Nutrient Supply and Cycling - Principles of Ecology - Lecture Slides, Slides of Ecology and Environment

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Nutrient Supply and Cycling

21 Nutrient Supply and Cycling

• Case Study : A Fragile Crust
• Nutrient Cycles and Losses
• Nutrients in Aquatic Ecosystems
• Case Study Revisited
• Connections in Nature : Nutrients, Disturbance, and Invasive Species

Case Study: A Fragile Crust

• Purpose
• Grazing
• Recreation

Introduction

• Biogeochemistry
• Availability of nutrients

Nutrient Transformations

• Chemical conversion of organic matter into inorganic nutrients is called remineralization.

Nutrient Transformations

• What drives the rate of nutrient transformations?

Nutrient Transformations

• Nitrogen transformations:
• Nitrification —NH 3 and NH 4 +^ are converted to NO 3 –^ by chemoautotrophic bacteria, in aerobic conditions.
• Denitrification —some bacteria use NO 3 –^ as an electron acceptor, converting it into N (^2) and N 2 O, in anoxic conditions.

Nutrient Cycles and Losses

• In order to determine nutrient inputs and losses, we must define ecosystem boundaries.
• For terrestrial ecosystems, a single drainage basin is often used, called a catchment or watershed —the terrestrial area that is drained by a single stream.

Nutrients in Aquatic Ecosystems

• Over time, the nutrient status of a lake may shift from oligotrophic to eutrophic, called eutrophication.
• Sediments accumulate over time, and the lake becomes more shallow. Summer water temperatures increase, decomposition increases, and the lake becomes more productive.

Nutrients in Aquatic Ecosystems

• Human activities accelerate the process of eutrophication by inputs of sewage, detergents, agricultural fertilizers, and industrial wastes.
• Water clarity in Lake Tahoe has declined because of N and P inputs from neighboring communities.

Connections in Nature: Nutrients,

Disturbance, and Invasive Species

• Cheatgrass lowers rates of nitrogen cycling by producing litter with a higher C:N ratio relative to native species.