Undisturbed Forest Areas Research Articles

Detecting and excluding disturbed forest areas improves site index determination using bitemporal airborne laser scanner data

Abstract Bitemporal airborne laser scanning (ALS) data are increasingly being used in forest management inventories for the determination of site index (SI). SI determination using bitemporal ALS data requires undisturbed height growth of dominant trees. Therefore, areas with disturbed top height development are unsuitable for SI determination, and should be identified and omitted before modelling, predicting and estimating SI using bitemporal ALS data. The aim of this study was to explore methods for classifying the suitability of forest areas for SI determination based on bitemporal ALS data. The modelling approaches k-nearest neighbour, logistic regression and random forest were compared for classifying disturbed (at least one dominant tree has disappeared) and undisturbed plots. A forest inventory with plot re-measurements and corresponding bitemporal ALS data from the Petawawa Research Forest in Ontario, Canada, was used as a case study. Based on the field data, two definitions of a disturbed plot were developed: (1) at least one dominant tree had died, was harvested or had fallen during the observation period, or (2) at least one dominant tree was harvested or had fallen during the observation period. The first definition included standing dead trees, which we hypothesized would be more difficult to accurately classify from bitemporal ALS data. Models of disturbance definition 1 and 2 yielded Matthews correlation coefficients of 0.46–0.59 and 0.62–0.80, respectively. Fit statistics of SI prediction models fitted to undisturbed plots were significantly better (P < 0.05) than fit statistics of SI prediction models fitted to all plots. Our results show that bitemporal ALS data can be used to separate disturbed from undisturbed forest areas with moderate to high accuracy in complex temperate mixedwood forests and that excluding disturbed forest areas significantly improves fit statistics of SI prediction models.

Short-term response of ground-dwelling arthropods to storm-related disturbances is mediated by topography and dispersal

Wind disturbances and consequent salvage logging lead to drastic changes in forest soil conditions, vegetation and microclimate, potentially affecting arthropod communities. In mountain regions, topography is expected to be particularly important to modulate the effect of canopy removal and soil disturbance potentially amplifying the ecological contrast between forest and disturbed areas. Here, we studied the short-term response of ground beetles (Carabidae), spiders (Araneae), and harvestmen (Opiliones) in wind-damaged spruce forests along statistically orthogonal gradients in elevation, slope, and aspect. We addressed three main ecological questions: (i) Does the effect of wind disturbance on diversity depend on topography? (ii) Are there specific taxon-related responses to disturbances?, and (iii) What is the role of dispersal in shaping species assembly dynamics? We generally observed that increasing slope and elevation amplified the differences between undisturbed forest and windfall areas. On the one hand, the diversity of ground beetles and harvestmen seemed to be negatively affected by wind disturbance, causing a loss of specialized forest species with a low rate of colonization of species typical of open habitats. On the other hand, several novel spider species were able to rapidly colonize windfalls and community composition strongly shifted from forest to disturbed areas. Species with long-range dispersal strategies (e.g. flying and ballooning) were those more likely to colonize windfalls. Our findings suggest that disturbance effects on ground-dwelling organisms were modulated by underlying environmental gradients and that short-term response of different taxa was dependent on their dispersal ability.

Increased carbon assimilation and efficient water usage may not compensate for carbon loss in European forests

Phenological responses of vegetation to global warming impact ecosystem gross primary production and evapotranspiration. However, high resolution and large spatial scale observational evidence of such responses in undisturbed core forest areas is lacking. Here, we analyse MODIS satellite data to assess monthly trends in gross primary productivity and evapotranspiration across undisturbed core forest areas in Europe between 2000 and 2020. Both parameters increased during the early spring and late autumn in nearly half of the total undisturbed core forest area (3601.5 km2). Enhanced productivity drove increased water-use-efficiency (the ratio of gross primary productivity to evapotranspiration). However, productivity increases during spring and autumn were not sufficient to compensate for summertime decreases in 25% of core forest areas. Overall, 20% of total gross primary productivity across all European forest core areas was offset by forest areas that exhibited a net decrease in productivity.

