Variation in nitrogen deposition and available soil nitrogen in a forest–grassland ecotone in Canada

Regional variation in nitrogen (N) deposition increases plant productivity and decreases species diversity, but landscape- or local -scale influences on N deposition are less well-known. Using ion-exchange resin, we measured variation of N deposition and soil N availability within Elk Island National Park in the ecotone between grassland and boreal forest in western Canada. The park receives regionally high amounts of atmospheric N deposition (22 kg ha⁻¹ yr⁻¹). N deposition was on average higher ton clay-rich luvisols than on brunisols, and areas burned 1–15 years previously received more atmospheric N than unburned sites. We suggest that the effects of previous fires and soil type on deposition rate act through differences in canopy structure. The magnitude of these effects varied with the presence of ungulate grazers (bison, moose, elk) and vegetation type (forest, shrubland, grassland). Available soil N (ammonium and nitrate) was higher in burned than unburned sites in the absence of grazing, suggesting an effect of deposition. On grazed sites, differences between fire treatments were small, presumably because the removal of biomass by grazers reduced the effect of fire. Aspen invades native grassland in this region, and our results suggest that fire without grazing might reinforce the expansion of forest into grassland facilitated by N deposition.     

Advances in mitochondria injury by Aβ in Alzheimer's disease

The β-amyloid protein (Aβ) has long been considered to associate with Alzheimers disease (AD). In addition, groups of evidence show that the soluble intracellular Aβ plays an important role in the disease development. The mitochondrial dysfunction induced by Aβ accumulation is a main pathologic process in early stage of AD. Matured Aβ is imported into the mitochondria through an unclear route. Once inside the mitochondria, Aβ is able to interact with a number of targets, including amyloid-binding alcohol dehydrogenase (ABAD) and cyclophilin D (CypD), which is a component of the mitochondrial permeability transition pore. Interference with the normal functions of these proteins results in mitochondrial injury, such as energy dyshomeostasis, production of reactive oxygen species, membrane permeability alteration and so on. This review explores the Aβ generation and location in mitochondria. The mitochondrial injury induced by the interaction between Aβ and its targets are also discussed.     

Role of NF-κB in pentetrazole-induced repeated seizure in developing rats

AIM:To investigate the role of NF-κB in pentetrazole-induced repeated seizure in developing rats with the inhibitor of NF-κB pyrrolidine dithiocarbamate (PDTC). METHODS:10-day-old Wistar rats (n=72) were prepared for epilepsy model and divided into three groups at random: the PTZ group, the PDTC+PTZ group and the control group. The behavioral changes, the cells morphology and neurons counts in hippocampus, the expression of NF-κB, BrdU (5-bromo, 2-deoxyuridine) immunoreactive cells in hippocampus and the mossy fiber sprouting were observed.RESULTS:(1) The NF-κB expressed in PTZ group was significantly higher than that in PDTC+PTZ group and control group (P<0.01). (2) The dentate gyrus granule cell count in PTZ group was significantly higher than that in control group (P<0.05). In PDTC+PTZ group cell counts in CA1, CA3 and hilar region were significantly lower than those in PTZ group (P<0.05). (3) The BrdU-immunoreactive cells counts in dentate gyrus in PTZ group and PDTC+PTZ group were significantly higher than those in control group (P<0.01), but in PDTC+PTZ group BrdU-immunoreactive cell count was significantly lower than that in PTZ group (P<0.01). Correlate analyzes between NF-κB expression and BrdU-immunoreactive cell counts/granule cell counts showed positive correlation (P<0.01). (4) The mossy fiber sprouting in both PTZ and PDTC+PTZ group was observed. However, the degrees of sprouting showed no significant differences between two groups. CONCLUSION:NF-κB plays a crucial role in epilepsy of developing rats. It encourages neurogenesis and protects neurons in hippocampus, but has no significant effect on mossy fiber sprouting.     

