Root Competition Research Articles

Agroforestry potential of a wild mango species (Mangifera sylvatica Roxb.)

In Bangladesh, very few native species have been incorporated into agroforestry systems, and common species are generally exotic pan-tropical species. This neglects the wealth of native genetic resources available and native species are under-valued, which can result in a lack of conservation interest in threatened species. The present study seeks to address this by considering the potential for including a locally threatened native species, Mangifera sylvatica Roxb. into the agroforestry systems of Bangladesh. We investigated farmers’ preferences, tree architecture and root competitiveness in comparison with other agroforestry species to assess the potential and to identify any barriers to use. According to farmers, M. sylvatica is a multipurpose tree species, with the main uses being for timber and provision of wild fruit. In addition, unripe fruits are sold to the pickle industry for seasonal income. The average observed height of matured M. sylvatica trees are approximately 14 m with a straight bole. The crown architecture, light quality under the canopy and root competitive index of M. sylvatica species is similar to popular agroforestry species like Mangifera indica, Artocarpus heterophyllus and Acacia auriculiformis. This indicates M. 9;/indica, A. auriculiformis and A. heterophyllus. Due to over-exploitation, illegal logging and habitat destruction, M. sylvatica is currently threatened in Bangladesh. The major barriers to use include: fruit collection being time consuming and laborious; ripe fruit quality not as good as Mangifera indica; fruits contain small amounts of flesh that often harbour insects; storage problems; irregular fruiting; and limited consumption. Farmer's preferences of wild mango are also simialr to M. indica and A. heterophyllus. Promotion of the species’ positive attributes will be necessary to develop its potential as a new native agroforestry species, which can provide a valuable conservation initiative that ultimately protects genetic diversity and quality of this native tree species.

Experimental Approach Alters N and P Addition Effects on Leaf Traits and Growth Rate of Subtropical Schima superba (Reinw. ex Blume) Seedlings

Nitrogen (N) and/or phosphorus (P) addition has controversial effects on tree functional traits and growth; however, this experimental approach may clarify these controversial results. In this study, field and pot experiments were designed with +N (100 kg N ha−1 yr−1), +P (50 kg P ha−1 yr−1), +NP (100 kg N plus 50 kg P ha−1 yr−1), and a control (no N or P addition) to comparatively investigate the effects of N and P addition on 24 leaf traits and the growth rate of Schima superba (Reinw. ex Blume ) seedlings in subtropical China. We found that the experimental approach alters N and P addition effects on leaf traits and tree growth. Nitrogen addition strongly altered leaf biochemical and physiological traits and limited tree growth compared to P addition in the pot experiment, while the effects of N and P addition on leaf traits and tree growth were weaker in the field, since the seedlings might be mainly limited by light availability rather than nutrient supplies. The inference from the pot experiment might amplify the impact of N deposition on forest plants in complicated natural systems. These findings will help guide refining pot fertilization experiments to simulate trees in the field under environmental change. Future directions should consider reducing the confounding effects of biotic and abiotic factors on fertilization in the field, and refinement of the control seedlings’ genetic diversity, mycorrhizal symbiont, and root competition for long-term fertilization experiments are required.

Interactive Effects of Intraspecific Competition and Drought on Stomatal Conductance and Hormone Concentrations in Different Tomato Genotypes

Plant physiological responses to various stresses are characterized by interaction and coupling, while the intrinsic mechanism remains unclear. The effects of intraspecific competition on plant growth, stomatal opening, and hormone concentrations were investigated with three tomato genotypes (WT-wild type, Ailsa Craig; FL-a abscisic acid (ABA) deficient mutant, flacca; NR-a partially ethylene-insensitive genotype) under two water regimes (full irrigation, irrigation amount = daily transpiration; deficit irrigation, 60% of irrigation amount in full irrigation) in this study. Three kinds of competitions were designed, i.e., root and canopy competition, non-root competition, and non-canopy competition, respectively. Intraspecific competition reduced plant leaf area and stomatal conductance (gs) of wild-type tomato, accompanied by ABA accumulation and ethylene evolution. Intraspecific competition-induced decrease in gs was absent in FL and NR, indicating ABA and ethylene involved in plant response to intraspecific competition. As soil water becomes dry, the competition decreased gs by elevating ABA and ethylene accumulations. Under severe drought, the competition-induced decline in gs was covered by the severe drought-induced decrease in gs, as hydraulic signals most probably dominate. The absence of canopy competition insignificantly influenced plant stomatal opening of well-watered tomato, as canopy separation minimized the plant neighbor sensing by ethylene and other signals. Whereas under water deficit condition, the absence of canopy competition significantly reduced ABA accumulation in roots and then stomatal conductance, indicating the belowground neighbor detection signals maybe enhanced by soil drought. The absence of root competition increased ethylene evolution, confirming the importance of ethylene in neighbor detection and plant response to environmental stress.

