Recovery Of Ecosystem Functions Research Articles

Ecological restoration at pilot-scale employing site-specific rationales for small-patch degraded mangroves in Indian Sundarbans

To date, degraded mangrove ecosystem restoration accomplished worldwide primarily aligns towards rehabilitation with monotypic plantations, while ecological restoration principles are rarely followed in these interventions. However, researchers admit that most of these initiatives' success rate is not appreciable often. An integrative framework of ecological restoration for degraded mangroves where site-specific observations could be scientifically rationalized, with co-located reference pristine mangroves as the target ecosystem to achieve is currently distinctively lacking. Through this experimental scale study, we studied the suitability of site-specific strategies to ecologically restore degraded mangrove patches vis-à-vis the conventional mono-species plantations in a highly vulnerable mangrove ecosystem in Indian Sundarbans. This comprehensive restoration framework was trialed in small discrete degraded mangrove patches spanning ~ 65 ha. Site-specific key restoration components applied are statistically validated through RDA analyses and Bayesian t-tests. 25 quantifiable metrics evaluate the restoration success of a ~ 3 ha degraded mangrove patch with Ridgeline distribution, Kolmogorov–Smirnov (K-S) tests, and Mahalanobis Distance (D2) measure to prove the site’s near-equivalence to pristine reference in multiple ecosystem attributes. This restoration intervention irrevocably establishes the greater potential of this framework in the recovery of ecosystem functions and self-sustenance compared to that of predominant monoculture practices for vulnerable mangroves.

Recovery of Ecosystem Functions on a Restored Limestone Mine area in the Foothills of Himalaya

Recovery of Ecosystem Functions on a Restored Limestone Mine area in the Foothills of Himalaya

Restoration and coral adaptation delay, but do not prevent, climate-driven reef framework erosion of an inshore site in the Florida Keys

For reef framework to persist, calcium carbonate production by corals and other calcifiers needs to outpace loss due to physical, chemical, and biological erosion. This balance is both delicate and dynamic and is currently threatened by the effects of ocean warming and acidification. Although the protection and recovery of ecosystem functions are at the center of most restoration and conservation programs, decision makers are limited by the lack of predictive tools to forecast habitat persistence under different emission scenarios. To address this, we developed a modelling approach, based on carbonate budgets, that ties species-specific responses to site-specific global change using the latest generation of climate models projections (CMIP6). We applied this model to Cheeca Rocks, an outlier in the Florida Keys in terms of high coral cover, and explored the outcomes of restoration targets scheduled in the coming 20 years at this site by the Mission: Iconic Reefs restoration initiative. Additionally, we examined the potential effects of coral thermal adaptation by increasing the bleaching threshold by 0.25, 0.5, 1 and 2˚C. Regardless of coral adaptative capacity or restoration, net carbonate production at Cheeca Rocks declines heavily once the threshold for the onset of annual severe bleaching is reached. The switch from net accretion to net erosion, however, is significantly delayed by mitigation and adaptation. The maintenance of framework accretion until 2100 and beyond is possible under a decreased emission scenario coupled with thermal adaptation above 0.5˚C. Although restoration initiatives increase reef accretion estimates, Cheeca Rocks will only be able to keep pace with future sea-level rise in a world where anthropogenic CO2 emissions are reduced. Present results, however, attest to the potential of restoration interventions combined with increases in coral thermal tolerance to delay the onset of mass bleaching mortalities, possibly in time for a low-carbon economy to be implemented and complementary mitigation measures to become effective.

How to increase the supply of native seed to improve restoration success: the US native seed development process

With the United Nations Decade on Ecosystem Restoration, restoration of damaged ecosystems is turning into a global movement. Restoration actions that are not based on science and an understanding of ecosystem function can thwart desired restoration outcomes at best and cause further damage to ecosystems at worst. Restoration often includes revegetation using seed. Where we source seed for restoration can make a difference for species establishment, restoration outcomes, and recovery of ecosystem function. However, sourcing seeds of native species, let alone genetically appropriate seed, is not currently possible for many restoration projects. The process of increasing and sourcing suitable seed for restoration includes many steps that need to be addressed typically years before a restoration project is initiated. These steps of seed collection, evaluation and development, field establishment, production, certification and procurement, storage, and finally restoration, need to be considered ideally at a scale larger than individual restoration projects and with research conducted in each step. We describe these steps as implemented in the United States, the challenges therein, and provide suggestions and examples of how groups can make efficient and effective progress toward getting the right seed in the right place at the right time.

