Ecological Restoration Strategies Research Articles

Spatial differences in the radial growth responses of black locust (Robinia pseudoacacia Linn.) to climate on the Loess Plateau, China

The black locust (Robinia pseudoacacia Linn.) is the dominant tree species in the “grain for green” project on the Loess Plateau (LP) of China, and brings many ecological benefits to this planted region. However, there are concerns regarding its suitability as a plantation forest species in different regions of the LP. We used a dendroclimatological approach to investigate the radial growth response of black locust to varying climate in two sites on the LP with differing precipitation gradients. We took tree-ring samples from black locust in Yongshou County (in the semi-humid southern LP) and Shenmu County (in the semi-arid northern LP), and developed tree-ring width (TRW) chronologies for each. We performed moving correlation analyses between TRW chronologies and aggregated thermal (maximum temperature (TMX), minimum temperature (TMN), mean temperature (TMP)) and hydroclimatic factors (precipitation, self-calibrated Drought Severity Index (scPDSI), and humidity). The results demonstrated the increased influence of thermal factors during autumn, and the generally decreased influence of hydroclimatic factors on black locust radial growth in Yongshou, compared with the decreasing influence of thermal factors (during all seasons) and increasing influence of hydroclimatic factors (precipitation during summer, scPDSI and humidity during autumn) on black locust radial growth in Shenmu. The results indicated that black locust radial growth might benefit from the current climatic conditions in the southern LP. However, black locust radial growth stressed by water availability in the northern LP, which may reduce its vitality and productivity as climate warms in the future. These results have implications for regional forestry planning and ecological restoration strategies on the LP.

Rock-Solubilizing Microbial Inoculums Have Enormous Potential as Ecological Remediation Agents to Promote Plant Growth

Anthropogenic overexploitation poses significant threats to the ecosystems that surround mining sites, which also have tremendous negative impacts on human health and society safety. The technological capacity of the ecological restoration of mine sites is imminent, however, it remains a challenge to sustain the green restorative effects of ecological reconstruction. As a promising and environmentally friendly method, the use of microbial technologies to improve existing ecological restoration strategies have shown to be effective. Nonetheless, research into the mechanisms and influences of rock-solubilizing microbial inoculums on plant growth is negligible and the lack of this knowledge inhibits the broader application of this technology. We compared the effects of rock-solubilizing microbial inoculums on two plant species. The results revealed that rock-solubilizing microbial inoculums significantly increased the number of nodules and the total nodule volume of Robinia pseudoacacia L. but not of Lespedeza bicolor Turcz. The reason of the opposite reactions is possibly because the growth of R. pseudoacacia was significantly correlated with nodule formation, whereas L. bicolor’s growth index was more closely related to soil characteristics and if soil nitrogen content was sufficient to support its growth. Further, we found that soil sucrase activity contributed the most to the height of R. pseudoacacia, and the total volume of root nodules contributed most to its ground diameter and leaf area. Differently, we found a high contribution of total soil carbon to seedling height and ground diameter of L. bicolor, and the soil phosphatase activity contributed the most to the L. bicolor’ s leaf area. Our work suggests that the addition of rock-solubilizing microbial inoculums can enhance the supply capacity of soil nutrients and the ability of plants to take up nutrients for the promotion of plant growth. Altogether, our study provides technical support for the practical application of rock-solubilizing microbes on bare rock in the future.

Soil N availability drives the shifts of enzyme activity and microbial phosphorus limitation in the artificial soil on cut slope in southwestern China.