Effect of soil surface disturbance on overland flow, sediment yield, and nutrient loss in a hyrcanian deciduous forest stand in Iran

Disturbance of forest watersheds has numerous effects on up and downstream environments, including erosion and reduction in productivity in disturbed areas, removal of nutrients, and deposition of pollutants on the land surface by runoff contamination of water resources. Little research has been conducted on forest ecosystems despite the environmental problems induced by nutrient transport. Therefore, the present study was conducted to quantitatively compare sediment yield, surface runoff, and nutrient and organic matter (OM) loss from undisturbed and disturbed forest areas during rain events in the Research and Educational Forest Watershed of Tarbiat Modares University in northern Iran. The study involved two treatments with three replications using 6-m2 plots. Results verified the significant effects of forest degradation (P < 0.05) on hydrological components and nutrient and OM loss. The surface runoff volume, runoff coefficient, sediment concentration, and sediment yield from plots located in the disturbed forest area were 5, 7, 5.5, and 18 times more, respectively than those measured in the undisturbed area. Also, the loss of carbon, nitrogen, phosphorus, and potassium in the disturbed area was more than in the undisturbed forest by 5, 10, 16, and 19 times. The maximum rate of loss of nutrients was 25 kg.ha−1. Enrichment ratios for carbon, nitrogen, phosphorus and potassium in the undisturbed area were 1.38 ± 0.33, 1.13 ± 0.11, 0.25 ± 1.86 and 1.24 ± 0.20, respectively, and 0.36 ± 1.59, 0.37 ± 1.57, 0.22 ± 1.98 and 0.29 ± 1.008, respectively, in the disturbed area. The study results should be applied to improve the management of Iranian forest ecosystems.

Insect Outbreak and Long-Term Post-Fire Effects on Soil Erosion in Mediterranean Suburban Forest

Our study was conducted in the suburban forest of Thessaloniki (Seich Sou), which constitutes one of the most significant suburban forests of Greece and is located northeast of Thessaloniki. In 1997, more than the half of the forest area was destroyed by a wildfire, while recently (May 2019), a significant insect outbreak by the bark beetle Tomicus piniperda was detected. The insect action still goes on, while the infestation has destroyed so far more than 300 ha of forest area. Extensive selective logging and removal of infected trees from the forest were carried out in order to mitigate and restrict the outbreak spread. In the current study, silt-fenced erosion plots were installed on representative locations of disturbed (by fire and insect action) and undisturbed areas, in order to quantify the effect of the above-mentioned forest disturbances on soil erosion and correlate the height and intensity of precipitation with the soil erosion rate. The results show that there was no statistically significant increase in soil erosion in the areas of insect outbreak compared with the control plots. However, there was a statistically significant increase in soil erosion in areas where logging works had been applied as an infestation preventive measure. In addition, the study revealed that 25 years after the forest fire, the erosion rate is still at higher level compared with the undisturbed forest areas. This study could be considered as one of the first attempts to evaluate the impact of an insect outbreak infestation on soil erosion, while there is also a great lack of information concerning the assessment of long-term post-fire effects on the soil erosion of a forest ecosystem.

Primary forest loss and degradation reduces biodiversity and ecosystem functioning: A global meta‐analysis using dung beetles as an indicator taxon

