Comparison of Leaf and Fine Root Traits Between Annuals and Perennials, Implicating the Mechanism of Species Changes in Desertified Grasslands

The altitudinal distribution characteristics of functional traits reflect the resource allocation strategy of Abies georgei var. smithii in southeast Tibet

To explore the adaptation strategies of the aboveground and underground functional traits of alpine plants along an altitudinal gradient, a typical stand of primitive dark coniferous forests (Abies georgei var. smithii.) in southeastern Tibet was taken as the research object in the present study. PCA and correlation analyses were carried out for different organ functional traits (19 key indicators in total), then RDA analysis was done in conjunction with 12 environmental factors. The variation characteristics of the functional traits of leaves, current-year twigs, trunks and fine roots in 6 continuous altitude gradients and the relationships between functional traits and environmental factors were explored. The results showed that soil organic carbon (SOC) may exert a positive effect on the construction of plant defense tissue via changes in functional traits, altitude (Alt) represents the primary influencing factor of wood density (WD) variation, particulate organic carbon (POC) content mainly affected fine root dry matter (RDWC) content and specific root length (SRL), and total potassium (TK) content was the main factor that affected fine root tissue density (RTD). Leaves, current-year twigs, and fine roots exhibited high production or nutrient acquisition capacity at an altitude of 4,000m and showed strong defense and relatively stable water and nutrient transport capacity. In conclusion, the ecological strategy of Abies georgei var. smithii. in Sejila Mountain was more conservative, and the optimal survival area of Abies georgei var. smithii. was located at 4, 000m on the shady slope of Sejila Mountain. It is of paramount significance for exploring the essence of terrestrial ecosystems and their functional processes in extremely high-altitude environments.

Coordinated variation in root and leaf functional traits of Hippophae rhamnoides treated at different stump heights in feldspathic sandstone areas of Inner Mongolia

This study was aimed to clarify the effects of stumping on root and leaf traits as well as the tradeoffs and synergies of decaying Hippophae rhamnoides in feldspathic sandstone areas, and to select the optimal stump height that contributed to the recovery and growth of H. rhamnoides. variations and coordination between leaf traits and fine root traits of H. rhamnoides were studied at different stump heights (0, 10, 15, 20 cm, and no stumping) in feldspathic sandstone areas. All functional traits of the leaves and roots, except the leaf C content (LC) and the fine root C content (FRC), were significantly different among different stump heights. The total variation coefficient was the largest in the specific leaf area (SLA), which is therefore the most sensitive trait. Compared to non-stumping, SLA, leaf N content (LN), specific root length (SRL) and fine root N content (FRN) all improved significantly at stump height of 15 cm, but leaf tissue density (LTD), leaf dry matter content (LDMC), leaf carbon to nitrogen ratio (LC : LN), fine root tissue density (FRTD), fine root dry matter content (FRDMC) and fine root carbon to nitrogen ratio (FRC : FRN) all decreased significantly. The leaf traits of H. rhamnoides at different stump heights follow the leaf economic spectrum, and the fine roots show a similar trait syndrome to the leaves. SLA and LN are positively correlated with SRL and FRN and negatively with FRTD and FRC : FRN. LDMC and LC : LN are positively correlated with FRTD and FRC : FRN, and negatively correlated SRL and RN. The stumped H. rhamnoides changes to the 'rapid investment-return type' resource trade-offs strategy, and the growth rate is maximized at the stump height of 15 cm. Our findings are critical to the prevention and control of vegetation recovery and soil erosion in feldspathic sandstone areas.

Identification and Characterization of Arthrobacter nicotinovorans JI39, a Novel Plant Growth-Promoting Rhizobacteria Strain From Panax ginseng

A bacterial strain JI39 that had plant growth-promoting traits was isolated from the rhizosphere soil of Panax ginseng. It had the ability to produce high indole-3-acetic acid (13.1 μg/ml), phosphate solubilization (164.2 μg/ml), potassium solubilization (16.1 μg/ml), and nitrogen fixation. The strain JI39 was identified to be Arthrobacter nicotinovorans based on morphological, physiological, and biochemical traits and through 16S rDNA sequence analysis. The optimal culture environment for strain growth was 1.0% NaCl, 30°C, pH 6.0, and without UV irradiation. The strain can produce cellulase and protease. The strain JI39 can significantly promote the growth of ginseng. After ginseng seeds were treated with 3 × 108 CFU/ml of JI39 bacterial suspension, the shoot's length was significantly increased by 64.61% after 15 days. Meanwhile, the fresh weight of 2-year-old ginseng roots was significantly increased by 24.70% with a treatment by the 108 CFU/ml bacterial suspension after 150 days in the field. The gene expression of phenylalanine ammonia-lyase (PAL), β-1.3 glucanase (β-1,3-GA), chitinase (CHI), superoxide dismutase (SOD), and peroxidase (POD) of ginseng was upregulated, and it also can improve the soil urease, phosphatase, invertase, and catalase activity. In conclusion, the bacterial strain JI39 could efficiently promote the growth of ginseng and has the potential to be a good microbial fertilizer for ginseng.