Plant Ecology最新文献

Interactions between plants and floral visitors have a significant influence on the structure and function of ecosystems. The study of these interactions can be performed through the analysis of ecological networks, allowing an understanding of the complexity of ecosystem functioning. The objective of the present study was to verify whether the characteristics of individuals of Byrsonima intermedia (Malpighiaceae) affects its role in the network of interactions with floral visitors in Brazilian palm swamps (veredas). Veredas with different levels of dryness were studied, including one degraded vereda (advanced stage of drying), one intermediate vereda (low drying), and one preserved vereda (no drying). For sampling, we selected 45 individuals of the Byrsonima intermedia plant, 15 in each area, where they were monitored to observe the behavior of floral visitor insects and to measure the characteristics of the plant individuals. As a result, the networks of all sampled area were significantly modular and specialized, with the preserved vereda showing greater specialization. In this study, we observed that the networks of individuals of Byrsonima intermedia and their floral visitors were mainly composed of non-oil-collecting bees. The results show that the abundance of resources offered by each individual in the network, the size of the flower and the plant height are some factors that can determine its role in the network of interactions in the studied veredas. Finally, it is concluded that individual plant interactions can be affected both by environmental characteristics and by plant morphological attributes.

Biodiversity is declining at unprecedented rates worldwide due largely to land use change and abnormal disturbance events. The high species diversity and endemicity found in California’s coastal sage scrub (CSS) are especially at risk from urban development and ongoing disturbance. However, several CSS plant species have disturbance adaptations which may allow them to serve as vital resources for insect pollinators when native plant diversity is threatened. Common fiddleneck (Boraginaceae; Amsinckia menziesii var. intermedia) is one of the first annual forbs to germinate in CSS and as a result, it occurs in high density patches in early spring which temporarily creates a near monoculture. Although fiddleneck is a prominent CSS plant, particularly in areas that have experienced a disturbance event, its larger ecological role is not well explored. Therefore, we monitored ten sites across a disturbance gradient for two spring seasons to assess the composition of plant-pollinator networks in fiddleneck-dominated plots. We found fiddleneck supported a diverse pollinator community with 68% of recorded taxa visiting fiddleneck. The plants most frequently visited included two native annual forbs (common fiddleneck and Phacelia distans) and two invasive annual forbs (Erodium cicutarium and Brassica tournefortii). Increased mean precipitation resulted in increased plant abundance but decreased native pollinator diversity. Additionally, plant-pollinator networks changed over time; the number of links per species increased throughout the season but did not differ among disturbance types. Despite the numerical dominance of fiddleneck, CSS supported a diversity of pollinator taxa and exhibited complex plant-pollinator networks across the disturbance gradient.

Abstract

Lianas (woody vines) are important components of forest ecosystems and are often found to proliferate in young forests that have experienced large-scale disturbances. However, little is known regarding the mechanisms of the spatial assembly patterns of co-occurring lianas and trees in the temperate secondary forest stands. In this study, we examined the woody plants (lianas and trees) with a stem diameter > 1 cm within a one-hectare plot on a steep mountain slope (32° average slope angle) in a temperate secondary forest in central Japan. We investigated the impact of the host trees, topography, and canopy gaps on the distribution of liana. We aimed to determine the factors that influence the spatial distribution differences between the co-occurring lianas and trees. The results were validated using the 10 m × 10 m quadrats (N = 40) distributed across 23 ha within the study site. We recorded 123 liana stems on 1536 trees belonging to 57 woody species in the one-hectare plot. The findings revealed that lianas are more abundant on larger host trees and less common in high tree density areas. Small and large lianas preferred steep and moderate slopes, respectively, whereas larger trees were primarily found on steep slopes. These variations in liana and tree distribution patterns on steep slopes, which we observed throughout their life history, may be attributed to the combined effects of varied historical anthropogenic disturbances and grazing impacts. This highlights the need to consider the diverse environmental responses of lianas and trees at the different life history stages to accurately understand liana colonization and proliferation in forests.

