydrolase activity and soil available nitrogen content. Changes in these factors could explain 68% and 86% of the variation of priming effect induced by plant leaf-derived DOM and root-derived DOM, respectively. The results suggested that if the soil is rich in available nitrogen, DOM input can accelerate the decomposition of exogenous organic matter through increasing microbial biomass and soil enzyme activity, and thus reducing the decomposition of SOC. Therefore, “substrate preferential utilization” is the main mechanism of soil priming effect in this study.

Aims Phosphorus is one of the major limiting nutrients for plant growth in subtropical areas, whereas increasing nitrogen deposition may be a limiting factor in determining the availability of soil phosphorus. Here, focusing on soil microorganisms and plant fine roots, we explored the transformation of soil phosphorus to unravel the maintenance of soil phosphorus supply and plant productivity with low availability under nitrogen deposition.

Methods At the Fuzhou Changʼan Mountain in Fujian Province, China, control (0 kg·hm^-2·a^-1), low nitrogen (40 kg·hm^-2·a^-1), and high nitrogen (80 kg·hm^-2·a^-1) treatments were set up to simulate nitrogen addition. Soil and root samples of Cunninghamia lanceolata seedlings were then collected to comprehensively analyze soil phosphorus and nutrient contents as well as microbiological-plant root characteristics.

Important findings The results showed that the contents of soil labile organic phosphorus, moderately labile inorganic phosphorus and occluded phosphorus were significantly increased, whereas those of primary mineral phosphorus and moderately labile organic phosphorus decreased under the low nitrogen treatment as compared to the control treatment. However, there were no significant changes under the high nitrogen treatment. Redundancy analysis indicated that soil acid phosphatase activity, relative abundance of mycorrhizal fungi, soil microbial biomass phosphorus content, and root biomass were important soil microbiological-plant root characteristics factors that could explain the changes in soil phosphorus components. Variance partitioning analysis revealed that the soil microbiological-plant root characteristics synergy explained 57% of the alternations in soil phosphorus components, whereas correlation analysis showed a significant positive correlation between the relative abundance of mycorrhizal fungi and root biomass. Overall, these results suggest that mycorrhizal colonization is promoted under a low level of nitrogen input and the synergistic action of mycorrhizal fungi and C. lanceolata fine roots promotes the conversion of moderately labile organic and primary mineral phosphorus to labile phosphorus, thus maintaining the growth of C. lanceolata seedlings.

Aims The formation of the geographical range boundary of species has always been an important topic in evolutionary biology. Although plant-microbe interactions have been extensively studied, we have a poor understanding of how plant's geographic range limits affect soil microorganisms. Cephalostachyum pingbianense is a rare bamboo species documented that produces bamboo shoots all year round in the wild, and is endemic to southeast Yunnan Province, China. The species is of great significance to study narrow endemic species in Bambusoideae. Here, we aim to reveal the relationship between the range limits of C. pingbianenseand soil fungal community.

Methods We assayed soil physical and chemical properties at the center, edge and beyond the range of C. pingbianense, and changes of fungal community were analyzed by means of Internal Transcribed Spacer (ITS) sequence based Illumina MiSeq high-throughput sequencing techniques.

Important findings (1) Soil pH and available phosphorus content at the range edges was significantly lower than other sites. (2) At the range center, species diversity of soil fungi was the highest, and relative abundance of Mortierella was significantly higher than other sites. At the range edges, species diversity of soil fungi was the lowest, and relative abundance of Basidiomycota was greater than 65.0%. (3) Soil pH played a crucial role in driving the variation of fungal community, which was negatively correlated with the relative abundance of ectomycorrhizal fungi, and positively correlated with the relative abundance of saprophytic fungi. Soil acidification and phosphorus deficiency may be important soil properties controlling the distribution range of C. pingbianense. Mortierella may be important mutualists of C. pingbianense, which can desorb phosphorus from soil minerals and reduce acidification of soil.

