Aims We conducted a simulated nitrogen (N) and sulfur (S) deposition experiment from 2006 to 2012 to answer the following questions: (i) does chronic N and S deposition decrease cation concentrations in the soil and foliage of understory plant species, and (ii) does chronic N and S deposition decrease plant diversity and alter species composition of the understory plant community in a boreal forest in western Canada where intensifying industrial activities are increasing N and S deposition?
Methods Our field site was a mixedwood boreal forest stand located ~100 km southeast of Fort McMurray, Alberta, Canada. The experiment involved a 2 × 2 factorial design, with two levels each of N (0 and 30 kg N ha^-1 yr^-1; applied as NH 4 NO 3) and S addition (0 and 30 kg S ha^-1 yr^-1; applied as Na 2 SO 4). Four blocks were established in July 2006, each with four plots of 20 × 20 m randomly assigned to the treatments. Soil and understory vegetation were sampled and cover (%) of individual species of herb (height ≤ 0.5 m) and shrub (height 0.5–1 m) layers was determined in August 2012.
Important findings Seven years after the treatments began, N addition increased dissolved organic carbon and N in the mineral soil (P < 0.05), whereas S addition decreased exchangeable cations (P < 0.05) in the forest floor. In the shrub layer, species evenness, and overall diversity were decreased by N addition (P < 0.05) due to increases in abundance of nitrophilous species and S addition (P < 0.01) due to decreased cation concentrations in soils. Total shrub cover decreased with S addition (P < 0.10). Nitrogen and S addition affected neither species richness nor evenness in the herb layer. However, permutational multivariate analysis of variance and non-metric multidimensional scaling analyses (based on plant cover) indicated that the effect of N and S addition on understory plant species composition in the both shrub and herb layers was species-specific. Addition of N decreased foliar phosphorus and potassium concentrations in some species, suggesting potential risk of N-meditated nutrient imbalance in those species. Our results indicate that long-term elevated levels of N and S deposition can negatively impact plant nutrition and decrease the diversity of the understory plant community in boreal forests in northern Alberta, Canada. However, considering that the current N and S deposition rates in northern Alberta are much lower than the rates used in this study, N and S deposition should not negatively affect plant diversity in the near future.

Aims Dune building processes are affected by interactions between the growth of ecosystem engineering dune grasses and environmental factors associated with disturbance such as sand burial and sea spray. Research investigating how species interactions influence dune community structure and functional trait responses in high abiotic stress environments is minimal. We investigated how species interactions influence the functional trait responses of three dominant dune grasses to common abiotic stressors.
Methods We performed a multi-factorial greenhouse experiment by planting three common dune grasses (Ammophila breviligulata Fern., Uniola paniculata L. and Spartina patens Muhl.) in different interspecific combinations, using sand burial and sea spray as abiotic stressors. Sand burial was applied once at the beginning of the study. Sea spray was applied three times per week using a calibrated spray bottle. Morphological functional trait measurements (leaf elongation, maximum root length, aboveground biomass and belowground biomass) were collected at the end of the study. The experiment continued from May 2015 to August 2015.
Important findings Species interactions between A. breviligulata and U. paniculata negatively affected dune building function traits of A. breviligulata, indicating that interactions with U. paniculata could alter dune community structure. Furthermore, A. breviligulata had a negative interaction with S. patens, which decreased S. patens functional trait responses to abiotic stress. When all species occurred together, the interactions among species brought about coexistence of all three species. Our data suggest that species interactions can change traditional functional trait responses of dominant species to abiotic stress.