In invasion ecology, the Residence Time (RT) hypothesis suggests that the longer a species has been introduced to a region, the likelier it is to become invasive. However, obtaining information about RT is challenging for many regions worldwide. Consequently, the time since the species was first recorded in the studied area (Minimum Residence Time, MRT) is commonly used. Nevertheless, the study of MRTs in invasive species is uneven across regions. In this study, we integrated online herbaria sources with literature records of both invasive and non-invasive alien species, along with native woody species, to assess whether invasive alien species in central Argentina exhibit longer MRT than non-invasives at two geographic scales. If RT proves to be a significant factor influencing the invasive potential of a species, one would expect invasive species to have extended RT in herbarium records compared to non-invasive ones, although shorter than those of natives that initially drew the attention of early botanists. We observed a higher MRT for native species compared to alien species, suggesting that the online herbaria data used are sensitive to the dynamics of plant communities over time. The patterns were consistent at both scales. Among alien species, invasives exhibited consistently higher average MRT compared to non-invasives at both scales, providing further evidence of the role of time in invasion dynamics. This study’s methodology is applicable to regions lacking information on the introduction history of alien species but having online herbaria, allowing the testing of the RT hypothesis in different world regions.

Abstract

Flower strips are a fundamental part of agri-environment schemes in the Common Agricultural Policy (CAP). Although vegetation is central for many arthropod groups, a few studies have evaluated the effects of flower strip structural and functional attributes on arthropod communities. In this study, we explored the relationship between flower strip attributes and the abundance of different arthropod functional groups in annual flower strips located in an organic apple orchard. We surveyed plant and arthropod communities in 30 1 m × 6 m plots. In each plot, we collected data on species composition and vegetation structure (e.g., total cover, density, number of floral displays). For each plant species, we also retrieved data on leaf palatability and nutritional value. Arthropods were collected using sweep netting technique. Structural and functional attributes of the flower strip revealed a crucial role in regulating arthropod abundance, which however depended on the specific arthropod functional group. We identified three main attributes (plant species richness, composition, and vegetation density) of flower strips that should be considered when implementing multifunctional flower strips. Specifically, plant species richness to ensure complementarity of resources and niches, plant species composition to ensure complementary floral resources, and vegetation density to ensure sheltering microhabitats and suitable microclimatic conditions and to increase the density of floral resources. Our results suggest that by considering structural and functional attributes of flower strips, it is possible to design multifunctional flower strips with greater effectiveness as measures for ecological intensification.

In seeds with impermeable coats, i.e., physical dormancy (PY), dormancy break may occur at room temperature during ex-situ storage or when seeds experiencing similar conditions when buried in the soil. Here, we tested the influence of initial seed moisture content and storage on dormancy break in the seeds of Adenanthera pavonina, Bauhinia racemosa, Cassia fistula, Dodonaea viscosa, and Delonix regia. Drying results in most seeds of these species becoming water-impermeable. We arbitrarily chose two moisture ranges, shallow (impermeable, high moisture content) and absolute (impermeable, low moisture content) PY, and stored the seeds at room temperature for 8.5 years. The moisture content at which the permeable to impermeable transition occurred and the range constituting shallow and absolute PY varied between species. Across species, the shallow PY group had a significantly higher number of nondormant seeds at the end of storage, whereas the absolute PY group did not show any germination, except c. 20% germination in A. pavonina and C. fistula. Thus, PY break in seeds stored at room temperature may occur after several years, but this largely depends on the initial seed moisture content.

The Cerrado, a Neotropical savanna, is the second largest vegetation domain in Brazilian territory and presents a gradient of physiognomies. Among the savanna formations, the cerrado stricto sensu stands out. The responses of woody species of the cerrado related to increased CO₂ concentration ([CO₂]), as predicted by global climate change, may differ among distinct leaf persistence groups. Elevated [CO₂] could enhance the resprouting capacity of woody species, which might intensify encroachment in grasslands, such as the cerrado stricto sensu. We investigated the influence of elevated [CO₂] (eCO₂) on vegetative growth, root non-structural carbohydrates (NSC), and biomass allocation pattern among roots, stems, and leaves in two deciduous and three evergreen cerrado woody species. We carried out the experiment in open-top chambers with five young individuals of cerrado woody species under ambient [CO₂] (aCO₂) and eCO₂ of 430 and 700 ppm, respectively. Measurements occurred in young plants with 294, 379, and 466 days old, i.e., after 104, 189, and 276 days of eCO₂ exposition. While the species under aCO₂ decreased the NSC in roots on the 189th day, the plants under eCO₂ did not show a decrease over time. The deciduous species under eCO₂ showed higher RGR at the beginning of the experiment (104 days) than the evergreens species under eCO₂. Also, the eCO₂ promoted fast leaf development in four out of five studied species (except Anadenanthera peregrina). The characteristics analyzed among the species could demonstrate that the deciduous grown under eCO₂ presented higher relative growth rate and root/stem ratio than the species with evergreen habit.

