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Plant litter decomposition is a key ecosystem process in carbon and nutrient cycling, and is heavily affected by changing climate. While the direct effects of drought on decomposition are widely studied, in order to better predict the overall drought effect, indirect effects associated with various drought‐induced changes in ecosystems should also be quantified. We studied the effect of an extreme (5‐month) experimental drought on decomposition, and if this effect varies with two dominant perennial grasses, plant parts (leaves vs. roots), and soil depths (0–5 cm vs. 10–15 cm) in a semi‐arid temperate grassland. After 12 months, the average litter mass loss was 43.5% in the control plots, while only 25.7% in the drought plots. Overall, mass loss was greater for leaves (44.3%) compared to roots (24.9%), and for Festuca vaginata (38.6%) compared to Stipa borysthenica (30.5%). This variation was consistent with the observed differences in nitrogen and lignin content between plant parts and species. Mass loss was greater for deep soil (42.8%) than for shallow soil (26.4%). Collectively, these differences in decomposition between the two species, plant parts, and soil depths were similar in magnitude to direct drought effect. Drought induces multiple changes in ecosystems, and our results highlight that these changes may in turn modify decomposition. We conclude that for a reliable estimate of decomposition rates in an altered climate, not only direct but also indirect climatic effects should be considered, such as those arising from changing species dominance, root‐to‐shoot ratio, and rooting depth. [ABSTRACT FROM AUTHOR]

Theavailability of seeds of native species in many countries for grassland restoration is limited; therefore, ex situ seed banks can gain importance as a source of germplasm in the future. We tested the usability of seed accessions of the Pannon Seed Bank for reintroduction with the aim to restore sandy grassland in Hungary. Seeds of 10 native sandy grassland species were seeded in the year of collection and after one or two years of storage. The establishment was estimated by counting seedlings along seeded transects for two vegetation seasons. This study produced the first numerical estimate we know about of native sand grassland species emergence in the field. A low establishment of the tested species was found, ranging from 0.002 to 8%. Within this range, Dianthus serotinus had the highest establishment, while Festuca vaginata, which was sown as matrix species, performed only medium establishment. The short‐term storage (1 or 2 years) of seeds had no significant effect, except for F. vaginata, where seed storage had a positive effect on reintroduction success. The year of seeding had the highest influence on recruitment. Four species were found to emerge over two years instead of only the first year. Based on our results, the weak seed yield of certain years and the low supply of native seeds in the market can be mitigated by using stored seeds. It is recommended to use multi‐year, scheduled seeding to reduce the negative impacts of particularly dry years and to increase the restoration success. [ABSTRACT FROM AUTHOR]

The impacts of year-round nocturnal warming or late spring rain exclusion on three plant functional types were studied in a plot-scale climate simulation experiment in a semiarid sand forest-steppe of Central Hungary. Ecophysiological traits were followed through six years for the C3 bunch grass Festuca vaginata, the spreading C4 grass Cynodon dactylon and shrub-sized root suckers of Populus alba. In general, experimental treatments had slighter effects than weather fluctuations yielding extremities did. Populus alba responded to nocturnal warming with developing slenderer leaves. Rain exclusion reduced leaf physiological activity or growth, but only during or just after the treatment, and in certain years. When assessing treatment and background climatic variation effects together, in spring, leaf area growth was consistently stimulated by increasing temperature, but decreased with longer rainless periods for P. alba and F. vaginata. Physiological responses in spring indicated low temperature limitation for C. dactylon, and both low and high temperature control for P. alba. Longer summer droughts reduced leaf gas exchange, particularly for F. vaginata with substantial drop in photochemical activity and chlorophyll content. These results suggest that shallow rooted C3 bunch grasses can be the most susceptible to climatic variation, thus their abundance is expected to decline in the Pannonian forest-steppe. In contrast, plants having deeper roots and clonal integration will probably be less affected by the projected warming and drying climate. C4 photosynthesis or southern geographical distribution may also be beneficial, thus, the abundance of such species is expected to diminish less or even increase. [ABSTRACT FROM AUTHOR]

