Abundance Of Shrubs Research Articles

Beaver foraging patterns in a human-dominated landscape: Effects on woody vegetation and mammals

Beavers can change habitat composition by cutting down trees, digging, and damming activities, thereby affecting species richness and abundance. Although there is large body of literature regarding the effects of beaver activity on a wide range of taxonomic groups, relatively little is known about how space use by ungulates is affected by beavers in the human-dominated landscapes of Europe. Here, we present a case study from Denmark that investigated potential effects of beaver activity on mammals, with a special focus on roe deer and red deer. Beavers could either facilitate the presence of deer by providing food resources (increased abundance of deciduous trees and shrubs) or compete with them for resources. Using transect counts recording both cut and uncut stems of woody plants, we describe beaver browsing patterns, providing evidence that they either select for areas with higher woody vegetation richness and diversity, or alter woody plant species composition. We then assessed deer presence and relative abundance in relation to the distance from water and in areas with varying beaver activity. Our findings provide limited evidence for exploitative competition between beavers and roe and red deer, as roe and red deer avoided proximity to water in areas with high beaver activity, and deer numbers were higher in areas with low beaver activity. We speculate that the weak effect of beaver activity on deer (and/or vice versa) might be related to the large human impacts in the area, e.g., forest management, potentially superseding effects of interspecific competition. An improved understanding of the complex effects beavers can have on ungulates in human-dominated landscapes will be relevant for wildlife and forestry management, potentially being an important tool to reduce human-wildlife conflicts.

Sandy Habitats Play an Important Role in Shrub Encroachment in Grasslands

Shrub species have increased in density and cover in desertification areas, however, the role of sandy habitats in contributing to the expansion of shrubs is poorly understood. Although the effect of sandy habitats on plant growth and reproduction have been demonstrated, most existing studies lack either experimental demonstration or an integrated study during the whole shrub life cycle. We performed field and laboratory experiments to examine the responses of four stages in the life cycle of shrubs (seed germination, plant growth, seed reproduction, clonal reproduction) to sandy habitats (including sand substrate, sand burial and wind erosion) for Caragana shrubs. Results showed that both sand substrate and sand burial facilitated seed germination, seedling biomass, sapling establishment, plant growth, and root-shoot ratio of Caragana. Meanwhile, they both strongly increased seed number and seed preservation, and thus enhanced sexual reproduction. Sand burial favored clonal reproduction of Caragana by promoting the formation of branch-derived ramets, while wind erosion benefited clonal reproduction by facilitating the formation of root-derived ramets. These results suggested that sandy habitats facilitated seed germination, plant growth, sexual reproduction, and clonal reproduction of Caragana, which could explain why shrub abundance, shrub area and shrub height of Caragana in sandy areas was higher than in grasslands. Our study provided an experimental demonstration that sandy habitats promoted the population growth of Caragana shrubs during the whole life cycle and highlighted the significant role of sandy habitats in facilitating shrub encroachment in grasslands.

Canopy plant composition and structure of Cape subtropical dune thicket are predicted by the levels of fire exposure.

The subtropical dune thicket (hereafter "dune thicket") of the Cape Floristic Region experiences a wide range of fire exposure throughout the landscape, unlike other dry rainforest formations that rarely experience fire. We sought to determine how fire exposure influences species composition and the architectural composition of dune thicket. We used multivariate analysis and diversity indices based on cover abundance of species to describe the species composition, architectural guild composition and structure of dune thicket sites subject to different levels of fire exposure, namely low (fire return interval of >100 years), moderate (fire return interval of 50-100 years), and high (fire return interval of 10-50 years). The diversity, cover abundance and architectural guild cover abundance of dune thicket canopy species were strongly influenced by the level of fire exposure such that each level was associated with a well-circumscribed vegetation unit. Dune thickets subject to low fire exposure comprises a floristically distinct, low forest characterized by shrubs with one-to-few upright stems (ca. 4-8 m tall) and a relatively small canopy spread (vertical growers). Of the 25 species in this unit, 40% were restricted to it. Dune thickets subject to moderate fire exposure had the highest abundance of lateral spreaders, which are multi-stemmed (ca. 3-6 m tall) species with a large canopy spread and lower stature than vertical growers. None of the 17 species found in this unit was restricted to it. Dune thickets subject to high fire exposure had the highest abundance of hedge-forming shrubs, these being low shrubs (ca. 0.6-1.4 m tall), with numerous shoots arising from an extensive system of below-ground stems. Of the 20 species in this unit, 40% were restricted to it. Multivariate analysis identified three floristic units corresponding to the three fire exposure regimes. Compositional structure, in terms of species and architectural guilds, was most distinctive for dune thickets subject to high and low fire exposure, while the dune thicket subject to moderate fire exposure showed greatest compositional overlap with the other units. Fire exposure profoundly influenced the composition and structure of dune thicket canopy species in the Cape Floristic Region. In the prolonged absence of fire, the thicket is invaded by vertical-growing species that overtop and outcompete the multi-stemmed, laterally-spreading shrubs that dominate this community. Regular exposure to fire selects for traits that enable thicket species to rapidly compete for canopy cover post-fire via the prolific production of resprouts from basal buds below- and above-ground. The trade-off is that plant height is constrained, as proportionately more resources are allocated to below-ground biomass.

