Dryland Restoration Research Articles

Seasonal effects of granivory on broadcast seeding restoration in a degraded semiarid grassland

Granivores, such as rodents and harvester ants, are common in dryland ecosystems. In intact dryland ecosystems, the effects of such granivores on soil seed banks, plant community structure, and ecosystem functioning are well established. However, the effects of granivores on dryland restoration have received much less attention. In this study, we evaluated the seasonality of seed removal by harvester ants, seed preference of harvester ants, and effects of granivore exclosure on the soil seed bank at four sites in southeastern Utah. We studied two species of harvester ants, Pogonomyrmex rugosus and P. occidentalis. The foraging behavior of Pogonomyrmex spp. was temperature‐dependent; they removed no seeds during winter months, and up to 80% of seeds during high activity in the summer. Despite seasonal differences in seed removal, Pogonomyrmex spp. did not show significant preferences for seed species. However, their seasonal foraging behavior translated into measurable differences in an experimental soil seed bank. Over the summer months, ants reduced the number of seeds in the seed bank by approximately 20%, but when ants were excluded during the winter, the number of seeds in the seed bank remained the same. This finding supports the timing of business‐as‐usual seeding practices of applying seeds in late fall. If seeds germinate in the first season after application, ant granivory is unlikely to pose a large barrier to establishment. However, if seeds remain dormant during the first year, as is common in many dryland species, seeds are vulnerable to ant granivory.

Vegetation restoration in dryland with shrub serves as a carbon sink: Evidence from a 13‐year observation at the Tengger Desert of Northern China

AbstractDryland area accounts for approximately 40% of worldwide land area, which plays a significant role in regulating the carbon sequestration capacity of land. Vegetation restoration in drylands adopted to prevent land degradation, and may also serve as a carbon sink in the earlier stage. However, the persistence of the carbon sink for the revegetated ecosystem in drylands is still unknown. Can the well‐established restoration vegetation in dryland areas serve as a carbon sink in long‐run? To address this question, we investigated the carbon sequestration capacity of planted vegetation in dryland areas with 13 years of observation (2009–2021) for established vegetation restoration, which began in 1989. We found that the revegetation area serves as a carbon sink in all years. The mean annual net ecosystem productivity (NEP) is 91.61 ± 36.17 gC m−2 yr−1 (mean ± standard deviation). Annual NEP showed a significant increasing trend over the study period with a rate of 5.65 gC m−2 yr−1 yr−1 (p < 0.05). The increase in spring temperature, the earlier start of net carbon uptake and the longer duration of net carbon uptake contribute to the gradual trend of NEP. The amount of annual NEP is predominantly determined by summer precipitation. Meanwhile, our results revealed that the increase in net carbon uptake by revegetation did not lead to excessive consumption of water resources. Our results have suggested that appropriate vegetation restoration in arid areas can increase ecosystem carbon sequestration over longer timescales and mitigate climate change, with relatively low environmental consequences and risks. Considering the vast area of degraded land in the global drylands, the carbon sequestration effect of this model should be given more attention.

Soil erodibility for water and wind erosion and its relationship to vegetation and soil properties in China's drylands

Drylands with fragile socio-ecological systems are vulnerable to soil erosion. China's drylands face the dual threat of water (WAE) and wind erosion (WIE). To mitigate soil erosion in drylands, China has implemented numerous ecological restoration measures. However, whether vegetation and soil have different effects on soil erodibility for water erosion (soil erodibility, K) and wind erosion (soil erodible fraction, EF) in drylands is unclear, hindering decision makers to develop suitable ecological restoration strategies. Here, we conducted a large-scale belt transect survey to explore the spatial variation of K and EF in China's drylands, and examined the linear and nolinear effects of aridity (aridity index), vegetation (fractional vegetation cover and below-ground biomass), and soil properties (bulk density, total nitrogen, and total phosphorus) on K and EF. The results showed in China's drylands that the K ranges from 0.02 to 0.07, with high values recorded in the northern Loess Plateau and the eastern Inner Mongolia Plateau. The EF ranges from 0.26 to 0.98, and shows longitudinal zonation with higher values in the east and lower values in the west. Aridity has a negative linear effect on K and an inverse U-shaped nonlinear effect on EF. Aridity can affect K and EF by suppressing vegetation growth and disrupting soil properties. However, K and EF had different responses to some vegetation and soil variables. K and EF had opposite relationships with soil bulk density, and EF was significantly affected by fractional vegetation cover, while K was not. Overall, the effects of aridity and soil properties on soil erodibility were more pronounced than those from vegetation, whose effect on soil erodibility was limited. This study provides relevant information to support reducing soil water and wind erosion by highlighting the hotspot areas of soil erodibility, relevant for implementing vegetation restoration and soil conservation measures in drylands.

