Complex edge effects on soil moisture and microclimate in central Amazonian forest

1995 ◽  
Vol 11 (2) ◽  
pp. 205-221 ◽  
Author(s):  
J. L. C. Camargo ◽  
V. Kapos
Keyword(s):  
Soil Moisture ◽  
Edge Effects ◽  
Vegetation Structure ◽  
Vapour Pressure ◽  
Vapour Pressure Deficit ◽  
Forest Edge ◽  
Vertical Profiles ◽  
Control Soil ◽  
Neutron Probe ◽  
Microclimatic Conditions

ABSTRACTWe investigated the influence of a four-year-old forest edge near Manaus, Brazil, on soil moisture and vertical profiles of air vapour pressure deficit (VPD) within the forest. Soil moisture was measured (with a neutron probe) 0, 5, 10, 20, 40, 60, 80, 100, 150 and 200 m into the forest from the edge, in undisturbed control areas, and in the pasture. Control soil moisture was better explained by rainfall in the previous 2 or 10 days than by longer-term totals. Soil water potentials ≤ – 1.5 MPa occurred at some forest locations during the driest period. The variation in soil moisture with distance from the forest edge was complex, with higher values just inside the edge and depleted zones at the edge and 40–80 m inside it. At a given height, VPD (standardized relative to measurements in the open) was not related to distance from the edge, but VPD increased more with height near the edge than in control areas. The complexity of the edge's influence and the contrast with earlier data from the same edge can be explained by the changing vegetation structure near the edge. Regrowth ‘seals’ the edge with more leaves that transpire and deplete soil moisture, while protecting the understorey just inside the edge from desiccating conditions. A mosaic of gaps of differing ages develops behind the edge, increasing the variation in microclimatic conditions near the ground and consequently in evapotranspiration and soil moisture.

Are leaf-litter frogs and lizards affected by edge effects due to forest fragmentation in Brazilian Atlantic forest?

2008 ◽  
Vol 24 (05) ◽  
pp. 551-554 ◽  
Author(s):  
Marianna Dixo ◽  
Marcio Martins
Keyword(s):  
Edge Effects ◽  
Vegetation Structure ◽  
Environmental Changes ◽  
Forest Edge ◽  
Habitat Types ◽  
Abiotic Conditions ◽  
Freshwater Habitats ◽  
Ecological Patterns ◽  
Predominant Factor ◽  
Landscape Level

Edge effects encompass biotic and abiotic changes resulting from the interaction between two different habitat types (Murcia 1995). Edge habitats are ecologically distinct from patch interiors, and understanding how ecological patterns change near edges is important in understanding landscape-level dynamics such as the impacts of fragmentation (Rieset al. 2004). Abiotic conditions at the forest edge, such as increased wind and solar radiation, increased fluctuations in temperature, and decreased humidity, may affect forest-adapted organisms (Harperet al. 2005, Murcia 1995). So, edges may affect lizards and amphibians due to their physiological needs (Lehtinenet al. 2003, Vallan 2000). Anurans are considered sensitive to environmental changes due to their permeable skin, shell-less eggs and use of land as well as freshwater habitats (Vallan 2000). Changes in vegetation structure and microclimate are likely to be the predominant factor affecting amphibian abundances across edges (Jellineket al. 2004, Marsh & Pearman 1997, Schaepfer & Gavin 2001, Urbina-Cardonaet al. 2006).

scholarly journals Computation of vapour pressure deficit and crop transpiration via development of a web based computer module

2021 ◽  
Vol 23 (4) ◽  
pp. 381-388
Author(s):  
MAHESH CHAND SINGH ◽  
J. P. SINGH ◽  
K. G. SINGH ◽  
O. P. GUPTA ◽  
G. KUMAR
Keyword(s):  
Vapour Pressure ◽  
Crop Yields ◽  
Production Systems ◽  
Vapour Pressure Deficit ◽  
Climatic Conditions ◽  
Effect Of Temperature ◽  
Plant Water ◽  
Web Based ◽  
Microclimatic Conditions ◽  
Cucumber Yield

The plant water or nutrient requirement under greenhouse conditions is mainly governed by crop transpiration in a linear relation to vapour pressure deficit (VPD), particularly in soilless production systems. Being a cooling process in plants, transpiration governs the plant water requirement in relation to the subjected microclimatic conditions and VPD can be used as a tool to maintain greenhouse crop transpiration to optimal range for obtaining desired crop yields. Thus, the present investigation was undertaken to study the integrated effect of temperature (Tapc), relative humidity (Eapc) and solar radiation (Irad) on VPD and crop transpiration. A computer module was developed to monitor the behavior of the VPD and thereby the crop transpiration through charts under greenhouse conditions. The VPD indicated a linear increasing trend with Tapc (R2≥0.84) and decreasing trend with Eapc (R2=0.99), demonstrating a strong correlation in both cases. The increasing crop transpiration with VPD, particularly under hot climatic conditions significantly increased the input water and nutrient requirements of the crop. Thus, transpiration in relation to VPD should be considered as a factor for fertigation scheduling and improving irrigation control in soilless systems. Moreover, maintaining Tapc, Eapc and VPD within range of 22-27°C, 60-80% and 0.53-1.10 kPa may help to control the crop transpiration, manage the greenhouse irrigation and fertigation, and thus improve the cucumber yield.