Resilience of a tropical montane pine forest to fire and severe droughts

Abstract Higher temperatures, declining precipitation, changing cloud cover and increased wildfires threaten tropical montane pine forests by overriding the environmental heterogeneity that typically buffers these systems from catastrophic fires. Severe fires threaten to overwhelm forest resilience and tip this biome into alternate vegetation states. This study focused on long‐term dynamics of montane Pinus occidentalis forests in the Cordillera Central, Dominican Republic after a ~1000 km2 fire in 2005, the largest since 1965. We used long‐term records to investigate climate before and after the fire, and 19‐year dataset of pre‐ and post‐fire vegetation change from a network of 55 permanent plots (20 small 0.05 ha plots and 35 large 0.1 ha plots) established in 1999 to model overstorey and understorey vegetation dynamics. The 2005 fire was synchronized with the most extreme drought in the region in over 60 years. The fire burned from <1600 to >3000 m a.s.l. in elevation across windward and leeward slopes, creating a mosaic of low‐, moderate‐ and high‐severity patches. Lower elevations, leeward slopes and stands with a higher proportion of smaller pine trees all burned at higher severities. Growth rates of trees that survived the fire remained lower than pre‐fire rates 13 years after the fire. The highest post‐fire mortality rates were soon after the fire and in the census immediately following subsequent post‐fire droughts. Post‐fire pine seedling abundance was significantly greater in stands with higher basal area of live canopy trees and significantly reduced by increased shrub abundance in the understorey. Understorey composition recovered rapidly to pre‐fire states in sites affected by low‐ and moderate‐severity fires, but sites affected by high‐severity fires remained dissimilar to pre‐fire composition 13 years after the fire. Even though high‐severity patches had persistently low pine regeneration, 100% of small plots and 96% of large plots had at least one pine sapling or canopy tree recruit by 2018. Shrub taxa survived the fire in higher numbers and recovered to pre‐fire densities much faster than the pine, especially in high‐severity burns. Synthesis. Climate change has increased the likelihood of wildfires in tropical montane pine forests, with long‐lasting effects on vegetation dynamics. However, this biome may prove resilient to increasingly severe fires in the near future, given the ongoing recovery of Pinus occidentalis forests in Hispaniola despite repeated severe droughts. Nevertheless, highly drought‐ and fire‐resistant taxa (e.g. shrubs) may form alternate stable states in drier portions of tropical montane landscapes in the future as droughts and high‐severity fires become more common.

Antioxidant, Antimicrobial and Physicochemical Properties of Beef Sausages Enriched with an Aqueous Extract of Senduduk (Melastoma malabathricum L.) Leaf

