Late Successional Stages Research Articles

Effects of Soil Properties and Plant Diversity on Soil Microbial Community Composition and Diversity during Secondary Succession

Soil microbial communities play an important role in maintaining the ecosystem during forest secondary succession. However, the underlying mechanisms that drive change in soil microbial community structures during secondary succession remain poorly defined in species-rich subtropical coniferous forests. In this study, Illumina high-throughput sequencing was used to analyze the variations in soil microbial community structures during forest secondary succession in subtropical coniferous forests in China. The role of soil properties and plant diversity in affecting soil bacterial and fungal communities was determined using random forest and structural equation models. Highly variable soil microbial diversity was observed in different stages of secondary succession. Bacterial community diversity rose from early to middle and late successional stages, whereas fungal community diversity increased from early to middle successional stages and then declined in the late stage. The relative abundance of Acidobacteria, Gemmatimonadetes, Eremiobacterota(WPS-2), Rokubacteria, and Mortierellomycota increased during succession, whereas the relative abundance of Ascomycota and Mucoromycota decreased. The community composition and diversity of the soil microbial community were remarkably influenced by plant diversity and soil properties. Notably, tree species richness (TSR) displayed a significant and direct correlation to the composition and diversity of both bacterial and fungal communities. The carbon-to-nitrogen (C:N) ratio had a direct impact on the bacterial community composition and diversity, and pH had a marked impact on the fungal community composition and diversity. Furthermore, succession stage and plant diversity indirectly impacted the composition and diversity of soil bacterial and fungal communities via soil properties. Overall, it can be concluded that soil intrinsic properties and plant diversity might jointly drive the changes in soil microbial community composition and diversity during secondary succession of subtropical coniferous forests.

Cryptogamic epiphytes as indicators of successional changes in megadiverse lowland rain forests of western Amazonia

The Amazonian rain forests of Yasuni National Park, Ecuador (YNP), count among the world's forests regions with highest biodiversity, but are strongly threatened by deforestation. Cryptogams (bryophytes and lichens) are common and characteristic organisms in these forests, are sensitive to environmental changes, and are considered effective ecological indicators. The objective of this study was to explore the response of epiphytic cryptogams to forest succession in the Amazonian forests of YNP. We hypothesized that alteration of structural and micro-environmental characteristics of the forest, including reduction of canopy cover and lowering of tree species richness, lead to a reduction of species richness and changes in species composition of epiphytic cryptogams. We assessed species richness and composition of cryptogams on the bases of 442 trees in three stage of forest succession (early, intermediate, late), using generalized linear mixed models, multivariate analysis, beta diversity components and Mantel test. We registered 146 species of cryptogams, including 50 of lichens and 96 of bryophytes (39 mosses, 57 liverworts). Diversity of epiphytic cryptogams was highest in late succession forest, and lowest in early succession forest. Major changes in species richness and composition correlated with changes in canopy openness relative to the shift from early to late stages of forest succession. The results demonstrate for the first time the importance of tree species richness for cryptogamic epiphyte richness in Amazonian rain forests. Maintenance of high tree species diversity and structural heterogeneity in late succession forests can considerably contribute to the conservation of the cryptogamic epiphytes of Amazonian rain forests.

An example of fast old field succession in a traditionally managed rural landscape on the Slovenian Karst

We report an exceptionally fast grassland recovery process from a karst plateau in SW Slovenia. Vegetation of old fields with different ages was sampled using a chronosequence of fields abandoned 1, 3, 6, 9, 13, 15 and 100 years ago. We prepared dendrogram dividing the data set into 9 clusters that were further analyzed: diagnostic species, ecological conditions and life forms were evaluated. The initial stage of succession was characterized by segetal weeds and indicated high levels of soil nutrients. The second stage was dominated by dense patches of perennial forbs (most of them ruderal species) preferring also high levels of soil nutrients. The third stage was dominated by caespitose hemicryptophyte grasses, many of them of sub-Mediterranean origin. The first two stages took 13 years and both could be considered as early successional stages developing on nutrient rich soils. These stages were switched to late successional stage characterized by seminatural grassland species. The quick succession can probably be attributed to the rich species pool of natural grassland flora, the small size and annual mowing of abandoned agricultural fields and the close proximity of seed sources.