The construction of highways in the subalpine mountains generates many cut slopes. Currently, the restoration of cut slope mainly focuses on the aboveground landscapes and slope stability. Yet, it remains elusive about the belowground ecosystem functions at the early stage of restoration. In this study, we evaluated the belowground ecosystem functions of cut slopes that had been restored approximately 3 years using soil enzymatic activities, microbial biomass, and stoichiometry as the proxies. The results indicated that the phenol oxidase activity was higher in cut slopes, while the activities of β-1,4-glucosidase, β-1,4-N-acetylglucosaminidase, leucine aminopeptidase, and acid phosphatase were lower in cut slope soils compared with natural soils. Soil nitrogen availabilities (total and/or ammonium nitrogen) showed high negative correlations with the phenol oxidase activity and positive correlations with the activities of almost all other enzymes. These results suggested that soil nitrogen was the key factor in driving the shifts of enzymatic activities across two types of soils. Moreover, we found the imbalance of soil nutrients in cut slope soils, especially the carbon vs. nitrogen and the nitrogen vs. phosphorus. By applying the vector analysis, we found that the vector A values were more than 45° in all samples, suggesting that microbial phosphorus limitation occurred in both cut slope and natural soils. These findings suggested that maintaining the balance of soil nutrient supplies is important to the recovery of the below-ground ecosystem functions at the early restoration stage of cut slopes. This study provided new insights into designing the ecological restoration strategies for cut slopes by considering the belowground ecosystem functions.

Eco-restoration of degraded lands through trees and grasses improves soil carbon sequestration and biological activity in tropical climates

Despite several studies, role of eco-restoration strategies involving trees and grasses on soil organic carbon pools and fractions, response of soil enzymes in degraded land of tropical climate has remain largely overlooked. Four native fast growing fodder trees, namely, Ficus infectoria, Morus alba, Acacia nilotica and Leucaena leucocephala with combination of grasses viz., Cenchrus ciliaris, Chrysopogon fulvus and Panicum maximum were used as eco-restoration tool in Bundelkhand region. Total organic carbon (TOC), microbial biomass C (MBC), and activities of important soil enzymes were measured. After 9 years, land under Ficus, Morus, Acacia and Leucaena had ~63, 105, 87 and 81% greater TOC than fallow land in surface layer and Cenchrus, Panicum, and Chrysopogon increased TOC by 84, 91 and 77% at surface layers, respectively, over fallow land. MBC increased by 2–2.5 folds in both soil layers. All C fractions responded positively to eco-restoration. Ficus, Morus, Acacia and Leucaena boosted up carbon management index (CMI) by 51, 84, 71 and 65% at surface layers, respectively over fallow land. Similarly, grasses also improved CMI by >60%. Soil organic carbon accumulation under Ficus, Morus, Acacia and Leucaena were ~ 55, 91, 77 and 71% higher than fallow land at surface layers, and 71, 85, 95 and 69% higher than fallow land at subsurface soil layers. We developed an index for comparing ecorestoration efficiency (ERE). We found Morus + Panicum, Acaia + Panicum to be effective restoration strategies for eco-restoration under degraded lands of tropical climates. Our study indicated that implementation of these ecological restoration strategies could be a quantitatively important component of national climate change mitigation strategies in India and thus should be continually paid a great attention.

Dynamic changes in water conservation in the Beijing–Tianjin Sandstorm Source Control Project Area: A case study of Xilin Gol League in China

The insufficient information on water conservation dynamics and potential in ecological engineering areas often restrict the selection and implementation of ecological restoration measures in arid and semiarid climates. Based on the regional water balance equation and GIS spatial analysis tools, this article assessed the spatial-temporal changes in water conservation in Xilin Gol League, a representative region of the Beijing–Tianjin Sandstorm Source Control Project Area. The results indicated that the yearly amount of water conservation in Xilin Gol League reached 1.27 billion cubic meters, and annual precipitation of approximately 6.36 mm was retained per hectare. The water conservation capacity in Xilin Gol League showed a notably increasing tendency during the period of 2000–2015 and increased from west to east. The northeast of East Ujimqin Banner had the highest capacity, contributing 16.19% of the total water conservation amount. Compared to 2000, approximately 65.86% of Xilin Gol League presented water conservation capacity increases in 2015, 15.25% of which were significant. The water conservation in Xilin Gol League correlated with the changes in precipitation, temperature, and vegetation coverage, and unfavorable changes in these factors led to a significant decline in regional water conservation capacity. Therefore, multiple ecological restoration strategies are proposed for the improvement of water conservation capacity in the low-efficiency areas.

