Tree Saplings Research Articles

Response of Rubber Tree Saplings to Dolomite and Kieserite Application and K:Mg Ratio

This study aimed to examine the effect of the application of dolomite and kieserite on the growth and nutrient uptake of rubber tree saplings and the relationship between K:Mg ratios in soils and nutrient uptake. The experiment followed a completely randomized design with five replicates. Budded stumps of RRIM 600 rubber were planted in soil with low extractable Mg (< 0.30 cmolc kg-1). Kieserite application at a rate of 0.5 cmolc Mg kg-1 significantly promoted the greatest sapling height, stem diameter, Mg and S concentrations, and leaf chlorophyll levels. High kieserite application rates (1.0 cmolc Mg kg-1) were more likely to decrease K and N uptake significantly. Applying dolomite (0.5 cmolc Mg kg-1) also significantly increased rubber growth compared with the control treatment but the significant increases were lower than those for kieserite application. Applying K at 72, 108, and 180 mg kg-1 significantly increased leaf K concentration, but significantly decreased Mg concentrations. Therefore, rubber plantations should apply Mg at a rate of 0.5 cmolc Mg kg-1 in the form of kieserite, and a ratio of K:Mg 2:1 is suitable for promoting rubber tree growth.

Fire‐ and herbivory‐driven consumer control in a savanna‐like temperate wood‐pasture: An experimental approach

Abstract Fire and herbivory are fundamental top‐down processes, structuring grass–tree ratios in ecosystems across a diversity of climates. Both are plant consumers that can strongly control the recruitment of woody seedlings and saplings to taller height classes. Without consumer control, many grass‐dominated ecosystems would convert into woodlands or forests. While extensively studied in savannas, few have explored the effects of these disturbance regimes on woody recruitment under temperate conditions. We exposed saplings of five common European tree species to fire and herbivory in a full factorial experiment in a savanna‐like wood‐pasture. After 3 years, we evaluated the effects of fire and herbivory on tree sapling survival and height increment. The tree species used, varying in traits and in expected response to fire and herbivory, were Scots pine Pinus sylvestris, Norway spruce Picea abies, European oak Quercus robur, Silver birch Betula pendula and Small‐leaved lime Tilia cordata. Fire and herbivory had a negative effect on sapling survival for all species except for Q. robur, which was not affected by fire. Both processes reduced height increment of B. pendula, while only herbivory reduced the height increment of P. sylvestris and Q. robur. At the same time, B. pendula and P. sylvestris had some of the highest increments, together with P. abies, which had unaffected height increment in all treatments. T. cordata, on the other hand, had a negative height increment across all treatments. Overall, the combined effect of fire and herbivory was similar to the effect of herbivory alone on both survival and height increment, indicating no additional effect of fire when herbivores were present. Synthesis. Our experiment showed how fire and herbivory can strongly affect the recruitment of European temperate tree saplings on a wood‐pasture, potentially leading to comparable consumer control described for ecosystems elsewhere (e.g. savannas). Two strategies to deal with fire and herbivory were identified: tolerance (Q. robur) and avoidance (P. sylvestris and B. pendula). We conclude that both fire and herbivory may have been important drivers of structure and species composition in open ecosystems in temperate Europe in the past.

Association between native tree sapling and spiny shrub mitigates browsing damage produced by large herbivores in fire-degraded forests

Spiny shrubs can generate positive interactions with palatable trees in sites affected by abiotic and biotic stress (e.g. fire, and consumption by herbivores). The objective of this study was to assess the role of native shrubs (Berberis microphylla) in mitigating large herbivore browsing on tree saplings (Nothofagus antarctica) in degraded (burnt) forests of the central area of Tierra del Fuego, Argentina. For that, we assessed, in 16 forest sites, the browsing intensity and the browsing height in N. antarctica saplings that were alone (n = 10 per site), and in saplings that were spatially associated with B. microphylla shrubs (n = 10 per site). The tree and shrub height were also measured. The results indicated that browsing damage on ñire trees occurred at a higher height and with lower intensity in the tree-shrub association than in trees that were alone. Furthermore, the browsing height was positively related with the shrub height and with the tree height. The shorter trees with greater shrub cover were more protected. Our results indicate that the presence of spiny shrubs decreases the damage caused by browsing, and protects trees during the early regeneration stage. However, the structural characteristics of shrubs are determinant of the protecting effect in these Patagonian forests. This tree-shrub interaction is highly relevant in the dynamics of degraded forests to ensure the system continuity in ecological and productivity terms.

