Aims Various colors combined with symbols are usually employed to differentiate vegetation types in vegetation mapping, aiming to convey the vegetation information to readers more visually and clearly. How to differentiate vegetation types by appropriate setting of color and symbol is a key step in vegetation mapping, especially for regions with diverse vegetation types. Usually, vegetation map legends are based on the vegetation classification system. Recently, the vegetation classification system of China has been revised according to the achievements in vegetation surveys and research over the past decade. Therefore, it is necessary to put forward a new color and symbol setting scheme for vegetation mapping. Our objective is to improve the scientificity and artistry of current vegetation mapping.
Methods The principles of color and symbol setting of existing vegetation maps and other thematic maps were summarized. Based on the principles of systematicness, scientificity and symbolism, the changes and combinations of the three color attributes (hue, lightness and saturation) and the basic visual variables (shape, size, direction, color, density and brightness) of the symbols were taken in consideration for the national vegetation map legends. In the legends, Vegetation Formation Groups were differentiated by hues, and Vegetation Formations and Vegetation Subformations were represented by different lightnesses and saturations. In addition, different symbols attached to the colors were employed to distinguish vegetation types. The colors and symbols were designed to reflect the physiognomy and habitats of the vegetation types as much as possible.
Important findings The principles of color and symbol setting for vegetation mapping and a new scheme of national vegetation map legends were presented. These results would provide guideline for vegetation cartographer to set the legends of the new Chinese vegetation map (1:500 000).

Aims When the external environment changes, plants can change their own functional traits and adjust adaptation strategies in a timely manner. Therefore, plant functional traits can effectively reflect the response of plants to the change of grassland use. However, there are few studies on the effects of grassland use patterns from the perspective of plant functional traits in the Nei Mongol grassland. Therefore, from the perspective of functional traits, this paper reveals the adaptation strategies of plants after external disturbances, aiming to provide basic data support and scientific basis for the sustainable management of natural grasslands.
Methods In this study, four important dominant species of Stipa grandis, Leymus chinensis, Cleistogenes squarrosa and Artemisia frigida in the typical grasslands of Nei Mongol were selected as the research objects to explore the differences in the functional traits of dominant species under the influence of long-term free grazing, mowing, short-term enclosed and long-term reservation.
Important findings We found that: 1) Vegetation height, root length and carbon and nitrogen concentration of dominant plants in Nei Mongol typical grasslands are reduced under long-term grazing. Changes in these traits can miniaturize individual plants and reduce their palatability, indicating that plants may adopt avoiding grazing strategy to adjust to the interference of long-term free grazing. Under the mowing management, the vegetation height and specific leaf area of the dominant species tend to increase. Among them, the nitrogen content of A. frigida is the most sensitive to the response of mowing. The nitrogen concentration in its roots, stems, leaves are the lowest in the mowing sites; the carbon and nitrogen concentration of plants increases under enclosure and long-term non-disturbance treatments, indicating that the plant transforms from resource acquisition strategy to resource storage strategy through changes in functional traits when the disturbance intensity is reduced. 2) The analysis of the assemblage of functional traits of dominant species shows that C. squarrosa has a small plant height and a high specific leaf area, and A. frigida has a high lignin and nitrogen concentration. The two species thus can adopt some avoidance (escaping from grazers) and tolerance (regrowth capacity after defoliation) strategies to improve their grazing resistance; S. grandis has the highest plant height, the largest leaf dry matter concentration, the highest stem and leaf cellulose concentration, which indicates that S. grandis is a very typical competitive species. Under management conditions with low interference intensity, the competitive pressure of S. grandis (Competitive strategy) against other species may be an important reason for its high dominance.

Aims The aim of this study is to address how the spatial variability of phenological phenotype is characterized in natural populations, and what drives such spatial variability (genetic variation or phenotype plasticity).
Methods The phenological process of 156 sample trees in 20 plots of five altitudes in Pailugou watershed was monitored for two consecutive years, and the saplings selected at different altitudes were transplanted in common garden. The investigation data were analyzed using ridge regression and lasso regression.
Important findings All phenological stages of Picea crassifolia were delayed with altitude (0.57-1.36 d per 100 m). This spatial variability reflected a certain degree of provenance effect (i.e. genetic variation), with an average contribution rate of 20.8% that maintained at a relatively stable level between years. An interesting finding is that the spring phenology timing of high-altitude populations in the common garden was significantly earlier than low-altitude populations, which may be related to the lower threshold of pre-season heat accumulation required for bud differentiation of high-altitude populations. In addition, we found that pre-season heat accumulation, altitude, pre-season precipitation and freezing injury frequency played key roles in explaining phenological dynamics at the population level.

