Vegetation recovery and plant facilitation in a human-disturbed lava field in a megacity: searching tools for ecosystem restoration

Unplanned urban development threatens natural ecosystems. Assessing ecosystem recovery after anthropogenic disturbances and identifying plant species that may facilitate vegetation regeneration are critical for the conservation of biodiversity and ecosystem services in urban areas. At the periphery of Mexico City, illegal human settlements produced different levels of disturbance on natural plant communities developed on a lava field near the Ajusco mountain range. We assessed natural regeneration of plant communities 20 years after the abandonment of the settlements, in sites that received low (manual harvesting of non-timber forest products), medium (removal of aboveground vegetation), and high (removal of substrate and whole vegetation) disturbance levels. We also tested the potential facilitative role played by dominant tree and shrub species. Plant diversity and vegetation biomass decreased as disturbance level increased. Sites with high disturbance level showed poor regeneration and the lowest species similarity compared to the least disturbed sites. Six dominant species (i.e., those with the highest abundance, frequency, and/or basal area) were common to all sites. Among them, three species (the tree Buddleja cordata, and two shrubs, Ageratina glabrata and Sedum oxypetalum) were identified as potential facilitators of community regeneration, because plant density and species richness were significantly higher under their canopies than at open sites. We propose that analyzing community structural traits of the successional vegetation (such as species diversity and biomass) and identifying potential facilitator species are useful steps in assessing the recovery ability of plant communities to anthropogenic disturbances, and in designing restoration strategies.     

Livestock Settlement Dynamics in Drylands: Model application in the Monte desert (Mendoza,Argentina)

Human settlements in arid environments are becoming widespread due to population growth, and without planning, they may alter vegetation and ecosystem processes, compromising sustainability. We hypothesize that in an arid region of the central Monte desert (Mendoza, Argentina), surface and groundwater availability are the primary factors controlling livestock settlements establishment and success as productive units, which affect patterns of degradation in the landscape. To evaluate this hypothesis we simulated settlement dynamics using a Monte Carlo based model of Settlement Dynamics in Drylands (SeDD), which calculates probabilities on a gridded region based on six environmental factors: groundwater depth, vegetation type, proximity to rivers, paved road, old river beds, and existing settlements. A parameter sweep, including millions of simulations, was run to identify the most relevant factors controlling settlements. Results indicate that distances to rivers and the presence of old river beds are critical to explain the current distribution of settlements, while vegetation, paved roads, and water table depth were not as relevant to explain settlement distribution. Far from surface water sources, most settlements were established at random, suggesting that pressures to settle in unfavorable places control settlement dynamics in those isolated areas. The simulated vegetation, which considers degradation around livestock settlements, generally matched the spatial distribution of remotely sensed vegetation classes, although with a higher cover of extreme vegetation classes. The model could be a useful tool to evaluate effects of land use changes, such as water provision or changes on river flows, on settlement distribution and vegetation degradation in arid environments.     

长白山红松阔叶混交林森林天然更新条件的研究

研究长白山红松阔叶混交林森林天然更新的变化规律及其条件,红松阔叶混交林是长白山主要的森林类型,保存不多,对于研究以前森林经营有重要意义。研究的目的在于揭示红松天然更新规律及其与森林组成结构的关系。研究结果表明,红松阔叶混交林天然更新与森林群落类型,海拔,森林植物条件及人类活动等干扰极大关系,一般在陡坡或山脊上胡枝子作树红松林中,那里林冠郁闭度达到80％－90％或更大,林分中红松组成也更大,红松天然更新良好。每公顷有红松幼苗和小幼树万株以上,但是在郁闭的红松林冠下,很少能长大。在大部分的阔叶红松混次林中,除了林冠比较郁闭的地方外,针叶树包括红松在内的天然更新通常稀少,每公顷仅有幼苗幼树数千株,其中大部是阔叶树,随着海拔上升到一定范围,在更新中云冷杉的成分增加,老择伐迹地由于林下植被密,常常缺乏更新。74．2％耐荫树种的幼苗幼树是在林冠下观查到,它们70％以上分布于离立木2．5 m以内,这正好等于林木平均冠幅的半径,所以,红松和耐荫树种幼苗的更新最好是在郁闭的林分下。     

