Riparian Forests and Macroinvertebrates Support Multiple Ecosystem Processes Across Temperate and Tropical Streams

Area of Science:

• Ecology
• Environmental Science
• Freshwater Biology

Background:

• Ecosystem processes often extend beyond physical boundaries, linking aquatic and terrestrial environments.
• The role of biological drivers in supporting multiple aquatic-terrestrial ecosystem processes is not well understood.
• Headwater streams are critical interfaces for cross-ecosystem interactions.

Purpose of the Study:

• To investigate the influence of riparian forests, macroinvertebrates, and leaf litter composition on ecosystem multifunctionality.
• To assess the relative importance of these factors on aquatic fungi biomass, nitrogen loss, and decomposition rates.
• To understand cross-regional effects in temperate and tropical headwater streams.

Main Methods:

• Utilized leaf litter bags to introduce terrestrial leaf litter into forested and non-forested headwater streams.
• Manipulated macroinvertebrate access and leaf litter mixture composition.
• Measured aquatic fungi biomass accrual, nitrogen loss, and local leaf litter decomposition rates.

Main Results:

• Ecosystem multifunctionality was positively associated with the presence of macroinvertebrates and riparian forests across both regions.
• Leaf litter nitrogen loss and decomposition rates increased significantly when macroinvertebrates had access to all leaf litter types.
• Decomposition rates were positively correlated with other measured ecosystem processes.

Conclusions:

• Riparian forests and macroinvertebrate detritivores play a consistent, cross-regional role in supporting freshwater detrital food web processes.
• Macroinvertebrates are key drivers of ecosystem multifunctionality in headwater streams.
• A holistic view incorporating cross-ecosystem interactions is essential for understanding headwater stream ecology.