Wim Clymans

Wim Clymans
Lund University | LU · Department of Geology

PhD

About

62
Publications
18,018
Reads
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2,521
Citations
Additional affiliations
June 2012 - present
Lund University
Position
  • PostDoc Position
Description
  • The research focuses on creating a better understanding of biogenic and pedogenic controls on Si dynamics within the soil-vegetation continuum, and its neglected importance in carbon dynamics in mineral weathering studies.
January 2008 - January 2012
KU Leuven
Position
  • PhD Student
Description
  • Land Use Related Si Dynamics in Terrestrial Ecosystems

Publications

Publications (62)
Article
Full-text available
Freshwater ecosystems are increasingly facing major global and local stressors, while monitoring surface water status by regulatory agencies is often limited by financial and political constraints. Citizen science-based approaches with robust quality control and training can support regulatory monitoring and decision-making. Herein, we outline the...
Article
Full-text available
In situ monitoring is fundamental to manage eutrophication in rivers and streams. However, in recent decades, the frequency and spatial coverage of regulatory monitoring have often been reduced due to funding and infrastructure limitations. This reduction has made it impossible to provide adequate coverage for most water bodies. In this study, trai...
Article
Full-text available
Conventional water quality monitoring has been done for decades in Lake Tanganyika, under different national and international programs. However, these projects utilized monitoring approaches, which were temporally limited, labour intensive and costly. This study examines the use of citizen science to monitor the dynamics of coliform concentrations...
Article
Review studies indicate that conservation tillage effectively reduces runoff generation measured on large plots, but less so on smaller plots. These tillage and scale effects have never been measured in a single study for temperate mechanized agriculture. With the objective to study how runoff production changes with scale as influenced by tillage...
Article
Full-text available
The involvement of volunteers in aspects of freshwater research and monitoring has a long history. However , the advent of smart technology and access to the internet has opened up the possibility of mass public participation in science, termed citizen science. The potential of citizen science to generate data over wider spatial and temporal scales...
Chapter
A highly seasonal and erratic rainfall pattern (Chapter 3) seems to provoke general water scarcity in Dogu’a Tembien for eight months a year. This chapter shortly describes the hydrogeological context and hydrodynamics of actual surface and groundwater flow of the mountain catchments around Hagere Selam. Further, some positive effects of water harv...
Poster
Full-text available
Our cities are increasingly impacted by climate change and growing urban populations. These changes are rapidly modifying urban environments, with knock-on effects on health and quality of life. In many cities, ecosystem functioning and services have been heavily compromised, requiring urgent action from actors in all sectors, public, corporate, ac...
Conference Paper
Full-text available
Sustainable management of water resources and associated freshwater ecosystems fundamentally requires datasets that describe water availability within a catchment. However, the required level of hydrological monitoring data (e.g. long term river gauging) is rarely available, in particular in developing countries, making the application of good wate...
Article
Full-text available
Biosilicification has driven variation in the global Si cycle over geologic time. The evolution of different eukaryotic lineages that convert dissolved Si (DSi) into mineralized structures (higher plants, siliceous sponges, radiolarians, and diatoms) has driven a secular decrease in DSi in the global ocean leading to the low DSi concentrations seen...
Article
Full-text available
We explore the distribution of sponges along dissolved silica (dSi) concentration gradients to test whether sponge assemblages are related to dSi and to assess the validity of fossil sponges as a palaeoecological tool for inferring dSi concentrations of the past oceans. We extracted sponge records from the publically available Global Biodiversity I...
Article
Full-text available
In terrestrial ecosystems, a large portion (20-80%) of the dissolved Si (DSi) in soil solution has passed through vegetation. While the importance of this ‘terrestrial Si filter’ is generally accepted, few data exist on the pools and fluxes of Si in forest vegetation and the rate of release of Si from decomposing plant tissues. We quantified the po...
Article
Full-text available
We investigated the vertical distribution, storage, landscape partitioning, and spatial variability of soil amorphous silica (ASi) at four different sites underlain by continuous permafrost and representative of mountainous and lowland tundra, in the circum-Arctic region. Based on a larger set of data, we present the first estimate of the ASi soil...
Article
Full-text available
