SEASONALLY DRIVEN VARIATION IN SPATIAL RELATIONSHIPS BETWEEN AGRICULTURAL LAND USE AND IN-STREAM NUTRIENT CONCENTRATIONS

2013 ◽  
Vol 30 (4) ◽  
pp. 476-493 ◽  
Author(s):  
A. G. Yates ◽  
R. B. Brua ◽  
J. Corriveau ◽  
J. M. Culp ◽  
P. A. Chambers
Keyword(s):  
Land Use ◽  
Agricultural Land ◽  
Nutrient Concentrations ◽  
Agricultural Land Use ◽  
Spatial Relationships

Phosphorus chemical changes under soils over a period of agricultural intensification

2020 ◽  
Author(s):  
Andrew Tweedie ◽  
Philip M. Haygarth ◽  
Anthony Edwards ◽  
Allan Lilly ◽  
Nikki Baggaley ◽  
...  
Keyword(s):  
Land Use ◽  
Agricultural Intensification ◽  
Agricultural Land ◽  
Ammonium Oxalate ◽  
Water Extraction ◽  
Nutrient Concentrations ◽  
Agricultural Land Use ◽  
Organic P ◽  
P Fertilizer ◽  
Over Time

<p>The use of phosphorus (P) fertilizer has been one of the defining contributors to productive agriculture since the green revolution during the middle of the last century. However, these increased yields have come at the cost of dependency upon the declining resources of P rock reserves and eutrophication of water bodies downstream. In this context, it is important to understand the long-term effects of these P fertilizer additions on soil chemistry over ~50 years in order explain past and current patterns in fertilizer usage and so to better inform future soil management.</p><p>We tested the hypothesis that phosphorus forms and availability in mixed use (arable and grazed) agricultural soil have changed over a period of 50 to 80 years of agricultural intensification. Spatially matched samples of soil from 34 agricultural sites in North East (NE) Scotland were collected at two timepoints. The first samples were taken between 1951 and 1981 and in all cases the resampling took place in the autumn of 2017. The soils sampled were representative of agricultural soils in NE Scotland.</p><p>The hypothesis was tested by employing a range of soil tests on the ‘old’ and ‘new’ time points.  These included water extraction for inorganic and organic P, nitrate and ammonium and dissolved organic carbon, acid ammonium oxalate extraction to investigate the soil P exchange complex and NaOH-EDTA extraction as a strong alkaline extractant which preserves organic P forms. Analysis by <sup>31</sup>P NMR was conducted on the NaOH-EDTA extracts from 5 pairs of samples, to investigate the organic P chemistry of in greater detail.</p><p>Phosphorus concentrations for stronger extractants (NaOH-EDTA, acid ammonium oxalate) did not increase significantly (P<0.05) over time. However, water extraction results showed increases in total P (P<0.01) and inorganic P but decreases in organic P. Additionally, analysis by <sup>31</sup>P NMR detected changes between timepoints in α-glycero-phosphate and pyrophosphate.</p><p>These results indicate that differences in the various chemical forms of P present in soil between the timepoints can be detected many decades apart. This indicates changes in the functioning of the P cycle in these soils under intensive agricultural land use over time. Knowledge of the P-cycling response of soils under agricultural land-use over decades provides an opportunity to understand changes in soil nutrient concentrations, balances and availability and inform studies seeking to improve the sustainable management of soil fertility.</p>

Effects of intermittency and land use on the in-stream phosphorus and organic carbon uptake

2020 ◽  
Author(s):  
Gabriele Weigelhofer ◽  
Matthias Pucher
Keyword(s):  
Land Use ◽  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Hyporheic Zone ◽  
Agricultural Land ◽  
Headwater Streams ◽  
Phosphorus Release ◽  
Nutrient Concentrations ◽  
Agricultural Land Use ◽  
First Results

