Primary Plant Succession Research Articles

Trait driven or neutral: understanding the change in functional trait diversity during early plant succession using Price partitions

Habitat filtering, species interactions and neutral colonization as well as extinction dynamics govern the sequence of community assembly and functional diversity (FD) during primary plant succession. To study the factors that influence changes in FD we here use data on plant seed size, seed numbers and specific leaf area from 107 study plots along a 7 year sequence of primary succession (2005–2011) in a 6 ha German artificial catchment. We show that the temporal variability in functional diversity can be partitioned into the effects of trait expression, species richness and plant cover. We observed a dominant role of species richness and community composition on FD. Trade-offs in the influence of species richness and plant cover tended to decrease the change in FD. Average FD steadily increased during the first 4 years of succession (2005–2008). The degree of annual changes in FD were highly plot specific. Average change in FD was comparatively low during the first 4 years and later high. Soil characteristics and light conditions did not significantly influence the detectable change in functional diversity. We conclude that the high plot-specific spatial variability of the annual changes in FD transformed the initially catchment-wide homogeneous distribution of plant species into a mosaic of very different local plant communities. Our partitioning results also indicate that the successional sequences in FD are in accordance with a hidden Markov series.

Unravelling the role of soil microflora from micro and macro aggregates in plant growth during primary and secondary successions

The role of microbial communities from soil aggregates in grasses and herbs’ development during plant succession is not clear. We isolated microbial communities in micro- (<250 μm) and macro-aggregates (>250 μm) and investigated their inoculation on plant communities. Microbial inoculums were added to sterilized soil substrates from primary and secondary plant succession. Soil substrates were collected from primary plant succession included early (ca. 10 years) and late (ca. 65 years) substrates, and secondary plant succession included ancient permanent meadows since the last few thousand years and the same soils restored by secondary succession after being used as arable land.Results showed that during primary plant succession, the late substrates had higher plant biomass than the early substrates, especially when they received microbial communities from the early substrates. When transferred from donor to recipient substrates, bacterial community structure was depending both on the donor and recipient soil, but fungal community structure was mainly controlled by the donor soils and soil aggregates. Micro-aggregate inoculum from the early substrates promoted the growth of herbs, while macro-aggregate inoculum increased the growth of grasses in the late substrates.In contrast, plants grew better during secondary plant succession in ancient and restored soils when they retained their original microbial communities. Inoculum from the ancient soils did not benefit plant growth in the restored soils. Macro-aggregate inoculum from the restored soils had higher plant biomass than micro-aggregates in the ancient soils. Structural equation modelling showed that bacterial community composition (e.g. actinobacteria) significantly controlled total plant community biomass in the primary successional substrates.Overall, our study showed the effect of microbial community in soil aggregates on grasses and herbs’ community development.

Modeling Cooperation and Competition in Biological Communities

The far-reaching consequences of ecological interactions in the dynamics of biological communities remain an intriguing subject. For decades, competition has been a cornerstone in ecological processes, but mounting evidence shows that cooperation does also contribute to the structure of biological communities. Here, we propose a simple deterministic model for the study of the effects of facilitation and competition in the dynamics of such systems. The simultaneous inclusion of both effects produces rich dynamics and captures the context-dependence observed in the formation of ecological communities. The approach reproduces relevant aspects of primary and secondary plant succession, the effect invasive species, and the survival of rare species. The model also takes into account the role of the ecological priority effect and stress the crucial role of facilitation in conservation efforts and species coexistence.

Initial carbonate weathering is linked with vegetation development along a 127-year glacial retreat chronosequence in the subtropical high mountainous Hailuogou region (SW China)

AimsThe retreat of glaciers is exposing new terrains to primary plant succession around the globe. To improve the understanding of vegetation development along a glacier retreat chronosequence, we (i) evaluated a possible link between base metal (Ca, Mg, K, Na) supply and vegetation establishment, (ii) determined the rates of the establishment of soil and plant base metal stocks, and (iii) estimated the size of the main base metal fluxes.MethodsWe determined base metal stocks in the soil organic layer, the mineral topsoil (0–10 cm), and in leaves/needles, trunk, bark, branches and roots of the dominating shrub and tree species and estimated fluxes of atmospheric deposition, plant uptake and leaching losses along the 127-yr Hailuogou chronosequence.ResultsTotal ecosystem Ca and Mg stocks decreased along the chronosequence, while those of K and Na were unrelated with ecosystem age. Fortyfour and 30% of the initial stocks of Ca and Mg, respectively, were leached during the first 47 years, at rates of 130 ± 10.6 g m−2 year−1 Ca and 35 ± 3.1 g m−2 year−1 Mg. The organic layer accumulated at a mean rate of 288 g m−2 year−1 providing a bioavailable base metal stock, which was especially important for K cycling.ConclusionsWe suggest that the initial high Ca bioavailability because of a moderately alkaline soil pH and carbonate depletion in 47 years, together with the dissolution of easily-weatherable silicates providing enough Mg and K to the pioneer vegetation, contributed to the establishment of the mature forest in ca. 80 years.

