Growth, survival, and root system morphology of deeply planted Corylus colurna 7 years after transplanting and the effects of root collar excavation

Urban trees are frequently planted with their root collars and structural roots buried well below soil grade, either because of planting practices, nursery production practices, or both. These deeply planted structural roots can impair tree establishment and are thought to reduce tree growth, lifespan, and stability, although research has provided few and contradictory results on these questions to date. This study examines container-grown (55 L) Turkish hazel trees (Corylus colurna L.), planted either at grade, 15 cm below grade, or 30 cm below grade into a well-drained silt loam soil, over nearly 8 years. Five years after planting, in 2004, remediation treatments (root collar excavations) were performed on two replicates of each below-ground treatment. Subsequently, all trees were subjected to flooding stress by being irrigated to soil saturation for approximately 6 weeks. In 2006, flooding stress was repeated. Trees root systems were partially excavated in 2007, and root architecture was characterized. Deep planting did not affect trunk diameter growth over 8 years. Survival was 100% for the first 5 years; however, one 30 cm below grade tree died after flooding in 2004 and another died after the 2006 flooding. Photosynthesis was monitored during the 2004 flooding and all trees experienced decline in photosynthetic rates. There was an apparent slight delay in the decline for trees with excavated root collars and those planted at grade. Girdling roots reduced trunk taper and occurred primarily on unremediated trees planted 30 cm below grade.

Selected individual roots were excavated and followed from the root ball and were observed to gradually rise to the upper soil regions. Analysis of roots emerging from excavation trench faces indicated that vertical root distribution at approximately 1.25 m from the tree trunks was the same regardless of planting depth. Longterm consequences of planting below grade are discussed.     

Quantifying urban tree canopy interception in the southeastern United States

Urban stormwater is a major contributor to surface water degradation in the United States, prompting cities to invest in ways to naturally capture, store, and slowly release runoff through green infrastructure (GI). An often overlooked, yet integral, component of GI is urban tree canopy, which functions as GI through the process of rainfall interception (i.e., rainfall captured and stored within the canopy prior to returning to the atmosphere via evaporation). Nine trees from three native species commonly found in urban areas in the southeastern United States were studied in three parks in Knoxville, TN, USA to quantify interception. Throughfall (rainfall that passes through the canopy) and stemflow (rainfall that travels down the trunk) data were collected with continuous measurements by a network of automatic rain gauges positioned underneath each tree canopy. Data were collected from January 2018 to May 2019 which resulted in 98 storm events collected for each red maple (Acer rubrum) and willow oak (Quercus phellos), and 97 storm events collected for each white pine (Pinus strobus). Annually, red maples, white pines, and willow oaks intercepted 24.4%, 52.4%, and 33.2% of gross throughfall, respectively. Seasonally, white pines performed the most consistently with interception varying only from 49.2% to 57.0% between seasons compared to an interception range of 13.2–39.7% and 17.5–54.2% for red maples and willow oaks, respectively. Results demonstrated the effect of event duration, rainfall intensity, and seasonality on the interception potential of each species. Overall, these observations are a step toward allowing the storage capacity of urban trees to be properly credited as part of efforts to reduce stormwater runoff.     

The effect of container shape on the development of roots and canopy of woody plants

The branching and spread of roots in containers was studied in a shallow rooting plant (Erythrina corralodendrum) and in a deep-rooting plant (oak, Quercus ithaburensis). In the Erythrina, the weight of the roots was found to decrease towards the base of the container. Sixty percent of the root system was laterals, which were evenly distributed throughout the container. In the oak, a higher root weight was found in the lowest third of the container than in the 2 upper thirds. Lateral roots comprised 14% of the complete root system, mostly in the base of the container. Severe pruning of oak roots resulted in a ratio of main-root/lateral roots comparable to that found in unpruned Erythrina.The growth and distribution of roots of plants with different growth characteristics in containers of various shapes, e.g. deep and narrow, or shallow and wide as compared to regular shape containers, were studied. Thus, in Ficus retusa, which has a shallow root system, the development of roots was stimulated in a shallow and wide container, but roots and canopy were restricted in a deep and narrow container. In Pistacia lentiscus, which has a deep root system, planting in a shallow and wide container resulted in retarded canopy and roots, while growing the same plant in a narrow and deep container showed a stimulated root growth. In Dodonea viscosa, whose root system is naturally deep and tends to spread laterally, a slight retardation of the root development was found when it was grown in a shallow and wide container. When grown in a deep and narrow container, canopy and root growth were stimulated.The study indicated that growth tends to be stimulated when there is a mutual matching between the natural growth pattern of roots and the shape of their container.     

