Changes In Plant Species Diversity Research Articles

Adaptive grazing enhances plant species richness and density in the soil seed bank in a semi-arid grassland

The soil seed bank plays a key role in vegetation resilience under environmental disturbances, and is especially important for the restoration of degraded vegetation. However, the responsive dynamics of the soil seed bank to animal grazing and its potential in the restoration of grazing degraded steppe grassland remain unclear. Here we examined the changes in plant species diversity and density in both the soil seed bank and the aboveground vegetation of a natural grassland along an experimental gradient of four grazing intensities (nil, light, moderate and heavy grazing) in an adaptive grazing management system that ensures grassland residual cover was always above a certain criteria. The grassland is a typical steppe dominated by Leymus chinensis, Stipa grandis, and Cleistogenes squarrosa in central Inner Mongolia, China. We found that (i) plant species richness and density of the seed bank in the top 10 cm soil layer increased with grazing intensity, though the density of the seed bank in the top 5 cm soil layer showed an decrease. (ii) Moderate and heavy grazing significantly decreased the density of perennial but increased annual and biennial plants in the top 5 cm soil layer, which dominate the changes in the top 10 cm soil layer. (iii) Plant species richness and density in the aboveground vegetation also increased with grazing intensity, so did the similarity between the species composition of the soil seed bank and aboveground vegetation in the top 10 cm. The increase in the richness and density of annual and biennial species dominated the responsive changes to grazing of the soil seed bank and aboveground vegetation in the studied grassland. Our results provide a reference basis for grazing management in the region from the perspective of the soil seed bank, and suggest that the adaptive grazing system with grassland residual height controlled above a criterion benefits to the soil seed bank thus the re-generation of vegetation.

Increasing plant species diversity suppresses free‐living N2 fixation in litter and soil of a subtropical karst forest

Abstract Free‐living N2 fixation (FNF) is an important source of bioavailable nitrogen for forests. Though increasing plant species diversity (PSD) benefits soil nitrogen accumulation, how it impacts FNF rate has not been explored. Forty‐five plots covering a PSD gradient were selected in a subtropical karst forest, southwest China. FNF rates in leaf litter and soil were measured using acetylene reduction assay calibrated with a 15N2 fixation method. Diazotrophic community, litter and soil properties were determined as well. The nifH gene abundance was not significantly altered in litter but was significantly decreased in soil by higher PSD. Diazotrophic community's Shannon diversity was significantly increased by higher PSD in both litter and soil. Increasing PSD inhibited litter FNF rate via aggravating phosphorus limitation and decreasing the relative abundance of Betaproteobacteria and Deltaproteobacteria. For the mineral soil horizon, increasing PSD suppressed FNF rate via decreasing nifH gene abundance caused by elevated N availability and lowered phosphorus and iron availability or through decreasing the relative abundance of Deltaproteobacteria but increasing that of Betaproteobacteria. Our findings, for the first time, reveal the microbial and abiotic controls on FNF in litter and soil in response to PSD, and hence benefit the prediction of nitrogen input via biological N2 fixation under changes in PSD. Read the free Plain Language Summary for this article on the Journal blog.

Response of the Biological Components to Climate Change in the Wetland Ecosystem of the Qinghai-Tibet Plateau

Alpine wetlands play a role in water conservation, climate regulation, carbon sequestration, and biodiversity protection. However, due to the unique geological structure and climate characteristics of alpine areas, climate change is highly likely to have an impact on alpine wetlands and their ecosystems, including the abundance and distribution of local species. This paper focuses on analyzing the composition, quantity, and distribution changes of wetland organisms, including producers, consumers, and decomposers. The research findings indicate that, with the intensification of human activities and climate change such as global warming, despite the emergence of some new wetlands, many natural alpine wetlands on Qinghai-Tibet Plateau are facing shrinkage and are gradually retreating towards higher altitudes, latitudes, and wetter areas, which means the extinction of some plants and the shrinkage of wildlife habitats. Changes in wetland environment, such as drying, resulting from increased temperature and decreased precipitation, have led to a decline in biodiversity and degradation of alpine wetland ecosystems. Despite an overall increase in vegetation cover, wetland degradation has caused changes in plant species diversity and community composition. Climate warming have also affected wildlife migration and the activity of microorganisms. The changes in plateau wetlands are primarily shaped by climate conditions, while human activities act as accelerators, causing significant damage to wetland environments, leading to fragmentation and accelerated degradation. This paper proposes strengthening ecological monitoring and risk assessment in these regions, conducting further research, and promptly implementing necessary restoration measures to reduce the ecological risks caused by these changes.

