scholarly journals Structural complexity governs seagrass acclimatization to depth with relevant consequences for meadow production, macrophyte diversity and habitat carbon storage capacity

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Susana Enríquez ◽  
Irene Olivé ◽  
Napo Cayabyab ◽  
John D. Hedley
Keyword(s):  
Carbon Storage ◽  
Light Attenuation ◽  
Structural Complexity ◽  
Shoot Density ◽  
Light Limitation ◽  
Initial Increase ◽  
Area Index ◽  
Leaf Physiology ◽  
Canopy Opening ◽  
Shoot Size

Abstract Analyses of the integrated seagrass response to depth support the previously documented low plasticity and consistent shade-adapted leaf physiology of a habitat-builder that dominates well-illuminated reef environments. Two structural responses, “canopy-opening” and “below-ground-mass-depletion”, govern the photoacclimatory response and facilitate, respectively, light penetration within the canopy and functional adjustments in whole-plant carbon balances. Conversely, “canopy-closing” may also explain dense canopies formed close to the waterline, as they provide shade and photoprotection to a susceptible leaf physiology under high-light. Canopy light attenuation is primarily regulated by the leaf area index (LAI), which is governed by changes in shoot size and density. Shoot density diminishes non-linearly with depth, while shoot size increases to a maximum followed by a decline. The initial increase in shoot size, which resembles a self-thinning response, increases LAI and meadow production in shallow depths. These seagrass structural adjustments have relevant ecological implications. Canopy-thinning allows macrophyte diversity to increase with depth, while seagrass production and carbon storage diminish exponentially, and are maximal only in a shallow coastal fringe. The results support the universality of plant self-thinning, from phytoplankton to complex canopies, likely the consequence of simple physical laws related to light limitation and pigment self-shading within photosynthetic structures and communities.

scholarly journals The growing season greenhouse gas balance of a continental tundra site in the Indigirka lowlands, NE Siberia

2007 ◽  
Vol 4 (6) ◽  
pp. 985-1003 ◽  
Author(s):  
M. K. van der Molen ◽  
J. van Huissteden ◽  
F. J. W. Parmentier ◽  
A. M. R. Petrescu ◽  
A. J. Dolman ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Soil Temperature ◽  
Greenhouse Gas ◽  
Growing Season ◽  
Light Limitation ◽  
Greenhouse Gas Balance ◽  
Area Index ◽  
North East ◽  
Methane Fluxes ◽  
Gas Balance

Abstract. Carbon dioxide and methane fluxes were measured at a tundra site near Chokurdakh, in the lowlands of the Indigirka river in north-east Siberia. This site is one of the few stations on Russian tundra and it is different from most other tundra flux stations in its continentality. A suite of methods was applied to determine the fluxes of NEE, GPP, Reco and methane, including eddy covariance, chambers and leaf cuvettes. Net carbon dioxide fluxes were high compared with other tundra sites, with NEE=−92 g C m−2 yr−1, which is composed of an Reco=+141 g C m−2 yr−1 and GPP=−232 g C m−2 yr−1. This large carbon dioxide sink may be explained by the continental climate, that is reflected in low winter soil temperatures (−14°C), reducing the respiration rates, and short, relatively warm summers, stimulating high photosynthesis rates. Interannual variability in GPP was dominated by the frequency of light limitation (Rg<200 W m−2), whereas Reco depends most directly on soil temperature and time in the growing season, which serves as a proxy of the combined effects of active layer depth, leaf area index, soil moisture and substrate availability. The methane flux, in units of global warming potential, was +28 g C-CO2e m−2 yr−1, so that the greenhouse gas balance was −64 g C-CO2e m−2 yr−1. Methane fluxes depended only slightly on soil temperature and were highly sensitive to hydrological conditions and vegetation composition.

scholarly journals Silvicultural Discipline to Maintain Acadian Forest Resilience

