Restoration Plots Research Articles

Does decline and recovery process affect clonal and genetic diversity of a coastal plant population?

The evaluation of genetic diversity is important for the conservation of species. However, changes in genetic diversity during conservation are complex processes that depend on the characteristics of the species and environment. To evaluate the changes in genetic diversity from decline to recovery, we surveyed the coastal herb Calystegia soldanella in areas with varying degrees of non‐coastal plant invasion. First, to evaluate genetic diversity before the conservation measures, the spatial clonal structure of adults was investigated in a population invaded by non‐coastal plants. Second, to evaluate genetic diversity after the conservation measures, the regenerated individuals were investigated in the restoration plot. Moreover, to predict future genetic diversity without conservation measures, the effects of non‐coastal plant invasion on the production and genetic diversity of seeds were investigated using individuals from areas with various levels of non‐coastal plant invasion. In the adult population, 16 genets were identified in an 80 m × 4 m area. The maximum genet size was 30.3 m, suggesting the importance of clonal reproduction for population maintenance. In the restoration plots comprising 10 m × 10 m × 3 replicates, many seedlings (1.14 ramets/m2) emerged, resulting in high clonal diversity compared to that of the adult population. Therefore, the biomass and genetic diversity were rapidly restored at the beginning of the conservation practice. Non‐coastal plant invasion did not affect the genetic diversity of the seeds. However, it significantly reduced seed production. This suggests that non‐coastal plant invasion reduces sexual reproduction, resulting in the long‐term loss of genetic diversity.

Effects of different afforestation years on soil moisture and nutrient content in Maxian Mountain of the Loess Plateau

In the area of “returning farmland to forest” on the Loess Plateau in China, it is difficult to cultivate artificially planted trees into forests. In the current study, abandoned cultivated land after 10 years of natural restoration served as controls (CK), while the treatments included afforestation periods of 2, 4, 6, 8, and 10 years. Soil samples were collected from various depths: 0–20, 20–40, 40–60, 60–80, to 80–100 cm. The findings revealed that with increasing years of artificial afforestation, soil pH gradually increased, and soil moisture content rose in the 0–20 cm layer while declining in deeper layers (20–100 cm) in the Maxian Mountain region of the Loess Plateau. Moreover, the total carbon, nitrogen, phosphorus, and potassium content initially increased and then decreased with the duration of artificial afforestation, reaching peak values after 8 years. Contents of organic matter, ammonium nitrogen, nitrate nitrogen, available phosphorus, and available potassium in the same soil layer increased with each year of afforestation. However, upon reaching 10 years of artificial afforestation, the effective nutrient content in the 60–80 and 80–100 cm soil layers exhibited a decrease. The values of Integrated Fertility Index (IFI) in different afforestation years were ranked as follows: 8 years > 6 years > 10 years > 4 years > 2 year, but all of them were significantly smaller than those of natural restoration plot CK (P < 0.05). Overall, soil fertility in the Maxian Mountain area of the Loess Plateau increases with each additional year of artificial afforestation. However, when the artificial afforestation period is 10 years, soil fertility decreases and marking a shift from enhancement to decline beyond this duration.

Restoration via the aggregate spray-seeding technique affected the soil proteobacteria on an Uninhabited Island: Community structure, metabolic function, nutritional type, and life strategy

