Evaluating the post-fire natural regeneration of Mediterranean-type scrublands in Central Spain

We performed a five-year assessment of the natural vegetation restoration capacity following the 2012 fires in Valdemaqueda (Madrid, Spain) via the characterization of the post-fire and residual vegetation and the analysis of soil physico-chemical characteristics. Six pilot-plots were established in the affected site. Forest species, representative of the potential natural vegetation of the area (Juniperus oxycedrus subsp. lagunae and Quercus rotundifolia woodlands) and broom shrubs (Cytisus scoparius, Retama sphaerocarpa) were planted to assess the relationship among the stages of ecological succession, competition, and soil restoration processes following devastating fire events. The fire-driven alteration of the soil’s physico-chemical properties was evident, given the increased pH and reduced C/N ratio in the first years of the study. However, we observed an increased soil enrichment in the last years of study, accompanied by the propagation of herbaceous species, su[1]pporting our seed bank findings, showing a clear difference in the sprouting rate between burnt and control plots (80% vs. 20%, respectively). The establishment of robust, pyrophyte shrub species (Cistus ladanifer, C. laurifolius, Rosmarinus officinalis) rather than natural succession evidenced the clear conversion of the vegetation in burnt areas. These findings in the pilot-plots allowed evidencing the high vulnerability of the natural vegetation to the settling of pyrophytes, given their low survival rate under the strong competitive pressure of these pyrophytic species. The proliferation of these pyrophytes could translate into changes in soil macro- and microbiota, nutrient dynamics, species diversity, and interaction, added to the alteration of fire regimes in the area. Overall, these results highlight the risk for soil impoverishment and possible erosion of the fire-affected sites. Moreover, they underline the importance of the establishment and regeneration of Genisteae species to outcompete pioneer pyrophytic species, favoring the restoration of the area’s potential natural vegetation

Nutritional Characteristics and Seed Germination Improvement of the Forage Shrub Retama sphaerocarpa (L.) Boiss

SummaryRetama sphaerocarpa shrubs form populations that can be an important forage resource during the dry season when pasture shortages are common in certain arid and semi-arid Mediterranean basin regions. The leaves of R. sphaerocarpa were analyzed for dry matter (DM), crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF) and acid detergent lignin (ADL) contents. Leaves were also analyzed for the concentration of macro- (P, K, Ca and Mg) and microelements (Mn, Zn, Fe, and Na). According to the contents of CP, NDF, ADF and ADL in the leaves examined, this species could strike an appropriate balance between available feed ingredients for daily nutritional needs of animals. The contents of Ca, K, Na, P, Fe, Mg, and Zn in Retama sphaerocarpa shrubs were found to be high, compared to a number of other forage shrub species. Conversely, the rate of natural regeneration of this shrub in situ was estimated at 2-5%. R. sphaerocarpa seeds are affected by seed coat dormancy that prevents seed germination under natural conditions. The seed germination was assessed at a laboratory after the chemical scarification of seeds by concentrated sulphuric acid in the duration range of 0 min and 240 min. The principal component analysis of data related to the germination ability and seedling emergence showed that the best pretreatment was 120 min immersion in sulphuric acid at 25°C (± 2°C), resulting in 86% of the final germination percentage (FGP) and 14.6 cm of the seedling length (SL). According to the results obtained, this species could be considered a ruminant feed of great nutritive value when drought decreases grazing herbaceous biomass yields. These results should encourage farmers and foresters to integrate R. sphaerocarpa into their planting programs.

Effect of Leaf Litter from Cistus ladanifer L. on the Germination and Growth of Accompanying Shrubland Species

Most communities with the presence of Cistus ladanifer are characterised by the low richness of accompanying species, with C. ladanifer, in most cases, exceeding 70% of the coverage of woody species. This fact could be due to the allelopathic activity attributed to compounds present in the leaves of C. ladanifer, which may have a negative effect on the germination and growth of woody species that share its habitat. One of the possible ways of incorporating allelopathic compounds to the soil is the degradation of leaf litter. Therefore, the aim of this study was to determine how the presence of leaf litter from C. ladanifer affects accompanying species. Under controlled conditions, we analysed the effect of C. ladanifer leaf litter on the germination and growth of seedlings of five species that share their habitat with C. ladanifer (Retama sphaerocarpa, Cytisus multiflorus, Lavandula stoechas, Cistus salviifolius, and Cistus crispus). Additionally, the effect of leaf litter on the species itself, C. ladanifer, has been studied. The experiments were designed with different concentrations of leaf litter (UL) and leaf litter from which the compounds with allelopathic activity were extracted (WL). The results show that such effect greatly depends on the analysed species, with L. stoechas being the most negatively affected species. On the other hand, C. multiflorus and C. salviifolius were only negatively affected at the stage of seedling growth. The results reveal the involvement of leaf litter in the allelopathic activity attributed to C. ladanifer and that its presence has a negative influence on the germination and growth of accompanying woody species. This shows the need to delve into the potential relevance of allelopathy as an interaction that determines the composition, structure and dynamics of a community.

