Ecosystem Productivity Research Articles

Different Types of Surface Chlorophyll Patterns of Oceanic Mesoscale Eddies Identified by AI Framework

AbstractOceanic mesoscale eddies (with scale 101–102 km) and their submesoscale fine structures (with scale 100–101 km) can effectively induce vertical motions and bring nutrients into the oceanic euphotic layer, which leaves abundant footprints on the ocean surface chlorophyll distributions and have the potential to promote primary productivity of oceanic ecosystem. In return, these surface chlorophyll footprints observed by ocean color satellites can serve as a useful tool to reveal the spatial structures of mesoscale eddies and their submesoscale fine structures. By combining artificial intelligence (AI) algorithms to develop a series of identification strategies for typical surface chlorophyll patterns around mesoscale eddies, we find that over 20% of mesoscale eddy observations exhibit identifiable typical chlorophyll patterns, which tends to regulate an increase of the surface chlorophyll concentration within the corresponding eddies, especially enhancing by about 30% in nutrient‐restricted subtropical regions compared with the background values. Based on their geometric features, typical chlorophyll patterns are primarily classified as Core, Spiral, Tail, Ring, Loop, and Eye respectively by clustering algorithm. Further spatial‐spectral analysis found that the typical patterns on eddies exhibit a much steeper wave‐number spectral slope about −3, compared to the non‐typical distributions on eddies and the non‐eddy background distribution (about −2.7–−2.2). This implies that the occurrence of different typical chlorophyll patterns may correspond to specific mesoscale and submesoscale dynamic processes.

The genus Eutreptiella (Euglenophyceae/Euglenozoa) across its global distribution range.

The genus Eutreptiella (Euglenophyceae/Euglenozoa) comprises unicellular organisms known for their photosynthetic capacity and significant role in marine ecosystems. This review highlights the taxonomic, ecological, and biotechnological characteristics of Eutreptiella species, emphasizing their morphological and genomic adaptations. Eutreptiella species exhibit high phenotypic plasticity, enabling adaptation to various environmental conditions, from nutrient-rich waters to high-salinity conditions. They play a crucial role in primary production and nutrient cycling in marine ecosystems. Genetic and transcriptomic studies have revealed their complex regulatory mechanisms and potential for biofuel and nutraceutical production. Eutreptiella blooms significantly impact local ecosystems, influencing nutrient availability and community dynamics. Additionally, interactions with associated bacteria enhance their growth and metabolic capabilities. The genus shows substantial genetic variability, suggesting potential misidentifications or a polyphyletic nature. Further comprehensive studies are needed to clarify their taxonomy and evolutionary relationships. Understanding and managing Eutreptiella populations is essential to leverage their biotechnological potential and ensure the health of marine ecosystems.

Gross primary productivity of terrestrial ecosystems: a review of observations, remote sensing, and modelling studies over South Asia

Gross primary productivity of terrestrial ecosystems: a review of observations, remote sensing, and modelling studies over South Asia

Tracing of fire‐induced soil phosphorus transformations using phosphate oxygen isotope ratio

AbstractThis study demonstrates that phosphate oxygen isotope (δ18OPO4) analysis effectively detects and monitors fire‐induced transformation in soil phosphorus (P). Fires increase bioavailable P, potentially limiting primary production in terrestrial ecosystems. However, understanding the effects of fire on soil P dynamics in the field remains challenging due to the interaction between fire spread and soil properties with high spatial heterogeneity. Soil burning experiments were conducted using a surface soil sample collected in central Japan. The soil was burned in an electric furnace from 50 to 550°C for 3 h, and P concentrations and δ18OPO4 values were determined. The results revealed that high temperatures (>350°C) depleted the soil of organic P (Po) and increased labile and stable inorganic P (Pi) concentrations while significantly decreasing δ18OPO4 values. By contrast, low temperatures (150°C) increased labile Pi and Po concentrations without isotopic shift, indicating that low‐intensity fires could increase bioavailable P while conserving soil organic matter. These findings indicate that δ18OPO4 analysis can provide insight into the relationship between P transformations and fire intensity and track subsequent changes in P dynamics over time. Our research highlights the potential of δ18OPO4 in predicting and managing postfire ecological and agricultural impacts.