Growth and establishment of container-grown London planetrees in response to mulch,root-ball treatment and fertilization

We conducted two experiments to evaluate the impact of cultural treatments on growth and establishment of container-grown London planetrees (Platanus × acerifolia’ Bloodgood’). In both experiments, 48 trees grown in 100 l (#25) black plastic containers were assigned at random to one of three root-ball treatments prior to planting; no treatment (Control), outer 3 cm of roots removed around entire root-ball (Shave), or outer circling roots disentangled from the root-ball (Tease). In Experiment 1, half of the trees were fertilized with 400 g of controlled release fertilizer (15-9-12; N-P₂O₅-K₂O) at planting and the remainder of the trees were not fertilized. In Experiment 2, half of the trees were mulched with an 8 cm deep × 2 m diameter ring of coarse ground pine bark at planting and the remainder of the trees were not mulched. In Experiment 1, fertilization at planting increased SPAD chlorophyll content on two of four measurement dates but did not affect cumulative height or caliper growth after two years. After two growing seasons, root-ball treatments (shaving or teasing) increased root growth outside the original root-ball compared to control trees. Both root-ball treatments also reduced circling roots. In Experiment 2, mulching at planting increased soil moisture and cumulative tree height and diameter growth. Shaving increased new root growth and both root-ball treatments improved root architecture and reduced circling roots. Overall, the study demonstrates that root-ball manipulations can stimulate new root growth and reduce circling roots. Mulch is a valuable aid to conserve soil moisture and increase tree growth. Fertilization at planting provided little benefit in this experiment, which may have been related to a high level of soil fertility at the site or nutrient loading of the trees from nursery culture prior to transplanting.     

A review of oak wilt management: A summary of treatment options and their efficacy

Oak wilt, caused by the invasive fungal pathogen Ceratocystis fagacearum (Bretz) Hunt, is a serious and fatal disease of oaks, Quercus spp., with red oaks (section Lobatae) generally being more susceptible than white oaks (section Quercus). Oak wilt was first recognized in North America in 1944 and has since been confirmed in 24 eastern, midwestern, and southern states. The purpose of this paper is to review relevant literature on the efficacy of oak wilt treatment options. Root disruption, sanitation, and chemical control methods have been used most often to manage the disease. Root disruption has primarily focused on severing root grafts between oaks. Sanitation has focused on removal and proper disposal of potential spore-producing trees. Chemical control has focused on the use of systemic triazole fungicides. Efficacy of treatments can vary significantly, for example from 54% to 100% for root graft barriers. Educational programs can increase prevention efforts, detection, compliance with recommended management methods, and overall efficacy. Our review confirms that management programs should address underground and overland spread and include an educational component.     

Climatic response and impacts of drought on oaks at urban and forest sites

This study focuses on the climate and growth response of the sessile oak (Quercus petraea (Matt.) Liebl.) and the northern red oak (Quercus rubra L.) using dendrochronological methods. Tree-ring series of street trees in the city of Dresden, Germany and in a nature reserve close to the urban area were analysed, and the climate and growth response and moving correlation functions (CF) were computed. Moreover, the impact of 13 years of drought was examined by superposed epoch analysis (SEA). Our results show that differences emerge from peculiarities of the different site conditions, indicating that city oaks contain a higher level of noise in their ring width data due to human activities that degrade the strength of growth-climate associations. Importantly, climatic conditions during the previous summer and autumn and during the current spring season display significant correlations with annual growth. The stability of the climate–growth relationship was tested via moving correlation functions. A strong increase in the correlation with the temperature and precipitation in April was found for the trees of northern red oak in forests. Drought years induced significant reductions in radial growth for the northern red oak only. Nevertheless, the long-term impact of drought years must be considered as marginal because of the fast recovery of the radial growth after one to two years. In the future, the growth of the northern red oak may be restricted by an increased frequency of droughts and warmer and drier conditions in April.     

