Herb Cover Research Articles

长白山阔叶红松林中影响乔木幼苗存活的关键因素分析

PDF HTML阅读 XML下载 导出引用 引用提醒 长白山阔叶红松林中影响乔木幼苗存活的关键因素 DOI: 10.5846/stxb201403040371 作者: 作者单位: 北京林业大学,北京林业大学 作者简介: 通讯作者: 中图分类号: 基金项目: 国家"十二五"科技支撑课题(2012BAD22B0203, 2012BAC01B03);北京市共建项目专项(天然林生物多样性保护技术与杨树抗逆机理研究2012) Effects of biotic and abiotic factors on tree seedling survival in a broad-leaved Korean pine (Pinus koraiensis) mixed forest on Changbai Mountain Author: Affiliation: Beijing Forestry University,Beijing Forestry University Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:应用广义线性混合模型,对长白山阔叶红松林中影响幼苗存活的生物因素和非生物因素进行分析。结果表明:(1)在群落水平上,幼苗存活率和生物因素中同种幼苗邻居显著负相关,说明在阔叶红松林群落中存在负密度制约效应。(2)生物因子和非生物因子对不同年龄阶段的幼苗存活率影响不同。对于1年生的幼苗,幼苗存活率与异种大树邻居呈显著负相关,与同种大树邻居呈显著正相关;对于2-3年生的幼苗,其存活率和同种幼苗邻居、同种大树邻居均呈显著负相关,和非生物因子相关不显著;对于4年生以上的幼苗,其存活率和土壤主成分分析的PC1(低的有机质、速效钾、速效氮等比较贫瘠的土壤)显著负相关。(3)种子的传播方式不同,幼苗存活率的影响因子也不同。对于风传播的物种,存活率与同种幼苗邻居密度显著正相关。对于重力传播的物种,幼苗存活率与土壤PC3(高的全氮和速效氮,含氮较高的土壤)、异种大树邻居、草本密度呈负相关,与林冠开阔度和草本盖度成正相关。(4)对于不同的物种,影响幼苗存活的因素也不同。紫椴的幼苗存活率与土壤PC3、异种大树邻居、草本密度呈显著负相关,与土壤主成分PC2(高的有机质和全氮等养分比较好的土壤)呈显著正相关。 Abstract:Seedling recruitment plays a key role in determining species composition and diversity. Exploring patterns of seedling dynamics can therefore provide crucial insights into the mechanisms that affect seedling recruitment. The broad-leaved Korean pine (Pinus koraiensis) mixed forest is a temperate forest typical of northeast China. In 2007, we established a 1 hm2 plot in a broad-leaved Korean pine mixed forest on Changbai Mountain, northeast China. We identified, tagged, and mapped each tree with diameter at breast height ≥ 1 cm. At the same time, we set up 100 seedling quadrats of 1m×1m which were censused every July. In total, we collected data on 1288 adult trees and 965 seedlings in the 1 hm2 plot between 2012 and 2013, and examined the importance of biotic and abiotic factors on seedling survival using a generalized mixed linear model. Biotic factors included presence of conspecific seedling neighbors and heterospecific seedling neighbors, presence of conspecific adult neighbors and heterospecific adult neighbors, and herb density and herb cover. Abiotic factors included soil organic matter, available soil phosphorus, available soil potassium, available soil nitrogen, total soil nitrogen, and canopy openness. Conspecific neighbors had a significant negative effect on seedling survival at the community level, indicating significant negative density-dependence effects. The effects of biotic and abiotic factors on seedlings differed with seedling age. Conspecific adult neighbors and canopy openness had significant positive effects on survival of, 1-year seedlings while heterospecific adult neighbors had a significant negative effect. In contrast, for 2- to 3-year-old seedlings, conspecific seedling neighbors and conspecific adult neighbors showed a significant negative effect on seedling survival, but abiotic factors had no significant effect. Moreover, for ≥ 4-year-old seedlings, soil PC axis 1 (associated with low organic matter available K, available N, and total N) showed a significant negative effect on survival. Factors that drove seedling survival varied with species dispersal-mode. For wind-dispersed species, conspecific seedling neighbors had a significant positive effect on seedling survival. For gravity-dispersed species, soil PC axis 3 (associated with high available N and total N, heterospecific adult neighbors, and herb density) had a significant negative effect on survival, whereas canopy openness showed a significant positive effect. The effects of biotic neighbors and habitat differed among species. For instance, soil PC axis 3, heterospecific adult neighbors, and herb density had significant negative effects on seedling survival of Tilia amurensis, while soil PC axis 2 (associated with high organic matter and total N) showed a significant positive effect. Finally, herbs might influence seedling survival. Both herb density and herb cover impacted seedling survival by modifying local habitat. However, there was no significant effect of herbs on survival due to limited data. We conclude that both local biotic and abiotic factors play important roles in determining seedling recruitment in this temperate forest. 参考文献 相似文献 引证文献