Tree species identity affects soil P bioavailability by altering labile organic P after tree mixing in subtropical China

AbstractConverting monocultures to mixed plantations has been emphasized to improve ecosystem productivity and services. However, the impact of tree species identity on phosphorus (P) bioavailability in acidic soils in subtropical China, where P is relatively scarce, is not fully understood. This study explored the changes in soil biologically‐based P fractions and the effect of mineral and microbial properties on P transformation after mixing five broadleaved trees (Bretschneidera sinensis, Manglietia conifera, Cercidiphyllum japonicum, Michelia maudiae and Camellia oleifera) individually with coniferous trees (Pinus massoniana). The results showed that most mixed plantations significantly increased pH and citric acid and decreased exchangeable Fe3+ and Al3+ and the activation of Fe and Al oxides compared with monospecific plantations, which significantly reduced P precipitation and adsorption. Mixed planting significantly increased phosphatase activity and altered the community composition of P‐mobilizing bacteria carrying phoD and pqqC genes, which contributed to organic P mineralization and inorganic P (Pi) desorption. Mixed planting increased microbial biomass and the relative rate of microbial biomass P turnover. Labile organic P (Enzyme‐P) was a potentially significant source of soluble Pi (CaCl2‐P) among the biologically‐based P fractions, plus microbial biomass P. Overall, introducing broadleaved species, especially in species (e.g. Cercidiphyllum japonicum, Michelia maudiae and Camellia oleifera) with relatively high litter quality and belowground secretions (e.g. citric acid, phosphatase), significantly increased the solubilization of recalcitrant Pi (HCl‐P), desorption of chemisorbed Pi (Citrate‐P) and accumulation and mineralization of Enzyme‐P, thereby increasing the available P pools. Redundancy analysis demonstrated that P fractions were mainly driven by phosphatases, exchangeable cations, floor fresh litter lignin/N and citric acid. Altogether, we highlight the importance of choosing tree species mixtures that have synergistic or complementary effects when constructing mixed plantations in order to alleviate soil P limitations.

Innovative Approaches for Climate-Resilient Farming: Strategies against Environmental Shifts and Climate Change

Climate change, driven predominantly by human activities such as burning fossil fuels and deforestation, is causing significant alterations to global weather patterns. This phenomenon results in more frequent and severe weather events, including prolonged droughts, intense rainfall, and shifting temperature regimes. Such changes pose a substantial threat to agriculture, a sector highly dependent on stable climatic conditions. Crop yields are increasingly unpredictable due to these extreme weather events and shifting growing seasons, impacting food security and livelihoods worldwide. To address these challenges, climate resilience agriculture has emerged as a pivotal solution. This approach involves adopting farming practices and technologies designed to withstand and adapt to changing climatic conditions. Strategies include diversifying crop varieties, precision agriculture, climate smart agriculture, nano biochar application, coated fertilizer applications, natural farming, site specific nutrient management, mulching, precise water management, seed bombing, direct seeding in rice, implementing soil conservation methods etc. Additionally, climate resilience agriculture promotes the integration of traditional knowledge with modern scientific advancements to enhance ecosystem robustness and productivity. By fostering adaptive capacity and reducing vulnerability, climate resilience agriculture aims to safeguard food systems and sustain agricultural productivity in the face of ongoing climate disruptions.

Coral mucus promotes the carbon metabolic potency of microorganisms in the coral reef ecosystem

AbstractCoral mucus, teeming with organic matter, releases nutrients and microorganisms, affecting element cycling and microbial communities in coral reefs. While terrestrial ecosystems exhibit well‐studied priming effects from root exudates, the influence of mucus in marine environments, particularly in coral reefs, remains underexplored. We hypothesize that coral mucus, through its nutrients and microbes, stimulates the surrounding microorganisms, regulating carbon metabolism and thus contributing to high coral reef productivity. Initially, natural samples (Acropora pruinosa mucus, seawater, and sediment) were collected for metagenomic assessment of microbial communities and functions. Results showed significant differences in microbial diversity, community structures, co‐occurrence modes, and unique functions among mucus, seawater, and sediment. Subsequent laboratory experiments demonstrated mucus's substantial influence on surrounding microorganisms. Analyses, including 16S rRNA sequencing and Eco‐plate results, revealed that mucus regulates microbial composition and activities. Quantitative gene‐chip analysis showed significant increase in the functional genes related to carbon fixation (e.g., the 3‐hydroxypropionate cycle) and degradation (e.g., pectin and hemicellulose hydrolysis) by 55.81% and 65.48%, respectively. Partial least squares path modeling identified mucus nutrients and microbial community composition as key contributors to carbon metabolic potential. This research confirms that mucus acts as a trigger, reshaping microbial profiles around corals and enhancing carbon utilization efficiency, highlighting its essential role in carbon metabolism and the maintenance of high productivity in coral reef ecosystems.