Maize and sorghum root growth and yield when intercropped with forage grasses

AbstractIntegrated crop–livestock systems that intercrop forage crops with grain crops are effective for increasing forage production and improving nutrient cycling and soil health. However, the potential for root competition when maize (Zea mays L.) and sorghum [Sorghum bicolor (L.) Moench] are intercropped with forages in sandy soils is unknown. The objectives of this study were (a) to evaluate the root growth and production characteristics of maize and sorghum intercropped with forage grasses and (b) quantify above‐ and belowground biomass in a tropical integrated cropping system. Two 3‐yr experiments were conducted in which maize and sorghum were intercropped with forage grasses: guineagrass (Panicum maximum Jacq.), ruzigrass [Urochloa ruziziensis (Germ. & Evrard) Crins], palisade grass [Urochloa brizantha (Hochst ex A. Rich.) R. Webster], or an Urochloa hybrid. Monocropped maize and sorghum were used as controls. Fine roots (≤3 mm) were sampled in the monocropped and intercropped systems at soil depths of 1.0 m. Intercropping guineagrass and palisade grass with maize and sorghum resulted in 40% greater dry matter production than intercropping with ruzigrass and the Urochloa hybrid. The positive effect of intercropping forage grasses in the low‐fertility sandy soil was greater for sorghum than for maize because of lower root growth competition. On average, intercropping maize and sorghum with forages increased the total above‐ and belowground biomass by 30 and 50%, respectively, compared with monocropping. In summary, intercropping maize and sorghum with forage grasses is a viable option to enhance biomass during the off‐season in tropical integrated crop–livestock systems.

Empirical survival model for European beech (Fagus sylvatica L.) seedlings in response to interactive resource gradients and (a-) biotic conditions within an experimental canopy gap study

The success of beech regeneration depends on resource availabilities, which are both heterogeneously distributed in forests and influenced by climate change impacts such as drought and heat waves. To ensure beech regeneration success in the future, it is therefore of great interest to understand the influences of different resource availabilities and their potentially interactive effects on beech seedling survival. In an experimental canopy gap study, we investigated the effects of direct (DIRSF) and diffuse (DIFFSF) solar radiation, soil fertility, groundwater influence, micro-site elevation, vegetation and root competition of overstorey trees on the survival of beech seedlings two years after planting in 2017. The inverse of fine root densities found for overstorey beech (BGRB) and oak (BGRO) was interpreted here as an approximation of the availability of below ground resources, mainly soil water. A logistic model demonstrated positive and interactive effects of DIFFSF, BGRB and soil fertility, emphasizing the complementary resource use pattern of beech seedlings. DIRSF showed a negative effect on survival that was enhanced on groundwater-dominated and higher elevated micro-sites and linked to intensified water limitation. The initial stature of seedlings, the presence and biomass of vegetation and BGRO had no significant effects on beech seedling survival. The unexpected extend to which DIFFSF affected beech seedling survival, the given significance of complementary effects of DIFFSF, BGRB and soil fertility, as well as found interactive effects of DIRSF are discussed in the context of the 2018/19 drought event. Our results suggest that silvicultural measures, such as the creation of larger gaps, can significantly improve resource availabilities, providing an opportunity to increase survival of beech seedlings in the face of climate change impacts.

Competition components along productivity gradients – revisiting a classic dispute in ecology

Competition is ubiquitous in plant communities with various effects on plant fitness and community structure. A long‐standing debate about different approaches to explain competition is the controversy between David Tilman and Philip Grime. Grime stated that the importance of competition relative to the impact of the environment increases along a productivity gradient, while Tilman argued that the intensity of competition is independent of productivity. To revisit this controversy, we assumed that the effects of plant–plant interactions are additive and applied the new competition indices by Díaz‐Sierra et al. (2017) in a field experiment along a productivity gradient in S‐Germany, using the rare arable plant Arnoseris minima as a study species. The ‘target technique' was applied, to separate the effects of root and shoot competition. The study plants were exposed to five competition treatments with three replicates in 18 sites, respectively. We investigated the expectation that root competition is more intense in unproductive sites than shoot competition. Additionally, we predicted survival to be less affected by competition than growth‐related plant parameters. Using the biomass of individuals without competition as a proxy for site productivity there was a positive relationship with competition importance but no relationship with competition intensity when plants experienced full competition. Survival of the target plants was unaffected by competition. Root competition was the main mechanism determining the performance of the target plants, whereas the effect of shoot competition was relatively low albeit increasing with productivity. We conclude that when considering plant–plant interactions additive both Grime's and Tilman's theories can be supported.

