Nonprofit organizations protect the civic foundation of a society by conveying social ailments and injustice to institutional elites. Based on a random sample of 129 human service nonprofits in Maryland, this study examines the organizational factors that influence advocacy participation. Viewing nonprofit advocacy as a legitimacy-building endeavor, this study derives an analytical framework from two theoretical lenses: organizational ecology and organizational institutionalism. The survey indicates that human service nonprofits engage in a variety of advocacy activities, but devote only limited resources to mobilize these efforts. Furthermore, resource competition, government funding, and constituency commitment help explain the variation of advocacy participation by human service nonprofits. The findings have implications for nonprofit education and leadership. Advocacy is an indispensable part of a democratic system. Through collective actions, individuals, groups, and organizations advocate to make public interest claims and pursue social and political changes. Among these actors, nonprofit organizations play a significant role. By identifying social problems that are neglected by the public and bringing the voices of the underrepresented to the policy process, nonprofits help protect public interest and social health. In this way, O’Neill considered advocacy to be “the ultimate defining characteristic of the nonprofit sector”. Conceptually, advocacy may be viewed as a deliberate attempt to influence public policy and government practice . Nonprofits may employ different advocacy tactics to achieve their advocacy goals, such as conducting lobbying, providing public education, and mobilizing voters, but the purpose of those advocacy efforts is largely the same, that is, to influence public policy. Despite the importance of nonprofit advocacy as a major force for the renewal of American Democracy, significant variation exists in the level of advocacy activities nonprofits perform. For example, Child and Gronbjerg observed that approximately 25% of Indiana nonprofits are involved in advocacy. Again, Bass, Arons, Guinane, and Carter’s national survey of public charities reported that 86% of nonprofits engage in some sort of policy advocacy. Although this divergence might result in part from the different definitions and measurements of advocacy, it indicates the variation in nonprofit advocacy participation. This observation leads to the research question of this study: What factors would motivate nonprofit involvement in the public policy process? Research on this question has been advanced considerably in recent years. This study adds to this body of literature by exploring the organizational attributes that affect advocacy engagement in human service nonprofits. In human service nonprofits, service provision and policy advocacy constitute the dual focus of their organizational activities. On the one hand, nonprofits serve vulnerable populations and moderate social problems by delivering various direct services to needy citizens to meet their diverse needs. On the other hand, nonprofits advance their mission by engaging with government agencies to shape the policies that address those social problems. Although delivering high quality services to meet clients’ needs is the top priority of human service organizations, the advocacy function, according to Salamon , is “as important to the nation’s social health as the service functions the sector also performs”. Human service nonprofits bring the voice of vulnerable groups to the policy process and represent their interest in policy deliberation, promoting the wellbeing of vulnerable populations and social justice at large. In this way, advocacy has long been considered as a defining feature of human service nonprofits . Arguably, the advocacy engagement function of human service nonprofits has been compromised by the service delivery function as their operating environment becomes increasingly turbulent because of forces such as increased competition, scarce resources, and greater accountability expectations. However, because of their roots in local communities and direct interactions with clients, human service organizations have unique knowledge of local concerns and the effect of government programs . Additionally, the increasing reliance of government on nonprofit contractors and grantees in service delivery further enhances the imperative of nonprofits to be civic intermediaries . Thus, how to balance their dual identities as service providers and social change agents presents a pressing challenge that service delivery nonprofits must confront. A first step to answer this puzzle is to understand the motivation behind nonprofit involvement in advocacy. This study considers advocacy to be one type of legitimacy-building endeavor that nonprofits employ to improve survival prospects under turbulent environments. Based on this assumption, this study derives analytical arguments from two theoretical lenses: organizational ecology and organizational institutionalism. Moreover, resource competition, government funding, and constituency commitment help explain the variation in advocacy participation by human service nonprofits. The remaining parts of the study first discuss the theoretical framework and then describe the research design and data collection. After presenting the quantitative findings, the study concludes after a discussion of the implications of the findings for nonprofit education and leadership. The development of a Scots pine dominated forest ecosystem is highly regular following a stand-replacing disturbance. Initially, ground vegetation dominates the ecosystem. Tree seedlings start growing slowly and eventually overcome the ground vegetation. Forest ecological and physiological research has resulted in valuable results on the metabolism and growth of trees and ground vegetation and of the decomposition of organic matter in the soil, to a large extent thanks to the development of measurement techniques such as chamber techniques and subsequent advances in eddy covariance measurements. The analysis of measurements has resulted in important knowledge on the effects of the environment on gas exchange, the structural relationships between tree organs and the active role of the soil microbes in nutrient recycling. Permanent sample plots and other growth and yield studies together with forest inventories have provided important information concerning stand growth and development Physics was facing a similar situation, as forest ecology now, in the late 17th century, when theoretical explanations for the observations by Tyko Brahe and Johannes Kepler, and Galileo Galilei’s experiments were missing. Isaac Newton studied the movements of planets around the sun and he explained the orbiting of planets with gravitation.In forest ecosystem metabolism of vegetation and microbes consumes and releases material, and at the same time physical phenomena convert energy to other forms resulting in concentration, pressure and temperature differences. These differences give rise to material and energy flows within atmosphere, vegetation and soil and between atmosphere, vegetation and soil. We hypothesize that these flows accumulate and consume material in vegetation and in soil. On a molecular level, large carbon molecules, cellulose, lignin, lipids, starch and proteins, form the structure of living systems. Proteins, that are nitrogen-rich molecules, play a key role in the metabolism as e.g. enzymes and membrane pumps. We study the flows of these carbon- and nitrogen-rich molecules and processes generating the flows.