Roots Of Shrubs Research Articles

Root distribution of Nitraria sibirica with seasonally varying water sources in a desert habitat.

In water-limited environments, the water sources used by desert shrubs are critical to understanding hydrological processes. Here we studied the oxygen stable isotope ratios (δ (18)O) of stem water of Nitraria sibirica as well as those of precipitation, groundwater and soil water from different layers to identify the possible water sources for the shrub. The results showed that the shrub used a mixture of soil water, recent precipitation and groundwater, with shallow lateral roots and deeply penetrating tap (sinker) roots, in different seasons. During the wet period (in spring), a large proportion of stem water in N. sibirica was from snow melt and recent precipitation, but use of these sources declined sharply with the decreasing summer rain at the site. At the height of summer, N. sibirica mainly utilized deep soil water from its tap roots, not only supporting the growth of shoots but also keeping the shallow lateral roots well-hydrated. This flexibility allowed the plants to maintain normal metabolic processes during prolonged periods when little precipitation occurs and upper soil layers become extremely dry. With the increase in precipitation that occurs as winter approaches, the percentage of water in the stem base of a plant derived from the tap roots (deep soil water or ground water) decreased again. These results suggested that the shrub's root distribution and morphology were the most important determinants of its ability to utilize different water sources, and that its adjustment to water availability was significant for acclimation to the desert habitat.

In situ study of deep roots of Capparis spinosa L. during the dry season: Evidence from a natural “rhizotron” in the ancient catacombs of Milos Island (Greece)

The growing period of the deep-rooted, winter-deciduous Capparis spinosa (caper) coincides with the dry season, in the Mediterranean Basin. Roots of wild shrubs of C. spinosa penetrated cracks of a pumice substrate and lengthened in the subterranean environment of the ancient catacombs of Milos Island (Greece); therein, they reached depths of up to 20 m and exploited water present in deep soil layers. Elevated water potential (Ψ) was measured in root segments (Ψr = −0.35 ± 0.06 MPa), a few centimetres from the root apices of C. spinosa found in the catacombs during the dry season. Also, estimates of foliar predawn water potential and gas exchange components, as well as of nocturnal floral water potential of C. spinosa grown on slopes above the subterranean monument were high and reflected the efficiency of roots in retaining acquisition of water from deep soil layers, during the dry season.

Validation of reference genes for quantitative real-time PCR in Périgord black truffle (Tuber melanosporum) developmental stages

The symbiotic fungus Tuber melanosporum Vittad. (Périgord black truffle) belongs to the Ascomycota and forms mutualistic symbiosis with tree and shrub roots. This truffle has a high value in a global market and is cultivated in many countries of both hemispheres. The publication of the T. melanosporum genome has given researchers unique opportunities to learn more about the biology of the fungus. Real-time quantitative PCR (qRT-PCR) is a definitive technique for quantitating differences in transcriptional gene expression levels between samples. To facilitate gene expression studies and obtain more accurate qRT-PCR data, normalization relative to stable housekeeping genes is required. These housekeeping genes must show stable expression under given experimental conditions for the qRT-PCR results to be accurate. Unfortunately, there are no studies on the stability of housekeeping genes used in T. melanosporum development. In this study, we present a morphological and microscopical classification of the developmental stages of T. melanosporum fruit body, and investigate the expression levels of 12 candidate reference genes (18S rRNA; 5.8S rRNA; Elongation factor 1-alpha; Elongation factor 1-beta; α-tubulin; 60S ribosomal protein L29; β-tubulin; 40S ribosomal protein S1; 40S ribosomal protein S3; Glucose-6-phosphate dehydrogenase; β-actin; Ubiquitin-conjugating enzyme). To evaluate the suitability of these genes as endogenous controls, five software-based approaches and one web-based comprehensive tool (RefFinder) were used to analyze and rank the tested genes. We demonstrate here that the 18S rRNA gene shows the most stable expression during T. melanosporum development and that a set of three genes, 18S rRNA, Elongation factor 1-alpha and 40S ribosomal protein S3, is the most suitable to normalize qRT-PCR data from all the analyzed developmental stages; conversely, 18S rRNA, Glucose-6-phosphate dehydrogenase and Elongation factor 1-alpha are the most suitable genes for fruiting body developmental stages.

