Dryland Restoration Research Articles

Biocrusts mediate the plant community composition of dryland restoration ecosystems

Degradation and expansion are current threats associated with drylands. During natural or artificial restoration, dryland ecosystems tend to contain a unique community, namely, biocrusts. Studies have shown that biocrusts serve multiple functions and have the potential to accelerate or inhibit degradation. However, the mechanisms by which biocrusts mediate dryland plant community structure and composition remain largely unknown. In this study, we performed a series of pot experiments under greenhouse conditions at three disturbance levels (strong, moderate and no disturbance) and at three rainfall gradients (− 50 %, normal, + 50 %) for different biocrust types. Our objective was to examine how biocrusts influence the introduction and establishment of different functional forms of plant species during the different succession stages of dryland recovery. Our results showed that biocrusts have significantly different effects on the seed germination and survival of the tested plant species. Although strong disturbances to the biocrusts and increasing rainfall alleviated the inhibitory effects of biocrusts on the perennial herb (S. glareosa) and subshrub (C. latens) species, these factors could only promote the temporary survival of these two plants in the revegetated area. These results indicate that biocrusts in revegetated systems play important sieving functions during plant species establishment. Additionally, the survival of S. viridis, a plant species with small seeds adapted to the current habitat, was promoted in the community, but two plant species that are currently unsuitable, S. glareosa and C. latens, were filtered out by the biocrusts. Our conclusions suggest that biocrusts play an ecological filtering role in plant species introduction and establishment in revegetated ecosystems and demonstrate the scientific significance of biocrusts in maintaining the health and stability of dryland ecosystems.

Restoring Palmer's agave in a Lehmann lovegrass dominated grassland in southeastern Arizona

Dryland restoration is becoming increasingly challenging in arid and semiarid regions, such as in the southwestern United States, due to rapid land degradation, the spread of non‐native species, and climate change. The development of strategies to enhance restoration of native species, particularly culturally and ecologically important native plants like Palmer's agave (Agave palmeri), is particularly critical in southeastern arid lands where scarce rainfall, herbivory, and invasive species dominance pose unique challenges to land management. In a large field experiment in southeastern Arizona, U.S.A., we assessed the utility of several management techniques to promote restoration and revegetation outcomes for Palmer's agave survival and growth, including protection from solar insolation and herbivory, and reduction in the competitiveness of Lehmann lovegrass (Eragrostis lehmanniana). We found that the combination of herbivory protection and shade resulted in the highest survival of planted agaves, while the shade treatment alone resulted in the largest agaves. In fact, our results suggest that dense Lehmann lovegrass cover protects agaves from direct sunlight and predation. If land managers are challenged by widespread Lehmann lovegrass, they can opt to mechanically reduce it. However, if population recovery of Palmer's agave is a priority and fire hazard is minimal, our work suggests that stakeholders concerned with population recovery of Palmer's agave can forgo removing existing vegetation and plant agaves in a matrix of (and/or under the canopy of) existing vegetation.

A cautionary note for forest landscape restoration in drylands: cattle production systems in northwest Madagascar’s dry forests

ABSTRACT Multiple global initiatives are underway to restore the world’s forests, and more recently, its rangeland ecosystems. Tenure security has been identified as a key enabling factor for successful restoration initiatives. However, in Madagascar, a global biodiversity hotspot, dry forests are considered unoccupied and unowned, even where communities have long-established claims under customary tenure systems. Collective tenure recognition efforts are underway, but limited knowledge on agropastoralist cattle production strategies hampers efforts to develop well-informed tenure reforms. Our qualitative study helps fill this knowledge gap by documenting cattle raising strategies among agropastoralists in northwestern Madagascar, as well as the core elements of semi-extensive and extensive pasturelands. Our analysis reveals the presence of four distinct cattle raising strategies in the study area but suggests that cattle raisers are transitioning away from extensive cattle production toward semi-extensive and intensive alternatives in response to high risk of cattle theft and expanding human settlement. Although our study focuses on Madagascar, the issues we raise are relevant to ongoing efforts throughout sub-Saharan Africa to engage agropastoralists in dry forest restoration and support their livelihoods.