Contribution of Sheep Grazing to Plant Diversity in Natural Grasslands

Global climate change and overgrazing have led to the degradation of natural grasslands and seriously threaten the diversity of grassland plant species, as plant species richness is very sensitive to natural grassland degradation. Therefore, we conducted a sheep grazing experiment in Zinniquan pasture on the northern slope of Xinjiang Tianshan Mountains to test the effects of grazing on plant species diversity in natural grasslands through the spatial and temporal characteristics of the foraging behavior of grazing sheep and the plant species composition on the grazing trajectories. Data on sheep grazing tracks were collected based on GPS, vegetation composition around the tracks was investigated and seeds were collected from sheep manure to determine germination rates by simulating rumen fistula uptake tests in sheep. We found that sheep grazing can bring seeds from agricultural fields to grow on natural grasslands, causing changes in plant species diversity and community structure. The results of this study provide new insights into natural grassland species restoration and offer a range of new strategies that can be applied to the management of natural grassland plant ecological restoration.

Changes in plant species diversity as affected by shading conditions and continuous agricultural practices in kiwifruit orchards

The environmental impact of commercial Mediterranean kiwifruit 'Hayward’ orchards was assessed after ten years of continuous cultivation. Species diversity seems to be influenced both by the subcanopy photosynthetically active radiation (PAR) budget, and the usual agricultural practices in conventional orchards. The largest reduction of species diversity (~64%) was observed in kiwifruit orchards with pergola canopy structure followed by that in T-bar canopy structure (~34%) in comparison with new installed kiwifruit orchards. In excessive shading conditions and particularly in well irrigated kiwifruit orchards with the synergistic effect of the above variables, the highest reduction of plant species has occurred. The continuous herbicides application and the soil compaction are strongly correlated with the reduction of taxa, while the long-term agricultural practices, such as inorganic fertilizers and Cu-fungicides application, have a negative impact on plant species diversity in kiwifruit orchards.

Quantifying Changes in Plant Species Diversity in a Savanna Ecosystem Through Observed and Remotely Sensed Data

This study examined the impact of climate change on plant species diversity of a savanna ecosystem, through an assessment of climatic trends over a period of forty years (1974–2014) using Masvingo Province, Zimbabwe, as a case study. The normalised difference vegetation index (NDVI) was used as a proxy for plant species diversity to cover for the absence of long-term historical plant diversity data. Observed precipitation and temperature data collected over the review period were compared with the trends in NDVI to understand the impact of climate change on plant species diversity over time. The nonaligned block sampling design was used as the sampling framework, from which 198 sampling plots were identified. Data sources included satellite images, field measurements, and direct observations. Temperature and precipitation had significant (p < 0.05) trends over the period under study. However, the trend for seasonal total precipitation was not significant but declining. Significant correlations (p < 0.001) were identified between various climate variables and the Shannon index of diversity. NDVI was also significantly correlated to the Shannon index of diversity. The declining trend of plant species in savanna ecosystems is directly linked to the decreasing precipitation and increasing temperatures.