Ground-penetrating radar-based automatic reconstruction of three-dimensional coarse root system architecture

The diverse functions of roots set requirements on specific root system architecture (RSA). Investigation on RSA holds potentials for studying the adaptation of plants to environmental stresses and to interspecific competitions. Ground-penetrating radar (GPR) has provided a non-invasive method for studying in situ RSA. However, previous GPR method relied on manually connecting root points detected between radargrams to restore each root branch, resulting in limited accuracy and efficiency of reconstructing RSA. The objective of this study is to improve the effectiveness of 3D RSA reconstruction using GPR root detection data. A total of 213 coarse root sections (with diameter >0.5 cm) were extracted from a distribution map of a reference shrub (Arctostaphylos pungens) root system to simulate the coarse roots identified by GPR. An automatic method was established to trace each root point to its optimum growing source point. Connections between discrete root points recovered the topology of the reference RSA. A spline curve smoothing method was applied to restore the 3D morphology of the reference RSA. The proposed protocol was then tested to rebuild the 3D RSA of a shrub (Caragana microphylla) growing in the sandy soils after in situ GPR survey. The accuracy of RSA reconstruction was quantitatively evaluated by a relationship matrix method and qualitatively assessed by direct comparisons between the reconstructed and the actual RSAs after in situ excavation. For both simulated and field collected GPR detection datasets, the reconstructed RSAs strongly corresponded to the real topology of the actual root systems. When adapting the best strategy, 186 of the 213 (87.32 %) root points on the reference root system of A. pungens were interlinked with correct topology, and the relationship matrix method detected an overall similarity of 82.75 % between the reconstructed and the actual RSAs. The proposed automatic RSA reconstruction method greatly enhances the interpretation of GPR detection data regarding coarse roots, making in situ non-invasive and long-term mapping and monitoring of RSA possible.

Deep Planting Long-Stem Nursery Stock: An Innovative Method to Restore Riparian Vegetation in the Arid Southwest

On the Ground The successful establishment of riparian shrubs in the arid Southwest has been accomplished by using “deep planting” methods in riparian areas that lack overbank flooding. This methodology involves the immediate exploitation of capillary fringe moisture by the existing root system of long-stem nursery stock and the deep burial of native shrub root crowns. The methodology precludes or drastically reduces the need to apply irrigation water in arid and semi-arid environments in order to establish riparian shrubs and trees by deep planting long-stem native nursery stock.

비탈면 안정을 위한 참싸리 뿌리의 토양보강 효과

To examine the soil reinforcement by the shrub with shallow root systems for slope stability, we developed insitu apparatus for direct shear test and conducted the insitu field tests for Lespedeza cyrtobotrya, a representative revegetation species for artificial hillslopes. The insitu field tests were conducted for two different soil conditions (the rooted soils and non-rooted soils) and we then compared the experimental values with those calculated from the Wu model. The results showed that the soil reinforcement derived from the insitu field tests ranged from 0.01525 to 0.1438 kgf/cm2 while the one calculated from the Wu model ranged from 0.1952 to 0.2696 kgf/cm2 . Our finding suggests more field tests are needed to collect the related parameters in the model application thereby predicting the reliable soil reinforcement by the shrub root systems.