Selection of Suitable Organic Amendments to Balance Agricultural Economic Benefits and Carbon Sequestration.

Long-term excessive use of fertilizers and intensive cultivation not only decreases soil organic carbon (SOC) and productivity, but also increases greenhouse gas emissions, which is detrimental to sustainable agricultural development. The purpose of this paper is to identify organic amendments suitable for winter wheat growth in the North China Plain by studying the effects of organic amendments on the economic benefits, carbon emissions, and carbon sequestration for winter wheat fields and to provide a theoretical basis for the wide application of organic amendments in agricultural fields. The two nitrogen rates were N0 (0 kg ha-1) and N240 (240 kg ha-1), and the four organic amendments were straw, manure, mushroom residue (M R), and biochar. The results showed that, compared to N0, N240 significantly increased the yield by 244.1-318.4% and the organic carbon storage by 16.7-30.5%, respectively, but increased the carbon emissions by 29.3-45.5%. In addition, soil carbon stocks increased with all three types of organic amendments compared to the straw amendment, with the biochar treatment being the largest, increasing carbon storage by 13.3-33.6%. In terms of yield and economic benefits, compared to the straw amendment, the manure and biochar amendments increased winter wheat yields by 0.0-1.5% and 4.0-13.3%, respectively, and M R slightly decreased wheat yield; only the economic benefit of the M R amendment was greater than that of the straw amendment, with an increase in economic benefit of 1.3% and 8.2% in the 2021-2022 and 2022-2023 seasons, respectively. Furthermore, according to the net ecosystem productivity (NEP), N0 was the source of CO2, while N240 was a sink of CO2. The TOPSIS results showed that N240 with a mushroom residue amendment could be recommended for increasing soil carbon stocks and economic benefits for winter wheat in the NCP and similar regions. Low-cost M R can increase farmer motivation and improve soil organic carbon, making a big step forward in the spread of organic materials on farmland.

Divergent metabolism estimates from dissolved oxygen and inorganic carbon: Implications for river carbon cycling

AbstractRivers efficiently collect, process, and transport terrestrial‐derived carbon. River ecosystem metabolism is the primary mechanism for processing carbon. Diel cycles of dissolved oxygen (DO) have been used for decades to infer river ecosystem metabolic rates, which are routinely used to predict metabolism of carbon dioxide (CO2) with uncertainties of the assumed stoichiometry ranging by a factor of 4. Dissolved inorganic carbon (DIC) has been less used to directly infer metabolism because it is more difficult to quantify, involves the complexity of inorganic carbon speciation, and as shown in this study, likely requires a two‐station approach. Here, we developed DIC metabolism models using single‐ and two‐station approaches. We compared metabolism estimates based on simultaneous DO and DIC monitoring in the Upper Clark Fork River (USA), which also allowed us to estimate ecosystem‐level photosynthetic and respiratory quotients (PQE and RQE). We observed that metabolism estimates from DIC varied more between single‐ and two‐station approaches than estimates from DO. Due to carbonate buffering, CO2 is slower to equilibrate with the atmosphere compared to DO, likely incorporating a longer distance of upstream heterogeneity. Reach‐averaged PQE ranged from 1.5 to 2.0, while RQE ranged from 0.8 to 1.5. Gross primary production from DO was larger than that from DIC, as was net ecosystem production by . The river was autotrophic based on DO but heterotrophic based on DIC, complicating our understanding of how metabolism regulated CO2 production. We suggest future studies simultaneously model metabolism from DO and DIC to understand carbon processing in rivers.