Interspecific interactions alter plant functional strategies in a revegetated shrub-dominated community in the Mu Us Desert, China.

Previous studies investigating plant-plant interactions have focused on plant growth, context dependence and shifts in interactive outcomes. However, changes in functional traits in the context of interactions have been inadequately explored; few studies have focused on the effects of interactions on the plasticity of functional strategies. We conducted a 4-year removal experiment for the xeric shrub Artemisia ordosica and perennial graminoids (PGs) in the Mu Us Desert, northern China. Soil nutrient content, biomass and 12 functional traits related to plant morphology and nutrient status were measured for the shrub species and a dominant PG species (i.e. Leymus secalinus) in the presence and absence of shrubs and PGs. Shrubs affected the functional traits of L. secalinus, reducing leaf dry matter content and increasing plant height, which probably promoted the functional strategy of L. secalinus towards a more resource-acquisitive and competitive strategy. In contrast, when the shrubs were affected by PGs, they shifted towards a resource-conservative and stress-tolerative strategy, by increasing leaf dry matter content and decreasing specific leaf area. Moreover, the shrub species relied more on internal nutrient recycling (higher nitrogen resorption efficiency) rather than on external nitrogen uptake under nitrogen competition; instead, L. secalinus tended to exhibit higher external nitrogen uptake from soil during nitrogen shortages. This study indicated that the functional strategies and nutrient cycling of the shrub species and the dominant PG were altered by each other. The shifts in functional traits may help plants to coexist in the community for a relatively long time. Our findings highlighted that interspecific interactions alter plant functional strategies and provided new insights into community assembly and succession mechanisms in a revegetated shrubland for ecological restoration of drylands.

Host and Tissue Affiliations of Culturable Endophytic Fungi Associated with Xerophytic Plants in the Desert Region of Northwest China

Endophytic fungi isolated from plants under drought stress have been evidenced to confer hosts adaptive benefits to withstand drought. In this study, endophytic fungi associated with five typical desert shrubs in different tissue from extremely arid desert in Northwest China were investigated based on ITS sequence analysis. A total of 158 endophytic fungal stains were isolated from 1088 tissue segments of 12 samples, and 28 taxa represented by 25 species and 15 genera were identified as Ascomycetes. Alternaria sp. was the dominant genus with generic abundance ranging from 20% to 65%. The colonization rate of root was significantly lower, but the root-endophytic fungi (19 species) conversely presented a higher diversity than stem and leaf (11 and 7 species, respectively). Endophytic fungi had pronounced relative host and tissue preferences, while tissue explained more endophytic fungal variation than plant species. Additionally, soil pH, organic carbon, and phosphatase elicited significant responses from fungal species, which significantly affected the species richness of Fusarium redolens, Alternaria chlamydospore, Didymella glomerata, and Xylariales sp. This research provides a basis for the further understanding of the ecological distribution of endophytic fungi associated with xerophytic plants and their potential application for vegetative restoration and agricultural cultivation in drylands.

Restoration priorities for Caatinga dry forests: Landscape resilience, connectivity and biodiversity value