2007 ◽  
Vol 24 (2) ◽  
pp. 91-97 ◽  
Author(s):  
Peter Salonius
Keyword(s):  
Structural Complexity ◽  
Energy Availability ◽  
Management Options ◽  
Canopy Opening ◽  
Forest Resilience ◽  
Clearcut Harvesting ◽  
Harvest Intervals ◽  
Forest Openings ◽  
Forest Floor Vegetation ◽  
Forest Rotation

Abstract Clearcut harvesting decreases structural complexity, eliminates old and genetically superior legacy trees, extirpates mature-forest floor vegetation, and creates hot and dry postharvest microclimates. The short-lived, exposure-tolerant, boreal tree species that regenerate in large forest openings are believed to be less able, than the late-successional Acadian species they replace, to adapt to the climate warming expected during the next forest rotation. A strip silviculture design is presented that includes limited canopy opening, “no-traffic” areas, maintenance of “full-cycle” survivors, and programmed return harvest intervals that approximate natural gap disturbance as a means of arresting the further increase of boreal species and restoring Acadian species on the landscape. Within the confines of this silvicultural discipline, two management options are described to accommodate extremes of future energy availability.

Analysing species-specific light transmission and related crown characteristics of Pinus sylvestris and Betula pendula using a shoot-level 3D model

2013 ◽  
Vol 43 (10) ◽  
pp. 929-938 ◽  
Author(s):  
Anna Lintunen ◽  
Pekka Kaitaniemi ◽  
Jari Perttunen ◽  
Risto Sievänen
Keyword(s):  
Pinus Sylvestris ◽  
Boreal Forests ◽  
Betula Pendula ◽  
Light Transmission ◽  
Light Attenuation ◽  
Mixed Forest ◽  
Ray Casting ◽  
Area Index ◽  
Crown Characteristics ◽  
Species Specific

This is a first attempt to analyse species-specific light attenuation in mixed boreal forests created by shoot-level 3D tree models. The models are configurations of real individual Scots pine (Pinus sylvestris L.) and silver birch (Betula pendula Roth.) trees grown in mixed-forest stands. We study species-specific differences in radiation transmission by using the ray-casting method. Light transmission was found to be higher in dense birch-dominated stands compared with dense pine-dominated stands because of the higher total foliage area and the higher location of foliage in the pine canopy. Transmission of light per leaf area index (LAI) was nevertheless higher in the pine canopy compared with the birch canopy because of foliage clumping. Especially in clumped canopy, species-specific shoot-level light simulations enable a more realistic estimation of light transmission compared with simpler calculations based on LAI and Beer–Lambert’s law. The observed differences in light-transmission characteristics of the studied species may influence the development of target crowns in the neighbourhood. Light attenuation caused by the dense foliage zone in the upper pine canopy could be avoided in dense stands by mixing species with different vertical foliage distributions.

Photosynthesis and respiration decline with light intensity in dominant and suppressed Eucalyptus globulus canopies

2008 ◽  
Vol 35 (6) ◽  
pp. 439 ◽  
Author(s):  
A. P. O'Grady ◽  
D. Worledge ◽  
A. Wilkinson ◽  
M. Battaglia
Keyword(s):  
Eucalyptus Globulus ◽  
Dark Respiration ◽  
Light Availability ◽  
Structural Complexity ◽  
Leaf Nitrogen ◽  
Leaf Nitrogen Content ◽  
Area Index ◽  
Respiration Rates ◽  
Leaf Dark Respiration ◽  
Photosynthesis And Respiration