螺旋环剥对幼龄荔枝树生长结果的调控作用

‘糯米糍’和‘桂味’荔枝幼树不挂果现象相当普遍。采用螺旋环剥能显著促进成花、改善花质、减少落果、增加产量,改善品质。糯米糍、桂味幼树在生理落果期间出现旺盛的根梢生长峰,但其成年树和坐果比较正常的怀枝幼树都没有出现这种旺盛生长,表明了品种和树龄特性的差异。螺旋环剥明显减少生理落果期间的根与梢的生长量,使果实在与根、梢之间的库力竞争中获得优势,因而有利于坐果和果实生长。     

苹果中间砧入土深度对根系生长及其激素含量和果实产量品质的影响

 以陕西杨凌试验区大田栽培的3 年生‘长富2 号’苹果为材料,结合凤翔、永寿和蒲城等 试验区的调查,研究比较矮化中间砧（M26）入土深度对富士苹果树基砧根系生长分布、根系激素含量和 果实产量品质的影响。结果表明,矮化中间砧入土深度为15 cm 时,树体细根（＜ 2 mm）主要分布在0 ~ 40 cm 土层,细根数比其他处理多13.6% ~ 41.5%,总根数多18.2% ~ 33.3%,根系干质量多11.2% ~ 68.4%, 果实产量高,单果质量大,可溶性固形物含量高,硬度大,可滴定酸含量少,着色率高,品质较好。矮 化中间砧入土深度为15 cm,树体根系中促进生长的IAA、ZR、GA 含量较高,抑制生长的ABA 含量较 少,（IAA + GA + ZR）/ABA 比值较大,有利于刺激根系的生长。研究表明矮化中间砧入土深度为15 cm 时,根系生长旺盛,细根数量较多,能够为果树生长发育提供较多养分,果实品质较好。     

Apple rootstock studies: growth of trees on three clonal rootstocks planted with or without roots

Trees of Cox's Orange Pippin on M.IXa, M.26 and MM. 106 were planted either normally with roots or without roots to simplify the planting operation. Pruning treatments were superimposed, the trees being cut back at planting, left unpruned the first year and cut back the second year, or left entirely unpruned. All trees survived. After two growing seasons the trees were lifted and weighed. Removal of all roots before planting reduced shoot growth, trunk girth increment, final tree weight and incremental weight. However, on all rootstocks, trees planted without roots and left unpruned were similar in size when lifted to those planted with roots and cut back at planting in the orthodox manner.

In a complementary trial lasting one season Cox's Orange Pippin trees on M.26 were planted with or without roots. All trees were cut back at planting, and four times of planting were compared. The mid-April planting included trees that had been stored at 2.8 °C and trees that had been bedded-in outdoors. There were no tree losses attributable to removal of the roots before planting. Removing the roots at planting again reduced growth and weight of tree at lifting. Month of planting had no effect upon shoot growth or trunk girth increment.

The results are discussed, together with their practical implications in relation to mechanical tree planting for high density orchards.     

Rootstock and pruning effects on first season dry weight distribution in delicious apple trees

Redchief Delicious apple trees on MM. 106 and M.9 rootstocks were left unpruned, dormant headed at planting, or summer headed 12 weeks after planting, to investigate pruning and rootstock effects on dry weight distribution between roots and shoots during the first growing season. Dormant heading stimulated new shoot dry weight and reduced new root dry weight during the first six weeks after planting. However, by 12 weeks differences in new root dry weight and new shoot dry weight were insignificant. Summer heading resulted in a significant increase in new shoot growth and decrease in new root growth. This caused the root/shoot ratio in headed trees to return to the unpruned value within six weeks after summer heading. New root growth was reduced over a longer time by dormant heading trees on MM. 106 than those on M.9. New shoot growth was increased longer in trees on M.9. Allometric constants (K) of new shoot growth relative to new root growth were significantly changed by dormant heading with both rootstocks. Summer heading had the greatest effect on K values by shifting growth heavily toward new shoots. Root/shoot ratios in all treatments for both rootstocks showed no differences 24 weeks after planting.     

