Animal burrowing and associated formation of large desiccation cracks as factors of a rapid restoration of soil cover in flooded farmlands Nizamettin Kazanci ® Omer Emre ® M. Cihat Alcicek Abstract The burrowing activity of annelids con- trols the spatial pattern and rapid formation of large desiccation cracks in the river flood-derived mud cover in recently inundated farmland areas in northwestern Anatolia, Turkey. The phenomenon is confirmed by laboratory experiments imitating the natural floodplain conditions. Keywords Mudcracks ® Bioturbation ® Flooding ® River Filyos ® Turkey Introduction River floods are a serious threat to farmlands in many parts of the world, because restoration of a flooded area takes a long time and much effort, particularly when the flooding has formed a thick sediment cover, usually con- sisting of mud. However, our observations from freshly flooded farmland in northwestern Anatolia, Turkey (Fig. 1) indicate that the development of large mudcracks instigated by annelids and medium-scale bioturbation leads to rapid restoration and/or rejuvenation of soil. Desiccation cracks are common surficial features of muddy terrestrial deposits, and their formation mecha- nisms have been described by Lachenbruch (1962) and Allen (1982) among others. The pattern of mudcrack polygons depends on the sediment characteristics, such as grain size, packing, density and plasticity, but may be controlled also by the surficial activity of various crawling organisms, including small larvae (Metz 1980). The main role of organisms in crack development is by forming grooves on the mud surface, which then become the lines of cracking during the desiccation (Hughes 1884 in Allen 1982). From a mechanical point of view, the mudcracks themselves develop according to the near-surface distri- bution of contractional stress in the shrinking mud (Lachenbruch 1962), while the biogenic grooves and burrows act as lines of weakness in the surficial crust. Biogenic control on mudcrack pattern was documented by field observations and experimental studies (Baldwin 1974; Kues and Siemers 1977; Metz 1980). Our field observations from the modern floodplain of River Filyos in northwestern Turkey indicate rapid development of large mudcracks, up to 5 cm wide and 25 cm deep, in connection with annelid horizontal burrows and intense vertical bioturbation. We have examined two areas of former farmland where the mud surface was drying more rapidly than in the surroundings, and where the subsurficial horizontal burrows made by the large annelid Lumbricus terrestris were the main cause of mudcrack formation. The cracks in the present case are considerably larger than the biogenically controlled mudcracks reported by others, which can be attributed to the sediment homogeneity and high rate of desiccation. This paper focuses on the formation of large mudcracks and their role in the post-flood restoration of the farmland soil layer. We also describe a laboratory experiment that has simulated the field conditions and resulted in similar desiccation features. Description of mudcracks and bioturbation pattern The floodplain areas studied are located in the lower reach of the River Filyos, near the towns of Comranli and Artukova (Fig. 1A). The river flows from central Anatolia to the Black Sea, and the study areas are about 15 and 25 km from the coast respectively. There are no dams, and the river has a mean water discharge of 102.9 m 3 /s and a Received: 15 July 2000 / Accepted: 17 October 2000 Published online: 3 April 2001 ª Springer-Verlag 2001 N. Kazanci (&) Ankara Universitesi Jeoloji Muhendisligi Bolumu, 06100 Ankara, Turkey E-mail: nkazanci@penta.gyte.edu.tr O. Emre Maden Tetkik ve Arama Genel Mudurlugu, 06535 Ankara, Turkey M. Cihat Alcicek Ankara Universitesi Jeoloji Muhendisligi Bolumu, 06100 Ankara, Turkey Present address: N. Kazanci Gebze Institut of Technology, 41400 Kocaeli, Turkey Cases and solutions 964 Environmental Geology (2001) 40:964–967 DOI. 10.1007/s002540100258