Extraction of non-timber forest products in the forests of Biligiri Rangan Hills, India. 5. Influence of dispersal mode on species response to anthropogenic pressures

We examined the response of forest tree species with different dispersal modes to anthropogenic pressure in a dry deciduous forest of South India. The species and their populations were sampled in two forest stands, one in proximity to a Soliga settlement (greater disturbance) and the other distant to the settlement (lower disturbance). Our results suggest that the populations of animal dispersed species than those of wind or passively dispersed species are more vulnerable to human disturbance. In fact wind dispersed species seem to be facilitated by human disturbances. The proximal site had a higher representation of understory plants and seedling belonging to wind dispersed species than that of animal dispersed species. We discuss the results in the context of the role of dispersal mode in shaping species response, and vegetation composition of forest to anthropogenic pressures.     

Local‐ and landscape‐level effects of land use change on bird diversity in Abiata‐Shalla Lakes National Park,Ethiopia

Understanding the effects of anthropogenic disturbances on biodiversity is important for conservation prioritization. This study examined the effects of vegetation degradation on bird diversity in Abiata‐Shalla Lakes National Park, Ethiopia. We surveyed birds and vegetation structure between January and March 2015 in disturbed (impacted by settlement and agriculture) and undisturbed (not impacted) transects of two vegetation types (savannah woodland and gallery forest). We compared between disturbed and undisturbed transects at local (within vegetation types) and landscape (across vegetation types) levels: (a) avian species richness of the entire assemblage and feeding guilds and (b) species assemblage composition. We found significantly greater mean and total bird species richness of the entire assemblage and insectivore and granivore feeding guilds in the undisturbed transects, while the nectarivore guild was totally absent in the disturbed transects. We also found significant differences in bird species assemblage composition between the disturbed and undisturbed transects both within and across the vegetation types, and bird species assemblage composition at the landscape level was positively correlated with tree abundance and understorey vegetation height. In conclusion, our results demonstrate and add to the increasing body of evidence concerning the adverse effects of human‐induced vegetation change on bird diversity.     

Diversity and distribution of ground-dwelling ants in a lowland rainforest in southeast Cameroon

Detailed information on the ground-dwelling ant diversity and distribution in the rainforests of the Congo Basin is lacking so far. A new ant species list from a continuous mixed secondary lowland rainforest on the northern periphery of the Dja Biosphere Reserve in southeast Cameroon is presented. We investigated the effect of vegetation type on ant species density, activity and composition. Ants were collected by pitfall trapping in seven vegetation types in each of three seasons during 12 months in 2003 and 2004–2005. Our site in Cameroon had a total observed ant diversity of 145 species. Vegetation type significantly influenced the ground-dwelling and -foraging (arboreal) ant assemblages. Differences in species density, activity and composition between vegetation types were explained not only by soil type (hydromorphous – terra firme), but also by developmental stage of vegetation types. The highly inundated Raphia-swamp had the lowest ant species density and activity. Older secondary forests still had a different species composition than near primary forest even after 25 years of recovery after anthropogenic disturbance. Finally, the high ant species number captured by our pitfalls, the absence of the invasive exotic ant Wasmannia auropunctata and the high Dorylus (Anomma) army ant diversity confirm the importance of the Cameroonian rainforest for biodiversity conservation programs. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. Received 4 October 2006; revised 4 June 2007; accepted 2 July 2007.     