This study aimed to explore the impact of aggregate spray-seeding (ASS) restoration measures on the soil proteobacterial community. Using environmental DNA sequencing, we analyzed the proteobacterial communities in the soils of 3 natural vegetation (NV) plots, 3 traditional afforestation (TA) plots, and 12 spray-seeding restoration (SR) plots located on Triangle Island in Zhuhai city, China, during both the summer and winter seasons. We estimated the metabolic function, nutritional type, and life strategy of Proteobacteria through the FAPROTAX and rrnDB databases. Our findings demonstrated that Proteobacteria was the predominant phylum (relative abundance = 40.1–48.4%) in the soil bacterial communities across all three treatments. The relative abundance of Alphaproteobacteria ranged from 28.5% to 38.1%, which was significantly greater (2.6–10.3 times, p < 0.05) than that of Betaproteobacteria or Gammaproteobacteria. Most (90%) proteobacterial genera and all rhizobial genera found in the NV and TA soils were also present in the SR soil, but there were distinct differences in the proteobacterial community structures between the SR soil and NV/TA soil. Across all seasons and treatments, the proteobacterial communities were related to functions such as ureolysis, nitrogen fixation, nitrate reduction, and hydrocarbon degradation. The relative abundance of Proteobacteria associated with chitinolysis was greater in the SR soil than in the NV and TA soils. Among the overall proteobacterial community, the chemoheterotrophic, chemoautotrophic, and phototrophic bacteria accounted for 65–77%, 19–31%, and less than 5%, respectively. Alphaproteobacteria tended to be K strategic, while Betaproteobacteria and Gammaproteobacteria tended to be r strategic. The soil pH, organic carbon content, and nitrogen content were significantly correlated with the metabolic function and nutritional type of the soil Proteobacteria according to the Mantel test results. In conclusion, the application of the ASS technique can effectively restore the biodiversity, metabolic function, and nutritional-type structure of the soil proteobacterial community. Additionally, this study highlights that certain metabolic functions of the proteobacterial community in SR soil undergo changes in response to the use of certain restoration materials. These findings suggest that the targeted addition of specific repair materials can modulate soil microorganism functionality and provide a valuable theoretical foundation for ecological restoration engineering practices.

Plant phylogenetic diversity influences arthropod communities in tropical forest restoration plots

AbstractConsideration of plant phylogenetic diversity in ecological restoration carries substantial potential, as communities with a greater diversity of lineages with older evolutionary histories can increase the diversity of niches and thus are likely to recover larger species networks than communities clustered in specific clades with reduced variation in functional traits. In this study, we experimentally assessed how arthropod communities were affected by the phylogenetic diversity of a set of tropical tree species. We established 12 experimental restoration plots with either high or low plant phylogenetic diversity while maintaining constant the number of plant species. After 1 and 3 years, arthropods with different feeding habits (herbivores, predators, pollinators, and detritivores) were collected and identified as morphospecies or operational taxonomic units using metabarcoding techniques. We provide insights on the influence of plant phylogenetic diversity on arthropod abundance and species diversity, particularly among predator, pollinator, and detritivore common and dominant species, which increased with plant phylogenetic diversity. The trend, however, was the opposite for the diversity of herbivore common and dominant species, which decreased as plant phylogenetic diversity increased. These findings highlight the importance of considering plant species richness when designing restoration strategies, but also their evolutionary histories, as the same number of plant species can produce different outcomes for higher trophic levels, as a function of their phylogenetic relationships.Abstract in Spanish is available with online material.

Dominant species establishment may influence invasion resistance more than phylogenetic or functional diversity

Abstract Phylogenetic and functional diversity are theorised to increase invasion resistance. Experimentally testing whether plant communities higher in these components of diversity are less invasible is an important step for guiding restoration designs. To investigate how phylogenetic and functional diversity of vegetation affect invasion resistance in a restoration setting, we used experimental prairie restoration plots. The experiment crossed three levels of phylogenetic diversity with two levels of functional diversity while species richness was held constant. We allowed invaders to colonise plots; these included native species from neighbouring plots and non‐native invasive species from a surrounding old field. We tested if invader biomass was influenced by phylogenetic and functional diversity, and phylogenetic and hierarchical trait distances between invaders and planted species. We binned each invader into three categories: native species from neighbouring experimental plots (site‐specific invaders), native species not part of the experimental species pool (native invaders) or non‐native species (non‐native invaders). Counter to expectation, both non‐native and native invaders became more abundant in more phylogenetically diverse plots. However, plots with higher abundance of planted Asteraceae, a dominant family of the tallgrass prairie, had lower invader biomass for both native and non‐native invaders. We also found that hierarchical trait differences shaped invasion. The species that became most abundant were non‐native invaders that were taller, and native invaders with low specific leaf area relative to planted species. Site‐specific invaders were not influenced by any plot‐level diversity metrics tested. Synthesis and application: Our results suggest that greater phylogenetic diversity may lower resistance to invasion. This effect may be due to more even but sparser niche packing in high‐diversity plots, associated with greater availability of unsaturated niche space for colonisation. However, trait composition fostered invasion resistance in two ways in our study. First, establishment of native species with strongly dominant traits may confer invasion resistance. Second, species mixes that optimise trait differences between planted vegetation and likely invaders may enhance invasion‐resistance.

