Reduced Plant Cover Research Articles

Non fire-adapted dry forest of Northwestern Madagascar: Escalating and devastating trends revealed by Landsat timeseries and GEDI lidar data.

Ankarafantsika National Park (ANP), the last significant remnant of Northwestern Madagascar's tropical dry forests, is facing rapid degradation due to increased incidences of fire. This poses severe threats to biodiversity, local livelihoods, and vital ecosystem services. Our study, conducted on 3,052-ha of ANP's pristine forests, employed advanced remote-sensing techniques to assess fire impacts during the past 37 years. Our aims were to understand historical fire patterns and evaluate forest recovery and susceptibility to repeated fires following initial burns. Using data from multiple Landsat satellite sensors, we constructed a time series of fire events since 1985, which revealed no fire activity before 2014. The Global Ecosystem Dynamics Investigation (GEDI) lidar sensor data were used to observe forest structure in both post-fire areas and undisturbed zones for comparison. We recorded six fire incidents from 2014-2021, during which the fire-affected area exponentially grew. A significant fire incident in October 2021 impacted 1,052 hectares, 59% of which had experienced at least one fire in two-to-four years prior, with 60% experiencing two preceding incidents: one in 2017 and another in 2019. The initial fire drastically reduced plant cover and tree height, with subsequent fires causing minor additional loss. Post-fire recovery was negligible within the initial four years, even in patches without recurrent fires. The likelihood for an initial burn to trigger subsequent fires within a few years was high, leading to larger, more severe fires. We conclude that ANP's dry forests exhibit high vulnerability and low resilience to anthropogenic fires. Prompt preventive measures are essential to halt further fire spread and conserve the park's unique and invaluable biodiversity.

Warmer Temperature and Spatiotemporal Dynamics during Primary Succession on Tropical Coastal Dunes.

Coastal dunes are sensitive indicators of climate change: it is expected that higher precipitation and warmer temperature will promote vegetation growth and sand stabilization. Alternatively, dunes may become active during severe droughts, which would reduce plant cover and increase sand mobility. Consequently, it is relevant to explore community shifts and self-organization processes to better understand how coastal dunes vegetation will respond to these projected changes. Primary succession allows the exploration of community assembly and reorganization processes. We focused on three environmental variables (bare sand, temperature, and precipitation) and five successional groups (facilitators, colonizers, sand binders, nucleators, and competitors). For 25 years (from 1991 to 2016), species turnover was monitored in 150 permanent plots (4 × 4 m) placed on an initially mobile dune system located on the coast of the Gulf of Mexico. The spatiotemporal dynamics observed during primary succession were consistent with the facilitation nucleation model. As late colonizers grew and expanded, psammophytes became locally extinct. The spatial patterns revealed that ecological succession did not occur evenly on the dunes. In addition, the increased mean yearly temperature during the last decades seemed to be associated with the accelerated increment in plant cover and species richness, which had not been registered before in Mexico.

Effects of Prickly Burnet (Sarcopoterium spinosum (L.) Spach.) Control and Sheep Grazing on Hay Yield and Quality on Gökçeada Island, Turkey.

(1) Background: The effects of prickly burnet (Sarcopoterium spinosum) control measures (pulling out, burning and cutting) and grazing on the botanical composition, grazeable dry matter (GDM) yield and nutritional values of rangeland were investigated on Imbros Island (Turkey) in 2010-2013. (2) Methods: The rangeland was grazed by Imbros sheep during the last year of the experiment. About 0.15 ha of rangeland was allocated to each sheep and five sheep were placed in each plot. Grazing was continuous throughout the year. (3) Results: Shrub levels decreased by 50-60% due to pulling out, burning and cutting in the first year and herbaceous species increased. Forbs increased more in the pulled and burnt plots and grasses increased more in the cut plots. In the third year, the shrub level increased to 60-65% and herbaceous species decreased. The decrease in herbaceous species was observed mostly in forbs. Plant cover was mostly (58%) composed of annual species. Development decreased plant cover ratios, but this decrease ceased in the burnt plot in the third year. Grazing also reduced plant cover. Crude protein (CP), NDF, ADF and digestible dry matter (DDM) content did not vary significantly over the experimental period. CP and DDM increased, NDF decreased and ADF did not change in the development plots. Overall, significant differences were not observed in GDM yield and nutritional values due to development efforts (pulling out, burning and cutting). (4) Conclusions: However, cutting is difficult over stony and rough terrain and pulling out creates erosion on sloping surfaces. Therefore, burning is recommended over the entire rangeland and burning or pulling out is recommended over smooth terrain for the temporary control of S. spinosum.

