National park system is currently widely used as a protected area pattern in various countries around the world. Based on the relevant documents of the "Web of Science Core Collection" from 1990 to 2019, this paper analyzes the knowledge map of the international research status of national park management system using CiteSpace software. The results show that the research on international national park management system in the past three decades can be divided into three stages. Since 2016, this field has been receiving more attention from international scholars. Most of the academic researches come from the United States, Australia, Canada, and other countries and institutions. The proportion of relevant research from China is small. Tourism or recreation, protection, and community are the three main issues studied in the field of national park management system in the past three decades. The corresponding objects of management research are roughly citizens or consumers, national park ecosystems, and stakeholders surrounding communities. Consumer behavior or preferences, management policies or guarantees, and benefit distribution mechanisms are the three key points of management system research. Econometric model analysis is currently an important research method in the field. Important research frontiers in this field include national park tourism or recreation under the concept of conservation, coordination of interests between community and national park, and recreation service of national park based on tourists' perception. This paper provides suggestions for the development of China's national parks from the following three aspects: top-level system construction, fund guarantee system, and community coordination mechanism.

In recent years, China has imported a large amount of grains from international market, which may threaten the national food security. It is of great significance for the national food security to investigate the international competitiveness of China's grain industry. Taking the United States (US) as the comparative study object, with the help of costs-returns data of Chinese and American agricultural products, this paper discusses the international competitiveness of China's grain industry from three aspects: land productivity, production cost and sales price. The results show that: 1) From 1998 to 2016, the land productivity of major food crops in China showed a fluctuating upward trend. Compared with the US, except for wheat, the land productivity of rice, corn and soybean in China was lower than that in the US, and the average differences between China and the US during the study period were 16.60% (rice), 30.00% (corn) and 33.08% (soybean), respectively. At the same time, the gaps in corn and soybean present a widening trend. 2) The costs of corn and soybean production in China have always been higher than that in US. China's rice and wheat production costs surpassed the US in 2011. Since then, the cost of food crops production in China has comprehensively surpassed that of the US, and the gap between them has been widening. In 2016, the gap between China and US in grain production costs, from large to small, was soybean, corn, wheat, and rice. 3) The high cost of grain production in China is mainly due to labor costs and land rent, which account for more than half of the total cost, especially the labor cost (30%-40%), which is much higher than that in the US (less than 10%). Since the cost of grain production plays a critical role in price of grains in the market, the price of grains of China has fully surpassed that of the US. 4) In order to enhance the competitiveness of China's grain industry, it is necessary to further enhance the level of agricultural mechanization to reduce rising labor costs, improve the land transfer service system, reduce transfer transaction costs, and pay more attention to improving the level of grain yield per unit area, especially the low-yield crops such as soybeans.

Quality of rural life(QRL) is an important indicator reflecting the level of rural economic development, which is directly related to the vital interests of rural residents and the well-being of the people. This paper constructed a model of QRL and analyzed the spatial differentiation characteristics and influencing factors of QRL by spatial auto-correlation and geographical detector. The results show that: (1) the spatial distribution of QRL has obvious regional differences, the QRL gradually reduces from west to east, and presents obvious spatial clustering characteristics. H-H cluster area is mainly distributed in the central and western regions of Hexi Corridor, L-L cluster area is mainly distributed in the southern regions of the province, both of which are in contiguous distribution, H-L cluster area only contains one county Diebu. (2) The main influencing factors of QRL include precipitation, slope, rate of rural construction land, distance from provincial capital city, total power of agricultural machinery, proportion of GDP of primary industry and total rural population. (3) There are significant spatial differences in the main influencing factors and in the intensity of their effects on the QRL in each evaluation unit. The central, eastern and southern areas of Gansu are dominated by human factors, the Hexi Corridor is dominated by natural factors, and the southeast of Gansu is dominated by human factors and pulled by comprehensive factors.

