High Plant Diversity Research Articles

An integrative approach supports the taxonomic distinction of the Sardo-Corsican endemic Euphorbia semiperfoliata from the widespread E. amygdaloides (Euphorbiaceae)

In the western Mediterranean, Corsica and Sardinia are characterised by high plant diversity and endemism, and exhibit a tight biogeographic connection. One of the endemic taxa thriving in forests, macchia, along riversides and in mountain grasslands of both islands is Euphorbia semiperfoliata. It was often considered a subspecies of the widespread European forest plant Euphorbia amygdaloides, or deemed closely related with the western Asian E. macroceras and E. oblongifolia. Here, we explored the evolutionary origin of E. semiperfoliata using nuclear ITS sequences that showed that E. semiperfoliata is divergent from E. amygdaloides and the other species of E. sect. Patellares, which indicates its old, likely Tertiary origin. In addition, its relative genome size is different from E. amygdaloides and other species and several morphological characters revealed by morphometric analyses differentiate E. semiperfoliata from E. amygdaloides. Finally, we provide a taxonomic treatment for E. semiperfoliata, including the typification and a morphological description.

Ethnoveterinary survey of trypanocidal medicinal plants of the beninese pharmacopoeia in the management of bovine trypanosomosis in North Benin (West Africa)

Cattle breeding is of great socio-economic importance for Benin's cattle farmers in general and those of North Benin in particular. The objective of this study is to inventory the natural products of medicinal plants of the Beninese pharmacopoeia for the management of trypanosomes in cattle in North Benin. The methodology consisted of individual and semi-structured interviews with cattle farmers on the use of medicinal plants. A total of 360 cattle farmers were selected and interviewed in twelve villages in four municipalities (Tchaourou, N'dali, Bembèrèkè and Gogounou) in northern Benin. Different quantitative ethnobotanical indices were calculated to determine the level of use of plant species. The Relative Frequency of Citation (RFC), the Informant Consensus Factor (ICF = 0.918) and the Generic Coefficient (Rg = 1.04) were evaluated. The knowledge of medicinal plants was influenced by the level of education and the main activity of those who practiced animal husbandry. The results yielded 48 medicinal plants for veterinary use belonging to 46 genera and 28 families. The Leguminosae family (12.50%) was the most represented. The most cited plants with a RFC above 10% were K. senegalensis, P. africana, K. africana, M. inermis, S. latifolius, M. polyandra. The parts used were leaves (46.15%); barks (24.62%) and roots (15.38%). Decoction (53.23%), plundering (32.26%) and maceration (11.26%) were the main methods of preparation. The administration was mainly by oral route. The calculated indices show a high diversity of medicinal plants with trypanocidal properties in the control of cattle trypanosomosis in the Sudanese and Sudano-Guinean zones of northern Benin. Plant species with high citation and RFC values should be selected for comprehensive pharmacological and phytochemical research to validate this ethnomedical knowledge in the management of cattle trypanosomosis.

Biome regulates the effects of long‐term grazing on soil microbial diversity

AbstractIntroductionLivestock overgrazing represents one of the most destructive uses of land in terrestrial ecosystems and threatens biodiversity. However, understanding the effects of livestock overgrazing on below‐ground soil microbial diversity is limited, despite soil microbes representing the majority of biodiversity and determining ecosystem functioning.Materials and MethodsTo investigate the effects of overgrazing on soil microbial richness, a long‐term grazing exclusion experiment was conducted at six sites including three meadow steppes and three typical steppes in northern China.ResultsOur results revealed that overgrazing decreased bacterial and fungal richness across temperate steppes in northern China, and the biome could regulate the overgrazing effects, especially for fungal richness. Specifically, the negative effects of overgrazing on microbial richness were highly significant in typical steppes while not significant in meadow steppes that contained higher plant diversity and precipitation. Partial least‐squares path model showed that overgrazing affected soil microbial richness in highly complex ways, and the affected pathways were different in meadow steppes and typical steppes. The direct negative effects of grazing and their indirect negative effects via soil properties resulted in a significant decrease in microbial richness in typical steppes. In meadow steppes, the indirect beneficial effects via plant attributes offset the direct negative effects of grazing. Consequently, the soil microbial community in meadow steppe resisted overgrazing disturbance.ConclusionOur study illuminates the complex and highly biome‐dependent grazing effects and pathways on soil microbiota and indicates that meadow steppe may be more resistant or resilient to human disturbance than typical steppe. These findings suggest that different grasslands might be managed differently considering their intrinsic characteristics to help biodiversity conservation. Moreover, future research should focus on the underlying mechanisms of grazing effects on soil microbial richness. Besides grazing‐induced plant and soil traits changes, other potential pathways could strongly influence soil microbial diversity.

