The vineyard ecosystem is an important part of agro-ecosystem, and contiguous vineyards have important ecological values. The research on carbon source/sink in vineyard ecosystem is an indispensable content of our understanding of carbon cycling. The mechanisms of carbon cycling and the carbon sink function of vineyard ecosystem have become hot topics. We found that a large amount of carbon was fixed in vineyard ecosystem that was distributed in annual organs (fruit, etc), perennial organs (trunk, etc) and soil carbon pool. The carbon input flux of the vineyard ecosystem was greater than the carbon output flux, suggesting a carbon sink. Soil was the largest carbon pool of vineyard ecosystem, accounting for 70% of total carbon stock, especially the soil-vines interface. Covering and non-tillage can reduce carbon emissions and increase soil fertility in vineyards. In order to clarify the carbon sink functions of vineyard ecosystem, we reviewed the latest research progress in the field, including the mechanisms of carbon cycling, and the strategies of carbon emission reduction. This paper provides a theoretical basis and prospects for future research directions and application.

Aims Liana is an important component of tropical forest, and exert a significant impact on community structure and function. Previous studies have found significant differences in hydraulic traits between lianas and trees, as indicated that lianas tended to have large and long vessels to compensate hydraulically to their thin stems, resulting in high hydraulic conductivity but low resistant to drought-induced cavitation. In order to reduce the influence of different genotypes on the comparative results, we aimed to compare the differences in hydraulic and photosynthetic characteristics between the two life forms from two genera Millettia and Gnetum.
Methods We measured branch and leaf hydraulic properties, sapwood density, gas exchange rates in the dry season for nine tree and liana species grown in common garden. We compared the hydraulic and photosynthetic traits between each species using one-way ANOVA. In addition, we analyzed hydraulic efficiency-safety trade-off, and the relationship between dry-season photosynthetic rates and hydraulic traits.
Important findings (1) There was a significant variations in hydraulic traits in genus Millettia, which was related to their light requirements and life forms. Compared with trees, the shade-tolerant liana species had lower hydraulic conductivity and higher resistance to cavitation. (2) Despite angiosperm-like characteristics such as vessels and broad pinnate-veined leaves, the Gnetum tree species had the lowest hydraulic conductivity among the nine species. However, the Gnetum liana species had higher hydraulic conductivity, comparable to light-demanding angiosperm species in this study. (3) There was no significant trade-off between hydraulic conductivity efficiency and hydraulic safety in both branch- and leaf-level across all the species, or within each plant group. (4) Compared to co-generic tree species, liana species’ leaves were more resistant to cavitation than branches, as indicated by higher maximum net photosynthetic rates and stomatal conductance during the dry season. These results support the hypothesis of “growth advantages at dry season” for liana species. This study reveals the high diversity and significance of hydraulic functioning in tropical lianas. Extensive measurements of hydraulic properties are needed to promote understanding of tropical species response to environmental change.

Aims The distribution pattern of green vegetation in urban streets has significant impacts on urban ecological environment and physical/mental health of local residents. Accurate detecting and monitoring of street green information is of great significance for precise urban planning and management, while there are few studies focusing on urban greenery estimation using profile image system.
Methods In this study, combining network information capturing and geospatial information analysis technology, Taiʼan city was selected as the case study area. Based on the Baidu application programming interface (API), a total of 3 276 Baidu Street View (BSV) images of 273 research samples were obtained and processed, and the green vegetation pixels in the image were extracted by computer supervised classification and compared with the artificial extraction results. Based on the proposed Baidu Street Vegetation Distribution Index (BSVDI), we monitored the street vegetation’s distribution characteristics from the pedestrian perspective, and analyzed the street- scale vegetation distribution pattern.
Important findings The BSV image could be used as the main data source to monitor the distribution of green trees and lawns in pedestrian’s perspective on the street scale. BSVDI was higher in the center, northeast and southeast of the study area than the other regions. BSVDI and remote sensing extracted vegetation covered area are significantly and positively correlated, with correlation coefficient of 0.76, 0.63 and 0.49 in the buffered distance of 10, 20 and 50 m, respectively. However, the change trends of the BSVDI and remote sensing results were not completely consistent in each study site. This study implies that the combination of BSVDI and remote sensing monitoring results can better guide urban green landscape planning and precise management.