Plant Community Assembly Mechanisms of a Subalpine Meadow Community Along Different Successional Time

The process of community assembly is important to explain species coexistence and the maintenance of species diversity. Succession provides a good opportunity to study the role of the deterministic and stochastic processes during the community species composition. We investigated species composition and environmental factors and calculated the change in species diversity, phylogenetic diversity, net relatedness index, and nearest taxon index along a successional chronosequence, with a series of 0.5 × 0.5 m2 plots (n = 20) from five successional subalpine meadow plant communities (ages 1, 3, 5, 15, and 30) in the Qinghai-Tibetan Plateau. In the plots, we found a significant change in species composition and abiotic environmental factors. Our redundancy analysis showed that soil nitrate nitrogen and soil organic carbon were the key environmental factors that affect the community composition in succession gradient. The community showed an overdispersion phylogenetic structure along with the early and medium succession. The ends of the succession stage showed a random or convergent phylogenetic structure. The results showed that the construction process of plant communities in the early and middle stages of succession was mainly affected by habitat filtering. In the late stage of succession, the process of community construction is more complex, which could be affected by the limiting similarity and neutral driving process. Our findings are important to be used in managing ecological restoration and protection.

Quantifying the temporal-spatial scale dependence of the driving mechanisms underlying vegetation coverage in coastal wetlands

Coastal wetland vegetation is at risk of severe degradation at multiple scales due to multiple stresses. Although numerous studies have emphasized the importance of scale dependence, few studies have quantitatively explored how temporal-spatial scales affect vegetation coverage (VC) in coastal wetlands. To identify the effect path of scale on the driving mechanisms of VC, we constructed a structural equation model (SEM) to quantify the temporal-spatial scale dependence of the driving mechanisms of VC in coastal wetlands in China at three spatial scales (national, regional and local) mainly over a 19-year period (2000–2018, including the initial, middle and later stages of vegetation succession). The results showed that at all spatial scales, natural factors were the strongest drivers of VC at the later stage of succession (14–39 a). With reduced spatial scales, soil and topography (only middle stage, 9–11 a) played more important roles at the middle and later stages, whereas human factors had the opposite effect. The common medial factors of the driving mechanisms underlying VC were topography and soil in all scale models. The across-scale model explained 21.8% and 40.4% of the elevation and pH, respectively. The temporal-spatial scale dependences of topography and soil were stronger than those of other variables. Our findings highlight that temporal-spatial scales mainly controlled the driving mechanisms underlying VC via topography and soil in coastal wetlands. This study is the first to quantitatively reveal the effect path of scale on the driving mechanisms underlying VC in coastal wetlands.

Phylogenetic and functional structures of succession in plant communities on mounds of Marmota himalayana in alpine regions on the northeast edge of the Qinghai–Tibet Plateau

Few studies have examined the succession of plant communities in the alpine zone. Studying the succession of plant communities is helpful to understand how species diversity is formed and maintained. In this study, we used species inventories, a molecular phylogeny, and trait data to detect patterns of phylogenetic and functional community structure in successional plant communities growing on the mounds of Himalayan marmots (Marmota himalayana) on the southeast edge of the Qinghai-Tibet Plateau. We found that phylogenetic and functional diversities of plant communities on marmot mounds tended to cluster during the early to medium stages of succession, then trended toward overdispersion from medium to late stages. Alpine species in early and late stages of succession were phylogenetically and functionally overdispersed, suggesting that such communities were assembled mainly through species interactions, especially competition. At the medium and late stages of succession, alpine communities growing on marmot mounds were phylogenetically and functionally clustered, implying that the communities were primarily structured by environmental filtering. During the medium and late stages of succession the phylogenetic and functional structures of plant communities on marmot mounds differed significantly from those on neighboring sites. Our results indicate that environmental filtering and species interactions can change plant community composition at different successional stages. Assembly of plant communities on marmot mounds was promoted by a combination of traits that may provide advantages for survival and adaptation during periods of environmental change.

