Increasing plant species diversity benefits soil organic carbon (SOC) accumulation in forest ecosystems, but how microbial necromass contributes to SOC accumulation in response to plant species ...diversity and the underlying mechanisms have not been well explored. In the present study, 45 plots covering a natural gradient of plant species diversity as indexed by Shannon's diversity index from 0.15 to 3.57 were selected in a typical subtropical forest with calcareous soil. Soil microbial necromass C including fungal necromass C and bacterial necromass C was estimated using amino sugars, with multiple soil biotic and abiotic variables being determined to explore the mechanisms underlying the effects of plant species diversity on microbial necromass C. Total microbial necromass C contents ranged from 4.28 to 85.7 g kg−1 soil with an average of 36.3 ± 17.6 g kg−1 soil, and accounted for 54.2% ± 22.2% of the SOC pool across the 45 plots. Fungal necromass C had a greater contribution to SOC than bacterial necromass C. Increasing plant species diversity was significantly and positively correlated with microbial necromass C content, but was not significantly related to the contribution of microbial necromass C to the SOC pool. Though increasing plant species diversity enhanced microbial biomass via stimulating C use efficiency and substrate availability, microbial biomass was not significantly linked to microbial necromass C accumulation. Instead, increasing plant species diversity benefited microbial necromass C accumulation via enhancing the mineral protection due to its positive effect on soil exchangeable calcium. Due to the proportionate increase of microbial necromass C and SOC, and the unaltered soil C:N ratio and C:N imbalance between soil organic matter and microbial biomass, the contribution of microbial necromass C to the SOC pool was not affected by plant species diversity. Our study highlights the key role of mineral protection in soil microbial necromass C accumulation, and provides a microbe-dependent linkage between plant species diversity and SOC accumulation.
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•Plant species diversity (PSD) stimulates microbial necromass C content.•Fungal necromass C contributes more than bacterial necromass C to soil organic C.•PSD enhances microbial necromass C accumulation via soil mineral protection.
•Woody plant diversity attributes enhance aboveground carbon stock.•Stand structural diversity was a major determining factor for the variation in aboveground carbon.•Woody plant species diversity ...indirectly enhanced aboveground carbon via stand structural diversity.•Silvicultural interventions need to be considered to enhance aboveground carbon stock.
Aboveground carbon (AGC) stock in forests is affected by several biotic and abiotic factors. Understanding those factors is crucial in managing forests for climate change mitigation and other ecosystem services. This study examined effects of diversity attributes (species and stand structural diversity of woody plants) and topographic attributes (altitude and slope) on AGC stock of a dry Afromontane forest. Data from individual woody plants for estimating AGC were collected from 252 plots (20 × 20 m) established in a systematic grid (2 × 2 km) covering the entire forest area. Woody plant diameter diversity and woody plant height diversity were used as proxies for stand structural diversity. Structural equation modelling was applied to test the effects of the selected attributes on AGC stock, and together they explained 71% of the variation. Stand structural diversity was the most important driving factor for the AGC stock. Woody plant species diversity had both direct and indirect effects on AGC stock, but the indirect effect through its influence on stand structural diversity was more pronounced. Altitude and slope were both negatively but weakly associated with AGC stock. Our results provide insight on the effects of diversity and topographic attributes on AGC stock, which can assist future management of the forest. Enhancing stand structural diversity by means of selection cutting systems and woody plant species diversity by means of enrichment planting can be effective treatments. When considering dry Afromontane forests’ widespread distribution, the potential contribution in carbon sequestration and thereby mitigating climate change is substantial. Hence, the results and management suggestions from the present study may have practical interest for the management of dry Afromontane forests not only in Ethiopia but also in Africa at large.