Evolutionary diversity impacts tropical forest biomass and productivity through disturbance‐mediated ecological pathways

Abstract Significant research efforts have been made to uncover links between biodiversity and biomass productivity in forest ecosystems. However, the causal link between these two ecosystem components, and the underlying mediation role of disturbance, are yet poorly understood for hyper‐diverse tropical forests, because multiple ecological mechanisms are sequentially or simultaneously in play, leading to contradictory results in observational studies. Here, we introduce a novel framework for inferring the expected effects of evolutionary diversity on biomass stocks and productivity within forest ecosystems using observational field data. This framework involves an analytical decomposition of stand biomass into three key components: the number of trees, the mean size of trees and the mean wood density. Through this approach, we can distinguish structure‐ and compositional‐based diversity effects, which likely have distinct ecological origins. We tested this framework in one of the oldest tropical forest experiments, where different levels of silvicultural disturbances were applied in the 1980s, with regular monitoring since then. Our results revealed that disturbance history mediates the effect of evolutionary diversity on forest biomass dynamics and that several Biodiversity Ecosystem Function (BEF) relationships may be hidden behind the composite biomass variable. We specifically found an overall significant negative relationship between evolutionary diversity and biomass productivity soon after disturbances (~5–8 years), mostly via mean tree size, despite a positive evolutionary diversity effect on mean wood density. This result reflects that the productivity of disturbed forests is driven by a few dominant and disturbance‐prone species with low wood density and large potential stature, and not by niche complementarity among species. However, these effects rapidly vanished with time, with non‐significant overall effect of evolutionary diversity on productivity both ~30 years after disturbance and in the undisturbed plots. Synthesis. By disentangling the effects of evolutionary diversity on the different components of forest biomass, our framework unveiled how evolutionary diversity impacts forest productivity through different ecological mechanisms, and suggests that it plays a major role, albeit mainly negative, only soon after a disturbance.

Nitrogen addition reduces soil phosphorus leaching in a subtropical forest of eastern Tibetan Plateau

Globally, increased atmospheric nitrogen (N) deposition has comprehensively altered phosphorus (P) biogeochemical cycling in terrestrial ecosystems. Phosphorus is the second most common nutrient limiting for ecosystem productivity. Even though, ultimately under enhanced atmospheric N deposition it is likely to be the primary one. However, the response of soil P leaching to the elevated atmospheric N deposition in subalpine forests are still elusive. Here, we examined the effects of >7-year N additions on soil P leaching in a subalpine forest of eastern Tibetan Plateau. We found that independent of soil horizon (organic versus mineral horizons) and N addition rate (control 0, low 8 and high 40 kg N/ha yr−1), dissolved inorganic P (DIP), rather than dissolved organic P (DOP), dominated soil P leaching. The N addition treatments reduced the leaching of total P and DIP throughout the soil profile by 13 % and 14 %, respectively. The enhanced biological immobilization and P adsorption capacity (increased by 15–33 % in organic horizon and 9–35 % in mineral horizon) under the N addition contributed to the decrease in soil P leaching. We conclude that the reduction in soil P leaching under the elevated atmospheric N deposition should boost the enhanced N driven forest productivity and ecosystem carbon sequestration in the subalpine forests.

Changes in soil arthropods and litter nutrients after prescribed burn in a subtropical moist pastureland