Carbon sequestration capacity of shifting sand dune after establishing new vegetation in the Tengger Desert, northern China

Reconstructing vegetation in arid and semiarid areas has become an increasingly important management strategy to realize habitat recovery, mitigate desertification and global climate change. To assess the carbon sequestration potential in areas where sand-binding vegetation has been established on shifting sand dunes by planting xeric shrubs located near the southeastern edge of the Tengger Desert in northern China, we conducted a field investigation of restored dune regions that were established at different times (20, 30, 47, and 55years ago) in the same area. We quantified the total organic carbon (TOC) in each ecosystem by summing the individual carbon contributions from the soil (soil organic carbon; SOC), shrubs, and grasses in each system. We found that the TOC, as well as the amount of organic carbon in the soil, shrubs, and grasses, significantly increased over time in the restored areas. The average annual rate of carbon sequestration was highest in the first 20years after restoration (3.26×10−2kg·m−2·year−1), and reached a stable rate (2.14×10−2kg·m−2·year−1) after 47years. Organic carbon storage in soil represented the largest carbon pool for both restored systems and a system containing native vegetation, accounting for 67.6%–85.0% of the TOC. Carbon in grass root biomass, aboveground grass biomass, litter, aboveground shrub biomass, and shrub root biomass account for 10.0%–21.0%, 0.2%–0.6%, 0.1%–0.2%, 1.7%–12.1% and 0.9%–6.2% of the TOC, respectively. Furthermore, we found that the 55-year-old restored system has the capacity to accumulate more TOC (1.02kg·m−2 more) to reach the TOC level found in the natural vegetation system. These results suggest that restoring desert ecosystems may be a cost-effective and environmentally friendly way to sequester CO2 from the atmosphere and mitigate the effects of global climate change.

Mszyce z rodziny bawełnicowatych (Pemphigidae) w pojemnikowej uprawie roślin ozdobnych

Summary The following species of woolly aphids appeared in containers with coniferous shrubs: Gootiella tremulae on yews (Juniperus chinensis, J. horizontalis, J. × media and J. squamata), Prociphilus (Stagona) pini on pines (Pinus sylvestris and P. mugo) and Pachypappa vesicalis on Norway spruce (Picea abies). In container production of perennial plants, Colopha compressa was feeding on roots of sedges (Carex buchananii and C. morowii) and Thecabius (Parathecabius) lysimachiae on roots of golden creeping jenny (Lysimachia nummularia). In containers with deciduous shrubs such as Thunberg's barberry (Berberis thunbergii), smooth hydrangea (Hydrangea arborescens), weigela (Weigela florida), shrubby cinquefoil (Potentilla fruticosa), Japanese spiraea (Spiraea japonica) and Grefsheim spiraea (Spiraea × cinerea), the lettuce root aphid (Pemphigus bursarius) was found. However, this aphid was not inhibiting roots of deciduous shrubs, but was feeding on roots of common dandelion (Taraxum officinale) – common weed in container production.

Common and distinguishing features of the bacterial and fungal communities in biological soil crusts and shrub root zone soils

Soil microbial communities in dryland ecosystems play important roles as root associates of the widely spaced plants and as the dominant members of biological soil crusts (biocrusts) colonizing the plant interspaces. We employed rRNA gene sequencing (bacterial 16S/fungal large subunit) and shotgun metagenomic sequencing to compare the microbial communities inhabiting the root zones of the dominant shrub, Larrea tridentata (creosote bush), and the interspace biocrusts in a Mojave desert shrubland within the Nevada Free Air CO2 Enrichment (FACE) experiment. Most of the numerically abundant bacteria and fungi were present in both the biocrusts and root zones, although the proportional abundance of those members differed significantly between habitats. Biocrust bacteria were predominantly Cyanobacteria while root zones harbored significantly more Actinobacteria and Proteobacteria. Pezizomycetes fungi dominated the biocrusts while Dothideomycetes were highest in root zones. Functional gene abundances in metagenome sequence datasets reflected the taxonomic differences noted in the 16S rRNA datasets. For example, functional categories related to photosynthesis, circadian clock proteins, and heterocyst-associated genes were enriched in the biocrusts, where populations of Cyanobacteria were larger. Genes related to potassium metabolism were also more abundant in the biocrusts, suggesting differences in nutrient cycling between biocrusts and root zones. Finally, ten years of elevated atmospheric CO2 did not result in large shifts in taxonomic composition of the bacterial or fungal communities or the functional gene inventories in the shotgun metagenomes.