Forest resilience to global warming is strongly modulated by local‐scale topographic, microclimatic and biotic conditions

Abstract Resilience of endangered rear edge populations of cold‐adapted forests in the Mediterranean basin is increasingly altered by extreme heatwave and drought pressures. It remains unknown, however, whether microclimatic variation in these isolated forests could ultimately result in large intra‐population variability in the demographic responses, allowing the coexistence of contrasting declining and resilient trends across small topographic gradients. Multiple key drivers promoting spatial variability in the resilience of rear edge forests remain largely unassessed, including amplified and buffered thermal exposure induced by heatwaves along topographic gradients, and increased herbivory pressure on tree saplings in defaunated areas lacking efficient apex predators. Here we analysed whether indicators of forest resilience to global warming are strongly modulated by local‐scale topographic, microclimatic and biotic conditions. We studied a protected rear edge forest of sessile oak Quercus petraea, applying a suite of 20 indicators of resilience of tree secondary growth, including multidecadal and short‐term indices. We also analysed sapling recruitment success, recruit/adult ratios and sapling thermal exposure across topographic gradients. We found large within population variation in secondary growth resilience, in recruitment success and in thermal exposure of tree saplings to heatwaves, and this variability was spatially structured along small‐scale topographical gradients. Multidecadal resilience indices and curves provide useful descriptors of forest vulnerability to climate warming, complementing assessments based in the analysis of short‐term resilience indicators. Species‐specific associations of trees with microclimatic variability are reported. Biotic factors are key in determining long‐term resilience in climatically stressed rear edge forests, with strong limitation of sapling recruitment by increased roe deer and wild boar herbivory. Our results also support non‐stationary effects of climate determining forest growth responses and resilience, showing increased negative effects of warming and drought over the last decades in declining stands. Synthesis. Our findings do not support scenarios predicting spatially homogeneous distributional shifts and limited resilience in rear edge populations, and are more supportive of scenarios including spatially heterogeneous responses, characterised with contrasting intra‐population trends of forest resilience. We conclude that forest resilience responses to climate warming are strongly modulated by local‐scale microclimatic, topographic and biotic factors. Accurate predictions of forest responses to changes in climate would therefore largely benefit from the integration of local‐scale abiotic and biotic factors.

The response of the invasive princess tree (Paulownia tomentosa) to wildland fire and other disturbances in an Appalachian hardwood forest

This study examined the response of princess tree (Paulownia tomentosa) to different disturbances and its potential to spread throughout its current range in the U.S. The study was established in Shawnee State Forest in southern Ohio, USA, which has historically experienced disturbances from mining, logging, ice storms and wildfire. Plots were established for vegetation sampling where fire had occurred with and without princess tree present, and where no fire had occurred with and without princess tree present. To determine the influence of disturbance types on the density of princess tree, redundancy analysis (RDA) was used. High stem density of princess tree seedlings occurred in areas that experienced high fire intensities and herbicide treatment. Seedlings on southwest slopes increased in abundance as the time from the last logging activity increases. Princess tree saplings were present in greater densities in areas that experienced medium fire intensities and the highest ice storm damage. Sapling density is greatest as ground cover and vegetation height increases and slope decreases. Princess trees reach maximum stem density on northeast slopes in areas not impacted by the 2009 fire. All disturbances considered, including wildfire, have created conditions conducive to princess tree growth and expansion into forest areas.

Drought stress recovery of hydraulic and photochemical processes in Neotropical tree saplings.

Climate models predict an increase in the severity and the frequency of droughts. Tropical forests are among the ecosystems that could be highly impacted by these droughts. Here, we explore how hydraulic and photochemical processes respond to drought stress and re-watering. We conducted a pot experiment on saplings of five tree species. Before the onset of drought, we measured a set of hydraulic traits, including minimum leaf conductance, leaf embolism resistance and turgor loss point. During drought stress, we monitored traits linked to leaf hydraulic functioning (leaf water potential (ψmd) and stomatal conductance (gs)) and traits linked to leaf photochemical functioning (maximum quantum yield of photosystem II (Fv/Fm) and maximum electron transport rate (ETRmax)) at different wilting stages. After re-watering, the same traits were measured after 3, 7 and 14days. Hydraulic trait values decreased faster than photochemical trait values. After re-watering, the values of the four traits recovered at different rates. Fv/Fm recovered very fast close to their initial values only 3 days after re-watering. This was followed by ETRmax, Ψmd and gs. Finally, we show that species with large stomatal and leaf safety margin and low πtlp are not strongly impacted by drought, whereas they have a low recovery on photochemical efficiency. These results demonstrate that πtlp, stomatal and leaf safety margin are a good indicators of plant responses to drought stress and also to recovery for photochemical efficiency.

