Restoration potential of soil seed bank in a changing climate

by Réka Kiss 1*, Balázs Deák 2, Péter Török 3, Béla Tóthmérész 1,2, Orsolya Valkó 4
1 University of Debrecen, Department of Ecology, Egyetem tér 1, Debrecen, H-4032 Hungary
2 MTA-DE Biodiversity and Ecosystem Services Research Group, Egyetem tér 1, Debrecen, H-4032 Hungary
3 MTA-DE Lendület Functional and Restoration Ecology Research Group, Egyetem tér 1, Debrecen, H-4032 Hungary
4 MTA-DE Lendület Seed Ecology Research Group, Egyetem tér 1, Debrecen, H-4032 Hungary *kissreka801@gmail.com

Climate change is a hot topic at the top of everyone’s mind. Increasing temperature and changes in precipitation patterns have led to irreversible changes in plant communities. Vascular plant species are among the most threatened organisms (IPCC 2013), due to their generally low dispersal ability (Thomas et al. 2004, Thullier et al. 2005). Many of the plant species and habitats face serious decline due to the predicted climatic and land use changes. Moreover, there is a considerable knowledge gap in the response of the soil seed bank to the changing climate. The soil seed bank serves a vital role in the conservation of plant species and restoration of plant communities (Valkó et al. 2011, Kiss et al. 2016, Török et al. 2018a). The are knowledge gaps in our understanding of seed banks of the different ecoregions, which make it challenging to predict how climatic changes affect the present plant communities.

In a recent special issue in Restoration Ecology edited by Péter Török, Aveliina Helm, Kathrin Kiehl, Elise Buisson, and Orsolya Valkó, the main topics were seed dispersal and seed bank ecology (Török et al. 2018b). In one of the review papers published in that issue we synthesized the existing knowledge about the seed bank of various open habitats and the effect of climate change on them (Kiss et al. 2018). Due to the very few direct climate manipulation studies in open habitats with respect to soil seed bank, we provided a new perspective to reveal the possible effect of climate change on the soil seed bank. Precipitation and temperature changes are primary effects of climate change, which lead to several indirect effects, like changes in fire regimes, drought and inundations. Therefore, we reviewed seed bank studies, which considered these effects of climatic changes on the soil seed bank of grasslands and wetlands. We also reviewed the restoration potential of the seed bank of various habitat types under changing climatic conditions. For climate change predictions we used the models of IPCC (2013) for the 2016-2035 time period.

Evaluating the reports of these papers we found that decreasing precipitation is a more important driver of soil seed bank changes than increasing temperature. Decreasing precipitation level likely affect the central portions of continents, while precipitation level may increase in the coastal areas. The changes in precipitation regimes combined with increasing temperature will have serious effects on the open habitats.

Fire regimes may change due to changes in the amount of fuel and ignition conditions. Less precipitation and higher temperature may increase the possibility of fire ignition while increasing precipitation increases the amount of combustible biomass. Open grassland habitats are especially fire-prone ecosystems, where changes in fire regimes will fundamentally change the structure of grasslands. The germination of many seeds is triggered by fire or fire components (Ghebrehiwot et al. 2011). Unfavorable climatic conditions (such as drought) after fires may increase seedling mortality and change vegetation and seed bank structure. Low-frequency fire can be beneficial even in temperate, non-fire-adapted ecosystems, but high-frequency fires are detrimental to the plant communities and can destroy the seed bank of fire-prone ecosystems.

Climatic changes will substantially alter fire regimes. Photo by Balázs Deák.

Climatic changes will substantially alter fire regimes. Photo by Balázs Deák.