Including tree spatial extension in the evaluation of neighborhood competition effects in Bornean rain forest.

Classical tree neighborhood models use size variables acting at point distances. In a new approach here, trees were spatially extended as a function of their crown sizes, represented impressionistically as points within crown areas. Extension was accompanied by plasticity in the form of crown removal or relocation under the overlap of taller trees. Root systems were supposedly extended in a similar manner. For the 38 most abundant species in the focal size class (10–<100 cm stem girth) in two 4‐ha plots at Danum (Sabah), for periods P1 (1986–1996) and P2 (1996–2007), stem growth rate and tree survival were individually regressed against stem size, and neighborhood conspecific (CON) and heterospecific (HET) basal areas within incremented steps in radius. Model parameters were critically assessed, and statistical robustness in the modeling was set by randomization testing. Classical and extended models differed importantly in their outcomes. Crown extension weakened the relationship of CON effect on growth versus plot species’ abundance, showing that models without plasticity overestimated negative density dependence. A significant negative trend of difference in CON effects on growth (P2−P1) versus CON or HET effect on survival in P1 was strongest with crown extension. Model outcomes did not then support an explanation of CON and HET effects being due to (asymmetric) competition for light alone. An alternative hypothesis is that changes in CON effects on small trees, largely incurred by a drought phase (relaxing light limitation) in P2, and following the more shaded (suppressing) conditions in P1, were likely due to species‐specific (symmetric) root competition and mycorrhizal processes. The very high variation in neighborhood composition and abundances led to a strong “neighborhood stochasticity” and hence to largely idiosyncratic species’ responses. A need to much better understand the roles of rooting structure and processes at the individual tree level was highlighted.

Performance of Some Plant Species Grown in Replacement Design under Different Competition Mode

A pot experiments was conducted at Grdarasha Experimental Farm / College of Agricultural Engineering Sciences / Salahaddin University / Erbil, during the winter growing season 2016 and 2017 to study the performance of Triticum aestivum L. and Cicer arietinum L. in sole cropping and intercropping in the presence of the Sinapis arvensis L. in a substitutive experiment arrangement with single, double and triple consortium. Experimental treatments were both pure stands and mix stands. Intercrops were symbolized by numbers and letters as (1A:2B:3C). The preceding number of each letter denotes the proportion of the land occupied by each of the Triticum aestivum (A), Cicer arietinum L. (B) and Sinapis arvensis L. (C). Pot experiment was consist of four modes of competition (full, shoot, root and no-competition) among three competitor plant species. As for wheat the relative plant height 1.05 was obtained in root competition mode, the same effect observed on grain yield relatively with values 1.29. In addition, it appears that mustard in treatment 2A3B1C has significantly outperformed all the other treatments with mean relative values 1.54 and 1.17 respectively in grain and biological yield measured originally as g plant−1.

While shoot herbivores reduce, root herbivores increase nutrient enrichment's impact on diversity in a grassland model.