Based on multi-temporal Landsat remote sensing image data, the temporal and spatial changes of lakes in Wuhan City Circle from 1994 to 2015 were monitored dynamically. At the same time, Using land use cover obtained from remote sensing images in 1994, 2003, 2009, and 2015, combining with climate and economic data, multivariate statistical methods were used to quantitatively analyze the driving factors of the lake evolution. The results show that during the 21 years, the lake area in Wuhan City Circle showed a decreasing trend overall. The evolution process can be roughly divided into three stages: the period of complex changes in lake area(1994-2003), the period of rapid reduction in lake area (2003-2009) and the period of slow reduction in lake area (2009-2015). The most prominent decrease in lake area occurred at the second stage with total lake area declining by 117 km² totally. The driving factors for lake area changes include human activities and climate change. Human activities are the main driving factors that dominate the evolution of lakes. Among them, urban expansion has the greatest impact in lake evolution, followed by population pressure and agricultural development. The impact coefficients are 0.54, 0.51, and 0.47 respectively. Climate change has also contributed to lake evolution in Wuhan City Circle, but it has less influence than human activities.

According to the ground-based multi axis differential absorption spectrometer (max-DOAS), from January 2017 to December 2018 the atmospheric NO₂ and SO₂ pollution status of valley type cities on the northern slope of Tianshan Mountains were analyzed in combination with meteorology, factory, vehicle flow and other factors. The results show that the vertical column concentration of NO₂ VCD was higher than SO₂ VCD in the northern slope of Tianshan Mountains at the same time, showing the characteristics of low at noon and high in the morning and evening, and from large to small in winter, spring, autumn and summer. Spatially, NO₂ VCD of factories, traffic arteries and atmospheric NO₂ VCD near Tianshan Mountains were higher in valley cities on the northern slope of Tianshan Mountains. The valley city on the northern slope of Tianshan Mountains is located at the bottom of the valley, which is easy to produce inversion layer and make the air pollutants difficult to diffuse. The characteristics of urban layout make the air pollution in Fukang and Wusu be aggravated, while that of Bole be reduced. Moreover, the air pollutants carried by foreign air masses will aggravate the atmospheric NO₂ and SO₂ pollution of valley cities on the northern slope of Tianshan Mountains. The pollution degree of NO₂ and SO₂ in the urban air was different with different industrial types. The pollution degree of the city from heavy to light is the secondary industry > the tertiary industry > the primary industry.

Three-dimensional fluorescence spectrum technology (EEMs) and parallel factor analysis (PARAFAC) were applied to study the space-time distribution characteristics and sources of the dissolved organic matter (DOM) in water of Cihu Lake, in order to provide references for the treatment of urban eutrophic lakes. The results show that in Cihu Lake, DOM mainly consisted of terrestrial humic-like component C1 (340/430 nm), unknown humic-like component C2 (390/480 nm), protein-like component C3 (290/350 nm) and the self-generated tryptophan component C4 (280/330 nm). Among them, C1 was the largest contribution to DOM of Cihu Lake, and C4 was the smallest. There were temporal and spatial differences between the four components of the Cihu Lake. The maximum fluorescence value (F_max) of each component was higher in summer and autumn, lower in winter and spring. The most obvious component was C1, followed by C3. In terms of spatial distribution, the F_max value was higher in the area which was close to residential areas, and component C1 changed most obviously. (3) The components of DOM in Cihu Lake was mainly derived from different kinds of humus, followed by endogenous protein-like substances degraded by microorganisms. (4) There was a significant positive correlation between components C1, C2 and C3 in Cihu Lake, which indicate that they had homology. (5) It showed a strong positive correlation with Chl-a conceatration in the absorption coefficient of a₃₅₀, which indicate that the fluorescence absorption property of DOM was closely related to phytoplankton.

The ecosystem services value of land use in industrial parks in Qinzhou city of Guangxi Zhuang Autonomous Region has been analyzed based on the ESV method, shadow engineering project method, and replacement cost method. The multi-objective programming model was constructed to form three basic ecological control line scenarios. The impact of land use change on ecosystem service value was studied and analyzed. The optimal scheme was selected among the scenarios from the perspective of ecosystem service value evaluation. The results show that the ecological service value per unit area of positive effect lands were in the order of mangroves > water bodies > ecological vegetation > public green space. The mangrove area had the greatest impact on the ecological service value of industrial parks. The total value of ecological services in each scenario was scenario 2 > scenario 3 > scenario 1. Scenario 2 was the optimal scenario good for the improvement of ecological services of industrial park with an increasing value of 45.136 7 million CNY by only reducing 0.57% of construction land. Based on this scenario, the basic ecological control line was dividing the industrial park into the first level control area and the second level control area. The value of ecological services of the industrial park under scenario 2 can be guaranteed to the maximum extent with the minimal impact on its development. The study scientifically predicts the ecological benefits, provides the basis for the ecological spatial pattern classification, and provides theoretical references for the ecological control and management of industrial parks.

