Aboveground Resources Research Articles

Functional Segregation of Resource Utilization Strategies between Invasive and Native Plants and Invasion Mechanisms in the Water Level Fluctuation Zone: A Case Study of Pengxi River in Three Gorges Reservoir, China

The ecosystem of the water level fluctuation (WLF) zone of the Three Gorges Reservoir (TGR) is highly vulnerable and sensitive due to its unique cyclical flooding and drought conditions. The ecological impact of biological invasion in this area is particularly severe, making it crucial to study the differences in resource utilization strategies between invasive plants (IPs) and native plants (NPs) using functional traits to explore the mechanisms of invasion. We selected the WLF zone of Pengxi River in the TGR area and conducted a multi-scale study along the elevation gradient. The results reveal that at the regional scale, IPs have a larger height and specific leaf area, smaller leaf tissue density, and specific root length compared to NPs, showing a preference for enhancing aboveground resource acquisition over leaf defense capabilities. They allocate more tissue construction resources to their roots to withstand environmental pressures, which may be the key to their successful intrusion, highlighting the role of niche differentiation. On the community scale, the H and SLA of IPs and NPs are positively correlated with elevation, while the LTD of IPs shows a negative correlation. At elevations of 175 m and below, IP and NP exhibit functional convergence, while above 175 m, functional divergence was observed. This indicates that although the different resource utilization strategies are crucial for successful IP invasion, the environmental filtering from periodic floods and drought pressures play a significant role in community assembly in the WLF zone, allowing IP to integrate into habitats with similar functional characteristics already inhabited by NP and establish their own communities.

Juvenile mangrove growth is restricted by belowground competition with mature tree roots

Mangroves provide important ecosystem services and are uniquely structured forests due to strong biotic and abiotic influences in their intertidal habitat. These challenging conditions often create above- and belowground resource limitations which can interact to suppress juvenile growth resulting in an understory dominated by supressed juveniles. Though the response of juvenile mangrove growth to experimental release from aboveground resource limitations has been tested, less is known about the effect of belowground competition with mature tree root systems on juvenile growth. We experimentally released juvenile mangroves from mature tree belowground competition by repeated soil cutting treatments over 52 weeks. When belowground competition was reduced and thus belowground resource limitations relaxed, juvenile mangroves grew taller. Undisturbed control juveniles did not grow, though they had similar survival probabilities as treated juveniles across our sampling year. We demonstrated that release from belowground resource limitations was sufficient to restart growth of understorey juvenile mangroves, even when mature tree aboveground competition remained. This result enhances our understanding of species distribution and forest maintenance in this unique and important coastal ecosystem.

Tarihsel Süreç İçerisinde Maraş ve Çevresindeki Ermeni İsyanlarına Genel Bir Bakış

Western states created the concept of the Eastern Question for the nations living in the eastern regions, which they considered to pose a danger. The plans, which were designed with the aim of repelling the Turkish communities when they came to Anatolia, did not achieve their goal from the 11th century to the 19th century, when the Turks became the dominant power in the region. As a result of the end of the glorious periods of the Ottoman Empire and the beginning of the rise of European states, Western states targeted the Ottoman Empire within the framework of the Eastern Question both against the Ottoman pressure they had felt for centuries and in order to continue their political and economic rise. In addition, factors such as the strategic position of the Ottoman Empire and its underground and aboveground resources attracted the attention of the West. In this direction, the Western states, which were ahead of the Ottoman Empire in the fields of knowledge and technique, could not confront the Ottoman Empire directly, and wanted to weaken the state through political, economic and sometimes military methods. Within the framework of these plans, the Western states utilised their own cognates and co-religionists living in the territory of the Ottoman Empire and promised them independent nation states. Affected by this, the Ottoman nations entered into a struggle for independence with the state. Armenians, one of these nations, started the struggle for independence with Muslim Turks, with whom they had lived in the same country for centuries. In the Ottoman Empire, the region of Maraş and Zeytun, where Armenians were densely populated, became the base of Armenian rebellion movements. In this study, the activities of Armenians in and around Maraş during the last period of the Ottoman Empire and the War of Independence and the Armenian Question will be analysed.

