Tree Roots Research Articles

Analysis of energy loss in the helical hedge flow channel of fruit tree root emitter

This paper proposes the design of a helical hedge flow channel with a high energy loss, which shows promising potential for application in fruit tree root emitters. The aim is to investigate the relationship between the energy loss form in the channel and its influencing factors. The hydraulic performance testing method is employed to analyze the factors that affect energy loss. The main influencing factors are determined using the response surface methodology (RSM) for experimental design. Based on the obtained experimental results, the energy loss form and influencing factors are analyzed, and a prediction model for the energy loss coefficient (ξ) is established. The results indicate that the ξ exhibits a decreasing trend with an increase in the diversion angle (α), a trend of first increasing and then decreasing with an increase in the channel width (b), and an increasing trend with an increase in the number of channel units (n). The effects of the straight section length (l1), convergence section length (l2), and bend radius (r) on the ξ can be neglected. The ranking of the geometric parameters' influence on the ξ is as follows: n > b > α > l1 > r > l2. The experimental results reveal that the ξ ranges from 19.2 to 234.3. Furthermore, the head loss along the flow channel constitutes merely 0.06–0.47% of the local head loss, The main form of energy loss in the spiral counter flow channel is local head loss. There is a significant linear relationship between α, b, n and the ξ, The established prediction model (R2 = 0.9691) can accurately predict the ξ of the channel.

An Integrative Review for the Role of Forests in Combating Climate Change and Promoting Sustainable Development

Forests play a critical role in combating climate change and promoting sustainable development. They are often referred to as the "lungs of the Earth" because they absorb carbon dioxide and release oxygen, making them vital for regulating the planet's climate and supporting life. Forests act as carbon sinks, absorbing and storing significant amounts of carbon dioxide from the atmosphere. Trees, through the process of photosynthesis, convert carbon dioxide into organic matter, which is stored in their biomass and in the soil. This process helps reduce the concentration of greenhouse gases, mitigating climate change. Forests are home to a vast array of plant and animal species. Biodiversity is essential for the stability and resilience of ecosystems. Maintaining healthy and diverse forests helps ensure that ecosystems can adapt to changing environmental conditions and continue to provide ecosystem services that support sustainable development. Forests contribute to climate regulation by influencing temperature, precipitation, and weather patterns. They release water vapor into the atmosphere through a process known as transpiration, which can lead to increased cloud cover and precipitation, thus affecting local and regional climates. Forests play a crucial role in protecting watersheds and maintaining the quality and availability of freshwater resources. Tree roots stabilize soil, reducing erosion and maintaining water quality. Forested areas often act as natural filters, removing pollutants and sediments from runoff. Forests provide livelihoods for millions of people worldwide, especially in rural areas. Sustainable forest management practices can ensure a steady supply of timber, non-timber forest products, and ecosystem services, contributing to the economic well-being of local communities. Forests offer various ecosystem services, including regulating services (climate regulation, water purification, erosion control), provisioning services (timber, fuelwood, non-timber forest products), cultural services (recreation, spiritual value), and supporting services (nutrient cycling, pollination). Adopting sustainable forest management practices is crucial to maintaining the benefits provided by forests. Sustainable logging, afforestation, and reforestation efforts can help maintain and even enhance the carbon sequestration capacity of forests. Recognizing and respecting the rights of indigenous peoples in forest management is essential. Indigenous communities often have valuable traditional knowledge of sustainable forest practices and can play a key role in conservation and sustainable development efforts. Efforts to restore degraded forests and establish new forested areas (reforestation and afforestation) can contribute to climate change mitigation and the protection of biodiversity. Global agreements such as the Paris Agreement and the United Nations Sustainable Development Goals (SDGs) acknowledge the importance of forests in climate action and sustainable development, providing a framework for global cooperation. In conclusion, forests are integral to addressing climate change and promoting sustainable development. Efforts to conserve and sustainably manage forests are essential to achieving environmental, social, and economic goals at both local and global levels. Recognizing the multifaceted benefits of forests and integrating them into climate and development strategies is crucial for a more sustainable and resilient future.