Aims Interspecific and intraspecific variation in flower color in natural populations provides an opportunity for us to understand the evolution and maintenance of diversity of floral traits. Compared to corolla color, little is known about the color polymorphism of sexual organs in flowering plants. To explore evolutionary transitions of androecium color and polymorphism within species, interspecific and intraspecific variation in androecium (anther and pollen) color in the genus Epimedium (Berberidaceae) was investigated.
Methods To explore the geographical patterns of anther/pollen color variation in Epimedium species, data of 45 species were collected and their phylogeny was constructed based on available DNA sequences. To investigate whether intraspecific variation in androecium color relates to habitat preference, three environmental factors were measured in the field population of Epimedium pubescens in northeastern Sichuan, China, which plants had green or yellow androecia. Vegetative and reproductive traits of this species were compared between the two color morphs.
Important findings Androecium (anther and pollen) color polymorphism in field populations of Epimedium pubescens is reported here where nine populations are monomorphic with a green androecium but three populations are dimorphic with individuals having either a green or a yellow androecium. Inflorescence stalk height, stalk diameter, leaf number, flower number and spur length (as well as spur and nectar volume) were not significantly different between two morphs. Compared to the yellow morph, the green morph had relatively larger leaves and anthers, but smaller sepals. The green morph produced more pollen and larger seeds, but the same number of ovules. Seed set was not significantly different between green and yellow morph. Investigations of environmental factors in the color dimorphic populations of E. pubescens indicated that the green morph was more likely to occur in habitats with relatively lower light intensity. The distribution survey of 45 Epimedium species showed that species with a green androecium tended to appear at lower elevations. Comparative phylogenetic analysis showed that transitions from yellow to a green androecium or to androecial color dimorphism occurred at least seven times. This genus, characterized by anther color diversity and containing some species with anther color polymorphism, provides a model system in which to study the evolution and maintenance of colorful sexual organs in flowering plants.

Aims Seed dormancy and the soil seed bank are crucial to plant regeneration strategy, especially in semiarid ecosystems with unpredictable precipitation. The aim of this study was to investigate how seed dormancy is controlled by environmental factors and how it is correlated with the soil seed bank and regeneration of the perennial legume Oxytropis racemosa, a dominant perennial herb in Mu Us Sandland of semiarid China.
Methods Germination and imbibition experiments on fresh intact and scarified seeds of O. racemosa were used to identify physical dormancy (PY) in seeds of this species. Soil seed bank dynamics, timing of seedling emergence and the fate of buried seeds in the natural habitat were investigated.
Important findings PY was broken by mechanical scarification or wet heat/ice water cycles but not solely by dry heat or wet heat treatment. The soil seed bank exhibited seasonal changes in the number of seeds, which was highest in September and lowest in July. Seeds buried at different sand depths gradually lost dormancy; 20–42% of the seeds remained dormant after 20 months of burial. Dormancy break occurs gradually throughout the year. Our results indicate that O. racemosa exhibits hardcoatedness heterogeneity that spreads germination of a seed cohort between seasons and years in the semiarid environment, where the amount of precipitation during the growing season is highly variable.

Aims The functional advantages of arsenic (As) hyperaccumulation by plants are poorly understood. One proposed benefit, termed elemental allelopathy, occurs when hyperaccumulated As is cycled from the plant back into the top layer of soil, allowing As hyperaccumulators to gain an advantage over intolerant species by increasing soil As concentrations ([ As]) underneath their canopy. To date, there are no studies that detail the presence of increased soil [ As] associated with As hyperaccumulators. In this study, we documented variation in the soil [ As] associated with the Chinese brake fern, Pteris vittata L. and also compared the effects of environmentally relevant soil and solution [ As] on competitor plant growth.
Methods Four populations of P. vittata were identified in central Florida, USA. P. vittata tissue samples and soil samples were collected at the base of and at 3 m away from ferns in each population (n = 36). Five sample locations were randomly selected from each site, and soils from the base and 3 m away from each fern were collected to examine the effects of naturally occurring soil [ As] on the germination and growth of a potential competitor plant (Oxalis stricta). Solutions with increasing [ As] were also used to examine the threshold for negative effects of [ As] on O. stricta growth. [ As] were measured using inductively coupled plasma mass spectrometry (ICP-MS).
Important findings Overall, soil [ As] from the base of ferns was nearly twice that of soil 3 m away indicating that ferns hyperaccumulate As. However, ferns and their associated soil, contained different [ As] depending on their collection site, indicating that these populations accumulate and use [ As] differently. O. stricta growth decreased and germination was delayed as solution and soil [ As] increased. However, the relative distance from the fern that the soil was collected from did not affect growth, which would be expected with elemental allelopathy. Our results show that P. vittata is associated with higher soil [ As] and these concentrations are sufficient to inhibit growth of competitors. However, the absence of a strong inhibitory relationship associated with proximity to the fern across all locations suggests that the possible functional advantages of elemental allelopathy may depend on site specific characteristics.

