Carbon and Nitrogen Contents Driven by Organic Matter Source within Pichavaram Wetland Sediments

Differences in grain size, total organic carbon (OC), total nitrogen (TN), OC/TN ratios, and stable isotope (δ13C and δ15N) were assessed in sediments from areas covered by mangrove and saltmarsh vegetation within Pichavaram estuary (Southeast India). The mean percentage contents of silt and clays (70 vs. 19%), OC (5.7 vs. 2.0%), and TN (0.39 vs. 0.14%) were consistently higher in the mangrove as compared to those observed in the saltmarsh tidal zone. These differences may obey the higher deposition and retention of fine particles in the presence of a mangrove root system that may facilitate the accumulation and preservation of organic matter within these sedimentary systems. Further, higher OC and TN contents were associated to higher terrestrial or mangrove-derived organic matter contribution with lighter δ13C signatures (−26.0‰) in both sedimentary tidal zones, whereas lower OC and TN contents were associated to heavier δ13C signatures. This study is in agreement with previous studies which indicate that the presence of wetland vegetation may increase the carbon and nutrient storage capacity within estuarine ecosystems, highly relevant information for the establishment of further conservation strategies for blue carbon ecosystems at global scales.

The structure of trees.

Trees are, by definition, the tallest land plants. To grow tall over multiple years they must solve several problems: structural strength; carbohydrate and nutrient storage capacity to survive and regrow after periods of stress; and conductive capacity for water, carbohydrates and nutrients must be increased/renewed over time to keep pace with increases in canopy size. Additionally, apical meristems must be capable of surviving through periods of stress (especially over winter or during drought). Structural strength, storage capacity and water, carbohydrate and nutrient conductive capacity are provided by cells derived from a sheath of meristematic cells (vascular cambium) that surround the body of trees (shoots, stems, branches, trunk, perennial roots). This chapter describes the structure of fruit trees.

Excessive energy expenditure due to acute physical restraint disrupts Drosophila motivational feeding response

To study the behavior of Drosophila, it is often necessary to restrain and mount individual flies. This requires removal from food, additional handling, anesthesia, and physical restraint. We find a strong positive correlation between the length of time flies are mounted and their subsequent reflexive feeding response, where one hour of mounting is the approximate motivational equivalent to ten hours of fasting. In an attempt to explain this correlation, we rule out anesthesia side-effects, handling, additional fasting, and desiccation. We use respirometric and metabolic techniques coupled with behavioral video scoring to assess energy expenditure in mounted and free flies. We isolate a specific behavior capable of exerting large amounts of energy in mounted flies and identify it as an attempt to escape from restraint. We present a model where physical restraint leads to elevated activity and subsequent faster nutrient storage depletion among mounted flies. This ultimately further accelerates starvation and thus increases reflexive feeding response. In addition, we show that the consequences of the physical restraint profoundly alter aerobic activity, energy depletion, taste, and feeding behavior, and suggest that careful consideration is given to the time-sensitive nature of these highly significant effects when conducting behavioral, physiological or imaging experiments that require immobilization.

Phenology explains different storage remobilization in two congeneric temperate tree species with contrasting leaf habit

