scholarly journals Prediction of Potentially Suitable Distributions of Codonopsis pilosula in China Based on an Optimized MaxEnt Model

2021 ◽  
Vol 9 ◽  
Author(s):  
Huyong Yan ◽  
Jiao He ◽  
Xiaochuan Xu ◽  
Xinyu Yao ◽  
Guoyin Wang ◽  
...  
Keyword(s):  
Distribution Area ◽  
Last Interglacial ◽  
Modeling Tools ◽  
Factors Affecting ◽  
Maxent Model ◽  
Codonopsis Pilosula ◽  
Diurnal Range ◽  
Precipitation Seasonality ◽  
Suitable Area ◽  
The Impact

Species distribution models are widely used in conservation biology and invasive biology. MaxEnt models are the most widely used models among the existing modeling tools. In the MaxEnt modeling process, the default parameters are used most often to build the model. However, these models tend to be overfit. Aiming at this problem, this study uses an optimized MaxEnt model to analyze the impact of past, present and future climate on the distributions of Codonopsis pilosula, an economic species, to provide a theoretical basis for its introduction and cultivation. Based on 264 distribution records and eight environmental variables, the potential distribution areas of C. pilosula in the last interglacial, middle Holocene and current periods and 2050 and 2070 were simulated. Combined with the percentage contribution, permutation importance, and jackknife test, the environmental factors affecting the suitable distribution area of this species were discussed. The results show that the parameters of the optimal model are: the regularization multiplier is 1.5, and the feature combination is LQHP (linear, quadratic, hinge, product). The main temperature factors affecting the distribution of C. pilosula are the annual mean temperature, mean diurnal range, and isothermality. The main precipitation factors are the precipitation seasonality, precipitation in the wettest quarter, and precipitation in the driest quarter, among which the annual average temperature contributes the most to the distribution area of this species. With climate warming, the suitable area of C. pilosula exhibits a northward expansion trend. It is estimated that in 2070, the suitable area of this species will expand to its maximum, reaching 2.5108 million square kilometers. The highly suitable areas of C. pilosula are mainly in Sichuan, Gansu, Shaanxi, Shanxi, and Henan Provinces. Our findings can be used to provide theoretical support related to avoiding the blind introduction of C. pilosula.

scholarly journals Impact of Climate Change on Potential Distribution of Chinese White Pine Beetle Dendroctonus armandi in China

Forests ◽  
2021 ◽  
Vol 12 (5) ◽  
pp. 544
Author(s):  
Hang Ning ◽  
Ming Tang ◽  
Hui Chen
Keyword(s):  
Climate Change ◽  
Potential Distribution ◽  
Greenhouse Gas Emission ◽  
Central China ◽  
Qinling Mountains ◽  
Climate Scenarios ◽  
Impact Of Climate Change ◽  
Precipitation Seasonality ◽  
Suitable Area ◽  
The Impact

Dendroctonus armandi (Coleoptera: Curculionidae: Scolytidae) is a bark beetle native to China and is the most destructive forest pest in the Pinus armandii woodlands of central China. Due to ongoing climate warming, D. armandi outbreaks have become more frequent and severe. Here, we used Maxent to model its current and future potential distribution in China. Minimum temperature of the coldest month and precipitation seasonality are the two major factors constraining the current distribution of D. armandi. Currently, the suitable area of D. armandi falls within the Qinling Mountains and Daba Mountains. The total suitable area is 15.83 × 104 km2. Under future climate scenarios, the total suitable area is projected to increase slightly, while remaining within the Qinling Mountains and Daba Mountains. Among the climate scenarios, the distribution expanded the most under the maximum greenhouse gas emission scenario (representative concentration pathway (RCP) 8.5). Under all assumptions, the highly suitable area is expected to increase over time; the increase will occur in southern Shaanxi, northwest Hubei, and northeast Sichuan Provinces. By the 2050s, the highly suitable area is projected to increase by 0.82 × 104 km2. By the 2050s, the suitable climatic niche for D. armandi will increase along the Qinling Mountains and Daba Mountains, posing a major challenge for forest managers. Our findings provide information that can be used to monitor D. armandi populations, host health, and the impact of climate change, shedding light on the effectiveness of management responses.