Research and utilization progress in banana germplasm resources in China北大核心CSCD

Banana is one of the main fruit crops and important food crops in the world, and it is also an important economic fruit in southern China. China is the border area of the origin of modern bananas, and one of the secondary origin centers as well. China has a history of banana cultivation for more than 2000 years and is the second largest country in banana production and consumption. Banana producing areas in China are mainly concentrated in Guangdong, Guangxi, Hainan, Yunnan, Fujian and Taiwan, with a small amount of cultivation in the south of Sichuan, Guizhou and Tibet. Most cultivated bananas are evolved from two wild species, Musa acuminate and Musa balbisiana, and their interspecific hybridization. The genome of Musa acuminata is called“genome A”, while the genome of Musa balbisiana is called“genome B”. According to the classification value of characteristics, banana cultivars can be divided into genotypes such as AA, AAA, AB, AAB, ABB, AAAA, AAAB, AABB, BB and BBB. Bananas cultivated in China are simply divided into four categories: Cavendish (AAA), Pisang Awak (ABB), Silk (AAB) and Dajiao (ABB). Cavendish banana is planted mostly in China (more than 80%), followed by Pisang Awak (more than 10%). Notably, in China, few people plant and consume Plantain (AAB), which is an important staple food in some area. Banana breeding mainly includes introduction (like Brazil and Williams banana), vegetative line selection (like GCTCV bananas), artificial mutation breeding (like Jiali banana), cross breeding (like Fenza No. 1 and Zhongjiao No. 9 banana), chromosome ploidy breeding, transgenic breeding and gene editing breeding. The introduction method is simple and direct. Our group took the lead in establishing the National Banana Germplasm Resource Garden in 1989. In the future, we should introduce not only high-quality varieties, but also multifunctional and diverse banana varieties to enrich China’s banana market. After introduction, people often get better lines that adapt to Chinese geographical and climatic conditions and planting habits, and then popularize them. Mutation breeding is easy, but the ideal excellent lines can only be obtained through a large number of screening and evaluation. The female flowers of some bananas, like Dajiao and Pisang Awak, have strong fertility, so they are often used as female parents to cross with wild bananas or cultivated varieties with certain fertility. Although sexual hybridization of banana needs a long period and is easy to fail, this method can often create new germplasm with diverse genetic background and relatively controllable traits, which is the most potential and promising method in traditional banana breeding at present. In recent years, researchers in China have created many new hybrid banana germplasm, and it can be predicted that a large number of new hybrid banana varieties will emerge in China in the near future. Banana transgenic and gene editing breeding have strong pertinence. China has made good achievements in the fields of banana transgenic and gene editing. However, as in many other parts of the world, these methods cannot be applied to business at present. At last, other breeding methods like somatic hybridization, rapid breeding and molecular-assisted breeding are rarely used at present. Banana Fusarium wilt and other diseases seriously threaten banana industry in China. At the same time, frequent typhoons and floods, severe frost and poor soil in the main banana producing areas in China also limit the further development of banana industry. Breeding new banana varieties with high yield, high quality and high stress resistance and adaptability is the key to break the bottleneck of banana industry development in China, and it is also a challenge for banana breeders in China. In addition, it is also an important direction to cultivate bananas with high nutrition and health care function, which are suitable for industrial processing or feed. During the last decades, China has made great achievements in banana breeding, but there are still many problems. First of all, banana biodiversity is relatively lacking, with few wild banana resources. Moreover, the careful evaluation of banana germplasm resources is not enough, limiting the utilization of them. Secondly, the main banana varieties in China were bred by introduction and mutation breeding, and only a few were bred by hybridization or other means. Moreover, due to many reasons, there is a lack of varieties with good comprehensive characteristics. Finally, it is difficult to study genes in banana through the forward or reverse genetic means, limiting the molecular research on banana. In the future, we should: (1) Continue to strengthen the collection, evaluation and utilization of global banana germplasm resources, and especially promote banana cross breeding vigorously; (2) Pay attention to the basic research on banana, dig out the key genes related to important economic traits, and analyze their regulatory networks, so as to lay the foundation for creating new banana varieties without transgene through gene editing technology in the future; (3) Continuously develop and upgrade new breeding techniques, promote the integration of various means, and breed efficiently and scientificly; (4) Breed new varieties that are resistant to various diseases and have good comprehensive properties, so as to win the banana defense war. In a word, we have summarized the research results of banana breeding in China in recent years, discussed the methods of banana breeding, the direction of new variety breeding and the main problems, in order to provide reference for banana breeding in China. © 2023 Journal of Fruit Science. All rights reserved.     