泸沽湖生态系统格局变化及其驱动力

运用遥感影像与地理信息系统技术结合,采用生态系统信息分类提取方法和景观指数方法对1990年至2015年泸沽湖风景区生态系统构成与格局变化进行分析,并进一步探析引起各类生态系统变化的驱动力因素,为泸沽湖风景区进一步生态与环境规划提供科学和理论依据。25年间,泸沽湖风景区内主要生态系统类型可分为农田、森林、草地、水域和人居环境等五类生态系统,1990年至2005年,主要表现为农田、森林、草地3个生态系统之间相互转化;2005年至2015年,主要表现为森林、草地、水域生态系统整体流向农田、人居环境系统。总体上泸沽湖景观破碎化与复杂程度呈下降趋势,连通性和整体性逐渐增强,但各生态系统类型之间比例差异增大。农田生态系统变化的主要驱动力是政策导向;森林与草地生态系统变化的主要驱动力是退耕还林还草工程与人类活动;水域生态系统变化主要驱动因素是湿地造林与人类活动入侵;人居环境系统变化的主要驱动因素为人类用地需求的增涨。针对泸沽湖生态系统变化存在的问题提出了相应的规划建议。     

Germinable soil seed banks of anthropogenic native grasslands and grassy forest remnants in temperate south-eastern Australia

Soil seed banks of anthropogenic native grassland and grassy forest remnants on the Gippsland Plain in south-eastern Australia were studied using the seedling emergence method. Intact examples of both ecosystems are rare, owing to extensive agricultural development. Both ecosystems are assumed to have been derived since European settlement from the same original, grassy forest ecosystem. It was hypothesised that species now restricted to grassland remnants might persist in the soil seed bank of forest remnants, and vice versa. This hypothesis was not supported. In total, 25554 seedlings of at least 155 species emerged from forest and grassland seed banks collectively. Small-seeded, annual and perennial herbs were most abundant. Forest seedbanks differed substantially in composition from grassland seedbanks, and both essentially contained a subset of the species in the vegetation. Forest seedbanks contained significantly more species and individuals of annual and perennial native dicotyledons than grassland seedbanks. Seedbanks made a major contribution to local diversity, since many species in the seed bank at each quadrat were not recorded from the vegetation, but only a minor contribution to regional diversity. Species in the seedbank that were absent from all vegetation samples were recorded at few quadrats, except Juncus species, which were widespread and abundant in the seedbank. The apparent absence from forest seed banks of species that are best represented in grassland remnants (and vice versa), suggests that there is little opportunity of recruiting grassland-restricted species in forest remnants by instigating grassland management practices.     

The legacy of forest logging on organic matter inputs and storage in tropical streams

Riparian forests play an important role in stream ecosystems, as they support biodiversity, reduce water erosion, and provide litter that fuels aquatic biota. However, they are affected by great array of anthropogenic threats (e.g., fire, logging, and organic pollution), which alter species composition and their physical structure. Although forest recovery after disturbance such as logging can take decades, the legacy of forest clear-cut logging on key processes in tropical riparian ecosystems is mostly unknown. Here, we investigated how litter inputs (leaves, twigs, and reproductive parts) and storage, key processes for carbon and nutrient recycling and for forest and stream biota, are influenced by riparian vegetation undergoing succession (after 28 years from logging) through the comparison of reference and logged forest sites in the Cerrado biome. Litterfall was overall similar between forest types, but litterfall of twigs was twofold higher at logged than reference sites. Similarly, litter inputs from the bank to the stream (i.e., lateral inputs) and streambed storage were 50–60% higher at logged than reference sites. The higher litterfall observed in logged forests could be related to higher proportion of tree species that are characteristic of primary and secondary successional stages, including fast-growing and liana species, which often are more productive and common in anthropogenic areas. Our results showed that the legacy impact of clear-cut logging, even if residual woody vegetation is maintained in riparian buffers, can shift the type, quantity, and seasonality of litter subsidies to tropical streams. This knowledge should be considered within the context of management and conservation of communities and ecosystem processes in the forest-stream interfaces.     

