Aboveground Systems Research Articles

Rotating permanent magnet antenna array for directional communication in pipeline monitoring system

As a novel pipeline monitoring technology, wireless sensor networks (WSN) have the advantages of low power consumption, flexibility, and robustness in aboveground, underground, and underwater pipeline monitoring systems. Using low-frequency (LF) rotating permanent magnet antennas (RPMA) for communications from sensor nodes (SN) to autonomous unmanned vehicles (AUV) has the advantages of low attenuation, low latency, and portable size. However, the communication ranges of different SNs may overlap and information from different SNs should be distinguished. Methods like time-division multiplexing (TDM) and frequency-division multiplexing (FDM) are not suitable in this case. Another way is to form RPMAs into an array so that directional communications from SNs to AUVs can be realized and there is no overlap between SNs. Therefore, this work analyzes and enhances the directivity of linear RPMA arrays in the near-field region. Based on the designed RPMA array prototype, the directional communication is realized at a distance of 5 m across concrete walls. This work paves the way for directional communications from SNs to AUVs in underground pipeline monitoring systems.

Anatomical and Transcriptome Analyses of Moso Bamboo Culm Neck Growth: Unveiling Key Insights.

The Moso bamboo culm neck, connected with the rhizome and the shoot bud, is an important hub for connecting and transporting the aboveground and belowground systems of bamboo for the shoot bud development and rapid growth. Our previous study revealed that the culm neck generally undergoes six different developmental stages (CNS1-CNS6), according to the primary thickening growth of the underground shoot bud. However, the molecular mechanism of the culm neck development remains unknown. The present study focused on the developmental process of the CNS3-CNS5 stages, representing the early, middle, and late elongation stages, respectively. These stages are densely packed with vascular tissues and consist of epidermis, hypodermis, cortex, and ground tissue. Unlike the hollow structure of the culms, the culm necks are solid structures. As the culm neck continues to grow, the lignin deposition increases noticeably, contributing to its progressive strengthening. For the transcriptome analysis, a total of 161,160 transcripts with an average length of 2373 were obtained from these stages using both PacBio and Illumina sequencing. A total of 92.2% of the reads mapped to the Moso bamboo reference genome. Further analysis identified a total of 5524 novel genes and revealed a dynamic transcriptome. Secondary-metabolism- and transport-related genes were upregulated particularly with the growth of the culm neck. Further analysis revealed the molecular processes of lignin accumulation in the culm neck, which include differentially expressed genes (DEGs) related to cell wall loosening and remodeling and secondary metabolism. Moreover, the upregulations of transcription factors such as MYBH and RSM in the MYB family play crucial roles during critical transitions in the culm neck development, such as changes in the angle between the rhizome and the culm neck. Our new findings provide essential insights into the cellular roadmaps, transcriptional networks, and key genes involved in the culm neck development.

Shrubs and semi-shrubs life forms of the temperate zone: Principles of organization of above-ground shoot systems

The aim of the study was to identify ways of forming of the main skeletal axes (MSA) in shrub and semi-shrub life forms. We identified 4 organization types of the MSA based on the nature of their accreting, the structure and degree of generative shoots participation in their formation. Type I – the MSA are formed as a result of sympodial accreting on the basis of generative shoots, both with apical and axillary inflorescences. Type II – the MSA are formed as a result of monopodial accreting changing to sympodial accreting and consist of vegetative and generative shoots. Type III – the MSA accrete monopodially and consist only of vegetative shoots or even of generative shoots with axillary inflorescences. Type IV – the MSA accrete sympodially and consist only of vegetative shoots or also of generative shoots with axillary inflorescences. Semi-shrub life forms have types I and II of organization of the main skeletal axes, shrubs – all four. Difficulties with the determination of life forms in species of types I and II are due to the influence of growing conditions on the degree of death of generative shoots. V.N. Golubev (1968) erroneously classified creeping woody monopodial errating dwarf shrubs as dwarf semi-shrubs, which is due to the emphasis not on long-term growing skeletal axes, but on annually dying off herbaceous elongated orthotropic generative shoots

