Multiple trade‐offs regulate the effects of woody plant removal on biodiversity and ecosystem functions in global rangelands

Woody plant encroachment is a major land management issue. Woody removal often aims to restore the original grassy ecosystem, but few studies have assessed the role of woody removal on ecosystem functions and biodiversity at global scales. We collected data from 140 global studies and evaluated how different woody plant removal methods affected biodiversity (plant and animal diversity) and ecosystem functions (plant production, hydrological function, soil carbon) across global rangelands. Our results indicate that the impact of removal is strongly context dependent, varying with the specific response variable, removal method, and traits of the target species. Over all treatments, woody plant removal increased grass biomass and total groundstorey diversity. Physical and chemical removal methods increased grass biomass and total groundstorey biomass (i.e., non‐woody plants, including grass biomass), but burning reduced animal diversity. The impact of different treatment methods declined with time since removal, particularly for total groundstorey biomass. Removing pyramid‐shaped woody plants increased total groundstorey biomass and hydrological function but reduced total groundstorey diversity. Environmental context (e.g., aridity and soil texture) indirectly controlled the effect of removal on biomass and biodiversity by influencing plant traits such as plant shape, allelopathic, or roots types. Our study demonstrates that a one‐size‐fits‐all approach to woody plant removal is not appropriate, and that consideration of woody plant identity, removal method, and environmental context is critical for optimizing removal outcomes. Applying this knowledge is fundamental for maintaining diverse and functional rangeland ecosystems as we move toward a drier and more variable climate.     

Trophic interactions and the relationship between species diversity and ecosystem stability

Several theoretical studies propose that biodiversity buffers ecosystem functioning against environmental fluctuations, but virtually all of these studies concern a single trophic level, the primary producers. Changes in biodiversity also affect ecosystem processes through trophic interactions. Therefore, it is important to understand how trophic interactions affect the relationship between biodiversity and the stability of ecosystem processes. Here we present two models to investigate this issue in ecosystems with two trophic levels. The first is an analytically tractable symmetrical plant-herbivore model under random environmental fluctuations, while the second is a mechanistic ecosystem model under periodic environmental fluctuations. Our analysis shows that when diversity affects net species interaction strength, species interactions--both competition among plants and plant-herbivore interactions--have a strong impact on the relationships between diversity and the temporal variability of total biomass of the various trophic levels. More intense plant competition leads to a stronger decrease or a lower increase in variability of total plant biomass, but plant-herbivore interactions always have a destabilizing effect on total plant biomass. Despite the complexity generated by trophic interactions, biodiversity should still act as biological insurance for ecosystem processes, except when mean trophic interaction strength increases strongly with diversity.     

环境DNA技术在地下生态学中的应用

地下生态过程是生态系统结构、功能和过程研究中最不确定的因素。由于技术和方法的限制,作为"黑箱"的地下生态系统已经成为限制生态学发展的瓶颈,也是未来生态学发展的主要方向。环境DNA技术,是指从土壤等环境样品中直接提取DNA片段,然后通过DNA测序技术来定性或定量化目标生物,以确定目标生物在生态系统中的分布及功能特征。环境DNA技术已成功用于地下生态过程的研究。目前,环境DNA技术在土壤微生物多样性及其功能方面的研究相对成熟,克服了土壤微生物研究中不能培养的问题,可以有效地分析土壤微生物的群落组成、多样性及空间分布,尤其是宏基因组学技术的发展,使得微生物生态功能方面的研究成为可能;而且,环境DNA技术已经在土壤动物生态学的研究中得到了初步应用,可快速分析土壤动物的多样性及其分布特征,更有效地鉴定出未知的或稀少的物种,鉴定土壤动物类群的幅度较宽;部分研究者通过提取分析土壤中DNA片段信息对生态系统植物多样性及植物分类进行了研究,其结果比传统的植物分类及物种多样性测定更精确,改变了以往对植物群落物种多样性模式的理解。同时,环境DNA技术克服传统根系研究方法中需要洗根、分根、只能测定单物种根系的局限,降低根系研究中细根区分的误差,并探索性地用于细根生物量的研究。主要综述了基于环境DNA技术的分子生物学方法在土壤微生物多样性及功能、土壤动物多样性、地下植物多样性及根系生态等地下生态过程研究中的应用进展。环境DNA技术对于以土壤微生物、土壤动物及地下植物根系为主体的地下生态学过程的研究具有革命性意义,并展现出良好的应用前景。可以预期,分子生物学技术与传统的生态学研究相结合将成为未来地下生态学研究的一个发展趋势。     

