Root Depth, Leaf Area and Daytime Water Relations of Jarrah (Eucalyptus marginata) Forest Overstorey and Understorey During Summer Drought

1992 ◽  
Vol 40 (2) ◽  
pp. 113 ◽  
Author(s):  
DS Crombie
Keyword(s):  
Stomatal Conductance ◽  
Leaf Area ◽  
Summer Drought ◽  
Root Depth ◽  
Jarrah Forest ◽  
Area Index ◽  
Eucalyptus Marginata ◽  
Water Deficits ◽  
Forest Sites ◽  
Understorey Plants

Foliage projective cover of trees on high and low rainfall jarrah forest sites was 1.6 and 1.2 times that of their understorey respectively. Corresponding leaf area index ratios were 7.2 and 3.4 times. Tree and understorey species developed substantial water deficits on both sites during the summer drought, although water deficits developed more rapidly and became more severe on the site receiving less rainfall. Stornatal conductances and midday water potentials of deeply rooted trees (root depth > 10m) remained higher than those of less deeply rooted understorey plants for 1-2 months in the absence of rain. Daily cycling of water potential and stomatal conductance was detected in most plants throughout the summer. This is interpreted as indicating that the plants did not become dormant during summer drought.

scholarly journals A Canopy Transpiration Model Based on Scaling Up Stomatal Conductance and Radiation Interception as Affected by Leaf Area Index

Water ◽  
2021 ◽  
Vol 13 (3) ◽  
pp. 252
Author(s):  
Muhammad Shahinur Alam ◽  
David William Lamb ◽  
Nigel W. M. Warwick
Keyword(s):  
Stomatal Conductance ◽  
Leaf Area Index ◽  
Leaf Area ◽  
Festuca Arundinacea ◽  
Radiation Energy ◽  
Scaling Up ◽  
Controlled Environment ◽  
Canopy Conductance ◽  
Individual Layer ◽  
Area Index

Estimating transpiration as an individual component of canopy evapotranspiration using a theoretical approach is extremely useful as it eliminates the complexity involved in partitioning evapotranspiration. A model to predict transpiration based on radiation intercepted at various levels of canopy leaf area index (LAI) was developed in a controlled environment using a pasture species, tall fescue (Festuca arundinacea var. Demeter). The canopy was assumed to be a composite of two indistinct layers defined as sunlit and shaded; the proportion of which was calculated by utilizing a weighted model (W model). The radiation energy utilized by each layer was calculated from the PAR at the top of the canopy and the fraction of absorbed photosynthetically active radiation (fAPAR) corresponding to the LAI of the sunlit and shaded layers. A relationship between LAI and fAPAR was also established for this specific canopy to aid the calculation of energy interception. Canopy conductance was estimated from scaling up of stomatal conductance measured at the individual leaf level. Other environmental factors that drive transpiration were monitored accordingly for each individual layer. The Penman–Monteith and Jarvis evapotranspiration models were used as the basis to construct a modified transpiration model suitable for controlled environment conditions. Specially, constructed self-watering tubs were used to measure actual transpiration to validate the model output. The model provided good agreement of measured transpiration (actual transpiration = 0.96 × calculated transpiration, R2 = 0.98; p < 0.001) with the predicted values. This was particularly so at lower LAIs. Probable reasons for the discrepancy at higher LAI are explained. Both the predicted and experimental transpiration varied from 0.21 to 0.56 mm h−1 for the range of available LAIs. The physical proportion of the shaded layer exceeded that of the sunlit layer near LAI of 3.0, however, the contribution of the sunlit layer to the total transpiration remains higher throughout the entire growing season.

Leaf area index measurements at the middle reaches of Heihe River forest sites

2008 ◽  
Author(s):  
Jie Zou ◽  
Guang-jian Yan ◽  
Wu-ming Zhang ◽  
Ling Zhu ◽  
Ling Chen
Keyword(s):  
Leaf Area Index ◽  
Leaf Area ◽  
Heihe River ◽  
Area Index ◽  
Forest Sites

Growth of spring barley under drought: crop development, photosynthesis, dry-matter accumulation and nutrient content

1981 ◽  
Vol 96 (1) ◽  
pp. 167-186 ◽  
Author(s):  
D. W. Lawlor ◽  
W. Day ◽  
A. E. Johnston ◽  
B. J. Legg ◽  
K. J. Parkinson
Keyword(s):  
Leaf Area Index ◽  
Leaf Area ◽  
Dry Matter ◽  
Spring Barley ◽  
Grain Filling ◽  
Dry Matter Accumulation ◽  
Area Index ◽  
Water Deficits ◽  
Maximum Value ◽  
Grain Filling Period

