Tall Species Research Articles

A comparison of the early growth and survival of lesser-known tree species for climate change adaptation in Britain

Globally, climate change is altering both seasonal climates and the occurrence of extreme climate events, resulting in a drive to ensure our forests are resilient to these changes and the challenges they will bring. In Great Britain (GB), there has been a reliance on a limited number of species grown in monospecific plantations and concerns over the resilience of these forests is leading to a growing recognition of the need to diversify tree species composition. However, evidence of the relative growth rate and survival of alternative tree species and provenances during the critical establishment phase (typically within five or six years of planting) is often limited, hampering consideration of the wider adoption of many potentially suitable species. To address this knowledge gap, we compared tree height and survival data six years after planting from 34 provenances across 18 tree species at five experimental sites established across GB in 2012 in monospecific plots. For coniferous species, we found that Larix decidua, Larix x marschlinsii and Pinus radiata (on drier sites) were consistently amongst the tallest species, but survival could be variable. Pseudotsuga menziesii and Pinus pinaster also showed good early growth, matching the growth rate of Picea sitchensis (the most widely planted conifer in GB) when co-occurring and often exhibited good survival. In contrast Picea orientalis was slow to establish and amongst the smallest species at all five sites after six years, with Cedrus atlantica also performing poorly where planted. Surprisingly, we found very few differences in both mean tree height and survival between most provenances of the same species across all experimental sites, though more obvious differences may emerge as these trees mature. Only a small number of broadleaf species were available for analysis at age six in this study, but as expected Betula pendula generally performed well, while Acer macrophyllum often had very high mortality. While there are concerns around the susceptibility of pine species to Dothistroma septosporum and the future use of larch species in GB forestry is currently limited by the disease Phytophthora ramorum, our results highlight the potential for these species to establish well and exhibit good initial growth and survival on drier sites, with the same true of P. menziesii on moister sites. Future work should aim to understand whether further differences between species and provenances emerge with age and explore the potential of these emerging species as components of mixed-species stands to increase GB forest resilience to climate change.

Phenotypic analysis of mezcal agaves from the Central Valleys of Oaxaca

Objective: Mezcal agaves in the state of Oaxaca have a high economic value due to the demand for mezcal production; therefore, the purpose of this work was to assess and highlight the importance of morphological diversity within and among cultivated Agave species. Design/Methodology/Approach: A completely randomized experimental design with 25 treatments (populations) and 11 replicates (individuals) was implemented. The plant (individual) was the experimental unit and 19 morphological descriptors proposed by the National Seed Inspection and Certification Service (SNICS) were assessed. A total of 275 individuals of the Agave angustifolia, Agave karwinskii, Agave marmorata, Agave rhodacantha, Agave potatorum, Agave seemanniana, and Agave nussaviorum species were assessed using a multivariate analysis to determine their phenotypic variability and existing relationships. Results: The dendrograms for the Q-mode and R-mode were obtained by means of a cluster analysis, forming 4 groups based on the average linkage generated from the standardized BDM of the sampled species of the genus Agave. Four groups were formed using the k-means clustering method, in accordance with field observations and a review of the taxonomic bibliography. The first two principal components (PC) accounted for 66.4% of the total variation, according to the principal component analysis (PCA). For PC1 and PC2, the variables with the highest contribution were those related to leaf shape (Fh), size of the lateral spine (FEL), number of leaves (Nh), plant height (H), uniformity in the size of the lateral spines (UTE), and terminal spine shape (FET). Study Limitations/Implications: A comprehensive study requires taxonomic keys to identify species, subspecies, and even varieties of Agave. Additionally, molecular characterization is essential to understand the variability and phylogenetic relationships of these populations, subject to a phylogenetic analysis. Findings/Conclusions: Multivariate analysis techniques revealed that three species showed high phenotypic variability in the maturation stage under cultivation conditions. The A. potatorum and A. karwinskii species had a greater intra-population phenotypic variability, with significant differences within the same species. Agave marmorata showed no intra- or inter-population variability. Leaf texture (Txh) was the only variable that explained the variation within its group. This is a tall species whose diameter is larger than in the other species. The variables of the Mexican (Agave rhodacantha) group showed low correlation, as their behavior was highly dispersed. The variables obtained in the field from this group of populations must be meticulously assessed to identify the degree of correlation between the variables and to confirm the behavior of this group.