Abstract Restoration actions can halt biodiversity loss and rescue its services. However, in order to be effective, priority areas for restoration should be chosen based on objective large‐scale restoration planning. Here, a multicriteria graph theory framework was used to propose restoration priority areas for the Brazilian Caatinga, the largest seasonally dry tropical forest of the New World, based on landscape resilience, landscape connectivity and biodiversity conservation value, focusing on threatened endemic plant species. We applied this graph theory framework to 10,406 Caatinga catchment basins. Vegetation cover and within‐catchment connectivity were used to select catchments of intermediate landscape resilience, which in principle offer more effective opportunities for restoration. Then, such catchments were independently classified into (a) three classes according their contribution for between‐catchment connectivity and (b) three classes according their value for biodiversity conservation, estimated by the richness of threatened, endemic plant species. By the integration of landscape resilience, landscape connectivity and biodiversity conservation values, three priority classes for restoration were generated. The multicriteria framework generated several restoration priority cut‐offs. Prioritization based on landscape resilience selected 36% of the Caatinga catchments as high priority for restoration. By independently adding landscape connectivity and biodiversity conservation value, only 12% and 3% of the catchments, respectively, were considered as high priority. By combining all three criteria, 9% of the catchments were selected as high priority and <1% as top priority for restoration. Synthesis and applications. Restoration of drylands can contribute immensely to the conservation of its threatened biodiversity but large‐scale planning is quintessential. Here, a multicriteria graph theory framework was applied to indicate priority areas for restoration, which maximizes the effectiveness of restoration actions, landscape connectivity for climate change adaptation and conservation of threatened species. The framework was applied to the Caatinga, the largest seasonally dry tropical forest of the new world, but it can be applied world‐wide under different budged limitations and spatial scales, being useful for private, state and federal initiatives.

Exogenous Microorganisms Promote Moss Biocrust Growth by Regulating the Microbial Metabolic Pathway in Artificial Laboratory Cultivation.

Moss-dominated biocrusts (moss crusts) are a feasible approach for the ecological restoration of drylands, but difficulty obtaining inoculum severely limits the progress of large-scale field applications. Exogenous microorganisms could improve moss growth and be conducive to moss inoculum propagation. In this study, we investigated the growth-promoting effects and potential mechanisms of exogenous microorganism additives on moss crusts. We used an incubator study to examine the effects of inoculation by heterotrophic microorganisms (Streptomyces pactum, Bacillus megaterium) and autotrophic microorganisms (Chlorella vulgaris, Microcoleus vaginatus) combined with Artemisia sphaerocephala gum on the growth of Bryum argenteum, the dominant moss crusts species in sandy deserts. Amplicon sequencing (16S and 18S rRNA) and PICRUSt2 were used to illustrate the microbial community structure and potential function in the optimal treatment at different developmental stages. Our results showed that exogenous microorganisms significantly promoted moss growth and increased aboveground biomass. After 30 days of cultivation, the Streptomyces pactum (1 g kg–1 substrate) + Chlorella vulgaris (3.33 L m–2) treatment presented optimal moss coverage, height, and density of 97.14%, 28.31 mm, and 2.28 g cm–2, respectively. The best-performing treatment had a higher relative abundance of Streptophyta—involved in moss growth—than the control. The control had significantly higher soil organic carbon than the best-performing treatment on day 30. Exogenous microorganisms improved eukaryotic community diversity and richness and may enhance soil microbial functional and metabolic diversity, such as growth and reproduction, carbon fixation, and cellulose and lignin decomposition, based on functional predictions. In summary, we identified the growth-promoting mechanisms of exogenous additives, providing a valuable reference for optimizing propagation technology for moss inoculum.

Design Optimization of Biocrust-Plant Spatial Configuration for Dry Ecosystem Restoration Using Water Redistribution and Erosion Models