Simulation and Modelling of Tree Roots using GPR and Numerical Analysis

Traditional methods to check tree roots are complicated due to their destructive nature and limited quantitative assessments in long-term research. Therefore, this study aims to understand the synergistic use of the Ground Penetrating Radar (GPR) to obtain accurate information on tree root health. For this purpose, geophysical and surveying techniques are used. In the study, image data of tree roots were obtained using IDS Duo GPR under normal conditions. To obtain the most accurate results in GPRMax, the simulation used the greatest contrast dielectric value of soil and roots. Then, an analysis is conducted to compare synthetic and real data. Modelling is crucial to understand electromagnetic wave propagation and interaction with tree roots. First, the synthetic hyperbola’s shape is compared with the real root’s hyperbola. Second, roots with increasing diameters were simulated and the time interval associated with each diameter was determined to produce a regression line model. Finally, depending on the real-time interval and the collected data, the regression model is utilised to estimate the true diameter. The study found the following: (1) the results show that the high dielectric value of the detected roots, real and synthetic hyperbola, have similar amplitude and tail; (2) the findings demonstrate that the estimation model is good with an average error of ±8 mm under ideal conditions and ±20 mm under normal conditions. The estimation variation is strongly influenced by soil moisture. The GPR resolution and signal deteriorate when the high soil moisture content is high. As a result, this study could provide vital insight for more effective assessment of tree roots and serve as an important reference for researchers seeking to expand on present findings.

Moderate size diversity of tree roots has largest effect on the carbon loss in tropical soils

Abstract Most studies focused on the above‐ground diversity on leaf litter decomposition and soil respiration in tropical ecosystems, however, the mechanism understanding of root diversity on decomposition is still unclear. We selected the fine‐roots of 21 dominant tree species from a tropical rainforest in Xishuangbannan, China, then conducted a 360‐day and well‐replicated (21 replications) incubation decomposition experiment with a 0, 1, 3, 6, 9, 12, 15, 18 and 21 species gradient of root diversity. The fine‐root mass loss, CO2 release, and their potential drivers were analysed. The results showed that as fine‐root diversity increased, soil properties, microbial diversity and fungal biomass changed nonlinearly, leading to higher litter mass loss and soil CO2 release in the moderate diversity with 9, 12 and 15 species mixtures. Non‐additive effect analysis also indicated that synergistic effects were greater in these three mixtures than others on soil CO2 release and litter mass loss. The indirect effects of soil properties and microbial communities were larger than the direct effect of fine‐root diversity. Our findings suggest that fine‐root diversity has nonlinear relationships with litter decomposition and soil CO2 release in tropical forests, thus highlighting the importance of plant diversity due to its role in the carbon cycle under global change scenario. Read the free Plain Language Summary for this article on the Journal blog.

Varied Macro- and Micronutrient Fertilization Rates Impact Root Growth and Distribution and Fruit Yield of Huanglongbing-affected Valencia Orange Trees

Candidatus Liberibacter asiaticus (CLas), which causes huanglongbing (HLB) in citrus trees, has a great impact on tree root health, fruit development, and juice quality. HLB-affected trees have a fibrous root density loss of ∼30% to 80%, resulting in the limited capacity of citrus trees to uptake nutrients. Therefore, this study was conducted for 3 years to 1) assess the temporal changes in root density as a result of varied fertilization, 2) determine dynamics of HLB with regard to root growth and distribution as a result of varied fertilization for Valencia orange trees, and 3) evaluate the impact of varied fertilization rate and method of fertilization on fruit yield for HLB-affected trees. Macronutrients and micronutrients were applied at varying fertilization rates (0×, 1×, 2×, and 4×, of University of Florida guidelines). Root scans were done using minirhizotrons at 0 to 19.1 cm, 19.1 to 40.7 cm, 38.2 to 59.8 cm, and 57.3 to 78.9 cm soil depths. Results obtained from the study showed that root growth and distribution were greater in 0 to 19.1 cm than 19.1 to 40.7 cm to 57.3 to 78.9 cm soil depths. Thus, root growth decreased (P < 0.0004) with increasing soil depth due to variation in nutrient availability for tree uptake. Increased nutrient availability at occurrence of physiological processes in citrus trees also influenced root growth and distribution, resulting in root growth flushes in the months of Nov to early Feb and Jul to early Aug. Fruit yield was significantly different between treatments in 2 of the 4 years of the study (P = 0.001 and P = 0.003), and largely ascribed to soil fertilization of micronutrients compared with foliar. Therefore, at higher fertilization rates, particularly via soil application, nutrient availability was increased, thus promoting root growth and distribution and fruit yield in HLB-affected orange trees.

