Global climate change profoundly influences the patterns of vegetation growth. However, the disparities in vegetation responses induced by regional climate characteristics are generally weakened in ...large-scale studies. Meanwhile, distinct climatic drivers of vegetation growth result in the different reactions of different vegetation types to climate variability. Hence, it is an extraordinary challenge to detect and attribute vegetation growth changes. In this study, the spatiotemporal distribution and dynamic characteristics of climate change effects on vegetation growth from 2000 to 2020 were investigated by the normalized difference vegetation index (NDVI) dataset during the growing season (April–October). Meanwhile, we further detected the climate-dominated factor between different vegetation types (i.e., forest, shrub, and grass) within the Chaohe watershed located in temperate northern China. The results revealed a continuous greening trend over the entire study period, despite slowing down since 2007 (p < 0.05). Growing-season precipitation (P) was identified as the dominant climatic factor of the greening trend (p < 0.05), and approximately 34.83% of the vegetated area exhibited a significant response to increasing P. However, continued warming-induced intensive evaporation demand caused the vegetation growth to slow down. Hereinto, the areas with a significantly positive response of forest growth to temperature decreased from 24.38% to 18.06% (p < 0.05). In addition, solar radiation (SW) corresponds to the vegetation trend in the watershed (p < 0.05), and the significantly positive SW-influenced areas increased from 9.24% and 2.64% to 11.78% and 3.37% in forests and shrubland, respectively (p < 0.05). Our findings highlight the nonlinearity of long-term vegetation growth trends with climate variation and the cause of this divergence, which provide vital insights into forecasting vegetation responses to future climate change.
•Gs was the primary biophysical factor regulating the ecosystem EF.•Cloudiness reduced the EF of this riparian plantation.•Water use strategy significantly altered by cloudy sky conditions.•Ecosystem ...ET exceeded rainfall, which would exacerbate regional drought.
Cloudiness is an important environmental variable that affects the total and proportion of diffuse radiation reaching the ground and thereby the rate of plant carbon assimilation. However, its regulations on ecosystem energy partitioning and water use strategy are not well understood, particularly for riparian ecosystems. We used the eddy covariance technique and micrometeorological sensors to measure the energy fluxes and environmental conditions for a poplar plantation adjacent to the Chaobai River in North China during the growing seasons (April–October) in 2014 and 2015. We found that canopy conductance (Gs) was the primary biophysical factor regulating the ecosystem energy partitioning, while vapor pressure deficit (VPD) did not impose significant effects on evaporative fraction (EF). Cloudiness suppressed EF primarily due to the stomatal closure caused by the decrease in direct radiation (Rdir). Furthermore, the ratio of stomatal sensitivity (m) and reference conductance (Gsref) was 0.36 and 0.48 mol m−2 s−1 ln(kPa)−1 during clear sky and cloudy sky conditions, respectively. These results indicated that this poplar plantation with an anisohydric behavior weakened stomatal control on water loss under clear skies by avoiding leaf burn arising from higher direct sunlight and temperature. Finally, the mean Priestley–Taylor coefficient (α) and EF was 1.01 and 0.61 across two growth periods, respectively, and ecosystem evapotranspiration (ET) exceeded rainfall, even in rainy year, suggesting that a certain amount of groundwater might be consumed by this riparian poplar plantation, which would exacerbate regional drought.
The Chaohe watershed is Beijing's primary potable water source.
The initiation of ecological restoration (ER), combined with the rapid acceleration of climate change (CC), has precipitated severe ...water shortages in North China. The seasonal responses of baseflow (BF), pivotal for sustaining rivers' fundamental flow and ecological equilibrium, to ER and CC are poorly understood. This study provides a precise depiction of the seasonal variations in BF by leveraging multiple separation methodologies. By applying the BFAST algorithm and a comprehensive sensitivity analysis, we unveil the nuanced seasonal patterns of BF adjustments in reaction to ER and CC.
