Assessing the effects of climate change on the distribution of Daphne mucronata in Iran.

Zagros Mountains are like an island in the Middle East and they are subjected to changes in climate. Daphne mucronata Royle is an important medicinal plant species preserved in the high elevation regions in these mountains. Maxent species distribution model was used to integrate presence data (2413 points) and environmental variables to model the current and future potential distribution of D. mucronata in Iran. The most important variables were Bio19 with 50.5% contribution, followed by Bio8 and Bio2 with 30% and 11.4% contributions, respectively. The best Maxent model included seven variables, 4 feature types (linear, quadratic, product, and hinge), and had a test AUC value of 0.894. The current potential distribution indicated that 8% of Iran's drylands are suitable for growing D. mucronata and this area could decrease to 5.2% under representative concentration pathway (RCP) 4.5, and 3.1% under RCP 8.5 due to climate change. Our results suggest that D. mucronata may lose overall about 2.8% and 4.9% of its current distribution under RCP 4.5 and RCP 8.5, respectively, by 2050. There would be only 0.7 and 0.2% gains under RCP 4.5 and 8.5, respectively. The species would locally disappear between 1500- and 2000-m elevation under RCP 4.5 and 8.5, respectively. The establishment of some stations for monitoring the changes in transition zone or lost areas especially on the southeastern parts of Zagros Mountain can help in detecting changes in the future. Additionally, stable habitats may be good target areas for future conservation planning.

Investigating lead and zinc uptake and accumulation by Stipa hohenackeriana trin and rupr. in field and pot experiments / Investigação sobre a captação e acúmulo de chumbo e zinco por Stipa hohenackeriana trin. & rupr. em experimentos de campo e em vaso

This study was conducted to evaluate Pb and Zn uptake, mobility, and accumulation in Stipa hohenackeriana using field soil in pot and field experiments. Moreover, the effects of Municipal Solid Waste Compost (MSWC) (0, 1, and 2%) and Nano-Silica (NS) (0, 250, and 500 mg/kg) on Stipa biomass, Pb and Zn availability in the soil, and Pb and Zn uptake and accumulation were studied using pot experiments. Samples of soil, root, and shoots of Stipa were collected from field and greenhouse and after drying, extraction of Pb and Zn was done by acid digestion. Bio- Concentration Factor (BCF) and Translocation Factor (TF) were calculated to determine Pb and Zn phytoremediation efficiency. The amount of Zn and Pb remediation by Stipa from soil was determined by remediation factor (RF). The results of field experiments showed the Pb and Zn level decreased in the order of: soil >shoot>root. Results of the pot experiments also showed that plants grown in NS500-amended pots had 33% and 32% higher Pb in roots and shoots compared to control pots, respectively. In comparison, roots Pb concentration in pots amended with MSWC1% and MSWC2% decreased 22.4% and 1.7%, respectively. Roots and shoots Zn concentration in NS500-amended pots was 5.6% and 6.5% higher, respectively. However, root Zn concentration in treatments of MSWC1% and MSWC2% decreased 52.3% and 39.4%, respectively. Shoots Zn concentration decreased 52.5% and 40.0%, respectively. Although MSWC decreased the uptake and accumulation of Pb and Zn in Stipa roots and shoots, it improved the plant growth and consequently increased RF and soil remediation compared to the NS. Thus, it seems that applying MSWC and NS simultaneously can be a suitable strategy for the purpose of improving phytoremediation capability of Stipa in the Pb and Zn contaminated soils. In general, Stipa can be a suitable candidate for the accumulation of heavy metals, especially for Pb and Zn contaminated soils.

Este estudo foi conduzido para avaliar a absorção, mobilidade e acumulação de Pb e Zn em Stipa hohenackeriana em experiências usando solo de campo em vaso e em campo. Além disso, os efeitos do Composto Municipal de Resíduos Sólidos (MSWC) (0, 1 e 2%) e de nanopartículas de sílica (NS) (0, 250 e 500 mg/kg) na biomassa de Stipa, na disponibilidade de Pb e Zn no solo, e na absorção e acúmulo de Pb e Zn foram estudados usando experiências em vaso. Amostras de solo, raiz e brotos de Stipa foram coletadas do campo e da estufa e, após a secagem, a extração de Pb e Zn foi feita por digestão ácida. O Fator de Bioconcentração (BCF) e o Fator de Translocação (TF) foram calculados para determinar a eficiência de fitorremediação de Pb e Zn. A quantidade de remediação de Zn e Pb pela Stipa a partir do solo foi determinada pelo Fator de Remediação (RF). Os resultados das experiências de campo mostraram que o nível de Pb e Zn diminuiu na seguinte ordem: solo > broto > raiz. Os resultados das experiências em vaso também mostraram que as plantas cultivadas em vasos corrigidos com NS500 apresentaram teores de Pb 33% e 32% maiores em raízes e brotos em comparação com vasos de controle, respectivamente. Em comparação, a concentração de Pb em raízes em vasos corrigidos com MSWC1% e MSWC2% diminuiu 22,4% e 1,7%, respectivamente. A concentração de Zn em raízes e brotos em vasos corrigidos com NS500 foi de 5,6% e 6,5% maior, respectivamente. No entanto, a concentração de Zn da raiz nos tratamentos de MSWC1% e MSWC2% diminuiu 52,3% e 39,4%, respectivamente. A concentração de Zn nos brotos diminuiu 52,5% e 40,0%, respectivamente. Embora o MSWC tenha diminuído a absorção e acumulação de Pb e Zn nas raízes e brotos de Stipa, melhorou o crescimento da planta e consequentemente aumentou o RF e a remediação do solo em relação ao NS. Assim, parece que aplicar MSWC e NS simultaneamente pode ser uma estratégia adequada com o objetivo de melhorar a capacidade de fitorremediação de Stipa nos solos contaminados com Pb e Zn. Em geral, a Stipa pode ser um candidato adequado para a acumulação de metais pesados, especialmente para solos contaminados com Pb e Zn.

