Root and shoot phenology, architecture, and organ properties: an integrated trait network among 44 herbaceous wetland species.

Integrating traits across above- and belowground organs offers comprehensive insights into plant ecology, but their various functions also increase model complexity. This study aimed to illuminate the interspecific pattern of whole-plant trait correlations through a network lens, including a detailed analysis of the root system. Using a network algorithm that allows individual traits to belong to multiple modules, we characterize interrelations among 19 traits, spanning both shoot and root phenology, architecture, morphology, and tissue properties of 44 species, mostly herbaceous monocots from Northern Ontario wetlands, grown in a common garden. The resulting trait network shows three distinct yet partially overlapping modules. Two major trait modules indicate constraints of plant size and form, and resource economics, respectively. These modules highlight the interdependence between shoot size, root architecture and porosity, and a shoot-root coordination in phenology and dry-matter content. A third module depicts leaf biomechanical adaptations specific to wetland graminoids. All three modules overlap on shoot height, suggesting multifaceted constraints of plant stature. In the network, individual-level traits showed significantly higher centrality than tissue-level traits do, demonstrating a hierarchical trait integration. The presented whole-plant, integrated network suggests that trait covariation is essentially function-driven rather than organ-specific.

Effects of N and P additions on twig traits of wild apple (Malus sieversii) saplings.

BACKGROUND: Wild apple (Malus sieversii) is under second-class national protection in China and one of the lineal ancestors of cultivated apples worldwide. In recent decades, the natural habitation area of wild apple trees has been seriously declining, resulting in a lack of saplings and difficulty in population regeneration. Artificial near-natural breeding is crucial for protecting and restoring wild apple populations, and adding nitrogen (N) and phosphorous (P) is one of the important measures to improve the growth performance of saplings. In this study, field experiments using N (CK, N1, N2, and N3: 0, 10, 20, and 40 g m- 2 yr- 1, respectively), P (CK, P1, P2, and P3: 0, 2, 4, and 8 g m- 2 yr- 1, respectively), N20Px (CK, N2P1, N2P2, and N2P3: N20P2, N20P4 and N20P8 g m- 2 yr- 1, respectively), and NxP4 (CK, N1P2, N2P2, and N3P2: N10P4, N20P4, and N40P4 g m- 2 yr- 1, respectively) treatments (totaling 12 levels, including one CK) were conducted in four consecutive years. The twig traits (including four current-year stem, 10 leaf, and three ratio traits) and comprehensive growth performance of wild apple saplings were analyzed under different nutrient treatments. RESULTS: N addition had a significantly positive effect on stem length, basal diameter, leaf area, and leaf dry mass, whereas P addition had a significantly positive effect on stem length and basal diameter only. The combination of N and P (NxP4 and N20Px) treatments evidently promoted stem growth at moderate concentrations; however, the N20Px treatment showed a markedly negative effect at low concentrations and a positive effect at moderate and high concentrations. The ratio traits (leaf intensity, leaf area ratio, and leaf to stem mass ratio) decreased with the increase in nutrient concentration under each treatment. In the plant trait network, basal diameter, stem mass, and twig mass were tightly connected to other traits after nutrient treatments, indicating that stem traits play an important role in twig growth. The membership function revealed that the greatest comprehensive growth performance of saplings was achieved after N addition alone, followed by that under the NxP4 treatment (except for N40P4). CONCLUSIONS: Consequently, artificial nutrient treatments for four years significantly but differentially altered the growth status of wild apple saplings, and the use of appropriate N fertilizer promoted sapling growth. These results can provide scientific basis for the conservation and management of wild apple populations.

How Eutrophication Promotes Exotic Aquatic Plant Invasion in the Lake Littoral Zone?

Eutrophication and exotic species invasion are key drivers of the global loss of biodiversity and ecosystem functions in lakes. We selected two exotic plants (Alternanthera philoxeroides and Myriophyllum aquaticum) and two native plants (Myriophyllum spicatum and Vallisneria spinulosa) to elucidate the effect of eutrophication on exotic plant invasiveness. We found that (1) elevated nutrient favored invasion of exotic species and inhibited growth of native plants. Species combinations and plant densities of native plants had limited effects on the resistance to invasion of the exotics. (2) A. philoxeroides featured the tightest connectivity among traits, which is consistent with its high competitive ability. Although eutrophication caused physiological stress to A. philoxeroides, it could effectively regulate enzyme activity and alleviate the stress. (3) M. aquaticum possessed strong tolerance to habitat disturbance and was highly disruptive to the surrounding plants. Eutrophication will exacerbate the adverse effects of M. aquaticum on the littoral ecosystem. (4) Nutrient enrichment reduced the biomass and relative growth rates of V. spinulosa and lowered phenolics and starch contents of M. spicatum, thereby making them more susceptible to habitat fluctuations. Overall, our study highlights how eutrophication alters the invasiveness of exotic plants and the resistance of native plants in the littoral zone, which is of relevance in a world with intensified human activities.

