Understorey Vegetation Research Articles

Distinct patterns of below- and aboveground growth phenology and litter carbon inputs along a boreal site type gradient

Forest ecosystem productivity is strongly linked to site nutrient availability, which is influenced by litter inputs and their decomposition rates. Fine roots and mycelia are key contributors in belowground soil carbon (C) accumulation, but studies have seldom reported how belowground litter C input is related to site types in boreal forests. In this study, three mature and one young Pinus sylvestris forests along a site type gradient in southern Finland were chosen for measurements of fine root biomass, fine root longevity, below- and aboveground growth phenology and annual litter input from tree and understorey vegetation. Site types were distinguished by understorey vegetation composition, which indicated the site fertility. Fine root biomass per tree stand basal area decreased significantly from nutrient-poor to nutrient-rich sites, the nutrient-poor sites with longer fine root longevity resulted in an equal belowground litter input with the nutrient-rich site. Above- and belowground annual litter inputs were 131–236 and 70–91 g m−2 year−1, respectively. Aboveground litter increased with site fertility, resulting into belowground litter having a decreasing trend from 37% to 23% of total litter inputs with increasing site fertility. Ectomycorrhizal mycelia and understory production contributed 8–13% and 18–41% of belowground production, respectively. Contribution of understorey vegetation to the belowground litter C input was lower than that of trees at xeric and sub-xeric sites but equaled to that of trees at the mesic site. Our study showed distinct dimensions of below- and aboveground litter inputs influenced by site types. Moreover, we emphasize that the belowground C inputs from ectomycorrhizal mycelia and the understorey in addition to those of trees should always be considered in C balances and C reporting in boreal conifers.

Management options for the conversion of allochthonous coniferous forest patches towards more natural species composition in the Vorpommersche Boddenlandschaft National Park, NE Germany

The conversion of coniferous tree plantations towards natural self-regenerating forests is one of the targets of forestry in Europe and particularly desirable in national parks. The aim of this study was to evaluate the effectiveness of different conversion approaches (conducted once) on natural forest development in man-made spruce plantations. We studied the effects of three distinct management options (partial-cutting [PC], clear-cutting with timber removal [CC] and clear-cutting with timber remaining [CCr]) six years after application on tree regeneration (sapling identity, abundance, height, browsing intensity) and understorey species composition in former spruce plantations within the Vorpommersche Boddenlandschaft National Park in Northeastern Germany. An unmanaged spruce [M] and near-natural beech [N] stands were considered as local references. The sites differed significantly in tree regeneration and understorey species composition. The abundance of native tree saplings was highest at site CCr, their height did not differ among sites, while browsing intensity was most pronounced at site CC. Understorey species composition of all management options was equally dissimilar to site N. However, site CCr contained more species that are typically abundant in local beech forests. Clear-cutting of spruce plantations with dead wood remaining on site favoured the natural regeneration of native trees and understorey vegetation compared to clear-cutting with timber removal, partial-cutting and no management. Herbivore browsing detrimentally affected tree regeneration independent of the treatment. Clear-cutting with timber removal promoted the dominance of competitive herbaceous species that may hamper long-term forest regeneration. We conclude that progression of site CCr appears to proceed fastest towards natural forest conditions. Further long-term data is required to derive clear trends regarding time and direction of forest regeneration. Keywords: forest conversion, spruce plantations, beech forest, natural tree regeneration, understorey species composition, deer browsing

Climate change impact on tree mortality differs with tree social status

Changes in temperature and rainfall linked to recent climate change increase the mortality rates of European temperate tree species. The economic importance of trees and the ecosystem services they provide differ according to their social status (dominant or suppressed trees) and their size. The extent to which climate change impacts these different categories in different ways remains little explored.Ecophysiological differences between tree size and status suggest different sensitivities to climate change. Dominant trees are exposed to more evapotranspiration than suppressed trees that benefit from buffered climatic conditions. Large trees are able to develop a network of fine roots that allow deeper water and nutrient uptake during water shortage periods, but that have higher water requirements and more physical constraints than small trees due to the fact that they must lift water to greater heights.We used 207,100 trees from the French forest inventory data (including 3,514 dead trees), representing eight common European tree species. For each species, we separated the tree population into three subsets of suppressed, small dominant and large dominant trees. For each subset, we modelled the mortality observed in a stand in the absence of disturbances (background mortality), with a focus on the differences in sensitivity to recent changes in temperature and rainfall.After having taken the main mortality drivers related to competition into account, as well as stand characteristics including logging intensity effect, we assessed the over-mortality linked to the recent changes in temperature and rainfall for each of the three subsets.When considering both changes in temperature and rainfall, the climate change related to over-mortality was greater for suppressed than for small or large dominant trees, for all the species. Over-mortality of suppressed trees was related to temperature increase, whereas a maximum vulnerability related to rainfall decrease was observed for large dominant trees.Over-mortality driven by climate change not only concerns large and dominant trees, but small and especially suppressed ones as well. These results suggest that in addition to wood production, forest renewal and ecosystem services associated with understorey vegetation are threatened by the recent changes in temperature and rainfall in European temperate forests.

