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
-Aguiar, M.R. and Sala, O.E., 1999. Patch structure, dynamics and implications for the functioning of arid ecosystems, Trends in Ecology and Evolution, v. 14, p. 273–277.
-Bestelmeyer, B.T., Waed, J.P. and Havstad, K.M., 2006. Soil-geomorphic heterogeneity governs patchy vegetation dynamics at an arid ecotone, Ecology, v. 87, p. 963-973.
-Bestelmeyer, B.T., Ellison, A.M., Fraser, W.R., Gorman, K.B., Holbrook, S.J., Laney, C.M., Ohman, M.D., Peters, D.B.C., Pillsbury, F.C., Rassweiler, A., Schmitt, R.J. and Sharma, S., 2011. Analysis of abrupt transitions in ecological systems, Ecosphere, v. 2, p. 1-26.
-Dakos, V., Scheffer, M., Van Nes, E.H., Brovkin, V., Petoukhov, V. and Held, H., 2008. Slowing down as an early warning signal for abrupt climate change, PNAS, v. 105, p. 14308-14312.
-Dakos, V., 2011. Expecting the Unexpected: Indicators of resilience as early-warning signals for critical transitions, Ph.D thesis. Wageningen University, The Neaderland, 163 p.
-Dakos, V., Carpenter, S., Brock, W., Ellison, A., Guttal, V., Ives, A., Kefi, S., Livina, V., Seekell, D., Van Nes, E. and Scheffer, M., 2012. Methods for detecting early warnings of critical transitions in time series illustrated using simulated ecological data, PLoS ONE, v. 7, p. 1-20.
-d’Herbe`s, J.M., Valentin, C., Tongway, D.J. and Leprun, J.C., 2001. Banded vegetation patterns and related structures, Ecological Studies, v. 149, p. 1–19.
-D’Odorico, P., Laio, F. and Ridolfi, L., 2006. Patterns as indicators of productivity enhancement by facilitation and competition in dryland vegetation, Geophysical Research (Biogeosciences), v. 111, p. G03010.
-D'Odorico, P., Caylor, K., Okin, G.S. and Scanlon, T.M., 2007. On soil moisture–vegetation feedbacks and their possible effects on the dynamics of dryland ecosystems, Journal of Geophysical Research, v. 112, p. G04010.
-Guttal, V. and Jayaprakash, C., 2007. Impact of noise on bistable ecological systems, Ecological Modelling, v. 201, p. 420–428.
-Greene, R.S. B., Valentin, C. and Esteves, M., 2001. Runoff and erosion processes, in banded vegetation patterning in arid and semiarid environment, edited by D. J. Tongway, C. Valentin, and J. Seghieri, Springer, New York, p. 52–77.
-Hennessy, J.T., Gibbens, R.P., Tromble, J.M. and Cardenas, M., 1983. Water properties of caliche, Journal of Range Management, v. 36, p. 723–726.
-Hamerlynck, E.P., McAuliffe, J.R. and Smith, S.D., 2000. Effects of surface and sub-surface soil horizons on the seasonal performance of Larrea tridentate (creosotebush), Journal of Functional Ecology, v. 14, p. 596–606.
-HilleRisLambers, R., Rietkerk, M., van den Bosch, F., Prins, H.H. and de Kroon, H.T., 2001. Vegetation pattern formation in semi-arid grazing systems, Ecology, v. 82. p. 50–61.
-Kefi, S., Rietkerk, M., van Baalen, M. and Loreau, M., 2007. Local facilitation, bistability and transitions in arid ecosystems, Theoretical Population Biology, v. 71, p. 367–379.
-Lajtha, K. and Schlesinger, W.H., 1988. The effect of CaCO3 on the uptake of phosphorus by two desert shrub species, Journal of Botanical Gazette, v. 149, p. 328–334.
-Ludwig, J.A., Wilcox, B.P., Breshears, D.D., Tongway, D.J. and Imeson, A.C., 2005. Vegetation patches and runoff-erosion as interacting ecohydrological processes in semiarid landscapes, Ecology, v. 86, p. 288–297.
-Lloyd, K.M., McQueen, A.A.M., Lee, B.J., Wilson, R.C.B., Walker, S. and Wilson, J.B., 2000. Evidence on ecotone concepts from switch, environmental and anthropogenic ecotones, Vegetation Science, v. 11, p. 903–910.
-McAuliffe, J. R., 1994. Landscape evolution, soil formation, and ecological patterns and processes in Sonoran desert bajadas, Journal of Ecological Monographs, v. 64, p. 111–148.
-Maestre, F.T., Cortina, J., Bautista, S., Bellot, J. and Vallejo, R., 2003. Small-scale environmental heterogeneity and spatio-temporal dynamics of seedling establishment in a semiarid degraded ecosystem, Ecosystems, v. 6, p. 630–643.
-Monger, H.C. and Bestelmeyer, B.T., 2006. The soil-geomorphic template and biotic change in arid and semi-arid ecosystems, Journal of Arid Environments, v. 62, p. 207-218.
-Ravi, S., D'Odorico, P. and Okin, G.S., 2007. Hydrologic and aeolian controls on vegetation patterns in arid landscapes, Geophysical Research Letters, v. 34, p. L24S23.
-Ravi, S., D'Odorico, P., Wang, L. and Collins, S., 2008. Form and function of grass ring patterns in arid grasslands: the role of abiotic controls, Oecologia, v. 158, p. 545-555.
-Ravi, S., Breshears, D.D., Huxman, T.E. and D'Odorico, P., 2010. Land degradation in drylands: Interactions among hydrologic–aeolian erosion and vegetation dynamics, Geomorphology, v. 116, p. 236-245.
-Rietkerk, M. and van de Koppel, J., 1997. Alternate stable states and threshold effects in semi-arid grazing systems, Oikos, v. 79, p. 69-76.
-Reitkerk, M., Boerlijdt, M.C., Langevelde, F.V., Hillerislamber, R., Van de Koppel, J., Kumar, L., Prins, H.H. and de Roos, A.M., 2002. Self-Organization of Vegetation in Arid Ecosystems, The American Naturalist, v. 160, p. 524 -530.
-Rietkerk, M., Dekker, S., de Ruiter, C.P.C. and Van de Koppel, J., 2004. Self-organized patchiness and catastrophic shifts in ecosystems, Science, v. 305, p. 1926–1929.
-Rietkerk, M. and van de Koppel, J., 2008. Regular pattern formation in real ecosystems, Trends in Ecology & Evolution, v. 23, p. 169-175.
-Scheffer, M., Carpenter, S., Foley, J.A., Folke, C. and Walker, B.H., 2001. Catastrophic shifts in ecosystems, Nature, v. 413, p. 591–596.
-Scheffer, M., Bascompte, J., Brock, W.A., Brovkin, V., Carpenter, S.R., Dakos, V., Held, H., Van Nes, E.H., Rietkerk, M. and Sugihara, G., 2009. Early-warning signals for critical transitions, Nature, v. 461, p. 53-59.
-Van Nes, E.H. and Scheffer, M., 2007. Slow recovery from perturbations as a generic indicator of a nearby catastrophic shift, The American naturalist, v. 169, p. 738 –747.
-Von Hardenberg, J., Meron, E., Shachak, M. and Zarmi, Y., 2001. Diversity of vegetation patterns and desertification, Physical Review Letters, v. 87, p. 198101-1-198101-4.
-Zeng, X., Shen, S.S.P. and Dickinson, R.E., 2004. Multiple equilibrium states and the abrupt transitions in a dynamical system of soil water interacting with vegetation, Geophysical Research Letters, v. 31, p. L05501.