Improve Tree Growth Research Articles

Variation in radial growth and wood density of Cyclocarya paliurus across its natural distribution

As a multiple function tree species, Cyclocarya paliurus is planted and managed for timber production and medicinal use. However, it remains unclear to what extent geographical gradients in growth and wood quality are shaped by the environment. We used data of 197 trees from 22 natural populations to assess geographic variation patterns in radial growth and wood density, and their correlations with environmental factors. Significant differences in mean annual DBH and wood basic density were observed among the 22 populations (p < 0.05). Based on mean annual DBH and wood basic density, the 22 populations were classified into three groups by hierarchical cluster analysis. Within its natural distribution, soil nutrients are more closely associated with DBH growth than are temperature and precipitation. However, correlations between wood density versus altitude and annual precipitation were found (p < 0.01). Trend surface analysis revealed that mean annual DBH growth and wood density displayed an increasing trend from north-west to south-east across its natural distribution. Our study provides valuable insights into the geographical patterns in growth and wood quality of C. paliurus, and an opportunity to improve tree growth and wood quality through phenotypic selection and selecting suitable sites for planting.

Spatial patterns of precipitation-induced moisture availability and their effects on the divergence of conifer stem growth in the western and eastern parts of China’s semi-arid region

Conifer forests in semi-arid regions are fragile and sensitive to climate change. As the climate changes, more frequent drought and higher temperatures may reduce conifer stem growth in these regions, but moistening and lengthening of the growing season may improve tree growth conditions. The relative influences of specific climate parameters on conifer stem growth, however, remain poorly quantified in Asian regions. We analyzed conifer stem growth responses to climate in the semi-arid region of China. Our analyses show a wetting trend since 1960 in the western part of this region, versus a drying trend in the east. We used tree-ring width data from a network of 33 forests as inputs for the process-based Vaganov–Shashkin-Lite growth model to assess how moisture patterns have affected tree growth in this region, and then used the resulting model to predict changes in tree growth during the 21st century. Tree-ring growth in our study region is mainly controlled by precipitation and soil moisture, and shows significant impacts of antecedent moisture conditions (the “water memory effect”). However, the contribution of soil moisture to tree growth was stronger in the eastern vs. western sub-regions (77% vs. 69%). Pointer-year analysis showed significantly stronger growth responses to soil moisture in the early growing season (April to June) in positive pointer years in the eastern sub-region, but showed no difference in the western sub-region. These results indicate that tree-ring growth in the eastern sub-region is more vulnerable to moisture availability. Our simulations suggest that tree growth will increase slightly under the RCP 4.5 and RCP 8.5 scenarios in both sub-regions, possibly due to the prolongation of the growing season caused by climate warming.

CO2 fertilization plays a minor role in long-term carbon accumulation patterns in temperate pine forests in the southwestern Pyrenees

Isolating the long-term fertilization effect of CO2 from other climate- and site-related effects on tree growth has been proven a challenging task. To isolate long-term effects of [CO2] on water use efficiency at ecosystem level, we used the FORECAST Climate forest model, calibrated for Scots pine (Pinus sylvestris L.) forests in the southwestern Pyrenees, growing at a Mediterranean montane site and at a continental subalpine site. Future climate scenarios (RCP 4.5 and RCP 8.5) were generated using a battery of six climate models to estimate daily values of temperature and precipitation in a 90-year series. A factorial experiment was designed to disentangle the importance on C pools of three growing limiting factors (nitrogen limitation, climate (temperature + precipitation) limitation and atmospheric CO2 concentration). The relative importance of each factor was quantified by comparing the scenario with the limitation of each individual factor turned on with the non-limitation scenario. Positive CO2 fertilization due to improvement in water use efficiency was detected by the model, but its quantitative impact improving tree growth was minimum: its average increase in ecosystem C pools ranged from 0.3 to 0.9%. At the site with cooler climate conditions (continental), the main limitation for tree growth was climate. Such limitation will be reduced under climate change and the ecosystem will store more carbon. At the site with milder climate conditions (Mediterranean), N availability was the main limiting factor albeit modulated by water availability. Such limitation could be reduced under climate change as N cycling could accelerate (higher litterfall production and decomposition rates) but also increase if droughts become more frequent and severe. In addition, the magnitude of the uncertainty related to climate model selection was much more important than CO2 fertilization, indicating that atmospheric processes are more important than tree physiological processes when defining how much carbon could be gained (or lost) in forests under climate change. In conclusion, due to the small changes in forest C pools caused by variation of atmospheric CO2 concentrations compared to changes caused by other growth limiting factors (nutrients, climate), reducing uncertainty related to climate projections seems a more efficient way to reduce uncertainty in tree growth projections than increasing forest model complexity.