AbstractBecause of continuing degradation or deforestation in areas of undisturbed primary forest, there is a need to study the relative merit of strategies that mitigate their impacts on biodiversity and associated ecological functionality.Here, we provide a global synthesis of forest degradation or deforestation using 48 studies published in peer‐reviewed journals that use dung beetles as indicators given their sensitivity to anthropogenic disturbance and their relevance in performing essential ecological functions in terrestrial ecosystems.We evaluated forest cover associated with undisturbed primary forest degradation (i.e. degraded primary forest) and undisturbed primary forest deforestation (i.e. secondary forest, forestry plantations and forestry restoration implementation) on species richness, total abundance, biomass, functional groups' presence and ecological functions provided by dung beetles. Additionally, we determined whether if dung beetle responses to forest disturbances were geographically dependent.We found lower diversity and a decrease in ecological functions associated with all classes of disturbance in primary forest. However, the effects were less severe in the case of forest degradation compared to complete deforestation with natural regeneration of secondary forest, development of forest plantations or active forest restoration by planting indigenous trees. The Neotropical and Oriental regions are particularly vulnerable, given the elevated rates of undisturbed primary forest deforestation and its negative impact on their assemblages' diversity and ecological functions.Synthesis and applications. Our results show that efforts for the conservation of remaining undisturbed primary forests need to be prioritized, especially in tropical latitudes. However, in regions where primary forest conservation is not feasible, logging management programs in degraded primary forest may have a potential role in reducing negative impacts for dung beetle diversity and ecological functions. Moreover, we conclude that despite the negative effect of primary forest deforestation and implementation of secondary forest, forestry plantation and forestry restoration, they can be useful for partial recovery of diversity and ecological functions performed by dung beetles in areas lacking any primary forest (undisturbed or degraded) vegetation cover.

Post-fire dynamics of tree vegetation in forests with and without a history of selective logging in the Eastern Amazon

Worldwide, forests are susceptible to fire. Forests with fire and selective logging interactions require monitoring and evaluation. This study evaluated the phytosociology and dynamics of tree vegetation in a disturbed forest (DF) and an undisturbed forest (UF) in selective logging areas affected by fire, in the Brazilian East Amazon. All trees with DBH ≥ 5 cm were measured and identified botanically in 93 plots (5 X 50 m) in the DF area and 58 plots (5 X 50 m) in the UF area, in 2010 (before logging), 2011, 2015 and 2017 (two years after the fire). Analysis of species and tree composition, diversity, similarity, mortality and recruitment were carried out. The fire affected the DF and UF areas in a similar proportion in terms of trees loss and basal area, intensifying the mortality rate. In the short term (2 years), the fire did not cause a significant reduction in species diversity, but there was a tendency towards a similarity loss in species composition in the area disturbed by logging. Subsequent assessments are necessary to understand the forest's recovery mechanisms.

Structural characterization using 2D NMR spectroscopy and TMAH-GC × GC-MS: Application to humic acids from soils of an integrated agricultural system and an Atlantic native forest

Understanding the chemical make-up of soils and their structure is critical for constraining the role of soil organic matter (SOM) into the global biogeochemical cycles, as well as to understand the capability of SOM to sequester carbon and mitigate greenhouse gas emissions. Here, we use two-dimensional 1H-13C heteronuclear single quantum coherence nuclear magnetic resonance (2D 1H-13C HSQC NMR) spectroscopy to structurally characterize the most refractory component of SOM, the humic acid (HA). The observations from 2D 1H-13C HSQC NMR were coupled with lignin phenol and fatty acid measurements using tetramethylammonium hydroxide (TMAH) thermochemolysis – two-dimensional gas chromatography – mass spectrometry (TMAH-GC × GC-MS). We studied humic acids extracted from an integrated Crop – Livestock – Forest System (CLFS) agricultural area and an undisturbed Atlantic Native Forest (NF) area. We evaluated soils from two different depths: the topsoil (0–20 cm) and subsoil (60–100 cm) layers, and reveal the presence of oxidized ligninaceous phenols as we had previously hypothesized. Collectively, our results indicate that there are significant oxidative processes with increasing soil depth which are more pronounced in the CLFS relative to the NF area. Degradation of stearic acid with increasing depth in the CLFS soils indicated that the CLFS is more microbiologically active than NF. Therefore, CLFS is less biochemically stable than we originally perceived. The enhanced bio-reactivity of CLFS is likely driving the enhanced carbon sequestration in the CLFS soils. This is perhaps due to the diversity of biomass remnants available at the CLFS soil rhizosphere which allows for more different types of biomass to be sequestered as oxidized ligninaceous phenols. Our results employing structural characterization with 2D 1H-13C HSQC NMR and TMAH-GC × GC-MS provide a new layer of knowledge about the practice of integrated agricultural systems and allow us to understand the structure and fate of sequestered carbon in soils from different soil environments.