Besides fire regimes, timing and duration of inundation are also expected to change in the future. The studied flood-dependent ecosystems in tropical and subtropical regions may benefit from an increased precipitation level, their species-richness and seed bank density are not in a direct danger (Bao et al. 2014). In temperate wetlands both increased and decreased precipitation level is forecasted in the future. Increased precipitation level will help wetlands restoration by rewetting. Where precipitation increases, the frequency or the severity of flooding events may also increase. In general, flooding increases the species richness and density of the soil seed bank but extreme floods can wash away the seeds (Herrick et al. 2007). However, in many riverine ecosystems decreased precipitation level is predicted, which may result in fewer inundations. In such communities persistent seed banks are particularly important.

Drying out of a wetland in Tebepuszta, North Hungary. The photos were taken in 2011, 2014, and 2018 by Judit Fekete. The lone willow shrub can serve as a reference point.

Drying out of a wetland in Tebepuszta, North Hungary. The photos were taken in 2011, 2014, and 2018 by Judit Fekete. The lone willow shrub can serve as a reference point.

Based on the seed bank type of the studied ecosystems we also concluded that habitats characterized by frequent or unpredictable disturbances, like fire-prone grasslands or flooded wetlands, can buffer the forecasted effects of climate change by their persistent seed bank. However, stable habitats like temperate grasslands have only transient seed banks (Kiss et al. 2016), which cannot buffer the predicted changes. To conserve these habitat types intervention is needed (Valkó et al. 2016): seed addition of native species that can tolerate the forecasted climatic conditions should be prioritized. Future restoration must account for the predicted climatic changes when selecting target species of restoration.

For the restoration of dry grasslands, high-diversity seed mixtures containing several native species that are able to tolerate the predicted future climatic conditions should be prioritized. In a large-scale grassland restoration in Hortobágy National Park, Hungary we used seed mixture of 35 native species (Valkó et al 2016). Photos by Tamás Miglécz.

For the restoration of dry grasslands, high-diversity seed mixtures containing several native species that are able to tolerate the predicted future climatic conditions should be prioritized. In a large-scale grassland restoration in Hortobágy National Park, Hungary we used seed mixture of 35 native species (Valkó et al 2016). Photos by Tamás Miglécz.

References

Bao, F., Pottm A., Ferreira, F.A., Arruda, R. (2014) Soil seed bank of floodable native and cultivated grassland in the Pantanal wetland effects of flood gradient season and species invasion. Brazilian Journal of Botany 37: 239-250.

Ghebrehiwot, H.M., Kulkarni, M.G., Kirkman, K.P., van Staden, J. (2011) Smoke and heat influence on seedling emergence from the germinable soil seed bank of mesic grassland in South Africa. Plant Growth Regulation 66: 119-127.

Herrick, B.M., Morgan, M.D., Wolf, A.T. (2007) Seed banks in diked and undiked Great Lakes coastal wetlands. The American Midland Naturalist 158: 191-205.

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Török, P., Kelemen, A., Valkó, O., Miglécz, T., Tóth, K., Tóth, E., Sonkoly, J., Kiss, R., Csecserits, A., Rédei, T., Deák, B., Szűcs, P., Varga, N., Tóthmérész, B. (2018a) Succession in soil seed banks and its implications for restoration of calcareous sand grasslands. Restoration Ecology 26: S134-S140.

Török, P., Helm, A., Kiehl, K., Buisson, E., Valkó, O. (2018b) Beyond the species pool: Modification of species dispersal, establishment and assembly by habitat restoration. Restoration Ecology 26 (S2): S65-S72.

Valkó, O., Török, P., Tóthmérész, B., Matus, G. (2011) Restoration potential in seed banks of acidic fen and dry-mesophilous meadows: can restoration be based on local seed banks? Restoration Ecology 19:.9-15.

Valkó, O., Deák, B., Török, P., Kirmer, A., Tishew, S., Kelemen, A., Tóth, K., Miglécz, T., Radócz, Sz., Sonkoly, J., Tóth, E., Kiss, R., Kapocsi, I., Tóthmérész, B. (2016) High-diversity sowing in establishment gaps: a promising new tool for enhancing grassland biodiversity. Tuexenia 36: 359-378.