scholarly journals Resistance and Resilience of Hyrcanian Mixed Forests Under Natural and Anthropogenic Disturbances

2021 ◽  
Vol 4 ◽  
Author(s):  
Mehdi Vakili ◽  
Zahed Shakeri ◽  
Saeed Motahari ◽  
Maryam Farahani ◽  
Zachary James Robbins ◽  
...  
Keyword(s):  
Species Composition ◽  
Simulation Modeling ◽  
Landscape Change ◽  
Mixed Forest ◽  
Negative Relationship ◽  
Leaf Beetle ◽  
Initial State ◽  
Northern Iran ◽  
Forest Diversity ◽  
Positive Effect

Biological disturbances are integral to forest ecosystems and have pronounced effects on forest resistance, resilience, and diversity. The Hyrcanian mixed forest, in northern Iran, is at risk of declining resistance, resilience, and diversity due to ongoing pressure from land use change, harvesting, and biological disturbances. We analyzed the resistance and resilience of this area under two biological disturbances (i.e., oak charcoal fungus, Biscogniauxia mediterranea, and alder leaf beetle, Galerucella lineola) and in concert with proposed harvesting. We used a simulation modeling approach whereby we simulated 12 combinations of biological disturbances and harvesting scenarios using the LANDIS-II landscape change model. We estimated the correlation between forest resistance and resilience and tree species diversity to harvesting and biological disturbance. We analyzed the full species composition and age class for 30 and 100 years after disturbances in order to assess resistance as the change in species composition over time. We considered resilience as the ability to recover from a disturbance back to a similar initial state. Results indicate a positive effect of biological disturbances and harvesting on diversity. Our simulations resulted in a negative relationship between diversity-resistance and diversity-resilience within high diversity areas. Our simulation of the Hyrcanian forest reveals that harvesting and biological disturbances, as tested, fulfill the goal of maintaining forest diversity. However, increasing diversity does not always follow by increasing forest resistance and resilience. Scenarios with oak charcoal fungus, both with and without harvesting indicate the lowest decrease in resilient and resistant.

Comparative study of the impact of two mechanical perforation densities on the behavior of a sandy soil

2012 ◽  
Vol 8 (1) ◽  
pp. 37-48
Author(s):  
S. Chehaibi ◽  
K. Abrougui ◽  
F. Haouala
Keyword(s):  
Soil Water ◽  
Sandy Soil ◽  
Water Infiltration ◽  
Cone Penetration ◽  
Initial State ◽  
Soil Water Infiltration ◽  
Good Improvement ◽  
The Impact ◽  
Positive Effect ◽  
Resistance To Penetration

The effects of mechanical perforation densities by extracting soil cores through an aerator Vertidrain with a working width of 1.6 m and equipped with hollow tines spaced of 65 mm, were studied on a sandy soil of a grassy sward in the Golf Course El Kantaoui in Sousse (Tunisia). The mechanical aeration was performed at two densities: 250 and 350 holes/m2. The cone penetration resistance and soil water infiltration were measured. These parameters were performed at initial state before aeration (E0) and then on the 10th, 20th and 30th day after aeration. These results showed that perforation density of 350 holes/m2 had a positive effect on the soil by reducing its cone resistance to penetration compared to the initial state (Rp = 14.8 daN/cm2). At 5 cm depth the decrease in resistance to penetration was 34% and 43% on the 10th and 20th day after aeration, respectively. However, on the 30th day after aeration the soil resistance to penetration tended to grow and its value compared to the initial state decreased only by 21 and 26%, respectively, at 5 and 15 cm of depth only by 10% and 9% with 250 holes/m2 density. The soil water infiltration made a good improvement after aeration compared to the initial state. This parameter increased from 4.8 cm/h to 8.3, 10.9 and 13.1 cm/h with 250 holes/m2 density and to 10, 12.9 and 14.8 cm/h with 350 holes/m2 density on the 10th, 20th and 30th day following the aeration.

