اثرات تغییرپذیری ادافیک بر دینامیک مکانی اکوسیستم‌های خشک

نوع مقاله : علمی -پژوهشی

نویسندگان

1 دانشجوی دکتری ژئومورفولوژی، گروه جغرافیا، دانشگاه فردوسی مشهد

2 دانشگاه فردوسی مشهد- دانشکده منابع طبیعی و محیط زیست

3 دانشیار گروه جغرافیا، دانشگاه فردوسی مشهد

4 استادیار گروه مهندسی بیوسیستم، دانشگاه فردوسی مشهد

چکیده

اکوسیستم­های خشک و نیمه­خشک به دلیل عدم تنوع در ساختارها و متغیرهای خود، در معرض وقوع تحولات سریع در ترکیب جوامع گیاهی در پاسخ به تغییرات محیطی هستند. فرایندها و آشوب­ها با تغییر الگوهای متداول خاک در مقیاس­های کوچک می­توانند زمینه ظهور دینامیک­های بزرگ مقیاسی را در ساختار چشم­انداز فراهم آورند. شکل­گیری هتروژنیتی­های پراکنده در ویژگی­های خاک و به تبع آن تغییرات در توزیع پوشش گیاهی می­تواند نشانه­ای از ظهور وضعیت­های پایدار متناوب (وضعیت همگن پوشش گیاهی و فاقد پوشش) در سطح چشم­انداز باشد. چنین تضادی از لحاظ توزیع الگوهای خاک و پوشش گیاهی، منجر به ظهور فیدبکی مثبت بین خاک، آب و گیاه می­شود. فیدبکی که می­تواند نقش مهمی در روند دینامیک اکوسیستم­های خشک داشته باشد. افزایش فیدبک­های مثبت با کاهش انعطاف­پذیری سیستم، چشم­انداز را مستعد وقوع گذری برگشت­ناپذیر به سمت وضعیتی تخریبی خواهند کرد. از آنجا که بررسی فیدبک­های بین این سه متغیر محیطی می­تواند در درک دینامیک چشم­اندازهای خشک و نحوه پاسخ این سیستم­ها به تغییرات و تنش­های محیطی موثر باشد، در مقاله حاضر به تشریح اثرات فیدبک­های مثبت بین آب، خاک و گیاه بر روی روند تحول اکوسیستم­های خشک پرداخته شده است. نتایج این پژوهش نشان داده است که چگونه ظهور هتروژنیتی­های پراکنده­ در ویژگی­های خاک غالب چشم­انداز با ایجاد فیدبک مثبت­ بین آب، خاک و گیاه می­تواند منجر به کاهش انعطاف­پذیری سیستم، ظهور وضعیت­های ناتعادلی و تسریع روند بیابان­زایی ­گردد. 

کلیدواژه‌ها


عنوان مقاله [English]

Edaphic variability impacts on spatial dynamic of arid ecosystems

چکیده [English]

Arid and semi-arid ecosystems due to lack of diversity in their structures and variables are prone to rapid degradation of vegetation composition in response to environmental changes. Processes and disturbances with subtle changes of the soil current patterns can result in the emergence of large scale dynamics across landscape. Occurrence of diffuse heterogeneities in soil attributes and consequently variations in vegetation patches can be a sign of the emergence of alternative stable states (as uniform vegetated and barren states) in arid ecosystems. Such contrast in distributions of vegetation and soil patterns may result in activation of positive feedbacks between soil-vegetation which have main role on the arid landscapes dynamics. Increasing positive feedbacks with decreasing system’s resilience lead to irreversible transformation onto degraded states. Since information on the soil-vegetation feedbacks can promote our understanding of how arid landscape responses to external stresses, in this paper has been noted impacts of positive feedbacks in evolution trends of arid ecosystems. Here has been shown that how the emergence of heterogeneities on the landscape dominant soil with occurrence of positive feedbacks between soil-vegetation can result in decreasing resilience and intensification of desertification trends.

کلیدواژه‌ها [English]

  • Soil Heterogeneity
  • Positive Feedback
  • Resilience
  • Landscape Dynamic
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