Plant Invasion: 2nd Edition

Nitrogen deposition continuously alters the invasibility of terrestrial ecosystems, but how the composition of local plant functional groups regulates this process by root-associated microbial during invasion, especially under the background of resource changes, remains unclear. This study focused on the invasive plant Cenchrus spinifex Cav. and conducted an interactive experiment using nitrogen addition and four different functional group combinations of local plant communities. The results show that the community with the closest phylogenetic distance (PD = 189) had the strongest resistance to invasion. Nitrogen addition was the core factor driving invasion (total effect 0.86), which promoted invasion by increasing soil nitrogen pools and altering microbial community structure. The role of leguminous plants changed fundamentally with nitrogen availability; they were competitors under low-nitrogen conditions, while under high-nitrogen conditions, they transformed into “synergistic invaders” by shaping the root-associated environment rich in microorganisms such as Proteobacteria that facilitate rapid nutrient turnover. Plant nitrogen and phosphorus content (PNP) is a key indicator reflecting the nutrient absorption capacity of invasive plants and is closely related to invasion success. It significantly promotes the ability of root resources acquisition. The study shows that invasion success depends on the dynamic balance among resource input, the phylogenetic background of the local community, and the microbial feedback regulated by it. Future ecological management should consider the coordinated regulation of aboveground functional group selection and underground microbial processes. Full article

In this study, we investigated how substrate moisture content affects the growth performance and adaptive responses of Myriophyllum aquaticum. Through a controlled simulation experiment, we systematically analyzed the morphological characteristics and physiological responses of plants under five moisture levels: 0–15%, 15–30%, 30–45%, 45–60%, and 60–75%. The results indicate that optimal growth of M. aquaticum occurred at a substrate moisture content of 60–75%, with significant increases in plant height, branching ability, and biomass. A drought acclimation response was triggered at moisture levels ≤45%, characterized by shortened root length, increased total senescent internode length, biomass allocation shift toward aboveground parts, decreased chlorophyll a content, and elevated accumulation of malondialdehyde. Plants died at moisture levels ≤15%. However, they survived at 15–30% moisture, although their biomass continued to decline. A key finding was that under conditions where the sediment surface lacked water but the substrate moisture remained at 60–75%, plants achieved efficient water utilization and canopy reconstruction through rapid root extension and stem node proliferation, and the relative growth rate was significantly higher than that of the drought group (≤45% moisture). This strong adaptive capacity under specific water conditions, combined with its dehydration tolerance, suggests that M. aquaticum could potentially have a competitive advantage over native submerged plants that rely on stable water bodies, particularly in hydrologically fluctuating habitats. This study revealed that morpho-physiological plasticity driven by water gradients may be a key mechanism contributing to the invasive potential of M. aquaticum, providing new insights into its possible expansion potential in zones with fluctuating water levels. Full article

Under the background of a supply gap expansion for high-quality forage grass in China and the high degree of dependence on foreign countries, it is necessary to clarify the best feeding and harvesting period for Cichorium intybus in the temperate continental monsoon climate zone of Northern China. To achieve this goal, this study systematically explored the agronomic traits and nutritional quality of Cichorium intybus during the nutritional period (June–July), flowering period (July–August), and fruiting period (August–September) in the Hohhot experimental base. We measured agronomic indexes, such as the plant height and basal stem, and nutrients, such as the dry matter (DM) and crude protein (CP), and calculated the total digestible nutrients (TDN) and other feeding value indexes. The results showed that the plant height of Cichorium intybus increased from 54.60 cm in the vegetative stage to 204.10 cm in the fruiting stage, and the fresh grass yield increased from 8775.045 kg/hm² in the vegetative stage to 19,035.09 kg/hm² in the fruiting stage. The DM content of the stems and leaves was the lowest (stem: 8.73%; leaf: 14.04%), but the CP (leaf: 20.32%) and crude fat (EE, leaf: 5.02%) contents were the highest. The TDN was 66.78%, the relative feed value (RFV) was 255.61, the comprehensive membership function value was 0.54 for the stems and 0.60 for the leaves, and the feeding value was the best. WSC accumulation was significant during the flowering stage; the fiber content of the DM (stem: 20.52%; leaf: 20.31%) and the acid detergent fiber (ADF, stem: 42.43%) were the highest during this stage; and the CP decreased to 10.97%. A correlation analysis showed that the plant height and stem diameter were significantly positively correlated with the yield and fiber accumulation. This study confirmed that the nutritional period was the best harvest period for obtaining high-protein and high-digestibility forage, and the fruiting period was suitable for processing hay or silage. These results provide a scientific basis for the large-scale feed development of Cichorium intybus. Full article