Late‐season drought exerts more negative effects on plant diversity and cover than early‐season drought through changing soil moisture in a semi‐arid grassland

AbstractQuestionsDrought timing during the growing season can profoundly influence plant diversity and cover, with subsequent impacts on ecosystem functions and services in terrestrial environments. However, the different responses of plant communities to drought in different periods of the growing season remain uncertain.LocationThe research was conducted in a semi‐arid grassland at the Duolun Restoration Ecology Research and Demonstration Station, in Inner Mongolia, China.MethodsThe responses of plant species richness and cover to early‐ and late‐season drought with a four‐year field experiment were examined in a semi‐arid grassland in northern China. Soil moisture at different depths was measured to explore the underlying mechanisms of the drought effects on plant richness and cover.ResultsOver the four years, late‐ rather than early‐season drought suppressed plant richness. Decreased species richness (−1.65 species) under late‐season drought was mainly due to suppressed perennial forb richness (−1.88 species). Late‐season drought also exerted greater negative effects on plant cover than early‐season drought. Effects of late‐season drought on plant cover depended on annual precipitation. Reduced plant cover (−7.5%) under early‐season drought stemmed from declines in shrubs and semi‐shrubs, particularly Artemisia frigida cover (−4.9%), which is sensitive to water deficits because of its shallow root depth (14.01 cm). Declined plant cover (−39.0%) under late‐season drought was mainly caused by suppressed perennial forb (−21.5%) and shrub and semi‐shrubs cover (−17.4%). The combined effects of early‐ and late‐season drought on plant cover were greater than the treatment alone, likely due to aggravating water deficits under growing‐season drought.ConclusionsOur results suggest late‐season drought is more critical for shifting plant communities. than early‐season drought. Our findings highlight the regulatory role of drought timing on plant community composition and development in arid and semi‐arid regions.

Middle Miocene Climate Transition as reflected by changes in ichnofacies and palaeosols from Patagonia, Argentina

The ichnofacies and palaeosols from the La Pava and Collón Curá formations were studied to shed light on the evolution of terrestrial ecosystems from Patagonia (Argentina) during the Middle Miocene Climate Transition. At Paso del Sapo, Cerrito Terciario and El Petiso localities (Chubut province), the La Pava Formation included Coprinisphaera ispp., Rosellichnus patagonicus, Rebuffoichnus casamiquelai, Feoichnus challa and burrows of spiders and earthworms, representing a case of the Rosellichnus ichnoassemblage of the Coprinisphaera Ichnofacies. Some of the components of this ichnoassemblage, scarce or absent in Cenozoic formations older than La Pava, are present in extant Patagonian habitats, pointing in the direction of extant invertebrate fauna. At El Petiso locality, the Collón Curá Formation included Celliforma ispp., Rosellichnus patagonicus, Fictovichnus ispp., Teisseirei barattinia and Teisseirei paladinco isp. nov., representing a case of the Celliforma Ichnofacies. The La Pava Formation comprises brownish, argillic, granular and strongly-developed palaeosols (Mollisols and Alfisols) formed in mildly stable to long-lasting landscapes, whereas the Collón Curá Formation comprises calcic, tuffaceous, paler and weakly-developed palaeosols (Andisols, Aridisols) formed in unsteady and ashy environments. The ichnofacies and palaeosols from the La Pava Formation indicate wooded grasslands developed in seasonal, subhumid and temperate-warm conditions, whereas those from the Collón Curá Formation indicate a habitat with reduced plant cover similar to semiarid and temperate-warm dry woodlands or bushlands. This shift towards more arid conditions in Patagonian landscapes would have been coeval with climatic changes corresponding to the Middle Miocene Climate Transition, a lapse of global temperature decrease associated with extensive drying.