The use of natural products in sausages has become a new trend for health reasons. A natural product that could be incorporated into sausages is an extract of the senduduk (Melastoma malabathricum L.) leaf. Senduduk is an abundant shrub herb in Indonesia. This kind of plant is mostly used as a traditional medical remedy and as an ingredient in some culinary recipes. This study was carried out to investigate the effect of an aqueous extract of senduduk leaf (SLE) on the antioxidant, antimicrobial and physicochemical properties of beef sausage. Four treatments were used: ingredients consisting of beef, vegetable oil, skim milk, tapioca, salt, phosphate, ice cubic, garlic, pepper, dan nutmeg as a Control; the Control ingredients plus 0.01% of butylated hydroxytoluene (BHT); the Control ingredients plus 0.83% of SLE (SLE-1), and the Control ingredients plus 1.1% of SLE (SLE-2). All ingredients of each formula were homogenously blended and the sausage mix was cooked. The addition of BHT and SLE affected the proximate composition, with the moisture content decreasing as the duration of chilled storage increased. The addition of SLE lowered the pH and aw value and both tended to increase during chilled storage. SLE also enhanced the WHC of the sausages which increased in value during chilled storage. The addition of BHT and SLE could increase the antioxidant activity of the sausages as indicated by scavenging DPPH free radicals. SLE in sausages could inhibit microbial growth during chilled storage. It can be summarized that the addition of an aqueous extract of senduduk could improve the physicochemical, antioxidant and antimicrobial properties of beef sausages.

Are vegetation influences on Arctic–boreal snow melt rates detectable across the Northern Hemisphere?

The timing and rate of northern high latitude spring snowmelt plays a critical role in surface albedo, hydrology, and soil carbon cycling. Ongoing changes in the abundance and distribution of trees and shrubs in tundra and boreal ecosystems can alter snowmelt via canopy impacts on surface energy partitioning. It is unclear whether vegetation-related processes observed at the ecosystem scale influence snowmelt patterns at regional or continental scales. We examined the influence of vegetation cover on snowmelt across the boreal and Arctic region across a ten-year reference period (2000–2009) using a blended snow water equivalent (SWE) data product and gridded estimates of surface temperature, tree cover, and land cover characterized by the dominant plant functional type. Snow melt rates were highest in locations with a late onset of melt, higher temperatures during the melt period, and higher maximum SWE before the onset of melt. After controlling for temperature, melt onset, and the maximum SWE, we found snow melt rates were highest in evergreen needleleaf forest, mixed boreal forest, and herbaceous tundra compared to deciduous needleleaf forest and deciduous shrub tundra. Tree canopy cover had little effect on snowmelt rate within each land cover type. While accounting for the influence of vegetative land cover type is necessary for predictive understanding of snowmelt rate variability across the Arctic–Boreal region. The relationships differed from observations at the ecosystem and catchment scales in other studies. Thus highlighting the importance of spatial scale in identifying snow-vegetation relationships.

Transformation of Buxus sinica into high-quality biocomposites via an innovative and environmentally-friendly physical approach

There are abundant shrub species resources in the world, but their natural defects such as short growth cycle, loose material, easy cracking plus deformation, and low strength have seriously affected their scope of application. With the ever-decreasing of natural forest resources, the research on quality improvement and efficiency enhancement of small-diameter timber of artificial shrub represents a promising effort in global continual advancement. In this study, an innovative and environmentally-friendly approach was developed to produce high-quality biocomposites from Buxus sinica. Pretreatment of Buxus sinica in an alkaline sodium sulfite solution had degraded part of the amorphous structure from the cell walls. The fiber cell walls collapsed completely in further thermoforming, resulting in a closer alignment of the fiber filaments before the formation of high-strength physical and chemical bonding, expanded crystalline regions, and enhanced dimensional stability. The resulted biocomposites show higher ultimate tensile strength (5.31 times) and ultimate flexural strength (5.22 times) than that of Buxus sinica. In addition, the preparation method also endows the biocomposites with excellent hydrophobicity and high chemical stability towards concentrated strong acid and alkali. Overall, this study reveals a promising method to effectively transform the artificial shrub resources into high-quality biocomposites with versatile applications.

Does shrub encroachment reduce foraging grass abundance through plant-plant competition in Lesotho mountain rangelands?