KEANEKARAGAMAN TUMBUHAN ANGIOSPERMAE DI HUTAN KOTA MALABAR, KOTA MALANG, JAWA TIMUR

The geographical area that belongs to Indonesia makes for a high diversity of plants. With so much diversity, it makes an area inhabited by certain species. One of these species is the Angiosperms, especially the dicot plants (in two pieces) which dominate the variety of plants in the Malabar City Forest, Malang City. Therefore, based on the previous description, this research will focus on the diversity of Angiosperm plants found in the Malabar City Forest, Malang City. The purpose of this study was to determine the diversity of dicot and monocot plants (Angiosperms) found in Malabar Malang City Forest. This research was conducted in the Malabar City Forest area of Malang City, East Java. The sampling technique used was to make three plots, 5 m x 5 m. Based on the results of research conducted on three plots in the Malabar City Forest of Malang City, 12 species of dicot plants were obtained which were divided into 9 families and 4 types of monocot plants which were divided into 3 families.

Attributes of host-specificity better explain the diversified wood-boring longhorn beetles in tropical SW China than plant species diversity

A long-debated question in ecology is whether the hyper-diversity of tropical plant-feeding insects is a direct consequence of high tropical plant diversity or should be attributed to increases in host plant specialization. In this study, we used Cerambycidae (the wood-boring longhorn beetles whose larval stages feed on the xylems of trees and lianas) and plants as study materials to explore which hypothesis is more favoured. Multiple analyses were used to show the differences in host specificity of Cerambycidae in tropical and subtropical forests. From these analyses, we found that the alpha diversity of beetles in tropical forests was significantly higher than that in subtropical forests but not in plants. The relationship between plants and beetles was also closer in tropical areas than in subtropical areas. Our results imply that the wood-boring longhorn beetles show higher degrees of niche conservatism and host-specificity in tropical forests than in subtropical forests. The high diversity of wood-boring longhorn beetles in tropical forests might be explained to a large extent by their more finely partitioned diet breadth.

Phenological, morpho-physiological, and biochemical attributes of barberry (Berberis integerrima L.) in different habitats of Iran

Berberis integerrima L. belongs to the Berberidaceae family and is one of the small fruits with many medicinal properties, which is considered among the horticultural products with high plant diversity and favorable genetic reserves. This research aimed to study barberry's phenological, morpho-physiological, and biochemical attributes in five different habitats in Kerman province, Iran (Bam, Jiroft, Anbarabad, Raber, and Baft) during 2019-2020. The results of the phenological traits showed that the Jiroft and Anbarabad habitats have the maximum number of days until the end of vegetative growth, the number of days from activation of buds to the beginning of fruit formation, the number of days until the physiological maturity of the fruit, the number of days from activation of buds to fruit coloring, and the lowest number of days until flowering. The mean comparison showed that in terms of yield, the investigated habitats from the highest production to the lowest included Anbarabad> Baft> Bam> Rabar> Jiroft. The highest average traits of panicle length (43.38 cm), number of fruits per panicle (26.6), 1000-fruit weight (141.9 g), 1000-seedless fruit weight (128.4 g), seed length (1.16 mm), seed diameter (0.97 mm), fruit length and diameter (19.03 and 5.41 mm), yield (16.69 kg per stem), and the number of thorns 10 cm (13.5 pieces) was observed in Anbarabad habitat. The yield was negatively and significantly correlated with fruit length, titratable acidity, anthocyanin, DPPH, and phenol. Interestingly, soil nitrogen, phosphorus, and potassium had a positive effect on increasing the barberry yield. On the other hand, increasing the longitude, latitude, and altitude decreases yield. Anbarabad and Jiroft habitats had the highest and lowest averages of pH, titratable acidity, total soluble solids, chlorophyll, and carotenoid content, respectively. Generally, the results of this study indicate a high genetic diversity in phenological, morphological, chemical, and physiological aspects in different habitats. Moreover, the results showed that Anbarabad was significantly superior in phenological, morphological, yield, and phytochemical traits compared to other ecotypes.

