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Background: Given the ubiquitous nature of mycorrhizal symbioses, different symbiotic fungi have obvious differences in structure and function, which may affect associated tree aboveground and belowground C allocation dynamics. However, the mechanisms underlying tree aboveground and belowground C allocation and its response to symbiotic mycorrhizal types and other factors (e.g., resource availability) remain poorly understood. Results: We used forest inventory data to explore the potential mechanism of tree aboveground and belowground C allocation patterns in Northeast China. Our results showed that tree-fungal symbioses were related to the patterns of tree C allocation. The ratio of aboveground to belowground C pool was significantly higher in ectomycorrhizal (EM)-associated trees than that in arbuscular mycorrhizal (AM)-associated trees. Symbiotic mycorrhizal types were associated with the responses of tree aboveground and belowground C allocation to different factors, such as mean annual precipitation (MAP) and mean annual temperature (MAT). Almost all factors significantly increased aboveground C allocation in AM-associated trees but significantly decreased it in EM-associated trees. Moreover, after controlling the other factors, the effects of climate factors (MAT and MAP) on the C allocation of AM- and EM-associated trees were similar. Increases in MAT and MAP significantly increased belowground and aboveground C allocation, respectively. Conclusions: Our results demonstrate symbiotic mycorrhizal types play an important role in controlling tree aboveground and belowground C allocation and dynamics. [ABSTRACT FROM AUTHOR]

Fungi play an important role in mediating soil functioning and plant nutrients absorption. Although nitrogen (N) addition and reduced precipitation can affect fungal community composition, the response of fungal taxonomic and functional groups to changes in soil N and water availability is still unclear. Here, we established a long-term field manipulations experiment of N addition and throughfall exclusion to investigate fungal communities' response to N addition and reduced precipitation. Illumina Sequencing of ITS amplicons was used to examine soil fungal communities in winter and summer. Results showed that N addition, reduced precipitation and their combined effect significantly altered the soil fungal community composition. Basidiomycetes associated with humus decomposition dominated in ambient soil and Ascomycetes abundance dramatically increased and dominated in N addition in both winter and summer. Reduced precipitation and the combined effect significantly increased fungal richness and diversity. Moreover, the relative abundance of mycorrhizal and saprotroph fungal communities responded positively to reduced precipitation. Our results indicate reduced precipitation alleviated the competition between fungi, while N addition could reduce the rate decomposition of humus. [ABSTRACT FROM AUTHOR]

Soil biota and energy flow within their food webs have a profound impact on various ecosystem functions. However, there are still significant gaps in our understanding of how climate change factors, such as nitrogen deposition and reduced precipitation, impact ecosystem functioning, particularly in temperate forest ecosystems. In this study, we evaluated the response of ecosystems to long-term nitrogen deposition and/or reduced precipitation due to climate change. We assessed these responses by examining nematode community energy fluxes and their associated ecosystem multifunctionality. Field experiments were conducted in a temperate forest to simulate nitrogen deposition (5.0 kg N·ha−1·yr−1) using NH 4 NO 3 application and to reduce precipitation (to 70 % of a normal year) using rain shelters. Our findings showed that nitrogen addition and/or precipitation reduction treatments altered soil nematode composition. Nitrogen addition alone reduced the abundance and energy fluxes of high trophic groups such as omnivore-predators, which served as proxies for total abundance and energy fluxes. In contrast, precipitation reduction did not exhibit significant effects on overall abundance and energy fluxes. Environmental factors influencing changes in soil nematode abundance and energy fluxes included soil pH, NH 4 +-N, and total nitrogen in the soil. Nitrogen addition increased ecosystem multifunctionality by promoting nutrient cycling, while precipitation reduction promoted plant productivity and inhibited carbon cycling, without changing ecosystem multifunctionality. Regression analysis showed that soil nematode energy fluxes were negatively correlated with ecosystem multifunctionality. The effects of these two factors on soil nematode food webs showed temporal variation, as well as indicators related to multiple functions of the ecosystem. Our study suggests that soil nematode energy fluxes are more sensitive than nematode abundance for quantifying the relationship between biodiversity and ecosystem multifunctionality. [Display omitted] • N addition and/or precipitation reduction change the composition of soil nematode communities. • N addition decreases the abundance and energy fluxes of soil nematode communities. • Soil pH, NH 4 +, and total N played important roles in driving the nematode abundance and energy fluxes. • Interaction of N and water mediate ecosystem multifunctionality by changing soil nematode abundance and trophic energy flux. [ABSTRACT FROM AUTHOR]