Shrub encroachment is understood to be an important problem facing rangeland ecosystems globally. The phenomenon is still poorly understood both in regard to its impacts (e.g., on diversity, productivity, and soil properties) and its causes. We study the impacts and causes of dwarf shrub encroachment in the highlands of Lesotho. There, shrubs have been described as indicators of generalized land degradation and soil erosion. Surprisingly, our findings show that grass abundance is not reduced by shrub abundance, but that forb abundance does decrease with shrub abundance. We suggest that not enough research has been done to examine the role of forbs in livestock diets, nor in assessing its role in plant-plant competition in grass-shrub systems. Equating shrub presence with declines in available forage may be hasty, as according to our results, grasses were not decreased by shrub expansion in this context; however, forbs are critical components of livestock diets. We propose that the role of forbs in this system should be further studied, focusing on the role that high-nutrient or N-fixing forbs could play in returning nutrients to the soil and affecting livestock grazing patterns, both of which could reduce shrub abundances and favor the establishment of a richer forb community.

Short-term effects of hardened wood ash and nitrogen fertilisation on understory vegetation in a Norway spruce forest in south-east Norway

ABSTRACT In a fertiliser experiment in a Norway spruce forest in SE Norway, four treatments were applied in a block design with three replicates per treatment. Treatments included 3 t wood ash ha−1 (Ash), 150 kg nitrogen ha−1 (N), wood ash and nitrogen combined (Ash + N), and unfertilised control (Ctrl). Treatment effects on understory plant species numbers, single abundances of species and (summarised) cover of main species groups were studied. Two years after treatment there were no significant changes for species numbers or abundances of woody species, dwarf shrubs or pteridophytes, nor for Sphagnum spp. in the bottom layer. The cover of graminoids decreased in Ctrl plots. Herb cover increased significantly in Ash + N and N plots due to the increase of Melampyrum sylvaticum. In Ash + N plots, mosses decreased significantly in species number, while their cover increased. Moss cover also decreased significantly in N plots. The species number and cover of hepatics decreased significantly in Ash and Ash + N plots. Hepatics cover also decreased in Ctrl plots. Both the lichen number and cover decreased in Ash + N plots. Single species abundances decreased for many bryophytes in fertilised plots. To conclude, fertilisation had modest effects on vascular plants, while bryophytes were more strongly affected, especially by Ash + N.

Ericoid shrubs shape fungal communities and suppress organic matter decomposition in boreal forests.

Mycorrhizal fungi associated with boreal trees and ericaceous shrubs are central actors in organic matter (OM) accumulation through their belowground carbon allocation, their potential capacity to mine organic matter for nitrogen (N) and their ability to suppress saprotrophs. Yet, interactions between co-occurring ectomycorrhizal fungi (EMF), ericoid mycorrhizal fungi (ERI), and saprotrophs are poorly understood. We used a long-term (19 yr) plant functional group manipulation experiment with removals of tree roots, ericaceous shrubs and mosses and analysed the responses of different fungal guilds (assessed by metabarcoding) and their interactions in relation to OM quality (assessed by mid-infrared spectroscopy and nuclear magnetic resonance) and decomposition (litter mesh-bags) across a 5000-yr post-fire boreal forest chronosequence. We found that the removal of ericaceous shrubs and associated ERI changed the composition of EMF communities, with larger effects occurring at earlier stages of the chronosequence. Removal of shrubs was associated with enhanced N availability, litter decomposition and enrichment of the recalcitrant OM fraction. We conclude that increasing abundance of slow-growing ericaceous shrubs and the associated fungi contributes to increasing nutrient limitation, impaired decomposition and progressive OM accumulation in boreal forests, particularly towards later successional stages. These results are indicative of the contrasting roles of EMF and ERI in regulating belowground OM storage.

IMPACT OF CLIMATE WARMING ON FLORISTIC DIVERSITY OF THE EAST EUROPEAN TUNDRA

IMPACT OF CLIMATE WARMING ON FLORISTIC DIVERSITY OF THE EAST EUROPEAN TUNDRA

Understory Plant Abundance Is More Important than Species Richness in Explaining Soil Nutrient Variation Following Afforestation on the Eastern Loess Plateau, China

