Long-term effects of different grassland management types on plant species composition in protected landscape areas

Ing. Jan Titěra

Doctoral thesis

Abstract:

1.Central European semi-natural hay grasslands Semi-natural grasslands are known to provide numerous ecosystem services, of which one of the most important is production of biomass. However, the contribution of individual plant species to the total biomass is much less well understood. This study addressed questions concerning community structure and responses of species-specific biomass (s-AGB) to gradients in soil acidity and fertility, topographical and climatic features, and disturbance regimes in mown and abandoned grasslands in the Sudetes Mountains (Central Europe). It identified pH as the most significant environmental gradient affecting turnover in s-AGB, and mowing cessation, temperature, and precipitation also had significant effects. Further, it showed high inequality in biomass among co-occurring plant species. It also showed that biomass inequality (measured by the Gini coefficient) among interacting species decreases with increasing functional diversity (Rao’s index). This study highlights that common plant species (in terms of frequency) play a major role in contributing to the total aboveground biomass (t-AGB). However, less frequent species are also significant contributors to the t-AGB. Thus, the combined contribution of infrequent species to the t-AGB should not be neglected. Our findings support the mass ratio hypothesis stating that ecosystem functions such as biomass production depend on dominant species. On the other hand, high niche differentiation ensures the coexistence of less competitive species with the dominants by the variety and complementarity of functional traits. Infrequent and non-dominant species were the core of the diversity seen in the studied grasslands. The maintenance of species diversity in grasslands should be prioritized in nature conservation policies to ensure the sustainability of ecosystem services. 2.Rengen Grassland Experiment Questions: Fertilizer application is a key driver affecting the diversity and conservation value grassland vegetation. Using a long-term fertilization experiment in mountain grassland we addressed the following questions: i) what is the effect of long-term fertilizer applications on species richness and plant species composition, and ii) is there any detectable trend in plant species composition during ten years of continuous observation? Location: the Rengen Grassland Experiment, Eifel Mountains, Germany (established in 1941). Methods: Five treatments including different fertilizers applied annually and one unfertilized control were analysed: Ca (718 kg Ca ha-1); CaN (752 Ca and 100 N kg ha-1); CaNP (752 Ca, 100 N and 35 P kg ha-1); CaNP-KCl (752 Ca, 100 N, 35 P and 133 K kg ha-1); CaNP-K2SO4 (752 Ca, 100 N, 35 P and 133 K kg ha-1). The experiment included five replicates per treatment in a fully randomised block design. All treatments were cut twice a year in late June or early July, and in mid-October. Percentage cover of individual plant species was estimated by visual observation in each plot in late June in the years 2005-2014. Results and discussion: Despite inter-annual variability in the cover of the individual vascular plant species, the multivariate data analyses revealed relatively similar response of the plant community to the different fertilizer applications throughout the ten years. No differences in botanical composition among treatments with phosphorus application were found; however, they differed from other treatments without phosphorus application. In the unfertilized control there was a certain directed trend in plant species composition in response to ongoing nutrient impoverishment. Conclusion: Species rich grasslands of high nature conservation value were only maintained under P-limitation in the control without fertilizer application (Violion caninae), in the liming treatment (Polygono-Trisetion), but also in the treatment with liming and pure N addition. It seems that some stage of equilibrium of grassland commun

Abstract:

