Life-form Groups Research Articles

The characteristics and environmental significance of BVOCs released by aquatic macrophytes

Biogenic volatile organic compounds (BVOCs) emitted by plants serve crucial biological functions and potentially impact atmospheric environment and global carbon cycling. Despite their significance, BVOC emissions from aquatic macrophytes have been relatively understudied. In this study, for the first time we identified there were 68 major BVOCs released from 34 common aquatic macrophytes, and these compounds referred to alcohols, aldehydes, alkanes, alkenes, arenes, ethers, furans, ketones, phenol. For type of BVOC emissions from different life form and phylogenetic group of aquatic macrophytes, 34 of the 68 BVOCs from emergent and submerged macrophytes are classified into alkene and alcohol compounds, over 50% BVOCs from dicotyledon and monocotyledon belong to alcohol and arene compounds. Charophyte and pteridophyte emitted significantly fewer BVOCs than dicotyledon and monocotyledon, and each of them only released 12 BVOCs. These BVOCs may be of great importance for the growth and development of macrophytes, because many BVOCs, such as azulene, (E)-β-farnesene, and dimethyl sulfide are proved to play vital roles in plant growth, defense, and information transmission. Our results confirmed that both life form and phylogenetic group of aquatic macrophytes had significantly affected the BVOC emissions form macrophytes, and suggested that the intricate interplay of internal and external factors that shape BVOC emissions from aquatic macrophytes. Thus, further studies are urgently needed to investigate the influence factors and ecological function of BVOCs released by macrophytes within aquatic ecosystem.

Revised checklist of endemic vascular plants of Kazakhstan.

We compiled a checklist of endemic vascular plants occurring in Kazakhstan, employing an exhaustive examination of literature sources, herbarium collections, databases and field observations. Our study reveals that 451 taxa can be considered endemic to Kazakhstan, constituting 7.97% of the total vascular plant diversity in the country. These endemic taxa, originating from 139 genera and 34 families, predominantly thrive in the southern regions of Kazakhstan, specifically in the mountain ridges of the Kazakh part of the Tian Shan, including Karatau (123 taxa), Dzungarian Alatau (80 taxa) and Trans-Ili and Kungey Alatau (50 taxa). Notably, 107 endemic species are granted legal protection. Detailed information regarding life form, life cycle, conservation status and geographical distribution across floristic regions was meticulously compiled for each endemic taxon. Of the six groups of life forms, herbs include the highest part of endemic taxa (367 taxa), followed by dwarf semishrubs (25 taxa), shrubs (23 taxa), subshrubs (20 taxa), undershrubs (13 taxa) and trees (3 taxa). The observed life cycles are perennials (408 taxa), annuals (33 taxa) and biennials (10 taxa). This paper serves as a fundamental groundwork for prospective investigations aimed at assessing population sizes and hotspots of plant endemism throughout Kazakhstan, crucial for determining conservation status of endemic plants.

Phosphorus addition increases the total abundance and favors microbivorous Collembola in subalpine plantation forest

Collembola are among the most abundant microarthropods in virtually all soils. Typically, taxonomic units based on life forms or trophic guilds are treated as proxies for functional groups to explore microarthropod responses to environmental changes. However, this approach may be misleading for understanding the role of Collembola as their ecological functions in soil food webs are affected by both life form and trophic group. In this study, we examined how Collembola communities respond to the addition of different levels of phosphorus (0, 50, 150 and 300 kg ha−1 yr−1) in subalpine forest on the eastern Tibetan Plateau eight years after establishment of the phosphorus enrichment gradients. Consistent with our expectations, phosphorus addition increased Collembola total abundance and this was closely related to decreased litter N/P ratio, increased relative abundance of saprotrophic fungi as well as increased infection rate of plant roots by ectomycorrhizal fungi. Notably, the response varied between Collembola functional groups defined by combining information on life forms and trophic groups. Epedaphic detritivores, hemiedaphic microbivores and euedaphic microbivores were most strongly affected by litter nutrient quality (N/P ratio), saprotrophic and ectomycorrhizal fungi, respectively. Furthermore, the results suggest that hemiedaphic microbivore Collembola preferentially fed on saprotrophic fungi in phosphorus addition treatments, which likely was due to increased relative abundance of saprotrophic fungi. By contrast, euedaphic microbivore Collembola mainly fed on ectomycorrhizal fungi indicating that they are closely linked to root-derived resources. Overall, the results highlight that Collembola functional groups respond differently to changes in the quality and availability of food resources. Furthermore, the results suggest that considering both life form and trophic group information allows to effectively link changes in Collembola community composition to changes in their functions.