Dendroecological Potential of Appalachian Riverscour Woodland Trees

Appalachian riverscour woodlands are intermittently flooded areas along high-energy rivers characterized by exposed bedrock and poorly developed sandy soils, high plant diversity, and scattered and stunted trees. These sites can be negatively impacted by dam construction and alterations to river hydrology, trampling associated with riverside recreation activities, and non-native species. In West Virginia, little is known about the development of riverscour woodlands or the growth and hydroclimate sensitivity of associated tree species. In this exploratory study, our objectives were to evaluate our ability to crossdate riverscour woodland trees (i.e., assign accurate calendar years to annual growth rings) as well as determine stand structure and tree establishment patterns at one site along the New River in Fayette County, West Virginia. In addition, for two species, Ulmus americana and Diospyros virginiana, we examined annual growth trends and relationships between tree growth and monthly hydroclimate, including streamflow, precipitation, and Palmer Drought Severity Index (PDSI). Seventy-three percent of all ring-width measurement series were crossdated, but results were mixed across species. Most trees were less than 50 years old and no trees established before the late 1940s. Both U. americana and D. virginiana were highly sensitive to April–August hydroclimate, but differed in response to previous year moisture availability. These findings provide new direction for the use of riverscour woodland trees in future dendroecological studies.

KEANEKARAGAMAN TUMBUHAN ANGIOSPERMAE DI KAWASAN TAMAN NASIONAL MATALAWA KABUPATEN SUMBA TIMUR

The highest plant diversity in the tropical rainforest area in Matalawa National Park is the Angiospermae plant. There are still many people in Praingkareha Village who are not familiar with Angiospermae plants or closed seed plants. This study aims to describe the diversity index of Angiosperm plants found in the Laputi Forest block, Matalawa National Park. This research was limited to the Laputi Forest block, so it did not cover the entire forest in Praingkareha Village, Matalawa National Park, East Sumba Regency. This study used a double plot method with a purposive sampling technique. The results showed that there were 30 species of Angiosperms from 17 families with a total of 499 individuals. The diversity of Angiosperm plants in the Laputi Forest block of the Matalawa National Park area is moderate with (Ĥ)=2.90.

Revealing cryptic diversity and population divergence in subtropical aphids throughDNAbarcoding

AbstractAphids are worldwide distributed pests, which feed on plant sap and cause serious losses to agricultural and forestry industries. Relatively few comprehensive studies have been conducted on aphid diversity in subtropics, although these regions may harbour hidden aphid diversity due to high plant diversity. In this study, we conducted DNA barcoding analysis for aphids in subtropical regions based on a comprehensive DNA barcode reference library including 5821 sequences and related ecological information (e.g. geography, host plant) of 379 morphospecies. In the reference library, 2140 sequences and related data of 151 morphospecies belonging to 77 genera and 11 subfamilies were newly produced by the current study. The average Kimura 2‐parameter distances within species, genera and subfamilies were 0.92%, 3.55% and 8.3%, respectively. The minimum interspecific distances were greater than the maximum intraspecific distances in 79.8% species, suggesting that barcode gaps existed in most aphid species. Automatic barcode gap discovery, Barcode Index Number, Bayesian Poisson tree processes and generalized mixed Yule‐coalescent revealed 419, 401, 462 and 455 single species‐representing clusters, respectively. A total of 32 morphospecies were assigned to more than one subclade respectively, suggesting geography or host plant‐mediated divergences and the existence of cryptic diversity. This study demonstrates that subtropical regions should have a higher species diversity of aphids, and cryptic species in certain morphospecies indicated in this study need to be investigated based on integrative taxonomic practices in the future. The DNA barcode reference library constructed herein provides a robust baseline data set to support future research in taxonomy, phylogenetics, ecology and evolution of aphids.