Aims Distylium chinense is endemic to central China, and can be dominant species in parts of the Three Gorges Reservoir area. Studying the characteristics of D. chinense communities and their relationships with soil environmental factors under different habitat conditions could help gain knowledge assisting the community protection and vegetation restoration in the water level fluctuation zone of the Three Gorges Reservoir.
Methods Measurements were made on species composition, floristic characteristics, and plant diversity in D. chinense communities in 24 plots (4 m × 4 m) covering six study sites across the water level fluctuation zone of the Three Gorges Reservoir. The relationships of varying community traits with soil environmental factors were determined by quantitative classification and ordination methods.
Important findings A total of 56 plant species were recorded across the 24 sampling plots, belonging to 36 families and 54 genera. The plant communities mainly composed of the cosmopolitan species, pantropical and north temperate of D. chinense community, predominantly as herbs and shrubs. In the natural water level fluctuation zone, D. chinense scored the highest importance value in the shrub layer, and Ficus tikoua in the herb layer. The companion species of D. chinense commumities were shrubs and perennial herbs with flooding tolerance, such as Swida paucinervis, F. tikoua, Imperata cylindrica, etc. However, in the off-season water level fluctuation zone, D. chinense was the only plant in the shrub layer, with dominance of Cynodon dactylon in the herb layer and other companion species as annual herbs, such as Xanthium sibiricum, Abutilon theophrasti, etc. Two-way cluster analysis divided the six sites into four community types: D. chinense + S. paucinervis, D. chinense + F. tikoua, D. chinense + Adina rubella, and D. chinense + C. dactylon. Canonical correspondence analyses showed that altitude and soil pH were the main environmental factors affecting the species distribution of D. chinense community, followed by the content of soil organic matter, total phosphorus, total nitrogen, and available potassium, which were the main influencing factors of species diversity index with nitrogen being the limiting factor. In rehabilitation of the off-season water level fluctuation zones of the Three Gorges Reservoir, small shrubs such as A. rubella and S. paucinervis should be used as the companion species of the upper slopes with increased supply of soil nitrogen and potassium, in order to promote higher species diversity of the D. chinense community and to maintain the stability of water level fluctuation zone ecosystems.

Aims Epichloë infection can affect the fungal disease resistance of host grasses. However, few studies have been reported on the effects of endophyte infection on non-symbiotic neighbours.
Methods We surveyed the plant diseases in natural grassland, and compared differences of total disease index between neighbor and non-neighbor plants of Achnatherum sibiricum. Then the laboratory experiments were conducted to investigate the effects of endophyte on the growth of four pathogen species as well as the brown patch of the host and its neighbor plants.
Important findings Major epidemic diseases of grasses were spot blight, rust disease and powdery mildew in Hulun Buir natural grassland. Among common herbages, the total disease index of endophyte-infected A. sibiricum was the lowest. Compared with non-neighbor plants, the brown patch disease index of Leymus chinensis, Stipa baicalensis and Agropyron cristatum was significantly reduced when neighbouring with A. sibiricum. The laboratory experiments results showed that the culture filtration of both Epichloë gansuensis and Epichloë sibiricum significantly restrained the growth of Curvularia lunata, Bipolaris sorokiniana, Sclerotinia sclerotioru and Sclerotinia trifoliorum. The two species of endophytes could reduce lesion area of detached host leaves. In the intact leaves, the endophyte reduced the disease resistance of both the host and its neighbor grasses L. chinensis to C. lunata and B. sorokiniana. This study first verified that the endophytes in A. sibiricum have a positive effect on disease resistance of neighbor grasses to brown patch.