Plant–plant interactions vary greatly along a flooding gradient in a dam-induced riparian habitat

Plant–plant interactions under extreme environmental stress are still controversial. The stress gradient hypothesis (SGH) proposes that facilitation prevails under extreme environmental stresses, while an alternative view states that facilitation collapses or even switches back to competition at the extreme end of stress gradients. However, how the relationship between plant–plant interaction and periodic extreme flooding stress varies and its underlying mechanism are still unclear in a dam-regulated riparian ecosystem. We established a controlled experiment using two dominant species pairs (Cynodon dactylon–Cyperus rotundus and C. dactylon–Xanthium sibiricum) in the water level fluctuating zone of the Three Gorges Dam to examine their growth responses to the periodic extreme flooding stress. The results showed that as flooding stress increased, the competitive effect of C. dactylon on X. sibiricum shifted to facilitation, whereas the effect of X. sibiricum on C. dactylon maintained a strong inhibition. The plant height of X. sibiricum was the most important driver of the interaction between X. sibiricum and C. dactylon along the flooding gradient. The net effect of C. dactylon on C. rotundus shifted from neutral to negative, and the inhibitory effect of C. rotundus on C. dactylon became stronger at the extreme end of flooding stress. The root biomass of the two species was the key trait regulating their interaction with increasing flooding stress. Overall, the SGH was partially supported along our periodic extreme flooding stress gradient. Aboveground resource (light) might be the dominant factor driving the response of the interaction between annual plants and perennial clonal plants to periodic flooding stress, whereas belowground resource (water and nutrients) was probably the dominant factor for perennial clonal plants. Our study will help to further understand the environmental responses of plant–plant relationships and their regulatory mechanism, and the succession of riparian plant communities under extreme environmental changes, providing a basic theoretical basis and data support for the ecological restoration and management of riparian wetland vegetation.

Quantitative assessment and development utilization modes of space resources in closed and abandoned mines

ABSTRACT With the increase of the number of closed and abandoned mines in the world, it has become an urgent need to study the assessment and reuse of various resources of closed and abandoned mines, as well as the transformation and development mode of mines. Various sources of data are used to identify the types of closed and abandoned mine resources, the classification system of aboveground and underground resources of mines is established. The calculation method of available space of ground buildings, underground tunnels and shafts, and the estimation method of underground residual coal quality are given, the determination method of transformation mode of closed and abandoned mines is proposed. The transformation and utilization modes of closed and abandoned mines in China and abroad are compared. Taking a closed mine in Shaanxi Province as an example, the optimal transformation mode is determined and the planning scheme is given. The main conclusions are as follows: (1) Aboveground resources of closed and abandoned mines mainly include surface water, idle land, mining equipment, and buildings of industrial squares and living areas, while underground resources mainly include groundwater, residual minerals, underground space and mining equipment left underground. (2) The aboveground development and utilization modes of closed and abandoned mine resources include mine park, mining museum, industrial relics, etc. while the underground development and utilization modes include underground storage, underground laboratory, energy development, etc. (3) It is calculated that the building space volume of a closed mine industrial square in Shaanxi Province, China is up to 1.04 × 105 m3, the available underground space volume including shaft, roadway, chamber and yard is 1.18 × 105 m3, and the mass of underground residual coal is nearly 56 million tons. (4) Based on the evaluation of suitability for mine transformation, three transformation modes have been identified for a closed mine in Shaanxi Province, China. Through the comprehensive benefit evaluation, the optimal utilization mode for the mine has been determined as mine park and mine museum, and a preliminary planning scheme is proposed. The research on the reuse of the remaining resources of closed and abandoned mines provides a new idea for the transformation and sustainable development of resource-depleted mines, which is of great significance for the realization of the global carbon peak and carbon neutrality.

Above‐ and belowground traits along a stress gradient: trade‐off or not?