Baseflow, primarily influenced by the wet season, constituted 64.21% of the annual aggregate. Considerable decreases in BF during the dry (−32.61%) and wet (−68.21%) seasons pose increasing threats to available water resources. The decrease in sub-surface runoff (−1.91 mm per decade) dominated the reduction of dry season BF. Indeed, vegetation regulated seasonal water distribution, maintaining the essential flow throughout the dry season. In the wet season, the reduction in BF acts as a supplemental water source to fulfill the escalating evapotranspiration needs due to afforestation and a drying climate. This study highlights the persistent hydrological consequences of ER and CC on water resources, emphasizing the crucial function of vegetation in baseflow, a key component for ecological restoration and water resource management in water-limited areas.
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•The Eckhardt filter method better captures baseflow variations in Northern China.•The dry and wet season baseflow reduced by 32.61% and 68.21%, respectively.•Sub-surface runoff plays a critical role in the decreased dry-season baseflow.•Vegetation restoration can optimize the seasonal distribution of water resources.
Shrubs are a key component of desert ecosystems, playing a crucial role in controlling desertification and promoting revegetation, yet their growth is often impeded by drought. Leaf hydraulic traits ...and economic traits are both involved in the process of water exchange for carbon dioxide. Exploring the characteristics, relationships, and anatomical basis of these two suites of traits is crucial to understanding the mechanism of desert shrubs adapting to the desert arid environment. However, the relationship between these two sets of traits currently remains ambiguous. This study explored the leaf hydraulic, economic, and anatomical traits of 19 desert shrub species. The key findings include the following: Relatively larger LT values and smaller SLA values were observed in desert shrubs, aligning with the “slow strategy” in the leaf economics spectrum. The relatively high P50leaf, low HSMleaf, negative TLPleaf, and positive HSMtlp values indicated that severe embolism occurs in the leaves during the dry season, while most species were able to maintain normal leaf expansion. This implies a “tolerance” leaf hydraulic strategy in response to arid stress. No significant relationship was observed between P50leaf and Kmax, indicating the absence of a trade-off between hydraulic efficiency and embolism resistance. Certain coupling relationships were observed between leaf hydraulic traits and economic traits, both of which were closely tied to anatomical structures. Out of all of the leaf traits, LT was the central trait of the leaf traits network. The positive correlation between C content and WPleaf and HSMleaf, as well as the positive correlation between N content and HSMtlp, suggested that the cost of leaf construction was synergistic with hydraulic safety. The negative correlation between SLA, P content, GCL, and SAI suggested a functional synergistic relationship between water use efficiency and gas exchange rate. In summary, this research revealed that the coupling relationship between leaf hydraulic traits and economic traits was one of the important physiological and ecological mechanisms of desert shrubs for adapting to desert habitats.
The Chaohe watershed is a meso-scale watershed in northern China, and the primary reservoir watershed for Beijing's drinking water supply.
This research aims to evaluate the effects of climate change ...on future seasonal streamflow regimes and understand the challenges to watershed management. The Regional Hydro-Ecological Simulation System (RHESSys) was applied to investigate the watershed's future hydrographic characteristics under the forcing of the downscaled precipitation and temperature projected by General Circulation Models (GCMs) under three emissions scenarios.
The future climate exhibits a drier and warmer trend in the summer monsoon period contrasting with other seasons in the watershed. Precipitation will decrease by 47.5–57.2 mm during the summer monsoon period while increasing annually. Future summer streamflow will decrease accordingly, which is also driven by increased evapotranspiration due to rising temperature. An increased dispersion coefficient of streamflow also indicates more dramatic variations in summer. The annual streamflow magnitude with a 5-year return period increases significantly (p < 0.01), indicating a reduced risk for future water shortages. However, the magnitude of streamflow will decrease with the prolonged return periods (p < 0.01). This study emphasizes the critical significance of predicting the seasonal variability of streamflow and other hydrological property changes at the local scale to provide valuable information for developing adaptive resource management and hazard relief strategies.