Investigation of Thermal Dynamics within Rainwater Harvesting Systems and Implications for Design

Rainwater harvesting (RWH) systems have long been used to supply water for a variety of end uses. RWH systems, when used correctly, have proven to be effective at reducing runoff volumes and improving runoff quality at the site and catchment scales. Stormwater runoff from impervious surfaces in urban areas is thermally enriched, causing detrimental impacts to receiving waters. Research has begun to identify stormwater control measures (SCMs) that can offset this thermal loading by reducing total runoff amounts or storing the water in cooler locales. To the authors’ knowledge, no evidence exists in the literature to support whether RWH systems are sources or sinks of thermal pollution or to inform the thermal dynamics within the tanks. Monitoring was undertaken to compare the thermal dynamics of paired above- and below-ground RWH systems from three locations across the eastern United States (Ohio, Virginia-North Carolina, and Florida) over a three-year period. Below-ground RWH systems had lower minimum, mean, and maximum temperatures than their above-ground counterparts. The difference in temperatures between above- and below-ground RWH systems was greatest in late spring and summer months. Water temperatures in the above-ground systems exceeded thermal sensitivity thresholds for regionally important cold-water fish for 0.7%–60.3% of the time. Below-ground tanks exceeded these limits less than 1% of the time; variance in below-ground RWH system water temperatures were 2–3 fold lower than for their above-ground counterparts. Both RWH system types formed a vertical thermal gradient with a temperature drop of 1.72°C–5.6°C from the top of the tank to the bottom. This thermal stratification suggests that RWH systems should be designed to overflow from the bottom of the tank in urbanizing watersheds that support cold-water fish species or are otherwise sensitive to spikes in receiving water temperature.

Interaction of Stress-Strain State of the Reinforced Soil Mass and Vertical Shaft Mouth Lining with the Mine Surface Building’s Foundations

Introduction. The mining of mineral deposits is related to the construction of sophisticated technological complexes on the surface being a liaison between underground operations and above-ground systems. During construction of the mining companies’ buildings and structures of the above-ground technological complexes there arise problems related to the complicated engineering, geological and hydrogeological conditions, as well as emerge difficulties caused by the presence of underground workings (mining, transport, ventilation, auxiliary) affecting the construction and operation of surface facilities. In this article a study was made of the stress-strain state (SSS) of a complex system comprising a mine surface building, a vertical shaft mouth with a ventilation duct under conditions complicated by the presence of subsiding soils and the need of reinforcement thereof.Materials and methods. In the study there were used: the analysis of existing methods of soil bases reinforcement as applied to the specific engineering and geological conditions of construction, subject to the interdependence of aboveground and underground structures; the mathematical modeling of the system "a vertical shaft mouth with a ventilation duct - a subsiding soil mass reinforced with soil piles - a mine surface building’s foundations"; the study of SSS features on models, determination of the main factors affecting the design decisions on enforcement of soil bases and building foundations receiving a compound combination of operational loads.Results. It has been found that the above-ground loadbearing structures, foundations and soil bases should be calculated taking into account the interdependence with the vertical shaft and the adjacent ventilation duct, based on the SSS parameters definition. The monolithic concrete mouth lining has a significant impact on the SSS of the foundation slab, increasing rigidity at the points of contact between the slab and the lining. The minimum vertical settlement of the slab is observed above the shaft mouth lining, the maximum - in the central part of the building, in the points of maximum load application.Discussion and Conclusions. The results of the stress-strain state study of a reinforced soil mass and a vertical shaft mouth lining in interaction with the mine surface building’s foundations are formulated, and recommendations are given on considering the affecting factors when designing such facilities.

Community assembly and metaphylogeography of soil biodiversity: Insights from haplotype-level community DNA metabarcoding within an oceanic island.