Plant litter decomposition is driven by soil biota and biophysiochemical conditions as well as substrate quality. Prescribed burns can affect the abundance and diversity of soil arthropods and the biophysiochemical conditions in terrestrial ecosystems. In this study, we examined the effects of a prescribed burn on soil arthropods and litter chemistry in decomposing litter during a total of 469-days field incubation using litter from two grasses, Dichanthium annulatum and Megathyrsus maximus, in a subtropical moist pastureland of Puerto Rico. We found the prescribed burn substantially elevated ultraviolet (UV) radiation and soil temperature; and significantly decreased the diversity of litter total arthropods, especially predators and Mesostigmata mites, during the initial 5 months after the burn. However, the prescribed burn had no effect on either the biophysical environment nor on arthropod abundance and diversity during the subsequent incubation period of >5 months after the burn. Furthermore, the prescribed burn substantially increased the immobilization of iron (Fe) and manganese (Mn), and decreased sulfur (S) concentration in the decomposing litter. Prescribed burn had no interactions with substrate quality for percent mass remaining (PMR) and elemental release or accumulation. Low substrate quality D. annulatum litter with a carbon to phosphorus (C/P) ratio of 614 was associated with higher microbivore diversity and higher predator density than higher substrate quality M. maximus litter with a C/P ratio of 266 during the entire incubation period. Lower initial concentration of litter P, magnesium (Mg) and calcium (Ca) in D. annulatum resulted in higher immobilization of these elements in decomposing litter than in M. maximus. Our study suggest that prescribed burn can impose short-term changes in biophysiochemical conditions and the diversity of arthropods in litter decomposition during the initial recovery period of about 5 months after a burn, thus highlighting a high resilience of the grassland ecosystem to fire disturbance, and that it can bring lasting changes in the cycling of Fe, Mn, and S in subtropical moist pastureland that can alter ecosystem productivity.

Global increase in the optimal temperature for the productivity of terrestrial ecosystems

Vegetation growth may adapt to climate warming by adjusting the relationship between photosynthetic capacity and temperature. However, changes in the optimal temperature for ecosystem productivity during recent decades of warming remain uncertain. Here we provide empirical evidence that global optimal temperature increased at a rate of 0.017 ± 0.002 °C y−1 from 1982 to 2016, using multiple datasets of satellite-derived productivity and climate variables. Model simulations show that the optimal temperature will increase by 0.027 ± 0.001 °C y−1 until the end of 21st century. The global increasing optimal temperature is consistent with increasing mean air temperatures and model simulations further confirm the key role of temperature in regulating changes in optimal temperature, while being co-regulated by other factors, such as CO2 and precipitation. These results suggest that vegetation is acclimating to warming and that the negative impacts of climate change on ecosystem productivity may be less severe than previously thought.

Diverse RNA viruses discovered in multiple seagrass species.

Seagrasses are marine angiosperms that form highly productive and diverse ecosystems. These ecosystems, however, are declining worldwide. Plant-associated microbes affect critical functions like nutrient uptake and pathogen resistance, which has led to an interest in the seagrass microbiome. However, despite their significant role in plant ecology, viruses have only recently garnered attention in seagrass species. In this study, we produced original data and mined publicly available transcriptomes to advance our understanding of RNA viral diversity in Zostera marina, Zostera muelleri, Zostera japonica, and Cymodocea nodosa. In Z. marina, we present evidence for additional Zostera marina amalgavirus 1 and 2 genotypes, and a complete genome for an alphaendornavirus previously evidenced by an RNA-dependent RNA polymerase gene fragment. In Z. muelleri, we present evidence for a second complete alphaendornavirus and near complete furovirus. Both are novel, and, to the best of our knowledge, this marks the first report of a furovirus infection naturally occurring outside of cereal grasses. In Z. japonica, we discovered genome fragments that belong to a novel strain of cucumber mosaic virus, a prolific pathogen that depends largely on aphid vectoring for host-to-host transmission. Lastly, in C. nodosa, we discovered two contigs that belong to a novel virus in the family Betaflexiviridae. These findings expand our knowledge of viral diversity in seagrasses and provide insight into seagrass viral ecology.

SOS1 gene family in mangrove (Kandelia obovata): Genome-wide identification, characterization, and expression analyses under salt and copper stress