The role of plant traits in shaping community assembly along environmental gradients is a topic of ongoing research. It is well accepted that plant traits of aboveground organs tend to be conservative in stressful conditions. However, there is limited understanding of how belowground traits respond. Plants may have similar strategies above and belowground, but an intriguing possibility is that there is a tradeoff between above and belowground traits of communities to both ensure efficient resource‐use and limit niche overlap along the gradient. To test this, we asked whether the response of above and belowground traits of communities is coordinated or not along a stress gradient in Mediterranean sand dune communities. We analyzed 80 vegetation plots in central Italy to test for coordinated vs independent patterns in above vs belowground plant traits using community weighted mean and standardized effect size of functional richness. Our results show that plant communities close to the sea, which experience higher stress, were characterized by higher convergence towards aboveground resource conservation and conservative water‐use strategies but belowground resource acquisition, consistent with a strong effect of habitat filtering and an above–belowground tradeoff favoring adaptation to harsh and dry conditions. At the opposite end of the gradient with lower stress, plants exhibited higher trait diversity for both above and belowground traits, but overall a dominance of aboveground fast resource acquisition and generally acquisitive water‐use strategies, combined with conservative belowground strategies. This suggests that fast growth rate aboveground was compensated by more conservative fine‐root strategies, but processes such as competition limited niche overlap overall. Our findings provide new insights into the relationship between functional traits and environmental gradients in plant communities, shedding light on the tradeoffs between the above and belowground dimensions.

Geodiversity and biodiversity on a volcanic island: the role of scattered phonolites for plant diversity and performance

Abstract. Oceanic islands are cradles of endemism, contributing substantially to global biodiversity. A similarity in magmatic origin translates into high global comparability of substrates of volcanic islands on the oceanic crust with, however, slightly chemically or physically differentiated petrography in some places. Phonolites are examples of rare localities with intermediate chemical characteristics between felsic and mafic and with diverse textures. They contribute to habitat heterogeneity and offer specific growth conditions in a significantly different matrix of basaltic substrates. The explicit contribution of geodiversity to island biodiversity has been little studied, despite growing evidence of its importance on continents. On the island of La Palma, Canary Islands, isolated phonolitic rocks are conspicuous due to their light colour and specific shape. Although these outcrops only cover small areas, their unique form and composition increase within-island geodiversity. To investigate how this affects biodiversity on La Palma, we sampled all vascular plant species in 120 plots on four sets of paired sites in order to test if plant diversity and performance is enhanced on phonolitic rocks compared to basaltic rocks. We recorded species number and abundance as well as individual plant height and diameter as proxies for aboveground resource allocation and tested for differences in vegetation cover and species composition between the bedrock types. We found higher species richness and abundance on phonolites than neighbouring basaltic substrates, and individuals of the same species were larger (in height and diameter) on phonolites compared to neighbouring basalt. An endemic woody species with two distinct varieties even appears almost exclusively on the small surfaces of phonolitic rock. Despite extremely limited spatial extent, phonolitic rocks can play an important role in plant biodiversity on islands.

