Connectivity assessment in Mediterranean vineyards using improved stock unearthing method, LiDAR and soil erosion field surveys

The interaction between processes and landforms is accelerated in vineyards due to bare tilled soils that enhance splash, runoff, and erosion. Traditionally, in order to assess these processes, the stock unearthing method (SUM) is considered a useful methodology that uses the graft union of the vine plant as passive bio-indicator of the topsoil level changes. However, SUM assumes that the topography between the rows is planar when development of a model of the current micro-topography is performed. Thus, we consider that there is a need to develop a new methodology (ISUM: improved SUM) that, by adding new measurements in the inter-row areas (at least 3), allows inclusion of the absent micro-topographical information of SUM. In this way, the main aim of this research was to estimate the micro-topographical changes and soil transport at three different slope positions (upper, middle and lower parts) in a 25-years-old vineyard in eastern Spain. LiDAR data were used to compare the connectivity processes at the catchment with the pedon scale. We obtained maps that showed topsoil level changes and detected soil depletion and accumulation signals. We estimated soil displacement rates of -1.6Mghayr(-1) (depletion), +2.8Mghayr(-1) and +13.3Mghayr(-1) (accumulation) at upper, middle and lower slope positions, respectively. The total average soil erosion rates in the inter-rows were -5.7Mgha(-1)yr(-1). In the row areas, deposition of +10.5Mghayr(-1) was measured. Field erosion marks surveyed after each rainfall event gave insights to the connectivity at the inter-row and the slope scale. It was found that at the row scale there were sinks of sediments underneath the vines and sources in the inter-row parts, although they are the highest and lowest local topographical terrain, respectively. This is due to tillage erosion that redistributed the sediments. At the slope scale, the lower part of the slope collected sediments from the upper slope positions, which were transported along the middle part of the slope, as the measurement of ISUM and the field survey after intense rainfall events demonstrated. Connectivity of the flows along the whole slope were rare (twice), and along individual slope parts connectivity was found eight times, and 19 at the inter-row scale after 8years of field observations. Copyright (c) 2018 John Wiley & Sons, Ltd.