Reduced Plant Diversity Research Articles

Effects of grazing exclusion on soil–vegetation relationships in a semiarid grassland on the Loess Plateau, China

AbstractGrazing exclusion (GE) is regarded as an effective practice to restore degraded grasslands. However, the patterns of vegetation recovery and related regulating factors in response to fencing have not been fully recognized. Hence, quantitative analysis of vegetation–soil relationships in response to GE was conducted in a semiarid grassland located on the Loess Plateau, North China. The results revealed that enclosure establishment significantly increased vegetation cover, height, and productivity but reduced plant diversity. Soil bulk density (0–20 cm) and pH (0–50 cm) clearly decreased after GE, whereas soil water (0–20 cm), organic matter (0–10 cm and 30–40 cm), and nutrient concentration (0–20 cm) increased significantly. Redundancy analysis of vegetation and environmental variables suggested that edaphic properties, including soil water, soil pH, total N, bulk density, and organic matter, was associated with plant community composition. Subsequent canonical correlation analysis indicated that soil bulk density, organic matter, and total N played an important role in shaping vegetation patterns in response to fencing whereas variations in soil pH and total N were the major contributors to variations in grazing rangeland. This work emphasized that fencing is a positive grassland management approach and suitable changes in grazing stock and soil variability are required to quantify vegetation recovery in response to grazing exclusion.

Evaluating Landscape Degradation Along Climatic Gradients During the 1930s Dust Bowl Drought From Panchromatic Historical Aerial Photographs, United States Great Plains

The U.S. Great Plains (USGP) are some of the most productive rangelands globally and a significant carbon sink for the atmosphere, but grassland response to precipitation is highly variable and poorly constrained over time and space. There is a rich historical aerial photographic record of the USGP which provides an unparalleled view of past landscapes and allows for evaluation of surficial response to drought beyond the satellite record, such as during the 1930s Dust Bowl Drought (DBD). This study classified the extent and loci of surficial denudation from seamless mosaics of radiometrically-corrected and georectified digitized aerial negatives acquired in the late 1930s from six counties distributed across USGP ecoregions. The dominant sources of degradation found for sites east of the 100th meridian are cultivated fields and fluvial deposits, associated with woody vegetation response to water availability in uncultivated areas. For sites to the west, denuded surfaces are predominantly eolian sandsheets and dunes, correlated with intensity of drought conditions and reduced plant diversity. Discrete spatial signatures of the drought are observed not only within the classically recognized southern Dust Bowl area, but also in the northern and central plains. Statistical analyses of site variability suggest landscape response to the DBD is most strongly influenced by the arid–humid divide and severity of precipitation and temperature anomalies. With a projected increase 21st century aridity, eolian processes cascading across western grasslands, like during the Dust Bowl, may significantly impact future dust particle emission and land and carbon storage management.

Impervious surface area is a key predictor for urban plant diversity in a city undergone rapid urbanization

Urban biodiversity has increasingly been recognized by the scientific community and environmental policymakers as a part of conservation efforts worldwide. However, most studies on urban biodiversity focus on cities in developed countries. An information gap exists for urban biodiversity of cities in developing countries. Here we focused on variability in plant diversity, a major component of biodiversity, in a Chinese city that has undergone rapid urbanization in recent time. The influence of urbanization was determined by comparing plant diversity and proportion of exotic/endemic plant species with the intensity of urbanization across the study area. We used percentage of total impervious surface area (PTIA) as an indicator of urbanization intensity, ranging from 5% to 95% across the study area. In the study area, a total of 321 plant species was recorded, totaling 83 trees, 113 shrubs and 125 herbs. Plant diversity, measured by number of plant taxa and other indices, was driven by PTIA; an increase in PTIA reduced plant diversity. In addition, the ratio of exotic to endemic plant species increased as PTIA increased. Among the exotic species, most of the tree and shrub species were purposely introduced. Above 40% PTIA, plant diversity decreased sharply and the proportion of exotic species rose. As a valuable predictor of urban biodiversity, PTIA can thus be used as a key criterion for urban planning to ameliorate urban biodiversity. Further, our findings extend current understanding of urban biodiversity for cities in developing countries.