Structure and composition of tree species in tropical moist deciduous forests of Eastern Ghats of Odisha, India, in response to human-induced disturbances

The changes in plant species diversity and community structure in response to human induced disturbances were studied in 12 ha of tropical moist deciduous forest stands of Eastern Ghats of Odisha, India. The forest stands were classified as undisturbed (UD), moderately disturbed (MD) and highly disturbed (HD) categories based on the types and levels of human-induced disturbance. Twenty four transects, each measuring 0.5 ha (5 m × 1000 m) were laid for enumeration of trees with ≥ 30 cm GBH. In total, 5451 trees under 101 species, 78 genera and 37 families were found to occur in the study site. The density of trees and basal area decreased with the increase in the level of disturbance. While the stand density varied in the range of 185.50 in HD stands to 744 stems ha−1 in UD stands, basal area ranged between 12.54 in HD to 36.95 m2 ha−1in UD stands. The number of individuals and number of species per unit area showed a declining trend with increase in girth class. Maximum number of species and density was recorded for trees of low girth class (30–60 cm) in all three stands. Shannon, Simpson, Fisher’s alpha and Margaleff’s indices varied greatly across the three stands experiencing different levels of disturbance. Shannon’s Index varied between 3.20 and 3.42 and Simpson Index ranged from 0.09 to 0.12. The range of variation in Evenness index, Fisher’s alpha index and Margaleff’s index were recorded between 0.75–0.79, 14.45–16.10 and 29.65–34.83, respectively. The diversity of shrub, liana and herb species and regeneration potential of tree species were assessed from two 5 m × 5 m sub-plots located within each transect. Dominance of trees in undisturbed forests, shrubs and lianas in moderately disturbed and herbs in highly disturbed forests were observed. The data generated in the present investigation may prove useful for formulation of appropriate forest management strategies.

Grazing exclusion-induced shifts, the relative importance of environmental filtering, biotic interactions and dispersal limitation in shaping desert steppe communities, northern China

Grazing exclusion is one of the most efficient approaches to restore degraded grassland but may negatively affects the recovery of species diversity. Changes in plant species diversity should be a consequence of the ecological assembly process. Local community assembly is influenced by environmental filtering, biotic interactions, and dispersal. However, how these factors potentially contribute to changes to species diversity is poorly understood, especially in harsh environments. In this study, two management sites within a Stipa breviflora desert steppe community (typical natural steppe) were selected in northern China. In one of the two management sites, grazing has been excluded since 2010 and in the other with open grazing by sheep. In August 2016, three plots were established and 100 sampling units were created within each plot in a 5 m×5 m area at the two management sites. To assess the effects of grazing exclusion on S. breviflora steppe, we analyzed the vegetation biomass, species diversity, soil organic carbon, and soil particle size distribution using paired T-tests. In addition, variation partitioning was applied to determine the relative importance of environmental filtering and dispersal limitation. Null mode analysis was used to quantify the influence of biotic interactions in conjunction with EcoSim niche overlap and co-occurrence values. Our results demonstrated that (1) species diversity significantly decreased and the main improvements in soil quality occurred in the topsoil 0–10 cm after the grazing exclusion; (2) environmental filtering was important for community assembly between grazed and fenced grassland and this appears particularly true for soil particle size distribution, which may be well correlated with soil hydrological processes; and (3) however, competitive exclusion may play a significant role within the exclusion. The multiple pathways of assembly may collectively determine negative effects on the restoration of species diversity. Therefore, designers should be aware of the risk of reducing grazing exclusion-induced species diversity and account for manipulating processes. This in turn will reduce dominant species and promote environmental heterogeneity to maximize species diversity in semi-arid regions.