Life form-dependent nitrogen–phosphorous allocation strategies of leaf and fine root in a temperate natural forest under long-term nitrogen addition

Abstract Nitrogen deposition has increased rapidly in eastern China, which can affect the stoichiometric characteristics of plants. However, the effects of N addition on the nitrogen (N) and phosphorous (P) allocation strategies for various plant life forms (e.g. trees, shrubs and herbs) have rarely been studied. In this study, we evaluated the effects of N addition on N and P stoichiometry and their scaling exponents in the leaves and fine roots of the different life form groups. N and P concentrations in the leaves of shrubs and herbs increased under N addition treatments, whereas tree leaves exhibited a more stable response. In contrast, N addition had no significant effect on N and P concentrations in the fine roots of the three plant life forms. N addition enhanced the allocation of more N and P to the leaves than to the fine roots in all three life forms. Furthermore, the N–P allocation scaling exponents of the leaves and fine roots of the trees were equal to 1.0, indicating an isometric pattern. In contrast, the N–P allocation scaling exponents of shrubs and herbs were less than 1.0, indicating an allometric pattern. Although high N availability promoted shrubs and herbs to distribute P to leaves at a higher proportion than N, only slight effects were detected in tree leaves. These changes in N–P allocation patterns indicate that life forms and N addition levels work together to modulate plants allocation strategies. These results suggest the importance of life form categories when evaluating N–P allocation strategies in forest plants.

Perennial herb diversity contributes more than annual herb diversity to multifunctionality in dryland ecosystems of North-western China.

Considerable attention has been given to how different aspects of biodiversity sustain ecosystem functions. Herbs are a critical component of the plant community of dryland ecosystems, but the importance of different life form groups of herbs is often overlooked in experiments on biodiversity-ecosystem multifunctionality. Hence, little is known about how the multiple attributes of diversity of different life form groups of herbs affect changes to the multifunctionality of ecosystems. We investigated geographic patterns of herb diversity and ecosystem multifunctionality along a precipitation gradient of 2100km in Northwest China, and assessed the taxonomic, phylogenetic and functional attributes of different life form groups of herbs on the multifunctionality. We found that subordinate (richness effect) species of annual herbs and dominant (mass ratio effect) species of perennial herbs were crucial for driving multifunctionality. Most importantly, the multiple attributes (taxonomic, phylogenetic and functional) of herb diversity enhanced the multifunctionality. The functional diversity of herbs provided greater explanatory power than did taxonomic and phylogenetic diversity. In addition, the multiple attribute diversity of perennial herbs contributed more than annual herbs to multifunctionality. Our findings provide insights into previously neglected mechanisms by which the diversity of different life form groups of herbs affect ecosystem multifunctionality. These results provide a comprehensive understanding of the relationship between biodiversity and multifunctionality, and will ultimately contribute to multifunctional conservation and restoration programs in dryland ecosystems.

Dataset for vascular plants in the Red Data Books of Transbaikalia: species distribution and pathways towards their conservation