Most of our understanding of island diversity comes from the study of aboveground systems, while the patterns and processes of diversification and community assembly for belowground biotas remain poorly understood. Here, we take advantage of a relatively young and dynamic oceanic island to advance our understanding of ecoevolutionary processes driving community assembly within soil mesofauna. Using whole organism community DNA (wocDNA) metabarcoding and the recently developed metaMATE pipeline, we have generated spatially explicit and reliable haplotype‐level DNA sequence data for soil mesofaunal assemblages sampled across the four main habitats within the island of Tenerife. Community ecological and metaphylogeographic analyses have been performed at multiple levels of genetic similarity, from haplotypes to species and supraspecific groupings. Broadly consistent patterns of local‐scale species richness across different insular habitats have been found, whereas local insular richness is lower than in continental settings. Our results reveal an important role for niche conservatism as a driver of insular community assembly of soil mesofauna, with only limited evidence for habitat shifts promoting diversification. Furthermore, support is found for a fundamental role of habitat in the assembly of soil mesofauna, where habitat specialism is mainly due to colonization and the establishment of preadapted species. Hierarchical patterns of distance decay at the community level and metaphylogeographical analyses support a pattern of geographic structuring over limited spatial scales, from the level of haplotypes through to species and lineages, as expected for taxa with strong dispersal limitations. Our results demonstrate the potential for wocDNA metabarcoding to advance our understanding of biodiversity.

Varied multi-season response of Aconitum heterophyllum Wall. to increased CO2 in the Indian Himalaya

Plant responses to increasing atmospheric CO2 vary among species. The present study investigates the effects of elevated CO2 on an Indian alpine rhizomatous herb Aconitum heterophyllum using four open-top chambers. Thirty seedlings per chamber were observed for three growing seasons. Atmospheric CO2 was elevated to 650 ppm in two chambers during June to October when above-ground shoot systems were present. Shoot morphometric data were assessed at day 45, 90 and 120 of each season, while biomass and nutrient composition were assessed at completion. Flowering time, flower morphometric data and seed biomass were recorded, and seed germination tests conducted. Elevated CO2 resulted in greater plant height, individual leaf area, stem and leaf thickness during seasons 1 and 2, but in season 3 these shoot morphometric data were either lower or not significantly different. Shoot biomass production in the third season was lower but root biomass was not affected, resulting in a higher root mass fraction. Tissue nitrogen decreased and potassium increased. The soil pH and available nitrogen in 650 ppm CO2 decreased, while other soil nutrients increased. Plants in 650 ppm CO2 flowered 14 days earlier and produced smaller pods with smaller and lighter seeds. Vigor index and seedling biomass were lower, reducing seedling survival, though germination percentage was not affected. Reduced biomass accumulation in the third season could be due to reduced available nitrogen, or the first expression of a longer-term trend. More multi-season studies are required to predict the implications of climate change to this species.

Merkezi Isıtma Sistemlerinde Yerüstü ve Yeraltı Ön Yalıtımlı Boruların Optimum Yalıtım Kalınlığı, Enerji Tasarrufu ve Yakıt Emisyon Hesabı