Reversal of nitrogen-induced species diversity declines mediated by change in dominant grass and litter.

Atmospheric nitrogen (N) deposition reduces plant diversity. However, it often remains unclear how dominant species and litter accumulation feedbacks mediate N-induced plant diversity declines. We tested mechanisms of N-induced diversity change through dominant grasses and litter in a 7-year field experiment. Nitrogen addition reduced species richness, Shannon-Wiener diversity (H') and evenness from the second to the fourth year, however, surprisingly, increased them in the sixth and seventh year. The reversal in the response of diversity to N addition was explained by changes in grass dominance and standing litter accumulation. The diversity recovery during later years in fertilized plots was attributed to a decrease in the dominant grass and an increase in standing litter: standing litter reduced bud numbers of the dominant grass by decreasing light availability. The decreased light availability by standing litter reduced completion from the dominant species, which resulted in diversity increase. The negative feedback between dominant grasses and standing litter led to transient N-induced diversity loss in the short-term, but recovery of plant diversity in the long-term. Grassland management that affects litter accumulation, such as firing, grazing and mowing, can therefore, have substantial effects on the long-term response of plant diversity to N deposition.

Palaeoecological perspectives on Holocene environmental change in Scotland

ABSTRACTPalaeoecology has been prominent in studies of environmental change during the Holocene epoch in Scotland. These studies have been dominated by palynology (pollen, spore and related bio-and litho-stratigraphic analyses) as a key approach to multi- and inter-disciplinary investigations of topics such as vegetation, climate and landscape change. This paper highlights some key dimensions of the pollen- and vegetation-based archive, with a focus upon woodland dynamics, blanket peat, human impacts, biodiversity and conservation. Following a brief discussion of chronological, climatic, faunal and landscape contexts, the migration, survival and nature of the woodland cover through time is assessed, emphasising its time-transgressiveness and altitudinal variation. While agriculture led to the demise of woodland in lowland areas of the south and east, the spread of blanket peat was especially a phenomenon of the north and west, including the Western and Northern Isles. Almost a quarter of Scotland is covered by blanket peat and the cause(s) of its spread continue(s) to evoke recourse to climatic, topographic, pedogenic, hydrological, biotic or anthropogenic influences, while we remain insufficiently knowledgeable about the timing of the formation processes. Humans have been implicated in vegetational change throughout the Holocene, with prehistoric woodland removal, woodland management, agricultural impacts arising from arable and pastoral activities, potential heathland development and afforestation. The viability of many current vegetation communities remains a concern, in that Scottish data show reductions in plant diversity over the last 400 years, which recent conservation efforts have yet to reverse. Palaeoecological evidence can be used to test whether conservation baselines and restoration targets are appropriate to longer-term ecosystem variability and can help identify when modern conditions have no past analogues.

Effects of experimental N addition on plant diversity in an old-growth temperate forest.

Temperate forest ecosystems have experienced mounting negative effects due to increasing levels of nitrogen (N) deposition. We examined the effects of experimental N addition on plant diversity in an old‐growth temperate forest to test the following hypothesis: Long‐term excessive N addition decreases plant diversity by affecting the growth of plants, which results from changes in the soil nutrient content and a decrease in the soil pH in temperate forests. Experimental N additions were administered at the following levels since 2008: control (0 kg N ha−1 year−1), low N (30 kg N ha−1 year−1), medium N (60 kg N ha−1 year−1), and high N (120 kg N ha−1 year−1). Additionally, plant diversity was studied from 2014 to 2016. The results showed that the experimental N additions had significant effects on plant diversity and soil properties in an old‐growth temperate forest. The high‐N treatment decreased the density, cover, and diversity of understory plants, and some herbs even appeared to undergo premature aging, whereas the species diversity of herbs and ferns in the low‐N treatment plots showed a slight increasing tendency. This may have been because the old‐growth temperate forest is an N‐limited ecosystem, so the moderate N input did not show a large influence on plant diversity. However, the long‐term high‐N treatment ultimately reduced plant diversity by changing the soil nutrient contents, decreasing the pH values, and damaging plant growth. Our results suggested that the long‐term excessive N addition negatively affected the forest ecosystem in an N‐limited temperature forest.