喜旱莲子草在增温背景下的密度制约与生长权衡

PDF HTML阅读 XML下载 导出引用 引用提醒 喜旱莲子草在增温背景下的密度制约与生长权衡 DOI: 10.5846/stxb202105111231 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 第二次青藏高原综合科学考察研究项目（2019QZKK0304）；西华师范大学基本科研业务费资金资助（17B007）；四川省教育厅重点项目（18ZA0462） Density dependence and growth trade-off of Alternanthera philoxeroides under warming Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:研究植株个体与种群数量的关系对探究植物的适应策略、理解植物入侵机理有重要意义。但多数研究着眼于常温处理下植株响应密度变化的生长权衡，对增温处理下植株的密度制约调节机理和常温与增温处理下响应密度变化的调节规律是否发生变化认识不足。以喜旱莲子草（Alternanthera philoxeroides）为研究对象，采用密度（1、5、9株/盆，37、186、335株/m2）和温度（常温、增温）双因素实验设计，探究了全球变暖背景下，密度制约与喜旱莲子草的关系、地上与地下部分的密度制约调节规律。结果表明：（1）地上构件特征与温度呈显著正相关关系（P<0.05），地上构件特征和比叶面积表现出明显密度依赖性（P<0.05）。温度与种群密度及其交互作用对地下指标无显著影响（P>0.05）。（2）无论增温与否，随密度压力增加，根生物量分配比率增大，各构件平均生物量、茎生物量分配比率降低。叶生物量分配比率在各密度下维持恒定。（3）用生物量-密度异速指数γ衡量种群密度调控强弱。常温处理下，γleaf（-1.685） < γabove-ground（-1.612） < γstem（-1.605） < γ individual（-1.558） < γroot（-1.524），受密度制约调控强度的大小依次为：叶>地上>茎>个体>根。增温处理下，γstem（-2.075） < γabove-ground（-2.038） < γindividual（-1.982） < γleaf（-1.933） < γroot（-1.800），受密度制约调控强度的大小依次为：茎 > 地上 > 个体 > 叶 > 根。喜旱莲子草种群地上构件受密度的调节作用强于地下构件。由此可见，无论增温与否，喜旱莲子草种群地下资源的竞争能力随密度增加而增强，地上资源竞争能力随密度增加而减弱，喜旱莲子草地上部分调节强于地下部分，常温处理下，叶受密度制约作用更强，增温处理下，茎受密度制约最强。根受密度制约最弱。地上资源的竞争占主导地位。 Abstract:Study on the relationship between plant individual and population is of great importance to explore plant adaptation strategies and to understand the mechanisms of plant invasion. However, most studies focused on the growth trade-off of plant response to density change under normal temperature treatment. There is a lack of understanding on the regulation mechanism of plant density restriction under increasing temperature treatment, and whether the regulation law of response to density change alters under normal temperature and warming treatment. In this study, taking Alternanthera philoxeroides as the focus species, the relationship between density restriction and A. philoxeroides, and the regulation law of density restriction between aboveground and underground parts under the background of global warming were studied by using two-factor experimental design of density (1, 5, 9 plants/pot, 37, 186, 335 plants/m2) and temperature (normal temperature, increasing temperature). The results showed that:(1) There was a significantly positive correlation between the characteristics of aboveground components and temperature (P<0.05), and there was a significant density dependence on the characteristics and specific leaf area of aboveground components (P<0.05). Temperature, population density and their interaction had no significant effect on underground index (P>0.05). (2) With the increase of density, the root biomass allocation ratio increased, while the average biomass and stem biomass allocation ratio decreased under two temperatures. The allocation ratio of leaf biomass remained constant at different densities. (3) The allometric index γ of biomass-density was used to measure the regulation of population density. Under normal temperature treatment, we found that γleaf (-1.685) < γabove-ground(-1.612) < γstem (-1.605) < γ individual (-1.558) < γroot(-1.524). Regulation intensity restricted by density was in the following order:leaf > aboveground > stem > individual > root. Under warming treatment, we found that γstem (-2.075) < γabove-ground (-2.038) < γindividual(-1.982) < γleaf (-1.933) < γroot (-1.800). The order of regulation intensity restricted by density was stem > aboveground > individual > leaf > root. The density regulation of the aboveground components of A. philoxeroides population is stronger than that of the underground ones. That's to say, whether warming or not, the competitiveness of underground resources of A. philoxeroides population increases with the increase of density, while the competitiveness of aboveground resources decreases with the increase of density. The regulation ability of the upper part of A. philoxeroides is stronger than that of underground part. Under normal temperature treatment, leaves are more restricted by density, while stems are most restricted by density under warming treatment. The competition for aboveground resources is dominant for A. philoxeroides. 参考文献 相似文献 引证文献

Differences in above-ground resource acquisition and niche overlap between a model invader (Phragmites australis) and resident plant species: measuring the role of fitness and niche differences in the field

Identifying the mechanisms that result in a “high impact” invasive species can be difficult. Coexistence theory suggests that detrimental invasive species can be better predicted by incorporating both niche differences and fitness differences than examining niche overlap alone. Specifically, detrimental invasive species should take up shared limited resources more efficiently than their neighbouring resident species. While there is clear evidence that invasive Phragmites australis is successfully displacing resident species, there remains few field studies that attempt to quantify the niche overlap and fitness difference between P. australis and the species it is displacing in the field. We measured differences in photosynthetic performance (carbon assimilation rate, δ13C, photosynthetic water use efficiency, biomass, light compensation point, light saturation point), canopy height and interception of photosynthetically active radiation, and niche overlap between P. australis and three resident freshwater wetland species (Calamagrostis canadensis, Carex aquatilis, and Typha spp.) growing with or without aboveground interspecific competition. Invasive P. australis intercepted more photosynthetically active radiation, had higher photosynthetic water use efficiency, a higher average light saturation point, and had a larger niche region compared to resident species. Resident plant species showed a significant decrease in photosynthetic performance when growing in competition with P. australis and had a high probability of overlap onto the niche space of P. australis. These results provide evidence that the ability of P. australis to reduce the availability of a required resource and more efficiently use it over the growing season, while exhibiting high niche overlap with resident species, likely contributes directly to its success in North American freshwater wetlands.

