Objective:
This study deals with a special microrelief landscape consisting of hummocks alternating with pits, often considered to be a specific Alpine phenomenon termed Bukkelwiesen. In German, the word Buckelwiese means "hummocky meadow" and was originally a name given to this type of landscape near the village of Mittenwald in Bavaria.
The hummocks have an average diameter of 200 to 400 cm and consist of calcareous debris in which the weathering is highly variable. They alternate with depressions at a density of approximately 600 hummocks and 600 pits per hectare. What makes this microrelief distinctive from features of similar dimensions (e.g. thufurs, landslide hummocks) are the gentle convex-concave slopes between hummocks and pits, together with a remarkable regularity in the general distribution pattern. The origin of this microrelief is still unknown. Four different theories of origin have been proposed but none of them has been generally accepted. In this study the origin of the Buckelwiesen phenomenon was investigated at two test sites in the Kräuterin Massif (eastern part of the Austrian limestone Alps).

Investigation methods:
Field investigations in each test site included a ground survey of the relief using a total station and the excavation of a trench through two hummocks and a pit to study their internal structure. In one of the two trenches the site specific solution rates in the subsurface material of pits and hummocks were measured. The trenches were further used to collect samples for lab analysis of the soil properties and for radiocarbon dating. The ground survey data were used for digital terrain modelling and subsequent morphometric analysis. Aerial photos provided further data.

Results:
The explanation of the relief as a special phenomenon of covered karst has been put forward before, whereby the prevailing geomorphic process within the relief is seen in a concentrated limestone solution acting in the pits. This process fosters their gradual subsidence, thereby giving the hummocks between them an increasingly prominent appearance. The Buckelwiesen of Mittenwald and the Kräuterin Massif display a significant change of vegetation- and soil type between hummocks and pits, which highlights this karstification process, but solution rates within the Buckelwiesen have not been yet measured.
The results of a field experiment carried out in the study for the first time suggests that there are enormous differences between the amount of water that penetrates deeper into the soil of pits and hummocks. By surface flow and interflow all the precipitation arriving on the hummocks is directed to the surrounding pits. Thus there is absolutely no downward percolation underneath the hummocks but the pits receive the equivalent of about double the amount of annual precipitation. Thus, solution rates are relatively high there with a measured denudation rate of 76,5mm/ 1000a.

Once the relief exists, it is gradually amplified through a self-reinforcing process (positive feedback), so the basic problem is to explain the origin of the initial hummocky relief. One of the two investigation sites in the Kräuterin Massif reveals that the initial hummocky relief is the result of uprooting of trees during storms. Soil and subsoil-material was shifted by the rootstocks, forming the mounds. Pits were created by karst processes acting in the depressions left when the tree roots were extracted. There is evidence for this formation process in the internal structure of the hummocks and in the general appearance of the Buckelwiese.
The centre of the hummock underneath the shallow A-horizon of the recent rendzina is made up of a very inhomogenous substratum with differing colouring and of differing weathering intensity. It is the fossil soil of an older and relatively thick rendzina - the former A and C horizon have been disturbed and displaced by the transport and accumulation within the rootplate of an uprooted tree and are now arranged in lenses and pockets. The wickerwork of roots (of which pieces can still be found) within this mound has made the soil and subsoil material quite friable.
The elongated hummocks on this site show a length/width ratio of 1.7 and the longitudinal axes are remarkably well aligned. The pits are also oval in plan view. They are never equidistant from the surrounding hummocks but lie very close to one hummock. This pattern of parallel-lying pairs of hummocks and pits perfectly corresponds with the arrangement of rootstock-pits and adjacent mounds of rootplates, soil material and debris in an area of uprooted trees. It is even possible to deduce the direction in which the trees were blown down.

A radiocarbon dating of the material of the fossil humus lenses in the centre of the hummock indicated that the uprooting of trees creating the initial relief of the Buckelwiese occurred between 1120 and 1280 AD. It is notable that this dating fits very well with a calculated age (1330 AD) of the initial rootstock-pit. This calculation was based on the measured solution rate, the volume of the pit in which the solution experiment was carried out and an estimate of the volume of the extracted rootplate which was inferred from characteristics of the form of hummock and pit.