Field surveys along habitat gradients revealed differences in herpetofauna assemblage in Margalla Hills National Park, Islamabad, Pakistan.

This study was conducted to see whether herpetofaunal assemblage differed amongst hiking trails, undisturbed forest and urban areas within the Margalla Hills National Park, Islamabad Capital Territory, Pakistan. Circular plot area-constrained searches (45 plots in each habitat, each plot with an area of 25 m2) were used from March 2018 to July 2019. We recorded seven amphibian species, nine lizard species and six snake species. The species richness of amphibians and lizards was the same in the studied strata, while the detection and encounter rate of snakes was lower in the undisturbed forest and urban areas. The encounter rate of amphibians differed significantly between urban areas and hiking trails/undisturbed forest. The encounter rate and population density of lizards differed significantly between undisturbed forest and urban areas. The most frequently encountered amphibian species along the hiking trail and urban areas was Duttaphrynus stomaticus, with Hoplobatrachus tigerinus in undisturbed forest. The most common and frequently encountered lizard species along the hiking trail and urban areas was Hemidactylus brookii, while the Ophisops jerdonii was the most frequently seen in undisturbed forest. The most common and frequently encountered snake species along the hiking trail and undisturbed forest was the Indotyphlops braminus, while Ptyas mucosa was the most common in urban areas. The subsequent bio-assessment, based on herpetofauna, of the Park revealed good to excellent biotic integrity The Park faces threats including livestock grazing, alien invasive vegetation and human disturbance due to settlements, restaurants and tourism-related activities. While several of these threats have been mitigated since the establishment of the Islamabad Wildlife Management Board, the Park still requires improved management, especially regarding regulating tourism.

Near-complete loss of fire-resistant primary tropical forest cover in Sumatra and Kalimantan

Deforestation in Indonesia in recent decades has made increasingly large parts of the region vulnerable to fires. Burning is particularly widespread in deforested peatlands, and it leads to globally significant carbon emissions. Here we use satellite-based observations to assess loss and fragmentation of primary forests and associated changes in fire regimes in Sumatra and Kalimantan between 2001 and 2019. We find that fires did not penetrate undisturbed primary forest areas deeper than two kilometres from the forest edge irrespective of drought conditions. However, fire-resistant forest now covers only 3% of peatlands and 4.5% of non-peatlands; the majority of the remaining primary forests are severely fragmented or degraded due to proximity to the forest edge. We conclude that protection and regeneration of the remaining blocks of contiguous primary forest, as well as peatland restoration, are urgently needed to mitigate the impacts of potentially more frequent fire events under future global warming.

Elevated natural radioactivity in undisturbed forest and mountain areas of arctic Norway – local geology, soil characteristics, and transfer to biota