A tale of two cities: Annapolis and St. Augustine balancing preservation and community values in an era of rising seas

PART 3. ENHANCING RESILIENCE, ADAPTATION AND SUSTAINABILITY - Linking Resilience, Sustainable Heritage and Community Livelihoods /// Annapolis, Maryland and St. Augustine, Florida, are colonial cities on the East Coast of the United States with National Historic Landmark designations recognizing the strong blends of natural and cultural resources that make each unique. Annapolis faces nuisance flooding that is challenging the above-ground resources and the natural settings and cultural frameworks that support and enhance them. St. Augustine has witnessed dozens of hurricanes and frequent coastal flooding, impacting the delicate balance of natural and cultural resources in a fast-growing population with significant vulnerabilities. The Federal Emergency Management Agency provides a model for determining community value in cultural resource hazard mitigation planning. These communities can prioritize the protection of historic places threatened by natural disasters by comparing that model against the United States Secretary of the Interior’s factors for determining historic integrity. This framework can serve as a model approach for evaluating public sentiment for the protection and preservation of historic places within the larger context of disaster preparedness and recovery. This can enable communities to evaluate and prioritize places that matter to prepare for and recover from rising waters.

Aboveground resource allocation in response to root herbivory as affected by the arbuscular mycorrhizal symbiosis

Arbuscular mycorrhizal (AM) fungi associate with the majority of terrestrial plants, influencing their growth, nutrient uptake and defence chemistry. Consequently, AM fungi can significantly impact plant-herbivore interactions, yet surprisingly few studies have investigated how AM fungi affect plant responses to root herbivores. This study aimed to investigate how AM fungi affect plant tolerance mechanisms to belowground herbivory. We examined how AM fungi affect plant (Saccharum spp. hybrid) growth, nutrient dynamics and secondary chemistry (phenolics) in response to attack from a root-feeding insect (Dermolepida albohirtum). Root herbivory reduced root mass by almost 27%. In response, plants augmented investment in aboveground biomass by 25%, as well as increasing carbon concentrations. The AM fungi increased aboveground biomass, phosphorus and carbon. Meanwhile, root herbivory increased foliar phenolics by 31% in mycorrhizal plants, and increased arbuscular colonisation of roots by 75% overall. AM fungi also decreased herbivore performance, potentially via increasing root silicon concentrations. Our results suggest that AM fungi may be able to augment plant tolerance to root herbivory via resource allocation aboveground and, at the same time, enhance plant root resistance by increasing root silicon. The ability of AM fungi to facilitate resource allocation aboveground in this way may be a more widespread strategy for plants to cope with belowground herbivory.

Plant diversity and soil stoichiometry regulates the changes in multifunctionality during pine temperate forest secondary succession

The shift in ecosystem multifunctionality during ecosystem succession (years to decades) remains largely unexplored. In this study, we used a 120-year-old pine temperate forest chronosequence (1: 1–19 years, stage 2: 20–39 years, stage 3: 40–59 years, stage 4: 60–79 years, stage 5: 80–99 years, stage 6: 100–120 years) to evaluate the role that time plays in shaping ecosystem multifunctionality (nutrient cycling, carbon stocks, water regulation, decomposition and wood production), and found that, over the first century, ecosystem functioning gradually increased every ~50 years. Such a result was maintained for individual groups of ecosystem functions and services including nutrient cycling, carbon stocks, decomposition and wood production. Plant diversity and soil stoichiometry (C:N ratio) were the major environmental predictors for the changes in ecosystem multifunctionality during forest secondary succession. Plant diversity increased during ecosystem succession and was positively related to ecosystem multifunctionality. The soil C:N ratio decreased during ecosystem succession and was negatively related to multifunctionality. Our results suggest that increases in aboveground resource heterogeneity (higher plant diversity) and organic matter quality (lower soil C:N ratios) could help explain the increases in multifunctionality over a century of forest development. Our work illustrates the importance of time in shaping multifunctionality during the first century of ecosystem succession, and further provide important insights for the management of temperate forest ecosystems.