Aims Lignin is generally considered as an important indicator of soil organic carbon (SOC) storage and dynamics. To evaluate the effects of plant communities and soil depth on soil lignin is critical to better understand forest carbon cycling.
Methods We compared lignin content and chemical signature in three soil depths of four major plant communities in a subtropical forest, which located in the north part of Wuling Mountains, China. Lignin was measured using CuO oxidation method.
Important findings Both lignin content and its biochemical signature in plant litter varied among communities. However, these differences were mostly no longer exist in the upper soil layers. Lignin chemistry in soils inherited some of the biochemical signature of lignin in litter, but in a diminished magnitude. These results suggest that different plant communities had similar decomposition process with varying rates, caused diminished differences in lignin content and its biochemical signature. Lignin content decreased with soil depth, but the biochemical signature of lignin was not significantly different among soil layers for all communities, which suggests that vertical movement of lignin within the soil profile is very likely a key process causing this similar biochemical signature. These results emphasized the important roles of lignin inputs and soil eluviation in shaping lignin characteristics and distribution in forest soils, which pinpoint the urgent need to consider hydrological processes in studying forest soil carbon cycling.

Aims Pigment composition is an important functional trait that can be affected by environmental factors. The objective of this study was to investigate the effect of soil salinity on pigment composition in Suaeda salsa by comparing chlorophyll and betacyanin content in the Liaohe estuary wetland, a typical coastal wetland in northeast China.
Methods We investigated the plant biomass, percentage of red leaves and pigment content (chlorophyll a, chlorophyll b and betacyanins) in S. salsa in intertidal and supratidal zones of the upper, middle and lower reaches of the Liaohe estuary wetlands. The Na + content of both the soil and plant was also measured. Full analysis of variance and multivariate analysis were used to compare differences in pigment content and Na + content between the supratidal and intertidal zones.
Important findings Pigment composition was significantly affected by soil salinity. With increasing soil salinity, the percentage of red leaves was higher in the intertidal zone than in the supratidal zone. In all three reaches, plants had lower chlorophyll a content and higher betacyanin content in the intertidal zone than in the supratidal zone. Compared to chlorophyll a, chlorophyll b was less sensitive to soil salinity. There were no differences in chlorophyll b content between the intertidal and supratidal zones in the upper and lower reaches. Furthermore, pigment composition was associated with both the plant tissue and soil Na + content. Compared to the supratidal zone, the intertidal zone had a higher Na + content in plants. There was a negative relationship between plant chlorophyll content and soil Na + content, but a positive relationship between betacyanin content and soil Na + content. Overall, the results indicated that there might be a trade-off between leaf chlorophyll and betacyanin content in S. salsa to maintain its growth and survival in high salinity environments.

Aims Understanding the drivers of grassland structure and function following livestock removal will inform grassland restoration and management. Here, we investigated the effects of fire and nutrient addition on structure and function in a subtropical semi-native grassland recently released from grazing in south-central Florida. We examined responses of soil nutrients, plant tissue nutrients, biomass of live, standing dead and litter, and plant species composition to experimental annual prescribed fire applied during different seasons (wet season vs. dry season), and nutrient additions (N, P and N + P) over 9 years.
Methods Experimental plots were set up in a randomized block split-plot design, with season of prescribed fire as the main treatment and nutrient addition as the subplot treatment. Species cover data were collected annually from 2002 to 2011 and plant tissue and plant biomass data were collected in 2002–2006 and 2011. Soil nutrients were analyzed in 2004, 2006 and 2011.
Important findings Soil total phosphorus (P) levels increased substantially with P addition but were not influenced by prescribed fire. Addition of P and N led to increased P and N concentrations in live plant tissues, but prescribed fire reduced N in live tissue. Levels of tissue N were higher in all plots at the beginning of the experiment, an effect that was likely due to grazing activity prior to removal of livestock. Plant tissue N steadily declined over time in all plots, with annually burned plots declining faster than unburned plots. Prescribed fire was an important driver of standing dead and litter biomass and was important for maintaining grass biomass and percent cover. Nutrient addition was also important: the addition of both N and P was associated with greater live biomass and woody forbs. Removal of grazing, lack of prescribed fire, and addition of N + P led to a reduction of grass biomass and a large increase in biomass of a woody forb. Annual prescribed fire promoted N loss from the system by reducing standing dead and litter, but maintained desirable biomass of grasses.