Predicting future stability of ecosystem functioning under climate change

To maintain food security under global change, we need to consider the stability of ecosystem functioning into the future, particularly in resource production landscapes such as agricultural pasture. With ongoing climate change, extreme climatic events are predicted to become more frequent and severe globally, impacting crop production. The whole process of farming will become more uncertain, from choice of crop and crop productivity to the timing of the windows of opportunity for management decisions. Future agricultural policies, therefore, should not only consider changes in grassland production, but also its future stability. We use a case study of agricultural pastures on the island of Ireland to project different components of ecosystem stability (resistance, recovery time and recovery rate) to 2050 and 2080 under different future climate scenarios: a peak and decline scenario; and a continued emissions scenario. We show that future climate change will have substantial effects on both the future resistance and the recovery of ecosystem functioning following environmental disturbances, but the spatial pattern of effect sizes is not the same for these two measures of stability. National level analyses and agricultural policies, therefore, are likely to ignore regional variation in future change. From this, we encourage the translation of stability-based constructs, as well as maximum yield considerations, into future agricultural policy at the regional level.

Ecosystem carbon exchange and nitrogen removal rates in two 33‐year‐old constructed salt marshes are similar to those in a nearby natural marsh

Human activities have led to 1–2% of coastal wetlands lost per year globally, with subsequent losses in ecosystem services such as nutrient filtering and carbon sequestration. Wetland construction is used to mitigate losses of marsh cover and services resulting from human impacts in coastal areas. Though marsh structure can recover relatively quickly (i.e., <10 years) after construction, there are often long‐term lags in the recovery of ecosystem functions in constructed marshes. We conducted a year‐long study comparing seasonal plant productivity, ecosystem respiration (), denitrification, and dissimilatory nitrate reduction to ammonium (DNRA) between two 33‐year‐old constructed marshes (CON‐1, CON‐2) and a nearby natural reference marsh (NAT). We found that CON‐1 and CON‐2 were structurally similar to NAT (i.e., plant aboveground and belowground biomass did not differ). Likewise, gross ecosystem productivity (GEP), , and net ecosystem exchange (NEE) were similar across all marshes. Further, DNRA and denitrification were similar across marshes, with the exception of greater denitrification rates at CON‐2 than at the other two sites. While pore‐water ammonium concentrations were similar across all marshes, organic matter (OM) content, pore‐water phosphate, nitrate + nitrite, and hydrogen sulfide concentrations were greater in NAT than CON‐1 and CON‐2. Collectively, this work suggests that current marsh construction practices could be a suitable tool for recovering plant structure and some ecosystem functions. However, the lag in recovery of pore‐water nutrient stocks and OM content also suggests that some biogeochemical functions may take longer than a few decades to fully recover in constructed marshes.

Canopy Leaf Traits, Basal Area, and Age Predict Functional Patterns of Regenerating Communities in Secondary Subtropical Forests

Secondary forests originate from natural regeneration after fallow (succession) or restoration. Species assembly in these communities, which can affect ecosystem functions and successional trajectories, is very unpredictable. Trait-based trajectories can shed light on the recovery of ecosystem functions and enable predictions of how the regenerating communities will change with forest age. Regeneration communities are affected by initial conditions and also by canopy structure and functional traits that alter dispersers' attractiveness and coexistence mechanisms. Here we evaluated how community functional traits change over time and tested if functional diversity and composition of the established canopy, as well as the structure of the canopy and forest age, influence the functional structure of regenerating tree communities when compared to their reference forests. For this, we calculated dissimilarity in trait composition (community-weighted means) and in functional diversity of regenerating communities of each succession/restoration stand, using the tree stratum of nearby mature forests as baseline values. Functional trait information comprises leaf, wood density, and reproductive traits from tree species. Our community data contain information from natural successional forests and restoration sites, in the South-Brazilian Atlantic Forest. Predictor variables of functional dissimilarities were forest age, canopy structural variables, canopy functional composition, and functional diversity. Results showed leaf traits (leaf dry matter content, leaf nitrogen content, leaf nitrogen-phosphorus ratio) and seed mass varying with forest age. Canopy functional composition based on leaf traits and total basal area significantly predicted multiple trait functional dissimilarity between the regeneration component of secondary forests and their reference community values. Dissimilarity increased when the canopy was composed of species with more acquisitive traits. Difference in functional diversity was only influenced by forest age. Mid-stage secondary forests showed lower functional diversity than early-stage forests. Our results indicated the importance of canopy traits on the natural regeneration of secondary subtropical forests. If functional similarity with reference forests is a desired objective in order to recover ecosystem functions through natural regeneration, leaf functional traits of canopy trees that establish or are planted in degraded areas must be considered in the successional processes.

