An Example from the Šumava Mountains, Czech Republic

Geomorphology 383 (2021) 107698 Contents lists available at ScienceDirect Geomorphology journal homepage: www.elsevier.com/locate/geomorph Biogeomorphological domination of forest landscapes: An example from the Šumava Mountains, Czech Republic Jonathan D. Phillips a,b,c,⁎, Pavel Šamonil c a Earth Surface Systems Program, Department of Geography, University of Kentucky, Lexington, KY 40506-0027, USA b Department of Geography, Planning, & Environment, East Carolina University, Greenville, NC 27858-4353, USA c Department of Forest Ecology, Sylva Tarouca Institute, Brno, Czech Republic article info abstract Article history: Biogeomorphological and ecological succession following a disturbance or the exposure of new ground often pro- Received 2 December 2020 ceeds in stages, from domination by abiotic, geophysical factors through stages characterized by increasing Received in revised form 9 March 2021 effects of biota, biotic-abiotic feedbacks, and eventual domination by ecological processes. However, some stud- Accepted 10 March 2021 ies in forest settings have found more varied development patterns, including persistence of states dominated by Available online 13 March 2021 biogeomorphic feedbacks. In this study we investigated this phenomenon In Norway spruce (Picea abies (L.) Keywords: Karst.) dominated forests on the main ridge of the Šumava Mountains in the Czech Republic along the German Biogeomorphic succession and Austrian borders. Throughout most of the Holocene, Picea has strongly influenced microtopography and Feedbacks soil/regolith characteristics so as to inhibit hydrological connectivity and development of surface drainage, and Drainage maintain hydromorphic soil conditions. These strongly historically and geographically contingent ecosystem en- Norway spruce gineering effects create and maintain habitat that favors spruce over other trees. These interactions have main- Ecosystem engineering tained a landscape dominated by biogeomorphic feedbacks. Contingency ©2021ElsevierB.V.Allrightsreserved. Šumava Mountains 1. Introduction fluvial and riparian environments. The concept was later applied to coastal, wetland, and other water-terrestrial interfaces in general After a disturbance or the exposure of new substrate, landscape evo- (Corenblit et al., 2015), glacial moraine slope development (Eichel lution often follows a general trend. At the outset, abiotic phenomena et al., 2016), subalpine alluvial fans (Lane et al., 2016), and recently de- and geochemical and geophysical processes are dominant. Biota soon glaciated areas (Miller and Lane, 2019). The sequence is implicit in pri- colonize, and begin influencing the abiotic environment via processes mary ecological succession in general, where sequences lead from such as biotic weathering of exposed rock, stabilization of substrates, newly exposed abiotic surfaces to mature ecosystems (Walker and del sediment trapping, and production of organic matter. The biotic/abiotic Moral, 2011). This is particularly evident in bare-rock succession, reciprocal interactions and feedbacks typically intensify, with increasing where the biogenic weathering that initiates soil formation and facili- domination by ecological interactions. In later stages, unless or until a tates subsequent biological colonization is strongly controlled by the large disturbance or change in boundary conditions occurs, ecological mineral composition of the material and its initial porosity and other processes dominate and abiotic processes are diminished in impor- physical properties (Chizhikova et al., 2016; Ciccazzo et al., 2016). In tance. However, in some cases more variable and complex developmen- some mature communities, however, vegetation and other biota may tal trends occur, and landscape states dominated by biogeomorphic have no direct dependence on properties of underlying rocks. interactions may persist. This paper examines one such case, in spruce As widely recognized by studies of biogeomorphic or ecological suc- dominated forests of the main ridge of the Šumava mountains in central cession in recent decades, there are often multiple possible succession Europe, to assess the persistence of biogeomorphic domination, and the pathways, and biogeomorphic changes may take the form of state tran- extent to which biogeomorphic ecosystem engineering in this environ- sitions that do not conform to a linear successional model. In some ment benefits the engineer species. coastal salt marshes, for example, Wang and Temmerman (2013) This general sequence above is explicit in the biogeomorphic succes- found that biogeomorphic feedbacks result in oscillation between alter- sion concept developed by Corenblit et al. (2009, 2014), who focused on native stable states. In Mojave Desert landscapes, Pietrasiak