Vegetation Boundaries Research Articles

Small-scale soil patterns drive sharp boundaries between succulent “dwarf” biomes (or habitats) in the arid Succulent Karoo, South Africa

Quartz fields, which are densely covered by angular quartz gravel, represent edaphically special habitats in the Succulent Karoo, a winter rainfall desert in South Africa. They are home to an endemic flora and vegetation communities that show strong species turnover at their boundaries. We interpret the vegetation changes along these boundaries as analogous to biome boundaries: a functional shift is accompanied by a change in structure. Our study aims to identify which abiotic variables are associated with the abrupt shift in species and life form composition at the boundaries and whether these variables change as abruptly as the species composition.We studied 56 transects of 6×1m2 plots across eight boundary types (6–9 replicate transects per type) between six different habitats (namely, two acidic quartz fields, two saline quartz fields, zonal habitat types and heuweltjies). For each plot, we sampled soil texture, soil pH, electrical conductivity, and the calcium carbonate content at the soil surface (0–2cm), as well as soil depth, plant species composition and species richness. We tested for trends in the group means of the abiotic parameters across the different boundary types with a polynomial-contrast ANOVA. We also aggregated the three plots left (1–3) and right (4–6) of the observed vegetation boundary and tested for differences between the mean ranks of the abiotic parameters using a Wilcoxon rank sum test. Abiotic differences were compared to an indicator of the fidelity of species to the vegetation types, identified through an Indicator Species Analysis.All boundary types exhibited a strong trend in either soil pH and/or electrical conductivity. Only in a few cases did calcium carbonate and soil texture also vary across boundary types. The boundary types between the most acidic quartz fields and adjacent vegetation types showed the strongest level of fidelity of species to one of the two habitat types. Acidic quartz fields (pH<5) were most species-poor and had only one species with a significant indicator value.We discuss the influence of parent material, microtopography, climatic aridity, size of plants, and properties of winter rainfall precipitation on the abrupt difference in soil properties and vegetation patterns. By comparing the soil patterns and plant responses on quartz fields to studies of other edaphically special habitats (e.g., gypsum, serpentine and saltmarsh soils), we argue that some of the morphological features of the dominant taxa (Aizoaceae lineages) may determine their success in these habitats.

Object-Based Approach for Multi-Scale Mangrove Composition Mapping Using Multi-Resolution Image Datasets

Providing accurate maps of mangroves, where the spatial scales of the mapped features correspond to the ecological structures and processes, as opposed to pixel sizes and mapping approaches, is a major challenge for remote sensing. This study developed and evaluated an object-based approach to understand what types of mangrove information can be mapped using different image datasets (Landsat TM, ALOS AVNIR-2, WorldView-2, and LiDAR). We compared and contrasted the ability of these images to map five levels of mangrove features, including vegetation boundary, mangrove stands, mangrove zonations, individual tree crowns, and species communities. We used the Moreton Bay site in Australia as the primary site to develop the classification rule sets and Karimunjawa Island in Indonesia to test the applicability of the rule sets. The results demonstrated the effectiveness of a conceptual hierarchical model for mapping specific mangrove features at discrete spatial scales. However, the rule sets developed in this study require modification to map similar mangrove features at different locations or when using image data acquired by different sensors. Across the hierarchical levels, smaller object sizes (i.e., tree crowns) required more complex classification rule sets. Incorporation of contextual information (e.g., distance and elevation) increased the overall mapping accuracy at the mangrove stand level (from 85% to 94%) and mangrove zonation level (from 53% to 59%). We found that higher image spatial resolution, larger object size, and fewer land-cover classes result in higher mapping accuracies. This study highlights the potential of selected images and mapping techniques to map mangrove features, and provides guidance for how to do this effectively through multi-scale mangrove composition mapping.

Vegetation change at high elevation: scale dependence and interactive effects on Niwot Ridge

Background: High-elevation mountain systems may be particularly responsive to climate change.Aims: Here we investigate how changes along elevation gradients in mountain systems can aid in predicting vegetation distributional changes in time, focusing on how changing climatic controls affect meso-scale transitions at the lower and upper boundaries of alpine vegetation (with forest and subnival zones, respectively) as well as micro-scale transitions among plant communities within the alpine belt. We focus on climate-related drivers, particularly in relation to climate change, but also consider how species interactions, dispersal and responses to disturbance may influence plant responses to these abiotic drivers.Results: Empirical observations and experimental studies indicate that changing climatic controls influence both meso-scale transitions at the upper and lower boundaries of alpine vegetation and micro-scale transitions among plant communities within tundra. Micro-scale heterogeneity appears to buffer response in many cases, while interactions between climate and other changes may often accelerate change.Conclusions: Interactions with microtopography and larger edaphic gradients have the capacity to both facilitate rapid changes and reinforce stability, and that these interactions will affect the responsiveness of vegetation to climate change at different spatial scales.

