Improvement In Light Conditions Research Articles

Norway spruce sapling plasticity in their responses of architecture and growth to light gradient decreases with altitude in subalpine stands

In their natural environments, trees are able to act adaptively by changing their morphology, functional traits and growth while facing different factors and stimuli. Yet, there is insufficient information on how intraspecific growth and architectural properties vary along elevation gradients, especially for young saplings of tree species regarded as highly important in forestry. We measured the height, diameter, crown growth and several architectural properties of Norway spruce (Picea abies (L.) H. Karst.) saplings along the light gradient in three elevational transects encompassing natural distributions of subalpine spruce forest in two different locations over a 3-year span. We employed generalized linear and mixed models to determine intraspecific differences in spruce architecture and growth responses to light at different elevations. Light was a better predictor of sapling growth compared to architecture properties. At higher altitudes, we observed limited abilities in the spruce saplings to change their crown architecture and enhance their height, crown length and crown width growth with the improvement in light conditions. However, the response of diameter growth to light was well pronounced in all elevational transects. Our results suggested that spruce sapling plasticity in shaping their crown morphology and growth decreased with altitude. Yet, we reported a similar improvement in diameter growth with an improvement in light conditions regardless of altitude. These results raised the question, to what extent do current climatic conditions at upper elevations inhibit Norway spruce diameter growth. We recommend that forest managers increase their efforts to obtain a desirable stem quality and crown shape by regulating light conditions mainly in the middle and lower parts of subalpine forests rather than at the elevational limit of this species.

Modeling seagrass bed dynamics under environmental impacts of intensive mariculture activities in Bolinao and Anda, the Philippines

This study assessed the estuarine-scale dynamics of mixed seagrass beds in Bolinao and Anda coastal areas in the Philippines, where seagrass beds have declined primarily due to eutrophication-induced degradation of light environment caused by unregulated mariculture activities in the adjacent areas. A seagrass model, driven by a coupled hydrodynamic-biogeochemical model, was developed and applied to the two-dominant species in the area – Thalassia hemprichii and Enhalus acoroides, and validated using observed spatial seagrass shoot density. The results showed the degradation of light environment in the seagrass beds, especially near mariculture areas, due to advective fluxes of water with high phytoplankton biomass and high nutrients from fish farms. The seagrass model driven by the reproduced water quality showed high reproducibility of seagrass above-ground biomass distribution of the two co-existing species, with R2 values of 0.78 and 0.60 for T. hemprichii and E. acoroides, respectively. Scenario analysis was conducted to examine the effectiveness of individual- and inter-municipality mariculture management (e.g., regulating fish feed input) in improving the light environment and facilitating the recovery of seagrasses. Results showed that the light environment could be significantly enhanced by an inter-municipality scheme compared to individual efforts of Bolinao and Anda municipalities, since their waters are interconnected through hydrodynamics. In conjunction with the improvement of light conditions, the recovery in seagrass abundance is most significant under the cooperative management scheme, thus highlighting its effectiveness.

Mixing effect on stand yield of Pinus tabulaeformis and Quercus liaotungensis is modulated by site quality and stand density in the Loess Plateau, China

ABSTRACT Interactions between plants are complicated: they can change resource availability, the proportion of resources acquired and the efficiency of resource use. This can eventually lead to changes in stand yield, but the driving mechanisms remain controversial. This study aimed to clarify the effects of mixing on stand yield. We established 120 mixed and pure plots of Chinese pine (Pinus tabulaeformis) and Liaodong oak (Quercus liaotungensis) in the Loess Plateau, China. Based on the inventory data in 2009 and 2016, we compared the differences in yields between mixed and pure stands. Our results indicated that the mixing of pine and oak resulted in over-yielding, but there was no transgressive over-yielding and pure pine stands consistently produced the highest yields. The over-yielding was due to facilitation between pine and oak, especially the improvement of light conditions in the understory, and an increase in the light use-efficiency of young pine and the availability of light to young oak. Mixing did not reduce competition: pine was dominant in interspecific competition and inhibited the growth of oak. The mixing effect was affected by site quality and stand density: improvements in site quality reduced over-yielding, while increases in stand density increased over-yielding.