The Invasive Tradescantia zebrina Affects Litter Decomposition, but It Does Not Change the Lignocellulolytic Fungal Community in the Atlantic Forest, Brazil.

Invasive plants affect ecosystems across various scales. In particular, they affect the quality and quantity of litter, which influences the composition of decomposing (lignocellulolytic) fungal communities. However, the relationship among the quality of invasive litter, lignocellulolytic cultivated fungal community composition, and litter decomposition rates under invasive conditions is still unknown. We evaluated whether the invasive herbaceous Tradescantia zebrina affects the litter decomposition in the Atlantic Forest and the lignocellulolytic cultivated fungal community composition. We placed litter bags with litter from the invader and native plants in invaded and non-invaded areas, as well as under controlled conditions. We evaluated the lignocellulolytic fungal communities by culture method and molecular identification. Litter from T. zebrina decomposed faster than litter from native species. However, the invasion of T. zebrina did not alter decomposition rates of either litter type. Although the lignocellulolytic fungal community composition changed over decomposition time, neither the invasion of T. zebrina nor litter type influenced lignocellulolytic fungal communities. We believe that the high plant richness in the Atlantic Forest enables a highly diversified and stable decomposing biota formed in conditions of high plant diversity. This diversified fungal community is capable of interacting with different litter types under different environmental conditions.

Plant species diversity, plant use, and classification of agroforestry homegardens in southern and southwestern Ethiopia

The attainment of ever more sustainable agricultural production and reconciling agriculture with conservation are the main challenges that human beings are confronted with head-on in the future. Through expanding and enhancing agroforestry homegardens at the agricultural landscape level, biodiversity can be increased and maintained while addressing several utility values, ensuring both ecological and socioeconomic sustainability. This study was conducted in agroforestry homegardens of southern and southwestern Ethiopia, to examine plant species richness and other diversity indices, plant use, and classify and identify different types of homegardens based on their species composition and abundance. In total, 93 homegarden owners participated in the study. Two hundred and six (mean 15.44 per homegarden) different plant species (excluding weeds) that belonged to 161 genera and 66 plant families were identified across the studied sites. Fifteen species (about 7.28% of all species recorded) are endemic and threatened to Ethiopia. The overall mean plant species richness per agroforestry homegardens, mean individual density and other diversity parameters varied strongly among sites (P < 0.05). In all of the agroforestry homegardens, roots, and tubers food producing plant species tended to be more dominant (based on summed dominance ratio, SDR) than other species, except the cereal crops barley and maize. Based on cluster analysis, four groups of agroforestry homegardens were identified including, ‘small-sized, low plant diversity, barley-potato-enset-apple homegardens (Cluster-1)’; ‘intermediate-sized, taro-enset-coffee homegardens (Cluster-2)’; ‘large-sized, maize-taro-sweet potato-teff-enset homegardens (Cluster-3)’; and ‘small-sized, high plant diversity with mixed-use category homegardens (Cluster-4)’. The results also indicate that agroforestry homegardens as ecological niches are valuable for the conservation and maintenance of biological diversity both for crop genetic as well as forest tree resources, including harboring of endemic and threatened species in those human-dominated landscapes.