Meta-analysis of salt marsh vegetation impacts and recovery: a synthesis following the Deepwater Horizon oil spill.

Marine oil spills continue to be a global issue, heightened by spill events such as the 2010 Deepwater Horizon spill in the Gulf of Mexico, the largest marine oil spill in US waters and among the largest worldwide, affecting over 1,000 km of sensitive wetland shorelines, primarily salt marshes supporting numerous ecosystem functions. To synthesize the effects of the oil spill on foundational vegetation species in the salt marsh ecosystem, Spartina alterniflora and Juncus roemerianus, we performed a meta‐analysis using data from 10 studies and 255 sampling sites over seven years post‐spill. We examined the hypotheses that the oil spill reduced plant cover, stem density, vegetation height, aboveground biomass, and belowground biomass, and tracked the degree of effects temporally to estimate recovery time frames. All plant metrics indicated impacts from oiling, with 20–100% maximum reductions depending on oiling level and marsh zone. Peak reductions of ~70–90% in total plant cover, total aboveground biomass, and belowground biomass were observed for heavily oiled sites at the marsh edge. Both Spartina and Juncus were impacted, with Juncus affected to a greater degree. Most plant metrics had recovery time frames of three years or longer, including multiple metrics with incomplete recovery over the duration of our data, at least seven years post‐spill. Belowground biomass was particularly concerning, because it declined over time in contrast with recovery trends in most aboveground metrics, serving as a strong indicator of ongoing impact, limited recovery, and impaired resilience. We conclude that the Deepwater Horizon spill had multiyear impacts on salt marsh vegetation, with full recovery likely to exceed 10 years, particularly in heavily oiled marshes, where erosion may preclude full recovery. Vegetation impacts and delayed recovery is likely to have exerted substantial influences on ecosystem processes and associated species, especially along heavily oiled shorelines. Our synthesis affords a greater understanding of ecosystem impacts and recovery following the Deepwater Horizon oil spill, and informs environmental impact analysis, contingency planning, emergency response, damage assessment, and restoration efforts related to oil spills.

Deepened snow cover mitigates soil carbon loss from intensive land‐use in a semi‐arid temperate grassland

Abstract Carbon (C) loss due to soil erosion is a major issue in semi‐arid grasslands. The extent of soil erosion is determined by soil properties and vegetation structure, especially during the non‐growing season. In many Inner Mongolian grasslands, intensive land‐use, such as overgrazing and mowing, has severely reduced plant cover and damaged soil structure, which has exacerbated soil C loss by erosion. At the same time, increasing winter snowfall due to climate change is stimulating plant growth and altering plant composition. However, we do not know how changes in winter snow cover interact with land‐use practices to regulate soil C loss due to erosion. Here, we conducted a 6‐year snow manipulation experiment under different land‐use practices (control; moderately mowed, MM; heavily mowed, HM) to measure net changes in soil depth, soil C, plant biomass and vegetation structure. After 6 years, soil C loss under ambient snow was three times greater in the MM and four times greater in the HM treatment compared with controls during non‐growing season. However, deepened winter snow alleviated erosion‐induced soil C loss by 14%, 47%, 16% in the controls, MM and HM treatments respectively. The severity of soil C loss declined with increasing above‐ground biomass (AGB), surface root biomass and vegetation structure. Vegetation structure and AGB explained more of the variation in soil C loss than surface root biomass, possibly because a complex canopy and plant cover increases overall surface roughness, thereby reducing soil C loss. Intensified land‐use reduced AGB, surface root biomass and vegetation structure, but deepened snow increased overall surface roughness by promoting AGB. Hence, our study demonstrates that deepened snow can alleviate soil C loss due to land‐use practices by promoting AGB. A free Plain Language Summary can be found within the Supporting Information of this article.