Nitrogen and phosphorus dynamics along the primary succession in the Hailuogou Glacier retreat area, eastern Tibetan Plateau, China.

In this study, seven sampling sites (glaciers retreated for 0, 10, 30, 40, 50, 80 and 127 years) were chosen along a primary succession sequence in the Hailuogou glacial retreat area in the eastern margin of the Tibetan Plateau, China. The accumulation and cycling characteristics of N and P under different succession stages were analyzed by measuring biomass and N and P contents in surface soil and each vegetation layer. The N and P contents in leaves, branches and roots of tree layers decreased along the succession sequence, whereas the N and P contents in stems were higher in the late succession stage. The changes of N and P contents in litter and soil O layer were consis-tent with those in the leaves and branches of tree layers. Ecosystem N and P storage increased along the succession sequence. Ecosystem N accumulation was mainly dependent on the vegetation layer in the early succession stage. After the community reached the climax, soil became the main N pool of the ecosystem. Vegetation P storage was higher than that in the surface soil after 80 years of glacial retreat. The nutrient accumulation rate in each layer of the ecosystem was rapid in the middle succession stage, with an order of surface soil > tree layer > understory vegetation layer. The nutrient cycling coefficients of N and P in broadleaved forest in the middle stage were higher than those in coniferous forest in the late stage, whereas the N and P utilization efficiency was lower than that in coniferous forest. Therefore, the mechanism of low nutrient cycling and high utilization efficiency of coniferous trees was conducive to the their competition with other species, thus finally forming the climax community.

Plant functional traits along an old-field succession in the high tropical andes

The páramo, a high tropical Andean ecosystem, presents very distinct climatic, floristic and ecological features. Paramo plants have adapted to pronounced daily temperature fluctuations, freezing temperatures any night of the year, high incoming radiation and seasonal unfavorable water availability conditions. Long fallow agricultural systems are common in the páramo, permitting partial recuperation of the vegetation through a secondary succession. Different hypothesis related to plant traits (water relations and gas exchange characteristics or biomass allocation patterns) during succession have been proposed. Particular traits have been associated to the stages along successional gradients from early species (traits related to high resource acquisition abilities) to late species (traits linked to internal conservation of resources). Our purpose was to study plant functional responses of different herbaceous species in an old-field succession in the high tropical Andes. Plant traits (specific leaf area (SLA), maximum CO2 assimilation rates (Amax), leaf nitrogen content (Nleaf), leaf water relations and biomass allocation) were studied in grasses and forbs along different successional stages. Clear trends in SLA, Amax on a mass basis, Nleaf and aboveground/belowground biomass allocation were found along the successional gradient for grasses, while patterns were not as well-defined for forbs in the latter two traits. No patterns in leaf water relations characteristics were observed for either plant-growth forms. Strategies associated to plant traits significantly influence plant species dominance and community assembly during secondary succession in tropical alpine open environments like the páramos. Plant traits linked to rapid growth (SLA, Amax and Nleaf) dominate during early succession. In contrast to previous studies, drought resistance traits were not found to dominate in late succession stages for either grasses or forbs.

Evolutionary responses of a dominant plant along a successional gradient in a salt-marsh system

The ecological responses of plant populations along a successional gradient have been intensively examined; however, the evolutionary responses received much less attention. Here, I explored genetic changes of key phenotypic traits of a dominant clonal plant (Elytrigia atherica) along a saltmarsh successional gradient by collecting samples along the successional gradient in the high and low marsh and growing them in a common environment (greenhouse). Additionally, to explore whether changes in traits are driven by abiotic (e.g. clay thickness) and biotic (e.g. grazing intensity) variables along the successional gradient, I measured these two variables in the field. I found that clay thickness (a proxy of total nitrogen) increased along the successional gradient both in the high and low marsh; grazing intensity from hares (the most important herbivores) decreased along the successional gradient in the high marsh but did not change in the low marsh. Meanwhile, I found that growth in number of leaves and ramets decreased, while rhizome length increased, along the successional gradient for E. atherica collected from the high marsh. Opposite trends were found for E. atherica collected from the low marsh. Results suggest that, in the high marsh, herbivores may overrule nutrients to drive trait changes. That is, at the early successional stages, E. atherica had higher growth in number of leaves and ramets to compensate for high-intensity grazing. In the low marsh, nutrients may be the dominant driver for trait changes. That is, at the late successional stages, E. atherica had higher growth in number of leaves and ramets but shorter rhizomes to maximize its expansion under the favorable conditions (higher nutrient availability). Results suggest that ecologically important abiotic and biotic variables such as nutrients and herbivores may also have a substantial evolutionary impact on plant populations.

