Generalized Competition Index of Primitive Digraphs

For any positive integers k and m, the k-step m-competition graph C^（D） of a digraph D has the same set of vertices as D and there is an edge between vertices x and y if and only if there are distinct m vertices vi, v2, .., Vm in D such that there are directed walks of length k from x to vi and from y to vi for all 1 ≤ i≤ m. The m-competition index of a primitive digraph D is the smallest positive integer k such that Ckm（D） is a complete graph. In this paper, we obtained some sharp upper bounds for the m-competition indices of various classes of primitive digraphs.

Generalized Competition Indices of Primitive θ-Graphs

As a generalization of the scrambling index and the exponent,m-competition index has been widely applied to stochastic matrices,food webs and memoryless communication systems in recent years. For a positive integer m,where 1 ≤ m ≤ n,the mcompetition index( generalized competition index) of a primitive digraph D of order n is the smallest positive integer k such that for every pair of vertices x and y,there exist m distinct vertices v_1,v_2,…,v_m such that there exist walks of length k from x to v_i and from y to v_i for 1 ≤ i ≤ m. By analyzing the structure of θ-graphs( theta graphs) and using enumeration investigation methods,the mcompetition indices of primitive θ-graphs are studied and an upper bound is provided. Moreover, some corresponding extremal θ-graphs are characterized.

Comparative Analysis of Rice Export Competitiveness in Heilongjiang Province of China Based on Index Method

Based on the analysis of rice planting and export development in Heilongjiang Province in 2013-2021,this paper comprehensively used three export competitiveness analysis methods,namely,trade competitiveness index,revealed comparative advantage(RCA)analysis and international market share analysis,to compare the four major rice exporters in the world and the three major rice export provinces and cities in China.Besides,it evaluated the rice export competitiveness of Heilongjiang Province from multiple perspectives.It analyzed the reasons for low competitiveness in terms of export product structure,export market structure,production and processing technology,and brand building.Finally,it is recommended to clarify the positioning of rice export quality and take more measures to ensure product quality;improve the level of industrialization of rice production and processing,and extend the rice industry chain;develop diversified rice export markets and improve export flexibility;adhere to the principle of"opening the door and going out",expand the international popularity of high-quality brands,so as to enhance the rice export competitiveness of Heilongjiang Province.

COMPETITION IN OLD GROWTH KOREAN PINE FOREST

Korean pine(Pinus koraiensis) interspecilic competition and intraspecifie companioned with other species competition in old growth Korean pine forest in northeast China were studied using Hegyi's competition index model for individual tree.The results show that differences of competitive intensity exist in interspecific and intraspecific for Korean pine with an order of intraspecific ＞Abies nephrolepis Picea koraiensis Tilia amurensis Betula costat＞Acer mono ＞Ulnuts propinqua＞Populus davidiana,and that relationship of competitive index to indivdual size (in DBH) of objective tree follows closely multiplieate eqtuation and that competitive intensity gradually reduces with inereasing of individual size of objective tree, but it is tending towards stability after individual of objective tree inerease to specified size (DBH about 20 cm).It provided a serviceable approach for researches of intraspecific relationship in population ecology.

从国家自然科学基金看西藏自治区的基础研究及其竞争力

文章基于国家自然科学基金2001—2019年资助项目统计资料和LetPub网站提供的国家自然科学基金项目数据库(2001—2020年),分析了西藏过去20年国家自然科学基金资助项目经费和项目数的变化趋势、学科分布情况、不同学科及高等院校和科研机构的基础研究竞争力。主要结果如下:(1)过去20年西藏获国家自然科学基金资助以地区科学基金为主,面上项目和青年基金占比很少;(2)西藏优势学科主要体现在生命科学、地球科学以及医学科学领域,数理、信息、工程与材料领域较弱,而化学和管理科学领域竞争力则更弱;(3)尽管过去20年资助经费总体呈增长态势,但总体竞争能力与其它地区相比明显较弱,且呈轻微下降趋势,可能与地球科学以及信息科学领域的竞争力下降有关;(4)过去20年共有14家单位获得过国家自然科学基金“面青地”项目资助,其中,西藏农牧学院、西藏大学和西藏民族大学三家高等院校基础研究竞争力相对较强。未来应加大对青年人才的挖掘和培养,加强对化学、管理学、地球科学以及信息科学等学科的建设,持续推动西藏基础研究向更广、更深的方向发展。