The study on ecological stoichiometry of alien species can help to understand the mechanism of successful invasion of alien species from the view of ecological stoichiometry. In this study, C, N and P content and their ratio in organs of alien species Rhynchelytrum repens and native species Digitaria multiflorum were determined in order to reveal the carbon, nitrogen and phosphorus stoichiometric characteristics and their nutrition strategy of alien species R. repens. The results show that: (1) The stems-P content of R. repens varies significantly, that the stem-P content of heavy invasive plant (2.858 g·kg^-1) was significantly higher than that of the other two invasive plants (1.197 and 1.284 g·kg^-1, respectively), suggesting that with the increasing of invasive degree the plant distributes more P to the stem. (2) Under three different invasive degrees, N content of leaf (14.35-16.55 g·kg^-1) was higher than that of root (5.376-6.057 g·kg^-1) and stem (4.204-4.238 g·kg^-1), and at heavy invasive site, P content in leaf (2.949 g·kg^-1) and stem (2.858 g·kg^-1) were higher than that of root (1.261 g·kg^-1). At medium and light invasion sites, P content of leaf were higher than that of stem and root. (3) Under the three different invasion degrees, N:P in stem were significant lower than that in root and leaf. Under medium and light invasion degrees, C:P in leaf were lower than that in root and stem. At heavy invasion sites, C:P of stem and leaf were lower than that of root, implying that the growth rate of stem increase with the invasive degree. (4) N and P content in stem, N content in leaf of R. repens were significantly higher than that of D. multiflorum, implying that R. repens has a strong ability to absorb and utilize environmental N and P elements. There was no significant difference in C:N of root, stem and leaf between R. repens and D. multiflorum. It is worth to note that C:P, N:P in stem of R. repens were significant lower than that of D. multiflorum, showing that the growth rate of stem for R. repens may be greater than that for D. multiflorum. (5) Comprehensive analysis of stoichiometric characteristics indicates that strong absorption and utilization of N and P elements, and rapid growth rate of stem contribute to competitive advantage of R.repens, to defeat the native species through "Growth Competition Strategy".

To provide basic information for protection of insect diversity of Xilingol Prairie National Nature Reserve, the butterfly communities were investigated from 2016 to 2018 for five different habitats-wetlands, mountain grassland, grassland with sparse woods, meadow steppe and typical steppe. Totally 1 174 butterflies were collected, which belong to 24 species, 18 genera and 3 families. Among them, Nymphalidae was collleced the most (650) and belonged to 14 species, 10 genera, and Lycaenidae was collected the least (68) and, belonged to 4 species, 4 genera. The analysis of the diversity characteristics of butterfly communities show that Nymphalidae was the highest in Margalef index (2.007 1) and Shannon-Wiener index (1.654 7), while Pieridae was the highest in Pielou index (0.635 9) and Lycaenidae was the highest in Simpson index (0.618 1). The investigation also found that the composition and diversity of butterfly in different habitats were significantly different. The most abundant butterflies (487) were belonged to 19 species and 15 genera from the grassland with sparse woods, which were the highest in Shannon-Wiener index (1.962 8) and Margalef index (2.908 7) among five different habitats. Comparably, the Simpson index (0.430 6) in wetlands was the highest and the Pielou index (0.806 1) was the highest in meadow grassland. In addition, the Jaccard index between different habitats was ranged from 0.25 to 0.5, suggesting a moderate dissimilarity. The Jaccard index (0.600 0) between mountain grassland and typical steppe was the highest. Meanwhile, the analysis revealed an obviously temporal feature of butterfly diversity in the Nature Reserve. The Shannon-Wiener index (2.335 6) and Margalef index (2.656 8) were the highest in July while the lowest were found in May (1.519 2 and 1.456 0, respectively).