Sediment transport and carbon sequestration characteristics along mangrove fringed coasts

Mangroves play an important role in sequestering carbon and trapping sediments. However, the effectiveness of such functions is unclear due to the restriction of knowledge on the sedimentation process across the vegetation boundaries. To detect the effects of mangrove forests on sediment transportation and organic carbon sequestration, the granulometric and organic carbon characteristics of mangrove sediments were investigated from three vegetation zones of four typical mangrove habitats on the Leizhou Peninsula coast. Based on our results, sediment transport was often “environmentally sensitive” to the vegetation friction. A transition of the sediment transport mode from the mudflat zone to the interior/fringe zone was often detected from the cumulative frequency curve. The vegetation cover also assists the trapping of material, resulting in a significantly higher concentration of organic carbon in the interior surface sediments. However, the graphic parameters of core sediments reflected a highly temporal variability due to the sedimentation process at different locations. The sediment texture ranges widely from sand to mud, although the sedimentary environments are restricted within the same energy level along the fluvial-marine transition zone. Based on the PCA results, the large variation was mainly attributed to either the mean grain size features or the organic carbon features. A high correlation between the depth and δ13C value also indicated an increasing storage of mangrove-derived organic carbon with time.

Environmental changes of the Okhotsk-Kolyma divide from glacial lake sediments during the Holocene

Investigations of glacial lake sediments located near the modern altitudinal boundary of a larch forest (between 750–810 m absolute elevation) reveal continuous records of the vegetation and climate changes over the last 12000 years in the area of the Okhotsk-Kolyma divide. For the first time, the pollen accumulation rates (PAR), which are suggestive of pollen productivity, were used as a key indicator to interpret the response of alpine plant communities to climate changes. The palynological data imply that several forest line fluctuations of ∼100–200 m occurred during the Holocene. A belt of tundra dominated by shrub pine was first established beyond the forest line near 7650 ± 50 BP. The abrupt appearance of the shrub pine in the studied area is characteristic of a sharp vegetation boundary found in other records from the north of the Far East that corresponds to the Boreal-Atlantic boundary of the Holocene. The birch pollen zone, which occurs in the earlier portions of the records, is characteristic of the transition from the Pleistocene to the Holocene.

Experimental evaluation of the sustainability of dwarf bamboo (Pseudosasa usawai) sprout-harvesting practices in Yangminshan National Park, Taiwan.

Sustainable harvest of natural products that meets the needs of local people has been viewed by many as an important means for sustaining conservation projects. Although plants often respond to tissue damage through compensatory growth, it may not secure long-term sustainability of the populations because many plants enhance individual well-being at the expense of propagation. Sustainability may further be threatened by infrequent, large-scale events, especially ill-documented ones. We studied the impacts of sprout harvesting on sprout growth in a dwarf bamboo (Pseudosasa usawai) population that has seemingly recovered from an infrequent, large-scale masting event. Experimental results suggest that although a single sprout harvest did not significantly alter the subsequent abundance and structure of sprouts, culm damage that accompanied sprout harvesting resulted in shorter, thinner, and fewer sprouts. Weaker recovery was found in windward, continually harvested, and more severely damaged sites. These findings suggest that sprout growth of damaged dwarf bamboos is likely non-compensatory, but is instead supported through physiological integration whose strength is determined by the well-being of the supplying ramets. Healthy culms closer to the damage also provided more resources than those farther away. Sustainable harvesting of sprouts could benefit from organized community efforts to limit the magnitude of culm damage, provide adequate spacing between harvested sites, and ensure sufficient time interval between harvests. Vegetation boundaries relatively resilient to infrequent, large-scale events are likely maintained by climatic factors and may be sensitive to climate change. Continual monitoring is, therefore, integral to the sustainability of harvesting projects.

Treeline advances along the Urals mountain range - driven by improved winter conditions?