Allelopathic potential of Ficus retusa L. leaf litter on understory vegetation in urban gardens

Pruning Ficus trees in urban green spaces may lead to the accumulation and spread of their leaf litter on the understory vegetation. This study was conducted to evaluate the allelopathic effect of Ficus retusa L. leaf litter on the understory species in urban gardens. A field study showed that the plant cover and species richness of litter-affected plots were lower than those of litter-free areas. The litter-affected soils had substantially lower pH and higher electrical conductivity. In a greenhouse experiment, litter-affected soil significantly inhibited the emergence and growth of understory species selected for the purpose of this study: Melilotus indicus (L.) All., Trifolium resupinatum L. and Amaranthus viridis L. Osmotic potentials equivalent to those of the litter-affected soils did not affect emergence or growth of these species. A spectrophotometric analysis indicated that the litter-affected soils contained larger amounts of phenolics and flavonoids. An HPLC analysis revealed that the litter-affected soils contained higher concentrations of free phenolic and flavonoid allelochemicals. These results demonstrate that F. retusa leaf litter may reduce plant cover and species richness. The significant inhibition in both field and greenhouse experiments could be attributed to phenolic and flavonoid allelochemicals released from the tree litter, as the osmotic potential of the litter had no effect on the understory species. The allelopathic potential of F. retusa leaf litter plays at least a partial role in reducing urban vegetation.

Effects of dust deposition from diamond mining on subarctic plant communities and barren-ground caribou forage.

Dust produced from mining has the potential to reduce plant cover, alter plant communities, and increase metal concentrations in vegetation-changes that may affect the amount, type, and quality of forage for barren-ground caribou (Rangifer tarandus groenlandicus). We quantified dust deposition from Diavik Diamond Mine (Northwest Territories, Canada) and investigated the changes on forage quality, type, and quantity for caribou. From 2002 to 2016, dust deposition was measured, and vegetation cover and richness were assessed in permanent plots established adjacent to the mine and in reference areas 1-6km from the mine. Lichen was collected from areas up to 100km from the mine to determine metal concentrations. Dust deposition rapidly decreased within 4km of the mine. Plant communities adjacent to the mine (within 500m) had disproportionately increased cover of vascular plants and decreased bryophyte and lichen cover. Lichen sampled within 4km from the mine had greater metal concentrations than those sampled farther afield. Concentrations of Al in lichen collected within 40km of the mine exceeded safe exposure limits for consumption, assuming lichen comprised 100% of caribou diet. We conclude that dust deposition from mining is altering adjacent vegetation communities but that such changes to forage are unlikely to cause negative effects to caribou due to reduced lichen intake in summer and autumn, their migratory nature, and avoidance of mine-influenced areas. However, minimization and reclamation of mine-related disturbances will be important for maintaining sufficient quality forage and available habitat or space in caribou ranges.

Plastics and sedimentation foster the spread of a non-native macroalga in seagrass meadows