More than trees: Stand management can be used to improve ecosystem diversity, structure and functioning 20 years after forest restoration in drylands

In Mediterranean drylands, extensive areas have been restored by reforestation over the past decades to improve diversity, soil fertility, and tree natural regeneration, contributing to halting desertification and land degradation. However, evaluating reforestation success usually relies on tree survival, while holistic and long-term evaluations of reforestation success based on ecosystem diversity, structure and functioning are scarce. In this work, we provide the first assessment that combines the evaluation of planted trees and indicators of ecosystem diversity, structure, and functioning in established reforestations with three native Mediterranean species along a climatic gradient. We sampled 43 20-year-old stands with umbrella pine, holm oak and cork oak in Portugal, and tested the effects of tree species composition, stand management (i.e., differences in tree density and shrub cover), and edaphoclimatic conditions, on the size of planted trees, species diversity, structural complexity and indicators of ecosystem functioning related to productivity, soil nutrients and tree natural regeneration.Our results show that, after 20 years of reforestation, stand management was an essential driver of plant diversity and ecosystem functioning. Higher tree density, particularly of oaks, and higher shrub cover improved plant diversity, ecosystem productivity, and oak regeneration. The latter was also improved by structural complexity. Tree composition effects highlighted the importance of pine management to avoid competition. Since we evaluated these reforestations along a climatic gradient, we also conclude that climate influenced pine and holm oak size, ecosystem productivity, and soil C/N. Our research, by being based on assessing the long-term reforestation success in a more holistic way, highlighted the importance of stand management for improving ecosystem diversity and functioning in these restored systems. Practices such as increasing tree density up to ~800 trees/ha and allowing a shrub cover of ca. 30 %, may improve the ecological condition of future and currently reforested areas across the Mediterranean region.

Under drought conditions, fungicide seed coating does not increase emergence of two native grass species in sagebrush stands of the Intermountain West, U.S.A.

Coating seeds with amendments to increase germination, emergence, and establishment is a promising strategy for dryland restoration. Seed coatings containing fungicides offer a potential solution in regions where fungal pathogens cause seed mortality during the winter stratification period between late fall seeding and spring germination. The effectiveness of the fungicide treatment, however, may be dictated by weather and within‐site microenvironment. We tested how fungicide coating influenced seedling emergence of native grasses within sagebrush stands by planting untreated seeds and seeds coated (encrusted) with and without active fungicide ingredients in furrows that extended from the canopy edge of sagebrush plants (Artemisia tridentata ssp. wyomingensis) into the interspace. This was replicated at four sites across the Intermountain West in two successive years. We planted two native grasses, bottlebrush squirreltail (Elymus elymoides) and bluebunch wheatgrass (Pseudoroegneria spicata). Emergence was extremely low in both years, with a complete seeding failure (i.e. zero emergence) at two sites in the first year and three sites in the second year. At one site where emergence was sufficient for statistical analysis: (1) the coating on the fungicide and blank treatments inhibited emergence under anomalously dry conditions and (2) across seed treatments, proximity to a sagebrush canopy slightly increased seedling emergence. The variable emergence patterns across sites and years (i.e. the highest emergence was for the site–year combination with the lowest precipitation) highlight the sensitivity of seeding outcomes to, and dependence of fungicide seed coatings on, site conditions, and the necessity of repeating experiments across different weather years.

