Life history responses of two ephemeral plant species to increased precipitation and nitrogen in the Gurbantunggut Desert

Potential distribution of three types of ephemeral plants under climate changes

BACKGROUND

Arid and semi-arid regions account for about 40% of the world's land surface area, and are the most sensitive areas to climate change, leading to a dramatic expansion of arid regions in recent decades. Ephemeral plants are crucial herbs in this area and are very sensitive to climate change, but it is still unclear which factors can determine the distribution of ephemeral plants and how the distribution of ephemeral plants responds to future climate change across the globe.

AIMS

Understanding the impact of climate change on ephemeral plant distribution is crucial for sustainable biodiversity conservation.

METHODS

This study explored the potential distribution of three types of ephemeral plants in arid and semi-arid regions (cold desert, hot desert, and deciduous forest) on a global scale using the MaxEnt software. We used species global occurrence data and 30 environmental factors in scientific collections.

RESULTS

Our results showed that (1) the average value of the area under the receiver operating curve (AUC) of each species was higher than 0.95, indicating that the MaxEnt model's simulation accuracy for each species was good; (2) distributions of cold desert and deciduous forest species were mainly determined by soil pH and annual mean temperature; the key factor that determines the distribution of hot desert species was precipitation of the driest month; and (3) the potential distribution of ephemeral plants in the cold desert was increased under one-third of climate scenarios; in the hot desert, the potential suitable distribution for Anastatica hierochuntica was decreased in more than half of the climate scenarios, but Trigonella arabica was increased in more than half of the climate scenarios. In deciduous forests, the ephemeral plant Crocus alatavicus decreased in nearly nine-tenths of climate scenarios, and Gagea filiformis was increased in 75% of climate scenarios.

CONCLUSIONS

The potential suitable distributions of ephemeral plants in the different ecosystems were closely related to their specific adaptation strategies. These results contribute to a comprehensive understanding of the potential distribution pattern of some ephemeral plants in arid and semi-arid ecosystems.

Responses of germination strategy of Agriophyllum squarrosum to rainfall pattern in the Tengger desert

Agriophyllum squarrosum (L.) Moq. (Chenopodiaceae) is an annual pioneer psammophyte that is strictly distributed along desert margins. However, little is known about how this species adapts to shifting dunes. In this study, seeds bank was selected and germination behaviors of A. squarrosum were tested in laboratory. In addition, the effects of rainfall patterns on population dynamics were observed in field at the southeastern edge of the Tengger Desert. Soil seed bank density was significantly different in different depth of sand dunes. Under adequate water in Petri dishes, seeds began to germinate in less than 3 h and the germination peak was reached in seven days after watering. It showed that there is no innate dormancy of A. squarrosum. The buried experiments showed that the germination percentage decreased with increasing buried depth, and deeply buried seeds (10 cm) remained ungerminated. Population dynamics in different rainfall pattern of three years in field showed that germination, survival and deaths of A. squarrosum were extremely sensitive to rainfall variation. Our results suggest that precipitation is the key factor in determining population of A. squarrosum. The germination strategy of A. squarrosum ensures the efficiency use of unpredicted and scarce precipitation. The high disturbance of moving sand endowed persistence seed bank of A. squarrosum, which is essential for population continuation, avoiding population extinction under unpredicted precipitation.

Responses and comprehensive evaluation of growth characteristics of ephemeral plants in the desert-oasis ecotone to soil types

The ecological environment of the Gurbantünggüt desert-oasis ecotone is extremely fragile. Ephemeral plants are an important part of the ecosystem and play an essential role in maintaining the ecological stability of the ecotone. However, few studies have focused on the growth, soil quality and system sustainability of ephemeral plants in different soils. This study was based on two typical soil types (grey desert soil, GS; aeolian soil, AS) in the aforementioned ecotone, considered four ephemeral plants (Tetracme recurvata, TR; Tetracme contorta, TC; Malcolmia scorpioides, MS; Isatis violascens, IV) as the research object, analysed plant characteristics and soil properties, and comprehensively evaluated the ephemeral plant system by analysing the soil quality index (SQI) and sustainability index (SI). The results showed that there were significant differences in biomass and nutrient accumulation between different ephemeral plants, which were significantly affected by soil types. In the two examined soils (GS and AS), the contents of nutrients and microbial carbon (MBC) and nitrogen (MBN) in the rhizosphere soil were higher than those in the bare soil (BS), and there were significant differences among different species. The key soil factors related to total biomass in GS and AS were also different. The SQI of ephemeral plants was significantly higher than that of the BS, and varied with soil types and plant species. The species with the highest SQI of the key factor data set in GS and AS were IV and TR, respectively. The SI analysis indicated that IV in GS and MS and IV in AS were sustainable, and the plant properties can be better used to assess the sustainability of ephemeral plant systems. In conclusion, ephemeral plants improved the soil quality and system sustainability of the study ecotone. Further, the growth of ephemeral plant and rhizosphere soil properties vary with plant species and soil types; thus, selecting suitable species for large-scale planting in different soil types is of great significance for improving the ecological stability of the ecotone.

