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Leadership Styles and Organizational Knowledge Management Activities: A Systematic Review

Leaders play a critical role in the success or failure of their organizations. Leaders can be effective in implementing changes, building their organization’s capabilities, and improving its performance, or the opposite, they could be ineffective. In this systematic review, the authors aim to summarize the findings of previous quantitative research, published between the period from 2000 to 2018, to identify the effect of various leadership styles on organizational Knowledge management (KM) capabilities and activities. The authors reviewed 50 articles found in wellknown databases included Emerald, ScienceDirect, Taylor and Francis, Ebsco, Google Scholar, and others, concerning the impact of leadership when implementing KM in business organizations. The review revealed that transformational, transactional, knowledge-oriented leadership, top executives, and strategic leadership have evidence of their constant and positive effect on the KM process. The authors encourage organizations to use a combination of those styles to maximize the effect of leadership on KM. The authors also recommend conducting further studies on the effect of the remaining leadership styles, such as the ethical and servant leadership styles on KM and the other specific KM activities.


Introduction
According to the literature, KM has a significant impact on organizational performance and innovation. Researchers have found a strong link between KM and different aspects of management innovation that provide an organization with a competitive advantage. KM's implementation in business organizations could be affected by several factors, such as the organization culture, budget, infrastructure, technology, and leadership.
The impact of leadership on business and organizational management has been recognized as a significant factor that could make a difference in organizational performance. The academic gurus proposed several theories, such as the great man theory, various behavioral theories, Lewin's theory, the contingency theory, the situational leadership theory, the transformational theory, the transactional theory (or managerial leadership), and many others.
Based on the existing literature, the outcome of implementing KM projects and processes in organizations varies according to the style of leadership. The evidence reveals a positive impact of leadership styles on KM, while other studies affirm a contradictory result. Therefore, this paper, as per the existing literature, is the first systematic review that aims to identify the leadership styles and roles recognized as facilitators or inhibitors of building KM capabilities in organizations and the contribution of those styles and roles to the successful implementation of KM activities. Also, it aims to summarize the evidence and come up with recommendations to guide researchers in their future projects.
To achieve the study goal, the authors conducted a systematic literature review of the quantitative studies published between the period from 2000 to 2018 concerning leadership and KM. Hence, we surveyed some well-known databases, including Emerald, ScienceDirect, Taylor and Francis, Ebsco, Google Scholar, and others.

Literature Review
Leadership is one of the important topics that are studied extensively by researchers. They have come up with several different theories and definitions of the concept. To help readers understand the history of the evolution of leadership theories, we have summarized the most common theories in Table 1.
As can be noticed above, there is a problem with the various definitions of leadership, as they are based on one isolated variable. Therefore, Winston and Patterson (2006) came up with a solution by reviewing over 90 variables that were used by previous researchers and academic gurus to define leadership, and then they proposed an integrated definition of leadership that is "A leader is one or more people who select, equips, trains, and influences one or more follower(s) who have diverse gifts, abilities, and skills and focuses the follower(s) on the organization's mission and objectives, causing the follower(s) to willingly and enthusiastically expend their spiritual, emotional, and physical energy in a concerted coordinated effort to achieve the organization's mission and objectives." Ribie`re1 and Sitar (2003) addressed the critical role of leadership in organizations that were willing to evolve their culture into a knowledge supporting culture and implement successful KM activities. According to Bolden (2010), leadership, management, and organizational development are all parts of one process for enhancing the capacity of organizations, and people, to improve their performance. According to the Center for Creative Leadership, leadership has several roles in developing an organization's capabilities and implementing strategic changes. Leadership enables executive teams to collaborate effectively to drive change and execute strategy, develop processes, skills, mindsets, and tools to navigate change together, ignite innovation across the organization, manage talent, and create the right culture.
On the other hand, the knowledge-based theory (Curado, 2006) of a firm, which is an extension of the resource-based theory (Barney, 1991), argued that knowledge is a unique strategic resource that does not depreciate the way traditional resources do. According to Polanyi (1966), knowledge, which is classified as explicit knowledge is transmitted formally between people, while tacit knowledge is transmitted informally. Nonaka (1994) developed the dynamic theory of organizational knowledge's creation, which proposed that organizational knowledge is created through a continuous exchange between tacit and explicit knowledge via four mechanisms for interactions: socialization, combination, internalization, and externalization.

Theory
Description Great man theories or hero Great man (hero) is a wise, gifted, noble-hearted man who stands behind an accomplishment in the world as an outcome of thoughts that dwelt in him (Carlyle, 1840). Lewin's leadership theory and styles It includes three popular leadership behavioral styles that are autocratic, democratic, and laissez-faire (Lewin, Lippitt, and White, 1939).