Soil phosphorus availability affects diazotroph communities during vegetation succession in lowland subtropical forests

Diazotrophs, nitrogen (N)-fixing microbes, play a pivotal role in N cycling in tropical/subtropical forests. However, little is known about the dynamics of diazotroph communities and the factors that drive their abundance during forest succession. Bulk soils were sampled across two chronosequences in two subtropical forests: a long-term natural succession (LS) and a short-term artificial-intervened succession (SS); both include an early-, mid- and late-successional stage. The results show that the diazotrophic diversity increased with forest succession for the SS, but did not change for the LS. The relative abundance of the dominant genus Bradyrhizobium was significantly greater in the early-successional stage than in the late-successional stage, and some occasional genera appeared in the late-successional stage, both for the LS and SS. Variation partitioning analyses showed that the diazotroph community composition was mainly correlated with soil phosphorus (P) concentration, especially the plant-available soil P concentration, which explained 33.3% of the diazotroph community variation. Our findings revealed the patterns of diazotroph community across forest succession and highlight the importance of soil P availability in mediating diazotroph community during succession in subtropical forests, which is valuable for guiding restoration practices in terms of nutrient management in subtropical forests.

Understanding Natural Regeneration in Burned Tropical Peatland: A Strategy to Accelerate the Forest Recovery Process

The 2015’s massive forest fires have left large areas of burned peatlands that need to be restored, demanding substantial number of resources. To understand natural regeneration on burned peatland and how planting might accelerate its recovery process, we measured recruitment on burned peatland with different fire frequency. Three transects were established each consisting of five 20x20 m2plots developed at a 30 m interval. Our finding suggests that the absence of remnant trees due to frequent or severe fires does not always impede the emergence of new recruitments, although diversity of forest regrowth is likely to be affected by its proximity to forest remnant. The floristic composition also showed a domination of pioneer species, giving evidence that forest recovery is initiated. We conclude that to support the recovery process through planting activity, the successional stage of the designated sites should be determined first. During the early phase of succession, stand initiation should be addressed first by the colonization of rapidly recruiting species to ensure continuous regeneration. Therefore, the common planting method on large areas with mixed climax-high valuable trees is unbeneficial unless the restoration sites have reached the later stages of succession.

A 249-yr chronosequence of forest plots from eight successive fires in the Eastern Canada boreal mixedwoods.

A combination of wildfires and defoliating insect outbreaks play an important role in the natural successional dynamics of North American boreal mixedwood forests, which, in the long term, change the post-disturbance composition and structure of forest stands. After stand-replacing disturbances (mainly wildfires), early successional hardwoods typically dominate the affected areas. Provided enough time following disturbances, the increasing recruitment of mid- to late-successional softwoods as well as the mortality of hardwoods gradually change forest composition from hardwoods to admixtures of hardwood-conifer species and conifer-dominated stands in mid and late successional stages, respectively. Such mixedwoods are abundant across the southern Canadian boreal forest. In boreal Canada, mixedwoods are the most structurally heterogeneous forest ecosystems, are highly productive, and form an important source of timber supply. Here we present the EASTERN BOREAL MIXEDWOODS CANADA data set, which documents the changes in composition and structure of stands originating from eight different wildfires representing a chronosequence of 249 yr since fire in eastern Canada. This data set has been used in several different projects to study and model the influence of natural (e.g., insect outbreaks) and anthropogenic disturbances (e.g., harvesting) on the dynamics of post-fire stands. The data set covers a high range of variability in stand composition and structure, explained by species establishment, dominance, and mixture. It thus constitutes a useful source of information to trace the dynamics of the main boreal tree species of eastern North America, from their establishment to their replacement at different spatial scales (e.g., from stand to landscape level). Please cite this data paper when the data are used in publications. We also request that researchers and teachers inform us of how they are using the data. We are open to collaborate in developing or co-authoring relevant research projects based on this data set.

