Soil properties can affect plant population dynamics and the coexistence of native and invasive plants, thus potentially affecting community structure and invasion trends. However, the different impacts of soil physicochemical properties on species diversity and structure in native and invaded plant communities remain unclear. In this study, we established a total of 30 Alternanthera philoxeroides-invaded plots and 30 control plots in an area at the geographical boundary between North and South China. We compared the differences in species composition between the invaded and native plant communities, and we then used the methods of regression analysis, redundancy analysis (RDA), and canonical correspondence analysis (CCA) to examine the impacts of soil physicochemical properties on four α-diversity indices and the species distribution of these two types of communities. We found that A. philoxeroides invasion increased the difference between the importance values of dominant plant species, and the invasion coverage had a negative relationship with the soil-available potassium (R² = 0.135; p = 0.046) and Patrick richness index (R² = 0.322; p < 0.001). In the native communities, the species diversity was determined with soil chemical properties, the Patrick richness index, the Simpson dominance index, and the Shannon–Wiener diversity index, which all decreased with the increase in soil pH value, available potassium, organic matter, and ammonium nitrogen. However, in the invaded communities, the species diversity was determined by soil physical properties; the Pielou evenness index increased with increasing non-capillary porosity but decreased with increasing capillary porosity. The determinants of species distribution in the native communities were soil porosity and nitrate nitrogen, while the determinants in the invaded communities were soil bulk density and available potassium. In addition, compared with the native communities, the clustering degree of species distribution in the invaded communities intensified. Our study indicates that species diversity and distribution have significant heterogeneous responses to soil physicochemical properties between A. philoxeroides-invaded and native plant communities. Thus, we need to intensify the monitoring of soil properties in invaded habitats and conduct biotic replacement strategies based on the heterogeneous responses of native and invaded communities to effectively prevent the biotic homogenization that is caused by plant invasions under environmental changes.

Variations in latitudinal gradients could lead to changes in the performance and ecological effects of invasive plants and thus may affect the species composition, distribution and interspecific substitution of native plant communities. However, variations in structure, similarity and beta (β) diversity within invaded communities across latitudinal gradients in heterogeneous habitats remain unclear. In this study, we conducted a two-year field survey along 21°N to 37°N in China, to examine the differential effects of the amphibious invasive plant Alternanthera philoxeroides on native plant communities in terrestrial and aquatic habitats. We compared the differences in the invasion importance value (IV), species distribution, community similarity (Jaccard index and Sorenson index) and β diversity (Bray−Curtis index and β_sim index) between terrestrial and aquatic communities invaded by A. philoxeroides, as well as analyzed their latitudinal trends. We found that the IV of A. philoxeroides and β diversity in aquatic habitats were all significantly higher than that of terrestrial, while the terrestrial habitat had a higher community similarity values. The aquatic A. philoxeroides IV increased with increasing latitude, while the terrestrial IV had no significant latitudinal trend. With increasing latitude, the component proportion of cold- and drought-tolerant species in the terrestrial communities increased, and the dominant accompanying species in the aquatic communities gradually changed from hygrophytes and floating plants to emerged and submerged plants. In addition, the aquatic communities had lower community similarity values and higher β diversity in higher latitudinal regions, while terrestrial communities had the opposite parameters in these regions. Our study indicates that the bioresistance capacities of the native communities to invasive A. philoxeroides in heterogeneous habitats are different; A. philoxeroides invasion leads to higher community homogenization in terrestrial habitats than in aquatic habitats, and terrestrial communities experience more severe homogenization in higher latitudinal regions. These findings are crucial for predicting the dynamics of invasive plant communities under rapid global change.

Soil nitrogen can significantly affect the morphology, biomass, nutrient allocation, and photosynthesis of alien vs. native plants, thereby changing their coexistence patterns; however, the effect of soil nitrogen on the interspecific relationship between alien plants is currently unclear. We conducted a nitrogen addition experiment in a greenhouse to explore the effect of soil nitrogen on the interspecific relationship between invasive alien weed Alternanthera philoxeroides and the noninvasive alien horticultural plant Oxalis articulata. We set three experimental factors—nitrogen treatment, planting type, and species and measured the morphology, biomass, carbon (C) and nitrogen (N) content, physiological traits, and photosynthetic fluorescence of the studied plant species. We then used multi-way ANOVA and multiple comparisons to examine the differences in the above indicators among treatment combinations. We found that, in mixed cultures, nitrogen addition significantly increased the root area of O. articulata by 128.489% but decreased the root length by 56.974% compared with the control, while it significantly increased the root length of A. philoxeroides by 130.026%. Nitrogen addition did not affect the biomass accumulation of these two plant species; however, the biomass and root/shoot ratio of O. articulata were significant higher than those of A. philoxeroides. Nitrogen addition significantly increased the N content of A. philoxeroides by 278.767% and decreased the C:N ratio by 66.110% in mixed cultures. Nitrogen addition caused a significant trade-off between flavonoid and anthocyanin in O. articulata, and decreased the initial fluorescence (F₀) and maximal fluorescence (F_m) of A. philoxeroides by 18.649 and 23.507%, respectively, in mixed cultures. These results indicate that nitrogen addition increased the N absorption and assimilation ability of A. philoxeroides in deep soil; furthermore, it significantly enhanced the advantages for O. articulata in terms of morphology, physiological plasticity, and photosynthetic efficiency. In addition, O. articulata had better individual and underground competitive advantages. Under intensified nitrogen deposition, the biotic replacement effect of O. articulata on A. philoxeroides in natural ecosystems could be further enhanced.