Effects of Artificial Restoration and Natural Recovery on Plant Communities and Soil Properties across Different Temporal Gradients after Landslides

Landslides cause significant disturbances to mountainous ecosystems and human activities. Due to climate change, the frequency of landslides as secondary disasters has notably increased compared to the past. Further exploration is needed to understand the effects of different restoration methods on post-landslide plant communities and soil properties over different periods of time. In this regard, we selected Lantian County in the northern foothills of the Qinling Mountains as our study area. We conducted surveys on artificially restored and naturally recovered plots at 1, 6, and 11 years after landslide events. Undamaged areas were chosen nearby as control plots. We identified vegetation types and species diversity after artificial and natural recovery and further analyzed the impact of different restoration strategies on vegetation patterns and soil properties. The research results indicate that, compared with natural recovery, artificial restoration can more quickly improve vegetation and soil. With the increasing time gradient, the average ground cover of the herbaceous layer in natural recovery decreased gradually from 47% at year one to 34% at year eleven. In contrast, in artificial restoration, the average ground cover of the herbaceous layer increased from 27% at year one to 44% at year eleven. For the shrub layer, in natural recovery, the average ground cover gradually increased to 39% over eleven years. While in artificial restoration, the average ground cover for the shrub layer gradually increased to 46% over the same period. In the artificial restoration plots, soil pH gradually increased (from 6.2 to 8.2), while TN content gradually decreased (from 1.7 g/kg to 0.9 g/kg). Similarly, TK content decreased (from 22.4 g/kg to 14.5 g/kg), and AP content showed a decreasing trend (from 20.7 mg/kg to 11.4 mg/kg). In the natural recovery plots, DNA content gradually increased (from 3.2 μg/g/d to 142.6 μg/g/d), and SC content gradually increased as well (from 2.4 mg/d/g to 23.1 mg/d/g). In contrast, on sites undergoing natural recovery, the short-term restoration rates of vegetation and soil are lower, but they show greater stability over a longer time. This study provides a new perspective on vegetation restoration strategies and is expected to offer insights for the optimization of post-landslide recovery in the future.

Lessons learned from over thirty years of eelgrass restoration on the US West Coast

AbstractSeagrass habitats, which provide essential ecosystem functions such as water quality improvement, biodiversity support, ocean acidification amelioration, and sediment carbon storage, are declining worldwide. Eelgrass (Zostera marina) habitats along the contiguous US West Coast are threatened by conflicting human uses and global change, resulting in significant protections of and efforts to restore areas where habitat is extant or degraded. Despite a history of eelgrass restoration in this region spanning nearly 60 years, very little work has been published on the subject. Here, we review all available literature on eelgrass restoration projects conducted in California, Oregon, and Washington. Of the 82 restoration projects included in this analysis, which were conducted from 1989 to 2020, only 6 were published in peer‐reviewed journals. Thus, despite the precedent for conducting restoration, a lack of data availability makes assessing regional success, drivers of failure, and best practices extremely difficult. From this synthesis, we find that the majority of restoration projects (73%) have been conducted for mitigation (compliance) purposes, contributing to the lack of peer‐reviewed literature on the subject. We find that while eelgrass mitigation policies serve to maintain eelgrass structure and regional acreages, they do not facilitate assessments of habitat function or incentivize advancements in regional best practices. We also find that when we could evaluate project outcomes, 32.3%–59.6% of restoration plots were unsuccessful by the end of the project, but this percentage is highly dependent on how success is defined. According to restoration practitioners, failure was likely to result from environmental factors such as light, nutrients, or macroalgal blooms, but was occasionally due to logistical factors such as restoration method or approach. From this work, we recommend a standardized, evidence‐based approach to restoration, improved data sharing practices, and careful consideration of existing eelgrass mitigation practices. As marine habitat restoration enters a new global stage, backed by public and private investment, burgeoning carbon markets, and global biodiversity initiatives, it is essential to learn from past work to understand and improve seagrass conservation and restoration success.