Colonization of 'Sampion' apple tree roots and rhizosphere by mycorrhizal fungi following the application of AquaGel or organic compost enriched with beneficial microorganisms

Colonization of 'Sampion' apple tree roots and rhizosphere by mycorrhizal fungi following the application of AquaGel or organic compost enriched with beneficial microorganisms

First report of Phytophthora macrochlamydospora associated with tree decline in Pinus taeda in Brazil

AbstractIn 2019, 18‐year‐old Pinus taeda trees with symptoms of chlorosis in the aerial part, shortening of needles and reduced plant growth, ultimately leading to tree decline, were found in plantations in southern Brazil. When collecting roots, a reduction in the volume of fine roots in trees and absence of ectomycorrhiza was observed. An oomycete was isolated from the roots and soil of the rhizosphere, and its pathogenicity was confirmed through Koch's postulates. The morphological characteristics of this oomycete were similar to the Phytophthora macrochlamydospora, which was confirmed by the molecular characterization from three gene regions (ITS‐rDNA, COX I and TEF1α). This is the first report of P. macrochlamydospora associated with tree decline in P. taeda in Brazil and worldwide.

Characterization of halotolerant phosphate-solubilizing rhizospheric bacteria from mangrove (Avicennia sp.) with biotechnological potential in agriculture and pollution mitigation

Mangroves represent intricate and ever-changing ecosystems, exhibiting fluctuations in water level, salinity, and nutrient (such as NPK) availability as well as a wide array of unique bacterial communities. Microbial interactions in different components (e.g., tree roots) of the mangrove ecosystem are crucial to understand the ecosystem functioning for potential application in pollution mitigation and agricultural production. This study aimed to isolate phosphate-solubilizing bacteria (PSB) from the rhizosphere sediment of mangrove (Avicennia sp.) in terms of heavy metals (HMs) and salinity tolerance as well as plant growth promoting (PGP) traits, where the effective PSB were used on Brassica chinensis for their seed priming and growth under salinity stress. The effective two PSB isolates were identified by 16S rRNA, where JKD01 and JKD02 were closely related (99%) to Enterobacter cloacae (OQ271412) and Kocuria rhizophila (OQ271413), respectively. Both the strains exhibited phosphate solubilization, IAA, NH3, and EPS production ability as well as HMs resistant ability where, E. cloacae (OQ271412) and K. rhizophila (OQ271413), are effectively remove the Cu from the water with 33.23% and 27.54%, respectively. The FTIR results showed functional group shifts (carboxyl, phosphate, and amino) in Cu-treated bacterial biomass and intracellular Cu presence, indicating the involvement of Cu in the bio-sorption and intracellular bioaccumulation process, respectively. The findings suggested PSB tolerance to salinity and HMs are present in mangroves, making them a valuable source for isolating effective bacteria to reduce stress in plants, lower HMs accumulation in mangroves, and aid in the bioremediation of HMs-contaminated environments.

