Overstory mortality and canopy disturbances in longleaf pine ecosystems

1996 ◽  
Vol 26 (11) ◽  
pp. 2035-2047 ◽  
Author(s):  
Brian J. Palik ◽  
Neil Pederson
Keyword(s):  
Natural Regeneration ◽  
Redundancy Analysis ◽  
Structural Characteristics ◽  
Longleaf Pine ◽  
Canopy Structure ◽  
Structural Complexity ◽  
Mortality Rates ◽  
Small Scale ◽  
Site Conditions ◽  
Second Growth

We studied longleaf pine (Pinuspalustris Mill.) ecosystems to determine causes and rates of overstory mortality, size of canopy disturbances, and the effects of disturbance on canopy structure. Further, we used redundancy analysis to relate variation in characteristics of mortality across a landscape to site and stand variables. We analyzed mortality that occurred from 1990 to 1994 in 70 second-growth plots that spanned a range of site conditions and stand structures, and in five large disturbances that occurred outside the random sample of plots. Half of pine mortality over 5 years in the 70 plots was from unknown causes. Lightning was the primary identifiable cause of mortality, followed by suppression and wind. Lightning mortality was most frequent on xeric sites, while windthrow was common on wet–mesic sites. Suppression mortality was frequent on wet–mesic sites and in higher density stands. Five-year mortality rates averaged 2.3 trees/ha, or 1.9% of original density. Most mortality consisted of single trees. Large disturbances (mostly from lightning) of 15–30 trees were rare, occurring once per 1000 ha in 5 years. Variation in amount of mortality and size of disturbance were unrelated to soil or stand structural characteristics. Low mortality rates from small-scale disturbances result in slow canopy turnover. These results indicate that large openings sufficient for natural regeneration of longleaf pine develop slowly in the absence of hurricanes. Silvicultural options for longleaf pine can be designed to mimic the canopy structure that results from natural canopy disturbances, which leave many live trees standing. Such options may be desirable if a goal of silviculture is to increase structural complexity in stands managed for timber.

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 Mass and Heat Transfer at Different Heat Exchange Surfaces and Their Suitability for Use in Thermal Desalination Plants

2016 ◽  
Vol 10 (1) ◽  
pp. 74-86 ◽  
Author(s):  
T. Schwarzer ◽  
H.J. Bart
Keyword(s):  
Heat Transfer ◽  
Salt Water ◽  
Structural Characteristics ◽  
Small Scale ◽  
User Friendliness ◽  
Multi Stage ◽  
Water Side ◽  
Thermal Desalination ◽  
Actual Use ◽  
Desalination Plants

A new concept for small scale multi-stage distillation (MSD) desalination plants is presented allowing an installation in remote rural areal due to low maintenance, operating and investment costs. It is based on extensive studies on heat and mass transfer using 6 different condensation / heat transfer surfaces or material combinations. Basically all 6 condensation surfaces except glass are of a sheet metal or an expanded metal (to the evaporation side) in combination to an acid- and heat-resistant foil (on the salt water side). The basic experiments were performed in a "lab scale" unit to determine their thermodynamic and structural characteristics and user-friendliness. After validation in a prototype novel oxidic condensation surfaces (AF) and material combinations are in actual use in the new MSD systems, following the requirements, including a good wetting and condensation behavior and a good heat transfer.

scholarly journals Zooplankton in seagrass and adjacent non-seagrass habitats in Tun Mustapha Park, Sabah, Malaysia

2020 ◽  
Vol 4 (1) ◽  
pp. 6-13
Author(s):  
Sing Lui Lo ◽  
Tzuen Kiat Yap ◽  
Cheng Ann Chen ◽  
Teruaki Yoshida
Keyword(s):  
Environmental Variables ◽  
Statistical Difference ◽  
Structural Complexity ◽  
Zooplankton Community ◽  
Small Scale ◽  
Zooplankton Abundance ◽  
Seagrass Bed ◽  
Seagrass Meadows ◽  
Marine Park ◽  
Study Sites