Afforestation plays an important role in controlling soil erosion and nutrient loss on the Loess Plateau in China. However, previous studies on soil nutrient changes have mainly focused on the effects of tree species, whereas little is known about how changes in shrubs and herbs caused by afforestation drive soil nutrient changes. In this study, we examined the variation characteristics of understory vegetation and soil nutrients for different vegetation types. The results showed that compared to abandoned farmland, plantations significantly increased soil organic carbon and total nitrogen but had no significant effect on total phosphorus. Robinia pseudoacacia L. forests were more effective than Pinus tabuliformis Carr. forests in increasing soil nutrient content. In addition, herbaceous vegetation in the R. pseudoacacia forest better explained the soil nutrient variation, and herb abundance was the best explanatory variable; however, shrub vegetation contributed more to soil nutrient variation in the P. tabuliformis forest, and shrub abundance contributed the most. Accordingly, we determined that understory plant abundance, rather than species richness, may be the most important factor driving soil nutrient changes. Specifically, herb abundance in the R. pseudoacacia forest may drive soil nutrient changes mainly by regulating herb biomass and litter biomass. By contrast, shrub abundance in the P. tabuliformis forest indirectly affected soil organic carbon mainly by altering shrub biomass. Furthermore, although the phylogenetic relationships had less effect on soil nutrients than species composition, they also made important contributions. Therefore, the phylogenetic relationships should also be considered in addition to species composition when assessing the impact of vegetation on soil properties in the future.

Late Holocene human-environment interactions on the central California coast, USA, inferred from Morro Bay salt marsh sediments

Coastal salt marshes and estuaries provide valuable ecosystem services, yet are susceptible to alteration from human activities. Records of past environmental change in these ecosystems can elucidate relationships between human activities, such as land-use practices, and physical and ecological processes, such as sediment accretion and vegetation changes. To reconstruct the environmental history of one such site, we present inferences based on analysis of sediment cores (including magnetic susceptibility, loss-on-ignition, and pollen) from the Morro Bay salt marsh, located in California’s central coast in the USA. Chronologic control for the sediments was established using radiocarbon dates, a spike in lead (Pb) sourced from gasoline combustion exhaust, and the first identified occurrences of the non-native taxa Erodium cf. cicutarium (filaree) and Eucalyptus. We demonstrate that the Morro Bay watershed was significantly altered following Spanish settlement in the region. Environmental changes associated with livestock grazing and agriculture become evident in the data starting after 1772 CE, when the Mission San Luis Obispo de Tolosa was established nearby. The most prominent changes observed are an increase in the accumulation rate of terrigenous sediment, organic matter, and carbonates, as well as a reduction in arboreal taxa concomitant with increased abundances of shrubs, herbs, and grasses. The expansion of Salicornia (pickleweed) in the 19th century suggests the salt marsh expanded at this time due to increased sediment accumulation and a resulting increase in local elevation. The timing and character of changes recorded in the Morro Bay salt marsh sediments are similar to those documented across California in estuaries, marshes, lakes, and meadows, demonstrating the magnitude of the impacts of European settlement and associated land-use practices in this region.

Logging legacies in a plant biodiversity hotspot: Altered distribution and abundance patterns of the shrub layer in the southern Appalachians

Altered disturbance regimes in forest ecosystems can lead to the formation of dense, persistent understory vegetation composed of a small number of dominant species. This understory layer often limits tree seedling recruitment, decreases biodiversity, and can alter forest ecosystem structure and functioning. In the southern Appalachians – one of the most biodiverse regions in North America – pervasive logging in the 19th and early 20th centuries may have contributed to the formation of a dense understory shrub layer that suppresses plant diversity and tree recruitment, but the evidence for this idea has been mixed. To help clarify this issue, we tested whether (a) the two dominant understory shrub taxa (Kalmia latifolia and evergreen Rhododendron species) were more common or more abundant in areas with a history of intense logging than in areas undisturbed by logging, and (b) the relationships between the understory shrub layer and environmental gradients that drive regional biodiversity and plant distributions in the Southern Appalachians (e.g., climate, soils) differ in logged versus undisturbed areas. We used publicly available, extensive, and spatially explicit data on vegetation, climate, topography, soils, solar radiation, and logging history in Great Smoky Mountains National Park to build beta and binomial regression models of shrub frequency and cover as a function of logging history and environmental variables. Contrary to our expectation and speculations in the literature, we found that the dominant shrub taxa were more common (frequent) in areas with no logging history. However, we also found that logging history effects on shrub abundance (cover) varied along environmental gradients. For example, in topographically shaded landscape positions evergreen Rhododendron thickets exhibited greater cover in logged areas than in areas with no logging history. On the other hand, Rhododendron thickets exhibited lower cover in logged areas than in areas with no logging history at low elevations. Thus, conservation planning and forest management in topographically complex regions need to consider both landscape context (e.g., elevation, landscape position) and past logging as important interacting drivers that either facilitate or suppress local formation of dense shrub understories that can ultimately impact tree regeneration patterns, biodiversity, and ecosystem functioning.