Leadership behavior and theories
Those theories focus on how leaders behave toward a task, people, and participation, rather than leadership traits (Vroom and Jago, 2007). Fiedler's contingency theory It proposes an interaction of three variables that are leader-member relations, task structure, and leader's positional power, as determinants for the extent of the situational control that the leader has (Fiedler, 1964).

Situational leadership theory
The style to be used by leaders, such as telling, selling, participating, or delegating depends upon factors, such as the situation, the people, and the task (Blanchard and Hersey, 1969).

Transformational leadership
The theory is about the leadership that transforms people and organizations, and raises people to higher levels of motivation and morality. Vision, culture, values, development, teamwork all have meaning in transformational leadership (Fairholm, 2001). Transactional leadership The theory is about persons who exercise the authority of their office under formal legality; they obey only the law, obligate others, and follow the principle of hierarchy (Weber, 1968, p. 238).

Servant leadership
According to Robert Greenleaf (as cited in Essays, UK, 2018), the servant-leadership starts with the leader's feeling to serve and, then, his role is changed to lead. Authentic leadership According to Walumbwa et al., (2008), authentic leadership is positively related to ethical leadership and transformational leadership. It includes self-awareness of one's strengths and weaknesses, self-moral perspective, balanced processing, and being true. Ethical leadership According to Brown, Trevino, and Harrison (2005), ethical leadership is the demonstration of appropriate conduct through communication, reinforcement, and decision-making.  Hansen, Nohria, and Tierney (1999) proposed two main KM strategies; firstly, the personalization strategy which theorized that tacit knowledge is shared through conversations and direct contact between people, and secondly, the codification strategy which described the process of conversion of knowledge into a resource that can be used later by people.
The evolution of KM in the last 20 years encouraged many authors to find an appropriate definition that explains the concept. Alavi and Leidner (2001, p. 114) defined KM as a process that involves various activities; minimally it includes the processes of creating, storing and retrieving, transferring, and applying knowledge. In his study, Heisig (2009) summarized the six most frequently used KM activities that are knowledge transfer, creation, application, storage, identification, and acquisition. Also, he listed the critical success factors of KM including: 1) human-oriented factors that are culture, people, and leadership, 2) organizational processes and structure, 3) technology's infrastructure and application, and 4) management processes, including strategies, goals, and outcome measurements. Young (2010) highlighted four levels of successful KM; firstly, the individual (or personal) level includes personal knowledge, capabilities, experiences, competence, and development that is managed by the individuals themselves, by using tools, e.g., mobiles, wireless and web-based applications; secondly, team KM is recognized as the collaboration between team members to produce new knowledge and transfer knowledge based on "share" or "pull" models of knowledge transfer; thirdly, the organizational KM that includes the introduction of a KM strategy and providing the infrastructure to imple-ment the KM process across the entire organization through the "top-down approach"; and fourthly the inter-organizational KM that adopts knowledge from outside resources, e.g., co-partners, customers, suppliers, and competitors.
Based on the above review, we will identify the various leadership styles and roles that facilitate or inhibit an organization's implementation of its KM activities.

Methods
The authors used the systematic review method to answer the research question and achieve their objectives. The systematic review has a high academic value as it is a collaboration of experts who synthesize strong evidence by reviewing and summarizing secondary data that is relevant to the question under review. This systematic review was undertaken from November 2018 to April 2019.

Inclusion criteria of studies
In this study, the authors have included all the papers that met the following criteria: 1. The title of the article includes the word "leadership or leader" or an alternative word, e.g., "manager or supervisor." 2. The title of the article includes the word "knowledge" or any of the KM activities, e.g., KM, creation, acquisition, identification, transfer, storage, or application. 3. Leadership is the independent variable or a moderating variable in the study, while KM is a dependent or a mediating variable. 4. Quantitative research. 5. Published in peer-review journals between the period 2000 and 2018.

Exclusion criteria of studies
In this study, the authors excluded all the papers that met the following criteria:

Search Strategy
The authors used "leadership," "leadership styles," "KM," and "KM activities" as the key search words to search well-known databases included Emerald, ScienceDirect, Taylor and Francis, Ebsco, Google Scholar, and others.
The authors used "AND & OR" as the main basic Boolean operators to combine keywords in a search. Thus, the main search strategy for this review was "leadership AND (knowledge AND/OR (knowledge management OR knowledge creation OR knowledge acquisition OR knowledge identification OR knowledge transfer OR knowledge storage OR knowledge application). Additionally, the authors used the filters recommended by some databases to search for the relevant papers.