基于地质灾害敏感性的生态安全格局关键区识别与修复——以济南市为例

区域生态安全格局构建对提升生态系统服务功能提供了重要路径，同时统筹各种生态要素进行生态保护与修复分区也是新时期做好生态修复的重要举措。以济南市为例，基于现状生态系统类型分布，聚焦生态本底和地质灾害敏感性的特征，基于形态学空间格局分析方法和自然保护区结合进行生态源地提取。采用夏季降水、植被覆盖度、坡度3个地质灾害敏感性因子修正基本生态阻力面。并采用最小成本路径方法（Least-Cost Path method，LCP）提取生态廊道，构建了市域的生态安全格局。采用电路理论进行生态关键区域（生态"夹点"和生态障碍点）的识别，进一步划分生态修复改善区，并对此提出针对性的生态保护修复策略和工程措施。研究表明：1）市域生态源地的个数为35个，面积为567.15 km²，主要类型为林地和草地。空间上主要分布南部山区。生态廊道818.42 km，平均廊道长度为12.99 km，廊道分布存在较为明显的空间分布差异性，整体呈现出"一屏、一带、三轴"的生态安全格局。2）识别的生态修复关键区包含生态"夹点"25处，历城区生态"夹点"分布最为密集。全市亟需修复的生态障碍点共34处，面积为6.90 km²，主要分布章丘区。生态改善区共识别2994.84 km²，近期亟需修复的面积为96.1 km²，主要分布在长清区、历城区、莱芜区。3）通过对比生态修复关键区和现状土地利用类型，因地适宜的制定了生态修复策略与工程措施布置指引方向。研究结果可为济南市国土空间生态修复规划提供一定的技术支撑，同时也可为其他地质灾害敏感性区域的生态修复规划提供指引。;Construction of a regional ecological security pattern provides an important path to enhance ecosystem service, while the coordination of various ecological elements for ecological protection and restoration zoning is also an important initiative for better ecological restoration in the new epoch. Taking Jinan city as a case study area, we focus on the basal characteristics of regional ecological environment and geohazard sensitivity based on the current spatial ecosystem distribution, the ecological source area was extracted based on Morphological Spatial Pattern Analysis and nature reserves. In addition, summer precipitation, vegetation coverage and slope three geohazard sensitivity factors were used to modify the basic ecological resistance surface, and the ecological corridors were identified using Least-Cost Path method (LCP), and as a result, the ecological security pattern of Jinan City was constructed. by the application of circuit theory, critical areas of ecological restoration (ecological pinch point and ecological barrier point) were identified and further demarcated into three different ecological restoration zones, for which targeted ecological protection and restoration strategies and engineering measures were proposed towards those restoration zones. Results indicate that there were 35 ecological sources and covered an area of 567.15 km², and the main ecosystem types were forestland and grassland. Those sources were mainly distributed in the southern mountainous. The ecological corridors with a total of 1548.36 km between them, and the average length of the corridor was 12.99 km. All of them constructed a one screen, one belt and three axes ecological security pattern. Key areas of ecosystem preservation and restoration were identified based on the circuit theory, including a total of 25 ecological pinch points, 34 ecological barrier points, and 6.90 km² of it, and the pinch and barrier points mainly distributed in the Licheng and Zhangqiu District, respectively. A total of 2994.84 km² of ecological improvement areas have been identified, with 96.1 km² in urgent need of restoration soon, mainly distributed in Changqing, Licheng and Laiwu District. Suggestions of restoration and direction of engineering measures were proposed, with a combination of the spatial ecological characteristics and land use types. The results of the study provide some technical supports for the territorial spatial planning and ecological protection and restoration in Jinan and also provide scientific guidance for other geohazard-sensitive areas.