Modeling Wood Encroachment in Abandoned Grasslands in the Eifel National Park - Model Description and Testing.

The degradation of natural and semi-natural landscapes has become a matter of global concern. In Germany, semi-natural grasslands belong to the most species-rich habitat types but have suffered heavily from changes in land use. After abandonment, the course of succession at a specific site is often difficult to predict because many processes interact. In order to support decision making when managing semi-natural grasslands in the Eifel National Park, we built the WoodS-Model (Woodland Succession Model). A multimodeling approach was used to integrate vegetation dynamics in both the herbaceous and shrub/tree layer. The cover of grasses and herbs was simulated in a compartment model, whereas bushes and trees were modelled in an individual-based manner. Both models worked and interacted in a spatially explicit, raster-based landscape. We present here the model description, parameterization and testing. We show highly detailed projections of the succession of a semi-natural grassland including the influence of initial vegetation composition, neighborhood interactions and ungulate browsing. We carefully weighted the single processes against each other and their relevance for landscape development under different scenarios, while explicitly considering specific site conditions. Model evaluation revealed that the model is able to emulate successional patterns as observed in the field as well as plausible results for different population densities of red deer. Important neighborhood interactions such as seed dispersal, the protection of seedlings from browsing ungulates by thorny bushes, and the inhibition of wood encroachment by the herbaceous layer, have been successfully reproduced. Therefore, not only a detailed model but also detailed initialization turned out to be important for spatially explicit projections of a given site. The advantage of the WoodS-Model is that it integrates these many mutually interacting processes of succession.

Multi-taxon alpha diversity following bark beetle disturbance: Evaluating multi-decade persistence of a diverse early-seral phase

Early-successional forest ecosystems developing after natural disturbances, such as fire, windthrow or insect outbreaks, can support high diversity of habitat structures, species and processes. However, the specific structural and multi-taxon responses that best define a distinct early-seral pre-forest phase, and the longevity of that phase, remain important research questions. To address these questions, we assessed stand structural heterogeneity and species density of various taxa across three biological kingdoms in the initial early-seral period (∼3years after severe bark beetle outbreak), advanced early-seral period (∼17–25years after severe bark beetle outbreak) and mature spruce forests in unmanaged montane/high-montane ecosystems in Southeastern Germany. We evaluated the hypothesis that changes in structural heterogeneity and increases in diversity would peak in the initial stage and attenuate toward mature forest conditions by 17–25years as the tree canopy closed.We found a clear change in forest structural heterogeneity following the outbreak – most prominently in reduced cover and more clustered patterning of live trees, increased light availability, increased cover of shrubs and herbs, and high volume of dead wood. Most of these structural changes were not ephemeral after outbreaks, but remained high or even increased after multiple decades, suggesting persistence of early-seral heterogeneity well into succession.Biodiversity as measured by species density and rarefaction curves showed variable responses to early-seral conditions depending on taxon and functional group. While some groups either showed no significant change with disturbance (e.g., most epigeics associated with the ground surface), or initially peaked after disturbance before declining quickly (e.g., saproxylic beetles specializing on fresh dead wood), several key groups showed maximum diversity in the advanced early-seral stage (e.g., herbs, herbivores, pollinators) – indicating that the timeframe over which increases occurred tended to be on the order of decades rather than years.Our findings suggest that in unmanaged forests after bark beetle attack, a structurally complex phase prior to tree canopy closure can last several decades, and that many aspects of early-seral biodiversity and ecosystem function only fully develop given this extended time period. Where management of montane forests includes objectives for sustaining biodiversity, accommodating the protracted early-seral stage is important to supporting the full range of organisms and functions associated with canopy-opening disturbances.