Land degradation is one of the main threats to dryland sustainability in the next decades, hence restoration of the degraded land from drylands is an urgent need to maintain ecosystem functionality and their ability to provide ecosystem services. To achieve this goal, restoration practices should pursue the recovery of the main ground components, arranged in an optimal spatial configuration, to mimic undisturbed natural conditions. Drylands function as complex ecohydrologically coupled systems in which interplant source areas, frequently covered by biocrusts, act as sources of runoff and nutrients to adjacent vegetation, which act as sinks for these resources. Thus, one way to increase dryland restoration success is through an optimal spatial configuration of biocrusts and plants that maximizes an efficient use of the limited resources within the system. In this study, we selected a degraded slope from a limestone quarry located in Almería province (SE Spain) and modeled how active restoration of the biocrust through soil inoculation with cyanobacteria and its combination with different spatial configurations of vegetation affected runoff redistribution and erosion. For that, we applied the spatially distributed Limburg Soil Erosion Model (LISEM) which was able to predict the erosion measured on the slope during the study period with low error (RMSE = 17.8%). Modeling results showed that the introduction of vegetation on the degraded slope reduced runoff between 2 and 24% and erosion between 4 and 17% for the scenario with plants compared to the one without restoration management. Of all the vegetation spatial configurations tested, the one that provided better results was the scenario in which plants were located in the areas of higher water accumulation (higher topographic wetness index). Moreover, we found that active biocrust restoration by cyanobacteria inoculation significantly reduced erosion by 70–90%, especially during the first stages of plant development, while maintaining water supply to vegetation. These findings highlight the potential of water redistribution and erosion simulation models to identify the most optimal spatial configuration of ground covers that maximizes water and nutrient supply to vegetation, while minimizes water, sediment, and nutrient losses by erosion, thus serving as an efficient tool to plan restoration actions in drylands.

Improving dryland seedling recruitment using fungicide seed coatings

Abstract The success of seed‐based restoration in dryland regions of the world is often low or sporadic, with most mortality occurring between germination and emergence. Fungal pathogenesis is one process that may reduce seedling emergence and limit restoration success. Our objective was to determine whether fungicide seed coatings constitute an economically viable strategy for increasing emergence by reducing fungal pathogenesis and mortality. We performed an experiment across two sites and three years, using bluebunch wheatgrass (Pseudoroegneria spicata) as a model species. We found that fungicide coatings increased germination by 8.8% and emergence by 54.0% on average compared to the control. A cost analysis indicated that the fungicide coating was economically viable with an average estimated effective cost reduction of 18.8% under the study conditions. There was a strong interaction (P < 0.001) between the effects of the fungicide coating, site and year on emergence. The fungicide coating increased emergence compared to the control in five of the six sites and years, with the effect ranging from a 33.7% decrease (P = 0.042) to a 150.9% increase (P = 0.004). The observed interaction was likely related to the effect of the hydrothermal microsite environment on disease severity. In the site and year that the fungicide coating performed worse than the control, prolonged periods of exceptionally low soil moisture may have reduced disease severity through a variety of individual and community scale mechanisms. Overall, these results indicate that fungicide seed coatings have the potential to improve dryland restoration efforts.

Kōkua aku, Kōkua mai: An Indigenous Consensus-driven and Place-based Approach to Community Led Dryland Restoration and Stewardship

The well-documented and forced migration of Indigenous Peoples from ancestral lands has fragmented connections to, and understandings of place. Yet Indigenous Peoples are reconceptualizing and revitalizing these connections including by leading forest landscape restoration efforts. Indigenous and Local Knowledge (ILK) supports the design and practice of ecological restoration across rural to urban gradients – including both ancestral lands and contemporary places, with thought leaders advocating for biocultural approaches to address biodiversity loss, land occupation, and the colonial legacies of social and economic marginalization of Indigenous Peoples. To date, there are few examples in Hawai‘i, where in 1893 the overthrow of the Hawaiian Kingdom disenfranchised most Indigenous People of land, freshwater, and coastal resources. Here we describe the Pu‘uwa‘awa‘a Community-Based Subsistence Forest Area (P-CBSFA), that was formed in 2017 to steward 34-ha of land within the Pu‘uwa‘awa‘a State Forest Reserve, North Kona, Hawai‘i Island and is led by multi-generational lineal descendants of Pu‘uwa‘awa‘a. We focus on how this stewardship initiative has relied on holistic acknowledgement in the engagement of historical context, a Native Hawaiian conceptualization of the restoration process, and a collaborative and consensus-based restoration practice that includes non-profit organizations and state and federal agencies. This initiative, the first community-based and subsistence-focused forest restoration project on State of Hawaiʻi administered lands, is using a biocultural framework to transform 34-ha of non-native and fire-prone grasses into a native species dominated dryland subsistence forest. To do this, the P-CBSFA relies on a relationship ethic to: (i) build trust among partners; (ii) articulate an exportable vision of ILK-based restoration; (iii) walk in awareness of historical and contemporary injustices; (iv) enhance cultural values of the landscape; (v) establish and rely on formal, empathy focused communication; (vi) focus on community directed benefits; and most importantly (vii) cultivate joy. From this framework, the P-CBSFA emerges to provide a multi-dimensional passageway through which lineal descendants of Pu‘uwa‘awa‘a are formalizing governance and decision-making authority over their ancestral lands.