The dataset of the Red Data Book vascular plants of Transbaikalia was created based on the latest editions of the Red Data Book of the Republic of Buryatia and the Red Data Book of the Zabaikalsky Krai (Russia). The dataset provides the most updated information regarding the distribution of 271 rare vascular plants (2920 distribution records). The distribution of the studied species was recorded during field surveys using GPS navigators, georeferenced from herbarium specimens, and digitised from printed distribution maps. Each entry in the dataset has various attributes, including belt zone, distribution, ecological, and life-form group features. Distribution patterns for various groups of rare and endangered species were analysed by means of QGIS 3.10 software. Our study has revealed a number of localities of vascular plants listed in the Red Data Book and clarified their distribution within the federal Protected Areas of Transbaikalia, among which Tunkinsky National Park has the highest diversity. Distribution of some rare and endangered species fall under federal protection, but some plants, including endemic species, require better protection. Analysis of various belt zones and distribution groups showed their distinct spread within the study region. Among the studied species, mesophytes and short rhizome perennial plants prevailed. It is also important to preserve vascular plants in the Red Data Book outside Protected Areas. Hence, information from our dataset can be useful for conservation monitoring programmes. Our study provides a basis for future conservation activities and can be applied in the establishment of new Protected Areas or Important Plant Areas in Transbaikalia.

Succession of aquatic and littoral vegetation in disused sandpits

AbstractVegetation succession in aquatic and littoral environments has received much less attention compared to terrestrial habitats. We sampled differently aged successional stages in 63 sandpits across the Czech Republic, Central Europe. They ranged in age since abandonment from 1 to 64 years. The chronosequence approach was adopted. Besides species identity itself, basic life‐history species traits were considered to describe the succession. Based on the location (elevation) of plots, two geographical regions were delimited based on temperature and precipitation. Alongside the vegetation data, several environmental variables were recorded: age, water depth, substratum type (i.e., proportion of sand, clay, gravel and organic material), pH, conductivity, elevation and additional disturbances. Altogether, 249 vascular plant species were determined. Individual successional series in aquatic and littoral habitats differed between the altitudinal regions. As generally expected, water table was one of the main driving factors alongside age and water conductivity. Moreover, the vegetation pattern was significantly affected by substrate composition and pH. The species composition at aquatic sites was most likely mainly driven by the accumulation of organic material. Hydrophytes dominated throughout these sites. In littoral vegetation, several distinct groups of life forms could be distinguished along the successional gradient. The young sites typically included stress‐tolerant therophytes and hemicryptophytes. With age, woody species started to dominate at littoral sites at higher elevations, while perennial graminoids dominated at lowland sites. Spontaneous succession at aquatic and littoral sites leads to valuable semi‐natural stages and is recommended as a passive restoration option in disused sandpits.

Ecological analysis of rare and endangered lichen species included in the Red Book of the Chuvash Republic

The paper provides an ecological analysis of rare and endangered lichen species included in the Red Book of the Chuvash Republic. The new edition, published in 2020, includes information on 256 species of plants and fungi. The Red Book of the Chuvash Republic includes 30 species of rare and endangered lichen species, 14 species are included in the list of those which are subject to special attention and need constant monitoring in the natural environment. Biomorphological analysis has shown that rare lichen species belong to 3 types, 4 classes and 7 groups of life forms. The predominant species are bushy (bushy hanging group 11 species, bushy branching group 1 species, bushy erect group 1 species) and foliose (parted-lobed rhizoidal group 10 species, broad-bladed rhizoidal group 2 species) lichens. Ecological-substrate analysis has revealed that lichens included in the Red Book of the Chuvash Republic grow on 8 phorophytes (Tilia cordata, Quercus robur, Betula pendula, Salix cinerea, Pinus sylvestris, Picea abies, Abies sibirica, Populus tremula), on soil, on dead organic substrate and mosses. The greatest number of rare lichens was found on the bark of Tilia cordata, on the bark of Pinus sylvestris and on soil.

Floristic description and ecological characteristics of the plants of Pashat Valley, Pak-Afghan border, district Bajaur, Pakistan