Within canopy gradients in light-saturated photosynthesis (Amax), foliar nitrogen ([N]area) and leaf dark respiration (R15) were studied in the canopies of dominant and suppressed trees within an even-aged (4-year-old) Eucalyptus globulus (Labill) stand in southern Tasmania. Despite being an even-aged stand growing in a relatively uniform environment with respect to nutrient and water availability, the stand exhibited considerable structural complexity. Diameter at 1.3 m ranged between 3 cm and 21 cm, trees average 12 m height and stand leaf area index was ~6 m2 m–2 leading to strong gradients in light availability. We were interested in understanding the processes governing canopy production in trees of contrasting dominance classes. Vertical gradients in photosynthesis and foliar respiration were studied within the canopies of dominant and suppressed trees during 2006 and 2007. Amax varied from ~18 μmol m–2 s–1 in the upper canopy to 3 μmol m–2 s–1 at lower canopy positions. On average, Amax were higher in the dominant trees than in the suppressed trees. However, at any given height, Amax were similar in suppressed and dominant trees and were strongly related to leaf nitrogen content. Dark respiration varied from ~1.4 μmol m–2 s–1 in the upper canopy to 0.2 μmol m–2 s–1 in the lower canopy positions. In contrast to the patterns for Amax, dark respiration rates in the suppressed trees were higher than dominant trees at similar canopy positions. Respiration rates were also strongly related to [N]area and to Amax.

scholarly journals Inter-annual chemical stratification in Brazilian natural lakes: meromixis and hypolimnetic memory

2012 ◽  
Vol 24 (2) ◽  
pp. 127-139 ◽  
Author(s):  
Luciana Gomes Barbosa ◽  
Francisco Antonio Rodrigues Barbosa ◽  
Carlos Eduardo de Mattos Bicudo
Keyword(s):  
Electrical Conductivity ◽  
Light Attenuation ◽  
Total Dissolved Solids ◽  
Light Limitation ◽  
Low Light ◽  
Dissolved Solids ◽  
Attenuation Coefficients ◽  
Natural Lakes ◽  
Chemical Stratification ◽  
High Chemical Stability

AIM: chemical stratification and the patterns of light limitation and nutrients of two natural lakes, one shallow and the other one deep, were comparatively evaluated, both lakes located in the southeast Brazil. METHODS: pH, electrical conductivity, dissolved oxygen, total dissolved solids and nutrients were monthly collected during 5 consecutive years at the vertical profile of the two lakes. RESULTS: multivariate analysis indicated that the long thermal stratification period favored the occurrence of chemical stratification in the two lakes. However, in the deeper lake the stratified thermal profile with high hypolimnetic nutrient concentration, electrical conductivity, total dissolved solids and redox potential indicated that the mixing was not complete even during the annual circulation period, suggesting a slight meromixis and a high chemical stability at the hypolimnion. In the shallower lake, high light attenuation and high availability of nitrogen forms (mainly N-NH4) and phosphorus was observed along the water column, even during stratification. In the deeper lake, N and P co-limitation and low light attenuation coefficients were detected. CONCLUSION: thermal and chemical stratification patterns indicated that the Carioca lake is a shallow, turbid, nutrient rich, whereas the Dom Helvecio lake is a deep, clear, oligotrophic system with a tendency towards meromixis and the isolation of solutes in the hypolimnion. Consequently, meromixis was compared to a "hypolimnetic memory", which was defined, in the case of the deeper lake, as the maintenance of the chemical stratification along the years, during the lake thermal circulation period.

An approach to modelling the effect of environmental and physiological factors upon biomass accumulation in winter wheat

2001 ◽  
Vol 136 (4) ◽  
pp. 369-381 ◽  
Author(s):  
A. G. GILLETT ◽  
N. M. J. CROUT ◽  
D. T. STOKES ◽  
R. SYLVESTER-BRADLEY ◽  
R. K. SCOTT
Keyword(s):  
Winter Wheat ◽  
Dry Matter ◽  
Nitrogen Availability ◽  
Light Attenuation ◽  
Biomass Accumulation ◽  
Management Decision ◽  
Physiological Factors ◽  
Area Index ◽  
Detailed Model ◽  
Radiation Conversion

