Tree Establishment Research Articles

How Weed Control Affects Eucalyptus globulus Labill. Productivity: Results from Two Long-Term Trials

Weed control is considered a critical management operation for the establishment and growth of Eucalyptus globulus and is often performed during the first two years following planting. However, no information has been found related to the effects of weed management on the long-term growth of E. globulus. This study aims to better understand how adjusting the timing of weed control, beyond tree establishment, affects the productivity of eucalypts on two commercial plantations in Central Portugal. Two treatments were considered: weed control when vegetation cover occupied at least 50% of the area with a mean height of at least 50 cm, and no weed control. At the northernmost site, weed control operations were performed during the first 3 years following planting. At the southernmost site, weed control interventions occurred between 1.5 and 8.2 years. Weed control demonstrated to be effective at diminishing vegetation cover density to a maximum of 79% and 94% in the northmost and southmost sites, respectively. Weed control significantly increased E. globulus productivity by the end of the study, demonstrating that the timing of weed management must be adjusted in accordance with the understory competing vegetation cover (weeds) and during the entire rotation, not only during tree establishment.

Adaptive Relationships in Hemi-Boreal Forests: Tree Species Responses to Competition, Stress, and Disturbance.

European Union forest policy calls for closer-to-nature forest management, but natural disturbances and forest succession are ecological phenomena that are difficult to characterize and integrate into sustainable forest management practices. Therefore, the aim of this study is to explore the adaptive properties of Lithuania's hemi-boreal forest ecosystems. To accomplish this, we first reviewed (i) the potential natural forest communities, (ii) the successional dynamics, and (iii) adaptive strategies of forest trees, and second, we synthesised the adaptive relationships using these three reviews. The results firstly identified that Lithuania's potential natural forests are broadly divided into two climatically based zonal formations: (i) mesophytic and hygromesophytic coniferous and broadleaved forests and (ii) mesophytic deciduous broadleaved and coniferous-broadleaved forests. Secondly, the review of successional dynamics showed that each tree species can be categorised into various end communities and plant functional groups. Using the differences in tree establishment and phenological development modes we identified four forest dynamic types of tree adaptive strategies: stress-resistant ruderals, competitive stress-sensitive ruderals, ruderal stress-sensitive competitors, and stress-resistant competitors. Such functional redundancy leads to a variety of tree responses to competition, stress, and disturbance, which reduces the risk of loss of forest ecosystem functioning. Finally, the synthesised review on the adaptive relationships of each forest tree community shows both the niche position of each hemi-boreal forest tree species and how they should be managed in the organization of plant communities. We believe that this research can serve as a guide for future relevant research and the development of appropriate methods for sustainable forest management.

Wood density and leaf traits independently relate to growth rate of naturally regenerated tree species in Araucaria angustifolia plantations in the Atlantic Forest, Argentina

Tree plantations can facilitate the establishment of native trees, thus providing opportunities for the ecological restoration or rehabilitation of degraded forest lands. Stand variables can influence the establishment of native tree species, but few studies have been carried out to determine how sapling growth response to stand variables varies among functionally different species. We evaluated the effect of stand age, stand basal area, tree density, and time since last logging on stem diameter growth rates, as well as the dependence of such effect on whole plant, stem, and leaf functional traits. We measured the stem diameter increment on 280 individuals of 22 species in permanent plots for a period of 2 years in araucaria ( Araucaria angustifolia (Bertol.) Kuntze) plantations in the Atlantic Forest, NE Argentina. Increasing all-species basal area and plantation age negatively affected the growth rates, and such effect tended to be higher in species with low wood density. Two functional axes independently explained growth rate differences between species in growth rate. Growth rates increase with decreasing wood density, increasing leaf phosphorus and potassium content, and decreasing specific leaf area. Among species that are similar in the traits associated with the first functional axis, plant growth increases with increasing leaf nitrogen content.