Directional selection shifts trait distributions of planted species in dryland restoration

Abstract The match between species trait values and local abiotic filters can restrict community membership. An often‐implicit assumption of this relationship is that abiotic filters select for a single locally optimal strategy, though difficulty in isolating effects of the abiotic environment from those of dispersal limitation and biotic interactions has resulted in few empirical tests of this assumption. Similar constraints have made it difficult to assess whether the type and intensity of abiotic filters shift along gradients of environmental harshness, as predicted by the stress‐dominance hypothesis. We planted 9,216 plants of 29 perennial grass and forb species that had a range of functional trait values and were assigned to a warm, intermediate or cool temperature tolerance pool across eight sites on the Colorado Plateau. We compared the distributions of traits of surviving individuals to null distributions to evaluate whether there were shifts in trait means and variation. Borrowing from phenotypic selection concepts in evolutionary biology, we assessed support for stabilizing, directional and disruptive abiotic filtering of trait distributions and whether these types of filtering varied with initial species pool. Functional composition was significantly different from null distributions for nearly all traits at all sites, with trait variation more restricted in harsher abiotic conditions, supporting the stress‐dominance hypothesis. Contrary to expectations, we primarily found evidence for directional selection, which increased in frequency in warm species pools while disruptive selection was found more often in cool and intermediate species pools. Synthesis. This study provides a controlled experimental approach to test the effect of the abiotic environment on plant trait filtering. We found that opportunistic strategies allowing for rapid water acquisition during favourable periods improved survival at warmer sites. Species with these strategies may be expected to benefit from increasing aridity and may be selected for active management efforts. More generally, the prevalence of directional selection may have important implications for dynamic vegetation models that rely on trait distributions for translating environmental variation into ecosystem processes.

Combining Rainwater Harvesting and Grass Reseeding to Revegetate Denuded African Semi-arid Landscapes

In African drylands, perennial grasses preferred by grazing livestock are disappearing at an alarming rate. This has led to recurrent livestock feed shortages threatening pastoralist’s livelihoods. Combining native grass reseeding and rainwater harvesting offers a viable and innovative solution to reverse this trend. However, studies to determine how biomass yields are affected by soil moisture availability attributed to in situ rainwater harvesting in African drylands are limited. We investigated how biomass yields of three grasses native to Africa, i.e., Enteropogon macrostachyus (Bush rye grass), Cenchrus ciliaris (African foxtail grass), and Eragrostis superba (Maasai love grass), are affected by soil moisture content in a typical semi-arid landscape. Rainwater harvesting structures included trenches, micro-catchments and furrows. Additionally, rain runoff was diverted from an adjacent road used as a catchment area. Soil moisture was measured between November 2018 and August 2019 using PlantCare Mini-Logger sensors installed at 40 and 50 cm depths and 0, 1, 5 and 15 m away from the trench. Quadrat method was used to determine biomass yields in August 2019. Peaks in soil moisture were observed after rainfall events. Soil moisture content gradually decreased after the rainy season, but was higher closer to the trench. This is attributed to the prolonged rainwater retention in the trenches. Biomass yields were in the order Eragrostis superba > Cenchrus ciliaris > Enteropogon macrostachyus. Biomass production was higher near the trenches for all the studied species. Sensitivity to soil moisture demonstrated by the magnitude to yield reduction during the growing season was in the order Eragrostis superba > Cenchrus ciliaris > Enteropogon macrostachyus. These results suggest that Eragrostis superba is more sensitive to drought stress than Enteropogon macrostachyus that is adapted to a wide range of soil moisture conditions. We demonstrated that in situ rainwater harvesting structures enhanced soil moisture availability and displayed great potential for revegetating denuded natural rangelands in semi-arid African landscapes. Thus, combining rainwater harvesting and reseeding techniques can produce measurable improvements in pastoral livelihoods and should be incorporated in dryland development policies in the region. Ultimately, incorporating such innovative strategies can strengthen the effectiveness of ecological restoration in African drylands to meet the objectives of the UN Decade on Ecosystem Restoration and achieving the UN Sustainable Development Goals.Graphical abstract

