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A key challenge for sustainable intensification of agriculture is to produce increasing amounts of food with less negative environmental impacts. The main goal of SOFT (Steering Organic Farming Transition) is to understand the role of soil biodiversity and networks for a sustainable farming, and the potential use of soil inoculation for soil regeneration. For this, I will use a chronosequence of farmers’ fields throughout The Netherlands that have been converted from conventional to organic farming. Taken together, SOFT will contribute to establish management practices that may help accelerate the transition from conventional farming to a more organic type of farming., This poster was presented at NERN-2021. Tuesday 9 February 2021. https://www.nern.nl/poster-session-1

We investigated the role of biotic factors in determining abundance of the low marsh species Phragmites australis and the high marsh species Epilobium hirsutum. In a 2-year field experiment, at a position where Phragmites and Epilobium co-occurred, responses of both species to each other's removal were measured. In the second year, we also tested if larvae of Archanara geminipuncta, which feed exclusively on Phragmites shoots, affect the competitive ability of Phragmites relative to Epilobium. For both species, removal of aboveground material by clipping did not enhance shoot size or decrease variability in shoot size of the removed species itself. Surprisingly however, shoot numbers of both species increased after removal of the other, which demonstrates that there was a mutual inhibition of each other's abundance. Comparing the responses of Archanara-infested and non-infested Phragmites shoots revealed no increased competitive suppression by Epilobium due to selective herbivory. Instead, we found that herbivore activity was lower in plots with Epilobium, which demonstrates that Archanara population size is reduced by the presence of non-host plant species. These results contradict the common assumption that biotic factors constrain a species upper limit along flooding gradients. Instead, our result suggest that different biotic interactions may counteract each other and thus slow down replacement by successive species. (C) 2003 Elsevier B.V. All rights reserved.

In shallow flooded parts of rich fens Mentha aquatica might thrive in deeper water than Epilobium hirsutum but previous experiments have provided no clear indication that the flooding tolerance of these species differs. In this study we investigated, by measuring growth, biomass allocation and vegetative reproduction, whether the impact of water level on vegetative reproduction might produce different lower boundaries on water level gradients. There was a striking contrast between biomass production at high water levels and the field distribution of both species. After 18 wk, the mean biomass of E. hirsutum grown in waterlogged and flooded conditions was 82% and 54%, respectively, of the mean biomass production of drained plants. Biomass of waterlogged and flooded M. aquatica was reduced to 57% and 37% in drained conditions. Waterlogged and flooded E. hirsutum had swollen stem bases and invested a high proportion of biomass in adventitious roots. Stems of M. aquatica did not swell, formed few adventitious roots and maintained an equal proportion of below-ground roots at all water levels. The effect of water level on vegetative reproduction corresponded well with the lower hydrological boundaries of both species. When waterlogged and flooded, most rhizomes of E. hirsutum emerged from above-ground parts of the stem base and were oriented in an upward direction. Plants in flooded soil allocated less biomass to rhizomes and also reduced the number and size of rhizomes. Rhizome formation of M. aquatica on the other hand was not directly affected by water level and only depended on plant size. These differences in vegetative reproduction are discussed in relation to the different abilities of both species to oxygenate their below-ground roots. It was concluded that the mode of adaptation to soil flooding might also affect vegetative reproduction and, therefore, a species' ability for long-term persistence in soil-flooded habitats.

In coastal foredunes marram grass (Ammophila arenaria) is used to stabilize windblown sand. The development of traditionally plantedAmmophila into a more natural foredune vegetation may take 5–10 yr. For economic reasons, traditional planting may be replaced by alternative techniques such as planting seeds or disk-harrowing rhizome fragments. In this paper, we compare the initial vegetation development of traditionally planted stands with stands established from seeds and from rhizomes. The experiments were conducted on an artificial foredune originating from dredged sea sand. The total experimental area covered more than 100 ha and the vegetation development was studied for 6 yr. The data were analysed bya priori grouping of plant species according to their ecology, as well as by Principal Components Analysis (PCA) and Redundancy Analysis (RA) of the percentage ground cover per plant species. Comparing ecological groups of plants showed that all planting methods delivered equal numbers of plant species that are indicative for coastal dunes. PCA and RA showed that methods based on the use of rhizome material resulted in a higher percentage cover of clonal perennials (Calammophila baltica, Festuca rubra ssp.arenaria, Carex arenaria andCirsium arvense) than the traditionally planted stands and the stands obtained from seeds. The latter two were characterized by the dominance of annuals, bi-annuals and (mostly nonrhizomatous) perennials. Initially, the rates of succession were highest in the stands obtained from rhizomes. However, after 3–6 yr there were no differences between the various stands. During the first four years, the percentage cover by rhizomatous foredune plants developed faster than that of annuals, bi-annuals and perennials. After 6 yr, the latter contributed almost as much to the percentage cover as the clonal species.