Which Has a Greater Impact on Plant Functional Traits: Plant Source or Environment?

The deterioration of water quality caused by human activities has triggered significant impacts on aquatic ecosystems. Submerged macrophytes play an important role in freshwater ecosystem restoration. Understanding the relative contributions of the sources and environment to the adaptive strategies of submerged macrophytes is crucial for freshwater restoration and protection. In this study, the perennial submerged macrophyte Myriophyllum spicatum was chosen as the experimental material due to its high adaptability to a variable environment. Through conducting reciprocal transplant experiments in two different artificial environments (oligotrophic and eutrophic), combined with trait network and redundancy analysis, the characteristics of the plant functional traits were examined. Furthermore, the adaptive strategies of M. spicatum to the environment were analyzed. The results revealed that the plant source mainly influenced the operational pattern among the traits, and the phenotypic traits were significantly affected by environmental factors. The plants cultured in high-nutrient water exhibited a higher plant height, longer leaves, and more branches and leaves. However, their physiological functions were not significantly affected by the environment. Therefore, the adaptation strategy of M. spicatum to the environment mainly relies on its phenotypic plasticity to ensure the moderate acquisition of resources in the environment, thereby ensuring the stable and efficient operation of plant physiological traits. The results not only offered compelling evidence on the adaptation strategies of M. spicatum in variable environments but also provided theoretical support for the conservation of biodiversity and sustainable development.

Linking trait network to growth performance of submerged macrophytes in response to ammonium pulse.

Extreme precipitation events caused by climate change leads to large variation of nitrogen input to aquatic ecosystems. Our previous study demonstrated the significant effect of different ammonium pulse patterns (differing in magnitude and frequency) on submersed macrophyte growth based on six plant morphological traits. However, how connectivity among plant traits responds to nitrogen pulse changes, which in turn affects plant performance, has not yet been fully elucidated. The response of three common submersed macrophytes (Myriophyllum spicatum, Vallisneria natans and Potamogeton maackianus) to three ammonium pulse patterns was tested using plant trait network (PTN) analysis based on 18 measured physiological and morphological traits. We found that ammonium pulses enhanced trait connectivity in PTN, which may enable plants to assimilate ammonium and/or mitigate ammonium toxicity. Large input pulses with low frequency had stronger effects on PTNs compared to low input pulses with high frequency. Due to the cumulative and time-lagged effect of the plant response to the ammonium pulse, there was a profound and prolonged effect on plant performance after the release of the pulse. The highly connected traits in PTN were those related to biomass allocation (e.g., plant biomass, stem ratio, leaf ratio and ramet number) rather than physiological traits, while phenotype-related traits (e.g., plant height, root length and AB ratio) and energy storage-related traits (e.g., stem starch) were least connected. V. natans showed clear functional divergence among traits, making it more flexible to cope with unfavorable habitats (i.e., high input pulses with low frequencies). M. spicatum with high RGR revealed strong correlations among traits and thus supported nitrogen accumulation from favourable environments (i.e., low input pulses with high frequencies). Our study highlights the responses of PTN for submerged macrophytes to ammonium pulses depends on their intrinsic metabolic rates, the magnitude, frequency and duration of the pulses, and our results contribute to the understanding of the impact of resource pulses on the population dynamics of submersed macrophytes within the context of global climate change.

Phosphorus enrichment affects trait network topologies and the growth of submerged macrophytes.

Significant differences in the morphological and physiological characteristics of submerged macrophytes have been studied following nutrient addition, but little research has investigated the changes in plant trait network topology structures and trait interactions at the whole-plant perspective along nutrient gradients. Plant trait interactions and coordination strongly determine ecosystem structure and functioning. Thirty plant traits were collected from a three-month experiment to construct plant trait networks to clarify the variations in trait connections and network organization arising from five total phosphorus (TP) addition concentrations in water, including a control (CK), 0.1 (TP1), 0.2 (TP2), 0.4 (TP3), and 0.8 (TP4) mg L-1. Nonmetric multidimensional scaling analysis showed a clear difference in the distribution of plant trait space among the different TP treatments. Distinct network structures showed that water TP-deficiency and TP-repletion changed the plant trait network into loose assemblages of more modules, which was related to low plant carbohydrate levels. Most plant functions involving biomass accumulation and carbohydrate synthesis were reduced under high TP conditions compared to moderate TP enrichment. Moreover, the percentage of significant relationships between plant functions and corresponding network modules was lower in the CK and TP4 treatments. These results suggested that low plant carbohydrates in high TP environments induced by high water chlorophyll a and tissue phosphorus could not support rapid resource transport among organs and thus inefficiently performed plant functions. Plant carbohydrates were a vital variable that impacted the network edge density, trait interactions, and plant growth. In summary, we demonstrated that high water TP enrichment reduces plant trait network connectedness and plant functional potentials, which may be correlated with reducing tissue carbohydrates. This study explores the correlations between plant trait network topology and functions to improve our understanding of physiological and ecological rules regulating trait interactions among organs and plant growth under eutrophic conditions.