Poor anchorage and growth of spur ‘Red Delicious’ apple trees with deep crown roots

Spur ‘Red Delicious’ apple Malus domestica (Bork.) trees on MM 111 and seedlings that had been blown over by high winds had greater depth to first root and had thinner trunks than adjacent undamaged trees.     

Genotypic variation in water relations and gas exchange of urban trees in Detroit,Michigan, USA

Increasing tree species diversity has become a key underpinning for communities to improve resilience of urban and community forests. Increasingly, urban forestry researchers are examining physiological traits to aid in selecting trees for urban sites. Knowledge of physiological responses also has implications for understanding species’ resilience to increased stresses associated with climate change. Here, we compare growth, leaf SPAD chlorophyll index, water relations, and gas exchange of seven genotypes of shade trees planted in two locations in downtown Detroit, MI, USA. Genotypes included Redpointe® maple (Acer rubrum ‘Frank Jr.’), Flashfire® maple (Acer saccharum ‘JFS-Caddo2′), Pacific Sunset® maple (Acer truncatum x platanoides ‘Warrenred’), Emerald City® tulip tree (Liriodendron tulipifera ‘JFS-Oz’), Chanticleer® pear (Pyrus calleryana ‘Glen’s Form’), swamp white oak (Quercus bicolor), and Emerald Sunshine® elm (Ulmus propinqua ‘JFS-Bieberich’). Trees were planted in either Lafayette Plaisance Park (Park), a large urban greenspace, or on the median of St. Aubin Avenue (Median), a nearby major thoroughfare. Tree height growth and leaf SPAD index were higher for trees planted in the Park location than on the Median. However, genotypic variation was larger than the effects of location or the interaction of Genotype × Location for most traits. Across measurement dates, midday leaf water potential was lowest for Pyrus trees and highest for Ulmus and Liriodendron trees. Pyrus and Quercus trees had relatively high rates of net photosynthesis (A) and stomatal conductance (g_s) while Liriodendron, Acer saccharum, and Ulmus trees had low rates of A and g_s. Liriodendron trees closed their stomata rapidly as leaf water potential (Ψ_w) declined (isohydric response), while Pyrus and Quercus trees maintained g_s across a range of leaf Ψ_w (anisohydric response). Liriodendron trees also had the highest relative growth rates, suggesting that drought stress avoidance through isohydry is a viable drought tolerance mechanism in urban trees.     

Piriformospora indica promotes adventitious root formation in cuttings

Adventitious root formation in excised plant shoots is a crucial process in the vegetative propagation of many plant species, and insufficient rooting causes substantial losses in the propagation industry. Based on the various physiological effects on whole plants described for the basidiomycete Piriformospora indica, it was hypothesized that inoculation of the substrate with this endophyte should promote the generation and growth of adventitious roots in cuttings. Inoculation experiments were conducted to study the effects of P. indica on adventitious rooting in three plant species. Inoculation with P. indica dramatically enhanced the number and length of the adventitious roots in pelargonium and poinsettia. Root colonization parameters suggest that the interaction between the endophyte and cuttings had already occurred before physical contact. In contrast, petunia showed no rooting response to P. indica inoculation. Very fast root formation in this plant indicates that a minimum time period for the fungus–plant interaction is required for establishment of a promoting effect. P. indica-based biotechnology is proposed as a new tool for improving plant propagation systems of plant species or cultivars with low to moderate capacity of adventitious root formation.     

Effect of different girdling dates on tree growth,fruit characteristics and reserve accumulation in a late-maturing persimmon

Trunks of 8-year-old vigorous ‘Fuyu’ persimmon (Diospyros kaki Thunb.) were girdled to a 1 cm width on April 20 and June 10 2004. Tree growth and fruit characteristics were monitored for two years, with special emphasis on the carry-over effect in 2005. Girdling reduced trunk and shoot growth especially of April-girdled trees over two consecutive years. However, the most significant effect of girdling was in the occurrence of water sprouts: a control tree had 29.5 in 2004 and 27.3 in 2005, whereas the April-girdled trees had only 0.3 and 5.3, respectively. Girdling increased fruit set by nearly 50% and enhanced fruit colour in 2004 only. Girdling date did not significantly affect fruit size and soluble solids for two years. Fruit flesh of girdled trees in 2004, especially in the April-girdled trees, had lower N and P concentrations. The levels of starch, soluble sugars, and inorganic elements in flower-bearing distal buds measured just before new growth in 2005 were not significantly altered by the girdling in 2004.     

