اثر آتش سوزي بر ترسيب كربن خاك و زيتوده گياهي در مراتع نيمه استپي زاگرس مركزي

The effect of fire on carbon sequestration of soil and plant biomass in Semi-Steppe rangelands of Central Zagros region, Iran

اﮐﻮﺳﯿﺴﺘﻢ ﻫﺎي ﻣﺮﺗﻌﯽ ﺣﺪود ﻧﯿﻤﯽ از ﺧﺸﮑﯽ ﻫﺎي زﻣﯿﻦ را ﺷﺎﻣﻞ ﺷﺪه و ﺣﺎوي ﺑﯿﺶ از ﯾﮏ ﺳﻮم ذﺧﺎﯾﺮ ﮐﺮﺑﻦ ﻣﻮﺟﻮد در ﺧﺸﮑﯽ ﻫﺎي ﺟﻬﺎن ﻣﯽ ﺑﺎﺷﻨﺪ. ﺑﻨﺎﺑﺮاﯾﻦ، ﻣﺮاﺗﻊ ﻧﻘﺶ ﻣﻬﻢ و ﭘﺘﺎﻧﺴﯿﻞ ﺑﺎﻻﯾﯽ ﺟﻬﺖ ﺗﺮﺳﯿﺐ ﮐﺮﺑﻦ دارا ﻣﯽ ﺑﺎﺷﻨﺪ. ﯾﮑﯽ از آﺷﻔﺘﮕﯽ ﻫﺎي ﻣﻬﻢ در ﻣﺮاﺗﻊ، آﺗﺶ ﺳﻮزي اﺳﺖ. ﮐﻪ ﻣﯽ ﺗﻮاﻧﺪ ﻧﻘﺶ ﻣﻬﻤﯽ در ﭼﺮﺧﻪ ﮐﺮﺑﻦ ﺟﻬﺎﻧﯽ داﺷﺘﻪ ﺑﺎﺷﺪ. در اﯾﻦ ﻣﻄﺎﻟﻌﻪ اﺛﺮ آﺗﺶ ﺳﻮزي ﺑﺮ ﻣﯿﺰان ﺗﺮﺳﯿﺐ ﮐﺮﺑﻦ ﺧﺎك و زﯾﺘﻮده ﮔﯿﺎﻫﯽ و ﻫﻤﭽﻨﯿﻦ ﺳﻬﻢ ﻫﺮ ﺑﺨﺶ از ﺗﺮﺳﯿﺐ ﮐﺮﺑﻦ ﮐﻞ در ﻣﺮاﺗﻊ زاﮔﺮس ﻣﺮﮐﺰي ارزﯾﺎﺑﯽ ﺷﺪ. ﺑﺪﯾﻦ ﻣﻨﻈﻮر در ﺷﻬﺮﺳﺘﺎن ﺑﻮﯾﯿﻦ و ﻣﯿﺎﻧﺪﺷﺖ اﺳﺘﺎن اﺻﻔﻬﺎن، ﺳﻪ ﺳﺎﯾﺖ ﻣﺮﺗﻌﯽ (ﺑﻪ ﻋﻨﻮان ﺗﮑﺮار) ﺑﺎ آﺗﺶ ﺳﻮزي ﯾﮑﺴﺎﻟﻪ اﻧﺘﺨﺎب ﺷﺪ و ﺑﺎ ﻣﻨﻄﻘﻪ ﻣﺠﺎور آن ﻣﻘﺎﯾﺴﻪ ﮔﺮدﯾﺪ. ﻣﻘﺎدﯾﺮ ﮐﺮﺑﻦ در زﯾﺘﻮده ﻫﻮاﯾﯽ، زﯾﺮزﻣﯿﻨﯽ، ﻻﺷﺒﺮگ و ﺧﺎك (ﻋﻤﻖ 15- 0 و 30-15 ﺳﺎﻧﺘﯽ ﻣﺘﺮي) اﯾﻦ دو ﻣﻨﻄﻘﻪ اﻧﺪازه ﮔﯿﺮي ﺷﺪ. ﻧﺘﺎﯾﺞ ﻧﺸﺎن داد ﮐﻪ ﻣﯿﺎﻧﮕﯿﻦ ﮐﻞ ﺗﺮﺳﯿﺐ ﮐﺮﺑﻦ در ﻣﻨﻄﻘﻪ ﺷﺎﻫﺪ 39/4 ﺗﻦ در ﻫﮑﺘﺎر و در ﻣﻨﻄﻘﻪ آﺗﺶ ﺳﻮزي 30/9 ﺗﻦ در ﻫﮑﺘﺎر ﺑﻮد. ﻧﺘﺎﯾﺞ ﻣﺮﺑﻮط ﺑﻪ ﺳﻬﻢ ﻫﺮ ﺑﺨﺶ از ﮐﻞ ﮐﺮﺑﻦ ﺗﺮﺳﯿﺐ ﺷﺪه ﻧﯿﺰ ﻧﺸﺎن داد ﮐﻪ ﺑﯿﺶ از 90 درﺻﺪ از ﮐﻞ ﺗﺮﺳﯿﺐ ﮐﺮﺑﻦ را ﮐﺮﺑﻦ آﻟﯽ ﺧﺎك ﺗﺸﮑﯿﻞ ﻣﯽ دﻫﺪ. ﺑﻪ ﻃﻮر ﮐﻠﯽ ﻣﯽ ﺗﻮان ﭼﻨﯿﻦ ﻧﺘﯿﺠﻪ ﮔﯿﺮي ﮐﺮد ﮐﻪ آﺗﺶ ﺳﻮزي در اﯾﻦ ﻣﺮاﺗﻊ ﺑﺎﻋﺚ ﻫﺪررﻓﺖ ﮐﺮﺑﻦ ﺗﺮﺳﯿﺐ ﺷﺪه در ﺣﺪود 8/5 ﺗﻦ در ﻫﮑﺘﺎر ﺷﺪه ﮐﻪ ﺳﻬﻢ ﺧﺎك از اﯾﻦ ﮐﺎﻫﺶ، 5/1 ﺗﻦ در ﻫﮑﺘﺎر و ﻣﺠﻤﻮع زﯾﺘﻮده ﮔﯿﺎﻫﯽ 3/4 ﺗﻦ در ﻫﮑﺘﺎر اﺳﺖ. ﺑﻨﺎﺑﺮاﯾﻦ، ﺑﺎ ﻣﺪﯾﺮﯾﺖ آﺗﺶ ﺳﻮزي در اﯾﻦ ﻣﻨﺎﻃﻖ، ﻣﯽ ﺗﻮان ﻧﻘﺶ ﻣﻬﻤﯽ در ﺣﻔﻆ ﮐﺮﺑﻦ ﺗﺮﺳﯿﺐ ﺷﺪه در زﯾﺘﻮده ﮔﯿﺎﻫﯽ و ﺧﺎك اﯾﻔﺎ ﻧﻤﻮد.

Rangeland ecosystems are occupied about half of the world’s lands and contain more than a third of the world’s terrestrial carbon reserves. Therefore, this type of ecosystems has an important role and high potential for carbon sequestration. One of the important disturbances in the rangelands is the fire, which could have a significant role in the global carbon cycle. This study is an evaluation on the effect of fire to soil carbon sequestration and plant biomass and the distribution on total carbon sequestration in central Zagros region. The case study consists of three sites (as the repeat) located in the Buin & Miandasht district within Isfahan province, they were selected whereas one year was passed after the last fire, then cases were compared with the neighbor region. The content of carbon in above and underground biomass, litter carbon and soil organic carbon (in two depths 0-15 cm, 15-30 cm) were measured. The results showed that the total carbon sequestration in control regions was 39.4 ton/ha-1s and in burned region was ton/ha-1. Carbon distribution also showed that the soil organic carbon contents were higher than 90% of total carbon sequestration. It was concluded that the fire in rangelands decreases the carbon sequestration approximately 8.5 ton/ha-1, where soil's share in this reduction was 5.1 ton/ha-1 and total plant biomass share was 3.4 ton/ha-1. Therefore, fire management plays an important role in maintaining carbon sequestrates in vegetation cover and soil.