Influences of Topographic Factors on Outcomes of Forest Programs and Policies in a Mountain Region of China: A Case Study

In China, the successive government has implemented ambitious programs and policies to reverse the decline in forest cover. As an essential source of freshwater and an ecological barrier for Beijing, Zhangjiakou City has implemented several forest expansion strategies. Topographic conditions in this mountainous area have generated spatially heterogeneous afforestation outcomes. Quantifying the impact of these conditions on implemented forest programs could improve ecological restoration strategies of Chinese mountain areas. Using remotely sensed data from the Landsat 5 Thematic Mapper and the Landsat 8 Operational Land Imager, we generated land cover data to identify forest cover changes in Zhangjiakou City in 1989, 2000, and 2015. Forest cover data, topographic information (elevation, slope, aspect, land relief, and terrain niches), and spatial statistical models (geographically weighted regression [GWR]) were used to analyze re- and afforestation over 2 periods (1989–2000 and 2000–2015). The results show that forest cover in Zhangjiakou City increased by one third from 1989 to 2015. The rate of afforestation from 2000 to 2015 was 4 times the rate observed between 1989 and 2000. A trend toward gradual afforestation of higher-elevation and gentler-slope areas and land relief and terrain niche zones was observed between the 2 periods. Expansion mostly occurred in grasslands, arable lands, and unused lands. Elevation, slope, and land relief were the dominant topographic factors influencing forest cover change. Such factors influenced afforestation directly through their effect on microclimates and local biophysical conditions and indirectly by limiting the geographic area where forest programs could be implemented. Terrain niche was also an important predictor of forest cover change under complex topographic conditions. The GWR results indicate heterogeneous forest cover change processes across the study area. Our analysis could guide the implementation of effective forest expansion programs and policies, particularly for degraded mountain ecosystems.

Soilless revegetation: An efficient means of improving physicochemical properties and reshaping microbial communities of high-salty gold mine tailings

Soilless revegetation is a cost-effective and eco-friendly method for the ecological restoration of gold mine tailings. However, due to gold mine tailings are high-salty, alkaline and low-nutrient, little research has been done on soilless revegetation of gold mine tailings. The aim of study was to apply soilless revegetation to gold mine tailings, and investigate the changes of physicochemical properties and microbial communities of tailings after soilless revegetation. Six selected herbaceous plants (Melilotus officinalis, Xanthium sibiricum, Festuca elata, Zoysia japonica, Amaranthus tricolor L., Artemisia desertorum) grew well on the bare tailings, and their heights reached as high as 16.28 cm after 90 days. After soilless revegetation, tailings salinity dramatically dropped from 547.15 to 129.24 μS cm−1, and pH went down from 8.68 to 7.59 at most. The content of available phosphorus (AP), available nitrogen (AN) and organic matter (OM) in tailings gradually improved, especially the content of AP and OM increased 53.36% and 52.58%, respectively. Furthermore, microbial metabolic activity and diversity in tailings obviously increased 70.33–264.70% and 1.64–13.97% respectively. The relative abundance of potential plant growth-promoting bacteria increased 1.40–3.05%, while the relative abundance of opportunistic pathogens and halophilic bacteria decreased 10.58–17.03% and 2.98–6.52% respectively. Such variations of microbial communities were beneficial for tailings restoration. This study provided insight into soilless revegetation and its impact on tailings microorganisms, which could be a new strategy for ecological restoration of gold mine tailings.

Growth, flowering and fruiting of Campomanesia adamantium (Cambess) O. Berg intercropped with green manure species in Agroforestry Systems

Besides enabling economic activity, the domestication of indigenous species in situ configures a strategy for the conservation of genetic resources in Agroforestry Systems (AFSs), as well as an ecological restoration strategy. Successful productivity and restoration through AFSs require active intervention with agroecological practices, e.g., the use of green manure. We evaluated how planting different green manure species in consortium with Guavira influences its reproductive period, growth, and productivity in different spatial arrangements. Guavira, Campomanesia adamantium, is a shrub that is native to the Brazilian Savannah and has fruticulture potential. To evaluate growth, we measured plant height and canopy cover and to evaluate fruit yield, we monitored reproductive phenology among different treatments. Guavira grows better in less dense areas with Crotalaria breviflora and Cajanus cajan rather than with Canavalia ensiformis. In all inter-row spacing of Guavira and green manure species, the reproductive phases were highly seasonal, with flowering and fruiting lasting for 2 and 4 months, respectively. Guavira plants that grew in consortium with green manure in different inter-row spacing presented different flowering times, but this difference was not reflected in fruit production. Fruiting and growth appear to be affected by inter-row spacing, as well as by the species used in the consortium. Thus, these variables must be considered carefully when implementing an agroforestry system.