High-altitude treelines are temperature-limited vegetation boundaries, but little quantitative evidence exists about the impact of climate change on treelines in untouched areas of Russia. Here, we estimated how forest-tundra ecotones have changed during the last century along the Ural mountains. In the South, North, Sub-Polar, and Polar Urals, we compared 450 historical and recent photographs and determined the ages of 11,100 trees along 16 altitudinal gradients. In these four regions, boundaries of open and closed forests (crown covers above 20% and 40%) expanded upwards by 4 to 8 m in altitude per decade. Results strongly suggest that snow was an important driver for these forest advances: (i) Winter precipitation has increased substantially throughout the Urals (~7 mm decade(-1) ), which corresponds to almost a doubling in the Polar Urals, while summer temperatures have only changed slightly (~0.05°C decade(-1) ). (ii) There was a positive correlation between canopy cover, snow height and soil temperatures, suggesting that an increasing canopy cover promotes snow accumulation and, hence, a more favorable microclimate. (iii) Tree age analysis showed that forest expansion mainly began around the year 1900 on concave wind-sheltered slopes with thick snow covers, while it started in the 1950s and 1970s on slopes with shallower snow covers. (iv) During the 20th century, dominant growth forms of trees have changed from multistemmed trees, resulting from harsh winter conditions, to single-stemmed trees. While 87%, 31%, and 93% of stems appearing before 1950 were from multistemmed trees in the South, North and Polar Urals, more than 95% of the younger trees had a single stem. Currently, there is a high density of seedlings and saplings in the forest-tundra ecotone, indicating that forest expansion is ongoing and that alpine tundra vegetation will disappear from most mountains of the South and North Urals where treeline is already close to the highest peaks.

English

There are numerous terms used to describe the vegetation boundary in high mountains. It is essential to define and agree on a unified usage for these terms. The literature review method had been used in this paper to clarify the vegetation boundary terms and their scopes. The result revealed that these terms were much diversified and ambiguous, and more or less related and infringed with each other in ecological concept and visible landscape, even mutually used as synonyms in some cases. We proposed a concise scheme for clarifying these terms and illustrating their relationship, including timberline [instead of previously used economic (rational, generative) forest-line, economic timberline, limit of continuous forest], forestline [instead of physiognomic (empirical, vegetative, biologic) forest-line, actual timberline, physiognomic forest-limit], treeline (instead of tree limit and treeline), krummholzline (instead of tree-species line, tree species limit, krummholz limit), and historic treeline. The 5 boundary terms could facilitate the comprehension of spatial sequence of vegetation transformation in high mountains. However, all boundaries do not necessarily occur in all mountains of the world concurrently. In some papers, the term timberline or treeline once referred to the ecotone from continuous forest to tree less landscape, but the term forest–tundra ecotone should obtain more commendations when vegetation transition is much more gradual particularly around the subarctic. To avoid the confusion from using these boundary terms, we suggest that authors studying boundary related issues should interpret their scope of terminologies and provide the basic description about environment and vegetation outlines in the complex high mountains. Key words: Timberline, forestline, treeline, krummholzline, high mountains.

Scrub encroachment into species-rich limestone grassland: recruitment, herbivory and the threat from incipient scrub

Background: ‘Scrub-grassland’ mosaics are valued owing to their notable biodiversity. However, they are dynamic and difficult to manage, largely because of our incomplete knowledge of vegetation boundary shifts.Aim: Increase our understanding of the ecological processes involved in woody plant establishment at scrub–grassland ecotones and assess whether current management practices in a reserve (Cressbrook Dale, UK) are controlling scrub encroachment.Methods: Vegetation structure, seed deposition and seedling density were studied for woody species across the scrub–grassland interface. Seedlings of successful colonisers were planted in the grassland to assess their palatability and susceptibility to grazers.Results: Vegetation structure changed radically at the scrub–grassland interface. Woody plant canopy cover decreased more sharply than did the density of woody species. Seed deposition was much higher within the scrub than in the grassland (71.3 vs. 9.0 seeds m−2 year−1). Corylus avellana and Crataegus monogyna were the most successful grassland colonisers, with Corylus being less palatable but less resistant to grazing.Conclusions: Although the current grazing regime is stopping scrub encroachment, there is a notable density of stunted woody plants in the grassland adjacent to the scrub, their growth suppressed by grazers. This incipient scrub could rapidly become closed scrub if grazing pressure were relaxed.