Effect of different lifting dates and different lengths of cold storage on plant vitality of silver birch and common oak

Woody ornamental bare-root plants transplanted in urban areas frequently show poor establishment and occasionally high mortality. Tolerance to different stress factors during transplanting is dependent on plant vitality. The significance of lifting date, in combination with different lengths of time in cold storage, was investigated with 2-year old plants of silver birch (Betula pendula Roth.) and common oak (Quercus robur L.). Plants were grown on a field site in Southern Sweden and were lifted on four occasions, at intervals of 4 weeks, during autumn and early winter. After lifting, plants were stored in a cold store for 90, 135 and 180 days and then (a) xylem water potential in roots and shoots, (b) root growth potential (RGP), (c) mortality and die-back, and (d) shoot and leaf growth were assessed. Lifting bare-root plants of silver birch and common oak too early in the autumn resulted in 62% mortality in birch and 43% in oak, and 31 and 26% die-back in birch and oak, respectively. Plants lifted at a later date showed no mortality in birch and <10% in oak, and almost no die-back. Plants lifted too early in autumn showed decreased root, shoot and leaf growth, compared with those lifted later in the autumn. A longer time in cold storage had a further negative effect on plant vitality in plants lifted too early. Plants lifted later in autumn showed little or no difference in mortality or die-back, for different periods of cold storage, and showed an increase in growth with longer periods of cold storage. Birch plants lifted too early had lower water potential, both in roots and shoots, compared to plants lifted at a later date, while oak plants had the lowest water potential when lifted late. Plants lifted on the first occasion had not been exposed to temperatures below +5°C before lifting, while plants lifted 4 weeks later had been exposed for 67 h to a mean temperature below +5°C. Plants lifted on the first occasion had high mortality and more die-back, while those lifted 4 weeks later showed almost no damage at all. These observations indicate that accumulated exposure to low temperature is probably an important factor in the development of stress tolerance in bare-root plants of silver birch and common oak.     

Designing food and habitat trees for urban koalas: Tree height,foliage palatability and clonal propagation of Eucalyptus kabiana

Koalas are iconic Australian tree-dwelling marsupials that are classified as vulnerable because of threatening processes that include urban development, habitat fragmentation and inbreeding. Koalas eat the leaves of specific eucalypt trees but urban planners and landowners often prefer to plant smaller trees that pose less risk from falling limbs. We have conducted a long-term project to develop shorter koala-food trees for planting in parklands, schools, streets and gardens. We identified a little-known and geographically-confined species, Eucalyptus kabiana, that had potential for urban plantings. We assessed the height of E. kabiana trees in cultivation, determined whether their foliage was palatable to koalas, and compared the amenability to vegetative propagation of E. kabiana with that of an extensively-propagated related species, E. tereticornis. Cultivated E. kabiana trees were short, reaching around 3–5 m height after 6 years. Their foliage was highly palatable to koalas, and their cuttings proved to be amenable to propagation. Average rooting percentages for E. kabiana cuttings were 31–46%, similar to values obtained with E. tereticornis cuttings. Over 600 E. kabiana trees have thus far been distributed for planting in wildlife corridors, parklands, schools and gardens. The planting of more koala-food trees will help to alleviate the risks of inbreeding faced by koala populations in fragmented urban landscapes. School plantings also provide opportunities for students to learn about and interact with organisms such as koalas that inhabit the Eucalyptus trees.     