Fear of the dark: decline in plant diversity and invasion of alien species due to increased tree canopy density and eutrophication in lowland woodlands

The abandonment of traditional forest management and the conversion of lowland woodlands from coppices to high forests may lead to a reduction in plant diversity. We studied long-term changes in semi-natural lowland woodland vegetation in the Czech Republic (Central Europe) by resampling 29 vegetation plots (releves) first sampled in the 1950s. The results indicated a shift to shady plant communities (i.e. loss of heliophilous species and expansion of shade-tolerant species), caused by an increase in the tree and shrub layer canopy due to the expansion of deciduous tree species. At the same time, species richness (alpha diversity) had declined significantly, though we noted no signs of homogenisation in the vegetation cover. Species typical of nutrient-rich habitats and alien and/or invasive species had expanded. We confirmed the shift in vegetation composition, which was probably caused by changes in lowland woodland forest management (decline in coppicing), eutrophication (deposition of atmospheric nitrogen, agricultural runoff) and disturbance effects of game, especially wild boar (Sus scrofa).

Cattle foraging in Mediterranean oak woodlands – Effects of management practices on the woody vegetation

Vegetation structure and composition of woodlands in the Mediterranean Basin have experienced extensive land-use change during recent decades. Decline in traditional foraging by goats is leading to more closed and spatially homogeneous woody vegetation, reduced plant diversity, and increased fire risk because of accumulation of inflammable material. We studied the use of cattle foraging as an alternative to goat foraging in Mediterranean oak woodlands. Our main goal was to provide basic information on the responses of woody vegetation to cattle foraging intensity, and on the factors affecting spatial patterns of woodland utilization. We conducted the study in the Western Galilee, Israel, in oak woodland dominated by Palestine oak (Quercus calliprinos Webb.) interspersed with patches of shrubs and herbaceous vegetation. Effects of two animal population densities, moderate (0.33 cow⋅ha−1) and high (0.55 cow⋅ha−1), on the structure, composition, and regeneration potential of dense and of open woody formations were examined. Four consecutive annual seasons of cattle foraging resulted in relatively large amounts of woody vegetation removal, especially under high animal density, but had no negative effects on woody species richness or regeneration potential from saplings. The type of vegetation formation and initial state of the woody vegetation were important factors affecting the degree of change. Woody biomass removal by cattle, as shown in this study, can reduce fire hazards and increase vegetation heterogeneity and plant diversity. These findings support the use of cattle as an efficient alternative tool for multi-purpose, sustainable management of Mediterranean oak woodlands.

4. The Impacts of Deer Overabundance in Kingston Forest Ecosystems and Surrounding Areas

White-tailed deer are generalists who can adapt to a wide variety of habitats from temperate forests to the open prairies. As a keystone species, they play a critical role in maintaining the structure of an ecological community (Rawinski, 2008). Despite record harvests in recent years, deer populations are at all-time highs around the Kingston region. Foraging deer consume or destroy the seedlings of highly preferred species, reducing plant diversity and on occasion, creating near monocultures. The objective is to analyze the impacts of white-tailed deer overabundance on vegetation within an urban forest ecosystem around Kingston, Ontario. This involves evaluating past, present, and future mitigation efforts in order to remediate the areas affected by overgrazing to ensure long term environmental sustainability. Critical to our evaluation on white-tailed deer in Kingston forest communities, we will be examining the ecosystems trophic relationships in the area including herbivory and selection pressures. Why have deer become so numerous? How are they affecting forest ecosystems? And why should landowners, forest managers, and the general public be concerned? After evaluating the current situation, we aim to propose a viable solution that will address the primary concerns highlighted above. In conclusion of our research we hope to restore the vegetative community and biodiversity of our local forests to their original state.

Weeds and ground-dwelling predators' response to two different weed management systems in glyphosate-tolerant cotton: A farm-scale study.