A comparison of zooplankton abundance and community in the seagrass and non-seagrass areas of Limau-limauan and Bak- Bak waters within the newly established Tun Mustapha Marine Park was made during 15-17 May 2017. Samples were collected via horizontal tow of a 140 μm plankton net. Environmental variables (temperature, salinity, DO, pH, turbidity) showed no significant differences among the study sites. However, zooplankton showed increasing abundance from non-seagrass, seagrass edge, to seagrass areas at Limau-limauan, while abundance values were comparable among the stations at Bak-bak. Overall zooplankton abundance was significantly higher at the seagrass areas relative to the non-seagrass station at Limau-limauan (p < 0.005), while no statistical difference was found at Bak-Bak (p < 0.21). Mean canopy height was 3-fold higher (p < 0.001) at Limau-limauan than Bak-Bak, suggesting the importance of seagrass bed structural complexity in habitat preference for zooplankton. Cluster analysis revealed the zooplankton community from the seagrass area at Limau-limauan was different from that at seagrass edge and non-seagrass areas, which may be attributed to the influence of seagrass meadows in forming characteristic zooplankton compositions. Marked differences in zooplankton composition and abundance even in close vicinity of sites suggest the importance of local small-scale variations in seagrass habitats in shaping the zooplankton community.

The effect of spatially variable overstory on the understory light environment of an open-canopied longleaf pine forest

2002 ◽  
Vol 32 (11) ◽  
pp. 1984-1991 ◽  
Author(s):  
Michael A Battaglia ◽  
Pu Mou ◽  
Brian Palik ◽  
Robert J Mitchell
Keyword(s):  
Spatial Variation ◽  
Spatial Patterns ◽  
Longleaf Pine ◽  
Light Availability ◽  
Canopy Structure ◽  
Basal Area ◽  
Pinus Palustris ◽  
Pine Forest ◽  
Large Group ◽  
The Relationship

Spatial aggregation of forest structure strongly regulates understory light and its spatial variation in longleaf pine (Pinus palustris Mill.) forest ecosystems. Previous studies have demonstrated that light availability strongly influences longleaf pine seedling growth. In this study, the relationship between spatial structure of a longleaf pine forest and spatial pattern of understory light availability were investigated by comparing three retention harvest treatments: single-tree, small-group, large-group, and an uncut control. The harvests retained similar residual basal area but the spatial patterns of the residual trees differed. Hemispherical photographs were taken at 300 stations to calculate gap light index (GLI), an estimate of understory light availability. Stand-level mean, variation, and spatial distribution of GLI were determined for each treatment. By aggregating residual trees, stand mean GLI increased by 20%, as well as its spatial variation. Spatial autocorrelation of GLI increased as the size of the canopy gaps increased and the gaps were better defined; thus, the predictability of GLI was enhanced. The ranges of detrended semivariograms were increased from the control to the large-group harvest indicating the spatial patterns of understory GLI became coarser textured. Our results demonstrated that aggregated canopy structure of longleaf pine forest will facilitate longleaf pine seedling regeneration.

scholarly journals Small-Scale variability of physical properties and structural characteristics of Antarctic fast ice

1994 ◽  
Vol 20 ◽  
pp. 61-66 ◽  
Author(s):  
A.L. Veazey ◽  
M.O. Jeffries ◽  
K. Morris
Keyword(s):  
Physical Properties ◽  
Structural Characteristics ◽  
Austral Summer ◽  
Ice Cores ◽  
Thin Layers ◽  
Small Scale ◽  
Axis Orientation ◽  
Layer Spacing ◽  
Frazil Ice ◽  
Fast Ice

