Disturbance Gradient Research Articles

Spatiotemporal responses of ant communities across a disturbance gradient: the role of behavioral traits

This study examined how chronic anthropogenic disturbance impacts the spatiotemporal dynamics of ant foraging activity and the role played by behavioral traits. Ten plots (0.1 ha) along a gradient of chronic disturbance intensity were sampled in Catimbau National Park (Caatinga vegetation, Brazil). Vegetative structure, ground surface temperature, and ant communities in shaded and sun-exposed microhabitats were characterized during the day and at night. Each ant species’ degree of nocturnality and shaded microhabitat use were determined. Along the disturbance gradient, the frequency of sun-exposed microhabitats increased, as did the daytime ground surface temperatures; also, community composition, but not ant abundance or species richness, changed. Independent of disturbance intensity, community composition differed between day and night, and ant abundance and species richness were higher during the day. Interestingly, most species did not display strictly diurnal habits, nor did they avoid foraging in sun-exposed habitats. However, species common in more disturbed areas were more diurnal and used sun-exposed microhabitats more than species common in less disturbed areas. Many species displayed marked behavioral plasticity that was unrelated to disturbance intensity. Disturbance intensity did influence shaded microhabitat use but not the degree of nocturnality. We conclude that Caatinga ants are already morphologically, behaviorally and physiologically adapted to harsh environmental conditions; that species with different behavioral traits replace each other along the disturbance gradient; and that more plastic species can persist by shifting their microhabitat use.

Rapid Assessment of Wetland Condition Reflects Amphibian Community Composition

Kentucky has lost over 80% of its wetlands, and because state-wide monitoring was historically minimal, this number is likely underestimated. The Kentucky Wetland Rapid Assessment Method (KY-WRAM) was developed to assess wetland condition. Our objective was to determine if the KY-WRAM reflects condition by comparing it to intensive assessment of amphibian communities, while simultaneously addressing which environmental variables explain the distribution and abundance of amphibian species in riverine wetlands. Wetlands (n = 44) were randomly selected and stratified by score for comparison of amphibian communities across a disturbance gradient. Factors including KY-WRAM score, nutrients, dissolved oxygen, landscape disturbance, predatory fish, and atrazine were included as model parameters to potentially explain species richness and abundance. KY-WRAM score explained the majority of variation in richness (R2 = 0.62), which was significantly greater at medium and high category sites compared to low. KY-WRAM was also an important predictor of abundance for seven amphibian species. Results indicate KY-WRAM is a good predictor of wetland condition and strongly relates to amphibian communities. Other variables that contributed to explaining abundance were landscape disturbance, wetland size, predatory fish, and river basin. Our study contributes to overall validation of the KY-WRAM. Future validation studies should focus on other basins, wetland types, and taxa.

Quantifying Topographic Characteristics of Wetlandscapes

Topography underpins natural processes ranging from incident solar radiation to overland flow and water pooling. Despite the influence of topography on natural processes, especially in wetland ecosystems reliant on uplands for water inputs, topography has not been adequately incorporated into reclamation planning. Instead, wetland reclamation projects are typically guided by height-to-length ratios that produce little resemblance to natural wetlands. We present a methodology to quantify the topographic characteristics in landscapes with an abundance of wetlands to guide the reclamation of naturally appearing and self-sustaining wetlandscapes. Topographic characteristics in over 3000 sample landscapes were quantified using terrain roughness and landform element composition and configuration. A large set of metrics was reduced to a statistically independent subset that was applied and compared across three natural regions and a gradient of disturbance. Our results showed that surface roughness and landform element patterns significantly differ among natural regions and that high disturbance landscapes significantly differ from other disturbance levels. To ensure reclaimed wetlandscapes are naturally appearing and self-sustaining, they should replicate the topographic characteristics found within the distribution of surrounding natural landscapes by applying topographic characteristic benchmarks to reclamation design. The presented methodology can be used as a step towards achieving this goal.

Changes in Fungal Communities across a Forest Disturbance Gradient.