Selection of Soil and Water Conservation Technologies and Native Tree Species for Rehabilitation of Degraded Arid Lands in Southeast Ethiopia

The large-scale commercial agriculture, mining, expansion of sedentary agricultural settlements, and overgrazing in Ethiopian pastoral areas have become a major cause of land degradation. Such activities reduce grazing capacities and impoverish already fragile living conditions of the pastoralists. Such an increase in land degradations necessitates urgent calls for interventions. The main objectives of this study were to select the best performing soil and water conservation technologies and native tree species to restore degraded lands of arid and semiarid conditions in Liben District of Guji Zone, Oromia Reginal State, Ethiopia. Four locally grown and locally preferred tree species, namely, Cordia africana, Acacia tortilis, Acacia goetzei, and Combretum molle, were planted in five soil and moisture conservation structures (control, half-moon, spot hoeing, mowing, and trench). The survival rate and height and root collar diameter (RCD) growth of planted tree species were collected two years after planting. A significantly higher survival rate, RCD, and height growth of planted seedlings were recorded from half-moon (52.44 ± 12.48%; 1.66 ± 0.31 cm; 51.57 ± 2.79 cm) and trench (64.00 ± 11.49%; 1.92 ± 0.27; 69.67 ± 2.62 cm) moisture conservation structures, respectively. Acacia tortilis (58.22 ± 12.38%) and Acacia goetzei (42.99 ± 8.81%) had better survival rate than Cordia africana (4.00 ± 1.91%) and Combretum molle (24.22 ± 7.34). Cordia africana attained the largest RCD (2.50 ± 0.34 cm) and height (95.83 ± 17.25 cm) growth, followed by Acacia tortilis and Acacia goetzei. It is concluded that Acacia tortilis and Acacia goetzei are better species to grow in degraded lands. The half-moon and trench moisture conservation structures have a great potential for degraded areas of the arid and semiarid conditions of Ethiopia for better tree establishment, survival, and enhanced growth thereby rehabilitation of degraded lands.

Inter-row cropping and rootstock genotype selection in a UK cider orchard to combat apple replant disease

Apple rootstock genotypes confer different levels of tolerance to apple replant disease (ARD) and vigour to a newly replanted apple tree. A hybrid management system of rotating the rootstock genotype planted between successive generations and inter-row planting in the alleyways of orchards may minimise the severity of ARD symptoms. High-throughput sequencing of the fungal ITS and bacterial 16S rDNA regions was used to investigate the diversity, and differential taxa present in soils displaying symptoms of ARD. Candidate pathogens and beneficial microorganisms were correlated with the above-ground establishment of each rootstock genotype in a UK cider orchard. Our results suggest that the same rootstock or rootstock with closely related parentage to the previous rootstock had more severe ARD symptoms. Planting in the alleyway appeared an effective strategy to minimise the severity of symptoms irrespective of rootstock genotype. The planting location effect had a higher contribution to the variation in the rhizosphere microbiome than that of the rootstock genotype. No predicted causal agents for ARD could be identified to a taxonomic level to predict their function but two species associated with mycorrhizae, Pteridiospora spinosispora and Paraglomus laccatum were identified as inversely correlated with ARD severity and could be candidate beneficial species for apple, warranting further investigation and research. Our findings suggest that planting in the alleyways and planting rootstocks genetically dissimilar to the previously planted rootstock can be beneficial for tree establishment. We have also identified species inversely associated with ARD severity, making candidates for future research to test the antagonistic effect of the species against ARD pathogens in apple roots.