Geoecology of limestone-hosted dryland calcicolous plants, North Otago, New Zealand

ABSTRACT Dryland calcicolous plants are drought-tolerant species that are adapted to survive on alkaline low-nutrient bare substrates derived from limestone around the world. Outcrops of the Otekaike Limestone of North Otago host some rare low-growing (<10 cm) endemic calcicoles, and conservation reserves have been created at some localities. The calcicoles occupy microhabitats in solution cavities in limestone outcrops, growing in thin (<10 cm) limestone debris accumulations, including detrital sand and silt. Calcicoles also grow in coarse and fine disaggregated limestone talus deposits at tops and bottoms of outcrops, commonly with the low-growing exotic hawkweed but the calcicoles are displaced by taller species, especially grasses. Calcicole substrates have pH 8 to 9, with a balance between calcite dissolution and calcite re-precipitation. Electrical conductivity is typically <500 µS/cm, but can be as high as 7 mS/cm with evaporative salts and salt weathering enhancing porosity. The limestone contains variably oxidised authigenic glaucony and pyrite, which provide some plant nutrients (K, Mg, Fe, S, N) as roots penetrate porous limestone, with apatite providing phosphate. Persistence of these rare calcicolous communities in soil-free settings is strongly affected by the underlying mineralogy and geochemistry, and some similar microhabitats may occur on other rock types.

Restoring charophytes is still a challenge: A call for developing successful methods

Submerged aquatic vegetation, and especially charophytes, which are an important habitat for many species, have declined in the Baltic Sea due to changes in light climate, eutrophication and physical disturbance. Physical disturbance in the form of small-scale dredging activities is commonplace in Sweden due to land uplift, but causes fragmentation of coastal habitats. Here we test three planting methods for restoration of the charophyte Chara aspera on an area of deposited sediment, and a single method for restoration of C. tomentosa in a dredged area. We found that none of the planting methods tested was more successful than natural recolonization of C. aspera on the deposited sediment. C. tomentosa planting was unsuccessful in the dredged area and was likely outcompeted for light by taller species. The C. aspera meadow was resilient to smaller disturbances, as experimental removal of up to 2.5% of C. aspera and sediment from the donor area did not reduce C. aspera coverage a month after removal. Even after an uncontrolled event that removed up to 50% of C. aspera in the experimental plots, C. aspera coverage had returned to pre-removal levels a year after the disturbance. We suggest future restoration experiments test transplanting sediment rich in oocytes and bulbils into areas with suitable light climates and low competition with other species. Restoration efforts are costly and highly uncertain of success, therefore we recommend discontinuing dredging activities in charophyte meadows to protect this important habitat.

Nitrogen addition alleviates the adverse effects of drought on plant productivity in a temperate steppe.

Drought and nitrogen enrichment could profoundly affect the productivity of semiarid ecosystems. However, how ecosystem productivity will respond to different drought scenarios, especially with a concurrent increase in nitrogen availability, is still poorly understood. Using data from a 4-year field experiment conducted in a semiarid temperate steppe, we explored the responses of aboveground net primary productivity (ANPP) to different drought scenarios and nitrogen addition, and the underlying mechanisms linking soil properties, plant species richness, functional diversity (community-weighted means of plant traits, functional dispersion) and phylogenetic diversity (net relatedness index) to ANPP. Our results showed that completely excluding precipitation in June (1-month intense drought) and reducing half the precipitation amount from June to August (season-long chronic drought) both significantly reduced ANPP, with the latter having a more negative impact on ANPP. However, reducing half of the precipitation frequency from June to August (precipitation redistribution) had no significant effect on ANPP. Nitrogen addition increased ANPP irrespective of drought scenarios. ANPP was primarily determined by soil moisture and nitrogen availability by regulating the community-weighted means of plant height, rather than other aspects of plant diversity. Our findings suggest that precipitation amount is more important than precipitation redistribution in influencing the productivity of temperate steppe, and nitrogen supply could alleviate the adverse impacts of drought on grassland productivity. Our study advances the mechanistic understanding of how the temperate grassland responds to drought stress, and implies that management strategies to protect tall species in the community would be beneficial for maintaining the productivity and carbon sequestration of grassland ecosystems under climate drought.