Vegetation and soil restoration in refuse dumps from open pit coal mines

Because the exploitation of mineral resources has resulted in the destruction of vast amounts of land and caused serious environmental problems, ecological restoration and mine reclamation have become important components of the sustainable development strategies of many countries. In this study, the changes in plant species diversity and succession of soil physicochemical properties were studied in revegetated refuse dumps of varying ages (1995, 1998, 2003, 2005 and 2014) and an undisturbed reference site of the Heidaigou opencast coal mine, which is located in the Inner Mongolia Autonomous Region, China. In addition, based on the space-for-time substitution approach, the rate and extent of recovery of the vegetation and soil characteristics in the above long-term chronosequence were estimated. The results showed that opencast mining revegetation have a positive effect on environmental restoration. The total species number and the richness, coverage and biomass of herbaceous species increased significantly with increasing site age. However, for shrub species, an initial increase was observed over a period of 10 years and then followed by a subsequent decrease. The mean soil water content in the oldest vegetated areas (1995 site, 2.3–5.9%) was significantly greater than in the younger vegetated areas (e.g., 2014 site, 1.1–2.5%) in the shallow layer (0–60cm); however, in the deeper layers (60–200cm), the mean soil water content in the oldest vegetated areas (4.2–8.1%) was significantly lower than in the younger vegetated areas (5.1–12.5%). The proportions of silt and clay, depth of topsoil and biological soil crusts, and concentrations of soil organic C, K, total N, and total P increased with the years since revegetation. The estimated time required for plant traits and soil properties in the revegetated site to reach the same levels as in the reference site was between 23 and 25 years. These results suggest that soil recovery and vegetation recovery are equally important in eco-restoration activities in semiarid areas, and the conservation of soil and vegetation habitat is therefore a crucial issue for land managers.

Patterns of Species Diversity are not Consistent between Shifting Cultivation in Bawangling Nature Reserves and Selective Logging in Diaoluoshan Nature Reserves, Hainan Island, China

Examining changes in plant species diversity after shifting cultivation and logging has taken place in a system can help generate an understanding of the differences in species' responses to these human disturbances. We established 17 plots (each 0.25 hm2) in young, middle-aged and old-growth forests (i.e. three recovery stages) in Bawangling and Diaoluoshan on Hainan Island, China, after shifting cultivation and selective logging had taken place. We divided each plot into four vertical communities. Changes in the species diversity of each plot (i.e. the overall community) and within the vertical communities were assessed across the three recovery stages. Results showed that, after shifting cultivation, species diversity increased across the three recovery stages for the overall community and for the four vertical communities. Species abundance decreased for the overall community but change was inconsistent for the four vertical communities. After selective logging, however, there was generally little change in species diversity and abundance across the three recovery stages, either overall or within the vertical communities. This suggests that patterns of species diversity between communities are different after shifting cultivation has occurred and when selective logging has taken place. Furthermore, Non-Metric Multidimensional Scaling showed differences in species composition across the three stages in the four vertical communities after shifting cultivation, but no differences in species composition across the three stages after selective logging. We also divided species dissimilarity coefficients into two parts, showing changes in species composition and abundance between the vertical communities under canopies and the canopy communities. We found that after shifting cultivation the coefficients between young-aged and old-growth forests, and middle-aged and old-growth forests were more than 0.77, but that they did not differ after selective logging had occurred. This suggests that changes in species turnover is unpredictable after shifting cultivation, but predictable after selective logging.

Increasing plant species diversity and extreme species turnover accompany declining soil fertility along a long‐term chronosequence in a biodiversity hotspot

Summary Long‐term soil chronosequences provide natural soil fertility gradients that can be used to explore linkages between soils and plant community composition and diversity. Well‐studied forested soil chronosequences have revealed that local (α) plant diversity increases with greater soil age and declining fertility, but corresponding changes in species turnover and beta (β) diversity have not been explored, particularly in extremely species‐rich regions. We quantified changes in plant species diversity and community composition, and identified the edaphic drivers of these changes, along a >2‐million year retrogressive dune chronosequence in the south‐west Australia biodiversity hotspot. We found greater plant species diversity across all growth forms as soil development proceeded and concentrations of soil nutrients, particularly phosphorus (P), diminished to extremely low levels (surface soil total P concentrations of 6 mg P kg−1). Despite the high plant α diversity on older nutrient‐impoverished soils, species turnover across the chronosequence was exceptionally high when all growth forms were considered (mean of 1% of species shared between the youngest and oldest soils), and there was complete turnover of woody species along the chronosequence. Such extreme species turnover across the chronosequence reflected large changes in soil chemical properties. In addition, β diversity within individual chronosequence stages increased with declining soil fertility. Shrubs remained the dominant and most speciose growth form throughout the chronosequence. Synthesis. The large increase in plant α diversity and the extreme species turnover associated with declining soil fertility highlight the central role of soil properties in driving plant community assembly during long‐term ecosystem development, previously only reported from comparatively species‐poor regions. Our finding that plant β diversity increased with declining soil fertility points to a novel mechanism whereby extremely low soil fertility, rather than high productivity, promotes high β diversity. These results suggest that the interaction of an exceptionally diverse plant species pool and nutrient‐impoverished soils provides the basis for the maintenance of such high β diversity at extremely low soil fertility.