One‐Dimensional Turbulence‐Ecosystem Model Reveals the Triggers of the Spring Bloom in Mesoscale Eddies

AbstractA lower trophic ecosystem model coupled with a one‐dimensional physical turbulence closure model was applied to study phytoplankton dynamics and spring bloom initiation in mesoscale anticyclonic eddies (AEs) and cyclonic eddies (CEs). The model simulated ecosystem dynamics between nutrient‐phytoplankton‐zooplankton‐detritus in AEs and CEs, while the physical model provided the seasonal cycle of convective turbulent mixing. The study was motivated by earlier work based on satellite and ship observations, which showed earlier initiation of the spring blooms in CEs with shallow mixed‐layer depths than in AEs with deeper mixed‐layer depths. The model results supported the hypothesis that mixed‐layer depths in eddies play an important role in the dynamics of the spring bloom initiation. Model results revealed that in AEs convective mixing causes light limitation for phytoplankton growth due to deep winter mixing, and the bloom initiation is delayed until relaxation of turbulent convective mixing. Conversely, in the shallow mixed‐layer CEs, blooms initiate before the end of convective mixing due to early improvement in light conditions following the increase in solar radiation. Furthermore, the model showed that the relaxation in zooplankton grazing for the deep mixing contributed to weak winter phytoplankton accumulation in AE, while winter phytoplankton accumulation was faster in the shallow mixed‐layer CE. Overall, the initiation mechanism and the dynamics of the spring phytoplankton blooms are different for AEs and CEs. Therefore, we suggest that, in many parts of the global ocean, eddies play an important role regulating the dynamics of phytoplankton blooms.

Structural and functional diversity and quantitative parameters of two-year shoot systems of pregenerative individuals of <em>Quercus robur</em> L. (Fagaceae) in different light conditions in the central part of European Russia

Based on topological characteristics and functional role in crown, diversity of the two-year shoot systems in pregenerative individuals of Q. robur L. growing in communities with different light level in southern part of Moscow region and reserve “Kaluzhskiye Zaseki” in Kaluga region have been typified. In full light conditions uniform branching, mesotonic and acrotonic two-year shoot systems with a great number of lateral twigs mainly contribute to the crown structure. In shadow conditions crown is formed basically from non-branching systems and two-year shoot systems with a small number of casually located lateral twigs. The number of nodes of the elementary shoots of different two-year system types is more constant than their internodes’ length. Branching types of two-year shoot systems have longer internodes than nonbranching ones do. In branching types of two-year shoot systems internodes become longer with the improvement of light conditions. Refs 26. Figs 3. Tables 3.

Do Small Canopy Gaps Created by Japanese Black Bears Facilitate Fruiting of Fleshy-Fruited Plants?

Japanese black bears often break branches when climbing trees and feeding on fruit in canopies, thereby creating small canopy gaps. However, the role of black bear-created canopy gaps has not been evaluated in the context of multiple forest dynamics. Our hypothesis was that small canopy gaps created by black bears improve light conditions, which facilitates fruiting of adult fleshy-fruited plants located beneath the gaps, and also that this chain interaction depends on interactions among the size of gaps, improved light conditions, forest layers, and life form of plants. The rPPFD, size of black bear-created canopy gaps, and fruiting/non-fruiting of fleshy-fruited plants were investigated in five forest layers beneath black-bear-created canopy gaps and closed canopies of Mongolian oak (Quercus crispula). We found that light conditions improved beneath black bear-disturbed trees with canopy gaps of large size, and the effect of improvement of light conditions was reduced with descending forest layers. Fruiting of fleshy-fruited plants, especially woody lianas and trees, was facilitated by the improvement of light conditions accompanied by an increase in the size of black-bear-created gaps. Data from this study revealed that canopy disturbance by black bears was key for improving light conditions and accelerating fruiting of fleshy-fruited trees and woody lianas in the canopy layers in particular. Therefore, our hypothesis was mostly supported. Our results provide evidence that Japanese black bears have high potential as ecosystem engineers that increase the availability of resources (light and fruit in this study) to other species by causing physical state changes in biotic materials (branches of Q. crispula in this study).