Blooming and Forage Characteristics of Twelve Native Forbs Subjected to Repeated Defoliation

Insect pollinators are in population decline due to environmental and chemical stressors. Including native forbs in pastures could benefit grazers and pollinators; however, their forage and flowering characteristics are not fully documented. The objectives of our research were to evaluate 12 native forbs for persistence, forage mass, nutrient composition, and flowering patterns under repeated defoliation. Twelve species were planted in a small-plot experiment in 2018. Response variables were measured from 2020 to 2022. Annual (partridge pea, PPEA, Chamaecrista fasciculata) and biennial (black-eyed Susan, BESU, Rudbeckia hirta) species established high (p &lt; 0.05) plant populations during the first season; however, the PPEA declined (p &lt; 0.05) in forage mass during 2021. Tall species (Maximilian sunflower, MSUN, Helianthus maximiliani; cup plant, CUPP, Silphium perfoliatum) increased in forage mass, produced high-quality forage, and flowered during early fall. Lanceleaf coreopsis (LCOR, Coreopsis lanceolata) produced consistent (p &gt; 0.05) forage mass and flowered in spring. The purple coneflower (PURC, Echinacea purpurea), Illinois bundleflower (ILBF, Desmanthus illinoensis), and oxeye sunflower (OSUN, Helopsis helianthoides) produced high-quality, consistent (p &gt; 0.05) forage mass and flowered mid-season. Interseeding the BESU, ILBF, PPEA, LCOR, PURC, OSUN, and MSUN or CUPP would produce high-quality forage and floral resources throughout summer.

TWO-YEAR FLOWER CULTURES IN THE COLLECTION OF THE BOTANICAL GARDEN OF BILA TSERKVA NATIONAL AGRARIAN UNIVERSITY

The article presents the results of the analysis of the collection of two-year-old flowering ornamental plants in the Botanical garden of Bila Tserkva national agrarian university. It was established that the biennial collection includes 17 species belonging to 15 genera and 10 families. The largest number of species is represented by the family Brassicaceae Burnett. – Brassica oleracea L. var. Acephala DC., Erysimum perovskianum Fisch.hort., Hesperis matronalis L., Lunaria biennis L. The collection presents species that have not only decorative, but also medicinal, fodder, and tanning properties. Diditalis grandiflora contains poisonous glycosides. Alcea rosea has ethnographic significance and belongs to amulet plants.&#x0D; The morphometric indicators of biennials by height and their flowering periods were analyzed. It was established that 41,2% of the collection of biennials of the Botanical Garden of the Bila Tserkva NAU belongs to low-growing species, medium-sized and tall plants are represented by the same number of species, which is 29,4% each. The largest number of species in the collection is represented by the group of summer-flowering biennials, 47,1%, late-spring-flowering ones make up 29,4%, and early-flowering ones – 23,5% of species. &#x0D; Most biennials are cultivated in open ground to decorate flower beds, only a few to create seasonal bouquets and phytocompositions. Thanks to the plasticity of biennials, which is manifested in non-standard sowing dates, relative frost resistance and early spring and early summer flowering periods, biennials reduce the costs of growing seedlings and care for them after planting in a permanent place, provide an annual change in the design of flower beds and fill the flowerless periods of early spring and early summer. Biennials are suitable for creating borders, flower beds, rabatoks, lawns, carpets, ribbons, for decorating flowerbed groups and balconies, container culture. Tall species can be used as a background for the entire composition. Varietal diversity of Bellis perennis L., Brassica oleracea L. var. Acephala DC, Dianthus caryophyllus L. var. Grenadine hort, Dianthus barbatus L., Viola wittrockiana Gams. allows you to create monoculture flower beds with a wide color palette.