Satellite remote sensing to monitor species diversity: potential and pitfalls

AbstractAssessing the level of diversity in plant communities from field‐based data is difficult for a number of practical reasons: (1) establishing the number of sampling units to be investigated can be difficult; (2) the choice of sample design can impact on results; and (3) defining the population of concern can be challenging. Satellite remote sensing (SRS) is one of the most cost‐effective approaches to identify biodiversity hotspots and predict changes in species composition. This is because, in contrast to field‐based methods, it allows for complete spatial coverages of the Earth's surface under study over a short period of time. Furthermore, SRS provides repeated measures, thus making it possible to study temporal changes in biodiversity. Here, we provide a concise review of the potential of satellites to help track changes in plant species diversity, and provide, for the first time, an overview of the potential pitfalls associated with the misuse of satellite imagery to predict species diversity. Our work shows that, while the assessment of alpha‐diversity is relatively straightforward, calculation of beta‐diversity (variation in species composition between adjacent locations) is challenging, making it difficult to reliably estimate gamma‐diversity (total diversity at the landscape or regional level). We conclude that an increased collaboration between the remote sensing and biodiversity communities is needed in order to properly address future challenges and developments.

Vegetation resurvey is robust to plot location uncertainty.

Resurveys of historical vegetation plots are increasingly used for the assessment of decadal changes in plant species diversity and composition. However, historical plots are usually relocated only approximately. This potentially inflates temporal changes and undermines results. Temperate deciduous forests in Central Europe. To explore if robust conclusions can be drawn from resurvey studies despite location uncertainty, we compared temporal changes in species richness, frequency, composition and compositional heterogeneity between exactly and approximately relocated plots. We hypothesized that compositional changes should be lower and changes in species richness should be less variable on exactly relocated plots, because pseudo-turnover inflates temporal changes on approximately relocated plots. Temporal changes in species richness were not more variable and temporal changes in species composition and compositional heterogeneity were not higher on approximately relocated plots. Moreover, the frequency of individual species changed similarly on both plot types. The resurvey of historical vegetation plots is robust to uncertainty in original plot location and, when done properly, provides reliable evidence of decadal changes in plant communities. This provides important background for other resurvey studies and opens up the possibility for large-scale assessments of plant community change.