Evaluating the dominant components of warming in Pliocene climate simulations

Abstract. The Pliocene Model Intercomparison Project (PlioMIP) is the first coordinated climate model comparison for a warmer palaeoclimate with atmospheric CO2 significantly higher than pre-industrial concentrations. The simulations of the mid-Pliocene warm period show global warming of between 1.8 and 3.6 °C above pre-industrial surface air temperatures, with significant polar amplification. Here we perform energy balance calculations on all eight of the coupled ocean–atmosphere simulations within PlioMIP Experiment 2 to evaluate the causes of the increased temperatures and differences between the models. In the tropics simulated warming is dominated by greenhouse gas increases, with the cloud component of planetary albedo enhancing the warming in most of the models, but by widely varying amounts. The responses to mid-Pliocene climate forcing in the Northern Hemisphere midlatitudes are substantially different between the climate models, with the only consistent response being a warming due to increased greenhouse gases. In the high latitudes all the energy balance components become important, but the dominant warming influence comes from the clear sky albedo, only partially offset by the increases in the cooling impact of cloud albedo. This demonstrates the importance of specified ice sheet and high latitude vegetation boundary conditions and simulated sea ice and snow albedo feedbacks. The largest components in the overall uncertainty are associated with clouds in the tropics and polar clear sky albedo, particularly in sea ice regions. These simulations show that albedo feedbacks, particularly those of sea ice and ice sheets, provide the most significant enhancements to high latitude warming in the Pliocene.

贡嘎山雅家埂峨眉冷杉林线种群的时空动态

通过对贡嘎山雅家埂峨眉冷杉种群林线附近6个3000 m²样地(阴阳坡各3个)中峨眉冷杉(<em>Abies fabri Craib</em>)种群的定位调查,分析了过去100a间该区峨眉冷杉种群的时间-空间动态。结果表明:1)雅家埂林线附近峨眉冷杉种群密度在过去100 a(主要是近50 a)有显著的升高,但树线的海拔位置并无明显的爬升;2)阴阳坡林线格局存在显著的坡向分异:阴坡林线和树线的海拔高度显著高于阳坡(分别比阳坡高152.5 m和135.8 m),阳坡林线附近峨眉冷杉早期的生长速率在大于阴坡,但后期的生长速率却低于阴坡;3)热量(温度)控制假说不能完全解释雅家埂目前的树线格局,除气候因素之外,其它因素也限制了雅家梗地区树线位置的变化。;The high-altitude limit of forests, commonly referred to as the treeline, timberline, or forest line, represents one of the most obvious vegetation boundaries. In most cases, however, the transition from the uppermost closed montane forest to the treeless alpine vegetation is not a line, but an ecotone characterized by stand fragmentation and stuntedness. Owing to its high altitude and complex ecological dynamics, the alpine treeline ecotone is very sensitive to climate changes. This ecotone has accordingly been extensively studied, and a growing body of evidence has already revealed that treelines are moving upslope in the Swedish Scandes, North America, and Eurasia. Although there is some photographic evidence of a rapid treeline advance in the Hengduan Mountains on the southeastern Tibetan Plateau, its dynamics have not been studied in detail. To model how alpine forests will adapt under the predicted temperature increase, a thorough understanding of alpine treeline dynamics is essential. In this study, we chose Gongga Mountain (29°20'-30°20'N, 101°30'-102°15'E, 7556 m asl), a typical mountain in the Hengduan Mountains, southwest China, as our study area. Six rectangular plots (each 3000 m², 30 m × 100 m) were established within the natural alpine treeline ecotone on shady and sunny slopes of the Yajiageng area, on the eastern slope of Gongga Mountain. On the basis of a detailed study of the age and distribution of treeline trees (<em>Abies fabri</em>) in the alpine treeline ecotone, the spatial-temporal dynamics of the <em>A. fabri</em> population were analyzed over a 50-year period. The results suggested that the six study plots showed a similar pattern of regeneration dynamics, characterized by a gradually increased recruitment in the last 100 years and an abrupt increase in the last 50 years. However, the position of the treeline has moved only slightly and insignificantly upslope, despite the apparent warming on the east slope of Gongga Mountain. Moreover, we found that there were some differences in the spatial-temporal dynamics of the <em>A. fabri </em>population between the sunny and shady slope. The altitude of the timberline and treeline on the shady slope was (3770.4±6.6) m and (3771±7.7) m, respectively, whereas that on the sunny slope was (3617.9±10.0) m and (3635.7±7.8) m. The altitude of the timberline and treeline on the shady slope was significantly higher than that on sunny slope (152.5 m and 135.8 m for timberline and treeline, respectively). In addition, we also discovered that the growth rate of <em>A. fabri</em> on the shady slope was higher than that on the sunny slope during the early stage of tree growth (tree age below 110 years), but lower during the later stage of growth. Our results showed that the thermal limitation hypothesis alone could not explain the present treeline pattern in the Yajiageng area. In addition to temperature, other environmental factors might also affect the formation of the treeline in Yajiageng. Hence, in the case of non-climatic climax treelines, such as those in our study area, both climate-driven model projections of future treeline positions and the use of the treeline position for bioclimatic monitoring should be used with caution.