Common Patterns and Diverging Trajectories in Primary Succession of Plants in Eastern Alpine Glacier Forelands

This paper deals with the vegetation development in four glacier forelands, aligned along a distance of 250 km from West to East in the siliceous Eastern Central Alps. The study employs a chronosequence approach, which assumes a temporal sequence in vegetation development by spatially different sites regarding time since deglaciation. The chronosequences cover the area between Little Ice Age (LIA) maximum glacier extent around 1850, and the current glacier terminus. Despite some shortcomings, chronosequences allow the identification of general patterns of primary succession of plants as a function of site age and local environmental conditions, e.g., changes in species richness, ground cover, plant functional traits, and community structure. While there is no shortage of chronosequence studies in glacier forelands of the Alps, a straightforward comparison aimed at the deduction of general successional trajectories is tricky, due to different procedures of vegetation sampling and data analyses. The comparative examination by a standardized sampling and analyzing protocol of four glacier forelands in the Eastern Central Alps presented here proves the existence of several common patterns in primary succession, but also diverging successional trajectories from West to East. While the pioneer stage in all glacier forelands is similar both floristically and structurally, from the early successional stage onwards, differences increase, leading to different phases in the late successional stage, which is shrub dominated throughout in the westernmost study site, herb–grass–dwarfshrub dominated throughout in the easternmost study site, and divided into an earlier herb–grass–dwarfshrub phase and a later shrub phase in the two study sites in between.

Primary plant succession on freshly degraded yedoma (ice complex) in Lena delta (Eastern Siberia)

Primary plant succession was studied on freshly eroded yedoma in the southern part of Lena River Delta. Four stages of vegetation development were clearly distinguished. The first stage starts on bare ground and lasts from two-three months to one year. Its vegetation is represented only by fragmented cover of young mosses and a few seedlings of vascular plants. The most abundant moss species at this moment is Ceratodon purpureus. The second stage lasts from one to three years depending on slope steepness. Plants cover 20 to 60% of the soil surface. Main dominants are Descurainia sophioides and Tephroseris palustris. The third stage of succession presented by closed species-poor grasslands with Arctagrostis arundinacea as main dominant. This stage lasts for up to 20 years. The fourth stage is represented by species-rich herbaceous communities, which also have Arctagrostis arundinacea as main dominant but enriched with many perennial herbs. There is not enough data to determine the duration of this stage but it is at least few tens of years. This successional system requires a long time for its development. It means that IC degradation is not a recent process but accompanied yedoma deposits through all of its history.

ОСОБЛИВОСТІ РОСЛИННОЇ СУКЦЕСІЇ У КАР'ЄРІ ЦЕГЕЛЬНОГО ЗАВОДУ В С. НОВИЙ ТІК (РІВНЕНСЬКА ОБЛАСТЬ)

Termination of quarries is the reason for the settlement of pioneer plants, which exploit "free" areas of soil in a certain sequence, called successions. The theoretical foundations of restorative plant successions in the quarries are still relatively poorly developed, although there is much empirical research on the subject. The object of our study is the quarry of a brick factory located in the eastern outskirts of the village. Novy Tik (Demydiv district, Rivne region) in the central part of Volyn height, 27 km south of Lutsk. Since 2008, when the brick factory ceased to function in the quarry, there has been a primary plant succession, which is now at a youth stage and is characterized by an increase in biodiversity. As of autumn 2019, 72 plants spices have been identified in the quarry, including 6 species of trees, 1 species of shrubs and 65 species of grasses. According to the results of the systematic analyze, the Asteraceae and Fabaceae families predominate. The prevailing ecological groups of plants in the quarry are determined: in relation to lighting prevail heliophytes; in relation to the thermal regime, the largestproportion is made up of temperate-warm climate species; in the vegetation cover at the present stage of succession, Central European species prevail. Based on the analysis of the population of plant associations and the appearance of interspecific and intraspecific competition, it is established that plant succession in the studied quarry is at a youth stage. Also, heterochrony and microzonal differentiation of succession processes in different parts of the quarry are found. The difference in the passage of succession stages depending on the features of the relief is taken as the basis for the quarry microzoning. It has been established that at the present stage of vegetation succession, the determining factor in the qualitative and quantitative composition of plant communities is abiotic quarry factors, especially morphology and relief dynamics and lithological-stratigraphic structure of deposits. The initial stage of soil succession was revealed, which became possible due to the accumulation of a significant amount of mortmass in recent years.