Plot scale comparison of runoff generalization between forest and coffee combination cassava landcover in Kuta Jungak Village, Siempat Rube District, Pakpak Bharat Regency

It has become a public opinion that forests will always reduce the amount of surface runoff compared to other types of land cover. However, previous research reports that the runoff generalization process is still not fully explained. The activity of converting forests into agricultural land will also have an impact on surface runoff. This study aims to compare the magnitude of surface runoff on the plot scale between forest and coffee combination cassava fields. The surface runoff measurement plot with a size of 8 x 10 meters in the direction of the slope. The higher average surface runoff occurs in a forest plot that is equal to 0.286 ± 0.438 mm, while coffee and cassava plots produce an average surface flow of 0.022 ± 0.057 mm. Understorey and litter are influential in generalizing runoff in both plots. The understorey vegetation cover in the forest plot is lower than in the coffee combination cassava plot. This research confirms the results of previous studies that forests with less understorey vegetation conditions and less litter cover the soil surface can still produce high runoff results.

Recent changes in mountain birch forest structure and understory vegetation depend on the seasonal timing of reindeer grazing

Abstract Subarctic forest‐tundra ecotones dominated by mountain birch (Betula pubescens ssp. czerepanovii) are an important habitat for semi‐domestic reindeer Rangifer tarandus. The seasonal timing of reindeer grazing may direct vegetation trajectories in these systems, because in the summer ranges, mountain birches are subjected to browsing, while in the winter ranges, reindeer feed on understorey vegetation and arboreal lichens but leave the mountain birches intact. Based on earlier research, we predicted that (a) summer browsing dampens ongoing vegetation ‘shrubification’ in semi‐dry and dry mountain birch forests and (b) ‘shrubification’ is accompanied by a decline in lichens. We tested these predictions through re‐analysing forest structure and understorey vegetation after 12 years in areas where winter and summer ranges had been separated since the 1980s. We also tested how changes in lichen abundances align with changes in shrub abundances through correlation analyses. The number of tall mountain birch seedlings had increased twice as fast in winter than summer ranges, while big mountain birches had increased in summer ranges. The dominant evergreen dwarf shrub mountain crowberry (Empetrum nigrum ssp. hermaphroditum) had increased to a greater extent in winter ranges in a semidry habitat, and to a greater extent in summer ranges in a dry habitat. Deciduous dwarf shrub and graminoid biomass had increased similarly in summer and winter ranges. We found no evidence to support that increasing shrub abundances had contributed to a decline in lichens; instead, the lichen cover increased with increasing number of mountain birch seedlings. Synthesis and application. The vegetation trajectories of dry and semi‐dry subarctic mountain birch forests depend greatly on whether the area is used as a winter or a summer range for the reindeer. The recent changes in vegetation are likely to lead to improved summer forage availability for the reindeer, while the opposite may be true for the winter forage availability.

Detecting the effects of logging and wildfire on forest fuel structure using terrestrial laser scanning (TLS)

Recent logging and wildfire have been linked to increased fire severity in forests around the world. The mechanisms driving this association are uncertain but increased vertical fuel connectivity in recently disturbed forests is often suggested as a possible cause. These suggestions often assume that the forest canopy is lost after logging and wildfire. However, the resprouting Eucalypt forests of south-eastern Australia may differ as the canopy can rapidly recover after wildfire, and some of the canopy is retained after logging to reflect this ecology. By contrast, stand replacement is common after wildfire in non-resprouting Eucalypt forests, which are also typically subject to clear-fell logging. Vertical fuel connectivity is not routinely measured in Australian forests due to the difficulty in reliably measuring tall elements of the fire fuel array. Here, we quantify the connectivity of understorey and canopy fuel using terrestrial laser scanning, to determine if it is affected by logging and wildfire history. We compare these findings between forests dominated by resprouting and non-resprouting Eucalypt species. The connectivity between the understorey vegetation and the canopy decreased with time since logging in both forest types, but only increased with time since wildfire in non-resprouting forests. These changes were largely driven by the increasing canopy base height. These findings support suggestions that logging and wildfire increase fire severity by increasing the vertical connectivity of fire fuel. However, this is only applicable where the canopy is replaced after disturbance, which does not happen after fire in resprouting Eucalypt forests. This research provides new insights into species dependent disturbance and fuel dynamics that are applicable to fire prone forests around the world.