Aims As a unique geographical unit of the earth, the Tibetan Plateau is extensively covered by various Stipa communities. However, their vegetation features have not been reported systematically till now, especially in some scantily explored regions. In this study, we endeavor to reveal the community types, quantitative characteristics and climatic distribution patterns of Stipa steppes in these areas based on primary relevés obtained from fieldwork.
Methods We collected a total of 223 plots in 79 study sites in the Changthang Plateau and the Yarlung Zangbo Valley, ranging from 79°E to 91°E. The categories of Stipa formations were identified according to the classification scheme in Vegetation of China and then verified by Nonmetric Multidimensional Scaling. We performed detrended correspondence analysis and detrended canonical correspondence analysis to hunt for the alteration of Stipa communities along the precipitation gradient. Quantitative characteristics including species richness, coverage, biomass as well as importance values (IV) of dominant species were calculated and visualized, respectively.
Important findings Stipa steppes in scantily explored regions of the Tibetan Plateau are classified into 11 formations but major formations are rather limited in number. Formation (form.) Stipa purpurea is the most widespread Stipa assemblages not only in scantily explored regions but also across the whole Tibetan Plateau. The characteristics of Stipa communities, including coverage, species richness, productivity and IV of dominant species, demonstrate the features of typical alpine steppes on the Tibetan Plateau. Precipitation proves to be the prime climatic factor controlling the distribution patterns of Stipa assemblages. Form. Stipa subsessiliflora var. basiplumosa and form. Stipa glareosa normally distribute in arid habitats, but rainfall for the former is of greater variance. Form. Stipa roborowskyi and form. Stipa capillacea favor moderately moist environment. Form. Stipa purpurea and form. Stipa roborowskyi can tolerate a fairly broad range of precipitation.

Aims The impact of global warming on belowground processes, especially on fine root production, is poorly understood in comparison with its aboveground counterpart.
Methods Here, we compiled 227 measurements to assess the influence of temperature and precipitation on fine root biomass of Norway spruce (Picea abies [L.] Karst) forest ecosystems in the Eurasia boreal region.
Important findings We found that fine root biomass decreased significantly with latitudes. There was a biomass increase of 0.63 Mg ha^-1 and 0.32 Mg ha^-1 for fine roots <2 and <1 mm in diameter, respectively, with 1°C increase of mean annual temperature. There was an increase of 0.5 and 0.1 Mg ha^-1 per 100 mm year^-1 precipitation for the two size classes of fine roots. If the adaption of root production can match the pace of global warming and water is not a limiting factor for plant growth, fine root biomass would be expected to increase by 40–140% in response to the predicted increase in temperature (3–10°C) over the next century. Our analyses highlighted the strongly positive influences of temperature and precipitation on belowground function, suggesting that predicted future climate change could substantially enhance belowground biomass in the boreal region where the greatest warming is anticipated. This potential increase of belowground biomass, coupled with aboveground biomass, may provide a better understanding of climate–ecosystem feedbacks.

Aims Lianas are expected to influence composition, structure and functioning of forest systems due to unequal distribution across the potential set of host plants. However, our understanding of mechanisms associated with preferences for specific hosts is still limited, and so is our ability to discern between endogenous and exogenous forces driving forest dynamics in the long run. In this paper, we evaluated whether the dominant liana Hedera helix can indirectly contribute to the eventual dominance of the small multi-stemmed tree Corylus avellana in a remnant temperate forest in central Iberian Peninsula from comparatively reduced liana infestation on C. avellana relative to co-occurring woody species.
Methods Through principal component analysis and co-occurrence analysis, we studied the distribution and spatial association between woody species and the liana H. helix. We analyzed the relationship between the number of species in a plot and the number of species infested by the liana to test the hypothesis that H. helix is a generalist liana. Through generalized linear mixed models, we tested the dynamic-multi-stemmed growth form of C. avellana as a plausible life strategy to withstand, in the long run, the liana infestation. In particular, we tested (i) the relationship between stem size and the probability of H. helix infestation including all the tree species within plots and (ii) the relationship between stem size and mortality as evidence of the stem turn over in the tree C. avellana .
Important findings Our results indicate that H. helix and C. avellana significantly co-occur in mature stands of this remnant temperate forest where pioneer woody species are absent. Hedera helix severely infests all the woody species whenever stem size exceed ≈25 cm perimeter and there is physical contact at the base of the stem. This implies that all the trees in the community are potential hosts for H. helix. Mixed models indicate that both, infestation by H. helix and stem mortality, are positively related to C. avellana stem perimeter. Reduced long-term infestation of the liana by means of a multi-stemmed growth form with high stem turnover in C. avellana might be an advantage with respect to unipodial tree species. Thus, the liana-tree coexistence pattern may be interpreted as an indirect positive interaction that, contrary to previous findings, results here in species dominance instead of species coexistence.

