Molecular evidence for recent land use change from a swampy environment to a pond (Lorraine, France)

作者：Bertrand O^*; Mansuy Huault L; Montarges Pelletier E; Losson B; Argant J; Ruffaldi P; Etienne D; Garnier E; Dezileau L; Faure P; Michels R

来源：Organic Geochemistry, 2012, 50: 1-10.

DOI：10.1016/j.orggeochem.2012.06.004

Evidence of a changing environment in the catchment area of a small pond (Lansquenet, Lorraine, France) during the last millennium was provided by coupling palynology data and organic ratios [terrestrial to aquatic ratio: TAR((HC)); the C-29 vs. C-27 sterols, C-29/C-27(ST); average chain length, ACL and aquatic/macrophytes ratio, P-aq]. The depositional and alteration conditions of organic matter (OM) were provided by the 5 alpha(H)-stanols/Delta(5)-sterols ratio. This study shows that quite simple organic ratios clearly allow identification of the different evolution steps of a watershed, from a swamp to the progressive settlement of a pond. During the swampy period, the C/N-(at) (ca. 11.1), TAR((HC)) (ca. 36.8), C-29/C-27(ST) (ca. 8.7) and P-aq (%26lt;0.3) show a high contribution of allochthonous OM associated with the presence of particular aquatic and mesohygrophilous species. A woody level dated to the XIIIth century reflects the period of the settlement of the pond in a more oxic environment [5 alpha(H)-stanol/Delta(5)sterol ratio %26lt;0.2]. Then, the progressive increase in aquatic input and the development of submerged and floating macrophytes are evidenced by low C/N-(at) (%26lt;7.6), TAR((HC)) (ca. 2.7), C-29/C-27(ST) (ca. 2) and high P-aq (ca. 0.5), suggesting an increase in the water level and eutrophication of the pond. A second oxic event [5 alpha(H)-stanols/Delta(5)sterols ratio averaging 0.16], associated with extensive OM degradation, corresponds to the most recent dredging in 2002 and reflects an important disturbance of sediments due to pond management.

• 出版日期2012-9