Elemental composition of tree rings: A new perspective in biogeochemistry

Chemical elements that are associated with the ionic composition of the cytoplasm of cells are crucial components of higher plants. They enable various pro� cesses throughout the lifetime of plants associated with cellular energy, operation of a large number of enzymes, etc. (1). Entering the plant from the soil, chemical elements perform their functions in the plant and with its demise close important biogeochemical cycles (2). Longliving woody plants are themselves components of biogeochemical cycles with varying characteristic times: from one year to centuries. Tree rings that form each year in woody plants record the current climatic conditions on one hand, and they accumulate information about longterm changes of their environment (3) on the other. Wood cells mature in one growing season as cell walls lignify, and upon death, they serve as a waterconducting system. Chemical elements that are rigidly linked to the com� ponents of the cell walls of wood and that preserve this link for many decades are thus valuable. They can be used as a potential source of information about the processes and factors that govern their content that took place during the maturing of wood cells. In this paper we present for the first time the changes in biologicallyimportant elements (P, K, Ca, Mg, Sr, Ba, Cl, Si) from 1300 to 2000 AD in the annual rings of larch ( Larix gmelinii Rupr.) from the Taimyr Peninsula (polar boundary of forest vegetation, 72° N). In this study we only consider selected elements that are considered most informative, although the method allowed us to determine the concentration of a total of 40 elements. There are many publications dedicated to the elemental composition of tree rings over short time intervals, however the potential of using the signal of the elements for making long reconstructions of the paleoenvironmental conditions remains unfulfilled. Such a long dendrochemical record for the elements is obtained for the first time. The conditions of tree growth on the permafrost soils of the Taimyr Peninsula are strictly limited by temperature. Wood samples (tree discs) were collected in 2006. Dating of discs was car� ried out using a long master chronology that was pre� viously obtained for this area (4). The actual lifespan of the trees was no more than 350-400 years; for each calendar period 3-6 samples from discs of different ages were measured. Covering the time interval of 700 years was achieved by using samples from both liv� ing and very well preserved dead trees. The total num� ber of samples analyzed from sixteen trees was 351. A single sample contained a 5�year or 10�year period of growth (5 or 10 calendardated tree rings). Chemi� cal analysis was carried out using the method of mass spectrometry with inductively coupled plasma (ICPMS) employing a quadrupole spectrometer Agilent 7500ce. Measurements were made on solu� tions obtained by dissolving wood specimens in con� centrated nitric acid and their subsequent dilution with water. The method of processing wood samples, their dissolution, and the subsequent sample prepara� tion and measurement is described in detail in (5). The longterm average values as well as the range of changes of concentrations of the elements in wood samples are given in the table. The most abundant ele� ments in the wood samples are K + and Ca 2+ , which are important components of the cytoplasm. Ba and Sr, which are the chemical analogs of Ca and Mg, have the lowest concentrations. Based on the temporal vari� ability of all investigated elements, they can be divided into three groups. The first group consists of K and P, which are characterized by the following dynamics: a relatively stable level of concentration during the period from 1300 to 1950 and then a sharp increase in

Lack of photosynthetic or stomatal regulation after 9 years of elevated [CO2] and 4 years of soil warming in two conifer species at the alpine treeline

