Intensity of Land Use in the Catchment Influences Ecosystem Functioning Along a Freshwater-Marine Continuum

Abstract

Intensification of catchment land use often adversely affects ecosystem health in rivers and estuaries via changes to physicochemistry and ecosystem functioning, but whether such land-use effects differ along a freshwater-marine continuum has not been studied. We investigated relationships between intensity of land use and two measures of ecosystem function in freshwater, estuarine and near-marine habitats. Standardized bioassays to determine cellulose breakdown (cotton and canvas strips) and algal accrual rates (ceramic tiles) were deployed in 10 river-to-marine continua whose catchment areas ranged from 2.6 to 99.6% developed. Using general linear models and an information-theoretic approach to select the best predictive models for our response variables, we found that higher dissolved phosphorus concentrations, linked with highly developed catchments, were associated with greater rates of cellulose decomposition (both tensile strength loss and mass loss). Furthermore, after controlling for the contribution of phosphorus or salinity, decomposition rates in freshwater and near-marine habitats generally responded curvilinearly to catchment development, indicating the involvement of additional unmeasured, land-userelated physicochemical or biological variables. The strength and shape of relationships between percentage developed land area and algal biomass accrual rates also contrasted among freshwater (strongest, curvilinear), mid-estuary (intermediate, positive), and near-marine sites (weakest, no obvious shape). Because land-use intensity can influence ecosystem functioning along the entire continuum from streams and rivers to estuaries and coasts, resource managers should adopt an integrated approach to decisions affecting catchment land use.

Counting on β-Diversity to Safeguard the Resilience of Estuaries

“…The percentage of land cover in the catchment of natural, pastoral and exotic (i.e. plantation forests) vegetation and urbanisation were used as surrogates for stress caused by human uses in the catchment [33], [36]. Tamaki and Waitemata estuaries were expected to be the most stressed as the percentage of urban cover was over 40%, while Parekura and Whananaki had the largest proportion of natural cover in the catchment (Table 1).…”

Measuring function and structure of urban headwater streams with citizen scientists

“…In larger streams across a gradient of freshwater to estuary sites (fourth to fifth order), cotton‐strip decomposition rate was hump‐shaped across a gradient of pristine catchment cover (percent native cover) but their response was the inverse of our expected relationship (i.e., lowest rates at 50% pristine cover) and only apparent when phosphorous concentrations and salinity were accounted for (Bierschenk et al. ). Across a range of functional indicators, catchment sizes, and land uses, another study found leaf litter and wooden stick decomposition rates responded negatively and linearly to land‐use stress scores, whereas cotton‐strip decomposition rates showed a threshold response; however, an urban gradient was not used in the study (Young and Collier ).…”

Spatial-temporal characteristics of land use intensity of coastal zone in China during 2000–2010

“…3) Revealing the spatial-temporal characteristics of land use intensity by mathematical models (Zhuang and Liu, 1997;Ferdous and Bhat, 2013). 4) Investigating the ecological effects of land use intensity changes (Bierschenk et al, 2012;Krausmann et al, 2013;Li et al, 2013;Macchi et al, 2013). However, researches focused on spatial-temporal dynamics of land use intensity in China′s coastal zone have not been reported so far.…”