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●Climate change strongly regulates future seasonal dynamics of the flow regime.●The summer climate in this watershed will be drier and warmer in the future.●Streamflow in summer will reduce, in opposition to its change in other seasons.●The summer flood risk of this region will reduce in the future.
To identify genes that respond to increased nitrogen and assess the involvement of the chlorophyll metabolic pathway and associated regulatory mechanisms in these responses,
seedlings were subjected ...to four nitrogen concentrations (N0, N6, N36, and N60: 0, 6, 36, and 60 mmol·L
nitrogen, respectively). The
seedling leaf transcriptome was analyzed by high-throughput sequencing (Illumina HiSeq 4000), and 332,420 transcripts and 276,423 unigenes were identified. The numbers of differentially expressed genes (DEGs) were 4052 in N0 vs. N6, 6181 in N0 vs. N36, and 3937 in N0 vs. N60. Comparing N0 and N6, N0 and N36, and N0 and N60, we found 1101, 2222, and 1234 annotated DEGs in 113, 121, and 114 metabolic pathways, respectively, classified in the Kyoto Encyclopedia of Genes and Genomes database. Metabolic pathways with considerable accumulation were involved mainly in anthocyanin biosynthesis, carotenoid biosynthesis, porphyrin and chlorophyll metabolism, flavonoid biosynthesis, and amino acid metabolism. N36 increased
-amino levulinic acid synthesis and upregulated expression of the magnesium chelatase H subunit, which promoted chlorophyll
synthesis. Hence, N36 stimulated chlorophyll synthesis rather than heme synthesis. These findings enrich our understanding of the
transcriptome and help us to research desert xerophytes' responses to increased nitrogen in the future.
The Budyko hypothesis, less parameters and definite physical significance, was used to quantitatively analyze the effects of climate changes and vegetation dynamics on actual evapotranspiration. It ...is of great significance to study the water balance and energy distribution in Chaohe watershed. We used the Budyko empirical model to verify the water-energy balance theory based on the hydrological and meteorological data from 1961 to 2015 in Chaohe watershed. The most suitable model of the basin and the optimal values for the model parameters were determined. Furthermore, we quantitatively analyzed the impacts of vegetation dynamics and climate changes on the actual evapotranspiration. Results showed that the Budyko model modified by underlying surface parameters improved the accuracy of predicting actual evapotranspiration compared to the classical Budyko models. The Fu Baopu model had the highest precision in the Chaohe watershed; the mean relative error, the Nash efficiency coefficient, and the coefficient of determination were 27. 66 mm,0. 82 and 0. 85, respectively. Using the optimizing model parameter(2. 54), the Fu Baopu model could better reflect the changed characteristics of the actual evapotranspiration. Finally, the scenario analysis indicated that vegetation dynamics and climate variation in Chaohe watershed played a positive role in actual evapotranspiration; climate changes are a major driver of the increase in actual evapotranspiration.
•Gc in spring and autumn primarily controlled EWUE.•FDR became the dominant biophysical factor regulating EWUE in summer.•FDR significantly enhanced EWUE by depressing ET and promoting GPP.•The ...stomatal optimization theory applied at VPD ≤ 3 kPa at the canopy level.•Large-scale poplar will exacerbate water source issues in northern China.
Ecosystem water use efficiency (EWUE), defined as the ratio of ecosystem gross primary production (GPP) and evapotranspiration (ET), is regulated by multiple biophysical factors and their interactions. One particular unknown is the relative importance of environmental control and canopy stomatal control on EWUE for their direct and indirect roles in different seasons. We employed the eddy covariance technique and micrometeorological sensors to measure the carbon and water fluxes and environmental variables over a riparian poplar plantation in northern China from 2014 to 2017. We found that canopy conductance (Gc) was the dominant factor regulating EWUE in spring and autumn, while the fraction of diffuse radiation (FDR) was the primary controlling variable in summer. During the growing season, FDR depressed ET and promoted GPP primarily through its direct role rather than indirectly affecting other environmental factors. This plantation could utilize diffuse radiation efficiently by regulating stomatal function when FDR was lower than 0.6. More importantly, the stomatal optimization theory worked merely under certain conditions (i.e., VPD ≤ 3 kPa). Correspondingly, the poplar plantation tended to show less conservative water use strategy with decreasing surface soil water content (SWC) when the non-stomatal function was dominant. Our study highlighted the importance of FDR and Gc on EWUE and the potential of future water resource impact resulting from extensive poplar plantation establishment in northern China.