Aims Litter decomposition plays a vital role in nutrient recycling of forest ecosystems. The decomposition rate of leaves can vary among tree species with different substrate quality and environmental conditions, such as the supply of exogenous nitrogen (N). However, the effects of exogenous N on leaf litter decomposition of different tree species in subtropical forests with high nitrogen deposition background remain poorly understood. Thus this study was designed to address the effect of N addition on litter decomposition of different tree species in a subtropical forest ecosystem.
Methods Leaf litters of four common tree species with contrasting substrate quality were collected and decomposed in fertilized (50 kg N·hm ^-2·a ^-1) and control (0 kg N·hm ^-2·a ^-1) plots for up to two years by using the nylon bag method, in Sanming Castanopsis kawakamii nature reserve of Fujian Province.
Important findings The litter decomposition rate in control plots ranked as follows: Michelia odora (0.557 a ^-1), Castanopsis carlesii (0.440 a ^-1), Acacia confusa (0.357 a ^-1), Cunninghamia lanceolata (0.354 a ^-1), while the decomposition rate in N addition plots ranked as follows: Michelia odora (0.447 a ^-1), Castanopsis carlesii (0.354 a ^-1), Cunninghamia lanceolata (0.291 a ^-1), Acacia confusa (0.230 a ^-1). Overall, N addition significantly increased the litter mass remaining of Michelia odora, Acacia confusa and Castanopsis carlesii, but not Cunninghamia lanceolata. N addition not only slowed down the release of N, but also retarded the degradation of lignin and cellulose in the decomposition process. Moreover, N addition increased the activities of β-glucosidase (βG) and acid phosphatase, had species-specific effects on the activity of cellulose hydrolase, and decreased the activity of β-N-acetylglucosaminidase and phenoloxidase (PHO). The litter mass loss rate was positively correlated with the activities of carbon acquiring enzyme (βG) in litter layer and the extractives, negatively correlated with carbon concentration, cellulose and lignin, but did not correlate significantly with the initial N concentration. Further analysis found an interactive effect of litter type and N addition on the degradation of cellulose and lignin, but not on dry mass loss. Overall, our results demonstrated that litter chemical components may be better parameters to predict the decomposition rate of leaf litters than the initial nutrient concentrations, and N addition could decrease leaf litter decomposition by inhibiting oxidase (e.g. PHO). We call for further experiments to involve more species and longer time for revealing the response of leaf litter decomposition and its extracellular enzyme activity to N addition.

Aims We investigated the growth and decomposition of Sphagnum, a principal plant involved in peat accumulation in wetlands, in subtropical wetlands.
Methods We selected a Sphagnum-dominated wetland in southwestern Hubei Province as the study area. In situ growth and litter decomposition experiments in different microhabitats were carried out, and the chemical composition of litter was measured in laboratory to examine the processes of its growth and decomposition.
Important findings The average height of Sphagnum in hummock and hollow were 2.9 and 2.7 cm, and the net production was 270.94 and 370.88 g·m ^-2, respectively, after 12 months. Growth time and microhabitats significantly affected on the height growth and the net production, and there was an interaction between time and microhabitats. However, the growth trend in two microhabitats was significantly different. The average growth rate of Sphagnum under the two microhabitats (July to October 2017) was 0.33 mm·d^-1, which was higher than that in the cold temperate zone. In addition, the decomposition time had an significant effect on the decomposition amount of Sphagnum, and the residual rate decreased first and then increased with time. By the end 12-month period, the final residual rates in hollow, hummock and pool were 100.67%, 90.54% and 85.63%, respectively. The content of carbon (C), carbon nitrogen (N) ratio (C:N) and polyphenols in the litters decreased, while the nitrogen content increased. During the first 3 months of decomposition, a significant difference of decomposed litter was found between the microhabitats, but no significant difference later on.