Deforestation has a substantial impact on aboveground biodiversity, but the response of belowground soil fungi remains poorly understood. In a tropical montane rainforest in southwestern China, plots were established along a forest degradation gradient ranging from mature and regenerated forests to open land to examine the impacts of forest degradation and deforestation on ecosystem diversity and function. Here, we evaluated the changes in belowground fungal diversity and community composition using a metabarcoding approach. Soil saprotrophic fungal richness declined with increasing forest disturbance. For example, Penicillium spp. (phosphorus [P]-solubilizing fungi) dominated in mature forest but were less abundant in regenerating forests and showed the lowest abundance in open land sites. Conversely, the abundance of facultative pathogenic fungi increased along the disturbance gradient. The decline in soil saprophytic fungi may be a direct result of forest disturbance or it may be associated with increased availability of soil phosphorus indirectly through an increase in soil pH. The increase in abundance of facultative pathogenic fungi may be related to reduced competition with saprotrophic fungi, changes in microclimate, or increased spore rain. These results demonstrate a loss of dominant P-solubilizing saprotrophic fungi along the disturbance gradient, indicating a change from soil P limitation in mature tropical forests to soil C limitation in deforested sites. The increased prevalence of pathogenic fungi may inhibit plant succession following deforestation. Overall, this research demonstrates that soil fungi can be used as a sensitive indicator for soil health to evaluate the consequences of forest disturbance.IMPORTANCE The soil fungal functional group changes in response to forest disturbance and indicates a close interaction between the aboveground plant community and the belowground soil biological community. Soil saprotrophic fungi declined in relative abundance with increasing forest disturbance. At the same time, the relative abundance of facultative pathogenic fungi increased. The loss of saprotrophic fungal richness and abundance may have been a direct result of forest disturbance or an indirect result of changes in soil pH and soil P. Furthermore, the dominant P-solubilizing saprotrophic fungi were replaced by diverse facultative pathogenic fungi, which have weaker C decomposition ability. These changes potentially indicate a shift from soil phosphate limitation to carbon limitation following deforestation. This study suggests that changes in fungal functional group composition can be used as an indicator of the effects of forest disturbance on soil carbon and nutrients.

The relationship between macroalgae taxa and human disturbance on central Pacific coral reefs

Climate change and human disturbance threatens coral reefs across the Pacific, yet there is little consensus on what characterizes a “healthy” reef. Benthic cover, particularly low coral cover and high macroalgae cover, are often used as an indicator of reef degradation, despite uncertainty about the typical algal community compositions associated with either near-pristine or damaged reefs. In this study, we examine differences in coral and algal community compositions and their response to human disturbance and past heat stress, by analysing 25 sites along a gradient of human disturbance in Majuro and Arno Atolls of the Republic of the Marshall Islands. Our results show that total macroalgae cover indicators of reef degradation may mask the influence of local human disturbance, with different taxa responding to disturbance differently. Identifying macroalgae to a lower taxonomic level (e.g. the genus level) is critical for a more accurate measure of Pacific coral reef health.

A novel approach involving the use of Odonata as indicators of tropical forest degradation: When family matters

• Odonata can be effective and cost-efficient indicators of habitat status. • Coenagrionidae and Libellulidae as indicator groups. • Odonata adult-based bioassessment method is reliable. • The method may be easily applied in any tropical forest habitat worldwide. Odonata have proven to be good indicators of freshwater as well as terrestrial habitat conditions. Several studies have shown changes in odonate species richness and/or community composition in response to deforestation, suggesting their potential as bioassessment tools in the tropics. However, former approaches using Odonata as an indicator group required comparative samples from differently disturbed sites and/or knowledge of the focal species environmental specificity. Here, we tested a robust, adult-based bioassessment method assuming that the level of tropical forest degradation reflects the proportional representation of the taxa above species. Based on Web of Science, ScienceDirect, and Scopus databases, we used data from previously published studies linking odonate assemblages to human-mediated disturbances in tropical forests. We hypothesized that along a disturbance gradient (from primary forest to non-forest), (i) the proportion of the suborder Zygoptera (mostly habitat specialists sensitive to deforestation) will decrease in favor of the suborder Anisoptera (high proportion of generalists); and (ii) the proportions of largely generalist families Coenagrionidae and Libellulidae will increase at the expense of other Zygoptera and Anisoptera, respectively. Our results revealed that a ratio of Zygoptera/Anisoptera is a poor indicator of tropical forest conditions, probably because of ecological diversity within these groups. However, the proportions of Coenagrionidae/other Zygoptera and Libellulidae/other Anisoptera significantly increased along a disturbance gradient, suggesting their potential to be a good indicator of well-preserved, altered, and heavily degraded forest habitats. Therefore, our results are in line with studies presenting the usefulness of adult Odonata as versatile indicators for assessing human-mediated changes in tropical forest environments, supporting the practical use of this group in biological monitoring.