Primary Research Methods
The review process started by reviewing the titles and abstracts of the selected articles against the inclusion and exclusion criteria. Then, the included articles were reviewed for the research question, method, sample, tools, and findings. In this study, the included articles are classified in appendixes 1 and 2.

The Study Flow
For this systematic review, the preferred reporting items on systematic reviews and meta-analyses (PRISMA) flow diagram was used to map out the flow of information through the different phases of the systematic review. PRISMA ( Figure 1) maps out the number of records identified, screened for eligibility, included, and excluded as justified by the inclusion and exclusion criteria (Mo-

The Study Coding Categories
The authors organized the information into tables, including several sub-sections. Those sub-sections included the author, the year of publication, the design, the sector, the country, the sample size, and the findings. The first author of the study analyzed all the articles and organized the data in the tables. The second and third authors double-checked the results and validated the conclusion and the recommendations.

Paper's Characteristics
Appendix 1 presents the authors of the included research papers, their year of publication, journals' names, databases, research design, countries, industries, and samples. An analysis of the contents of Table 1 shows that the number of published papers that are relevant to the systematic review's question has significantly increased with time. According to the review, 7 (14%) of the research papers were published between 2001 and 2009, 16 (32%) between 2010 and 2014, and 27 (54%) between 2015 and 2019. The authors found 26 (52%) of those papers in Google Scholar, Emerald had 11 (22%), DirectScience contained 3 (6%), Taylor and Francis had 2 (4%), and others held 8 (16%).
On the other hand, the effects of transformational leadership were studied on particular KM activities. Eight studies into the effect of transformational leadership on knowledge sharing found that transformational leadership had a direct, significant, and positive impact on knowledge sharing and Bokhari, 2011). Another study found a significant relationship of transformational leadership with the internal component of knowledge sharing (Chen and Barry, 2006).
Some components of transformational leadership, particularly individual's consideration and individual's inspirational impact positively on knowledge sharing activities, while the intellectual stimulation and inspirational motivation do not significantly encourage activities related to knowledge sharing (Rawung, Wuryaningrat, and Elvinita, 2015). Furthermore, the idealized influence is significant only when considered with socialization, the intellectual stimulation leadership is significantly correlated with all the dimensions of knowledge sharing (socialization, externalization, combination, and internalization), and the individualized consideration is significant for knowledge externalization (Bradshaw, Chebbi, and Oztel, 2015).
Furthermore, a few studies revealed that transformational leadership had a positive effect on negotiation, which is a component of knowledge acquisition (Politis, 2001), while leadership constructs including emotional intelligence, leadership traits, and transformation team (i.e. a team of experts who lead a project) significantly influence the transfer of knowledge (İdris, Ali, and Godwin, 2015) and transformational leadership positively affects all the strategic variables, including knowledge slack, absorptive capacity, and tacitness directly and indirectly (Garcı´a-Morales, Llore´ns-Montes, and Verdu´-Jover, 2008).
On the other hand, particular components of transactional leadership were found to positively affect knowledge management activities. Contingent rewards, one of the transactional dimensions, was found to have  (Farooq, Hanif, and Khan, 2018), with socialization, and combination (Bradshaw, Chebbi, and Oztel, 2015), and with both internal and external knowledge sharing with customers (Chen and Barry, 2006). Also, the initiating structure, one of the transactional dimensions, was found to be positively correlated with communication and the problem of understanding the components of knowledge acquisition, and negatively correlated with the personal traits, organization, and negotiation (Politis, 2001).