Recovering ecosystem functions through the management of regenerating community in agroforestry and plantations with Khaya spp. in the Atlantic Forest, Brazil

Our aims were to describe the role of the selective management of regenerating community (RC) on the recovery of ecosystem functions in production areas of African mahoganies under mixed stands and agroforestry systems, established on abandoned farmland. A randomized block experiment was set up with the following treatments: (T1) mixed-plantation of African mahogany under conventional system (including herbicide application); (T2) mixed-plantation of African mahogany with selective conduction of RC; (T3) agroforestry system with African mahogany; (T4) agroforestry system with African mahogany with selective conduction of RC. The parameters of horizontal structure, diversity and ecological attributes of species of the regenerating community were studied. In addition, the production of aboveground biomass and nutrient stocks, soil fertility, and soil microbial activity were assessed. In T1, herbicide application (glyphosate) affected the floristic composition of the regenerating community by reducing the dominance of monocots and Pteridium arachnoideum, allowing the regeneration of other taxonomic groups of herbaceous species. In response, there was a reduction in the litter biomass stock comparing to the other treatments. The treatments with selective management of the RC (T2 and T4) produced more biomass and accumulated higher amounts of C and nutrients than the conventional treatments (T1 and T3). These treatments also allowed other shrub and tree species to overcome the ecological filter imposed by grasses and colonize the experimental area. Baccharis dracunculifolia, Vismia guianensis, Cecropia pachystachya and Inga sp. were the most important regenerating species that contributed most to the stocks of all nutrients in living aboveground biomass. Pruning and selective management in T4 increased the soil effective cation exchange, while in the T1 treatment there was a lower activity of the β-glucosidase enzyme. The selective management of RC in agroforestry systems through the manipulation of competitive relationships allowed the colonization of native tree and shrubby species that provide several additional ecosystem services, including pollination, fauna attraction, food production, pest control and environmental regulation for the agroecosystem.

Combined effects of soil fertility and vegetation structure on early decomposition of organic matter in a tropical riparian zone

Monitoring forests undergoing restoration is important to evaluate not only the development of trees, but also the recovery of ecosystem functions. The decomposition of the organic matter is an important ecological process, and nutrient cycling in ecosystems is a good indicator of forest ecosystem functions because it responds to physical, chemical, and biological characteristics of the vegetation and the soil. We hypothesized that both soil fertility and vegetation structure have direct and positive effects on decomposition processes. We used the Tea Bag Index (Keuskamp et al., 2013) to evaluate early decomposition of the organic matter in three land use categories, pasture, riparian forest undergoing restoration, and riparian forest remnant. Each category extended along a gradient of soil nutrients, enabling to jointly evaluate the effects of soil nutrients and vegetation structure on the decomposition process, using structural equations models to also describe the covariance between soil nutrients and vegetation. The decomposition rates (k) were negatively related to vegetation development, possibly due to less light in the forest floor, and less activity of the decomposer community. On the other hand, soil fertility had direct positive effects on k, possibly with higher microbial activity due to higher nutrient availability. The stabilization factor (S) was not influenced by soil nutrients or vegetation structure. However, in the riparian forest remnant plots, S increased with soil base saturation, indicating an interaction between the effects of soil fertility and land use category. Therefore, the decomposition process in this system responded to soil fertility and vegetation structure, but the magnitude of these effects varied with land use. The monitoring of this ecosystem function to evaluate ecosystem recovery should include simultaneously both soil and vegetation variables.