Does restoration of plant diversity trigger concomitant soil microbiome changes in dryland ecosystems?

Abstract Drylands are highly vulnerable to land degradation, and despite increasing efforts, restoration success remains low. Although often ignored in the design and deployment of management strategies, soil microbial communities might be critical for dryland restoration due to their central role in promoting soil stability, nutrient cycling and plant establishment. We collected soil samples from eight dryland restoration sites within RestoreNet, a restoration field trial network, and determined their soil microbiome using 16S rRNA (bacteria and archaea) and ITS (fungi) amplicon sequencing. Each previously degraded site was treated with monoculture (single species) and polyculture (multiple species) seedling plantings. Contrary to our initial expectations, we found that these different revegetation interventions did not trigger changes in microbial diversity, composition or relative abundance of functional groups across sites after 1 year of revegetation. Synthesis and applications. Considering the crucial role of soil micro‐organisms in dryland ecosystem functions, our results suggest that site‐specific targeted microbiome restoration should be considered to accelerate the establishment of desired microbial communities. Plant community‐based restoration practices such as revegetation have a limited impact on soil micro‐organisms in the short term.

Biocrust cyanobacteria inoculants biomineralize gypsum and preserve indigenous bacterial communities in dryland topsoil

Biocrust cyanobacteria are ubiquitous organisms in dryland environments that can enhance soil stability and improve nutrient conditions in reconstructed or disturbed soils. Despite the demonstrated benefits of cyanobacterial inoculation for promoting soil fertility, there is limited knowledge about the impacts of introducing cultured cyanobacteria on the indigenous microbial communities. Here, we conducted a microcosm experiment under controlled conditions using indigenous biocrust cyanobacteria and locally sourced topsoil substrate commonly used in dryland restoration in the Australian arid zone. We inoculated the topsoil with a consortium composed of Leptolyngbya sp. and Scytonema sp. cyanobacteria, to assess the effects of the inoculated cyanobacteria on (i) the soil chemical properties, i.e., pH, electrical conductivity (EC), total organic carbon (TOC), and nitrogen (TN) of the inoculated topsoil, (ii) the early formation of an artificial soil biocrust and iii) the composition and diversity of the resident bacterial community. Our results showed that the inoculated cyanobacterial consortia decreased the EC, but changes in the TOC and TN were not significant after 80 days. A higher content of chlorophyll a in the inoculated samples compared to the control, confirmed the survival of the cyanobacterial inoculants after 80 days. The inoculated cyanobacteria promoted gypsum formation on the soil surface indicating that they are actively modifying the upper layers of the soil profile and improving habitability. Although immediately after inoculation cyanobacteria dominated the abundance of bacterial phylotypes, these were replaced by other phyla such as Actinobacteria, after 80 days. The Shannon diversity and Simpson diversity indexes between control and inoculated soils differed at the time of inoculation but were similar at the end of the experiment. These results suggest that, in the short term, the introduced cyanobacteria do not significantly affect the native resident bacterial communities and are capable of colonizing the topsoil without affecting the natural community.

