Leon P. M. Lamers

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In wetland soils and underwater sediments of marine, brackish and freshwater systems, the strong phytotoxin sulfide may accumulate as a result of microbial reduction of sulfate during anaerobiosis, its level depending on prevailing edaphic conditions. In this review, we compare an extensive body of literature on phytotoxic effects of this reduced sulfur(More)
The majority of studies on rhizospheric interactions focus on pathogens, mycorrhizal symbiosis, or carbon transformations. Although the biogeochemical transformations of N, S, and Fe have profound effects on vegetation, these effects have received far less attention. This review, meant for microbiologists, biogeochemists, and plant scientists includes a(More)
This paper describes forms of risk sharing between insurers and the regulator in a competitive individual health insurance market with imperfectly risk-adjusted capitation payments. Risk sharing implies a reduction of an insurer's incentives for selection as well as for efficiency. In a theoretical analysis, we show how the optimal extent of risk sharing(More)
One of the most frequently quoted ecosystem services of seagrass meadows is their value for coastal protection. Many studies emphasize the role of above-ground shoots in attenuating waves, enhancing sedimentation and preventing erosion. This raises the question if short-leaved, low density (grazed) seagrass meadows with most of their biomass in belowground(More)
Peat forming Sphagnum mosses are able to prevent the dominance of vascular plants under ombrotrophic conditions by efficiently scavenging atmospherically deposited nitrogen (N). N-uptake kinetics of these mosses are therefore expected to play a key role in differential N availability, plant competition, and carbon sequestration in Sphagnum peatlands. The(More)
Survival of an acute myocardial infarction (AMI) and subsequent prognosis are highly dependent on the time between onset of symptoms and medical intervention. The purpose of this study is to investigate which psychological and cardiovascular knowledge factors may contribute to the time the AMI patient takes to decide to seek medical help (patient delay).(More)
Internal phosphorus (P) mobilisation from aquatic sediments is an important process adding to eutrophication problems in wetlands. Salinisation, a fast growing global problem, is thought to affect P behaviour. Although several studies have addressed the effects of salinisation, interactions between salinity changes and nutrient cycling in freshwater systems(More)
OBJECTIVE The purpose of this study was to examine whether number and type of chronic conditions are related to psychological distress, fatigue, and the use of psychoactive medications. METHODS Data were taken from a community-based sample of adults who had responded to a health survey mailing (N = 9428). Chronic conditions were assessed by self-report.(More)
Adequate biogeochemical characterization and monitoring of aquatic ecosystems, both for scientific purposes and for water management, pose high demands on spatial and temporal replication of chemical analyses. Near-infrared reflectance spectroscopy (NIRS) may offer a rapid, low-cost and reproducible alternative to standard analytical sample processing(More)
In pristine ombrotrophic Sphagnum-dominated peatland ecosystems nitrogen (N) is often a limiting nutrient, which is replenished by biological N2 fixation and atmospheric N deposition. It is, however, unclear which impact long-term N deposition has on microbial N2 fixing activity and diazotrophic diversity, and whether phosphorus (P) modulates the response.(More)