The species evenness of “prey” bacteria correlated with Bdellovibrio-and-like-organisms (BALOs) in the microbial network supports the biomass of BALOs in a paddy soil

2020 ◽  
Vol 96 (12) ◽  
Author(s):  
Hang Qian ◽  
Chunli Hou ◽  
Hao Liao ◽  
Li Wang ◽  
Shun Han ◽  
...  
Keyword(s):  
Soil Properties ◽  
Paddy Soil ◽  
High Throughput Sequencing ◽  
Abiotic Factors ◽  
Negative Relationship ◽  
Sequencing Analysis ◽  
Nitrogen Use ◽  
Microbial Network ◽  
Α Diversity ◽  
Positive Effect

ABSTRACT To seek how soil biotic and abiotic factors which might shape the Bdellovibrio-and-like-organisms community, we sampled paddy soils under different fertilization treatments including fertilization without nitrogen (Control), the nitrogen use treatment (N) and the nitrogen overuse one (HNK) at three rice growing stages. The abundances of BALOs were impacted by the rice-growing stages but not the fertilization treatments. The abundances of Bdellovibrionaceae-like were positively associated with soil moisture, which showed a negative relationship with Bacteriovoracaceae-like bacteria. High-throughput sequencing analysis of the whole bacterial community revealed that the α-diversity of BALOs was not correlated with any soil properties data. Network analysis detected eight families directly linked to BALOs, namely, Pseudomonadaceae, Peptostreptococcaceae, Flavobacteriaceae, Sediment-4, Verrucomicrobiaceae, OM27, Solirubrobacteraceae and Roseiflexaceae. The richness and composition of OTUs in the eight families were correlated with different soil properties, while the evenness of them had a positive effect on the predicted BALO biomass. These results highlighted that the bottom-up control of BALOs in paddy soil at least partially relied on the changes of soil water content and the diversity of bacteria directly linked to BALOs in the microbial network.

scholarly journals MONETARY POLICY AND TELECOMMUNICATION OUTPUT IN NIGERIA

2020 ◽  
Vol 3 (2) ◽  
pp. 62-73
Author(s):  
John Abiodun Akinde ◽  
Elijah Oludayo
Keyword(s):  
Monetary Policy ◽  
Money Supply ◽  
Negative Relationship ◽  
Negative Influence ◽  
Favourable Effect ◽  
Data Series ◽  
Long Run ◽  
Integration Test ◽  
Short Run ◽  
Positive Effect

Different policies impact on the growth of the telecommunication sector in Nigeria. One of these policies which influence the expansion or contraction of the telecommunication output is monetary policy. To this end, this research examined the effect of monetary policy on telecommunication output in Nigeria. For the purpose of analysis, time series secondary data were sourced from Central Bank of Nigeria (CBN) statistical bulletin covering the periods1986 to 2018. Autoregressive Distributed Lag (ARDL) technique was employed after examining the stationarity of the data series using Augmented Dickey-Fuller technique. The bound co-integration test revealed that there is long run equilibrium between the monetary policy variables employed and telecommunication output. The ARDL result revealed that money supply had significant and positive effect on telecommunication output in the short and long run; liquidity ratio produced an insignificant and negative relationship with telecommunication output in the short run and insignificant positive effect in the long run; exchange rate had insignificant negative effect in the short run and a significant positive effect on telecommunication output in the long run; consumer price index had significant negative influence on telecommunication outputboth in the short run and long run. The study concluded that monetary policy stimulates telecommunication output in Nigeria. Thus, it was recommended that the monetary authority should pursue an expansionary monetary policy to sustain the positive influence of money supply on telecommunication output in Nigeria while rolling out policy to reduce the liquidity ratio of banks in the short run but increase it in the long run so that the long term favourable effect of liquidity ratio can be felt on telecommunication output.  

scholarly journals Estimation of Tree Heights in an Uneven-Aged, Mixed Forest in Northern Iran Using Artificial Intelligence and Empirical Models

Forests ◽  
2020 ◽  
Vol 11 (3) ◽  
pp. 324 ◽  
Author(s):  
Mahmoud Bayat ◽  
Pete Bettinger ◽  
Sahar Heidari ◽  
Azad Henareh Khalyani ◽  
Meghdad Jourgholami ◽  
...  
Keyword(s):  
Artificial Intelligence ◽  
Mixed Forest ◽  
Empirical Models ◽  
Ann Model ◽  
Mixed Stands ◽  
Anfis Model ◽  
Northern Iran ◽  
Inference System ◽  
Intelligence Models ◽  
Artificial Intelligence Models