基于Sentinel-2数据的草地植物功能多样性遥感反演及其与生产力的关系

生物多样性与生态系统功能的关系是当前生态学研究的焦点和难点。植物功能多样性是影响生态系统功能的重要指标, 开展植物功能多样性的研究对了解生物多样性与生态系统功能之间的关系有着重要意义。传统的草地植物功能多样性研究多以实地调查为主, 不仅费时费力, 而且由于受到时空的限制, 很难拓展到大尺度的研究中。遥感技术的发展为评估草地功能多样性提供了一种经济、有效的手段。该研究选取内蒙古自治区锡林郭勒盟乌拉盖管理区草甸草原为研究区, 利用Sentinel-2卫星影像和野外实测数据, 选取了波段及植被指数等46个特征变量, 探讨了逐步回归、偏最小二乘法(PLSR)和随机森林(RFR)等3种不同方法对草地植物功能丰富度(FRic)、功能均匀度(FEve)和功能离散度(FDiv)的反演精度, 并基于PLSR反演草地地上生物量, 进一步分析了研究区功能多样性与生产力的关系。研究结果表明: (1)波段B11、优化型土壤调节植被指数(OSAVI)、水波段指数(WBI)对FRic解释度最高; 波段B6、B10、B12、类胡萝卜素反射指数1 (CRI1)、双峰光学指数(D)、归一化差值指数45 (NDI45)等6个特征变量对FEve解释度最高; 波段B5、B9、B10、B11、加权差分植被指数(WDVI)、凸包面积等对FDiv解释度最高; (2)基于十折重复交叉验证, 利用逐步回归估算的FRic和FEve反演精度远高于其他两种回归方法, R²分别为0.52和0.44; 而利用PLSR方法估算的FDiv反演精度最高(R² = 0.61); (3)群落地上生物量反演精度为R² = 0.61; FRic与地上生产力的关系最好(R² = 0.40), 其次为FDiv (R² = 0.28)和FEve (R² = 0.27)。研究发现, 基于Sentinel-2卫星影像能较好地反演草地功能多样性和生产力, 为下一步能在大尺度上进行草地功能多样性估算及其与生产力关系研究提供了参考和依据。     

From selection to complementarity: shifts in the causes of biodiversity-productivity relationships in a long-term biodiversity experiment

In a 10-year (1996-2005) biodiversity experiment, the mechanisms underlying the increasingly positive effect of biodiversity on plant biomass production shifted from sampling to complementarity over time. The effect of diversity on plant biomass was associated primarily with the accumulation of higher total plant nitrogen pools (N g m-2) and secondarily with more efficient N use at higher diversity. The accumulation of N in living plant biomass was significantly increased by the presence of legumes, C4 grasses, and their combined presence. Thus, these results provide clear evidence for the increasing effects of complementarity through time and suggest a mechanism whereby diversity increases complementarity through the increased input and retention of N, a commonly limiting nutrient.     