Nutrient enrichment is widespread throughout grassland systems and expected to increase during the Anthropocene. Trophic interactions, like aboveground herbivory, have been shown to mitigate its effect on plant diversity. Belowground herbivory may also impact these habitats' response to nutrient enrichment, but its influence is much less understood, and likely to depend on factors such as the herbivores' preference for dominant species and the symmetry of belowground competition. If preferential toward the dominant, fastest growing species, root herbivores may reduce these species' relative fitness and support diversity during nutrient enrichment. However, as plant competition belowground is commonly considered to be symmetric, root herbivores may be less impactful than shoot herbivores because they do not reduce any competitive asymmetry between the dominant and subordinate plants. To better understand this system, we used an established, two-layer, grassland community model to run a full-factorially designed simulation experiment, crossing the complete removal of aboveground herbivores and belowground herbivores with nutrient enrichment. After 100yr of simulation, we analyzed communities' diversity, competition on the individual level, as well as their resistance and recovery. The model reproduced both observed general effects of nutrient enrichment in grasslands and the short-term trends of specific experiments. We found that belowground herbivores exacerbate the negative influence of nutrient enrichment on Shannon diversity within our model grasslands, while aboveground herbivores mitigate its effect. Indeed, data on individuals' above- and belowground resource uptake reveals that root herbivory reduces resource limitation belowground. As with nutrient enrichment, this shifts competition aboveground. Since shoot competition is asymmetric, with larger, taller individuals gathering disproportionate resources compared to their smaller, shorter counterparts, this shift promotes the exclusion of the smallest species. While increasing the root herbivores' preferences toward dominant species lessens their negative impact, at best they are only mildly advantageous, and they do very little reduce the negative consequences of nutrient enrichment. Because our model's belowground competition is symmetric, we hypothesize that root herbivores may be beneficial when root competition is asymmetric. Future research into belowground herbivory should account for the nature of competition belowground to better understand the herbivores' true influence.

Reduced row spacing improved yield by optimizing root distribution in maize

Roots play major roles in plant anchorage, water and nutrient uptake, crop growth and yield. Knowledge regarding yield responses to root spatial distribution is still limited in maize. Here we designed three plant densities in the tube and in the field, respectively. The tube study included plant densities of 1, 2, and 3 plants tube–1 and field study included 50025 (D50025), 67500 (D67500), and 100050 (D100050) plants ha–1, with two row spacings in D50025 (60 and 80 cm), three row spacings in D67500 (40, 60, and 80 cm), and two row spacings in D100050 (40 and 60 cm). With increased plant density and decreased row spacing grain yield improved, but root size and root biomass per plant decreased. Root dry weight per plant increased by 25–32 % at D50025 and decreased by 29–38 % at D100050 compared to D67500. Horizontally, reducing row spacing increased inner roots and reduced outer roots. There were significant correlations of yield with inner (R2 = 0.603** for D67500) and outer (R2 = −0.544* for D67500) root dry matter. Vertically, reducing row spacing increased root dry weight and most of the roots were distributed in the top 0–10 cm soil layer. Overall, high plant density inhibited root growth, but narrow row spacing compensated this inhibition to some extent by optimizing root distribution, thus increasing grain yield. Horizontal root distribution had a greater effect on grain yield than vertical distribution under high density condition, which alleviated inter-plant root competition and increased yield.

No neighbour-induced increase in root growth of soybean and sunflower in mesh-divider experiments after controlling for nutrient concentration and soil volume.

Root competition is a key factor determining plant performance, community structure and ecosystem productivity. To adequately estimate the extent of root proliferation of plants in response to neighbours independently of nutrient availability, one should use a set-up that can simultaneously control for both nutrient concentration and soil volume at plant individual level. With a mesh-divider design, which was suggested as a promising solution for this problem, we conducted two intraspecific root competition experiments: one with soybean (Glycine max) and the other with sunflower (Helianthus annuus). We found no response of root growth or biomass allocation to intraspecific neighbours, i.e. an ‘ideal free distribution’ (IFD) norm, in soybean; and even a reduced growth as a negative response in sunflower. These responses are all inconsistent with the hypothesis that plants should produce more roots even at the expense of reduced fitness in response to neighbours, i.e. root over-proliferation. Our results suggest that neighbour-induced root over-proliferation is not a ubiquitous feature in plants. By integrating the findings with results from other soybean studies, we conclude that for some species this response could be a genotype-dependent response as a result of natural or artificial selection, or a context-dependent response so that plants can switch from root over-proliferation to IFD depending on the environment of competition. We also critically discuss whether the mesh-divider design is an ideal solution for root competition experiments.

