Abandonment and Expansion of Arable Land in Europe

Abandonment of arable land is often assumed to happen mostly in marginal areas where the conditions for arable cultivation are relatively unfavorable, whereas arable expansion is expected to occur mostly in areas with favorable conditions. This assumption, used in many land-use change forecasts, was never properly tested, mainly because the relatively short period of full-coverage land-use inventories did not allow a systematic analysis of the phenomena. With the recent release of CORINE 2006 this has changed. In this article, we explore the typical locations of abandonment and expansion of arable land in Europe during the period 1990–2006 by means of logistic regressions. More specifically, we test whether or not locations of abandonment and expansion can be inferred from the location characteristics of arable land in 1990. If the above assumption holds, this should be the case. We demonstrate that although arable expansion indeed happens in locations that resemble the bulk of arable land in 1990 (the presumably favorable locations), arable abandonment does not necessarily happen in locations that resemble the bulk of uncultivated land (that is, the presumably unfavorable locations). In other words, the assumption does not hold. Particularly, areas close to the road network were found to be associated with both high abandonment rates and high expansion rates, which suggest that abandonment is not limited to areas that are marginal in terms of agricultural production.     

European Vegetation Survey: update on progress

Abstract. Progress in the European Vegetation Survey is described. 25 countries are now represented in a network committed to common data standards in phytosociological survey, the development of compatible software for data analysis and mapping, the encouragement of national programmes and the development of an overview of European plant communities. Advances in each of these areas of activity is summarised and plans for the future are outlined, most notably the production of a book ‘The Vegetation of Europe’.     

Invasive Congeners Differ in Successional Impacts across Space and Time

Invasive species can alter the succession of ecological communities because they are often adapted to the disturbed conditions that initiate succession. The extent to which this occurs may depend on how widely they are distributed across environmental gradients and how long they persist over the course of succession. We focus on plant communities of the USA Pacific Northwest coastal dunes, where disturbance is characterized by changes in sediment supply, and the plant community is dominated by two introduced grasses – the long-established Ammophila arenaria and the currently invading A. breviligulata. Previous studies showed that A. breviligulata has replaced A. arenaria and reduced community diversity. We hypothesize that this is largely due to A. breviligulata occupying a wider distribution across spatial environmental gradients and persisting in later-successional habitat than A. arenaria. We used multi-decadal chronosequences and a resurvey study spanning 2 decades to characterize distributions of both species across space and time, and investigated how these distributions were associated with changes in the plant community. The invading A. breviligulata persisted longer and occupied a wider spatial distribution across the dune, and this corresponded with a reduction in plant species richness and native cover. Furthermore, backdunes previously dominated by A. arenaria switched to being dominated by A. breviligulata, forest, or developed land over a 23-yr period. Ammophila breviligulata likely invades by displacing A. arenaria, and reduces plant diversity by maintaining its dominance into later successional backdunes. Our results suggest distinct roles in succession, with A. arenaria playing a more classically facilitative role and A. breviligulata a more inhibitory role. Differential abilities of closely-related invasive species to persist through time and occupy heterogeneous environments allows for distinct impacts on communities during succession.     

Effect of Low Vegetation on the Recruitment of Plants in Successional Habitat Types1

I assessed the role of low vegetation (plants ca 1 yr old and ≤50 cm tall) as a biotic facilitator or barrier in the recruitment of different growth forms and species in primary forests, secondary forests, and old‐fields (abandoned pastures) in southeastern Mexico. I removed by hand all plants (≤100 cm tall, including roots) and litter from 20, 0.25 m² plots in each habitat. For 1 yr, I counted the number of plant species (5–50 cm tall) recruited, grouped them into different growth forms, and compared them to undisturbed control plots. Prior to manipulation, the standing density of trees and lianas was highest in primary and secondary forests. Shrubs were more abundant in secondary forests, whereas herbs, epiphytes, and hemi‐epiphytes were more abundant in old‐fields. Herbaceous plants appeared as important components of the community in all habitats. The removal of low vegetation increased total plant recruitment in all habitats. Considering each growth form, the absence of vegetation increased recruitment in primary forests for herbs, in secondary forests for epiphytes and hemi‐epiphytes, in old‐fields for trees, and for lianas in primary forests and old‐fields. In vegetation removal plots, recruitment of species was greater in pastures, lower in secondary forest, and similar in primary forest with respect to control plots. Depending on habitat type, species, and growth form, the presence of low vegetation may act as a recruitment barrier or facilitator for different species, affecting plant community structure, diversity, and composition in different habitats.     

