تاثير شدت هاي مختلف چرايي بر تنوع و تركيب پوشش گياهي مراتع نيمه خشك (مطالعه موردي: مراتع محمد آباد، جيرفت)

Effect of Different Grazing Intensities on Diversity and Plants Cover Composition in Semi-Arid Grazing (Case study: Mohammad Abad, Jiroft)

زﻣﯿﻨﻪ و ﻫﺪف: آﮔﺎﻫﯽ از ﻓﺸﺎرﻫﺎي ﻣﺤﯿﻄﯽ ﻣﺨﺮب ﺑﺮ اﮐﻮﺳﯿﺴﺘﻢ ﮐﻪ ﺑﺎﻋﺚ ﺗﺨﺮﯾﺐ زﯾﺴﺘﮕﺎه ﻫﺎ و ﺑﯿﻮم ﻫﺎ و در ﻧﺘﯿﺠﻪ ﮐﺎﻫﺶ ﺗﻨﻮع ﮔﻮﻧﻪ اي ﻣﯽ ﮔﺮدد، ﺿﺮوري اﺳﺖ. ﯾﮑﯽ از ﻓﺸﺎرﻫﺎي ﻣﺨﺮب ﻓﯿﺰﯾﮑﯽ ﺑﺮ ﻋﺮﺻﻪ ﻣﺮﺗﻊ ﮐﻪ ﺑﺎﻋﺚ ﮐﺎﻫﺶ ﺗﻨﻮع و از ﺑﯿﻦ رﻓﺘﻦ ﻋﻨﺎﺻﺮ ﮔﯿﺎﻫﯽ ﺣﺴﺎس ﻣﯽ ﮔﺮدد، ﭼﺮاي ﻣﻔﺮط ﻣﯽ ﺑﺎﺷﺪ. ﻫﺪف از اﻧﺠﺎم اﯾﻦ ﺗﺤﻘﯿﻖ ﺑﺮرﺳﯽ اﺛﺮ ﺷﺪت ﻫﺎي ﻣﺨﺘﻠﻒ ﭼﺮاﯾﯽ ﺑﺮ ﺗﻨﻮع و ﻏﻨﺎي ﮔﻮﻧﻪ اي در ﻣﺮاﺗﻊ ﻧﯿﻤﻪ ﺧﺸﮏ ﺑﺨﺶ ﻣﺤﻤﺪ آﺑﺎد، ﺷﻬﺮﺳﺘﺎن ﺟﯿﺮﻓﺖ، اﺳﺘﺎن ﮐﺮﻣﺎن ﺑﻮده اﺳﺖ. روش ﺑﺮرﺳﯽ: ﺑﻪ ﻣﻨﻈﻮر ﺑﺮرﺳﯽ اﺛﺮ ﺷﺪت ﻫﺎي ﻣﺨﺘﻠﻒ ﭼﺮاﯾﯽ ﺑﺮ ﺗﻨﻮع و ﻏﻨﺎي ﮔﻮﻧﻪ اي ﺳﻪ روﯾﺸﮕﺎه ﻣﺘﻔﺎوت ﻗﺮق، ﭼﺮاي ﻣﺘﻮﺳﻂ و ﭼﺮاي ﺷﺪﯾﺪ اﻧﺘﺨﺎب و ﺑﺎ اﺳﺘﻔﺎده از 90 ﭘﻼت 4 ﻣﺘﺮ ﻣﺮﺑﻌﯽ در ﻃﻮل 18 ﺗﺮاﻧﺴﮑﺖ اﻗﺪام ﺑﻪ ﻧﻤﻮﻧﻪ ﺑﺮداري ﮔﺮدﯾﺪ. در داﺧﻞ ﻫﺮ ﻗﺎب، ﻓﻬﺮﺳﺖ ﮔﻮﻧﻪ ﻫﺎي ﻣﻮﺟﻮد، درﺻﺪ ﺗﺎج ﭘﻮﺷﺶ و ﺗﻌﺪاد اﻓﺮاد ﻫﺮ ﮔﻮﻧﻪ ﯾﺎدداﺷﺖ ﺷﺪ. ﺑﺮاي ارزﯾﺎﺑﯽ ﺷﺎﺧﺺ ﻫﺎي ﺗﻨﻮع و ﻏﻨﺎ، ﺷﺎﺧﺺﻫﺎي ﻏﻨﺎي ﻣﺎرﮔﺎﻟﻒ و ﻣﻨﻬﯿﻨﮓ و ﺷﺎﺧﺺ ﻫﺎي ﺗﻨﻮع ﺳﯿﻤﭙﺴﻮن، ﺷﺎﻧﻮن-واﯾﻨﺮ، N0 ﻫﯿﻞ و N1 ﻫﯿﻞ ﻣﺤﺎﺳﺒﻪ ﮔﺮدﯾﺪ. ﺗﺠﺰﯾﻪ و ﺗﺤﻠﯿﻞ دادهﻫﺎ در ﻧﺮم اﻓﺰار SPSS اﻧﺠﺎم ﺷﺪ و ﻣﻘﺎﯾﺴﻪ ﺷﺎﺧﺺ ﻫﺎي ﻣﺨﺘﻠﻒ ﺗﻨﻮع و ﻏﻨﺎ ﺑﯿﻦ ﻣﻨﺎﻃﻖ ﺑﺎ ﺷﺪت ﻫﺎي ﭼﺮاﯾﯽ ﻣﺨﺘﻠﻒ ﺗﻮﺳﻂ آزﻣﻮن ﺗﻮﮐﯽ ﺻﻮرت ﭘﺬﯾﺮﻓﺖ. ﯾﺎﻓﺘﻪ ﻫﺎ: ﻧﺘﺎﯾﺞ ﺣﺎﺻﻞ از ﻣﺤﺎﺳﺒﻪ ﺷﺎﺧﺺ ﻏﻨﺎي ﻣﺎرﮔﺎﻟﻒ ﻧﺸﺎن داد ﮐﻪ ﺑﯿﻦ ﺗﻤﺎﻣﯽ ﻋﺮﺻﻪ ﻫﺎي ﭼﺮاﯾﯽ از ﻧﻈﺮ آﻣﺎري اﺧﺘﻼف ﻣﻌﻨﯽ داري وﺟﻮد دارد. از ﻃﺮف دﯾﮕﺮ ﺑﯿﻦ ﻣﻨﺎﻃﻖ ﻣﺨﺘﻠﻒ ﭼﺮاﯾﯽ از ﻧﻈﺮ ﺷﺎﺧﺺ ﻏﻨﺎي ﻣﻨﻬﯿﻨﮓ اﺧﺘﻼف ﻣﻌﻨﯽ داري وﺟﻮد ﻧﺪارد. ﻧﺘﺎﯾﺞ ﺣﺎﺻﻞ از ﻣﺤﺎﺳﺒﻪ ﺷﺎﺧﺺ ﻫﺎي ﺗﻨﻮع، در ﻫﺮ ﭼﻬﺎر ﺷﺎﺧﺺ ﺳﯿﻤﭙﺴﻮن، ﺷﺎﻧﻮن-واﯾﻨﺮ، N0 ﻫﯿﻞ و N1 ﻫﯿﻞ ﻧﺸﺎن دادﻧﺪ ﮐﻪ ﺑﯿﻦ ﺗﻤﺎﻣﯽ ﻋﺮﺻﻪ ﻫﺎي ﭼﺮاﯾﯽ اﺧﺘﻼف ﻣﻌﻨﯽ داري وﺟﻮد دارد ﺑﺤﺚ و ﻧﺘﯿﺠﻪ ﮔﯿﺮي: ﺑﻪ ﻃﻮر ﮐﻠﯽ در ﻣﻨﻄﻘﻪ ﻣﻮرد ﻣﻄﺎﻟﻌﻪ ﺷﺎﺧﺺ ﻫﺎي ﺗﻨﻮع و ﻏﻨﺎي ﮔﻮﻧﻪ اي ﺑﻪ دﻟﯿﻞ ﻣﯿﺰان ﺑﺎرﻧﺪﮔﯽ ﮐﻢ ﻣﻨﻄﻘﻪ و ﻗﺮارﮔﯿﺮي در ﻧﺎﺣﯿﻪ ﻧﯿﻤﻪ ﺧﺸﮏ ﻧﺴﺒﺘﺎً ﭘﺎﯾﯿﻦ اﺳﺖ. ﺑﻨﺎﺑﺮاﯾﻦ ﺑﻪ ﻋﻠﺖ ﺣﺴﺎس و ﺷﮑﻨﻨﺪه ﺑﻮدن اﯾﻦ ﻧﻮع ﻣﺮاﺗﻊ در ﺑﻬﺮه ﺑﺮداري از آن ﻫﺎ ﺑﺎﯾﺪ ﺗﻮﺟﻪ ﺑﯿﺶ ﺗﺮي داﺷﺖ ﺗﺎ از ﺗﺨﺮﯾﺐ ﺑﯿﺶ ﺗﺮ ﺟﻠﻮﮔﯿﺮي ﺷﺪه و ﺗﺮﮐﯿﺐ ﮔﯿﺎﻫﯽ ﻧﯿﺰ اﺻﻼح ﮔﺮدد.