Relationships between seed germination response to plant-derived smoke and various plant traits (habitat requirements, life form, seed morphology, seed bank type) were analysed for 97 species of the Hungarian flora using published data. It was hypothesized that smoke-responsive species – those displaying enhanced germination in response to smoke – differ from non-responsive species – smoke having an indifferent or inhibitory effect on germination – in habitat requirements and/or certain life history traits. To our knowledge, no such comparison has previously been reported for a European flora. We found that species indicating disturbance and those preferring soils rich or moderately rich in nitrogen were more frequent in the smoke-responsive group (80% and 41%, respectively) than in the non-responsive group, while the non-responsive group contained a high percentage of natural species (i.e. species dominant or characteristic in natural plant communities; 47%) and species indicative of nutrient poor (38%) or (sub)mesotrophic (38%) soils. Annuals or biennials (67%) dominated the smoke-responsive group, whereas in the non-responsive group these short-lived species and perennial herbs were equally abundant (43% each). There was a tendency for higher frequency of long-term persistent seed bank among smoke-responsive species (78%) than in the non-responsive group (54%). These findings suggest that smoke-stimulated germination is associated with only a few specific plant traits for species from a semiarid temperate region of Europe, but highlight the frequent occurrence of smoke-enhanced germination among short-lived, nitrophilous or disturbance tolerant species. These results can contribute to a better understanding of post-fire regeneration of plant communities, and could also be considered during vegetation restoration or weed management. [ABSTRACT FROM AUTHOR]

Abstract: Transient and steady state responses of leaf gas exchange (photosynthesis (A) and stomatal conductance to water vapor (g s)) to marked changes in photosynthetic photon flux density (PPFD) were studied for two invasive [Cynodon dactylon (L.) Pers. and Sorghum halepense (L.) Pers.] and two non-invasive, native [Bothriochloa ischaemum (L.) Keng and Chrysopogon gryllus (Torn.) Trin.] perennial C4 grass species from semiarid temperate grasslands or croplands. Following an abrupt drop in PPFD from 1300 to 270μmol photon m−2 s−1, the two invasive species reduced g s to a greater extent than A, resulting in higher intrinsic photosynthetic water use efficiency (PWUE= A/g s) at low, compared to high-light conditions. For non-invasives, a comparable drop in g s and A led to invariant PWUE, which was lower than that for the invasive group under low light. The duration and speed of stomatal closure was similar for the four species. However, unlike the other grasses, the noxious weed S. halepense exhibited a negligible net loss in PWUE during the high-to-low light transition. Responses of the native B. ischaemum were mostly intermediate between those of the two invasive species and the non-invasive C. gryllus, which is in agreement with the species’ ecological intermediacy: non-invasive but often reaches local dominance following a disturbance. With a sudden reverse change in PPFD photosynthetic light induction was not faster for invasives than for non-invasives. These results indicate more efficient water use under variable light for invasive compared to non-invasive perennial C4 grasses which may contribute to their success in semiarid temperate habitats with a heterogeneous light regime. Yet, rapid photosynthetic light induction appears to be of less importance in such environments. [Copyright &y& Elsevier]