Abstract Decreased precipitation and increased anthropogenical by derived nitrogen (N) are important climate change factors that alter the availability of soil water and N which are crucial to root function and morphological traits. However, these factors are seldom explored in forests. To clarify how altered precipitation and N addition affect the uptake of organic and inorganic N by fine roots, a field hydroponic experiment using brief 15N exposures was conducted in a temperate forest in northern China. The root traits related to nutrient foraging (root morphology and mycorrhizal colonization) were measured simultaneously. Our results showed that all three tree species preferred ammonium (NH 4 +) over glycine and nitrate (NO 3 −), and NH 4 + contributed 73% to the total N uptake from the soil. Uptake of glycine was higher than that of NO 3 −. Decreased precipitation, N addition, and their interaction increased NH 4 + uptake rate compared with the control. Decreased precipitation decreased the glycine and NO 3 − uptake rate. Moreover, N addition, decreased precipitation and their interaction changed root morphological traits and significantly decreased mycorrhizal colonization. Although our treatments resulted in changes to the root traits and the forms of N uptake by plants, the total amount of N uptake did not change among all treatments. We conclude that although fine root traits of dominant tree species in temperate forests have high plasticity in response to climate change, nutrient balance in plants causes the total amount of N uptake to remain unchanged. Graphical abstract Unlabelled Image Highlights • Trees showed a strong preference for NH 4 + uptake over glycine and NO 3 − uptake. • Plasticity in root traits use allowed trees to acclimation to environmental change. • The change of root physiology may be the key to the increase of NH 4 + uptake. • The total amount of plant N uptake did not change after long-time treatments. [ABSTRACT FROM AUTHOR]

Nitrogen (N) deposition and change of snowpack are two critical factors for soil microbial community in temperate forests. The responses of soil microbial community composition and diversity to snowpack changes and N deposition are rarely investigated in winter. Therefore, we conducted an experiment to detect the microbial responses to the different snowpack depths (0 cm and 40 cm) and N addition (0 g N m −2  yr −1 and 5 g N m −2  yr −1 for four years) in a cold temperate forest in northeastern China in winter. The results indicated that decreased snowpack and increased N caused the significant changes in the soil microbial community composition in winter. The N addition significantly decreased bacterial abundance and diversity, which may be caused by decrease of pH and increase of inorganic N concentration under N addition. The decreased temperature associated with the removal of snowpack was considered to be able to trigger the variability in the soil fungal and bacterial community composition and diversity. The reduction in snowpack also decreased the soil respiration rate and the microbial biomass carbon (C) and N. However, the inhibition effect of N addition on soil respiration only occurred in the no snowpack treatments during the winter in our study, which indicates that N addition might change the activity of cold-tolerant microorganisms. In general, increased N deposition and reduced snowpack might potentially affect ecosystem functioning and terrestrial ecosystem C cycling in temperate forests under global change scenarios. [ABSTRACT FROM AUTHOR]

• We expound the ecological function of EE-GRSP for the first time in a temperate forest. • N addition, precipitation reduction and their interaction all had significantly negative impacts on EE-GRSP. • N addition and precipitation reduction had a synergistic effect on the content of T-GRSP. • The important role of microbial C derive in the soil C pool was confirmed. • The GRSP can be used as an index to predict the soil organic C dynamics. As a microbial-derived carbon (C) compound, the glomalin-related soil protein (GRSP) is not only a considerable amount of soil active organic C, but also an effective aggregate binder. At present, due to various global change factors, the forest ecosystem C stock and soil stability are facing unprecedented challenges. As the two of important global change factors, the effects of increased nitrogen (N) deposition, precipitation pattern change and their interaction on the soil organic C (SOC) stock, aggregate stability and GRSP and their correlations are not clear. Based on this, we conducted a long-term field experiment in a temperate forest to simulate N addition and precipitation reduction (n = 3). The experimental design included a control, decreased precipitation (DP), N addition (+N) and their interaction (+N×DP). Compared with the control, the negative effect of N addition on the total GRSP (T-GRSP) was not significant, but it significantly reduced the easily extractable GRSP (EE-GRSP) and mean weight diameter (MWD) (P < 0.05). The T-GRSP, EE-GRSP and MWD all showed significant negative responses to the DP treatment (P < 0.05). Compared with the single treatment, the +N×DP treatment further strengthened the negative effects on the EE-GRSP and MWD (P < 0.05). In addition, we found that the MWD was mainly controlled by large aggregates (>2 mm), and the DP and +N×DP treatments destroyed the seasonal stability of aggregate. The correlation analysis showed that the T-GRSP had a strong correlation with the SOC, while the EE-GRSP had a more significant correlation with the MWD (P < 0.001). Through this study, we emphasized the profound impact of global change factors on temperate forest, clarified the ecological functions of the T-GRSP and EE-GRSP, and confirmed the reciprocal mechanism of the GRSP, SOC and MWD. Collectively, our results will be helpful to evaluate the impact of climate change on forest ecosystems from the perspective of microbial derivatives. [ABSTRACT FROM AUTHOR]