Nutrient and metal concentrations in nepenthes macfarlanei hemsl. (nepenthaceae) from a malaysian montane forest

Palaeotropical pitcher plants (Nepenthes) are a fascinating evolutionary case but their nutrient relationships are poorly known. To determine nutrient and metal concentrations in Nepenthes macfarlanei from Peninsular Malaysia, and contribute to our understanding of nutrient relationships in this genus, plants were sampled from the Genting Highlands – a disturbed montane forest location. Whilst many foliar nutrients showed typical concentrations, the foliar N concentration was, surprisingly, greater than most lowland species although the N:P ratio (c. 24) indicated nitrogen limitation in line with other studies on Nepenthes. Of particular note was the variable but high (< 240 µg g-1) lead concentrations that have not been reported in carnivorous plants before. This data adds to our understanding of the nutrient relationships of carnivorous plants and shows that they may accumulate high concentrations of certain metals

Geo-ecological studies on two ultramafic sites in western Ireland

© 2018, The Ecological Society of Japan. Ultramafic soils are found in many sites around the world where they can vary from exceptionally barren to reasonably fertile. Two ultramafic sites in western Ireland were studied: grassland at Dawros, County Galway and grassy heath near the base of Croagh Patrick, County Mayo. Rock and soil chemistry was examined along with foliar nutrients (at Dawros only). Ellenberg reaction values of all plant species recorded were determined. Two bioassays were conducted to determine relative differences in fertility between ultramafic and adjacent non-ultramafic soils and to assess nutrient limitation in the Croagh Patrick soil. Both soils showed many of the chemical characteristics typical of other ultramafic sites including a moderately high nickel concentration; in general, soil metal concentrations were higher in Dawros soils. However, nitrogen, phosphorus and calcium (with a calcium:magnesium ratio c. 0.6) were all at high concentrations at Dawros leading to a fertile grassland with both calcicole and calcifuge species present spanning six Ellenberg reaction values. Foliar nutrient concentrations were not unusual although calcium:magnesium ratios were approximately double in non-ultramafic soils compared to ultramafic soils. Croagh Patrick soil had lower concentrations of most nutrients and presented a grassy heath vegetation with more acidic reaction values. The bioassays showed plant growth to be reduced in this soil relative to that at Dawros and to be clearly limited by phosphorus availability. Whilst these two Irish ultramafic sites do not show the extreme features associated with other sites across the world they indicate the global diversity of serpentine ecologies

Ectomycorrhizal Associations of the Dipterocarpaceae

Dipterocarps are one of the most important tree families in the lowland forests of Southeast Asia and are somewhat unusual among tropical trees in that they form ectomycorrhizal (EcM) symbiotic root-inhabiting fungal associations. It has been hypothesized that dipterocarps have been partnered in this mutualistic association prior to the separation of Gondwana. Under many conditions EcMs form rapidly on dipterocarp seedlings through inocula present in the soil, although few studies have been conducted to provide evidence that they improve seedling establishment and performance. There are hundreds of EcM species associated with dipterocarps. Fungal fruit body surveys suggest that the most important families are Amanitaceae, Boletaceae, and Russulaceae, although Thelephoraceae also become numerically important when root tips are examined. EcM communities are affected by various biotic and abiotic factors, as well as anthropogenic perturbations, and the importance of these in structuring EcM communities is examined herein. © 2012 The Author(s). Journal compilation © 2012 by The Association for Tropical Biology and Conservation

Providing students with formative audio feedback

The provision of timely and constructive feedback is increasingly challenging for busy academics. Ensuring effective student engagement with feedback is equally difficult. Increasingly, studies have explored provision of audio recorded feedback to enhance effectiveness and engagement with feedback. Few, if any, of these focus on purely formative audio feedback on draft submissions of written assignments. This study encouraged a cohort of 40 students to submit drafts of written assignments, two weeks before formal submission, in order to receive audio recorded feedback. Nearly half the cohort either did not submit drafts or submitted only brief outlines. The level of draft completeness impacted on the characteristics of the lecturer's feedback. While students receiving audio feedback gained significantly higher marks for finished work, this cannot be directly attributed to receipt/use of feedback as analysis suggests generally more able students are more likely to submit more complete drafts, which leads us to ask the question, are we simply helping better students to perform even better? Audio feedback was reported as clear, engaging and helpful; however, timing of feedback (before formal submission) may be of greater importance in terms of impact on attainment than the audio format. We suggest a model that focuses efforts on formative feedback (in advance of formal submission) and selective provision of summative feedback (targeted feed forward). © 2013 G. Scott, The Higher Education Academy

Fine root and soil nitrogen dynamics during stand development following shifting agriculture in Northeast India

Nitrogen (N) dynamics during changes in land use patterns in tropical forests may profoundly affect fine root dynamics and nutrient cycling processes. Variations in fine root biomass and soil N dynamics were assessed in developing stands of increasing ages following shifting agriculture in Mizoram, Northeast India, and comparisons were made with a natural forest stand. Concentrations of soil available N (NH4-N and NO3-N) and the proportion of NH4-N in total available N increased with stand age. The N-mineralization rate also increased with stand age whilst the proportion of nitrification relative to ammonification declined during succession. Fine root biomass and N-mineralization increased, and available N decreased during the monsoon season while this pattern was reversed during the winter season. A greater proportion of fine roots were <0.5 mm diameter in the younger sites, and turnover of fine roots was more rapid in the developing stands compared to the natural forest. Fine root biomass was correlated positively with N-mineralization rate and soil water content. Thus, it can be concluded that the fine root growth was aided by rapid N-mineralization, and both fine root growth and N-mineralization increase as stands redevelop following shifting cultivation disturbance