Primary succession of plants of technogenic dumps of the Kabardino-Balkarian Republic

The article presents data on the regularities of the flow of primary succession on the terraces of the tailing dump of the Tyrnyauz tungsten-molybdenum combined plant. In the accumulative ecotope of old-age terraces of the lower level of the dump, grass-wormwood and herb-wormwood communities dominate with a projective cover of up to 60 %. In the transeluvial ecotope of middle-aged terraces, there are ruderal-natural grass-forb grass communities with a projective cover of 37 %. In the eluvial ecotope of young terraces of the upper level, there are monodominant explent communities with a projective cover of 13 %. Old age terraces have the greatest similarity with the zonal flora and have characterics of relatively high species richness and saturation. With an increase of succession length, there are changes in the dominant life forms (from terophytes to hemicryptophytes), a decrease in the proportion of species with wide ranges (pluriregional, holarctic, and palaearctic), an increase in the number of stenobionts and hemistenobionts. A number of species growing in extreme conditions of ecotopes of middle and upper terraces are characterized by the absence of deviations from ecological regimes and indifference to elevated concentrations of Mo and W. High toxicity of the substrate constrains the speed of transition from initial to subsequent stages of primary succession. To restore vegetation, it is necessary to carry out both biological and technical remediation.

Impact of parent material, vegetation cover, and site wetness on variability of soil properties in proglacial areas of small glaciers along the northeastern coast of Sørkappland (SE Spitsbergen)

Climate warming that began after the Little Ice Age (LIA) and glacier recession due to this warming are responsible for exposure of new areas, which previously had been covered with an ice mass in many parts of the world. Areas newly abandoned by glaciers are sites where primary plant succession and development of soil cover occur. The main aim of this study was to determine impact of parent material, vegetation cover, and site wetness on spatial variability of physical and chemical properties of surface soil layers in the oldest parts of proglacial areas of small and rapidly retreating glaciers such as Kambreen, Bevanbreen, and Coryellbreen, which are located along the northeastern coast of Sørkappland (SE Spitsbergen). Surface soil samples (up to a depth of 10 cm) were collected from sites, which differed in terms of the parent material of the soil (glaciofluvial deposits, glacial till), vegetation cover (bare soils, initial tundra vegetation, moss tundra vegetation), and site wetness (dry, moist, wet). Physical and chemical soil properties such as content of sand, silt, clay, TOC, TN, Si, Al, Ca, Mg, K, Na, P as well as soil pH and soil EC were determined. The obtained research results indicate that the studied surface soil layers are characterized by very high spatial variability of physical and chemical properties. The different parent material of soil (glacial till and glaciofluvial deposits) in the studied proglacial areas affects particle-size distribution, soil pH, soil EC, and content of TN, Ca, and Na. The surface layer of soils developed from glacial till has a finer texture, lower mean soil pH and EC, lower mean content of Ca and Na as well as higher mean content of TN relative to the surface layer of soils formed from glaciofluvial deposits. Vegetation cover, which is very sparse in the study area, has a very low impact on the variability of the properties of the studied surface soil layers. A comparison of bare soils with soils covered with initial and moss tundra vegetation communities indicates that only the more dense and best developed moss tundra vegetation community affects the higher mean content of TOC and TN in the soil. Site wetness is the most important among the studied three soil-forming factors affecting the spatial variability of the physical properties (particle-size distribution) and chemical properties (soil EC, content of TOC, TN, Si, Al, Mg, K, P) of the surface layer of the studied soils. Soils occurring at dry and moist sites are characterized by very similar physical and chemical properties, while soils occurring at wet sites exhibit significantly higher mean soil EC and higher mean content of the sand and Si as well as significantly lower mean content of TOC, TN, silt, clay, Al, Mg, K, and P.

