Environmental conditions to support blue carbon storage in mangrove forest: A case study in the mangrove forest, Nusa Lembongan, Bali, Indonesia

Pricillia CC, Patria MP, Herdiansyah H. 2021. Environmental conditions to support blue carbon storage in mangrove forest: A case study in the mangrove forest, Nusa Lembongan, Bali, Indonesia. Biodiversitas 22: 3304-3314. Mangrove ecosystems can provide ecosystem services to mitigate climate change by absorbing and storing carbon in their systems. The question arises of how to manage a mangrove forest to store more carbon. The Nusa Lembongan mangrove forest was examined to assess the optimal environmental settings for blue carbon storage in the mangrove ecosystem. Five stations were selected purposively. The parameters observed in each station were aboveground living biomass, mangrove stand density, clay percentage in soil, bulk density, water content, soil organic carbon (%C), and soil organic nitrogen (%N). Based on this study, the total carbon stock in mangrove forest Nusa Lembongan was 68.10 ± 20.92 Mg C ha-1 and equals to 249.95 ± 76.77 MgCO2 ha-1 with a significant contribution of soil carbon stock. This study indicates that the essential parameters that can promote carbon sequestration in mangrove forest Nusa Lembongan were aboveground living biomass, soil organic carbon content and soil organic nitrogen content. In addition, as soil organic carbon content also negatively correlates with bulk density, it also can be considered. These findings can contribute to blue carbon planning and management to improve the effectiveness of the blue carbon project.

Root-Derived Proteases as a Plant Tool to Access Soil Organic Nitrogen; Current Stage of Knowledge and Controversies

Anthropogenic deterioration of the global nitrogen (N) cycle emerges mainly from overuse of inorganic N fertilizers in nutrient-limited cropping systems. To counteract a further dysregulation of the N cycle, we need to improve plant nitrogen use efficiency. This aim may be reached via unravelling all plant mechanisms to access soil N, with special attention to the dominating high-molecular-mass N pool. Traditionally, we believe that inorganic N is the only plant-available N pool, however, more recent studies point to acquisition of organic N compounds, i.e., amino acids, short peptides, and proteins. The least known mechanism of plants to increase the N uptake is a direct increase of soil proteolysis via root-derived proteases. This paper provides a review of the knowledge about root-derived proteases and also controversies behind this phenomenon.

Silicon fertilizer and biochar effects on plant and soil PhytOC concentration and soil PhytOC stability and fractionation in subtropical bamboo plantations

<p>The use of exogenous silicon (Si) amendments, such as Si fertilizers and biochar, can effectively increase crop Si uptake and the formation of phytoliths, which are siliceous substances that are abundant in numerous plant species. Phytolith-occluded carbon (C) (PhytOC) accumulation in soil plays an important role in long-term soil organic C (SOC) storage. Nevertheless, the effects of both Si fertilizer and biochar application on PhytOC sequestration in forest plant-soil systems have not been studied. We investigated the impact of Si fertilizer and biochar applications on 1) the PhytOC pool size, the solubility of plant and soil phytoliths, and soil PhytOC in soil physical fractions (light (LFOM) and heavy fractions of organic matter (HFOM)) in Moso bamboo (<em>Phyllostachys pubescens</em>) forests; and 2) the relationships among plant and soil PhytOC concentrations and soil properties. We used a factorial design with three Si fertilizer application rates: 0 (S0), 225 (S1) and 450 (S2) kg Si ha<sup>−1</sup>, and two biochar application rates: 0 (B0) and 10 (B1) t ha<sup>−1</sup>. The concentrations of PhytOC in the bamboo plants and topsoil (0–10 cm) increased with increasing Si fertilizer addition, regardless of biochar application. Biochar addition increased the soil PhytOC pool size, as well as the LFOM- and HFOM-PhytOC fractions, regardless of Si fertilizer application. The Si fertilizer application increased or had no effect on soil phytolith solubility with or without biochar application, respectively. Soil PhytOC was correlated with the concentration of soil organic nitrogen (R<sup>2</sup>=0.32), SOC (R<sup>2</sup>=0.51), pH (R<sup>2</sup>=0.28), and available Si (R<sup>2</sup>=0.23). Furthermore, Si fertilizer application increased plant and soil PhytOC by increasing soil available Si. Moreover, biochar application increased soil PhytOC concentration in LFOM-PhytOC and the unstable fraction of PhytOC. We conclude that Si fertilizer and biochar application promoted PhytOC sequestration in the plant-soil system and changed its distribution in physical fractions in the Moso bamboo plantation in subtropical China.</p>