氮素和水分添加对贝加尔针茅草原植物多样性及生物量的影响

Increases in atmospheric nitrogen deposition and changes in precipitation patterns are important phenomena related to changes in the global environment. These changes have created a series of increasingly serious ecological problems affecting the structure and function of grassland ecosystems. Therefore,grasslands have become a focus of ecological research in China and around the world in recent years. High nitrogen deposition can acidify grassland soils and lead to nutritional imbalances,decreases in biodiversity and productivity,and grassland degradation,all of which are seriousthreats to the function of grassland ecosystems. Precipitation can increase the efficiency of nitrogen fertilizer used by plants,and climate warming is accompanied by changes in precipitation. Studies of the interactive effects of nitrogen deposition and variation in rainfall on natural grassland ecosystems can help to increase our understanding of the responses of such ecosystems to changes in the global climate. In China,the Stipa baicalensis steppe,a type of meadow steppe,is mainly distributed in the forest steppe zone of the Songliao Plain and the east Inner Mongolian Plateau. In Inner Mongolia,farmers mainly use S. baicalensis steppe as natural pasture; therefore,it has an important role in livestock production. The aim of this study was to evaluate the responses of grassland plant community species diversity and the aboveground biomass of several common plant species to nitrogen deposition and irrigation. We set up a factorial experiment to test the interactive effects of eight nitrogen treatments and water addition in S. baicalensis steppe in Inner Mongolia in June 2010. This involved nitrogen( NH4NO3) application levels of 0( the control treatment,CK),15,30,50,100,150,200,300 kg N hm-2a-1( referred to as N0,N15,N30,N50,N100,N150,N200,N300,respectively) and simulated 100 mm summer rainfall. In mid-August 2013,we established 96 1 m × 1 m sample plots. The vegetation was harvested from each plot and the biomass of each species was measured to determine the effects of nitrogen and water addition on species diversity and the aboveground biomass of several common plants. Nitrogen and water application reduced plant species diversity in the steppe community,and there was a significant interaction effect between nitrogen and moisture. When water was added,increasing nitrogen application levels resulted in decreases in plant species richness,Shannon-Wiener index,and Pielou evenness index. When water was not added,increasing nitrogen application levels resulted in changes in species richness,ShannonWiener index,and Pielou evenness index that showed a "single-peak",but overall downward trend. Plant species differed in their responses to nitrogen and water addition. With increasing nitrogen application levels,the aboveground biomass of Leymus chinensis increased significantly, reaching a maximum at N300; the aboveground biomass of S. baicalensis,Achnatherum sibiricum,Cleistogenes squarrosa,Carex duriuscula,and Artemisia frigida first increased and then decreased,showing a "single-peak "trend; and the aboveground biomass of Potentilla acaulis,Thermopsis lanceolata,Melilotoides ruthenica,and Filifolium sibiricum decreased gradually. There was a significant interaction effect between water and nitrogen application level on the biomass of S. baicalensis,A. sibiricum,and M. ruthenica. We concluded that the changes in plant species diversity and aboveground biomass were related to nutrient application levels, water availability, their own characteristics,and interspecific and intraspecific competition.

Variability of plant species diversity during the natural restoration of the subalpine birch forest in the Central Great Caucasus

The northern slopes of the Central Great Caucasus of Georgia were covered by birch (Betula litwinowii ) forests in the past, but forest degradation resulted in subalpine secondary meadows. Over the past 20 years birch forest natural reforestation processes have taken place. The aim of this study was to determine the changes in plant species diversity during reforestation. Different habitat types were selected to trace the development of birch forests from subalpine meadows. Species richness was determined in 100 research plots (25 m 2 each) of different habitat types. Pioneer succession was distinguished by the highest level of species richness due to the mixture of two habitat types. Degraded forest showed the lowest species richness. At the initial stages of forest restoration we observed several species of subalpine dwarf shrubs. They grow only in open canopy areas and are absent in closed forests. The alpine treeline habitat type and pioneer succession of subalpine meadows revealed close relations in species composition and diversity. These similarities show forest restoration in lower elevations as it is restricted in the treeline ecotone by local climatic conditions. The natural regeneration is apparently in close relation with the global climate change, but the most important factor is the reduction of uncontrolled sheep grazing.

Dynamics of ruderal species diversity under the rapid urbanization over the past half century in Harbin, Northeast China

Urbanization has resulted in obvious changes in plant species diversity. We analyzed the dynamics of ruderal species diversity in Harbin over the past half century using historical data collected in 1955 and data of the present spatial distribution in 2010–2011. The results show that, the number of ruderal species decreased from 611 to 175 with remarkable tendency of decreasing in perennial species and increasing in winter annual species in the past half century, which caused the shift of life form spectrum from perennial mono-dominant type to summer annual and perennial co-dominant type. Meanwhile, the proportion of tropical originated species increased and the proportion of temperate originated species decreased which were considered to relate with the increase of temperature in urban area during the past half century. Moreover, there was a distinct decrease of the proportion of aquatic and hygrophytic ruderal species while an increase of mesic and xeric ruderal species which suggested a drought trend in urban habitats that consistent with the change of land use characterized as decrease of natural water bodies and wetlands and increase of urban land. Comparison of ruderal species along urbanization gradient also got the similar results with the above results from analysis on temporal scales and confirmed the effect of urbanization on decreasing plant richness. Our results suggested that land use change combined with its effect on temperature and disturbance regimes in urban habitats preferred species with short life span, high drought tolerance, fast growth rates and high seed yields.