scholarly journals MaxEnt Modeling Based on CMIP6 Models to Project Potential Suitable Zones for Cunninghamia lanceolata in China

Forests ◽  
2021 ◽  
Vol 12 (6) ◽  
pp. 752
Author(s):  
Yichen Zhou ◽  
Zengxin Zhang ◽  
Bin Zhu ◽  
Xuefei Cheng ◽  
Liu Yang ◽  
...  
Keyword(s):  
Climate Change ◽  
Species Distribution ◽  
Water Conservation ◽  
Critical Role ◽  
Cunninghamia Lanceolata ◽  
Distribution Area ◽  
Timber Species ◽  
Diurnal Range ◽  
The Future ◽  
Suitable Area

Cunninghamia lanceolata (Lamb.) Hook. (Chinese fir) is one of the main timber species in Southern China, which has a wide planting range that accounts for 25% of the overall afforested area. Moreover, it plays a critical role in soil and water conservation; however, its suitability is subject to climate change. For this study, the appropriate distribution area of C. lanceolata was analyzed using the MaxEnt model based on CMIP6 data, spanning 2041–2060. The results revealed that (1) the minimum temperature of the coldest month (bio6), and the mean diurnal range (bio2) were the most important environmental variables that affected the distribution of C. lanceolata; (2) the currently suitable areas of C. lanceolata were primarily distributed along the southern coastal areas of China, of which 55% were moderately so, while only 18% were highly suitable; (3) the projected suitable area of C. lanceolata would likely expand based on the BCC-CSM2-MR, CanESM5, and MRI-ESM2-0 under different SSPs spanning 2041–2060. The increased area estimated for the future ranged from 0.18 to 0.29 million km2, where the total suitable area of C. lanceolata attained a maximum value of 2.50 million km2 under the SSP3-7.0 scenario, with a lowest value of 2.39 million km2 under the SSP5-8.5 scenario; (4) in combination with land use and farmland protection policies of China, it is estimated that more than 60% of suitable land area could be utilized for C. lanceolata planting from 2041–2060 under different SSP scenarios. Although climate change is having an increasing influence on species distribution, the deleterious impacts of anthropogenic activities cannot be ignored. In the future, further attention should be paid to the investigation of species distribution under the combined impacts of climate change and human activities.

scholarly journals Range Shift in Response to Climate Change of Chinese Caterpillar Fungus Based on Species Redundancy

2021 ◽  
Author(s):  
Jian Chen ◽  
Yuan Feng ◽  
Wu Kui ◽  
Dai Dong ◽  
Wang Dong ◽  
...  
Keyword(s):  
Climate Change ◽  
Distribution Pattern ◽  
Host Plants ◽  
Climatic Conditions ◽  
Range Shift ◽  
Distribution Area ◽  
Maxent Model ◽  
Pattern Similarity ◽  
Caterpillar Fungus ◽  
Suitable Area

The presence of the Chinese caterpillar fungus (CCF) depends on the distribution of its host insects and host plants. However, its distribution pattern in response to climate change and interspecific relationships in geographical distribution is unknown. We used the MaxEnt model to obtain areas suitable for the CCF, considering its host insects and host plants under different historical climate backgrounds. We then superimposed and analyzed them to explore the range shift in response to climate change of Chinese caterpillar fungus based on species redundancy. From the Last Glacial Maximum (LGM) to 2050, the suitable distribution pattern of the CCF is estimated to change from fragmentized to concentrated and connected. The high redundancy area (HRA) continued to increase from the Middle Holocene (MH) to the present and 2050, with an increased area of 31.46×104 km2. The suitable area moved to the northwest and the total movement distance of its average coordinates was about 500 km. The altitude of the suitable area increased continuously from the LGM to the present and to 2050, and the average altitude of HRA increased from 2740.89 m (LGM) to 4246.76 m (2050). The distribution pattern and changes of CCF under different climatic conditions provides a reference for the current and future geographical regional planning for conservation and sustainable utilization. The distribution pattern similarity of the CCF suitable area, suitable area for host insects, and host plants HRA of distribution area, might be the result of their long-term co-evolution. The decreasing trend of CCF yield under human disturbance was not as severe as expected, suggesting that climate change may be beneficial to distribution expansion of the CCF.