Plastics are found in marine environments worldwide, and their effects on macrophytes (seagrasses and macroalgae) colonizing sandy bottoms are still poorly known. Seagrass meadows are valuable but declining ecosystems due to local and global-change related stressors, including sediment disturbance and introduced macroalgae. Understanding whether plastics pose a further threat to seagrasses is critically important. In two simultaneous additive experiments performed in an aquaculture tank, we examined the individual and combined effects of macroplastics (non-biodegradable high-density polyethylene and biodegradable starch-based) and sedimentation (no and repeated sedimentation) on the performance (in terms of biomass and architectural variables) of a native Mediterranean seagrass (Cymodocea nodosa) and an introduced macroalga (Caulerpa cylindracea), and on the intensity of their interactions. Macroplastics were still present in sediments after 18 months. Cymodocea nodosa produced a greater biomass and longer horizontal rhizome internodes forming clones with more spaced shoots probably to escape from plastics. Plastics prevented C. nodosa to react to sedimentation by increasing vertical rhizome growth. Under C. cylindracea invasion, C. nodosa allocated more biomass to roots, particularly to fine roots. In the presence of C. nodosa, C. cylindracea performance was reduced. High-density polyethylene (HDPE) plastic and sedimentation shifted species interactions from competitive to neutral. These results suggest that both HDPE and biodegradable starch-based macroplastics, if deposited on marine bottoms, could make seagrasses vulnerable to sedimentation and reduce plant cover within meadows. HDPE plastic and sedimentation could contribute to the decline of seagrass habitats by facilitating the spread of non-native macroalgae within meadows. Overall, the study highlights the urgent need to implement more effective post-marketing management actions to prevent a further entering of plastics in natural environments in the future, as well as to establish to conservation measures specifically tailored to protect seagrass habitats from plastic pollution.

Tillage Versus No-Tillage. Soil Properties and Hydrology in an Organic Persimmon Farm in Eastern Iberian Peninsula

There is an urgent need to implement environmentally friendly agriculture management practices to achieve the Sustainable Goals for Development (SDGs) of the United Nations by 2030. Mediterranean agriculture is characterized by intense and millennia-old tillage management and as a consequence degraded soil. No-Tillage has been widely examined as a solution for soil degradation but No-Tillage relies more on the application of herbicides that reduce plant cover, which in turn enhances soil erosion. However, No-Tillage with weed cover should be researched to promote organic farming and sustainable agriculture. Therefore, we compare Tillage against No-Tillage using weed cover as an alternative strategy to reduce soil losses in persimmon plantations, both of them under organic farming management. To achieve these goals, two plots were established at “La Canyadeta” experimental station on 25-years old Persimmon plantations, which are managed with Tillage and No-Tillage for 3 years. A survey of the soil cover, soil properties, runoff generation and initial soil losses using rainfall simulation experiments at 55 mm h−1 in 0.25 m2 plot was carried out. Soils under Tillage are bare (96.7%) in comparison to the No-Tillage (16.17% bare soil), with similar organic matter (1.71 vs. 1.88%) and with lower bulk densities (1.23 vs. 1.37 g cm3). Tillage induces faster ponding (60 vs. 92 s), runoff (90 vs. 320 s) and runoff outlet (200 vs. 70 s). The runoff discharge was 5.57 times higher in the Tillage plots, 8.64 for sediment concentration and 48.4 for soil losses. We conclude that No-tillage shifted the fate of the tilled field after 3 years with the use of weeds as a soil cover conservation strategy. This immediate effect of No-Tillage under organic farming conditions is very promising to achieve the SDGs.

Restoration of abandoned subtropical highland grasslands in Brazil: mowing produces fast effects, but hay transfer does not

Subtropical Campos Sulinos grasslands, in South Brazil, are among the most biodiverse grasslands of the world. As climatic conditions lead to high productivity, disturbance are critical to maintain their diversity. Long-term exclusion, on the other hand, leads to plant species losses and changes in composition. No studies on the restoration of these grasslands after abandonment exist to date. We tested combinations of restoration techniques with the aim of increasing plant diversity in an abandoned and species-poor grassland in the South Brazilian highland region. In a bi-factorial experiment, we tested the effects of two different frequencies of mowing and of hay transfer. Mowing reduced plant cover, vegetation height, and abundance of erect grasses and shrubs, and increased species richness, diversity (Shannon diversity index) and prostrate forb and grass cover. No differences were found between mowing frequencies. Hay transfer was not effective at reintroducing species. The results of the present study provide further evidence that the reintroduction of plants is a major challenge in the restoration of subtropical and tropical grasslands. The study shows that mowing is a fast way to increase plant diversity in Campos Sulinos after long periods of abandonment.