Long-term effects of restoration on the links between above-and belowground biodiversity in degraded Horqin sandy grassland, Northern China

Long-term ecological restoration plays an important role in the sustainable development of degraded grassland ecosystem. In this study, the levels of species diversity, genetic diversity and soil microbial diversity in restored grassland were measured by vegetation survey, DNA barcoding and soil microbial high-throughput sequencing technology, so as to explore the relationship between above- and belowground biodiversity and its driving factors in Horqin sandy grassland. In this study, the results found that herb are dominated in restoration grassland types. Plant species richness (SR) from post-non-grazing restoration plot (NGR) communities was significantly higher than other restoration communities (10 ± 1.1, p = 0.004). Genetic diversity indices of dominant plant species in chloroplast DNA (cpDNA), were remarkable greater than nuclear DNA (nrDNA) in each recovering sandy grassland plots (amplitude of difference was 44.8%–70.5% in allelic richness (AR), 81.9%–128.1% in expected heterozygosity (HE)). The soil bacterial and fungal richness from natural mobile dune grassland (NM) communities was notably lower than that from recovering grassland types (1641.9 ± 100.4, p &amp;lt; 0.001; 533 ± 16.6, p &amp;lt; 0.001). In this study, heterogeneous levels of genetic variability among different recovering sandy grassland types were detected. Correlation analyses revealed that there were positive correlations between species diversity and genetic diversity (SR &amp;amp; AR: r = 0.56, R2 = 0.31, p &amp;lt; 0.001; SR &amp;amp; HE: r = 0.33, R2 = 0.11, p = 0.045) and a negative correlation between soil microbial diversity and genetic diversity (r = -0.44, R2 = 0.19, p = 0.005). The final structural equation model explained 38% of the variance in SR, 57% in AR, 52% in soil microbial diversity (SD), 49% in aboveground biomass (AGB), 87% in soil organic carbon (SOC), 47% in soil alkali-hydrolyzable nitrogen (SAN) and 69% in soil available phosphorus (SOP). Long-term ecological restoration had significant direct positive effects on AGB, SOC, SAN, SOP, AR, SR and SD. There was a negative correlation between above- and belowground biodiversity and biological and abiotic factors. The results of this study have clarified the above- and underground biodiversity levels of sandy grassland and the relationship with driving factors under long-term ecological restoration measures, and will provide effective support for the management and sustainable development of sandy grassland.

Diversity and composition of beetle assemblages attracted to dung in cloud forests under active and passive restoration practices.

Ecosystem loss and degradation has become a worldwide concern. The implementation of ecological restoration plans has been proposed to facilitate the recovery of ecosystems. It is imperative that once restoration strategies have been implemented, the effects of these actions in the medium and long term be evaluated, particularly the structure and functioning of the ecosystem. Diversity (α- and β-diversity) of beetles attracted to dung was assessed and compared in 3 habitat conditions (conserved forest, passive restoration, and active restoration) at 2 different seasons during the year (dry vs. rainy season) in cloud forest in San Luis Potosí (central Mexico). We found that the dry season was slightly richer than the rainy season, but the latter was significantly more diverse. Species diversity and composition in active restoration were more similar to passive restoration, and both differed greatly from the conserved forest. In contrast, conserved and passive restoration conditions exhibited similar patterns in β-diversity of insects likely because they maintain more species associated with the original vegetation of the cloud forest. Beetle assemblages could be of more habitat generalists, as they actively distribute across the restoration sites. Beetles attracted to dung provide an overview of the effect of restoration in early faunal recovery, even though we monitored this entomofauna for a short period (31 months after the restoration plots were established). These beetles can be a useful indicator for exploring the main forces driving species diversity for the management and conservation status of cloud forests, a threatened ecosystem.

Spatial design improves efficiency and scalability of seed‐based seagrass restoration