In many estuarine areas around the world, the safety of human societies depends on the functioning of embankments (dikes) that provide protection against river floods and storm tides. Vegetation on ...land-side slopes protects these embankments from erosion by heavy rains or overtopping waves. We carried out a field experiment to investigate the effect of plant species diversity on soil loss through erosion on a simulated dike. The experiment included four diversity treatments (1, 2, 4, and 8 species). In the third year of the experiment, we measured net annual soil loss by measuring erosion losses every 2 weeks. We show that loss of plant species diversity reduces erosion resistance on these slopes: net annual soil loss increased twofold when diversity declines fourfold. The different plant species had strongly diverging effects on soil erosion, both in the single-species and in the multi-species plots. Analysis of the dynamics of the individual species revealed that the main mechanism explaining the strong effects of plant species diversity on soil erosion is the com pensation or insurance effect, that is, the capacity of diverse communities to supply species to take over the functions of species that went extinct as a consequence of fluctuating environmental conditions. We conclude that the protection and restoration of diverse plant communities on embankments and other vegetated slopes are essential to minimize soil erosion, and can contribute to greater safety in the most densely populated areas of the world.
Water and nitrogen (N) often affect plant species diversity and interspecific relationship among plant populations in global terrestrial ecosystems. However, the effects of water and N addition on ...plant diversity and interspecific relationship remain poorly understood. In the study, we designed a three-year field experiment in a desert grassland to assess the effect of increased water (natural +50 %) and N addition (10 g·N·m-2·a-1) on plant diversity and interspecific relationship. Our results showed that the alpha diversity was significantly changed under increased water (W), N addition (N), and water plus N addition (WN). The species richness was decreased significantly on year scales (10 %-27 %), whereas the Pielou index first increased and then decreased over three years and was significantly affected by the interaction between increased water and N addition. The total and pairwise beta diversity were significantly increased by N addition, the community was mainly caused by the turnover component after N addition, especially in 2019 and 2020 (16.6 % and 9 %, respectively). There were significant negative associations among overall populations and dominant populations under N addition, especially Stipa bungeana and Gypsophila davurica, Gypsophila davurica and Oxytropis acemose, Artemisia dalai-lamae, and Haplophyllum dauricum. Our findings suggested that plant community structure and composition changes may be due to competition for resources among dominant populations and the turnover component under increased water and N addition, which should be considered in ecosystem management.
Plant species diversity (PSD) benefits soil organic carbon (SOC) accumulation, but mechanisms underlying the stimulative effects of PSD on SOC pools have not been well explored, especially in terms ...of how PSD impacts plant-derived C accumulation. Here, 45 plots covering a natural gradient of PSD ranging from 0.15 to 3.57 (Shannon's diversity index) were selected in a subtropical forest with calcareous soil to determine the pattern of and controls on the variation of plant-derived C as indexed by lignin phenols along with PSD. The absolute contents of lignin phenols ranged from 1.18 to 6.62 mg g−1 soil with an average of 2.48 ± 1.13 mg g−1 soil across the 45 plots. PSD significantly enhanced soil lignin accumulation via three mechanisms. First, PSD benefited lignin accumulation by stimulating plant detritus inputs. Second, PSD directly and indirectly increased reactive minerals, so that enhanced mineral protection of lignin. Third, decrease in microbial C limitation due to increased soil C availability resulted in lowered peroxidase activity and subsequently lignin degradation, which in turn benefited lignin accumulation. Our study provides mechanisms underlying SOC accumulation in response to increased PSD, which may be integrated into Earth system models in order to better predict SOC dynamics under PSD alteration.
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•Plant species diversity (PSD) effects on soil lignin accumulation are presented.•Lignin content increased with increasing PSD.•Three mechanisms were proposed to explain PSD induced lignin accumulation.
•Flower colour diversity determined public aesthetic response.•Flower colour diversity determined bumblebee and hoverfly abundance.•Plant species diversity not a determinant of public response.•Low ...plant species diversity supported significantly more flies, thrips and bugs.•Public ability to assess biodiversity accurately is limited at the species level.