IMPACT OF FOREST SHELTER BELTS ON THE DEVELOPMENT OF SPRING WHEAT IN THE NEAR-EDGE ZONE OF CROPS

The system of shelterbelt forests is a long-lasting ecological framework of an agrarian territory. Their main function is to prevent the degradation of arable soils, improve the microclimate of fields, and preserve the stability and biological diversity of landscape. However, the presence of forest belts complicates field cultivation, and along their borders zones (strips) of depression in crop development could formed, reducing the productivity of lands. This impedes field-protective afforestation, and, consequently, the solution of the problem of reliable protection of land resources. The aim of the work is to establish the causes and regularities of formation of depressive zones in agrocenoses, and to determine the possibility and methods of suppressing their development. The research has been conducted for 8 years in the experimental-production system of 30 to 53-year old 2 to 4-row forest belts of Betula pendula ROTH, Pinus silvestris L., Ulmus laevis PALL. and other species on the automorphic chestnut soil of the Kulunda steppe (the Altai territory) by the generally accepted methods. It was found that the depressive zone in agrocenoses is the least wide for relatively sparse forest belts of birch and pine, and also for forest belts with marginal rows of xerophytic shrubs (3-7 m in total on windward and leeward sides), and the largest (up to 25-30 m) for elm and poplar (Populus laurifolia LEDEB.), i. e. for plantations of hydrophylous tall species with dense crowns. It is 1-3 m wider on the leeward side of forest belts, where more snow is deposited in winter and soil moisture is better in spring. The increase in height and density of stands, influencing the length and intensity of day-time soil shading, stimulates the expansion of the zone. Crop depression is more pronounced in wet years. The increased amount of atmospheric precipitation during the cold season, as well as at the beginning of the growing season and during the reaping season till the onset of stable cold weather also contributes to it. The development of depressive zones is suppressed by abundant precipitation during the period of active growth of field crops. Thus, the formation of depressive zone in agrocenoses of shelterbelt forests depends on many factors. Under arid conditions, the most effective factors are the need for soil moisture and moisture availability for the stand. The most active expansion of the tree root system in the field and the suppression of crops occur in wet years and during the periods with high soil moisture in the absence or weakened competition of field crops. To reduce damage to their productivity, it is necessary to implement a set of coordinated organizational, silvicultural and agrotechnological measures aimed at increasing moisture availability and limiting the expansion of tree root system of forest belts in the field.

The accumulation of anthropogenic stressors induces a progressive shift in the ecological preferences and morphological traits shared by riparian plant communities

Abstract In riverine ecosystems, human‐induced stressors related to flow regulation and bank stabilisation have accumulated over time. The restoration of these highly anthropised ecosystems has become a major issue over the last few decades, with ambitious stated objectives. However, while the individual impact of flow regulation and channelisation on river functioning has been extensively studied, the response of ecological communities to multiple co‐occurring human‐induced stressors remains largely unexplored. Using a sampling design based on five river reaches in the Rhône catchment, ranging from unregulated in flow and bedload transport to intensively regulated reaches, we sought to understand how the accumulation of anthropogenic stressors influenced the functional response of riparian plants communities on gravel bars. By using 12 ecological and morphological traits, we performed a classification analysis to construct six riparian guilds and investigated whether their representativeness, as well as the mean value of individual traits, varied with increasing levels of anthropogenic stressors. Species cover and redundancy in several guilds increased or decreased significantly with increasing pressures. Thus, the guild of small taproot herbs with low nutrient and soil moisture requirements (xero‐oligotro‐taproot species guild) and the guild of taproot herbs adapted to very bright and dry conditions (mesoxero‐mesotro‐taproot species guild) dominated the unregulated reaches with active bedload transport. Conversely, regulated reaches with stabilised baseflow and inactive transport were dominated by the guild of flood‐tolerant trees (hygro‐perennial tall species guild) and the guild of vegetatively reproducing and flood‐tolerant perennial herbs (hygro‐perennial clonal species guild). Analysis of individual traits revealed a shift in environmental conditions, from full light to shade tolerance and from dry to humid, with increasing anthropogenic stressors. In response to this decrease in drought levels, plants traits shifted from annual to perennial species, from sexual to vegetative strategies and from taproots to a fibrous root system. Our results highlight the accumulated effects that anthropogenic stressors can have on riparian communities, inducing a progressive shift in certain traits related to life history, reproductive strategies, and drought adaptations. This effect on a set of shared traits reveals the strong influence that human infrastructures can have on the ecological niche of species and the morphological adaptations of riparian vegetation. From an applied point of view, and for highly anthropised rivers, our results suggest that restoration actions targeting a single stressor will not be sufficient to reorient riparian plant communities towards an ecological state closer to reference systems. Since human‐induced stressors have often deeply altered the flow and sediment regimes of rivers, a more integrated approach based on the restoration of erosion and flooding processes is essential to allow the expression of a wider diversity of riparian plant communities and habitats.