Modern pollen rain in mangroves from San Andres Island, Colombian Caribbean

The precise characterisation of present-day mangrove ecosystems from modern pollen rain facilitates the accurate use of fossil pollen data for late Quaternary sea level and environmental reconstructions. Here, we investigate whether the analysis of pollen rain data corroborates existing floristic and structural characterisation of different mangrove types at the Caribbean island of San Andrés, Colombia. At 82 plots along 20 transects of four distinct mangrove types, samples were obtained of (i) surface sediments for pollen analysis, and (ii) a range of environmental parameters (including inundation levels, salinity and pH). This information was compared to previously sampled mangrove composition and tree basal area. In surface sediment samples 82 pollen taxa were found, from which 19 were present in the vegetation plots. However, because pollen may be transported by wind and/or watercourses, the overall floristic composition of the different forest types may not necessarily be reflected by the pollen spectra. Local vegetation (i.e. mangroves and beach) represented > 90% of the pollen spectra, while the regional one (i.e. hinterland forests) represented < 5% of it. Unlike the four mangrove types that were previously described in the vegetation, the analysis of pollen samples suggested only three distinct types of forest.The groups were characterised based on (i) the dominance of at least one of the true mangrove species from pollen data ordination and the presence of associated species, and (ii) their relationship with environmental parameters. Rhizophora was present in all plot samples, but did not contribute to forest type separation. In fact, just three true mangrove species proved reliable indicators of (i) high salinity and fringe mangroves (i.e. Avicennia), (ii) high pH levels and landward mangroves (i.e. Conocarpus), and (iii) natural or anthropogenic caused disturbance of forest stands (Laguncularia and associated Acrostichum fern). Hence our study confirms that mangrove pollen spectra can be accurately used to describe different mangrove environments for fossil based palaeoecological reconstructions.     

Forest cover and heterogeneous pastures shape the diversity of predatory rove beetles in tropical riparian habitats

In tropical landscapes, forest remnants have been reduced to narrow strips of vegetation along rivers and streams surrounded by agricultural land that affects biodiversity, depending on the habitat and landscape characteristics. To assess the effect of riparian forest loss on the diversity of Staphylininae predatory rove beetles, we considered two habitat conditions (river sites with riparian vegetation and sites with heterogeneous pastures) within two micro-basin types (with >70% and <40% forest cover) in a tropical montane cloud forest landscape, Mexico. Beetles were collected using baited pitfall traps during the rainy season of 2014. No differences were found between micro-basin types and, although species richness (⁰D) was similar between habitat conditions, when the diversity of common (¹D) and dominant (²D) species was considered, sites with heterogeneous pastures were almost twice as diverse as those with riparian vegetation. All diversity measurements were greater in sites with heterogeneous pastures of either micro-basin type. Air temperature and canopy cover were the environmental variables that best explained the variation in beetle species composition. The greatest environmental differences related to species composition were detected between habitat conditions and were more evident in sites with heterogeneous pastures and low forest cover in the surroundings. The results suggest that replacing riparian vegetation with heterogeneous pastures, within micro-basins that lost between 30% and 60% of their forest cover, does not significantly reduce the diversity of predatory rove beetle but rather modifies the beetle composition. Effective formulation of management strategies to mitigate the impact of land use modification therefore requires an understanding of the interaction between vegetation remnants and landscape characteristics.     

Effects of an invasive alien tree on the diversity and temporal dynamics of an insect assemblage on an oceanic island

