The critical scale of small-scale spatial variation in ecological patterns and processes in intertidal macrobenthic seagrass assemblages

2012 ◽  
Vol 98 ◽  
pp. 119-125 ◽  
Author(s):  
R.S.K. Barnes ◽  
M.D.F. Ellwood
Keyword(s):  
Spatial Variation ◽  
Small Scale ◽  
Ecological Patterns ◽  
Patterns And Processes ◽  
Critical Scale

Net precipitation assessment in a grassland and soil moisture response at plot scale in a temperate climate

2021 ◽  
Author(s):  
Gökben Demir ◽  
Johanna Clara Metzger ◽  
Janett Filipzik ◽  
Christine Fischer ◽  
Beate Michalzik ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Spatial Variation ◽  
Canopy Structure ◽  
Sampling Period ◽  
Temperate Climate ◽  
Small Scale ◽  
Spatial Effects ◽  
Mixed Effect ◽  
Canopy Development ◽  
Canopy Effect

<div> <p>Evidence on spatial variation of net precipitation in grasslands is scarce. Challenges arise due to a small-scale canopy structure of grasslands.</p> <p>In this study, we designed and tested a new in-situ measurement device (interception grid) to assess net precipitation in grasslands. The collector allows the natural development of the canopy. We tested the device both in the lab for splash loss and in the field to test its capacity to assess net precipitation. In the field, we installed 25 collectors on a grassland within the Hainich Critical Zone Exploratory (Thuringia, Germany), 23 of which were paired with soil moisture sensors. We conducted weekly measurements gross and net precipitation (above and below the canopy), along with grass height in 2019 (March-August) and 2020 (January -February). We categorized the data into two groups (‘covered,’ ‘uncovered’), accounting for canopy development.</p> <p>In the lab, we found that the drop size strongly affects splash loss. Drops of ca. 2 mm, created more than 16% splash loss, decreasing to less than 3% for drops <1.5 mm. Drop sizes <1.75 mm during the sampling period (2019) suggest low to intermediate splash loss in the field, further decreased in the covered period as the canopy contact slows down the drops. Grid measurements corrected with estimated splash loss during the uncovered period agreed well with gross precipitation. Using linear mixed effect models, we found that wind speed and grass height significantly affected the grid measurements of covered periods. Therefore, grids were able to capture net precipitation variation due to grass development. These steps encouraged us to examine the canopy effect in the soil moisture response to rainfall.</p> <p>Soil moisture response over the entire period was not related to the spatial variation of net precipitation. However, for the drier period (June-August 2019), when the spatial variation in soil moisture is higher, and the overall response to rain events stronger, net precipitation slightly affected soil moisture response. LMEM analysis to estimate factors on soil moisture response showed that grass height, net precipitation are significant predictors. Yet, there is no remarkable difference between using net precipitation and gross precipitation as potential drivers for soil moisture response, indicating that the spatial effects are comparatively small. Overall, our findings suggest that the grids are cable to catch canopy effects on the precipitation, while the effect of wind on under-catch still needs to be investigated further.</p> </div>

scholarly journals Diploptene <i>δ</i><sup>13</sup>C values from contemporary thermokarst lake sediments show complex spatial variation

2016 ◽  
Vol 13 (8) ◽  
pp. 2611-2621 ◽  
Author(s):  
Kimberley L. Davies ◽  
Richard D. Pancost ◽  
Mary E. Edwards ◽  
Katey M. Walter Anthony ◽  
Peter G. Langdon ◽  
...  
Keyword(s):  
Spatial Variation ◽  
Lake Sediments ◽  
Methane Oxidation ◽  
Methane Production ◽  
Small Scale ◽  
Δ13c Values ◽  
Thermokarst Lakes ◽  
Methane Ebullition ◽  
Methane Efflux ◽  
Isotopic Signal