An Experiment in Pruning Cox’s Orange Pippin Apple Trees in Alternate Years

Five pruning treatments were compared on Cox’s Orange Pippin on M.II rootstock, viz.

1. Open-centre tree, established-spur pruned

2. Open-centre tree, renewal-pruned

3. Delayed open-centre tree, established-spur pruned

4. Delayed open-centre tree, renewal-pruned

5. Regulated-pruned tree.

At 15 years, secondary pruning treatments were begun and carried on for a further 7-year period, the trees being pruned by the same methods but either annually or in alternate years. Differences in growth and cropping between trees pruned to open-centre and delayed open-centre shapes were small, but open-centre trees cropped more heavily than did delayed open-centre trees when renewal-pruned, probably on account of their greater branch spread. The method used in pruning the laterals had an effect upon cropping during the first 10 years. At the end of the trial there was no effect of either primary or secondary treatments upon trunk girth, neither was there a significant difference in girth increment between the secondary treatments. Almost the same amount of wood was removed from trees pruned in alternate years as from those pruned annually, but a greater proportion of old to new wood was removed from trees pruned in alternate years. Pruning in alternate years increased the cropping of established-spur pruned trees but not with regulated or renewal-pruned trees. There was no consistently adverse effect upon fruit size but, when a year of heavy setting followed a winter when the trees were left unpruned, fruit size was reduced and early fruit thinning would have been necessary to lessen the proportion of fruit in the two smallest size grades. With this variety fruit colour was unaffected by pruning in alternate years.     

Spatiotemporal dynamics of plant diversity in response to farmers’ evolved settlements in Shanghai

The expansion of the Shanghai metropolitan region has caused a substantial amount of farmland to become urbanized. Most farmers have lost their land and have been relocated from villages to new collective settlements, resulting in dramatic changes in the landscape pattern. This study explores the effects of this transformation on the spatiotemporal dynamics of plant diversity. We randomly sampled 22 plots comprising 294 subplots within two crossed transects that pass through 5 traditional villages and 17 new settlements. The results show that resettlement has exerted significant effects on plant species diversity, both temporally and spatially. Temporally, the Gleason index (GI) of total species over time could be ordered as 1990s > 2000s > 1980s, while Shannon’s diversity index (SHDI) was ordered as 2000s > 1990s > 1980s. Spatially, the GI of total species decreased from the urban center to the exurbs or from the inside to the outside of the built-up areas. SHDI was highest in suburbs or ecotones. Furthermore, the GI of total species had significant correlations with those of indigenous species, exotic species, and planted species (r > 0.90, p < 0.01) as well as with the region and location of settlement (r < −0.48, p < 0.01). Both indigenous and exotic species had significant positive correlations with total species richness at 0.01 levels. Generally, compared with traditional settlements, new settlements displayed greater richness and diversity of plant species, primarily because of the exotic species present in new settlements. The farmers’ socio-economic status was found to be the primary cause of differences in species richness. To protect indigenous and wild species, it is necessary to take into account local knowledge in villages to encourage Chinese farmers to participate actively in community greening. A bridge should be built between traditional villages and modern settlements and between the past and future for farmers.     

Seasonal changes in cellular compartmentation and membrane permeability to sugars in relation to early or high temperature-induced watercore in ‘Orin’ apples

Summary

The intensity of watercore in ‘Orin’ apples (Malus domestica Borkh.) from the outer canopy increased from early-July to mid-August, followed by a decrease through late-October, while no watercore was detected in inner canopy fruit during the same period. Seasonal changes in sorbitol content in each cellular compartment paralleled the development of watercore. Significantly higher sorbitol, fructose and glucose contents in the vacuoles of cells in outer canopy fruit than in inner canopy fruit suggest that active metabolism and uptake of sorbitol might occur in watercored apples in mid-August. The permeability of sorbitol across the tonoplast was significantly higher in outer than in inner canopy fruit after mid-August, whereas no difference was observed between bearing position for the other sugars or for the plasma membrane. These data suggest that elevated sorbitol levels in the intercellular spaces might result from active apoplastic unloading and not from an inhibition of metabolism and/or an increase in leakage from cells.     