Starting points for the restoration of desertified drylands: puesteros’ cultural values in the use of native flora

ABSTRACT In rural dryland areas, the socioeconomic diagnosis of the population and their traditional knowledge of the flora are key to restoration. In this study, we asked rural people (locally called “puesteros”) about their knowledge of the native flora, in a settlement of 160 inhabitants, located in drylands of Argentine. For this, semi-structured surveys and open interviews were carried out with 30 puesteros. The surveys collected information about the puesteros’ socio-economic characteristics, their knowledge and value about the use of species, and their interest in planting those species in their farms. Once the list of multipurpose species was obtained, we reviewed the scientific literature to know some of their favorable ecological attributes. The interviews were carried out to know the limitations and advantages associated with planting native species in the puesteros’ home gardens. Our results show that 33% of the people surveyed were illiterate, and their primary economic source of income was livestock. In the surveys, the puesteros mentioned 44 multipurpose species, which were classified by their uses. 97% of respondents expressed interest in planting on their farms and mentioned 21 potentially useful species. Of the 44 multipurpose species mentioned by the puesteros, we found that 22 had ecological attributes for restoration. In the interviews, the puesteros identified the factors that limited and favored plantations. They had already planted 44 species in their home gardens for different purposes. The implications of current local knowledge for future socio-ecological approaches to productive restoration in drylands are discussed.

Drivers of seedling establishment success in dryland restoration efforts.

Restoration of degraded drylands is urgently needed to mitigate climate change, reverse desertification and secure livelihoods for the two billion people who live in these areas. Bold global targets have been set for dryland restoration to restore millions of hectares of degraded land. These targets have been questioned as overly ambitious, but without a global evaluation of successes and failures it is impossible to gauge feasibility. Here we examine restoration seeding outcomes across 174 sites on six continents, encompassing 594,065 observations of 671 plant species. Our findings suggest reasons for optimism. Seeding had a positive impact on species presence: in almost a third of all treatments, 100% of species seeded were growing at first monitoring. However, dryland restoration is risky: 17% of projects failed, with no establishment of any seeded species, and consistent declines were found in seeded species as projects matured. Across projects, higher seeding rates and larger seed sizes resulted in a greater probability of recruitment, with further influences on species success including site aridity, taxonomic identity and species life form. Our findings suggest that investigations examining these predictive factors will yield more effective and informed restoration decision-making.

The effects of site preparation equal those of seeding at a dryland restoration site: 6 years of plant community development

Dryland ecosystems generally require active restoration to recover from severe land degradation caused by resource and energy extraction operations. While seeding remains one of the most used forms of active restoration, land managers in dryland systems have generally had difficulty re‐establishing desirable plant communities, due in part to alterations in supporting ecosystem processes and the episodic nature of resource availability. In this study, we examined the impacts of site preparation, seeding, and livestock grazing on developing plant communities after the construction of a buried natural gas pipeline corridor in the southwestern United States. We monitored plant species cover and composition beginning with the second season of growth through the sixth. Analysis of each individual year show that conclusions from the initial year of data collection did not well represent the findings in the following years. The site preparation and topsoil treatment had an ongoing positive effect on richness and cover compared to the nearby baseline conditions, while seeding only further increased cover and richness in the first year of monitoring (second season of growth). However, without seeding, the plant communities were driven by ruderal, annual species, whereas the seeded plant communities were driven by desirable seeded perennial grasses and forbs. Grazing and trampling effects were not significant overall, and the effects of livestock may have been confounded with effects of small mammals due to the exclosure configuration. We suggest that the site preparation, topsoil treatment, and configuration linearity of the disturbance corridor allowed for high levels of natural recruitment.