To explore the impact of the construction of cascade reservoir on water ecological environment in inland river, macrozoobenthos of the upper and middle reaches of Heihe River (reservoir area and natural river) were investigated from July to August in 2018. In terms of biodiversity index, dominance index and ABC comparative curve, the community and diversity of macrozoobenthos and its response relationship with human activities such as hydro-power cascade construction were analyzed. The results indicate that 43 species of macrozoobenthos were collected, of which 76.75% belong to arthropods, 18.60% belong to molluscs, and 4.65% belong to annelids, and significant spatial differences of the species number and diversity were found, with the values in natural river section significantly higher than those of the reservoir area. In addition, the reservoir area was dominated by static water species. ABC curve analysis show that the habitat in cascade reservoir area gradually became simplified due to the influence of cascade reservoir construction, with the species succession turned gradually from the river type to the static water type of the reservoir. The reaches of the river below the dam were influenced by the disturbance of tail water, where the species composition and diversity of macrozoobenthos showed a decreasing trend. In the middle natural river reaches, as the sewage produced by industry, agriculture and domestic life was directly or indirectly injected into the river, the pollution degree of the river was therefore aggravated, and the concentration of organic matter and nutrients increased significantly, the habitat heterogeneity were improved, the species composition was rich, showing the pollution-resistant dominant type. In addition, climate factors, such as altitude and water temperature were also the key factors affecting the distribution of macrozoobenthos community.

In this study, the bacterial diversity, enzyme activity and soil physicochemical properties of 72 soil samples collected from maize fields of three typical ecological regions (Eastern humid mountain area, central semi humid plain area and western semi-arid plain area) from east to west of Jilin Province were analyzed, and the environmental driving mechanism of bacterial community diversity in typical soils in Jilin Province was discussed. The results show that the organic matter content of Maize Soil in the three typical ecological regions of Jilin Province was in the order of East > Central > West; the number of bacteria in Central area was the highest, and in the East and West was lower. The diversity index showed a gradually decreasing trend from west to east. The activities of neutral and acid phosphatase also showed similar rules, while the activities of sucrase and alkaline phosphate showed opposite trends. Proteobacteria and Actinobacteria were the dominant bacteria phylum in the three ecological regions; and Gemmatimonas and Ochrobactrum were the dominant genera; the abundance of Actinobacteria increased gradually from east to west, while the content of Proteobacteria was opposite. Gemmatimonas showed a trend of Central semi humid plain area > Eastern semi humid Mountain Area > Western semi-arid plain area, and Ochrobactrum showed decreasing trend from east to west. The results of canonical analysis show that, among the climatic factors, rainfall and latitude had a greater impact on the composition of bacterial microbial community. pH value, alkali hydrolyzable nitrogen and organic matter were the main driving factors for the change of soil bacterial dominant groups, which was of great significance to the improvement of the management strategy of maize planting soil in Jilin Province.

To grasp the spatial differentiation characteristics of soil nitrogen and phosphorus ecological stoichiometry and its main influencing factors in a small watershed in the black soil area of Northeast China was of great significance for rational fertilization application. This paper took the Haigouhe River Basin as an example, the spatial variability, distribution pattern and influencing factors of the ecological stoichiometry of soil nitrogen and phosphorus on the surface soil (0-20 cm) were analyzed by applying classical statistical, geostatistical model methods, and integrating "3S" technology. The results show that the mean of total nitrogen (TN) content, total phosphorus (TP) content and soil N to P ratio (N/P) were 2.60 g·kg^-1, 0.55 g·kg^-1 and 4.78, respectively, and the spatial variability of TN content, TP content and N/P were moderate, which were significantly affected by structural elements, e.g. terrain factors and parent materials. The TN, TP and soil N/P showed a stepwise change from east to west, a slight change from north to south, the changes were in good agreement with the change of inland deformation. There was a quite difference in TN content, TP content and N/P under different land use types, the TN content was higher in forestland than that in corn and rice land, while the TP content in forestland was lower than that in corn and rice land. The soil N/P was higher in the agriculture-pasture ecotone where was in the middle of the basin. The N/P was lower in cultivated land than that in other land in general. Cultivated land was also the important area of fertilization management and prevention and control of agricultural non-point source pollution in the agricultural production process. The accumulative effects of agricultural management measures, rural residential, road and other factors on agricultural production and spatial distribution of soil nutrients were more significant.