The use of glyphosate, as a post-emergence broad-spectrum herbicide in genetically modified glyphosate-tolerant (GT) cotton, supposes a big change in weed management programs with respect to a conventional regime. Thus, alterations in arable flora and arthropod fauna must be considered when evaluating their potential impacts. A 3-year farm-scale study was conducted in a 2-ha GT cotton crop, in southern Spain, to compare the effects of conventional and glyphosate herbicide regimes on weed abundance and diversity and their consequences for ground-dwelling predators. Surveys reveal that weed density was relatively low within all treatments with a few dominant species, with significantly higher weed densities and modifications of the floristic composition in glyphosate-treated plots that led to an increase in the abundance of Portulaca oleracea and to a reduction in plant diversity. The activity-density of the main predatory arthropod taxa (spiders, ground beetles, rove beetles and earwigs) varied among years, but no significant differences were obtained between conventional and glyphosate herbicide regimes. However, significant differences between treatments were obtained for ground beetles species richness and diversity, being higher under the glyphosate herbicide regime, and a positive correlation with weed density could be established for both parameters. The implications of these findings to weed control in GT cotton are discussed.

Rewilding defaunated Atlantic Forests with tortoises to restore lost seed dispersal functions

The extinction of frugivores has been considered one of the main drivers of the disruption of important ecological processes, such as seed dispersal. Many defaunated forests are too small to restore function by reintroducing large frugivores, such as tapirs or Ateline monkeys, and the long-term fate of large-seeded plants in these areas is uncertain. However, such small fragments still host many species and play relevant ecosystem services. Here, we explore the use of two tortoise species, the red-footed tortoise (Chelonoidis carbonarius) and the yellow-footed tortoise (Chelonoidis denticulatus), as ecological substitutes for locally extinct large seed dispersers in small forest patches in the Brazilian Atlantic Forest. We employed prior knowledge on the known occurrences of Chelonoidis species and used ecological niche modeling (ENM) to identify forest patches for tortoise rewilding. Based on habitat suitability, food availability and conservation co-benefits, we further refined our analysis and identified that the more suitable areas for tortoise reintroduction are forest patches of northern Atlantic Forest, areas with high defaunation intensity. Giant tortoises have been used to restore lost ecological services in island ecosystems. We argue that reintroducing relatively smaller tortoises is an easy-to-use/control conservation measure that could be employed to partially substitute the seed dispersal services of extinct large disperser species, mitigating the negative cascading effects of defaunation on reducing plant diversity.

Comparison of aquatic macrophyte community structure between natural wetlands and rice fields with different cultivation ages.

Recent studies indicate that rice fields contribute to the conservation of aquatic plants, however, repeated cultivation can reduce the species diversity harbored by rice fields. Repeated tillage, agrochemical application and environmental homogeneity can reduce plant diversity and select for species more tolerant to disturbance. Our hypotheses were: 1) macrophyte richness and biomass decrease with increased rice crop age; and 2) macrophyte species of rice fields are a subsample of natural wetlands and species loss will increase with crop age. We investigated three rice fields of each different ages (old, intermediate and new ones) and three natural intermittent wetlands for this study. Each area was sampled four times throughout the rice cultivation cycle (off-season, initial growth, final growth and post-harvest). Our results showed that the mean macrophyte richness and biomass were similar between rice fields of different ages and lower than that of natural wetlands. Although species composition in the different-aged rice fields was not markedly different, there was nestedness in the rice fields as age increased. In this study, we verified that macrophyte richness and biomass in rice fields was lower than natural wetlands and the species composition was different among wetland types (rice fields and natural wetlands), however our hypothesis that species richness and biomass will decrease with crop age was not confirmed. All rice crops had similar macrophyte assemblage structure (richness, biomass and species composition). However, the another hypothesis tested was confirmed, macrophyte assemblage of rice fields is a subset of natural wetlands and as, the age of a rice field increases, the species that occur in older rice field are subsets of species that occur in younger ones.

Links between plant and fungal diversity in habitat fragments of coastal shrubland.