Aims This study is to examine the relative changes and regulation in photosynthetic energy partitioning components of a typical desert shrub Artemisia ordosica in Northwest China.
Methods The minimum fluorescence yield (F_o), maximal fluorescence yield (F_m), actual fluorescence yield (F_s), maximal fluorescence yield in the light-adapted state (F_m′), net photosynthetic rate (P_n), dark respiration (R_d), transpiration rate (E) and stomatal conductance (g_s) of A. ordosica were investigated from April to October, 2018 using a multi-channel fluorometer and a portable photosynthesis analyzer. The specific leaf area (SLA), nitrogen per leaf area (N_area), chlorophyll content (C_Chl) and the ratio of chlorophyll a to chlorophyll b content (Chl a/b) were also measured. We analyzed the fraction of energy used for CO₂ assimilation (Φ_A), the fraction of energy used for photorespiration (Φ_PR), the fraction of regulate heat dissipation (Φ_NPQ) and the fraction of non-regulate heat dissipation in energy allocation (Φ_NO) during the photosynthetic process in A. ordosica and their responses to fluctuating environment.
Important findings The photochemical reaction component (Φ_A and Φ_PR) and the heat dissipation component (Φ_NPQ and Φ_NO) showed a negative competition relationship, and exhibited positive synergistic relationship within components. E was positively correlated with Φ_A and Φ_PR, and negatively correlated with Φ_NPQ and Φ_NO. Under low soil water content (SWC) and high saturated water vapor pressure (VPD) conditions, Φ_A, Φ_PR and SLA were significantly decreased, while Φ_NPQ and Φ_NO were significantly increased. The results indicate that A. ordosica avoids excessive loss of water under the condition of the long drought or high evapotranspiration via reducing SLA. Synergistically, excessive light energy is transferred from photorespiration to thermal dissipation pathway. The relative changes and long-term regulation of photosynthetic energy partitioning in A. ordosica under fluctuating environment, fully reflect the acclimation of plants to adversity via its synergistic morphologic and physiological plasticity.

Aims The high-precision data measured by the Dendrometer includes not only the stem radial growth process caused by the enlargement of xylem cells but also the reversible changes caused by the consumption and replenishment of the stem water. Our objectives were to assess the difference in stem water relations of Picea meyeri obtained by different de-trending methods and their responses to water conditions in soil and air.
Methods Hourly stem radius variations in P. meyeri and corresponding environmental factors were monitored in the lower limit of the coniferous forest on the northern slope of Luya Mountain, northern Shanxi Province, China. Gompertz growth model (GPZ), linear growth model (LG), and zero growth model (ZG), daily approach (D), and stem cycle approach (SC) were used to fit the stem growth trend in the growing season of 2015. Then, the growth trend and extract five different types of tree water deficit-induced stem shrinkage (TWD_GPZ, TWD_LG, TWD_ZG, TWD_D, and TWD_SC) were removed to characterize the dynamic of stem water relations. Moving window correlation (31 days) and ordinary least square regression were further employed to analyze the responses of different types of stem water relations to soil and air moisture conditions.
Important findings The results showed that: 1) stem water relations derived from different de-trending methods had contrasting trends and amplitude, which could be clustered into three groups: TWD_LG and TWD_ZG, TWD_GPZ, and TWD_D and TWD_SC. Each month, significant correlations between stem water relations in the same group or a lower clustering distance showed, however, TWD_LG, TWD_ZG, and TWD_GPZ had weaker correlations with TWD and TWD_SC in August. 2) TWD_D and TWD_SC had a closer and more stable positive relationship with vapor pressure deficit (VPD) than TWD_GPZ, TWD_LG, and TWD_ZG did. The responses of all types of stem water relations to soil water content (SWC) varied greatly during the growing season. 3) All stem water relations significantly increased as the water stress (VPD/SWC) intensified (p < 0.05). When the stress was low, TWD_SC was most sensitive to the changes of VPD/SWC (R² = 0.39, p < 0.001), whereas it was not much different from TWD_ZG (R² = 0.37, p < 0.001); when the stress was high, TWD_ZG showed the greatest sensitivity to VPD/SWC (R² = 0.59, p < 0.001). Our results suggested that the zero-growth model was more suitable to detrend the stem radius variations during the growing season, and provided a crucial reference for predicting the stem water status and dynamics, especially under drought stress.

Aims Variations in temperature and snow accumulations in winter will change the structure and function of the soil-microbial system. As a key biological factor in the terrestrial ecosystem, microorganisms play an important role in regulating soil nutrient cycles. However, they are very sensitive to environmental disturbances, especially to winter climate changes. It is in great need to study the response of soil nutrients and microbial properties of typical semi-arid grasslands to climate change in winter, in order to predict the ecological process and functional changes of grassland ecosystem in the long term.
Methods In the present study, the semi-arid grassland in the Yunwushan National Nature Reserve in Ningxia Province was taken as the research object. The four treatments including warming (W), snow reduction (S), interaction of warming and snow reduction (WS), and control (CK) were set to explore the responses of soil nutrients, enzyme activities and soil bacterial communities in the 0-5 cm soil layer of the typical grassland of the Loess Plateau to variations in winter temperature and snow cover.
Important findings Our results indicated that: (1) Warming, snow reduction and their interaction in winter increased the 0-5 cm soil temperature, lowered the relative humidity of the soil, but significantly increased the number of soil freeze-thaw cycles. (2) Compared with the control, other different treatments generally reduced the microbial biomass and bacterial diversity, which led to reduced activity of soil β-1,4-glucosidase (BG), β-1,4-N-acetylglucosaminidase (NAG) and alkaline phosphatase (AKP). The content of soil organic carbon, total nitrogen, available phosphorus, and nitrate nitrogen in the soil increased, while the content of nitrate nitrogen decreased. (3) The soil bacterial species in the study area were mainly Acidobacteria, Proteobacteria, Actinobacteria and Gemmatimonadetes. The dominant bacteria at the class level included Acidobacteria, γ-Proteobacteria, Thermophiles and σ-Proteobacteria. Redundancy analysis (RDA) results showed that available phosphorus (AP) content had the most significant impact on the bacterial community composition, with an explanation rate of 21.3% for the community variation. In conclusion, winter climate change can significantly affect soil temperature and humidity, especially the freezing and thawing cycles, which might further influence soil nutrients cycles, enzyme activities, and soil bacterial diversity. These results are of great significance for enriching and expanding the understanding of the process and mechanism of climate change on grassland ecosystem, as well as predicting the mid and long-term dynamic changes of typical grassland ecosystems.