Monoterpenes from tropical forest and oil palm plantation floor in Malaysian Borneo/Sabah: emission and composition.

Regional estimates of VOC fluxes focus largely on emissions from the canopy and omit potential contributions from the forest floor including soil, litter and understorey vegetation. Here, we measured monoterpene emissions every 2 months over 2 years from logged tropical forest and oil palm plantation floor in Malaysian Borneo using static flux chambers. The main emitted monoterpenes were α-pinene, β-pinene and d-limonene. The amount of litter present was the strongest indicator for higher monoterpene fluxes. Mean α-pinene fluxes were around 2.5-3.5 μg C m-2 h-1 from the forest floor with occasional fluxes exceeding 100 μg C m-2 h-1. Fluxes from the oil palm plantation, where hardly any litter was present, were lower (on average 0.5-2.9 μg C m-2 h-1) and only higher when litter was present. All other measured monoterpenes were emitted at lower rates. No seasonal trends could be identified for all monoterpenes and mean fluxes from both forest and plantation floor were ~ 100 times smaller than canopy emission rates reported in the literature. Occasional spikes of higher emissions from the forest floor, however, warrant further investigation in terms of underlying processes and their contribution to regional scale atmospheric fluxes.

Keystone Perennial Grassland Species Control Soil Nitrogen Flows

Restoration of many grassland ecosystems is dependent on restoring native N cycling regimes, through methods such as nutrient stripping, C addition, and/or re-establishment of keystone species. We studied topsoil N pools and fluxes under five different understorey vegetation communities of different degradation states of grassy eucalypt woodlands across 11 sites in New South Wales, Australia, in order to identify whether high N flux but low standing N concentrations were responsible for the success of reference Themeda triandra communities. The presence of NO3− was the main differentiator between the annual exotic (AE) and reference states, which both demonstrated twofold-threefold increases N flux relative to the depleted states. Reference states were characterised by high proteolysis and dissolved organic N (DON) mineralisation rates, but also low δ15N and a high C:N ratio, which taken together indicate fresh organic matter inputs that turn over quickly. In quantifying fast rates of N cycling yet low NO3− pools in the reference states, our data highlight a productive ecosystem dominated by rapidly cycling DON rather than NO3− in its reference state. The higher NO3− concentrations coupled with fast N cycling in the degraded AE state indicate that although available N production is high in both systems, uptake is lower in the AE state, perpetuating a larger standing NO3− pool that may prevent re-establishment of native species. Steps that promote rapid DON cycling while inhibiting nitrification may lead to a soil biogeochemical status more suitable for the restoration of highly productive native grasslands.

Disaggregating the effects of nitrogen addition on gross primary production in a boreal Scots pine forest

Adding nitrogen to boreal forest ecosystems commonly increases gross primary production (GPP). The effect of nitrogen addition on ecosystem GPP is convoluted due to the impacts of and interactions among leaf scale photosynthetic productivity, canopy structure, site fertility, and environmental constraints. We used a unique controlled nitrogen fertilisation experiment combined with eddy covariance measurements and the calibration of a LUE-based (light use efficiency) photosynthetic production model in order to reveal differences in photosynthetic capacity due to nitrogen addition.A systematically designed soil moisture survey was conducted to characterise the within-site spatial heterogeneity and validate the difference of water stress between fertilised and control sites. The canopy photosynthetic light responses and environmental constraints were evaluated using an inverse modelling approach. We found that nitrogen fertilisation elevated ecosystem GPP by 24% according to model simulations. This was caused by increases in ecosystem light interception (through an increase in leaf area index (LAI)) and LUE by 7% and 17%, respectively. Nitrogen addition increased canopy potential LUE for both low and high photosynthetic photon flux density (PPFD) conditions. The calculations of leaf area and light interception indicated that the understorey vegetation contributed 9% of ecosystem GPP in the fertilised site and 7% in the control site when assuming a same LUE for trees and shrubs. The constraint arising from atmospheric water demand, rather than soil water stress, was the dominating control of the intra- and inter-annual GPP variations. The uncertainty propagated from soil moisture data is negligible for GPP predictions, but influential in the inference on the severity of the drought. This study demonstrates the combination of the controlled field experiment with the inverse modelling approach provides a powerful tool to quantitatively describe and disaggregate N addition effects on forest ecosystem GPP.