Availability of ectomycorrhizal fungi to black spruce above the present treeline in Eastern Labrador.

Ectomycorrhizal fungi (ECMF) are an important biotic factor in the survival of conifer seedlings under stressful conditions and therefore have the potential to facilitate conifer establishment into alpine and tundra habitats. In order to assess patterns of ectomycorrhizal availability and community structure above treeline, we conducted soil bioassays in which Picea mariana (black spruce) seedlings were grown in field-collected soils under controlled conditions. Soils were collected from distinct alpine habitats, each dominated by a different ectomycorrhizal host shrub: Betula glandulosa, Arctostaphylos alpina or Salix herbacaea. Within each habitat, half of the soils collected contained roots of ectomycorrhizal shrubs (host+) and the other half were free of host plants (host−). Forest and glacial moraine soils were also included for comparison. Fungi forming ectomycorrhizae during the bioassays were identified by DNA sequencing. Our results indicate that ECMF capable of colonizing black spruce are widespread above the current tree line in Eastern Labrador and that the level of available inoculum has a significant influence on the growth of seedlings under controlled conditions. Many of the host− soils possessed appreciable levels of ectomycorrhizal inoculum, likely in the form of spore banks. Inoculum levels in these soils may be influenced by spore production from neighboring soils where ectomycorrhizal shrubs are present. Under predicted temperature increases, ectomycorrhizal inoculum in soils with host shrubs as well as in nearby soils without host shrubs have the potential to facilitate conifer establishment above the present tree line.

Research on the Slope Protection Mechanism of Roots

This study aims to investigate the slope protection mechanism of roots. In ecological slope protection, plant roots can fix soil and protect slop through biological and mechanical action. However, previous studies on the slope protection mechanism are still not deep enough and inadequate. By taking four kinds of typical plant roots along Wu-Shen Expressway as the research object, through the indoor tensile test and root morphology observation analysis, the tensile strength and ultimate tension were studied and the influence to the stability of the slope was discussed in this study. The results show that the mean ultimate tension of roots is 7.19~29.96 N. The mean tension of shrub roots is 2~4 times greater than that of herb roots. The ultimate tension of the same plant roots increases with the diameter significantly. To the range of improvement, Shrub roots exceed herb ones. It also indicates that the mean tensile strength of roots are 24.48~74.25 MPa. Compared with the steel HRB235, the tensile strength of herb roots is as great as 1/5~1/3, while Shrub roots is about 1/10~1/5. The slope stability coefficient with plant growing is a positive correlation with roots tension and root number through the sliding surface and is a negative correlation with plants weight. In addition, the slope stability coefficient is related to plant density and root morphology. The test results demonstrate that the roots tension with acute angle or right angle to the landslide surface and the roots shear stiffness with obtuse angle can improve the performance of slope’s anti-slide. Four kinds of plants can improve the stability coefficient of shallow soil. As for the slope protection effect, herbage is superior to shrub. In general, grass-shrub mixed community is the ideal system for slope protection.

Wood anatomical analysis of Swiss willow (Salix helvetica) shrubs growing on creeping mountain permafrost

Permafrost and related landforms (rockglaciers) are widespread phenomena in alpine geosystems. In the context of changing environments due to the significant warming, there is a need for thorough monitoring and analyzing the complex responses of these cryospheric geosystems. Here, the first-time application of wood anatomical methods in this context is presented in order to investigate whether rockglacier movement is reflected in varying cell structures of plants growing on top of the rockglaciers.In order to determine the influence of ground movements (by permafrost creep) and their influence on the conductive elements within roots of plants, wood-samples were taken from active and inactive rockglaciers in the Turtmann Valley, southern Swiss Alps. Since the occurrence of trees is limited altitudinally, the investigation was restricted to Swiss willow shrubs (Salix helvetica) frequently growing in permafrost areas above the timberline in the European Alps. This rather new approach concentrates on general vessel size differences as a result of mechanical stresses. The comparison of vessel sizes in roots of Swiss willow shrubs growing on active and inactive permafrost bodies depicts differences within the roots, which are related to the activity status of the respective rockglacier creep.