The silicon isotope composition of biogenic silica (δ30SiBSi) in the ocean is a function of the δ30Si of the available dissolved Si (DSi; H2SiO4), the degree of utilisation of the available DSi, and, for some organisms, the concentration of DSi. This makes δ30SiBSi in sediment archives a promising proxy for past DSi concentrations and utilisation....
Article
Full-text available
We studied bacterial and fungal colonization of submerged plant litter, using a known Si-accumulator (Equisetum arvense), in experimental microcosms during one month. We specifically addressed the microbial decomposer role concerning biogenic silica (bSiO2) dissolution from the degrading litter. To vary the rates and level of microbial colonization...
Article
Full-text available
The Ganges is one of the world's largest rivers and lies at the heart of a body of literature that investigates the interaction between mountain orogeny, weathering and global climate change. Three regions can be recognised in the Ganges basin, with the Himalayan orogeny to the north and the plateaus of peninsular India to the south together delimi...
Article
Full-text available
Biogenic silica (BSi) is used as a proxy by soil scientists to identify biological effects on the Si cycle and by palaeoecologists to study environmental changes. Alkaline extractions are typically used to measure BSi in both terrestrial and aquatic environments. The dissolution properties of volcanic glass in tephra deposits and their nanocrystall...
Article
The biogeochemical cycling of silicon (Si) along the land-to-ocean continuum is studied by a variety of research fields and for a variety of scientific reasons. However, there is an increasing need to refine the methodology and the underlying assumptions used to determine biogenic silica (BSi) concentrations. Recent evidence suggests that contribut...
Article
Full-text available
We investigated the distribution, storage and landscape partitioning of soil amorphous silica (ASi) in a central Canadian region dominated by tundra and peatlands to provide a first estimate of the amount of ASi stored in Arctic permafrost ecosystems. We hypothesize that, similar to soil organic matter, Arctic soils store large amounts of ASi which...
Article
Full-text available
Despite increasing recognition of the relevance of biological cycling for Si cycling in ecosystems and for Si export from soils to fluvial systems, effects of human cultivation on the Si cycle are still relatively understudied. Here we examined stable Si isotope (d 30 Si) signatures in soil water samples across a temperate land use gradient. We sho...
Article
Full-text available
Biogenic silica (BSi) is used as a proxy by soil scientists to identify biological effects on the Si cycle and by paleoecologists to study environmental changes. Alkaline extractions are typically used to measure BSi in both terrestrial and aquatic environments. The dissolution properties of volcanic glass in tephra deposits and their nano-crystall...
Article
Amorphous silica (ASi) carried in suspension by rivers is an important component in the global Si budget. Water erosion processes in cultivated catchments are likely to drive ASi delivery to the river system. However, no studies have investigated the controls on ASi mobilisation by erosional processes in croplands. Rainfall experiments were perform...
Article
Full-text available
Despite increasing recognition of the relevance of biological cycling for Si cycling in ecosystems and for Si export from soils to fluvial systems, effects of human cultivation on the Si cycle are still relatively understudied. Here we examined stable Si isotope (δ(30)Si) signatures in soil water samples across a temperate land use gradient. We sho...
Article
Full-text available
Basaltic weathering from volcanic islands plays a critical role in the climate feedback loop. Geochemical and climate models require information on the rate of secondary mineral formation. We provide direct evidence for precipitation of amorphous Si in organic rich and acidic Histic Andosols compared to preferential allophane formation in organic p...
Article
Full-text available
Rivers transport ∽6 x1012 mol yr-1 of dissolved Si (DSi) from the continents to the oceans. They also carry amorphous silica (ASi), solid phases likely to dissolve in seawater. Unfortunately, the magnitude of this flux is poorly constrained at a global scale. We present 92 new ASi values from suspended particulate matter (SPM) from the Ganges basin...
Article
Dissolved organic carbon (DOC) is one of the most active and mobile carbon pools, and thus an important component of the global carbon cycle. Previous research on DOC transport in the soil and on factors controlling DOC export towards the river system focused mainly on forest and wetland areas, with only limited information available from agricultu...
Article
The primary source of dissolved silicon (Si: DSi) is the weathering of silicate minerals. In recent years, it has been shown that Si cycling through vegetation creates a more soluble Si pool in the soil, as amorphous Si (ASi) deposits in plants (phytoliths) are returned to the soil through litter. Amorphous Si accumulation in soils depends on a num...
Article
Weathering of silicate minerals releases dissolved silicate (DSi) to the soil-vegetation system. Accumulation and recycling of this DSi by terrestrial ecosystems creates a pool of reactive Si on the continents that buffers DSi export to the ocean. Human perturbations to the functioning of the buffer have been a recent research focus, yet a common a...