Initial plant community responses to hardwood control treatments in restoration of remnant longleaf pine (Pinus palustris) woodlands

Changes in land use over the past century have contributed to substantial losses of longleaf pine (Pinus palustris) woodlands in the southeastern USA and replacement with higher density, mixed pine and hardwood stands that suppress understory development and limit application of prescribed fire. To increase understanding of limiting factors and identify potential approaches for restoring longleaf pine woodlands, we studied initial availability of light and soil water and 2-year (2018–2019) plant community responses after controlling overstory hardwoods in five remnant longleaf pine woodlands having no evidence of previous agriculture at the Savannah River Site near Aiken, SC, USA. Seven hardwood control treatments and a non-treated check were compared in a randomized compete block experiment: cutting, cutting + shredding of logging residues, stem injection with imazapyr herbicide, cutting + basal spray with imazapyr herbicide, cutting + basal spray with triclopyr herbicide, cutting + directed foliar spray with a mixture of glyphosate and imazapyr herbicides, and cutting + broadcast foliar spray with the same herbicide mixture. In the year prior to hardwood cutting (2016), understory light availability averaged 23% of full sun. Throughout the year of treatment installation (2017), average soil water content (SWC) was below permanent wilting point (5.5% SWC) where overstory hardwoods were retained; whereas, it was above wilting point (7.5%) where they had been cut. Thus, combined effects of shade and root competition from overstory hardwoods probably limited cover of herbaceous species in the non-treated check. In the 2 years following treatment, hardwood survival averaged > 99%, 62%, 42% and < 1% for the non-treated check, cutting, shredding, and herbicide treatments, respectively. Relative to the non-treated check, herbaceous species richness was increased by shredding, stem injection, basal spray, or directed foliar treatments; herbaceous cover was increased by basal spray or directed foliar treatments; and woody cover was decreased by directed or broadcast foliar treatments. The directed foliar spray was the most effective treatment for achieving many of the desired understory characteristics of a longleaf pine woodland, including a diverse understory dominated by herbaceous vegetation capable of supporting periodic prescribed fires. Although the imazapyr basal spray treatment increased cover of remnant woodland indicator species, none of the treatments increased richness of this species group, suggesting that restoration of native species composition will be expedited by enrichment seedings or plantings.

Belowground competition and growth of juvenile trees in a long-unburnt Australian savanna

Most research on tropical savanna vegetation has focused on the factors promoting the co-existence of trees and grasses, and competition between savanna trees has received relatively little attention. Northern Australian savannas are amongst the most-fire prone landscapes on Earth and are dominated by a uniquely fire-adapted group of trees: eucalypts. Other northern Australian savanna trees tend to be largely suppressed by frequent fires. We used a root-exclusion experiment in a long-term (ca. 40-year) fire-excluded savanna to investigate the growth responses of juveniles of four dominant savanna tree species, both eucalypt (Eucalyptus miniata and Eucalyptus tetrodonta) and non-eucalypt (Terminalia ferdinandiana and Buchanania obovata), with and without root competition from neighbouring trees. Our results provide evidence of juvenile trees are not subjected to strong competition from neighbouring adult trees, as there was no difference in growth between root-excluded treatments and controls. However, Eucalyptus miniata, a dominant tree species in these savannas, had reduced growth, in terms of both height and diameter, regardless of the root-exclusion treatment. Our study suggests that growth of juvenile trees is not strongly limited by root competition from other trees. However, our results provide support that fire exclusion favour non-eucalypts by limiting the growth and recruitment of savanna eucalypts. Large reductions in fire frequency and/or intensity may lead to a shift in dominance away from eucalypts in the tropical savannas of northern Australia.

Impacts of underground competition and establishment on growth and root architecture of breadfruit (Artocarpus altilis) and māmaki (Pipturus albidus)

Replacing conventional monocultures with more diverse agroecosystems can positively impact environmental quality, but their adoption is limited, in part, due to inadequate understanding of how these systems operate regarding belowground competition. We examined how root competition between breadfruit (Artocarpus altilis) and māmaki (Pipturus albidus) affected aboveground performance. Our 2 × 3 factorial design consisted of two competition treatments and the three establishment treatments. Plants were grown together on either side of 47-gallon pots. For non-competition groups, a sheet of vinyl plastic was used to keep the roots of each species separate while maintaining above ground conditions. We used root cores to quantify the spatial allocation of root biomass to explore competition strategies of the two crops and measured biomass production to determine how growth was affected by competition. The two species demonstrated different responses to below-ground competition, with above ground biomass (AGBM) decreased for breadfruit but increased for māmaki. Below ground biomass increased for both plants under competition. Prior establishment enhanced māmaki's response to competition, while breadfruit's response to competition was exacerbated by post establishment and mitigated by simultaneous establishment. We suggest that māmaki's response is due to a more aggressive strategy that targets resource patches, while breadfruit is unable to compete within established māmaki zones and employs an avoidance strategy for root allocation.