The Use of Leptodyctium riparium (Hedw.)Warnst in the Estimation of Minimum Postmortem Interval

The estimation of the postmortem interval (PMI) is still one of the most challenging issues in forensic investigations, especially in cases in which advanced transformative phenomena have taken place. The dating of skeletal remains is even more difficult and sometimes only a rough determination of the PMI is possible. Recent studies suggest that plant analysis can provide a reliable estimation for skeletal remains dating, when traditional techniques are not applicable. Forensic Botany is a relatively recent discipline that includes many subdisciplines such as Palynology, Anatomy, Dendrochronology, Limnology, Systematic, Ecology, and Molecular Biology. In a recent study, Cardoso et al. (Int J Legal Med 2010;124:451) used botanical evidence for the first time to establish the PMI of human skeletal remains found in a forested area of northern Portugal from the growth rate of mosses and shrub roots. The present paper deals with a case in which the study of the growth rate of the bryophyte Leptodyctium riparium (Hedw.) Warnst, was used in estimating the PMI of some human skeletal remains that were found in a wooded area near Perugia, in Central Italy.

Utilización de especies nativas del “bosque seco” para la recuperación del paisaje en el proceso de cierre del botadero a cielo abierto del distrito las Lomas – Piura

La investigación se refiere a la fragmentación del paisaje del distrito de Las Lomas en Piura, afectado por la existencia de un botadero a cielo abierto. El estudio se focaliza en la posible restauración del paisaje durante el proceso de clausura. Para lo cual se estudiaron las especies vegetales nativas del bosque seco piurano seleccionando las más resistentes y útiles en el proceso de recuperación, las mismas que fueron colocadas paisajísticamente sobre la cobertura final. Este proceso denominado fito-remediación ayudará a que las raíces de árboles y arbustos estabilicen el área clausurada, degraden los residuos y absorban los lixiviados. Una correcta colocación y posterior crecimiento de la vegetación recuperará el paisaje, ayudará al retorno de la fauna desplazada y permitirá que se acelere este proceso regenerador para el bienestar de la población vecina.

Hydraulic redistribution by two semi-arid shrub species: Implications for Sahelian agro-ecosystems

Hydraulic redistribution is the process of passive water movement from deeper moist soil to shallower dry soil layers using plant roots as conduits. Results from this study indicate that this phenomenon exists among two shrub species (Guiera senegalensis and Piliostigma reticulatum) that co-exist with annual food crops in Sahelian agro-ecosystems. Real-time measurements were conducted for soil water content, soil water potential and microclimate variables notably; air temperature, relative humidity, wind speed, precipitation and solar irradiance. Additionally, sap flow measurements were conducted in shrub roots using the thermal dissipation technique on intact and coppiced shrubs. Monthly predawn leaf water potential was measured using a portable pressure chamber. Soil water potential (Ψs) at the 20 cm depth declined significantly during the dry season with diel changes in Ψs of −0.6 to −1.1 MPa. These variations were attributed to passive water release from shrub roots resulting in overnight rewetting of drier upper soil layers. Sap flow measurements on tap and lateral shrub roots indicated daily reversals in the direction of flow. During the peak of the dry season, both positive (toward shrub) and negative (toward soil) flows were observed in lateral shrub roots with sap flow in the lateral roots frequently negative at night and rapidly becoming positive soon after sunrise. The negative sap flow at night in superficial lateral roots and the periodic positive flow in the descending tap roots were indicative of hydraulic redistribution. Hydraulic redistribution may be an important mechanism for drought stress avoidance while maintaining plant physiological functions in both shrubs and neighboring annuals in water-limited environments.

