Plant Ecology最新文献

Tropical forests were long viewed as relatively stable systems, with little biologically important variation in climate. However, in recent years, accumulating evidence has suggested that tropical forests vary widely both in climate and phenology, that climate and phenology are inextricably linked, and that tropical forests increasingly display the effects of climate change. It is critically important to understand these climate-phenology interactions to be able to predict the cascading impacts on resource availability that will affect wildlife. There are many important and unanswered questions regarding how the mechanistic drivers and proximate cues of tropical forest reproductive phenology will vary in response to environmental change. Addressing these questions remains a huge challenge due to a paucity of long-term comparable data that hampers our ability to connect observed phenology patterns with fundamental theory. In this review, we highlight ten focal papers that have advanced our ability to identify phenological patterns, improved our understanding of the drivers of flowering and fruiting, and have innovatively linked fruiting patterns with impacts on wildlife diet, reproduction, and survival. We end with a call for increased collaboration among forest and wildlife ecologists, theoretical ecologists, meteorologists, and decision-makers to advance and apply phenological research in the tropics and reduce the negative impact of climate change on vital ecological functions, and services, of tropical forest ecosystems.

Anthropogenic activities have altered resource availability and disturbance regimes, to reduce the richness of native plant species and favoring the invasion of exotic species in grasslands. Therefore, it is crucial to understand the factors that control the establishment and expansion of exotic plants, as well as the limitations for the reestablishment of native species. The objective of this study was to experimentally evaluate in the field whether grazing rest, fertilization, and interactions with established vegetation modulate the spontaneous recruitment of exotic and native grasses, and whether these factors modify the interactions between established vegetation and seedlings. This experiment had a split-plot factorial design with 5 replicates in randomized complete blocks. After two years of grazing exclusion with cages, nutrient addition, and continuous removal of exotic and native groups, the total number and dry weight of newly established seedlings were measured. Fertilization and grazing rest were found to modulate the establishment of both exotic and native grass seedlings, while no significant changes were observed in the competitive situation. The number of exotic grass seedlings increased by 79% with grazing rest and by 149% with nutrient addition, while the establishment of natives was halved with grazing rest. In conclusion, both grazing rest and fertilization significantly impacted the establishment of native and exotic grasses in a short period. The results of this study provide evidence of a key process, establishment, and could help design management plans for temperate grasslands to prevent the invasion of exotic forage grasses and maintain the recruitment of native grasses.

Understanding the effects of seed predation, dispersal, and recruitment on the population dynamics of rare plant species is essential for generating effective management strategies. Unfortunately for most rare plants, the parameterization of these processes is limited and generally not included in demographic analyses. This exclusion can lead to biased estimates of vital rates and overall population growth rates, as well as limit inferences about inter-population processes like colonization and demographic rescue that can affect population viability. Based on previous empirical studies from Fort Liberty (formerly Fort Bragg) North Carolina (USA), we constructed a spatially explicit demographic model that accounts for pre-dispersal seed predation, dispersal, and habitat suitability for Lindera subcoriacea (bog spicebush), a rare shrub in the southeastern United States. We demographically modeled three scenarios: S1 did not include any of the three parameters; S2 accounted for seed predation and dispersal; and S3 included all three of the parameters. Results suggested that pre-dispersal seed predation, dispersal, and habitat suitability negatively impact the population growth rates of bog spicebush relative to the naïve demographic model. After 100 annual time steps, scenarios S1, S2, and S3 led to a 96%, 49%, and 1% increase in population size, respectively. In addition, over the course of 100 years, results of scenarios S2 and S3 demonstrated limited increases in site occupancy, with newly occupied areas located < 1 km from previously occupied habitat. Our results suggest additional parameterization of plant demographic models may be an informative endeavor and warranted, even in the absence of empirical data.

Wild lupine (Lupinus perennis) is a perennial plant originally found primarily throughout the United States and Canada in oak savannas, which are considered an ecotone between prairie and forest. Because of primary habitat loss, this early successional plant is declining and now persists in managed edge habitats such as power line rights-of-way and roadsides across much of its range. Many edge populations of wild lupine are small and isolated, which can hinder the reproduction of this pollinator-dependent plant. Here, we synthesize current literature about the biology and management of wild lupine and associated plants and insects. We also highlight current gaps of knowledge to guide future research on wild lupine and, more generally, on savanna-like habitats. The information provided here on lupine serves as a case study for how edge habitat conserves rare plant species reliant on disturbance. Overall, habitat characteristics that seem best for wild lupine include a gradient of canopy cover from moderate to open, well-drained soils, and a low abundance of understory woody plants. Land management, including prescribed burning, mowing, and mechanical thinning, can promote the conservation of wild lupine and other forest edge plants. However, additional research in regards to ideal management regimes and intensity is needed to further plant conservation in forest edge habitat.