A 17 year successional enrichment plantation of tree recruitment and restoration in a tropical rainforest forest

The Enrichment Plantation of Akure Forest Reserve is one of the forests currently experiencing a17-year-long post-disturbance following deforestation and fragmentation in the country. To better understand the contribution of enrichment planting on forest regeneration and restoration, the Enrichment Plantation after 17 years of post-disturbance was examined. We studied the recruitment drive of aboveground and underbrush stands of an Enrichment plantation in a tropical forest. We assess the trees diversity, species compositions, species richness, and growth forms of the vegetations. A total of 3 (50 m × 50 m) plots were sampled with a total of 47 aboveground tree species and 45 underbrush stands from Enrichment plantation were identified. The result shows an increase in the diversity and an even distribution of the species of the aboveground forest trees, compared to the underbrush stands. Conversely, the aboveground forest trees have lower species richness as compared to the level of underbrush stands. The sapling density was significantly higher than the aboveground tree of the forest (one-way ANOVA: P < 0.05 and P = 0.000). The mean ± standard deviation of 2.41 ± 1.55 aboveground tree species was extremely low to what was obtained of tree sapling (17.55 ± 8.06) in the forest structure. It was also observed that the aboveground forest trees and underbrush stands are somewhat similar in species compositions, which implies that sapling recruitment is a key determinant of the tree species composition of the forest. It is then concluded that the method adopted for restoration encouraged species diversity in this successional forest among the aboveground trees species and underbrush.

Olfactory cues of large carnivores modify red deer behavior and browsing intensity.

This study examined the effect of perceived predation risk imposed by lynx (Lynx lynx) and wolf (Canis lupus) on red deer (Cervus elaphus) foraging behavior under experimental conditions. We hypothesized that in response to large carnivore scent red deer would increase their vigilance, although reducing the frequency and duration of visits to foraging sites. Consequently, browsing intensity on tree saplings was expected to decrease, whereas a higher proportion of more preferred species was expected to be browsed to compensate for higher foraging costs. We expected stronger responses towards the ambush predator lynx, compared with the cursorial predator wolf. These hypotheses were tested in a cafeteria experiment conducted within three red deer enclosures, each containing four experimental plots with olfactory cues of wolf, lynx, cow, and water as control. On each plot, a camera trap was placed and browsing intensity was measured for one consecutive week, repeated three times. Red deer reduced their visitation duration and browsing intensity on plots with large carnivore scent. Despite red deer showing a clear preference for certain tree species, the presence of large carnivore scent did not change selectivity towards different tree species. Contrary to our hypothesis, we found more pronounced effects of wolf (cursorial) compared with lynx (ambush). This study is the first to experimentally assess the perceived risk effects on the red deer foraging behavior of large carnivores differing in hunting modes. Our findings provide insights into the role of olfactory cues in predator–prey interactions and how they can modify fine-scale herbivore–plant interactions.

Frost hinders the establishment of trees in highland grasslands in the Atlantic Forest ecotone region of southern Brazil

AbstractQuestionsCold temperatures and freezing may hinder the process of forest expansion in moist climate regions, as predicted by the frost hypothesis. We examined the role of frost on the survival and regrowth of tree saplings under field conditions of open grasslands.LocationCambará do Sul, Rio Grande do Sul.MethodsWe established a field experiment protecting one of two groups of saplings of forest species from frost in grassland areas during the winter. We monitored 672 saplings from a total of seven species for 56 days. Saplings were brought back to the laboratory to evaluate regrowth rate and height. Survival curves of the two groups were compared using a Kaplan–Meier estimator. Correlation analysis was undertaken to estimate the relationship between survival and regrowth rate and a variance analysis was used to compare plant height between both groups.ResultsSpecies respond distinctly to frost incidence, with some not being affected by frost (two gymnosperms andMyrcianthes pungens). Most protected saplings had a higher above‐ground survival rate than unprotected ones (96.4% and 73.2%, respectively). Moreover, saplings that were damaged by frost showed differences in regrowth and height according to species identity, notwithstanding the fact that those from protected plots showed higher regrowth and height (88% and 25.65 cm compared to 68% and 17.15 cm).ConclusionsOur results showed clear negative effects of frost on the survival rate of aerial parts of saplings during the winter and the regeneration of damaged plants. Species‐specific traits can offer frost resistance; however, together with other disturbances, frost may hinder the establishment of forest trees over grassland areas where frost events are common during the winter.