Abstract Coastal ecosystem restoration is often ineffective and expensive in practice. As a consequence, upscaling restoration efforts to functionally relevant spatial scales remains one of the largest hurdles for coastal restoration practice. On small scales, restoration success of vegetated ecosystems (i.e. salt marshes and seagrasses) can be amplified by spatial designs that harness positive interactions. However, it remains unknown if positive interactions can be harnessed with seed‐based approaches, that are considered to be more cost‐effective and scalable than traditional shoot‐based restoration methods. Here, we investigated with a full‐factorial seeding experiment if (1) restoration scale (4, 40 and 400 m2) and (2) seeding density (10 and 50 injections/m2) affected multi‐year recruitment efficiency (measured as restored plants/seed injection) of annual eelgrass Zostera marina in the Dutch Wadden Sea. We found that the largest restoration scale (400 m2) increased second‐generation recruitment efficiency by suppressing a sedimentation‐related negative feedback. With increased restoration scale, the inner parts of the restoration plots captured less sediment, which decreased the desiccation stress of the restored eelgrass during low tide. Due to this stress alleviation, plants grew larger and produced more seed‐bearing spathes, which the following year resulted in two and three times higher recruitment efficiency at the largest restoration scale compared to the smaller scales. Moreover, lower seeding density more than doubled second‐generation recruitment efficiency compared to the higher density, supporting recent work showing that the effectiveness of ‘clumped’ spatial designs is context dependent. Synthesis and applications. The efficiency of restoration efforts is seldom taken into account, but can offer restoration projects a valuable metric with which workload, donor material and cost‐requirements can be reduced. We demonstrate that simple modifications to seed‐based coastal restoration designs (e.g. scale and density) can have a substantial impact on recruitment efficiency and multi‐year restoration yields. Thus, optimised restoration designs can strongly contribute to the upscaling potential of coastal ecosystem restoration. However, optimal restoration designs are expected to be strongly context dependent and we therefore argue that investigating optimal designs should be adopted as common practice, providing a crucial steppingstone between ‘proof‐of‐concepts’ and true large‐scale restoration attempts (km2).

Rapid faunal colonization and recovery of biodiversity and functional diversity following eelgrass restoration

Seagrass meadows and their associated biodiverse assemblages have declined globally due to environmental and anthropogenic stressors. Restoration of these critical habitats has the potential to reverse coastal biodiversity loss. Here, we tested the role of patch size (which can affect recruitment, food availability, and/or predation) in driving faunal colonization in an eelgrass (Zostera marina) restoration trial in Sweden. Eelgrass shoots were transplanted in plots with different configurations (continuous vs. checkerboard patterns with three patch sizes), and we followed invertebrate colonization (biodiversity and functional diversity) during the first two growing seasons. We found rapid faunal colonization following the transplantation of eelgrass shoots in all plots with invertebrate densities reaching 50–80% of the reference meadow after only one growing season (3 months). After two growing seasons (15 months), the faunal density, biodiversity, and functional diversity were similar to the reference meadow, despite eelgrass density and biomass still being lower than the reference meadow. Biodiversity, functional diversity, and community structure were similar among the different planted plots, that is, there was no indication that patch size influenced faunal colonization. We therefore consider that smaller patches embedded within larger restoration plots can be as effective for promoting biodiversity as continuous patches, with reduced costs and fewer shoots required. We also noted high natural variability between years both in the reference meadow and planted plots, showing the dynamic nature of seagrass ecosystems, and the importance of a well‐planned monitoring scheme that considers the reference area and restored area within the same temporal scale.

Non-native fallows hold high potential for restoration through agroforestry in a Pacific Island ecosystem

Agricultural land abandonment affects millions of hectares of cultivated lands globally. While ending cultivation can lead to spontaneous reforestation and ecological benefits, the resulting landscapes often have lower social and agricultural benefits than the native forests and agricultural systems they replace, especially when non-native species dominate successional pathways. This is the case in many Pacific Islands including Hawaiʻi, where approximately 45 % of agricultural lands are unmanaged and non-native forests make up nearly 40 % of total forest cover. Agroforestry systems that integrate native and non-native culturally important plants present a potential pathway to increase social and ecological benefits of unmanaged agricultural lands; however, understanding what the restoration potential is of different agroforestry systems remains a question. We collaborated with a Native Hawaiian-led, community-based organization to explore this potential. We asked, 1) does the composition of agroforestry species planted (i.e., treatment) affect restoration success, and if so, do other factors mediate the effect of treatment, and 2) how do ecological conditions two years after starting restoration compare to conditions pre-restoration? We set up ten 12 × 15 m restoration plots and one reference plot on former pasture land regenerating as non-native forest. Then, we used a functional trait-based approach to select two agroforestry species mixes. Both mixes had high cultural value and each had traits to address a different primary ecological goal: erosion control and early successional facilitation. We monitored the plant communities before restoration and at six months, one year, and 1.5 years post-planting. We used multivariate analysis and structural equation modeling (SEM) to analyze the differences between treatments over time. We found that measures of restoration success did not vary significantly between treatments but did change from baseline. Results of the SEM indicated that understory weed cover was a significant driver of understory cover of agroforestry species, but that variability in agroforestry cover was primarily a result of management factors not tested in the model. This study provides a first step in documenting what non-native forest to agroforest transitions can look like. Our findings suggest that non-native fallows have a high potential for restoration through agroforestry in Pacific Island ecosystems.