Sorghum Growth and Yield as Influenced by Farmyard Manure and Inorganic Fertilizer in Post Mined Soils

Mining plays an important role in Kenyan Economic development through provision of employment, raw materials as well as foreign income. Despite the important role played by this sector, it is associated with land degradation, impacting food security. Closure of mines calls for rehabilitation process through establishment of native trees, grass or crops. In order to promote crop production as a reclamation measure, performance of sorghum in post mined soils was evaluated in the south dune site of base titanium limited Kwale Company. The experiments were laid down in Randomized Complete Block Design (RCBD) with split plot arrangement and replicated thrice. Fertilizer, Manure, Manure + Fertilizer, Control (unfertilized) and Gadam and Silla sorghum varieties were tested. Data collected included: Initial soil properties, plant height, number of leaves, leaf length, leaf width, stem circumference, panicle length, panicle circumference and grain yield per hectare. Data collected was subjected to analysis of variance using Genstat software and means separated using the Fisher’s protected least significant difference at (P≤0.05). The soils were slightly acidic with low levels of exchangeable P, K, S, Cu and Bn. Manure + fertilizer significantly (P≤0.05) increased plant height by 14% (gadam), and 28% (silla), number of leaves per plant by 28% (gadam) and 29% (silla), panicle length by 18% (gadam), 8% (silla), dry matter by 30% (gadam) 40% (silla) and grain yield by 50% for both gadam and silla varieties compared to control plots in both varieties. Average yields in both seasons for manure + fertilizer treated plants were significantly high (5.3 tones/ha) for Silla variety and (5.7 tones/ha) for Gadam variety. Where gadam produced slightly high grain yield than silla variety by 7%. Combined application of farmyard manure and inorganic fertilizer were most effective in enhancing sorghum growth, dry matter and yield. Growth and yield data collected showed that combined farmyard manure + fertilizer can support optimal sorghum production in the post mined soils. Owing to the fact that the soils have compromised profile, soil structure and fertility, long term trials and simulation models are required to ascertain optimal sorghum production while ensuring sustainable soil health in such soils.

Dendroecological Potential of Appalachian Riverscour Woodland Trees

Appalachian riverscour woodlands are intermittently flooded areas along high-energy rivers characterized by exposed bedrock and poorly developed sandy soils, high plant diversity, and scattered and stunted trees. These sites can be negatively impacted by dam construction and alterations to river hydrology, trampling associated with riverside recreation activities, and non-native species. In West Virginia, little is known about the development of riverscour woodlands or the growth and hydroclimate sensitivity of associated tree species. In this exploratory study, our objectives were to evaluate our ability to crossdate riverscour woodland trees (i.e., assign accurate calendar years to annual growth rings) as well as determine stand structure and tree establishment patterns at one site along the New River in Fayette County, West Virginia. In addition, for two species, Ulmus americana and Diospyros virginiana, we examined annual growth trends and relationships between tree growth and monthly hydroclimate, including streamflow, precipitation, and Palmer Drought Severity Index (PDSI). Seventy-three percent of all ring-width measurement series were crossdated, but results were mixed across species. Most trees were less than 50 years old and no trees established before the late 1940s. Both U. americana and D. virginiana were highly sensitive to April–August hydroclimate, but differed in response to previous year moisture availability. These findings provide new direction for the use of riverscour woodland trees in future dendroecological studies.

Synthesis of plant-soil feedback effects on eastern North American tree species: implications for climate-adaptive forestry