Recovery of ecosystem functions after experimental disturbance in 73 grasslands differing in land‐use intensity, plant species richness and community composition

Abstract Drivers of ecosystem stability have been a major topic in ecology for decades. Most studies have focused on the influence of species richness on ecosystem stability and found positive diversity‐stability relationships. However, land use and abiotic factors shape species richness and functional composition of plant communities and may override species richness‐stability relations in managed grasslands. We analysed the relative importance of land‐use intensity (LUI), resident plant species richness and functional composition for recovery of plant communities (plant species richness, plant cover, above‐ and below‐ground biomass) and release of soil nutrients after a severe mechanical disturbance. Experimental sward disturbance was applied to 73 grassland sites along a LUI gradient in three German regions. We considered relative (ln(disturbance/control)) and absolute (disturbance − control) treatment effects. Using structural equation modelling, we disentangled direct effects of LUI and resident species richness on recovery and indirect effects via changes in functional richness. Community‐weighted‐mean traits rarely mattered for recovery or nutrient release, while functional richness especially increased relative recovery of plant communities but also relative release of NO3‐N and NH4‐N. These effects were enhanced by increasing resident plant species richness and decreasing LUI. Next to these indirect influences of LUI and resident plant species richness via functional community composition, grasslands of high compared with grasslands of low resident plant species richness generally showed decreased recovery of plant communities. In grasslands of high LUI, absolute recovery of some aspects of plant communities was decreased. We did not find consistent differences between the relative importance of the different drivers of recovery after the first and the second season. Overall, resident species richness seemed most important for relative recovery and less important for absolute recovery, where direct effects of LUI were more common. Synthesis. The stability of ecosystems in managed grasslands depends on more than species richness. Thus, drivers that directly affect species richness and functional community composition have to be considered when studying the stability of real‐world ecosystems. More specifically, in managed grasslands high resident species richness but also high land‐use intensity (LUI) decreased the stability of ecosystem functions, which was partially buffered by increases in functional richness.

Effects of post-fire hillslope stabilisation techniques on chemical, physico-chemical and microbiological soil properties in mediterranean forest ecosystems

Postfire restoration practices encompass those which aim to reduce negative wildfire impacts and to improve burned area rehabilitation. Contour-felled log debris (CFD) and log erosion barriers (LEB) are two techniques used worldwide on hillslopes after wildfires in order to avoid soil erosion. In this context, it is essential to evaluate how these restoration techniques can affect soil properties by increasing or decreasing wildfire impacts. The effects on several physico-chemical and biological soil parameters were here investigated by comparing three differently treated post-fire zones. Three randomly 20 × 20 m distributed plots were set up five years after wildfire in the burned and contour-felled log debris areas (CFD plots), three others in the burned and log erosion barriers area (LEB plots) and three others in the burned and unmanaged plots (BNa plots). Three more plots were set up in an unburned area close to the burned area (UB plots). The results revealed that LEB and, to a lesser extent CFD, improved postfire soil quality, which a priori favoured helped the recovery of ecosystem functions. Our results also indicate greater efficacy of LEB and CFD in retaining sediments by limiting loss of nutrients, which is considered essential to recover vegetation after a wildfire. Post-fire restoration plans should consider the use of LEB and CFD when aiming to favour ecosystem recovery processes after wildfires.

Биополимерная технология восстановления экосистемных функций нефтезагрязненных почв

Биополимерная технология восстановления экосистемных функций нефтезагрязненных почв

