The Modulation of Water, Nitrogen, and Phosphorous Supply for Growth Optimization of the Evergreen Shrubs Ammopiptanthus mongolicus for Revegetation Purpose

Surface mining is a critical anthropogenic activity that significantly alters the ecosystem. Revegetation practices are largely utilized to compensate for these detrimental impacts of surface mining. In this study, we investigated the effects of five water (W) regimes [W40: 40%, W48: 48%, W60: 60%, W72: 72%, and W80: 80% of field capacity (FC)], five nitrogen (N) (N0: 0, N24: 24, N60: 60, N96: 96, and N120: 120 mg kg−1 soil), and five phosphorus (P) fertilizer doses (P0: 0, P36: 36, P90: 90, P144: 144, and P180: 180 mg kg−1 soil) on morpho-physiological and biochemical parameters of Ammopiptanthus mongolicus plants to assess the capability of this species to be used for restoration purposes. The results showed that under low W-N resources, A. mongolicus exhibited poor growth performance (i.e., reduced plant height, stem diameter, and dry biomass) in coal-degraded spoils, indicating that A. mongolicus exhibited successful adaptive mechanisms by reducing its biomass production to survive long in environmental stress conditions. Compared with control, moderate to high W and N-P application rates greatly enhanced the net photosynthesis rates, transpiration rates, water-use efficiency, chlorophyll (Chl) a, Chl b, total Chl, and carotenoid contents. Under low-W content, the N-P fertilization enhanced the contents of proline and soluble sugar, as well as the activities of superoxide dismutase, catalase, and peroxidase in leaf tissues, reducing the oxidative stress. Changes in plant growth and metabolism in W-shortage conditions supplied with N-P fertilization may be an adaptive strategy that is essential for its conservation and restoration in the desert ecosystem. The best growth performance was observed in plants under W supplements corresponding to 70% of FC and N and P doses of 33 and 36 mg kg−1 soil, respectively. Our results provide useful information for revegetation and ecological restoration in coal-degraded and arid-degraded lands in the world using endangered species A. mongolicus.

Desert Climate Regionalization for Joshua Tree National Park and Surrounding Areas Using New Climate Network Observations

A new amalgamation of weather stations in and around Joshua Tree National Park in southeastern California, USA has allowed for objective climate analysis regionalization at a much finer scale than past studies. First, it sets a baseline for many regions within the park’s boundaries which were not subject to direct observations. Second these new observations are key to understanding shifting microclimate regimes in a desert ecosystem prone to the effects of climate change. Principal component analysis was used to regionalize the climate network based on monthly temperature and precipitation climate observations and standardized anomalies. Both the observation values and standardized climate anomalies identified regional boundaries. In general, these boundaries align with traditional ideas and past studies of the Mojave and Sonoran Deserts based on elevation (specifically the 1000m contour) for the National Park. Standardized anomaly values identified a boundary based on seasonal precipitation, while observation values identified a boundary based on elevation. The boundary line within the park is similar for both data approaches, with the boundary running along the higher western third of the park. Conversely, the two methods differ significantly in the Coachella Valley, where low elevations and low precipitation meets winter dominated seasonal precipitation. This study highlights the importance and opportunity of field observations to create climatological and ecological regionalization, as well as constructs a baseline to monitor and manage shifting desert regions in the future.

Selection of the reference genes for quantitative gene expression by RT-qPCR in the desert plant Stipagrostis pennata

The desert pioneer plant Stipagrostis pennata plays an important role in sand fixation, wind prevention, and desert ecosystem recovery. An absence of reference genes greatly limits investigations into the regulatory mechanism by which S. pennata adapts to adverse desert environments at the molecular and genetic levels. In this study, eight candidate reference genes were identified from rhizosheath development transcriptome data from S. pennata, and their expression stability in the rhizosheaths at different development stages, in a variety of plant tissues, and under drought stress was evaluated using four procedures, including geNorm, NormFinder, BestKeeper, and RefFinder. The results showed that GAPDH and elF were the most stable reference genes under drought stress and in rhizosheath development, and ARP6 and ALDH were relatively stable in all plant tissues. In addition, elF was the most suitable reference gene for all treatments. Analysis of the consistency between the reverse transcription-quantitative PCR (RT-qPCR) and RNA sequencing data showed that the identified elF and GAPDH reference genes were stable during rhizosheath development. These results provide reliable reference genes for assuring the accuracy of RT-qPCR and offer a foundation for further investigations into the genetic responses of S. pennata to abiotic stress.

Stoichiometry of C:N:P in the Roots of Alhagi sparsifolia Is More Sensitive to Soil Nutrients Than Aboveground Organs

The stoichiometry of carbon, nitrogen, and phosphorus (C:N:P) among leaves, stems, and roots reflects trade-offs in plants for acquiring resources and their growth strategy. The widely distributed plant Alhagi sparsifolia is an ideal species to study the ecological stoichiometry in different organs in response to the availability of nutrients and water in the desert ecosystem. However, which response of organs is most sensitive to environmental conditions is still unclear. To answer this question, we collected samples of plants and soils including not only aboveground leaves and stems, but also underground roots and soils from a wide range of arid areas during the growing season. The C, N, P, C:N, C:P, and N:P ratios in leaves, thorns, stems, and roots were derived to explore their relationship as well as their response mechanisms to nutrients and water spanning 1 m deep in the soil. The results showed that the order of N concentration was leaves > thorns > stems > roots, that the concentration of P in the leaves, thorns, and stems was similar, and that their values were higher than those in the roots. First, the C:N ratios in the leaves and stems were significantly positively correlated with the ratio in roots. The C:N ratios in each organ showed a significant relationship with the soil alkali hydrolyzable nitrogen (SAN) above a depth of 60 cm. In addition to SAN, soil available phosphorus (SAP) and soil organic carbon (SOC) affect the C:N ratio in the roots. Second, the C:P and N:P ratios in aboveground organs showed no correlations with the ratios in roots. The C:P and N:P ratios in the leaves and thorns have no relationship with soil nutrients, while the C:P ratio in roots was influenced by SAN and SOC in all soil layers. Finally, the N:P ratios in roots were also affected by nutrients in different soil depths at 0–20 and 60–80 cm. These results illustrate that the roots were more sensitive to soil nutrients than the aboveground parts. Our study of ecological stoichiometry also suggests a novel systematic approach for analyzing the sensitivity of responses of an organ to environmental conditions.