This study was conducted during 2018–19 to evaluate the floristic composition and ecological characteristics of vegetation of Pashat valley, Bajaur. Floristic list of the valley contains 385 species distributed in 291 genera and 102 families. The dicotyledons having 83 families with 311 species and monocotyledons with 12 families contains 61 species. Pteridophytes having 05 families with 11 species and gymnosperm with a single family of two species. The leading family was Asteraceae with 42 species (10.90%) followed by Poaceae with 39 species (10.10%), Papilionaceae (Fabaceae) with 24 species (6.23%), Lamiaceae with 20 species (5. 19%) and Rosaceae with 15 species (3.90%). Therophytes 180 species (46.80%), hemicryptophytes 53 species (13.80%), nanophanerophytes 51 species (13.20%) and geophytes 35 species (9.09%) were the dominant life form groups. Leaf size class was dominated by microphylls (138 species, 35.84%) followed by nanophylls (124 species, 32.21%) and mesophylls (89 species, 23.12%). Habit wise the vegetation was mostly herbs (289 species) followed by shrubs (54 species), trees (38 species) and lianas (4 species). According to flowering phenology, most plants (62.30%) bloomed in spring followed by in summer (34%), in autumn (1.82%), in the whole year (1.30%) and in winter (0.52%). Based on chorological affinities, most of the species were bioregional in distribution (170 species, 44.15%) followed by mono-regional (157 species, 40.78%), pluri-regional (43 species, 11.17%) and cosmopolitan (15 species, 3.89%). The ecological characteristics like life form and leaf size spectra of the vegetation have a strong correlation with the prevailing environmental conditions such as altitude, slope, precipitation and temperature.

Analysis of flora of the medicinal plants of the Atyrau region

Medicinal plants are important sources of biologically active substances and phytopreparations for the prevention and treatment of diseases. In Kazakhstan, the regions of the Western Kazakhstan remain poorly studied in relation to wild medicinal plants. The purpose of the present study was to analyze the species composition of medicinal plants of the flora of the Atyrau region and their ranking by life forms, ecological groups, the degree of distribution and possibility of application in medical practice. Based on the analysis of literary sources and the results of own field studies in the Atyrau region, 177 species of medicinal plants belonging to 118 genera and 46 families are identified. The largest number of species of medicinal plants is noted in Asteraceae, Lamiaceae, Brassicaceae, Rosaceae, Chenopodiaceae, Fabaceae and Polygonaceae families. According to the degree of distribution, 4 groups of plants are identified: i) widespread plants, but growing sporadically, not forming thickets (128 species); ii) rare and endangered plants, not to be harvested for raw materials (11 species); iii) plants, forming small thickets (23 taxa); iv) plants, forming significant thickets suitable for industrial harvesting (15 taxa). Among the medicinal plants of the Atyrau region, 6 ecological groups were identified in relation to humidification conditions: hydrophytes, hygrophytes, mesophytes, mesoxerophytes, xerosesophytes and xerophytes. 8 groups of life forms are defined. The largest number of species is concentrated in the group of perennial herbaceous plants — 105 taxa. 128 taxa are allocated for use in folk medicine, 49 species — in official medicine. 12 pharmaceutical-therapeutic groups of plants for treatment of diseases of various etiologies are identified.

Differential responses of tree species to a severe ice storm and their implications to forest composition in the southeast United States

The unique terrain, geography, and climate patterns of the eastern United States encourage periodic occurrences of catastrophic ice storms capable of large-scale damage or destruction of forests. However, the pervasive and persistent effects of these glaze events on regional forest distribution and composition have rarely been studied. In the southeastern US, ice storm frequency and intensity increase with increasing latitude and along the complex gradients from the coast (low, flat, sediment controlled and temperature moderated near the ocean) to the interior (high, rugged, bedrock controlled, distant from warming ocean). To investigate the potential influence of this disturbance gradient on regional forest composition, we studied the differential responses of trees (canopy position, lifeform group, and species group) to a particularly severe ice storm. Our results indicated that tree mortality and damage (canopy damage, bent bole, snapped bole, and uprooted) varied significantly between overstory and understory trees, and among species and lifeform groups. Overstory trees were more prone to glaze damage than understory trees, and evergreen broadleaf species were the most susceptible to glaze damage, while deciduous species were the least susceptible. Among the pine species studied, slash pine (Pinus elliottii Engelm.) and longleaf pine (P. palustris Mill.) suffered more severe damage and mortality than loblolly pine (P. taeda L.). Further, ice damage was correlated with distribution-based differences in injury susceptibility among pine and deciduous tree species. The most ice storm-tolerant pine species, loblolly pine, had the most northerly distribution (39.51°N), while the least resistant species were those with more southerly distribution (e.g., 33.29°N for slash pine). These results support hypotheses that the distributions of evergreen tree species are regulated by periodic catastrophic ice storms. Therefore, predicting future distributions of tree species in response to climate change should consider the role of ice storms in shaping the forest composition.