scholarly journals Climatic Suitability of the Geographic Distribution of Stipa breviflora in Chinese Temperate Grassland under Climate Change

2018 ◽  
Vol 10 (10) ◽  
pp. 3767 ◽  
Author(s):  
Xiaomin Lv ◽  
Guangsheng Zhou
Keyword(s):  
Climate Change ◽  
Geographic Distribution ◽  
Quantitative Description ◽  
Temperate Grassland ◽  
Distribution Area ◽  
Climatic Suitability ◽  
Maxent Model ◽  
Northward Expansion ◽  
Four Levels ◽  
Suitable Area

Stipa breviflora, a dominant species of Chinese temperate grassland, is vulnerable to climate change. A quantitative description of the changes in the geographic distribution of S. breviflora under climate change can provide a reference for potential changes in Chinese temperate grassland and the necessary countermeasures to cope with climate change. In this study, the relationship between the geographic distribution of S. breviflora and the climate, and its inter-decadal change in geographic distribution and climatic suitability from 1961 to 2040 were investigated. The results showed that S. breviflora’s geographic distribution could be simulated very well by the MaxEnt model, and its climatic suitability could be divided into four levels—most suitable, medium suitable, less suitable, and unsuitable areas—based on its existence probability from the MaxEnt model. In the past 50 years, the total climate-suitable area for S. breviflora’s potential geographical distribution exhibited an obvious increase and a trend of northward expansion, which was larger than the current distribution area. The total climate-suitable area would increase by about 6.7% and decrease by 11.5% from 2011–2040 under RCP4.5 and RCP8.5 climate scenarios, respectively; however, the most suitable area increased and moved to western areas of Tibet, Qinghai, and Ningxia. The results revealed that the distribution area of S. breviflora still has greater potential for expansion.

scholarly journals Predicting the Potential Distribution of Two Varieties of Litsea coreana (Leopard-Skin Camphor) in China under Climate Change

Forests ◽  
2020 ◽  
Vol 11 (11) ◽  
pp. 1159
Author(s):  
Jinwen Pan ◽  
Xin Fan ◽  
Siqiong Luo ◽  
Yaqin Zhang ◽  
Shan Yao ◽  
...  
Keyword(s):  
Climate Change ◽  
Potential Distribution ◽  
Greenhouse Gas Emission ◽  
Climatic Conditions ◽  
Raw Material ◽  
Vegetation Growth ◽  
Maxent Model ◽  
Diurnal Range ◽  
Huai River ◽  
Suitable Area

Climate change considerably affects vegetation growth and may lead to changes in vegetation distribution. Leopard-skin camphor is an endangered species, and the main raw material for hawk tea, and has various pharmacodynamic functions. Studying the potential distribution of two leopard-skin camphor varieties under climate change should assist in the effective protection of these species. We collected the distribution point data for 130 and 89 Litsea coreana Levl. var. sinensis and L. coreana Levl. var. lanuginosa, respectively, and data for 22 environmental variables. We also predicted the potential distribution of the two varieties in China using the maximum entropy (MaxEnt) model and analyzed the key environmental factors affecting their distribution. Results showed that the two varieties are mainly located in the subtropical area south of the Qinling Mountains–Huai River line in the current and future climate scenarios, and the potentially suitable area for L. coreana Levl. var. lanuginosa is larger than that of L. coreana Levl. var. sinensis. Compared with current climatic conditions, the potentially suitable areas of the two leopard-skin camphor varieties will move to high-latitude and -altitude areas and the total suitable area will increase slightly, while moderately and highly suitable areas will be significantly reduced under future climatic scenarios. For example, under a 2070-RCP8.5 (representative of a high greenhouse gas emission scenario in the 2070s) climatic scenario, the highly suitable areas of L. coreana Levl. var. sinensis and L. coreana Levl. var. lanuginosa are 6900 and 300 km2, and account for only 10.27% and 0.21% of the current area, respectively. Temperature is the key environmental factor affecting the potential distribution of the two varieties, especially the mean daily diurnal range (Bio2) and the min temperature of the coldest month (Bio6). The results can provide a reference for relevant departments in taking protective measures to prevent the decrease or extinction of the species under climate change.