Ecological significance of standing dead phytomass: Marcescence as a puzzle piece to the nutrient cycle in temperate ecosystems

Abstract The plant economics spectrum (PES) drives nutrient cycling through effects on soil decomposers. However, dead phytomass may remain standing or unshed (marcescent), hardly accessible to decomposers and be photodegraded. In arid zones, the significant part of marcescent phytomass can be decomposed without touching the ground. In temperate zones, photodegradation of marcescent phytomass is low but prompts important chemical changes, which affect its subsequent decomposability in the soil and alters the surrounding environment. It is unknown, however, how common marcescence is among different taxa and in which habitats, and how it is coordinated by PES traits. We sampled standing (marcescent) and lying (shed) dead phytomass from a broad spectrum of 127 herbaceous temperate species in a common garden experiment and related these parameters to PES traits, species ecological preferences and phylogeny. Nearly all species (97%) kept their phytomass marcescent. Tall species with a small leaf area and high leaf carbon had a high level of marcescence. Marcescent species also preferred sites affected by severe (but not necessarily frequent) disturbance. The degree of marcescence was considerably conserved in phylogeny. Synthesis. Marcescence extends PES trait effects on ecosystems, particularly in immature habitats, being a common but overlooked phenomenon of the temperate flora.

Fitness and niche differences are both important in explaining responses of plant diversity to nutrient addition.

Plant species loss due to eutrophication is a common phenomenon in temperate perennial grasslands. It occurs in a non-random fashion and is usually explained by increased competitive size asymmetry between co-occurring winner (tall species with optima in productive habitats) and loser species (small-statured plants typical for unproductive habitats). It remains unclear why nutrient addition decreases diversity in communities consisting of losers only, whereas it has little effect on winner-only communities. Here, I used the framework of modern coexistence theory to explore fertilization-driven changes in fitness and niche differences between different combinations of field-identified winner (W) and loser (L) species. I experimentally estimated competition parameters for plant species pairs constructed from a pool of eight species, including pairs of species from the same (WW, LL) and different species categories (LW) grown for approximately two years in control and fertilized conditions. Concurrently, I also followed plant species diversity in mesocosm communities constructed from the same species pool (four-species communities including winners, losers, or both) exposed to control and nutrient addition. I found that nutrient addition can reduce but, unexpectedly, also promote species coexistence depending on the type of species pairs. Whereas nutrient addition eroded coexistence of losers with winners, but also with other losers, treatment had the opposite effect on the persistence of winner species. Fertilization induced large fitness differences between species in loser-winner and loser-loser combinations, but had little effect on the fitness differences of species within the winner-winner combination. In addition, the persistence of winner pairs was promoted by larger niche differences compared to loser species, irrespective of soil nutrients. The differences in how nutrient addition modified coexistence at the pairwise level was reflected by differences in evenness of multispecies communities assembled from the corresponding species categories. These results suggest that the effect of eutrophication on plant species richness cannot simply be explained by an increased competitive asymmetry. To fully understand the effect of fertilization on the diversity of temperate grasslands, interspecific and intraspecific interactions should be explored while considering differences in species' ecological optima. This article is protected by copyright. All rights reserved.

Common, showy, and perennial species dominate a restoration species pool

Native seed vendors are a primary source of germplasm for restoration projects; however, most plant species are not commercially available. Preferences in the types of species that vendors grow and sell may limit the similarity between reference communities and reconstructed ones established from seed mixes. We tested whether a restoration species pool shows preference for certain groups of species, focusing on the Ozark Highland Ecoregion (midcontinent United States). We identified the pool of 1,082 candidate herbaceous plant species appropriate for restoration projects on upland habitats in this region, and then surveyed nine regional seed vendors to assess their commercial availability. Commercially available species were more likely to be forbs over graminoids, perennials over annuals, and common species with larger ranges and moderate conservatism scores. Within forbs, taller species and those with longer bloom durations were favored. Species with affinity to open habitats (e.g. grassland) were more likely to be available from multiple vendors than those from woodlands and forests. Encouragingly, 454 (42%) of the species in this regional pool were available. However, this means that most species in the region are not likely to be included in seed mixes, unless they are hand‐collected from remnant populations. This restoration pool favors common and showy species, which is consistent with previous studies showing these kinds of species tend to dominate seed mixes and restored plant communities. We identified 39 species that were not available from any of the vendors surveyed, which we recommend as candidates for expansion of the Ozark restoration species pool.