“Active” and “passive” ecological restoration strategies in meta‐analysis

One of the means of creating a more robust methodology for ecological restoration involves reducing the gap between ecological theory and restoration practices. A common strategy to do so is using meta‐analysis to understand key drivers of restoration outcomes. “Active” and “passive” is a dichotomy often used to separate restoration strategies in such meta‐analyses. We investigate previously raised concerns about selection bias and subjective categorization of strategies. We promote a paired experimental design in future empirical research and propose the use of three categories of restoration strategy in lieu of “passive” and “active” to alleviate inconsistency in definitions and categorization.

Ecological restoration impact on total terrestrial water storage

Large-scale ecological restoration (ER) has been successful in curbing land degradation and improving ecosystem services. Previous studies have shown that ER changes individual water flux or storage, but its net impact on total water resources remains unknown. Here we quantify ER impact on total terrestrial water storage (TWS) in the Mu Us Sandyland of northern China, a hotspot of ER practices. By integrating multiple satellite observations and government reports, we construct a TWS record that covers both the pre-ER (1982–1998) and the post-ER (2003–2016) periods. We observe a significant TWS depletion (P < 0.0001) after ER, a substantial deviation from the pre-ER condition. This contrasts with a TWS increase simulated by an ecosystem model that excludes human interventions, indicating that ER is the primary cause for the observed water depletion. We estimate that ER has consumed TWS at an average rate of 16.6 ± 5.0 mm yr−1 in the analysed domain, equivalent to a volume of 21 km3 freshwater loss during the post-ER period. This study provides a framework that directly informs the water cost of ER. Our findings show that ER can exert excessive pressure on regional water resources. Sustainable ER strategies require optimizing ecosystem water consumption to balance land restoration and water resource conservation. While ecological restoration has been promoted for curbing degradation and improving ecosystem health, the impacts on water flux and storage have been understudied. This article finds that large-scale restoration efforts can actually deplete terrestrial water storage, requiring more effort to balance ecosystem needs.

Monitoring and Assessment of the Oasis Ecological Resilience Improved by Rational Water Dispatching Using Multiple Remote Sensing Data: A Case Study of the Heihe River Basin, Silk Road

The suboptimal management and utilization of water resources from the “Asian water towers” contributed to serious ecological crises in river basins along the arid Silk Road, such as the Aral Sea and the Heihe River in the 20th century. To improve the ecological resilience of the Ejina Oasis in the Heihe River downstream basin, the Chinese government implemented the ‘Ecological water dispatching project’ in 2000. However, it is still unclear what the optimal rational water allocation is for the sustainable development of economic, social, and ecological environments (so called “triple bottom line”) in these inland river basins. This study presents a decision-tree-based methodology for ecological monitoring and restoration strategies for Silk Road’s oasis eco-system. Using Landsat TM/OLI data as well as meteorological, hydrological, and water utilization data, we show that ~69% of the originally degraded land has been restored since 2000. Previously dry tail-end lakes in the Heihe River downstream basin have been rejuvenated, and the precipitation has also significantly improved (ρ = 0.047). We propose that the downstream water allocation should be no more than ~11 × 108 m3 and that the optimal ratio between downstream and midstream allocation is 0.4–1.7. This study provides an excellent example for ecological monitoring and assessment in the optimization of strategies for the restoration of Silk Road’s oasis eco-system.