Fished species uniformly reduced escape behaviors in response to protection

Predation is a critical ecological process that alters the structure and functioning of ecosystems through density-mediated and trait-mediated effects on lower trophic levels. Although studies have focused on harvest-driven reductions in abundances and sizes of targeted species, human harvest also alters species morphologies, life histories, and behaviors by selection, plasticity, and shifts in species interactions. Restricting harvest can recover the biomass of targeted species, but it is less clear how behavioral phenotypes recover, particularly relative to the impacts of potentially opposing pathways of human influence. We investigated the effects of protection on the behavioral traits of a marine fish assemblage, recording behavior of 1377 individual fishes of nine targeted kelp forest species across 16 California marine protected areas (MPAs) varying in age, protection level, and diver visitation. With long-term, full protection from harvest, all fish species exhibited shorter flight initiation distance (FID, or the distance at which an animal flees from an approaching threat) and longer time delays before fleeing, despite differences in trophic position, microhabitat use, and other ecological characteristics. These escape behaviors were amplified across new MPAs regardless of protection level, suggesting that recovery is slow and likely the result of differences in genetic or early-life experience among individuals in these long-lived species. Although the effects of full protection from harvest were partially offset by recovering populations of large piscivorous predators, the net effect of long-term, full protection on fish behavior was shorter FID. Additionally, all species had shorter FID at sites more frequently visited by divers, and this effect was greater in sites with long-term, full protection from fishing. To the extent that escape behavior is correlated with foraging behavior and predation rates, these results suggest that human-induced behavioral changes may affect ecosystem processes, even after abundances have recovered. If recovery of ecosystem functioning and services are the management goal, assessments should be broadened to include the recovery of functional traits (including behavior).

Factors Affecting Natural Regeneration of Tropical Forests across a Precipitation Gradient in Myanmar

Natural regeneration is an essential component of forest dynamics and the recovery of ecosystem functions. Therefore, understanding regeneration status, and how abiotic and biotic factors affect it, is important for ecological studies. This study discovered different regeneration statuses of tropical forests in response to differences in rainfall in Myanmar, and the environmental and overstory factors that had the most influence on understory regeneration. Study sites were set up in regions with 625 to 2035 mm of annual rainfall, and ecological characteristics were measured. According to the results, natural regeneration increased with rainfall, showing a good regeneration status at all sites. Forests within a range of 1411–2035 mm of annual rainfall had a significantly higher density and species diversity at specific natural regeneration stages than those with 625–1029 mm. Not only abiotic but also overstory structure affected the natural regeneration of forests. However, not all factors influenced natural regeneration status. Overstory size distribution parameters did not show a significant influence on natural regeneration. Average annual rainfall (abiotic), as well as ecosystem complexity, density, species richness, and diversity (overstory), were found to be the most influential factors for the density and diversity of natural regeneration. The results of this study will support silviculture and the management of tropical forests.

Measuring the success of reforestation for restoring biodiversity and ecosystem functioning

Summary Effective assessment of the success of ecological restoration projects is critical in justifying the use of restoration in natural resource management as well as improving best practice. One of the main goals of ecological restoration is the recovery of ecosystem function, yet most researchers assume that increasing species and or functional diversity equates with restoration of ecosystem function, rather than empirically demonstrating these mechanistic relationships. In this study, we assess how dung beetle species diversity, community composition, functional diversity and ecological functions vary along a restoration chronosequence and compare restored areas with reference (rain forest) and degraded (pasture) systems. We also directly investigate the dung beetle diversity – ecosystem functioning relationship in the context of ecological rain forest restoration by testing the predictive power of traditional taxonomic indices and functional diversity metrics for functionality. Species richness, abundance, biomass and functional richness all increased with restoration age, with the oldest restoration sites being most similar to rain forest, whereas functional evenness and functional divergence decreased with restoration age. Community composition in the restored areas was clearly progressing towards the rain forest sites and deviating from the pasture sites with increasing restoration age. Secondary seed dispersal rates increased with restoration age, but there was only a weak positive relationship between dung removal and soil excavation and restoration age. Biodiversity metrics explained 47–74% of the variation in functions mediated by dung beetles; however, functional trait‐based indices provided greater explanatory power of functionality than traditional species‐based metrics. Synthesis and applications. Our results provide empirical evidence on the potential of tropical forest restoration to mitigate biodiversity losses, recovering not only faunal species diversity, but also functional diversity and ecosystem functions in a relatively short period of time. We also demonstrate that functional trait‐based metrics are better predictors of functionality than traditional species‐based metrics but that the relationship between restoration age, diversity and ecosystem functioning is not straightforward and depends on the functions, traits and metrics used.

