Here, we present the second part of a quantitative theory for the structure and dynamics of forests under demographic and resource steady state. The theory is based on individual-level allometric scaling relations for how trees use resources, fill space, and grow. These scale up to determine emergent properties of diverse forests, including size-frequency distributions, spacing relations, canopy configurations, mortality rates, population dynamics, successional dynamics, and resource flux rates. The theory uniquely makes quantitative predictions for both stand-level scaling exponents and normalizations. We evaluate these predictions by compiling and analyzing macroecological datasets from several tropical forests. The close match between theoretical predictions and data suggests that forests are organized by a set of very general scaling rules. Our mechanistic theory is based on allometric scaling relations, is complementary to ''demographic theory,'' but is fundamentally different in approach. It provides a quantitative baseline for understanding deviations from predictions due to other factors, including disturbance, variation in branching architecture, asymmetric competition, resource limitation, and other sources of mortality, which are not included in the deliberately simplified theory. The theory should apply to a wide range of forests despite large differences in abiotic environment, species diversity, and taxonomic and functional composition.allometry ͉ mortality rate ͉ plant ecology ͉ size distribution ͉ competitive thinning U nderstanding the key forces that shape the structure, function, and dynamics of ecosystems is a fundamental goal of ecology (1-6). Current approaches to plant communities focus on questions such as what allows for species coexistence (7), why tropical sites have more species than temperate ones (8), and what environmental factors determine the structure, dynamics, and species composition of communities (9). Detailed models have been developed to integrate how species-specific traits ''scale-up'' to inf luence community and ecosystem dynamics (10, 11).Here, we present a complementary but alternative approach. We use a few key principles to show how variation in resource supply together with general cross-taxa patterns of plant architecture and growth give rise to predictable emergent patterns of resource use, spatial structure, and demography. In our previous article (12) we incorporated these principles to derive the first part of a general quantitative theory for the structure and dynamics of a single-species stand. In this article we evaluate these predictions, using data from several tropical forests composed of multiple tree species including: (i) a 20-year record from Costa Rica (13); (ii) a 10-year time series from Panama; (iii) a 40-year survey from a Malaysian forest dataset; (iv) and a successional sequence of Costa Rican forests ranging from recently abandoned pasture to mature uncut forests (14) (for methodology and additional detail, see supporting information (SI) Tex...