A holistic microclimate model

You are here: Technical Model Webpage » ENVI-met Knowledgebase Overview » Obtaining Leaf Area Density Data

Differences

This shows you the differences between two versions of the page.

Link to this comparison view

Both sides previous revisionPrevious revision
Next revision		Previous revision
Last revisionBoth sides next revision
kb:lad [2012/08/15 22:31] – enviadminkb:lad [2012/08/15 22:53] – enviadmin
Line 1: Line 1:
 ====== Obtaining Leaf Area Density Data ====== ====== Obtaining Leaf Area Density Data ======
-{{:kb:leafs_at_treee.jpg?300 |Leafs on a tree}}+{{:kb:leafs_at_treee.jpg?350 |Leafs on a tree}}
 The **Leaf Area Density (LAD)** is the portion of leaf surface ($m^2$) within a volume of air ($m^3$). The formal unit is  The **Leaf Area Density (LAD)** is the portion of leaf surface ($m^2$) within a volume of air ($m^3$). The formal unit is 
 $$ \frac{ \text{Leaf surface } (m^2)}{ \text {Reference volume } (m^3)} $$ $$ \frac{ \text{Leaf surface } (m^2)}{ \text {Reference volume } (m^3)} $$
  
-In ENVI-met, like in most other models, the LAD is counted **one-sided** which means that only one side of the leaf is counted as active surface area. This accounts to the fact, that most plants only have stomata on one side of the leaf, typically on the back (but there are others as well). So for the exchange of latent heat ($LE$) it makes sense to count only one side of the leaf as active surface. Also, for the exchange of sensible heat ($H$), normally only one side is exposed to the wind while the other is in the lee of the leaf so that its exchange coeficient approaches zero. This is - of course- a simplicifcation which can be discussed.    +In ENVI-met, like in most other models, the LAD is counted **one-sided** which means that only one side of the leaf is counted as active surface area. This accounts to the fact, that most plants only have [[wp>Stoma|stoma]] on one side of the leaf, typically on the back (but there are others as well). So for the exchange of latent heat ($LE$) it makes sense to count only one side of the leaf as active surface. Also, for the exchange of sensible heat ($H$), normally only one side is exposed to the wind while the other is in the lee of the leaf so that its exchange coeficient approaches zero. This is - of course- a simplicifcation which can be discussed.    
  
 ===== Objective ===== ===== Objective =====
Line 26: Line 26:
 ==== Methodology 1b: Leaf collection  ==== ==== Methodology 1b: Leaf collection  ====
  
-{{:kb:leafs_collected.jpg?200 |Collected leafs}}+{{:kb:leafs_collected.jpg?300 |Collected leafs}}
 This methode is straight forward and has certain drawbacks for the tree. You can define your reference volume (1 cubemeter or less) and then collect all the leafs that are inside this volume. You place them on a sheet of paper as close as you can get them and then calculate the leaf surface area. There are also more sophisticated methods available using digital image processing. But as we talk about rude methods here, we restrict outselves to the very basic approach...  This methode is straight forward and has certain drawbacks for the tree. You can define your reference volume (1 cubemeter or less) and then collect all the leafs that are inside this volume. You place them on a sheet of paper as close as you can get them and then calculate the leaf surface area. There are also more sophisticated methods available using digital image processing. But as we talk about rude methods here, we restrict outselves to the very basic approach...