Selection of Different Trees/Shrubs Species for Rehabilitation of Degraded Lands in Wag-Lasta Area, Northeastern Ethiopia

Due to human and livestock population pressure, land degradation is the main problem in many part of Ethiopia. To avert the situation, tree and shrub species selection on degraded lands are valuable tool for ecological restoration. Therefore, the aim of this study was to select the best performing tree and shrub species in three agro-ecological zones of Waglasta area, Ethiopia. The experiment was conducted in randomized block design with three replications in highland, mid altitude, and lowland sites. For total experimental setup 21 (seven for lowland, eight for mid altitude and six for highland) tree and shrub species were used. Growth and survival rate data were collected every 3 months interval for one year and every 6 months up to the end of the experiment. The result indicated that L. pallid (2.52 ± 0.19 m) at lowland site, Acacia senegal (1.32±0.23 m) at mid altitude and Acacia decurrens (4.0 ± 0.46 m) at highland site had shown better performance in height. Similarly, Moringa stenopetala at lowland, Jatropha carcus at mid altitude and Acacia saligna at highland site had shown 8.63 ± 2.37 cm, 3.1 ± 0.2 cm and 7.06 ± 0.75 cm performance in root collar diameter, respectively. However, the survival rate was higher for A. senegal (43 ± 7%) and M. stenoptella (44 ± 17%) at lowland site, A. senegal (98 ± 2%) at mid altitude and A. saligna (63.9 ± 20.0%) at highland site. Therefore, to restore degraded lands and to support the on-going land rehabilitation programs of Wag-lasta area, we recommend A. senegal and M. stenoptella for lowland site, A. senegal for mid altitude areas and A. saligna for highland site of Lalibela, Abergele and Sekota and similar agro-climatic zones. However, additional studies regarding soil nutrient dynamics, fostering effect and tree nursing should be integrated to develop sound ecological restoration strategies in the growth corridor as well as in the region.

Evaluating ecosystem functioning following river restoration: the role of hydromorphology, bacteria, and macroinvertebrates

Ecological restoration of freshwater ecosystems is now being implemented to mitigate anthropogenic disruption. Most emphasis is placed on assessing physico-chemical and hydromorphological properties to monitor restoration progress. However, less is known about the structural integrity and ecosystem health of aquatic ecosystems. In particular, little is known about how ecosystem function changes following river habitat restoration, especially in China. Leaf litter decomposition can be used as an indicator of stream ecosystem integrity. Therefore, the leaf breakdown rate was measured to assess the ecosystem function of restored rivers. By comparing leaf breakdown rates in urban rivers undergoing habitat restoration with that in degraded urban rivers and rivers in forested areas (i.e., reference conditions), we aimed to determine: (i) how habitat restoration affected leaf litter decomposition? (ii) the relationship between leaf litter decomposition to both environmental (habitat and physico-chemical variables) and biological factors (benthic communities), and (iii) identify the factors that contribute most to the variance in leaf litter breakdown rates. The results demonstrated a significant increase in leaf breakdown rate (120% in summer and 28% in winter) in the restored rivers compared to the degraded rivers. All environmental and biotic factors evaluated contributed synergistically to the differences in leaf litter decomposition among the three river types. The role of macroinvertebrates, mainly shredders, appeared to be particularly important, contributing 52% (summer) and 33% (winter) to the variance in decomposition, followed by habitat characteristics (e.g. substrate diversity, water velocity; 17% in summer, 29% in winter), physico-chemical variables (e.g. nutrient and organic pollutants; 11% in summer, 1% in winter) and biofilm bacteria (0% in summer, 15% in winter). Habitat restoration positively affected the structure and function of the previously degraded streams. Knowledge on controlling variables and their attribution to changes of ecosystem functioning provides guidance to assist the future planning of ecological restoration strategies.

Ecological network construction of the heterogeneous agro-pastoral areas in the upper Yellow River basin

