Leaf-area index

Several plant parameters are important to the design of ET landfill covers. Among the most important are parameters describing rooting depth, leaf-area-index (LAI), temperature requirements, time to maturity, and water requirements. Models that are suitable for use in design of ET covers will utilize these parameters. The quality of the plant model controls the quality of AET estimates. 

The theoretical initial concentration on leaves is 10 ug/cm2, based on an application rate of 1 kg/ha, no loss of spray to the ground or into the air, and a leaf area index (LAI) of only 1, which means that the total foliar surface in a treated area is equal to the ground surface. 

The results of the DFR assessment of different crop zones indicate that low-volume applications result in a more homogeneous distribution over the crop compared to high-volume applications. A recent study on the interception of high-volume applications in the cultivation of chrysanthemums revealed interception ratios from 0.2 to 1 related to the leaf area index (LAI) (Veerman et al., 1994). In our study, it was not easy to assess the LAI because of the structure of the carnation crop. Estimation of the LAI based on the results of estimation of the crop density (leaf volume index) was not reliable enough and resulted in a large variance of the calculated interception ratio (from 0.4 up to 5). 

The photo synthetic aquatic biomass comprises cyanobacteria (formerly called blue-green algae), planktonic, filamentous and macrophytic algae, and vascular macrophytes. The net productivity of the floodwater depends on the level of primary production by the photosynthetic biomass versus its consumption by grazing animals, particularly cladocerans, copepods, ostracods, insect larvae and molluscs. Their role will change as the canopy develops and at a leaf area index of about 6-7 there will be no more photosynthetically active radiation available to them. 

Lindenberg Aerosol Characterization Experiment 1998 Leaf Area Index... 

The mean vg as reported in all experiments with elemental iodine in Table 3.4 is 18 mm s-1. If the leaf area index is 5, counting the area of one side of each leaf, this is consistent with a vg to individual leaves of 3.6 mm s 1 (compare Fig. 3.3). 

Fassnacht, K. S., Gower, S. T., MacKenzie, M. D., Nordheim, E. V. and Lillesand, T. M. (1997) Estimating the leaf area index of north central Wisconsin forest using the landsat thematic mapper. Remote Sensing Environ. 61, 229-45. 

Pas ko (1973) categorized clones into three classes based upon the number of stems arising from the seed tuber (1) >3 (strong), (2) 2 to 3 stems (intermediate), and (3) a single stem (weak). Multiple stems facilitate a rapid increase in leaf area index early in the development of the plant. The number of stems also varies with agronomic practices and seed tuber size. Some clones are highly variable in the number of stems produced, while others are less so. 

Stem number is partly determined by the size of the seed tuber (Barloy, 1988 Louis, 1985) and is closely related to the early canopy development and leaf area index (Baillarge, 1942 Cors and Falisse, 1980). Branching type is genetically controlled, although the number of branches is largely regulated by plant density. 

Canopy light extinction coefficient (k) Calculated using the function LI = 1 — exp( t LAI), where LI is the fraction of light intercepted by the canopy and LAI is leaf area index (m2 leafm-2 land) Varies3 ... 

Leaf area index (LAI) Leaf area/unit area of land varies during the season the following is the maximum reported (m2 leaf-m 2 land) 9.8 Hay and Offer, 1992... 

Various methods of measuring leaf area index are in common use, including destructive harvesting and direct leaf measurement, and indirect nondestructive methods involving optical instrumentation. In addition to plant age, the leaf area index is partially determined by genotype,... 

In a French study, late cultivars (e.g., Violet de Rennes ) produced more total biomass than early cultivars (e.g., Blanc precoce ), but tuber yields were the same. The superior leaf area index of late cultivars could not be translated into superior tuber yields due to constraints on the life cycle as a result of unfavorable fall climatic conditions (Barloy, 1988b). Planting early in the spring ensures a longer growing season. In Southern Europe, this equates to February and not later than March. Later plantings result in reduced yields. 

Scurlock, J.M.O., Asner, G.P, and Gower, S.T., Worldwide Historical Estimates and Bibliography of Leaf Area Index, 1932-2000, ORNL Technical Memorandum TM-2001/268, Oak Ridge National Laboratory, Oak Ridge, TN, 2001. 

Thus, when the average leaf area index is 7.5 for such grasses, 5% of the PPF incident on the canopy reaches the soil surface (Fig. 9-6). For 95% of the PPF to be absorbed for a leaf area index of 3, by Equation 9.5 a much higher k is required ... 

---