In order to explore the remediation effect of halophyte (Suaeda salsa) and indigenous microbial on the removal of nitrogen and phosphorus from mariculture wastewater at different pollution levels, two comparative experiments with and without microbial inhibitors were designed. The concentration changes of nitrate nitrogen, nitrite nitrogen, ammonia nitrogen and active phosphate, and the number of nitrifying and denitrifying bacteria before and after the repair of Suaeda salsa were determined respectively. The results showed that under the synergistic effect of halophyte and microbial remediation, the removal rates of ammonia nitrogen at high, medium and low levels were 65.11%, 51.06% and 77.82%, respectively. The removal rates of nitrate nitrogen were 91.47%, 81.98%, 52.42%, and the removal rates of active phosphate were 68.39%, 40.10%, and 28.96%, respectively. Under the action of adding microbial inhibitors to phytoremediation, which means with only the function of halophyte the removal rates of ammonia nitrogen were 94.56%, 48.22%, and 77.97%, the removal rates of nitrate nitrogen were 44.98%, 59.92%, and 47.71%, and the removeal rates of active phosphate were 33.12%, 45.41% and 54.21%, respectively, and the nitrite bacteria decreased by 1-2 orders of magnitude, while the nitrifying bacteria and denitrifying bacteria increased by 1-2 orders of magnitude. It is thus proved that the absorption by halophytes is the main way to remove ammonia nitrogen and active phosphate from saline mariculture wastewater, and the removal of nitrate nitrogen mainly depends on the combined action of denitrifying bacteria and halophyte absorption. With the increase of pollutant concentration, the presence of microorganisms can significantly promote the removal of pollutants.

To explore the application effect of different "VIP+n" technology (V, planting of low-cadmium accumulation varieties; I, optimized irrigation management; P, applying lime; n, spraying foliar inhibitor) on Cd content of double-cropping rice from acidic paddy field with different degrees of heavy metal pollution, the "VIP+n" technology were carried out in the lightly, mediumly and heavily cadmium-polluted rice fields in Xiangtan City of Hunan in 2017. The "VIP+n" technology had significant or extreme significant effects on the content of Cd in brown rice of double-cropping paddy field and soil pH (P<0.05 or 0.01). The pollution degree of Cd in paddy field had significant or extremely significant effects on the content of Cd in brown rice of double-cropping paddy field and the contents of total Cd and extractable Cd in soil (P<0.05 or 0.01). And their interaction effects on the content of Cd in brown rice of late-rice were significant (P < 0.05). The Cd contents of brown rice for early-rice were 0.29, 0.88 and 3.85 mg·kg^-1, respectively, under lightly, moderately and heavily Cd polluted soil, and those for late rice were 0.22, 0.55 and 2.64 mg·kg^-1, respectively. However, the Cd contents of early-rice with "VIP+n" technology were 0.09, 0.34 and 1.17 mg·kg^-1 with a reduction of 70.00%, 61.19% and 69.66%, respectively, significantly different from the control (P<0.05), and those for late-rice were 0.03, 0.32 and 1.01 mg·kg^-1 with a reduction of 87.16%, 41.49% and 61.71%, respectively, significantly or extremely significantly different from the control (P<0.05 or 0.01). Hence, the application effect of "VIP" technology was better for late-rice than that for early-rice. The correlation analysis show that the Cd contents of brown rice at the mature stage of double-cropping rice were negatively correlated with soil pH (r_early=-0.002;r_late=-0.181), but positively correlated with the extractable Cd content of soil (r_early=0.658,P<0.01;r_late= 0.772,P<0.01). The "VIP+n" technology can effectively improve the soil pH, reduce the Cd content of brown rice from double-cropping paddy fields with different degrees of Cd pollution, and under light Cd pollution make it meet the National Food Safety Standards (GB 2762-2017).