Tree mortality and biomass loss in drought-aff ected forests of East Texas,USA

Changes in tree mortality due to severe drought can alter forest structure,composition,dynamics,ecosystem services,carbon fl uxes,and energy interactions between the atmosphere and land surfaces.We utilized long-term(2000‒2017,3 full inventory cycles)Forest Inventory and Analysis(FIA)data to examine tree mortality and biomass loss in drought-aff ected forests for East Texas,USA.Plots that experienced six or more years of droughts during those censuses were selected based on 12-month moderate drought severity[Standardized Precipitation Evaporation Index(SPEI)-1.0].Plots that experienced other disturbances and inconsistent records were excluded from the analysis.In total,222 plots were retained from nearly 4000 plots.Generalized nonlinear mixed models(GNMMs)were used to examine the changes in tree mortality and recruitment rates for selected plots.The results showed that tree mortality rates and biomass loss to mortality increased overall,and across tree sizes,dominant genera,height classes,and ecoregions.An average mortality rate of 5.89%year−1 during the study period could be incited by water stress created by the regional prolonged and episodic drought events.The overall plot and species-group level recruitment rates decreased during the study period.Forest mortality showed mixed results regarding basal area and forest density using all plots together and when analyzed the plots by stand origin and ecoregion.Higher mortality rates of smaller trees were detected and were likely compounded by densitydependent factors.Comparative analysis of drought-induced tree mortality using hydro-meteorological data along with drought severity and length gradient is suggested to better understand the eff ects of drought on tree mortality and biomass loss around and beyond East Texas in the southeastern United States.

The growth and production modeling of individual trees of Eucalyptus urophylla plantations

Individual tree models(ITMs)are classified as growth and production models for projecting current and future forest stands.ITMs are more complex than other growth and production models,show a higher level of detail and,consequently,produce a better modeling resolution.However,the accuracy and efficiency of ITMs have not been properly assessed to date.In this study,we estimated the growth in height,diameter,and individual tree volume of a Eucalyptus urophylla plantation by applying an ITM.We used a continuing forest inventory dataset in which 1554 individual trees within 29 permanent plots were measured in the field over a 6-year period(24 to 72 months).Each individual tree volume was estimated for future tree age.To achieve this,we adjusted the model to predict the height and diameter growth,and the probability of mortality as a function of the competition index.The ITM accuracy was assessed based on the analysis of variance results and,subsequently,the multiple mean comparison test at the 5%significance level.The tree volumes predicted by the ITM for the forest stand aged 72 months,beginning at ages 24,36,48,and 60 months,were compared to the field measured tree volume acquired from the 72-month forest inventory that was used as the reference age.Estimated and observed tree volumes were similar when the estimation was based on the 48-month forest plots.These results might help to reduce financial costs of forest inventory because the ITM produces accurate future predictions of forest stand stocks.Our estimated ITM for Eucalyptus plantations using measurement intervals up to 2 years is recommended because it significantly reduced the projected volume discrepancy compared to the field measurements.

Growth and yield of Solanum khasianum in Pinus roxburghii forest based silvi-medicinal system in mid hills of Indian Himalaya

Background：In mid hills of Western Himalayas,Himachal Pradesh India,growth,yield and economics of Solanum khasianum as a potential medicinal herb under Pinus roxburghii（Chir pine） plantation has been studied for two consecutive years to assess the performance of Solanum khasianum in undercanopy of Pinus roxburghii for developing Solanum khasianum and Pinus roxburghii based innovative silvi-medicinal system.Methods：Growth parameters such as plant height,number of branches per plant and leaf area index followed by yield were estimated after Solanum khasianum was grown on three topographical aspects as;Northern,North- western and Western at a spacing of 45 cm x 45 cm,followed by three tillage depths as;minimum（0 cm）,medium（up to 10 cm）and deep tillage（up to 15 cm）,in open and below canopy conditions treatment.The study was conducted to explore the possibility of using Solanum khasianum based silvi-medicinal system to utilize the below canopy of Chir pine forest for enhancing the productivity of forests besides the conservation of the medicinal herb.Results：The growth parameters such as plant height,number of branches per plant and leaf area index were nonsignificantly affected by topographical aspects and tillage practices,both below canopy and open conditions except fresh weight and dry weight of berries during harvesting stage.The maximum yield（0.61 t·ha^（-1）） was observed on Western aspect in open conditions as compared to below canopy of Chir pine.The highest gross returns were observed for the crop cultivated on Western aspect under deep tillage in open conditions than other aspect and tillage combinations.However the positive net returns from the crops raised in below canopy of Chir pine indicates its possible economic viability under agroforestry system as the gross returns was higher than the cost of cultivation.Conclusion：Solanum khasianum when grown in below canopy of Pinus roxburghii,its growth and yield indicated positive net returns.Solanum khasianum and Pinus roxburghii based silvi-medicinal system has the potential to enhance the overall productivity of Chir pine forest.This silvi-medicinal system gives scope for utilizing floor Chir pine forests for growth and production of Solanum khasianum beside conservation of the medicinal herb.