Investigations of exogenous applications of carbohydrates on the growth and vitality of live oaks

Some practitioners within the green industry have lauded the application of sugar-containing products to the soil around trees as a method to improve plant health. A research study was initiated to evaluate the effects of exogenous applications of glucose and starch on the growth and vitality of healthy live oaks (Quercus virginiana P. Miller). Glucose, starch, or a 50:50 mixture of both carbohydrates were applied as soil drenches around 60 young live oaks growing at a field nursery. Carbohydrates were dissolved in water and applied at concentrations of 0, 40, 80, and 120 g L^?1 within 0.5 m from the trunk. Solutions were applied using 10 L per application every four months during an 18-month period. Trunk diameter, root and canopy growth, and carbohydrate content of twigs and roots were measured every four months, and net photosynthetic rate, chlorophyll fluorescence, and soil respiration were measured every six months. Tissue samples from twigs and roots were collected after 16 months to measure carbon isotope composition (δ¹³C) as an indicator of carbohydrate uptake. Chlorophyll fluorescence varied throughout the experiment but did not demonstrate a clear trend. Higher carbohydrate applications did influence the concentration of glucose in twigs although the results did not clearly indicate that this effect was caused by an uptake of glucose from roots. δ¹³C signatures did not provide any evidence about potential carbohydrate uptake. Even though there was a significant increase in soil respiration after being treated with starch, no significant increase in growth or vitality was detected on healthy live oaks.     

从调节源—库关系看环剥对荔枝幼树根梢生长与坐果的调控

荔枝常因幼树花而不实而颗粒无收.糯米糍品种4年生幼树盛花期主干环剥,并保持不愈合至采果.对照树全年根、梢各有3个生长期,环剥树采前无根、梢生长;对照树有4次生理落果峰,环剥树第2、3落果峰不明显,采前落果峰也很低.研究认为荔枝幼树根系的“库”力在竞争中占优势,根与梢的生长相克又相促,果实在竞争中处于劣势,环剥完全抑制了根与梢的生长,使果实在“库”力的竞争中得以转弱为强.     

Recovering the urban forest: The role of trees,tree culture,and place attachment before and after Hurricane Harvey

Trees can be powerful symbols that contribute to the production and consumption of places. Disaster events, such as hurricanes, alter the physical landscape, causing tree damage and loss. In places with strong tree cultures, the reforestation of damaged landscapes becomes an implicit element of recovery plans; however, less is known about the implications of tree loss to community recovery. In 2017, Hurricane Harvey made landfall near the coastal communities of Rockport and Fulton, Texas. Rockport-Fulton, known for its beach tourism, is home to a remnant live oak (Quercus virginiana) forest shaped by coastal onshore winds. Many of Rockport-Fulton’s windswept oaks were damaged or lost along with native and non-native palm trees. Rockport-Fulton’s history is imbued with stories situated around its oak forest. Drawing from multiple sources and participant observations from repeated site visits, we analyzed references to Rockport-Fulton’s trees in news media, organizational communications, and public exhibits before and after Harvey to understand the area’s tree culture and its associated discourses. We also interviewed tourists, business owners, and community members nine months after Harvey to understand their perceptions of recovery efforts. Our findings show that tree narratives pre- and post-Harvey amplify social-ecological systems definitions of resilience and that tree loss was a dominant theme in the recovery process for all participants. Yet we also found that tourists discussed the damage to palm trees, whereas community members focused on the loss of live oaks. Despite these preferences, trees available through replanting efforts contained few live oak and palm species; furthermore, recovery plans did not amplify trees in recovery strategies. Overall, our findings highlight the importance of replanting trees during the disaster recovery process in a way that not only enhances local biodiversity but also reaffirms place characteristics to meet community members’ and visitors’ expectations.     

植物不定根诱导生成机制研究进展

不定根诱导发生是研究植物发育和形态建成的一个重要理论课题,也是优良林木无性繁殖、成功实现转基因材料植株再生以及加速林业产品原料植物规模化栽培的关键问题。植物不定根的发生是一个十分复杂且多因素影响的过程,是植物体内的内源因素和体外的外源因子共同作用的过程。该研究通过归纳国内外关于不定根发生的形态解剖、生理生化、植物分子方面的研究进展,分析不定根发生过程中存在的不同影响因素及其影响效果,以期为植物不定根诱导研究提供有力的理论依据,并为实践中植物无性繁殖诱导不定根提供参考依据。