Linking reliance on deep soil water to resource economy strategies and abundance among coexisting understorey shrub species in subtropical pine plantations

Strategies for deep soil water acquisition (WAdeep ) are critical to a species' adaptation to drought. However, it is unknown how WAdeep determines the abundance and resource economy strategies of understorey shrub species. With data from 13 understorey shrub species in subtropical coniferous plantations, we investigated associations between the magnitude of WAdeep , the seasonal plasticity of WAdeep , midday leaf water potential (Ψmd ), species abundance and resource economic traits across organs. Higher capacity for WAdeep was associated with higher intrinsic water use efficiency, but was not necessary for maintaining higher Ψmd in the dry season nor was it an ubiquitous trait possessed by the most common shrub species. Species with higher seasonal plasticity of WAdeep had lower wood density, indicating that fast species had higher plasticity in deep soil resource acquisition. However, the magnitude and plasticity of WAdeep were not related to shallow fine root economy traits, suggesting independent dimensions of soil resource acquisition between deep and shallow soil. Our results provide new insights into the mechanisms through which the magnitude and plasticity of WAdeep interact with shallow soil and aboveground resource acquisition traits to integrate the whole-plant economic spectrum and, thus, community assembly processes.

A simple skeletal measurement effectively predicts climbing behaviour in a diverse clade of small mammals

AbstractArboreal locomotion allows access to above-ground resources and might have fostered the diversification of mammals. Nevertheless, simple morphological measurements that consistently correlate with arboreality remain indefinable. As such, the climbing habits of many species of mammals, living and extinct, remain speculative. We collected quantitative data on the climbing tendencies of 20 species of murine rodents, an ecologically and morphologically diverse clade. We leveraged Bayesian phylogenetic mixed models (BPMMs), incorporating intraspecific variation and phylogenetic uncertainty, to determine which, if any, traits (17 skeletal indices) predict climbing frequency. We used ordinal BPMMs to test the ability of the indices to place 48 murine species that lack quantitative climbing data into three qualitative locomotor categories (terrestrial, general and arboreal). Only two indices (both measures of relative digit length) accurately predict locomotor styles, with manus digit length showing the best fit. Manus digit length has low phylogenetic signal, is largely explained by locomotor ecology and might effectively predict locomotion across a multitude of small mammals, including extinct species. Surprisingly, relative tail length, a common proxy for locomotion, was a poor predictor of climbing. In general, detailed, quantitative natural history data, such as those presented here, are needed to enhance our understanding of the evolutionary and ecological success of clades.

Effects of root and leaf litter identity and diversity on oribatid mite abundance, species richness and community composition.

Habitat heterogeneity is an important driver of aboveground species diversity but few studies have investigated effects on soil communities. Trees shape their surrounding by both leaf litter and roots generating small scale heterogeneity and potentially governing community patterns of soil organisms. To assess the role of vegetation for the soil fauna, we studied whether tree species (Fagus sylvatica L., Acer pseudoplatanus L., Fraxinus excelsior L., Tilia cordata Mill.), markedly differing in leaf litter quality and root associated mycorrhizal symbionts, affect oribatid mite communities by shaping below- and aboveground resources and habitat complexity and availability. Oribatid mite abundance, species richness, community structure and the proportion of litter living and parthenogenetic individuals were analyzed and related to microbial biomass and the amount of remaining litter mass. Although leaf litter species with higher nutritional values decomposed considerably faster, microbial biomass only slightly differed between leaf litter species. Neither root species nor leaf litter species affected abundance, species richness or community structure of oribatid mites. However, root species had an effect on the proportion of parthenogenetic individuals with increased proportions in the presence of beech roots. Overall, the results suggest that identity and diversity of vegetation via leaf litter or roots are of minor importance for structuring oribatid mite communities of a temperate forest ecosystem.