Effects of grazing exclusion on vegetation and seed bank composition in a mesic mountain grassland in Argentina

ABSTRACTBackground: Grazing is a major factor that affects grassland composition and species richness. While the long-term effects of grazing are well documented, information about the short-term effects of grazing is necessary for adaptive conservation management.Aims: Our objective was to ascertain how this held over varying time periods after herbivore removal vs. exclosures of different ages for grassland and soil seed bank composition in the Argentine Pampas.Methods: The composition of the vegetation and the seed bank assessed in plots with 2 and 12 years of grazing exclusion and in nearby grazed areas. Multivariate analyses were used to evaluate treatment effects.Results: Grazing increased bare ground and reduced plant cover. Grazing reduced grass specific richness in the seed bank, while increased the richness and density of shrubs. The composition of the vegetation and the seed bank was not related. There was a trend whereby grazed areas were characterised by shrub species and non-palatable or annual grasses; the 2-year-old exclosures by forb species and the 12-year-old exclosures were dominated by perennial grasses.Conclusions: The removal of herbivores has changed vegetation and seed bank composition. The observed trend in reduction of species and life form diversity may be countered by controlled grazing for conservation purposes.

Short Research Report: high level of soil carbon addition causes possible manganese and aluminium phytotoxicity

SummaryA restoration trial of grassy woodland on former agricultural land applied carbon at a standard rate (840 g C/m2/year) and at a high rate (4,200 g C/m2/year), to test whether further benefits to native plants and suppression of exotics would emerge. Carbon addition at the high rate reduced plant cover further than the standard rate but led to severe loss of plant species; it also reduced soil pH. Soil Al, Fe and Mn levels increased across the gradient of C addition, which would be consistent with the reduction in soil pH for Al and Mn, and a decrease in soil redox potential for Mn and Fe. Nutrient analysis of leaf tissue confirmed that uptake of Fe and Mn increased over the range of C addition, with the concentration of Mn in the high carbon treatment exceeding the threshold for toxicity for a range of species. The soil and plant tissue data are consistent with the induction of increased soil acidity and of stronger reducing conditions in the soil by high level of carbon addition and localised soil flooding. Plant uptake of Mn to toxic levels occurred subsequently, leading to negative effects on plants; aluminium phytotoxicity may also have occurred.

The influence of climatic legacies on the distribution of dryland biocrust communities.

Predicting the distribution of biocrust species, mosses, lichens and liverworts associated with surface soils is difficult, but climatic legacies (changes in climate over the last 20k years) can improve our prediction of the distribution of biocrust species. To provide empirical support for this hypothesis, we used a combination of network analyses and structural equation modelling to identify the role of climatic legacies in predicting the distribution of ecological clusters formed by species of mosses, lichens and liverworts using data from 282 large sites distributed across 0.6 million km2 of eastern Australia. Two ecological clusters contained 87% of the 120 moss, lichen and liverwort species. Both clusters contained lichen, moss and liverwort species, but were dominated by different families. Sites where the air temperature increased the most over 20kyears (positive temperature legacies) were associated with reductions in the relative abundance of species from the lichen (Peltulaceae and Teloschistaceae) and moss (Bryaceae) families (Cluster A species), greater groundstorey plant cover and lower soil pH. Sites where precipitation has increased over the past 20kyears (positive precipitation legacy) were associated with increases in the relative abundance of lichen (Cladoniaceae, Lecideaceae and Thelotremataceae) and moss (Pottiaceae) families (Cluster B species) and lower levels of soil pH. Sites where temperatures have increased the most in the past 20kyears suppressed the negative effects of plant cover on Cluster B by reducing plant cover. Increased intensity of grazing suppressed the negative effect of soil pH and the positive effect of soil carbon, on the relative abundance of Cluster B taxa. Finally, increasing temperature and precipitation legacies reduced the negative effect of soil pH on Cluster B. Understanding of the importance of climatic legacies improves our ability to predict how biocrust assemblies might respond to ongoing global environmental change associated with increasing land use intensification, increasing temperature and reduced rainfall.