Electricity pylons may be potential foci for the invasion of black cherry Prunus serotina in intensive farmland

Electricity pylons are used by birds for nesting platforms, song posts, roosting, perching and therefore as defecation sites. Consequently we predict that pylons may facilitate the dispersal of endozoochorous plants, such as black cherry Prunus serotina, an invasive species in Europe producing fruits that are often eaten by birds. To test the influence of electricity pylons on the abundance of P. serotina in farmland in western Poland we surveyed 124 areas under pylons and 124 paired control plots within fields under power lines. P. serotina occurred under 81.5% of the investigated pylons but only in 2.4% of the control plots. The vast majority of P. serotina plants occurred under pylons (99.9% of 5820 individuals) of which only 0.7% (42 individuals), found under 12 pylons, were fruiting. The few plants in control plots were all seedlings. The density of plants was related to landscape variables; the occurrence of P. serotina was higher when pylons were situated within arable crops, had a lower level of herb cover and were closer to human settlements. These results suggest that one approach to protect semi natural or even anthropogenic landscapes from exotic and invasive species is by encouraging permanent land use involving some form of annual disturbance, such as hay cutting or ploughing.

Hide or die: use of cover decreases predation risk in juvenile North Axmerican porcupines

Abstract In many mammals, juveniles are vulnerable to predators because of their low mobility and small body size. Cover hides juveniles from predators and has been assumed to lower predation risk. However, among mammal species, studies relating use of cover to fitness remain infrequent and have been predominantly performed on ungulates. We measured habitat selection and survival of juvenile North American porcupines (Erethizon dorsatum). We tested whether juveniles selected for cover, use of cover depended on meteorological conditions (there could be a trade-off between predation risk and radiative heat gain during sunny days), and use of cover influenced survival. We also examined how sex, body mass, mobility of the juvenile, and distance to the mother affected survival. We found that juvenile porcupines (14 individuals observed on 299 occasions) selected high protective cover (microhabitat scale) within areas with low herb cover (local scale). Use of cover partly depended on weather, with use of dens d...

More than just drought: complexity of recruitment patterns in Mediterranean forests.

Understanding community dynamics during early life stages of trees is critical for the prediction of future species composition. In Mediterranean forests drought is a major constraint for regeneration, but likely not the only factor determining the observed spatial patterns. We carried out a sowing experiment aimed at identifying main filters during seed-seedling transition. Specifically, we studied seed fate (predation, fungi infection, emergence) and subsequent seedling performance (mortality during the first summer and overall recruitment after 2 years) of four co-occurring Mediterranean tree species (Quercus ilex, Quercus faginea, Juniperus thurifera, Pinus nigra). We related these processes to the dominant species composition, microhabitat heterogeneity, herb cover and seed mass. The identity of the dominant species in the forest canopy was more important for recruitment than the forest canopy being dominated by conspecific vs. heterospecific species. The patterns we found suggest that biotic interactions such as facilitation (lower mortality under the canopies) and herb competition (during emergence of J. thurifera) are relevant during recruitment. Moreover, our results pointed to ontogenetic conflicts regarding the seed mass of Q. faginea and to density-dependent seed mortality for Q. ilex, rarely described in Mediterranean ecosystems. We propose that our study species experience population growth in forests dominated by heterospecifics where the recruitment success depends on habitat heterogeneity and on moderated biotic and abiotic stresses created by each species. Our results reveal patterns and mechanisms involved in recruitment constraints that add complexity to the well-known drought-related processes in Mediterranean ecosystems.