Multi‐nutrient vs. nitrogen‐only effects on carbon sequestration in grassland soils

Human activities have greatly increased the availability of biologically active forms of nutrients [e.g., nitrogen (N), phosphorous (P), potassium (K), magnesium (Mg)] in many soil ecosystems worldwide. Multi-nutrient fertilization strongly increases plant productivity but may also alter the storage of carbon (C) in soil, which represents the largest terrestrial pool of organic C. Despite this issue is important from a global change perspective, key questions remain on how the single addition of N or the combination of N with other nutrients might affect C sequestration in human-managed soils. Here, we use a 19-year old nutrient addition experiment on a permanent grassland to test for nutrient-induced effects on soil C sequestration. We show that combined NPKMg additions to permanent grassland have 'constrained' soil C sequestration to levels similar to unfertilized plots whereas the single addition of N significantly enhanced soil C stocks (N-only fertilized soils store, on average, 11 t C ha(-1) more than unfertilized soils). These results were consistent across grazing and liming treatments suggesting that whilst multi-nutrient additions increase plant productivity, soil C sequestration is increased by N-only additions. The positive N-only effect on soil C content was not related to changes in plant species diversity or to the functional composition of the plant community. N-only fertilized grasslands show, however, increases in total root mass and the accumulation of organic matter detritus in topsoils. Finally, soils receiving any N addition (N only or N in combination with other nutrients) were associated with high N losses. Overall, our results demonstrate that nutrient fertilization remains an important global change driver of ecosystem functioning, which can strongly affect the long-term sustainability of grassland soil ecosystems (e.g., soils ability to deliver multiple ecosystem services).

Mean age of carbon in fine roots from temperate forests and grasslands with different management

Abstract. Fine roots are the most dynamic portion of a plant's root system and a major source of soil organic matter. By altering plant species diversity and composition, soil conditions and nutrient availability, and consequently belowground allocation and dynamics of root carbon (C) inputs, land-use and management changes may influence organic C storage in terrestrial ecosystems. In three German regions, we measured fine root radiocarbon (14C) content to estimate the mean time since C in root tissues was fixed from the atmosphere in 54 grassland and forest plots with different management and soil conditions. Although root biomass was on average greater in grasslands 5.1 ± 0.8 g (mean ± SE, n = 27) than in forests 3.1 ± 0.5 g (n = 27) (p < 0.05), the mean age of C in fine roots in forests averaged 11.3 ± 1.8 yr and was older and more variable compared to grasslands 1.7 ± 0.4 yr (p < 0.001). We further found that management affects the mean age of fine root C in temperate grasslands mediated by changes in plant species diversity and composition. Fine root mean C age is positively correlated with plant diversity (r = 0.65) and with the number of perennial species (r = 0.77). Fine root mean C age in grasslands was also affected by study region with averages of 0.7 ± 0.1 yr (n = 9) on mostly organic soils in northern Germany and of 1.8 ± 0.3 yr (n = 9) and 2.6 ± 0.3 (n = 9) in central and southern Germany (p < 0.05). This was probably due to differences in soil nutrient contents and soil moisture conditions between study regions, which affected plant species diversity and the presence of perennial species. Our results indicate more long-lived roots or internal redistribution of C in perennial species and suggest linkages between fine root C age and management in grasslands. These findings improve our ability to predict and model belowground C fluxes across broader spatial scales.