Anthropogenic Habitats Facilitate Dispersal of an Early Successional Obligate: Implications for Restoration of an Endangered Ecosystem

Landscape modification and habitat fragmentation disrupt the connectivity of natural landscapes, with major consequences for biodiversity. Species that require patchily distributed habitats, such as those that specialize on early successional ecosystems, must disperse through a landscape matrix with unsuitable habitat types. We evaluated landscape effects on dispersal of an early successional obligate, the New England cottontail (Sylvilagus transitionalis). Using a landscape genetics approach, we identified barriers and facilitators of gene flow and connectivity corridors for a population of cottontails in the northeastern United States. We modeled dispersal in relation to landscape structure and composition and tested hypotheses about the influence of habitat fragmentation on gene flow. Anthropogenic and natural shrubland habitats facilitated gene flow, while the remainder of the matrix, particularly development and forest, impeded gene flow. The relative influence of matrix habitats differed between study areas in relation to a fragmentation gradient. Barrier features had higher explanatory power in the more fragmented site, while facilitating features were important in the less fragmented site. Landscape models that included a simultaneous barrier and facilitating effect of roads had higher explanatory power than models that considered either effect separately, supporting the hypothesis that roads act as both barriers and facilitators at all spatial scales. The inclusion of LiDAR-identified shrubland habitat improved the fit of our facilitator models. Corridor analyses using circuit and least cost path approaches revealed the importance of anthropogenic, linear features for restoring connectivity between the study areas. In fragmented landscapes, human-modified habitats may enhance functional connectivity by providing suitable dispersal conduits for early successional specialists.     

海南坡鹿栖息地植被覆盖变化研究

根据不同时期的Landsat TM卫星遥感图像,分别提取海南坡鹿Cervus eldi hainanus栖息地海南大田国家级自然保护区及周边地区的归一化植被指数(Normalized Difference Vegetation Index, NDVI).1991年保护区和周边地区的NDVI平均值分别为0.2485和0.291,而2001年的NDVI平均值分别为0.1272和0.0827,表明海南大田国家级自然保护区和周边地区的植被覆盖均下降,且周边地区植被覆盖下降幅度较大.保护区植被覆盖的下降是植被改造的结果,有利于坡鹿及栖息地的保护与发展;保护区周边地区植被覆盖下降是垦荒和采伐等人为干扰所致,是导致坡鹿栖息地丧失或破坏的重要原因.人类活动是植被覆盖变化的主要因素.建议自然保护区的规划应为濒危物种保护的未来留下空间.     

Impacts of ozone on forests: a European perspective

In comparison with the effects of extended drought periods or severe nutrient stress, those of ozone are generally much milder, at least with respect to growth. However, there is substantial evidence from experiments, in the main using young saplings, that O₃ does impose a stress on forest trees under European conditions. Decreased chlorophyll contents and photosynthetic rates, changes in carbon allocation, increased antioxidant activity, and reductions in biomass due to O₃ have often been recorded, particularly in fast-growing species. Furthermore, ₃ appears to weaken the trees' resilience to a range of biotic and abiotic stresses. Interactions between O₃ and climatic stress, in particular drought and frost hardiness, are likely to result in potentially detrimental effects.
A link between the occurrence of O₃ and forest damage is not unequivocally established in Europe, and the problem remains of extrapolating and/or scaling up from studies on seedlings to predict responses to O₃ of mature trees and forest stands, because we know so little about acclimation to O₃. An accurate assessment is also lacking of the magnitude of the O₃ effect on European trees both in terms of the forest areas affected and its extent. In this review we suggest that C allocation is the key factor underlying the responses of trees to O₃. Stomata also play a key role, since the acquisition of C must be achieved while an effective control over water consumption is retained.     

Prediction of Vegetation Succession in Human-Disturbed Habitats Using an Expert System

Detailed information, both quantitative and observational, on the course of vegetation succession in various human-disturbed habitats in Central Europe was used to construct an expert system named SUCCESS. Using the system, it is possible to predict tentatively the sequence of seral stages and dominant species exchange in successional seres initiated on bare ground and lasting up to 50 years. Simple information on geographical position, type of substratum, relief, moisture, nutrient content, character of surrounding vegetation, and size of the disturbed area is taken into consideration to predict site-specific succession in the particular habitats. The expert system is supposed to help landscape managers, nature conservationists, and environmental impact assessment experts in decision-making procedures to take into account the development of vegetation in man-made sites. Moreover, it also summarizes scientific information on the pattern of vegetation change in human-disturbed habitats in the geographical area considered.     