Enerji ihtiyacının her geçen gün arttığı dünyamızda enerjiyi verimli kullanmak çok önemli bir hale gelmiştir. Enerji verimliliğinde en etkin yöntemlerden biri de ısı yalıtımı uygulamalarıdır. Bu çalışmada merkezi ısıtma sisteminde yer üstü ve yer altı olmak üzere iki farklı ön yalıtımlı borulama sistemi için 50, 100, 200, 400, 600, 800 ve 1000 mm boru çaplarında ikinci yalıtımın optimum yalıtım kalınlığına bağlı ekonomik ve çevresel etkiler hesaplanmıştır. Hesaplamalarda derece-gün yöntemi kullanılmıştır. Hesaplamalar için Balıkesir ili seçilmiştir. Yalıtım malzemesi olarak XPS ve taş yünü, yakıt türü olarak ise doğalgaz, kömür ve fuel-oil kullanılmıştır. Çalışmada yaşam döngüsü maliyet (YDM) analizi kullanılarak 10 yıllık ömür süresi için hesaplamalar yapılmıştır. Yer üstü borulama sistemlerinde tüm parametreler değerlendirildiğinde optimum yalıtım kalınlığı 5,4 cm ile 15,3 cm arasında, yer altı borulama sistemi için ise 5,1 cm ile 12,8 cm arasında değiştiği hesaplanmıştır. Enerji tasarrufu yer üstü borulama sistemi için 8,69 $/m-yıl ile 281,33 $/m yıl arasında, yer altı borulama sistemi için 6,26 $/m-yıl ile 72,43 $/m-yıl arasında hesaplanmıştır. CO2 emisyonu yer üstü borulama sistemi için 2,1 kg/m ile 33,06 kg/m arasında, yer altı borulama sistemi için ise 2,04 kg/m ile 32,14 kg/m arasında gerçekleşmiştir. SO2 emisyonu yer üstü borulama sistemi için 0,011 kg/m ile 0,088 kg/m arasında, yer altı borulama sistemi için 0,011 kg/m ile 0,086 kg/m arasında değişmektedir.

Development of strength of materials for underground energy systems

In order to utilize underground space as a site for energy extraction and material circulation, it is a prerequisite to ensure the mechanical reliability of subsurface systems as well as aboveground systems. For this purpose, it is essential to address the issues related to strength of materials in rocks under the unique underground environment. In this presentation, research activities concerning the underground development, such as design and formation of engineered geothermal reservoirs by using hydraulic stimulation technology, are reviewed and future issues are discussed. The topics to be covered include modeling of the crack propagation behavior in underground systems under mechanical loads and characterization of subsurface complex crack systems using the fluid flow behavior in rocks.

Ecological and biological features of <i>Rosa glauca</i> Pourr., <i>Rosa canina</i> L., <i>Rosa majalis</i> Herrm. in using as rootstocks of garden roses in the forest-steppe of Western Siberia

The paper presents the results of a comprehensive comparative study of Rosa glauca Pourr and Rosa canina L. rose hips used as rootstocks of garden roses in a continental climate. A representative of the local flora Rosa majalis Herrm served as a model object for studying seasonal rhythmics, winter hardiness, as well as histochemical features. Based on studies of the objects ecological morphology, the nature of damage to aboveground shoot systems during wintering is described, the determining role of the minimum air temperature in assessing the adaptive potential of plants is noted. Differences in the seasonal dynamics of starch in the tissues of shoots of three species are most characteristic in the pre-winter period: as for R. glauca, the average amount of starch is observed in the perimedular zone while the low one is in single-row core rays. As for R. canina, a low amount of starch is observed in the perimedular zone and in single cells of single-row core rays. As for a representative of the local flora of R. majalis, almost complete starch hydrolysis occurs; it was recorded only in single cells of the perimedular zone. The paper also contains the results of joint research with the Nikitsky Botanical Garden, including X-ray examination of seeds and expedition studies to increase the collection gene pool of wild rose rootstocks.

Состояние и продуктивность хлопчатника в Сальянской степи Азербайджана

The article presents the results of observations of Gossypium crop performance by development phases. The issues of the development of cotton under different irrigation regimes and levels of mineral nutrition, the state of the aboveground and root systems of the plant on sierozem-meadow soils of the Salyan steppe are considered.