Stem anatomy at various developmental stages of secondary growth in Turbina corymbosa (Convolvulaceae)

Background – Population growth of lianas in the tropical forest is credited to their ability of CO2 sequestration and efficiency of the narrow stems to supply water required for the amount of foliage it bears. Turbina corymbosa (L.) Raf. (Convolvulaceae Juss.) is one of the fast-growing invasive species of scrambling woody lianas. It covers trees entirely within a short period to compete with above-ground resources (particularly sunlight). However, no information is available on how it manages to cope up with an increasing demand of water supply and mineral nutrients. What are the structural and developmental patterns adapted by this species to expand the stem diameter for efficient supply of below-ground resources? Therefore, our aim was to investigate the secondary growth patterns and structure of secondary xylem and phloem in T. corymbosa.Methods – Several samples of the stem with various diameters were studied using a histological method. Morphological and anatomical analyses were carried out using light microscopy.Key results – With the initiation of secondary growth, stems lose their circular outline rapidly due to unequal deposition of secondary xylem and formation of successive cambia. New successive cambia initiate from parenchymatous cells as small crescent-shaped fragments on asymmetric/opposite sides and result in a different stem conformation. Though several segments of successive cambia are formed, very few stem samples form complete cambium rings. The secondary xylem formed by successive cambia is diffuse porous with indistinct growth rings and is composed of both wide and narrow (fibriform) vessels, tracheids, fibres, axial and ray parenchyma cells. The secondary phloem consists of sieve tube elements, companion cells, axial and ray parenchyma cells. In fully grown plants, cambial action (internal cambium) occurrs between the intraxylary phloem and protoxylem and produces secondary xylem and phloem near the pith region.Conclusion – Structural alterations and unequal deposition of conducting elements, occurrence of intraxylary phloem and flattening of the stem are suggested to facilitate rapid growth of the plants by providing required minerals and nutrients. Internal cambium formed at the periphery of the pith is bidirectional and produces secondary xylem externally and intraxylary phloem internally. Continued development of intraxylary phloem from the internal cambium provides an additional path for rapid and safe translocation of photosynthates.

Key drivers of competition and growth partitioning among Robinia pseudoacacia L. trees

Competition for above- and below-ground resources depends on their availability and results in varied growth partitioning. This becomes clear as the supply and limitation of the main resources influence the slope of the size-growth relationship in stands. Nevertheless, growth partitioning among trees, especially among black locust (R. pseudoacacia) trees is not understood in sufficient detail. To scrutinize and estimate the mode of competition of R. pseudoacacia, this research analyzed 1333 trees in Germany in 10 study sites, consisting in total 27 sample plots, with similar climate but varying soil conditions. The stand age ranged from 2 to 32 years, with a diameter at breast height ranging from 0.6 to 29.1 cm. The main focus of the study was to evaluate the impact of nitrogen, phosphorus, and water supply on the competition mode of R. pseudoacacia by varying growth partitioning. We applied the size–growth relationship in a mixed-effects model with a random intercept and slope. Fixed effects were the basal area, phosphorus, water, the sunlight competition index, and the interactions between below- and above-ground resources. Site specific effects of the analyzed stands were quantified with the aid of the random effects. Depending on the supply and limitation of phosphorus and water, this study determined how the competition mode as well as the growth partitioning among R. pseudoacacia trees were influenced. Hence, if phosphorus and water availability increased, then the competition for above-ground resources (primarily sunlight) and the slope of the size–growth relationship increased. Large trees grew disproportionately more than smaller trees. If the available phosphorus and water decreased, then the competition for the below-ground resources increased and the slope of the size–growth relationship decreased – to be more flattened. Moreover, it was found that available nitrogen as a below-ground resource had no influence on the mode of competition. In summary, phosphorus was the most important nutrient and, together with water, was the main driver of growth partitioning among R. pseudoacacia trees.

Functional traits of coffee along a shade and fertility gradient in coffee agroforestry systems