Mechanisms underlying increased nest predation in natural gas fields: a test of the mesopredator release hypothesis

AbstractAnthropogenic activities are changing landscapes and the context in which predator–prey dynamics evolved, thereby altering key ecological processes and community structure. Yet, the specific mechanisms underlying such changes are rarely understood. We tested whether a mesopredator release explained increased rodent density and concomitant predation of songbird nests near natural gas development. From 2015 to 2016, we surveyed apex predators (coyotes, badgers, raptors, and corvids) and measured apparent survival and perceived predation risk of deer mice (Peromyscus maniculatus; a primary nest predator), at 12 plots spanning a gradient of surface disturbance caused by energy development in Wyoming, USA. Additionally, we measured densities of three nest predators: deer mice, least chipmunks (Tamias minimus), and thirteen‐lined ground squirrels (Ictidomys tridecemlineatus). Contrary to the mesopredator release hypothesis, counts of apex predators and perceived predation risk of deer mice increased with surface disturbance from energy development, whereas apparent survival of mice decreased. Densities of mice and ground squirrels, however, increased with surface disturbance, despite increased predation pressure. We therefore rejected the mesopredator release hypothesis as a potential mechanism underlying altered trophic dynamics near energy development. Our results suggest that apex predator control measures would not benefit declining songbirds on natural gas fields. Rather, apex predator abundance may be regulated from the bottom‐up by rodents in this system. Our results corroborate a pattern showing weakened effects of mesopredator release in habitats modified by humans. Understanding how predator–prey dynamics may be altered in novel environments requires an understanding of how predators and prey alike respond to habitat change under different contexts.

Striving for consistency in the National Wetland Condition Assessment: developing a reference condition approach for assessing wetlands at a continental scale

One of the biggest challenges when conducting a continental-scale assessment of wetlands is setting appropriate expectations for the assessed sites. The challenge occurs for two reasons: (1) tremendous natural environmental heterogeneity exists within a continental landscape and (2) reference sites vary in quality both across and within major regions of the continent. We describe the process used to set reference expectations and define a disturbance gradient for the United States (US) Environmental Protection Agency’s National Wetland Condition Assessment (NWCA). The NWCA employed a probability design and sampled 1138 wetland sites across the conterminous US to make an unbiased assessment of wetland condition. NWCA vegetation data were used to define 10 reporting groups based on ecoregion and wetland type that reduced the naturally occurring variation in wetland vegetation associated with continent-wide differences in biogeography. These reporting groups were used as a basis for defining quantitative criteria for least disturbed and most disturbed conditions and developing indices and thresholds for categories of ecological condition and disturbance. The NWCA vegetation assessment was based on a reference site approach, in which the least disturbed reference sites were used to establish benchmarks for assessing the condition of vegetation at other sites. Reference sites for each reporting group were identified by filtering NWCA sample data for disturbance using a series of abiotic variables. Ultimately, 277 least disturbed sites were used to set reference expectations for the NWCA. The NWCA provided a unique opportunity to improve our conceptual and technical understanding of how to best apply a reference condition approach to assessing wetlands across the US. These results will enhance the technical quality of future national assessments.

The 2011 National Wetland Condition Assessment: overview and an invitation

The first National Wetland Condition Assessment (NWCA) was conducted in 2011 by the US Environmental Protection Agency (USEPA) and its federal and state partners, using a survey design that allowed inference of results to national and regional scales. Vegetation, algae, soil, water chemistry, and hydrologic data were collected at each of 1138 locations across the conterminous United States (US). Ecological condition was assessed in relation to a disturbance gradient anchored by least disturbed (reference) and most disturbed sites identified using chemical, physical, and biological disturbance indices based on site-level data. A vegetation multimetric index (VMMI) was developed as an indicator of condition, and included four metrics: a floristic quality assessment index, relative importance of native plants, number of disturbance-tolerant plant species, and relative cover of native monocots. Potential stressors to wetland condition were identified and incorporated into two indicators of vegetation alteration, four indicators of hydrologic alteration, a soil heavy metal index, and a nonnative plant indicator and were used to quantify national and regional stressor extent, and the associated relative and attributable risk. Approximately 48 ± 6% of the national wetland area was found to be in good condition and 32 ± 6% in poor condition as defined by the VMMI. Across the conterminous US, approximately 20% of wetland area had high or very high stressor levels related to nonnative plants. Vegetation removal, hardening, and ditching stressors had the greatest extent of wetland area with high stressor levels, affecting 23–27% of the wetland area in the NWCA sampled population. The results from the 2016 NWCA will build on those from the 2011 assessment and initiate the ability to report on trends in addition to status. The data and tools produced by the NWCA can be used by others to further our knowledge of wetlands in the conterminous US.