Two Decades of Experimental Manipulation Reveal Potential for Enhanced Biomass Accumulation and Water Use Efficiency in Ponderosa Pine Plantations Across Climate Gradients

AbstractIn this study, we report 20 years of data from three ponderosa pine plantations in northern California. Our sites span a natural gradient of forest productivity where climate variability and edaphic conditions delineate marked differences in baseline productivity (approximately threefold). Experimental herbicide application and fertilization significantly reduced competition and improved tree growth by 1.4‐ to 2.2‐fold across sites. At the site of lowest productivity, where soils are poorly developed and water limiting, tree growth increased strongly in response to understory suppression. Small but significant improvements in tree growth were observed in response to understory suppression at the moderate‐productivity site. At the site of highest productivity, where climate is favorable and soils well developed, fertilization increased productivity to a greater extent than did understory suppression. In most cases, the effect of understory suppression and fertilization caused an unexpected growth release, exceeding the anticipated maximum productivity by &gt;5 m of additional height and 60–100% more basal area. At the site of highest productivity, however, understory suppression caused a weak increase on late‐season growth compared to fertilization alone, suggesting a beneficial effect of understory vegetation on long‐term growth at that site. Tree ring cellulose carbon isotopes indicate a negative relationship between intrinsic water use efficiency (iWUE) and tree growth in control stands, which shifted to a positive relationship as both iWUE and tree growth increased in response to management. Cellulose oxygen isotope ratios (δ18O) were positively correlated with iWUE and negatively correlated with vapor pressure deficit across sites, but δ18O was not a strong predictor of tree growth.

Long-Term Effect of Charcoal Accumulation in Hearth Soils on Tree Growth and Nutrient Cycling

There is a lack of long-term field approach investigating biochar impact on soil properties and vegetation, particularly in forest ecosystems. Relic charcoal hearths (RCHs), the result of the historical charcoal production in the forests, preserve a charcoal-enriched topsoil horizon, thus representing a suitable proxy for studying the long-term effect of biochar addition to soil. In this study, we analyzed the chemical properties of a soil as impacted by charcoal accumulation in three RCH plots in southern Wallonia (Belgium) compared to the soil outside RCHs. We further evaluated the effects of RCHs soil properties on the growth performances of silver birch and European beech as well as the leaves’ nutrient concentration of the latter. RCHs soil stored much more carbon and nitrogen than the reference ones. Most of the C in RCHs derived from charcoal (70‒94% of total organic carbon), which would correspond to a total input of 342 tons of biochar per hectare in these soils. Such an accumulation of charcoal still affects nutrient status of soil even after 150 years since charcoal hearths abandonment: CEC and K, Ca, Mg, Na, Mn and Zn concentration remained higher in RCHs soil compared to the reference one. In spite of a seemingly higher fertility of RCHs soil, elemental concentrations of European beech leaves grown in RCHs did not show any significant difference compared to the reference plots, except for C and Mn concentration, higher and lower, respectively, in the leaves of European beech trees grown inside than outside RCHs. Overall, RCHs soil chemical properties were not a decisive factor in significantly improving tree growth. On the contrary, tree ring width average values of both tree species was slightly lower in RCH plots, suggesting to better investigate the potential long-term detrimental effect of a large biochar addition to soil on forest trees.