Intraspecific variation in leaf functional traits has gained widespread attention as a means to evaluate, predict, and manage plant responses to environmental conditions, however there are considerable uncertainties regarding the extent and drivers of intraspecific trait variation (ITV) in domesticated plants. In a coffee (Coffea arabica) agroforestry system, we quantified ITV in seven leaf traits [i.e. area (LA), mass per area (LMA), dry matter content (LDMC), thickness (Lth), nitrogen concentrations (LNC), maximum photosynthetic rate on area and mass bases (Asat, Amass, respectively)] across managed gradients of soil fertility and light availability. Leaf physiological traits (Asat, Amass), as well as LA, showed the greatest extent of variation within coffee, while morphological traits (LMA, LDMC, Lth) and leaf N were less variable. All traits differed significantly as a function of light and fertilization treatment, however light was more influential in driving ITV in coffee leaves. Low light availability resulted in greater ITV for physiological leaf traits (Asat and Amass), while high light constrained ITV in most morphological-(LA, LMA, LDMC), physiological-(Asat, Amass) and chemical-(LNC) traits. Fertilization treatments did not induce systematic shifts in the extent of ITV. In addition, shade management treatments explained 9.2% of the variation in multivariate trait syndromes, while nutrient management regimes explained only 2.9%. Our results indicate that highly heterogeneous aboveground resource environments such those created by agroforestry, results in greater ITV for key crop physiological parameters. Based on ecological theory, such patterns indicate that management systems promoting resource heterogeneity should promote higher rates of resource partitioning, and greater resource-use efficiency in agroecosystems.

Early growth interactions between a mangrove and an herbaceous salt marsh species are not affected by elevated CO2 or drought

Increasing atmospheric carbon dioxide (CO2) concentrations are likely to influence future distributions of plants and plant community structure in many regions of the world through effects on photosynthetic rates. In recent decades the encroachment of woody mangrove species into herbaceous marshes has been documented along the U.S. northern Gulf of Mexico coast. These species shifts have been attributed primarily to rising sea levels and warming winter temperatures, but the role of elevated CO2 and water availability may become more prominent drivers of species interactions under future climate conditions. Drought has been implicated as a major factor contributing to salt marsh vegetation dieback in this region. In this greenhouse study we examined the effects of CO2 concentration (∼380 ppm, ∼700 ppm) and water regime (drought, saturated, flooded) on early growth of Avicennia germinans, a C3 mangrove species, and Spartina alterniflora, a C4 grass. Plants were grown in monocultures and in a mixed-species assemblage. We found that neither species responded to elevated CO2 over the 10-month duration of the experiment, and there were few interactions between experimental factors. Two effects of water regime were documented: lower A. germinans pneumatophore biomass under drought conditions, and lower belowground biomass under flooded conditions regardless of planting assemblage. Evidence of interspecific interactions was noted. Competition for aboveground resources (e.g., light) was indicated by lower S. alterniflora stem biomass in mixed-species assemblage compared to biomass in S. alterniflora monocultures. Pneumatophore biomass of A. germinans was reduced when grown in monoculture compared to the mixed-species assemblage, indicating competition for belowground resources. These interactions provide insight into how these species may respond following major disturbance events that lead to vegetation dieback. Site variation in propagule availability and physico-chemical conditions will determine plant community composition and structure following such disturbances when these two species co-occur.

Transformation of jackfruit (Artocarpus heterophyllus Lam.) orchard into multistory agroforestry increases system productivity

A number of traditional and modern agroforestry systems are common in the agricultural landscape of Bangladesh. Jackfruit (Artocarpus heterophyllus Lam.) based agroforestry is one of them and predominantly found in terrace ecosystems. There is an enormous opportunity to improve the system through utilizing available space by growing compatible associated crops. For this, a jackfruit orchard was transformed into a multistoried agroforestry system during the period from 2012 to 2013, where jackfruit trees were kept as overstory, and associated crops, such as papaya and eggplant were grown as middle and lower story crops, respectively. In the improved system, jackfruit yield increased by 32.7% due to fertilizers and irrigation applied for the middle and lower-storied crops. Yields of papaya and eggplant were reduced by 22.8 and 17.4%, respectively, because of competition for both belowground and aboveground resources. For example, light interception by the middle and lower story crops were 55.5 and 30.8%, respectively. However, the total production per unit area (by combining the yields of jackfruit, papaya, and eggplant) in the multistoried agroforestry system was remarkably higher than the monoculture system for the same area due to intensive land use. The benefit–cost ratio and land equivalent ratio for the studied multistoried agroforestry systems were 5.47 and 2.59, respectively. These results suggest that the traditional jackfruit orchard could be transformed to multistoried agroforestry systems for its higher system productivity including higher yield, and increased income that ultimately will improve the livelihood of the farming community.