This study deals with the geology in areas close to a large unexploited uranium deposit and the impact of bedrock characteristics on levels of radionuclides and other elements in soil and biota. Factors influencing soil inventory and ecosystem transfer are discussed, focussing on 238U, 226Ra, and 210Pb. Field work was carried out in Salangen Valley in Northern Norway. Sampling stations for soil and biota covered different habitats – grassland, birch forest and low alpine heathland. The geological survey confirmed uranium-bearing minerals in granitic gneiss and pegmatites. There was large variation in the local occurrence of uranium, reflecting the irregular nature of the pegmatite. Activity concentrations of 238U, 226Ra, and 210Pb in surface soil were elevated at sites close to U-enhanced bedrock, compared to sites with other types of bedrock. Particularly high soil levels were found for 226Ra and 210Pb, whereas activity concentrations of 238U were more variable, depending of local soil characteristics. Levels of other natural radionuclides (40K, 232Th) merely increased with soil mineral content, and concentrations of heavy metals were generally low at all sites. External dose rate (1 m above ground surface) was closely correlated with 226Ra levels in soil. Plant levels of 238U and 226Ra varied by several orders of magnitude depending on soil level and plant species, whereas plant levels of 210Pb and 210Po were largely affected by aerial fallout. Berries generally contained lower levels of 238U and 226Ra than green plant parts. As was the case for plants, the levels of 238U in earthworms were strongly correlated with the respective concentrations in the soil. Soil-to-plant transfer was markedly higher for 226Ra than for 238U. For both radionuclides, a positive correlation was found between concentration ratios of V. myrtillus (heath) and soil organic matter content. The 238U concentration ratios for earthworms were generally two orders of magnitude higher than for plants.

Distance from the Forest Edge Influences Soil Fungal Communities Colonizing a Reclaimed Soil Borrow Site in Boreal Mixedwood Forest

Soil fungi are important components of boreal forest ecosystems; for example, saprotrophic fungi regulate nutrient cycling, and mycorrhizal species facilitate nutrient uptake by plants. This study aimed to assess soil fungal communities in a reclaimed area and an adjacent natural mixedwood forest and to identify the distribution of taxa available for seedling colonization. Soil fungal microbiomes were assessed along three transects (from 10 m inside the interior of the undisturbed forest to 40 m inside the reclaimed area) and in the roots of small aspen within the natural forest. Using high-throughput deoxyribonucleic acid (DNA) sequencing of internal transcribed spacer amplicons, a total of 2796 unique fungal taxa were detected across fine roots, forest floor, and mineral soils collected along the transects, whereas 166 taxa were detected in the aspen roots from the natural forest. Within the interior of the forest, ectomycorrhizal fungi were more common, whereas in the reclaimed areas, arbuscular mycorrhizae and saprophytes were more common. This survey showed that natural areas of adjacent undisturbed forest can act as a source of ectomycorrhizal fungi for dispersal into reclaimed areas. Notably, soil fungal taxa colonizing the root systems of small aspen included species that are specifically associated with soils from the undisturbed forest (primarily ectomycorrhizae) or the reclaimed clearing (saprotrophs and plant pathogens).

Soil mycobiota under managed and unmanaged forests of &lt;i&gt;Nothofagus pumilio&lt;/i&gt; in Tierra del Fuego, Argentina

Background: Management practices can modify the productivity of forests and the associated microbial diversity of soil. The soil mycobiota is considered a key factor in the ecological functions of forests. Forests of Nothofagus pumilio (Poepp. &amp; Endl.) Krasser (Nothofagaceae) are the main source of timber and one of the most important economic resources in the province of Tierra del Fuego (Argentina). However, there is no information on the impact of forest management interventions for the soil mycobiota, which can be reliable biological indicators of disturbance.Methods: Fungi were isolated from samples of soil collected under several Nothofagus pumilio forests subjected to different types of management and periods of time since the intervention. Types of management were represented by harvested forest with a shelter wood cutting, stockpile area and control forest without intervention and the periods of time since intervention were 1, 5–10 and 50 years. Species richness, evenness and Shannon’s diversity index of the mycobiota in each condition of management were calculated. Additionally, the effect of seasonality was analysed.Results: The soil mycobiota was represented by 70 taxa. Richness and/or Shannon’s diversity index of the mycobiota between undisturbed forest and stockpile area were higher in May (autumn) than in September or November. There were no differences in mycobiota diversity between dates in the harvested forest.Conclusions: Our results indicate that the forest intervention per se did not negatively affect the soil culturable mycobiota composition of N. pumilio forests in Tierra del Fuego (Argentina).