Climate change represents an existential threat to many forest ecosystems because tree populations are often adapted to local climate means and variability. If tree populations cannot migrate or adapt, they risk becoming increasingly maladapted with climate change. This emerging mismatch underscores the need for climate adaptive management techniques, such as assisted migration of tree species, to help mitigate climate change impacts on forest ecosystems. Although biotic and abiotic factors are known to constrain tree establishment success, the extent to which they may determine the success of assisted migration plantings is poorly understood. Thus, defining the extent to which trees affect—and in turn are affected by local soil environments and microbial communities (i.e., plant-soil feedbacks; hereafter PSFs) remains important for guiding effective climate-adaptive forest management. Our objectives were to synthesize the current state of knowledge about the direction and magnitude of PSF effects on temperate tree species of eastern North America, and to identify key hypotheses important for guiding future research. To accomplish these goals, we conducted a meta-analysis of 26 peer-reviewed publications that addressed our criteria. Our compiled database included 61 tree species and was composed primarily of short-term greenhouse experiments that studied PSF effects by manipulating the soil biota in three ways: (1) soil was previously inoculated by a conspecific or heterospecific tree species (i.e., home vs. away), (2) soil was live or sterilized, or (3) soil was untreated or treated with fungicide. We found that PSF had significant effects on tree growth, with the direction and magnitude of PSF strongly dependent on tree mycorrhizal guild. Arbuscular mycorrhizal tree species grown in live or home soils grew 13–33% less than those in sterile or away soils, while ectomycorrhizal tree species grew 11–44% more in live or home than sterile or away soils. PSF effects were associated with several plant functional traits, including specific leaf area, tissue nitrogen, and specific root length. We provide suggestions on incorporating PSFs into assisted migration trials and outline key knowledge gaps for future research. Our synthesis of context-dependent effects of PSFs on tree performance will help inform management decisions involving assisted migration.

Changes in seedlings’ composition and abundance following soil scarification and amendments in a northern hardwood forest

A combination of global changes (e.g., soil acidification, invasive species, forest management, climate) impacts the regeneration dynamics of sugar maple-dominated stands in northeastern North America. More specifically, there are concerns about the regeneration of sugar maple and other high-value species due to the expansion of American beech and its bark disease, killing mature trees, compromising fiber supply and other ecosystem services. Here, we set up a field trial to study the effect of soil scarification, amendments (nitrogen fertilization, liming, and wood ash), and their interactions, on tree species establishment following understory vegetation removal in a beech-invaded sugar maple stand to promote the establishment of high-value species (i.e. sugar maple and yellow birch), to control beech regeneration, and help reduce the impacts of beech bark disease on stand development. After four years of monitoring, we found that maple-beech stands with well-drained soils were promising sites for the success of sugar maple and yellow birch establishment. Soil scarification had a limited effect on sugar maple and beech establishment while it enhanced that of yellow birch, pin cherry and red maple. The combination of soil scarification and amendments was more effective in promoting the recovery of yellow birch and pin cherry and controlling the recovery of beech and red maple than their separated effects. Lime amendment promoted sugar maple establishment without favouring competitors such as yellow birch, pin cherry and red maple, and limited beech establishment. Overall, our results suggest that combining soil scarification and amendments on targeted site types could help fine-tune tree establishment conditions in northern hardwood forests.

Construction and analysis of prediction model for sales of child car seats

Based on the Carseats data set in the ISLR package, this paper constructs a regression model of the data set and predicts some variables. In addition, it also includes the establishment of regression trees and other models for variables. The final task requirement is to construct the classification model of the data, divide the classification model into the training set and the test set, and construct the linear discriminant analysis, logistic regression, random forest and so on with another variable. By making some models, the prediction accuracy on the test set is relatively high, and the evaluation effect of the model is also very good, which can provide a sufficient theoretical basis for the prediction of the sales of children's car seats.

Developing Integrated Strategies to Address Emerging Weed Management Challenges in Christmas Tree Production

Weed control is an important aspect during the first few years of Christmas tree establishment, as weed competition directly relates to the rate of Christmas tree growth during this time. The objectives of this study were to evaluate the weed control efficacy of organic mulch and herbicide combinations and to determine their phytotoxic effects on four different species of Christmas trees during the establishment stage: Fraser fir (Abies fraseri (Pursh) Poir), blue spruce (Picea pungens Engelm.), white pine (Pinus strobus L.), and Scotch pine (Pinus sylvestris L.). Twelve weed control treatments were established in a complete randomized block design with four replications in each of five fields. Weed control treatments included cypress bark organic mulch and herbicides applied alone and in combinations as well as an untreated control. Herbicides included clopyralid, oxyfluorfen, and glyphosate. All herbicides were applied at their highest labeled rate. Data collection included visual estimations of weed control and phytotoxicity to trees at 30, 60, and 90 days after treatment (DAT). Tree growth and foliar nitrogen concentration were also measured. Mulch combined with herbicide provided 60%–100% weed control in all cases; at two farms, mulch provided a significant increase in weed control when compared to the same treatments without mulch. Combinations of mulch + clopyralid + glyphosate and clopyralid + oxyfluorfen + glyphosate resulted in the highest phytotoxicity ratings. Tree growth was decreased due to some treatments at Gobles farm, and foliar N did not differ among any of the treatments.