<p>Understanding the consequences of the interplay between land use and climate change is among the most pressing challenges of the 21<sup>st</sup> century for river managers. Over the past decades, agricultural land use has altered nutrient concentrations and stoichiometric ratios in stream ecosystems, thereby affecting aquatic biogeochemical cycles and the coupling among carbon, phosphorus, and nitrogen. In addition, the frequency and duration of droughts has increased dramatically across Europe, causing perennial streams to shift to intermittency and changing the capacity of sediments for the uptake and storage of macronutrients.</p><p>Our study aims to understand the effects of drying and re-wetting on the uptake, storage, and release of phosphorus and organic carbon from the benthic and the hyporheic zone of headwater streams under the additional stressor of agricultural land use. In specific, we are interested in the potential coupling and decoupling of phosphorus and dissolved organic carbon cycling in autotrophic and heterotrophic benthic biofilms. We sampled headwater streams before, during, and after the dry period in 2018 and 2019 and performed laboratory experiments with artificial drying and re-wetting and additions of dissolved organic carbon. We measured nutrient uptake and release, microbial biomass, respiration, and the activity of extra-cellular enzymes. The first results show an increased phosphorus release from the sediments immediately after re-wetting, foolowed by a reduced uptake capacity. The uptake of DOC was correlated with phosphorus in autotrophic biofilms, but not in heterotrophic ones.</p>

scholarly journals Effects of intensive agriculture and hydrological changes on macrophyte and macroinvertebrate assemblages in lowland riverine wetlands

2021 ◽  
Author(s):  
Paula Altieri ◽  
Carolina Ocon ◽  
Roberto Jensen ◽  
Alberto Rodrigues Capítulo
Keyword(s):  
Land Use ◽  
Agricultural Land ◽  
Nutrient Concentrations ◽  
Agricultural Land Use ◽  
Total Density ◽  
Land Uses ◽  
Dry Period ◽  
Riverine Wetlands ◽  
Macroinvertebrate Assemblages ◽  
Agricultural Wetlands

Abstract The aim of this study was to investigate the effects of agricultural land use and periods of hydrological variability on the environmental variables, as well as macrophyte and macroinvertebrate assemblages in lowland riverine wetlands. We compared two wetlands with intensive agricultural land use against two others with extensive livestock considered references for the region during a normal and a dry flow period. Nutrient concentrations were significantly higher in agricultural riverine wetlands. These wetlands exhibited higher relative coverage of floating anchored macrophytes and the absence of submerged vegetation. They showed significantly lower taxonomic richness and density of macroinvertebrates and a higher relative abundance of scrapers and predators. Wetlands of both land uses had a lower total density of macroinvertebrates and a higher proportion of tolerant desiccation taxa in the dry period. Particular differences between land uses, such as lower dissolved oxygen concentrations and lower macroinvertebrate diversity in agricultural wetlands, were found during the dry period. These findings indicate that the differences between land uses increased during the aforementioned period. This study provides evidence of the effects of the surrounding landscape and hydrologic periods in the environmental characteristics as well as the macrophyte and macroinvertebrate assemblages of the riverine wetlands studied.

scholarly journals Agroforestry Systems of the Tehuacán-Cuicatlán Valley: Land Use for Biocultural Diversity Conservation

Land ◽  
2019 ◽  
Vol 8 (2) ◽  
pp. 24
Author(s):  
Mariana Vallejo ◽  
M. Isabel Ramírez ◽  
Alejandro Reyes-González ◽  
Jairo López-Sánchez ◽  
Alejandro Casas
Keyword(s):  
Land Use ◽  
Agricultural Land ◽  
Agroforestry Systems ◽  
World Heritage Site ◽  
Biocultural Diversity ◽  
Semiarid Region ◽  
Agricultural Land Use ◽  
Visual Interpretation ◽  
Natural Ecosystems ◽  
Human Settlements

The Tehuacán-Cuicatlán Valley, Mexico, is the semiarid region with the richest biodiversity of North America and was recently recognized as a UNESCO's World Heritage site. Original agricultural practices remain to this day in agroforestry systems (AFS), which are expressions of high biocultural diversity. However, local people and researchers perceive a progressive decline both in natural ecosystems and AFS. To assess changes in location and extent of agricultural land use, we carried out a visual interpretation of very-high resolution imagery and field work, through which we identified AFS and conventional agricultural systems (CAS) from 1995 to 2003 and 2012. We analyzed five communities, representative of three main ecological and agricultural zones of the region. We assessed agricultural land use changes in relation to conspicuous landscape features (relief, rivers, roads, and human settlements). We found that natural ecosystems cover more than 85% of the territory in each community, and AFS represent 51% of all agricultural land. Establishment and permanence of agricultural lands were strongly influenced by gentle slopes and the existence of roads. Contrary to what we expected, we recorded agricultural areas being abandoned, thus favoring the regeneration of natural ecosystems, as well as a 9% increase of AFS over CAS. Agriculture is concentrated near human settlements. Most of the studied territories are meant to preserve natural ecosystems, and traditional AFS practices are being recovered for biocultural conservation.

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