Analysis of Chinese A gricultural Product Trade

This paper clarifies thestatus of Chinese agricultural product trade through the calculation of Chinese agricultural product trade competitive advantage index for a total of 21 years from 1999 to 2019.

Renminbi Nominal Effective Exchange Rate for Third Market Competition:An Approach Based on Disaggregated Trade Data

When measuring the nominal effective exchange rate （NEER）, three factors should be considered： direct import competition, direct export competition and third market competuion. The traditional NEER methodology using aggregated export trade data underestimates the competition between countries producing homogeneous goods, so that the weight of the effective exchange rates is too reliant on trade scale. Based on 2002 6-digit items of the Harmonized Commodity Description and Coding System, this paper employs the competitive stress index to adjust the weighting system of the renminbi NEER for third market competition. In the new weighting system, European countries and some emerging economies have higher weights compared with some of the developed countries, including the USA, Japan and resources-dominated eeonomies~ This research will facilitate the understanding of changes in China＇s export competitiveness.

The competitiveness of China’s seaweed products in the international market from 2002 to 2017

China is the most productive seaweed farming country in the world and her seaweed imports and exports have a significant impact on global seaweed trade commodities and food security.Nevertheless,few studies had delved into the main characteristics and development of China’s seaweed farming industry.This paper aims to narrow this research gap by analyzing trade patterns in China’s seaweed products and the international competitiveness of seaweed product by using the international market share index(IMS),the trade competitiveness index(TC),and revealed comparative advantage index(RCA)from 2002 to 2017.The results showed that Japan,the Association of Southeast Asian Nations(ASEAN),Chile,Peru,and the Republic of Korea are China’s main trade partners,the total trade value of China’s seaweed products has grown rapidly,its imports have gradually exceeded exports,the trade deficit continues to expand,and its competitiveness keeps decreasing.The reasons for this trend may include the changing seaweed trade commodity structure,product differentiation,increased government support in competing countries,and trade barriers among the trade partners.We propose actively expanding international trade markets,establishing a strong seaweed product processing industry to develop high value-added seaweed products,optimizing the trade commodity structure,and differentiating of seaweed products to improve the competitiveness of China’s seaweed products.

How competitive is the‘pioneer-climax’tree species Nothofagus alpina in pristine temperate forests of Chile?

Aims Nothofagus species are constitutive elements of the temperate forests along the Southern Andes Mountains.The deciduous Nothofagus alpina is a fast-growing,but long-lived opportunistic pioneer spe-cies(‘pioneer-climax species’)and co-occurs with the evergreen N.dombeyi.We tested whether N.alpina is competitively superior to N.dombeyi in mature stands and whether intra-specific competition in N.alpina is stronger than inter-specific competition with N.dombeyi.Methods In a pristine old-growth forest in South-Central Chile,we compared the growth of N.alpina trees in pure stands and in mixture with N.dombeyi to the growth of N.dombeyi and calculated compe-tition indices.We related growth variables to climate data and weather extremes.Important Findings In N.alpina,juvenile basal area increment was signifi-cantly higher in pure than in mixed stands.Contrary to our hypothesis,N.dombeyi exhibited larger radial stem increments than N.alpina in the most recent 40 years.In the most recent two decades,this was caused by high growth rates of large N.dombeyi trees.In both Nothofagus species,stem growth was negatively related to temperature,but N.dombeyi responded more sensitively to weather conditions than N.alpina.In N.alpina,stem increment was negatively related to the intensity of competition,but the size of the competition effects on this species was similar in pure and mixed stands.Thus,compared to N.alpina,the‘pioneer-climax species’concept is even more appropriate for N.dombeyi with its relatively high growth rates even in the early stages of its life.

Research on Measurement of China’s Inter-Provincial Trade,International Trade and Low-Carbon Trade Competitiveness

In this paper,Embodied carbon emission competitiveness in international trade and inter-provincial trade is measured and comparative analysis is conducted.Specifi cally the non-competitive input-output model and low-carbon trade competitiveness index are constructed to study the embodied carbon emission competitiveness of 31 Chinese provinces in international trade and inter-provincial trade from the perspectives of the whole,three industries and product sectors.We find that Shanghai is the most competitive in low-carbon trade,while Qinghai is the least;carbon leakage in international trade is severe;the performance of different product sectors differ widely in embodied carbon emission competitiveness in international trade and inter-provincial trade;the primary and secondary industries are competitive in low-carbon inter-provincial trade and the tertiary industry is competitive in low-carbon international trade.The innovations of this paper is as follows:methodology in low-carbon trade competitiveness index is innovated;macro,meso and micro perspectives are taken;factors in international trade and inter-provincial trade are combined in content.In the end,development of low-carbon trade is promoted and references for policy are provided for a new round of trade competition.