The small-scale variability of physical properties and structural characteristics of multiple pairs of fast-ice cores obtained during the austral summer of 1991-92 at two Antarctic sites, McMurdo Sound (MCM) and Pine Island Bay (PIB), are examined and discussed with respect to the growth and decay of the sea ice. The ice at the MCM site was thicker than that at the PIB site and was covered by a somewhat thinner snowpack. While mean salinity and temperature of the ice at the two sites were similar, small-scale variations in both salinity and temperature were greater at PIB than at MCM. The ice sheet at MCM was a two-layer medium consisting of congelation ice overlying platelet ice. The ice from the PIB site, however, was composed of mainly frazil ice and layers of congelation ice with occasional thin layers of snow-ice at the surface of the cores. Crystal sub-structure measurements, c-axis orientation and brine-layer spacing from the MCM cores revealed that the congelation ice had moderately aligned, horizontally oriented c axes, suggesting that east-west currents off the southwest tip of Hut Point Peninsula control crystal-growth orientation.d others: Variability of physical and structural characteristics of Antarctic fast ice

scholarly journals Hierarchical System Decomposition Using Genetic Algorithm for Future Sustainable Computing

2020 ◽  
Vol 12 (6) ◽  
pp. 2177
Author(s):  
Jun-Ho Huh ◽  
Jimin Hwa ◽  
Yeong-Seok Seo
Keyword(s):  
Genetic Algorithm ◽  
Software Architecture ◽  
Large Scale ◽  
Structural Characteristics ◽  
Optimal Solution ◽  
Hill Climbing ◽  
Software Systems ◽  
Small Scale ◽  
Hill Climbing Algorithm ◽  
Architecture Management

A Hierarchical Subsystem Decomposition (HSD) is of great help in understanding large-scale software systems from the software architecture level. However, due to the lack of software architecture management, HSD documentations are often outdated, or they disappear in the course of repeated changes of a software system. Thus, in this paper, we propose a new approach for recovering HSD according to the intended design criteria based on a genetic algorithm to find an optimal solution. Experiments are performed to evaluate the proposed approach using two open source software systems with the 14 fitness functions of the genetic algorithm (GA). The HSDs recovered by our approach have different structural characteristics according to objectives. In the analysis on our GA operators, crossover contributes to a relatively large improvement in the early phase of a search. Mutation renders small-scale improvement in the whole search. Our GA is compared with a Hill-Climbing algorithm (HC) implemented by our GA operators. Although it is still in the primitive stage, our GA leads to higher-quality HSDs than HC. The experimental results indicate that the proposed approach delivers better performance than the existing approach.

scholarly journals Accessing the diffracted wavefield by coherent subtraction

2017 ◽  
Vol 211 (1) ◽  
pp. 45-49 ◽  
Author(s):  
Benjamin Schwarz ◽  
Dirk Gajewski
Keyword(s):  
Field Data ◽  
Single Channel ◽  
Structural Complexity ◽  
Aegean Sea ◽  
Data Driven ◽  
Small Scale ◽  
Additional Filter ◽  
Directional Filter ◽  
Scattering Geometry ◽  
Summation Operator

Abstract Diffractions have unique properties which are still rarely exploited in common practice. Aside from containing subwavelength information on the scattering geometry or indicating small-scale structural complexity, they provide superior illumination compared to reflections. While diffraction occurs arguably on all scales and in most realistic media, the respective signatures typically have low amplitudes and are likely to be masked by more prominent wavefield components. It has been widely observed that automated stacking acts as a directional filter favouring the most coherent arrivals. In contrast to other works, which commonly aim at steering the summation operator towards fainter contributions, we utilize this directional selection to coherently approximate the most dominant arrivals and subtract them from the data. Supported by additional filter functions which can be derived from wave front attributes gained during the stacking procedure, this strategy allows for a fully data-driven recovery of faint diffractions and makes them accessible for further processing. A complex single-channel field data example recorded in the Aegean sea near Santorini illustrates that the diffracted background wavefield is surprisingly rich and despite the absence of a high channel count can still be detected and characterized, suggesting a variety of applications in industry and academia.

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