Effects of Non-Native Shrubs on Caterpillars and Shrubland-Dependent Passerines within Three Transmission Line Rights-of-Way in Southeastern New Hampshire

Caterpillars (Lepidoptera, Hymenoptera: Symphyta) are a critical food that breeding passerines use for raising young and serve as an important source of carotenoids that support nestling growth and feather pigmentation. When non-native, invasive plants grow abundant enough to reduce native plant diversity they can cause a reduction in caterpillar abundance. The goal of this study was to determine whether a reduction in caterpillars caused by non-native, invasive shrubs affects nestling health and/or the reproductive success of a shrubland-dependent passerine, Geothlypis trichas trichas (Common Yellowthroat). I first quantified caterpillar abundance on the dominant native and nonnative shrubs comprising Common Yellowthroat territories in shrubby transmission-line rights-of-way and estimated total caterpillar abundance in each territory based on the shrub species composition. I then determined if differences in shrub species composition and caterpillar abundance affected: (1) adult Common Yellowthroat reproductive success, (2) nestling Common Yellowthroat diet composition, or (3) nestling Common Yellowthroat growth rate, plasma carotenoids, and carotenoid-based plumage color. Nonnative, invasive shrubs did not reduce caterpillar abundance until they comprised ≥55% of the shrub volume and significantly reduced the diversity and abundance of native shrubs in bird territories. Differences in caterpillar abundance among sites did not result in differences in Common Yellowthroat productivity, but where non-native shrubs comprised ≥55% of the shrub volume, adults increased their frequency of feeding visits to nestlings and fed nestlings the greatest proportion of non-caterpillar prey. Daily surveys of shrubland bird presence/absence at study sites indicated that most shrubland-dependent bird species were absent where non-native shrubs comprised ≥55% of the shrub cover; such conditions likely equated to habitat loss for bird species less able than Common Yellowthroats to adapt to low shrub diversity and low caterpillar abundance.

Cumulative impacts of a gravel road and climate change in an ice-wedge-polygon landscape, Prudhoe Bay, Alaska

Environmental impact assessments for new Arctic infrastructure do not adequately consider the likely long-term cumulative effects of climate change and infrastructure to landforms and vegetation in areas with ice-rich permafrost, due in part to lack of long-term environmental studies that monitor changes after the infrastructure is built. This case study examines long-term (1949–2020) climate- and road-related changes in a network of ice-wedge polygons, Prudhoe Bay Oilfield, Alaska. We studied four trajectories of change along a heavily traveled road and a relatively remote site. During 20 years prior to the oilfield development, the climate and landscapes changed very little. During 50 years after development, climate-related changes included increased numbers of thermokarst ponds, changes to ice-wedge-polygon morphology, snow distribution, thaw depths, dominant vegetation types, and shrub abundance. Road dust strongly affected plant-community structure and composition, particularly small forbs, mosses, and lichens. Flooding increased permafrost degradation, polygon center-trough elevation contrasts, and vegetation productivity. It was not possible to isolate infrastructure impacts from climate impacts, but the combined datasets provide unique insights into the rate and extent of ecological disturbances associated with infrastructure-affected landscapes under decades of climate warming. We conclude with recommendations for future cumulative impact assessments in areas with ice-rich permafrost.

Functional Leaf Traits, Foliar Water Uptake and Abundance of Shrubs in Ferruginous Campo Rupestre

Functional Leaf Traits, Foliar Water Uptake and Abundance of Shrubs in Ferruginous Campo Rupestre

Trees growing in Eastern North America experience higher autumn solar irradiation than their European relatives, but is nitrogen limitation another factor explaining anthocyanin-red autumn leaves?: A comment on Peña-Novas and Marchetti 2021 (https://doi.org/10.1111/jeb.13903).