Taxonomic differentiation and functional homogenization of flora in the middle part of European Russia as a result of naturalization of alien species

«Вестник Санкт-Петербургского университета. Науки о Земле» — научно-теоретический рецензируемый журнал, обобщающий результаты исследований в области геологии, гидрогеологии и геохимии, петрологии и экологии, ландшафтного планирования и геоморфологии, экономической и социальной географии.

The Effect of Biochar Used as Soil Amendment on Morphological Diversity of Collembola

Biochar was reported to improve the chemical and physical properties of soil. The use of biochar as a soil amendment have been found to improve the soil structure, increase the porosity, decrease bulk density, as well increase aggregation and water retention. Knowing that springtails (Collembola) are closely related to soil properties, the effect of biochar on morphological diversity of these organisms was evaluated. The main concept was the classification of springtails to the life-form groups and estimation of QBS-c index (biological quality index based on Collembola species). We conducted the field experiment where biochar was used as soil amendment in oilseed rape and maize crops. Wood-chip biochar from low-temperature (300 °C) flash pyrolysis was free from PAH (polycyclic aromatic hydrocarbon) and other toxic components. Results showed that all springtail life-form groups (epedaphic, hemiedaphic, and euedaphic) were positively affected after biochar application. The QBS-c index, which relates to springtails’ adaptation to living in the soil, was higher in treatments where biochar was applied. We can recommend the use of Collembola’s morphological diversity as a good tool for the bioindication of soil health.

Fine-scale temporal turnover of jarrah forest understory vegetation assemblages is independent of fire regime

BackgroundPrescribed burning is an important management tool in jarrah (Eucalyptus marginata Sm.) forests of southwest Western Australia to reduce the risk of damaging bushfires. In 1986 to 1987, we established long-term study sites in dry (mean annual rainfall ~700 mm) and moist (mean annual rainfall ~1000 mm) jarrah forests to assess the effects of prescribed burning, as well as other fire treatments including fire exclusion, on the composition, richness, and relative abundance of forest understory vegetation.ResultsOver almost 30 years, species assemblages within all fire treatments changed significantly through time, but the changes were independent of treatment. The pattern of change in composition of fire response types over elapsed time was different between sites. At the dry site, changes in species assemblages were initially relatively large in the first decade or so of the study, but slowed thereafter. At the moist site, compositional change driven by obligate seeding shrubs occurred faster and more uniformly with time across all treatments. Species richness was also independent of fire treatment at both sites. Species richness decreased with elapsed time on the moist site but increased with elapsed time on the dry site. The stronger elapsed-time effect rendered the time since fire effect on loss of species richness on the moist site to be insignificant, but there was an inverse relationship with time since fire at the dry site. Within each site, there were clear patterns of changing abundance based on life form and fire response groups, but this was not consistent between sites.ConclusionsAt the scale of the current study, jarrah forest plant communities displayed resilience to imposed experimental fire regimes. Over time, either elapsed time or time since fire, species assemblages across all treatments changed regardless of fire treatment, but changes were mostly associated with specific plant life forms and fire response traits, suggesting that the process is both deterministic and stochastic. While many species changed in abundance over time, no species were lost as a result of the fire treatments. Within the fire frequency and intensity ranges investigated in this study, there was flexibility in the application of prescribed fire to achieve management objectives without loss of plant diversity.

Environmental Characteristics and Anthropogenic Impact Jointly Modify Aquatic Macrophyte Species Diversity.