BackgroundSalt Overly Sensitive 1 (SOS1), a plasma membrane Na+/H+ exchanger, is essential for plant salt tolerance. Salt damage is a significant abiotic stress that impacts plant species globally. All living organisms require copper (Cu), a necessary micronutrient and a protein cofactor for many biological and physiological processes. High Cu concentrations, however, may result in pollution that inhibits the growth and development of plants. The function and production of mangrove ecosystems are significantly impacted by rising salinity and copper contamination.ResultsA genome-wide analysis and bioinformatics techniques were used in this study to identify 20 SOS1 genes in the genome of Kandelia obovata. Most of the SOS1 genes were found on the plasma membrane and dispersed over 11 of the 18 chromosomes. Based on phylogenetic analysis, KoSOS1s can be categorized into four groups, similar to Solanum tuberosum. Kandelia obovata's SOS1 gene family expanded due to tandem and segmental duplication. These SOS1 homologs shared similar protein structures, according to the results of the conserved motif analysis. The coding regions of 20 KoSOS1 genes consist of amino acids ranging from 466 to 1221, while the exons include amino acids ranging from 3 to 23. In addition, we found that the 2.0 kb upstream promoter region of the KoSOS1s gene contains several cis-elements associated with phytohormones and stress responses. According to the expression experiments, seven randomly chosen genes experienced up- and down-regulation of their expression levels in response to copper (CuCl2) and salt stressors.ConclusionsFor the first time, this work systematically identified SOS1 genes in Kandelia obovata. Our investigations also encompassed physicochemical properties, evolution, and expression patterns, thereby furnishing a theoretical framework for subsequent research endeavours aimed at functionally characterizing the Kandelia obovata SOS1 genes throughout the life cycle of plants.

Land use and cover change accelerated China’s land carbon sinks limits soil carbon

Land use and cover change (LUCC) significantly impacts global carbon cycles and land surface properties, accounting for 25% of the historical atmospheric CO2 increase. We explore a previously overlooked role of LUCC in driving the land carbon cycle by using a three-level meta-analysis and Land Use Harmonization data to drive an ecosystem model. Our findings reveal that a loss of 39.2% of soil organic carbon (SOC) change in China due to LUCC, mitigated by afforestation, doubles gross primary productivity at 0.02 Pg C yr−1, countering central China’s urbanization decline. Indirect climate effects, especially soil bulk density, significantly impact SOC compared to direct climate effects. LUCC has significantly increased the Chinese terrestrial carbon sink, with net ecosystem productivity reaching 0.02 ± 0.12 Pg C yr−1. Our study underscores the importance of reforestation and afforestation in addressing climate change and enhancing carbon sinks in future carbon management.

Microeukaryote metabolism across the western North Atlantic Ocean revealed through autonomous underwater profiling

Microeukaryotes are key contributors to marine carbon cycling. Their physiology, ecology, and interactions with the chemical environment are poorly understood in offshore ecosystems, and especially in the deep ocean. Using the Autonomous Underwater Vehicle Clio, microbial communities along a 1050 km transect in the western North Atlantic Ocean were surveyed at 10–200 m vertical depth increments to capture metabolic signatures spanning oligotrophic, continental margin, and productive coastal ecosystems. Microeukaryotes were examined using a paired metatranscriptomic and metaproteomic approach. Here we show a diverse surface assemblage consisting of stramenopiles, dinoflagellates and ciliates represented in both the transcript and protein fractions, with foraminifera, radiolaria, picozoa, and discoba proteins enriched at >200 m, and fungal proteins emerging in waters >3000 m. In the broad microeukaryote community, nitrogen stress biomarkers were found at coastal sites, with phosphorus stress biomarkers offshore. This multi-omics dataset broadens our understanding of how microeukaryotic taxa and their functional processes are structured along environmental gradients of temperature, light, and nutrients.

The food-water-climate nexus of green infrastructure: Examining ecosystem services trade-offs of peri-urban agriculture

Emission reduction, heat mitigation, and improved access to water and food provision are increasingly critical challenges for urban areas in the context of global climate change adaptation and mitigation. The revival of local agricultural production is often lauded as a potential nature-based solution. However, an expansion of peri-urban agriculture (peri-UA) may entail significant ecosystem trade-offs. This study explores the impacts on the food-water-climate nexus of different scenarios of peri-urban agricultural expansion in a semi-arid, Mediterranean climate, addressing local food provision, freshwater use, local temperature regulation, global climate change mitigation, and the trade-offs thereof. We estimate food provision and irrigation water requirements based on a georeferenced urban metabolism approach along with atmospheric and biosphere models to examine four land-use scenarios in the Metropolitan Area of Barcelona.Our study reveals that a 31 % (+17.27 km2) and 115 % (+64.25 km2) increase in the current peri-UA in the AMB, results in an increase in local food production of 24 % (+16,503 tons year−1) and 86 % (+58,940 tons year−1), and irrigation water requirements by 10.0 % (+3.2 hm3) and 43.5 % (+14.1 hm3), respectively. The expansion of irrigated peri-UA potentially reduces near-surface temperatures by 0.7 °C, albeit temperature reductions in the densest urban areas are minimal. Since the additional peri-UA is achieved by replacing natural non-forested and forest areas, the simulations predict reductions in the net ecosystem productivity of up to 18.5 % and total carbon stocks by 3.3 %. This integrated approach combining urban metabolism and atmospheric modelling to determine the trade-offs appears to be a promising tool for informing land-use decision-making in the context of urban climate adaptation and mitigation.