The Efficacy of Semiselective Chemicals and Chloropicrin/1,3-Dichloropropene-Containing Fumigants in Managing Apple Replant Disease in South Africa.

Apple replant disease (ARD) is a biological phenomenon that is encountered when old apple orchards are replanted, resulting in tree growth and yield reductions in young trees. Three ARD orchard trials were conducted, which showed that semiselective chemicals (fenamiphos, metalaxyl, imidacloprid, and phosphonates) used independently, two fumigant formulations (33.3% chloropicrin and 60.8% 1,3-dichloropropene [Pic33-1,3D] and 57.% chloropicrin and 38% 1,3 dichloropropene [Pic57-1,3D]), and semiselective chemicals combined with Pic33-1,3D or Pic57-1,3D all contributed to significant increases in tree growth (trunk diameter and shoot length) relative to the untreated control 3 to 4 years postplanting. The treatments did not differ significantly from each other in improving tree growth. Yield was more indicative of treatment efficacy, but this varied between the three orchards. The Pic33-1,3D fumigant in combination with semiselective chemistries was the most consistent in significantly increasing cumulative yields. The Pic57-1,3D treatment was superior in increasing yields relative to the Pic33-1,3D treatment, because (i) it significantly increased cumulative yields in comparison with the Pic33-1,3D treatment in one orchard and (ii) in another orchard, a significant increase in yield was obtained with Pic57-1,3D relative to the control treatment but not with the Pic33-1,3D treatment. The quantification of ARD causative agents 20 months postplant showed that Phytophthora cactorum contributed to disease development in all three orchards; significant negative correlations existed between the quantity of P. cactorum DNA detected in tree roots and tree growth and less often, yield. In two orchards, only some of the treatments that significantly reduced the quantity of P. cactorum DNA in tree roots relative to the control also resulted in a significant increase in tree growth. Some of the aforementioned trends were also evident for Pratylenchus spp. root densities in two of the orchards. There was a significant positive correlation between P. cactorum root DNA quantities and Pratylenchus spp. root densities. Pythium spp. and "Cylindrocarpon"-like DNA quantities detected in tree roots typically were not indicative of treatment efficacy. However, a significant positive correlation existed between these two pathogen groups, suggesting complex interactions not associated with pathogen quantities per se.

Irrigation Regime and Soil Conditioners Impact on Characteristics of Sandy Soil and Washington Navel Orange Trees

Due to limited water resources it has become needed to study the best ways to decrease irrigation water use, increasing the water use efficiency, improve tree growth and sustain citrus crop production under those circumstances. Afield experiment was conducted during 2015/2016 and 2016/2017 seasons at El-Nubaria city, Beheira Governorate to investigate the effect of irrigation regime (80% and 60% from full irrigation) and soil conditioners (hydrogel at rate of 50 and 100g/tree as synthetic water absorbing soil amendments or organic plant residues at rate of 3.5 and 6.5kg/tree as natural absorbing soil amendments) on some properties of sandy soil, growth, yield, quality and productivity of irrigation water (PIW) for Washington navel orange trees under drip irrigation system. The obtained results pointed out that: The application of soil conditioners led to enhancing the properties and microorganisms activities and macronutrients of sandy soil especially with the high rates. Whereas, the low values of soil field capacity (10.47%), wilting point (4.26%) and available water (6.21%) were recorded with full irrigation without conditioners while, the high values (11.31 to 12.28%), (4.35 to 4.68%), (6.78 to 7.62%) respectively under irrigation regime combined conditioners. Soil conditioners application combined with irrigation regime increased the available nitrogen (up to 22.76%, phosphours (up to 9.98%), potassium (up to 15.14%), organic matter (up to 41.79%, CEC (up to 16.53%) and salinity (up to 4.64%) while soil bulk density was decreased (up to 5.66%) compared to full irrigation without conditioners. Moderate irrigation plus organic plant residues at rate of 6.5 kg/tree (T5) or plus hydrogel at 100g/tree (T3) significantly increased the most growth parameters (canopy volume, number of shoots/branch and leaf area), fruit set and decrease the fruit drop. Lowest percentage of fruit splitting (6.58 and 5.87 %) coated with T3 and T5 compared to deficit irrigation treatments plus the lowest rate of hydrogel or organic plant residues (T8 and T9). The highest yield was obtained by T3 (78.6 kg/tree) and T5 (79. 6 kg/tree). Control treatment (T1) followed by T3 and T5 tended to improve the physical fruit quality meanwhile deficit irrigation treatments T8 and T9 increased the most of chemical fruit quality. PIW mean values of Washington navel orange with full irrigation without conditioners were low (2.75 kg m-3) while, irrigation regime at 80 % and 60% recorded high values (3.49 kg m-3 and 3.88 kg m-3, respectively). PIW was increased with the high rates of soil conditioners.