There is increasing evidence of the benefits of introducing urban meadows as an alternative to amenity mown grass in public greenspaces, both for biodiversity, and human wellbeing. Developing a better understanding of the meadow characteristics driving human and wildlife response is therefore critical. We addressed this by assessing public and invertebrate response to eight different annual meadow mixes defined by two levels of plant species diversity and two levels of colour diversity, sown in an urban park in Luton, UK, in April 2015. On-site questionnaires with the visiting public were conducted in July, August and September 2015. Invertebrate responses were assessed via contemporaneous visual surveys and one sweep net survey (August 2015). Flower colour diversity had effects on human aesthetic response and the response of pollinators such as bumblebees and hoverflies. Plant species diversity, however, was not a driver of human response with evidence that people used colour diversity as a cue to assessing species diversity. Plant species diversity did affect some invertebrates, with higher abundances of certain taxa in low species diversity meadows. Our findings indicate that if the priority for sown meadows is to maximise human aesthetic enjoyment and the abundance and diversity of observable invertebrates, particularly pollinators, managers of urban green infrastructure should prioritise high flower colour diversity mixes over those of high plant species diversity. Incorporating late-flowering non-native species such as Coreopsis tinctoria (plains coreopsis) can prolong the attractiveness of the meadows for people and availability of resources for pollinators and would therefore be beneficial.
Ecosystem functioning plays a crucial role in maintaining human welfare. Terrestrial ecosystems provide multiple ecosystem services simultaneously, such as carbon sequestration, nutrient cycling, ...water purification, and biodiversity conservation, known as ecosystem multifunctionality (EMF). However, the mechanisms by which biotic and abiotic factors, and their interactions regulate EMF in grasslands are unclear. We conducted a transect survey to illustrate the single and combined effects of biotic factors (including plant species diversity, trait-based functional diversity, community-weighted mean (CWM) of traits, and soil microbial diversity) and abiotic factors (including climate and soil) on EMF. Eight functions were investigated, including aboveground living biomass and litter biomass, soil bacterial biomass, fungal biomass, arbuscular mycorrhizal fungi biomass, and soil organic carbon storage, total carbon storage and total nitrogen storage. We detected a significant interactive effect between plant species diversity and soil microbial diversity on the EMF; Structural equation model showed that soil microbial diversity indirectly affected EMF by regulating plant species diversity. These findings highlight the importance of the interaction effect of above- and below-ground diversity on EMF. Both plant species diversity and functional diversity had similar explanatory power for the variation in EMF, implying that niche differentiation and multifunctional complementarity among plant species and traits are essential in regulating the EMF. Furthermore, the effects of abiotic factors on EMF were stronger than those of biotic factors via direct and indirect pathways affecting above- and below-ground biodiversity. As a dominant regulator, the soil sand content was negatively correlated with EMF. These findings indicate the vital role of abiotic mechanisms in affecting EMF, and deepen our understanding of the single and combined effects of biotic and abiotic factors on EMF. We conclude that soil texture and plant diversity, representing crucial abiotic and biotic factors, respectively, are important determinants of the EMF of grasslands.
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•The interplay between above- and below-ground diversity significantly affected ecosystem multifunctionality (EMF).•The niche differentiation and multifunctional complementarity among plant species and traits were vital in regulating EMF.•Abiotic mechanisms had stronger effects on EMF than biotic mechanisms, and soil sand content was the dominant factor.
Soil erosion, which is pronounced on the Loess Plateau of China, is generally caused by heavy rain or thunderstorms. To control soil and water losses and improve the eco-environmental condition of ...the Loess Plateau, the Chinese Central Government issued the “Grain for Green (GFG)” policy in 1999 to restore vegetation on previously farmed steep lands. This study will explore the value of the “GFG” policy by examining the response of three different “GFG” vegetation types (grassland, woodland and orchard) in controlling erosion from an extreme rainfall event in the Northern Shaanxi Province on the Loess Plateau of China.
The vegetation types, coverage, biological soil crust (BSC) coverage, plant species diversity, slope gradient, gully erosion of different “GFG” vegetation types under extreme rainstorm conditions (called “727” rainstorm) were assessed using field surveys.
It was found that the grassland and woodland are more effective at reducing gully erosion than orchards, and compared with the sloping farmland, the conversion of sloping farmland to grassland or woodland can reduce gully erosion by more than 90%, whereas conversion of sloping farmland to orchards actually increases gully erosion by more than 60%. Furthermore, having a high surface vegetation cover and well-developed BSC were the most important factors in reducing soil erosion.