Aims The monsoon broad-leaved evergreen forest is a typical zonal vegetation of south subtropical China, where forest dynamics plot is a study platform of mechanisms of biodiversity maintenance and community assembly. Our objectives were to obtain plant association types in a 30 hm² forest dynamic monitoring plot in the Pu’er City, Yunnan Province.
Methods We identified typical association types by the methods of multivariate regression trees, importance value, principal component analysis and indicator species based on 750 subplots (20 m × 20 m), and analyzed the differences of topography factors and community characteristics among different plant associations.
Important findings The results showed that the specie richness of woody species (diameter at breast height (DBH) ≥ 1 cm) was 271, which belonged to 78 families and 178 genera in the forest dynamic plot. The community formation was Formation Castanopsis echidnocarpa. Forest was divided into four associations: (1) Lyonia ovalifolia + Aporosa villosa - Castanopsis echidnocarpa + Lithocarpus fenestratus Association, (2) Tapiscia yunnanensis + Lithocarpus grandifolius - Castanopsis echidnocarp + Schima wallichii Association, (3) Elaeocarpus sikkimensis + Polyspora chrysandra - Castanopsis echidnocarp + Schima wallichii Association, and (4) Betula alnoides + Alnus nepalensis - Castanopsis echidnocarp + Castanopsis calathiformis Association. There were many transitional overlaps in the distribution of associations, while indicator species was the main reference for distinguishing the types of associations. In addition, altitude and slope aspect had a great influence on the plant association types, while slope per se had a relatively weak impact on the association types.

Aims- Planting density, as one of the most important factors affecting crop yield and quality, will result in plant competition for light, water and nutrients. The objective of this study is to explore the effect of planting density on growth and yield of Medicago sativa population.
Methods The population density experiments of M. sativa was conducted in a greenhouse with six planting densities, i.e. 25, 100, 400, 800, 1 500 and 2 000 plants·m ^-2. At each plot, we measured plant height, basal diameter, branch number, biomass, and number of survivors.
Important findings The results showed that the average planting density was 25, 100, 373, 745, 1 255 and 1 938 plants·m ^-2 in the 15 days after sowing. With the growth of M. sativa, except for the low density treatments (25 and 100 plants·m ^-2), the number of plant individuals under other density treatments decreased, and self-thinning occurred at some degrees. At the second harvest (187 days after sowing), the number of surviving plants decreased to 297, 571, 759 and 839 plants·m ^-2, respectively. The plant height, basal diameter and branch number of individual plants decreased exponentially with the increase of existing density. The relationships between individual biomass and existing density followed the competitive density effect law, that is, individual biomass decreased with the increase of density. The results also showed that the aboveground biomass of M. sativa per unit area has no significant differences among different densities, but the underground biomass tended to increase first and then decrease with the increase of planting density.

Aims Trees are the basic components of forest ecosystems, and their growth is affected by meteorological factors. It is important to explore the response mechanism of forest ecosystems in this region to climate change if radial growth dynamics of dominant tree species and their relationship with meteorological factors are determined. Furthermore, previous studies on tree growth were mostly based on tree-ring chronology, whereas short- term studies on the stem radial growth dynamics of trees are scare. Therefore, this study aims to investigate the daily and seasonal dynamics of radial growth in Pinus sylvestris var. mongolica and its relationship with meteorological factors.
Methods In this study, dendrometer increment sensor was used to monitor the stem radial dynamic changes of P. sylvestris var. mongolica for three years from 2016 to 2018 in the Saihanba, Hebei Province, China.
Important findings Due to the water absorption and transpiration of the stems, the diurnal variation of the stem radial can be divided into four periods: spring germination period; summer growth period; autumn-winter alternating period; winter dormant period. Stem radial growth begins at early April in each year during water recovery from early April to mid-May. The fast-growing stage occurred from mid-May to mid-July. From mid-July to mid-October, trees entered a slow-growing stage. The radial growth tended to stop during mid- and late-October. Temperature was the main meteorological factor influencing the stem radial growth. On the time scale of one day, the stem radial growth was mainly affected by temperature during the rapid growth stage, but by rainfall and air temperature during slow growing stage. On the time scale of 15 days, only temperature had a significant effect on the stem radial growth. Under the conditions of extreme low temperature and drought, our results provide important reference for the growth status of P. sylvestris var. mongolica in semi-arid areas.