Changes in soil exchangeable nutrients across different land uses in steep slopes of Mizoram, north-east India

Land use change resulting from anthropogenic pressure on land has led to degraded soil quality, especially in the hilly tropical regions where ecosystems are generally fragile and susceptible to soil degradation from cultivation. Hence, sustainable land uses and management practices are crucial for agricultural production and ecological balance, particularly in these regions. The present study investigates the impact of various hill land uses (Natural forest-NAF, Jhum fallow-JF, Home garden-HG, Acacia pennata plantation-AP and Current Jhum-CJ) on soil exchangeable nutrients in steeply sloping agro-ecosystems of Mizoram, North-east India. Soil samples were collected from three different depths (0-10, 10-20 & 20-30 cm) and analyzed for pH, Pavail, Na, K, Mg, Mn and Ca. Our results indicated that land use and soil depths had a significant impact on soil pH, Pavail and soil exchangeable cations (p12 years) led to increases in soil available nutrients indicating the role of vegetation cover in conserving and enhancing soil available nutrients and vice-versa. In addition, Home garden (HG) showed moderately higher available soil nutrients signifying the role of sustainable management practices such as the addition of organic amendments and mixed cropping, leading to increased soil available nutrient content

Soil characteristics influence species composition and forest structure differentially among tree size classes in a Bornean heath forest

© 2019, Springer Nature Switzerland AG. Background and aims: Whilst several studies have shown that edaphic variability influences species composition in nutrient-poor tropical forests, the determinants of local species distributions and, in particular, how these change from younger to mature individuals in such forests are still under debate, and have been poorly explored in tropical heath forests that are among the least fertile tropical forest ecosystems. Methods: We investigated the influence of soil fertility and topography on a Bornean heath forest species composition, α-, β-diversity and tree size structure among size classes by recording all trees ≥1 cm DBH in 16 forest plots totalling 0.36 ha. Results: Tree species distributions generally followed gradients in available Al and soil depth; α- and β-diversity were linked to soil depth, and to some extent also to pH and the H:Al ratio. In contrast, forest structural attributes (basal area and stem density) were negatively correlated with both available and total P and a wider suite of soil nutrients, although trees ≥10 cm DBH were positively correlated with total P. Conclusion: Our study shows that heath forest species distribution, richness and structure is related to both edaphic and topographic characteristics and that soil acidity might have a strong influence in shaping these forests’ features. Among size classes, small trees are less influenced by soil and topography, whereas the sensitivity to these variables increases with tree size. We thus highlight that multiple edaphic factors influence different aspects of tropical forest structure, including different tree life stages, and species composition

Secondary Succession after Slash-and-Burn Cultivation in Papuan Lowland Forest, Indonesia

Papuan forests have been subjected to shifting cultivation for centuries by indigenous people affecting the ecological processes therein; during secondary succession, fallow forests recover naturally. However, the information on ecological succession after swidden practices remains poorly understood in Papuan lowland forests. This study aimed to examine the plant species richness and density of different plant lifeforms in fallows of increasing time after slash-and-burn cultivation along with basic edaphic factors. We performed data collection in the northern part of the lowland evergreen tropical forest near Manokwari, West Papua, Indonesia. The sampling consisted of 26 plots distributed in the primary forest (n = 6) and in secondary/fallow forests 2-, 4-, 7-, and 9-years after cultivation (n = 5 for each age class). The plant community in primary forest clearly differed from the secondary forests. The plant species richness was about twice as high in primary compared to secondary forests. The density of trees and shrubs increased during succession whereas that of lianas declined. The soil fertility declined in secondary forests, although soil organic matter was greatest two years after swidden and then decreased gradually over time. This research underlined that indigenous swidden practices alter ecological conditions and that secondary forests will take a long time to fully recover to resemble primary forest. Hence, the monitoring of vegetation during the process is necessary to inform conservation programs

Differences in soil properties among contrasting soil types in Northern Borneo

Soil in the tropics is high in diversity, and despite the diversity of Borneo's forest-soil associations, there is a paucity of data on its soil properties. We investigated the differences between three soil types in the Kabili-Sepilok Forest Reserve, Sabah, Malaysia, encompassing the contrasting alluvial, sandstone and heath forest typologies. We examined the distribution of nutrients between soil types and through soil depths, and assessed the extent of spatial autocorrelation in the three soil types. We confirmed the fertility gradient from alluvial to heath forest soil found by others. Soil elemental concentrations declined in deeper horizons with the exception of exchangeable sodium and aluminium that remained constant through alluvial and sandstone soil profiles. Spatial autocorrelation was present in all three soil types and strongest in the sandstone soil. Overall, we show how bedrock, erosion, leaching and topography influence soil properties across this mosaic of soil types and note their importance in influencing tree communities and their ecological functioning