Plant invasions are closely related to environmental filtering and biointeractions; however, the variations in invasive plant niches along latitudinal gradients in heterogeneous habitats remain unclear. In this study, we conducted a two-year survey in China spanning 21° N–37° N to explore the niche characteristics of plant species within communities invaded by the amphibious alien weed Alternanthera philoxeroides in both terrestrial and aquatic habitats as well as their latitudinal trends. We found that A. philoxeroides had the greatest niche breadth in the studied communities. The species pairs with the highest niche similarity were A. philoxeroides–Digitaria sanguinalis in terrestrial communities and Cyperus rotundus–Kyllinga brevifolia in aquatic communities. The niche similarity between A. philoxeroides and its accompanying species in terrestrial habitats was significantly higher than that in aquatic habitats (t = 5.954; p < 0.001). The niche breadth of A. philoxeroides had no obvious latitudinal trend, while the niche breadth of its accompanying species in the terrestrial community significantly decreased with increasing latitude (F_{7, 57} = 4.364, p = 0.001). In the terrestrial communities, the niche similarity between A. philoxeroides and its accompanying species significantly decreased with increasing latitude (F_{7, 57} = 3.671, p = 0.003), while the niche overlap significantly increased with increasing latitude (F_{7, 57} = 8.916, p < 0.001). However, the aquatic species’ niche characteristics had no obvious latitudinal trends. These findings indicated that habitat heterogeneity significantly affected the species’ niche characteristics in A. philoxeroides-invaded communities. Environmental filtering at low latitudes allowed the invasive and accompanying species to evolve similar niches, while the cold climate at high latitudes increased the niche overlap between the invader and accompanying species. Our findings are crucial for predicting the dynamics of invasive plant communities under global change and for understanding the mechanisms of species coexistence.

Biological invasions can lead to changes in the interspecific association and coexistence patterns of plant species; however, the differences in the interspecific association characteristics of invaded plant communities in heterogeneous habitats and their variations along latitudinal gradients remain unclear. Here, we established 40 terrestrial plots and 40 aquatic plots invaded by the amphibious invasive species Alternanthera philoxeroides (Mart.) Griseb. within the range of 21–37°N in China to explore the interspecific associations and association intensities of A. philoxeroides-invaded plant communities and their latitudinal trends. We found that there was a significantly positive interspecific association in the overall terrestrial communities, with A. philoxeroides having a strong association with many accompanying species. However, there was a nonsignificant negative interspecific association in the overall aquatic communities. The ratio of species pairs with positive/negative associations (PNR) in terrestrial communities dramatically decreased at higher latitudes. The values of the Jaccard index (J_A), Ochiai index (O_I), and Dice index (D_I) which represent the interspecific association intensity in terrestrial communities, were extremely significantly greater than those in aquatic communities. The association intensity between terrestrial accompanying species significantly decreased with increasing latitude, and the association intensity between aquatic accompanying species varied weakly along the latitudinal gradient. Our study revealed that A. philoxeroides invasion aggravated interspecific competition among accompanying species in terrestrial plant communities in higher latitude regions, whereas the aquatic A. philoxeroides-invaded communities presented more mutualistic relationships to resist abiotic stress in higher latitude regions.

To improve the estimation accuracy of wood density and study the linear correlation between drill feed resistance and wood density, a new micro drill instrument prototype that can simultaneously measure the rotation resistance and feed resistance of the drill needle was designed. The test tree species included hard and soft broad-leaved trees and coniferous trees, and the absolute dry density of each wood sample was measured. The drill resistance data were tested by our newly proposed prototype and a Resistograph 650-SC, and four linear models were established to define the relation between drill resistance and the absolute dry density of the wood. The results showed that (1) the statistical indicators of each model for our proposed prototype were better than the corresponding indicators of the Resistograph 650-SC for three of the four species tested; (2) the coefficient of determination of the linear regression model between the feed resistance of our proposed prototype and the absolute dry density of wood was 0.946; and (3) the statistical indicators of the model that included rotation resistance and feed resistance were better than those of the model that only including rotation resistance. Although the proposed prototype produced a competitive level of accuracy and explicitly demonstrated that including feed resistance improved wood density measurement accuracy, the prototype should be considered a first iteration as further hardware design changes and in-forest performance assessments across wider diverse set of test species are required before a conclusive evaluation can be rendered.