Assessing reforestation failure at the project scale: The margin for technical improvement under harsh conditions. A case study in a Mediterranean Dryland

Poor reforestation outcomes imply failure to fulfill program goals and tend to erode institutional willpower and political momentum towards reforestation efforts, affecting both public and private support. However, program improvement in real reforestation projects is challenging, due to the conjunction of many different variables that mutually interact and feed back on each other inextricably. This study develops a comprehensive assessment framework for reforestation programs, for which technical and environmental information is gathered and related to indicators of performance in both the short- and mid-term. This assessment, tested on a case study, aimed to provide reliable end-results for survival and growth, revealed pitfalls in successful plantation establishment and taught us how to improve plantation performance and what the margin for this improvement was. The selected project was carried out on harsh site conditions, with different species, cultivation treatments and contractors, and was affected by the driest year on record. Plantation mortality was high and increased progressively over time, particularly in the short-term when the rate was 53% (rising to 83% after ten years), showing high variation between sites and species (Pinus pinaster and Quercus faginea died more than 94% after ten years while Junipus phoenicea only 40%). All the hardwoods and the juniper showed lower growth rate after ten years (average stem volume < 40 cm3) than pines (stem volume > 470 cm3). Technical variables (project planning and execution) had a relatively important impact on plantation performance in the first two years (11–29%), but decreased with time, whilst environmental variables (site and meteorological) were more important ten years after planting (>50%). In the short-term, soil moisture and meteorology during the planting season were identified as key factors that triggered the effects of both technical decisions (planting date and planting technique) and other environmental variables on performance. In the design phase, some decisions related to zoning, species selection and cultural treatments were related to poor performance. The results provide practical information and guidelines about all potential drivers of plantation performance and contribute to identify those aspects more related to success of forest restoration in Mediterranean drylands.

English

The East African drylands cover about 47% of the land surface and host about 20 million people. Rural people living in the drylands are mainly pastoralists who depend on livestock for both economic and social well-being. During the dry season, pastoralists apply strategic mobility to access grazing resources efficiently. However, this strategy has experienced change and constraints due to various demographic- and climate-related challenges. Pastoral lands have been cleared for large-scale agriculture while pastoralists have shifted towards agro-pastoralism. This has eroded many dryland trees and forests leading to environmental degradation. This review discusses important indigenous trees that can be utilized in ecological restoration of drylands as well as providing ecosystem goods and services. These include trees for gums and resins (Acacia, Commiphora and Boswellia), indigenous fruit trees (IFTs) (Adansonia digitata, Tamarindus indica and Balanites aegyptiaca), trees for wood (Melia volkensii and Terminalia brownie) and fodder (Acacia tortilis and Faidherbia albida). They are not only drought-tolerant but also have minimal disruption to the ecosystem. Various dryland restoration strategies and constraints are also discussed. For successful establishment, seedling planting should be integrated with other appropriate practices such as natural regeneration, silviculture and enrichment planting for sustainable dryland management.&nbsp; Key words: Ecological restoration, drylands, indigenous trees, pastoralism.

Incorporating Biogeochemistry into Dryland Restoration

Dryland degradation is a persistent and accelerating global problem. Although the mechanisms initiating and maintaining dryland degradation are largely understood, returning productivity and function through ecological restoration remains difficult. Water limitation commonly drives slow recovery rates within drylands; however, the altered biogeochemical cycles that accompany degradation also play key roles in limiting restoration outcomes. Addressing biogeochemical changes and resource limitations may help improve restoration efforts within this difficult-to-restore biome. In the present article, we present a synthesis of restoration literature that identifies multiple ways biogeochemical understandings might augment dryland restoration outcomes, including timing restoration around resource cycling and uptake, connecting heterogeneous landscapes, manipulating resource pools, and using organismal functional traits to a restoration advantage. We conclude by suggesting ways to incorporate biogeochemistry into existing restoration frameworks and discuss research directions that may help improve restoration outcomes in the world's highly altered dryland landscapes.