Three successive emergent macrophytes (Typha latifolia L., Phragmites australis (Cav.) Steudel and Glyceria maxima (Hartman) Holmbly) were each grown in substrates collected from three different zones of shoreline vegetation development (non- vegetated sediment, the interface between T. latifolia and P. australis, and degenerating P. australis). The aim of the study was to assess whether accumulation of litter changes growth conditions of P. australis, and to determine its effects on pre- and post successional plant species. The study was carried out by means of pot experiments in a glasshouse. Seedlings of the three species were cultured in fertilized and unfertilized substrates under both waterlogged and drained conditions. In its own litter, growth of P. australis was strongly reduced, compared with the productivity of plants in substrates from preceeding successional stages, and could not be compensated for by fertilization or soil drainage. The redox potential of the substrate was not strongly reduced and the sediment density was well above the critical level. Soil sterilization by gamma- irradiation did not improve growth substantially, although there was some positive effect in unfertilized substrate. Phytotoxic compounds might have caused poor growth of P. australis in its own litter. T. latifolia and G. maxima were relatively less affected by the P. australis litter. The possible importance of litter accumulation on species replacement in shoreline vegetation is discussed. It is concluded that the accumulation of organic matter should be considered as a factor affecting spatio-temporal processes in littoral vegetation owing to its specific impact on the functioning of individual dominant plant species. [KEYWORDS: littoral vegetation; succession; phytotoxins; Phragmites australis; anaerobe decomposition Spartina-alterniflora; soil; marsh; vegetation; sediment; plants; roots; reed; decomposition; netherlands]

Die-back and healthy stands of Phragmates australis (Cav.) Trin. ex Steud. in the UK and Hungary were compared in terms of stand architecture, plant morphology and anatomy, sediment redox potential and sulphide levels, plant resistance to internal Poiseuille gas flow, and convective flow characteristics of culms. Compared with healthy sites, die-back sites were characterized by lower sediment redox potentials, and in Hungary by very high sulphide levels. Plants at die-back sites showed a markedly clumped distribution, with fewer new shoots and fewer old flower heads than those at healthy sites, a high incidence of dead and decaying rhizomes and roots, and dead 'overwintering' and 'growing season' buds, and occasional prematurely senesced culms. Dead and stunted adventitious roots with short peg-like laterals were very common, and there was abnormal lignification and suberization within the cortex and epidermis/hypodermis of adventitious root apices, and in the epidermis of lateral roots. Callus was found blocking the internal aeration pathways in root aerenchyma, root-rhizome junctions, rhizome nodes and the bases of buds and culms. Blockages of the Vascular elements of both xylem and phloem in rhizomes and roots were also common. At the die-back sites, callus accounted for a greater resistance to gas flow from the dead aerial culms into the rhizome system. Compared with healthy culms, prematurely senesced culms from die-back sites exhibited smaller potentials for aerating the rhizome system by humidity-induced convection. It is suggested that die-back in Phragmites might be brought about and perpetuated at least partly by phytotoxins which induce (a) blockages within the aeration pathways due to callus development, (b) stunting of roots and the development of abnormal root wall lignification and suberisation causing interference with water and mineral absorption, and (c) internal blockages causing interference with vascular transport. A tentative scheme for Phragmites die- back is presented. [KEYWORDS: aeration; Phragmites die-back; callus;phytotoxins; sulphide Trin-ex-steudel; spartina-alterniflora; flood tolerance; reed beds; australis; oxygen; rhizosphere; inhibition; resistance; transport]

Plant-parasitic nematodes have traditionally been studied in agricultural systems, where they can be pests of importance on a wide range of crops. Nevertheless, nematode ecology in natural ecosystems is receiving increasing interest because of the role of nematodes in soil food webs, nutrient cycling, influences on vegetation composition, and because of their indicator value. In natural ecosystems, plant-parasitic nematode populations can be controlled by bottom-up, horizontal and top-down mechanisms, with more than one mechanism acting upon a given population. Moreover, in natural ecosystems soil nematodes inhabit probably more heterogeneous environment than in agricultural soils. New breakthroughs are to be expected when new molecular-based methods can be used for nematode research in natural ecosystems. Thus far, nematode ecology has strongly relied on coupling conventional abundance and diversity measurements with conceptual population ecology. Biochemical and molecular methods are changing our understanding of naturally co-evolved multitrophic plant-nematode-antagonist interactions in nature, the inter-connections within the soil food web and the extent to which nematodes are involved in many, disparate, soil processes. We foresee that finer nematode interactions that lead to their management and control can only be fully understood through the joint effort of different research disciplines that investigate such interactions from the molecular to the ecosystem level.