The positive relationships between plant coverage, species richness, and aboveground biomass are ubiquitous across plant growth forms in semi-steppe rangelands.

The positive relationships between biodiversity and aboveground biomass are important for biodiversity conservation and greater ecosystem functioning and services that humans depend on. However, the interaction effects of plant coverage and biodiversity on aboveground biomass across plant growth forms (shrubs, forbs and grasses) in natural rangelands are poorly studied. Here, we hypothesized that, while accounting for environmental factors and disturbance intensities, the positive relationships between plant coverage, biodiversity, and aboveground biomass are ubiquitous across plant growth forms in natural rangelands. We applied structural equation models (SEMs) using data from 735 quadrats across 35 study sites in semi-steppe rangelands in Iran. The combination of plant coverage and species richness rather than Shannon's diversity or species diversity (a latent variable of species richness and evenness) substantially enhance aboveground biomass across plant growth forms. In all selected SEMs, plant coverage had a strong positive direct effect on aboveground biomass (ß = 0.72 for shrubs, 0.84 for forbs and 0.80 for grasses), followed by a positive effect of species richness (ß = 0.26 for shrubs, 0.05 for forbs and 0.09 for grasses), and topographic factors. Disturbance intensity had a negative effect on plant coverage, whereas it had a variable effect on species richness across plant growth forms. Plant coverage had a strong positive total effect on aboveground biomass (ß = 0.84 for shrubs, 0.88 for forbs, and 0.85 for grasses), followed by a positive effect of species richness, and a negative effect of disturbance intensity across plant growth forms. Our results shed light on the management of rangelands that is high plant coverage can significantly improve species richness and aboveground biomass across plant growth forms. We also found that high disturbance intensity due to heavy grazing has a strong negative effect on plant coverage rather than species richness in semi-steppe rangelands. This study suggests that proper grazing systems (e.g. rotational system) based on carrying capacity and stocking rate of a rangeland may be helpful for biodiversity conservation, better grazing of livestock, improvement of plant coverage and enhancement of aboveground biomass.

Abiotic and biotic drivers of aboveground biomass in semi-steppe rangelands.

Rangelands play an important role in the biodiversity conservation and ecosystem functions. Yet, few studies have assessed the effects of biotic and abiotic factors on aboveground biomass across plant growth forms and at whole-community level in rangelands. Here, we hypothesized that aboveground biomass is driven by both biotic (plant coverage, species richness and evenness) and abiotic factors (soil textural properties and topographic factors) but biotic factors may best predict aboveground biomass, probably due to small spatial scale. To test this hypothesis, we performed multiple linear mixed model by including abiotic and biotic factors as fixed effects while sites aspects and plant community types across sites, and disturbance intensities as random effects, using data from 735 quadrats across 35 sites in semi-steppe rangelands in Iran. The optimal model for shrubs showed that aboveground biomass was positively related to plant coverage, species richness, elevation, sand, silt and clay. Aboveground biomass of forbs and grasses was positively related to plant coverage, species richness, elevation and slope. Whole-community aboveground biomass was positively related to plant coverage, species richness and elevation, but negatively to species evenness and slope. We conclude that higher aboveground biomass is related to high species richness and plant coverage, and located on high elevation and/or slope across plant growth forms while having medium-coarse-textured to fine-textured soils for adaptation of shrubs only. Few dominant species or niche overlap in whole-community may also drive high aboveground biomass, and located on high elevation with gentle slope. Therefore, we found support for both the niche complementarity and selection effects across plant growth forms and at whole-community. In addition, this study shows that plant coverage is the best proxy for aboveground biomass in the studied rangelands.