An Efficient Dynamic Programming Algorithm for Finding Group Steiner Trees in Temporal Graphs

The computation of a group Steiner tree (GST) in various types of graph networks, such as social network and transportation network, is a fundamental graph problem in graphs, with important applications. In these graphs, time is a common and necessary dimension, for example, time information in social network can be the time when a user sends a message to another user. Graphs with time information can be called temporal graphs. However, few studies have been conducted on GST in terms of temporal graphs. This study analyzes the computation of GST for temporal graphs, i.e., the computation of temporal GST (TGST), which is shown to be an NP-hard problem. We propose an efficient solution based on a dynamic programming algorithm for our problem. This study adopts new optimization techniques, including graph simplification, state pruning, and A ∗ search, are adopted to dramatically reduce the algorithm search space. Moreover, we consider three extensions for our problem, namely the TGST with unspecified tree root, the progressive search of TGST, and the top-N search of TGST. Results of the experimental study performed on real temporal networks verify the efficiency and effectiveness of our algorithms.

The seasonal origins and ages of water provisioning streams and trees in a tropical montane cloud forest

Abstract. Determining the sources of water provisioning streams, soils, and vegetation can provide important insights into the water that sustains critical ecosystem functions now and how those functions may be expected to respond given projected changes in the global hydrologic cycle. We developed multi-year time series of water isotope ratios (δ18O and δ2H) based on twice-monthly collections of precipitation, lysimeter, and tree branch xylem waters from a seasonally dry tropical montane cloud forest in the southeastern Andes mountains of Peru. We then used this information to determine indices of the seasonal origins, the young water fractions (Fyw), and the new water fractions (Fnew) of soil, stream, and tree water. There was no evidence for intra-annual variation in the seasonal origins of stream water and lysimeter water from 1 m depth, both of which were predominantly comprised of wet-season precipitation even during the dry seasons. However, branch xylem waters demonstrated an intra-annual shift in seasonal origin: xylem waters were comprised of wet-season precipitation during the wet season and dry-season precipitation during the dry season. The young water fractions of lysimeter (< 15 %) and stream (5 %) waters were lower than the young water fraction (37 %) in branch xylem waters. The new water fraction (an indicator of water ≤ 2 weeks old in this study) was estimated to be 12 % for branch xylem waters, while there was no significant evidence for new water in stream or lysimeter waters from 1 m depth. Our results indicate that the source of water for trees in this system varied seasonally, such that recent precipitation may be more immediately taken up by shallow tree roots. In comparison, the source of water for soils and streams did not vary seasonally, such that precipitation may mix and reside in soils and take longer to transit into the stream. Our insights into the seasonal origins and ages of water in soils, streams, and vegetation in this humid tropical montane cloud forest add to understanding of the mechanisms that govern the partitioning of water moving through different ecosystems.

Maintenance of host specialisation gradients in ectomycorrhizal symbionts.

Many fungi that form ectomycorrhizas exhibit a degree of host specialisation, and individual trees are frequently colonised by communities of mycorrhizal fungi comprising species that fall on a gradient of specialisation along genetic, functional and taxonomic axes of variation. By contrast, arbuscular mycorrhizal fungi exhibit little specialisation. Here, we propose that host tree root morphology is a key factor that gives host plants fine-scale control over colonisation and therefore opportunities for driving specialisation and speciation of ectomycorrhizal fungi. A gradient in host specialisation is likely driven by four proximate mechanistic 'filters' comprising partner availability, signalling recognition, competition for colonisation, and symbiotic function (trade, rewards and sanctions), and the spatially restricted colonisation seen in heterorhizic roots enables these mechanisms, especially symbiotic function, to be more effective in driving the evolution of specialisation. We encourage manipulation experiments that integrate molecular genetics and isotope tracers to test these mechanisms, alongside mathematical simulations of eco-evolutionary dynamics in mycorrhizal symbioses.

