مزايا و معايب روش هاي اندازه گيري شاخص سطح برگ در بوم سازگان هاي جنگلي

Advantages and disadvantages of leaf area index (LAI) measuring methods in forest ecosystems

ﺳﺎﺑﻘﻪ و ﻫﺪف: ﺷﺎﺧﺺ ﺳﻄﺢ ﺑﺮگ ﻣﻌﺎدل ﺳﻄﺢ روﯾﯽ ﺑﺮگ اﺳﺖ ﮐﻪ ﻧﺸﺎن دﻫﻨﺪه ﺳﻄﺢ ﻓﺘﻮﺳﻨﺘﺰﮐﻨﻨﺪه ﺑﺮگ اﺳﺖ. ﺗﺨﻤﯿﻦ ﺳﺮﯾﻊ و ﻗﺎﺑﻞ اﻋﺘﻤﺎد ﺷﺎﺧﺺ ﺳﻄﺢ ﺑﺮگ ﺑﺮاي ﻣﻄﺎﻟﻌﺎت ﺑﻮم ﺷﻨﺎﺧﺘﯽ ﻣﻮردﻧﯿﺎز اﺳﺖ زﯾﺮا ﺷﺎﺧﺺ ﺳﻄﺢ ﺑﺮگ اﻏﻠﺐ ﯾﮏ ﭘﺎراﻣﺘﺮ ﻣﻬﻢ در ﻣﺪل ﻫﺎﯾﯽ اﺳﺖ ﮐﻪ واﮐﻨﺶ رﺳﺘﻨﯽ ﻫﺎ و ﺑﻪ ﺧﺼﻮص درﺧﺘﺎن را ﺑﻪ ﺗﻐﯿﯿﺮات ﻣﺤﯿﻄﯽ در ﻣﻘﯿﺎس ﺟﻬﺎﻧﯽ و ﻣﺤﻠﯽ ﻧﺸﺎن ﻣﯽ دﻫﺪ. روش ﻫﺎي ﻣﺘﻌﺪدي ﺑﺮاي ﺗﻌﯿﯿﻦ ﺷﺎﺧﺺ ﺳﻄﺢ ﺑﺮگ وﺟﻮد دارد ﺣﺎل آن ﮐﻪ در اﯾﺮان از روش ﻫﺎي ﻣﻌﺪودي اﺳﺘﻔﺎده ﺷﺪه اﺳﺖ؛ ﺑﻨﺎﺑﺮاﯾﻦ ﻫﺪف از ﻣﻘﺎﻟﻪ ﻣﻌﺮﻓﯽ روش ﻫﺎي ﮔﻮﻧﺎﮔﻮن اﻧﺪازه ﮔﯿﺮي ﺷﺎﺧﺺ ﺳﻄﺢ ﺑﺮگ، ﺑﯿﺎن ﺗﻮاﻧﻤﻨﺪي ﻫﺎ و ﻣﺤﺪودﯾﺖ ﻫﺎي ﻫﺮ روش ﻣﯽ ﺑﺎﺷﺪ ﺗﺎ ﭘﮋوﻫﺸﮕﺮان ﺑﺘﻮاﻧﻨﺪ ﻣﺘﻨﺎﺳﺐ ﺑﺎ اﻣﮑﺎﻧﺎت و ﺷﺮاﯾﻂ ﭘﮋوﻫﺶ ﯾﮑﯽ از آن ﻫﺎ را اﻧﺘﺨﺎب ﮐﻨﻨﺪ. ﻣﻮاد و روش ﻫﺎ: در اﯾﻦ ﻣﻘﺎﻟﻪ روش ﻫﺎي ﻣﺴﺘﻘﯿﻢ و ﻏﯿﺮﻣﺴﺘﻘﯿﻢ ﺑﺮاي اﻧﺪازه ﮔﯿﺮي ﺷﺎﺧﺺ ﺳﻄﺢ ﺑﺮگ ﻣﻌﺮﻓﯽ ﻣﯽ ﺷﻮﻧﺪ. روش ﻫﺎي ﻣﺴﺘﻘﯿﻢ در ﺗﻮده ﻫﺎي ﻫﻤﮕﻦ اﺳﺘﻔﺎده ﻣﯽ ﺷﻮﻧﺪ ﺑﻨﺎﺑﺮاﯾﻦ ﻣﻨﺎﺳﺐ ﺟﻨﮕﻞ ﮐﺎري ﻫﺎ ﻫﺴﺘﻨﺪ. در اﯾﻦ روش ﻫﺎ دو ﮔﺎم ﺷﺎﻣﻞ ﺟﻤﻊ آوري ﺑﺮگ و ﺳﭙﺲ اﻧﺪازه ﮔﯿﺮي ﺳﻄﺢ آن ﻫﺎ وﺟﻮد دارد. در روش ﻫﺎي ﻏﯿﺮﻣﺴﺘﻘﯿﻢ ﻣﺴﺎﺣﺖ ﺑﺮگ ﺑﺎ اﺳﺘﻔﺎده از ﻣﺘﻐﯿﺮﻫﺎي دﯾﮕﺮي ﻣﺎﻧﻨﺪ وﺿﻌﯿﺖ ﻫﻨﺪﺳﯽ ﺗﺎج، ﻣﯿﺰان رﺑﺎﯾﺶ ﻧﻮري، ﻃﻮل