Abstract. Cryospheric changes in northern high latitudes are linked to significant greenhouse gas flux to the atmosphere, for example, methane that originates from organic matter decomposition in thermokarst lakes. The set of pathways that link methane production in sediments, via oxidation in the lake system, to the flux of residual methane to the atmosphere is complex and exhibits temporal and spatial variation. The isotopic signal of bacterial biomarkers (hopanoids, e.g. diploptene) in sediments has been used to identify contemporary ocean-floor methane seeps and, in the geological record, periods of enhanced methane production (e.g. the PETM). The biomarker approach could potentially be used to assess temporal changes in lake emissions through the Holocene via the sedimentary biomarker record. However, there are no data on the consistency of the signal of isotopic depletion in relation to source or on the amount of noise (unexplained variation) in biomarker values from modern lake sediments. We assessed methane oxidation as represented by the isotopic signal of biomarkers from methane oxidising bacteria (MOB) in multiple surface sediment samples in three distinct areas known to emit varying levels of methane in two shallow Alaskan thermokarst lakes. Diploptene was present and had δ13C values lower than −38 ‰ in all sediments analysed, suggesting methane oxidation was widespread. However, there was considerable variation in δ13C values within each area. The most 13C-depleted diploptene was found in an area of high methane ebullition in Ace Lake (diploptene δ13C values between −68.2 and −50.1 ‰). In contrast, significantly higher diploptene δ13C values (between −42.9 and −38.8 ‰) were found in an area of methane ebullition in Smith Lake. δ13C values of diploptene between −56.8 and −46.9 ‰ were found in the centre of Smith Lake, where ebullition rates are low but diffusive methane efflux occurs. The small-scale heterogeneity of the samples may reflect patchy distribution of substrate and/or MOB within the sediments. The two ebullition areas differ in age and type of organic carbon substrate, which may affect methane production, transport, and subsequent oxidation. Given the high amount of variation in surface samples, a more extensive calibration of modern sediment properties, within and among lakes, is required before down-core records of hopanoid isotopic signatures are developed.

scholarly journals Size-effect, asymmetry, and small-scale spatial variation in otolith shape of juvenile sole in the Southern North Sea

Hydrobiologia ◽  
2018 ◽  
Vol 845 (1) ◽  
pp. 95-108 ◽  
Author(s):  
Sophie Delerue-Ricard ◽  
Hanna Stynen ◽  
Léo Barbut ◽  
Fabien Morat ◽  
Kelig Mahé ◽  
...  
Keyword(s):  
Size Effect ◽  
Spatial Variation ◽  
North Sea ◽  
Small Scale ◽  
Otolith Shape ◽  
Southern North Sea

Spatial Variation of Soil Organic Matter in Gully Bed with the Seabuckthorn Flexible Dam: A Case Study of EG1 in Zhun-Ge-Er County of Inner Mongolia, China

2014 ◽  
Vol 1073-1076 ◽  
pp. 619-627
Author(s):  
Fang She Yang ◽  
Shu Zhen Su ◽  
Juan Juan Zhang ◽  
Ci Fen Bi
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
Spatial Autocorrelation ◽  
Spatial Variation ◽  
Inner Mongolia ◽  
Small Scale ◽  
Obvious Effect ◽  
Small Catchment ◽  
Variation Characteristics ◽  
Random Variation

In this paper, based on geostatistics and GIS techniques, spatial variation characteristics of soil organic matter (acronym: SOM) on a small scale were analyzed and discussed in east-one-branch gully (EG1) bed with the seabuckthorn flexible dam and the contrastive gully bed (which is non-vegetated any vegetation) located in zhun-ge-er county, Erdos, inner Mongolia, which belongs to the typical Pisha Sandstone area. The results show that the seabuckthorn can significantly increase SOM in the small catchment gully bed in the Pisha sandstone area, and the mean SOM content in gully bed with the seabuckthorn flexible dam is approximate 1.75 times that in the contrastive gully. Apparent spatial variation characteristics of SOM were found in the gully with the seabuckthorn flexible dam and the contrastive gully bed, moreover, the medium spatial autocorrelation of SOM was detected in gully bed with the seabuckthorn flexible dam, and the spatial variation of SOM was together led to by the structural and random variation at 1-6.5 m range, and of which the random variation accounts for 40%. Additional, the spatial autocorrelation of SOM in the contrastive gully bed is higher, the spatial variation of SOM was dominantly brought about by the structural variation at 1-4.5 m range, and of which the random variation accounts for 37%. Furthermore, the fractal dimension values reveal that dependence of SOM of the gully bed with the seabuckthorn flexible dam on spatial is weaker than that of the contrastive gully bed. It is judged that the seabuckthorn has an obvious effect on spatial distribution patterns and heterogeneity of SOM on a small scale.