The influence of nitrogen availability on anatomical and physiological responses of Populus alba \xd7 P. glandulosa to drought stress

BackgroundDrought and nitrogen (N) deficiency are two major limiting factors for forest productivity in many ecosystems. Elucidating the mechanisms underlying the influence of soil N availability on drought responses of tree species is crucial to improve tree growth under drought.ResultsThe root proliferation under drought was enhanced by adequate N application. Vessel frequency in xylem increased upon drought, with more significant increase under adequate N conditions compared with that under low N conditions, possibly leading to increased hydraulic safety. Nitrogen application under drought increased indole acetic acid (IAA), which contributed to the adaptive changes of xylem. Nitrogen application increased leaf abscisic acid (ABA) concentration, therefore regulated stomata adjustment, and promoted intrinsic water use efficiency (WUEi). Moreover, N application promoted antioxidant defense in leaves by showing increased level of free proline and carotenoid, which improved drought tolerance and growth performance of poplars.ConclusionsAnatomical and physiological responses of Populus to drought were suppressed by N deficiency. Adequate N application promoted adaptive changes of root and xylem under drought and increased hydraulic safety. Nitrogen addition under drought also increased leaf ABA level which may regulate stomata adjustment and promote WUEi. Moreover, nitrogen application improved antioxidant defense in leaves with increased levels of antioxidants. These positive regulations improved drought tolerance and growth performance of poplars.

How do mixing tree species and stand density affect seasonal radial growth during drought events?

Forecasted climate change impacts on temperate forest ecosystems include increased summer drought. Forest managers can increase the resistance of forest stands against summer drought by reducing stand density and favoring tree species mixtures. These strategies have been studied separately, but their combined effect on increasing forest stand resistance to summer drought is unknown.The main objective of our study was to quantify tree species interaction effects on radial growth during a water stress period and to determine whether these effects changed with different levels of competition reflected by stand density.The study was based in the Orleans state forest (Central France) at a long-term triplet experimental site (OPTMix) with pure and mixed stands of mature Quercus petraea and Pinus sylvestris. The experimental design comprised three repetitions of two densities (low and medium) in each composition (pure oak, mixed stands, pure pine). We monitored tree radial growth with 216 manual dendrometers placed throughout 18 plots, on small, medium and large trees. We analyzed three consecutive years with contrasted water stress: no water stress, a summer stress period, and a late summer stress period.We found that mixture did not improve tree growth of the either species during the summer water stress period. On the other hand, there was a mixture effect during the late summer water stress period but only in medium-density stands inversely for the two species studied. More growth occurred for oaks in mixtures while, inversely, more growth occurred for pines in monocultures. A density effect occurred only for oaks, which grew more in lower-density stands than in medium-density stands. Finally, tree size did not influence seasonal resistance to drought.