The dependence of trees on carbon and nutrient storage is critical to predicting the forest vulnerability under climate change, but whether evergreen and deciduous species differ in their use and allocation of stored resources during spring phenology is unclear. Using a high temporal resolution, we evaluated the role of spring phenology and shoot growth as determinants of the carbon and nutrient storage dynamics in contrasting leaf habits. We recorded the phenology and shoot elongation and determined the concentrations of total non-structural carbohydrates (NSC), starch, soluble carbohydrates (SC), nitrogen (N) and phosphorus (P) in buds, expanding shoots and previously formed shoots of two sympatric Nothofagus species with contrasting leaf habit. Species reached similar shoot lengths, though shoot expansion started 35 days earlier and lasted c. 40 days more in the deciduous species. Thus, while the deciduous species had a relatively constant shoot growth rate, the evergreen species experienced a conspicuous growth peak for c. 20 days. In the evergreen species, the greatest decreases in NSC concentrations of previously formed shoots and leaves coincided with the maximum shoot expansion rate and fruit filling, with minimums of 63% and 65% relative to values at bud dormancy, respectively. In contrast, minimum NSC concentrations of the previously formed shoots of the deciduous species were only 73% and occurred prior to the initiation of shoot expansion. Bud N and P concentrations increased during budbreak, while previously formed shoots generally did not decrease their nutrient concentrations. Late spring phenology and overlapping of phenophases contributed to the greater dependence on storage of proximal tissues in the studied evergreen compared to deciduous species, suggesting that phenology is a key determinant of the contrasting patterns of storage use in evergreen and deciduous species.

Nutrient Storage and Stoichiometry of the Forest Floor Organic Matter in Japanese Forests

Nutrient storage in the forest floor is regulated through litter decomposition and nutrient cycling. Stoichiometry of nutrients can provide characterization of the forest floor. To quantify nutrient storage in the forest floor and to determine stoichiometry among different forest types, available data on nutrients were meta-analyzed. The data on nutrients—nitrogen, phosphorus, potassium, calcium, and magnesium—were collected from published reports and original data on Japanese forests. The relationship between nutrient storage and forest floor mass was also examined. Japanese cypress and cedar plantations had small N and P storage in the forest floor with high C:N and C:P ratios, whereas subalpine conifers had large N and P storage in the forest floor with low C:N and C:P ratios; cedar plantations showed large Ca-specific storage in the forest floor. The stoichiometry of the forest floor varied between different forest types, namely C:N:P ratios were 942:19:1 for cedar and cypress plantations, 625:19:1 for broad-leaved forests, and 412:13:1 for subalpine conifers and fir plantations. N storage was closely correlated; however, P and other mineral storages were weakly correlated with the forest floor mass. Nutrient storage and stoichiometry can provide a better perspective for the management of forest ecosystem.

Effect of Humic Acid Addition on Buffering Capacity and Nutrient Storage Capacity of Soilless Substrates

Excessive application of fertilizers has become a major issue in croplands of intensive agricultural systems in China, resulting in severe non-point source pollution; thus, reduction in the use of chemical fertilizers has received significant attention. Improving the nutrient storage capacity of soils or substrates is an effective approach for solving this problem. Humic acids (HA) are excellent soil conditioners. Thus, in the present study, their ability to improve the physico-chemical properties of three substrates with different textures was evaluated. HA treatments included 1% HA root application in three different types of substrates, including pure sand, pure cocopeat, and a mixture of sand:cocopeat (1:1, v/v) and their relative controls. We examined the morphological parameters of cucumber seedlings as well as pH buffering capacity (pHBC), total organic carbon (TOC), organic matter (OM), cation exchange capacity (CEC), and nutrient storage capacity of the three substrates. The results show that HA application improved the morphological parameters of cucumber seedlings (plant height, stem diameter, and biomass) in pure cocopeat and cocopeat-sand mixture treatments. On the contrary, HA addition had harmful effects on the cucumber seedlings cultivated in sand due to the low pHBC of sand. The seedlings cultivated in pure cocopeat showed the best morphological parameter performances among the seedlings grown in the three substrates. Furthermore, pHBC, TOC, OM, and CEC were enhanced by HA application. Incorporation of HA improved ammonium (NH4+) and potassium (K+) storage capacity while decreasing phosphorus (P) storage. Pure cocopeat had the highest pHBC, TOC, OM, CEC, and nutrient storage capacity among the three substrates. In conclusion, mixing 1% HA into substrates promoted cucumber growth, improved substrate properties, and enhanced fertilizer use efficiency. Pure cocopeat is a suitable substrate for cucumber cultivation, and mixing cocopeat with sand amends the substrate properties and consequently improves plant growth.