Decreases in turbidity during neap tides initiate late winter blooms of Eucampia zodiacus in a macrotidal embayment

Eucampia zodiacus Ehrenberg is harmful, as it causes reduction in the quality of the aquacultured Porphyra thalli owing to nutrient depletions during dense blooms in the late winter in the macrotidal Ariake Sea, Japan. To understand the mechanism of bloom development, changes in the abundance of E. zodiacus during a bloom were investigated along vessel transects from February to April 2012. In addition, marine environmental variables were continuously monitored by the Ariake Sea Monitoring Tower, which revealed that turbidity periodically decreased during neap tides. During the 16 February neap tide, a high Secchi depth (4.3 m) was recorded at offshore stations and the Z 1% depth, at which the light intensity attenuates to 1 % of that at the sea surface, exceeded the water depth. On 16 February, the abundance of E. zodiacus was 52–732 cells mL−1, peaking at 7.0 m depth offshore. Subsequently, abundance increased at all stations. During the 22 February spring tide, abundance became vertically uniform. On 19 March, abundance at the tower reached 3758 cells mL−1 at the surface. We conclude that an improvement in light conditions in the deeper layer triggered the bloom, although the size and the duration of the bloom were determined by nutrient availability. Thus, decreases in turbidity during neap tides and subsequent strong vertical mixing during spring tides may be instrumental in the population dynamics of the large diatom E. zodiacus in macrotidal environments.

Seasonal variability of primary production in a fjord ecosystem of the Chilean Patagonia: Implications for the transfer of carbon within pelagic food webs

We characterized the seasonal cycle of productivity in Reloncaví Fjord (41°30′S), Chilean Patagonia. Seasonal surveys that included measurements of gross primary production, community respiration, bacterioplankton secondary production, and sedimentation rates along the fjord were combined with continuous records of water-column temperature variability and wind forcing, as well as satellite-derived data on regional patterns of wind stress, sea surface temperatures, and surface chlorophyll concentrations. The hydrography and perhaps fjord productivity respond to the timing and intensity of wind forcing over a larger region. Seasonal changes in the direction and intensity of winds, along with a late-winter improvement in light conditions, may determine the timing of phytoplankton blooms and potentially modulate productivity cycles in the region. Depth-integrated gross primary production estimates were higher (0.4–3.8 g C m −2 d −1) in the productive season (October, February, and May), and lower (0.1–0.2 g C m −2 d −1) in the non-productive season (August). These seasonal changes were also reflected in community respiration and bacterioplankton production rates, which ranged, respectively, from 0.3 to 4.8 g C m −2 d −1 and 0.05 to 0.4 g C m −2 d −1 during the productive and non-productive seasons and from 0.05 to 0.6 g C m −2 d −1 and 0.05 to 0.2 g C m −2 d −1 during the same two periods. We found a strong, significant correlation between gross primary production and community respiration (Spearman, r=0.95; p<0.001; n=12), which suggests a high degree of coupling between the synthesis of organic matter and its usage by the planktonic community. Similarly, strong correlations were found between bacterioplankton secondary production and both gross primary production (Spearman, r=0.7, p<0.05, n=9) and community respiration (Spearman, r=0.8, p<0.05, n=9), indicating that bacterioplankton may be processing an important fraction (8–59%) of the organic matter produced by phytoplankton in Reloncaví Fjord. In winter, bacterial carbon utilization as a percentage of gross primary production was >100%, suggesting the use of allochthonous carbon sources by bacterioplankton when the levels of gross primary production are low. Low primary production rates were associated with a greater contribution of small cells to autotrophic biomass, highlighting the importance of small-sized plankton and bacteria for carbon cycling and fluxes during the less productive winter months. Fecal pellet sedimentation was minimal during this period, also suggesting that most of the locally produced organic carbon is recycled within the microbial loop. During the productive season, on the other hand, the area exhibited a great potential to export organic matter, be it to higher trophic levels or vertically towards the bottom.

Seasonal changes in the nutritional status and yielding of Anthurium cultorum Birdsey. Part I. Macroelements

Abstract The aim of the research, which was carried out in the years 2002 − 2004, was the determination of the natural tendencies in the macroelement nutritional status and in the yielding of the standard cultivars of Anthurium cultorum Birdsey (‘Baron’, ‘Choco’, ‘Midori’, ‘Pistache’, ‘President’, ‘Tropical’ from Anthura B.V., the Netherlands) in the autumn-winter and spring-summer vegetations periods. The anthurium was grown in expanded clay with the use of standard nutrients in a drip fertigation system. It was found that an improvement of light conditions caused a significant increase in plant yielding. During the three years of the study, it was found that an essential influence was exerted by the vegetation period on the amount of phosphorus and potassium in the plants’ leaves. In the spring-summer period, a considerable decrease of phosphorus content in the plants was observed, but at the same time, there was an increase of potassium content. In the springsummer period, plant age affected the phosphorus and calcium content of the plants, while in the autumn-winter period, the phosphorus, potassium and calcium content was affected. A decrease in calcium, nitrogen and magnesium content was found in the spring-summer period, while the content of sulphur tended to increase. The obtained results could be a valuable instrument for the interpretation of index parts of plant analyses for diagnostic purposes.