How can forest fragments support protected areas connectivity in an urban landscape in Brazil?

Cities continue to grow worldwide, and the highly modified urban landscape becomes an inhospitable environment for many species because the natural vegetation cover is commonly fragmented, and the remnants are often isolated. Protected Areas (PAs) located surrounding or within urban areas may not achieve their goal of protecting local or regional biodiversity. Thus, an urban ecological network is essential to support their PAs. Thus, this study aimed at assessing the PAs connectivity in an urban landscape in Brazil and understanding whether urban forest fragments can support an urban ecological network. Besides spatial models based on functional connectivity and graph theory, we used participatory techniques to design the resistance surface and the least-cost paths (LCPs) for Atlantic Forest birds. The results showed critical paths (LCPs), important areas for restoration programs for improving PAs connectivity, and essential forest fragments for conservation and restoration. Although the landscape has a forest structure with 1873 forest fragments and 516 links through which the LCPs were structured, most forest fragments and LCPs cannot provide the necessary support for the PAs connectivity. The current ecological network is dependent on forest fragments neighboring (outside PAs) and the flux dispersions occurred mainly in the peri-urban areas. Riparian zones and anthropic grasslands also showed importance for the PAs connectivity. We identified only 28 forest fragments spatially connected, presenting several sizes, and located near large forest areas, relevant PAs, and riparian zones. Six of these forest fragments, smaller than ten hectares and strategically located in the urban matrix, were indicated for restoration actions. The current low connectivity among PAs brings the importance of native vegetation restoration in the riparian zone and anthropic grassland and the importance of the periurban areas to promote biodiversity connectivity in the urban landscape.     

Characterization of bud-burst potential in Rhododendron catawbiense ‘Album’ plants from in vitro culture by measuring the manganese contents in the distal buds

Summary

It had been established that photoperiodic conditions influence morphogenesis in Rhododendron catawbiense ‘Album’ (Ericaceae). Plants developed from cuttings obtained by in vitro culture were grown in a greenhouse for one or two years, under different photoperiodic treatments. Under long days, the upper buds followed a rhythmic development. Under short days, the inhibition of the growth of the distal buds allowed the development of shoots from the plant base. When plants were placed under long days after six weeks under short days, the distal buds recovered their capacity to form a new growth unit. To find a method to characterize growth potential of vegetative buds, measurements of their mineral content were made. A relationship between the changes in manganese level of the distal buds and their growth potential during the formation of the vegetative system has been established. Under short-day conditions, manganese increased to reach more than 500 mg kg^-1 dry matter in several weeks. Under long days, the manganese level in the upper buds gradually decreased before burst. These results may not provide an explanation for the role of manganese in relation to the buds physiological activity. On the other hand, manganese measurements may be a useful test to estimate growth potential in Rhododendron buds.     

Integrating Fire Risk Considerations in Forest Management Planning in Spain – A Landscape Level Perspective

It is reasonable to assume that there is a relationship between the spatial distribution of forest fuels and fire hazards. Therefore, if fire risk is to be included into numerical forest planning, the spatial distribution of risky and non-risky forest stands should be taken into account. The present study combines a stand-level fire risk model and landscape level optimization to solve forest planning problems in which the fire risk plays an important role. The key point of the method was to calculate forest level fire resistance metrics from stand level indices and use these metrics as objective variables in numerical optimization. This study shows that maximizing different landscape metrics produces very different landscape configurations with respect to the spatial arrangement of resistant and risky stands. The landscapes obtained by maximizing different metrics were tested with a fire spread simulator. These tests suggested that the mean fire resistance of the landscape, which is a non-spatial metric, is the most important factor affecting the burned area. However, spatial landscape metrics that decrease the continuity of fire resistance in the landscape can significantly improve the fire resistance of the landscape when used as additional objective variables.     