Six sites of variable soil type and environments in England and Scotland were sown with winter wheat (Triticum aestivum L. cv. Mercia) in the autumns of 1992 and 1993 with optimum inputs for growth. Crop monitoring between February and grain maturity provided data to investigate environmental and physiological factors important in controlling biomass accumulation.With increasing use of crop modelling as a tool for interpreting experiments and as crop management decision support systems, it is important that all influences on crop productivity are understood. The ‘radiation use efficiency’ or radiation conversion coefficient provides a convenient basis to study these influences.Significant differences in seasonal radiation conversion coefficients were observed between sites (P < 0·001), ranging from 2·82 to 3·87 g total dry matter/MJ absorbed photosynthetically active radiation. A series of simple dry matter models were developed to help explain biomass accumulation in relation to a number of environmental variables (using the measured green area index as an input) with correlation coefficients [ges ] 0·98 obtained across all sites. Apart from sunlight, differences in the canopy's ability to accumulate nitrogen and maintenance respiration costs were the most significant factors (P < 0·001). The nitrogen effect suggests changes in the conversion of assimilates with nitrogen availability, despite relatively high nutrition levels ([ges ] 180 kg N/ha).Over all sites the canopy extinction coefficient could be described as a linear function of the site spring time plant population (P < 0·01). A more detailed model considered canopy light attenuation to vary between sites according to sowing date and autumn/winter plant establishment and environment.

RESPONSES OF EUCALYPTUS CAMALDULENSIS SPROUTS TO SHADE: AN EVALUATION OF CANOPY PLASTICITY

2015 ◽  
Vol 52 (3) ◽  
pp. 346-358 ◽  
Author(s):  
CIRO ABBUD RIGHI ◽  
VINCENT COUDERC ◽  
CARLOS RODRIGUES PEREIRA ◽  
HILTON THADEU ZARATE COUTO
Keyword(s):  
Food Production ◽  
Production Systems ◽  
Eucalyptus Camaldulensis ◽  
Agroforestry Systems ◽  
Solar Irradiation ◽  
Cellulose Production ◽  
Area Index ◽  
Canopy Opening ◽  
Canopy Volume ◽  
Leaf Density

SUMMARYEucalyptus spp. is the main tree used in cellulose production worldwide, cultivated mostly in extensive monocrop plantations. However, due to concerns on environmental impacts, fear on decrease of food production related to the size of cultivated area, its location near human settlements with few jobs generation, eucalypt cultivation is no longer encouraged in many places. At the same time, large plantations hold the opportunity to integrate eucalypt into agroforestry systems (AFS) in a variety of production systems with many social, economical and environmental advantages. In this study we studied canopy modifications of E. camaldulensis sprouts under different degrees of shade. The plants were located on a gradient of available solar irradiation ranging from 51 to 94%. E. camaldulensis showed canopy plasticity with modified radiation interception patterns under diverse irradiations. Most of these variations were of small amplitude with some important variables remaining almost unchanged (leaf density, canopy percentage, tree, trunk and canopy height) or increasing only slightly (leaf area index and canopy opening). The main changes presented by E. camaldulensis, with a steep increase towards full sun, were: foliage area, canopy surface, canopy volume and area of canopy projection. In order to design appropriate agroforestry systems with young eucalypt growing under the shade of other crops, it is necessary to determine at which point the observed variable changes can support reasonable production.

scholarly journals Carbon Storage of some Rubber Trees (Hevea brasiliensis) Clones in HEVECAM’s Plantations in South Cameroon

2021 ◽  
Author(s):  
Menoh A Ngon René ◽  
Tsoata Esaïe ◽  
Tsouga Manga Milie Lionelle ◽  
Owona Ndongo Pierre-André
Keyword(s):  
Leaf Area Index ◽  
Leaf Area ◽  
Carbon Storage ◽  
Rubber Tree ◽  
Tree Height ◽  
Allometric Equation ◽  
Morphological Parameters ◽  
Area Index ◽  
Significant Difference ◽  
Total Tree