Background and Objective: It is necessary to be aware of the destructive factors in the ecosystem. These factors cause shelter and biomass destruction, thus decreasing species diversity. Livestock over grazing is one of the most physical destructive pressures on rangeland that leads to a decrease in diversity and vegetation elements. The aim of this study has been conducted to investigate the effect of different grazing intensities on the diversity and richness of plant species in the semi-arid rangelands of Mohammad Abad area of Jiroft, Kerman Province, Iran. Method: We selected 3 sites that included light, moderate and heavy grazing intensities. Sampling was performed using 90 plots (2 m2) along 18 transects. The list of specie, canopy coverage and number of individuals per species were recorded for each sampling unit. To evaluate diversity and richness of the plant species, Margalef and Menhing richness indices, and Simpson, Shannon, Hill N0 and Hill N1 diversity indices were calculated. SPSS software was applied for data analysis. Comparison of different indices of diversity and richness among study sites was performed by the Tukey test. Findings: The results of Margalef richness index showed significant differences between all grazing sites. No significant difference existed in the Menhing richness index of different grazing categories (p<0.01). Results of calculations of diversity indices for Simpson, Shannon, Hill N0 and Hill N1 showed that there were significant difference (p<0.01) between all grazing sites. Discussion and Conclusion: Generally, diversity and species richness indices due to low rainfall and placement in the semi-arid region are relatively low in the case study. Therefore, because of the sensitive and fragile nature of these types of rangelands in the operation, we should pay more attention to prevent further destruction and amended the composition