Vegetation structure and composition determine snowshoe hare (Lepus americanus) activity at arctic tree line

Snowshoe hares (Lepus americanus Erxleben, 1777) are keystone herbivores supporting many boreal-forest predators. Understanding habitat use of hares can help predict how hares and their predators will be affected by disturbances such as climate change, which will have a particularly strong effect at tree line. We examined hare activity at arctic tree line near Churchill, Manitoba, using fecal pellet transects established in August 2012. We counted all hare fecal pellets at two plots per transect and measured plant abundance and vegetation structure surrounding the plots, then used model selection to determine the combinations of habitat features or plant species that best explained hare activity or presence. Hare pellets occurred at a higher density where tall shrub cover was high. Pellet density also increased with increasing canopy cover, tree size, tree density, visibility, and small shrub cover, but was negatively correlated with medium-sized shrub and herb cover. Hares preferred areas with willow (genus Salix L.) and avoided areas with unpalatable black spruce (Picea mariana (Mill.) Britton, Sterns & Poggenb.). With climate warming, tree line is expected to advance northward and the increased tall shrub and willow cover predicted with increasing temperatures should benefit hares by providing greater predator protection and food.

Resilience and Resistance of Sagebrush Ecosystems: Implications for State and Transition Models and Management Treatments

In sagebrush ecosystems invasion of annual exotics and expansion of piñon (Pinus monophylla Torr. and Frem.) and juniper (Juniperus occidentalis Hook., J. osteosperma [Torr.] Little) are altering fire regimes and resulting in large-scale ecosystem transformations. Management treatments aim to increase resilience to disturbance and enhance resistance to invasive species by reducing woody fuels and increasing native perennial herbaceous species. We used Sagebrush Steppe Treatment Evaluation Project data to test predictions on effects of fire vs. mechanical treatments on resilience and resistance for three site types exhibiting cheatgrass (Bromus tectorum L.) invasion and/or piñon and juniper expansion: 1) warm and dry Wyoming big sagebrush (WY shrub); 2) warm and moist Wyoming big sagebrush (WY PJ); and 3) cool and moist mountain big sagebrush (Mtn PJ). Warm and dry (mesic/aridic) WY shrub sites had lower resilience to fire (less shrub recruitment and native perennial herbaceous response) than cooler and moister (frigid/xeric) WY PJ and Mtn PJ sites. Warm (mesic) WY Shrub and WY PJ sites had lower resistance to annual exotics than cool (frigid to cool frigid) Mtn PJ sites. In WY shrub, fire and sagebrush mowing had similar effects on shrub cover and, thus, on perennial native herbaceous and exotic cover. In WY PJ and Mtn PJ, effects were greater for fire than cut-and-leave treatments and with high tree cover in general because most woody vegetation was removed increasing resources for other functional groups. In WY shrub, about 20% pretreatment perennial native herb cover was necessary to prevent increases in exotics after treatment. Cooler and moister WY PJ and especially Mtn PJ were more resistant to annual exotics, but perennial native herb cover was still required for site recovery. We use our results to develop state and transition models that illustrate how resilience and resistance influence vegetation dynamics and management options.

Impacts of ecological water conveyance on groundwater dynamics and vegetation recovery in the lower reaches of the Tarim River in northwest China.

The ecological water conveyance project (EWCP) in the lower reaches of the Tarim River provided a valuable opportunity to study hydro-ecological processes of desert riparian vegetation. Ecological effects of the EWCP were assessed at large spatial and temporal scales based on 13years of monitoring data. This study analyzed the trends in hydrological processes and the ecological effects of the EWCP. The EWCP resulted in increased groundwater storage-expressed as a general rise in the groundwater table-and improved soil moisture conditions. The change of water conditions also directly affected vegetative cover and the phenology of herbs, trees, and shrubs. Vegetative cover of herbs was most closely correlated to groundwater depth at the last year-end (R = 0.81), and trees and shrubs were most closely correlated to annual average groundwater depth (R = 0.79 and 0.66, respectively). The Normalized Difference Vegetation Index (NDVI) responded to groundwater depth on a 1-year time lag. Although the EWCP improved the NDVI, the study area is still sparsely vegetated. The main limitation of the EWCP is that it can only preserve the survival of existing vegetation, but it does not effectively promote the reproduction and regeneration of natural vegetation.