Immediate and long-term facilitative effects of cattle grazing on a polyphagous caterpillar

Mammalian herbivores induce changes in the composition, abundance, architecture and chemistry of vegetation which can affect insects in their habitat. Many studies addressed the long-term effects of mammalian grazing on insect herbivores, yet few examined the effects during grazing (or right after it takes place). We investigated the immediate and long-term effects of cattle grazing on the abundance and distribution of the herbivorous spring webworm caterpillar (Ocnogyna loewii), via excluding cattle (by fencing) within a grazed paddock. In addition, we estimated the caterpillar density in replicated grazed and non-grazed paddocks (maintained as so for dozens of years), in moderate and heavy grazing intensities. Since the caterpillars develop during the cold winter months, we predicted that cattle grazing would positively affect them by reducing plant height and increasing their exposure to direct warm sunlight. Therefore, we examined caterpillar preference for sun-exposed areas using shade-manipulation experiments. Overall, cattle grazing positively affected the caterpillars, increasing their numbers two-fold on average, regardless of grazing intensity. This effect was immediate, as the caterpillars rapidly responded to exclusion of cattle by moving away from non-grazed areas. Caterpillar growth rate was similar when feeding on grazed and non-grazed vegetation. Most caterpillars (over 80%) preferred sun over manipulated shaded microhabitats. Furthermore, we found that cattle usually do not ingest caterpillars while feeding. Cattle grazing likely benefited the caterpillars that develop under low temperatures by reducing plant cover, thus creating a warmer habitat. This study demonstrates how changes in vegetation structure caused by mammalian herbivores can rapidly and positively affect the abundance and distribution of herbivorous insects.

Long-term soil alteration in historical charcoal hearths affects Tuber melanosporum mycorrhizal development and environmental conditions for fruiting.

Abandoned charcoal hearths constitute a very particular habitat for spontaneous fruiting of Tuber melanosporum, leading some harvesters to hypothesise that the fungus could benefit from the alterations that these soils underwent. However, ecological mechanisms involved in this relation are not fully elucidated yet. As a first step to understand it, the influence of long-term soil alteration on the symbiotic stage of T. melanosporum and on selected soil properties considered key to fruiting was assessed by conducting a greenhouse bioassay and a field observational study. In the bioassay, percent root colonisation and relative abundance of T. melanosporum were significantly lower in hearth than in control soils. Hearth soils showed significantly lower resistance to penetration, larger temperature fluctuation, reduced plant cover and reduced herbaceous root abundance. The results do not support the hypothesis that soil from historical charcoal hearths currently enhances development of T. melanosporum mycorrhizas. However, whether this is due to increased infectivity of native ectomycorrhizal communities or to worse conditions for development of T. melanosporum mycorrhizas remains unresolved. Native ectomycorrhizal communities in hearths showed altered composition, although not a clear change in infectivity or richness. Direction of change in hearth soil properties is compared to alteration occurring in soils spontaneously producing T. melanosporum. The interest of these changes to improve T. melanosporum fruiting in plantations is discussed.

Termite effects on soils and plants are generally consistent along a gradient in livestock grazing

ABSTRACTLivestock grazing is a major driver of ecosystem functions in drylands and would be expected to influence soil biota such as termites. We examined changes in soil chemistry and plant community composition on mounds constructed by the subterranean termite Anacanthotermes ahngerianus along a gradient in grazing intensity in an arid steppe in north-eastern Iran. The grazing gradient was represented by increasing distance from an area used by resting livestock, and plant and soil attributes measured within three adjacent microsites (termite mounds, non-mound controls, intervening annular zone surrounding the mounds). Values of soil EC; pH; exchangeable Ca, Mg, and Na; and total nitrogen and organic carbon were greatest in mound soils and declined from mounds to control microsites. Mounds were completely devoid of plants. Annular zones had three-times less cover than the control sites, but there were no differences in diversity or evenness. Electrical conductivity values were ten-times greater on mounds than controls close to resting sites, but the difference diminished rapidly with distance from resting sites. For all other soil and plant variables, differences between microsites were consistent across the grazing gradient. Increased grazing intensity was associated with increasing soil pH, EC and sand content, and reduced plant cover. Overall our study shows that the effects of termites on soil chemistry and plant cover varied little across the grazing gradient. Our results suggest that termite mounds may sustain their role as sites of enhanced soil nutrients under even high levels of grazing.