Aims Natural population of Picea purpurea in Gahai-Zecha Nature Reserve and Kache and Yeliguan forest regions in the Taohe River upstream was selected, to reveal the demographic status of P. purpurea populations. The results from the current study will provide theoretical basis for the protection, management and structural restoration of P. purpurea.
Methods Based on field surveys and data analysis, population structure diagram was drawn, static life table was designed, and survival curve of P. purpurea was fitted and analyzed. Quantitative methods were used to study the population dynamics. The population development trend was predicted by time-sequence model.
Important findings In the three forest regions, P. purpurea population showed signs of strong natural regeneration ability with abundant seedling and sapling reserves, yet the mortality rate of saplings was high. The population in Gahai-Zecha forest manifested a Deevey-III type survival curve representing a stable population with a complete population structure, and the population in Kache forest and Yeliguan forest manifested Deevey-II type survival curves with partial declines present in both forests. With population dynamics indexes (V_pi) > 0, the populations of all three forests were in growth. The growth potentials ranking from highest to lowest were Gahai-Zecha > Kache > Yeliguan. The P. purpurea population in Kache forest showed the highest sensitivity to random interference followed by that in Yeliguan forest while Gahai-Zecha population was the most stable. This study showed that competition and self-thinning were the common causes of low survival rate of P. purpurea saplings and that different living situation in the three forests reflected the difference of survivability of P. purpurea populations in different habitats and life histories. The key to regeneration and development of P. purpurea populations was to protect the habitat of seedlings and to improve their quality and survival rate. The P. purpurea population in Gahai-Zecha forest grew well and the survivorship of that population was mainly affected by its own biological characteristics and environmental factors. The population structure of Kache forest was damaged under human interference. The population structure of Yeliguan forest was unstable due to its limited distribution. Appropriate anthropogenic interference measures should be adopted to promote population renewal and growth.

Aims The genetic variation caused by long-term adaptation to the environment has significant influence on plant’s growth and development. Leaves serve as the most important and sensitive organs to environmental changes. Understanding the adaptive variation of leaf anatomical structure in different environments is the basis for exploring the adaptation of plants to the environment.
Methods Common garden experiment is an effective method to study the effects of genetic and environmental factors on plant growth and metabolism. In this study, the influence of environmental gradients was eliminated by using the common garden experiment. Then we analyzed anatomical structures of leaves and its driving factors of Caryopteris mongholica from seven different provenances by using conventional paraffin section, multiple comparisons, correlation analysis, and general linear model analysis method.
Important findings Caryopteris mongholica from seven provenances had typical isolateral leaves, with no differentiation of spongy tissue, and the upper epidermal cell was thicker than the lower epidermal cell. Meanwhile, the upper palisade tissue was thicker than the lower palisade tissue. There was a significant autocorrelation among anatomical parameters of leaves, and there were important differences among the anatomical structures of leaves from different provenances. With increasing mean annual temperature of provenances, the thickness of the leaves and palisade also showed an increasing trend, and the largest thickness of the upper palisade tissues, lower palisade tissues and leaf thickness were in the leaves of Alxa Left Banner, Nei Mongol, indicating a stronger resistance to drought. The latitude, longitude, temperature and precipitation of different provenances had significant effects on the index of anatomical structure, with the explanatory power from 34.09% to 81.43%. The common garden experiment showed that the genetic variation driven by climate was one of the major factors that caused the difference in anatomical structure of leaves from different provenances.