Plant‐parasitic nematodes are major crop pests in agro‐ecosystems while in nature their impact may range from substantial to no significant growth reduction. The aim of this review is to determine if nematode population control in natural ecosystems may provide us with a model for enhancing sustainable control of nematodes in crops. In agricultural systems, monocultures, narrow rotations, alteration of the soil habitat, and fertilization may alter plant‐parasitic nematode dynamics and boost nematode numbers while reducing diversity and effectiveness of top–down control organisms and protective mutualisms (endophytes and arbuscular mycorrhizal fungi). Traditional agro‐ecosystems (still applied in tropical regions) involve the development of complex practices such as a broad range of plant species of high genetic diversity grown in associations, rotations, and shifting cultivation, which all influence the complexity of plant‐parasitic nematode communities and of control organisms. In nature, plant‐parasitic nematodes (and other root feeders and soil pathogens) drive plant community processes, such as succession and plant species diversity. Natural soils contain a wide variety of potential nematode control organisms, but the consequences of this diversity are not known. Wild plant populations also contain more genetic variability than crops, but consequences for coevolution and Red Queen processes for nematode populations have not been studied. We conclude that integrated crop pest control may benefit from studying plant‐parasitic nematode—natural antagonist interactions in natural systems, which have been coevolved for longer than crop‐nematode–antagonist systems. Understanding how wild plants control their plant‐parasitic nematodes may ultimately result in improving the sustainability of crop protection against plant‐parasitic nematodes.

• Community ecologists often assume a hierarchy of environmental sieves to predict the impact of multiple stresses on species distribution. We tested whether this assumption corresponds to physiological responses using impact of water level and shade in wetland vegetation as a model. • Seedlings of four wetland species were grown under full light and simulated canopy shade, both in drained and waterlogged soils. When subject to both stresses simultaneously, waterlogging and shade independently affected growth of the two waterlogging tolerant species. For the intolerant species, however, waterlogging had the largest impact and the additional effect of shade was smaller than the effect of shade in drained soil. Soil flooding decreased specific leaf area but only if plants were in full light. Waterlogging did also not constrain a higher investment in stems of shaded plants. • These results demonstrate that light limitation in flooded habitats only plays a role if species can tolerate waterlogging and therefore correspond with the notion that water level determines the potential species pool and that standing crop consequently determines which species can actually persist.

We investigated how water level and different sediment types affect the growth of wetland plant species. Twelve different species were grown in drained and waterlogged sediments, which represented types normally encountered in wetlands: a mineral sediment from exposed sites, a sediment from a sheltered site rich in labile organic matter and an organic sediment with decomposing litter of Phragmites australis (Cav.) Steudel. The tested species included both subordinate and dominant species inhabiting flooded or dry parts of the water-depth gradient. Due to nutrient limitation, biomass production of most species was lowest in the mineral sediment. In this substrate waterlogging only affected Cirsium arvense and Eupatorium cannabinum which were reduced to 30% and 16% of the production in the drained sediment. Most species performed best in the sediment with labile organic matter, even when waterlogged. Waterlogging in the reed litter sediment, when compared to the drained reed litter, decreased growth of six species: Iris pseudacorus by 40%, Myosotis scorpioides by 60%, Rorippa amphibia by 25%, Sium latifolium by 50%, Eupatorium cannabinum by 80%, and Epilobium hirsutum by 70%. The differences in plant performance between both organic sediments may be due to the presence of refractory organic matter. The specific responses in the reed litter sediment contrasted with the similar response to both other sediments. These results show that accumulation of litter, instead of accumulation of organic matter in,general, will be an important factor in determining species composition of littoral zones. They also indicate that, although litter does not favor subordinates above clonal dominants, litter accumulation may enhance species diversity on a large scale. [KEYWORDS: littoral vegetation; litter; organic matter; species diversity; zonation Emergent vegetation; growth; macrophytes; lake; decomposition; limitation; aeration; detritus; patterns; zonation]

Ammophila arenaria (marram grass) is the most important plant species for sand stabilization in European coastal foredunes. Stand degeneration due to poor supply of wind-blown sand enhances the susceptibility for wind erosion when successional species do not become established. Replanted A. arenaria often fails to become established. In the present study we examined whether management practices such as mowing, fertilizing, burning or below-ground cutting of plants may be applied to re-establish the vigour of A. arenaria. Field experiments performed at exposed sites, where naturally succeeding plant species are not supposed to become established due to salt spray, showed that none of the applied methods resulted into enhanced tiller density of A. arenaria. Thus, further studies are necessary to solve this type of management problem. At the leeward side of foredunes, the successional species Festuca rubra ssp. arenaria and Elymus athericus could be established successfully as both pre-grown seedlings and planted bundles of cuttings (all further experiments were fertilized). When planted in spring, cuttings of successional plant species established less than those planted in early winter. Water repellency of the sand surface is supposed to be the main cause for this. Pre-grown seedlings were less susceptible for the season of planting. Direct sowing was not effective. Rabbit browsing had to be omitted to obtain successful establishment. When living rhizomes of successional plant species were still present in the soil profile, fencing alone turned out to be effective to re-establish vegetation at initially bare sites