Spatial heterogeneity of nitrification contributes to tree–grass coexistence in West African savannas

Abstract In savannas, the coexistence between trees and grasses is determined by complex mechanisms based on water partitioning and disturbances. But little is known about the contribution of other resources, such as soil nitrogen (N). In West African savannas, nitrification inhibition by grasses and nitrification stimulation by trees create spatial heterogeneity in nitrification fluxes and N stocks. Savanna trees can also extend part of their roots in the surrounding open area to absorb N. To investigate the role of the spatial heterogeneity of nitrification in tree–grass coexistence, we used a two‐patch model that simulates N dynamics between an open patch (without trees) and a tree clump patch (trees with grasses under their canopy). The open patch was characterized by a low nitrification rate, while the tree clump patch was characterized by a high nitrification rate. Both patches were connected through horizontal fluxes due to soil horizontal exploration by tree roots. We tested coexistence for different spatial tree distributions, as they are known to strongly influence savanna dynamics. Our results show that the spatial heterogeneity of nitrification induces spatial partitioning between ammonium (NH4+) and nitrate (NO3−) promoting tree–grass coexistence. As nitrification inhibition by grasses leads to high NH4+ availability in the open, the possibilities of coexistence are optimized when trees have different preferences in the open versus under their canopy. Thus, tree–grass coexistence is observed when grasses prefer NH4+, while trees prefer NH4+ in the open and NO3− under their canopy. Contrary to random tree distribution, tree clumping enhances tree–grass coexistence. Intraspecific aggregation strengthens the effect of spatial heterogeneity, which decreases interspecific competition and favours tree–grass coexistence. On the contrary, increasing the surface explored by tree roots in the open tends to increase tree–grass competition. This enhances the competitive ability of trees for N acquisition and consequently favours tree invasion. Synthesis. This study shows that this new coexistence mechanism based on mineral N partitioning into NH4+ and NO3− can be determinant in the functioning of West African humid savannas. This mechanism likely interacts with mechanisms based on disturbances, but such interactions should be studied using new models.

Fundamental but underrepresented: root carbon stocks in African montane forests

African montane forests harbor some of the greatest biodiversity worldwide, with high levels of species endemism. However, the loss of these forests through fragmentation, deforestation and climate change has been rapidly increasing in recent years. Montane forests in Africa are more susceptible to changes in climate than their lowland counterparts, yet their ecological value is still underrepresented. These montane forests have recently been highlighted as a major aboveground carbon (C) stock. The estimated 149.4 Mg C ha−1 from aboveground live trees surpasses estimates from the Intergovernmental Panel on Climate Change for these endangered forests, and exceeds reported values for neotropical montane and lowland forests by up to 70%. Despite the tremendous implications of these findings, coordinated and available research on the C storage potential of the other share of African montane forest biomass, that is in tree roots, is largely missing. Broadly estimated from the allometry of aboveground C stocks and from root:shoot ratios in lowland forests, more than 60 Mg C ha−1 can be stored in African montane forest roots, about 40% more than previously determined. While this broad estimation points at the potential importance of root C stocks in African montane forests, it also unveils a far-reaching knowledge gap. Here, we advocate for a more quantitative representation of the root C stock from dominant forest tree species of African tropical montane forests and ultimately for a better grasp on tree C stocks from this endangered ecosystem.

Exploring Microbial Dysbiosis in Orchards Affected by Little Cherry Disease

The phytoplasma ‘ Candidatus Phytoplasma pruni’, a causative agent of little cherry disease (LCD), has become an increasing problem for sweet cherry growers in Washington State, which is the largest producer of cherry fruit in the United States. The control of LCD currently relies on the identification and removal of infected trees, which has proven to be difficult because of the prolonged asymptomatic but still contagious state of the disease, and the lack of reliable and economical tests. Thus, the development of new approaches for early detection of LCD will be an important step in the successful control of this tree fruit disease. To identify potential microbial indicators of ‘ Ca. P. pruni’ infection, we evaluated the bacterial and fungal communities in the roots of cherry trees from two different orchards that were (i) infected with ‘ Ca. P. pruni’ and symptomatic; (ii) infected with ‘ Ca. P. pruni’ but remained asymptomatic; and (iii) healthy, with non-‘ Ca. P. pruni’-infected trees. We found significant variation in the microbiomes between the two cherry orchards, with the location being a stronger driving factor determining the fungal compared with the bacterial community. The fungal communities were less affected by the disease conditions compared with the bacterial microbiome. Overall, this study demonstrates the feasibility of the microbiome approach for the early detection of LCD caused by ‘ Ca. P. pruni’ but also demonstrates that more orchards need to be sampled because location was a stronger contributor to the microbiome of cherry tree roots than disease condition.