et al. (2014) showed that biotically or abiotically-dominated evolutionary trajecto- ries may occur, depending on bioturbation. Complex patterns of ⁎ Corresponding author at: Earth Surface Systems Program, Department of Geography, University of Kentucky, Lexington, KY 40506-0027, USA. geomorphological/ecological state transitions were found in coastal E-mail address: [email protected] (J.D. Phillips). landscape responses to sea-level rise by Phillips (2018a). https://doi.org/10.1016/j.geomorph.2021.107698 0169-555X/© 2021 Elsevier B.V. All rights reserved. J.D. Phillips and P. Šamonil Geomorphology 383 (2021) 107698 In the abiotic domination phase (Fig. 1), organisms and biological ef- mound pairs. Surface runoff is dominated by the pit-mound topography fects may be present, but are minimal compared to geophysical and created by uprooting, with short, unconnected overland flow paths de- geochemical processes and are overwhelmed by the latter. In the abi- livering flow to tree throw depressions. Based on these results, Phillips otic/biotic feedbacks stage, biological effects are still secondary, but et al. (2017) produced an alternative state-and-transition type model have begun to have important impacts on landforms and surface pro- to the biogeomorphic succession sequence (Fig. 1). The key points of cesses. The word reversal in the biotic/abiotic feedbacks phase indicates the alternative scheme are that a progression from abiotic to biotic the biological processes are at least co-dominant—this is the stage domination is not inevitable, other transitions are possible; and that, where biogeomorphological domination may occur. Finally, in the biotic at least in a forest with minimal direct human interventions, a phase, geophysical and geochemical processes are secondary to biolog- biogeomorphic domination state may persist for long periods. ical factors, or at least manifested chiefly through ecological effects. In another Czech old-growth forest, ŽofínskýPrimeval Forest (here- after Zofin) on granite, Šamonil et al. (2020a) examined the role of tree 1.1. Studies in old-growth forests uprooting in soil erosion and deposition on both millennial and decadal time scales using meteoric and in situ 10Be and 239+240Pu, respectively, In a beech-dominated old-growth forest in the flysch Outer Western combined with 43 years of monitoring of tree layer changes, including Carpathians in the Czech Republic, Phillips et al. (2017) found that hill- uprooting. They found that tree uprooting is the main driver of denuda- slope processes at the Razula forest preserve are dominated by tree tion over the last several millennia in this fir-spruce-beech (Abies alba- uprooting. Regolith disturbed by uprooting is the major form of mass Picea abies-Fagus sylvatica) forest. At a third site (BoubínskýPrimeval wasting at the site, and secondary forms (soil and rock creep, ravel, Forest on gneiss and migmatite) dominated by spruce and beech, and small avalanches) occur mainly on slopes of the resulting pit-and- Šamonil et al. (2018) evaluated biomechanical geomorphic effects of 4000 standing and lying trees in a 10.2 ha area. Such effects were re- corded for 59% of standing and 51% of lying dead trees (not counting effects associated with nearly all trees such as soil displacement by thickening trunks and roots and the infilling of decayed stumps). Active bioprotection (sediment trapping and promoting deposition, vs. the ubiquitous passive bioprotection of nearly all living plants) was the most frequent phenomenon observed, while uprooting prevailed in terms of areas and soil volumes affected. The other eight studied biomechanical effects of trees were not so frequently observed, but still geomorphologically significant. A key issue is the extent to which the biogeomorphic ecosystem engineering (BEE) effects favor the engineer species. At Razula, tree throw mounds are favorable sites for establishment of new trees, which (like the uprooted trees) are mostly European beech (Fagus sylvatica); simi- lar results have been found in other central European beech forests (Šebkova et al., 2012). However, It is difficult to prove positive ecosystem engineering effects, as the seed and propagule source is over- whelmingly beech, and the habitat conditions on the mounds, which include good drainage and increased sunlight, are favorable for many plants. If propagules of other trees were present, they might fare equally well on the mounds. Kern et al. (2019), for example, found that mounds in mixed hemlock and hardwood forest favored light-seeded tree species sensitive to browsing. The limited overland flow and increased infil- tration associated with uprooting effects (Phillips et al., 2017) also create favorable soil drainage conditions for Fagus,

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