Species turnover differentiates diversity–disturbance relationships between aboveground vegetation and soil seedbank

An understanding of relationships between species diversity and disturbance gradient is important to comprehend the role of disturbances in the structure of plant communities. Although some studies have demonstrated incongruence in diversity–disturbance relationships (hereafter DDRs) between aboveground vegetation and soil seedbank, the process that causes the difference remains unclear. This incongruence between the two DDRs could result in the decrease in the source of recovery of aboveground vegetation following disturbances being overlooked when only aboveground vegetation is surveyed. Here, we verified a process that species turnover across the disturbance gradient causes the incongruence. Based on a vegetation and seedbank survey, we examined DDRs and species turnover of aboveground vegetation and seedbank along disturbance duration (i.e., excluding years of ungulate grazing). The degree of species turnover was considerably greater in aboveground vegetation than in seedbank; thus, the degree of species turnover along a disturbance gradient caused the difference in DDR between aboveground vegetation and seedbank.

A functional diversity approach of crop sequences reveals that weed diversity and abundance show different responses to environmental variability

Abstract Combining several crop species and associated agricultural practices in a crop sequence has the potential to control weed abundance while promoting weed diversity in arable fields. However, how the variability in environmental conditions that arise from crop sequences affects weed diversity and abundance remains poorly understood, with most studies to‐date simply opposing weed communities in monoculture and in crop rotation. Here, we describe crop sequences along gradients of disturbance and resource variability using a crop functional trait and associated agricultural practices. We tested the hypothesis that in disturbances reduces weed abundance, whereas variability in resources promotes weed diversity. We used functional Hill's numbers to compute crop sequence functional diversity based on sowing date, herbicide spectrum and crop height—these are the respective proxies of disturbance timings, disturbance types and light availability. Using a large‐scale weed monitoring database, we assessed crop sequence diversity for 1,045 crop sequences of five consecutive cropping seasons. We computed weed richness and abundance at pluri‐annual (pool of weeds observed across five cropping seasons) and annual (pool of weeds observed during a winter cereal cropping season preceded by five cropping seasons) scales. We also accounted for herbicide and tillage intensities to test whether management intensity affects the response of weed diversity and abundance to crop sequence diversity. At the pluri‐annual scale, weed richness increased with the diversity of crop height and sowing date, whereas weed abundance decreased with sowing date diversity. Annual weed richness decreased with sowing date diversity, whereas annual weed abundance poorly relied on crop sequence diversity. Synthesis and applications. This study establishes a scientific basis for designing crop sequences according to specific weed management goals. We show that farmers may enhance arable weed diversity on a pluri‐annual scale by sequentially sowing crop species that differ in their competitive ability and sowing date. They may also achieve a better control of weed abundance by increasing the diversity of crop sowing dates across the crop sequence.

Are orchid bees useful indicators of the impacts of human disturbance?

Biodiversity and ecosystem functions are threatened by human disturbance, and tropical forests are one the most vulnerable habitats. Monitoring the impacts of disturbance and the success of conservation projects is crucial, and to do this effectively it is important to identify suitable measures that are sensitive to ecosystem disturbance. Orchid bees (Euglossini) are a specialist group with mutualistic relationships with many plant species and can fly long distances, making them important pollinators of widely dispersed plant species. A loss of specialist pollinators such as these could have severe consequences for the plants that rely on their services. We therefore aimed to answer the following question: are orchid bees useful indicators of the impacts of human disturbance? If so, what measures of orchid bee diversity are most sensitive? And do orchid bees provide any indication of changes in pollination services along a disturbance gradient? Orchid bees were collected from 18 sites across a gradient of disturbance in a tropical forest region in southeast Peru. Alpha diversity across the gradient was compared using Hills numbers. Beta diversity was assessed using community composition, species contributions to beta diversity, beta diversity partitioning and novel measures of redundancy and representativeness. The potential pollination services available at each site were measured using artificial flowers and counts of pollinator visits. Alpha diversity of orchid bees showed low sensitivity to disturbance. Beta diversity measures were more informative, with disturbed sites found to be highly redundant in the ecosystem compared to the less disturbed sites. However, the most sensitive measure across the gradient was abundance – there was a significant decrease in the number of bees caught as disturbance increased, with likely consequences for pollination services. These results suggest that orchid bees may be useful indicators of the impacts of human disturbance, but alpha diversity is a poor metric for this purpose. In order to understand how human disturbance is affecting biodiversity, multiple diversity indices should be considered, and in the case of orchid bees, redundancy and abundance could be useful for detecting sensitive responses to forest disturbance.