Effects of landscape structure on restoration success in tropical premontane forest

Reversing large-scale habitat degradation and deforestation goes beyond what can be achieved by site-level ecological restoration and a landscape ecology perspective is fundamental. Here we assess the relative importance of tree cover and its configuration on forest-dependent birds and late-successional tree seedlings in restoration sites in southern Costa Rica. The abundance and species richness of birds increased in landscapes with more corridors, higher tree cover, and lower levels of fragmentation, highlighting the importance of riparian corridors for connectivity, and continuous tree cover as suitable habitat. Landscape variables affected abundance and species richness of seedlings similarly, but effects were weaker, possibly because seedlings face establishment limitation in addition to dispersal limitation. Moreover, the scale of landscape effects on seedlings was small, likely because proximal individual trees can significantly influence recruitment in restoration plots. Results underscore the importance of incorporating landscape-level metrics to restoration projects, as knowing the extent, and how the landscape may affect restoration outcomes can help to infer what kind of species will arrive to restoration plots.

Trade‐offs at applying tree nucleation to restore degraded high Andean forests in Colombia

Tree islands, the more recognizable type of applied nucleation, and passive restoration have been proven as cost‐effective restoration strategies. Comparison between them is a priority, particularly through paired experiments in ecosystems wherein restoration research is scarce, such as high forest in the northern Andes (high Andean forests [HAF]). This ecosystem is important given its environmental benefits but also because vegetation development is more limited by abiotic conditions, unlike tropical moist forests. To address these gaps, we set up an experiment in a logged pine plantation comparing the effect of nuclei and passive restoration on vegetation structure and diversity as well as natural regeneration. In this case, we divided emergent shoots into three functional groups related to restoration goals: invasive herbs, páramo species, and woody recruits. After 3 years, nuclei had higher coverage, height, and diversity, but this was exclusively due to planted trees, as nuclei did not affect the abundance of invasive herbs and páramo species. More importantly, the abundance and richness of woody recruits were kept low and constant under nuclei, likely as a by‐product of plantation density. Conversely, it gradually increased at passive restoration plots. Since nuclei contribute to structure and diversity and passive restoration contributes to woody recruits, we propose a combination of both to restore HAF. Possible changes in the direction of the interaction between planted trees and recruits confirm the need for long‐term monitoring to accurately determine the potential of tree nuclei in HAF.

Competition rather than facilitation affects plant performance across an abiotic stress gradient in a restored California salt marsh

The Stress Gradient Hypothesis predicts facilitation will become more important than competition where abiotic stress is high, and the framework successfully predicts positive interactions between species in many systems. Fewer studies have focused on intraspecific facilitation, and to our knowledge none examine intraspecific interactions in Pacific Coast salt marshes of North America. We used two species that tend to occur in large, monospecific patches to test for intraspecific facilitation in a restored California marsh, where tides and evaporation during summer create moisture and salinity gradients across elevation. We tested performance of Frankenia salina or Jaumea carnosa in restoration plots using two treatments: clustered plantings to promote facilitation, and widely spaced plantings to limit interaction between individuals. We characterized the soil water potential gradient and measured plant survival, cover, physiology, and susceptibility to herbivory across elevation and planting treatments. Soil water potential declined sharply with elevation, suggesting plant stress should be higher upslope. However, tissue water potential was unaffected by elevation, and survival was high—suggesting growing conditions remained benign. A seawater addition treatment did not alter the response of plants or plant interactions to the abiotic gradient. At 19 months, intraspecific competition prevailed across the entire elevation gradient for both species, with less transplant cover in clustered plantings. However, clustered Frankenia fared better during a transient period of heavy rabbit herbivory. Aside from this temporary benefit, clustering did not reduce stress and strongly suppressed growth—suggesting that restoration designs for the high marsh should minimize competition.