Soil microbial diversity–biomass relationships are driven by soil carbon content across global biomes

The relationship between biodiversity and biomass has been a long standing debate in ecology. Soil biodiversity and biomass are essential drivers of ecosystem functions. However, unlike plant communities, little is known about how the diversity and biomass of soil microbial communities are interlinked across globally distributed biomes, and how variations in this relationship influence ecosystem function. To fill this knowledge gap, we conducted a field survey across global biomes, with contrasting vegetation and climate types. We show that soil carbon (C) content is associated to the microbial diversity–biomass relationship and ratio in soils across global biomes. This ratio provides an integrative index to identify those locations on Earth wherein diversity is much higher compared with biomass and vice versa. The soil microbial diversity-to-biomass ratio peaks in arid environments with low C content, and is very low in C-rich cold environments. Our study further advances that the reductions in soil C content associated with land use intensification and climate change could cause dramatic shifts in the microbial diversity-biomass ratio, with potential consequences for broad soil processes.Subject terms: Biodiversity, Microbial ecology     

Resource-Mediated Indirect Effects of Grassland Management on Arthropod Diversity

Intensive land use is a driving force for biodiversity decline in many ecosystems. In semi-natural grasslands, land-use activities such as mowing, grazing and fertilization affect the diversity of plants and arthropods, but the combined effects of different drivers and the chain of effects are largely unknown. In this study we used structural equation modelling to analyse how the arthropod communities in managed grasslands respond to land use and whether these responses are mediated through changes in resource diversity or resource quantity (biomass). Plants were considered resources for herbivores which themselves were considered resources for predators. Plant and arthropod (herbivores and predators) communities were sampled on 141 meadows, pastures and mown pastures within three regions in Germany in 2008 and 2009. Increasing land-use intensity generally increased plant biomass and decreased plant diversity, mainly through increasing fertilization. Herbivore diversity decreased together with plant diversity but showed no response to changes in plant biomass. Hence, land-use effects on herbivore diversity were mediated through resource diversity rather than quantity. Land-use effects on predator diversity were mediated by both herbivore diversity (resource diversity) and herbivore quantity (herbivore biomass), but indirect effects through resource quantity were stronger. Our findings highlight the importance of assessing both direct and indirect effects of land-use intensity and mode on different trophic levels. In addition to the overall effects, there were subtle differences between the different regions, pointing to the importance of regional land-use specificities. Our study underlines the commonly observed strong effect of grassland land use on biodiversity. It also highlights that mechanistic approaches help us to understand how different land-use modes affect biodiversity.     

Intensified grazing affects endemic plant and gastropod diversity in alpine grasslands of the Southern Carpathian mountains (Romania)

Alpine grasslands in the Southern Carpathian Mts, Romania, harbour an extraordinarily high diversity of plants and invertebrates, including Carpathic endemics. In the past decades, intensive sheep grazing has caused a dramatic decrease in biodiversity and even led to eroded soils at many places in the Carpathians. Because of limited food resources, sheep are increasingly forced to graze on steep slopes, which were formerly not grazed by livestock and are considered as local biodiversity hotspots. We examined species richness, abundance and number of endemic vascular plants and terrestrial gastropods on steep slopes that were either grazed by sheep or ungrazed by livestock in two areas of the Southern Carpathians. On calcareous soils in the Bucegi Mts, a total of 177 vascular plant and 19 gastropod species were recorded. Twelve plant species (6.8%) and three gastropod species (15.8%) were endemic to the Carpathians. Grazed sites had lower plant and gastropod species richness than ungrazed sites. Furthermore, grazed sites harboured fewer gastropod species endemic to the Carpathians than ungrazed sites. On acid soils in the Fagaras Mts, a total of 96 vascular plant and nine gastropod species were found. In this mountain area, however, grazed and ungrazed sites did not differ in species richness, abundance and number of endemic plant and gastropod species. Our findings confirm the high biodiversity of grasslands on steep slopes in the Southern Carpathian Mts and caution against increasing grazing pressure in these refuges for relic plants and gastropods as well as for other invertebrates.     