Native vegetation is frequently replaced by alien plants on isolated oceanic islands. The effects of such replacements by invasive plants on the diversity and temporal dynamics of island-endemic insects remain unclear. We examined flying insect communities using Malaise traps on the small island of Nishi-jima in the oceanic Ogasawara Archipelago in the northwestern Pacific. On the island, an alien tree, Casuarina equisetifolia, has become dominant, occupying 57.3?% of the vegetation area. The species richness, composition, and abundance of pollinators (bees), predators (wasps), and wood-boring beetles (cerambycids, mordellids, and elaterids) were compared in each summer season of 4?years among three vegetation types: C. equisetifolia forest, natural forest, and grassland. In the traps, 82.3?% of species captured were endemic to the archipelago. The grassland harbored the highest species richness of native bees and wasps, whereas the natural forest had the highest species richness of native wood-boring beetles. The C. equisetifolia forest had the poorest species richness for most insect groups. Principal response curves indicated that differences in species composition among the three vegetation types were consistent through time for all insect groups. Most insect species were more abundant in natural forest or grassland than in C. equisetifolia forest. Standard deviations in both the numbers of individuals and species estimated under a Bayesian framework suggested that annual fluctuations of abundance and species density were similar among vegetation types (except for elaterid abundance). Therefore, replacement by C. equisetifolia has likely altered insect species composition but has not necessarily dramatically affected the temporal dynamics of insect assemblages on the island.     

India's biodiversity hotspot under anthropogenic pressure: A case study of Nilgiri Biosphere Reserve

This paper presents data on the impact of biotic pressure in terms of grazing by livestock and wood cutting by humans on the plant community in the Nilgiri Biosphere Reserve of India. Grass, and herbaceous plant biomass, number of cattle dung piles, number of woody stems available and damaged by human activities and weed biomass were assessed at different proximity along transects radiating from village-forest boundary to forest interior to measure the ecological impact of livestock grazing and fire wood collection. The grass biomass was positively correlated to overgrazing indicating the adverse effect on natural vegetation by cattle. Woodcutting was intense along the forest boundary and significantly declined as distance increased. Similarly, weed biomass and number of thorny species declined positively with proximity from village-forest boundary and the weed biomass was significantly higher in the pastoral sites compared to residential sites. The results suggest that human impact adversely affects natural vegetation and promotes weed proliferation in forest areas adjoining human settlements in the ecologically important Nilgiri Biosphere Reserve. Continued anthropogenic pressure could cause reduction in fodder availability to large herbivores like elephants, which in turn leads to an increase in human–elephant conflict.     

Pastoralist's livestock and settlements influence game bird diversity and abundance in a savanna ecosystem of southern Kenya

We investigated the vegetation structure and density of game birds along a successional gradient created by varying intensity of human settlement in a pastoral community in Shompole group ranch in southern Kenya. We examined four habitat types including heavily-grazed grass in currently occupied settlements, short grass in seasonal settlements, patches of bushed woodland in settlement sites that had been abandoned up to 30 years ago, and tall grass in a wildlife sanctuary. Vegetation biomass was the highest in the sanctuary where livestock are excluded and the lowest in the vicinity of currently occupied settlements. Abundance of doves ( Oena spp . and Streptopelia spp. ) was best associated with moderate grazing and per cent green grass, which provide good foraging opportunities. Francolin and spurfowl ( Francolinus spp .) were positively associated with vegetation biomass. Quail ( Coturnix spp .) were positively associated with tree cover. These data reflect the importance of maintaining a balance of wildlife and livestock grazing with patches of ungrazed grasslands and bushed woodlands in providing a mosaic of habitats that support a diverse population of game birds. The results have wide application for an integrated management approach to livestock, wildlife and game bird management in the savannas.     

How pastoralism changes savanna vegetation: impact of old pastoral settlements on plant diversity and abundance in south-western Kenya