New insights in the molecular events underlying actinorhizal nodulation in the tropical tree Casuarina glauca

Background Actinorhizal root nodules result from the interaction between a nitrogen-fixing actinomycete called Frankia and roots of dicotyledonous trees and shrubs belonging to 8 plant families and 25 genera. Most actinorhizal plants are capable of high rates of nitrogen fixation comparable to those found in legumes. As a consequence, these trees are able to grow in poor and disturbed soils and are important elements in plant communities worldwide. This facility for adaptation has drawn great interest to actinorhizal plants, particularly to several species of Casuarinaceae such as Casuarina glauca, which can be used for fuelwood production, agroforestry, and land reclamation in the tropics and subtropics. The basic knowledge of the symbiotic association between Frankia and actinorhizal plants is still poorly understood, although it offers striking differences with the Rhizobium-legume symbiosis [1]. Recently, the development of genomics in some actinorhizal plants such as C. glauca[2], together with the possibility to obtain transgenic actinorhizal plants following Agrobacterium gene transfer [3], offer new approaches to understand the molecular basis of the actinorhizal process. We will highlight recent progress in the molecular knowledge of the early stages of the actinorhizal symbiosis. A comparative analysis of the symbiotic pathway in actinorhizal trees and legumes will be presented.

Untangling positive and negative biotic interactions: views from above and below ground in a forest ecosystem

In ecological communities, the outcome of plant-plant interactions represents the net effect of positive and negative interactions occurring above and below ground. Untangling these complex relationships can provide a better understanding of mechanisms that underlie plant-plant interactions and enhance our ability to predict population, community, and ecosystem effects of biotic interactions. In forested ecosystems, tree seedlings interact with established vegetation, but the mechanisms and outcomes of these interactions are not well understood. To explore such mechanisms, we manipulated above- and belowground interactions among tree seedlings, shrubs, and trees and monitored seedling survival and growth of six species (Pinus banksiana, Betula papyrifera, P. resinosa, Quercus rubra, P. strobus, and Acer rubrum) in mature pine-dominated forest in northern Minnesota, USA. The forest had a moderately open canopy and sandy soils. Understory manipulations were implemented in the forest interior and in large gaps and included removal of shrubs (no interactions), tieback of shrubs (belowground), removal of shrubs with addition of shade (aboveground), and unmanipulated shrubs (both below- and aboveground). We found that shrubs either suppressed or facilitated seedling survival and growth depending on the seedling species, source of interaction (e.g., above- or belowground), and ecological context (e.g., gap or forest interior). In general, shrubs strongly influenced survival and growth in gaps, with more modest effects in the forest interior. In gaps, the presence of shrub roots markedly decreased seedling growth and survival, supporting the idea that belowground competition may be more important in dry, nutrient-poor sites. Shrub shade effects were neutral for three species and facilitative for the other three. Facilitation was more likely for shade-tolerant species. In the forest interior, shrub shade negatively affected seedling survival for the most shade-intolerant species. For several species the net effect of shrubs masked the existence of both positive and negative interactions above and below ground. Our results highlight the complexity of plant-plant interactions, demonstrate that outcomes of these interactions vary with the nature of resource limitation and the ecophysiology of the species involved, and suggest that ecological theory that rests on particular notions of plant-plant interactions (e.g., competition) should consider simultaneous positive and negative interactions occurring above and below ground.