The “GFG” measures are beneficial in reducing soil erosion on the Loess Plateau, and rehabilitation efforts should focus on grassland and/or woodlands rather than attempting to achieve dual goals with economic gain (i.e., from orchard crops), as it appears that orchards are not conducive for controlling soil erosion.
•The natural grassland and ecological forest are more effective at reducing soil erosion than the orchard.•High surface vegetation cover and well developed BSC were the most important factors in reducing soil erosion.•Rehabilitation efforts should focus on grassland and/or ecological forests.
Biodiversity is crucial for human health, but previous methods of measuring biodiversity require intensive resources and have other limitations. Crowdsourced datasets from citizen scientists offer a ...cost-effective solution for characterizing biodiversity on a large spatial scale. This study has two aims: 1) to generate fine-resolution plant species diversity maps in California urban areas using crowdsourced data and extrapolation methods; and 2) to examine their associations with sociodemographic factors and identify subpopulations with low biodiversity exposure. We used iNaturalist observations from 2019 to 2022 to calculate species diversity metrics by exploring the sampling completeness in a 5 × 5-km2 grid and then computing species diversity metrics for grid cells with at least 80 % sample completeness (841 out of 4755 grid cells). A generalized additive model with ordinary kriging (GAM OK) provided moderately reliable estimates, with correlations of 0.64–0.66 between observed and extrapolated metrics, relative mean absolute errors of 21 %–23 %, and relative root mean squared errors of 27 %–30 % for grid cells with ≥80 % sample completeness from 10-fold cross-validation. GAM OK was further applied to extrapolate species diversity metrics from saturated grid cells (N = 841) to the remaining grid cells with <80 % sample completeness (N = 3914) and generate diversity maps that cover the grid. Further, generalized linear mixed models were used to examine the associations between species diversity and sociodemographic indicators at census tract level. The wild vascular plant species diversity metrics were inversely associated with neighborhood socioeconomic status (i.e., unemployment, linguistic isolation, educational attainment, and poverty rate). Minority populations (i.e., African American, Asian American, and Hispanic) and children had significantly lower diversity exposure in their neighborhoods. Crowdsourcing data offers a cost-effective solution for characterizing large-scale biodiversity in urban areas.
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•Developed an analytic framework for mapping plant species diversity using crowdsourced data.•Estimated wild vascular plant species diversity in large areas at 5 km resolution.•Revealed an inequitable distribution of plant species diversity by sociodemographic status factors in California.
Eutrophication generally promotes but destabilizes grassland productivity. Under eutrophication, plants tend to decrease biomass allocation to roots but increase aboveground allocation and light ...limitation, likely affecting community stability. However, it remains unclear to understand how shifting plant biomass allocation and light limitation regulate grassland stability in response to eutrophication. Here, using a 5-yr multiple nutrient addition experiment in an alpine meadow, we explored the role of changes in plant biomass allocation and light limitation on its community stability under eutrophication as well as traditionally established mechanisms (i.e., plant Shannon diversity, species asynchrony and grass subcommunity stability). Our results showed that nitrogen (N) addition, rather than phosphorus (P) or potassium (K) addition, significantly reduced the temporal stability of the alpine meadow. In accordance with previous studies, we found that N addition decreased plant Shannon diversity, species asynchrony and grass subcommunity stability, further destabilizing meadow community productivity. In addition, we also found the decrease in biomass allocation to belowground by N addition, further weakening its community stability. Moreover, this shifts in plant biomass allocation from below- to aboveground, intensifying plant light limitation. Further, the light limitation reduced plant species asynchrony, which finally weakened its community stability. Overall, in addition to traditionally established mechanisms, this study highlights the role of plant biomass allocation shifting from belowground to aboveground in determining grassland community stability. These “unseen” mechanisms might improve our understanding of grassland stability in the context of ongoing eutrophication.
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•N addition, rather than P or K addition, significantly reduced plant community stability.•N-caused reduction in biomass allocation to roots directly reduced plant community stability.•N-intensified aboveground light limitation indirectly reduced plant community stability through decreased species asynchrony.
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