Social information affects prospecting, but not settlement, by Black‐and‐white Warblers (Mniotilta varia)

Birds use social as well as environmental cues to inform their habitat selection decisions. By manipulating social cues with song playbacks, biologists can influence where individuals search for breeding territories, which could be useful for conservation. Yet before we can predict how birds will respond to playback treatments, we must first understand how they integrate social cues with information about habitat quality at different stages in the habitat selection process. In this experiment, we examined whether vegetation structure and/or social cues affected Black‐and‐white Warbler Mniotilta varia abundance at three study areas that differed in habitat quality. We monitored Black‐and‐white Warbler habitat use across the breeding season, from the early prospecting period until after settlement decisions were made. During seasons without playback treatments, Black‐and‐white Warbler abundance was positively associated with levels of understorey vegetation cover. We then played Black‐and‐white Warbler songs daily for 5–6 weeks at selected survey sites at all study areas. We found that the model‐predicted abundance of Black‐and‐white Warblers was nearly three times greater at playback sites than at control sites during the prospecting period. During seasons with playbacks, understorey vegetation cover was no longer associated with Black‐and‐white Warbler abundance, indicating that individuals prioritized social information when searching for breeding territories. However, during the post‐settlement period, neither playbacks nor levels of understorey vegetation cover were associated with increased abundance, suggesting that playback treatments did not influence final breeding territory choice. We also found no difference in abundance between playback and control sites at a study area that represented low‐quality habitat, which suggests that playbacks should not induce maladaptive site selection.

Exotic avenue plantations turning foe: Invasive potential, distribution and impact of Broussonetia papyrifera in Chandigarh, India

Broussonetia papyrifera (L.) L'Hér. ex Vent. (common name: paper mulberry; family: Moraceae) is an invasive exotic tree from eastern Asia, which has been introduced to different parts of the world, including India, for both commercial and non-commercial purposes. It has been intentionally planted as an avenue tree in tropical and subtropical urban landscapes. Recently, it has spread beyond original plantings to become invasive in urban areas. The present study was conducted to determine the invasive potential, distribution, and impact of B. papyrifera on understorey vegetation and soil characteristics in a subtropical urban ecosystem in Chandigarh, India. It was observed that both sexual and vegetative reproduction contribute to the invasion success of B. papyrifera. The distribution of B. papyrifera in Chandigarh, India, was estimated according to the Importance Value Index, and the 14 study sites were classified into four invasion categories, i.e., uninvaded, sparsely invaded, moderately invaded, and highly invaded. The results revealed that B. papyrifera is rapidly invading the city, particularly at urban-forest interfaces. The impact of B. papyrifera on the alpha diversity of invaded areas was assessed by quantifying the diversity, richness, and evenness of the understorey species. The soil in highly invaded areas was more acidic with greater conductivity, phenolic content, and organic carbon content, implying that either B. papyrifera alters soil physico-chemical properties or prefers to inhabit soil with such characteristics. Invasion of B. papyrifera results in displacement of vegetation either via competitive exclusion or allelopathy. Thus, we advise that conservation managers and government bodies discourage its further cultivation and take necessary actions to control its spread.

Understorey changes after an extreme drought event are modulated by overstorey tree species mixtures in thermophilous deciduous forests

