The Stream Biome Gradient Concept: factors controlling lotic systems across broad biogeographic scales

Abstract

We propose the Stream Biome Gradient Concept as a way to predict macroscale biological patterns in streams. This concept is based on the hypothesis that many abiotic and biotic features of streams change predictably along climate (temperature and precipitation) gradients because of direct influences of climate on hydrology, geomorphology, and interactions mediated by terrestrial vegetation. The Stream Biome Gradient Concept generates testable hypotheses related to continental variation among streams worldwide and allows aquatic scientists to understand how results from one biome might apply to a less-studied biome. Some predicted factors change monotonically across the biome/climate gradients, whereas others have maxima or minima in the central portion of the gradient. For example, predictions across the gradient from drier deserts through grasslands to wetter forests include more permanent flow, less bare ground, lower erosion and sediment transport rates, decreased importance of autochthonous C inputs to food webs, and greater stream animal species richness. In contrast, effects of large ungulate grazers on streams are expected to be greater in grasslands than in forests or deserts, and fire is expected to have weaker effects in grassland streams than in desert and forest streams along biome gradients with changing precipitation and constant latitude or elevation. Understanding historic patterns among biomes can help describe the evolutionary template at relevant biogeographic scales, can be used to broaden other conceptual models of stream ecology, and could lead to better management and conservation across the broadest scales.

Effects of intensive agriculture in the structure and functioning of tropical headwater streams

“…These results are in agreement with the Stream Biome Gradient Concept, which hypothesizes that stream biological features changes predictably along climate characteristics (DODDS et al, 2015). Interestingly and supporting our hypothesis, nitrate concentrations did not demonstrate effects on diatom functional diversity, as commonly observed in temperate streams (BIGGS;CLOSE, 1989;PASSY, 2007;LANGE et al, 2015).…”

“…Deforestation changes the hydrological patterns in the catchments through the changes in the total water yield produced by precipitation, which increase with forest cutting due to the reduction of evapotranspiration and consequently, increase in the stream discharge (Figure 1.2). Changes in stream discharge modulate biological communities in streams (POFF et al, 1997;DODDS et al, 2015) with consequences for the entire aquatic ecosystem. Figure 1.2 -Schematic view of the effects of deforestation on stream discharge: Evapotranspiration rates (ET) diminish with forest cutting; Total water yield (R) and discharge (D) increase with forest cutting Source: Changes in runoff due to deforestation and agriculture have effects on water quality.…”

“…In running waters, many of the predicted changes to ecosystems are linked to changes in the hydrological cycle and water temperature (DODDS et al, 2015). Evidence suggests that in the tropics these changes may be abrupt, with effects unprecedented in the last 5200 years (THOMPSON et al, 2006).…”

“…The accelerated development is degrading the freshwater habitats, which contain about 9.5% of the described animal species in one of the most biodiverse ecosystems on Earth (DUDGEON et al, 2006;WANTZEN et al, 2006;BOULTON et al, 2008). Tropical streams differ from temperate streams especially in terms of climatic conditions, geomorphology, landscape evolution and geological history (WANTZEN et al, 2006) therefore, it is likely that processes and functioning of tropical streams may differ from temperate streams due to differences in hydrological cycle and water temperature (DODDS et al, 2015). These characteristics make tropical streams an important subject of study, considering the lack of information about these ecosystems and the rapid development in tropical regions.…”

Metabolismo em riachos subtropicais: variação espaço-temporal e influência de gradiente de condições ambientais

“…Os pulsos contínuos e de longa duração proporcionam adaptações da biota para a utilização da rápida ciclagem de matéria orgânica e nutrientes disponíveis na zona de transição aquática/terrestre. Mais recentemente, Dodds et al (2015) observaram que a estrutura ecossistêmica de riachos pode ser modificada devido a alterações climáticas (e.g., precipitação e temperatura), além de diversos fatores abióticos e bióticos como a hidrologia, geomorfologia, vegetação ripária (Figura 1).…”