Seasonal patterns in hydrochemical mixing in three Great Lakes rivermouth ecosystems

Rivermouth ecosystems in the Laurentian Great Lakes represent complex hydrologic mixing zones where lake and river water combine to form biologically productive areas that are functionally similar to marine estuaries. As urban, industrial, shipping, and recreational centers, rivermouths are the focus of human interactions with the Great Lakes and, likewise, may represent critical habitat for larval fish and other biota. The hydrology and related geomorphology in these deltaic systems form the basis for ecosystem processes and wetland habitat structure but are poorly understood. To this end, we examined hydrogeomorphic structure and lake-tributary mixing in three rivermouths of intermediate size using water chemistry, stable isotopes, and current profiling over a five-month period. In rivermouths of this size, the maximum depth of the rivermouth ecosystem influenced water mixing, with temperature-related, density-dependent wedging and layering that isolated lake water below river water occurring in deeper systems. The inherent size of the rivermouth ecosystem, local geomorphology, and human modifications such as shoreline armoring and dredging influenced mixing by altering the propensity for density differences to occur. The improved scientific understanding and framework for characterizing hydrogeomorphic processes in Great Lakes rivermouths across a disturbance gradient is useful for conservation, management, restoration, and protection of critical habitats needed by native species.

Soil physiochemical properties and landscape patterns control trace metal contamination at the urban-rural interface in southern China

This study examined the influences of three subsets of environmental factors (i.e. soil physicochemical properties including pH, organic matters and soil texture, landscape patterns, and parent materials) on the spatial variations and sources of soil trace metal contamination across an urban-rural environmental gradient in Guangzhou City, southern China. We collected 318 surface soil samples from forests, orchards, farmlands, and urban lawns using a random tessellation design for selecting sample sites. The geo-accumulation indices showed that 18%–88% of soil samples were contaminated: moderate to high contamination with Cd and Hg, low to moderate contamination with Cu, Pb, Zn and Ni, and low contamination with As and Cr. However, less than 13% of soil samples were considered to have exceeded the national standards causing environmental and human health concerns. The mean geo-accumulation indices increased in the order of forest, paddy field/orchard, vegetable, road/residential, and park/residential areas for As, Cd, Ni, Pb, Zn, closely following a land disturbance gradient. Spearman Correlation and Cluster Analyses showed that Pb-Cu-Zn had traffic-related origins, Cd-Hg were mainly influenced by fertilization or industrial emissions, and As-Cr-Ni had geogenic origins for agricultural soils. In contrast, the Ni, Hg and Cd contamination sources for urban soils included both anthropogenic and geogenic origins. The Stepwise Regression and Partial Redundancy Analyses showed that three subsets of environmental factors explained 43%–87% of variations of soil contamination for both agricultural and urban soils. We concluded that soil contamination was mainly controlled by soil physiochemical properties followed by landscape patterns. Soil absorption of aerial loads of trace metal pollutants dominated the soil contamination processes. Our findings implied that improving soil physiochemical properties and landscape designs can strengthen environmental buffering and carrying capacity, thus alleviating soil contamination and reducing non-point-source pollution in the study region.

Influence of grazing intensity on patterns and structuring processes in plant–pollinator networks in a subtropical grassland

Understanding how disturbances influence interaction networks is a central but still poorly explored issue in ecology and management. The goal of this study was to test how the structure of plant–pollinator networks and the structuring processes are influenced by grazing in a subtropical grassland community on the southern hemisphere. Twelve sampling plots were allocated in order to cover a grazing gradient ranging from overgrazed to ungrazed sites. For each plot, we created a quantitative matrix containing all observed pairwise insect–plant interactions and described morphology, phenology and abundances of each species. We fitted a series of models to test the influence of grazing intensity on metrics describing networks structure. We finally used probabilistic matrices, maximum likelihood and model selection to investigate the processes influencing frequencies of interactions across the gradient of disturbance. Grazing intensity influenced connectance, specialization and interaction evenness, while the number of species and links, nestedness and modularity were less variable. Species abundance was the most important determinant of interaction frequencies regardless of grazing intensity. In contrast to northern hemisphere pollination networks studied so far, these subtropical plant–pollinator networks and their structuring processes were remarkably consistent along the grazing gradient. We argue that this results from the dominance of generalist Asteraceae species, which are selectively avoided by cattle and play a core role in attracting a wide range of pollinators and thereby structuring plant–pollinator interactions, providing therefore stability.