Chemical Cues from Entomopathogenic Nematodes Vary Across Three Species with Different Foraging Strategies, Triggering Different Behavioral Responses in Prey and Competitors

Chemical cues play important roles in predator–prey interactions. Semiochemicals can aid predator foraging and alert prey organisms to the presence of predators. Previous work suggests that predator traits differentially influence prey behavior, however, empirical data on how prey organisms respond to chemical cues from predator species with different hunting strategies, and how foraging predators react to cues from potential competitors, is lacking. Furthermore, most research in this area has focused on aquatic and aboveground terrestrial systems, while interactions among belowground, soiling-dwelling organisms have received relatively little attention. Here, we assessed how chemical cues from three species of entomopathogenic nematodes (EPNs), each with a different foraging strategy, influenced herbivore (cucumber beetle) and natural enemy (EPN) foraging behavior. We predicted these cues could serve as chemical indicators of increased predation risk, prey availability, or competition. Our findings revealed that foraging cucumber beetle larvae avoided chemical cues from Heterorhabditis bacteriophora (active-foraging cruiser EPNs), but not Steinernema carpocapsae (ambusher EPNs) or Steinernema riobrave (intermediate-foraging EPNs). In contrast, foraging H. bacteriophora EPNs were attracted to cues produced by the two Steinernema species but not conspecific cues. Notably, the three EPN species produced distinct blends of olfactory cues, with only a few semi-conserved compounds across species. These results indicate that a belowground insect herbivore responds differently to chemical cues from different EPN species, with some EPN species avoiding prey detection. Moreover, the active-hunting EPNs were attracted to heterospecific cues, suggesting these cues indicate a greater probability of available prey, rather than strong interspecific competition.

Drought, windthrow and forest operations strongly affect oribatid mite communities in different microhabitats

Climate change is enhancing the annual mean temperature and the risk for droughts and natural disasters. Hot and dry summers not only have a negative impact on forest performance, but also affect fundamental ecosystem processes such as litter decomposition and nutrient cycling and the organisms involved. Oribatid mites are sexually or parthenogenetically reproducing soil-living microarthropods substantially involved in these processes. We compare oribatid mite communities (abundance, species richness, effective Shannon diversity and life-history parameters such as sex ratio, gravidity, number of eggs) in four microhabitats (litter, dead wood, moss and bare soil) before (2016) and after a sequence of disturbance events (2020). These disturbances include the severe drought of 2018/2019 in Germany, a single summer storm event in August 2019, and subsequent forest operations in spring 2020. Abundance and species richness were reduced up to 87% in all microhabitats and so was the effective Shannon diversity in moss (65%). Communities in moss were most affected, while effects were buffered in litter. In litter and moss, sexual species suffered slightly more than parthenogenetic species. Life history parameters were largely unaffected. In bare soil, microarthropods were almost absent. Our study demonstrates that consequences of climate change – drought, windthrow, necessary forest operations – are not restricted to above-ground systems but also strongly affect soil-living microarthropod communities. If natural and human-introduced disturbances remain in the long-term, severe consequences for forest soil arthropods must be expected. Since life-history parameters were unaffected, species probably recover over time if climate becomes more moderate in the short-term.

The state, transport, and fate of aboveground terrestrial arthropod eDNA

AbstractEnvironmental DNA (eDNA) analyses have become invaluable for detecting and monitoring aquatic and terrestrial species and assessing site biodiversity within aquatic environments or soil. Recent studies have extended these techniques by using eDNA to identify the presence of aboveground terrestrial arthropods directly from vegetative surfaces. However, while the dynamics of eDNA state, transport, and fate (its “ecology”) have been explored within aquatic environments and soil, they have yet to be explored within aboveground terrestrial systems. Here, we explore the ecology of terrestrial eDNA deposited by fluid‐feeding arthropods on leaf surfaces. We carried out a series of experiments to evaluate the optimal filter pore size for intracellular eDNA collection, how eDNA is affected by rain events, and its degradation rate under different solar radiation conditions. We found that the captured concentration of intracellular eDNA was not significantly affected by an increase in filter pore size, suggesting a wide range of viable pore size options exist for targeting intracellular eDNA. We also found extracellular eDNA from fluid excrement degrades more rapidly than intracellular when exposed to solar radiation, indicating the latter is a more viable target for collection. Finally, we identified that rainfall or mist will remove most terrestrial eDNA present on vegetation surfaces. We provide researchers and environmental managers key insights into successfully designing and carrying out aboveground terrestrial arthropod eDNA surveys that maximize detection probability.