The role of a mound-building ecosystem engineer for a grassland butterfly

Both land use intensification and abandonment within grasslands lead to a homogenisation of vegetation structure. Therefore, specially structured microsites such as vegetation gaps with bare ground play an important role for species conservation within grasslands. Vegetation gaps are crucial for the establishment of low-competitive plant species and offer special microclimatic conditions essential for the development of the immature stages of many invertebrate species. The influence of small-scale soil disturbance in the form of mounds created by ecosystem engineers such as ants or moles on biodiversity is therefore of special scientific concern. The effects of mound-building species on plant species diversity have been extensively studied. However, knowledge on the significance of these species for the conservation of other animals is rare. In this study we analyse the importance of mounds created by the European mole (Talpa europaea) as an oviposition habitat for the small copper (Lycaena phlaeas) within Central European mesotrophic grasslands. Our study showed that host plants occurring at molehills were preferred for oviposition. Oviposition sites were characterised by an open vegetation structure with a high proportion of bare ground (with a mean coverage of about 50 %), a low cover of herbs and low-growing vegetation (mean height: 4.5 cm). Our study clearly illustrates the importance of small-scale soil disturbance for immature stages of L. phlaeas and the conservation of this species within mesotrophic grasslands. Mound-building ecosystem engineers, such as T. europaea, act as important substitutes for missing dynamics within mesotrophic grasslands by diversifying vegetation structure and creating small patches of bare soil.

Effects of forest management on ground beetle diversity in alpine beech (Fagus sylvatica L.) stands

European beech forests are of particular importance for biodiversity, although relatively little is known about how beech forest management impacts on invertebrate communities. In this paper we investigated the influence of beech forest management history [i.e. over-mature coppices (OC) and coppices in conversion to high forests (CCHF)], climatic, topographic and microhabitat characteristics on ground beetle diversity (measured as total relative abundance, species richness, Shannon diversity and abundance of the endangered endemic species Carabus olympiae) in northern Italy. The diversity of forest specialist carabids was higher in OC and in forest stands characterized by a higher mean temperature and lower relative humidity. Moreover, we detected a positive response of several diversity variables to coarse wood debris cover or volume, herb cover, and the standard deviation of tree diameter. Currently, OC seems to be a more favorable habitat for forest carabids, including C.olympiae, although succession over time can lead to a progressive homogenization of the vegetation structure, with negative consequences for the conservation of the forest carabid assemblage.Based on our results, we suggest that the traditional management of beech coppice and its conversion to high forest be modified by including practices aimed at promoting structural and microhabitat diversity such as retention of large trees, creation of canopy gaps, retention of coarse wood debris and the preservation of ‘islands’ of older trees in the managed stands.

Effects of Native Herbs and Light on Garlic Mustard (Alliaria petiolata) Invasion

AbstractThe degree to which invasive species drive or respond to environmental change has important implications for conservation and invasion management. Often characterized as a driver of change in North American woodlands, the invasive herb garlic mustard may instead respond to declines in native plant cover and diversity. We tested effects of native herb cover, richness, and light availability on garlic mustard invasion in a Minnesota oak woodland. We planted 50 garlic mustard seeds into plots previously planted with 0 to 10 native herb species. We measured garlic mustard seedling establishment, survival to rosette and adult stages, and average (per plant) and total (per plot) biomass and silique production. With the use of structural equation models, we analyzed direct, indirect, and net effects of native cover, richness, and light on successive garlic mustard life stages. Native plant cover had a significant negative effect on all life stages. Species richness had a significant positive effect on native cover, resulting in indirect negative effects on all garlic mustard stages, and net negative effects on adult numbers, total biomass, and silique production. Light had a strong negative effect on garlic mustard seedling establishment and a positive effect on native herb cover, resulting in significant negative net effects on garlic mustard rosette and adult numbers. However, light's net effect on total garlic mustard biomass and silique production was positive; reproductive output was high even in low-light/high-cover conditions. Combined effects of cover, richness, and light suggest that native herbs provide biotic resistance to invasion by responding to increased light availability and suppressing garlic mustard responses, although this resistance may be overwhelmed by high propagule pressure. Garlic mustard invasion may occur, in part, in response to native plant decline. Restoring native herbs and controlling garlic mustard seed production may effectively reduce garlic mustard spread and restore woodland diversity.