SUMMARYThe effects of water deficit on growth of spring barley were analysed under five irrigation treatments. One crop was irrigated at weekly intervals from emergence throughout the growing season, and one was not irrigated at all after emergence. Soil water deficits in the other treatments were allowed to develop early, intermediate or late in the crop's development.Weekly irrigation produced a crop with a large leaf area index (maximum value 4) and maintained green leaf and awns throughout the grain-filling period. Early drought decreased leaf area index (maximum value 2) by slowing expansion of main-stem leaves and decreasing the number and growth of tiller leaves. Leaf senescence was also increased with drought. Drought late in the development of ears and leaves and during the grain-filling period caused leaves and awns to senesce so that the total photosynthetic areas decreased faster than with irrigation. Photosynthetic rate per unit leaf area was little affected by drought so total dry-matter production was most affected by differences in leaf area.Early drought gave fewer tillers (550/m2) and fewer grains per ear (18) than did irrigation (760 tillers/m2 and 21 grains per ear). Late irrigation after drought increased the number of grains per ear slightly but not the number of ears/m2. Thus at the start of the grain-filling period crops which had suffered drought early had fewer grains than irrigated (9·5 and 18·8 × 103/m2 respectively) or crops which suffered drought later in development (14 × 103/m2).During the first 2 weeks of filling, grains grew at almost the same rate in all treatments. Current assimilate supply was probably insufficient to provide this growth in crops which had suffered drought, and stem reserves were mobilized, as shown by the decrease in stem mass during the period. Grains filled for 8 days longer with irrigation and were heavier (36–38 mg) than without irrigation (29–30 mg). Drought throughout the grainfilling period after irrigation earlier in the season resulted in the smallest grains (29 mg).Grain yield depended on the number of ears, the number of grains per ear and mass per grain. Early drought decreased tillering and tiller ear production and the number of grains that filled in each ear. Late drought affected grain size via the effects on photosynthetic surface area.Drought decreased the concentrations of phosphorus, potassium and magnesium in the dry matter of crops, and irrigation after drought increased them. Concentration of nitrogen was little affected by treatment. Possible mechanisms by which water deficits and nutrient supply affect crop growth and yield are discussed.

Leaf area index measurements at Fluxnet-Canada forest sites

2006 ◽  
Vol 140 (1-4) ◽  
pp. 257-268 ◽  
Author(s):  
Jing M. Chen ◽  
Ajit Govind ◽  
Oliver Sonnentag ◽  
Yongqin Zhang ◽  
Alan Barr ◽  
...  
Keyword(s):  
Leaf Area Index ◽  
Leaf Area ◽  
Area Index ◽  
Forest Sites

scholarly journals Canopy structure and topography effects on snow distribution at a catchment scale: Application of multivariate approaches

2018 ◽  
Vol 66 (1) ◽  
pp. 43-54 ◽  
Author(s):  
Michal Jenicek ◽  
Hana Pevna ◽  
Ondrej Matejka
Keyword(s):  
Leaf Area Index ◽  
Leaf Area ◽  
Snow Depth ◽  
Forest Canopy ◽  
Snow Water Equivalent ◽  
Canopy Structure ◽  
Catchment Scale ◽  
Area Index ◽  
Forest Sites ◽  
Hemispherical Photographs

Abstract The knowledge of snowpack distribution at a catchment scale is important to predict the snowmelt runoff. The objective of this study is to select and quantify the most important factors governing the snowpack distribution, with special interest in the role of different canopy structure. We applied a simple distributed sampling design with measurement of snow depth and snow water equivalent (SWE) at a catchment scale. We selected eleven predictors related to character of specific localities (such as elevation, slope orientation and leaf area index) and to winter meteorological conditions (such as irradiance, sum of positive air temperature and sum of new snow depth). The forest canopy structure was described using parameters calculated from hemispherical photographs. A degree-day approach was used to calculate melt factors. Principal component analysis, cluster analysis and Spearman rank correlation were applied to reduce the number of predictors and to analyze measured data. The SWE in forest sites was by 40% lower than in open areas, but this value depended on the canopy structure. The snow ablation in large openings was on average almost two times faster compared to forest sites. The snow ablation in the forest was by 18% faster after forest defoliation (due to the bark beetle). The results from multivariate analyses showed that the leaf area index was a better predictor to explain the SWE distribution during accumulation period, while irradiance was better predictor during snowmelt period. Despite some uncertainty, parameters derived from hemispherical photographs may replace measured incoming solar radiation if this meteorological variable is not available.

scholarly journals Effects of Potassium Management on Physiological Traiats, Enzyme Activity and Cotton Fiber Cellulose Content

2021 ◽  
Author(s):  
Fábio Echer ◽  
Vinicius José Souza Perez ◽  
Giuliano Oliveira Carnevalli Baltazar ◽  
Gustavo Ricardo Aguiar Silva ◽  
Adriana Lima Moro ◽  
...  
Keyword(s):  
Enzyme Activity ◽  
Stomatal Conductance ◽  
Leaf Area Index ◽  
Leaf Area ◽  
Cover Crops ◽  
Cotton Fiber ◽  
Cover Crop ◽  
Nutrient Use Efficiency ◽  
Cellulose Content ◽  
Area Index

