Understanding neighborhood effects to increase restoration success of woody plant communities

Revegetation is the most common procedure in the restoration of disturbed areas; this practice usually aims at reconstructing plant communities that can last without further management. A low‐cost strategy to assist these efforts is the application of ecological knowledge in the design of the restoration. Promoting ecological processes that enhance the functioning of the restored community could result in higher restoration success. Among these processes, plant–plant interactions, e.g., facilitation and competition, can play an important role, both facilitating and impeding the development of a self‐sustaining plant community. Although these processes have been well‐studied in nature, we rarely have sufficient knowledge about the whole plant community. To develop that knowledge, we leverage on a restoration experiment that took place after a mine toxic spill, where ~15,000 woody plants from 13 species were planted and geolocated. Species were planted in three mixtures mimicking natural communities found along soil moisture gradients (xerophyte, intermediate, and hydrophyte). Plantings also varied in density. Approximately 2,600 plants were monitored for damage status, survival, and growth, for 4 yr. We analyzed growth performance of six targeted species as a function of their damage status, planted mixture, and density. Growth was also assessed on the basis of neighboring plants, accounting for the species identity and distance to the focal plant. Results show that survival among planted species was relatively high and was mostly unaffected by mixture or density of the plantings. Only very damaged plants in one species experienced a decrease in survival with increasing density. Neighborhood effects on growth show positive, neutral, and negative interactions among the tested species; these also varied depending on the type of growth performance considered (height, crown area, diameter). The species‐specific results ranged from positive to negative, varying between pair of species and growth performance metric. Results gathered from our neighborhood analyses on plant growth provide valuable information for the design of planting schemes that could enhance the performance of the target species. The methods developed can be applied to other systems and species. Given the potential impacts that facilitation and competition may have during revegetation, these interactions could be considered in restoration operations.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/155969/1/eap2098-sup-0002-AppendixS2.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/155969/2/eap2098.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/155969/3/eap2098-sup-0001-AppendixS1.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/155969/4/eap2098_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/155969/5/eap2098-sup-0004-MetadataS1.pd

Seed Mucilage Improves Seedling Emergence of a Sand Desert Shrub

The success of seedling establishment of desert plants is determined by seedling emergence response to an unpredictable precipitation regime. Sand burial is a crucial and frequent environmental stress that impacts seedling establishment on sand dunes. However, little is known about the ecological role of seed mucilage in seedling emergence in arid sandy environments. We hypothesized that seed mucilage enhances seedling emergence in a low precipitation regime and under conditions of sand burial. In a greenhouse experiment, two types of Artemisia sphaerocephala achenes (intact and demucilaged) were exposed to different combinations of burial depth (0, 5, 10, 20, 40 and 60 mm) and irrigation regimes (low, medium and high, which simulated the precipitation amount and frequency in May, June and July in the natural habitat, respectively). Seedling emergence increased with increasing irrigation. It was highest at 5 mm sand burial depth and ceased at burial depths greater than 20 mm in all irrigation regimes. Mucilage significantly enhanced seedling emergence at 0, 5 and 10 mm burial depths in low irrigation, at 0 and 5 mm burial depths in medium irrigation and at 0 and 10 mm burial depths in high irrigation. Seed mucilage also reduced seedling mortality at the shallow sand burial depths. Moreover, mucilage significantly affected seedling emergence time and quiescence and dormancy percentages. Our findings suggest that seed mucilage plays an ecologically important role in successful seedling establishment of A. sphaerocephala by improving seedling emergence and reducing seedling mortality in stressful habitats of the sandy desert environment

Arbuscular mycorrhizal colonisation of roots of grass species differing in invasiveness

Recent research indicates that the soil microbial community, particularly arbuscular mycorrhizal fungi (AMF), can influence plant invasion in several ways. We tested if 1) invasive species are colonised by AMF to a lower degree than resident native species, and 2) AMF colonisation of native plants is lower in a community inhabited by an invasive species than in an uninvaded resident community. The two tests were run in semiarid temperate grasslands on grass (Poaceae) species, and the frequency and intensity of mycorrhizal colonisation, and the proportion of arbuscules and vesicles in plant roots have been measured. In the first test, grasses representing three classes of invasiveness were included: invasive species, resident species becoming abundant upon disturbance, and non-invasive native species. Each class contained one C3 and one C4 species. The AMF colonisation of the invasive Calamagrostis epigejos and Cynodon dactylon was consistently lower than that of the non-invasive native Chrysopogon gryllus and Bromus inermis, and contained fewer arbuscules than the post-disturbance dominant resident grasses Bothriochloa ischaemum and Brachypodium pinnatum. The C3 and C4 grasses behaved alike despite their displaced phenologies in these habitats. The second test compared AMF colonisation for sand grassland dominant grasses Festuca vaginata and Stipa borysthenica in stands invaded by either C. epigejos or C. dactylon, and in the uninvaded natural community. Resident grasses showed lower degree of AMF colonisation in the invaded stand compared to the uninvaded natural community with F. vaginata responding so to both invaders, while S. borysthenica responding to C. dactylon only. These results indicate that invasive grasses supposedly less reliant on AMF symbionts have the capacity of altering the soil mycorrhizal community in such a way that resident native species can establish a considerably reduced extent of the beneficial AMF associations, hence their growth, reproduction and ultimately abundance may decline. Accumulating evidence suggests that such indirect influences of invasive alien plants on resident native species mediated by AMF or other members of the soil biota is probably more the rule than the exception

Population studies on the dune-building grass Leymus arenarius

SIGLEAvailable from British Library Document Supply Centre- DSC:DX96939 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Germination of Leymus arenarius and its Significance for Land Reclamation in Iceland

Leymus arenarius is used to stabilize the extensive areas of eroded volcanic sand in Iceland, both inland and on the coast. It has been reported previously to produce seeds of generally low viability. We investigated the potential for seed dormancy and the responses of germination to temperature, light and salinity, as part of a re-assessment aimed at improving reclamation procedures. Contrary to previous reports, high rates of germination could be obtained under certain conditions. All caryopses were soaked in water (24 h) and stratified for 2 weeks (5 °C) before the subsequent germination tests. Constant temperatures or exposure to light resulted in very poor germination. Close to 100% germination could be obtained within 2 weeks in continuous darkness, under alternating temperatures with an amplitude of 10-20 °C on a 12 h cycle; high day temperatures appear to be important. Diurnal fluctuations in temperature of this order occurred under average weather conditions in the black, volcanic sands in Iceland during the growing season (May-Sep.). The dark requirement is interpreted as a selective response to the adverse conditions for establishment at the surface of the sand; the alternating temperature requirement may be a response to ensure dormancy under deep burial with accreting sand, although it could have a role in gap-sensing under established canopies. Scarification, surface sterilization and treatment with n -butanol or KNO3 were all generally ineffective in promoting germination. Nearly all caryopses that did not germinate, in all treatments, remained viable. Caryopses of coastal populations of Leymus arenarius showed significantly higher total germination and more rapid germination in 100 mmol l-1 and 300 mmol l-1 NaCl solutions than inland populations. The inhibition of germination by salinity was an osmotically enforced dormancy effect rather than a lethal, toxic one; caryopses that had not germinated in saline solution generally were able to germinate subsequently, when transferred to non-saline conditions