Ectomycorrhizas and tipping points in forest ecosystems.

The resilience of forests is compromised by human-induced environmental influences pushing them towards tipping points and resulting in major shifts in ecosystem state that might be difficult to reverse, are difficult to predict and manage, and can have vast ecological, economic and social consequences. The literature on tipping points has grown rapidly, but almost exclusively based on aquatic and aboveground systems. So far little effort has been made to make links to soil systems, where change is not as drastically apparent, timescales may differ and recovery may be slower. Predicting belowground ecosystem state transitions and recovery, and their impacts on aboveground systems, remains a major scientific, practical and policy challenge. Recently observed major changes in aboveground tree condition across European forests are probably causally linked to ectomycorrhizal (EM) fungal changes belowground. Based on recent breakthroughs in data collection and analysis, we apply tipping point theory to forests, including their belowground component, focusing on EM fungi; link environmental thresholds for EM fungi with nutrient imbalances in forest trees; explore the role of phenotypic plasticity in EM fungal adaptation to, and recovery from, environmental change; and propose major positive feedback mechanisms to understand, address and predict forest ecosystem tipping points.

Short‐term biochar effects on greenhouse gas emissions and phosphorus availability for maize

Short‐term biochar effects on greenhouse gas emissions and phosphorus availability for maize

Nitrogen deposition and increased precipitation interact to affect fine root production and biomass in a temperate forest: Implications for carbon cycling

Fine roots connect belowground and aboveground systems and help regulate the carbon balance of terrestrial ecosystems by providing nutrients and water for plants. To evaluate the effects of atmospheric nitrogen (N) deposition and increased precipitation on fine root production and standing biomass in a temperate deciduous forest in central China, we conducted a 6-year experiment. From 2013 to 2018, we applied N (25 kg N ha−1 yr−1) and water (336 mm, 30% of the ambient annual precipitation) above the forest canopy, and we quantified fine root production and biomass in 2017 and 2018. At 0–10 cm soil depth, the statistical interaction between addition of N and water was not significant in terms of fine root production or biomass. At 0–10 cm soil depth, N addition significantly increased fine root production by 18.1%, but did not affect fine root biomass. Water addition significantly increased fine root production and biomass by 13.6 and 17.0%, respectively. Both N and water addition had significant direct positive effects on fine root production, and water addition had indirect positive effects on fine root biomass through decreasing soil NO3− concentration. At 10–30 cm soil depth, the statistical interaction between N addition and water addition was significant in terms of both fine root production and biomass, i.e., the positive effect of N addition was reduced by water addition, and vice versa. These findings indicate that fine roots and therefore belowground carbon storage may have complex responses to increases in atmospheric N deposition and changes in precipitation predicted for the future. The findings also suggest that results obtained from experiments that consider only one independent variable (e.g., N input or water input) and only one soil depth should be interpreted with caution.

Shifting the imbalance: Intentional reuse of Dutch sewage effluent in sub-surface irrigation

Worldwide, agricultural irrigation currently accounts for 69% of freshwater withdrawal. Countries with a temperate climate, such as the Netherlands, experience periodic freshwater shortages in agriculture. The pressure on available freshwater will increase due to climate change and a growing demand for freshwater by e.g. industrial activities. Possible alternative water resources are considered in order to meet the current and future water demand. In this study we explore where, and how much, sewage treatment plant (STP) effluent can directly be reused in agricultural sub-surface irrigation (SSI) during an average and a dry season scenario, for all active (335) Dutch STPs. SSI systems may have a higher water demand as part of the STP effluent is transported with groundwater flow, although aboveground irrigation has a loss of water due to interception. Furthermore, such aboveground irrigation systems provide direct contact of crops with irrigation water. SSI systems provide a soil barrier which may function as a filter and buffer zone. In the Dutch situation, direct intentional reuse of STP effluent can fulfill up to 25% of croplands SSI water demand present within a five-kilometer transport buffer from the STPs during an average season and 17% during a dry season. Hereto, respectively, 78% and 84% of the total available Dutch STP effluent would be used. Thus, the intentional direct STP effluent reuse in agricultural SSI has the potential to satisfy a significant amount of the agricultural water demand at a national scale, presuming responsible reuse: safe applications for humans and environment and no limiting effects on water availability for other actors.

