Tree functional diversity affects litter decomposition and arthropod community composition in a tropical forest

Disturbance can alter tree species and functional diversity in tropical forests, which in turn could affect carbon and nutrient cycling via the decomposition of plant litter. However, the influence of tropical tree diversity on forest floor organisms and the processes they mediate are far from clear. We investigated the influence of different litter mixtures on arthropod communities and decomposition processes in a 60-year-old lowland tropical forest in Panama, Central America. We used litter mixtures representing pioneer and old growth tree species in experimental mesocosms to assess the links between litter types, decomposition rates, and litter arthropod communities. Overall, pioneer species litter decomposed most rapidly and old growth species litter decomposed the slowest but there were clear non-additive effects of litter mixtures containing both functional groups. We observed distinct arthropod communities in different litter mixtures at 6 mo, with greater arthropod diversity and abundance in litter from old growth forest species. By comparing the decay of different litter mixtures in mesocosms and conventional litterbags, we demonstrated that our mesocosms represent an effective approach to link studies of litter decomposition and arthropod communities. Our results indicate that changes in the functional diversity of litter could have wider implications for arthropod communities and ecosystem functioning in tropical forests

Degradation of native and exotic riparian plant leaf litter in a floodplain pond

1. A litter-bag experiment was undertaken in a pond on the margins of a large temperate floodplain in south-western France to assess the potential influence of the replacement of native by exotic riparian species on organic matter degradation. We determined initial litter chemical composition, breakdown rates and the invertebrate assemblages associated with the litter for five pairs of native dominant and exotic invasive species co-occurring at different stages along a successional gradient. 2. Litter chemical composition, breakdown rates and abundance and diversity of detritivorous invertebrates were similar for the exotic and native species overall. No overall changes in organic matter degradation can thus be predicted from the replacement of dominant natives by exotic invasives. Breakdown rates were primarily driven by the C⁄N ratio. 3. One invasive species (Buddleja davidii) showed significantly higher breakdown rates than its native counterpart (Populus nigra), resulting in the disappearance of leaf litter 6 months prior to the next litterfall. In some cases, therefore, invasion by exotic species may result in discontinuity of resource supply for decomposers

Heterogeneous View Integration via Sketches and Equations

. In the paper a new approach to semantic modeling and view integration is proposed. The underlying data model is graph-based yet completely formalized so that graphical schemas themselves are precise specifications suitable for implementation: the approach is an adaptation of a familiar in the mathematical category theory specification framework based on the so called sketches. On this ground, a procedure of automated view integration is developed. Its distinctive feature consists in specifying correspondence between different views (on the same universe of discourse) by equations that reduces the integration task to a sequence of formal algebraic procedures. 1 Introduction and preliminary discussion The term view (or, sometimes, schema) integration refers to the activity aimed at producing a global conceptual schema of an information domain from a set of locally developed user-oriented schemas (views). Integration is called heterogeneous if local views are specified in different da..

Variable Sets and Functions Framework for Conceptual Modeling: Integrating ER and OO via Sketches with Dynamic Markers

. In the paper a graph-based specification language for semantic modeling is proposed. It is as handy as conventional graphical languages but, in contrast to them, possesses a precisely formalized semantics based on certain ideas of the mathematical category theory. In particular, it provides mathematically correct semantics for formerly somewhat mythical notions of object identity and weak entity type. Among other benefits of the approach there are provable (!) universality w.r.to simulation of any other formal data specification, flexibility and unification in treating various kinds of associations and relationships, precise semantic basis for the familiar distinguishing between the specialization and generalization ISA-relationships, intrinsic objectorientedness. 1 Introduction It appears that currently there are two central questions in the area of conceptual modeling and design: the first one is how to handle heterogeneity of semantic data models, and the second consists in inte..

Some Suggestions on Mathematics Relevant to the Database Theory

. In the paper there is discussed a mathematical framework suitable for specificational problems of modern theory of databases. The main thesis is that a proper framework for a majority of hot problems should be built on the ground of graph-based logic and algebra as opposed to string-based logics and algebras over sets currently employed in the DB theory. Such a graph-based machinery was developed in the mathematical category theory so that the latter can provide a proper foundation. The general problem of building the categorial framework for the DB theory is decomposed into a sequence of special tasks. ? Supported by Grant 94.315 from the Latvian Council of Science Since the seminal Codd's papers, databases (DBs) became one of the most theoretically supported branches of computer technologies. Indeed, the seventies were the time of relational model (RDM), and a major factor in that success was the existence of data definition/manipulation languages possessing precise yet easy-to-..

Algebraic Graph-Based Approach to Management of Multibase Systems,I: Schema Integration via Sketches and Equations

. In the paper a new approach to semantic modeling and view integration is proposed. The underlying data model is graph-based yet completely formalized so that graphical schemas themselves are precise specifications suitable for implementation. The formalism is a kind of graph-object-based generalization of the relational data model: analytical assertions about elements (values) are replaced by synthetic assertions about diagrams of sets (object classes) and functions (references); correspondingly, queries are operations on such diagrams. On the other hand, the principal idea is an adaptation of a familiar in the mathematical category theory specification framework based on the so called sketches. On this ground, a novel approach to schema and data integration is suggested. Its distinctive characteristics is in a essentially algebraic way of specifying correspondence between different views on the same universe of discourse. The specifications are formalized and based on equations whic..

Algebraic Graph-Based Approach to Schema Integration

The language of sketches is as concise and powerful as higher order logic and as handy as conventional ER-diagrams. We discuss its benefits in respect to problems of schema integration