Effect of vegetation control, harvest intensity, and soil disturbance on 20-year jack pine stand development

Currently, there are uncertainties regarding the impacts and (or) efficacy of biomass harvesting and silvicultural practices on stand production on coarse-textured boreal soils. Replicated factorial field experiments examining effects of complete vegetation control (repeated glyphosate application) following operational stem-only harvest with disc trenching (SOT), operational whole-tree harvest with (WTT) and without (WT) disc trenching, and whole-tree harvest with complete forest floor removal by blading (WTB) and blading followed by compaction (WTBC) were installed on four sandy northern Ontario jack pine (Pinus banksiana Lamb.) sites. Over 20 years, WTB improved planted-tree survival but decreased longer term stand productivity in comparison with other harvest intensity – soil disturbance treatments. Vegetation control improved tree growth and stand productivity initially, but over time, benefits declined substantially. SOT and WTT had similar impacts on stand production. Disc trenching improved initial planted-tree growth (WTT vs. WT), particularly without vegetation control. Jack pine natural regeneration was greatest with SOT, accounting for 25% of stand biomass at year 20. Stand structure effects included increased size inequality of naturals with WTB and reduced size inequality and asymmetry of naturals with vegetation control. Overall, impacts of forest floor removal and natural regeneration on stand development have become increasingly important over time compared with those of vegetation control.

Wood ash as a soil amendment in Canadian forests: what are the barriers to utilization?

The contribution of forest biomass to Canada’s energy production is small but growing. As the forest bioenergy industry in Canada expands, there is growing interest in more sustainably managing the wood ash that is generated as a by-product. Despite being rich in nutrients, wood ash is usually landfilled in Canada. Soil applications of ash in Canadian forests could be used to mimic some of the effects of wildfire, to replace nutrients removed during harvesting, to counteract the negative effects of acid deposition, and to improve tree growth. At present, the provincial and territorial processes for obtaining regulatory approval to use wood ash as a forest soil amendment can be challenging to navigate. Furthermore, the costs for obtaining approval and transporting and applying wood ash to the soil can render landfilling a more cost-effective method of ash management. To ensure that wood ash applications in Canadian forests are conducted safely, effectively, and efficiently, experience from European countries could provide a useful starting point for developing best practices. The results of Canadian research trials will assist policy makers and forest managers in refining management guidelines that encourage soil applications of wood ash as a forest management tool while protecting the ecology, water quality, biodiversity, and productivity of Canadian forests.

Growing on the street: Multilevel correlates of street tree growth in Montreal

Tree planting has been favoured in many North American cities, including Montreal which aims to increase its canopy from 20% to 25% in 2025. However, the mortality rate of street trees is especially high in the first few years after planting. Studies have shown that variables that are intrinsic to the tree and those related to its location, the urban form and the socio-demographic characteristics of the surrounding environment are significantly associated either with trees’ survival rate or with vegetation cover. In this research we examine variables that have statistical associations with tree growth, which is the diameter at breast height divided by the number of years on the ground, for approximately 28,000 street trees in Montreal. Independent variables were nested into three spatial scales: the tree (species and physical variables), the street section (urban form variables), and the census tract (socio-demographic variables). Multilevel models reveal that 65.51% of the growth variance is potentially explained by the species and planting physical conditions such as the east and north sides (positive associations with the growth), signage as an obstruction (negative association). 28.54% of the grow variance is potentially explained by the urban form, in our case building age (convex relationship with the growth), mixed zoning (negatively) and residential zoning (positively). At the neighbourhood level, although none of our variables is significant, 6.95% of the growth variance is be potentially explained by other missing variables. New planting programs should hence consider the urban form in order to improve tree growth.

Effects of understory management on trade-offs and synergies between biomass carbon stock, plant diversity and timber production in eucalyptus plantations