Traits help explain species' performance away from their climate niche centre

AbstractAimClimate change impacts on biota are variable across sites, among species and throughout individual species' ranges. Niche theory predicts that population performance should decline as site climate becomes increasingly different from the species' climate niche centre, though studies find significant variation from these predictions. Here, we propose that predictions about climate responses can be improved by incorporating species' trait information.LocationEurope.MethodsWe used observations of plant species abundance change over time to assess variation in climate difference sensitivity (CDS), defined as how species performance (colonization, extinction and abundance change) relates to the difference of site climate from the mean temperature and precipitation of each species' range. We then investigated if leaf economics, plant size and seed mass traits were associated with the species' CDS.ResultsSpecies that performed better (e.g. increased in abundance) towards sites progressively cooler than their niche centre were shorter and had more resource‐acquisitive leaves (i.e. lower leaf dry matter content or LDMC) relative to species with zero or the opposite pattern of temperature difference sensitivity. This result supports the hypothesis that if sites cooler than niche centres are more stressful for a species, then shorter stature is advantageous compared with taller species. The LDMC result suggests the environment selects for more resource‐acquisitive leaf strategies towards relatively cooler climates with shorter growing seasons, counter to expectations that conservative strategies would be favoured in such environments. We found few consistent relationships between precipitation difference sensitivities and traits.Main ConclusionsThe results supported key a priori foundations on how trait‐based plant strategies dictate species responses to climate variation away from their niche centre. Furthermore, plant height emerged as the most consistent trait that varied with species CDS, suggesting height will be key for theory development around species response to climate change.

Divergent trait responses to nitrogen addition in tall and short species

Abstract Asymmetrical light competition and direct detrimental effect of nitrogen have been proposed as two main mechanisms driving species richness declines following nitrogen (N) addition. N addition is also known to alter functional trait composition towards increased dominance of tall and fast‐growing species. However, whether trait changes vary between species and, in particular, how the traits of tall and short species respond to N addition has rarely been studied. Understanding whether different trait changes occur for tall and short species would provide insight into mechanisms underlying N addition effects. Based on a long‐term N addition experiment, we measured the natural height of 44 plant species and the photosynthetic active radiation (PAR) at seven heights in the vegetation and identified a clear stratification of the plant community into tall species (&gt;30 cm tall), which experienced high light conditions, and short species that grew under the canopy. We also measured four functional traits, including maximum plant height, specific leaf area, leaf dry matter content and leaf thickness, on 35 species that occurred in fertilized and unfertilized plots. Structural equation modelling revealed that nitrogen (N) addition significantly reduced species richness by enhancing light asymmetry and had no direct effects, suggesting that N detrimental effects are negligible in our system. Consistent with this, we found different responses of traits and diversity for the tall and short species. Specifically, N addition reduced the number of short species but increased the number of tall species. In addition, specific leaf area increased, and leaf dry matter content decreased, for short species only, suggesting that they shifted to a fast growth strategy to cope with lower light levels. In contrast, tall species increased their height further to capture more light at the top of the canopy. Synthesis. The divergent trait responses observed for tall and short species show that although certain traits, like height and leaf traits, show correlated responses at the whole community level, these correlations may not be consistent across all species. Together, our results highlight that light competition is the main mechanism driving species loss following N addition.

Size-biased compositional impacts of small mammal herbivores in an old-field plant community

Plant species height (mature height), which strongly correlates with other measures of size, is widely considered an important functional trait. Taller species contribute greatly to ecosystem function and are frequently identified as strong competitors. Additionally, important ecological processes like self-thinning scale with plant species size. In spite of the clear functional importance of species size, evidence for size-based plant community assembly rules has been scant. While herbivory can be species specific and there are reasons why herbivores may target larger plant species, it is unknown whether herbivory has size-biased impacts on species composition. In an old-field plant community, we compared plant species composition in herbivore exclusion (caged) and control plots over five years to test whether herbivore activity favors species at one end of the size spectrum. Across 5 years, smaller species were modestly, but consistently, underrepresented in caged plots compared to control plots. This underrepresentation of relatively smaller plant species in caged plots, where seedling herbivory was greatly diminished, was driven by lower small plant species richness and abundance in those plots; the abundance and richness of tall species did not differ across treatments. Our findings demonstrate that reducing herbivore activity in our study community modestly but consistently altered plant species composition, slightly favoring larger species. There was no evidence that larger species are preferentially targeted by herbivores. Some research suggests, although it will require further investigation, that seedling herbivory, regardless of the species eaten, produces vegetation gaps that small plant species are more successful in colonizing.