A soil‐quality index for soil from Mediterranean forests

Treatments involving vegetation thinning have become more frequent in Mediterranean forest ecosystems. Under extreme climate conditions, this practice can affect the balance between physicochemical, microbiological and biochemical soil properties, modifying the soil quality and the ability of these forest ecosystems to regenerate. The aim of this study was to use principal component analysis (PCA) to develop a multivariable soil‐quality index (SQI) applicable to the Mediterranean forest ecosystems of the Cuenca mountain range in central‐eastern Spain. To achieve this, seven physicochemical properties (moisture, pH, electrical conductivity, carbonate, total organic carbon, total nitrogen and available phosphorus) and six microbiological properties (basal respiration and microbial biomass carbon, as well as the activity of dehydrogenase, urease, phosphatase and β‐glucosidase enzymes) were measured seasonally between 2011 and 2012. Soil samples were obtained from seven unmanaged and undisturbed forest areas and these data were used to create the SQI. Subsequently, we applied this SQI to soil samples from other forests in the Cuenca mountain range, which had been affected by different thinning treatments. Our analysis showed that the greater was the canopy present in these treated forests, the larger were the average values for all 13 variables. The smallest SQI values were in areas that had been intensively thinned. Therefore, our results suggest that this SQI is an important tool for the development of appropriate measures to maintain the quality of forest soil in Spanish Mediterranean forest ecosystems.HighlightsWe developed a multivariable soil quality index (SQI) to assess status of Mediterranean forest ecosystems.This index is adequate to detect changes quickly in forest soil of Mediterranean ecosystems.The SQI helped to assess the effects of thinning treatments on forest soil.The SQI enabled establishment of different levels of soil quality (very high, high, medium and low).

Effect of Climatic Conditions and Land Cover on Genetic Structure and Diversity of Eunica tatila (Lepidoptera) in the Yucatan Peninsula, Mexico

Fragmentation is the third cause of the biodiversity declination. Population genetic studies using Lepidoptera as the model species in the context of loss of habitat are scarce, particularly for tropical areas. We chose a widespread butterfly from Mexico as the model species to explore how changes of habitat characteristics (undisturbed forest, anthropogenic disturbances, and coastal areas), and climatic conditions affect genetic diversity and population structure. The Nymphalidae Eunica tatila is a common species in the Yucatan Peninsula considered to be a bio-indicator of undisturbed tropical forest, with migratory potential and a possible sex-biased dispersal. We genotyped 323 individuals collected in eight undisturbed areas, using four Inter Simple Sequence Repeats primers. Results show a high genetic diversity and no population structure. Temperature and shrub density present a positive and significant relationship with polymorphism values. Furthermore, our results show the positive effect of surrounding forest habitat on genetic diversity, confirming that E. tatila is a bio-indicator of undisturbed tropical forest. We found evidence of sex-biased dispersal. This paper represents one of the few studies on population genetics of tropical butterfly in a fragmented landscape and is, therefore, an important step in understanding the impact of habitat fragmentation on the risk of a butterflies’ decline.

English

Anthropogenic activities, including replacing natural forests with human settlements and increased agricultural activities have environmental impacts. The activities can contaminate aquatic ecosystems including spring waters that are sources of major rivers like the Amala and Nyangores, tributaries of Mara River in Mau Complex. In the complex, forestlands have been converted to human settlements and agricultural lands. Although residents of the Mara River Basin use the spring waters for domestic and animal watering purposes, evaluation of the impact the activities have on the spring water quality has not been done. This study evaluated the site and seasonal variations of zinc, copper, selenium, manganese, chromium, cadmium and lead concentrations in spring waters within the Mau Complex where forests have been cleared and converted to anthropogenic activities. The study covered areas along Amala and Nyangores rivers. There were variations (p≤0.05) in the heavy metals levels with sites and seasons. Except for Mn, Cu and Cd which were lower, the levels of the other heavy metals in water from the control points (undisturbed forest areas) were higher in downstream areas that had undergone massive anthropogenic activities. Although there were seasonal variations (p≤0.05), the pattern was not clear. Some heavy metals levels were higher in wet seasons while others were higher in dry season. But the heavy metals levels were within the recommended international standards for domestic/animal use. These results demonstrate that the anthropogenic activities were not yet causing pollution of the spring waters. Maintaining the anthropogenic activities at present levels is recommended. However, periodic monitoring to ascertain the quality of the spring water is necessary to mitigate increase to detrimental levels with time. These results contribute knowledge helping regulatory agencies and management of Lake Victoria basin to formulate monitoring polices to curb water quality deterioration. Key words: Anthropogenic activities, heavy metals, spring water, River Mara, Mau Complex.