The increasing landscape heterogeneity in the agro-pastoral areas and the contradiction between the development and biodiversity conservation is becoming more and more prominent, especially in Northwest China. Rational ecological network construction has become an important issue for ecological restoration and ecological security pattern strategy. Taking a typical agro-pastoral ecotone in the upper Yellow River valley as the study area, an ecological network was established using Graphab software based on the integral landscape heterogeneity analysis, in which the morphological spatial pattern analysis (MSPA) and structural equation model (SEM) were used to identify the ecological source regions and determine the resistance surface. The results showed that grazing and agricultural activities are the main reasons for the landscape complexity and heterogeneity. SEM also revealed the interactions between geographical conditions and landscape heterogeneity. The regression coefficients showed that the contribution of various factors on landscape heterogeneity were in order from strong to weak elevation, roads, settlements and slope. The influencing effects on landscape patterns were mainly reflected by the patch density, fractal dimension and landscape division indexes, with coefficients of −0.94, −0.91 and −0.88, respectively. The established ecological network shows that the overall planning of natural habitat and cultivated land will effectively improve the landscape quality. The presence of "stepping stone" patches in the central and eastern regions of the study area increases the landscape connectivity. In addition, the rational planning and utilization of high heterogeneity areas in the landscape are critical for maintaining the structure and function of the landscape. Findings from our study could provide a reference method for maintaining the landscape stability and sustainable development of heterogeneous agro-pastoral ecotones.

Ecological function evaluation and restoration strategy of rivers in urban built-up areas: a case study of the Dasha River in Shenzhen

With the rapid development of urbanization and national economy, the ecological function of rivers has been seriously threatened. In order to evaluate the present situation of ecological function of rivers in urban built-up areas and provide theoretical basis for subsequent river ecological restoration and sponge city planning, we carry out a case study of the Dasha River in Shenzhen city. We construct the ecological function evaluation index system at the reach scale for the Dasha River, in which 10 indicators and 14 indexes of four functions of hydrological support, water environment sustainment, habitat and biodiversity maintenance are evaluated by index evaluation method with aquatic organisms as the core. The index weight is calculated by the analytic hierarchy process method. The results show that the middle reach of the Dasha River is in class Ⅱ level, which is less disturbed by human activities and has relatively integral ecological functions. The upper and middle upper reaches are class Ⅲ areas and some ecological functions are threatened. The lower estuary section is class Ⅳ reach, which is seriously affected by human activities. Combing with the evaluation results of ecological function, we put forward the ecological restoration strategies for each reach, and suggest the daily management measures from the aspects of pollutant, biological species management, ecosystem regulation, and public education. This study provides basis and guidance for the evaluation and restoration of the ecological function and the sponge city construction in urban built-up areas.

Combining genotype, phenotype, and environmental data to delineate site-adjusted provenance strategies for ecological restoration.

Despite the importance of climate-adjusted provenancing to mitigate the effects of environmental change, climatic considerations alone are insufficient when restoring highly degraded sites. Here we propose a comprehensive landscape genomic approach to assist the restoration of moderately disturbed and highly degraded sites. To illustrate it we employ genomic data sets comprising thousands of single nucleotide polymorphisms from two plant species suitable for the restoration of iron-rich Amazonian Savannas. We first use a subset of neutral loci to assess genetic structure and determine the genetic neighbourhood size. We then identify genotype-phenotype-environment associations, map adaptive genetic variation, and predict adaptive genotypes for restoration sites. Whereas local provenances were found optimal to restore a moderately disturbed site, a mixture of genotypes seemed the most promising strategy to recover a highly degraded mining site. We discuss how our results can help define site-adjusted provenancing strategies, and argue that our methods can be more broadly applied to assist other restoration initiatives.

Naturalness Assessment of Forest Management Scenarios in Abies balsamea–Betula papyrifera Forests

Research Highlights: This research provides an application of a model assessing the naturalness of the forest ecosystem to demonstrate its capacity to assess either the deterioration or the rehabilitation of the ecosystem through different forest management scenarios. Background and Objectives: The model allows the assessment of the quality of ecosystems at the landscape level based on the condition of the forest and the proportion of different forest management practices to precisely characterize a given strategy. The present work aims to: (1) verify the capacity of the Naturalness Assessment Model to perform bi-directional assessments, allowing not only the evaluation of the deterioration of naturalness characteristics, but also its improvement related to enhanced ecological management or restoration strategies; (2) identify forest management strategies prone to improving ecosystem quality; (3) analyze the model’s capacity to summarize the effect of different practices along a single alteration gradient. Materials and Methods: The Naturalness Assessment Model was adapted to the Abies balsamea–Betula papyrifera forest of Quebec (Canada), and a naturalness assessment of two sectors with different historical management strategies was performed. Fictive forest management scenarios were evaluated using different mixes of forestry practices. The sensitivity of the reference data set used for the naturalness assessment has been evaluated by comparing the results using data from old management plans with those based on Quebec’s reference state registry. Results: The model makes it possible to identify forest management strategies capable of improving ecosystem quality compared to the current situation. The model’s most sensitive variables are regeneration process, dead wood, closed forest and cover type. Conclusions: In the Abies balsamea–Betula papyrifera forest, scenarios with enhanced protection and inclusion of irregular shelterwood cuttings could play an important role in improving ecosystem quality. Conversely, scenarios with short rotation (50 years) could lead to further degradation of the ecosystem quality.