Simulation of potential vegetation distribution in arid areas at regional scale

Awareness of potential natural vegetation (PNV) is imperative in ecological restoration. Extensive global and national PNV simulation with coarse spatial resolution is increasingly seen to mitigate land degradation under climate change. However, precise PNV modeling in drylands at a small regional scale with high enough spatial resolution usually receives little attention. This study developed a precise regional multiple PNV framework in drylands based on climatic variables, soil properties, groundwater depth, and topographical variables through a maximum entropy algorithm (MaxEnt). The effects of three different input variable combinations and five background point numbers on PNV prediction were compared. Applying the model to the lower Tarim River Basin, Northwest China, the results showed that the model developed incorporating groundwater depth exhibited better performance in regional PNV simulation, and the AUC of the tree, grass, and shrub was improved by 0.21, 0.18 and 0.09, respectively. Furthermore, the results showed that the probability of growing natural vegetation decreased with the increase of distance from the river within 100 m; and the probability of occurring tree, grass, and shrub was higher when the groundwater depth was close to −3 m, −2 m, and −7 m, respectively. Moreover, the suitable habitat of the tree, grass, and shrub was mainly concentrated in the riparian zone, accounting for 34.5%, 21.9%, and 72.4% of the study area, respectively. Comparisons of reconstructed PNV and existing land use patterns revealed that the lower Tarim River still has enormous land potential for ecological restoration. The model developed here can assist in precise ecosystem restoration in drylands.

Precise vegetation restoration in arid regions based on potential natural vegetation and potential normalized difference vegetation index

Precise vegetation restoration is critical in drylands, as some inappropriate restoration attempts have even increased water scarcity and degradation in afforestation areas. Potential natural vegetation (PNV) is widely used to provide a reference for the appropriate location and vegetation type of restoration programs while the appropriate restored areas remain unknown. Therefore, we proposed a PNV–potential normalized difference vegetation index (PNDVI) coupling framework based on multiple machine learning (ML) algorithms for precise dryland vegetation restoration. Taking the lower Tarim River Basin (LTRB) with a total area of 1,182 km2 as a case study, its present suitable restoration locations, area, and appropriate planting species were quantitatively estimated. The results showed that the model developed by incorporating PNDVI into PNV with easily measurable and available data such as temperature and soil properties can accurately identify dryland restoration patterns. In LTRB, the potentially suitable habitats of trees and grass are closer to the riverbank, while shrubby habitats are further away from the course, covering 1.88, 2.96, and 25.12 km2, respectively. There is still enormous land potential for further expansion of the current trees and grass in the LTRB, with 2.56 and 1.54% of existing land supposed to be trees and grass, respectively. This study's novel aspect is combining PNV and PNDVI to quantify and estimate precise restoration patterns through multiple ML algorithms. The model developed here can be used to evaluate the suitable reforestation locations, area, and vegetation types in drylands and to provide a basis for precise vegetation restoration.

Seed biopriming at different concentrations to assess the effects of Cyanobacteria on germination and seedling performance of keystone arid species

AbstractIntroductionBiocrust cyanobacteria have a large potential as biofertilizers for restoring degraded ecosystems because of their ability to improve soil nutrition and stabilisation, and to produce metabolites such as phytohormones to enhance plant growth. However, important aspects regarding the effects of cyanobacteria on native plants, such as metabolite production or concentration of inoculants, remain unknown. Here, we investigated the effects of different concentrations of cyanobacteria, on the germination and seedling growth of keystone plant species used in dryland restoration. We hypothesised that the studied inoculant would improve germination and seedling growth rates, with specific effects associated with the inoculant's concentration and metabolomic profiles.MethodsWe bioprimed seeds of four native plant species, using a cyanobacterial inoculant with different proportions of Nostoc and Leptolyngbya at two different concentrations. We recorded germination, measured seedling growth, and determined the corrected vigour for each treatment and species. Metabolites produced by the cyanobacterial inoculant were assessed to identify plant growth hormones potentially driving any effects.ResultsThere was a clear positive effect on the total germination of Triodia epactia and Triodia wiseana, but negative impacts for Senna notabilis and Grevillea wickhamii. There were also positive effects on root growth, but only for T. epactia, with negative or neutral impacts on the root and shoot growth of other species tested. We detected phytohormones, salicylic acid and indole‐3‐acetic acid, that were produced by our cyanobacteria inoculant, which are strongly linked to positive effects in early plant growth stages, but also known to inhibit growth when in higher concentrations.ConclusionThe positive effects of the biopriming protocol used are not uniform and highlight the need to improve our understanding of the effects provided both from different consortia and the concentrations applied when inoculating. There is a very high value in improving restoration outcomes for native vegetation communities in arid and semi‐arid regions.