Aims As a key factor for the redistribution of rainwater or meltwater, soil infiltration has a substantial effect on forest eco-hydrological processes. This study aims to investigate the characteristics of soil infiltration and its structural controlling factors in the early stage of a post-fire Pinus tabulaeformis plantation in Beijing.
Methods After a fire occurred in March of 2019, the 0-20 cm soils in both post-fire and control plots were monthly collected from May to December 2019. Soil structure and infiltration were determined to analyze their response to fire disturbance and explore how they changed with soil depth and time. Path analysis was employed to discuss the effects of fire and soil structural properties on infiltration.
Important findings The results showed that: 1) In general, the surface soil had higher values of structural indexes (except small aggregates) than subsoils, and values of structural indexes recorded from June to August were higher than those recorded in other months. The vertical distribution characteristics and seasonal dynamics of soil structure were changed by fire. The content of soil aggregates >5, 2-5 and 1-2 mm and bulk density increased significantly two months after fire, while other indicators decreased significantly after fire. The effect of fire was weakened as soil layers deepened and time went by. Also, we observed distinct interactions among fire, soil depth and time. 2) Soil infiltration characteristics changed slowly with soil depth, but changed significantly with time. In addition, soil initial infiltration rate, steady infiltration rate, cumulative-infiltration volume and saturated hydraulic conductivity were largest in August (with higher rainwater and heavy rainfall events). After the fire, soil infiltration in 0-5 cm and that from June to September considerably varied. Soil infiltration characteristics generally decreased, and the peak value in post-fire plots occurred one or two months ahead of that in control plots. 3) Fire significantly affected soil structural properties, while soil infiltration was mainly and directly affected by soil structural properties. Excluding the impact of fire disturbance, the infiltrability of soil had a significant positive correlation with soil aggregate, bulk density and water holding capacity, and a negative correlation with porosity. Although organic matter content and initial water content had no significant effect on infiltrability, organic matter content could indirectly affect infiltrability by affecting porosity or water holding capacity. However, only initial water content had a significant and direct effect on infiltrability at the early stage of a post-fire forest, and the higher the initial moisture content was, the slower the soil infiltration was. Taken together, fire could change or decouple the way soil structure affected soil infiltration and its internal part, and indirectly affected soil infiltration in the early period of post-fire.

The main vegetation types of Desert Grassland Nature Reserve in Qitai, Xinjiang were investigated in this paper. Based on the data from 65 plot samples, the characteristics of the main desert plant communities from the main vegetation types were quantitatively described. The results showed that, the vegetation in this reserve can be divided into 12 major plant community types: Haloxylon ammodendron Simi-Arbor and Shrub Desert Alliance, Ephedra przewalskii Simi-Arbor and Shrub Desert Alliance, Gymnocarpos przewalskii Simi-Arbor and Shrub Desert Alliance, Reaumuria soongarica Simi-Arbor and Shrub Desert Alliance, Iljinia regelii Semi-Shrub and Herb Desert Alliance, Anabasis brevifolia Semi-Shrub and Herb Desert Alliance, Tamarix laxa Deciduous Broadleaf Shrubland Alliance, Kalidium foliatum Semi-Shrub and Herb Desert Alliance, Ajania fruticulosa Semi-Shrub and Herb Desert Alliance, Achnatherum splendens Tussock Grassland Alliance, Leymus angustus Tussock Grassland Alliance, Phragmites australis Tussock Grassland Alliance. Finally, 15 associations were derived from these 12 major community types.