Trait and phylogenetic patterns reveal deterministic community assembly mechanisms on Mount St. Helens

Primary plant succession provides an excellent natural experiment to test ecological questions about community assembly following major disturbances. Temporal phylogenetic and functional trait dispersion patterns can give insight into the relative importance of stochastic and deterministic processes, as well as the potential identity of deterministic (biotic vs. abiotic) drivers (e.g. dispersal, growth, nutrient acquisition, and herbivore resistance ability). We used 28 years of plant composition data across four primary succession sites at Mount St. Helens (collected since the 1980 volcanic eruption) to examine phylogenetic dispersion and trait patterns over time. We expected to find more evidence of clustering or random phylogenetic patterns early in succession (where environmental filtering and stochasticity are thought to dominate), with a switch to overdispersion via processes such as niche differentiation later in succession. Contrary to expectations, phylogenetic relatedness and trait dispersion patterns were idiosyncratic. We found evidence of deterministic community assembly even early in succession, suggesting that both local-scale abiotic filtering and biotic interactions start playing a role shortly after the initiating disturbance. Traits were less predictive of successional patterns, with few consistent changes in trait distribution across all sites, even though the traits we examined are linked to the processes thought to be important during succession. Together, these results suggest that the drivers of community assembly during succession may be less generalizable and more complex than previously thought. We suggest that combining experiments and these analytical tools with long-term monitoring could be a useful step forward.

Differences between primary and secondary plant succession among biomes of the world

Abstract Successional theory lacks an explicit, conceptual integration across types of disturbances and biomes. Most successional research addresses site‐ or process‐specific questions, but extrapolation of the findings to broad scales is limited. Studies of plant succession are often distinguished by the severity of the disturbance that triggers them (severely disturbed: primary; less severely disturbed: secondary). Here, we examine the common assumption that primary and secondary succession differ. We use two anthropogenic disturbances for this comparison, mining and ploughing. Successional generalizations are confounded by a complexity of environmental factors including climatic and geographic variation. We address these issues by contrasting succession across multiple biomes. We selected 166 studies of succession on mining sites (n = 73) or abandoned fields (n = 93) that allowed us to compare successional trajectories in terms of the likelihood of a return to target vegetation, changes in species richness, type of trajectories, and the importance of alien species. Success of both types of succession (a return to target vegetation) differed significantly among biomes, with more likely success in cold than warm biomes (for both primary and secondary seres) and in humid than arid biomes (primary seres only). Primary seres were also more likely than secondary seres to have increases in species richness, a predominance of divergent trajectories, and a lower likelihood that alien species influenced succession. Synthesis. The probability of reaching target vegetation by spontaneous succession is generally greater in biomes at higher versus lower latitudes. Primary and secondary seres differed regarding species richness, trajectories, and the role of alien species. Our results highlight that broad generalizations about succession are possible, despite a paucity of comparable data and our use of only two types of anthropogenic disturbances. Any generalizations that might be found among seres across disturbances and biomes will provide a practical framework for land managers to guide restoration efforts, particularly in poorly studied areas.

High‐speed colonization of bare ground—Permanent plot studies on primary succession of plants in recently deglaciated glacier forelands

AbstractGlacier forelands are highly suitable environments to study vegetation dynamics. Due to time constraints, the method of ‘space for time substitution’ is commonly employed, using spatially different sites to reconstruct a temporal sequence. However, migration patterns, growth performance, shifts in frequency or abundance of species, changes in biological traits, setbacks, etc. can only be detected by long‐term monitoring on permanent plots. In 2005, a set of permanent plots were established immediately in front of two glacier termini in the European Alps (Goldbergkees, Austria; Lenksteinferner, Italy), which were revisited every second year thereafter. Changes in ground cover and individual numbers of vascular plants as well as structural features such as life‐form composition and dispersal biology types are recorded. The six visits between 2005 and 2015 allow for a detailed appraisal of early vegetation development in glacier forelands, which is surprisingly swift and primarily progressive, but locally interrupted by temporary setbacks due to disturbances. This study contributes to a better understanding of high alpine vegetation dynamics in paraglacial landscapes, that is, transitional landscapes characterized by particular rate and direction of change.