Gradient Analysis and Classification of Tall Forb Communities in the Bridger-Teton National Forest, United States

Tall forb−mixed upland−herb communities are exemplified by high plant diversity and a profusion of luxuriant wildflowers throughout subalpine mountain parklands of the interior western United States. These unique and ecologically important communities remain largely unclassified in terms of their biological and physical attributes and ecological responses to management and disturbances. Land managers need respective classifications to evaluate and guide conservation planning and management for tall forb communities where they occur. In this study, 23 sites from four subalpine areas representing reference tall forb plant communities on the Bridger-Teton National Forest were identified and selected for analysis after a sustained cessation of grazing activities. The purpose of the study was to quantitatively examine tall forb community stands and provide a basis for developing a classification system for identifying future ecological sites, which are essential in conservation planning, implementation and management, and monitoring. Seven tall forb cluster groups were identified with unique plant composition and specific environmental gradients (i.e., plant species richness, diversity indices, elevation, average annual precipitation, surficial geology, three-dimensional geomorphic descriptions, soil clay content diversity dynamics, and foliar, ground, and surface cover). Among the seven cluster groups, we identified 31 families, 112 genera, and 158 plant species on the sample sites (61 species representing native indicator reference species, 86 native secondary indicator species, and 10 introduced non-native species). Beta diversity and plant species turnover ranged from 6.7% to 41.9% among the seven cluster groups, indicating discrete differences in plant species assemblages, plant associations, and site dynamics. The seven tall forb clusters are characteristic of specific and unique plant species composition, species diversity, and environmental factors. Therefore, a specialized site approach with respective guidelines is recommended for assessing and conserving discrete tall forb ecological sites and maintaining key dominant native indicator reference species, rangeland health and proper functioning condition, and defined monitoring protocols.

Biotic pressures and environmental heterogeneity shape beta‐diversity of seedling communities in tropical montane forests

Many theories have been proposed to explain the high diversity of plants in the tropics. However, we lack an understanding of the processes that drive plant diversity and community assembly at different spatial scales. Here, we applied beta‐diversity partitioning to test how biotic and abiotic factors are associated with seedling beta‐diversity in a tropical montane forest in southern Ecuador. We recorded seedling communities on 81 subplots in nine plots located at three elevations along a 2000 m elevational gradient. We measured biotic pressures (i.e. herbivory and fungal pathogen attacks) and environmental conditions (i.e. soil moisture and canopy closure) in all subplots and related them to species turnover and richness differences in seedling communities within and between elevations. We found that species turnover increased with differences in biotic dissimilarity within elevations, while differences in species richness within elevations increased with increasing environmental dissimilarity. Between elevations, species turnover increased with increasing environmental dissimilarity. Our findings show that species turnover and changes in species richness are related differently to abiotic and biotic factors, and that the importance of these factors for shaping seedling diversity is scale‐dependent. Our study contributes to better understand the processes driving seedling beta‐diversity and the assembly of plant communities in highly diverse tropical montane forests.

Phytosociological survey of spontaneous plant communities in a conventional corn crop area in the region of Carajás, Pará, Brazil

The presence of spontaneous plants in agricultural cultivation areas can result in damage to the crop of interest due to competition for natural resources and allelopathy, requiring systematic monitoring for an adequate cultivation management. In this way, the objective was to identify the spontaneous plant communities species in an area of a one-year fallow conventional corn crop in the southeastern of Pará state, in the Brazilian amazon. A phytosociological survey of the plants in the experimental area of the Technological Center of Family Agriculture (CETAF) was carried out, by applying the inventory square method with 1.0 m2, randomly launched twenty times in an area corresponding to 1.1 hectare. The phytosociological parameters analyzed were frequency, relative frequency, density, relative density, abundance, relative abundance and importance value index (IRI). It was found 19 species of spontaneous plants distributed in 11 botanical families, being, Euphorbiaceae (4), Asteraceae (3), Amaranthaceae (2) and Poaceae (2) the most representative in numbers of species sampled. The most important species were Sorghum arundinaceum (IRI = 55.70), Commelina benghalensis (IRI = 47.78) and Synedrella nodiflora (IRI = 42.39). A high diversity of spontaneous plants was verified, emphasizing the need for phytosociological surveys for the definition of integrated control practices in face of the type of cultivation system adopted.