Alpine treelines are temperature-limited vegetation boundaries. Understanding the effects of elevated [CO2 ] and warming on CO2 and H2 O gas exchange may help predict responses of treelines to global change. We measured needle gas exchange of Larix decidua Mill. and Pinus mugo ssp. uncinata DC trees after 9 years of free air CO2 enrichment (575 µmol mol(-1) ) and 4 years of soil warming (+4 °C) and analysed δ(13) C and δ(18) O values of needles and tree rings. Tree needles under elevated [CO2 ] showed neither nitrogen limitation nor end-product inhibition, and no down-regulation of maximal photosynthetic rate (Amax ) was found. Both tree species showed increased net photosynthetic rates (An ) under elevated [CO2 ] (L. decidua: +39%; P. mugo: +35%). Stomatal conductance (gH2O ) was insensitive to changes in [CO2 ], thus transpiration rates remained unchanged and intrinsic water-use efficiency (iWUE) increased due to higher An . Soil warming affected neither An nor gH2O . Unresponsiveness of gH2O to [CO2 ] and warming was confirmed by δ(18) O needle and tree ring values. Consequently, under sufficient water supply, elevated [CO2 ] induced sustained enhancement in An and lead to increased C inputs into this ecosystem, while soil warming hardly affected gas exchange of L. decidua and P. mugo at the alpine treeline.

Forecasting possible changes in zonal vegetation boundaries in European Russia and Western Siberia in connection with global warming

This paper discusses the relationships of zonal vegetation boundaries with some climatic indicators. Possible changes in subzonal vegetation boundaries in the territory of European Russia and Western Siberia are forecasted within the framework of one of the global warming scenarios. The revealed regularities make it possible to suggest a mathematical cartographic model of vegetation zonality for the 2046–2065 period.

Phytoliths of Southeastern Vancouver Island, Canada, and their potential use to reconstruct shifting boundaries between Douglas-fir forest and oak savannah

Phytolith assemblages in terrestrial soils have the potential to reveal local shifts between open savannah and conifer forests in the past. On southeastern Vancouver Island, this could help quantify the range of variability of Garry oak savannahs prior to European colonization, and the degree of influence of indigenous people in maintaining open savannahs. We catalogued the phytolith morphotypes found in 72 of the most common plant species in this system, and extracted phytoliths from two soil cores on either side of the boundary between a conifer forest and an oak savannah. Grasses are the most prolific producers of phytoliths in savannahs. In forests, Douglas-fir (Pseudotsuga menziesii) produces large, distinctive asterosclereid phytoliths. Phytolith assemblages from soil cores showed that phytoliths from grasses dominated, even in soils from the forest, where grasses are rare. However, the presence of asterosclereid phytoliths reliably distinguished between Douglas-fir forest and Garry oak savannah habitats within 20m of the vegetation boundary. This finding may be useful for reconstructing past vegetation not only on Vancouver Island, but also across a large geographic area in North America where grasslands tend to be invaded by Douglas-fir following fire suppression. The use of the phytolith record from terrestrial soils at local sites where the history of human occupation is well-known could help establish the degree of influence of indigenous peoples in maintaining open savannahs on southeastern Vancouver Island.

A Broad Approach to Abrupt Boundaries: Looking Beyond the Boundary at Soil Attributes within and Across Tropical Vegetation Types

Most research on boundaries between vegetation types emphasizes the contrasts and similarities between conditions on either side of a boundary, but does not compare boundary to non-boundary vegetation. That is, most previous studies lack suitable controls, and may therefore overlook underlying aspects of landscape variability at a regional scale and underestimate the effects that the vegetation itself has on the soil. We compared 25 soil chemistry variables in rainforest, sclerophyll vegetation and across rainforest-sclerophyll boundaries in north-eastern Queensland, Australia. Like previous studies, we did find some contrasts in soil chemistry across vegetation boundaries. However we did not find greater variation in chemical parameters across boundary transects than in transects set in either rainforest or woodland. We also found that soil on both sides of the boundary is more similar to “rainforest soil” than to “woodland soil”. Transects in wet sclerophyll forests with increasing degrees of rainforest invasion showed that as rainforest invades wet sclerophyll forest, the soil beneath wet sclerophyll forest becomes increasingly similar to rainforest soil. Our results have implications for understanding regional vegetation dynamics. Considering soil-vegetation feedbacks and the differences between soil at boundaries and in non-boundary sites may hold clues to some of the processes that occur across and between vegetation types in a wide range of ecosystems. Finally, we suggest that including appropriate controls should become standard practice for studies of vegetation boundaries and edge effects worldwide.