Species richness and spatial variation in community composition (i.e., beta diversity) are key measures of biodiversity. They are largely determined by natural factors, but also increasingly affected by anthropogenic factors. Thus, there is a need for a clear understanding of the human impact on species richness and beta diversity, the underlying mechanisms, and whether human-induced changes can override natural patterns. Here, we dissect the patterns of species richness, community composition and beta diversity in relation to different environmental factors as well as human impact in one framework: aquatic macrophytes in 66 boreal lakes in Eastern Finland. The lakes had been classified as having high, good or moderate status (according to ecological classification of surface waters in Finland) reflecting multifaceted human impact. We used generalized least square models to study the association between different environmental variables (Secchi depth, irregularity of the shoreline, total phosphorus, pH, alkalinity, conductivity) and species richness. We tested the null hypothesis that the observed community composition can be explained by random distribution of species. We used multivariate distance matrix regression to test the effect of each environmental variable on community composition, and distance-based test for homogeneity of multivariate dispersion to test whether lakes classified as high, good or moderate status have different beta diversity. We showed that environmental drivers of species richness and community composition were largely similar, although dependent on the particular life-form group studied. The most important ones were characteristics of water quality (pH, alkalinity, conductivity) and irregularity of the shoreline. Differences in community composition were related to environmental variables independently of species richness. Species richness was higher in lakes with higher levels of human impact. Lakes with different levels of human impact had different community composition. Between-lake beta diversity did not differ in high, good or moderate status groups. However, the variation in environmental variables shaping community composition was larger in lakes with moderate status compared to other lakes. Hence, beta diversity in lakes with moderate status was smaller than what could be expected on the basis of these environmental characteristics. This could be interpreted as homogenization.

Đa dạng hệ thực vật bậc cao tại khu đất ngập nước Hòa An thuộc huyện Phụng Hiệp, tỉnh Hậu Giang

The investigation was conducted from July 2016 to May 2017 at Hoa An wetland, Phung Hiep district, Hau Giang province. The vascular plants were collected in six biotopes through standard square and investigation line sampling method. The list of vascular plants was constructed. There were 56 species belonging to 51 genera of 38 families in 2 phyla of the vascular plants. In the term of species diversity, the genera, family and the average of genera in family index of the vascular plants system at the Hoa An wetland were 1,1, 1,47 and 1,34, respectively. Of the 7 existing groups of life forms, the grass group has the highest percentage. There were 55 useful plants found, of which medicinal plants have the highest number of species and one species was listed for conservation by Vietnam Red Book (2007). In six biotopes, each biotopes has specific plant groups.

The ecophysiology of leaf cuticular transpiration: are cuticular water permeabilities adapted to ecological conditions?

When the stomata are closed under drought, the only route for water loss from the leaf interior to the atmosphere is across the cuticle. Thus, the extent of cuticular transpiration in relation to the reservoirs of water in the plant and the water acquisition from the soil determines the fitness and survival of the plant. It is, therefore, widely assumed that the cuticular water permeability of plants regularly experiencing drought is comparatively low and, thus, adapted to the environment. To test this hypothesis, 382 measurements of cuticular permeability from 160 species were extracted from the literature published between 1996 and 2017. The data had been produced either by using isolated cuticles and astomatous leaf sides or by measuring the minimum leaf conductance under conditions assumed to induce maximum stomatal closure. The species were assigned to 11 life form groups. Except for two particular cases (epiphytes, and climbers and lianas), the cuticular permeabilities of all groups either did not differ significantly or the available data did not allow a statistical test. In conclusion, present knowledge either does not support the hypothesis that ecological adaptions of cuticular water permeability exist or the available data are insufficient to test it.

Convergence of community composition during secondary succession on Zokor rodent mounds on the Tibetan Plateau