Great Green Walls: Hype, Myth, and Science

Visions of planting walls of trees to block the expansion of the desert have long been promoted but never realized. The green wall myth persists today even though it is premised on outdated understandings of desertification. We review the history of the idea of green walls and focus on two sets of contemporary initiatives to assess their outcomes: peri-Saharan programs (Algeria's Green Dam and Great Green Wall in sub-Saharan Africa) and China's Three Norths Shelterbelt Program. This review reveals a mixed record of technical success with low rates of the establishment of monocultures of fast-growing trees vulnerable to disease. While there is evidence for reduced wind erosion in some areas, afforestation is also associated with reduced soil moisture and lowering of water tables. Social impacts include increased water scarcity for people and livestock in some cases, and resource enclosures that particularly work against pastoralist livelihoods.

Thermal failure analysis of special-shaped crown spring connectors for rail vehicles

With the fast development of the rail transit system and the continuous speed increase of rail vehicles in China, the rated current of the power supply system in the trains rises accordingly, so the thermal reliability of the electrical connection system used in the power supply system has become one of the crucial factors whether the train can run normally for a long time. In this paper, aiming at an ablative failure of a special-shaped crown spring connector during the operation of a subway, both the failure mechanism and the solution method are studied. Firstly, the main influencing factors of the failure, both the cable size and the contact resistance degradation of the connector, were screened by fault tree establishment. Then the capacity of the selected cable was evaluated to be insufficient by current carrying test, with 11.6% lower than the safe margin. Further, the contact resistance degradation of the connector caused by vibration and corrosion was about 23%, studied by the experiments and thermal theory. By combining the theoretical model of temperature rise in the contact interface and the finite element simulation, the heat production of the connection system under actual working conditions was estimated to make the insulating materials near the contacts attain to the decomposition temperature, which was verified by the analysis of the failed samples with various service stages. The thermal analysis results was demonstrated to be consistent (less than 5% error) among the finite element simulation, the experiments and an existed thermal design method. Finally, a solution to increase the cable specification from 50 mm2 to 70 mm2 under complicated service conditions is proposed to reduce bulk resistance of the cables and increase the heat dissipation by cable heat conduction, the maximum temperature rise can reduce 18.4% so that the ablation failure of the connectors can be avoided.

Early vegetation recovery following a mid to high‐severity fire in the Andean‐Patagonian forests

AbstractA change in fire regimes is occurring worldwide, affecting post‐fire succession. Under this context, there is an increasing need to prioritize restoration areas and focus on their particular goals. To assess the emergent understorey represents the first approximation of post‐fire re‐vegetation, necessary to establish appropriate restoration guidelines. In this study, we aimed to assess the initial post‐fire response in a mid to high‐severity fire in the Andean‐Patagonian forests. We (1) compared plant community structure among fire severities, (2) evaluated the response of plant community structure to the interaction between fire severity and forest type, (3) compared plant composition among fire severity‐forest type categories and (4) evaluated woody species regeneration after fire. We found that the vegetation cover of the lower stratum began to recover early after the fire and to a greater extent in mid than in high severity, whereas the upper stratum was incipient in the mid and nil in high severity. Native species predominated in burned and unburned plots, although they were less in the burned plots. Among the growth form, shrubs and trees were similarly affected by fire, independently of the forest type. Plant community composition varied among most fire severity‐forest type categories. The frequency of woody species regenerated by resprouts and by seeds was lower in burned than unburned plots. These results suggest that although there is an early recovery of vegetation, the high cover of exposed soil and the loss of the upper vegetation stratum may favour erosion and difficult tree establishment. Besides, tree species that only regenerate from seeds will probably not recover naturally. In addition, the presence of exotic species with high invasive risk may need control. Thus, since fire severity and forest type may drive different post‐fire natural recovery scenarios, different restoration actions should be taken to promote resilient systems for the future.