Range restricted old and young lineages show the southern Western Ghats to be both a museum and a cradle of diversity for woody plants.

The Western Ghats (WG) mountain chain is a global biodiversity hotspot with high diversity and endemicity of woody plants. The latitudinal breadth of the WG offers an opportunity to determine the evolutionary drivers of latitudinal diversity patterns. We examined the spatial patterns of evolutionary diversity using complementary phylogenetic diversity and endemism measures. To examine if different regions of the WG serve as a museum or cradle of evolutionary diversity, we examined the distribution of 470 species based on distribution modelling and occurrence locations across the entire region. In accordance with the expectation, we found that the southern WG is both a museum and cradle of woody plant evolutionary diversity, as a higher proportion of both old and young evolutionary lineages are restricted to the southern WG. The diversity gradient is likely driven by high geo-climatic stability in the south and phylogenetic niche conservatism for moist and aseasonal sites. This is corroborated by persistent lineage nestedness at almost all evolutionary depths (10-135 million years), and a strong correlation of evolutionary diversity with drought seasonality, precipitation and topographic heterogeneity. Our results highlight the global value of the WG, demonstrating, in particular, the importance of protecting the southern WG-an engine of plant diversification and persistence.

Tree diversity increases decadal forest soil carbon and nitrogen accrual.

Increasing soil carbon and nitrogen storage can help mitigate climate change and sustain soil fertility1,2. A large number of biodiversity-manipulation experiments collectively suggest that high plant diversity increases soil carbon and nitrogen stocks3,4. It remains debated, however, whether such conclusions hold in natural ecosystems5-12. Here we analyse Canada's National Forest Inventory (NFI) database with the help of structural equation modelling (SEM) to explore the relationship between tree diversity and soil carbon and nitrogen accumulation in natural forests. We find that greater tree diversity is associated with higher soil carbon and nitrogen accumulation, validating inferences from biodiversity-manipulation experiments. Specifically, on a decadal scale, increasing species evenness from its minimum to maximum value increases soil carbon and nitrogen in the organic horizon by 30% and 42%, whereas increasing functional diversity enhances soil carbon and nitrogen in the mineral horizon by 32% and 50%, respectively. Our results highlight that conserving and promoting functionally diverse forests could promote soil carbon and nitrogen storage, enhancing both carbon sink capacity and soil nitrogen fertility.

Effect of Grafting Position on Grafting Success Rate of Local Durian (Durio zibethinus L.) from Maluku

Indonesia is the centre of origin and distribution of durian plants globally, so it has a high genetic diversity of durian plants. Durian propagation can be done vegetatively through grafting. The success of durian grafting is primarily determined by many factors, one of which is the grafting position. This study aimed to examine the best grafting positions on the success rate of grafting of local durian (Durio zibethinus L.) from Maluku. The research was carried out in a nursery located in Telaga Kodok hamlet, Hitulama Village, Leihitu District, Central Maluku Regency, which lasted for six months, namely from December 2021-February 2022. The study was in an experimental form using a randomized block design (RAK) 1 factor with five repetitions. The factor being tested is the position of the grafting, which consists of 5 levels: grafting on the stem hump, grafting 10 cm, 15 cm, 20 cm, and 25 cm above ground level. The study's results obtained information that the grafting position treatment had a significant effect on the percentage of success and the increase in the number of leaves at the end of the observation. The highest rate of grafting success in the study was found in the treatment of the grafting position on the stem stump, which resulted in a success percentage of 98%.

An annotated plant checklist of the transboundary volcanic Mt Elgon, East Africa.