Depth-related plasticity in the diet composition of Pseudechinus magellanicus (Echinoidea, Temnopleuridae) in nearshore environments off central Patagonia, Argentina

Pseudechinus magellanicus is one of the most abundant sea urchins in southern South America, but many aspects of its feeding ecology in nearshore environments remain unknown. Here, we aimed to analyze the variability of the diet composition along a coastal depth gradient from intertidal tidepools to upper circalittoral zones and examine the relation between seaweed availability and the diet composition at intertidal tidepools. A total of 118 food items, including seaweeds and animal components, were identified. The diet composition showed a large variation between the different coastal habitats present along the depth gradient studied. In tidepools, articulate coralline seaweeds (Corallina spp.), mussel shell fragments and small crustaceans were frequent in the gut contents, suggesting that this species behaves like a general omnivore but can also act as a mussel bioeroder when consuming epizoic algae and microeuendolithic organisms. In intertidal tidepools, the species showed a negative preference toward typical species of late successional stages such as Dictyota dichotoma, Adenocystis utricularis, Codium fragile and Chondria macrocarpa. Sea urchins from kelp forests showed higher dietary diversity than those from intertidal and deeper subtidal habitats, but with prevalence of kelps. At upper circalittoral soft bottoms, diverse detrital items as benthic diatoms, cyanobacteria and drifted algae were observed in gut contents, usually associated with fine sediments, indicating that P. magellanicus captures drifted algae and behaves like a biofilm feeder. This trophic plasticity may allow this species to occupy contrasting habitats and may also contribute to explain its wide distribution in southern South America.

Temporal and Spatial Succession Law of Abor Diversity in Xiaoxing’an Mountains

The national forest nature reserve in the Xiaoxing’anling area was studied. Based on the diversity of α and β, three forest types of grassland, birch forest, and larch forest were analyzed. Based on the diversity law of latitude gradient, the nature reserve was discussed in forest type. A difference in a diversity of different forest types was succession changes. A method based on quantitative evaluation of species conservation value was constructed. The community structure and species composition of nature reserves were systematically analyzed, and the conservation value of species and the conservation value of rare and endangered species were scientifically evaluated. The results showed that the Shannon Wiener index and Margalef index of grassland, birch forest, and larch forest showed a decreasing trend with the increase of latitude. Compared with the other four latitudes, the grassland, birch forest and larch forest of Dazhanhe Nature Reserve showed a decreasing trend from the north to south Jaccard index and Sorenson index, and the Cody index showed an increasing trend. The Jaccard index and the Sorenson index have peaks in friendly areas, and the species similarity is high, indicating that the friendly areas may be the interlaced areas of Xiaoxing’anling. The Shannon Wiener index and the Margalef index of the nature reserve from the early stage of succession to the middle and late succession increased continuously, reaching the maximum in the middle and late stages, and began to decline in the later stage of succession, which is consistent with the mid-specie.

Long-term ecological trends of small secondary forests of the atlantic forest hotspot: A 30-year study case

Forest dynamics are driven by a myriad of factors and link directly to ecosystem services. The dynamics of the highly degraded Brazilian Atlantic Forest (AF) hotspot is mostly driven by its anthropogenic context. Currently, most of the AF region is composed of small disturbed secondary forest fragments that have received partial or full environmental protection with recent environmental norms. Such protection prevents further disturbances and consequently shifts the course of forest dynamics and ecosystem services in AF. Here, we assess long-term forest dynamics trends of a small secondary AF fragment to test the hypothesis that disturbed AF fragments are reaching advanced successional stages. We used a unique dataset of 126 permanent subplots (totaling 5.04 ha) monitored for 30 years (8 inventories between 1987 and 2017) of a disturbed secondary AF fragment (6.35 ha) that has been fully protected since 1986. In each inventory, we measured all living trees with a diameter at breast height (DBH) ≥ 5 cm and counted survivors, recruits and dead individuals between intervals. We monitored the temporal trends of (i) structural variables (biomass, tree density and species richness), (ii) functional composition (wood density and maximum potential size), (iii) and species dominance. Our results indicate that, now under full protection, the fragment is shifting towards a late successional stage: we observed increasing biomass, decreasing tree density (self-thinning) and increasing abundance of late-successional species with conservative strategies. Species richness and dominant species composition were stable throughout the monitoring period, suggesting an absence of substantial changes in community assembly. These results underscore the role played by small secondary AF fragments in ecosystem service provision (e.g., carbon uptake and shelter for biodiversity) and point to their forest dynamics trends.