The Impact of Land Abandonment on Species Richness and Abundance in the Mediterranean Basin: A Meta-Analysis

Land abandonment is common in the Mediterranean Basin, a global biodiversity hotspot, but little is known about its impacts on biodiversity. To upscale existing case-study insights to the Pan-Mediterranean level, we conducted a meta-analysis of the effects of land abandonment on plant and animal species richness and abundance in agroforestry, arable land, pastures, and permanent crops of the Mediterranean Basin. In particular, we investigated (1) which taxonomic groups (arthropods, birds, lichen, vascular plants) are more affected by land abandonment; (2) at which spatial and temporal scales the effect of land abandonment on species richness and abundance is pronounced; (3) whether previous land use and current protected area status affect the magnitude of changes in the number and abundance of species; and (4) how prevailing landforms and climate modify the impacts of land abandonment. After identifying 1240 potential studies, 154 cases from 51 studies that offered comparisons of species richness and abundance and had results relevant to our four areas of investigation were selected for meta-analysis. Results are that land abandonment showed slightly increased (effect size  = 0.2109, P<0.0001) plant and animal species richness and abundance overall, though results were heterogeneous, with differences in effect size between taxa, spatial-temporal scales, land uses, landforms, and climate. In conclusion, there is no “one-size-fits-all” conservation approach that applies to the diverse contexts of land abandonment in the Mediterranean Basin. Instead, conservation policies should strive to increase awareness of this heterogeneity and the potential trade-offs after abandonment. The strong role of factors at the farm and landscape scales that was revealed by the analysis indicates that purposeful management at these scales can have a powerful impact on biodiversity.     

Insect Herbivory and Leaf Disease in Natural and Human Disturbed Habitats: Lessons from Early‐Successional Heliconia Herbs

The interaction of plants with insect herbivores and fungal pathogens can affect community dynamics, but there is little information on how this antagonistic interaction may be altered in human‐disturbed tropical systems. We examined whether the amount and quality of foliar damage on the pioneer herbs Heliconia latispatha and Heliconia collinsiana are distinct on road edges and secondary riparian vegetation compared with natural gaps in continuous forest (controls) in Mexico. We also investigated some physical and biological mechanisms that may jointly explain such differences. The overall insect damage in H. latispatha was similar between road edges and natural forest gaps (8.0% vs. 7.2% of leaf area). Damage by caterpillars, however, decreased from 4.2 percent in forest gaps to 0.5 percent on road edges, whereas damage by leaf‐cutting ants increased from 0 to 5.8 percent. In secondary riparian vegetation, where none of the leaves sampled were attacked by ants, overall herbivore damage in H. collinsiana was less than half that observed in forest gaps (3.0% vs. 6.7%), and driven mainly by differences in caterpillar damage (2.5% vs. 6.2%). By contrast, attack by leaf fungal pathogens was two to three times greater in both human‐disturbed habitats than in gaps (8.2–9.6% vs. 3.7–4.2%). Potential mechanisms underlying these differences involved human‐induced shifts in air and soil temperature driven by greater light availability, as well as changes in relative humidity, leaf toughness, foliar condensed tannins, and local abundance of herbivores. Our results indicate that human disturbance alters insect herbivory and may increase proliferation of leaf disease. Abstract in Spanish is available in the online version of this article.     

Microtopography Influences Early Successional Plant Communities on Experimental Coal Surface Mine Land Reclamation

Surface mining for coal represents one of the dominant forms of anthropogenic disturbance to forests of the eastern United States. Reclamation methods adopted under federal law in the 1970s have led to a state of arrested succession, failing to achieve pre‐disturbance conditions. New methods of reclamation have been proposed with the goal of returning mined land to its former forested state through the use of compaction reducing techniques that significantly increase fine‐scale heterogeneity. The Forestry Reclamation Approach creates topographic heterogeneity by loosely dumping overburden material into large piles to serve as a tree‐planting medium. We examined the effect of fine‐scale topographic relief, soil physical properties, and reclamation method on early plant community development on a mine site in eastern Ohio. We sampled plots at four microtopographic positions and three distances from the remaining forest edge in both experimentally and traditionally reclaimed areas of a surface mine. Multivariate analysis of variance (ANOVA) on distance matrices indicated significant differences in plant community composition among microtopographic positions and reclamation methods. Microtopographic positions also exhibited significant differences in measured soil properties significantly affecting plant community composition. Plots in the traditionally reclaimed areas had no woody plant colonization, indicating arrested succession common to sites reclaimed using traditional methods. Our results suggest that the creation of topographic heterogeneity at the time of reclamation markedly accelerates ecological succession and promotes enhanced plant community diversity. Expanded application of the methods used here could allow for a faster return to the former forested state of mined lands than traditional reclamation methods.     