Habitat fragmentation is widespread across ecosystems, detrimentally affecting biodiversity. Although most habitat fragmentation studies have been conducted on macroscopic organisms, microbial communities and fungal processes may also be threatened by fragmentation. This study investigated whether fragmentation, and the effects of fragmentation on plants, altered fungal diversity and function within a fragmented shrubland in southern California. Using fluorimetric techniques, we assayed enzymes from plant litter collected from fragments of varying sizes to investigate enzymatic responses to fragmentation. To isolate the effects of plant richness from those of fragment size on fungi, we deployed litter bags containing different levels of plant litter diversity into the largest fragment and incubated in the field for one year. Following field incubation, we determined litter mass loss and conducted molecular analyses of fungal communities. We found that leaf-litter enzyme activity declined in smaller habitat fragments with less diverse vegetation. Moreover, we detected greater litter mass loss in litter bags containing more diverse plant litter. Additionally, bags with greater plant litter diversity harbored greater numbers of fungal taxa. These findings suggest that both plant litter resources and fungal function may be affected by habitat fragmentation’s constraints on plants, possibly because plant species differ chemically, and may thus decompose at different rates. Diverse plant assemblages may produce a greater variety of litter resources and provide more ecological niche space, which may support greater numbers of fungal taxa. Thus, reduced plant diversity may constrain both fungal taxa richness and decomposition in fragmented coastal shrublands. Altogether, our findings provide evidence that even fungi may be affected by human-driven habitat fragmentation via direct effects of fragmentation on plants. Our findings underscore the importance of restoring diverse vegetation communities within larger coastal sage scrub fragments and suggest that this may be an effective way to improve the functional capacity of degraded sites.

Sequential Aminopyralid and Imazapyr Applications for Japanese Knotweed (Fallopia japonica) Management

Japanese knotweed is an invasive plant that occurs along waterways, highways, abandoned agricultural land, and other disturbed areas. It reduces plant diversity and can increase shoreline erosion. An experiment was conducted in Bible Hill and Antigonish, NS, Canada to evaluate early POST aminopyralid at 120 g ae ha−1 and POST imazapyr applications at 720 g ae ha−1 at maximum shoot height, flowering, senescence, maximum height+flowering, maximum height+senescence, flowering+senescence, and maximum height+flowering+senescence. Early POST aminopyralid only provided 10% to 15% control at 52 wk after treatment (WAT) whereas 83% to 100% control occurred following imazapyr applications at all application timings. Percent control at 2, 4, and 8 WAT tended to be higher where imazapyr followed aminopyralid. By 52 WAT, equivalent damage ratings and reductions in stem density occurred at both sites in all plots where imazapyr was applied. The use of aminopyralid or multiple imazapyr applications provided no additional benefit over a single imazapyr application. We conclude that early POST aminopyralid suppresses knotweed growth, which should facilitate late-season imazapyr applications, especially in large stands.

Shifts in swidden agriculture alter the diversity of young fallows: Is the regeneration of cloud forest at stake in southern Mexico?

Abstract For centuries, the milpa shifting cultivation, a maize-bean-squash polyculture in itinerant fields has been an essential component of the landscape (MS), in tropical montane cloud forest (TMCF) areas managed by Mesoamerican indigenous communities. At present, milpas are being replaced by a maize based semi-permanent system (SP) characterized by tillage, fire suppression, application of synthetic fertilizers, and short fallow periods. The effects of this substitution on post-cultivation fallows are unknown, but may have critical consequences for biodiversity and forest regeneration. In the TMCF area of Sierra Norte, Oaxaca, Mexico, the fallowed areas resulting from both cultivation systems are intermixed across the landscape. We compared the composition, richness, and diversity of vascular plant species in 2–3-year-old MS and SP fallows in this area, and explored the possible role of the adjoining forested areas on fallow plant species richness and density. Tree and herb species composition in the fallows separated into two clusters, one belonging to MS and the other to SP. Pioneer and late-successional TMCF tree species were distinctive of MS fallows, whereas native perennial grass and forb species were distinctive of SP fallows. The composition of other life forms could not be distinguished based on cultivation system. The species richness and diversity of trees, tree seedlings, shrubs, and vines were higher in MS fallows, whereas herb species richness and diversity was similar in both fallow types. In MS and SP fallows, the tree seedling species richness increased with the proportion of adjoining forested areas that were >20 years old, but not with forests younger than that age. Tree seedling density increased with the proportion of adjoining forested areas >20 years old in SP fallows but not in MS fallows. The density of trees and shrubs were significantly higher in MS fallows than in SP fallows, whereas herb density was significantly higher in SP fallows than in MS. We concluded that the replacement of MS by SP on the one hand, reduces plant diversity in early fallows and the fallow potential for TMCF regeneration; on the other hand, increases the dependence on adjoining >20-year-old forests as propagule sources.