The anniversary conference "Structural Components of Forest Ecosystems: ecology, conservation and management" held in honour of Prof. Nicolae Donita

The anniversary conference "Structural Components of Forest Ecosystems: ecology, conservation and management" held in honour of Prof. Nicolae Donita

Coffee income and its determinants: A case of Deusa village, Nepal

Understanding economic contribution of coffee production and influencing socioeconomic and environmental factors for coffee income are vital for its promotion. The primary aim of this study was therefore to assess the contribution of coffee income to the household total cash income and identify influencing socioeconomic and environmental factors for coffee income in Deusa, Solukhumbu district of Nepal. A semi-structured questionnaire survey gather data from 55 coffee-growing households. We used Ordinary Least Square regressions (OLS) for identifying influencing factors for coffee income. Household annual gross income, from farm and off-farm income sources, estimated was around NPR 161 thousand, and the median value was 57.4 thousand. On average, coffee farming contributed almost 9% of the total household income in the study area. The OLS regression showed that sufficient labor availability (p&lt;0.05), access to coffee-related trainings (p&lt;0.05), and access to irrigation facilities (p&lt;0.05) significantly increased coffee earnings. Likewise, environmental variables - elevation (negatively, p&lt;0.05) and shade trees availability for coffee farming (positively, p&lt;0.05) also influenced earnings from the coffee farming. We recommend provisions of trainings, improved irrigation facilities and tree saplings for shade management for sustainable coffee production in the study area.

Managing climate change microrefugia for vascular plants in forested karst landscapes

Microrefugia are small areas that support favourable climate and allow species to persist during regional and global climate changes. Dolines in karst landscapes may provide such areas for many climate change-vulnerable species. Here we provide a better understanding on how plant species indicate changes in their environment (temperature, soil moisture and light availability) after a few years of partial canopy removal from dolines and their close surroundings (logged areas: >1 ha). We place our results in the context of the most widely used forest management practices within the study area (Mecsek Mts, Hungary), in addition to presenting a general framework for the maintenance of doline microrefugia in forested karst landscapes. Three types of habitats were investigated: dolines before logging, dolines after logging, and the forested plateau. Three large dolines and three sites on the plateau were selected for vegetation sampling. All dolines were sampled before logging and 5–10 years after partial canopy removal. Logging resulted in a 50–80% reduction of canopy cover in the dolines and their close surroundings. We established a transect across each doline from north to south passing through doline bottoms, and across each plateau site. We estimated the percentage cover of vascular plant species (tree saplings – up to 1 m in height, shrubs and herbs) along the transects using 1 m × 1 m vegetation plots, determined the diagnostic species of the doline and plateau habitats, and used multivariate methods and linear mixed-effects models during analyses. Plant species indicated clear gradients of the main microclimatic factors within the dolines and that significant changes took place after logging. Canopy removal caused substantial changes in the main microclimatic factors of most doline microhabitats (e.g., south-facing slopes). The vegetation of the dolines before logging indicated moister conditions than that of the plateau and cooler and shadier conditions than that of the dolines after logging. These and our previous results suggest that logging may directly and indirectly influence dolines to be microrefugia under global warming. By applying our framework to refugia conservation and management for the karst landscape in the Mecsek Mts, we can conclude that the protection of old forests and natural forest dynamics in as many large dolines as possible and the implementation of close-to-nature forestry practices may be essential to maintain regional biodiversity in the long run.

Genomic Characteristics and Comparative Genomics Analysis of Two Chinese Corynespora cassiicola Strains Causing Corynespora Leaf Fall (CLF) Disease.