scholarly journals Predicting Mango Sudden Decline Due to Ceratocystis fimbriata Under a Changing Climate

2021 ◽  
Vol 39 (3) ◽  
pp. 215-223
Author(s):  
Amna M. Al-Ruheili ◽  
◽  
Alaba Boluwade ◽  
Ali M. Al-Subhi ◽  
◽  
...  
Keyword(s):  
Climate Change ◽  
Fruit Trees ◽  
Climate Change Scenarios ◽  
Ceratocystis Fimbriata ◽  
Jackknife Test ◽  
Maxent Model ◽  
Diurnal Range ◽  
Bioclimatic Variables ◽  
Climatic Scenarios ◽  
Suitable Area

Mango fruit trees are an important fruit crop due to their high value. Mango sudden decline (MSD) is a major disease that threatens mango trees in Oman and worldwide. The objective of this study was to identify those areas in northern Oman in which Ceratocystis fimbriata (a plant fungal pathogen causing MSD) may establish itself under various climate change scenarios. The MaxEnt model used in this study was based on data for the period 1970-2000 and then projected to future climate periods. This study modeled the future distribution of C. fimbriata for 2021–2040, 2041–2060, 2061–2080, and 2081–2100 climatic scenarios. Fifteen affected locations and seven bioclimatic variables were investigated in this study. The model showed values between 0.896 and 0.913 (habitat suitability) which represented a good model outcome. The jackknife test showed that the mean diurnal range in temperature, precipitation of the driest month, and elevation contributed to C. fimbriata distribution. From 2021 through 2040, a total area of 1,889 km2 was found to be highly suitable for C. fimbriata in Northern Oman. Compared with the 2021–2040 period, the poorly suitable area would increase in both 2041–2060 and 2081–2100 periods. The moderately suitable regions for C. fimbriata would decrease under all scenarios investigated. However, the total area of the suitable areas, with all scenarios, would increase, except during the 2041-2060 period. This research offers a tool to better manage and prevent the possible Ceratocystis blight (C. fimbriata) and bark beetle (Hypocryphalus mangiferae) invasions under future projected climatic scenarios. Keywords: Mango sudden decline (MSD), “Ceratocystis fimbriata”, bioclimatic variables, climate change, Sultanate of Oman, Maxent.

scholarly journals The potential distribution of Chiranthodendron pentadactylon (Malvaceae) through time: Phylogeography revisited and predicted environmental suitability under alternative future climate change scenarios.

2021 ◽  
Author(s):  
Diana Hernandez Langford ◽  
Jaime Escoto Moreno ◽  
Joaquín Sosa Ramírez
Keyword(s):  
Climate Change ◽  
Potential Distribution ◽  
Future Climate ◽  
Future Climate Change ◽  
Climate Change Scenarios ◽  
Last Interglacial ◽  
Modeling Tools ◽  
Southern Mexico ◽  
Environmental Suitability ◽  
The Impact

Aim: Mexican hand tree Chiranthodendron pentadactylon is an evergreen temperate tree species restricted to cloud forests and pine-oak forests of southern Mexico, Guatemala and possibly Honduras. Climate is believed to significantly contribute to the species establishment, viability and distribution. Insights into the impact of climate change on the species potential distribution throughout time were approached by ecological niche modeling tools. Location: Southern Mexico, Guatemala and Honduras. Methods: Past (Last Interglacial 120-140 KA, Last Glacial Maximum 22 KA, Mid-Holocene 6 KA), historical (1910-2009) and future (2021-2040, 2041-2060, 2061-2080 and 2081-2100) potential distributions and corresponding environmental suitability were modelled using the Maximum Entropy algorithm. Current (historical) models were based on the most up to date historical environmental variables and constituted the baseline for past and future projections. Past predictions are revisited in a phylogeographic context. Future predictions were made for four different emissions scenarios. Results: Increase in potential distribution range comes about during cold and humid periods but higher suitability possibly relates to humid conditions. Potential distribution alongside environmental suitability diminishes during warm and dry periods. Future climate change implies warmer periods whence environmental suitability declines following a linear trend. Main conclusions: Future warmer conditions are predicted to linearly reduce environmental suitability throughout time. Biotic and anthropogenic factors further threaten the species distribution. Demographic trends and genetic diversity estimated through a recent phylogeographic study, complement the statement that populations viability is increasingly being threatened by current and future climate change, underscoring the need for the implementation of conservation actions.