Soil restoration increases soil health across global drylands: A meta‐analysis

Abstract Soil degradation is one of the greatest environmental issues our planet faces today, with over 33% of Earth's soils currently degraded. Drylands are especially vulnerable to soil degradation given their history of intensive land use and desertification. Active soil restoration has been identified as a leading strategy to combat soil degradation and promote ecosystem recovery. However, soil‐based dryland restoration techniques have shown varying success, potentially due to a lack of understanding of the ecological contexts in which soil‐based treatments are most beneficial. To improve our understanding of how to best use active soil restoration to restore degraded drylands, we conducted a global meta‐analysis of soil treatment effectiveness at improving soil health across varying environmental gradients. The soil health metrics we analysed were aggregate stability, bulk density, soil moisture, soil organic carbon (SOC), soil nitrogen, mycorrhizal colonization and basal respiration. For this meta‐analysis we collected 155 publications, yielding 1403 unique studies spanning six continents. We found that overall, soil restoration had a beneficial effect on all measures of soil health ranging from a +11% increase in bulk density (inverse) to a +6967% increase in mycorrhizal colonization. Aridity and soil texture greatly influenced restoration effectiveness for certain soil health metrics. Specifically, for soil carbon and nitrogen, restoration was found to be most effective in arid, fine‐textured soils and mesic, coarse‐textured soils. Additionally, we found that organic amendments were most effective at increasing SOC, while fungi inoculation was most effective at increasing mycorrhizal colonization. Synthesis and applications: Our findings indicate that active soil restoration is an effective tool for increasing soil health and provide information on optimal treatments and site conditions for improving certain aspects of soil health. This could greatly help inform decision‐making, and thus improve outcomes, in dryland restoration worldwide.

Plant water‐use strategies predict restoration success across degraded drylands

Abstract Plant strategies for coping with water limitation are likely to mediate restoration outcomes in degraded dryland ecosystems. Trade‐offs in traits related to water acquisition and use can intensify in more arid environments, making their effects on dryland restoration success even more salient. However, isolating the effects of drought responses from those of other environmental factors, as well as identifying the specific drought resistance traits that influence restoration success, can be difficult. In the present study, we couple a controlled dry‐down experiment with a cross‐site restoration field trial of out‐planted seedlings (RestoreNet) using a suite of dryland herbaceous plant species from the same seed sources. We quantified interspecific variation in physiological responses to drought, specifically reductions in stomatal conductance (gs) and stem water potential (SWP), by comparing well‐watered control plants to those experiencing decreasing soil moisture. Drought responses of SWP and gs varied independently among species, but both were related to survival in the cross‐site restoration field trial when effect sizes were aggregated across all sites. Responses were consistent with acquisitive water‐use strategies resulting in greater success, where species with greater declines in SWP or weaker declines in gs under drought had greater survival. The correlation between SWP drought response and survival also intensified in sites with lower accumulated precipitation following restoration. Differences among functional groups revealed two different paths to restoration success: forbs that maintain high gs and narrow safety margins to maximize exploitation of moisture pulses before going into drought dormancy, or C4 grasses that maintain efficient water uptake in drying soils while risking cavitation. C3 grass species varied between these two strategies. Synthesis and applications. Taken together, the results of this study and others conducted at RestoreNet sites indicate that while a diversity of physiological responses to drought may exist in dryland plant communities, successfully restoring herbaceous species through out‐planting in degraded conditions is likely to be achieved with species that maximize water uptake via one of two strategies, with tolerance of low SWP being particularly important in the most arid settings.

Soil surface treatments and precipitation timing determine seedling development across southwestern US restoration sites.