Ezrin蛋白信号转导通路及其对肿瘤侵袭转移的最新进展

肿瘤转移是一个多阶段、多途径、涉及多基因及其信号通路变化的一系列复杂过程。了解肿瘤转移相关基因的信号传导通路以及对肿瘤转移的作用机制,为寻找抑制肿瘤转移的关键靶点具有重要的意义。Ezrin高表达与肿瘤转移密切相关,它可通过改变肿瘤细胞极性及细胞运动、调节肿瘤细胞间黏附及细胞与细胞外基质黏附、参与肿瘤细胞内信号转导而影响恶性肿瘤转移。Ezrin过度表达可以破坏正常细胞内信号传递网络的平衡,其中主要涉及的为细胞信号转导相关分子(Rho)及受体酪氨酸蛋白激酶等信号传导途径。Ezrin借助于细胞内错综复杂的信号转导网络调控细胞的形态构成、黏附、吞噬、运动、血管形成等一系列的生物学过程,最终实现肿瘤细胞的侵袭和转移。本文就Ezrin蛋白的信号转导通路及其对肿瘤转移作用的研究进展做一综述。     

Vegetation of European springs: High-rank syntaxa of the Montio-Cardaminetea

Abstract. A survey of high-rank syntaxa of vegetation of European springs (class Montio-Cardaminetea) is presented. It shows the complexity of the class and the relations between the units. More than 1200 relevés were arranged into six phytosociological tables, each representing an alliance. A synoptic table comprising all alliances is presented. Bryo-phytes are the most important group in most of the communities, both regarding biomass and cover. The Adiantetea and the Montio-Cardaminetea are combined into one class. As to floristics and ecology, there are no obvious reasons to distinguish more than one order in this class. The vegetation of European springs is divided into six alliances: (1) Adiantion, split into two new suballiances, Adiantenion and Lycopodo-Cratoneurenion; (2) Cratoneurion commutati; (3) Cardamino-Montion - incl. three new suballiances: Mniobryo-Epilobienion hornemannii, Swertio-Anisothecienion and Cardamino-Montenion; (4) Dermatocarpion; (5) Epilobio nutantis-Montion; (6) Caricion remotae - incl. two new suballiances: Caricenion remotae and Cratoneuro filicini-Calthenion laetae. The alliances are floristically and ecologically characterized and their distributions in Europe shown on maps.     

European Vegetation Survey: Current state of some national programmes

Abstract. Vegetation survey programmes in Austria, Great Britain, the Netherlands and Germany are described. The aims of these programmes are discussed and their origin and motivation elucidated against the historical background of the development of phytosociology (as part of vegetation science) in particular countries. The Austrian, British and Dutch national vegetation surveys have been logistically supported by either basic-research (Austria) or nature-conservation (Great Britain and the Netherlands) funding organisations. They are either being published (British Plant Communities) or heading for publication of their first volumes within the next two years. The German vegetation survey is a voluntarily-based enterprise expected to complete its work by the end of this century. The experience gained by the management of these national surveys is of fundamental importance in launching the European Vegetation Survey (a project under preparation).     

Linking Land and Sea: Different Pathways for Marine Subsidies

Nutrients and energy derived from marine autotrophs subsidize shore ecosystems, increasing productivity and affecting food web dynamics and structure. In this study we examined how the inland reach of such inflow effects depends on vectors carrying the marine inflow inland and on landscape structure. We used stable isotopes of carbon and nitrogen to examine the roles of arthropod vectors in carrying marine-derived nutrients inland in two very different shore ecosystems: shore meadows in Sweden with marine inflows of algae and emerging chironomid midges; and sandy beaches and shore dunes in south-western Australia with marine inflows of algae and seagrass. In a colonization experiment, we found that deposited wrack on the beach is quickly colonized by both grazers and predators. However, in both systems we found a larger inland reach of the marine subsidy than could be accounted for by deposited macrophytes on shores alone, and that dipterans and spiders potentially functioned as vectors for the inflow. Our results indicate that marine inflows are important for near-shore terrestrial ecosystems well above the water’s edge, and that this effect is largely due to arthropod vectors (mainly dipterans and spiders) in both low-productivity sandy beach ecosystems at the Indian Ocean coast of Australia, and more productive shore meadows on the Baltic Sea coast of Sweden. Our findings also suggest that the type of vector transporting marine material inland may be as important as the productivity contrast between ecosystems for explaining the degree of marine influence on the terrestrial system.     

