Soil greenhouse gas (GHG) fluxes relate to soil carbon and nitrogen budgets and have a significant impact on climate change. Nevertheless, the temporal variation and magnitude of the fluxes of all three major GHGs (CO₂, CH₄ and N₂O) and their influencing factors have not been elucidated clearly in primary forests on the eastern Qinghai-Tibetan Plateau. Herein, field chamber GHG fluxes from May to November, soil microbial community and enzyme activity were analyzed in a fir-dominated (Abies fargesii var. faxoniana) primary forest. The emission rates of CO₂ and N₂O ranged between 64.69–243.22 mg CO₂ m⁻² h⁻¹ and 1.69–5.46 ug N₂O m⁻² h⁻¹, exhibiting a temporally unimodal pattern with a peak in July. The soil acted as a CH₄ sink, and the uptake rate varied between 52.96 and 84.67 μg CH₄ m⁻² h⁻¹ with the higher uptake rates in June and November. The temporal variation in the CO₂ flux was significantly correlated with the geometric mean of enzyme activities, suggesting that the soil CO₂ flux was determined by microbial activity rather than soil microbial biomass. The soil N₂O flux was positively related to nitrate concentration with marginal significance, probably because N₂O was a byproduct of nitrification and denitrification processes. The soil CH₄ uptake was closely associated with methanotrophic biomass (18:1ω7c). The results highlight divergent temporal dynamics of GHG fluxes owing to different driving mechanisms and an important CH₄ sink in the primary forest soil, helping to evaluate the carbon and nitrogen budgets of primary forests on the eastern Qinghai-Tibetan Plateau.

Non-structural carbohydrates (NSCs) can reflect the balance of resource allocation and trade-offs, as well as the adaptability of plants to the environment. Alterations in environmental conditions across an elevation gradient may impact the carbon balance within leaves. Nonetheless, it remains highly uncertain whether the effect of elevation on NSCs differs among species and sexes. To reveal the response patterns of leaf NSCs in dioecious plants with elevation, Populus cathayana Rehd. and Hippophae rhamnoides L., distributed at four elevations in the subalpine region of western Sichuan, China, were selected, and female and male leaves were sampled and measured for their contents of NSCs, soluble sugar, and starch. Meanwhile, the relationships of NSCs, soluble sugar, and starch with leaf nitrogen and phosphorus were analyzed. The results showed that the elevational patterns of NSCs were mainly dependent on species and were slightly affected by sex. Leaf NSCs in both sexes of P. cathayana did not exhibit significant linear changes, whereas those in H. rhamnoides increased significantly and linearly with elevation. For P. cathayana, a significant increase in leaf starch with elevation was only found in female plants and may benefit from phosphorus deficiency, as it was significantly negatively correlated with phosphorus. However, leaf soluble sugar and starch between sexes of H. rhamnoides showed similar patterns of significant increases with elevation, and they were not correlated significantly with nitrogen and phosphorus. This might be due to H. rhamnoides, which is a nitrogen-fixing plant and thereby did not show deficiencies or limitations in nitrogen and phosphorus, as shown by the decreased or unchanged elevational patterns of nitrogen/phosphorus, starch/phosphorus, and soluble sugar/phosphorus. Overall, our results emphasize that species, rather than sex, is an important factor influencing the elevational pattern of NSCs, but for specific species, such as P. cathayana, in this study, there was a divergence in the elevational response of the allocation of starch and soluble sugar between sexes, reflecting the specific adaptive strategies of different plant species or sexes in response to changes in the growing environment.

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Land-use changes are widely recognized as important drivers of terrestrial carbon sinks. However, how changes in land-use patterns affect the interannual variability of net ecosystem productivity (NEP) remains unclear. This study analyzed the impacts of land-use patterns on NEP in Hubei Province from 2001 to 2025, utilizing MODIS NPP data, the China Land Cover Dataset (CLCD), and meteorological observations. Linear and nonlinear trends of NEP were examined using the Mann–Kendall (M-K) trend test and Ensemble Empirical Mode Decomposition (EEMD), respectively. Four landscape metrics, the contagion index (CONTAG), largest patch index (LPI), patch density (PD), and Patch Richness (PR), were calculated to characterize land-use pattern changes, and Pearson correlation analysis was employed to explore their interannual relationships with NEP. The results showed that the linear increasing trend of NEP masked widespread nonlinear shifts: while the M-K trend test indicated significant increases in 40.6% of the area, EEMD revealed that only 11.91% exhibited true monotonic increases, whereas 44.8% presented an increasing-to-decreasing trend. These shifts were predominantly concentrated in the Jianghan Plain, Northeast Hubei, and eastern Northwest Hubei, where cropland-to-impervious conversion was relatively intense and landscape metrics exhibited relatively pronounced nonlinear changes. LPI and CONTAG were significantly negatively correlated with NEP in these areas, which was consistent with the fragmentation of contiguous landscapes by urban expansion. In contrast, PD showed contrasting correlation directions. It was positively correlated with NEP in the plain areas, but negatively correlated in the mountainous areas, suggesting divergent associations of landscape fragmentation under different landscape matrices. PR exhibited the weakest correlations with NEP overall. This study highlights that nonlinear trend analysis is essential for accurately assessing carbon sink dynamics and that landscape patterns exert spatially heterogeneous effects on NEP, providing a scientific basis for differentiated land-use management strategies for carbon sequestration in Hubei Province.