Influence of land use on stream ecosystem function in a Mediterranean catchment

Abstract

1. Due to the hierarchical organization of stream networks, land use changes occurring at larger spatial scales (i.e. the catchment) can affect physical, chemical and biological characteristics at lower spatial scales, ultimately altering stream structure and function. Anthropogenic effects on streams have primarily been documented using structural metrics such as water chemistry, channel alteration and algal biomass. Functional parameters, including metrics of nutrient retention and metabolism, are now being widely used as indicators of stream condition. 2. Within this hierarchical context, we used a multivariate approach to examine how structural and functional (i.e. nutrient retention and metabolism) attributes of streams are related to catchment variables, including land use. The study was done in 13 streams located within a single Mediterranean catchment, but draining sub-catchments with contrasting land use. 3. At the catchment scale, results showed two contrasting land use gradients: (i) from forested-to urban-dominated catchments and (ii) from low to moderate agriculturaldominated catchments. Variation in structural and functional parameters was strongly related to these land use gradients. Specifically, NH 4 + demand (measured as the uptake velocity, V f ) decreased along the gradient from forested-to urban-dominated catchments primarily in response to increases in stream nutrient concentrations [NH 4 + , dissolved organic nitrogen (DON) and carbon (DOC)]. Both primary production and respiration increased along the gradient of agricultural development in response to increases in algal biomass (chlorophyll a). Soluble reactive phosphorus demand was not related to any of the land use gradients. 4. Our results illustrate the connections among factors operating at different spatial scales (i.e. from catchments to streams) and their distinct influence on stream ecosystem function. Managers should take into consideration these connections when designing stream management and restoration plans. Because ecologically successful stream management and restoration is expected to restore function as well as structure to streams, the use of appropriate measures of functional processes is required. Nutrient retention and metabolism parameters are good candidates to fill this gap.

Longitudinal Changes in Water Quality to Landscape Gradients along Jialu River Basin

“…Consequently, cities or villages intensity has increased over these ten years, particularly in the upper and lower reaches of the stream. As we know, this extensive and ever-increasing urbanization leads to a threat to stream ecosystem [18]. The results confirmed our prediction that urban land was the primary factor to explain the deterioration of water quality.…”

“…Statistic analysis. Sites were subjectively split into three groups: (1) headwater (sites 1-8); (2) mid-reach (sites 9-15); and (3) lower reaches (sites [16][17][18][19][20]. Differences between sites were compared with a parameteric analysis of variance (ANOVA) and significant differences were accepted at P < 0.05.…”

Land use influences stream nitrate uptake in the Lake Taupo catchment

“…Some studies have shown that inorganic N uptake decreases with increasing developed land use as a result of higher stream inorganic N concentrations reducing biotic demand for uptake (Niyogi et al 2004;Von Schiller et al 2008). However, this effect can be offset, or exceeded, by higher resource availability in developed land use streams increasing biotic biomass and metabolism, and thus increasing nutrient demand (Hall et al 2009).…”

Riparian vegetation metrics as tools for guiding ecological restoration in riverscapes

“…Rivers and riparian areas of Iberia, Southwestern Europe, have been subjected to huge human disturbances for millennia, such as water diversion, regulation, land-use, afforestation, grazing, physical interventions on riverbanks, amongst others Hooke, 2006;von Schiller et al, 2008). These manifold types of pressures often result in biodiversity and habitat loss, and invasion by alien plant species, as well as an overall degradation of the riparian ecosystem (Aguiar et al, 2001;Allan, 2004;Aguiar and Ferreira, 2005).…”