Aims Community assembly persists as a key topic in ecology due to the complex variation in the relative importance of assembly forces and mechanisms across spatio-temporal scales and ecosystems. Here we address a forest–savanna vegetation mosaic in the Brazilian Atlantic forest to examine the role played by soil attributes as determinants of community assembly and organization at a landscape spatial scale.
Methods We examined soil and plant assemblage attributes across 23 plots of forest and savanna in a 1600 km 2 landscape exposed to the same climatic conditions in the Atlantic forest region of northeast Brazil. Assemblage attributes included species richness, taxonomic and functional composition (community weighted mean, CWM) and functional diversity (quadratic diversity; Rao's quadratic entropy index) relative to plant leaf area, specific leaf area, leaf dry matter content, thickness and succulence.
Important findings Our results suggest that forest and savanna patches exposed to the same climatic conditions clearly differ in terms of soil attributes, plant assemblage structure, taxonomic and functional composition. By selecting particular plant strategies relative to resource economy, soil potentially affects community structure, with forest assemblages bearing more acquisitive resource-use strategies, while conservative plant strategies are more frequent in savannas. Accordingly, savanna–forest mosaics in the Atlantic forest region represent spatially organized plant assemblages in terms of taxonomic and functional features, with a signal of trait convergence in both vegetation types. Soil-mediated filtering thus emerges as a potential deterministic assembly force affecting the spatial organization of savanna–forest boundaries and mosaics.

Aims Studies have showed that arbuscular mycorrhizal fungi (AMF) can greatly promote the growth of host plants, but how AMF affect flowering phenology of host plants is not well known. Here, we conducted a pot experiment to test whether life cycle and flowering phenology traits of host plant Medicago truncatula Gaertn can be altered by AMF under low and high soil phosphorus (P) levels.
Methods The experiment was conducted in a greenhouse at Zhejiang University in China (120°19′E, 30°26′N) and had a completely randomized design with two factors: AMF treatments and soil P levels. Six AMF species (Acaulospora scrobiculata, As; Gigaspora margarita, Gma; Funneliformis geosporum, Fg; Rhizophagus intraradices, Ri; Funneliformis mosseae, Fmo and Glomus tortuosum, Gt.) were used, and two soil P levels (24.0 and 5.7 mg kg^-1 Olsen-soluble P) were designed. The six AMF species were separately inoculated or in a mixture (Mix), and a non-AMF control (NAMF) was included. When plants began to flower, the number of flowers in each pot was recorded daily. During fruit ripening, the number of mature fruits was also recorded daily. After ~4 months, the biomass, biomass P content and AMF colonization of host plant were measured. Correlation between root colonization and first flowering time, or P content and first flowering time was analyzed.
Important findings Under the low P level, first flowering time negatively correlated with root colonization and biomass P. Only host plants with AMF species As, Fg, Ri, or Mix were able to complete their life cycle within 112 days after sowing. And treatment with AMF species Fg, Gt, or As resulted in two periods of rapid flower production while other fungi treatments resulted in only one within 112 days after sowing. The cumulative number of flowers produced and biomass P content were highest with species Fg. Host biomass allocation significantly differed depending on the species of AMF. Under both soil P levels, the host plant tended to allocate more biomass to fruits in the Mix treatment than in the other treatments. These results indicated that the effects of AMF on host flowering phenology and biomass allocation differed depending on AMF species and soil P levels.

