Climate change is shifting the amount and frequency of precipitation in many regions, which is expected to affect seedling recruitment across ecosystems. However, the combined effects of precipitation amount and frequency on seedling recruitment remain largely unknown. An understanding of the effects of precipitation amount and frequency and their interaction on seedling emergence and growth of typical desert plants is vital for managing populations of desert plants. We conducted two experiments to study the effects of variation in precipitation on Reaumuria soongarica (Pall.) Maxim. First, greenhouse experiments were conducted to examine the effects of three precipitation amount treatments (ambient, +30%, and −30%) and two precipitation frequency treatments (ambient and −50%) on seedling emergence. Second, the morphological responses of R. soongarica to changes in precipitation amount and frequency were tested in a controlled field experiment. Stage-specific changes in growth were monitored by sampling in different growth seasons. Our results showed that precipitation amount significantly affected germination, seedling emergence, and growth of R. soongarica, and there was a larger effect with decreased precipitation frequency compared with ambient. Germination and seedling emergence increased as precipitation increased under the same frequency of precipitation. The highest emergence percentage was obtained with a 30% increase in precipitation amount and a 50% reduction in precipitation frequency. Compared with ambient precipitation, a 30% increase in precipitation amount increased above-and below-ground biomass accumulation of R. soongarica during the growth season. A decrease of 30% in precipitation amount also resulted in an increase in below-ground biomass and root/shoot ratio in the early stages of the growth season, however, above-and below-ground biomass showed the opposite results at the end of the growth season, with larger effects on above-ground than below-ground biomass under decreased precipitation frequency. When precipitation frequency decreased by 50%, values of all growth traits increased for a given amount of precipitation. We concluded that precipitation frequency may be as important as precipitation amount to seedling emergence and growth of R. soongarica, and that understanding the effects of precipitation variability on seedling recruitment requires the integration of both precipitation amount and frequency. In particular, the combination of a 30% increase in precipitation amount and 50% reduction in precipitation frequency increased the emergence and growth of seedlings, suggesting that alteration of amount and frequency of precipitation caused by climate change may have significant effects on seedling recruitment of R. soongarica.

The golden shiner Notemigonus crysoleucas is the major species of baitfish raised and sold in the United States. They are shipped in trucks from large farms to distributors up to 2,500 km distant. The costs associated with shipping could be greatly reduced if truck loading were increased, but higher densities of fish elevate ammonia concentrations to detrimental levels. In our work, we have simulated live hauling conditions to measure the ammonia excretion rates of golden shiners at 15, 20, and 25°C. The experiments were conducted for 24 h in three recirculating systems after fingerling golden shiners were fasted and acclimated for 2 d. The experiment was repeated four times using different lots and sizes of golden shiners. The results indicated that there were no significant differences in the hourly ammonia excretion rates (HER) between two lots of same‐size golden shiners. The hourly ammonia excretion rates were inversely proportional to fish weight and increased with temperature. The average HER for all sizes of fish ranged from 2.9 to 7.4 g NH3‐N/kg fish/h at 15°C, 5.2–11.2 g NH3‐N/kg fish/h at 20°C, and 6.2–15.0 g NH3‐N/kg fish/h at 25°C. The results of this study will be used to design ammonia control systems to safely increase fish density on commercial fish hauling trucks.

The resurrection plant Reaumuria soongorica is widespread across Asia, southern Europe, and North Africa and is considered to be a constructive keystone species in desert ecosystems, but the impacts of climate change on this species in desert ecosystems are unclear. Here, the morphological responses of R. soongorica to changes in rainfall quantity (30% reduction and 30% increase in rainfall quantity) and interval (50% longer drought interval between rainfall events) were tested. Stage‐specific changes in growth were monitored by sampling at the beginning, middle, and end of the growing season. Reduced rainfall decreased the aboveground and total biomass, while additional precipitation generally advanced R. soongorica growth and biomass accumulation. An increased interval between rainfall events resulted in an increase in root biomass in the middle of the growing season, followed by a decrease toward the end. The response to the combination of increased rainfall quantity and interval was similar to the response to increased interval alone, suggesting that the effects of changes in rainfall patterns exert a greater influence than increased rainfall quantity. Thus, despite the short duration of this experiment, consequences of changes in rainfall regime on seedling growth were observed. In particular, a prolonged rainfall interval shortened the growth period, suggesting that climate change‐induced rainfall variability may have significant effects on the structure and functioning of desert ecosystems.

Understanding the relationships among species is central to ecological research; however, many knowledge gaps remain regarding how desert plant species interact. In the present study, we assessed the effect of rainfall on the belowground interactions and root morphology of two desert shrubs, Reaumuria soongorica (Tamaricaceae) and Salsola passerina (Chenopodiaceae), from three communities with similar landforms and soil environments. The roots of both R. soongorica and S. passerina were deeper when grown together than grown singly. Interestingly, the belowground biomass of R. soongorica was higher, but the belowground biomass of S. passerina was lower when grown together than when grown alone. This suggests that S. passerina benefitted from the association with R. soongorica. When grown together under conditions of low rainfall, the roots of R. soongorica were deeper than those of S. passerina, which suggests that R. soongorica is more robust than S. passerina when subjected to periods of decreased rainfall. We concluded that the symbiotic relationship between these two shrub species can lead to deeper roots and that the plants are affected by rainfall availability. Combined with the output results of climate change models, we speculated that the distribution area of these two species will expand to the west, which has important implications on how the interactions of other desert species may change in response to climate variability.

The Zuli River is in the northwest of the Loess Plateau. As an important center of production and domestic water source, variations in the water quality of this basin and their influencing factors are important considerations for improving the river water environment. In order to identify and predict changes in the water quality of the watershed, the following water quality indicators, namely, dissolved oxygen content (DO), five-day biological oxygen demand (BOD5), ammonia nitrogen concentration (NH3-N), the high-manganese salt index (CODMn), volatile phenol concentration (VP), total phosphorus (TP), fluoride concentration (F−), and nitrite nitrogen concentration (NO3-N), were studied together with their change trends, influencing factors, and main variation cycles in the basin from 2001 to 2021. The results were as follows: (1) All the water quality indicators except for DO and F- showed an increasing trend before 2011, and DO showed an extreme, significant downward trend. There was an increase in the content of pollutants in the water caused by chemical fertilizer and aquaculture, resulting in a decrease in the DO content. (2) There was an extreme, significant upward trend in DO after 2011, while a significant downward trend was observed in the other water quality indicators except for NO3-N. (3) According to the main variation cycle of the other water quality indicators, the DO will remain in its peak period, while the other water quality indicators except for NO3-N will remain in a trough period (which began in 2021). The increase in precipitation and runoff reduced the content of pollutants in the water. Therefore, the overall water quality of the Zuli River Basin gradually improved after 2011. This may be due to (1) increased precipitation and runoff, thereby diluting the concentration of pollutants in the river, or (2) a decreased concentration of pollutants entering the river with the decrease in soil erosion.