Trees growing at a particular latitude in Eastern North America (ENA) receive more autumn solar irradiation than do trees growing at the same latitude in Europe, a difference that could partly explain the higher percentage of anthocyanin-producing deciduous species in ENA compared with European floras. A proposed link between autumn light intensity and the production of anthocyanins is their function in photoprotection, which enables plants with red leaves to resorb nutrients for a longer time than can yellow or brown leaves. The innately 4-week-shorter foliage period of ENA trees compared with European ones may also play a role, as may stronger nitrogen limitation in poorer soils in ENA. We here test for a correlation between nitrogen access and fall anthocyanin in 126species (55genera, 22 families) from different temperate forests, using a Hierarchical Bayesian model and accounting for phylogenetic structure in the data. None of 81species with nitrogen-fixing symbionts produce autumn anthocyanin, whereas 42% of non-nitrogen-fixers do. Thus, when ample nitrogen is available from symbionts, the benefits of anthocyanin-derived photoprotection apparently do not outweigh the costs of anthocyanin production. If nitrogen limitation indeed plays a role in the dominance of red-autumn-colouring trees in ENA floras - while European floras predominantly produce yellow autumn leaves - there might also be continental differences in the frequency or abundance of nitrogen-fixing trees and shrubs, a new hypothesis that deserves testing.

Poređenje florističkog sastava brdske bukove šume i veštačkih podignutih sastojina smrče području Kosmaja

The paper presents the comparative characteristics of the floristic composition in the association of the submontane beech forest (Helleboro odori-Fagetum moesiacae Soo & Borhidi 1960.) and artificially established spruce stands (Picea abies (L.) Karst.) in the area of Kosmaj. According to the obtained results, the cover in the shrub and ground flora layers of the artificially established spruce stands increased significantly compared to the autochthonous beech forests, but the floristic diversity decreased. Regarding the spectrum of floral elements, a higher percentage of mesophilic (51%) and frigophilic plants (11%) was observed in the artificially established spruce stands compared to the beech forests. Significant differences could also be observed regarding the spectrum of life forms since there were twice as many phanerophytes in the artificially established spruce stands (48%) than in the beech forests (23%). This resulted from the open canopy of artificially established spruce stands and the influx of a greater amount of light, which made conditions favourable for an abundant shrub layer to develop in this community. A comparative study of the mean plant indicator values showed that in the artificially established spruce stands, the mean values of the ecological factors for moisture, light and soil nitrogen supply increased, while the value of the ecological factors for temperature and soil acidity decreased compared to the beech forests.

Delayed and altered post-fire recovery pathways of Mediterranean shrubland under 20-year drought manipulation

Increasing water deficits and severe droughts are expected to alter the dynamics of vegetation post-disturbance recovery by decreasing new recruitment and limiting growth in semi-arid Mediterranean ecosystems in future. However, which vegetation metrics will be shifted and how they respond over time are not clear, and the experimental evidence is still limited. Here we assessed the impacts of a long-term (20 years) experimental drought (−30% rainfall) on the pathways of vegetation metrics related to species richness, community composition and abundance dynamics for an early-successional Mediterranean shrubland. The results indicate that the pathways of vegetation metrics were differently affected by experimental drought. The abundance of Globularia alypum follows pathway 1 (altered mature state). Simpson diversity and abundance of Erica multiflora follow pathway 2 (delayed succession) while species richness, community abundance and shrub abundance follow pathway 3 (alternative stable state). There were no significances for the resilience to extremely dry years (the ratio between the performance after and before severe events) between control and drought treatment for all vegetation metric. But, their resilience for the metrics (except Simpson diversity) to extremely dry years in 2016–17 were significantly lower than that of 2001 and of 2006–07, possibly caused by the severe water deficits in 2016–17 at mature successional stage. Principal component analysis (PCA) shows that the first two principal components explained 72.3 % of the variance in vegetation metrics. The first axis was mainly related to the changes in community abundance, shrub abundance and species richness while the second axis was related to Simpson diversity and abundance of G. alypum and E. multiflora. Principal component scores along PC1 between control and drought treatment were significantly decreased by long-term experimental drought, but the scores along PC2 were not affected. Further research should focus on successional pathways in more water-deficit conditions in Mediterranean ecosystems and the consequences of changes in vegetation recovery pathways on ecosystem functions such as biomass accumulation and soil properties.