Abstract Understory vegetation management is prevalent in successive short rotation eucalyptus plantations to control interspecies competition and improve tree growth and timber yields. Managing for multiple ecosystem services is critical for sustainable forests. Yet trade-offs and synergies between plant diversity, biomass carbon stock, and timber yields under different management approaches is poorly understood. Using eucalyptus plantations under different understory vegetation management approaches, in subtropical China, we examined the effects of understory vegetation management on tree growth, biomass carbon stocks, timber production, the composition and diversity of understory plant communities. We then assessed trade-offs and synergies among biomass carbon stocks, plant diversity attributes and timber production. Manual band tending (manual removal of the above-ground portion of understory vegetation in a 1 m band around the eucalyptus trees) did not affect the diversity of understory plant communities and favored biomass carbon stock and timber production. Thus, this treatment resulted in positive synergies between biomass carbon stock, plant diversity and timber production. Repeated broadcast herbicide application led to declines in understory plant diversity and increased exotic plant invasion, but also improved biomass carbon stock and stand volume. Trade-offs favoring carbon stock and timber production existed in broadcast herbicide application plots. Intensive disturbance of the understory and 0–5 cm topsoil removal led to declines in biomass carbon stock, plant diversity and timber production, and a negative synergy existed among these services. Our results confirm that manual band tending of understory vegetation in eucalyptus plantations, which results in positive synergies among plant diversity, biomass carbon stock, and timber production, should be a favorable management strategy for multiple ecosystem services. Although broadcast herbicide application can effectively improve carbon stock and timber production, attention should be paid to controlling invasive species after application.

Species-specific tree growth and intrinsic water-use efficiency of Dahurian larch (Larix gmelinii) and Mongolian pine (Pinus sylvestris var. mongolica) growing in a boreal permafrost region of the Greater Hinggan Mountains, Northeastern China

Increasing air temperature and atmospheric CO2 concentrations (Ca) can profoundly affect photosynthesis and intrinsic water-use efficiency (iWUE). However, the response of trees in boreal permafrost regions to rapid warming and Ca increases is poorly constrained by prior research. Here, we evaluated long-term changes in growth (using regional curve standardization [RCS]) and iWUE of Dahurian larch (Larix gmelinii) and Mongolian pine (Pinus sylvestris var. mongolica) in the boreal permafrost region of northeastern China and species-specific responses to increasing Ca and temperature. From 1930–2010, RCS growth of Dahurian larch and Mongolian pine decreased, while iWUE increased by 25.5 and 21.1%, respectively. RCS growth of both species was negatively correlated with winter temperatures, but Mongolian pine depended most strongly on previous December to current February temperatures and Dahurian larch depended most strongly on March temperatures. Moisture conditions only weakly influenced growth.We found similar long-term changes of tree-ring δ13C in the two species. Carbon isotopic discrimination of Dahurian larch and Mongolian pine was determined mainly by growing season temperature (positive) and moisture (negative), but with different signal strengths, suggesting that stomatal conductance influenced tree-ring δ13C. Commonality analysis showed that RCS growth was affected mainly by temperature, but also by the combined effect (interaction) of iWUE and temperature. However, the contribution of iWUE alone was lower for Mongolian pine. Our results suggest that the increased iWUE caused by increasing Ca will not improve tree growth sufficiently to compensate for temperature-induced water stress. The rate of temperature increase has slowed around 1990, which would have stabilized the degree of temperature-induced water stress, and this could be helpful to tree growth recovery in the permafrost region of northeastern China.

Nitrogen fertilization improves the growth of lodgepole pine and white spruce seedlings under low salt stress through enhancing photosynthesis and plant nutrition

The effectiveness of nitrogen (N) fertilization in improving tree growth in saline forest soils is poorly understood. Hence, in this study, the interactive effect of N fertilization and salt stress on seedling physiology and growth was examined to improve our understanding of possible mechanisms for fertilization to mitigate salt stress. We compared physiological characteristics, growth, and foliar and root nutrient concentrations in lodgepole pine (Pinus contorta) and white spruce (Picea glauca) seedlings planted in a peat-mineral soil mix during a three months study with N fertilization (0 and 300mgN seedling−1) and salinity (0, 50, 100, 150mmolL−1 NaCl) in a greenhouse experiment. Nitrogen fertilization significantly increased net photosynthetic rates (Pn) and N concentrations in needles and roots, resulting in improved seedling height and root collar diameter growth and total seedling biomass for both species when seedlings were subjected to low salinity (50mmolL−1 NaCl), while it did not help tree growth under high salinity (150mmolL−1 NaCl). The physiological responses to combined salt stress and N fertilization did not differ between the two species; however, fertilization improved the growth of pine seedlings more than that of spruce seedlings under different salinity levels. The results suggest that the effectiveness of N fertilization in mitigating the salinity effect on seedling growth was species specific. Our study demonstrates that N fertilization improves tree growth through enhanced photosynthesis and N nutrition under low salinity and provides valuable insights into strategies to manage N nutrition in saline boreal forest soils.