Variability in organic matter lost by combustion in a boreal bog during the 2001 Chisholm fire

2003 ◽  
Vol 33 (12) ◽  
pp. 2509-2513 ◽  
Author(s):  
Brian W Benscoter ◽  
R Kelman Wieder
Keyword(s):  
Organic Matter ◽  
Species Composition ◽  
Spatial Variability ◽  
Spatial Variation ◽  
Fire Severity ◽  
Small Scale ◽  
Western Canada ◽  
Direct Combustion ◽  
Site Variation

Fire directly releases carbon (C) to the atmosphere through combustion of biomass. An estimated 1470 ± 59 km2 of peatland burns annually in boreal, western Canada, releasing 4.7 ± 0.6 Tg C to the atmosphere via direct combustion. We quantified within-site variation in organic matter lost via combustion in a bog peatland in association with the 116 000-ha Chisholm, Alberta, fire in 2001. We hypothesized that for peatlands with considerable small-scale microtopography (bogs and treed fens), hummocks will burn less than hollows. We found that hollows exhibit more combustion than hummocks, releasing nearly twice as much C to the atmosphere. Our results suggest that spatial variability in species composition and site hydrology within a landform and across a landscape could contribute to considerable spatial variation in the amounts of C released via combustion during peatland fire, although the magnitude of this variation may be dependent on fire severity.

scholarly journals Fragmented Landscape, Fragmented Knowledge: A Synthesis of Renosterveld Ecology and Conservation

2019 ◽  
Vol 46 (2) ◽  
pp. 171-179 ◽  
Author(s):  
Emmeline N Topp ◽  
Jacqueline Loos
Keyword(s):  
Cape Floristic Region ◽  
Fragmented Landscape ◽  
Biodiversity Hotspots ◽  
Current State ◽  
Ecological Patterns ◽  
Local Patch ◽  
Populated Region ◽  
Patterns And Processes ◽  
First Time ◽  
Effective Conservation

SummaryKnowledge of ecological patterns and processes is key to effective conservation of biodiversity hotspots under threat. Renosterveld is one of the most critically endangered habitats in the biologically unique Cape Floristic Region, South Africa. For the first time, we map and synthesize the current state of knowledge on renosterveld ecology and conservation. We investigated 132 studies for the themes, locations and taxa of renosterveld research and the fragmentation, threats, recommendations and barriers to renosterveld conservation. More studies focused on plants than any other taxa (48% of articles) and are conducted mostly in larger, intact renosterveld fragments. The most commonly identified threat to renosterveld was agricultural intensification; conservation recommendations spanned improved farming practices, formal protection and local patch management. Conservation implementation has been piecemeal and has depended largely on the goodwill of landowners, which can be constrained by costs of conservation measures and a lack of suitable restoration means. Citizen science is a promising potential solution to some barriers. Fragmented knowledge in such a transformed and relatively densely populated region highlights the scale of knowledge gaps for other biodiversity hotspots and has implications for ongoing conservation work.

scholarly journals Observations of Magnetic Features with the German Solar Telescopes at the Observatorio del Teide/Tenerife

1990 ◽  
Vol 142 ◽  
pp. 113-117
Author(s):  
F. Kneer ◽  
D. Soltau ◽  
E. Wiehr
Keyword(s):  
Magnetic Field ◽  
Fine Structure ◽  
Spatial Variation ◽  
Velocity Fluctuation ◽  
Small Scale ◽  
Field Variation ◽  
Magnetic Field Variation ◽  
Quiet Sun ◽  
Magnetic Features ◽  
Solar Telescopes

The German solar facilities at the Obsrvatorio del Teide are described first. Then, a few examples of recent results from magnetic features are given: spatial variation and velocity fluctuation of small-scale magnetic fluxtubes in the quiet Sun, Evershed flow and magnetic field in connection with penumbral fine structure, and magnetic field variation in sunspot umbrae.

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