DAMPAK KEBIJAKAN FISKAL TERHADAP KINERJA SEKTOR PERTANIAN DI SULAWESI TENGGARA

2017 ◽  
Vol 1 (1) ◽  
Author(s):  
La Ode Jabuddin ◽  
Ayub M Padangaran ◽  
Azhar Bafadal Bafadal
Keyword(s):  
Fiscal Policy ◽  
Interest Rates ◽  
Agricultural Sector ◽  
Simultaneous Equations ◽  
Poor People ◽  
Land Area ◽  
Factors Affecting ◽  
Historical Simulation ◽  
The Impact ◽  
Direct Expenditure

This study aims to: (1) Knowing the dynamics of fiscal policy and the performance of the agricultural sector, (2) Analyze the factors that influence fiscal policy and the performance                   of the agricultural sector, and (3) Analyzing the impact of fiscal policy on the performance of the agricultural sector. The data used in this study were pooled 2005-2013 data in the aggregate. Econometric model the impact of fiscal policy on the performance of the agricultural sector is built in the form of simultaneous equations, consisting of 7 equations with 25 total variables in the model, 7 endogenous variables, 12 exogenous variables, and 6 variables lag. The model is estimated by 2SLS method SYSLIN procedures and historical simulation with SIMNLIN procedure.The results showed that: (1) The development of fiscal policy in Southeast Sulawesi from year to year tends to increase, (2) The performance of the agricultural sector from the aspect of GDP has decreased, from the aspect of labor is still consistent, in terms of investment to grow positively, and assign roles which means to decrease the number of poor people, (3) factors affecting fiscal policy is local revenues, equalization funds, other revenues, as well as the lag fiscal policy, (4) the factors that affect the performance of the agricultural sector from the aspect GDP is labor, direct expenditure and GDP lag; from the aspect of labor is the total labor force, investment, land area, direct expenditure, as well as the lag of labor; from the aspect of investment is influenced by GDP per capita, land area, interest rates and investment lag; as well as from the aspect of poor people, are affected by population, investments, direct expenditure and poverty lag, (5). Fiscal policy impact on the agricultural sector GDP increase, a decrease in the number of poor, declining agricultural laborers, and a decrease in the amount of investment in the agricultural sector.Keywords: Fiscal policy, the performance of the agricultural sector, the simultaneous equations

Structural Model of Service Quality Factors Affecting Loyalty Sustainability

2020 ◽  
Vol 11 (2) ◽  
Author(s):  
Eman Al-erqi ◽  
◽  
Mohd Lizam Mohd Diah ◽  
Najmaddin Abo Mosali ◽  
◽  
...  
Keyword(s):  
International Students ◽  
Service Quality ◽  
Goodness Of Fit ◽  
Structural Model ◽  
Quality Factors ◽  
Factors Affecting ◽  
Measurement Models ◽  
Confirmatory Factor ◽  
The University ◽  
The Impact

This study seeks to address the impact of service quality affecting international student's satisfaction towards loyalty tothe Universiti Tun Hussein Onn Malaysia(UTHM). The aim of thestudy is to develop relationship between service quality factor and loyalty to the university from the international students’ perspectives. The study adopted quantitative approach where data was collected through questionnaire survey and analysed statistically. A total of 246 responses were received and found to be valid. The model was developed and analysed using AMOS-SEM software. Confirmatory factor analysis (CFA) function of the software was to assessed the measurement models and found that all the models achieved goodness of fit. Then path analysis function was used to assessed structural model and found that service qualityfactors have a significant effect on the students’ satisfaction and thus affecting the loyaltyto the university. Hopefully the outcome form this study will benefit the university in providing services especially to the international students.

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