Water use characteristics of the common tree species in different plantation types in the Loess Plateau of China

Knowledge concerning the water use characteristics of revegetated species has profound implications for understanding soil–plant interaction mechanisms and guiding ecological restoration strategies in water-limited ecosystems. Although afforestation is an important way to improve ecosystem functions and services in degraded ecosystems, there is limited understanding about the water use characteristics of dominant species within and between different types of plantations. We investigated plant water use characteristics in three representative types of plantations on the Chinese Loess Plateau: mixed plantation consisting of three deciduous tree species Robinia pseudoacacia, Armeniaca sibirica and Ailanthus altissima (Mspa), pure R. pseudoacacia plantation (Pp) and pure A. sibirica plantation (Ps). We measured the leaf δ13C of the dominant species within each plantation type and the δ2H and δ18O of xylem and soil water within 400 cm of the soil surface. The results showed that three main species in the mixed plantation exhibited significant difference (p < 0.05) in proportional contributions of water sources, suggesting that the plants had water source segregation. A. sibirica in the mixed plantation utilized more proportional shallow soil water than that in the pure plantation and correspondingly lessened deep soil water depletion. However, no significant difference was found in the water uptake proportions of R. pseudoacacia between the different plantation types. The leaf δ13C values of the plant species in the mixed plantation were significantly higher than those in the pure plantations. The leaf δ13C values of R. pseudoacacia under different plantation were positively associated with SWCs, but this relationship was not observed in A. sibirica. These results indicate that plantation type affected plant water use characteristics with species-specific responses to plantation type and different water source competition effects between interspecific versus intraspecific competition.

Investigation of the relationship between precipitation extremes and sediment discharge production under extensive land cover change in the Chinese Loess Plateau

To quantify the effects of rainfall and catchment characteristics on sediment yield is of essential importance for sustainable land management. Precipitation extremes are the external cause of the majority of serious soil erosion and suspended sediment yield (SSY) events in the Chinese Loess Plateau (CLP), which has undergone extensive land use/cover change (LUCC). The investigation of the linkage between climate variables and SSY production is crucial to the precise implementation of ecological restoration strategies, thereby reducing soil loss in the CLP. In this study, a partial least squares regression (PLSR) approach is used to investigate this issue using 1961–2015 data from 16 main catchments in the CLP. This period includes the reference period (1961–1979, Period-I), integrated soil conservation project period (1980–1999, Period-II), and the “Grain for Green” program period (2000–2015, Period-III). The results indicate that the dominant climate factors driving SSY are precipitation extremes including maximum precipitation events, heavy precipitation (daily precipitation ≥25 mm), consecutive wet days, erosive precipitation (daily precipitation ≥12 mm), and annual total precipitation. The effects of the precipitation extremes on sediment yield generation are stronger in drier catchments. The influence of the precipitation extremes on sediment generation can be strengthened by cultivation and weakened by revegetation (especially reforestation). The climate-driven sediment yield decreased by 951 t·km−2·yr−1 during Period-II and 505 t·km−2·yr−1 during Period-III in comparison with Period-I. The dominant cause of the sediment yield reduction was LUCC, with the contribution increasing from 73% in Period-II to 92% in Period-III. This study provides a greater understanding of the effects of climate variation and LUCC on sediment yield, and is beneficial for better catchment management.