Transitional responses of tree growth to climate warming at the southernmost margin of high latitudinal permafrost distribution

The marked increase in temperature warming and permafrost degradation has raised apprehensions about the fate of forests of boreal forests in permafrost regions. However, the impact of climate on tree growth is not limited to direct effects but also involves complex interactions with permafrost. The degradation of permafrost poses a threat to forest growth that has received insufficient attention thus far, after analyzing the impact of permafrost degradation and climate on Dahurican larch (Larix gmelinii) growth from six forest sites with two maximum active layer thickness (ALT) classifications (more and less than tree root length) across the southern margin of the permafrost region. We found that accompanying the continued degradation of permafrost, tree growth was inhibited (slope = −0.67, p < 0.05) by the degradation of permafrost and the growth-climate relationship was shifted from positive to negative at maximum ALT less than tree root length sites. However, the growth rate of trees significantly accelerated (slope = 5.46, p < 0.05) at maximum ALT more than tree root length sites. Path analysis indicated that tree growth did not benefit from temperature warming and more stress could be caused by waterlogging due to permafrost degradation at maximum ALT less than tree root length sites, however, enhanced tree growth primarily by reducing the physical spatial constraints and root layer additional water source with permafrost degradation at maximum ALT more than tree root length sites. It also implies that the matchiness between tree root and maximum active layer depth is critical to the effect of permafrost degradation on tree growth. The transitional response to climate warming and the opposite trend of tree growth at two ALT classification sites suggest that future tree growth responds to the different stages of permafrost degradation differently. Our study provides a new insight on permafrost degradation impact on tree growth.

Temporal colonization of macadamia tree roots by Phytophthora cinnamomi based on a newly developed quantitative real‐time PCR assay

AbstractPhytophthora cinnamomi is an important soilborne pathogen causing root rot and stem cankers on macadamia in South Africa and other countries. It is unknown whether a temporal pattern exists in the colonization of macadamia tree roots by P. cinnamomi. To investigate this, three macadamia orchards were studied bimonthly for 2 years. The study also examined whether two types of feeder roots contained varying levels of P. cinnamomi DNA. A new sensitive P. cinnamomi‐specific quantitative real‐time PCR (qPCR) assay was used to conduct the assessments. Only symptomatic trees were studied in two of the orchards (ZC and ZD), while symptomatic and asymptomatic trees were assessed in the third orchard (ZA). In the ZC and ZD orchards, white non‐suberized feeder roots from a new root flush had higher levels of P. cinnamomi DNA than suberized feeder roots. In orchard ZD, autumn and winter yielded the highest P. cinnamomi root quantities in suberized roots. The symptomatic and asymptomatic trees in orchard ZA generally contained higher P. cinnamomi root quantities in winter than in summer. However, in orchard ZC, no significant temporal pattern was evident, although a trend was noticeable towards higher P. cinnamomi root colonization in autumn, winter and spring. Principal component analyses supported autumn and winter as the months yielding the highest P. cinnamomi root colonization levels. The study has contributed to a better understanding of the temporal nature of P. cinnamomi root colonization, and feeder root types that are optimal for qPCR quantifying the pathogen in macadamia.

Peyzaj Tasarımında ve Yönetiminde Ağaç-Yapı İlişkisi

The study aims to examine the tree-structure relationship based on the literature, determine the damages tree roots can cause to the structures, and suggest potential solutions. As a result of the literature review, we examined the following topics in this study: The structure of tree roots, the effects of tree roots on the soil, the risks that trees might create in structures, the methods for minimizing these risks, and finally the criteria to be taken into account when selecting the plant species nearby buildings. As a result of the literature review, we conclude that if the plant species selected are incompatible with the area, the structures might be damaged. Accordingly, we suggest potential solutions to prevent this damage. Furthermore, we examine factors to be considered when selecting plant species and the species we recommend not to prefer. Lastly, we explain the GPR technology used to observe tree root growth and prevent damage.