Exploring how nitrogen deposition alters the competitive interactions between invasive plants and native plants is critical for predicting the invasion trends of invasive plants and for formulating their control strategies. In this study, the invasive plant Solanum rostratum and its native congener S. nigrum were selected as research subjects, and three different nitrogen (N) concentration treatments (N1: 50 mg·kg⁻¹, N2: 100 mg·kg⁻¹, N3: 150 mg·kg⁻¹) were set up to compare the two species in terms of growth and development, leaf nutrient utilization strategies, stress tolerance, and rhizosphere microbial community differences under competitive conditions. The results showed that the biomass of S. rostratum was 1.4 to 2.3 times that of S. nigrum; the former had a lower root–shoot ratio and a larger crown width, enabling it to seize more living space and light resources. Across all nitrogen treatments, the net photosynthetic rate of S. rostratum leaves was significantly higher than that of S. nigrum, reflecting a stronger carbon sequestration capacity. With the increase in soil nitrogen concentration, the malondialdehyde content in S. rostratum leaves showed a decreasing trend; meanwhile, its leaf soluble sugar and catalase contents were 3.5 to 4.3 times and 1.5 to 2.5 times those of S. nigrum, respectively, indicating a lower oxidative stress level and higher stress tolerance in S. rostratum. The leaf C/P and C/N ratios of S. rostratum increased with the rise in soil N, demonstrating a higher nutrient use efficiency, while the decrease in leaf phosphorus (P) content might be attributed to the element dilution effect caused by the rapid plant growth. In addition, the diversity and stability of the rhizosphere microbial community of S. rostratum gradually increased with increasing soil N and were significantly higher than those of S. nigrum. The rhizosphere-recruited microbes of the genera Comamonas and Chryseobacterium may help promote its root nutrient absorption and thus enhance its competitive ability. Collectively, our findings reveal that under exogenous N application, S. rostratum gains a significant growth advantage over S. nigrum, which is attributed to its stronger capacities for carbon assimilation and spatial resource acquisition, a nutrient strategy characterized by low acquisition and high utilization, as well as a stable and diverse rhizosphere microbial community. Full article

Prosopis juliflora is a highly invasive tree species in semi-arid and arid regions in eastern Africa. Its ability to displace herbaceous and woody species has been attributed to allelopathic effects, but this has rarely been tested in competition experiments on natural soil and experimentally binding potentially allelopathic substances. We tested the effect of soil collected underneath and outside of P. juliflora canopy, or treated with P. juliflora leaf litter, on the survival, growth, and competitive ability of three resident tree species in the presence and absence of activated carbon. Survival and growth of tree seedlings were reduced on soil collected underneath P. juliflora canopy and on soil collected outside P. juliflora canopy mixed with leaf litter, compared to seedlings growing on soil collected outside P. juliflora canopy. When activated carbon was added, seedling performance increased on soil collected underneath P. juliflora canopy and particularly on soil collected outside P. juliflora canopy mixed with leaf litter. Competition reduced seedling height irrespective of the type of competitor (P. juliflora or resident tree species). There was no significant interaction between soil type and competition, indicating that the effect of competition was independent of soil type. The results suggest that P. juliflora releases allelochemicals into the soil, which have allelopathic effects on resident tree species, and that at least part of these allelochemicals originate from leaf material. Full article

Invasive alien plants (IAPs) disrupt biodiversity, ecosystem functions, rural livelihoods, and human health/well-being. Hence, the negative impact of Cenchrus setaceus (syn. Pennisetum setaceum) as an invasive weed poses many concerns in terms of environmental and socio-economic impact. The abundance in previous research on invasion ecology, weed biology, and the management of C. setaceus establishes the chance to carry out an in-depth evaluation of this invasive alien species for a cohesive understanding, closely linked to policy development. This systematic review aims to provide a comprehensive evaluation of previous research, identify knowledge gaps, and incorporate recent practical research findings on C. setaceus to elucidate management options. Standard methods were used to collect the literary evidence on multiple thematic aspects linked with its traits and management. Results revealed the substantial negative impacts of C. setaceus on ecosystems, ascribed to multiple physiological, biochemical, and ecological features. Further, a multitude of plant traits such as rapid seed distribution and efficient reproductive strategies imposed serious challenges in the control of C. setaceus. Deployment of integrated control methods for at least three years in depleting seed bank conjunction by planting native grass may help in its confinement. In conclusion, policy measures like strict biosecurity/legal regulations, explicit elucidation of weed biology, early detection and response, ecological modeling, and long-term monitoring with community participation can expand the horizon of C. setaceus control and help achieve its sustainable management. Full article