Traits of dominant plant species drive normalized difference vegetation index in grasslands globally

AbstractAimTheoretical, experimental and observational studies have shown that biodiversity–ecosystem functioning (BEF) relationships are influenced by functional community structure through two mutually non‐exclusive mechanisms: (1) the dominance effect (which relates to the traits of the dominant species); and (2) the niche partitioning effect [which relates to functional diversity (FD)]. Although both mechanisms have been studied in plant communities and experiments at small spatial extents, it remains unclear whether evidence from small‐extent case studies translates into a generalizable macroecological pattern. Here, we evaluate dominance and niche partitioning effects simultaneously in grassland systems world‐wide.LocationTwo thousand nine hundred and forty‐one grassland plots globally.Time period2000–2014.Major taxa studiedVascular plants.MethodsWe obtained plot‐based data on functional community structure from the global vegetation plot database “sPlot”, which combines species composition with plant trait data from the “TRY” database. We used data on the community‐weighted mean (CWM) and FD for 18 ecologically relevant plant traits. As an indicator of primary productivity, we extracted the satellite‐derived normalized difference vegetation index (NDVI) from MODIS. Using generalized additive models and deviation partitioning, we estimated the contributions of trait CWM and FD to the variation in annual maximum NDVI, while controlling for climatic variables and spatial structure.ResultsGrassland communities dominated by relatively tall species with acquisitive traits had higher NDVI values, suggesting the prevalence of dominance effects for BEF relationships. We found no support for niche partitioning for the functional traits analysed, because NDVI remained unaffected by FD. Most of the predictive power of traits was shared by climatic predictors and spatial coordinates. This highlights the importance of community assembly processes for BEF relationships in natural communities.Main conclusionsOur analysis provides empirical evidence that plant functional community structure and global patterns in primary productivity are linked through the resource economics and size traits of the dominant species. This is an important test of the hypotheses underlying BEF relationships at the global scale.

Evolutionary effects of nitrogen are not easily predicted from ecological responses.

Anthropogenic nitrogen (N) addition alters the abiotic and biotic environment, potentially leading to changes in patterns of natural selection (i.e., trait-fitness relationships) and the opportunity for selection (i.e., variance in relative fitness). Because N addition favors species with light acquisition strategies (e.g., tall species), we predicted that N would strengthen selection favoring those same traits. We also predicted that N could alter the opportunity for selection via its effects on mean fitness and/or competitive asymmetries. We quantified the strength of selection and the opportunity for selection in replicated populations of the annual grass Setaria faberi (giant foxtail) growing in a long-term N addition experiment. We also correlated these population-level parameters with community-level metrics to identify the proximate causes of N-mediated evolutionary effects. N addition increased aboveground productivity, light asymmetry, and reduced species diversity. Contrary to expectations, N addition did not strengthen selection for trait values associated with higher light acquisition such as greater height and specific leaf area (SLA); rather, it strengthened selection favoring lower SLA. Light asymmetry and species diversity were associated with selection for height and SLA, suggesting a role for these factors in driving N-mediated selection. The opportunity for selection was not influenced by N addition but was negatively associated with species diversity. Our results indicate that anthropogenic N enrichment can affect evolutionary processes, but that evolutionary changes in plant traits within populations are unlikely to parallel the shifts in plant traits observed at the community level.

Declining temperature and increasing moisture sensitivity of shrub growth in the Low-Arctic erect dwarf-shrub tundra of western Greenland.

Evergreen dwarf shrubs respond swiftly to warming in the cool and dry High Arctic, but their response in the warmer Low Arctic, where they are expected to be outcompeted by taller species under future warming, remains to be clarified. Here, 12,528 annual growth increments, covering 122 years (1893-2014), were measured of 764 branches from 25 individuals of the evergreen dwarf shrub Cassiope tetragona from a Low-Arctic erect dwarf-shrub tundra site in western Greenland. In addition, branch initiation and mortality frequency time series were developed. The influence of seasonal climate and correspondence with fluctuations in regional normalized difference vegetation index (NDVI), a satellite-proxy for vegetation productivity, were studied. Summer temperatures were the main driver of growth, while winter temperatures were the main non-summer-climate driver. During past and recent warm episodes, shrub growth diverged from summer temperatures. In recent decades, early summer precipitation has become the main growth-limiting factor for some individuals, likely through micro-topography-determined soil moisture availability, and more than half of the shrubs studied became irresponsive to summer temperatures. There was correspondence between climatic drivers, C. tetragona growth and branch initiation frequency, and satellite-observed vegetation productivity, suggesting the area's shrub-dominated tundra vegetation is limited by similar climatic factors. Winter warming events were likely the predominant cause of branch mortality, while branching increased after years with poor growth and cooler-than-average summers. These findings show that the erect dwarf-shrub tundra in the Low Arctic has already and will likely become decreasingly temperature- and increasingly moisture-limited and that winter warming supports shrub growth, but increased extreme winter warming event frequency may increase branch mortality and vegetation damage. Such counter-acting mechanisms could offer an explanation for the vegetation stability observed over large parts of the Arctic.