Ecological stoichiometry of the honeybee: Pollen diversity and adequate species composition are needed to mitigate limitations imposed on the growth and development of bees by pollen quality.

The least understood aspects of the nutritional needs of bees are the elemental composition of pollen and the bees’ need for a stoichiometrically balanced diet containing the required proportions of nutrients. Reduced plant diversity has been proposed as an indirect factor responsible for the pollinator crisis. We suggest stoichiometric mismatch resulting from a nutritionally unbalanced diet as a potential direct factor. The concentrations and stoichiometric ratios of C, N, S, P, K, Na, Ca, Mg, Fe, Zn, Mn, and Cu were studied in the bodies of honeybees of various castes and sexes and in the nectar and pollen of various plant species. A literature review of the elemental composition of pollen was performed. We identified possible co-limitations of bee growth and development resulting mainly from the scarcity of Na, S, Cu, P and K, and possibly Zn and N, in pollen. Particular castes and sexes face specific limitations. Concentrations of potentially limiting elements in pollen revealed high taxonomic diversity. High floral diversity may be necessary to maintain populations of pollen eaters. Single-species crop plantations, even if these species are rich in nectar and pollen, might limit bee growth and development, not allowing for gathering nutrients in adequate proportions. However, particular plant species may play greater roles than others in balancing honeybee diets. Therefore, we suggest specific plant species that may (1) ensure optimal growth and production of individuals by producing pollen that is exceptionally well balanced stoichiometrically (e.g., clover) or (2) prevent growth and development of honeybees by producing pollen that is extremely unbalanced for bees (e.g., sunflower). Since pollen is generally poor in Na, this element must be supplemented using “dirty water”. Nectar cannot supplement the diet with limiting elements. Stoichiometric mismatch should be considered in intervention strategies aimed at improving the nutritional base for bees.

Catastrophic wind and salvage harvesting effects on woodland plants

Compound disturbances may result in novel forest successional and developmental patterns. This study investigated effects of post-wind disturbance salvage harvesting, a unique compound disturbance of which the ecological consequences are unresolved, in fire-restored longleaf pine woodlands of the Alabama Fall Line Hills, a characteristically biodiverse and rare ecosystem. Plot-level data were collected May–June 2016 in areas undisturbed, wind-disturbed, and compound-disturbed (salvage harvested within seven months of an April 2011 EF3 tornado). Disturbance-mediated differences in (1) physical site conditions, (2) woody plant composition and structure, and (3) ground flora (herbaceous and woody plants≤1m in height) were assessed. Multivariate analyses revealed distinct differences in ground flora across disturbance categories. Biophysical drivers most correlated with differences in species assemblages included volume of coarse woody debris, sapling density, percent canopy cover, and basal area. Unharvested wind-disturbed plots had the greatest diversity of saplings and ground flora, and had indicator species with unique habitat requirements (specialists). Indicator species of compound-disturbed plots were mostly generalists that also had a relatively high frequency and abundance in the other disturbance categories. Reduced plant diversity on compound-disturbed plots was attributed to salvage harvest-mediated reductions in habitat heterogeneity and resource availability. Thus, leaving patches unharvested within salvaged stands is recommended to promote stand-scale plant diversity.

Phylogeny is a powerful tool for predicting plant biomass responses to nitrogen enrichment.