Understorey vegetation is a key component of plant biodiversity in forests. Events of extreme drought are a potential major driver of change of this layer. Although these are predicted to increase in frequency and duration due to climate change, their impacts on understorey communities are still unknown. In this paper, we re-surveyed a set of 36 plots in mature thermophilous deciduous forests eight months after the end of an extremely dry period in 2016–2017. The plots are part of a European network representing a gradient of overstorey richness from 1- to 5-tree species mixtures, with variable composition. We took advantage of this model system to test the hypothesis that species richness and identity of dominant trees in the overstorey may modulate the impact of drought on understorey cover, diversity and composition. In spring 2018, a ca. 50% reduction of understorey cover occurred in both mono-specific and mixed plots. Species evenness and Shannon α-diversity increased in the monospecific plots, due to a reduction of abundance of tree species at juvenile stage and the appearance of non-forest specialists that did not occur in the mixtures. Overstorey species identity effects on understorey diversity were negligible. Overall compositional changes were moderate, though larger in the mixed plots and in those with the less drought-adapted tree species in the overstorey. Ellenberg ecological profile of the community did not change significantly but light values tended to increase in the monospecific plots, contrary to the mixtures. Overall, our findings provide circumstantial support to a higher diversity stability in the understorey of mixed plots shortly after drought, despite compositional variations. More studies and monitoring programs are needed to assess understorey recovery capacity and resilience after such events in the long-term.

Overstorey composition shapes across‐trophic level community relationships in deciduous forest regardless of fragmentation context

Abstract Communities across trophic levels, and the functional roles they play, are vital for the sustained provision of ecosystem services. In forest systems, diversification of overstorey composition has been shown to be a key driver of biodiversity, but its influence on across‐trophic level relationships remains scarcely known. Species across trophic levels in varied overstorey compositions are also differentially susceptible to fragmentation context. We hypothesise that fragmentation will disrupt community relationships associated with particular overstorey compositions. We test this hypothesis using a tree diversity research platform across 53 deciduous woodland plots in central Belgium. We estimate species’ abundances within nine, generally taxonomic, community groups across trophic levels: understorey vegetation; leaf miners and gall formers; woodlice, millipedes; carabid beetles, harvestmen, spiders, birds, bats. We use multiple co‐inertia analyses to examine how taxonomic and trophic role community matrices covary across gradients of overstorey composition, via three different tree species diversification pathways, and fragmentation. For all trophic role groups, across all plots, there was at least one significant pairwise comparison. Apart from comparisons involving bats, there was at least one significant pairwise correlation between taxonomic groups too. These results indicate correlated community matrices across trophic levels. Overstorey composition related to community tightness, that is, the level of co‐ordinated change among taxonomic and/or trophic role groups as revealed by multiple co‐inertia analyses. Notably, diversifying woodlands of beech Fagus sylvatica or red oak Quercus rubra with pedunculate oak Quercus robur correlated with increased taxonomic community tightness. Diversifying pedunculate oak forest stands with other overstorey species related to unchanged community tightness. Evidence was lacking for fragmentation affecting community tightness, singly or by interacting with overstorey composition. Synthesis. Overall, changing tree species composition and fragmentation level affected across‐trophic level community relationships differently. Yet, we demonstrated a clear signal that diversifying monoculture stands with particular species correlated with greater community tightness, and co‐ordinated change among sets of community groups, across trophic levels and regardless of fragmentation context. We postulate that having tighter community relationships suggests that measures to improve biodiversity at one trophic level (i.e. trees) could affect other groups, and their associated roles, in a co‐ordinated manner.

Darker, cooler, wetter: forest understories influence surface fuel moisture

The moisture content of dead leaves, twigs and bark on the forest floor is a key determinant of fire behaviour. The microclimate inside forests, which drive the moisture content of these dead fuel components, is typically measured at screen height (150 cm). However, in some forest types, the surface fuel at ground level may be subject to additional sheltering from low shrubs, ferns and grasses, which could alter the microclimate near the surface (hereafter near-surface). In such cases, screen height measurements may not adequately represent the near-surface conditions that determine dead fuel moisture contents.We sought to quantify the effect of understorey vegetation on near-surface microclimate. We measured in-forest temperature, relative humidity and solar radiation in eucalypt forests over two fire seasons at both screen height and the near-surface using weather stations at 25 sites. The sites encompassed wet eucalypt forest (n=18) with a dense, mesic understorey and dry eucalypt forest (n=7) with a sparser, scleromorphic understorey.Wet forests with dense understorey vegetation had near-surface air temperatures that averaged 1.3°C lower, relative humidities that averaged 13.1% higher and total solar radiation that was 0.84 MJ less per day compared with those measured at screen height. These microclimate differences led to predicted fuel moistures which averaged 4.7% higher at the near-surface compared with screen height – this was statistically significant. In contrast, dry forests with less understorey vegetation, had near-surface air temperatures that averaged 4.2°C higher, and relative humidities that averaged 3.1% lower compared to screen height. These differences were not large enough to translate into statistically significant differences in predicted fine fuel moisture between heights.Overall, these findings show that understorey vegetation plays an important role in moderating near-surface microclimate in some forest types and this needs to be taken into consideration when predicting fuel moisture.