Identifying source and transformation of riverine nitrates in a karst watershed, North China: comprehensively using major ions, multiple isotopes and Bayesian model

<p>The identification of nitrate (NO<sub>3</sub><sup>-</sup>) sources and biogeochemical transformations is critical for understanding and controlling diffuse pollution in surface water in drainage basins. This study combines water chemistry, environmental isotopes (δ<sup>2</sup>H<sub>H2O</sub>, δ<sup>18</sup>O<sub>H2O</sub>, δ<sup>15</sup>N<sub>NO3</sub>, and δ<sup>18</sup>O<sub>NO3</sub>), with land use data and a Bayesian isotope mixing model (Simmr), for reducing the uncertainty in estimating the contributions of different pollution sources in a Karst drainage basin of Jinan, North China. 64 samples were collected from Yufu River (YFR) of Jinan city in September and December, 2019. The results revealed that the NO<sub>3</sub><sup>−</sup>-N (4.41mg/L) was the predominant form of inorganic nitrogen in YFR watershed, accounting for about 58% of total nitrogen (8.06 mg/L). There were significant temporal and spatial variations in nitrate concentrations in the area. The nitrate concentration in time was low in December and high in September, while the process of first rising and then attenuating from upstream to downstream in space. Moreover, according to the surface water flow path, different biogeochemical transformations were observed throughout the study area: microbial nitrification was dominant in the upstream with elevated NO<sub>3</sub><sup>−</sup>-N concentrations; in the middle stream a mixing of different transformations, such as nitrification, denitrification, and/or assimilation, were identified, associated to moderate NO<sub>3</sub><sup>−</sup>-N concentrations; whereas in the downstream the main process affecting NO<sub>3</sub><sup>−</sup>-N concentrations was assimilation, and/or denitrification, resulting in low NO<sub>3</sub><sup>−</sup>-N concentrations. Water chemical and dual isotope of δ<sup>15</sup>N<sub>NO3</sub> and δ<sup>18</sup>O<sub>NO3 </sub>indicated that the river water was significantly affected by soil organic nitrogen and ammonium fertilizer inputs. Simmr mixing model outputs revealed that soil organic nitrogen (SON 55.5%) and ammonium fertilizer inputs(AF 29.5%) were the primary contributors of N pollution, whereas nitrate fertilizer(NF 7.1%), sewage & manure (M&S 3.6%), and atmospheric deposition (AP3.4%) played a less important role. The chemical fertilizer (AF and NF) and SON collectively mean contributing > 50 % of nitrate both in September and December in the watershed. Therefore, reducing fertilizer application and adopting water-saving irrigationare key to control nitrate pollution in the area. The results provide scientific basis for the water quality protection and sustainable water management in the study area or similar areas.</p>

Soil organic nitrogen: an overlooked but potentially significant contribution to crop nutrition

Background For more than a century, crop N nutrition research has primarily focused on inorganic N (IN) dynamics, building the traditional model that agricultural plants predominantly take up N in the form of NO3− and NH4+. However, results reported in the ecological and agricultural literature suggest that the traditional model of plant N nutrition is oversimplified. Scope We examine the role of organic N (ON) in plant N nutrition, first by reviewing the historical discoveries by ecologists of plant ON uptake, then by discussing the advancements of key analytical techniques that have furthered the cause (stable isotope and microdialysis techniques). The current state of knowledge on soil ON dynamics is analyzed concurrently with recent developments that show ON uptake and assimilation by agricultural plant species. Lastly, we consider the relationship between ON uptake and nitrogen use efficiency (NUE) in an agricultural context. Conclusions We propose several mechanisms by which ON uptake and assimilation may increase crop NUE, such as by reducing N assimilation costs, promoting root biomass growth, shaping N cycling microbial communities, recapturing exuded N compounds, and aligning the root uptake capacity to the soil N supply in highly fertilized systems. These hypothetical mechanisms should direct future research on the topic. Although the quantitative role remains unknown, ON compounds should be considered as significant contributors to plant N nutrition.