Assessing the Importance of Native Mycorrhizal Fungi to Improve Tree Establishment after Wildfires.

The Chilean matorral is a heavily threatened Mediterranean-type ecosystem due to human-related activities such as anthropogenic fires. Mycorrhizal fungi may be the key microorganisms to help plants cope with environmental stress and improve the restoration of degraded ecosystems. However, the application of mycorrhizal fungi in the restoration of the Chilean matorral is limited because of insufficient local information. Consequently, we assessed the effect of mycorrhizal inoculation on the survival and photosynthesis at set intervals for two years after a fire event in four native woody plant species, namely: Peumus boldus, Quillaja saponaria, Cryptocarya alba, and Kageneckia oblonga, all dominant species of the matorral. Additionally, we assessed the enzymatic activity of three enzymes and macronutrient in the soil in mycorrhizal and non-mycorrhizal plants. The results showed that mycorrhizal inoculation increased survival in all studied species after a fire and increased photosynthesis in all, but not in P. boldus. Additionally, the soil associated with mycorrhizal plants had higher enzymatic activity and macronutrient levels in all species except in Q. saponaria, in which there was no significant mycorrhization effect. The results suggest that mycorrhizal fungi could increase the fitness of plants used in restoration initiatives after severe disturbances such as fires and, consequently, should be considered for restoration programs of native species in threatened Mediterranean ecosystems.

Dynamic Fire Regimes and Forest Conditions Across Three Centuries in a Shortleaf Pine-Oak Forest in the Ouachita Mountains, Arkansas, USA

In the interior highlands of the eastern United States, there is evidence that fire was frequent in some forests during the eighteenth and nineteenth centuries before declining drastically in the twentieth century. To better understand past fire regimes and how they shaped forest dynamics during periods of change, we conducted a dendroecological study at Lake Winona Research Natural Area (LWRNA), a 110-ha unlogged forest dominated by shortleaf pine (Pinus echinata Mill.) in the Ouachita Mountains of Arkansas. We used remnant wood and living tree cores to construct a multicentury record of fire occurrence and tree recruitment. Our results indicate the forest at LWRNA passed through multiple fire regime transitions that altered forest dynamics. During the protohistoric period (1701–1834), prior to widespread European American settlement (EAS), fire was frequent, but limited sample depth results in greater uncertainty regarding fire frequency and forest conditions. During EAS (1835–1929), fire was very frequent and tree establishment was dominated by shortleaf pine. After 1930, effective fire protection led to establishment shifting toward increasingly fire-intolerant hardwoods. Evidence of temporal variations in the fire regime, age structure, and contemporary composition broaden our understanding of reference conditions in this pine-oak forest and demonstrate that fire management could be used to restore a range of vegetation conditions from frequently burned pine- and oak-dominated woodlands to fire-excluded, closed-canopy mesophytic communities.

Small mammal granivory as a biotic filter for tree establishment beyond elevation range boundaries

Small mammal granivory as a biotic filter for tree establishment beyond elevation range boundaries

Liana abundance and diversity increase along a successional gradient, even with homogeneous closed canopy