The effect of seasonal flooding and livelihood activities on retention of nitrogen and phosphorus in Cyperus papyrus wetlands, the role of aboveground biomass

With growing demand for food production in Africa, protecting wetlands and combining increased agricultural production with conservation of the ecological integrity of wetlands is urgent. The role of aboveground biomass of papyrus (Cyperus papyrus) in the storage and retention of nitrogen (N) and phosphorus (P) was studied in two wetland sites in East Africa under seasonally and permanently flooded conditions. Nyando wetland (Kenya) was under anthropogenic disturbance from agriculture and vegetation harvesting, whereas Mara wetland (Tanzania) was less disturbed. Maximum papyrus culm growth was described well by a logistic model (regressions for culm length with R2 from 0.70 to 0.99), with culms growing faster but not taller in Nyando than in Mara. Maximum culm length was greater in permanently than in seasonally flooded zones. Total aboveground biomass was higher in Mara than in Nyando. The amounts of N and P stored were higher in Mara than in Nyando. In disturbed sites, papyrus plants show characteristics of r-selected species leading to faster growth but lower biomass and nutrient storage. These findings help to optimize management of nutrient retention in natural and constructed wetlands.

Genome wide analysis in Drosophila reveals diet by gene interactions and uncovers diet-responsive genes

Genetic and environmental factors play a major role in metabolic health. However, they do not act in isolation, as a change in an environmental factor such as diet may exert different effects based on an individual’s genotype. Here, we sought to understand how such gene-diet interactions influenced nutrient storage and utilization, a major determinant of metabolic disease. We subjected 178 inbred strains from the Drosophila Genetic Reference Panel (DGRP), to diets varying in sugar, fat and protein. We assessed starvation resistance, a holistic phenotype of nutrient storage and utilization that can be robustly measured. Diet influenced the starvation resistance of most strains, but the effect varied markedly between strains such that some displayed better survival on a high carbohydrate diet compared to a high fat diet while others had opposing responses, illustrating a considerable gene x diet interaction. This demonstrates that genetics plays a major role in diet responses. Furthermore, heritability analysis revealed that the greatest genetic variability arose from diets either high in sugar or high in protein. To uncover the genetic variants that contribute to the heterogeneity in starvation resistance, we mapped 566 diet-responsive SNPs in 293 genes, 174 of which have human orthologues. Using whole-body knockdown, we identified two genes that were required for glucose tolerance, storage and utilization. Strikingly, flies in which the expression of one of these genes, CG4607 a putative homolog of a mammalian glucose transporter, was reduced at the whole-body level, displayed lethality on a high carbohydrate diet. This study provides evidence that there is a strong interplay between diet and genetics in governing survival in response to starvation, a surrogate measure of nutrient storage efficiency and obesity. It is likely that a similar principle applies to higher organisms thus supporting the case for nutrigenomics as an important health strategy.

Flexibility in the critical period of nutrient sequestration in bumble bee queens

Bumble bee queens undergo a nutrient storage period prior to entering diapause wherein they sequester glycogen and lipids that are metabolized during overwintering. In the laboratory under optimal food availability conditions, the majority of nutrients are sequestered during the first few days of adulthood. However, if food resources are scarce during this narrow window of time, wild queen bumble bees might be limited in their ability to obtain adequate food resources for overwintering. Here we used a laboratory experiment to examine whether queen bumble bees exhibit flexibility in the timing of pre-overwintering nutrient sequestration, by limiting their access to either nectar (artificial) or pollen, the two primary foods for bumble bees, for varying periods of time. In response to these treatments, we quantified queen survival, changes in weight, and glycogen and lipids levels. We found evidence that queens are able to recuperate almost entirely from food resource limitation, with respect to nutrient storage, especially when it is experienced for shorter durations (up to 6 days). This study sheds light on how bumble bee queens are impacted by food resource availability at a critical life stage.