Edge disturbance can affect forest vegetation and soil properties, causing shifts in plant community structure. We investigated how linear forest edges influence tree community structure, soil properties, and the relationship of tree species composition with soil properties in a moist semi-deciduous forest, Ghana. We quantified tree community structure in 35 20 × 20-m plots each in forest edge and interior areas, and analyzed soil properties in the plots. Our findings revealed no significant difference in tree diversity between the forest edge and interior, although species composition differed considerably. The forest interior supported a significantly higher tree density than the forest edge, although basal area was similar between the edge and interior. Individual tree species exhibited different responses to the forest edge at varying magnitudes. Generally, light-demanding and shade-tolerant species showed associations with the forest edge and interior, respectively. Soils at the forest edge contained significantly lower Mg and higher Na concentrations than soils in the forest interior, while concentrations of other soil properties were similar between the forest edge and interior. Many of the soil properties (Na, Ca, P, Mg, effective cation exchange capacity, organic matter, soil texture) were uniquely associated with tree species composition in either the forest edge or interior. This study increases our understanding of linear edge effects on tree communities and soil properties, which can contribute to developing comprehensive edge theory for forest management.

Biological invasion is regarded as one of the most important disturbance parameters and threats for sustaining biodiversity. Global warming, industrialization, and open niche created due to the expansion of development initiatives contribute to the successful spread of invasive species around the world. The contributions of various biotic and abiotic factors in different spatial scales are crucial for an invasive to establish in its invaded area. We assessed the spatial distribution of invasion by Lantana camara in the Corbett Tiger Reserve and Rajaji Tiger Reserve within the Terai Arc Landscape Complex. The presence locations of Lantana were assessed within 10 m × 10 m plots (n = 666), and information on habitat variables such as tree density, canopy cover, shrub density, shrub cover, and anthropogenic pressures were collected. We also synthesized information on climate and topography data of the region from global databases. Confirmatory factor analysis was done using the presence of Lantana as response variable and habitat, anthropogenic, climatic, and topographic variables as predictor variables. We found that for Rajaji Tiger Reserve, habitat and anthropogenic variables were the major influencing factors for Lantana invasion, whereas, for Corbett Tiger Reserve, climate and topography were the major determining factors. Mean diurnal temperature, precipitation of warmest quarter, lopping, and logging were the factors determining the Lantana invasion in the landscape. The influence of different factors affecting the invasion of Lantana differs between Rajaji Tiger reserve and Corbett Tiger Reserve. The result of the study will be helpful for formulating effective policy intervention to reduce the invasion of Lantana in these ecologically important tiger reserves.

The coordination of stomatal conductance and hydraulic conductance in plants is often indicated by a positive relationship between stomatal density and vein density. However, when both hydraulic conductance and stomatal conductance increase simultaneously, there can be conflicting demands that causes a competition for epidermal space, leading to a negative association between stomatal density and vein density. Therefore, the interplay between these traits and how it is influenced by different growth forms is still a subject of debate. In this study, we conducted a common garden experiment to investigate the coordination between stomata, veins, and photosynthesis in 22 species of Ficus with varying growth forms, including free-standing, hemiepiphyte, and climber forms. Our findings revealed that growth form had a significant impact on stomatal and hydraulic traits in Ficus. Hemiepiphyte species exhibited a drought tolerance strategy during their epiphytic stage, characterized by thinner leaves with low stomatal density but higher stomatal size, as well as higher leaf water content and vein density (vein length per area, VLA) compared to free-standing and climber fig species. Climber figs, on the other hand, showed a lower specific leaf area and net photosynthetic rate compared to the other two forms. Contrary to many of previous studies, we found a negative correlation between VLA and stomatal density, as well as a positive correlation between VLA and stomatal size. Our study also suggests that other variables contribute to the variation in photosynthetic rate in Ficus, as stomatal morphology and vein density did not account for the observed variation significantly. Additionally, our analysis revealed non-random patterns of evolution for stomatal density, stomatal size, and VLA. The correlation between vein density and stomatal morphology was observed throughout the evolutionary history of Ficus, which appears to be associated with the diversification of growth forms. Overall, our findings support the “competition hypothesis,” which proposes antagonistic demands on the epidermal area between stomata and veins in Ficus.