The objective of this work was to estimate the quantity of carbon stored by four main clones of rubber tree cultivated in South Cameroon: GT 1, PB 217, PR 107 and RRIC 100. The forest inventory method was used to measure trees morphological parameters, the latter used to calculate carbon storage using the allometric equation of Wauters et al., (2008). The main morphological parameters measured were: leaf area index (LAI), circumference (C), diameter at breast height (DBH) and total tree height (h). Comparing the morphological parameters of clones two by two using a Dunn test, we observe significant differences in the circumference, the diameter and even very significant in the leaf area index, but not in the height. The clones GT 1, PR 107, PB 217, and RRIC 100 stored on average: 111.05 tC / ha, 150.18 tC / ha, 165.25 tC / ha, and 187.25 tC/ha respectively. A significant difference was established between the means of carbon storage of the clones GT 1 and PB 217 (p = 0.0488) on one hand and, that of the clones GT 1 and RRIC 100 (p = 0.0240), on the other hand. These results are an estimation of models, further research can be undertaken for exact measurements.

Phytoplankton biomass, light attenuation and mixing in the Shannon Estuary, Ireland

1992 ◽  
Vol 72 (3) ◽  
pp. 709-720 ◽  
Author(s):  
T. G. McMahon ◽  
R. C. T. Raine ◽  
T. Fast ◽  
L. Kies ◽  
J. W. Patching
Keyword(s):  
Suspended Matter ◽  
River Discharge ◽  
Phytoplankton Biomass ◽  
Light Attenuation ◽  
Phytoplankton Growth ◽  
Light Limitation ◽  
Underwater Irradiance ◽  
Highly Correlated ◽  
Dominant Influence

Distributions of suspended matter, light attenuation and chlorophyll a were measured in the Shannon Estuary over the period 1988–1990. Light attenuation was found to be highly correlated with levels of suspended matter, and the availability of underwater irradiance was found to be the dominant influence on phytoplankton biomass and chlorophyll levels over most of the estuary. Though levels of suspended matter, and hence light attenuation, were highest in the upper estuary, depths of mixing were relatively shallow resulting in less light limitation of phytoplankton growth than elsewhere. Turbidity maxima in the upper estuary were associated with chlorophyll maxima, the magnitude of which appeared to be related to river discharge.

Variations in Posidonia oceanica meadow structure along the coast of the Dugi Otok Island (eastern Adriatic Sea)

2008 ◽  
Vol 88 (5) ◽  
pp. 883-892 ◽  
Author(s):  
Petar Kru΂ić
Keyword(s):  
Adriatic Sea ◽  
Structural Characteristics ◽  
Outer Part ◽  
Posidonia Oceanica ◽  
Shoot Density ◽  
The Other ◽  
Impact Factors ◽  
Index Number ◽  
Area Index ◽  
The Status

Although the anthropogenic impact on Posidonia oceanica meadows in the Mediterranean Sea has been studied over the last few decades, the data about the status of this endemic magnoliophyte are scarcer from the Adriatic Sea. Samples of P. oceanica meadows were collected in June and July 2004 using SCUBA diving at 8 sites in the area of the Dugi Otok Island, all at depths of 10 m. The meadow's shoot density was measured, and shoots were collected to be examined and compared through number of leaves per shoot, leaf surface per shoot, leaf area index, number and biomass of taxa of epiphytic flora. Significant differences in P. oceanica meadow structure were found among investigated sites, especially between sites in the vicinity of the fish farm and the other sites. Meadow density decreased at sites in the Dugi Otok channel and the main impact factors seem to be the input of organic matter, originating from the fish cages and sewage input. These human activities are a source of nutrient pollution and stimulate blooms of phytoplankton and higher algae. The sea grass meadow vitality seems to be more negatively affected in the channel. The highest values of shoot density were recorded at investigated sites VR and ME at the outer part of the Dugi Otok Island. The shoot density was very low at site FU, situated in the channel. Biomass of the epiphytic algae exhibited the highest values at the site FU, while at the other investigated sites the values were significantly lower. Concerning the epiphytic macroflora, a total of 55 taxa of epiphytic macroalgae were identified and the class Rhodophyta dominated in all samples. The present study shows the high differences in morphological and structural characteristics of Posidonia oceanica meadows among various sites with and without anthropogenic influence.

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