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ABSTRACT. The emerging discipline of sustainability science is focused explicitly on the dynamic interactions between nature and society and is committed to research that spans multiple scales and can support transitions toward greater sustainability. Because a growing body of place-based social-ecological sustainability research (PBSESR) has emerged in recent decades, there is a growing need to understand better how to maximize the effectiveness of this work. The Programme on Ecosystem Change and Society (PECS) provides a unique opportunity for synthesizing insights gained from this research community on key features that may contribute to the relative success of PBSESR. We surveyed the leaders of PECS-affiliated projects using a combination of open, closed, and semistructured questions to identify which features of a research project are perceived to contribute to successful research design and implementation. We assessed six types of research features: problem orientation, research team, and contextual, conceptual, methodological, and evaluative features. We examined the desirable and undesirable aspects of each feature, the enabling factors and obstacles associated with project implementation, and asked respondents to assess the performance of their own projects in relation to these features. Responses were obtained from 25 projects working in 42 social-ecological study cases within 25 countries. Factors that contribute to the overall success of PBSESR included: explicitly addressing integrated social-ecological systems; a focus on solutionand transformation-oriented research; adaptation of studies to their local context; trusted, long-term, and frequent engagement with stakeholders and partners; and an early definition of the purpose and scope of research. Factors that hindered the success of PBSESR included: the complexities inherent to social-ecological systems, the imposition of particular epistemologies and methods on the wider research group, the need for long periods of time to initiate and conduct this kind of research, and power asymmetries both within the research team and among stakeholders. In the self-assessment exercise, performance relating to team and context-related features was ranked higher than performance relating to methodological, evaluation, and problem orientation features. We discuss how these insights are relevant for balancing place-based and global perspectives in sustainability science, fostering more rapid progress toward inter-and transdisciplinary integration, redefining and measuring the success of PBSESR, and facing the challenges of academic and research funding institutions. These results highlight the valuable opportunity that the PECS community provides in helping build a community of practice for PBSESR.

Measurement of tree root systems by conventional methods is a Herculean task. The electrical capacitance method offers a rapid and non-destructive alternative, but it has largely been restricted to herbaceous species. The Dalton Model has been the main concept for understanding equivalent root circuitry; it proposed that roots were cylindrical capacitors with epidermis and xylem being the external and internal electrodes. Capacitance (C) therefore varied in proportion to root surface area (A), mass (M), length (L) and relative permittivity of the plant tissue ε(r). We used the capacitance method on forest and plantation trees (13 to circa 100 y.o.) in situ to test hypotheses derived from implicit assumptions about tree-root-soil circuitry. We concluded: C was not confounded by intermingled root systems; C was strongly related to diameter at breast height (DBH); C was less strongly related to DBH for multiple species at the same site; and C was a poor indicator of DBH, M and L across species, ages and sites. We proposed that ε(r) was proportional to root tissue density ρ and fitted a model with P < 0.05 and R(2) = 0.70 when the three immature (13 y.o.) trees were excluded. There was no significant difference (P = 0.28) between the parameters of the tree model (excluding the immature trees) and one of the same form fitted to data from bean (Vicia faba L.; R(2) = 0.55). Together, the data sets suggested (R(2) = 0.94; n = 26) that there may exist a general relationship of this form applied over two orders of magnitude of L.

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The deciduous tropical dry forest at Chamela (Jalisco, Mexico) occurs in a seasonal climate with eight rainless (November through June) and four wet months (700 mm annual precipitation). The forest reaches a mean height of 10 m. Tree density in the research area was 4700 trees per ha with a basal area at breast height of 23 m 2 per ha. The above-and below-ground biomass of trees, shrubs, and lianas was 73.6 Mg ha-and 31 Mg ha -1, respectively. A root:shoot biomass ratio of 0.42 was calculated. Nearly two thirds of all roots occur in the 0-20 cm soil layer and 29% of all roots have a diameter of less than 5 mm.