Design and analysis of biodiversity field experiments

The design and analysis of field experiments have figured prominently in the current debate about biodiversity and ecosystem function. These debates have identified important issues about species traits, functional groups, and community assembly, but a broader debate needs to include discussions about the scale (grain and extent) of experiments relative to natural spatial and temporal heterogeneity. In addition, alternative statistical analyses need to be explored that focus on comparison among several statistical models rather than simple hypothesis testing. Analyses of the first 2 years of data from a new biodiversity field experiment are used to illustrate these concepts. A traditional one-way ANOVA demonstrates the expected increase in aboveground biomass with higher levels of vascular plant diversity. Further analysis demonstrates that this relationship is absent when the community contains either Arrhenatherum elatius or Holcus lanatus, two dominant species of grass. Variance in biomass is also a function of diversity and both spatial and temporal heterogeneity are significant factors in the analysis despite precautions taken to minimize them. These examples illustrate the degree to which the analysis of a field experiment influences the interpretation of the observed results. Ultimately, results from field experiments must be validated through continued comparisons among field experiments, mathematical models, laboratory trials, and mesocosm experiments.     

DNA from soil mirrors plant taxonomic and growth form diversity

Ecosystems across the globe are threatened by climate change and human activities. New rapid survey approaches for monitoring biodiversity would greatly advance assessment and understanding of these threats. Taking advantage of next-generation DNA sequencing, we tested an approach we call metabarcoding: high-throughput and simultaneous taxa identification based on a very short (usually <100 base pairs) but informative DNA fragment. Short DNA fragments allow the use of degraded DNA from environmental samples. All analyses included amplification using plant-specific versatile primers, sequencing and estimation of taxonomic diversity. We tested in three steps whether degraded DNA from dead material in soil has the potential of efficiently assessing biodiversity in different biomes. First, soil DNA from eight boreal plant communities located in two different vegetation types (meadow and heath) was amplified. Plant diversity detected from boreal soil was highly consistent with plant taxonomic and growth form diversity estimated from conventional above-ground surveys. Second, we assessed DNA persistence using samples from formerly cultivated soils in temperate environments. We found that the number of crop DNA sequences retrieved strongly varied with years since last cultivation, and crop sequences were absent from nearby, uncultivated plots. Third, we assessed the universal applicability of DNA metabarcoding using soil samples from tropical environments: a large proportion of species and families from the study site were efficiently recovered. The results open unprecedented opportunities for large-scale DNA-based biodiversity studies across a range of taxonomic groups using standardized metabarcoding approaches.     

Size, activity and catabolic diversity of the soil microbial biomass in a wetland complex invaded by reed canary grass

Reed canary grass (Phalaris arundinacea, L.) invasion of wetlands is an ecological issue that has received attention, but its impact on soil microbial diversity is not well documented. The present study assessed the size (substrate-induced respiration), catabolic diversity (CLPP, community level physiological profiles) and composition (selective inhibition) of the soil microbial community in invaded (>95% P. arundinacea cover) and in non-invaded areas of a wetland occupied by native species grown either as a mixed assemblage (22 species) or as quasi-monotypic stands of Scirpus cyperinus (74% cover). The study also tested the hypothesis that decomposition of lignin- and phenolics-rich plant tissues would be fastest in soils exhibiting high catabolic diversity. Results showed that soil respiration, microbial biomass and diversity were significantly higher (P?<?0.03; 1.5 to 3 fold) in P. arundinacea-invaded soils than in soils supporting native plant species. Fungal to bacterial ratios were also higher in invaded (0.6) than in non-invaded (0.4) plots. Further, canonical discriminant analysis of CLPP data showed distinct communities of soil decomposers associated with each plant community. However, these differences in microbial attributes had no effect on decomposition of plant biomass which was primarily controlled by its chemical composition. While P. arundinacea invasion has substantially reduced plant diversity, this study found no parallel decline in the size and diversity of the soil microbial community in the invaded areas.     