Restoration in dryland ecosystems often has poor success due to low and variable water availability, degraded soil conditions, and slow plant community recovery rates. Restoration treatments can mitigate these constraints but, because treatments and subsequent monitoring are typically limited in space and time, our understanding of their applicability across broader environmental gradients remains limited. To address this limitation, we implemented and monitored a standardized set of seeding and soil surface treatments (pits, mulch, and ConMod artificial nurse plants) designed to enhance soil moisture and seedling establishment across RestoreNet, a growing network of 21 diverse dryland restoration sites in the southwestern USA over 3 years. Generally, we found that the timing of precipitation relative to seeding and the use of soil surface treatments were more important in determining seeded species emergence, survival, and growth than site-specific characteristics. Using soil surface treatments in tandem with seeding promoted up to 3× greater seedling emergence densities compared with seeding alone. The positive effect of soil surface treatments became more prominent with increased cumulative precipitation since seeding. The seed mix type with species currently found within or near a site and adapted to the historical climate promoted greater seedling emergence densities compared with the seed mix type with species from warmer, drier conditions expected to perform well under climate change. Seed mix and soil surface treatments had a diminishing effect as plants developed beyond the first season of establishment. However, we found strong effects of the initial period seeded and of the precipitation leading up to each monitoring date on seedling survival over time, especially for annual and perennial forbs. The presence of exotic species exerted a negative influence on seedling survival and growth, but not initial emergence. Our findings suggest that seeded species recruitment across drylands can generally be promoted, regardless of location, by (1) incorporation of soil surface treatments, (2) employment of near-term seasonal climate forecasts, (3) suppression of exotic species, and (4) seeding at multiple times. Taken together, these results point to a multifaceted approach to ameliorate harsh environmental conditions for improved seeding success in drylands, both now and under expected aridification.

Planning a water-constrained ecological restoration pattern to enhance sustainable landscape management in drylands

Ecological restoration is an important approach to improving landscape sustainability. However, ecological restoration in drylands is strongly limited by water resources. Therefore, a technical route for ecological restoration in drylands that creates sustainable landscapes based on those water constraints is needed. In this study, we develop a spatially explicit framework named “Constraint-Pattern-Benefit” to plan ecological restoration patterns in Inner Mongolia, China. Based on a prediction of the ecosystem service (ES) increase under limited evapotranspiration as a water constraint, we constructed 5 landscape sustainability-related strategies with 100 ecological restoration scenarios, which considered fragmentation of restoration locations, distance to city, water consumption, and the allocation scale to determine the spatial arrangement of ecological restoration. Results show that the ES increase potential of ecological restoration under water constraints is distributed in the center of Inner Mongolia. The multi-objective scenario simultaneously achieves 59.1% water yield, 74.2% soil conservation, 57.2% sand fixation, and 52.8% carbon sequestration with 50% restored landscape. Considering the indicators of fragmentation, water consumption, and distance to city decreases the restored landscape fragmentation from 0.44 to 0.26, improves the restoration efficiency by 14.41%, and increases the beneficiary population by 35.5%, respectively. Small-scale allocation can further increase the ES realization efficiency, which is on average 4.8% higher at the city scale than at the provincial scale. Moreover, this approach focuses on the sustainable effect of the spatial arrangement on dryland landscapes at different scales, which provides methodological support for improving the sustainability of drylands.

Dynamic Effects of Climate and Land Use Policies on Water Yield in Drylands—A Case Study in the Northwest of China

Water yield as an important ecosystem service for mitigating water scarcity in drylands, is quite sensitive to land use and climate change. Evaluating the response of water yield to land use policies in drylands under climate change is conducive to sustainable water resource management. Taking the Hohhot-Baotou-Ordous-Yulin region in the northwest of China as an example, this study used the methods of the InVEST model, trend analysis, comparative experiment, PLUS model to explore the spatial-temporal trends and driving factors of water yield variation, as well as to simulate the future water yield under different land use policy scenarios. The results showed that (1) water yield in the study area fluctuated and increased from 14.14 mm to 46.59 mm during 2000 to 2020, the places with a significant increasing trend of water yield were mainly distributed in the southeast loess hilly area; (2) climate change is the major driving factor of water yield variation with a contribution rate of 85.8–99.6%, but land use change played an increasingly important role in affecting water yield; (3) the Grain-Security-Dominated (GSD) land use policy scenario would generate the highest water yield in 2030 under climate conditions of SSP1-2.6, SSP2-4.5, SSP3-7.0, SSP5-8.5, while the Regional-Greening-Dominated (RGD) land use policy scenario has the lowest water yield in the future. The results could provide reference for the decision-making process of ecological restoration and land use planning in drylands.