Evaluating multifunctionality and adaptive capacity of mountain forest management alternatives under climate change in the Eastern Alps

Future provisioning of ecosystem services (ES) from mountain forests is uncertain due to potential impacts of climate change. For a case study catchment in the Eastern Alps in Austria we analysed how management and climate change may affect the provisioning of four ES (timber production, carbon sequestration, biodiversity and bird habitat quality, and protection against gravitational hazards). We used the PICUS forest ecosystem model to project seven management alternatives that differed with regard to cutting pattern size (SLIT, PATCH, STRIP) and two harvesting intensity levels (in terms of return interval) under historic climate and five transient climate change scenarios over 100 years. In addition no management and sanitary management were simulated. In total twelve indicators were linked to model output to quantify ES provisioning. Results under historic climate showed increased volume and carbon stocks in low-intensity management, while high-intensity management decreased stocks. Bird habitat quality was maintained only by low-intensity management using SLIT and PATCH cuts. In particular rockfall protection decreased strongly under the STRIP cut scenario. Improved tree growth in warming scenarios was counterbalanced by increasing damage from bark beetle disturbances. Canopy openings and increased deadwood supply from disturbances partly fostered bird habitat quality in no-management alternatives. Overall none of the management alternatives performed best for all ES. PATCH and SLIT regimes at (currently practiced) low intensity appeared as compromise to achieve multifunctionality at small scale. As involved trade-offs among ES can be substantial, partial segregation with priority on specific services in designated zones is recommended.

Treatments for improving tree growth, yield and fruit quality and for reducing double fruit and deep suture incidence in “Desert red” peach trees

Five years old “Desert red” peach trees budded on Nemaguard rootstock and grown in sandy soil at commercial orchard Al-Nubaria city, El-Behira Governorate-Egypt were treated with some agricultural treatments involving thinning out pruning, fruit thinning and foliar application of potassium silicate (25% S +10% K2O) at 0.1% and super grow (20% N, 20% P2O5 and 20% K2O) at 0.3% in 2014 and 2015 seasons, to study their effects on yield and fruit quality and the relationship between nutrient balance and yield of “Desert red” peach trees. Beside, testing the influence of used treatments on two physiological disorder, double fruit and deep suture %. Also, economic evaluation of different treatments was done. All obtained data were statistically analyzed using a randomized complete block design. Depending on the obtained results in this study, it could be concluded that application of thinning out pruning 35%, fruit thinning by leaving 15 cm between fruits on one-year old shoot at 20 days after full bloom and foliar application of potassium silicate which sprayed five times during each growing season at fruit set, the second fruit development stage, the beginning of the fruit color change and twice after month from harvest, most profitable treatment for peach trees grown under conditions of this investigation. This treatment gave the best vegetative growth, yield, fruit quality, higher crop value with high net income /fed. from “Desert red” peach trees, in addition, reduced the percentage of double fruit and deep suture by more than 50% in both seasons, therefore, the study recommends this treatment for “Desert red” peach growers.

Organic amendments decrease bulk density and improve tree establishment and growth in roadside plantings