Linking root morphology, longevity and function to root branch order: a case study in three shrubs

Root branching order supports a powerful approach to understanding complex root systems; however, how the pattern of root morphological characteristics, tissue carbon (C) and nitrogen (N) concentrations, and root lifespan are related to anatomical features of variable root orders for mature shrubs (∼19 years old) in sandy habitats is still unclear. In this study, these relationships were investigated for three typical shrubs in Horqin Sand Land, Northeast China. Root diameter, individual root length, tissue carbon concentration, C:N ratio, root lifespan, root cross-sectional area (CSA), stele CSA, proportion of stele in root CSA, mean xylem vessel CSA and the number of xylem vessels all increased with root order for the three shrubs, while specific root length and nitrogen concentration decreased with root order. The combined root biomass of the first two orders accounted for more than 63% of the first–fourth order root biomass for all the three shrubs. Proportion of stele to root CSA and number of xylem vessels of third-order root segments were significantly higher than that of the first two orders, and third-order roots showed secondary development with a continuous cork layer. All first-order and most second-order roots exhibited primary development, had an intact cortex, a lower proportion of stele to root CSA, and a smaller number of vessels. Our research suggests that the first two order roots of shrubs in sandy habitats are responsible mainly for absorption, and that they play a major role in root turnover and C and N flux in the soil organic matter pool due to their high proportion of biomass and N concentration, as well as their short lifespan.

Phytomass and primary production of mire ecosystemsin Surgut Polesie

В работе дана количественная характеристика биологической продуктивности наиболее заболоченного региона Западной Сибири - Сургутского полесья. По запасам общей фитомассы болотные олиготрофные экосистемы достоверно различались в зависимости от занимаемого в микрорельефе положения: на микроповышениях (грядах и рямах) запас фитомассы составил 2500-3500 г/м2, в микропонижениях (мочажинах) - 1010-1250 г/м2. Тем не менее, чистая первичная продукция повышенных и пониженных элементов рельефа болотных экосистем Сургутского полесья оценивается в пределах 530-630 г/м2 в год и значимо не различается. Впервые изучен вклад древесного яруса болотных экосистем повышенного микрорельефа, который составил 30-40% от запаса всей живой фитомассы и 11-16% - от чистой первичной продукции.

Untangling positive and negative biotic interactions: views from above and below ground in a forest ecosystem

In ecological communities, the outcome of plant–plant interactions represents the net effect of positive and negative interactions occurring above and below ground. Untangling these complex relationships can provide a better understanding of mechanisms that underlie plant–plant interactions and enhance our ability to predict population, community, and ecosystem effects of biotic interactions. In forested ecosystems, tree seedlings interact with established vegetation, but the mechanisms and outcomes of these interactions are not well understood. To explore such mechanisms, we manipulated above- and belowground interactions among tree seedlings, shrubs, and trees and monitored seedling survival and growth of six species (Pinus banksiana, Betula papyrifera, P. resinosa, Quercus rubra, P. strobus, and Acer rubrum) in mature pine-dominated forest in northern Minnesota, USA. The forest had a moderately open canopy and sandy soils. Understory manipulations were implemented in the forest interior and in large gaps and included removal of shrubs (no interactions), tieback of shrubs (belowground), removal of shrubs with addition of shade (aboveground), and unmanipulated shrubs (both below- and aboveground). We found that shrubs either suppressed or facilitated seedling survival and growth depending on the seedling species, source of interaction (e.g., above- or belowground), and ecological context (e.g., gap or forest interior). In general, shrubs strongly influenced survival and growth in gaps, with more modest effects in the forest interior. In gaps, the presence of shrub roots markedly decreased seedling growth and survival, supporting the idea that belowground competition may be more important in dry, nutrient-poor sites. Shrub shade effects were neutral for three species and facilitative for the other three. Facilitation was more likely for shade-tolerant species. In the forest interior, shrub shade negatively affected seedling survival for the most shade-intolerant species. For several species the net effect of shrubs masked the existence of both positive and negative interactions above and below ground. Our results highlight the complexity of plant–plant interactions, demonstrate that outcomes of these interactions vary with the nature of resource limitation and the ecophysiology of the species involved, and suggest that ecological theory that rests on particular notions of plant–plant interactions (e.g., competition) should consider simultaneous positive and negative interactions occurring above and below ground.