Nutrient recycling mechanisms

When rain forests are cut down, for example, and converted to fields of rice or corn, the nutrient recycling mechanisms are destroyed, and as a result, the productivity of the field quickly declines. A much better approach would be to devise a production system whereby the nutrient recycling mechanisms are left intact. Extractive reserves for Brazil nuts and rubber are examples of management approaches that are compatible with sustainability of harvest (Brown et al. this volume). The trees are not destroyed when the nuts and the rubber are harvested, and consequently, the nutrient recycling mechanisms of the forest remain intact. A problem with extractive reserves however, is... 

When considering the availability of nutrients, it is also necessary to examine the significance of nutrient re-use within the waterbody. These internal sources amount not to an additional load, but a multiplier on the recyclability of the same load. This nutrient recycling and the internal stores from which they are recycled are often misunderstood, but there is a dearth of good published data about how these recycling mechanisms operate. Microbial decomposition in the water column is one of several internal loops recognized in recent years, but these are not closed and the flux of nutrients recycled through them is delayed rather than retained. 

Vanni, M., and C. Layne. 1997. Nutrient recycling and herbivory as mechanisms in the top-down effect of fish on algae in lakes. Ecology 78 21-40. 

Productivity and C-isotope records—Attributing trends in bulk S Corg only to the trade-off between dominance of respiration-influenced local carbon reservoirs versus dominance of production-influenced global carbon reservoirs is clearly a gross oversimphfication, as a number of other factors may influence C-isotope fractionation in the biogenic and aqueous reservoirs of the carbon cycle. However, this hypothesis finds support in the observations of Cretaceous and Devonian basins summarized herein. In each of these case studies, relative depletion of S Corg values are observed in association with units interpreted to represent examples of the anoxia-nutrient feedback mechanism, and recycling of... 

The two prime mechanisms of carbon transport within the ocean are downward biogenic detrital rain from the photic zone to the deeper oceans and advection by ocean currents of dissolved carbon species. The detrital rain creates inhomogeneities of nutrients illustrated by the characteristic alkalinity profiles (Fig. 11-9). The amount of carbon leaving the photic zone as sinking particles should not be interpreted as the net primary production of the surface oceans since most of the organic carbon is recycled... 

Biogeochemical cycle Mechanism by which water and elements that serve as nutrients are recycled. 

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