Species richness promotes ecosystem carbon storage: evidence from biodiversity-ecosystem functioning experiments

Plant diversity has a strong impact on a plethora of ecosystem functions and services, especially ecosystem carbon (C) storage. However, the potential context-dependency of biodiversity effects across ecosystem types, environmental conditions and carbon pools remains largely unknown. In this study, we performed a meta-analysis by collecting data from 95 biodiversity-ecosystem functioning (BEF) studies across 60 sites to explore the effects of plant diversity on different C pools, including aboveground and belowground plant biomass, soil microbial biomass C and soil C content across different ecosystem types. The results showed that ecosystem C storage was significantly enhanced by plant diversity, with stronger effects on aboveground biomass than on soil C content. Moreover, the response magnitudes of ecosystem C storage increased with the level of species richness and experimental duration across all ecosystems. The effects of plant diversity were more pronounced in grasslands than in forests. Furthermore, the effects of plant diversity on belowground plant biomass increased with aridity index in grasslands and forests, suggesting that climate change might modulate biodiversity effects, which are stronger under wetter conditions but weaker under more arid conditions. Taken together, these results provide novel insights into the important role of plant diversity in ecosystem C storage across critical C pools, ecosystem types and environmental contexts.     

Nutrient concentrations and fibre contents of plant community biomass reflect species richness patterns along a broad range of land-use intensities among agricultural grasslands

Understanding changes in biodiversity in agricultural landscapes in relation to land-use type and intensity is a major issue in current ecological research. In this context nutrient enrichment has been identified as a key mechanism inducing species loss in Central European grassland ecosystems. At the same time, insights into the linkage between agricultural land use and plant nutrient status are largely missing. So far, studies on the relationship between chemical composition of plant community biomass and biodiversity have mainly been restricted to wetlands and all these studies neglected the effects of land use. Therefore, we analyzed aboveground biomass of 145 grassland plots covering a gradient of land-use intensities in three regions across Germany. In particular, we explored relationships between vascular plant species richness and nutrient concentrations as well as fibre contents (neutral and acid detergent fibre and lignin) in the aboveground community biomass.We found the concentrations of several nutrients in the biomass to be closely linked to plant species richness and land use. Whereas phosphorus concentrations increased with land-use intensity and decreased with plant species richness, nitrogen and potassium concentrations showed less clear patterns. Fibre fractions were negatively related to nutrient concentrations in biomass, but hardly to land-use measures and species richness. Only high lignin contents were positively associated with species richness of grasslands. The N:P ratio was strongly positively related to species richness and even more so to the number of endangered plant species, indicating a higher persistence of endangered species under P (co-)limited conditions. Therefore, we stress the importance of low P supply for species-rich grasslands and suggest the N:P ratio in community biomass to be a useful proxy of the conservation value of agriculturally used grasslands.     

Does complementary resource use enhance ecosystem functioning? A model of light competition in plant communities

Recent experiments on grassland ecosystems have shown that biodiversity can enhance ecosystem processes such as plant biomass production. Functional complementarity is generally regarded as the main class of mechanisms generating these effects of biodiversity on ecosystem functioning. Although intuitively appealing and supported by some data, the complementarity hypothesis has been little explored theoretically using mechanistic approaches. Here, we present a simple dynamical model for a light-limited terrestrial ecosystem to assess the effects of species diversity on light competition and total biomass in plant communities. Our model shows that competitive relaxation (reduction in average light competition intensity) due to differences in foliar architecture among species enhances total plant biomass in mixtures, but that competitive imbalance (generated by the variance of the average light competition intensity experienced by different species) can either reinforce the effect of competitive relaxation or counteract it and contribute to reducing total plant biomass. Thus, complementary resource use is not enough to increase total plant biomass in species-rich communities; competitive balance among species also plays an important role. We propose an operational measure of light-use complementarity using empirical field data on light absorption to test the presence of complementarity in natural plant communities.     