Yield Performance of Intercropped Marantha arundinacea L. (Arrowroot) in Two Rubber Plantation Designs

Developing rubber agroforestry systems is crucial to ensure the sustainable development of natural rubber cultivation. This study focuses on the starch crop Maranta arundinacea (arrowroot) and assesses its productivity and influencing factors when intercropped in 6–7-year-old conventional single-row and double-row rubber plantations. We analyze various aspects, including light resources, root distribution, soil nutrients, arrowroot growth characteristics, and product quality. The results indicate that the daily average photosynthetically active radiation (PAR) in the double-row rubber agroforestry system intercropping area ranges from 896.4 to 940.2 μmol·m−2·s−1. Additionally, the rubber tree roots near the intercropping area are less dense (107.0 g cm−3). In contrast, the conventional single-row rubber agroforestry system has a significantly lower daily average PAR of only 145.7 μmol·m−2·s−1, and the nearby rubber tree roots are more abundant (616.2 g cm−3). Although soil nutrient levels were slightly lower in the intercropping area on the double-row treatment compared to the single-row treatment, there was no statistical difference (p &lt; 0.05). Arrowroot’s photosynthetic capacity in the double-row rubber agroforestry system intercropping area is significantly greater than in the single-row rubber agroforestry system intercropping area. The yield per unit area in the former (23.46–27.47 t·ha−1) is also significantly higher than in the latter (2.87–4.75 t·ha−1, p &lt; 0.05), with higher starch content. Therefore, arrowroot exhibits higher productivity when intercropped in double-row rubber agroforestry systems, making it suitable for establishing a “rubber–arrowroot” agroforestry model to enhance the yield per unit area of rubber plantations.

Ash Dieback in Forests and Rural Areas—History and Predictions

Ash trees are an important component of both forests and the countryside. Emerging new diseases like ash dieback poses new challenges to Fraxinus spp., which not only have to adapt to global warming but also defend themselves against new threats from pathogenic fungi and insect pests. A new species of fungus, Hymenoscyphus fraxineus, has arrived in Europe from Asia and has severely damaged shoots which alters the structure of ash tree crowns. While some older trees have survived, younger trees are dying en masse, so the only hope is that the surviving trees will produce a younger generation that may be more resistant to the new diseases. The fine roots of ash trees are also attacked by pathogenic oomycetes, and others by Armillaria spp. The current stressed condition of ash trees in Europe is exacerbated by a new threat from insects. Agrillus planipennis, emerald ash borer, migrating from the east (from near Moscow airport) towards the borders of the European Union, killing thousands of ash trees on its way. This raises the question of future prospects for ash cultivation in Europe. This article takes a closer look at the information described in the literature.

Warming nondormant tree roots advances aboveground spring phenology in temperate trees.

Climate warming advances the onset of tree growth in spring, but above- and belowground phenology are not always synchronized. These differences in growth responses may result from differences in root and bud dormancy dynamics, but root dormancy is largely unexplored. We measured dormancy in roots and leaf buds of Fagus sylvatica and Populus nigra by quantifying the warming sum required to initiate above- and belowground growth in October, January and February. We furthermore carried out seven experiments, manipulating only the soil and not air temperature before or during tree leaf-out to evaluate the potential of warmer roots to influence budburst timing using seedlings and adult trees of F. sylvatica and seedlings of Betula pendula. Root dormancy was virtually absent in comparison with the much deeper winter bud dormancy. Roots were able to start growing immediately as soils were warmed during the winter. Interestingly, higher soil temperature advanced budburst across all experiments, with soil temperature possibly accounting for c. 44% of the effect of air temperature in advancing aboveground spring phenology per growing degree hour. Therefore, differences in root and bud dormancy dynamics, together with their interaction, likely explain the nonsynchronized above- and belowground plant growth responses to climate warming.