8800 years of high-altitude vegetation and climate history at the Rutor Glacier forefield, Italian Alps. Evidence of middle Holocene timberline rise and glacier contraction

Sedimentary archives at or near the timberline ecotone in Alpine glaciated areas contain records to study Holocene climate change and the interplay between climate, ecosystems, and humans. We focused on records of timberline and glacier oscillations in the Rutor Glacier forefield (Western Italian Alps) in the last 8800 years. Human activity in this area was negligible for most of the Holocene. We adopted an integrative stratigraphic approach including proxies for glacier advance and timberline estimation, sedimentary events, and reconstructed temperatures. Changes in timberline ecotone correlate to climate until the Middle Ages. Pollen-stratigraphic evidence of a primary plant succession highlights a lag beween local deglaciation and the first reliable 14C age. The radiocarbon chronology points to a prolonged phase of glacier contraction between 8.8 and 3.7 ka cal BP. Even later the glacier remained within its LIA limits. Between 8.4 and 4 ka cal BP MAT-inferred TJuly fluctuated near 12.4 °C, ca. 3.1 °C higher than today. During this period, a Pinus cembra forest belt grew at 2600 m asl with an upper limit of tree groves placed 434 ± 310 m above the current open forest limit. This Holocene phase of thermal maximum ended between 3.98 and 3.51 ± 70 ka cal BP and with a substantial rearrangement of forest composition; temperature reconstruction shows a decrease of 1.8 °C. This climate deterioration concluded the Subboreal thermal optimum, mirroring glacial advances widely documented in the Alps. The Rutor Glacier advanced at ca. AD 1093 ± 65, and remained inside the LIA maximum extent. The LIA started since AD 1594, and culminated between AD 1751 and 1864.

Spatial distribution of functional traits indicates small scale habitat filtering during early plant succession

Two major theories on community assembly (habitat filtering and limiting similarity) predict contrasting patterns in the spatial distribution of plant species. The respective distribution of species functional traits has received much less attention but is essential to understand facilitative and competitive species interactions. Here we apply a recently developed technique for phylogenetic analysis to study the spatial distribution of major functional traits during seven years of primary plant succession at a re-established catchment in a German lignite mine. Habitat filtering induced a significant temporal trend towards underdispersed functional trait diversity leading to patches of functionally similar vegetation. This functional convergence was not mirrored by a respective trend towards species aggregation. Differences in soil pH and nitrogen content were positively correlated with respective differences in trait expression. Separate analyses of trait distribution for aggregated and segregated species revealed trait convergence in co-occurring and random patterns in spatially segregated species pairs except for leaf size showing a strong temporal tendency for trait convergence in spatially segregated species. Contrasting patterns of species co-occurrence did not translate into respective contrasts in trait distribution. We interpret the prevalence of random trait associations in spatially segregated species as an indication that species occurrence patterns alone are weak predictors of assembly mechanisms. Mechanistic inference of species co-occurrence needs to be accompanied by a detailed assessment of the patterns of functional trait assembly.

Klebelsberg revisited: did primary succession of plants in glacier forelands a century ago differ from today?

Since the Little Ice Age maximum in mid-nineteenth century, glaciers of the Alps lost more than half of their respective area. The chance to observe primary succession in deglaciated areas has motivated researchers ever since with quite a number of studies on vegetation dynamics in glacier forelands dating back to the nineteenth and early twentieth century. Harsh site conditions make glacier forelands challenging environments for the colonization. Due to high mortality rates during establishment, plant colonization and vegetation dynamics in glacier forelands are commonly considered slow and delayed. Recent research, however, shows that primary succession of plants in glacier forelands is accelerated, most likely due to climate warming. This is demonstrated by a speedup of the colonization process itself as well as by changed colonization strategies of the plant species involved. Employing a virtually complete species list for 1911 provided by Raimund v. Klebelsberg and our data collected along a chronosequence roughly a century later, we compare the floristic composition and structural attributes of the plant species governing primary succession within the glacier foreland of Lenksteinferner (ferner is a Tyrolean toponym for glacier) (South Tyrol, Italy). We address questions of changes in the dynamics of colonization, the plant species involved and their respective biological traits. Our study confirms that present-day vegetation dynamics in the glacier foreland are accelerated, colonization occurs faster and more species are involved in early colonization than a century ago. However, the dominant early colonizers are essentially the same and there are no fundamental differences concerning the spectra of biological traits between the two sampling dates. Altered colonization strategies due to climate change could not be detected within the glacier foreland of the Lenksteinferner, probably due to a compensation of climate warming during the twentieth century by the shift of the glacier terminus to a higher elevation. As the difference in temperature between the two sampling areas matches the magnitude of warming between the two sampling dates, similar temperature conditions in front of the glacier terminus today and at Klebelsberg’s times can be assumed.