ECOLOGICAL RESTORATION INDICATORS IN AGROFORESTRY SYSTEMS IN THE ATLANTIC FOREST

The Agroforestry Systems (SAF) are forms of land use and land occupation in which woody plants are managed in association with herbaceous and agricultural ones. They present the possibility to recover degraded areas, as comprehended in legislation. Thus, the monitoring and assessment of areas recovered with Agroforestry Systems are extremely important, seeking to evaluate if their environmental functions can be equivalent to areas recovered only with native species. Thereby, the objective of this study was to evaluate, through forest restoration indicators, the recovery of ecosystem functions in SAF implanted in Ribeirão Grande, São Paulo State. The sample design was randomized by 3 installments (15 x 15 m each) randomly allocated in a SAF area and other 3 installments in a reforestation area with native species only (RN), both five years old, in the same watershed. The indicators were crown diameter, forest litter stock, height and diameter above the base of the individual trees, temperature, and humidity. The assumptions of normality and homogeneity of variance were verified through the Waste Analysis, with subsequent analysis using the nonparametric Wilcoxon-Mann-Whitney test. Statistical analyzes were performed using the R software (R Delopment Core Team, 2012) with a significance level of 5% (α = 0.05). It is concluded that the recovery area only with native species presents better development of vertical structure, with greater canopy closure. For soil indicators there were no differences. SAF, run by natural succession, can be presented as an alternative to the recovery of degraded areas, because they are more similar to the structure of native forests.

Resilience of Mediterranean terrestrial ecosystems and fire severity in semiarid areas: Responses of Aleppo pine forests in the short, mid and long term

In recent decades, the fire regime of the Mediterranean Basin has been disturbed by various factors: climate change; forest management policies; land cover; changed landscape. Size and severity have notably increased, which in turn have increased large fires events with >500ha burned (high severity). In spite of Mediterranean ecosystems' high resilience to fire, these changes have implied more vulnerability and reduced natural recovery with irreparable long-term negative effects. Knowledge of the response of ecosystems to increasing severity, mainly in semiarid areas, is still lacking, which is needed to rehabilitate and restore burned areas.Our approach assessed the resilience concept by focusing on the recovery of ecosystem functions and services, measured as changes in the composition and diversity of plant community vegetation and structure. This will be validated in the long term as a model of ecosystem response. Also, depending on the pre-fire characteristics of vegetation, fire severity and the post-fire management, this approach will lead to tools that can be applied to implement post-fire restoration efforts in order to help decision making in planning activities.Regarding Mediterranean ecosystems' ability to recover after wildfires, this study concludes that pre-fire communities are resilient in these fire-prone areas, but the window for natural recovery in semiarid areas of Aleppo pine forest in SE Iberian Peninsula varied from 3 to 15 post-fire years. Fire severity was also key for effects on the ecosystem: the vegetation types of areas burned with low and medium severity recovered naturally, while those areas with a high-severity burn induced shrublands. We concluded that very strong regeneration activity exists in the short term, and that the negative effects of medium- and high-severity fire are evidenced in the mid and long term, which affect natural recovery. Adaptive forest management to rehabilitate and restore burned Mediterranean ecosystems should be implemented.

Complex Interrelationships Among Aboveground Biomass, Soil Chemical Properties, and Events Caused by Feral Goats and Their Eradication in a Grassland Ecosystem of an Island

This study examined the recovery, via biotic and abiotic pathways, of a grassland ecosystem after eradication of introduced exotic goats. We used path analyses to evaluate the relative strength of relationships among aboveground biomass, soil chemical properties (carbon, nitrogen, and phosphorus content; soil acidity), presence of nesting seabirds after goat eradication, extent of vegetation degraded by goats before their eradication, plant species composition after removal of goats, and topography. Models including the same variables with different paths were constructed using the Bayesian estimation method, and the best-fit models were constructed by comparing deviance information criterion values. Results of the path analyses demonstrated that vegetation degradation and soil erosion prior to goat eradication increased soil exchangeable acidity, which resulted in limitation of aboveground biomass. Seabird nesting after goat eradication increased the quantity of soil nutrients, possibly through inputs of feces, eggshells, and dead chicks or adults. The increase in nutrients was affected indirectly, via seabird nesting, by topography and vegetation type after goat eradication. The direct and indirect relationships demonstrated by our results suggest the existence of complex interrelationships during recovery of ecosystem function after eradication of exotic mammals.

