The role of vegetation patches and antecedent soil moisture conditions in runoff and erosion connectivity in a 4-times burnt pine stand.

Taco Regensburg, Oscar Gonzalez Pelayo, M. Martins, M.R. Hosseini, S.D. Keesstra, Jan Jacob Keizer

Research output: Contribution to conferenceAbstractAcademic


As part of the EU-FP7 project CASCADE, which addresses tipping-points in land degradation of Mediterranean
ecosystems, the degradation drivers of repeated wildfires and post-fire drought spell are being studied in maritime
pine stands in north-central Portugal. Preliminary results indicated that overland flow and sediment losses were
markedly higher at 4–times burnt sites than at one-time burnt sites and, at the same time, that they were markedly
higher at recently burnt than long-unburnt sites. These results, however, concerned micro-plots where post-fire
recovery was mainly due to seeders and, as a consequence, rather reduced during the study period of the first two
years following the wildfire (“inter-patches”). In the framework of COST Action ES1306 (Connecting European
Connectivity Research), the present follow-up study aimed at assessing how the overland flow and erosion generated
at such inter-patches would be “handled” by downslope vegetation patches and, in particular, patches where
the main shrub species in the study area, Pterospartum tridentatum, had re-sprouted. More specifically, this study
wanted to assess: (i) how the sink function of these vegetation patches was influenced by potential flow length or
the length of the upslope inter-patch; and (ii) how it varied through time and, in particular, with antecedent soil
moisture content. The study site is a south-west facing slope in an area that had burnt, with moderate severity, in
early September 2012 and three more times before that since 1975 (as of when burnt area maps are available).
By the time of the 2012-fire, it was covered by a sparse maritime pine stand that was roughly 7-years old. During
October 2014, the study site was instrumented with a total of 12 bounded runoff plots, equally divided over the
three slope sections (upper, middle and lower). At each slope section, four types of plots were laid out using square
plots of 50 cm x 50 cm as basic building blocks. They were: (i) single inter-patch (50 cm x 50 cm); (ii) double interpatch
(50 cm x 100 cm); (iii) vegetation patch plus single upslope inter-patch (50 cm x 100 cm); (iv) vegetation
patch plus double upslope inter-patch (50 cm x 150 cm). This experimental design was envisaged to address the
following hypotheses: (i) runoff and erosion connectivity increase with increasing length of up-slope inter-patches;
(ii) vegetation patches act as effective sinks of run-on and transported sediments from upslope inter-patches; (iii)
the sink function of the vegetation patches is related to the influence of the shrubs on antecedent soil moisture conditions.
The latter hypothesis is tested by means of replicate but unbounded plots next to the above-mentioned 150
cm-long bounded, being instrumented with EC-5 soil moisture sensors to automatically record topsoil moisture
contents in a vegetation patch and upslope inter-patches. The very first results are pointing towards a confirmation
of the first two of the above-mentioned hypotheses.
Original languageEnglish
Number of pages870
Publication statusPublished - 2015
EventEGU General Assembly 2015 - Vienna, Austria
Duration: 12 Apr 201517 Apr 2015


ConferenceEGU General Assembly 2015

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