A micro-plot experiment was conducted to study the effects of bast fiber mulching film returning (0 to 10 times) on the nutrients and available heavy metals in soil, the growth, and nutrients and the heavy metals contents in pakchoi. Five treatments were performed, including 0 (T₀), 35 (T₁), 70 (T₂), 175 (T₃) and 350 g·m^-2 (T₄). The above five treatments represented the application times of bast fiber mulching film as 0, 1, 2, 5, and 10 times, respectively. The results indicate that the soil alkaline hydrolysis N, available P and K significantly increased by up to 4.47%, 20.70% and 24.62% (P<0.05), respectively, compared with the control (T₀). The bast fiber mulching film returning promoted the growth of pakchoi, with the highest increase in fresh weight of pakchoi and the contents of N, P and K in pakchoi by 110.79%, 18.31%, 14.76%, and 39.99% (P<0.05), respectively. And these physiological properties were increased with the increasing of the bast fiber mulching film returning times. There were no significant difference on the change of available Pb, Ni and Zn in soil and the Zn and Mn concentration in pakchoi under these treatments. Although the content of Pb and Ni in pakchoi were significantly decreased by up to 24.95% and 21.77% (P<0.05). The Cd concentration was slightly increased after the bast fiber mulching film returning. In conclusion, the bast fiber mulching film returning can increase the soil available nutrients contents, and promote the growth and the absorption of N, P and K of pakchoi, but has no significant influence on the micronutrients or heavy metals availability.

Effects of calcium superphosphate (SP, 4.4% dry weight) and ferrous sulfate (LF, 4.1% dry weight) on nitrogen loss and humification were studied during co-composting of cattle manure with straw. Changes in temperature during composting, the chemical properties and humus compositions of the compost products were characterized. The results show that SP and LF groups both met the maturity requirements after 55 days of composting. The C/N ratios of compost products were 11.61 and 13.71, E4/E6 ratios were 1.96 and 1.57, and NH₄⁺-N contents were 34.19 and 35.74 mg·kg^-1, the seed germination indices were 143% and 144%, respectively. The addition of calcium superphosphate and ferrous sulfate had no adverse effect on the phytotoxicity of compost products. The addition of ferrous sulfate had a good nitrogen retention effect (the nitrogen loss of the control group and the LF group were 40.78% and 25.18%, respectively), while the addition of calcium superphosphate had no obvious nitrogen retention effect. It was found that the degradation of organic matter was inhibited in the presence of calcium superphosphate and ferrous sulfate, the loss of organic matter in the control group, SP and LF groups were 58.59%, 49.44% and 34.67%, respectively. The addition of calcium superphosphate and ferrous sulfate could improve the quality of humus. The percentages of humic acid in SP and LF groups were 45.23% and 51.60%, respectively, which were higher than 36.85% in the control group. Therefore, the addition of ferrous sulfate can significantly reduce the nitrogen loss during co-composting of cattle manure with straw, and improve the humus quality of the compost effectively.

In order to explore the physicochemical characteristics and organic matter migration characteristics of thermal hydrolysis pretreatment on high solids sludge, a small thermal hydrolysis reactor was used to simulate the sludge hydrolysis test indoors, and the viscosity of thermal hydrolysis treatment on high solids sludge. Specific resistance, thermal conductivity and other physical characteristics and the influence of organic matter migration characteristics such as COD dissolution rate, SS dissolution rate and VSS dissolution rate was studied. Results show that after thermal hydrolysis treatment of urban sludge with solids content of 9% at 190 ℃ and 50 min, the thermal conductivity was increased by about 15%, and the viscosity and specific resistance were reduced by about 99.5%. The COD dissolution rate, SS dissolution rate, and VSS dissolution rate of the sludge were about 40%, 35%, and 70% under the conditions of 170 ℃ and 30 min thermal hydrolysis treatment, respectively. Thermal hydrolysis treatment can improve the physical properties of sludge for facilitating subsequent treatment; the COD in the sludge was also transferred from the solid phase to the liquid phase, which improved the anaerobic digestion performance of the sludge. During the thermal hydrolysis of the sludge, the kinetic model of the organic matter showed that the dissolution of the VSS in the thermal hydrolysis process was in line with the first-order reaction kinetic model by R²=0.990 9, P<0.01.