Arbuscular mycorrhizal fungi communities shaped by host‐plant affect the outcome of plant–soil feedback in dryland restoration

Abstract Plant inoculation with arbuscular mycorrhizal fungi (AMF) can be a useful tool to overcome challenges in dry forest restoration. However, advances are still needed to guide choices regarding soil origin and inoculum production methods, since outcomes can vary due to plant–soil feedbacks (PSF). We evaluate how soil origin and host plant used for inoculum production affect AMF community and therefore the plant biomass accumulation and functional traits. In the conditioning phase, we investigated whether soils originating from a recovered area (Quarry) and a vegetation fragment (Caatinga) would have their AMF communities modified due to the growth of Sorghum bicolor (used for inoculum production) and Senna uniflora (used in Brazilian semiarid restoration). In the feedback phase, we compared the performance of four plants species growing on a degraded soil and inoculated or not by a mixture of AMF isolates in comparison to soil inoculum prepared from the conditioning phase. The inoculum from Caatinga presented seven times more AMF species compared to that from the Quarry, which presented ruderal and stress tolerant species. The soil inoculum conditioned by S. uniflora, regardless of origin, presented greater evenness compared to the soil inoculum produced with S. bicolor and promoted 33% more plant biomass compared to the control without inoculation. Root colonization by AMF increased PSF and decreased plant investment in functional traits such as specific root length (SRL) and specific leaf area (SLA). Our results demonstrate the importance of adopting strategies that preserve local adaptation of inoculants produced. The use of native plant for propagation of native AMF in the conditioning phase provided more positive responses for Mesosphaerum suaveolens and Rhaphiodon echinus than inoculated with introduced AMF isolates. This is probably due to the interaction of inoculated plants with responsive AMF present in the soil. Synthesis and applications. Our study shows that conditioning field‐collected soil with Senna uniflora and using it for inoculation can be a simple technique to promote biomass accumulation for other native herbaceous species. This preserves the compatibility between the soil inoculum produced with native AMF and native plants, representing an important tool for restoration programs.

Water-use characteristics of two dominant plant species in different community types in the Mu Us Desert

Shrubs are pioneer species for ecological restoration in drylands and can promote the growth of herbaceous plants. Knowledge of the water-use characteristics of these revegetated species in different community types is crucial for understanding interspecific and intraspecific interactions and guiding ecological restoration; however, few studies have focused on this process. In this study, we explored the water sources and root distribution of plants in three community types in the Mu Us Desert: a mixed community including a shrub species Artemisia ordosica and a grass species Leymus secalinus, a pure A. ordosica community, and a pure L. secalinus community. We measured the δ18O of the plant xylem and soil water within 100 cm of the soil surface and surveyed the root biomass distribution. The main water source for both A. ordosica and L. secalinus in mixed communities was from the shallow soil layer (0–20 cm) and it overlapped most of the time. When soil moisture in the shallow soil layer was low, L. secalinus still used water from the shallow soil layer, whereas A. ordosica mainly used water from the dry deep soil layer (60–100 cm). The water sources for A. ordosica were significantly different among different communities. In contrast, L. secalinus had similar water sources in different communities. We also found that the root biomass of shrubs was significantly lower in mixed communities than in pure communities. Moreover, when available soil water increased, the root biomass of grasses increased significantly, whereas that of shrubs did not significantly change. These results suggest grasses have an advantage over shrubs in competing for water and this may lead to the exclusion of shrubs from the community, and grasses dominated community. Our study can be used as a reference for assessing the persistence of shrub species to guide future ecological restoration.