Can the Results of Biodiversity-Ecosystem Productivity Studies Be Translated to Bioenergy Production?

Biodiversity experiments show that increases in plant diversity can lead to greater biomass production, and some researchers suggest that high diversity plantings should be used for bioenergy production. However, many methods used in past biodiversity experiments are impractical for bioenergy plantings. For example, biodiversity experiments often use intensive management such as hand weeding to maintain low diversity plantings and exclude unplanted species, but this would not be done for bioenergy plantings. Also, biodiversity experiments generally use high seeding densities that would be too expensive for bioenergy plantings. Here we report the effects of biodiversity on biomass production from two studies of more realistic bioenergy crop plantings in southern Michigan, USA. One study involved comparing production between switchgrass (Panicum virgatum) monocultures and species-rich prairie plantings on private farm fields that were managed similarly to bioenergy plantings. The other study was an experiment where switchgrass was planted in monoculture and in combination with increasingly species-rich native prairie mixtures. Overall, we found that bioenergy plantings with higher species richness did not produce more biomass than switchgrass monocultures. The lack of a positive relationship between planted species richness and production in our studies may be due to several factors. Non-planted species (weeds) were not removed from our studies and these non-planted species may have competed with planted species and also prevented realized species richness from equaling planted species richness. Also, we found that low seeding density of individual species limited the biomass production of these individual species. Production in future bioenergy plantings with high species richness may be increased by using a high density of inexpensive seed from switchgrass and other highly productive species, and future efforts to translate the results of biodiversity experiments to bioenergy plantings should consider the role of seeding density.     

Linking plant diversity–productivity relationships to plant functional traits of dominant species and changes in soil properties in 15‐year‐old experimental grasslands

Positive plant diversity–productivity relationships are known to be driven by complementary resource use via differences in plant functional traits. Moreover, soil properties related to nutrient availability were shown to change with plant diversity over time; however, it is not well‐understood whether and how such plant diversity‐dependent soil changes and associated changes in functional traits contribute to positive diversity–productivity relationships in the long run. To test this, we investigated plant communities of different species richness (1, 2, 6, and 9 species) in a 15‐year‐old grassland biodiversity experiment. We determined community biomass production and biodiversity effects (net biodiversity [NEs], complementarity [CEs], and selection effects [SEs]), as well as community means of plant functional traits and soil properties. First, we tested how these variables changed along the plant diversity gradient and were related to each other. Then, we tested for direct and indirect effects of plant and soil variables influencing community biomass production and biodiversity effects. Community biomass production, NEs, CEs, SEs, plant height, root length density (RLD), and all soil property variables changed with plant diversity and the presence of the dominant grass species Arrhenatherum elatius (increase except for soil pH, which decreased). Plant height and RLD for plant functional traits, and soil pH and organic carbon concentration for soil properties, were the variables with the strongest influence on biomass production and biodiversity effects. Our results suggest that plant species richness and the presence of the dominant species, A. elatius, cause soil organic carbon to increase and soil pH to decrease over time, which increases nutrient availability favoring species with tall growth and dense root systems, resulting in higher biomass production in species‐rich communities. Here, we present an additional process that contributes to the strengthening positive diversity–productivity relationship, which may play a role alongside the widespread plant functional trait‐based explanation.     

Long‐term study of root biomass in a biodiversity experiment reveals shifts in diversity effects over time