Mt Elgon is an ancient transboundary volcanic mountain found at the Kenya-Uganda boarder possessing high plant diversity. This study documents an updated checklist of the mountain's vascular plants obtained through random-walk field excursions and retrieval of herbarium specimen tracing back to 1900. We compiled 1709 species from 673 genera in 131 families. One new species of the family Cucurbitaceae was also reported. This checklist records respective habitat, habits, elevation ranges, voucher numbers and global distribution ranges of each species. Native and exotic species were also distinguished, where 8.4% of the total species in 49 families were exotic species. There were 103 endemic species, while 14 species were found to be both rare and endemic. IUCN conservation status revealed 2 Critically Endangered, 4 Endangered, 9 Vulnerable and 2 Near Threatened species. This study presents the first and most comprehensive plant inventory of Mt Elgon that will facilitate further ecological and phylogenetic studies.

Optimized Plant Diversity and Carbon Storage for Priority Protection Areas in China

Biodiversity and carbon storage are two key ecosystem functions that are crucial to protect and maintain ecosystem balance. However, there is often little overlap between hotspots for these two different conservation purposes. Additionally, it is not well understood how these different spatial metrics affect these functions in protected ecosystems in China. Here, we explored the relationships between plant diversity metrics and carbon storage by using a large vascular plant distribution dataset, as well as soil fragile organic carbon and biomass carbon datasets in specific spatial areas across China. We also defined priority protection areas (PPAs) using a conservation prioritization method, where 30% of the study areas displayed the highest combined conservation value in carbon storage and plant species richness (SR), phylogenetic diversity (PD), phylogenetic endemism (PE) and evolutionary distinctness (ED). Our results indicated that the correlations between biodiversity metrics and carbon storage were very weak in spatial relationship. However, by including both of these functions in conservation targets, the PPAs could account for more than 95% of the species and evolutionary diversity (PD, ED), and stored large amounts of carbon. Additionally, we broadly divided the PPAs into win–win, high plant diversity, and high carbon areas based on the overlap of biodiversity and carbon storage hotspots. Altogether, our results highlight the importance of understanding and optimizing conservation efforts for different ecosystem functions in different PPAs. Ultimately, this work establishes an urgent need to expand protection in these areas to support mutual biodiversity and carbon storage beneficial solutions.

Spatial effects of nitrogen deposition on soil organic carbon stocks in patchy degraded saline-alkaline grassland

Soil organic carbon (SOC) represents the largest carbon sink and plays a critical role in mitigating global warming. Elevated nitrogen (N) deposition has substantial effects on soil carbon sequestration in grassland ecosystems. However, almost no study has examined the effects of N deposition in widely degraded saline-alkaline grasslands. This is a critical knowledge gap because saline-alkaline degradation is one of the key global threats to carbon sequestration services provided by grasslands. Here, we conducted a 3-year N addition experiment in a patchy degraded saline-alkaline grassland to examine the effects of simulated N deposition on SOC stocks, along with spatial effects for five types of saline-alkaline degraded patches (multi-species-mixture patches; Leymus chinensis patches; Puccinellia tenuiflora patches; Chloris virgata patches and Artemisia anethifolia patches). N addition had no overall effect on SOC stocks in the degraded saline-alkaline grassland, but showed pronounced spatial effects depending on the saline-alkaline characteristics of degraded patches. Specifically, SOC decreased in multi-species-mixture patches with low saline-alkaline stress (soil 7 < pH < 8), but no change was observed in other types of degraded patches with high saline-alkaline stress (soil pH > 9). Although N addition promoted plant growth and increased aboveground biomass in all degraded patches, the resulting aboveground carbon input did not further contribute to soil carbon sequestration. Rather than aboveground biomass, soil pH was the critical controlling factor for soil carbon in the saline-alkaline grassland. However, N addition did not alter soil pH in all degraded patches. In multi-species-mixture patches with lightly saline-alkaline soils, N addition reduced species richness and increased microbial C:N ratio, which could accelerate soil carbon decomposition, thereby decreasing SOC stocks. Our findings suggest that increased global N deposition would not restore natural soil carbon in degraded saline-alkaline grassland, and instead, may further deteriorate soil carbon sequestration in lightly degraded patches with high plant diversity and low saline-alkaline stress.