Multi-scale associations of grassland birds in response to cost-share management of conservation reserve program fields in Illinois

The Illinois State Wildlife Action Plan targeted the Conservation Reserve Program (CRP) as important improvable acres for grassland and grassland-successional bird species of greatest need for conservation. A large portion of CRP grasslands in Illinois and elsewhere lack floristic and structural diversity because of the absence of management and the extensive planting of monotypic grasses such as tall fescue (Schedonorus phoenix). The 2006 Farm Bill included the mid-contract management (MCM) provision requiring landowners with new CRP enrollments to provide habitat improvement midway through the 10–15-year contract duration. We compared the effects of 3 approved MCM regimes (i.e., fall strip disking, fall glyphosate spraying, fall glyphosate spraying followed by spring legume drill-seeding) on grassland bird communities in 60 tall fescue-dominated CRP fields in south-central Illinois during 2006–2008. We modeled relative density of dickcissels (Spiza americana), Henslow's sparrows (Ammodramus henslowii), and eastern meadowlarks (Sturnella magna) as a function of microhabitat, patch-level patterns, and landscape composition using a multi-scale assessment approach. We detected 10 grassland-associated bird species (e.g., Henslow's sparrow, northern bobwhite [Colinus virginianus], sedge wren [Cistothrus platensis], Savannah sparrow [Passerculus sandwichensis], grasshopper sparrow [Ammodramus savannarum]) that are recognized as species of greatest need for conservation under the Illinois State Wildlife Action Plan. Mean total bird densities and species richness were greater in glyphosate-sprayed fields (5.0 birds/ha; 11.5 species) and glyphosate drill-seeded fields (4.4 bird/ha; 12.4 species) than in disked (3.4 birds/ha; 8.7 species) and reference (3.1 birds/ha; 7.5 species) fields. The avian conservation value of glyphosate sprayed and glyphosate drill-seeded fields increased 34.2% and 32.6% post-management, respectively, but we did not detect change in disked and reference fields. Our models indicate that density of each of the focal species is likely associated with changes in plant species diversity and habitat structure resulting from management actions but is also influenced by landscape composition. Despite an overall positive response of the grassland bird communities to glyphosate-based treatment regimes in tall fescue CRP fields in south-central Illinois, the response of Henslow's sparrow density to glyphosate was not consistently positive. © 2013 The Wildlife Society.

Plant species diversity and dynamics in forests invaded by Moso bamboo (Phyllostachys edulis) in Tianmu Mountain Nature Reserve

Moso bamboo (Phyllostachys edulis) is an economically important plant, widely cultivated not only for its delicious shoots and versatile culms, but also as an important biomass resource in southern China. However, with its robust growth and strong rhizomes, it has recently been shown to be a problem tree, capable of dominating some forest stands. Indeed, it may displace species within the community it invades with considerable potential impacts. However, little is known about the consequences of its invasion on plant community composition. We compared plant biodiversity change in different communities where we monitored and removed bamboo over a seven years period (2005 to 2011) in Tianmu Mountain Nature Reserve, so as to elucidate the impacts of Moso bamboo invasion. The results showed that Moso bamboo invasion had negative effects on plant communities. Simpson’s Diversity Index in tree and shrub layers of bamboo forest was lower than that of forests consisting of needle and broad-leaved species, and also those containing a mixture of bamboo with needle and broad-leaved plants. However, Simpson’s Diversity Index in the herb layer of bamboo forest was higher than that in the two other forest types. Plant species richness, Simpson’s Diversity Index, and Pielou’s Eveness Index varied greatly among the different forest types over time. In the tree and shrub layers of forests containing bamboo growing with both needle and broad-leaved species, these 第 3期 白尚斌等: 天目山保护区森林群落植物多样性对毛竹入侵的响应及动态变化 289 three indices declined significantly over the monitoring period (P 0.05). Plant species richness increased in the herb layer of forests containing bamboo mixed with needle and broad-leaved species, while Simpson’s Diversity Index and Pielou’s Eveness Index did not change greatly over time. The removal of Moso bamboo resulted in an increase in plant species richness and Simpson’s Diversity Index in the tree and shrub layers. In contrast, plant species richness, Simpson’s Diversity Index, and Pielou’s Eveness Index decreased significantly in the herb layer. In summary, in the Tianmu Mountain Nature Reserve, Moso bamboo invasion was found to cause substantial changes in plant species diversity and had strong negative effects on plant communities. These results suggest that, in addition to scientific management, removal of Moso bamboo may be required to restore plant species diversity in these communities.