Phosphorus and Nitrogen Modulate Plant Performance in Shrubby Legumes from the Iberian Peninsula

We investigated the impact of phosphorus nutrition on plant growth and biological nitrogen fixation in four leguminous plants in the Tribe Genistea. The main objective of the study was to analyze Phosphorus and Nitrogen use efficiency under drought. We also tested for the effects of rhizobial inoculation on plant performance. Plants inoculated with Rhizobium strains isolated from plants of the four species growing in the wild were cropped under controlled conditions in soils with either low P (5 µM) or high P (500 µM). The experiment was replicated in the presence and absence of plant irrigation to test for the effects of drought stress of inoculated and non-inoculated plants under the two P levels of fertilization. Low-P treatments increased nodule production while plant biomass and shoot and root P and N contents where maximum at high P. Low P (5 µM) in the growing media, resulted in greater N accumulated in plants, coupled with greater phosphorus and nitrogen uptake efficiencies. Drought reduced the relative growth rate over two orders of magnitude or more, depending on the combination of plant species and treatment. Genista cinerea had the lowest tolerance to water scarcity, whereas Genista florida and Retama sphaerocarpa were the most resistant species to drought. Drought resistance was enhanced in the inoculated plants. In the four species, and particularly in Echinospartum barnadesii, the inoculation treatment clearly triggered N use efficiency, whereas P use efficiency was greater in the non-inoculated irrigated plants. Nodulation significantly increased in plants in the low P treatments, where plants showed a greater demand for N. The physiological basis for the four species being able to maintain their growth at low P levels and to respond to the greater P supply, is through balanced acquisition of P and N to meet the plants’ nutritional needs.

Dendrološke značajke Arboretuma Trsteno

Arboretum Trsteno je povijesni ladanjski posjed s perivojima, starim maslinicima i prirodnom vegetacijom, kojim upravlja Hrvatska akademija znanosti i umjetnosti. Povijest ladanjske cjeline može se pratiti od 1494. godine, a Arboretum površine 28 ha osnovan je 1948. godine. Radi utvrđivanja sadašnjega bogatstva drvenastih svojti, biljke su determinirane tijekom 2017. i 2018. godine. Napravljena je dendrološka analiza te je učinjena usporedba sadašnjega bogatstva dendroflore u odnosu na literaturne podatke dostupne iz sredine i kraja prošloga, kao i početka ovoga stoljeća. U Arboretumu Trsteno sada raste 317 drvenastih svojti, od čega je 233 vrsta, 8 podvrsta, 2 varijeteta, 10 križanaca i 64 kultivara. Svojte pripadaju u 179 različitih rodova iz 82 porodice. Golosjemenjača je 19 svojti, a kritosjemenjača 298 svojti. Svojti autohtonih u Hrvatskoj je 84, odnosno 26 %, a među njima prevladavaju medite­ranske biljke. Od egzotičnih vrsta i podvrsta, odnosno onih koje rastu isključivo izvan europskoga kontinenta, najviše je azijskih vrsta (64), zatim slijede vrste s područja Amerike (45 vrsta), Afrike (14 vrsta) i Australije (6 vrsta). Jedinstvene ili vrlo rijetko prisutne svojte u Hrvatskoj su npr. Acacia cyclops A. Cunn. ex G. Don, A. karoo Hayne, Albizia amara (Roxb.) B. Boivin, Callitris preisii Miq., Casuarina cunninghamiana Miq., Persea indica (L.) Spreng., Retama sphaerocarpa Raf., Schinus weinmannifolius Engl. i Vitex negundo var. heterophylla (Franch.) Rehder. Od prvog popi­sa biljaka prije 65 godina do danas u Arboretum su unošene nove svojte. Ukupan broj svojti povećan je s 226 na 317. Tome je znantno pridonijelo obogaćanje zbirki pojedinih rodova, ali također i revizije prijašnjih determinacija koje su donijele na svjetlo brojne stare kultivare, kao npr. rodova Olea, Citrus, Aloe, Pelargonium i dr. Svojti koje su se od popisa 1953. godine do danas zadržale u Arboretumu je 148, što znači da je od današnjih 317 svojti nešto manje od pola bilo u Arboretumu i prije 65 godina. To je posljedica djelovanja niza čimbenika, uključujući klimu, uvjete uzgoja, požare, ali i bolesti i štetnike. Egzotične biljke toplih područja drugih kontinenata uglavnom su dobro prilagođene na stanišne uvjete u Arboretumu, međutim, povremeno stradaju od ekstremno niskih temperatura koje traju više dana. Arboretum Trsteno jedini je naš arboretum koji je pod upravom znanstvene institucije – Hrvatske akademije znanosti i umjetnosti te ispunjava zadatke postavljene pred povijesni arboretum u suvremenom svijetu.

Diversidad y composición florística del Bosque Los Búhos ubicado la Escuela Superior Politécnica de Chimborazo, Ecuador

Para promover procesos de conservación es fundamental conocer la biodiversidad objeto de análisis. En este sentido el objetivo del presente trabajo fue determinar la composición, diversidad e importancia florística del Bosque Los Búhos para generar una línea base que permita el manejo del recurso con propósitos académicos. Por tal motivo en la presente investigación se realizó una descripción de la composición florística, se determinó los índices de biodiversidad alfa (α) y beta (β), finalmente se calculó la importancia ecológica de las especies (IVI´s). Los datos indican que la composición florística del bosque se encuentra conformada en tres estratos por 56 especies, 18 órdenes y 27 familias. El estrato arbóreo presenta una biodiversidad media (2,534-Margalef) y dominancia alta (0,8367-Simpson), el estrato arbustivo tiene baja biodiversidad (1,811-Margalef) y baja dominancia (0,4441-Simpson), y el estrato herbáceo presenta biodiversidad media (3,882-Margalef) y dominancia alta (0,7101-Simpson). Las especies con el mayor IVI´s para el estrato arbóreo son Mimosa quitensis Benth., Acacia retinodes Schltdl., y Tecoma stans (L.) Juss. ex Kunth. Para el estrato arbustivo son Agave americana L., Lantana megapotamica (Spreng.) Tronc., Retama sphaerocarpa y Opuntia cylindrica. Finalmente para el estrato herbáceo es Carpobrotus edulis.