The diameters and heights of trees are two of the most important components in a forest inventory. In some circumstances, the heights of trees need to be estimated due to the time and cost involved in measuring them in the field. Artificial intelligence models have many advantages in modeling nonlinear height–diameter relationships of trees, which sometimes make them more useful than empirical models in estimating the heights of trees. In the present study, the heights of trees in uneven-aged and mixed stands in the high elevation forests of northern Iran were estimated using an artificial neural network (ANN) model, an adaptive neuro-fuzzy inference system (ANFIS) model, and empirical models. A systematic sampling method with a 150 × 200 m network (0.1 ha area) was employed. The diameters and heights of 516 trees were measured to support the modeling effort. Using 10 nonlinear empirical models, the ANN model, and the ANFIS model, the relationship between height as a dependent variable and diameter as an independent variable was analyzed. The results show, according to R2, relative root mean square error (RMSE), and other model evaluation criteria, that there is a greater consistency between predicted height and observed height when using artificial intelligence models (R2 = 0.78; RMSE (%) = 18.49) than when using regression analysis (R2 = 0.68; RMSE (%) = 17.69). Thus, it can be said that these models may be better than empirical models for predicting the heights of common, commercially-important trees in the study area.

Carbon exchange in a hemiboreal mixed forest in relation to tree species composition

2019 ◽  
Vol 275 ◽  
pp. 11-23 ◽  
Author(s):  
Alisa Krasnova ◽  
Mai Kukumägi ◽  
Ülo Mander ◽  
Raili Torga ◽  
Dmitrii Krasnov ◽  
...  
Keyword(s):  
Species Composition ◽  
Tree Species ◽  
Mixed Forest ◽  
Carbon Exchange ◽  
Tree Species Composition

scholarly journals Firm Growth and R&D in the Korean Pharmaceutical Industry

2019 ◽  
Vol 11 (10) ◽  
pp. 2865 ◽  
Author(s):  
Hyunseog Chung ◽  
Soomin Eum ◽  
Chulung Lee
Keyword(s):  
Growth Rate ◽  
Pharmaceutical Industry ◽  
Firm Growth ◽  
Negative Relationship ◽  
High Growth ◽  
Sales Growth ◽  
Young Firms ◽  
The Government ◽  
The Impact ◽  
Positive Effect

We explore the impact of research and development (R&D) on sales growth rate with firm-specific factors under the Korean pharmaceutical industry structure using listed Korea pharmaceutical company data from 2007 to 2018 with the quantile regression technique. We find that R&D intensity has a positive effect on firm growth rate while R&D scale a negative effect on the firm growth rate at the upper quantile, whereas the result is opposite at the lower quantile. Firm size has a mixed relationship with sales growth at the upper quantile, thus Gibrat’s law is rejected in the Korean pharmaceutical industry. Firm age has a negative relationship with the sales growth rate at the upper quantile, which shows the consistent result with previous research that young firms grow faster. Patent persistence has a negative relationship with sales growth at the upper quantile, while a positive effect at the lower quantile. We show that young firms and firms with high R&D intensity contribute to the high growth rate, while the relationship is not clear at the lower quantile. Therefore, policy implication in this research is that the government should pay attention to encouraging and supporting R&D investment activities and small firms as well as consider ways to enhance patent rights.

Predictability of Change in Shoreline Vegetation in a Hydroelectric Reservoir, Northern Sweden

1988 ◽  
Vol 45 (11) ◽  
pp. 1896-1904 ◽  
Author(s):  
Christer Nilsson ◽  
Paul A. Keddy
Keyword(s):  
Species Composition ◽  
Water Level ◽  
Control Variable ◽  
Important Variable ◽  
Strongly Correlated ◽  
Northern Sweden ◽  
Initial State ◽  
Independent Variables ◽  
Hydroelectric Reservoir ◽  
High Degree