Abstract AimsPotassium (K) is prone to be washed out of plant tissues independent of mineralization since it is not strongly bound to organic structures in the plant. Therefore, cover crops can enhance K cycling in cropping systems increasing the nutrient use efficiency by taking it up deep in the soil profile and releasing it on the soil surface. However, it is not clear if this cycling would have an effect on cotton morphophysiology, enzyme activity, and eventually on fiber quality. MethodsPotassium was applied to two cotton cultivars, either to the cover crop ruzigrass (Urochloa ruzisiensis), or to cotton grown after the grass or not, and split between the cover crop and cotton. ResultsCotton leaf area index was increased late in the season by K, with small differences between fertilized treatments, but was highest at full bloom when at least part of the K was applied to cotton. Stomatal conductance was improved, mainly late in the season and when cotton was grown after ruzigrass. Consequently, the enzymatic activity and accumulation of cellulose in the cotton fiber were also increased. ConclusionPotassium fertilization improves cotton physiological parameters such as leaf area index and stomatal conductance, but the effect on enzyme activity depends on the enzyme and on the cotton cultivar. Early cellulose accumulation in the fiber is favored by potassium fertilization and cotton rotation with ruzigrass.

Improving Seed Potato Leaf Area Index, Stomatal Conductance and Chlorophyll Accumulation Efficiency through Irrigation Water, Nitrogen and Phosphorus Nutrient Management

2016 ◽  
Vol 4 (1) ◽  
pp. 127 ◽  
Author(s):  
Gathungu Geofrey Kingori ◽  
Aguyoh Joseph Nyamori ◽  
Isutsa Dorcas Khasungu
Keyword(s):  
Stomatal Conductance ◽  
Leaf Area Index ◽  
Leaf Area ◽  
Chlorophyll Content ◽  
Seed Potato ◽  
Irrigation Water ◽  
Potato Leaf ◽  
Area Index ◽  
Water Rate ◽  
P Application

A study was conducted in a Rainshelter (RTrial) at Horticultural Research and Teaching Farm, Egerton University to determine the effect of integration of irrigation water, nitrogen (N) and phosphorus (P) application on seed potato leaf area index (LAI), stomatal conductance and chlorophyll content. The treatments arranged in a split-split plot layout in a completely randomised block design, consisted of three irrigation water rates (40%, 65% and 100% field capacity), four N rates (0, 75, 112.5 and 150 kg N/ha) supplied as urea (46% N), and four P rates (0, 50.6, 75.9, 101.2 kg P/ha) supplied as triple superphosphate, replicated three times and repeated once. During the growth leaf area, stomatal conductance, and chlorophyll content were measured. Data collected were subjected to analysis of variance and significantly different means separated using Tukey’s Studentized Range Test at P≤0.05. Leaf area index was greater with high irrigation water at 100%, N at 150 kg N/ha and P at 101.2 kg P/ha, which was 2.6 and 1.3 at 51 days after planting (DAP) and 3.5 and 3.1 at 64 DAP. Furthermore, low irrigation water rate at 40% together with low N and P rates of 0 kg N/ha and 0 kg P/ha had the least LAI, which was 0.28 and 0.19 at 51 DAP and 0.28 and 0.24 at 64 DAP both in RTrials I and II, respectively. Subjecting potato to 100% compared to 40% irrigation rate increased stomatal conductance at 87 days after planting (DAP) by 32.82 and 31.99 mmolm⁻²s⁻¹, leaf chlorophyll content index by 16.2 and 16.5, 19.8 and 19.6, and 15 and 20.3, when integrated with high compared with low N and P application rates at 59, 73 and 87 DAP, in RTrials I and II respectively. Irrespective of N and P rates LAI, stomatal conductance and chlorophyll content were significantly greater with high irrigation water at 100% followed by 65% and was lowest with 40% irrigation water rate.

Dawn Water Potential and Root Depth of Trees and Understorey Species in Southwestern Australia

1988 ◽  
Vol 36 (6) ◽  
pp. 621 ◽  
Author(s):  
DS Crombie ◽  
JT Tippett ◽  
TC Hill
Keyword(s):  
Water Potential ◽  
Annual Rainfall ◽  
Soil Profiles ◽  
Seasonal Patterns ◽  
Summer Drought ◽  
Root Depth ◽  
Jarrah Forest ◽  
Southwestern Australia ◽  
Water Potentials ◽  
Average Annual Rainfall

Water relations of selected tree and understorey species in the jarrah forest of south-western Australia were studied during summer drought and the results related to root morphology. Seasonal patterns of predawn water potential (Ψp) differed between species according to root depth and between sites according to average annual rainfall. Dawn water potentials fell most rapidly and by the greatest amount in plants with the shallowest roots. Dawn water potentials of medium and deep rooted species were not consistently different. Separation of Ψp between sites of different annual rainfall was less marked than was separation by root depth. Changes in Ψp, were consistent with a top-to-bottom drying of the soil profiles. We suggest that measurements of Ψp of plants of appropriate root depth can be used to monitor the drying of soils as an alternative to more expensive mechanical and electrical methods.

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