Soil conservation techniques in vineyards increase passerine diversity and crop use by insectivorous birds

Capsule Bird communities are better conserved in vineyards with mechanically managed herbaceous cover corridors.Aims To determine the advantages of herbaceous cover corridors for the conservation of farmland birds.Methods We studied birds in three vineyards subjected to different crop management schemes. Two vineyards had a herbaceous cover planted between crop rows to prevent soil erosion. In one vineyard these herbaceous cover corridors were chemically managed to prevent competition between the herb cover and the crop, whereas in a second the herbaceous cover was subject to mechanical management through some clearing, crop coverage, and height checks. A third vineyard was under conventional management (bare soil and soil tillage) and served as a control. We compared landscape structure and metrics, and passerine species richness, abundance, and diversity between the three vineyards.Results Overall bird species richness and diversity, as well as abundance of insectivorous passerine birds were highest in the mechanically managed vineyard. The chemically managed vineyard had lower species richness and abundance in comparison to the mechanically managed vineyard. In contrast, the conventionally managed plot had the lowest bird diversity, abundance, and species richness of all three plots. Landscape diversity was similar across the three vineyards.Conclusion Although our findings are preliminary and more research and replications are needed, we demonstrate that mechanically managed herbaceous cover corridors in vineyards, have positive impacts on the resident bird communities.

Disparate responses of above‐ and belowground properties to soil disturbance by an invasive mammal

Introduced mammalian herbivores can negatively affect ecosystem structure and function if they introduce a novel disturbance to an ecosystem. For example, belowground foraging herbivores that bioturbate the soil, may alter process rates and community composition in ecosystems that lack native belowground mammalian foragers. Wild boar (Sus scrofa) disturb the soil system and plant community via their rooting behavior in their native range. Given their size and the numbers in their populations, this disturbance can be significant in forested ecosystems. Recently, wild boar were introduced to Patagonian forests lacking native mammalian herbivores that forage belowground. To explore how introduced wild boar might alter forested ecosystems, we conducted a large‐scale wild boar exclusion experiment in three different forest types (Austroducedrus chilensis forest, Nothofagus dombeyi forest, and shrublands). Wild boar presence altered plant composition and structure, reducing plant biomass 3.8‐fold and decreasing both grass and herb cover relative to areas where wild boar were excluded. Decomposition rates and soil compaction also declined by 5% in areas where boar had access; however, rooting had no effect on soil nutrient stocks and cycling. Interestingly, there were no differences in wild boar impacts on different forest types. We found that after 3‐years of exclusion, belowground foraging by wild boar had a larger impact on plant community structure and biomass than it did on soil nutrient processes.

Butterfly (Lepidoptera) Assemblage Composition and Distribution Patterns in King Sabata Dalindyebo Municipality, Eastern Cape, South Africa