Biogeochemical stoichiometry of soil and plant functional groups along a primary successional gradient following glacial retreat on the eastern Tibetan plateau

Di-nitrogen (N2)-fixing plants are crucial for vegetation development following glacial retreat; however, there is currently limited understanding of how the shifting of N2-fixing and non N2-fixing plant groups may influence the stoichiometric composition of the developing plant community and associated soils. Carbon (C), nitrogen (N), and phosphorus (P) concentrations and elementary stoichiometry were investigated in soil and the N2-fixing and non-N2-fixing plant communities across a 127-yr glacial primary succession chronosequence on the eastern slope of the Qinghai-Tibetan Plateau. Soil organic C (SOC), total N (TN), and available P (AP) gradually increased along succession, but total P (TP) was greatest at the 37-yr site, resulting in an increasing trend of soil N:P and a decreasing trend of N:AP ratios along the chronosequence. N2-fixing species had higher foliar N and P concentrations than non-N2-fixing species and exhibited a higher leaf N:P ratios in early stages (37 yr and younger) of the succession. Elementary concentration and C, N, P stoichiometry in plant leaves were strongly associated with both N2-fixing and non-N2 fixing plant biomasses, while those in soils were related only with the biomass of non-N2 fixing species. The community-weighted leaf N:P ratios increased from 14.0 at 7-yr to 19.9 at 59-yr and then decreased to 12.9 at 127-yr after glacial retreat, suggests the ecosystem as a whole is not N- or P-limited at the beginning of primary succession, but may become P-limited at the middle stages and then shift towards N limitation at the late successional stages. The results confirm that both N2-fixing and non-N2-fixing species can overcome N limitation in the early primary succession and highlights the different roles of pioneer N2-fixing and non-N2-fixing species in mediating vegetation and soil C, N and P stoichiometry with primary succession following glacial retreat.

Applications of Integrating Wildlife Habitat Suitability and Habitat Potential Models

ABSTRACTAssessment of habitat suitability provides natural resource managers with insights on the quality and spatial distribution of habitat for wildlife species. However, habitat suitability models only provide information on current habitat parameters, and do not consider changes in habitat due to forest succession and disturbances. Habitat potential models have been developed by identifying habitat types and their successional trajectories to provide insights on how landscapes change with time. We developed habitat suitability index (HSI) models and habitat potential models for elk (Cervus elaphus nelsoni) on public and private lands within the Michigan elk range (1,220 km2) in northeastern lower Michigan, USA. Our objective was to demonstrate how integration of habitat suitability and habitat potential models can provide spatiotemporal insights on wildlife habitat. When constructing public‐lands models, we used state forest compartment‐inventory data to identify cover types important to elk, and assigned suitability values (0 = low, 1 = high) to each cover type for elk life requisites (i.e., spring food, winter food, winter thermal cover). Additionally, we modified suitability values based on stand conditions acquired from state forest inventory records (e.g., stand size, percent canopy closure, age of aspen [Populus spp.]). For our private‐lands models, we used satellite imagery to classify cover types and assigned suitability values to cover types for each elk life requisite, and modified values based on percent canopy closure for winter thermal cover. Elk habitat potential was modeled by delineating habitat types by overlaying digital spatial data layers (soils, land‐type associations, vegetation) and identifying successional trajectories using habitat classification guides and literature. We assigned suitability values to each habitat type for life requisites at early to late successional stages. The highest suitability value of each habitat type's successional stage determined the habitat potential for each habitat type. Our winter thermal cover HSI model indicated several large areas (5–13 km2) of high suitability (i.e., lowland conifers) in the southern third of our study area. Our winter food HSI model indicated a heterogeneous arrangement of high suitability areas (hardwoods, upland conifers, aspen) throughout our study area. Our spring food HSI model indicated few areas of high suitability (openings) primarily on private lands. Our habitat potential models indicated high potential for each elk life requisite across the elk range. Comparisons between current elk habitat suitability and habitat potential identify key areas where managers can maximize management efforts for elk in Michigan. Areas determined to have high habitat potential (e.g., mature aspen stands) may become focus areas if they currently have low habitat suitability. Conversely, managers can avoid committing resources to areas with low habitat potential. Integrating habitat suitability and potential models provides insights on how wildlife habitats may respond to forest succession, land management practices, and disturbances, and ultimately help natural resource professionals prioritize and meet a diversity of wildlife management goals. © 2021 The Wildlife Society.