Invasive exotic species produce impacts of different magnitudes in the environment. The colonization success of a species depends on several factors. Different research demonstrated that chill hours accumulation is one of the most important factors affecting the germination of the tree species Elaeagnus angustifolia L. This non-native species is considered invasive, even noxious, in different parts of the world, modifying terrestrial and aquatic environments. We investigate the chill hours accumulation effect on the seed germination of E. angustifolia under two soil moisture conditions (field capacity and half-field capacity). We also evaluated the survival of seedlings of the species for 240 days under the two mentioned moisture conditions. With the data obtained, we made two heat maps (one for each moisture condition) with the probability of germination of E. angustifolia in Argentina related to the natural availability of chill hours. We found that as the chill hours accumulation increased, germination of E. angustifolia increased in half-field capacity treatment and decreased in field capacity conditions. Seedling survival was 100% in both water regimes. Heat maps show the break dormancy probability of E. angustifolia seeds throughout the Argentine territory, with high potential of germination in Patagonia. In addition to contributing to the prevention of the invasion of E. angustifolia in Argentina, the information generated in our study can be helpful in other regions of the world since the significant genetic variability that the studied species presents can make its environmental distribution range unpredictable.

Future climate change will have severe impacts on the geographic distribution of species, likely leading to shifts in their suitable habitat and eventually to the extinction of some species whose distribution areas are restricted. However, some species may respond differently to climate change. In this study we model the current and future potential habitats of three Juniperus species with different population trends: J. jaliscana, J. monticola and J. pinchotii. Occurrence records were collected across their distribution, combined with environmental and topographical variables to generate a MaxEnt model of the potential distributions in the years 2050 and 2070. The most important environmental variables were precipitation of wettest quarter for J. jaliscana, maximum temperature of warmest month for J. monticola, and mean temperature of coldest quarter for J. pinchotii. Our results showed that the habitat suitability of these three Juniperus species decreased overall by more than 50% under the climate change scenarios. These findings contributed to a better understanding of the impacts of climate change on ecological distribution of these species and could inform decisions regarding to their conservation, and management, and sustainable use strategies, as well as to implement active ex situ conservation strategies.

Since the type of forest influences vegetation patterns from the edge-to-interior forest, site-specific edge studies are needed but there have been few studies in open-canopied forests such as oak savannahs. Our objective was to compare patterns of herbaceous plant diversity along the forest edge-to-interior gradient between open areas and underneath oak trees in the Zagros Forest in Iran. We established eighteen transects from the forest edge to the interior in small and large forest fragments to sample herbaceous species in five 0.25 m² quadrats at 1 m intervals from the base of the tree to the open area at different distances from the forest edge. We analyzed the data using randomization tests for edge influence and generalized linear mixed models. Edge influence had a positive effect on herbaceous species richness and diversity underneath oak trees but a negative effect in open areas. At forest edges, species richness and diversity significantly decreased from the tree base toward open areas, but exhibited the opposite pattern away from the edge. Edge influence extended up to 50 m from the forest edge to the interior. Our findings highlight the importance of considering forest type and stand heterogeneity when studying edge influence on plant diversity. Our results show that edge studies are needed for specific forest types, particularly in heterogeneous landscapes, to ensure appropriate conservation of species diversity. We recommend establishing a 50-m buffer zone along edges in the Zagros Forest in Iran to minimize negative edge influence on herbaceous plant diversity.

Seedlings are the most critical bottleneck in plant recruitment, yet there is no practical and widely accepted definition of what a seedling is. Typically, the end of the seedling stage has been defined as the point when it stops being dependent on seed resources, or at the point of maximum growth rate. However, these definitions are of limited use for ecological studies based on field surveys. I analyzed 25 years of literature and 1766 publications to provide a first quantitative assessment of how tree and shrub seedlings are defined in forest field studies. I counted 282 unique definitions of seedlings, and I found that 24.4% of studies did not provide a clear definition. The most widely used definitions were “newly emerged” seedlings, followed by individuals less than 50 cm and less than 100 cm tall. Only 6.9% of the studies cited previous work to justify their choice. The most used definitions were generally consistent between tropical and extra-tropical studies, and between single versus multiple species studies. Three simple steps, if adopted by authors, could help to improve the clarity of what is meant by seedlings: (1) to always provide a clear definition of seedling, (2) to refer to previous studies, and (3) to adopt the most widely used definitions reported here (i.e., < 50 cm or < 100 m tall) whenever possible.

River ecosystems of regulated rivers are threatened by water extraction and flow regime alteration in the context of climate change and increasing human populations. Riparian plant root growth is important to sustain plant health and provide functions including bank stabilization. The root systems of riparian plants on regulated rivers may suffer from lower soil moisture due to lack of natural flow variability. This study aimed to evaluate how soil moisture influences the root system of a herbaceous riparian plant. Plants of Juncus amabilis were dug out along a soil moisture gradient, corresponding with positions close to or distant from the water margin and low or high relative bank elevation. Root depth, belowground space occupation, root mass fraction, and mean fractal dimension were used to evaluate root structural dynamics in relation to bank position and soil moisture. The ratio between root and aboveground dry weights of sampled plants was constant over the elevation range sampled. Plant root systems tended to grow deeper, occupy more belowground space, and have fewer branches as soil moisture declined. These findings indicate that lower soil moisture levels and reduced river flows may significantly influence herbaceous riparian plant growth and survival. Riparian plant health and function will likely be promoted by flow regimes that provide adequate and timely water delivery.