Aroma volatiles emission in relation to chilling injury in ‘Kensington Pride’ mango fruit

Summary

Mature green mango fruit (Mangifera indica L. ‘Kensington Pride’) were stored at 0, 5, 10, 15 or 20°C for 1, 3, 7, 14, 21 or 28 d to induce different levels of chilling injury (CI) and to elucidate its relationship with aroma volatile production. The fruit were removed from storage and allowed to ripen at 22 ± 1°C and CI index was assessed on fully ripe fruit. Aroma volatile compounds were estimated from the pulp of fully ripe fruit. CI index significantly increased as the storage temperature was lowered and the storage period was extended, particularly in the fruit stored at 0, 5 or 10°C. CI symptoms did not develop on fruit stored at 15 or 20°C. Fifty-six aroma volatile compounds were identified from mango fruit pulp using headspace solid phase microextraction (SPME) technique with gas chromatography (GC-FID) and GC combined with mass spectrometry (GC-MS). Among the 56 aroma volatile compounds, 25 were quantified using GC, which included monoterpenes (±-pinene, ²-pinene, myrcene, 2-carene, ±-phellandrene, 3-carene, ±-terpinene, limonene, ocimine, ³-terpinene, ±-terpinolene, and a-terpineol), sesquiterpenes (±-copaene, ±-gurjunene, trans-carophyllene, aromadendrane, ±-humulene, alloaromadendrane, ³-gurjunene, and ledene), hydrocarbon (p-cymene), esters (methyl octanoate and ethyl caprylate), aldehyde (decanal), and norisoprenoid (²-ionone). A significant reduction in total aroma volatiles, monoterpenes, sesquiterpenes, hydrocarbon, esters, aldehyde, and norisoprenoid production were observed in fruit stored at 0, 5, 10 or 15°C compared with fruit stored at 20°C. The degree of reduction in aroma volatile compounds depended on the severity of CI, induced with different storage temperatures and storage periods. In conclusion lower temperature storage induced CI in mango fruit and adversely affected the aroma volatiles production.     

Patentierung in der Pflanzenzüchtung

Mitteilungen

Patentierung in der Pflanzenzüchtung     

Socioecological features of plant diversity in domestic gardens in the city of Bogotá, Colombia

Domestic gardens contribute substantially to green spaces in cities, where urbanization removes and fragments natural landscapes, causing the loss of biodiversity and the homogenization of biota. We analyzed the diversity and composition of the flora of 70 domestic gardens in seven localities in Bogotá, Colombia, which represent different periods of expansion of the city. Floristic composition and diversity were related to the origin and use of plants, the urbanization history, and the income of owners. We recorded 4110 individuals belonging to 238 species. The mean species richness per garden was 15.4, with older localities having significantly higher species richness. The similarity among the localities, which evaluated the distinctness of assemblages, ranged from 0.42 to 0.50. Plants from the Neotropical region and exotic plants were the most abundant in all gardens. The most common use was ornamental, and use depended on the socioeconomic status of the owner. The lower-income homes cultivated larger proportions of edible and medicinal plants. Gardens at the oldest localities, with the largest number of native species, contribute to the conservation of flora because they contain the largest number of native species. Furthermore, domestic gardens are good sources of employment for gardeners and are useful places to keep senior citizens active, helping these citizens relieve stress, maintain good health and teach young people the cultural uses of plants. The receptivity of the homeowners to the study opens the door to future research and conservation programs in the city.     

Roles of dendritic cells treated with 17β-estradiol in immune tolerance induction in skin allograft

AIM: To study the roles of bone marrow-derived dendritic cells from donor mouse treated with 17β-estradiol (E₂) in immune tolerance induction in skin allograft. METHODS: Bone marrow-derived dendritic cells from C57 mouse as donor were cultured respectively treated with E₂ (E₂ group). BALB/c mouse as recipient received respectively one injection of dendritic cells of E₂ group, mature dendritic cell group and immature dendritic cell group intravenously. Skin transplantation was performed in the absence of immunosupression after 7 d. Mice that received PBS were served as control. The time of skin survival was observed after transplantation. Flow cytometry was used to analyze the percentage of CD4+CD25+ T cells in peripheral blood respectively before and after transplantation. RESULTS: Compared with immature dendritic cells and control group, the time of skin survival in E₂ group was significantly longer (P<0.01), especially, the time of skin survival still prolonged 10.6 d after skin rejection in immature dendritic group. The percentage of CD4+CD25+ regulatory T cells in E₂ group was significantly higher than that in immature dendritic cell group and control group (P<0.01). CONCLUSION: In skin allograft model, dendritic cells treated with E₂ prolong the allograft survival time.     

