Long‐term outcome of nitrogen immobilization to restore endemic sand grassland in Hungary

Abstract

Summary1. Soil nitrogen immobilization by carbon amendment is a management technique used for conservation purposes to increase the competitive ability of late-seral plant species over earlyseral species based on their different tolerance of low soil nitrogen content. 2. We immobilized nitrogen over six growing seasons on three ex-arable fields with poor sandy soils in the Hungarian lowland in order to restore endemic sandy grassland. Sucrose and sawdust were applied at rates based on previous laboratory experiments using local soils. We tested the efficacy of long-term carbon amendment for lowering soil nitrogen availability and favouring late-seral native species over early-seral weed species. 3. Carbon amendments resulted in significant increase in soil microbial biomass C and reduced soil nitrogen availability after 2 years. 4. Total vegetation cover was reduced by reducing soil nitrogen availability, but total species richness was not impacted. Cover of early-seral species decreased, and species richness and cover of late-seral species increased irrespective of nitrogen immobilization. However, after 4-6 years reducing soil nitrogen availability hampered the spread of moss under vascular vegetation. 5. Synthesis and applications. This study supports the efficacy of carbon amendment as a tool to immobilize available soil nitrogen in the upper soil layers. However, the desired impact on vegetation was not fully achieved despite application over several years. Nitrogen immobilization was most relevant to bryophytes, lacking deep root systems, which may explain the responsiveness of this group to N limitation. The different impact of N availability on the complex of early-seral, late-seral vascular species and that of the bryophyte layer provides opportunity for directing state transformations in arid grasslands. Bryophyte cover can be suppressed through carbon amendments in order to enhance the germination and establishment of grassland species. The advantage of the method is that it opens bryophyte cover gradually without disturbing the soil surface, possibly avoiding the establishment of invasive species. However, further studies are required for deeper insight.

The application of a filter‐based assembly model to develop best practices for Pannonian sand grassland restoration

“…In our case, ploughing as pre‐treatment might have induced N leaching from the upper soil layer, compared to an earlier study where perennial dominated stands conserved soil available nitrogen (Török et al . ). Carbon amendment slowed down the closure of the vegetation indicating a shortage in plant‐available nutrients and prevented the establishment of mosses, but had little impact on vegetation composition as observed earlier (Török et al .…”

“…Carbon amendment slowed down the closure of the vegetation indicating a shortage in plant‐available nutrients and prevented the establishment of mosses, but had little impact on vegetation composition as observed earlier (Török et al . ). Our results confirm earlier findings that on oligotrophic soils, high nutrient availability is not a limiting factor; rather, species‐specific response might be taken into account to help the establishment of target species (Eschen et al .…”

“…Mowing opened up space for the establishment of both vascular plants and mosses by lowering the amount of litter, but carbon amendment resulted in nutrient shortage preventing vegetation establishment and was lethal to mosses (Török et al . ). Synergistic effects were found between the abiotic and biotic filter for bare ground and litter.…”

Oriental bittersweet (Celastrus orbiculatus): Spreading by fire

“…While treatments that reduce nutrient or resource availability, e.g. sugar, sawdust or compost addition that modify the microbial community (Ishikawa et al, 2013;Török et al, 2014), might aid in control by slowing the rate of post disturbance recovery, their relevance and effectiveness might vary with community. Season of cutting had no effect on cover by the second year, suggesting that the response relative to timing of cutting did not make a difference as far as change in cover and relative cover.…”

Dél-alföldi pókközösségek szerkezete

“…A Kiskunság évi csapadék-mennyisége 550-600 milliméter, az átlaghőmérséklet 10-11°C (Török et al 2003). A régió gyepterületein a kaszálás mellett a legelés a legjellemzőbb tájhasználati típus.…”