Comparative analysis of the competition of stands of different species composition in relation to the Siberian stone pine undergrowth

Under the canopy of the parent native berry-green-moss Siberian stone pine forest and derivatives berry-green-moss pine and birch forests on the Urals, using the previously proposed complex of light, root, and integral competition indices of the stand, a comparative analysis of the parameters of the Siberian stone pine undergrowth is carried out. Under the canopy of Siberian stone pine forest two main determining factors have a negative complex effect on the growth of the Siberian stone pine undergrowth: the light competition of the stand (the level of photosynthetically active radiation interception by its canopy) and, almost equal to it, the root competition for soil nutrition. Under the pine forest canopy with the combined negative effect of factors of light and root competition of the stand on the development of Siberian stone pine undergrowth, light competition is decisive. The effect of the root competition is less than almost two times. Under the birch forest canopy the main factor determining the development of Siberian stone pine undergrowth is the light competition of the stand. The connection with the root competition of stand is not expressed.

Potassium fertilization for white oat and maize in integrated crop‐livestock system under no‐tillage

AbstractIntegrated crop‐livestock systems (ICLS) are diversified agroecosystems characterized by the rotation, succession or mixtures of agricultural, livestock or forestry activities, in no‐tillage systems. In ICLS with trees, the tree modifies the light and water availability, and might generate root competition for nutrients, like potassium (K). The study aims to evaluate dry matter (DM) and macronutrients accumulation in white oat, DM and grain yield of maize, and the K use efficiency (KUE) by these crops cultivated in an ICLS with eucalyptus. The experimental design was a randomized block in a split‐plot design with three replications. Plots consisted of four cultivation positions (CP) between the tree rows, where CP1 (0 to 4 m distance) refers to a position close to the trees; CP2 (4 to 8 m distance) and CP4 (12 to 16 m distance) corresponds to two intermediate positions between rows; and CP3 (8 to 12 m distance) corresponds to a central position between rows. In subplots, four potassium oxide (K2O) annual doses were assigned, with potassium chloride being applied on the surface, where each rate was half the rate applied at sowing of each crop. DM and macronutrients accumulation in white oat shoot decreased due to eucalyptus shadow (64.5% light restriction). Responses of maize DM and grain yield to K2O addition were different among CPs, possibly owing to different light patterns. No changes in the maize yield were observed with K2O application in CP1 and CP2. However, for other positions, quadratic responses in grain yield were observed. In ICLS with eucalyptus in a subtropical region of Brazil, the reduction of K fertilization led to lower yields in white oat and maize. As KUE was high in plots with low K rate, the production cost in ICLS with trees may be decreased if massive production is not required.

Effects of mulch and irrigation regimes on water distribution and root competition in an apple–soybean intercropping system in Loess Plateau, China

Water scarcity seriously hinders the sustainable development of the fruit tree–crops intercropping system in the Loess Gully Area of western Shanxi. The combination of mulch measures and appropriate irrigation would help to maintain soil moisture and improve crop yield and water use efficiency (WUE). This study investigated the combined effects of mulch and irrigation on soil water and root distribution, yield, and water use of an apple–soybean intercropping system. A three-year field trial was performed with two factors: two types of mulch, namely straw mulch (M1), and plastic mulch (M2), and three levels of maximum irrigation (55%, 70%, or 85% of field capacity [Fc]), which were designated W1, W2, and W3, respectively. Three groups of non-irrigation controls i.e., CK0 (no mulch), CK1 (straw mulch), and CK2 (plastic mulch) were also included. These results indicated that the soil water contents (SWC) in each treatment initially decreased and then increased with increasing distance from the tree, whereas it increased gradually with depth. The SWCs in various sampling points under straw mulch was generally higher than under plastic mulch. The root length density (RLD) of apple tree decreased with increasing distance from the tree in the horizontal direction, while the opposite trend was observed for soybean. The RLD of both apple tree and soybean in the soil layer (0–60 cm) under plastic mulch was higher than that under straw mulch, and increased with increased irrigation level. The underground interspecific competition intensity index (UICII) of the apple–soybean intercropping system under straw mulch was higher than that under plastic mulch, and increased with the increased irrigation amount. Water consumption, soybean yield, and WUE under plastic mulch were significantly higher than under straw mulch. The results of this study suggested that the combination of plastic mulch and irrigation water supplied at 70–85% Fc could effectively increase the yield and WUE of the apple–soybean intercropping system.