Alteration of intracellular density is a pathological response in adrenaline-induced acute pulmonary edema in mice

AIM: To investigate the change of intracellular density as a pathological response in the lungs. METHODS: A mouse model of acute pulmonary edema (APE) was induced by overdose of adrenaline. The intracellular density alteration was determined by discontinuous sucrose gradient centrifugation of the lung homogenates. Lung wet/dry weight ratio was measured to evaluate the development of APE. Glycogen content, and the mRNA expression of IL-1β and IL-6 in the liver were quantitatively determined. RESULTS: After injection of adrenaline, change of intracellular density was observed in the lungs in a time-and dose-dependent manner, and this change was found to be significantly correlated with the lung wet/dry weight ratio. The mRNA levels of IL-1β and IL-6 in the liver significantly increased, with a peak at 1 h after injection of adrenaline. CONCLUSION: Alteration of intracellular density in the lungs is a pathological response, which can be induced by overdose of adrenaline. This pathological change could be used in the localization of tissues/cells targeted by drugs and in the study of pathogenesis in vivo.     

Flowering and Fruiting in ‘Arbequina’ Olives in Subtropical Climates Where Olives Normally Remain Vegetative

Abstract

It is generally assumed that lack of flowering and fruiting in olives in subtropical climates of southern Texas (e.g. Weslaco Texas area; N 26.16° Latitude 97.96° Longitude) is due to fewer chilling days (<7.2°C) during winter than most olive growing areas of the world. However using controlled environmental chambers we have recently shown that flowering and fruiting in the ‘Arbequina’ cultivar of olives can be achieved without any chilling days. This raised the question of why olive trees don't flower in southern Texas where they do experience some chilling days. We hypothesize that the absence of flowering in olives growing in southern Texas and a similar climate elsewhere is due not to the lack of enough chilling days but most likely due to high temperatures during the day (≥°C) that inhibit flowering. To test our hypothesis we provided cooling to olive trees growing under Weslaco Texas climate by simple shading or by evaporative cooling. These treatments resulted in good flowering and fruiting in ‘Arbequina’ olives in Weslaco Texas after a typical winter period although normally olive trees in this subtropical climate remain vegetative even after winter months.     

‘Just green enough’ in urban renewal: A multifunctional and pragmatic approach in realizing multiscale urban green space optimization in built-up residential areas

Urban green spaces (UGSs) play an essential role in sustainable urban development and are closely related to public health and human well-being. Previous studies seldom consider the relationships between spatial patterns and equity for the heterogeneity of built-up residential types in the city, not to mention how to place the pragmatic design strategies to explore green injustice for vulnerable neighborhoods. To address this gap, our study adopts a cascade of three methodological stages: 1) applying an urban morphological spatial pattern analysis (MSPA) to compare urban UGS patterns and the UGS-adapted Gini coefficient to measure the spatial equity of UGS distributions in three local built-up areas, 2) employing the minimum cumulative resistance (MCR) model to determine the location of the newly added UGSs and adopting the ‘just green enough’ strategy into the redistribution of UGSs for the marginal neighborhood and at the same time to avoid inequality associated with green gentrification, and 3) exploring an integrated design and implementation method for the newly added UGSs that can accommodate both normal conditions and the possibility of future pandemics. The results indicate that there is a strong correlation between socioeconomic status and the distributional justice of UGSs among built-up types, while disadvantaged people living in the densest residential neighborhoods have lower UGS provisions. This paper demonstrates a multifunctional and pragmatic approach for realizing multiscale UGS optimization by exploring it at the subdivision and neighborhood scales. This implication can also help guide decision-makers and planners to understand the complex interplay between social vulnerabilities, gentrification, and urban greening, thus formulating effective policies and hands-on strategies to address green injustice that are not only crucial for this study region but also of great significance for developing countries in the Global South.     