Urbanisation-related land use change from forest and pasture into turf grass modifies soil nitrogen cycling and increases N<sub>2</sub>O emissions

Abstract. Urbanisation is becoming increasingly important in terms of climate change and ecosystem functionality worldwide. We are only beginning to understand how the processes of urbanisation influence ecosystem dynamics, making peri-urban environments more vulnerable to nutrient losses. Brisbane in South East Queensland has the most extensive urban sprawl of all Australian cities. This research estimated the environmental impact of land use change associated with urbanisation by examining soil nitrogen (N) turnover and subsequent nitrous oxide (N2O) emissions using a fully automated system that measured emissions on a sub-daily basis. There was no significant difference in soil N2O emissions between the native dry sclerophyll eucalypt forest and an extensively grazed pasture, wherefrom only low annual emissions were observed amounting to 0.1 and 0.2 kg N2O ha−1 yr−1, respectively. The establishment of a fertilised turf grass lawn increased soil N2O emissions 18-fold (1.8 kg N2O ha−1 yr−1), with highest emissions occurring in the first 2 months after establishment. Once established, the turf grass lawn presented relatively low N2O emissions for the rest of the year, even after fertilisation and rain events. Soil moisture was significantly higher, and mineralised N accumulated in the fallow plots, resulting in the highest N2O emissions (2.8 kg N2O ha−1 yr−1) and significant nitrate (NO3−) losses, with up to 63 kg N ha−1 lost from a single rain event due to reduced plant cover removal. The study concludes that urbanisation processes creating peri-urban ecosystems can greatly modify N cycling and increase the potential for losses in the form of N2O and NO3−.

Submerged macrophyte decline in shallow lakes: What have we learnt in the last forty years?

Over the last 40 years there has been substantial evidence that high biomasses of submerged aquatic plants and phytoplankton rarely occur together in shallow lakes, but it is clear that when present, plants have a competitive advantage over algae.Aquatic plants provide habitat structure, which influences the fish community such that zooplankton and other macroinvertebrates maintain a top-down control on algal growth, and this control is largely independent of the nutrient supply to the lake. Nonetheless it is clear that many, but not all, lakes lose their vegetation as nutrient loading increases. However, in eutrophic lakes, the subsequent dominance by phytoplankton is more likely to be a result of the loss of vegetation rather than the cause.At higher nutrient levels, grazing or mechanical damage can reduce plant cover allowing rapid development of algae. Changes to fish community structure or the influence of toxic chemicals can reduce invertebrate algal grazers, overcoming the positive feedback loops that stabilise the plant dominance.The longer-term stability of macrophyte dominance is also reduced if there are few surviving plant species. Such loss of species richness is associated with increased nitrogen loading. Submerged plants also depend on a spring clear-water phase to become established, and local weather conditions during winter and spring may determine the relative success of phytoplankton and plant growth, leading to a progressively longer period of algal dominance and fewer surviving plant species.The loss of submerged vegetation from lakes, although often perceived as a rapid change, is more likely to be the final conclusion of a process in which the competitive advantage of a diverse plant community is eroded by many pressures that are collectively interpreted as eutrophication.In attempts to manage our environment we hope to find simple, closed stable systems that will respond to measures designed to meet our perceptions of improved ecological quality. What we increasingly find are more complex open systems, which do not necessarily respond as expected. We look for simple and widely applicable explanations where none are likely to exist.