Article
Full-text available
Colluvial soils are enriched in soil organic carbon (SOC) in comparison to the soils of upslope areas due to the deposition and progressive burial of SOC. This burial of SOC has important implications for the global carbon cycle, but the long-term dynamics of buried SOC remain poorly constrained. We addressed this issue by determining the SOC buria...
Article
Amorphous Silica (ASi) is present in considerable amounts in most soils and serves as a (micro-)nutrient for many plants. However, our understanding of the response of this important nutrient pool to human or natural disturbances is still very limited. One of the reasons for this is the long time scales involved. This explorative study focuses on t...
Article
Full-text available
Silicon (Si) is a key element in global biogeochemical cycling and recent research has shown that changes in the biological component of the Si cycle may lead to more rapid variations in the land–ocean Si transfer than previously thought. The objective of this paper is to better understand the controls on temporal Si dynamics in terrestrial ecosyst...
Article
Full-text available
Colluvial soils are enriched in soil organic carbon (SOC) in comparison to the soils of upslope areas due to the deposition and subsurface burial of SOC. It has been suggested that the burial of SOC has important implications for the global carbon cycle, but the long-term dynamics of buried SOC remains poorly constrained. We address this issue by d...
Article
Full-text available
Sediments mobilized by interrill erosion are often highly enriched in soil organic carbon (SOC) in comparison to source soils. This selectivity may lead to the preferential mobilization of SOC with specific properties, e.g., SOC that is especially susceptible to decomposition. This may then have important implications with respect to the role of so...
Article
Full-text available
This paper reviews the processes which determine the concentrations of dissolved silicon (DSi) in soil water and proposes a conceptual mechanistic model for understanding the transport of Si through soils to rivers. The net DSi present in natural waters originates from the dissolution of mineral and amorphous Si sources in the soil, as well as prec...
Article
One of the most frequently used techniques to combat soil erosion on agricultural fields is conservation agriculture (CA). Conservation tillage techniques (CT), together with residue management and rotation are the pillars of CA. Studies have shown that CT can indeed be very effective in combating soil erosion. While several studies have demonstrat...
Article
Soil erosion models need detailed runoff and infiltration data as input. This information can be deduced from empirical relationships or from dynamic models. Here we investigate to what extent it is possible to derive meaningful parameterizations for the Green–Ampt Mein-Larson infiltration model (GAML) using a dataset consisting of 350 rainfall sim...
Article
Full-text available
Amorphous, biogenic Si (ASi) is stored in large amounts in terrestrial ecosystems. The study of terrestrial ASi mobilization remains in the pioneer research stage: most Si budget studies have not included the biogenic amorphous Si stock and fluxes. This hampers our ability to accurately quantify terrestrial mobilization of Si, which is—through ocea...
Article
The correct analysis of amorphous silica concentration (CASi) in natural waters is crucial if one wants to correctly quantify terrestrial and/or riverine ASi fluxes. Soil ASi measurements are conducted with a constant solid to solution ratio (σ). As the suspended particulate matter concentration (CSPM), and therefore σ, cannot be exactly known a pr...
Article
Silica (Si) is of great concern to agronomists because it has a beneficial effect on plant resistance to various stresses, enabling yield optimization in economically important crop species. Yet biogenic silica (BSi) cycling in soils controls a large part of the Si export fluxes to rivers and oceans. Despite the importance of agricultural-harvest-r...
Article
Full-text available
Human land use changes perturb biogeochemical silica (Si) cycling in terrestrial ecosystems. This directly affects Si mobilisation and Si storage and influences Si export from the continents, although the magnitude of the impact is unknown. A major reason for our lack of understanding is that very little information exists on how land use affects a...
Article
Full-text available
Human land use changes directly affect silica (Si) mobilisation and Si storage in terrestrial ecosystems and influence Si export from the continents, although the magnitudes of the impact are unknown. Yet biogenic silica (BSi) in soils is an understudied aspect. We have quantified and compared total biogenic (PSia) and easily soluble (PSie) Si pool...
Article
A hydrogeological study was undertaken in the Zenako-Argaka catchment, near Hagere Selam in Tigray, northern Ethiopia, during the rainy season of 2006. A geological map was produced through geophysical measurements and field observations, and a fracture zone identified in the north west of the catchment. A perched water table was found within the T...
