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How communities of living organisms assemble has long been a central question in ecology. The impact of habitat filtering and limiting similarity on plant community structures is well known, as both processes are influenced by individual responses to environmental fluctuations. Yet, the precise identifications and quantifications of the potential abiotic and biotic factors that shape community structures at a fine scale remains a challenge. Here, we applied null model approaches to assess the importance of habitat filtering and limiting similarity at two spatial scales. We used 63 natural vegetation plots, each measuring 5 × 5 m, with three nested subplots measuring 1 × 1 m, from the 2021 field survey, to examine the alpha diversity as well as beta diversity of plots and subplots. Linear mixed‐effects models were employed to determine the impact of environmental variables on assembly rules. Our results demonstrate that habitat filtering is the dominant assembly rules at both the plot and subplot levels, although limiting similarity assumes stronger at the subplot level. Plot‐level limiting similarity exhibited a positive association with fine‐scale partitioning, suggesting that trait divergence originated from a combination of limiting similarity and spatial partitioning. Our findings also reveal that the community assembly varies more strongly with the mean annual temperature gradient than the mean annual precipitation. This investigation provides a pertinent illustration of non‐random assembly rules from spatial scale and environmental factors in plant communities in the loess hilly region. It underscores the critical influence of spatial and environmental constraints in understanding the assembly of plant communities. [ABSTRACT FROM AUTHOR]

The grasslands in high-latitude areas are sensitive to climate warming and drought. However, the drought stress effect on the long-term variability of grassland productivity at the continental scale still hinders our understanding. Based on aboveground net primary production (ANPP) surveys, satellite remote sensing Normalized Difference Vegetation Index (NDVI), and meteorological data, we comprehensively analyzed three Aridity metrics and their effect on ANPP in Eurasian grassland from 1982 to 2020. Our results showed that the ANPP had an overall uptrend from 1982 to 2020, increasing most in the Tibetan Plateau alpine steppe subregion (TPSSR). Among three Aridity indicators, vapor pressure deficit (VPD) had an overall uptrend, while the trend of Aridity and soil moisture (SM) was insignificant from 1982 to 2020. Soil drought had negative effects on ANPP for all Eurasian grassland, while the atmospheric VPD had a positive effect on ANPP for TPSSR and the Mongolian Plateau steppe subregion (MPSSR), but a negative effect for the Black Sea–Kazakhstan steppe subregion (BKSSR) which was the driest subregion. SM had been the predominant driving factor for the interannual variability of ANPP in MPSSR since 1997. The increasing VPD had facilitated grassland productivity in alpine grasslands due to its cascading effect with an increasing temperature after 2000. The cascading effects networks of climate factors—drought factors (VPD, Aridity, and SM)—ANPP (CDA–CENet) indicated that SM was the predominant driving factor of the interannual variability of ANPP in MPSSR and BKSSR, and the dominance of SM had enhanced after the year 1997. The inhibitory effect of VPD on ANPP transformed into a facilitating effect after 1997, and the facilitating effect of SM is weakening in TPSSR. [ABSTRACT FROM AUTHOR]

Light use efficiency (LUE) is a crucial indicator used to reflect the ability of terrestrial ecosystems to transform light energy. Understanding the long-term trends in LUE and its influencing factors are essential for determining the future carbon sink and carbon sequestration potential of terrestrial ecosystems. However, the long-term interannual variability of LUE in grasslands in northern China at the ecosystem scale is poorly understood due to the limitations of the year length and the coverage of the site data. In this study, we assessed the long-term LUE trends in the grasslands of northern China from 1982 to 2018 and then revealed the relationships between interannual variability in LUE and climate factors. Our study showed a substantial rising trend for LUE from 1982 to 2018 in the grasslands of northern China (3.42 × 10−3 g C/MJ/yr). Regarding the different grassland types, alpine meadow had the highest growth rate (4.85 × 10−3 g C/MJ/yr), while temperate steppe had the lowest growth rate (1.58 × 10−3 g C/MJ/yr). The climate factors driving LUE dynamics were spatially heterogeneous in grasslands. Increasing precipitation accelerated the interannual growth rate of LUE in temperate steppe, and increasing temperature accelerated the interannual growth rate of LUE in other types. In addition, the temporal dynamic of LUE showed different trends in relation to time scales, and the growth trend slowed down after 1998. Our results should be considered in developing future grassland management measures and predicting carbon cycle–climate interactions. [ABSTRACT FROM AUTHOR]

• Appropriate Na amendment facilitate leaf litter decomposition. • Na amendment increases similarity of microbial community in oak and pine forests. • Soil fauna show higher preference for Na-added litters. • Regardless of direction, Na amendment significantly decreased the strength of HFA. Sodium (Na) can affect ecosystem function by altering soil fauna and microbial community composition and abundance. Sodium's potential influences on plant-soil interactions, such as home-field advantage (HFA: enhanced decomposition in a home environment compared to an away environment), in relation to litter decomposition remains unclear. To fill this knowledge gap, we conducted a ten-month reciprocal litter transplant field experiment with Na amendments (0.005% and 0.5% water solution of NaCl) in both a subtropical broad-leaved forest dominated by Quercus variabilis (oak) and a coniferous artificial forest planted by Pinus massoniana (pine) in China. Litterbags with different mesh sizes were used to partition the impact of soil biota groups on the HFA. The results showed that 0.005% Na amendment facilitated litter decomposition as well as carbon (C) and nitrogen (N) mineralization by enhancing soil extracellular enzyme activity and soil faunal abundance. But 0.5% Na amendment inhibited litter decomposition in fine-mesh litterbags by decreasing microbial activity, and promoted litter decomposition in coarse-mesh litterbags by attracting more soil fauna. In the control plots, we observed a negative HFA in coarse-mesh litterbags (with most soil fauna and all soil microorganisms), and a positive HFA in fine-mesh litterbags (with complete exclusion of meso-and macrofauna). Whether the HFA was positive or negative (i.e. regardless of the direction of the HFA), Na amendments significantly decreased the magnitude of HFA by increasing the similarity of microbial community composition between the incubation fields ('home' vs. 'away') and decreasing selective foraging of soil fauna for different leaf litters. In sum, our results indicate that anthropogenic Na enrichment can decrease the effects of HFA through the modification of soil microbial and faunal communities, and thereby affect C sequestration and N cycling in subtropical forests. [ABSTRACT FROM AUTHOR]