For centuries, pastoralists have influenced savanna ecology through their construction of settlements, traditional movement patterns in search of forage, water and safety for their livestock. Construction of settlements initiates localised changes in the vegetation due to clearance of vegetation at construction and collection of construction materials. During the occupation period a lot of dung is deposited in and around settlements. When pastoral families abandon settlements and move away, they leave behind mud huts and livestock corrals surrounded by fences. These sites become nutrient-rich patches supporting a different abundance and diversity of plants and large mammals compared to the rest of the savanna. This study aimed to broaden our understanding of how pastoral land use influences plant diversity in East African savannas. Past work on the effects of settlements has been done in dry places (<600 mm rainfall) with relatively poor soils. To complement and extend these studies, we selected a contrasting site with high rainfall and rich soils in the Mara ecosystem of south-western Kenya. We sampled the occurrence of different plant species along transects radiating from 28 settlements abandoned by pastoralists and ranging in age from 2 months to 48 years on two different soil types. Mean plant species richness and abundance peaked at intermediate distances, 12.5 and 25 m from the edges of settlements. We recorded a total of 210 plant species during the study, 65 of which occurred only within the impact ring of the abandoned settlements. The effects of settlements on plants were stronger on shallow sandy soils than on deep clay soils. Our findings show that abandoned settlements were key sites for regeneration and replenishment of shrubs harvested by the Maasai, but support few other plants of biodiversity value. These unique habitat patches in the savanna ecosystem are under threat as pastoral Maasai become increasingly sedentary and as wildlife conservancies are established, thus reducing the number of abandoned settlements. In essence, the Maasai, by changing their traditional lifestyle, will reduce these nutrient hotspots and hence landscape heterogeneity and biodiversity.     

The activity of a subterranean small mammal alters Afroalpine vegetation patterns and is positively affected by livestock grazing

Subterranean rodents can act as ecosystem engineers by shaping the landscape due to soil perturbation and herbivory. At the same time, their burrow density is affected by environmental conditions, vegetation and anthropogenic factors. Disentangling this complex interplay between subterranean rodents and their environment remains challenging. In our study, we analysed the interplay of abiotic conditions, vegetation patterns and human land-use and the burrow density of the giant root-rat (GRR; Tachyoryctes macrocephalus), a subterranean rodent endemic to the Afroalpine ecosystem of the Bale Mountains in south-east Ethiopia. Specifically, we examined the effects of GRR on plant species richness and vegetation cover and vice-versa, and how these reciprocal effects might be modulated by temperature, habitat wetness and grazing. Our results showed that increasing GRR burrow density led to decreased vegetation cover, and that effects of GRR on vegetation cover were slightly stronger than vice-versa. Considering the reciprocal causation models, we found that increasing plant species richness led to increased GRR burrow density, while GRR burrow density decreased as vegetation cover increased. Increases in habitat wetness and livestock grazing intensity also directly led to increased GRR burrow density. Our results stress the importance of subterranean ecosystem engineers on vegetation and highlight the vulnerability of these complex interactions to human activity.     

Temperature‐related shifts in butterfly phenology depend on the habitat

Many species are becoming active earlier in the season as the climate becomes warmer. In parallel to phenological responses to climate change, many species have also been affected by habitat changes due to anthropogenic land use. As habitat type can directly affect microclimatic conditions, concurrent changes in climate and habitat could have interacting effects on the phenology of species. Temperature‐related shifts in phenology, however, have mostly been studied independent of habitat types. Here, I used long‐term data from a highly standardized monitoring program with 519 transects to study how phenology of butterflies is affected by ambient temperature and habitat type. I compared forests, agricultural areas and settlements, reflecting three major land use forms, and considered butterfly species that were observed in all three of these habitats. Seasonal appearance of the butterflies was affected both by the ambient temperature and the habitat type. As expected, warmer temperatures led to an overall advancement of the appearance and flight period of most species. Surprisingly, however, phenology of species was delayed in settlement habitats, even though this habitat type is generally associated with higher temperatures. A possible explanation is dispersal among habitat types, such that source–sink effects affect local phenology. When there is little productivity in settlement areas, observed butterflies may have immigrated from forest or agricultural habitats and thus appear later in settlements. My findings suggest that a spillover of individuals among habitats may affect phenology trends and indicate that phenological studies need to be interpreted in the context of habitat types. This becomes especially important when defining strategies to prevent or mitigate effects of climate and land‐use changes on phenology and abundance of species.     