Vegetation restoration dominates increase in water use efficiency in drylands of China

Dryland ecosystems are crucial components within the Earth and atmospheric systems, and a number of projects have been implemented to restore vegetation in drylands in the recent years. However, these regions are experiencing extreme climatic changes, and the impact of these projects are unclear. To gain a better understanding of the effectiveness of these projects, we employed water use efficiency (WUE), the ratio of gross primary production (GPP) to terrestrial evapotranspiration (ET), to predict future dryland ecosystem dynamics, and detected the underlying causes of WUE changes. We analysed the WUE trends and the decomposed components of WUE, namely the GPP to plant transportation ratio (GPP/T) and the plant transportation to terrestrial evapotranspiration (T/ET) ratio, between 2003 and 2018 in China’s drylands. The results indicated that 70.3 % of the study area had an upward WUE trend, and T/ET was the dominant factor of the WUE trend in 74.9 % of the areas investigated. Furthermore, the increase in T/ET was associated with growth in leaf area index (LAI). The rising WUE rate in the vegetation restoration project areas was significantly higher than that in other areas along with the drought gradient (P < 0.05), which indicated WUE increasing was strongly influenced by the increase in LAI resulting from vegetation restoration. Thus, our research affirms that vegetation restoration greatly influences WUE increase. However, over time, WUE in these restored drylands is likely to decrease due to increased VPD and plantation saturation, so future strategies for vegetation restoration in drylands are therefore required.

Natural climate solutions in Indonesia: wetlands are the key to achieve Indonesia’s national climate commitment

Indonesia offers a dramatic opportunity to contribute to tackling climate change by deploying natural climate solutions (NCS), increasing carbon sequestration and storage through the protection, improved management, and restoration of drylands, peatlands, and mangrove ecosystems. Here, we estimate Indonesia’s NCS mitigation opportunity for the first time using national datasets. We calculated the maximum NCS mitigation potential extent using datasets of annual national land cover, peat soil, and critical lands. We collated a national emissions factor database for each pathway, calculated from a meta-analysis, recent publications from our team, and available literature. The maximum NCS mitigation potential in 2030 is 1.3 ± 0.04 GtCO2e yr−1, based on the historical baseline period from 2009–2019. This maximum NCS potential is double Indonesia’s nationally determined contribution (NDC) target from the forestry and other land use sector. Of this potential opportunity, 77% comes from wetland ecosystems. Peatlands have the largest NCS mitigation potential (960 ± 15.4 MtCO2e yr−1 or 71.5 MgCO2e ha−1 yr−1) among all other ecosystems. Mangroves provide a smaller total potential (41.1 ± 1.4 MtCO2e yr−1) but have a much higher mitigation density (12.2 MgCO2e ha−1 yr−1) compared to dryland ecosystems (2.9 MgCO2e ha−1 yr−1). Therefore, protecting, managing, and restoring Indonesia’s wetlands is key to achieving the country’s emissions reduction target by 2030. The results of this study can be used to inform conservation programs and national climate policy to prioritize wetlands and other land sector initiatives to fulfill Indonesia’s NDC by 2030, while simultaneously providing additional co-benefits and contributing to COVID-19 recovery and economic sustainability.

Native bacteria and cyanobacteria can influence seedling emergence and growth of native plants used in dryland restoration

Abstract Seed‐based ecosystem restoration has huge potential to restore degraded drylands. However, fewer than 10% of directly sown seeds transition to established seedlings. One of the potential factors restricting plant establishment in degraded soils is the low abundance and diversity of native soil micro‐organisms. In this study, we investigated whether returning indigenous bacteria and cyanobacteria consortia to degraded dryland soils improved seedling emergence, survival and growth of native plants. We inoculated ‘culturable whole soil’ native heterotrophic bacteria and biocrust cyanobacteria individually and as a mixed inoculant into extruded pellets containing Acacia inaequilatera (Fabaceae) and Triodia epactia (Poaceae) seeds. The pellets were planted in an active minefield for 28 weeks and seedling emergence and total biomass of plants were determined. Cyanobacteria and bacteria inoculants increased the emergence of A. inaequilatera by 55% and 48%, respectively. Seedling emergence in T. epactia was increased by 20% by cyanobacteria but was not increased by bacteria. The only effect of inoculation on seedling survival or mass per surviving seedling in either species was an 11% reduction of the growth of T. epactia seedlings that were inoculated with cyanobacteria. Synthesis and applications: Our results suggest that the benefit of micro‐organisms on plant establishment is both species specific and life stage specific, with particularly strong benefits in the early stages of recruitment. Our experiment was conducted under shade and with additional water, so a worthwhile future direction would be to quantify the effect of inoculation under unmodified field conditions. It would also be worthwhile monitoring the outcomes for longer than 28 weeks. Since seedling emergence is one of the critical challenges in dryland restoration, our study provides direct evidence in the use of native micro‐organisms to potentially improve seedling emergence in seed‐based dryland restoration.