Initial Carbon Storage in New Tephra Layers of Mt. Talang in Sumatra as Affected by Pioneer Plants

ABSTRACTTo date, no global data on carbon sequestration at the initial weathering phase of tephra deposits are available. To study carbon storage in the new volcanic deposit, tephra layers were reconstructed for a period of 46 months. The tephra samples were collected immediately after eruption of Mount (Mt.) Talang on 12 April 2005, over portions of the Solok District in West Sumatra, Indonesia. Pot experiments were filled with and without soil materials and covered with the collected tephra. The pot experiments were conducted in a wired house. The tephra was applied in 0, 2.5 and 5 cm depths to simulate natural tephra deposition. Every day 250 ml of filtered water was added and allowed to percolate. Solid fraction from the tephra layer was collected and analyzed at regular intervals and primary plant succession was observed over a period of 4 years. After 2 months, blue-green algae (cyanobacteria) started to colonize the bare surface tephra layer to form an algae mat. After 16 months, the surface was transformed into a green biofilm of lichen. Vascular plants (grasses and shrubs) started to be established after 2 years. Total carbon (TC) content of the tephra layer was increased significantly from 0.19 to 1.75% or eight times higher after 46 months of incubation. Higher TC storage was found in the 2.5 cm compared to that of the 5.0 cm tephra layer, which was reconstructed above the soil, with values of 1.75 and 0.89%, respectively. On the contrary, lesser amount of TC was accumulated in the single tephra layer (without soil underneath). Between 71 and 90% of TC was considered as total organic carbon (TOC). The labile organic carbon (LOC) content in the 2.5 cm and 5.0 cm of tephra layer was found to be 0.22 and 0.77%, respectively, at the end of incubation. This experiment confirmed the potential of tephra to capture carbon from the atmosphere with the help of nonvascular plants and then by vascular plants and finally sink them in the tephra layer.

Environmental factors that affect primary plant succession trajectories on lahars (Popocatépetl Volcano, Mexico)

The earliest stages of plant succession on severely disturbed sites usually follow highly unpredictable trajectories. However, in the Popocatepetl volcano area (50 km SE of Mexico City), the development of physiognomically distinct primary plant communities suggests the occurrence of various successional trajectories only 10 years after the onset of colonization of a temperate forest on lahars. To characterize plant communities and determine the environmental factors that drive the differences observed between plant communities and their successional trajectories, we monitored 64 circular sample plots (3.14 m2) from 2002 to 2011. We examined the plant communities’ composition and structure in terms of their species richness and abundance, plant cover, and maximum stem height, and recorded 13 environmental factorsrelated to the volcanic deposit characteristics, microclimate, soil, flow dynamics and gravitational processes. A cluster analysis of the species abundance data showed that, by 2011, six plant community types (CT’s) had established, including grasslands, and open, dense and very dense shrub lands. As these communities developed over the same period of time and within the same overall ecosystem, then these plant community types were interpreted as different stages of the same successional trajectory. Two sequential main stages that drive regeneration were identified from this successional trajectory: a) the first four years are characterized by a steady increase in species richness and physiognomic development (plant size and coverage), mostly dominated by Baccharis conferta,Eupatorium glabratum andSenecio barba-johannis; b) from the sixth year onwards, a continued increase in the abundance of those same species led to the development of the dense shrubland communities. Differences in the availability of soil resources and disturbances linked to recent lahar flows were the main factors accounting for such differences.

Succession of pitfall-trapped insects and arachnids on eight Norwegian glacier forelands along an altitudinal gradient: Patterns and models