One-half of the pantropical forests are regrowth that develop in certain stages along the succession gradient. As lianas can colonize rapidly in disturbed areas, they play a key role in forest succession and carbon sequestration. However, current knowledge remains limited and is from only a few sites in neotropical forests. Here we investigated liana succession in a chronosequence located in a Southeast Asian Forest. We determined liana abundance (stem density, basal area, prevalence) and diversity along the succession gradient with ages in the range 3–100 years. We also analyzed community composition, size structure, and the correlation with host tree size. We found that liana abundance and diversity increased non-linearly along the succession gradient, suggesting that the stem exclusion stage (35–41 years)—homogeneous closed canopy with low light penetration—did not inhibit liana colonization. Assuming the reverse J-shaped distribution, we fitted the size structure of each plot with the exponential distribution. The results demonstrated no differences among the fitted parameters of plots in the stem exclusion and the old-growth stage, suggesting the same capability of recruitment and colonization in both stages. Furthermore, we found a weak correlation between liana and host tree size (R2 ≤ 0.16, which varied among plots, implying that many lianas recruited after the establishment of large host trees in the past. The results regarding community composition perhaps suggested a stochastic process of liana colonization during the early stage (3–20 years) because of high spatial heterogeneity (a mosaic of open area alternating with closed canopy). In the stem exclusion and old-growth stages, we observed a predictable trajectory, with the composition of plots in the same stage being clustered. This implied that forest structure or unpredictable treefall gaps of old-growth forests have a limited impact on community dissimilarity. Collectively, these results suggested that (1) some liana species may be generalists or even shade-tolerant species, or (2) there was no seed dispersal limitation in the landscape. The contrary direction of the succession patterns reported here suggests a need for more studies across tropical forests including investigating life history trade-offs such as light tolerance.

Subsoiling for planting trees in dehesa system: long-term effects on soil organic carbon

Incorporating trees into agricultural systems, including grasslands, increases the soil organic carbon sequestration and contributes to climate change mitigation. Site preparation for tree establishment is a common practice that can involve a variety of techniques and agricultural implements such as subsoiling. This study aimed to evaluate the long-term effects of subsoiling on soil organic carbon (SOC) concentrations and stocks in a Mediterranean grassland afforested with holm oaks 22 years ago and now converted into a Dehesa agroforestry system. The study was conducted in a dehesa farm in Southwest Spain. Soil samples were taken at six depths under 10 tree canopies within and outside the original subsoiling line. Subsoiling significantly decreased SOC concentration. Mean SOC concentration in the first 20 cm was 30% lower at the subsoiling line. SOC stocks for the first 60 cm were 2660 g m−2 within the subsoiling line and 4320 g m−2 outside the line. There was a clear reduction in SOC concentration and stock with increasing depth. Root abundance and deeper rooting increased with subsoiling but did not translate into sufficient carbon accumulation in the soil, which is moderate even after 22 years. This study reveals that, in the long term, there is a trade-off in CO2 sequestration between tree planting and soil subsoiling, highlighting the need for further research into the potential benefits and detriments of subsoiling.

The effects of the invasive species, Lantana camara, on regeneration of an African rainforest

AbstractInvasive plants adversely affect native communities by altering ecosystem function and disrupting natural regeneration. We investigate the effect of invasive Lantana camara L. (Verbenaceae) on forest regeneration in Kibale National Park, Uganda. We appraise the efficacy of cutting and uprooting Lantana for promoting native tree recruitment. Sample plots comprised three types: (i) currently invaded by Lantana; (ii) cleared of Lantana and now managed; and (iii) forest reference plots uninvaded by Lantana. Tree species numbering 51, 19 shrubs, and 17 herb species were identified. Lantana reduced tree, shrub, and herb cover and diversity, and suppressed tree regeneration. The short‐term management of Lantana did not promote tree establishment. The tree community in cleared areas was not converging on uninvaded adjacent forest. Lantana is known to allelopathically suppress tree seedling establishment, but even at sites cleared of Lantana, tree species recruitment was poor. While insufficient time may have passed for tree recruitment, we argue that an increase in shrub and herb cover and diversity arrested forest tree regeneration. Sustained follow‐up clearing of dense secondary shrubs and herbs and resprouted L. camara in cleared areas is key to ensuring long‐term recovery of the forest tree community.