Rubber tree Corynespora leaf fall (CLF) disease, caused by the fungus Corynespora cassiicola, is one of the most damaging diseases in rubber tree plantations in Asia and Africa, and this disease also threatens rubber nurseries and young rubber plantations in China. C. cassiicola isolates display high genetic diversity, and virulence profiles vary significantly depending on cultivar. Although one phytotoxin (cassicolin) has been identified, it cannot fully explain the diversity in pathogenicity between C. cassiicola species, and some virulent C. cassiicola strains do not contain the cassiicolin gene. In the present study, we report high-quality gapless genome sequences, obtained using short-read sequencing and single-molecule long-read sequencing, of two Chinese C. cassiicola virulent strains. Comparative genomics of gene families in these two stains and a virulent CPP strain from the Philippines showed that all three strains experienced different selective pressures, and metabolism-related gene families vary between the strains. Secreted protein analysis indicated that the quantities of secreted cell wall-degrading enzymes were correlated with pathogenesis, and the most aggressive CCP strain (cassiicolin toxin type 1) encoded 27.34% and 39.74% more secreted carbohydrate-active enzymes (CAZymes) than Chinese strains YN49 and CC01, respectively, both of which can only infect rubber tree saplings. The results of antiSMASH analysis showed that all three strains encode ~60 secondary metabolite biosynthesis gene clusters (SM BGCs). Phylogenomic and domain structure analyses of core synthesis genes, together with synteny analysis of polyketide synthase (PKS) and non-ribosomal peptide synthetase (NRPS) gene clusters, revealed diversity in the distribution of SM BGCs between strains, as well as SM polymorphisms, which may play an important role in pathogenic progress. The results expand our understanding of the C. cassiicola genome. Further comparative genomic analysis indicates that secreted CAZymes and SMs may influence pathogenicity in rubber tree plantations. The findings facilitate future exploration of the molecular pathogenic mechanism of C. cassiicola.

The long-term development of temperate woodland creation sites: from tree saplings to mature woodlands

Abstract Tree planting is at the forefront of the current environmental agenda to mitigate climate change and tackle the biodiversity crisis. In the United Kingdom (UK), tree planting has been a priority for more than a century and has helped increase woodland cover from a historic low of 5 per cent at the beginning of the 20th century to a current figure of 13 per cent. However, we still know relatively little about the long-term development of woodland creation sites (particularly of native woodlands) over ecologically realistic timescales. We surveyed a chronosequence of 133 temperate woodland patches encompassing 106 woodland creation sites (10–160 years old) and 27 mature ‘ancient’ woodlands (&amp;gt;250 years old), using a combination of field surveys and remote sensing techniques to quantify vegetation structural changes associated with woodland development. Woodland creation sites displayed similar vegetation development patterns to those described for other woodland systems, i.e. a gradual transition as woodlands undergo ‘stand initiation’, ‘stem exclusion’ and ‘understorey re-initiation’ stages, and became more similar to ‘ancient’ woodlands over time. Structural heterogeneity, average tree size and tree density were the attributes that varied the most among woodland developmental stages. In general, structural heterogeneity and average tree size increased with woodland age, whilst tree density decreased as would be expected. Younger sites in stand initiation were strongly dominated by short vegetation, stem exclusion sites by taller trees and older sites had a more even vegetation height distribution. There was a large degree of overlap between the vegetation characteristics of woodlands in understorey re-initiation stages and older ancient woodlands (partly driven by a lack of regeneration in the understorey); these results suggest that it takes between 80 and 160 years for woodland creation sites to develop certain vegetation attributes similar to those of mature ancient woodlands included in this study. Woodland management practices to create canopy gaps and reducing grazing/browsing pressure to promote natural regeneration are likely to accelerate this transition, increase the structural heterogeneity and biodiversity value of woodland creation sites and enable adaptation and resilience to climate change.

Influence of Light and Substrate Conditions on Regeneration of Native Tree Saplings in the Hawaiian Lowland Wet Forest1

Understanding microsite preferences of species at the sapling stage is crucial for successful forest restoration, as efforts can be concentrated onto the most promising sites, and invaded sites can be manipulated toward more suitable conditions for target species. The Hawaiian Lowland Wet Forest is a highly endemic and endangered ecosystem that has received limited attention in terms of research on recruitment dynamics. Our study combined density records and sapling-based measurements within a forest reserve, an invaded forest, a traditional restoration project and a novel restoration project. We recorded substrate type, soil depth, surface roughness, and light availability for 382 saplings of the four native tree species Metrosideros polymorpha, Myrsine lessertiana, Pipturus albidus, and Psychotria hawaiiensis, and 146 spots where the target species were absent. The invaded forest had the lowest native sapling density, lower light availability, and lower surface roughness than the remaining management units. The novel restoration project had more moss/nurselog sites and higher light availability than the remaining management units. The traditional restoration project was mainly characterized by rocky substrate. Metrosideros and Pipturus showed significantly higher light demand than Myrsine and Psychotria. Pipturus was associated with rough microsites and Metrosideros with moss/nurselog substrates. Our findings suggest that restoration strategies considering manipulation of the canopy light environment and microsite preferences of target species can better facilitate native recruitment into heavily invaded forests.