Diversity in mind: Towards a differentiated understanding of migrants’ recreational practices in urban forests

This paper presents results of a study investigating the relationship between migration and recreation in urban forests in two German cities. Research in this field is growing in Europe, yet in certain countries, such as Germany, it remains underdeveloped. Until now, it has revealed ambiguities and diverging results. Furthermore, it has been the subject of criticism and calls for more differentiation between and within migrant groups, as well as for more reflection on the categorisation of “migrant” or “ethnic group”. This paper builds on these claims and aims to shed new light on forest recreation and ethnicity through a context-sensitive research approach in the tradition of symbolic interactionism. It draws upon the analysis of 42 qualitative interviews conducted with people with a Turkish, Russian-German and no migration background. The analysis leads to the construction of five narratives, each of them regrouping respondents who share a similar perspective on a specific theme. The narratives show how personal life context and its interlinkages with migration influence the individual's perspectives on and uses of urban forest. They also show how lifestyle and gender shape recreational practices independently from migration background. Beyond the focus on individual experience, collective recreational practices attributed to some groups are expressed in the narratives. This paper addresses the social aspect of leisure and discusses how forest recreation affects the social construction of groups such as migrant groups.     

Progress in research on meteorological disaster indicators of major fruit trees in China北大核心CSCD

China is an important fruit-producing country in the world. In recent years, the fruit planting area in China increased significantly, and the total fruit output has also rapidly increased. In this context of development, the characteristic fruit industry has become an important source of rural agricultural economic income in China. The stable production of characteristic fruits and disaster prevention and mitigation are of great significance for improving people's living standards and promoting the development of agricultural economy. At the same time, China has a vast territory, spanning three main climatic zones from north to south, and the damage caused by meteorological disasters of fruit trees is extremely serious and frequent. Therefore, research on meteorological disasters of fruit trees is one of the hot topics in agrometeorological disasters research. Especially, the research on meteorological disaster indicator of economic fruit trees is particularly important, which is an inevitable link in disaster monitoring, early warning, defense, planting planning, risk zoning and other research. In this paper, the main meteorological disaster indicators of fruit trees in China are classified and systematically expounded, by using the method of classification and summary. In this paper, the basic concept and significance of meteorological disaster indicators of fruit trees are defined firstly, and then the research history and progress of meteorological disaster indicators of fruit trees in China are summarized. The main research methods of meteorological disaster indicator of fruit trees in China, including fruit trees and disaster types, technology level and main achievements, were summarized in two periods before and after the 21st century. On this basis, the existing meteorological disaster indicators of fruit trees in China are divided into three categories according to their construction methods: the empirical indicator construction method based on disaster verification and disaster investigation; the comprehensive indicator construction method based on the relationship between disaster-causing factors and yields; and the experimental construction method based on artificial climate chamber or artificial climate box. According to the composition types of meteorological disasters of fruit trees in China, the existing meteorological disasters indicators of fruit trees are divided into three categories: single factor indicators, multi-factor indicators and comprehensive indicators. According to the key meteorological factors causing meteorological disasters of fruit trees, the existing meteorological disasters indicators of fruit trees are divided into several categories: low temperature disaster indicators, high temperature disaster indicators, drought disaster indicators, rainstorm disaster indicators and so on. Secondly, aiming at the northern fruit trees, this paper summarizes the research on late frost damage indicator of apple, pear, apricot, plum and grape in spring, drought disaster indicators of apple and walnut, hot damage indicators of apple and kiwifruit in summer, rainstorm disaster indicator of apple and jujube in autumn, and freezing injury indicators of pear, apricot and jujube in winter. For southern fruit trees, it summarizes the research on high temperature damage indicator of citrus, and the research on freezing damage indicator of citrus, litchi, longan, mango and loquat in winter. At the same time, this paper summarizes the types, construction methods, uses, advantages and disadvantages of the above meteorological disaster indicators of fruit trees in agrometeorological service. Finally, this paper discusses the existing problems and the future development direction of the research on meteorological disaster indicators of fruit trees, from the aspects of indicator composition, indicator construction method, fruit tree species, industrial development needs, and new technology and methods. It is expected that the results of this study can provide reference for the distribution of main fruit trees, industrial optimization, disaster prevention and mitigation, and provide scientific guarantee for the healthy, stable and sustainable development of fruit tree growing industry in China. © 2019 Journal of Fruit Science