Butterflies (Lepidoptera) have attracted more attention as bio-indicators of terrestrial ecosystems than other terrestrial arthropods. This study determined butterfly species turnover at a priori selected habitat patches inside Nduli Nature Reserve and its surrounding landscape, and their response to measured environmental variables. Using the line transect method, 516 butterfly individuals belonging to 22 species were sampled from all 16 sampling units (Sus), of which 13 species occurred in two or more Sus across the study site. Habitat patches outside the reserve were higher in butterfly species richness and abundance than inside the reserve. Papilio demodocus Esper, Borbo gemella Mabille, Precis octavia (Cramer) and Hypolimnas missipus (Linnaeus) were each restricted to one sampling unit. Hierarchical clustering using Bray-Curtis similarity matrices and correspondence analyses grouped sampling units according to butterfly species sampled. Canonical correspondence analysis results indicated that certain site (environmental) variables, e.g. percentage herb cover, grazing intensity, distance to the city centre and average flower density accounted for species distribution patterns across Sus. The implications of the study suggest that habitat patch level management for conservation action should aim at preserving sufficient herb cover and nectaring plants, especially during the summer season to cater for all developmental stages of butterfly species in the study area. Furthermore, species richness within the reserve can be encouraged by using vegetation linkages and corridors between the reserve and its surrounding landscape. Butterflies identified during the study can serve as indicator species for assessing the conservation value of habitat patches in the study area and for increasing public awareness of the need to conserve butterflies and the invertebrate fauna of the King Sabata Dalindyebo Municipality between the months of November and April.

Direct and indirect effects of tree canopy facilitation in the recruitment of Mediterranean oaks

Summary Tree recruitment in Mediterranean ecosystems is strongly limited at the seedling stage by drought. Increasing evidence shows the critical positive role of the canopy nurse effect on seedling survival which results from direct and indirect, positive and negative interactions between species. Most studies, however, have only focused on the effects of tree canopy on water and light, ignoring other critical factors affecting seedling regeneration, such as canopy effects on high temperatures and the competing herb biomass. Here, we evaluate how tree canopy cover and removal of herbs affect the survival and growth of seedlings of two dominant Mediterranean Quercus species during a 3‐year study. We use an integrated model that combines several data sets to quantify and predict regeneration dynamics along environmental gradients of soil moisture, temperature and light. Low soil moisture, increased soil temperature and herb biomass negatively affected seedling survival of both Quercus species. Seedling growth was positively associated with increasing soil moisture and light. Although tree canopy cover directly facilitated seedling survival in both Quercus species, it also negatively affected herb biomass and thus indirectly facilitated the survival of Quercus suber, but not of Quercus ilex seedlings at low levels of soil moisture. Overall, tree canopies increased seedling survival but not growth during the establishment phase, mainly by ameliorating the effects of low soil moisture and high temperatures. Tree canopy indirectly facilitated survival of Q. suber seedlings by negatively affecting the competing herb layer. Synthesis and applications. To improve tree recruitment and conserve Mediterranean Quercus woodlands, the removal of herbs should be integrated into management plans for dry habitats. Interactions between abiotic and biotic factors may also effect the regeneration of these tree species. In particular, a healthy tree canopy will become important for providing conditions to facilitate seedling establishment if these habitats become drier and warmer, as predicted by some climate change scenarios.

Diversity and structure of herbaceous plant community in typical water-level-fluctuation zone with different spacing elevations in Three Gorges Reservior

Plant community structure characteristics are affected by its habitat. Plant community structure characteristics with different elevations and districts are different because of the unique hydrological condition of the Three Gorges Reservoir( TGR) and geographical condition of different districts. Low( L),Middle( M) and High( H) of typical water-level-fluctuating zone( WLFZ) divided depending on different spacing water level elevations( 145-155 m,155-170 m,170-175 m),were investigated in TGR in order to understand the herbaceous composition,diversity and synusia structure. In the 49 herbaceous species identified,only 4,18and 45 species were present in the L,M and H,respectively. The herb coverage,average density and average height of WLFZ of different water level elevations were( 2. 58% ± 1. 29%)-( 74. 83% ± 2. 57%),( 43. 58 ± 85. 93)-( 466. 08 ± 48. 04) shoots /m2and( 4. 89 ± 0. 56)-( 77. 02 ± 9. 31) cm,respectively. Comprehensive analysis shows that the composition of herbaceous plant species and synusia structure of WLFZ tend to be simple. The species diversity and structure characteristics vary along with water level elevation for different flooding stress and different stages of succession. Our results suggest that the classification of species collocation and optimization of interspecific relationship would be an effective measure for improving herbaceous plants development in the WLFZ.

