Summary of Ecosystems, Sustainability, and Global Change

Ecosystem processes are biological, physical, and chemical actions that link organisms to their environment, including decomposition, primary productivity, and nutrient cycling.
Ecosystem services classification (Millennium Assessment): - Provisioning: Food, fresh water, and biomedical products. - Regulating: Carbon sequestration, flood mitigation, and erosion control. - Supporting: Soil movement, pollination, and nutrient cycling. - Cultural: Recreation, aesthetic values, and human wellbeing.
Valuation: Global ecosystem services are estimated to be worth US $33$ trillion, significantly higher than the global GNP of US $18$ trillion.

Biodiversity (Convention of Biological Diversity): The variability among living organisms from all sources, including diversity within species, between species, and of ecosystems.
Components of Biodiversity: - Genetic: Total genetic characteristics and variability within a species. - Ecosystem: Variation in biological communities and trophic levels across regions or the planet. - Species: Defined by richness (total count) and evenness (equality of abundance).
Spatial Scales: - Alpha ( $\alpha$ ): Local diversity within a site. - Beta ( $\beta$ ): Differentiation in diversity among habitats. - Gamma ( $\gamma$ ): Total landscape diversity.

Ecotron Biodiversity Experiment: A controlled study using terrestrial microcosms showing that higher biodiversity levels lead to increased productivity and distinct $CO_2$ flux patterns.
BIODEPTH: A Pan-European study confirming that plant species richness generally increases aboveground biomass.
Jena Biodiversity Experiment: Research demonstrating that plant species richness positively influences processes like weed suppression, decomposition, and pollination.
Specific Empirical Studies: - Jonsson & Malmqvist (2000): Higher numbers of stream-dwelling stonefly species increase leaf mass decomposition rates. - Zak et al. (2003): Increased plant species richness leads to higher gross nitrogen mineralization. - Garcia et al. (2018): Analyzes how temperature influences the relationship between species richness and ecosystem functioning.

Models of Relationship: Null, Idiosyncratic, Rivet, Non-linear, Redundant, and Humped models describe how biotic diversity affects ecosystem processes.
Complementarity Hypothesis: Species with different niches utilize resources more effectively, increasing overall productivity.
Facilitation Hypothesis: Interactions between species enhance the collective performance of the ecosystem.
Sampling Effect Hypothesis: More diverse plots have a higher statistical probability of containing species with the highest inherent productivity.