Changes in Soil Carbon and Nitrogen following Land Abandonment of Farmland on the Loess Plateau,China

The revegetation of abandoned farmland significantly influences soil organic C (SOC) and total N (TN). However, the dynamics of both soil OC and N storage following the abandonment of farmland are not well understood. To learn more about soil C and N storages dynamics 30 years after the conversion of farmland to grassland, we measured SOC and TN content in paired grassland and farmland sites in the Zhifanggou watershed on the Loess Plateau, China. The grassland sites were established on farmland abandoned for 1, 7, 13, 20, and 30 years. Top soil OC and TN were higher in older grassland, especially in the 0–5 cm soil depths; deeper soil OC and TN was lower in younger grasslands (<20 yr), and higher in older grasslands (30 yr). Soil OC and N storage (0–100 cm) was significantly lower in the younger grasslands (<20 yr), had increased in the older grasslands (30 yr), and at 30 years SOC had increased to pre-abandonment levels. For a thirty year period following abandonment the soil C/N value remained at 10. Our results indicate that soil C and TN were significantly and positively correlated, indicating that studies on the storage of soil OC and TN needs to focus on deeper soil and not be restricted to the uppermost (0–30 cm) soil levels.     

Species Richness-Environment Relationships of European Arthropods at Two Spatial Grains: Habitats and Countries

We study how species richness of arthropods relates to theories concerning net primary productivity, ambient energy, water-energy dynamics and spatial environmental heterogeneity. We use two datasets of arthropod richness with similar spatial extents (Scandinavia to Mediterranean), but contrasting spatial grain (local habitat and country). Samples of ground-dwelling spiders, beetles, bugs and ants were collected from 32 paired habitats at 16 locations across Europe. Species richness of these taxonomic groups was also determined for 25 European countries based on the Fauna Europaea database. We tested effects of net primary productivity (NPP), annual mean temperature (T), annual rainfall (R) and potential evapotranspiration of the coldest month (PET_min) on species richness and turnover. Spatial environmental heterogeneity within countries was considered by including the ranges of NPP, T, R and PET_min. At the local habitat grain, relationships between species richness and environmental variables differed strongly between taxa and trophic groups. However, species turnover across locations was strongly correlated with differences in T. At the country grain, species richness was significantly correlated with environmental variables from all four theories. In particular, species richness within countries increased strongly with spatial heterogeneity in T. The importance of spatial heterogeneity in T for both species turnover across locations and for species richness within countries suggests that the temperature niche is an important determinant of arthropod diversity. We suggest that, unless climatic heterogeneity is constant across sampling units, coarse-grained studies should always account for environmental heterogeneity as a predictor of arthropod species richness, just as studies with variable area of sampling units routinely consider area.     

Recovery of a Subtropical Dry Forest After Abandonment of Different Land Uses1

We studied the ecological characteristics of 45–50‐yr‐old subtropical dry forest stands in Puerto Rico that were growing on sites that had been deforested and used intensively for up to 128 yr. The study took place in the Guánica Commonwealth Forest. Our objective was to assess the long‐term effects of previous land use on this forest—i.e., its species composition, structure, and functioning. Previous land‐use types included houses, farmlands, and charcoal pits. Stands with these land uses were compared with a nearby mature forest stand. The speed and path of forest recovery after deforestation and land‐use abandonment depended on the conditions of the land. Study areas where land uses had removed the forest canopy and altered soil conditions (houses and farmlands) required a longer time to recover and had a different species composition than study areas where land uses retained a forest canopy (charcoal pits). Different forest attributes recovered at different rates. Crown area index, stem density, and litterfall rate recovered faster than stemwood and root, biomass, tree height, and basal area. Where previous land uses removed the canopy, Leucaena leucocephala, a naturalized alien pioneer species, dominated the regrowth. Native species dominated abandoned charcoal pits and mature forest. The change in species composition, including the invasion of alien species, appears to be the most significant long‐term effect of human use and modification of the landscape.     

Regional-Scale Assessment of Deer Impacts on Vegetation Within Western Connecticut,USA

Abstract: High densities of white-tailed deer (Odocoileus virginianus) are believed to cause broad-scale forest regeneration failure and loss of plant diversity. But, the empirical basis for such presumptions is limited. We, therefore, conducted a survey in western Connecticut, USA, woodlots to examine how spatial variation in deer densities influences variation in impacts on plant species abundance, identity and diversity, and tree regeneration. We also used a Geographic Information System to quantify trends between land-cover type and deer density. Deer density was not correlated with any vegetation or land use variable. This suggests that deer density is not a leading factor determining variation in vegetation impacts across western Connecticut.