و ﻋﺮض ﺑﺮگ ﺗﺨﻤﯿﻦ زده ﻣﯽ ﺷﻮد. اﯾﻦ روش ﻫﺎ ﻣﯽ ﺗﻮاﻧﻨﺪ ﺑﺮاي ﻧﻤﻮﻧﻪ ﻫﺎﯾﯽ در ﻣﺤﺪوده ﻫﺎي ﺟﻐﺮاﻓﯿﺎﯾﯽ وﺳﯿﻊ ﺑﻪ ﮐﺎر ﮔﺮﻓﺘﻪ ﺷﻮﻧﺪ. ﯾﺎﻓﺘﻪ ﻫﺎ: داﻣﻨﻪ ﺷﺎﺧﺺ ﺳﻄﺢ ﺑﺮگ در اﯾﺮان ﺑﯿﻦ 1/6 ﺗﺎ 7/7 ﺑﺮاي ﮔﻮﻧﻪ ﻫﺎ و ﺗﻮده ﻫﺎي ﻣﺨﺘﻠﻒ ﺟﻨﮕﻠﯽ ﺑﻪ دﺳﺖ آﻣﺪه اﺳﺖ. ﺷﺎﺧﺺ ﺳﻄﺢ ﺑﺮگ از روش ﻣﺴﺘﻘﯿﻢ در ﺗﻮده ﺑﻠﻮط اﯾﺮاﻧﯽ 1/6، در ﺗﻮده راش ﺷﺮق ﻫﯿﺮﮐﺎﻧﯽ 7/5، ﺗﻮده راش ﻣﻤﺮز 7/5 ﺗﺎ 7/7، ﺗﻮده ﺑﻠﻨﺪﻣﺎزو اﻓﺮا 5/96 و ﺗﻮده ﺑﻠﻨﺪﻣﺎزو آزاد 3/63، در ﮔﻮﻧﻪ اوري 3/33 و ﺑﺮاي ﮔﻮﻧﻪ اﻗﺎﻗﯿﺎ 3/78 ﺑﻪ دﺳﺖ آﻣﺪه اﺳﺖ. ﺷﺎﺧﺺ ﺳﻄﺢ ﺑﺮگ از روش ﻏﯿﺮﻣﺴﺘﻘﯿﻢ ﺑﺮاي ﮔﻮﻧﻪ داﻏﺪاﻏﺎن 3/7 و ﺑﺮاي ﮔﻮﻧﻪ ﻫﺎي ﺑﺎﻏﯽ ﻣﺎﻧﻨﺪ ﺳﯿﺐ، آﻟﻮ، ﮔﻼﺑﯽ و ﮔﯿﻼس ﺑﯿﻦ 1 ﺗﺎ 5 ﺑﻪ دﺳﺖ آﻣﺪه اﺳﺖ. ﻧﺘﯿﺠﻪ ﮔﯿﺮي: ﺑﺎ ﺗﻮﺟﻪ ﺑﻪ ﺟﺪﯾﺪ ﺑﻮدن ﻧﺴﺒﯽ ﻣﻄﺎﻟﻌﺎت ﻣﺮﺗﺒﻂ ﺑﺎ ﺷﺎﺧﺺ ﺳﻄﺢ ﺑﺮگ در اﯾﺮان ﻧﯿﺎز ﺑﻪ ﻣﺤﺎﺳﺒﻪ و ﻣﻘﺎﯾﺴﻪ ﺷﺎﺧﺺ ﺳﻄﺢ ﺑﺮگ در ﺑﻮم ﺳﺎزﮔﺎن ﻫﺎي ﻣﺨﺘﻠﻒ ﺗﻮﺳﻂ روش ﻫﺎ و اﺑﺰارﻫﺎي ﻣﺨﺘﻠﻒ اﺣﺴﺎس ﻣﯽ ﺷﻮد. ﺑﺮاي ﺗﻌﯿﯿﻦ ﺷﺎﺧﺺ ﺳﻄﺢ ﺑﺮگ در ﺟﻨﮕﻞ ﻫﺎي اﯾﺮان اﺳﺘﻔﺎده از روش ﻣﺴﺘﻘﯿﻢ دام ﻻﺷﺮﯾﺰه و روش ﻏﯿﺮﻣﺴﺘﻘﯿﻢ ﻋﮑﺲ ﻫﺎي ﻧﯿﻤﮑﺮه ﺗﻮﺻﯿﻪ ﻣﯽ ﺷﻮد. در ﺻﻮرت ﺗﻌﯿﯿﻦ رواﺑﻂ آﻟﻮﻣﺘﺮﯾﮏ ﺑﺎ اﺟﺰاي ﭼﻮﺑﯽ درﺧﺘﺎن )ﺟﺰو روش ﻫﺎي ﻏﯿﺮﻣﺴﺘﻘﯿﻢ ﺗﻤﺎﺳﯽ( ﺗﻌﯿﯿﻦ ﺷﺎﺧﺺ ﺳﻄﺢ ﺑﺮگ در ﺟﻨﮕﻞ ﻫﺎ ﺑﻪ ﺳﺮﻋﺖ و ﺑﺎ دﻗﺖ ﻗﺎﺑﻞ ﻗﺒﻮل اﻣﮑﺎن ﭘﺬﯾﺮ اﺳﺖ. ﭘﯿﺸﻨﻬﺎد ﻣﯽ ﮔﺮدد ﺑﺎ اﺳﺘﻔﺎده از روش ﻫﺎي ﻣﻌﺮﻓﯽ ﺷﺪه در اﯾﻦ ﻣﻘﺎﻟﻪ ﭘﮋوﻫﺸﮕﺮان ﺗﺨﻤﯿﻦ و اﻧﺪازه ﮔﯿﺮي ﺷﺎﺧﺺ ﺳﻄﺢ ﺑﺮگ را ﻣﺘﻨﺎﺳﺐ ﺑﺎ ﺷﺮاﯾﻂ ﭘﮋوﻫﺶ ﺧﻮد اﻧﺠﺎم دﻫﻨﺪ.

Background and Objectives: Leaf Area Index (LAI) is equal to top leaf surface that demonstrate photosynthetic leaf area. Fast and reliable estimation of LAI is need for ecological studies because LAI is often an important parameter in models that showed vegetation, especially trees response to environmental changes in a global and local scale. There are several methods for determining LAI while few methods have used in Iran. So the goal of article was introducing a variety of ways for measuring LAI, declaring capabilities and limitations of each method, to investigator choose one of them based on facilities and fieldwork conditions. Material and Methods: In this paper, direct and indirect methods to measuring LAI were introducing. Direct methods are convenient for homogenous stands therefore suitable to plantations. Two steps of these methods are collecting leaves and then measuring areas. In indirect methods LAI is estimating using other variables such as geometric crown status, the level of light kidnapping, leaf length and width. These methods can be used in broad geographic regions.