answer question 1 and 2 in paragraph form each QUANTIFYING ECOLOGY 4.1 Beer\'s L

Question

answer question 1 and 2 in paragraph form each

QUANTIFYING ECOLOGY 4.1 Beer's Law and the Attenuation of Light ue to the absorption and reflection of light by leaves, there scribes the attenuation of light through a homogeneous medium. The medium in this case is the canopy of leaves. Beer's law can be applied to the problem of light attenuation through a plant 2 Figure 1 Relationship between leaf area index above the quantity of light attenuated per unit of leaf area index (LAI)curve. Knowing the amount of leaves (LAI) above any position in angle (see Figure 4.4) and the optical properties of the leaves. light reaching the top of the canopy, the quantity of light at any quantity of light (or photosynthetically active radiation) reaching The availability of light at any point in the canopy will directly levels and rates of light-limited photosynthesis for each of the ver- levels are expressed as a proportion of values for fully exposed leaves at the top of the canopy (1500 mol/m3/s). As one moves 5 0 presses the attenuation of light per unit of LAI, these values ofk are expressed as the attenuation of light per unit of water depth (such as centimeter, meter, inches, or feet). Beer's law can then be used to estimate the quantity of light reaching any depth (z) by Figure 2 Relationship between available light (PAR) and kelp (see Figure 4.1), seagrass, or other plants that are rooted in Available light is expressed as the proportion of PAR at the top of the canopy (assumed to be 1 500 mol/mis). from the top of the canopy downward, the amount of light reaching describing the attenuation of light as a function of LAI can then the top of the plant canopy to the sediment surface. Beer's law can also be used to describe the vertical attenuation of light in aquatic environments, but applying the light extinction coefficient (k) is more complex. The reduction of light with water depth is a function of various factors: (1) attenuation by the water itself (see Section 3.3, Figure 3.7); (2) attenuation by phytoplank ton (microscopic plants suspended in water), typically expressed 1. If we assume that the value of k used to calculate the verti- cal profile of light in Figure 1 (k0.6) is for a plant can- to the forest floor), how would the value of k differ (higher or lower) for a forest where the leaves were oriented at a 60-degree angle? (See the example in Figure 4.4.) in the water for some time before once again settling to the lates. Each of these factors has an associated light extinction coef ficient, and the overall light extinction coefficient (T) is the sum of

Explanation / Answer

1)

The inclination angle distribution of leaf always determines a canopy light extinction coefficient (K). Canopies have horizontal leaves when the K = 1.0. Canopies have wide range of broadleaf when the K = 0.5 K 0.7. So, at this K (0.5 K 0.7) value leaves have grater surface area. Hence, less light will penetrate the canopy and reach the ground. In a forest where the leaves were oriented at 60o angle, then the K value will be reduced to half. However, Extinction coefficient decreases because due to reduction of K value to half.

2)

Attenuation of light in water is the sum of the individual attenuation coefficients of several factors like attenuation by water itself, attenuation by phytoplankton, attenuation by dissolved substances, and attenuation by suspended particulates. Increase in attenuation by any one of these factors will increase the attenuation. The value of kT increases if there is an increase in the suspended particulate in the water until the matter sediments.

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