Increasing rates of anthropogenic nitrogen (N) enrichment to soils often lead to the dominance of nitrophilic plant species and reduce plant diversity in natural ecosystems. Yet, we lack a framework to predict which species will be winners or losers in soil N enrichment scenarios, a framework that current literature suggests should integrate plant phylogeny, functional tradeoffs, and nutrient co-limitation. Using a controlled fertilization experiment, we quantified biomass responses to N enrichment for 23 forest tree species within the genus Eucalyptus that are native to Tasmania, Australia. Based on previous work with these species' responses to global change factors and theory on the evolution of plant resource-use strategies, we hypothesized that (1) growth responses to N enrichment are phylogenetically structured, (2)species with more resource-acquisitive functional traits have greater growth responses to N enrichment, and (3) phosphorus (P) limits growth responses to N enrichment differentially across species, wherein P enrichment increases growth responses to N enrichment more in some species than others. We built a hierarchical Bayesian model estimating effects of functional traits (specific leaf area, specific stem density, and specific root length) and P fertilization on species' biomass responses to N, which we then compared between lineages to determine whether phylogeny explains variation in responses to N. In concordance with literature on N limitation, a majority of species responded strongly and positively to N enrichment. Mean responses ranged three-fold, from 6.21 (E.pulchella) to 16.87 (E.delegatensis) percent increases in biomass per g N·m-2 ·yr-1 added. We identified a strong difference in responses to N between two phylogenetic lineages in the Eucalyptus subgenus Symphyomyrtus, suggesting that shared ancestry explains variation in N limitation. However, our model indicated that after controlling for phylogenetic non-independence, eucalypt responses to N were not associated with functional traits (although post-hoc analyses show a phylogenetic pattern in specific root length similar to that of responses to N), nor were responses differentially limited by P. Overall, our model results suggest that phylogeny is a powerful predictor of winners and losers in anthropogenic N enrichment scenarios in Tasmanian eucalypts, which may have implications for other species.

Plant diversity enhances moth diversity in an intensive forest management experiment.

Intensive forest management (IFM) promises to help satisfy increasing global demand for wood but may come at the cost of local reductions to forest biodiversity. IFM often reduces early seral plant diversity as a result of efforts to eliminate plant competition with crop trees. If diversity is a function of bottom-up drivers, theory predicts that specialists at lower trophic levels (e.g., insect herbivores) should be particularly sensitive to reductions in plant diversity. We conducted a stand-level experiment to test bottom-up controls on moth community structure, as mediated by degrees of forest management intensity. Using a dataset of 12,003 moths representing 316 moth species, moth richness decreased only slightly, if at all, as herbicide intensity increased (P=0.062); themoderatetreatment, which is most commonly applied in the northwestern USA, was estimated to have 4.72 (±2.14 SE, P=0.039) fewer species than the control. Structural equation modeling revealed strong support for an effect of herbicide on plant abundance, which influenced plant species richness and subsequently moth species richness. Moth species richness was associated with plant species richness and followed a power law function (z=0.42, P=0.006), which is surprisingly consistent with a recent large-scale experiment in agricultural systems, and provides support for bottom-up drivers of moth community structure. Moth abundance was not influenced by the direct effects of silvicultural herbicide treatments. Site-level effects and variation in pre-harvest vegetation communities resulted in residual broadleaf and herbaceous vegetation in even the most intensive treatment. Even at low densities, these residual deciduous and herbaceous plants supported higher than expected moth abundance and richness. We conclude that forest management practices that retain early seral vegetation diversity are the most likely to conserve moth communities.

Soil fertilisation contributes to mitigating forest fire hazard associated with Cistus monspeliensis L. (rock rose) shrublands

Cistus monspeliensis shrublands are strongly exposed to fire hazard and are rapidly expanding on oligotrophic soils as a consequence of the abandonment of silvopastoral activities. We hypothesised that nitrogen (N) and phosphorus (P) fertilisation could contribute to reduce Cistus cover and biomass and to direct the regeneration of the vegetation from seed bank after fire to grasslands able to prevent recurrent wildfires. Two experiments were performed to evaluate the effects of NP fertilisation on plant assemblage composition, diversity, grazing value, dry matter production and Cistus shrubland regeneration in (i) established shrublands, or (ii) recovering vegetation in burned areas. In the shrublands, NP fertilisation negatively affected Cistus cover, regeneration and biomass and significantly improved grazing value without significant effect on plant diversity. In burned areas, NP fertilisation significantly suppressed C. monspeliensis seedlings, increased the grazing value during the first 3 years since the last fire while it significantly reduced plant diversity. The increased grazing value following fertilisation in both burned and unburned areas is high enough to support silvopastoral activities. Soil fertilisation can be a key tool to support the conversion of shrublands in oligotrophic soils into productive grasslands, particularly when surrounding forests and urbanised areas, to reduce wildfire hazards through pastoral activities.