The community succession theory is much debated in ecology. We studied succession on Zokor rodent mounds on the Tibetan Plateau to address several fundamental questions, among them: (i) During secondary succession, does the community composition converge towards one community state or multiple states depending on the initial colonization? (ii) Do mound communities located in different background communities exhibit different assembly trajectories? In a sub-alpine meadow, we investigated a total of 80 mound communities at several successional stages in three different background communities resulting from different management histories and compared their changes in species composition. The distribution of plant communities over time was analyzed with quantitative classification and ordination methods. The co-occurrence patterns of species were evaluated at each successional stage, and the degree of convergence/divergence among communities was obtained by calculating two beta-diversity indices. During secondary succession, species richness of mound communities changed over time, and this change was dependent on the background community. Five life-form groups exhibited different dynamic patterns in species richness and plant cover. Community composition and the degree of species co-occurrence between communities increased over time since disturbance. There was much variation in species composition at earlier stages of succession, but communities on older mounds became more similar to each other and to their surrounding vegetation over the course of secondary succession. Post-disturbance succession of Zokor mound communities transitioned from ‘multiple alternative states’ to ‘background-based deterministic community assembly’ over time. Tradeoffs between competition and colonization, as well as the characteristics of different life-forms and mass effects within a limited species pool are the mechanisms responsible for convergence of mound communities.

Disturbance gradient shows logging affects plant functional groups more than fire.

Understanding the impacts of natural and human disturbances on forest biota is critical for improving forest management. Many studies have examined the separate impacts on fauna and flora of wildfire, conventional logging, and salvage logging, but empirical comparisons across a broad gradient of simultaneous disturbances are lacking. We quantified species richness and frequency of occurrence of vascular plants, and functional group responses, across a gradient of disturbances that occurred concurrently in 2009 in the mountain ash forests of southeastern Australia. Our study encompassed replicated sites in undisturbed forest (~70yr post fire), forest burned at low severity, forest burned at high severity, unburned forest that was clearcut logged, and forest burned at high severity that was clearcut salvage logged post-fire. All sites were sampled 2 and 3yr post fire. Mean species richness decreased across the disturbance gradient from 30.1 species/site on low-severity burned sites and 28.9 species/site on high-severity burned sites, to 25.1 species/site on clearcut sites and 21.7 species/site on salvage logged sites. Low-severity burned sites were significantly more species-rich than clearcut sites and salvage logged sites; high-severity burned sites supported greater species richness than salvage logged sites. Specific traits influenced species' sensitivity to disturbance. Resprouting species dominated undisturbed mountain ash forests, but declined significantly across the gradient. Fern and midstory trees decreased significantly in frequency of occurrence across the gradient. Ferns (excluding bracken) decreased from 34% of plants in undisturbed forest to 3% on salvage logged sites. High-severity burned sites supported a greater frequency of occurrence and species richness of midstory trees compared to clearcut and salvage logged sites. Salvage logging supported fewer midstory trees than any other disturbance category, and were distinctly different from clearcut sites. Plant life form groups, including midstory trees, shrubs, and ferns, were dominated by very few species on logged sites. The differences in biotic response across the gradient of natural and human disturbances have significant management implications, particularly the need to reduce mechanical disturbance overall and to leave specific areas with no mechanical disturbance across the cut area during logging operations, to ensure the persistence of resprouting taxa.

Phenological complementarity in plant growth and reproduction in a green roof ecosystem

Green roofs are often planted with multiple species to improve aesthetics and other ecosystem services. If diverse species mixtures contain species with phenological differences in growth and reproduction, this could enhance ecosystem functioning by increasing the duration over which a valuable process operates. Phenological complementarity describes a species mixture where plant growth or reproduction is more evenly spread over time among species than predicted by chance. Here we report general phenological patterns of growth and reproduction from the third year of a four-year modular green roof experiment involving 13 species from five life form groups, planted in mixtures and monocultures. The relationships between phenological complementarity in canopy density (a surrogate for aboveground biomass) in species mixtures and thermal and hydrological functions were determined for the fourth year of the study.Timing of peak growth occurred from May to July, differing greatly among species. Flowering times also differed among species and occurred from May to October. Six species showed variation in phenology depending on whether they were planted in monocultures or species mixtures, suggesting competitive or facilitative interactions with other species. Phenological complementarity in canopy density was observed in four of the species mixture treatments, with mixtures of species from the same life form tending to have the highest complementarity values. Phenological complementarity was weakly negatively correlated with the temporal coefficient of variation in stormwater capture, indicating the potential for greater process stability over time in complementary mixtures.