The potential role of an alien tree species in supporting forest restoration: Lessons from Shiretoko National Park, Japan

Restoring forests has recently received considerable attention in the context of sequestering carbon and supporting biodiversity. Although considering alien species as a tool for natural forest restoration still remains controversial, harnessing alien species when they are already present in an ecosystem might result in overall benefits for nature and society. In this study we evaluated whether the presence of an alien tree species supports or hinders the establishment of naturally regenerating forests in Shiretoko National Park, Japan. In particular, we focused on Larix kaempferi, which is widely present yet non-native to the region, and examined how this alien species affects two factors influencing the success of restoration: wind disturbance and deer herbivory. We examined the following effects of L. kaempferi plantations on natural regeneration: (1) the windbreak function for protecting native tree growth and (2) the nursery function to promote the regeneration of native tree saplings and seedlings under high herbivory pressure. We assessed tree height and regeneration, using large-scale remotely sensed data and terrestrial inventory data in five major vegetation types. We found that L. kaempferi plantations can protect native species from predominant winds. Additionally, L. kaempferi canopy cover promoted abundance and species richness in understory saplings and seedlings compared to other vegetation types such as primary and secondary forests, even under excessive browsing pressure. No regenerating L. kaempferi individuals were observed during the field census, suggesting the species is likely not invasive in our study system. The positive relationship between alien tree species and the regeneration of native tree assemblages emphasizes that existing alien species have the potential to act as nurse plants. Our findings imply that the presence of alien species can contribute to natural forest restoration by improving the local environmental conditions for native species in the short-term. Given the multiple ecological and social needs in our changing world, careful consideration is required to evaluate the long-term consequences of alien species. Especially in ecosystems in which alien species have already established, using their positive functions rather than swiftly eradicating them from the landscape might be beneficial for long-term restoration goals. We conclude that managers need to be aware of the context-dependency of alien species to make restoration more effective.

Climatic control on the growth and regeneration of Juniperus przewalskii at alpine treeline in the eastern Qilian Mountains, northwest China

Temperature was the dominant climatic factor that controlled Juniperus przewalskii growth before 1988. However, the limiting effect of temperature on trees gradually weakened after 1988. Treeline shifted upward since 1890, especially during the 1930–1949. The saplings of the species died due to the warming. Forest mortality triggered by drought and treeline dynamics due to the regional warming has been widely reported. In the eastern Qilian Mountains, northwestern China, sapling of Juniperus przewalskii was found dead in the high elevation at the fringe of its spatial distribution. Tree-ring widths were measured, and climatic records were related to the tree-ring width to understand the sapling’s death and the mechanism of the treeline dynamics in this region. Results showed that tree-ring widths were positively correlated with the temperatures of previous year’s September to current year’s February. However, this correlation weakened in the late twentieth century as the mean annual temperature increased. Treeline shifted upwards, and the regeneration of J. przewalskii trees peaked during 1930–1949, of which most grew at higher elevations. Sapling trees (less than 2 m tall) started to die after 1959 and the death rate peaked 2000–2004, which lagged the warming induced drought. Drought stress induced by rising temperatures explained the death of the sapling trees. This study sheds light on the impacts of climate changes for tree growth, forest dynamics, and tree mortality, and provides insights that will be useful to forest managers for managing vulnerable arid and semi-arid forests.

Testing for functional significance of traits: Effect of the light environment in tropical tree saplings.