Article
Many infiltration models rely on an effective hydraulic conductivity parameter (K(e)) which is often determined in the field from rainfall simulation experiments on small plots. K(e) can be defined as the spatially averaged infiltration capacity when the soil is 'field-saturated' and steady state is reached. Then it equals the infiltration rate (f)...
Article
An overall approach to assess the effectiveness of soil conservation measures at catchment scale is the comparison of sediment budgets before and after implementation of a catchment management programme. In the May Zeg-zeg catchment (187 ha – Fig. 1) in Tigray, north Ethiopia, integrated catchment management has been implemented since 2004: stone b...
Article
Large uncertainties still exist on both the rates of soil organic carbon (SOC) mobilization by soil erosion as well as the fate of the eroded C. Using a range of techniques we characterized soil C redistribution by water erosion in two small agricultural catchments in the Belgian Loess Belt. Results from rainfall simulations showed that C enrichmen...
Article
Full-text available
Continental export of Si to the coastal zone is closely linked to the ocean carbon sink and to the dynamics of phytoplankton blooms in coastal ecosystems. Presently, however, the impact of human cultivation of the landscape on terrestrial Si fluxes remains unquantified and is not incorporated in models for terrestrial Si mobilization. In this paper...
Article
Effective hydraulic conductivity (Ke) can be estimated with statistical models derived from datasets of field measured conductivities. Pedotransfer functions (PTFs) estimate constant Ke values, but suffer from large prediction errors because the functions usually do not account for soil structural heterogeneities. Rainfall-runoff data have shown th...
Article
Full-text available
Impact studies of catchment management in the developing world rarely include detailed hydrological components. Here, changes in the hydrological response of a 200-ha catchment in north Ethiopia are investigated. The management included various soil and water conservation measures such as the construction of dry masonry stone bunds and check dams,...
Article
Our understanding of the biogeochemical cycle of Si lags behind our knowledge of other nutrient cycles. However, silica cycling impacts on two of the major global carbon sinks. At first, the weathering of mineral silicates is an important sink for atmospheric CO2. Secondly, the import of Si from the terrestrial environment into coastal zones is ess...
Article
Imbalances of nutrient concentrations (N:P:Si) determine the water quality of aquatic systems. Recent research pointed out that land use change can exert a strong influence on the Si-fluxes through terrestrial ecosystems. These ecosystems store a large amount of amorphous, biogenic Si (SiO2nH2O, ASi), a fraction which was not accounted for when con...
Article
Soil carbon redistribution by water erosion at the catchment level in an intensively cultivated area: characteristics, budgets and implications
Article
Amorphous, biogenic Si (ASi) is stored in large amounts in terrestrial ecosystems. The study of this terrestrial ASi pool and its influence on watershed scale silica fluxes, remains in an absolute pioneer research stage. These Si budget studies have not included the biogenic amorphous Si stock and related fluxes. This hampers our ability to accurat...
Article
An overall approach to assess the effectiveness of soil conservation measures at catchment scale is the comparison of sediment budgets before and after implementation of a catchment management programme. In the May Zeg-zeg catchment (187 ha) in Tigray, north Ethiopia, integrated catchment management has been implemented since 2004: stone bunds were...
Article
Global agricultural soil erosion has been proved to be a carbon sink. Water erosion and tillage erosion are the two dominant forms of soil redistribution processes in agricultural catchments. However, there is still no research trying to evaluate whether they play different roles in perturbing the carbon dynamics of agricultural land. By calibratin...
Article
Different techniques are used to analyse runoff, soil and plant samples for extractable amorphous silica (ASi). Most methods that are used are modified versions of a method originally proposed by DeMaster (1981). Generally a sequential alkaline extraction is applied on 0.025-0.030 10-3 kg of material using 0.025l of a 0.1M solution of Na2CO3 to mea...
Article
In recent years awareness has grown that biogeochemical cycles are strongly affected by processes occurring in the critical zone. Global carbon dynamics, for instance, may be affected by soil erosion and deposition processes that affect carbon dynamics within the critical zone. Silica is another element of which the cycling may be strongly influenc...
Article
Full-text available
Runoff generation by infiltration excess at steady state is usually modelled with a single, constant final infiltration capacity and it represents the averaged effective hydraulic conductivity (Ke), which is assumed to be independent of rainfall intensity. Experimental data and advances in the conceptualization of the infiltration process, however,...

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