Aims In this study, we sought to determine changes in soil extracellular enzyme activities and their stoichiometric characteristics during the process of karst rocky desertification and their ecological response to environmental variation.

Methods Soil ecosystems at five stages of rocky desertification were selected for investigation and we applied the theory and methods of ecological stoichiometry to systematically study the effects of rocky desertification on the activities of six extracellular enzymes (β-1,4-glucosidase, cellobiohydrolase, β-1,4-xylosidase, β-1,4-N- acetylglucosaminidase, leucine aminopeptidase, and acid phosphatase). We also analyzed correlations between enzyme activities and environmental factors.

Important findings The results revealed that the extracellular activities of β-1,4-glucosidase, cellobiohydrolase, β-1,4-xylosidase, and leucine aminopeptidase, in the no, potential, and slight stages of rocky desertification were significantly higher than those in the moderate and severe stages. In contrast, the stoichiometric characteristics of soil extracellular enzymes showed no significant differences among the different stages of rocky desertification. The quality of soil at the different stages of desertification could be roughly divided into three categories, namely, the biochemical properties of non-rocky desertification soil were superior to those at the potential and slight stages, which in turn were superior to those at the moderate and severe stages. In addition, soils at the no, potential, and slight stages of rocky desertification were found to be phosphorus deficient (the enzyme vector angle was greater than 45°), whereas soils at the moderate and severe stages were deficient in nitrogen (the enzyme vector angle was less than 45°). Moreover, we established that during the process of rocky desertification, the changes in soil extracellular enzyme activities and their stoichiometric characteristics were mainly influenced by soil total nitrogen, available phosphorus, nitrate nitrogen, ammonium nitrogen, and litter phosphorus contents. The observed changes in soil extracellular enzyme activities were found to be correlated with changes in nutrient contents, and tended to be limited by litter phosphorus content. On the basis of these findings, as measures to alleviate the associated nutrient limitations, we would recommend supplementation with phosphorus in the potential and slight stages of rocky desertification and the supplementary application of nitrogen in the moderate and severe stages during the restoration of rocky desert ecosystems.

Plot-based data are an important foundation for studying plant community characteristics and compiling vegetation monographs, vegetation map, and vegegraphy. It is the key data source of studies in vegetation ecology. To understand the species composition, community characteristics, and distribution pattern of special plateau vegetation on the Qingzang Plateau (QZP), this study uses the data of 338 sites including 758 plots in different regions of the QZP from 2018 to 2021 to analyze the species composition, floristic characteristics, and vegetation classification of plateau plant communities. A plot-based dataset of plant community on the QZP is then established. The 758 plots have 837 plant species belonging to 279 genera from 65 families in the alpine and temperate vegetation communities. The largest number of species are found in five families: Asteraceae (134 species), Poaceae (88 species), Fabaceae (75 species), Rosaceae (43 species), and Cyperaceae (40 species), as well as five genera: Artemisia (29 species), Pedicularis (27 species), Saussurea (25 species), Astragalus (23 species), and Poa (23 species). The floristic composition is mainly temperate (145 genera) and cosmopolitan (36 genera). The growth forms of the species are mainly herbs (83.51%) and shrubs (10.87%), and the life forms of herbs and woody plants are mainly perennial herbs (88.23%) and deciduous shrubs (83.67%), respectively. A total of 338 sites can be divided into four vegetation formation groups, 10 vegetation formations, 20 vegetation subformations, 78 alliance groups, and 117 alliances, in which 34 are steppe alliances, 33 are meadow alliances, 33 are desert alliances, 14 are shrubland alliances, and 3 are coniferous forest alliances. This dataset covers most of the alpine shrubland, meadow, steppe, desert, and temperate steppe, desert vegetation regions of the QZP. This work provides a solid foundation for exploring the vegetation characteristics and regularity of vegetation zonal differentiation and determining the impacts of climate change and human disturbances on alpine vegetation and their ecological restoration. The dataset also provides a reference for the updating of the next generation of China's vegetation map.