Comparison of aboveground vegetation and soil seed bank composition at sites of different grazing intensity around a savanna-woodland watering point in West Africa.

Grazing removes a plant's aboveground vegetative and reproductive tissues and can modify the soil seed bank, potentially impacting the restoration of preferred species. Knowledge about aboveground vegetation and species composition of soil seed bank and the processes that contribute to vegetation recovery on and surrounding watering points subjected to grazing is lacking. Successful restoration strategies hinge on addressing these knowledge gaps. We assessed the effects of livestock grazing on aboveground vegetation and soil seed bank characteristics along a river bank and surrounding areas subject to different grazing intensities and draw implications for restoration. Plots (50 × 50m) were established along five transects representing differing levels of grazing intensity. Soil samples were taken from three layers within each plot to determine soil properties and species composition of soil seed bank using the seedling emergence method. Heavy grazing resulted in the disappearance of perennial grasses, a reduction in species diversity and a decrease in soil nutrients with increased soil depth. Overall, the similarity between the extant aboveground vegetation and flora within the soil seed bank was low. The soil seed bank was dominated by herbaceous species and two woody species, suggesting that many woody species are not accumulating in the soil. With increasing soil depth, the seed density and richness declined. Canonical correspondence analyses (CCAs) showed that emerged seedlings from the soil seed bank were significantly influenced by soil carbon, organic matter, total nitrogen, total potassium and soil cation exchange capacity. This finding suggests that current grazing practices have a negative impact on the vegetation surrounding watering points; hence there is a need for improved grazing management strategies and vegetation restoration in these areas. The soil seed bank alone cannot restore degraded river banks; active transfer of propagules from adjacent undisturbed forest areas is essential.

Long-Term Changes in the Dominance of Drought Tolerant Trees Reflect Climate Trends on a Micronesian Island

Background: The Ogasawara (Bonin) Islands of Micronesia lie in the western Pacific Ocean and are unique in terms of their isolation, climate, soils and diversity of rare plant species. We hypothesized that the vegetation on the islands will be a robust model system to study long-term climate change impacts on vegetation dynamics.&#x0D; Methods: A large, long-term vegetation monitoring plot was established on Chichijima Island and measured in 1976 and 2017. It was located in an undisturbed dry forest area that contained many endemic and endangered species.&#x0D; Results: During the 41 year study period, total basal area of tree species increased by 24.6% and was dominated by Schima, Distylium and Pouteria, whereas tree density declined by 30%. Tree genera exhibiting the largest increases in basal area were Elaeocarpus, Ilex, Pandanus, Pouteria, Rhaphiolepis, Syzgium and Schima. During the study period, the annual average (23.2ºC), minimum and maximum temperatures increased by 0.5 to 0.8ºC, respectively. The average annual precipitation was 1276 mm with severe droughts occurring in 1980, 1990 and 2016. The largest increases in the basal area were exhibited in trees species with wide functional distribution and attributes, including drought tolerance.&#x0D; Conclusions: The results of this study suggest a link between the drought tolerance, species dominance and climate change at the study location. Our unique approach of linking functional attributes with long-term vegetation and climate change can serve as a model for other studies of global change impacts.