Invertebrate primary succession based on pitfall traps is described in eight glacier-foreland chronosequences across a major geo-ecological gradient in the Jotunheimen and Jostedalsbreen subregions of southern Norway. Regional (predominantly altitudinal) and local environmental gradients are shown to be effective influences on the nature and rate of colonization and succession at both species- and community-levels of analysis. Inclusion of flying taxa identified only to higher taxonomic units had little effect on the species-level results for epigeal taxa because the flying taxa were found more-or-less evenly throughout each chronosequence. A relatively large number of pioneer taxa colonize within &lt;20 years of deglacierization in the alpine zone (46–61% of taxa, compared with 22–43% in the subalpine and boreal zones) and contribute to a relatively simple, two-stage succession. Later colonizers are proportionately more important in the subalpine and boreal zones where a three-stage succession results in several divergent late-successional trajectories conditioned by local exposure and moisture differences. The Pioneer Persistence Index (PPI), which measures the percentage of pioneer taxa that persist into the mature stage of succession, is consistently high (65–86%), while the Pioneer Importance Index (PII), which measures the percentage of the taxa at the mature stage that comprise the persistent pioneer element, is higher in the Jotunheimen chronosequences (49–52%) than those of Jostedalsbreen (21–45%). Results support the addition and persistence model of succession, which is seen as being driven primarily by the individualistic behaviour of highly mobile (mainly carnivorous) species that apparently exhibit low dependence on the vegetation succession. Although this model differs substantially from models of primary plant succession, a relatively small element of replacement change increases with decreasing altitude. This contributes to a more complex community structure in subalpine and boreal zones and is attributed to greater biotic interaction, involving not only predators but also an increasing number of herbivores and omnivores.

Plant colonization and soil properties on newly exposed shoreline during drawdown of Lake Mead, Mojave Desert

Drawdown of Lake Mead from 1998 to 2011 reduced the lake's perimeter by more than 400 km while exposing more than 25,000 ha of formerly submerged land. To evaluate primary plant succession and soil properties in this new shoreline habitat, we sampled surfaces last submerged 3, 6, 9, or 13 years before sampling (including a never-submerged control) using 150, 100 m2 plots at 3 sites varying in topography and soil parent material. Consistent with previous research, abundance of the exotic saltcedar (Tamarix ramosissima) declined with increasing surface age. Conversely, cover of native species was greatest overall on older surfaces across sites. Early successional native perennial species colonized the 13-year-old surface. Unexpectedly, multivariate soil properties did not differ between never-submerged and formerly submerged surfaces. Based on the first 13 years of plant colonization along the Lake Mead shoreline and previous research on longer term Mojave Desert vegetation succession, managers can likely anticipate (1) continued development of an early colonizing native shrubland persistent for several decades, and (2) eventual colonization by species of the mature vegetation inhabiting never-submerged surfaces. Moreover, we observed colonization of formerly submerged land by a rare plant of special conservation designation, California bearpoppy (Arctomecon californica), suggesting that even after many years of submersion, rare plant habitat along the Lake Mead shoreline may be reclaimed. While Lake Mead's drawdown might be viewed negatively from a perspective of maintaining full-pool water storage, it has re-exposed a vast area of new terrestrial habitat increasingly colonized by native species as invasive species abundance declines through time.

Changes of soil phosphorus speciation along a 120-year soil chronosequence in the Hailuogou Glacier retreat area (Gongga Mountain, SW China)

The Hailuogou Glacier (Gongga Mountain, SW China) has been retreating in response to global warming. A soil chronosequence (Hailuogou Chronosequence) has developed in the retreat area, and a primary plant succession has developed on it. To investigate the changes of soil phosphorus (P) fractions along the young soil chronosequence in the cold and humid climate, soil samples were collected at seven sites of different ages (0 to 120years). In all soil samples, concentrations of total P and of different P fractions (Bioavailable P, Al/Fe-bound P (P bound by Al and Fe oxides or hydroxides), Ca-bound P, and residual P) were determined using a sequential extraction technique. Organic P was determined using the high temperature ignition method. For the youngest (0years, 12years) soils, P forms were dominated by residual P, and topsoil forms of Ca-bound P, Al/Fe-bound P, organic P, microbial biomass P and bioavailable P were less than 1.86%. From 30 to 120years, for the topsoil, concentrations of Ca-bound P and organic P gradually increased; the concentration of bioavailable P in surface soil also showed a trend of increase, with percentages of 5–11.5% to total soil P; the concentration of residual P decreased; the concentration of Fe/Al-bound P contributed less than 5% to total soil P at all sites. Ca-bound P and organic P were the dominant P fractions at the older sites (ages: 80 and 120years). Soil P bioavailability and solubility were influenced by the changes of pH, and concentrations of Fe and Al oxide and hydroxide. The variations of vegetation and microbial activity are also considered as the impact factors of soil P forms. In the later stage of soil development (80~120years), plenty of soil P was transformed into biomass P pool (299.3kgha−1).