Spatiotemporal dynamics of the ant community in a dry forest differ by vertical strata but not by successional stage

AbstractAnts are diverse and ecologically important organisms in tropical forests, where their spatiotemporal distribution can be highly complex. This complexity arises mainly from marked differences in microclimatic conditions and resource availability through space and time that is even more evident in highly seasonal environments, such as tropical dry forests. However, it is unclear how seasonality interacts with other factors that might shape temporal variation of ant composition (β‐diversity), like vertical strata and habitat disturbance. Our goal was to examine the potential influence of vertical stratification and the successional stage on the spatiotemporal variation of a tropical dry forest's ant species composition. We assessed whether species turnover or nestedness was the main component determining the spatiotemporal β‐diversity of ant communities across the canopy and litter strata. We sampled canopy and litter ants in ten plots, half in the early and half on the late stage of secondary succession at four times, twice in wet and twice in dry season. A high species turnover defined the spatiotemporal β‐diversity of canopy and litter ant communities across years and seasons in our focal dry forests. Importantly, the temporal ant species composition was much more stable in the canopy than in the litter. Moreover, we found that the ant community's temporal dynamics was consistently high across successional stages, not differing in the temporal β‐diversity between early and late succession. Our results provide valuable insights into the potential underlying causes of community assembly and spatiotemporal dynamics in seasonal habitats, like the highly threatened and diverse tropical dry forests.Abstract in Portuguese is available with online material.

午潮山常绿次生阔叶林主要木本植物功能群及其演替特征

为了理解午潮山次生林群落结构和演替特征，分析了不同演替阶段功能群物种的生态位和种间关系。对研究区70个20×20 m森林样地内胸径≥1 cm的木本植物进行分析调查，并按照11个功能性状（叶片氮含量、叶片磷含量、叶片钾含量、比叶面积、木材密度、叶片干物质含量、叶片叶绿素含量、生长型、寿命、喜光性和最大潜在树高）将主要的45个物种划分为4个功能群：早期先锋树种（PFG1）、中期中性树种（PFG2）、中后期树种（PFG3）和后期耐阴树种（PFG4）。结果表明种间正负联结比接近1，但显著正联结多于显著负联结，群落整体稳定，而演替中后期功能群（PFG2、PGF3和PFG4）的种间生态位重叠和种间联结强度较高，种间竞争激烈。午潮山森林群落正向演替后期发展，可伐除部分与演替中后期树种相互竞争的早期树种加速演替，并且补植有价值的喜阳先锋种减少开放地，为修复森林生态系统和加速群落演替提供策略。;To understand the community structure and succession characteristics of Wuchao Mountain secondary forest, we analyzed niche and interspecific relationships of functional groups presenting succession stages. We investigated woody plants with diameter at breast height ≥ 1 cm in 20 m×20 m forest samples in the study area. Eleven functional traits were measured including leaf nitrogen content, leaf phosphorus content, leaf kalium content, specific leaf area, woody density, leaf dry matter content, chlorophyll content, growth form, longevity, shade tolerance, and maximum potential height. The 45 species were grouped into four functional groups, such as early successional species (PFG1), mid successional species (PFG2), mid and late successional species (PFG3), and late successional species (PFG4). The results of the interspecific association showed that the ratio of positive and negative association was close to 1, and the significant positive pairs were greater than the significant negative pairs, which indicated that the community was in a relatively stable succession statue. However, the values of niches overlap and interspecific association among PFG2, PGF3, and PFG4 were high and interspecific competition was intense. Our results suggest that the forest community of Wuchao Mountain is developing towards the later stage of succession. To restore forest ecosystems and accelerate succession, thinning of the early species competing with late species could be undertaken and commercial pioneer species could be used to reduce the amount of opening area.