Root stoichiometric dynamics and homeostasis of invasive species Phyllostachys edulis and native species Cunninghamia lanceolata in a subtropical forest in China

The community species abundance and diversity declined with bamboo invasion had been widely reported worldwide. However, the physiological strategies used during root competition between native species and invasive bamboo are poorly understood. To clarify the mechanisms underlying such strategies, the stoichiometric dynamics and homeostasis of nitrogen, phosphorus, organic carbon in root orders of Phyllostachys edulis (I du [=I-Pe, years 1 and 2]; II du [=II-Pe, years 3 and 4]), Cunninghamia lanceolata in transition and pure forests were analyzed. With increasing intensity of bamboo invasion, N, P, and C content of C. lanceolata root orders declined, N and P content in P. edulis rhizome orders declined, while C increased, the stoichiometric ratios in mixed forest interface mainly increased, and the stoichiometric differences within native and invasive species root orders narrowed. Meanwhile, the stoichiometric homeostasis index (H) of elements in the same root order and even the same elements in different root orders were not consistent. H of most root orders (except some HP) was greater than 4, the H ranked order was I-Pe > Cl > II-Pe in mixed interfaces, and the N:P ratio of most species root orders was greater than 16, despite being affected by invasion. Our research concluded that the bamboo invasion narrows stoichiometric differences within root orders, and the juvenile bamboo rhizome has a stronger capacity for homeostatic regulation than in adult bamboo and C. lanceolata, which is a key determinant of bamboo invasion success.

Does sex ratio bias and sexual dimorphism occur in Lindera benzoin L. (Lauraceae) prior to fruit production? 1

Secondary (flowering) sex ratio of a wild population of the dioecious woody shrub Lindera benzoin (spicebush) in Maryland has been persistently female biased over a time span of ∼ 17 years. Female-biased secondary sex ratios are relatively uncommon in dioecious woody plants, and are not readily explained by differential costs of reproduction, which are generally higher in females. In fact, prior studies of reproductive adults in L. benzoin populations have shown higher growth rates in males. This leads to questions concerning the source of female-biased sex ratios in some populations. Using seeds collected from 15 maternal plants at the Maryland site in 2013, a potted plant study was conducted from 2014–2020 in which periodic flowering censuses were taken, and plant size parameters were recorded. This study improves upon an analogous common garden study conducted under highly competitive conditions that induced considerable preflowering mortality. In the current study, plants were grown in pots to eliminate root competition and in a loose array to minimize shoot competition; mortality was thus kept to ∼ 1% after seed germination. Like the source population, genet sex ratios in the current study were significantly female-biased, partly due to a trend toward female-biased sex ratios in the offspring of a number of maternal plants. Estimates of plant size were generally higher for females in 2018, just prior to the onset of significant fruit production, supporting earlier results suggesting that females may compensate for differential costs of reproduction that can manifest after fruiting begins. Even in the absence of biased primary sex ratios, formation of female bias in wild populations could involve development of a relatively larger size in the pre-fruiting stage that gives females a temporary advantage over males. This could lead to relatively greater survival and/or earlier flowering of female plants in the early stages of population establishment, and could thus explain observed patterns of sex ratio bias.

Factors affecting success in natural regeneration works of cedar (Cedrus libani A. Rich.) In Kas region of Antalya

Plants are living things that form the basis of food pyramid, provide numerous products and are considered as the source of life. Many professions such as agriculture, forestry and landscaping work on plant growing. The fast growth of plants is of prime importance since it provides advantage in light and root competition in the areas where plants are grown. For this reason, it is highly important to identify the factors affecting plant development and to change these factors in favour of the target species. In order to achieve this, first of all, the factors affecting the development of the target species in the study area should be known. In this study, which was carried out in the natural regeneration areas of Taurus Cedar (Cedrus libani A. Rich) found in the Kasaba Forest Sub-District Directorate in Kas region of Antalya, and was prepared as a term project, 3-year-old young cedars naturally grown in different stands were compared in terms of their root collar diameters, seedling length and number of seedlings, and the factors affecting the natural regeneration success were tried to be identified by factor analysis. As a result of the study, it was found that the average root collar diameter was between 2.5 and 4.7 mm, the average seedling length was between 4.5 and 11.3 cm, and the average number of young cedars per square meter was between 6 and 47. When the factors affecting the natural regeneration success were examined, it was found that the factors such as soil moisture, precipitation, amount of organic matter, light intensity and number of healthy seeds were the most important factors that played a role in this success, and that those factors explained 78.32% of the total variance.