Methods and approaches to advance soil macroecology

AbstractMotivation and aimSoil biodiversity is central to ecosystem function and services. It represents most of terrestrial biodiversity and at least a quarter of all biodiversity on Earth. Yet, research into broad, generalizable spatial and temporal patterns of soil biota has been limited compared to aboveground systems due to complexities of the soil system. We review the literature and identify key considerations necessary to expand soil macroecology beyond the recent surge of global maps of soil taxa, so that we can gain greater insight into the mechanisms and processes shaping soil biodiversity. We focus primarily on three groups of soil taxa (earthworms, mycorrhizal fungi and soil bacteria) that represent a range of body sizes and ecologies, and, therefore, interact with their environment at different spatial scales.ResultsThe complexities of soil, including fine‐scale heterogeneity, 3‐D habitat structure, difficulties with taxonomic delimitation, and the wide‐ranging ecologies of its inhabitants, require the classical macroecological toolbox to be expanded to consider novel sampling, molecular identification, functional approaches, environmental variables, and modelling techniques.Main conclusionsSoil provides a complex system within which to apply macroecological research, yet, it is this property that itself makes soil macroecology a field ripe for innovative methodologies and approaches. To achieve this, soil‐specific data, spatio‐temporal, biotic, and abiotic considerations are necessary at all stages of research, from sampling design to statistical analyses. Insights into whole ecosystems and new approaches to link genes, functions and diversity across spatial and temporal scales, alongside methodologies already applied in aboveground macroecology, invasion ecology and aquatic ecology, will facilitate the investigation of macroecological processes in soil biota, which is key to understanding the link between biodiversity and ecosystem functioning in terrestrial ecosystems.

Nutrient limitations for overstory and understory plants during Robinia pseudoacacia afforestation in the Loess Plateau, China

AbstractOverstory trees and understory herbs are in different niches in the community; however, how their nutrient limitations change following afforestation remains unclear. Therefore, we used plant nutrient resorption and ecological stoichiometry to illustrate the nutrient relationship between plants and soil while exploring the nutrient limitations of different plants during afforestation. Soil and plant samples were collected from farmland and three Robinia pseudoacacia L. (RP) forests that were 17, 26, and 42 yr old. The physical characteristics of the soil and the content and stoichiometric ratios of C, N, and P in the plants, litter, soil microbes, and soil were measured. Additionally, the resorption of N and P in RP and understory herbaceous biomass (UHB) was assessed. Results showed that, at all sites, N resorption (0.45–0.52) and P resorption (0.39–0.49) were approximately equal in RP, while P resorption (0.48–0.65) was significantly higher than N resorption (0.06–0.32) in UHB. With afforestation age, the N/P resorption ratios (1.06–1.25) were not significantly different in RP but declined significantly from 0.50 to 0.14 in UHB. Results suggest that RP is co‐limited by N and P while understory herbs are limited by P. Although the nutrient limitation of RP and UHB may be different, their nutrient relationship with the soil is consistent after afforestation. There was a significant positive relationship for C and N content but a negative relationship of the C/N ratios between soil and plants. These findings deepen the understanding of a linkage between the aboveground and belowground systems and provide evidence that nutrient limitation changes occur in plants of different ecological niches after afforestation in the Loess Plateau.