Aims The Cape Peninsula is a small area (471 km 2) situated on the south-westernmost tip of the Core Cape Subregion (CCR) of South Africa. Within the Cape Peninsula, Fabaceae are the third most species-rich plant family (162 species) and they have the second highest number of endemic species after the Ericaceae. However, legumes are not the dominant taxa in the vegetation. They tend to show patchy distributions within the landscape and different species assemblages usually occupy particular niches at any given locality. The present study undertook to establish if edaphic factors influence legume species distribution in the Cape Peninsula and to determine the key indicator species for the different assemblages.
Methods Soils from 27 legume sites, spanning all major geological substrates of the Cape Peninsula, were analysed for 31 chemical and physical properties. Legume species present at each site were recorded and a presence/absence matrix was generated. Cluster analysis and discriminant function analysis (DFA) were run to group the sites based on overall similarity in edaphic characteristics and to identify the soil parameters contributing towards discriminating the groups. Canonical correspondence analysis (CCA) was used to test for a correlation between legume species compositions and edaphic factors. The strength of the association between legume species and site groupings based on edaphic properties was assessed using indicator species analysis.
Important findings Based on similarity in overall soil characteristics, the sites formed three clusters: one comprising sites of sandstone geology, one with dune sand sites and the third cluster comprising sites of both shale and granite geologies (hereafter referred to as soil types). The DFA confirmed the distinctness of these clusters and the CCA showed a significant correlation between legume species composition and edaphic factors. The key edaphic parameters were clay content, iron (Fe), potassium (K), sulphur (S) and zinc (Zn). These findings reveal that the Cape Peninsula is edaphically heterogeneous and edaphically distinct habitats contain discrete legume species assemblages that can be distinguished by unique indicator species. Furthermore, multiple soil parameters, rather than a single parameter, are involved. Therefore, edaphic factors play a significant role in driving the distribution of legume species in the Cape Peninsula and discrete legume species assemblages occupy distinct habitats.

Aims Distyly is one of the most widespread floral polymorphisms promoting cross-fertilization. Evolutionary transition from obligate cross-fertilized distyly to predominantly self-fertilized homostyly is frequently documented in various groups. However, empirical studies concerning the ecological factors connected with this transition are still lacking. Primula chungensis, suggested to be evolving from distyly to homostyly, provides an ideal model for the study of the ecological factors concerned with this transition. We study P. chungensis to understand if autonomous self-fertilization would provide reproductive assurance for the self-fertilized homo-styled morph in the field.
Methods The incompatibility features of P. chungensis were tested with hand-pollination experiments. We compared the capacity of autonomous self-fertilization between the distylous and homo-styled morph of P. chungensis in the field by excluding the pollinators with bags. In addition, the degrees of herkogamy of some P. chungensis plants were between the short-styled and homo-styled morphs. These plants were studied to understand whether they were able to obtain greater reproductive assurance when the herkogamy in the flowers was reduced.
Important findings All three morphs of P. chungensis were highly self- and intra-morph compatible. The degree of herkogamy positively correlated with the capacity for autonomous self-fertilization. A negative correlation between the degree of herkogamy and the magnitude of pollen limitation was found, but no significant correlation was found between the degree of herkogamy and the contribution of cross-fertilization to overall fertilization. This study suggests that reducing the degree of herkogamy can significantly increase the reproductive assurance for a self-compatible plant. Our results provided evidence that the homo-styled morph of P. chungensis had the highest capacity for autonomous self-fertilization and the highest seed production in the field, because autonomous self-fertilization provided reproductive assurance for the homo-styled morph. This may cause selection towards the transition from distyly to homostyly.

Aims The relative plant type sensitivity and selected community interactions under increased UV-B radiation where examined. Specifically, we investigated: (i) if there are differences among growth forms in regard to their sensitivity to UV-B radiation, (ii) if increased UV-B radiation influences the plant competitive balance in plant communities and (iii) the response mechanisms of the UV-B radiation-sensitive species that might increase their fitness.
Methods To answer our research questions, we used a mechanistic model that, for the first time, integrated the effects of increased UV-B radiation from molecular level processes, whole plant growth and development, and community interactions.
Important findings In the model simulations, species types exhibited different levels of sensitivity to increased UV-B radiation. Summer C₃ and C₄ annuals showed similar growth inhibition rates, while biennials and winter C₃ annuals were the most sensitive. Perennials exhibited inhibitions in growth only if increased UV-B radiation results in increases in metabolic rates. In communities, species sensitive to UV-B radiation may have a competitive disadvantage compared to resistant plant species. But, sensitive species may have a wide array of responses that can increase their fitness and reproductive success in the community, such as, increased secondary metabolites production, changes in timing of emergence and reproduction, and changes in seed size. While individual plants may exhibit significant inhibitions in growth and development, in communities, these inhibitions can be mitigated by small morphological and physiological adaptations. Infrequent or occasional increased UV-B radiation events should not have any lasting effect on the structure of the community, unless other environmental factors are perturbing the dynamic equilibrium.