Study on the Characteristics of Soil Erosion in the Black Soil Area of Northeast China under Natural Rainfall Conditions: The Case of Sunjiagou Small Watershed

In the black soil area, where soil erosion is severe and the soil is in urgent need of ecological restoration, providing reasonable and practical measures to prevent soil erosion and restore the soil is an urgent issue at present. In this study, nine runoff plots were deployed in Bin County, the core area of soil erosion control, to monitor runoff and soil loss long-term, simulated by the erosion potential method (EPM) for comparison. Studies have shown that soil erosion is strongly influenced by soil conservation measures, land use, and vegetation cover. In contrast, slope, pre-soil moisture content, and soil crusting due to rainfall can affect erosion in a single rainfall event. The most severe soil erosion was in bare land, up to 1093.58 t km−2 a−1, followed by longitudinal ridge tillage land (751.88 t km−2 a−1) and cross ridge tillage land (31.58 t km−2 a−1). The shrublands and mixed forests planted for ecological restoration experienced almost no erosion. The soil loss rate of the cross ridge tillage and ecological restoration plots was much lower than the allowable soil loss rate (200 t km−2 a−1). Under erosive storms, longitudinal ridge tillage can produce soil loss rates that far exceed those of bare ground. The change from longitudinal ridge tillage to cross ridge tillage on gentle slopes can effectively prevent soil erosion in the study area. The vegetation restoration measures of planting shrubs such as Amorpha fruticosa Linn. are incredibly effective in the ecological restoration of wastelands in black soil areas. For the black soil area after the retreat, the vertical structure of vegetation can be improved by planting shrubs at the bottom, thus achieving a good restoration effect.

Nitrogen Dynamics and Sweet Potato Production under Indigenous Soil Moisture Conservation Practices in the Leeward Kohala Field System, Hawai’i Island

Intensive cultivation of ‘uala (sweet potato) in the Leeward Kohala field system on Hawai’i Island supported substantial populations of Native Hawaiians prior to its abandonment in the 19th century. Productivity is influenced by the heterogeneity of the climate and biogeochemical soil characteristics across the substantial ecological gradient. Agricultural infrastructure and associated practices were developed to manage crop production eventuating from the variation in inter- and intra-annual rainfall. Mechanisms of sustaining soil nitrogen (N) are still unclear; however, a pronounced source of N is soil organic matter decomposition. This study investigated in situ the effects of indigenous Hawaiian mulching practices against two control treatments on soil moisture and temperature dynamics to facilitate N mineralization in soil mounds cultivated with ‘uala. Field experiments were set in two agricultural restoration plots with distinct climatic and soil characteristics. Data included soil moisture and temperature, soil and plant N, growth and development of ‘uala, and real-time weather data. Concurrently, N mineralization was also investigated under controlled conditions. All indigenous mulching treatments were found to significantly increase soil moisture, regulate temperature variation, and improve N availability compared to control. Differences in soil properties between treatments translated to significant differences in above-ground biomass. The data suggest that these differences would extend to tuber production, but the use of a long-gestation variety limited tuber production in the study. Increased temperatures in the controlled experiments were observed to increase inorganic N significantly, but less substantially than soil moisture. Indigenous practices in the region could have greatly mitigated plant stress due to moisture, temperature, and N availability, increasing productivity and reducing the variability of the Leeward Kohala Field System.

Restoration plantations accelerate dead wood accumulation in tropical premontane forests

Dead wood stores 10–20% of global forest carbon stocks, but its recovery and restoration in secondary tropical forests are poorly documented. In this study, we evaluated (1) the recovery pattern of dead wood volumes across a chronosequence of secondary tropical forests that used to be former coffee plantations, and (2) the efficiency of two common restoration strategies to recover dead wood volumes similar to those found in old-growth forests, all in a tropical premontane landscape in southern Costa Rica. Restoration strategies consisted of plantations and natural regeneration. Plantations consist of plots where two endemic (Terminalia amazonia and Vochysia guatemalensis) and two naturalized (Inga edulis and Ertyhrina poeppegiana) species were planted in rows. Natural regeneration consists of plots where no trees were planted, but where agriculture or cattle are excluded though fencing and vegetation is allowed to regenerate naturally. We hypothesized that (1) dead wood volumes increase with forest age following a logistic shape, and that (2) restoration plantations recover dead wood volumes more quickly compared to naturally regenerated forests. We measured dead wood volumes in a total of 35 forest fragments that were former coffee plantations or are currently old-growth forests and 10 restoration plots containing either natural regeneration or restoration plantations that were former fallow or pasture using strip transects. Dead wood volumes significantly increased with forest age following a logistic shape, starting with very low values in early ages (3–5 years), increasing rapidly (6–50 years), and ending with high and relatively stable values after 50 years of age. In addition, plantations (16 to 17 years old) recovered 41% of dead wood volumes found in old-growth forests > 100 years old, whereas naturally regenerated forests of the same age only recovered 1.7% of dead wood volumes found in old-growth forests. Our study shows that restoration plantations not only accelerate the recovery of above ground biomass, but also accelerate the recovery of dead wood in premontane Neotropical ecosystems. This indicates that tree planting positively affects carbon storage, and potentially the preservation of dead wood-associated biodiversity.