河岸植生域境界における水平せん断層の空間発達過程に関する数値計算

Quasi-3D model and SDS (sub-depth scale) turbulence model are combined to simulate the horizontal shear layer development along the interface of bank vegetation. Turbulence productions caused by bottom friction and vegetation drag are formulated based on previous experiments on turbulence intensity in flows in an open channel and through model vegetation (cylinder arrays). Computations are made for two flow conditions of flume experiment with vegetation model published in literatures. Good agreements are obtained for transverse and streamwise velocity profiles in the developing shear layer containing horizontal coherent vortices. The characteristics of turbulence components are also predicted well. Furthermore, simulation results suggest that strong SDS turbulence is generated near vegetation boundary and transported to vegetation zone and main channel by horizontal coherent vortices.

Crop, field boundary, productivity and disturbance influences on ground beetles (Coleoptera, Carabidae) in the agroecosystem

Ground beetles were sampled in nine crops and four field boundary types on a split conventional/organic farm in northern England in the five years 2005–2009. Multivariate analyses indicated that a combination of crop type, management and boundary type influenced ground beetle species and group activity. Short vegetation boundaries with bare ground had similar activity, mainly of small species, to that in organic arable crops, contrasting with activity in conventional arable and more densely vegetated boundaries. Large, medium-sized, herbivorous and Collembola feeding species all had considerable activity in oilseed rape and activity was generally greatest in conventional arable crops but least in conventional grass. Disturbance and productivity estimations provided basic insights into ground beetle activity. Most small and medium-sized species were found in areas with low productivity but high and low disturbance, respectively. Large and Collembola feeding species were most active in highly productive areas with medium and low disturbance whilst most herbivorous species preferred medium values of both drivers. In crops, species richness was greatest in organic beans and conventional oilseed rape and lowest in conventional grass. There were more species in short vegetation boundaries than in more densely vegetated field edges. There may be potential for the use of productivity and disturbance estimations in the provision of ecosystem services, especially in assessing the conditions required to optimise ground beetle activity for pest control.

Do vegetation boundaries display smooth or abrupt spatial transitions along environmental gradients? Evidence from the prairie–forest biome boundary of historic Minnesota, USA

AbstractQuestionsTwo alternative mechanisms of abrupt vegetation change across ecological boundaries have been proposed: (1) concomitantly abrupt gradients in physical environmental variables and vegetation across the boundary, and (2) gradual environmental gradients that vegetation responds to in a non‐linear or threshold manner. Here, we evaluate spatial patterns of climate and vegetation across a grassland–forest biome boundary to examine evidence in favour of either of these alternatives.LocationMinnesota, USA.MethodsVegetation data represented the presence of prairie vs. forest vegetation in Minnesota from 1847 to 1908, generally prior to European settlement of the region, while the climatic variables represented an index of long‐term average moisture availability (precipitation minus potential evapotranspiration (P – PET). Using linear and sigmoidal regression models, we evaluated spatial patterns of change in vegetation, climate and vegetation–climate relationships across 22 transects (170–400 km) oriented perpendicular to the biome boundary. We also evaluated boundary characteristics in light of dominant topographical controls and position along the boundary.ResultsVegetation followed a sigmoidal pattern of change across the boundary, with mean boundary width of ca. 100 km. The P – PET increased by ca. 100 mm across the boundary following a comparatively smooth pattern of change. Climate–vegetation relationships were clearly non‐linear across the boundary, indicating these variables did not change in a common spatial pattern. Regional topographical controls modified relationships between vegetation and climate along the length of the boundary.ConclusionsOur results document strong non‐linear relationships between the presence of forest vegetation and its dominant climate control across a grassland–forest biome boundary. An average change of ca. 100 mm in P – PET moving across the boundary is about 40% of the long‐term mean annual range of this variable, suggesting that modest changes to P – PET may potentially cause substantial shifts in the location of the prairie–forest boundary.

FORECASTED TRENDS IN CHANGES OF VEGETATION IN THE EUROPEAN PART OF RUSSIA IN CONNECTION WITH GLOBAL WARMING

The paper discusses connections between zonal boundaries of vegetation and productivity of forest stands and some climatic parameters. It also suggests mathematical-cartographic models of these connections. The models are used to forecast changes in the boundaries of the vegetation sub-zones and of forest stands productivity in the European Part of Russia and on the adjacent areas for 2046–2065 under one of the scenarios of global warming.