Functional traits have been examined to explain the growth rates of forest communities in different sites. However, weak or nonexistent relations are often found, especially due to the following methodological aspects: 1) lack of an environmental context (e.g., light, water, or nutrient supply), 2) use of nonfunctional traits, 3) an approach that does not contemplate phenotypic integration, and 4) neglect of intraspecific variation.Here we measured relative growth rates, crown, and leaf traits in saplings of six tropical tree species growing in two light environments (Gap and Understory) to test whether contrasting light environments modulates trait–trait and trait–growth relationships. Moreover, we tested whether models that integrate traits of different dimensions of the plant (crown and leaf) improve the strength of trait–growth relations.Light availability changed both trait–trait and trait–growth relationships. Overall, in Understory, crown traits (crown length and total leaf area) have a stronger effect on growth rates, while physiological traits related to nutrient acquisition (nitrogen concentration), photochemical efficiency (chlorophyll pigments and chlorophyll a fluorescence), and biochemical efficiency (potassium use efficiency) are strong in Gap. Models including multiple traits explained growth rates better in Gap (up to 62%) and Understory (up to 47%), but just in Gap the best model comprises traits that are representative of different dimensions of the plant. Synthesis. We advanced the knowledge behind the light effects on tree sapling by posit that trait–trait and trait–growth relationships vary across light environments. Therefore, light availability is a key environmental factor to be considered when choosing the set of traits to be measured in functional approach studies using tropical tree saplings. In compliance with the phenotype integration hypothesis, functional traits are better predictors of growth rates when grouped in a set of traits of different dimensions of the plant that represent different functional mechanisms.

‘seeing’ with/in the world: becoming-little

Critical posthumanism is an invitation to think differently about knowledge and educational relationality between humans and the more-than-human. This philosophical and political shift in subjectivity builds on, and is entangled with, poststructuralism and phenomenology. In this paper we read diffractively through one another the theories of Finnish architect Juhani Pallasmaa and feminist posthumanists Karen Barad and Rosi Braidotti. We explore the implications of the so-called ‘ontological turn’ for early childhood education. With its emphasis on a moving away from the dominant role of human vision (knowing and seeing) in educational research we show how videoing and photographing works as an apparatus in an analysis of data from an inner-city school in Johannesburg, South Africa. We are struck by children’s seeing with the ‘eyes of their skin’ (Pallasmaa) and ‘seeing’ with/in the world (posthumanism), as their obvious distress is felt when a small tree sapling has been mowed down in a nearby park. We analyse the event with the help of a variation on Deleuze’s notion of ‘becoming-child’: ‘becoming-little’, and Anna Tsing’s ‘the arts of noticing’. ‘Becoming-little’ as a methodology disrupts the adult/child binary that positions ‘little’, younger humans as inferior to their ‘bigger’ fully human counterparts. We exemplify ‘becoming-little’ through 4 and 5 year-olds’ learning with the little tree and adopt Barad’s temporal diffraction to ‘see’ what is in/visible in the park: the extractive, exploitative, colonising mining practices of White settlers. These are still part of the land on which the park was created but are in/visible beneath the ‘skin’ of the earth.

Management options for the conversion of allochthonous coniferous forest patches towards more natural species composition in the Vorpommersche Boddenlandschaft National Park, NE Germany

The conversion of coniferous tree plantations towards natural self-regenerating forests is one of the targets of forestry in Europe and particularly desirable in national parks. The aim of this study was to evaluate the effectiveness of different conversion approaches (conducted once) on natural forest development in man-made spruce plantations. We studied the effects of three distinct management options (partial-cutting [PC], clear-cutting with timber removal [CC] and clear-cutting with timber remaining [CCr]) six years after application on tree regeneration (sapling identity, abundance, height, browsing intensity) and understorey species composition in former spruce plantations within the Vorpommersche Boddenlandschaft National Park in Northeastern Germany. An unmanaged spruce [M] and near-natural beech [N] stands were considered as local references. The sites differed significantly in tree regeneration and understorey species composition. The abundance of native tree saplings was highest at site CCr, their height did not differ among sites, while browsing intensity was most pronounced at site CC. Understorey species composition of all management options was equally dissimilar to site N. However, site CCr contained more species that are typically abundant in local beech forests. Clear-cutting of spruce plantations with dead wood remaining on site favoured the natural regeneration of native trees and understorey vegetation compared to clear-cutting with timber removal, partial-cutting and no management. Herbivore browsing detrimentally affected tree regeneration independent of the treatment. Clear-cutting with timber removal promoted the dominance of competitive herbaceous species that may hamper long-term forest regeneration. We conclude that progression of site CCr appears to proceed fastest towards natural forest conditions. Further long-term data is required to derive clear trends regarding time and direction of forest regeneration. Keywords: forest conversion, spruce plantations, beech forest, natural tree regeneration, understorey species composition, deer browsing