Aerial Phytomass Production and Growth Performances of Five Common Tall Species in Andean Grasslands at Harvesting and Application of Natural Fertilizers

The objective of the research was to evaluate: aerial cover, canopy height and aerial phytomass production in five of the most common tall species in the area, in order to articulate it to a plant fiber production project. For the evaluation, 5 plots of 900 m2 were fenced, including 50 subplots of 32 m2, which were fertilized with cattle manure and phosphate rock. Monthly measurements were made from October 2020 to June 2021. At the end of the control, significant differences were observed for P = .01. Between plots they ranged from 1533±508 to 2909±192 cm2 in canopy cover (CC), from 36.9±0.89 to 38.3±2.31 cm in canopy height (CH) and 44±9.11 to 129±9.11 g DM/plant in Aerial Phytomass Production (AFP). Between species, they ranged from 2067±876 to 2975±200 cm2 in CC, from 33.2±3.86 to 40.3±1.24 cm in CH, and from 49.4±11.52 to 162.4±8.49g DM/plant in AFP. By fertilization effect the AFP varied as follows: those fertilized with phosphate rock reached 109.5±6.72 g DM/plant (14.7%), with cattle manure 88.8±6.72 g DM/plant (-5.3%), and finally the control plants with 93.5±15.03 g DM/plant, which means. A high canonical correlation was also observed between biological variables (canopy cover, canopy height, and dry matter production) and climatic variables (maximum temperature, minimum T. in °C, and rainfall in liters/m2). It was shown that tussock species respond quickly to cutting and natural fertilization has beneficial effects on biological indicators, despite the altitudinal difference between the plots and the particular species.

Deferment associated to contrasting grazing intensities affects root/shoot biomass allocation in natural grasslands

AbstractQuestions(i) How does a strategic deferment influence both shoot and root biomass in South American Campos natural grassland after a long time of contrasting livestock grazing intensities? (ii) How do functional strategies of plants to tolerate or avoid grazing affect patterns of aboveground and belowground biomass?LocationA natural Campos grassland in the Central Depression of Rio Grande do Sul State, Southern Brazil (latitude 30°05′27″ S, longitude 51°40′18″ W, and altitude 46 m).MethodsWe studied the effects of deferments (spring or autumn) at moderate and severe livestock grazing intensities (maintained by adjusting contrasting forage allowances during 25 years) on the cover of dominant species, and aboveground and belowground biomass. The experiment was arranged in a completely randomized design with three replications of grazing exclusions, applied simultaneously at moderate and severe grazing intensities. Measurements of above‐ and belowground biomass and the coverage of the five dominant species were performed before and after grazing exclusion periods.ResultsUnder severe grazing intensity, erect‐growing grasses were replaced by prostrate species, which were able at least to maintain the belowground biomass found at moderate grazing intensity. In response to deferments, severe grazing intensity changed toward a significant increase in aboveground biomass and in the coverage of plants with erect growing habit. However, total belowground biomass remained unaffected by exclusions in both grazing intensities. The relation of root:shoot biomass was lower under moderate grazing intensity, and showed a negative response to deferment treatments at severe grazing intensity.ConclusionLong‐term contrasting grazing intensities applied in South American Campos grasslands determine several changes in above‐ and belowground relationships. Prevalence of prostrate plants under severe grazing is associated with a high partitioning capacity of assimilates toward the subterranean biomass, higher than in the tall species predominant under moderate grazing. The fast recovery of aboveground biomass, the maintenance of the underground biomass and the increase of tall grasses in response to deferments reveals the high resilience capacity of this ecosystem after a long‐term period of overgrazing.