تاثير خزه ها بر ايجاد و توسعه ي لاپيه ها ي حفره اي در سنگ هاي كربناته

The Influence of Mosses on the Creation and Development of Lapies in the Carbonate Rocks

ازجمله اشكال كارست سطحي، حفره هاي كوچك انحلالي روي سنگ ها هستند كه در اصطلاح لاپيه هاي حفره اي ناميده مي شوند. در ايجاد لاپيه هاي حفره اي، عواملي چون، اثر قطره‎هاي باران، انحلال سنگ در محل تقاطع درزها و تبلور نمك موثر هستند. در اين پژوهش اثر خزه‎هاي سطح سنگ در ايجاد اين اشكال بررسي شده است. بر اين اساس حداكثر ابعاد هر كدام از خزه ها، به‎همراه حداكثر ابعاد حفره ي سنگي موجود در زير 414 مورد از خزه ها با استفاده از دستگاه كوليس اندازه گيري شد. سپس رابطه‎ي تعداد خزه‎هاي سطح سنگ با تعداد حفره‎هاي زير آنها در شرايط رويشي خزه‎ها روي دو نوع سنگ كربناته با آزمون كاي‎دو بررسي شد. براي نشان دادن تاثير شكل خزه‎ها در شكل حفره‎هاي زير خزه‎ها نيز، ابعاد حفره ها به ابعاد خزه ها محاسبه و اختلاف آنها در شرايط مختلف سطح سنگ شامل، جنس، شيب و جهت سنگ با استفاده از آزمون تي جفتي در سطح معنادار 5/0 بررسي شد. نتايج نشان داد كه بين ابعاد خزه ها و ابعاد حفره هاي سنگي زير آنها، همبستگي معناداري وجود دارد. در زير 70 درصد خزه هايي كه روي سنگ آهك رشد كرده بودند، حفره‎ي سنگي قابل اندازه گيري مشاهده شد. در حالي‎كه در نمونه هاي مربوط به سنگ دولوميت، تنها در زير 20 درصد خزه ها حفره ي سنگي قابل انداره گيري مشاهده شد؛ ولي آزمون تي جفتي درباره‎ي آنها به نتايج مثبتي منجر نشد و از اين رو تلاش شد اين آزمون درباره‎ي مرحله‎ي تحول به‎اجرا گذاشته شود. درنتيجه آزمون نشان داد در شرايطي كه لاپيه‎ها رشد مي‎كنند، شكل آنها و به‎ويژه، عمق آنها با خزه‎هاي رويي تطابق پيدا مي‎كنند.

Extended Abstract Introduction The German word Karren and the French word Lapies are commonly used to refer to small-scale solution sculpture. Lapies range in size from a few millimeters to several meters. Present or absence of soil and vegetation cover, the rock and climate are the controls on lapies. The studies on the role of vegetation cover on lapies development have focused either on general functions of plants on solution or on influences of present or absence of vegetation on the development of lapies. However, it is not clear if the plants affect to producing and development of karstic landforms such as lapies, and whether there is any significant correlation between plant sizes and lapis sizes in different kinds of carbonate rocks and aspect and gradients of slopes. So, in this research we have tried to study the influences of mosses growing on Zagross slopes on the size of lapies. Methodology Char-zeber col as the study area is located south of Kermanshah to a 40 Km distance. In this place, the mean annual temperature is about 10 to 11?C and the mean annual precipitation is almost 450 mm, mostly falling from October to May. Outcrop of two groups of carbonate rocks has created a background to producing variety of lapies and to growing some mosses that more of them has located on the lapies. It is selected two sites in this area for sampling: one on the Tale-Zeng limestone and the other on the Shahbazan dolomites. Statistical society was 414 samples, out of which 311 samples taken from the first area and 103 samples from the second one accidently. The sampling points picked out from sites where rocks had an almost even and intact surface and they had capability for measurement dimensionally. Thus, characteristics of the mosses and lapies under them including maximum width, maximum length and maximum depth were measured by a vernier caliper. The coordinates of these points specified carefully by a GPS receiver, map330 model, and their gradient and aspects obtained by brunt on compass. Using ?2 test on numbers of mosses and number of present or absent lapies under them and making a correlation and a paired t test between dimensions of mosses and dimensions of lapiez elucidated the role of mosses on production of lapies and relationship between shapes of mosses and that’s of lapies. The last analysis was used to determine the roles of the kind of rock, aspect and gradient in producing pits similar to mosses. Results and Discussion The results showed that under 281 cases of all 311 mosses samples taken from the limestone had pits and 93 cases lacked any pits, however, there were only 21 pits under cases of 103 dolomite samples and under 82 cases no pits were not seen. The application of ?2 test on the two kinds of rocks showed that the number of mosses having pits under their selves on the limestone is significantly more than the ones under dolomites. On the other words, with the assumption that the mosses grow up simultaneously; intensity of lapies development by solution on the limestone under the mosses was more than the ones on the dolomites. Nevertheless, results of ?2 test didn’t show any significant differences between numbers of pits under the mosses in gradients and aspects. So we should expect the same number of pits in different slopes and aspects but different number of pits in different rocks. The correlation and t test between dimensions of pits and mosses of over them only showed a poor relationship. So, there isn’t any fitness between dimensions of a moss and pit under it and development of dimensions of pits occur independent of development of mosses. However, there is a relation between mosses and lapis, because if there weren’t such a relation, it wouldn’t be any pits under mosses and then there were equal pits under mosses of every kind of rocks. On the other hand, results of this research showed different developments of lapis based on rocks and also another researches have shown role of vegetation cover on lapies. Then, we can select some parts of data to analysis may be it apparent some relations. Correlation of data cleared lapies depth to mosses depth proportion as index of evolution stage. Analysis of data based on correlation and t test in different steps elucidated a significant relation when index come to arrive 0.8. This means that the dimensions of mosses and lapies go to match together as the diameters become larger. Conclusion Thus, mosses make solution with their Biological and chemical activities. The result of these activities on Zagros slopes is creation of alveolar lapies that their next step of transformation to another lapies depend on another factors. The onset of rock surface changes is marked by traces of weathering by young mosses. They can’t superimpose their cast on lapies shapes at the first steps, but over the time , when lapies to be enlarger, mosses dimensions, especially their depth go to be closer to lapies dimensions.