Distribution and habitat characteristics of the Troidine butterfly community in the Western Ghats, a biodiversity hotspot in India

Investigation on the distribution patterns and habitat requirements of the butterfly tribe, Troidini was carried out in undisturbed forest habitats and disturbed, human-modiûed habitats in the Western Ghats, a biodiversity hotspot in south India. Compared various ecological and biological traits of the four species of this group which included a CITES (Convention on International Trade in Endangered Species of Wild Fauna and Flora) listed species, Troides minos Cramer, an endemic species Pachliopta pandiyana Moore, a protected species, Pachliopta hector Fabricius and Pachilopta aristolochiae Linnaeus. Comparisons were based on transect counts conducted at 66 transects in 22 locations covering six types of habitat systems with a gradient of disturbance and management regimes during 2009 and 2010. Results indicated that P. aristolochiae was the most widely distributed species occurring in 90% of the transects sampled and P. pandiyana had a restricted distribution (36 %), while both P. hector and T. minos were observed in 73% of the transects. Sampling of the juveniles on the six species of host plants in the various habitats provided insights into host plant partitioning between these species in the different habitats. Life history traits and morphological characteristics of adult troidines, larval host plant characteristics and habitat characteristics were evaluated and characterized.

Forest degradation and biomass loss along the Choc\xf3 region of Colombia

BackgroundWet tropical forests of Chocó, along the Pacific Coast of Colombia, are known for their high plant diversity and endemic species. With increasing pressure of degradation and deforestation, these forests have been prioritized for conservation and carbon offset through Reducing Emissions from Deforestation and forest Degradation (REDD+) mechanisms. We provide the first regional assessment of forest structure and aboveground biomass using measurements from a combination of ground tree inventories and airborne Light Detection and Ranging (Lidar). More than 80,000 ha of lidar samples were collected based on a stratified random sampling to provide a regionally unbiased quantification of forest structure of Chocó across gradients of vegetation structure, disturbance and elevation. We developed a model to convert measurements of vertical structure of forests into aboveground biomass (AGB) for terra firme, wetlands, and mangrove forests. We used the Random Forest machine learning model and a formal uncertainty analysis to map forest height and AGB at 1-ha spatial resolution for the entire pacific coastal region using spaceborne data, extending from the coast to higher elevation of Andean forests.ResultsUpland Chocó forests have a mean canopy height of 21.8 m and AGB of 233.0 Mg/ha, while wetland forests are characterized by a lower height and AGB (13.5 m and 117.5 Mg/a). Mangroves have a lower mean height than upland forests (16.5 m), but have a similar AGB as upland forests (229.9 Mg/ha) due to their high wood density. Within the terra firme forest class, intact forests have the highest AGB (244.3 ± 34.8 Mg/ha) followed by degraded and secondary forests with 212.57 ± 62.40 Mg/ha of biomass. Forest degradation varies in biomass loss from small-scale selective logging and firewood harvesting to large-scale tree removals for gold mining, settlements, and illegal logging. Our findings suggest that the forest degradation has already caused the loss of more than 115 million tons of dry biomass, or 58 million tons of carbon.ConclusionsOur assessment of carbon stocks and forest degradation can be used as a reference for reporting on the state of the Chocó forests to REDD+ projects and to encourage restoration efforts through conservation and climate mitigation policies.