Moderate Human Disturbance of Rain Forest Alters Composition of Fruiting Plant and Bird Communities

Forests worldwide are experiencing rapid environmental change due to human activity. We aimed to increase understanding of anthropogenic impacts on community composition and species interactions. In a natural experiment, we asked whether subsistence human land use has altered the community composition of a Neotropical rain forest on the island of Tobago, in the West Indies. We surveyed fruiting plants and birds in three adjacent habitat types that varied in level of disturbance, and used multivariate analyses to determine whether changes in the plant community were associated with differences in avifauna composition. The three forest habitats had similar plant and bird diversities, yet markedly different species compositions and abundances. Primary forest had the most diverse plant community, while disturbed habitats had a more homogeneous plant composition. Primary and disturbed forest had distinct community compositions, with canopy cover and the relative abundance of plant types explaining 83 percent of the variation in bird species assemblages. Seemingly moderate human disturbance has led to substantial changes in the plant and bird assemblages of Tobago's rain forest, outside of a protected reserve. Our study highlights the direct links between human disturbance and the structure of rain forests, underscoring the impact of even moderate activity on community composition.     

Disturbances and species distribution of the riparian vegetation of a Rift Valley stream

The Njoro River riparian vegetation species composition, distribution, disturbances and uses are presented and discussed. Montane Juniperus procera-Olea europaea spp. africana and submontane Acacia abyssinica forests were identified as the main riparian vegetation groups. Approximately 55% of the riparian vegetation species are used for herbal medicine, treating more than 330 health problems, and only 11% of the plants are edible. Albizzia gummifera in the Syzygium cordatum-Pittosporum abyssinicum-Hibiscus diversifolius forest is cut selectively for herbal medicine preparations. Disturbances on the riparian vegetation zone are broadly classified as those induced by man, livestock and wildlife. Comprehensive effects of disturbance included loss of vegetation vertical strata, increase/decrease of species diversity, introduction of alien plant species, and reduction of plant sizes and vegetation hectarage. The effects of grazing on the vegetation were severe around livestock watering points. Grazing and browsing by wildlife were the main disturbances of the vegetation near the Njoro River estuary at the Lake Nakuru National Park. Periodic flooding, as a natural disturbance, regulates growth and survival of vegetation at the Lake Nakuru drawdown. Quantification of species diversity and the extent of disturbance by humans and livestock is important for future management of the vegetation and, consequently, the river.     

The impact of forest transformation on stand structure and ground vegetation in the southern Black Forest, Germany

The goal of this study was to investigate the effects of 'ecologically orientated' forest transformation on forest floor vegetation. Forest transformation, as defined by the BMBF southern Black Forest project group, is the process which converts even-aged spruce forest into structured continuous-cover forest, consisting principally of spruce (Picea abies), fir (Abies alba) and beech (Fagus sylvatica). In order to analyse the transformation process, four transformation stages were defined as part of a 'conceptual forest development model' (pure even-aged, species enrichment, structuring and continuous cover forest stage). Four forest districts representative of the southern Black Forest were selected for the study. The analysis included the separate classification of structures, sites, and ground vegetation. In a second step, the relationships between the three complexes were analysed. The influence of forest structure on ground vegetation was investigated by examining the relationships between so-called substructure types and ground vegetation types. The substructure types associated with the pure spruce stand, species enrichment and continuous cover forest stages exhibited a ground vegetation resembling that of the Luzulo-Fagetum and Luzulo-Abietetum, whereas the structuring stages exhibited a ground vegetation of the Galio-Fagetum type. Transformation of pure, even-aged spruce forest into mixed, uneven-aged continuous cover forest is considered an important silvicultural tool to combine the demands of sustainable timber production and nature conservation. Transformation brings about greater diversity in stand structure and tree species composition. The frequencies of acidophytic mosses and vascular plants in spruce forest decrease during the transformation process. The species requiring moderate base supply increase over the transitional stages. The continuous cover forest, the final stage of transformation, increasingly contains ground species of both, i.e., species normally associated with both conifer and deciduous forest.