ity was achieved in all treatments receiving any type of fertilizer application after 74 years, but less so in the unfertilized control treatment. 3.Admont Grassland Experiment Fertiliser application is a widely used management technique for increasing forage production from agricultural grassland. Fertilisation is also a key driver of changes in soil nutrient status and plant species composition of grassland as shown in many short-term studies. Results from long-term experiments can further improve understanding of plant-soil relationships and help with management recommendations for agricultural and environmental outcomes. We collected data from a long-term experiment on alluvial meadow (Admont Grassland Experiment, Austria; established 1946) with 24 fertilisation treatments managed under a three-cut regime. Soil sampling in autumn 2015 and vegetation sampling in spring 2016 were conducted in seven selected treatments. Combinations of N (nitrogen 80 kg ha-1), P (phosphorus 35 kg ha-1) and K (potassium 100 kg ha-1) were applied annually and compared with a non-fertilised control. Treatments were: Control, N, P, K, NP, NK, PK and NPK fertilisation. Long-term different fertilisation affected soil pH and nutrient concentrations in the soil and plant species composition, but no significant effects on species richness were found. Short species (< 0.5 m height) prevailed in all treatments regardless of nutrient application, probably as a result of the three-cut defoliation. The dry matter biomass (DMB) yield in the Control was limited by N and P and synergisticly co-limited by N, P and K, and DMB yields of more than 5 t ha-1 per year were achieved under nutrient combinations containing P (NP, PK, NPK) without loss of species richness. Results from the Admont Grassland Experiment show that the tested nutrient combinations significantly increased DMB yield and changed the species composition, but without significant effects on species richness. Long-term biomass yields of more than 5 t ha-1 DMB per year can be achieved with any nutrient combination containing P without loss species richness in an alluvial meadow managed under a three-cut regime. 4.Nízké Tatry Mts. grassland experiment Rumex obtusifolius infestation is a serious problem in gathering places of livestock in mountain grasslands. In order to control this weed a long term experiment was established in the Nízké Tatry Mts (Slovakia) in 2004. The treatments were: i) unmanaged control, ii) cutting twice per year, iii) herbicide application (glyphosate) and grass/forbs mixture reseeding in the first experimental year followed by cutting twice a year in all subsequent experimental years. Cover of plant species (%) were visually estimated in the experimental plots every year (2004 -2011) in late June. The results showed that one-time herbicide application with consequent grass/forbs mixture reseeding reduced the cover of R. obtusifolius to 3 % after the first experimental year. Consequently, this cover was further decreased by cutting twice a year and even led to R. obtusifolius disappearance in 2008, which remained until the end of the experiment. Cutting twice a year led to a gradual reduction of R. obtusifolius from 77 % to 3 % during the experimental time, but it did not lead to its complete eradication. On contrary, unmanaged plots supported R. obtusifolius and its high cover about 75% maintained during all experimental years. This long-term experiment showed that single-use herbicide application with subsequent grass/forb mixture reseeding and cutting twice a year in the following years can completely suppress R. obtusifolius and establish grasslands with desirable species composition. However, the long term cutting twice per year seems to be also efficient to control R. obtusifolius, especially on sites where herbicide application is prohibited. 5.Malá Strana grassland experiment Questions: Typha latifolia causes serious problems in wet meadows by overgrowing and suppressing other native plants. To find suitable management for T. latifolia control, we addressed the following question: What are the effects of long-term cutting at different frequencies (once or twice per year and no management) and biomass removal on cover and other characteristics of T. latifolia, and on sward productivity and plant species composition? Location: Malá Strana nature reserve, situated in the Jizerské hory Mountains, Czechia. Methods: A long-term experiment arranged in a randomised block design with three blocks was established in 2005. Data were collected from five treatments: unmanaged control; cutting once a year in June without biomass removal and with biomass removal; cutting twice per year in June and August without biomass removal and with biomass removal. Percentage cover of T. latifolia and other vascular plant species was visually estimated and T. latifolia characteristics (tiller density, height, dry matter biomass (DMB) yield and litter), sward height and DMB yield were measured during 2005-2018 at the end of June. Results and discussion: Regular cutting once or twice per year regardless of cut biomass removal led to reductions in tiller density, height, litter and DMB yield of T. latifolia. Biomass removal had only a slight tendency to affect T. latifolia characteristics. The higher rate of cutting intensity significantly decreased the mean T. latifolia cover, litter and DMB yield. Cutting once or twice per year regardless of biomass removal led to the successive changes in plant species composition but had no effect on the number of plant species and evenness. Conclusions: Cutting at least once per year without biomass removal seems to be sufficient to achieve a decrease in cover, DMB yield and litter of T. latifolia plants, and thereby maintain the wet-meadow vegetation without loss of species richness and also preventing the overgrowth of shrubs and trees.

Keywords

Biomass inequality, Niche differentiation, botanical composition, Abandonment, fertilizer applications, vegetation equilibrium, Cutting, Species richness, dock weed, reseeding, biomass removal, dry matter biomass yield, Typha latifolia characteristics

Jazyk práce: English

Datum vytvoření / odevzdání či podání práce: 24. 1. 2023

Obhajoba závěrečné práce

• Vedúci: prof. Dr. Ing. Vilém Pavlů
• Oponent: Josef Hakl, prof. Ing., Ph.D., František Krahulec, externi

Czech University of Life Sciences Prague

Faculty of Environmental Sciences

Doctoral programme / odbor:
Ecology / Ecology