Stand structure and growth patterns of understorey trees in a coniferous forest, Taisetsuzan National Park, northern Japan

AbstractStand structure was studied with special reference to growth and mortality patterns of sapling and understorey trees in a coniferous Picea jezoensis and Abies sachalinensis forest in Taisetsuzan National Park, Hokkaido, northern Japan. Picea jezoensis was dominant in the basal area, while A. sachalinensis was abundant in large numbers in the canopy. Estimated mortalities increased significantly with diameter at breast height (DBH) for both P. jezoensis and A. sachalinensis in the canopy, but the tendency was different between the two species. Picea jezoensis had a lower mortality rate than A. sachalinensis, especially at small DBH classes. The spatial distribution of understorey individuals of A. sachalinensis did not show any significant correlation with the spatial distribution of canopy gaps, but that of P. jezoensis showed a significant correlation. Abies sachalinensis can grow higher than P. jezoensis under suppressed conditions; while P. jezoensis requires canopy gaps for steady height growth. This growth pattern leads to a different waiting height in the understorey (≥2 m in height and 10 cm in diameter at breast height). Abies sachalinensis waited for an improvement in light conditions at higher strata (max. 7 m), while P. jezoensis waited at lower strata (max. 3 m). The estimated mortality of understorey A. sachalinensis increased with size, while that of understorey P. jezoensis decreased. Therefore, P. jezoensis gives priority to survival while A. sachalinensis gives priority to understorey growth. The difference in the ‘waiting pattern’ between the two species in the understorey was considered a significant feature for the canopy recruitment process of P. jezoensis and A. sachalinensis.

Significance of Architecture and Allometry in Saplings

Species differences in branching architecture and allometry were analysed for co-occurring forest floor saplings of 10 species of shadetolerant evergreen broad-leaved tree, representative of primary warm-temperate rain forests in southern Japan, from the viewpoints of assimilative efficiency and significance for regeneration. Considerable diversity was found in the architecture of branching and in the leaf size of saplings. The differences in branching and leaf size were related to differences in allometric relationships between various properties of the saplings. It was hypothesized that this architectural and allometric diversity is related to the alternative of 'choosing' either the pattern of assimilate allocation, which is adaptive in competition when there is an early improvement in light conditions, or the allocation pattern which is favourable for surviving long periods under persistently dark conditions. Measurements of sapling growth in closed stands and in gaps supported the hypothesis. Key-words: Allocation, allometry, branching architecture, leaf size, light condition, regeneration niche, saplings, warm-temperate rain forest

Physiological aspects of crop choice

As a result of the lag in the spring rise in temperature behind the improvement in light conditions, crop growth in the spring is frequently limited by the rate at which assimilates can be used in growth rather than by the rate of production of assimilates in photosynthesis. Hence there is a loss of potential dry matter production in the spring, both in perennial crops such as grasses, and in spring sown arable crops. There is considerable genetic variation within and between crop species in ability to grow in cool conditions, and there are good prospects for achieving earlier growth of grasses and arable crops in the spring by breeding. Spring sown arable crops, such as sugar beet and potatoes, are slow to build up an adequate leaf cover and greater yields can be achieved in mild southwestern areas than in the traditional areas for these crops. Climatic conditions in lowland areas in the west are quite favourable for crop growth, and much land in these areas at present under permanent grass is potentially capable of producing high yields of arable crops. Some alternatives to the present extensive use of home grown barley and wheat for animal feed are discussed and it is shown that certain root crops produce higher yields of metabolizable energy (m.e.) and protein than cereals. Since silage is relatively rich in protein in relation to its content of m.e., luxury levels of protein have to be consumed and a re-examination of the cost of using silage for winter feed is required in the light of increased costs of nitrogenous fertilizers. On poor marginal land yields of animal protein from sheep are very low and such land would seem to be better suited for forestry, which can produce high yields of wood for relatively low inputs of soil nutrients.