Summary: After clearcutting xerothermic oakwoods once natural in semiarid temperate loess regions of Hungary the perennial understorey grass Brachypodium pinnatum (L.) Beauv. may persist through decades and often dominates grasslands maintained by grazing and/or cutting in the place of former oakwoods. This grass also successfully establishes from low- to high-light microenvironments co-ocurring as forest regeneration commences after pasture abandonment. It was assumed that B. pinnatum must possess a high degree of phenotypic plasticity for such an ecological versatility. This assumption was tested by comparing leaf and shoot morphology and leaf photochemistry in the species’ three typical microenvironments (full shade under oak canopy, half shade near shrubs, and full sun in unshaded grassland) for plants growing in situ and for those reciprocally transplanted between these microhabitats. Aboveground standing crop of B. pinnatum was greatest near shrubs, indicating that in this microhabitat light limitation (typical in oak shade) and water stress (appearing temporarily in the grassland) are ameliorated. Average leaf lifespan was greatest under oak canopy, while leaf senescence was highest in the grassland. An efficient adjustment to low light was observed both in leaf morphology (specific leaf mass, leaf thickness and bulk tissue density were lowest in oak shade) and in leaf photochemistry (quantum yield of PSII (ΦPSII), photochemical quenching (qP), and non-photochemical energy dissipation (NPQ) were lower, while PSII antenna efficiency (Fv’/Fm’) was higher for leaves in oak shade than for others). Transplanted plants showed remarkable phenotypic plasticity since after one year of transfer their leaves did not differ in photochemistry and/or morphology from those growing in situ in the new microenvironment. However, transplants appeared to be more sensitive to the high radiation load in the grassland than in situ ones. Our results confirm the high capacity of B. pinnatum for phenotypical adjustment to habitat light environment, that is consistent with the species’ original forest-steppe coenological affinity and also may contribute to the species’ persistence after deforestation. Nevertheless, temporary water stress associated with high radiation load in the unshaded grassland appear to pose a limitation on the ecological distribution of this species in Central Europe. [Copyright &y& Elsevier]

• Transgenerational effects of drought were found for a subordinate annual grass. • Transgenerational effects of drought changed from negative to positive with age. • Drought in the maternal environment reduced the early growth of offspring. • Drought in the maternal environment increased the adult shoot biomass of offspring. • Drought in the maternal environment increased the seed production of offspring. Drought can induce shifts in plant species or functional group abundances, which may favor coexisting subordinate species at the expense of previous dominants. Within-generation and transgenerational phenotypic plasticity can be important mechanisms to shape species responses to drought. Although a handful of studies have already investigated transgenerational plasticity in the context of drought, they provided variable results, and usually focused on species that currently dominate communities. We performed pot experiments with Secale sylvestre , a typical subordinate species in semiarid grasslands of Central Hungary. We tested if this annual grass shows reduced growth or reproduction in response to drought, and whether drought in the maternal environment affects offspring performance. For both maternal and offspring generations, plant height, shoot biomass, flowering onset, and seed number showed no within-generation plasticity in response to drought, and drought only decreased the seed mass of mother plants. In contrast, we found strong transgenerational effects on the overall performance of progenies, which changed with offspring age. At an early life stage, shoots were shorter for the offspring of drought-treated mothers than for the progenies of control mothers. This difference turned in the opposite direction later, and tiller number was also greater for the offspring of drought-treated mothers. Furthermore, the offspring of drought-treated mothers had over two-times higher adult shoot biomass and seed production compared to the offspring of control mothers. These beneficial transgenerational effects may help S. sylvestre to gain dominance in sand grasslands following dry years that decrease the abundance of perennial grasses, a vegetation change often observed in these grasslands after droughts. Our study provides the first evidence for positive transgenerational plasticity in response to drought for a subordinate species, which may be adaptive when the suppression of dominant species in the offspring environment is predictable from drought in the maternal environment. [ABSTRACT FROM AUTHOR]

Direct measurements of aboveground plant biomass are often not feasible, thus various biomass proxies are in use. To obtain biomass estimates, these proxies are calibrated against actual biomass, and the resulting proxy-biomass relationship is often used across multiple years and experimental treatments within a study. We investigated how the proxy-biomass relationship varied across years and considered interannual precipitation variability as a contributing factor. We sampled a perennial grassland for ten consecutive years (2003–2012) in central Hungary and estimated vegetation cover and Normalized Difference Vegetation Index (NDVI); two frequently used biomass proxies representing two contrasting methods. Aboveground live herbaceous plant biomass was harvested from each plot after sampling, and regression models were used to assess the relationship between biomass proxies and actual aboveground biomass. We found that cover and NDVI were equally effective at estimating biomass. However, the relationship between either biomass proxy and actual biomass varied amongst years, and this was related to the amount of precipitation. In wetter years, proxy-biomass relationships were steeper than in drier years. These results indicate that using the same proxy-biomass relationship across different years or precipitation regimes may not be valid and may introduce systematic error into biomass estimations in long-term studies or precipitation manipulation experiments. [ABSTRACT FROM AUTHOR]