滇西北高原入湖河口退化湿地生态修复效益分析

In the present study,Jianhu,a typical degraded plateau wetland in Northwesten Yunnan,is selected as the study site and for the efficiency assessment of an ecological restoration project. The aim of the this study is to provide a scientific basis for restoring degraded wetlands and treating water pollution problems in Yunnan Plateau area,and to maintain ecological stability of associated lake ecosystems. The result showed that after two years' ecological restoration effort,estuarine landscape structure has been greatly improved with diversified landscape and optimized spatial structure. Also,water quality has been improved,with the transparency of the water body increased by 101%,and the concentrations of TN,NH+ 4-N,NO-3-N,TP and COD significantly decreased by 62.5%,89.3%,62.5%,91.7% and 68.0%,respectively.The purification process of water suggests that the sediment treatment has improved the hydrological conditions in the estuarine environment,and the selection of plant species should be based on nutrient content of the sewage. Also,a high proportion of submerge plants could be used to enhance purification effect. However,the purification effect varied for wetlands with different plant communities,which suggest that aquatic plants have different preference to nitrogen and phosphorus,and they have established complex interactions. Also,once exposed to different nutrient content,the same plant species could display varying levels of water purification function. Therefore,to better deal with sewage problem,it is essential to select the right plant species for community assembly purpose according to water pollution levels. Meanwhile,it is necessary to adjust the composition of plant community according to the change of water quality so that plants could grow well,the stability of the wetland ecosystem could be maintained,and the recovery of ecosystem functions and services could be sustained. After the degraded wetland is restored,it would offer multiple ecosystem services each year,with the yield value of the water purifying effect estimated as RMB 1850000 yuan,the yield value of biodiversity conservation,ecological tourism and other ecosystem services estimated as RMB 327000 yuan,and the market value of the ecological agriculture system estimated as RMB 2700000 yuan. Therefore,the comprehensive benefits of economy,society and ecology could be accomplished,and the goal of demonstrating restoration feasibility of a degraded plateau wetland is fulfilled.

Spatial analysis of remnant tree effects in a secondary Abies-Betula forest on the eastern edge of the Qinghai–Tibetan Plateau, China

Remnant trees, remaining after large-scale disturbance of forests, have been shown to exhibit noticeable ecological effects on the recovery of ecosystem functions. Although it is well known that remnant trees may serve as dispersal foci, their effects on the spatial pattern of later stages of dominant tree species in natural secondary forest have not been fully appreciated. To explore the spatial influences of remnant trees on later stages of dominant tree species of a secondary Abies-Betula forest on the eastern edge of the Qinghai–Tibetan Plateau, we mapped all the trees in a 200m×200m plot. We used spatial point pattern analysis including O-ring statistics to analyze the spatial associations between old-growth remnant trees and two dominant tree species of later stages. Abies faxoniana and Betula albo-sinensis, comparing different size-classes at different spatial scales. Our results showed that saplings, small trees, and medium trees of the shade-tolerant species, A. faxoniana, showed significantly positive associations to the old-growth remnant trees of both dominant species, suggesting that remnant trees provided favourable sites for the regeneration of shade-tolerant species. In contrast, small, and medium trees of the shade-intolerant species, B. albo-sinensis, showed significantly negative associations to old-growth remnant trees of both dominant species, suggesting that the remnant trees hinder their regeneration. For old-growth remnant trees, the O12(r) function value (density) of their seedlings, saplings, small trees, and medium trees was calculated at increasingly greater concentric scales (with radius from 0 to 100m from the remnant trees). Tree density first increased rapidly from 0 to 10m or 20m radius (distance from remnant tree) and then decreased continually away from remnant trees, consistent in part with the population recruitment curve proposed by the Janzen–Connell model. We found that saplings, small trees, and medium trees of A. faxoniana tended to distribute within a particular range of annuli around the remnant trees of A. faxoniana, with the densities of the three largest size-classes reaching a maximum within 3–6m of the remnant tree. The densities beyond the parent remnant trees continued to show an increasingly expanding zone of attraction around the remnant tree. In effect, the small and medium A. faxoniana trees coalesced around remnant trees to create increasingly enlarged canopy cover areas, which served simultaneously as protected zones for A. faxoniana regeneration and extended exclusion zones for B. albo-sinensis and similar shade intolerant species.