scholarly journals Patch size and vegetation structure drive changes to mixed-species flock diversity and composition across a gradient of fragment sizes in the Western Andes of Colombia

The Condor ◽  
2020 ◽  
Vol 122 (2) ◽  
Author(s):  
Harrison H Jones ◽  
Scott K Robinson
Keyword(s):  
Species Richness ◽  
Functional Diversity ◽  
Edge Effects ◽  
Vegetation Structure ◽  
Phylogenetic Diversity ◽  
Patch Size ◽  
Forest Edge ◽  
Mixed Species ◽  
Functional And Phylogenetic Diversity ◽  
Diversity Metrics

Abstract Forest fragmentation is a leading driver of biodiversity loss, yet its effects on positive species interactions remain poorly known. We examined the effects of fragmentation on mixed-species bird flocks in the Western Andes of Colombia. Using 500-m transect surveys (n = 14 transects), we sampled flocks in 8 fragments (range: 10–173 ha) and an unfragmented reference site within the same altitudinal band (1,900–2,200 m.a.s.l.) and matrix type (cattle pasture). We evaluated the relative contributions of 9 predictor variables, including patch size, distance from edge, and selective aspects of vegetation structure on the composition, size, species richness, functional diversity, and phylogenetic diversity of flocks. We found effects of both patch size and vegetation structure on flock species richness, size, and functional diversity, but no support for edge effects. Generally, flock richness and size responded differently to fragmentation than did functional and phylogenetic diversity metrics. Both flock size and richness increased with patch size, but this variable had no effect on functional and phylogenetic diversity. Flock richness and size increased in high-canopy forests with greater foliage height diversity, whereas unlogged, old-growth primary forests with large-diameter trees had lower flock richness and size, but significantly greater functional diversity. Phylogenetic diversity was not affected by patch size, edge effects, or vegetation structure. We found differences in flock composition in response to fragmentation. Richness of Furnariidae in flocks increased with increasing distance from edge and foliage height diversity, whereas that of Thraupidae and boreal migrant species increased in early successional and forest edge flocks, respectively. All flock diversity metrics differed significantly seasonally, with smaller, less diverse flocks observed in January–March than in June–August. Flocking behavior persisted in 10-ha fragments, likely because Andean flocks are “open membership” in nature, but there was extensive species turnover as forest edge and generalist species replaced forest-interior species in smaller fragments.

Seasonal Patterns in Soil Moisture, Vapour Pressure Deficit, Tree Canopy Cover and Pre-dawn Water Potential in a Northern Australian Savanna

1997 ◽  
Vol 45 (2) ◽  
pp. 211 ◽  
Author(s):  
G. A. Duff ◽  
B. A. Myers ◽  
R. J. Williams ◽  
D. Eamus ◽  
A. O'Grady ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Seasonal Variation ◽  
Water Potential ◽  
Vapour Pressure ◽  
Canopy Cover ◽  
Vapour Pressure Deficit ◽  
Dry Season ◽  
Tree Canopy ◽  
Wet Season ◽  
Tree Canopy Cover

The wet–dry tropics of northern Australia are characterised by extreme seasonal variation in rainfall and atmospheric vapour pressure deficit, although temperatures are relatively constant throughout the year.This seasonal variation is associated with marked changes in tree canopy cover, although the exact determinants of these changes are complex. This paper reports variation in microclimate (temperature, vapour pressure deficit (VPD)), rainfall, soil moisture, understorey light environment (total daily irradiance), and pre-dawn leaf water potential of eight dominant tree species in an area of savanna near Darwin, Northern Territory, Australia. Patterns of canopy cover are strongly influenced by both soil moisture and VPD. Increases in canopy cover coincide with decreases in VPD, and occur prior to increases in soil moisture that occur with the onset of wet season rains. Decreases in canopy cover coincide with decreases in soil moisture following the cessation of wet season rains and associated increases in VPD. Patterns of pre-dawn water potential vary significantly between species and between leaf phenological guilds. Pre-dawn water potential increases with decreasing VPD towards the end of the dry season prior to any increases in soil moisture. Decline in pre-dawn water potential coincides with both decreasing soil moisture and increasing VPD at the end of the dry season. This study emphasises the importance of the annual transition between the dry season and the wet season, a period of 1–2 months of relatively low VPD but little or no effective rainfall, preceded by a 4–6 month dry season of no rainfall and high VPD. This period is accompanied by markedly increased canopy cover, and significant increases in pre-dawn water potential, which are demonstrably independent of rainfall. This finding emphasises the importance of VPD as a determinant of physiological and phenological processes in Australian savannas.