C, N, P, K stoichiometric characteristics of the “leaf-root-litter-soil” system in dryland plantations

• Tree species and afforestation years affected nutrient cycling of plantations. • The highest C was in fine roots and the highest N, P and K was in green leaves. • Green leaves absorbed more P and maintained P homeostasis to alleviate P limitation. • Caragana korshinskii was more suitable for ecological restoration in drylands. Plantation’s nutrient cycling can regulate and affect the material cycling of ecosystems, which is the key to maintain the sustainable development of the plantation ecosystem. However, the current understanding of the nutrient cycling characteristics of the “leave-root-litter-soil” continuum of dryland plantation ecosystems is limited. Therefore, in the Longzhong Loess Plateau of China, we selected nine typical dryland plantations to carry related research, including two evergreen ( Platycladus orientalis (13-years and 50-years) and Pinus tabuliformis ) and four deciduous ( Caragana korshinskii (13-years, 35-years and 55-years), Armeniaca sibirica , Populus hopeiensis and Tamarix chinensis ) tree species, and measured C, N, P and K contents of green leaves, fine roots, leaf litter and surface soil (0–20 cm). Results showed tree species and afforestation years strongly changed C, N, P and K contents and ratios of green leaves, fine roots, leaf litter and soil components, and also significantly affected leaf N, P and K reabsorption efficiencies. The average N, P and K contents of four components and soil available nitrogen (AN), available phosphorus (AP) and available potassium (AK) contents in deciduous plantations were higher than those in evergreen plantations, resulting in the lower C:N:P:K stoichiometry of deciduous plantations than evergreen plantations. Especially in 55-years C. korshinskii plantation, its soil C, N, AN, AP and AK contents were higher than those in A. sibirica , P. hopeiensis , P. orientalis and P. tabuliformis plantations. Moreover, soil C, N, P, AN, AP and AK contents in C. korshinskii plantations increased significantly with the increase of afforestation years. Thus, C. korshinskii was more suitable for ecological restoration in drylands. Due to the P limitation in plantations, P reabsorption efficiency was higher than N reabsorption efficiency, and significantly negatively correlated with P contents of four components. And green leaves had the homeostasis to soil AP, which may be the nutrient utilization strategies for plantations to alleviate P limitation. Correlation analysis revealed that the C cycling appeared in green leave-fine root and green leave-leaf litter, the N cycling appeared in green leave-leaf litter-soil-fine root, and the P cycling and K cycling appeared in green leave-leaf litter- soil and leaf litter-fine root. These results will provide guidance for ecological restoration and plantation management in drylands.

Ecological Compensation Mechanism in a Trans-Provincial River Basin: A Hydrological/Water-Quality Modeling-Based Analysis

Ecological compensation is an important economic means of water pollution control and quality management, especially for trans-regional rivers with unbalanced economic and social development between upstream and downstream. The Tangbai River Basin (TRB), a watershed crossing Henan province and Hubei province, China, forms one of the nation’s most productive agricultural regions. The TRB has been exposed to high doses of fertilizers for a long time. This study simulates hydrologic and nutrient cycling in the TRB using Soil and Water Assessment Tool (SWAT) with limited data available. The results indicate that dryland fields, which constitute 62% of the basin area, produce 80% of total nitrogen (TN) and 85% of total phosphorus (TP) yields of the whole river basin. The water quality of river sections at the provincial boundary shows that only 29% of the time from 2000 to 2019 met the Class III standard regarding TN and TP concentrations, and the concentrations in the spring flood season are approximately three times the mean in the non-flood season. The Grain for Green ecological restoration measure in Henan province shows that restoration of non-flat drylands can reduce nutrient loads at trans-provincial sections by 3.5 times compared to that of slope-independent drylands; however, the water quality compliance rate remains similar. The value of ecological compensation can also vary widely depending on different quantitative criteria. The SWAT-based pollutant quantification method adopted in this study could have implications for ecological compensation in trans-regional rivers.