Herbivores equalize the seedling height growth of three dominant tree species in an African tropical rain forest

Determining the impact of insect herbivores on forest tree seedlings and saplings is difficult without experimentation in the field. Moreover, this impact may be heterogeneous in time and space because of seasonal rainfall and canopy disturbances, or ‘gaps’, which can influence both insect abundance and plant performance. In this study we used fine netting to individually protect seedlings of Microberlinia bisulcata, Tetraberlinia bifoliolata and Tetraberlinia korupensis trees (Fabaceae = Leguminosae) from insects in 41 paired gap-understorey locations across 80 ha of primary rain forest (Korup, Cameroon). For all species, growth in height and leaf numbers was negligible in the understorey, where M. bisulcata had the lowest survival after c. 2 years. In gaps, however, all species responded positively with pronounced above-ground growth across seasons. When exposed to herbivores their seedling height growth was similar, but in the absence of herbivores, M. bisulcata significantly outgrew both Tetraberlinia species and matched their leaf numbers. This result suggests that insect herbivores might play an important role in maintaining species coexistence by mitigating sapling abundance of the more palatable M. bisulcata, which in gaps was eaten the most severely. The higher ratio in static leaf damage of control-to-caged M. bisulcata seedlings in gaps than understorey locations was consistent with the Plant Vigour Hypothesis. This result, however, did not apply to either Tetraberlinia species. For M. bisulcata and T. korupensis, but not T. bifoliolata (the most shade-tolerant species), caging improved relative seedling survival in the understory locations compared to gaps, providing restricted support for the Limiting Resource Model. Approximately 2.25 years after treatments were removed, the caged seedlings were taller and had more leaves than controls in all three species, and the effect remained strongest for M. bisulcata. We conclude that in this community the impact of leaf herbivory on seedling growth in gaps is strong for the dominant M. bisulcata, which coupled to a very low shade-tolerance contributes to limiting its regeneration. However, because gaps are common to most forests, insect herbivores may be having impacts upon functionally similar tree species that are also characterized by low sapling recruitment much more widely than currently appreciated. An implication for the restoration and management of M. bisulcata populations in forests outside of Korup is that physical protection from herbivores of new seedlings where the canopy is opened by gaps, or by harvesting, should substantially increase its subcanopy regeneration, and thus, too, its opportunities for adult recruitment.

Immigrant Incorporation in Western Europe

Immigrant incorporation (or integration) is a subfield of migration studies, and it constitutes a genuinely interdisciplinary undertaking of sociologists, political scientists, anthropologists, lawyers, and historians. In none of these disciplines, however, has it carved out an established niche for itself. In contrast to the United States, where the study of immigrant integration (or “assimilation” as US researchers prefer to say) is more firmly grounded in sociology than in political science, a characteristic of the European scene is a larger prominence of political scientists, macro comparativists, and legal-institutional scholars. This reflects the fact that immigrant integration in Europe is, to a much larger degree than in the United States, framed by public policies, and it often goes along with major transformations of state institutions (most importantly citizenship) and national identities. European states (even France) are ethnic nation-states, where sedentariness and not moving is the norm, and they stand for countries that are much less attuned to, and constituted by, international migration than the classic immigrant nations of North America and Oceania. Overall, European scholarship is marked, on one side, by single-country studies by national experts, which are often solicited by their respective governments interested in policy advice (but increasingly also supported by supranational research bodies). On the other side, most agenda-setting work has grown out of qualitative single-person studies (often dissertations) by macro sociologists and political comparativists not (or only incidentally) rooted in national university systems and disconnected from policy contexts. The field is in need of further conceptual development and of theoretically reflected, genuinely comparative work of the second type, which is mostly off the public funding radar.

Tracks of immigrant political incorporation

Models of Immigrant Political Incorporation brings together a multidisciplinary group of scholars to consider pathways by which immigrants may be incorporated into the political processes of western democracies. It builds on a rich tradition of studying immigrant incorporation, but each chapter innovates by moving beyond singular accounts of particular groups and locations toward a general causal model with the scope and breadth to apply across groups, places, and time. Models of Immigrant Political Incorporation addresses three key analytic questions: what, if anything, are the distinctive features of immigrants or immigrant groups? How broadly should one define and study politics? What are the initial premises for analyzing pathways toward incorporation; does one learn more by starting from an assumption of racialization and exclusion or from an assumption of engagement and inclusion? While all models engage with all three key analytic questions, chapters vary in their relative focus on one or another, and in the answers they provide. Most include graphical illustrations of the model, as well as extended examples applying the model to one or more immigrant populations. At a time when research on immigrant political incorporation is rapidly accumulating - and when immigrants are increasingly significant political actors in many democratic polities — this volume makes a timely and valuable intervention by pushing researchers to articulate causal dynamics, provide clear definitions and measurable concepts, and develop testable hypotheses. Furthermore, the wide array of frameworks examining how immigrants become part of a polity or are shunted aside ensure that activists and analysts alike will find useful insights. By including historians, sociologists, and political scientists, by ranging across North America and Western Europe, by addressing successful and failed incorporative efforts, this handbook offers guides for anyone seeking to develop a dynamic, unified, and supple model of immigrant political incorporation.

How immigrant adolescents' self-views in school and family context relate to academic success in Germany

Immigrants' sense of self can be derived both from being members of their ethnic in-group and their country of residence. We examined how the ways in which immigrant adolescents integrate these self-views in relation to academic success in German schools. Students describe themselves at school and when with family. Using a standardized literacy performance test, analyses revealed that immigrants whose school-related self-view did not include Germany were less successful: Students who described their self as including both aspects of their ethnic group and Germany, and students who saw themselves predominantly as German, outperformed students with purely ethnic school-related selves. As expected, though, an ethnic family-related self-view did not have a negative impact on scholastic achievements.

Buffer capacity: capturing a dimension of resilience to climate change in African smallholder agriculture

Building resilience to climate change in agricultural production can ensure the functioning of agricultural-based livelihoods and reduce their vulnerability to climate change impacts. This paper thus explores how buffer capacity, a characteristic feature of resilience, can be conceptualised and used for assessing the resilience of smallholder agriculture to climate change. It uses the case of conservation agriculture farmers in a Kenyan region and examines how their practices contribute to buffer capacity. Surveys were used to collect data from 41 purposely selected conservation agriculture farmers in the Laikipia region of Kenya. Besides descriptive statistics, factor analysis was used to identify the key dimensions that characterise buffer capacity in the study context. The cluster of practices characterising buffer capacity in conservation agriculture include soil protection, adapted crops, intensification/irrigation, mechanisation and livelihood diversification. Various conservation practices increase buffer capacity, evaluated by farmers in economic, social, ecological and other dimensions. Through conservation agriculture, most farmers improved their productivity and incomes despite drought, improved their environment and social relations. Better-off farmers also reduced their need for labour, but this resulted in lesser income-earning opportunities for the poorer farmers, thus reducing the buffer capacity and resilience of the latter.