scholarly journals Mechanisms linking plant productivity and water status for a temperate Eucalyptus forest flux site: analysis over wet and dry years with a simple model

2008 ◽  
Vol 35 (6) ◽  
pp. 493 ◽  
Author(s):  
David A. Pepper ◽  
Ross E. McMurtrie ◽  
Belinda E. Medlyn ◽  
Heather Keith ◽  
Derek Eamus
Keyword(s):  
Soil Moisture ◽  
Water Availability ◽  
Vapour Pressure ◽  
Water Status ◽  
Vapour Pressure Deficit ◽  
Co2 Flux ◽  
Lower Sensitivity ◽  
Forest Site ◽  
Eucalyptus Forest ◽  
Dry Conditions

A simple process-based model was applied to a tall Eucalyptus forest site over consecutive wet and dry years to examine the importance of different mechanisms linking productivity and water availability. Measured soil moisture, gas flux (CO2, H2O) and meteorological records for the site were used. Similar levels of simulated H2O flux in ‘wet’ and ‘dry’ years were achieved when water availability was not confined to the first 1.20 m of the soil profile, but was allowed to exceed it. Although the simulated effects of low soil and atmospheric water content on CO2 flux, presumably via reduction in stomatal aperture, also acted on transpiration, they were offset in the dry year by a higher vapour-pressure deficit. A sensitivity analysis identified the processes that were important in wet versus dry years, and on an intra-annual timeframe. Light-limited productivity dominated in both years, except for the driest period in the dry year. Vapour-pressure deficit affected productivity across more of each year than soil moisture, but both effects were larger in the dry year. The introduction of a reduced leaf area tended to decrease sensitivity in the dry year. Plant hydraulic architecture that increases plant available water, maximises productivity per unit water use and achieves lower sensitivity to low soil moisture levels should minimise production losses during dry conditions.

scholarly journals Atmospheric aridity and apparent soil moisture drought in European forest during heatwaves

2020 ◽  
Author(s):  
Ryan Teuling ◽  
Eva Lansu ◽  
Chiel van Heerwaarden ◽  
Annemiek Stegehuis
Keyword(s):  
Boundary Layer ◽  
Soil Moisture ◽  
Data Analysis ◽  
Vapour Pressure ◽  
Vapour Pressure Deficit ◽  
Sensible Heat ◽  
Large Database ◽  
Significant Temperature ◽  
European Forest ◽  
Soil Dryness

<p>Land-atmosphere feedbacks, in particular the response of land evaporation to vapour pressure deficit (VPD) or the dryness of the air, remain poorly understood. Here we investigate the VPD response by analysis of a large database of eddy-covariance flux observations and simulations using a conceptual model of the atmospheric boundary layer. Data analysis reveals that under high VPD, forest in particular reduces evaporation and emits more sensible heat. In contrast, grass increases evaporation and emits less sensible heat. Simulations show that this VPD feedback can induce significant temperature increases over forest of up to 2 K during heat wave conditions. It is inferred from the simulations that the effect of the VPD feedback corresponds to an apparent soil moisture depletion of more than 50%. This suggests that previous studies may have incorrectly attributed the effects of atmospheric aridity on temperature to soil dryness.</p>

Soil Moisture Deficits in South-Central Sweden

1989 ◽  
Vol 20 (2) ◽  
pp. 109-122 ◽  
Author(s):  
Lotta Andersson
Keyword(s):  
Soil Moisture ◽  
Field Capacity ◽  
Interannual Variations ◽  
Neutron Probe ◽  
South Central ◽  
Normal Ranges ◽  
Moisture Fluxes ◽  
In The Beginning ◽  
Probe Measurements ◽  
Different Parts

Some commonly used assumptions about climatically induced soil moisture fluxes within years and between different parts of a region were challenged with the help of a conceptual soil moisture model. The model was optimised against neutron probe measurements from forest and grassland sites. Five 10 yrs and one 105 yrs long climatic records, from the province of Östergötland, situated in south-central Sweden, were used as driving variables. It was concluded that some of the tested assumptions should not be taken for granted. Among these were the beliefs that interannual variations of soil moisture contents can be neglected in the beginning of the hydrological year and that soils usually are filled up to field capacity after the autumn recharge. The calculated climatic induced dryness was estimated to be rather insensitive to the choice of climatic stations within the region. Monthly ranges of soil moisture deficits (1883-1987) were shown to be skewed and it is therefore recommended to use medians and standard deviations in statistical analyses of “normal” ranges of soil moisture deficits.

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