The relationship between environmental variables, detection probability and site occupancy by Tasmanian nocturnal birds, including the Tasmanian masked owl (Tyto novaehollandiae castanops)

Knowledge of the habitat requirements of nocturnal birds is vital for the development of effective conservation strategies. This study is the first intensive systematic survey of the occurrence of the threatened Tasmanian masked owl (Tyto novaehollandiae castanops), the Tasmanian boobook (Ninox leucopsis) and the Australian owlet-nightjar (Aegotheles cristatus) in Tasmania using call playback, spotlighting and listening techniques. Occupancy models were created that explain the spatial distribution of the three species. Temperature and wind influenced the detectability of all species. Detectability of the Tasmanian boobook was also associated with nightlight. The Tasmanian masked owl was most often found in low-elevation mature dry eucalypt forest. This may be related to a combination of availability of nesting sites, food availability and accessibility, and physiological factors. The Australian owlet-nightjar also showed a broad preference for dry eucalypt forest and avoided open country. In contrast, the Tasmanian boobook was most often found in wet eucalypt forest with higher temperatures and fewer roads. We conclude that mature dry and wet forest types at low elevations need to be carefully managed to maintain populations of Tasmania’s nocturnal birds, particularly the threatened Tasmanian masked owl. Consideration should be given to retention of a network of contiguous areas of undisturbed mature forest across forested landscapes.

Soil nitrogen mineralization in a wind-disturbed area on Changbai Mountain after 30 years of vegetation restoration

Wind-disturbed (1986) and undisturbed primary forest areas (controls) on Changbai Mountain (China) were studied to compare levels of soil nitrogen mineralization. Soil samples were collected at 0–10cm (topsoil) and 10–20cm (subsoil) depths from the vegetation zones of a broadleaf Korean pine forest (BKPF), spruce-fir forest (SFF), and an Erman's birch forest (EBF) at different altitudes. Nitrogen status and mineralization characteristics were studied in the soil samples from a wind-disturbed area where vegetation cover has been restored after 30years of regrowth. Soil organic carbon (SOC) and total nitrogen (TN) contents in the topsoil layer of the three vegetation types were significantly higher than in the subsoil layer. SOC and TN contents in the topsoil layer increased, and soil C/N ratio significantly decreased with increasing altitude. No significant differences in SOC, TN or pH were detected in the wind-disturbed and control area soils of BKPF and EBF. SOC and TN levels in the subsoil layer of SFF were significantly higher in wind-disturbed than in control areas. The topsoil C/N ratios of BKPF and SFF were significantly higher in the control area vs. the wind-disturbed area. After 21d incubation, inorganic nitrogen contents (ammonium nitrogen NH4+-N and nitrate nitrogen NO3−-N) in the soils of BKPF, SFF and EBF increased in both the wind-disturbed and control areas. Ammonium nitrogen (NH4+-N) was the primary inorganic form of nitrogen. The changes in the amount of NH4+-N formed from ammonification contributed to the 57.1–76.2% total amount of nitrogen mineralized (net nitrogen mineralization) and the net nitrogen mineralization rate. The nitrogen mineralization process was mainly the result of net ammonification. Correlation analysis on the soil nitrogen mineralization rate and chemical properties showed that the ammonification rate had strong positive correlation with SOC and the C/N ratio. Nitrification rate was highly correlated with SOC and TN contents, as well as soil pH. Net nitrogen mineralization rate was significantly correlated with SOC and TN contents, C/N ratio, and soil pH. Multiple comparisons analysis of variance (ANOVA) demonstrated that soil nitrogen mineralization was greatly influenced by vegetation type, soil depth, and wind disturbance in the forest soils at different altitudes. Net ammonification and net nitrogen mineralization were significantly affected by wind disturbance. The vegetation cover has undergone restoration for nearly 30years in the wind-disturbed area on Changbai Mountain, but our data demonstrate that differences in soil quality between primary forest and wind-disturbed areas remain significant due to the different vegetation types.