植物-土壤反馈与草地群落演替:菌根真菌和土壤病原菌的调控作用

由植物引起的根际土壤生物或非生物环境的改变能够反馈影响群落中不同植物的生长，直接改变共存植物的相对竞争关系，推动群落结构的动态变化。作为土壤生物群落的重要组成部分，土壤微生物在植物-土壤反馈关系中起到重要的调控作用，对解释植物群落的演替进程和方向有着重要的意义。在草地植物群落演替的早期阶段和外来物种入侵的过程中，宿主植物对丛枝菌根真菌（AMF）的依赖性较低，受本地病原菌的影响较小，一般不存在负反馈。在演替后期，植物对AMF更具依赖性，而积累的病原菌则产生较强的负反馈效应，从而促进群落物种共存和植物多样性，提高草地生产力和稳定性。研究微生物-植物反馈机制不仅有助于完善草地退化与恢复理论，还对退化草地恢复治理的实践有着指导意义。未来关于根际微生物-植物反馈在草地群落演替中的作用应该加强以下几方面的研究：（1）在实验方法上，开展专性微生物-植物反馈研究；（2）在测定指标上，进一步量化不同微生物在反馈关系中的功能差异；（3）在研究对象上，加强土壤微生物在植物群落水平的反馈研究；（4）在应用上，明晰植物-土壤反馈在退化草地恢复过程中的作用，指导草地管理实践。;Biotic and abiotic changes of soil properties (e.g. physical, chemical and biotic) caused by a plant affect the growth of other plant species within the same communities, reshape the competitive relationship between different species, and restructure the dynamic changes of species composition. The feedback between plant and soil has become an important concept for explaining the diversity, stability, dynamics and succession of plant communities. Its process and mechanism are also key scientific issues to understand the responses of terrestrial ecosystems to global changes. However, biotic factors, in particular soil microbes mediated plant-soil feedback are still poorly understood. These changes in key microbial groups, such as arbuscular mycorrhizal fungi (AMF) and soil pathogens may increase or decrease the plant growth, resulting in positive or negative plant-soil feedbacks. In the early successional stage or during exotic plant invasion, host plants preferentially utilizing abundant soil nutrients have low dependence on the AMF and are less affected by native pathogens. Generally, there is no negative feedback. In the late successional stage, as the nutrients are being depleted, AMF help host plants with better access to soil nutrients and increased resistance to stress and pathogens, which could generate positive feedback and potentially accelerate succession. However, the accumulated pathogens can generate negative feedback and contribute to plant species coexistence and diversity, and thus improved productivity and stability of grassland. The study of microbial feedbacks on plant community dynamic is not only helpful to improve the theory of grassland degradation and restoration, but also instructive to the practice of restoration and management of degraded grassland. In the future, the key issues of plant-microbe feedback in grassland community succession were suggested as follows. (1)In experimental methods, it is necessary to test the net effect of obligate microbes dynamics on the plant succession using a fully reciprocal inoculation experiment which involves host-mediated differentiation of microbial communities and differential effects of the microbes on the plant fitness. (2)Regarding measurement indexes, further work quantizing the trade-off between the nutrient uptake and the carbon allocated to the microbes by host plant is needed. Comparing the ratios of nutrient benefit versus carbon cost between plants reciprocally inoculated with own and foreign microbial communities would enable us to evaluate functional variation between different microbes. (3)For research objects, the impacts of microbes on plant community structure require more empirical attention. In terms of application, the role of plant-microbe feedback on the restoration of degraded grassland is clarified to guide grassland management.