Microbial necromass is crucial for soil organic carbon (SOC) sequestration and stable carbon pools. The impact of various combinations of agricultural management systems on microbial necromass is ...poorly understood and merits investigation. In the present study, we compiled 63 global studies comprising 344 observations and used a hierarchical meta-analysis to assess the effects of tillage systems, cropping systems, fertilization systems, and cover crops on microbial necromass. Our meta-analysis revealed that tillage systems and cropping systems lowered the total microbial necromass by 16.4 % and 3.9 %, respectively while fertilization systems and cover crops raised the total microbial necromass by 21.7 % and 25.3 %, respectively. We observed that crop rotation and cover crops mitigated the negative effects of tillage on microbial necromass. No-tillage and fertilization enhanced the negative effects of crop rotation on microbial necromass. No-tillage and cover crops when combined with fertilizer management, jointly increased total microbial necromass but depleted bacterial necromass. Cover cropping under crop rotation effectively restored the soil amino sugars. PiecewiseSEM and multivariate analyses disclosed that the initial SOC content and the mean annual temperature are key factors affecting the changes in the soil amino sugar profile under different agricultural management systems. Crop rotation systems are generally more effective in areas with better soil fertility and higher mean annual temperatures. In regions with abundant rainfall, tillage has a strong negative effect on soil microbial necromass. To minimize the consumption of microbial necromass, cropland management should integrate diverse practices rather than solely considering local climate and soil conditions.
•Crop rotation and cover crops mitigated the negative effect of the tillage system on amino sugars.•No-tillage and cover crops boosted fertilizer management's effect on microbial necromass but reduced bacterial necromass.•Cover cropping under crop rotation effectively restored the soil amino sugars.•Initial soil organic carbon and mean annual temperature were key factors affecting amino sugar variation in agriculture.
To identify genes that respond to increased nitrogen and assess the involvement of the chlorophyll metabolic pathway and associated regulatory mechanisms in these responses, Nitraria tangutorum ...seedlings were subjected to four nitrogen concentrations (N0, N6, N36, and N60: 0, 6, 36, and 60 mmol·Lsup.−1 nitrogen, respectively). The N. tangutorum seedling leaf transcriptome was analyzed by high-throughput sequencing (Illumina HiSeq 4000), and 332,420 transcripts and 276,423 unigenes were identified. The numbers of differentially expressed genes (DEGs) were 4052 in N0 vs. N6, 6181 in N0 vs. N36, and 3937 in N0 vs. N60. Comparing N0 and N6, N0 and N36, and N0 and N60, we found 1101, 2222, and 1234 annotated DEGs in 113, 121, and 114 metabolic pathways, respectively, classified in the Kyoto Encyclopedia of Genes and Genomes database. Metabolic pathways with considerable accumulation were involved mainly in anthocyanin biosynthesis, carotenoid biosynthesis, porphyrin and chlorophyll metabolism, flavonoid biosynthesis, and amino acid metabolism. N36 increased δ-amino levulinic acid synthesis and upregulated expression of the magnesium chelatase H subunit, which promoted chlorophyll a synthesis. Hence, N36 stimulated chlorophyll synthesis rather than heme synthesis. These findings enrich our understanding of the N. tangutorum transcriptome and help us to research desert xerophytes’ responses to increased nitrogen in the future.
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