Effect of the coniferous forest – grassland edge on ground vegetation in the mixed European forest zone, Lithuania

Abstract. The objective of this study was to estimate the edge effect on the species richness in agricultur-ally maintained forest-grassland boundaries of coniferous forest and to determine how species respond to a forest edge. We hypothesised that species number, cover of herbs and mosses is higher in the edge, and spe-cies penetrates from nearby grasslands into forest interior. The study was conducted in the Southwestern Lithuania. The edge effect on overall herbaceous species composition of coniferous forests was evaluated by Canonical Correspondence Analysis. The species richness of herbs and mosses in the coniferous forest was highest in the forest edge and declined towards interior. The highest decrease in the number of species occurred within 0 to 5 m to the edge. The highest cover of herbs and mosses was in the forest edge and decreased towards the forest interior. CCA biplot showed a good correlation of overall species composition and the distance to the forest edge. Distribution of species along edge to interior gradient depended on the species response to different ecological factors. Ellenberg value of light was higher in the edge. Ellenberg value of nitrogen was higher in the forest interior.Additional key words: canonical correspondence analysis, Ellenberg indicator values, forest edge effect, forest fragmentation, species richnessAddress: Institute of Environment and Ecology, Aleksandras Stulginskis University, Studentu 11, Lt-53361 Akademia, Kaunas r., Lithuania; Fax +370 7 752224; e-mail vitas.marozas@asu.lt

THE EFFECT OF FRAGMENTATION AND INTENSIVE MANAGEMENT ON CARABID BEETLES IN CONIFEROUS FOREST

We studied the effects of forest fragmentation an d management practices on carabid beetle (Coleoptera: Carabidae) assemblages in the Japanese red pine forests of Naju City, South Korea. A total of 2,058 carabid individuals, representing 15 speci es, were collected by pitfall trapping from May to September 2010 in three forest types: native forest (relatively undisturbed forest), managed forest (planted trees with clear-cutting of the herb layer ), and forest patch (fragmented forest). We showed that the different forest types differed significantly i n terms of their carabid assemblages. The managed f orest had the most distinct assemblage, with a lower spec ies richness and abundance than the other two fores t types. Although forest fragmentation did not signif icantly affect the species richness of carabid beet le assemblages, the abundance of some carabid beetles (forest specialists and large-sized species) was significantly altered by forest fragmentation and i ntensive forest management. Sub-tree layer and herb cover were the strongest environmental variables de termining the carabid assemblage composition. Forest fragmentation is an inevitable change in landscape structure, particularly in urbanized and pre-urban areas, and it constitutes a threat to biodiversity through landscape homogenization. Therefore, it is necessary to identify appropriate management practi ces, designed to minimize the damage caused by the loss and modification of natural habitats, together with maintenance and enhancement of the biodiversity in urban areas.

Limited effect of hare grazing and short-term climatic variations on the most common alpine vegetation community in the Snowy Mountains, Australia

Background: In the alpine zone of the Snowy Mountains, grazing by mammals is limited. However, introduced European hare numbers have increased since the 1970s. Aims: To estimate the density of hares and hence grazing pressure among years. To assess the response of biomass, vegetation height and composition to a cessation of hare grazing. Methods: We used indices of hare abundance based on spotlighting and counts of hare pellets on a transect. The effect of hare grazing on tall alpine herbfield was assessed by using 15 paired exclosure and control quadrats for six years. Results: The indices of hare abundance suggested densities similar to those in upland areas of Britain. Grazing did not affect the composition, cover of herbs or graminoids or, for 2010, vegetation height or biomass. Variation in vegetation and hare numbers among years was not correlated with climatic variables. Observations of selective grazing suggested that impacts on vegetation may be localised and restricted to certain species. Prior analyses of hare pellets indicated that hares might spread seed of native and exotic species. Conclusions: Hares are having no general effect on tall alpine herbfield but may affect certain plant species via selective grazing or by spread of viable seed.