Acoustic assessment of experimental reforestation in a Costa Rican rainforest

Effective forest restoration requires tools for evaluating and comparing restoration approaches. Nevertheless, measuring restoration progress can be difficult and expensive. Passive acoustic monitoring (PAM) can be an inexpensive assessment strategy to collect large amounts of biodiversity information at scale. Nevertheless, analyzing and interpreting this information remains a difficult challenge. In this study we applied and compared three approaches to assess restoration treatments using recordings collected from PAM. We tested the hypothesis that variation in forest structure translates into differences in the species composition and acoustic signature of sites. For this purpose we used a reforestation experiment on the Osa Peninsula of Costa Rica, where we compared the mature forest to four restoration treatments. The treatments included natural regeneration and three treatments that varied the ratio of balsa, a pioneer tree species, and other native species. Our first approach consisted of visual and acoustic review of recordings to describe taxonomic groups found in each location. Our second approach consisted of measuring the acoustic energy present in the 10–30 kHz frequency band, an acoustic range primarily occupied by the mating signals of katydids and other insects, important elements of the food web and are often less mobile than birds and mammals. In our third approach we created 24-hour spectrograms that represented sites and treatments. Using the 24-hour spectrograms, we calculated a PCA and used a tSNE to evaluate the differences in acoustic signature and visualize clusters of treatments. The first approach revealed that relying on visual and acoustic review would fail to find the diel acoustic patterns that were captured in the other two approaches. The approaches varied substantially in the amount of acoustic data incorporated and the amount of human processing time. Subsampling recordings demonstrated that using only 10 sec instead of 40 sec per recording generated comparable results. The failure to differentiate among restoration treatments could reflect insensitivity in the approaches, but more likely represents the fact that the restoration plots are newly established and that substantial differentiation is more likely to arise during the time course of restoration.

Proximity and abundance of mother trees affects recruitment patterns in a long‐term tropical forest restoration study

Remnant trees and forest fragments in agricultural landscapes can be important sources of propagules to facilitate forest recovery. However, many studies simply quantify forest cover in the surrounding landscape as a percentage, with little attention given to species composition, and subsequently fail to detect an effect on recruitment patterns. We assessed the relative importance of the spatial distribution and life‐history traits of 77 tree species on recruitment patterns at a landscape scale in a well‐replicated long‐term restoration study in southern Costa Rica. We censused and mapped potential mother trees in a 100‐m buffer surrounding eight replicate restoration plots and quantified respective tree recruits within each plot. We assessed how mother tree abundance, species life‐history characteristics (seed size, dispersal mode), tree size (DBH, height) and distance to restoration plot affected recruitment at coarse (plot: 50 × 50 m) and fine (quadrat: 3 × 3 m) spatial scales. The presence of a mother tree within 100 m of a restoration plot resulted in a 10‐fold increase in potential mean recruitment. Mother tree abundance was also an important driver of recruit density, and particularly so for large‐seeded (≥ 5 mm) zoochorous species with a fivefold increase in recruit density across the observed mother tree abundance range. An interaction between mother tree abundance and proximity demonstrated that the effect of mother tree abundance on recruit density was important but waned with increasing distance from restoration plots. At the fine spatial scale, proximity was uniformly important; height and DBH of the closest potential mother tree also affected recruit abundance but responses differed by seed size. Results highlight the importance of remnant vegetation composition to the recovery of adjacent degraded habitats, underscoring the outsized role nearby remnant forest and isolated trees can play for the persistence of localized biodiversity.