Comparative analysis of soil organic carbon and soil properties in landscapes of Kerala: insights from the Western Ghats of India.

Soil organic carbon (SOC) is known to vary among different ecosystems and soilscapes, yet the degree of variation remains uncertain. Comparing SOC levels in undisturbed ecosystems like forests with those in gradually altered ecosystems can provide valuable insights into the impact of land use on carbon dynamics. This study aimed to evaluate the effects of different land uses on soil fertility parameters in the tropical region of Kerala, focusing on forests as well as cultivated agricultural landscape such as coconut, pepper, tapioca, acacia plantations, and mixed home garden cropping systems. Significant variations were observed among different crops and land use systems in terms of soil fertility. Forests exhibited the highest SOC content at 3.78 g kg-1,while acacia plantations showed the lowest at 0.76 g kg-1. Additionally, various soil properties such as different carbon fractions (e.g., humic acid, fulvic acid), total nitrogen, carbon, available nutrients, physical properties, aggregate size fractions, microbial biomass carbon, and spectral signatures differed significantly across the different land uses. These findings suggest a decline in soil fertility in altered ecosystems compared to adjacent forest soils, highlighting the vital role of forests in conserving natural resources and maintaining soil health. In addition, among the different landscapes studied, mixed cropping systems of home gardens sustained soil fertility better than monocropping systems. The observed variations in soil physicochemical properties among different land use types indicate a threat to sustainable crop production. Effective management practices aimed at improving soil fertility and sustaining crop production in these altered ecosystems are essential. This study highlights the importance of adopting appropriate management strategies to conserve soil health and ensure sustainable crop production in tropical landscapes like Kerala. The holistic approach adopted in this study, encompassing a wide range of soil fertility parameters across various land uses, along with its implications for sustainable land management, adds significant novelty and relevance to the existing literature on soil dynamics in tropical regions like Kerala.

Ecosystem multifunctionality is more related to the indirect effects than to the direct effects of human management in China's drylands

Drylands provide a wide range of important ecosystem functions but are sensitive to environmental changes, especially human management. Two major land use types of drylands are grasslands and croplands, which are influenced by intensive grazing activities and agricultural management, respectively. However, little is known about whether the ecosystem functioning of these two land use types is predominated affected by human management, or environmental factors (intrinsic environmental factors and factors modified by human management). This limits our understanding of the ecosystem functions under intensive human management in drylands. Here we reported a study where we collected data from 40 grassland and 30 cropland sites along an extensive aridity gradient in China's drylands to quantify the effects of human management intensity, intrinsic environmental factors (i.e., aridity), and environmental factors modified by human management (i.e., soil bulk density and plant density) on specific ecosystem functions (ecosystem multifunctionality, productivity, carbon storage, soil water, and soil nutrients). We found that the relative importance of each function differed between croplands and grasslands. Ecosystem functions varied with human management intensity, with lower productivity and plant carbon storage in grasslands under high grazing intensity than un-grazed, while multifunctionality and carbon storage increased with greater fertilization only in arid croplands. Furthermore, among environmental factors, soil bulk density had the greatest negative effects, which directly reduced multifunctionality in grasslands and indirectly reduced multifunctionality in croplands via suppressing crop density. Crop density was the major environmental factor that positively related to multifunctionality in croplands. However, these effects would be exacerbated with increasing aridity. Our study demonstrated that compared with the direct impacts of human management, environmental factors modified by human management (e.g., soil bulk density) are the major drivers of ecosystem functions, indicating that improving soil structure by alleviating human interferences (e.g., reducing livestock trampling) would be an effective way to restore ecosystem functions in drylands under global warming and drying.