Other Leadership Styles
Regarding knowledge leadership, evidence was found that knowledge-oriented leadership had a positive effect on KM (Jad et al., 2017;Sadeghi and Rad, 2018;Donate and De Pablo, 2015), and it also had positive effects on knowledge creation and application (Safari and Azadehdel, 2015).
About the other leadership styles, some papers revealed that leadership, in general, correlated with KM (Kafashpoor, Shakoori, and Sadeghian, 2013) and had a positive moderating effect on the relationship between knowledge sharing and organizational learning (Khalid and Ahmed, 2015), while leadership behavior (i.e. leadership style, professional authority, and counseling skills) had a positive relation with KM (Tang, 2017). Furthermore, one study inferred that senior managers' attitudes, subjective norms, and perceived behavioral control all had a positive influence on the intention to encourage knowledge-sharing, which in turn is the main determinant of corporate knowledge-sharing behavior (Lin and Lee, 2004). Additionally, the strategic dimension of leadership had a positive relationship with the success of KM practices (Mas -Machuca, 2014).
Regarding the directive, participative, and supportive leadership styles, they had minor positive influences on KM (Aldulaimi, 2015). One prior study revealed that the directive and supportive styles had negative associations with KM practices, while the consulting and delegating styles had significant positive relationships with KM practices (Singh, 2008).
Regarding leadership powers, the expert power had positive effects on both knowledge's acquisition and dissemination, the reward power had a positive effect on knowledge dissemination in small firms, the legitimate power had a negative effect on knowledge acquisition, the coercive power had only a detrimental effect in small organizations, whereas the referent power did not affect anything in the knowledge-based context (Jayasingam, Ansari, and Jantan, 2010).
The remaining papers studied a variety of individual leadership styles, the mentor leadership style was positively related to knowledge sharing behavior, whereas the facilitator leadership style was not found to be related to knowledge sharing behavior (Jahani, Ramayah, and Effendi, 2011), the cognitive styles (i.e. radical and innovative-collaborator styles) had a negative impact on KM practices; while the cognitive adaptor style had a positive impact on KM practices (Jain and Jeppesen, 2013), the leader-member exchange (LMX) affected knowledge sharing and performance positively and meaningfully (Sharifkhani, Pool, and Asian, 2016), the telling, selling, participating, and delegating styles had a significant influence on KM (Pringgabayu and Ramdlany, 2017), the democratic style affected KM activities more successfully in small enterprises and enterprises oriented toward international markets, whereas the autocratic style affected KM more in large enterprises (Miloloža, 2018), the command leadership style had a great effect on the KM process, while the supportive leadership style positively and significantly affected three aspects of KM, which are knowledge generation, sharing, and utilization (Akhavan, Zahedi, Dastyari, and Abasaltian, 2014), and the charismatic and human-oriented leadership (communicative styles) had a significant relationship with knowledge sharing, while the task-oriented (non-communicative) style had no relation with knowledge sharing (De Vries, Bakker-Pieper, and Oostenveld, 2010).

Discussion
This study reviewed prior quantitative research to identify the effect of various leadership styles and roles on KM's capabilities in business organizations, summarize the findings, and come up with recommendations that could guide researchers in the future. The review found that the role and influence of the transformational, transactional, knowledge-based leadership, and top executives that were studied influenced KM's activities in several contexts. Other leadership styles were also studied to a limited extent in a certain context. However, the transformational leadership style was studied in more than half of the included research papers. One-fifth of the included papers pointed out strong evi-dence for a positive effect of transformational leadership on knowledge management's capabilities in all contexts, as well as having a strong significant, positive effect on a particular knowledge management activity, namely knowledge sharing. Besides, transformational leadership was also found to have a positive effect on knowledge acquisition, knowledge transfer, and strategic knowledge variables, such as knowledge slack, absorptive capacity, and tacitness in a limited number of studies.
Regarding transactional leadership, four studies provided a significant, positive relationship of transactional leadership with the entire capability and activities of KM. Also, particular components of transactional leadership were found to affect knowledge management activities positively, mainly the contingent rewards, which had a positive correlation with KM and knowledge sharing. On the other hand, a few studies revealed contradicting evidence that transactional leadership had no effect on KM and knowledge sharing.
Regarding the general leadership styles, three studies revealed a positive correlation between leadership and leadership behavior with KM and knowledge sharing. Three studies revealed a positive effect of knowledge leadership on KM, as well as knowledge creation and application, while another two studies provided positive evidence for the relationship between senior managers and strategic leadership on KM and knowledge sharing. Furthermore, the effects of many other leadership styles on KM had been studied, but by an insufficient number of studies. The findings of those studies vary and, in our opinion, do not provide solid evidence for the effects of those styles on KM.
Lastly, the authors conclude that the transformational, transactional, knowledge-based, top executives and strategic leadership were all found to have constant positive effects on KM activities, although in different contexts.

Conclusion
Based on the above discussion, this review found that the transformational, transactional, knowledge-based, top executives and strategic leaderships have positive effects on KM activities. Thus, the authors argue that organizations should use a combination of all those leadership styles to maximize the effect of leadership on KM. In other words, organizations should involve their top executives and strategic leadership, as well as transformational and transactional leadership styles at all organizational levels, as independent variables to build an efficient KM capability and implement KM activities. Furthermore, the authors suggest that knowledge-orientation could enhance the above-discussed relationship if used as a moderating variable.

Recommendations
The authors encourage researchers to direct their future studies to fill the gaps in the literature and concentrate on the inadequately examined leadership styles and KM activities. Furthermore, they should consider conducting longitudinal studies and using representative samples.
On the other hand, the authors encourage interested researchers to conduct quantitative studies to examine the above-suggested model in various contexts. This will provide evidence of the effectiveness of the model, or suggest new modifications, as well as confirming, or not, the generalizability of the model.

Limitations
All those papers used a cross-sectional design, some of those studies used small samples, and the papers did not consider several well-known leadership styles, such as the ethical and servant leadership style Akhavan