Tree encroachment impacts on seed predator selection and seedling establishment in degraded pine woodlands

AbstractQuestionsWhile much is known about the impact of tree encroachment on flammability in degraded pine woodlands, little is known about how encroachment is impacting other important ecosystem functions. We investigated how the availability of seed from four encroaching tree species and the presence of a midstorey and litter layer affect seed predator selection. Additionally, we investigated how seed predators, the midstorey, overstorey basal area, substrate availability, and vegetation cover affect germination for a foundational species (Pinus palustris) compared to an encroaching species (Pinus taeda).LocationSandhills Ecoregion, NC, USA (35°3′34.6932″ N, 79°22′22.0872″ W).MethodsWe measured seed depredation of Pinus palustris, Pinus taeda, Liquidambar styraciflua, Acer rubrum, and Quercus nigra in cafeteria trials. Each trial was held within a 2 × 2 factorial involving vertebrate seed predator exclusion and midstorey and litter layer removal across a gradient of overstorey basal area (6–25 m2). Additionally, we measured Pinus palustris and Pinus taeda germination within each treatment and correlated germinant density to substrate and understorey vegetation cover.ResultsGranivory generally varied inversely with seed size, with small‐seeded Liquidambar styraciflua experiencing the highest (27%) and large‐seeded Quercus nigra (7%) and Acer rubrum (6%) the lowest depredation pressure. Pinus palustris and Pinus taeda germinant density was significantly highest where vertebrate seed predators were excluded and the midstorey and litter layer were removed. For both pine species, this result corresponded with a significant positive association with mineral soil and negative associations with hardwood and pine litter where vertebrate predators were excluded. Basal area did not affect granivory or germination for any species.ConclusionsOur results demonstrate that granivores did not select Pinus palustris, and that large‐seeded species encroachment was less inhibited by seed predators. Pinus palustris and Pinus taeda are depredated at comparable rates and germinate best under similar understorey conditions.

Variation in feral cat density between two large adjacent islands in Australia’s monsoon tropics

Despite contributing to the ongoing collapse of native mammal populations across northern Australian savannas, we have limited understanding of the ecological constraints of feral cat population density in this system. Addressing such knowledge gaps is a crucial step towards mitigating the impacts of feral cats, and is particularly important for the large islands off northern Australia that remain as strongholds for numerous species vulnerable to cat predation. Here, we investigated cat density across Melville and Bathurst Island, two large islands in Australia’s monsoon tropics. We deployed large grids (~13 km2) of 70 camera-traps at four locations to investigate how feral cat density varies under different combinations of fire frequency, and feral herbivore presence. Using spatially-explicit capture-recapture models, we estimated feral cat density on Melville Island to be 0.15 cats km−2. We did not record any cat detections on Bathurst Island. Using simulations, we predicted that if cat density on Bathurst Island was equal to that on Melville Island, we would have expected to record 27.9 detections of 9.9 individual cats. Our results, coupled with other recent surveys, suggest that the density of cats is much lower on Bathurst Island than the adjacent Melville Island. The absence of feral herbivores on Bathurst Island may have contributed to this variation in cat density. Management that enhances understorey vegetation density, through feral herbivore control, as well as fire management, could help mitigate the impact of feral cats on northern Australian savanna biodiversity.

Karakteristik Area Tempat Bertelur Penyu Sisik (Eretmochelys imbricata) Pantai Faong Taman Nasional Manusela

This study aims to determine the Hawksbill Turtle nesting area (Eretmochelys imbricata) Faong Beach, Manusela National Park. The method used in this research is the survey method, namely the direct field data collection and the 2x2 meter square plot method to see the understorey vegetation. The results showed that the characteristics of the hawksbill nesting area (Eretmochelys imbricata) at Faong beach were chosen as one of the most suitable places for turtle nesting.