Is the Life History Flexibility of Cold Desert Annuals Broad Enough to Cope with Predicted Climate Change? The Case of Erodium oxyrhinchum in Central Asia

Interannual seasonal variability in precipitation may strongly affect the life history and growth of desert annual plants. We compared the effects of dry and wet springs and dry and wet autumns on growth and F2 seed dormancy of plants from spring (SG)- and autumn (AG)-germinated seeds of the cold desert annual Erodium oxyrhinchum. Vegetative and reproductive growth and F2 seed dormancy and germination were monitored from September 2016 to November 2020 in the sandy Gurbantunggut Desert in NW China in Central Asia. Dry autumns decreased the density of AG plants, and dry springs decreased the density of SG plants and growth of SG and AG plants. In dry springs, SG plants were more sensitive to precipitation than AG plants, while in wet springs SG and AG plants had similar responses to precipitation. During growth in both dry and wet springs, most morphological characters of SG and AG plants initially increased rapidly in size/number and then plateaued or decreased, except for SG plants in dry springs. In dry springs, most morphological characters of AG plants were larger or more numerous than those of SG plants, and they were larger/more numerous for SG plants in wet than in dry springs. The percentage biomass allocated to reproduction in SG plants was slightly higher in a wet than in a dry spring. A much higher proportion of dormant seeds was produced by AG plants in a wet spring than in a dry spring. Projected changes in precipitation due to climate change in NW China are not likely to have much of an effect on the biology of this common desert annual plant.

Effects of Water and Energy on Plant Diversity along the Aridity Gradient across Dryland in China

Plants need water and energy for their growth and reproduction. However, how water and energy availability influence dryland plant diversity along the aridity gradient in water-limited regions is still lacking. Hence, quantitative analyses were conducted to evaluate the relative importance of water and energy to dryland plant diversity based on 1039 quadrats across 184 sites in China's dryland. The results indicated that water availability and the water-energy interaction were pivotal to plant diversity in the entire dryland and consistent with the predictions of the water-energy dynamic hypothesis. The predominance of water limitation on dryland plant diversity showed a weak trend with decreasing aridity, while the effects of energy on plants were found to be significant in mesic regions. Moreover, the responses of different plant lifeforms to water and energy were found to vary along the aridity gradient. In conclusion, the study will enrich the limited knowledge about the effects of water and energy on plant diversity (overall plants and different lifeforms) in the dryland of China along the aridity gradient.

Life history response of Echinops gmelinii Turcz. to variation in the rainfall pattern in a temperate desert

BACKGROUND

Current and future changes in rainfall amount and frequency may particularly impact annual plants in desert ecosystems. The winter annual Echinops gmelinii Turcz. is widely distributed in the desert habitats of northern China and is a dominant pioneer annual plant following sand stabilization in the Tengger Desert. This species plays a vital role in dune stabilization during spring and early summer, when wind erosion is the most severe and frequent. However, seedling emergence and regeneration in sandy soil are mainly determined by rainfall patterns. Therefore, understanding the life history response of this species to rainfall variation is necessary for understanding the change of population dynamics under the future climate change.

METHODS

A field simulation rainfall pot experiment using rainout shelter was conducted that included five amounts and five frequencies of rainfall based on historical and predicted values to monitor the life history responses of E. gmelinii in a near-natural habitat.

RESULTS

We found that rainfall amount and frequency significantly affected seedling survival, growth and reproduction. The plant height, biomass, capitula number, seed number, seed mass and reproductive effort, but not the root/shoot ratio, significantly increased with increasing rainfall. Further, these traits exhibited the greatest response to low-frequency and larger rainfall events, especially the optimal rainfall frequency of 10-day intervals. Offspring seed germination showed increasing trends with decreasing rainfall, suggesting that the maternal effects may have occurred.

CONCLUSIONS

Our study shows that the plasticity in growth and reproduction of E. gmelinii in response to rainfall variations may help it to gain dominance in the harsh and unpredictable desert environment. Furthermore, population development of this winter annual species should be promoted under the likely future scenarios of large rainfall events and increasing cool-season precipitation in temperate desert.