Temperature increasing and precipitation alteration are predicted to occur in arid and semiarid lands; however, the response mechanism of carbon and water exchange at community level is still unclear in semiarid sandy land. We investigated the responses of carbon and water exchanges to warming and precipitation enhancement along a sand dune restoration gradient: mobile sand dunes (MD), semifixed sand dunes (SFD), and fixed sand dunes (FD). The average net ecosystem productivity (NEP) and evapotranspiration (ET) between May and August increased by 98% and 59%, respectively, from MD to SFD, while they had no significant differences between FD and the other two habitats. Warming inhibited ecosystem NEP, ET, and water use efficiency (WUE) by 69%, 49% (p < .001), and 80%, respectively, in SFD, while it nearly had no significant effects in MD and FD. However, precipitation addition by 30% nearly had no significant effects on community NEP, ET, and WUE, except for warming treatment in FD. In general, precipitation addition of 30% may still not be enough to prevent drought stress for growth of plants, due to with low water holding capacity and high evaporation rates in sandy land. Temperature increase magnified drought stress as it increased evapotranspiration rates especially in summer. In addition, community NEP, ET, and WUE were usually influenced by interactions between habitats and temperature, as well as the interactions among habitats, temperature, and precipitation. Species differences in each habitat along the restoration gradient may alter climate sensitivity of sandy land. These results will support in understanding and the prediction of the impacts of warming and precipitation change in semiarid sandy grassland.

Soil respiration is a major pathway by which carbon dioxide (CO₂) fixed by terrestrial plants returns to the atmosphere. Studies of the dynamics of soil respiration in sandy land are rare and the contribution (R_c) of plant root respiration to the total soil respiration (R_t) is not well known. In this study, R_t in a semi-fixed dune planted with Artemisia halodendron was separated into autotrophic (root) respiration (R_a) and heterotrophic respiration (R_h) by the root-exclusion method. R_t and its two components were measured or calculated during 2013 on seven dates during the growing season when variation during the day was measured. Both R_a and R_h showed similar dynamics, with the maximum rates observed in July and with large daily variability observed on the earlier dates. R_c ranged from 39.3% to 53.1% during the growing season and exhibited a single peak in early August. Soil temperature at a depth of 20 cm was significantly correlated with soil respiration. R_a was more sensitive to soil temperature than R_h and the temperature sensitivity coefficients (Q₁₀) were 3.39, 2.52, and 2.79 for R_a, R_h, and R_t, respectively. In summary, A. halodendron roots contributed an average of 46% to the total soil respiration, although this contribution varied during the growing season.

Responses of plants exposed to drought and rewatering have been well documented; however, little is known concerning strategies of psammophyte to drought and rewatering under different soil nutrient regimes. For this study, Pennisetum centrasiaticum under two soil nutrient regimes was subjected to progressive drought and subsequent rewatering. Soil water status, gas exchange characteristics, chlorophyll a fluorescence characteristics as well as biomass traits were measured to investigate ecophysiological responses. Net photosynthesis rate (P _n), stomatal conductance (g _s), water use efficiency, maximum quantum efficiency of photosynthesis system II (PSII, F _V/F _M), electron transport flux per cross section (ET₀/CS₀), and performance index on cross section basis (PI_CS) were suppressed during drought periods for both nutrient regimes. Meanwhile, leaf intercellular CO₂ concentration (C _i ), minimal fluorescence intensity (F ₀), and dissipated energy flux per cross section (DI₀/CS₀) increased. Reversible downregulation of PSII photochemistry and enhanced thermal dissipation of excess excitation energy (DI₀/CS₀) contributed to enhanced photo-protection in drought-stressed plants. Thus, the results indicate that P. centrasiaticum is capable of withstanding and surviving extreme drought events, and the recovery pattern of stressed P. centrasiaticum under both nutrient regimes was similar. However, fertilization increased the biomass and the variation in gas exchange and chlorophyll a fluorescence characteristics during drought periods. Additionally, fertilization accelerated the process of drought and aggravated stress under extreme drought events. Thus, the fertilization strategy used in P. centrasiaticum restoration should be carefully selected—fertilization may not always be beneficial.

Global warming and changes in rainfall patterns may put many ecosystems at risk of drought. These stressors could be particularly destructive in arid systems where species are already water-limited. Understanding plant responses in terms of photosynthesis and growth to drought and rewatering is essential for predicting ecosystem-level responses to climate change. Different drought responses of C₃ and C₄ species could have important ecological implications affecting interspecific competition and distribution of plant communities in the future. For this study, C₄ plant Pennisetum centrasiaticum and C₃ plant Calamagrostis pseudophragmites were subjected to progressive drought and subsequent rewatering in order to better understand their differential responses to regional climate changes. We tracked responses in gas exchange, chlorophyll fluorescence, biomass as well as soil water status in order to investigate the ecophysiological responses of these two plant functional types. Similar patterns of photosynthetic regulations were observed during drought and rewatering for both psammophytes. They experienced stomatal restriction and nonstomatal restriction successively during drought. Photosynthetic performance recovered to the levels in well-watered plants after rewatering for 6–8 days. The C₄ plant, P. centrasiaticum, exhibited the classic CO₂-concentrating mechanism and more efficient thermal dissipation in the leaves, which confers more efficient CO₂ assimilation and water use efficiency, alleviating drought stress, maintaining their photosynthetic advantage until water deficits became severe and quicker recovery after rewatering. In addition, P. centrasiaticum can allocate a greater proportion of root biomass in case of adequate water supply and a greater proportion of above-ground biomass in case of drought stress. This physiological adaptability and morphological adjustment underline the capacity of C₄ plant P. centrasiaticum to withstand drought more efficiently and recover upon rewatering more quickly than C. pseudophragmites and dominate in the Horqin Sandy Land.

Accurate forecasting of construction material prices is essential for effective cost control and risk management in construction projects. However, due to the influence of various complex factors, building material prices exhibit high nonlinearity and instability, often making traditional prediction methods inadequate for achieving optimal results. This study introduces an innovative prediction model, CEEMDAN-VMD-GRU-ARIMA, specifically designed for forecasting the price of prestressed steel bars. This model uniquely combines CEEMDAN and VMD to address nonlinear characteristics, and it innovatively incorporates sample entropy for the adaptive selection of either GRU or ARIMA for prediction. Additionally, a VMD decomposition mode number K value optimization method, based on a sparse index, is proposed. Experimental results demonstrate that the model performs exceptionally well, achieving an adjusted R-squared value of 81.10%, with various error indicators significantly surpassing the results for the baseline model. This approach offers new insights for short-term price prediction of building materials and contributes to enhancing the economic benefits and management efficiency of construction projects.