Long‐term fuel and understorey vegetation response to fuel treatments in oak and chaparral stands of northern California

AbstractAimsFuel reduction treatments are broadly implemented to reduce the risk of extreme wildfire, but research on the long‐term effectiveness and impacts of these treatments is lacking. In this study, we examined short‐ and long‐term (two and 15 years) changes in fuels and understorey vegetation after treatment in chaparral and oak‐dominated stands.LocationWhiskeytown National Recreation Area, California, USA.MethodsTreatments, including hand thinning, mastication only, burn only, and mastication + burning, were applied randomly to one or two units within each of 10 blocks across two vegetation types (chaparral and oak‐dominated). Vegetation data were initially measured two years after treatment and remeasured 15 years later with additional sampling of dead surface fuels and shrubs. Fuel and vegetation data were analyzed to examine the effect of treatment, time, and vegetation type.ResultsIn chaparral stands, shrub height and cover in the hand‐thinning, mastication, and mastication + burning treatments were still lower than in the control after 15 years. However, only the hand‐thinning treatment reduced fine woody fuels. Hand thinning and mastication + burning increased native species richness after two years, but this was also associated with an increase in exotic species richness and cover that persisted after 15 years. In oak‐dominated stands, treatments had varied and relatively fewer changes to fuels and vegetation. Shrub height was reduced in both the hand‐thinning and Burn‐only treatments, but only mastication reduced shrub cover. Species richness and vegetative cover were largely unaffected by treatment in oak‐dominated stands, except for lower native plant cover in mastication and mastication + burning treatments.ConclusionTreatments varied in their level of effectiveness and most involved trade‐offs between their impacts on fuels and vegetation responses that differed by vegetation type and time. Our findings provide insights for managers interested in balancing these trade‐offs when making fuel treatment decisions and emphasize the importance of examining longer‐term effectiveness of fuels treatments.

Impacts of alien tree species on the abundance and diversity of terricolous bryophytes

Bryophytes comprise an important element of temperate forest biodiversity and functioning. Although numerous studies reported impacts of alien tree species on understorey vegetation, few focused on impacts on bryophytes. Here we checked whether three invasive tree species in Europe (Prunus serotina Ehrh., Quercus rubra L. and Robinia pseudoacacia L.) influence terricolous bryophyte communities, alpha and beta diversity, and cover. We used a set of 186 study plots in western Poland with data on the cover of bryophytes species, as well as light availability, soil C:N ratio and pH. We found that light availability was the main driver of bryophyte species richness, cover and composition. Poor Pinus sylvestris L. forests invaded by P. serotina hosted more species and higher species richness than non-invaded P. sylvestris forests, while forests invaded by Q. rubra and R. pseudoacacia hosted fewer species than native forest types. Low differences among forest types studied resulted from small pools of species and the presence of generalist species. Fagus sylvatica L. forest, Q. rubra and R. pseudoacacia forests hosted the smallest number of species, while the most species rich stands were poor P. sylvestris forest invaded by P. serotina and non-invaded P. sylvestris forests. We concluded that light limitation by invasive species might be more important than dominant tree species identity in limiting terricolous bryophyte species richness and abundance. This requires further studies, accounting for varied abundances of invasive tree species. Therefore, the conservation of sites with high terricolous bryophyte biodiversity needs to be focused on canopy cover.

Grazing by over-abundant native herbivores jeopardizes conservation goals in semi-arid reserves

Relaxation of predation pressure following the removal of mammalian predators has led to the irruption of large herbivores and excessive levels of herbivory in many regions of the Earth. Conservation reserves in dryland regions aim to restore ecological processes and facilitate biodiversity conservation by functioning as refuges from grazing by livestock. However, grazing pressure in conservation reserves may be high and hamper conservation objectives because wild herbivore populations have irrupted in the surrounding landscape due to predator control as well as the absence of hunting and competition with livestock within reserves. Here, we assess the relative abundance of native herbivores (kangaroos) and introduced herbivores (rabbits) using driving transects and dung surveys, and use selective exclosures to assess wild herbivores’ impacts on vegetation and soils in four conservation reserves in semi-arid Australia. Kangaroos were the dominant herbivore in each reserve. Grazing by kangaroos and/or rabbits was linked to reduced complexity of understorey vegetation, grass cover, species richness of grasses, forbs and shrubs, the depletion of soil carbon and phosphorous, and increased soil bulk density. The marked impacts of grazing by wild herbivores, particularly kangaroos, on vegetation and soils that we report are symptomatic of overgrazing. Our study provides evidence that grazing by kangaroos may jeopardize conservation efforts across a large region of semi-arid Australia. We contend that managing the total grazing pressure exerted by wild herbivores is crucial to prevent overgrazing in dryland conservation reserves where herbivore populations are not regulated by predators.