Biosphere reserve zones are equal in terms of katydid ecoacoustics

ABSTRACTGlobally, biosphere reserves (BRs) conserve biodiversity across a gradient of human disturbance, yet there is very little empirical research investigating the effectiveness of BRs. The aim here is to compare katydid song diversity and abundance across the three zones of the Kogelberg BR using acoustic monitoring techniques. An index of Acoustic Activity was used to determine katydid abundances from recordings. Only eight katydid species were recorded over the entire summer season, with the species accumulation curve reaching an asymptote. Katydid diversity and abundances were very similar across the three zones. Habitat quality had a greater effect on abundance than on species richness. No single katydid species was identified as a bioindicator, rather the entire assemblages are responsive to habitat quality. The low diversity of katydids relative to other biomes and to other insects within the KBR appears to come from a long history of fire and extreme weather events, as is the case for other vegetation dependent insect taxa in the region. While we expect lower biodiversity away from the BR core zone, some groups, like these katydids, are maintained equally well in the three zones, and have not to date been adversely affected by human activity.

Carbon stocks and factors affecting their storage in dry Afromontane forests of Awi Zone, northwestern Ethiopia

BackgroundTropical montane forests played an important role in the provision of ecosystem services. The intense degradation and deforestation for the need of agricultural land expansion result in a significant decline of forest cover. However, the expansion of agricultural land did not completely destruct natural forests. There remain forests inaccessible for agricultural and grazing purpose. Studies on these forests remained scant, motivating to investigate biomass and soil carbon stocks. Data of biomass and soils were collected in 80 quadrats (400 m2) systematically in 5 forests. Biomass and disturbance gradients were determined using allometric equation and disturbance index, respectively. The regression modeling is employed to explore the spatial distribution of carbon stock along disturbance and environmental gradients. Correlation analysis is also employed to identify the relation between site factors and carbon stocks.ResultsThe result revealed that a total of 1655 individuals with a diameter of ≥ 5 cm, representing 38 species, were measured in 5 forests. The mean aboveground biomass carbon stocks (AGB CS) and soil organic carbon (SOC) stocks at 5 forests were 191.6 ± 19.7 and 149.32 ± 6.8 Mg C ha−1, respectively. The AGB CS exhibited significant (P < 0.05) positive correlation with SOC and total nitrogen (TN) stocks, reflecting that biomass seems to be a general predictor of SOCs. AGB CS between highly and least-disturbed forests was significantly different (P < 0.05). This disturbance level equates to a decrease in AGB CS of 36.8% in the highly disturbed compared with the least-disturbed forest. In all forests, dominant species sequestrated more than 58% of carbon. The AGB CS in response to elevation and disturbance index and SOC stocks in response to soil pH attained unimodal pattern. The stand structures, such as canopy cover and basal area, had significant positive relation with AGB CS.ConclusionsStudy results confirmed that carbon stocks of studied forests were comparable to carbon stocks of protected forests. The biotic, edaphic, topographic, and disturbance factors played a significant variation in carbon stocks of forests. Further study should be conducted to quantify carbon stocks of herbaceous, litter, and soil microbes to account the role of the whole forest ecosystem.

Carbon and Nitrogen Responses in Litterfall and Litter Decomposition in Red Pine (Pinus densiflora S. et Z.) Stands Disturbed by Pine Wilt Disease

Research Highlight: Forest disturbance by insects or disease can have a significant influence on nutrient return by litterfall and decomposition, but information regarding disturbance gradients is scarce. This study demonstrated that the disturbance intensity caused by pine wilt disease greatly altered the quality and quantity of carbon (C) and nitrogen (N) in litterfall components and decomposition processes. Background and Objectives: This study was conducted to evaluate the C and N status of litterfall and litter decomposition processes in a natural red pine (Pinus densiflora S. et Z.) stand disturbed by pine wilt disease in southern Korea. Nine red pine plots with varying degrees of disturbance caused by pine wilt disease were established based on differences in the stand basal area. Litterfall and the decomposition of needle litter and branches under different degrees of disturbance were measured for three years. Results: There was a significant correlation (p &lt; 0.05) between disturbance intensity and the C and N concentration of litterfall components depending on the time of sampling. The annual C and N inputs through litterfall components decreased linearly with decreasing disturbance intensities. The decomposition rates of branches were higher in slightly disturbed plots compared with severely disturbed plots for the late stage of branch decomposition, whereas the decomposition rates of needle litter were not affected by the disturbance intensity of pine wilt disease. Carbon and N concentrations from needle litter and branches were not linearly related to the intensities of disturbance, except for the initial stage (one year) of needle litter decomposition. Conclusions: The results indicated that the incidence of pine wilt disease was a major cause of C and N loss through litterfall and decomposition processes in pine wilt disease disturbed stands, but the magnitude of loss depended on the severity of the disease disturbance.