Biodiversity experiments generally report a positive effect of plant biodiversity on aboveground biomass (overyielding), which typically increases with time. Various studies also found overyielding for belowground plant biomass, but this has never been measured over time. Also, potential underlying mechanisms have remained unclear. Differentiation in rooting patterns among plant species and plant functional groups has been proposed as a main driver of the observed biodiversity effect on belowground biomass, leading to more efficient belowground resource use with increasing diversity, but so far there is little evidence to support this. We analyzed standing root biomass and its distribution over the soil profile, along a 1–16 species richness gradient over eight years in the Jena Experiment in Germany, and compared belowground to aboveground overyielding. In our long‐term dataset, total root biomass increased with increasing species richness but this effect was only apparent after four years. The increasingly positive relationship between species richness and root biomass, explaining 12% of overall variation and up to 28% in the last year of our study, was mainly due to decreasing root biomass at low diversity over time. Functional group composition strongly affected total standing root biomass, explaining 44% of variation, with grasses and legumes having strong overall positive and negative effects, respectively. Functional group richness or interactions between functional group presences did not strongly contribute to overyielding. We found no support for the hypothesis that vertical root differentiation increases with species richness, with functional group richness or composition. Other explanations, such as stronger negative plant–soil feedbacks in low‐diverse plant communities on standing root biomass and vertical distribution should be considered.     

Microbial Diversity and Community Structure in Two Different Agricultural Soil Communities

Abstract In this study, two different agricultural soils were investigated: one organic soil and one sandy soil, from Stend (south of Bergen), Norway. The sandy soil was a field frequently tilled and subjected to crop rotations. The organic soil was permanent grazing land, infrequently tilled. Our objective was to compare the diversity of the cultivable bacteria with the diversity of the total bacterial population in soil. About 200 bacteria, randomly isolated by standard procedures, were investigated. The diversity of the cultivable bacteria was described at phenotypic, phylogenetic, and genetic levels by applying phenotypical testing (Biolog) and molecular methods, such as amplified rDNA restriction analysis (ARDRA); hybridization to oligonucleotide probes; and REP-PCR. The total bacterial diversity was determined by reassociation analysis of DNA isolated from the bacterial fraction of environmental samples, combined with ARDRA and DGGE analysis. The relationship between the diversity of cultivated bacteria and the total bacteria was elucidated. Organic soil exhibited a higher diversity for all analyses performed than the sandy soil. Analysis of cultivable bacteria resulted in different resolution levels and revealed a high biodiversity within the population of cultured isolates. The difference between the two agricultural soils was significantly higher when the total bacterial population was analyzed than when the cultivable population was. Thus, analysis of microbial diversity must ultimately embrace the entire microbial community DNA, rather than DNA from cultivable bacteria.     

Plant diversity positively affects short‐term soil carbon storage in experimental grasslands

Increasing atmospheric CO₂ concentration and related climate change have stimulated much interest in the potential of soils to sequester carbon. In ‘The Jena Experiment’, a managed grassland experiment on a former agricultural field, we investigated the link between plant diversity and soil carbon storage. The biodiversity gradient ranged from one to 60 species belonging to four functional groups. Stratified soil samples were taken to 30 cm depth from 86 plots in 2002, 2004 and 2006, and organic carbon contents were determined. Soil organic carbon stocks in 0–30 cm decreased from 7.3 kg C m^?2 in 2002 to 6.9 kg C m^?2 in 2004, but had recovered to 7.8 kg C m^?2 by 2006. During the first 2 years, carbon storage was limited to the top 5 cm of soil while below 10 cm depth, carbon was lost probably as short‐term effect of the land use change. After 4 years, carbon stocks significantly increased within the top 20 cm. More importantly, carbon storage significantly increased with sown species richness (log‐transformed) in all depth segments and even carbon losses were significantly smaller with higher species richness. Although increasing species diversity increased root biomass production, statistical analyses revealed that species diversity per se was more important than biomass production for changes in soil carbon. Below 20 cm depth, the presence of one functional group, tall herbs, significantly reduced carbon losses in the beginning of the experiment. Our analysis indicates that plant species richness and certain plant functional traits accelerate the build‐up of new carbon pools within 4 years. Additionally, higher plant diversity mitigated soil carbon losses in deeper horizons. This suggests that higher biodiversity might lead to higher soil carbon sequestration in the long‐term and therefore the conservation of biodiversity might play a role in greenhouse gas mitigation.