Soil compaction significantly impacts urban tree survival and herbaceous vegetation recruitment along roadsides. Soil samples were collected at two highway tree planting sites in Ontario, Canada. The average soil bulk density in the 0–10 and 20–30cm range was 1.45gcm−3 and 1.55gcm−3, respectively, at Site 1. At site 2, the average soil bulk density in the 0–10 and 20–30cm range was 1.49gcm−3 and 1.67gcm−3, respectively. Six treatments were established on each site to determine the amount of organic amendment required to decrease bulk density and increase tree growth as a measurement of successful tree establishment. Compost was incorporated into the soil at 0%, 10%, 25% and 50% on a volume-to-volume basis at both sites. In 2014 Acer x freemanii Autumn Blaze® ‘Jeffersred’ whips were planted into each treatment bed (Site 1, n=36 and Site 2 n=42). Bulk density, porosity, soil pH, EC, tree survival, height, shoot extension and chlorophyll content were measured for the 2014 and 2015 growing seasons. Incorporation of 25% v/v compost consistently decreased bulk density to below-root restricting thresholds, resulting in improved tree growth. Significant differences were observed in chlorophyll content between organic-amended remediated treatment beds compared to the control; chlorophyll content was significantly higher (p<0.05) for the 25% and 50% treatments throughout the 2015 growing season at both sites. Incorporation of compost at 10% and 25% v/v effectively reduced soil bulk density, leading to increased growth and reduced tree stress at both sites. This study demonstrates the importance of understanding the baseline of soil physical structure in prescribing remediation strategies, including organic amendments, in urban tree planting

Functional diversity enhances silver fir growth resilience to an extreme drought

Summary It is expected that extreme climate events such as droughts will increase in both severity and intensity as a consequence of forecasted climate change. Complementarity among tree species in resource acquisition strategy may reduce interspecific competition and increase the occurrence of facilitative interactions, resulting in an improved tree growth and resilience to extreme climatic events. However, the response of individual trees growing in more functionally diverse stands to extreme events is still under debate. We investigate the growth response of silver fir (Abies alba) to an extreme drought event which occurred in 1985–1986 in the Central Spanish Pyrenees and how the growth and resilience of trees relate to their neighbourhood functional diversity, stand heterogeneity and intraspecific and interspecific competition. Dendroecological methods were used to reconstruct radial growth. We recorded all tree species living around each sampled tree and calculated indices of intra‐ and interspecific competition among coexisting trees. Functional diversity around each focal tree was calculated by using the Rao's quadratic entropy. Silver fir growth decreased significantly in response to the drought in the vast majority of trees, but most of them showed a growth recovery 3 years later. Despite most trees showed negative growth trends following the drought event (70%), those trees growing in more functionally diverse stands were more resilient, recovered more quickly and displayed greater growth and growth trends. Synthesis. The presented findings support the growing body of evidence that shows a positive impact of diversity on forest function. In addition, we provide a direct linkage between tree growth response to climate at the individual tree scale and a direct quantification of neighbourhood functional diversity and competition. An enhanced functional diversity facilitating a more efficient use of resources at the interspecific level and potentially increasing facilitative interactions contributes to lessening the negative impacts of extreme events as droughts on forest growth.

Phylogenetically diverse AM fungi from Ecuador strongly improve seedling growth of native potential crop trees.

In many deforested regions of the tropics, afforestation with native tree species could valorize a growing reservoir of degraded, previously overused and abandoned land. The inoculation of tropical tree seedlings with arbuscular mycorrhizal fungi (AM fungi) can improve tree growth and viability, but efficiency may depend on plant and AM fungal genotype. To study such effects, seven phylogenetically diverse AM fungi, native to Ecuador, from seven genera and a non-native AM fungus (Rhizophagus irregularis DAOM197198) were used to inoculate the tropical potential crop tree (PCT) species Handroanthus chrysanthus (synonym Tabebuia chrysantha), Cedrela montana, and Heliocarpus americanus. Twenty-four plant-fungus combinations were studied in five different fertilization and AMF inoculation treatments. Numerous plant growth parameters and mycorrhizal root colonization were assessed. The inoculation with any of the tested AM fungi improved seedling growth significantly and in most cases reduced plant mortality. Plants produced up to threefold higher biomass, when compared to the standard nursery practice. AM fungal inoculation alone or in combination with low fertilization both outperformed full fertilization in terms of plant growth promotion. Interestingly, root colonization levels for individual fungi strongly depended on the host tree species, but surprisingly the colonization strength did not correlate with plant growth promotion. The combination of AM fungal inoculation with a low dosage of slow release fertilizer improved PCT seedling performance strongest, but also AM fungal treatments without any fertilization were highly efficient. The AM fungi tested are promising candidates to improve management practices in tropical tree seedling production.