We asked whether we could predict the responses of vegetation to specified perturbations acting on a known initial state using 10 yr of vegetation data and precise water level records from the Gardiken Reservoir on the Ume River in Sweden; this has a restricted flora and one obvious controlling factor: water level. Abundance and species richness were strongly correlated for both vascular and nonvascular plants (bryophytes and lichens). Duration of flooding was the most important variable controlling those independent variables chosen for study. The change from year t to t + 1 could be roughly predicted for community attributes such as richness and cover (R2 > 0.33) but not for species composition (R2 < 0.04). The initial (preceding-year) state of the system and the duration of flooding (also in the preceding year) were always the two most important independent variables. The major conclusions were that (1) even in this "simple" system with presumably one major control variable, our best regression equation accounted for only 41% of the variation, (2) community properties were more predictable than species composition, and (3) the similarity of the species pool, the lack of coupling from competitive interactions, and the high degree of immaturity may have reduced predictability of species composition.

scholarly journals The Wealth Effects Of Managerial Turnover: Implications For The Spanish Corporate Governance System

2011 ◽  
Vol 1 (10) ◽  
Author(s):  
Carlos Fernandez Mendez
Keyword(s):  
Corporate Governance ◽  
Negative Relationship ◽  
Wealth Effects ◽  
Governance System ◽  
Managerial Turnover ◽  
Study Results ◽  
Managerial Succession ◽  
Corporate Governance System ◽  
Institutional Shareholders ◽  
Positive Effect

Managerial succession decisions constitute crucial events for the company, as they can generate important organizational changes that affect the shareholders wealth, and at the same time, entail important conflicts of interests between the managers and the shareholders. Our study of the market reactions to managerial turnover announcements in the Spanish market, reveal that these decisions have a positive effect on the shareholders wealth. These wealth effects are especially intense in the case of outsider successions and when the company preturnover performance has been poor. These findings suggest that managerial turnover is a restructuring decision that is most welcome under conditions of low performance. These results are reinforced by the existence of a negative relationship between the turnover wealth effects and the firm's preturnover performance. Our results also have implications regarding the effectiveness of the Spanish corporate governance system, suggesting that the Board's outsiders and the institutional shareholders play a major monitoring role in the managerial succession processes. The Board outsiders and the institutional shareholders influence the succession process protecting the shareholders interests against particular professional interests of the managers. We have also found evidences of the existence of entrenchment effects linked to managerial stock ownership. Finally, consistently with our event study results, we have found evidences of a positive effect of outside succession on the market's reaction to managerial turnover, in the case of a poor presuccession performance context. We have obtained no evidence about any effect from outside succession in good performing companies or inside succession in any company independently of its previous performance.

scholarly journals Preliminary data on centipedes (Chilopoda: Scolopendromorpha and Scutigeromorpha) in Ta Xua natural reserve, Son La Province, Vietnam

2018 ◽  
Vol 40 (1) ◽  
pp. 100-107
Author(s):  
Tran Thi Thanh Binh ◽  
Nguyen Duc Hung ◽  
Ha Kieu Loan ◽  
Vu Thi Ha
Keyword(s):  
Species Composition ◽  
New Records ◽  
Diversity Index ◽  
Mixed Forest ◽  
Natural Forest ◽  
Northwestern Part ◽  
Bamboo Forest ◽  
Natural Forests ◽  
Natural Reserve ◽  
Study Results

 Study on centipedes was conducted in Muong Thai commune, Ta Xua Natural Reserve, Son La in May and November 2017. Samples were collected in four typical habitats: natural forests, bamboo mixed forests, bamboo forests and agro-residental areas. As a result, a total of 17 species and subspecies in two orders (Scolopendromorpha and Scutigeromorpha) was recorded in that region. Of which, the order Scolopendromorpha has 15 recorded species and subspecies belonging to 7 genera, 3 families (Cryptopidae, Scolopendridae, Scolopocryptopidae). The other order, Scutigeromorpha, has only one species in one family (Scutigeridae). The study results also contributed new records of 13 species in 7 genera to the centipede fauna of the northwestern part of Vietnam, and 1 genus, Thereuonema, to the Vietnamese fauna.Among four habitats, natural and bamboo forests have highest similarity on species composition, but agro-residental area and bamboo forest have lowest value on species composition. The diversity index (H’) is highest in bamboo forests (2,98), decreases in mixed forest (2,31), natural forest (1,67) and agro-residental area (0,74). In contrast, centipede density is highest in natural forest (0,60 ind./m2), reduces in bamboo forest (0,47 ind./m2) and mixed forest (0,20 ind./m2).

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