Effects of Organic Enrichment of Mine Spoil on Growth and Nutrient Uptake in Oak Seedlings Inoculated with Selected Ectomycorrhizal Fungi

Abstract Poor growth of Quercus robur L. (oak) trees has been reported on mine sites where overburden and subsoil have been used in the reinstatement of surface layers. This stunting has been attributed to a lack of macronutrients and to an adverse soil environment for root growth and mycorrhizal development. Growth, mineral nutrition, and ectomycorrhizal colonization of Q. robur seedlings were studied in an experiment carried out under controlled growing conditions in which mine spoil material was enriched with a leaf litter mulch. Enrichment of mine spoil material was found to produce a significant increase in growth and foliar N concentrations of oak seedlings. Inoculation with three taxa of ectomycorrhizal fungi did not benefit seedlings when mine spoil was the only substrate, possibly due to the poor physical properties of the unamended spoil and lack of nutrients. Inoculation with two taxa, Laccaria laccata and Hebeloma crustuliniforme, isolated from 3‐year‐old trees produced a significant stimulation of growth in the organically enriched treatment, which was believed to be due to greater uptake of mineralized N. However, Cortinarius anomalus isolated from fruit bodies associated with a 15‐year‐old tree did not increase biomass. The presence of organic matter was found to result in a significant stimulation of mycorrhizal infection by both inoculum and contaminant mycobionts. Recommendations are made for improving the establishment and growth of oak seedlings on reinstated sites.     

Seed and seedling responses to inoculation with mycorrhizal fungi and root nodule bacteria: implications for restoration of degraded Mediterranean‐type Tuart woodlands

Inoculation with beneficial soil microorganisms has the potential to enhance success of restoration, particularly in harsh Mediterranean‐type ecosystems (MTEs). We investigated the effects of microorganisms (mycorrhizal fungi and root nodule bacteria) and planting material (seed and nursery‐raised seedlings) on early establishment and growth of two key postdisturbance colonizing species with different life histories, life forms and functional types (Eucalyptus gomphocephala and Acacia saligna) under field conditions. Establishment and growth were monitored at 13 months, following the first MTE drought period. For E. gomphocephala, establishment was higher for seedlings (81%) than for seeding (7.5%). Inoculation with ectomycorrhizal fungal spores was not beneficial. For A. saligna, establishment was also higher for seedlings (84%) than for seeding (42.5%). Mycorrhizal fungal inoculum had no effect on establishment or growth. This study has shown that in harsh MTE conditions, the use of seedlings is more effective than seeding in degraded woodlands even when attempting to reintroduce key colonizing species. The microorganism treatments tested did not result in significant improvement in establishment or growth.     

Seedling Establishment and Survival on Restored Campsites in Subalpine Forest

This study experimented with common restoration techniques (scarification, soil amendments, mulch, and seeding) on six closed wilderness campsites in subalpine forests in Oregon. Effectiveness in encouraging seedling establishment, growth, and survival was assessed every year for the first 7 years following treatment. Closure and restoration of the campsites increased the density of plants established from seed. Despite an original density of virtually zero, mean density of perennial plants was 55 plants/m² 7 years after closure. All the treatments, with the exception of the biodegradable mulch mat, increased plant density. Seven years after treatment, seeding had increased plant density 5‐fold, whereas scarification and soil amendments (organic matter, compost, and soil inoculum) had each increased density 3‐fold. The organic and compost amendments also had the positive benefit of increasing growth rates and shortening the time‐to‐reproductive maturity. Results suggest that restoration of the herbaceous cover on these campsites can occur rapidly using the techniques employed. All but one of the species we seeded established in substantial quantities and survived at densities exceeding their density in the naturally sparse herbaceous cover on these sites. Thirty‐six perennial species volunteered on these sites. The remaining challenge is reestablishment of the shrub species that comprise much of the ground cover in these forests. These species seldom establish from seed.     

Effectiveness of seed sowing techniques for sloped restoration sites

Practitioners are challenged with choosing among many potentially effective methods for sowing seed in ecological restoration projects to achieve sufficient native plant establishment. We tested the effectiveness of seed sowing techniques on moderate and steep slopes in a Mediterranean climate by measuring native seedling density immediately following germination, as well as plant density, recruitment success, and soil movement through the second growing season. We calculated cost effectiveness of different methods as the native plant density per dollar spent sowing seed. While all sowing techniques resulted in significant native establishment compared with unseeded controls, hydro seeding on moderate slopes was the most cost effective (native seedlings established per dollar spent). Although all steep‐sloped seeding techniques resulted in high densities of native species, all methods also resulted in significant soil loss. Shrubs preferred hand seeding followed by jute netting on steep slopes, while forbs reached greatest densities with hydro seeding on moderate slopes. Seedlings of species with heavy seeds were present in greater densities than species with lighter seeds in imprint sowing treatments. The “best” seed sowing technique varied depending on slope and metric of success (native density, species richness, shrub density, or forb density). Different combinations of slope, technique, and success metric resulted in significantly different project costs, which implies opportunities for savings given careful decision‐making relative to mitigation needs on heterogeneous landscapes. Evaluations of techniques for restoring slopes are limited, yet critical for expanding the area capable of being restored and the application of limited conservation funding.     

Woody plant encroachment reduces species richness of herb‐rich woodlands in southern Australia

Abstract Woody plants have been increasing in many woodland and savanna ecosystems owing to land use changes in recent decades. We examined the effects of encroachment by the indigenous shrub Leptospermum scoparium (Myrtaceae) on herb‐rich Eucalyptus camaldulensis woodlands in southern Australia. Species richness and compositional patterns were examined under the canopy of L. scoparium and in surrounding open areas to determine the species most susceptible to structural changes. Richness was significantly lower in areas of moderate to high L. scoparium cover (>15%), suggesting that a threshold shrub cover caused major change in this ecosystem. Shrubs were associated with a significant reduction in above‐ground biomass of the ground‐layer flora and a significant shift in community composition. The few species that were positively associated with high L. scoparium cover were also common in the woodland flora; no new species were recorded under the shrub canopy. Important environmental changes associated with L. scoparium cover were decreased light availability and increased litter cover, which were likely a consequence of encroachment. Leptospermum scoparium cover was also associated with greater surface soil moisture, which may be a consequence of increased shading under the shrub canopy or indicate favourable soil conditions for L. scoparium establishment. Reductions in species richness and abundance of the germinable seed bank were found in soil samples taken from under L. scoparium. With ongoing recruitment of L. scoparium and consequent increases in shrub cover, ground‐layer diversity in these species‐rich woodlands should continue to decline over time.     

Soil Water Retention on Gold Mine Surfaces in the Mojave Desert

An experimental analysis of soil water retention was conducted on three substrates (an abandoned road, an overburden pile, and a heap leach) created by gold mining activities in the Mojave Desert in southeastern California. We mixed each substrate with straw, and the overburden pile and heap leach with growth medium, then applied surface rock mulch to half the plots in an attempt to increase soil water‐holding capacity for revegetation efforts. For each of the six treatments (controls included) we monitored soil water with time domain reflectometry following both a simulation of a rainfall event and a natural rainfall that occurred immediately following the simulation. Both the simulation and the rainfall increased soil water between 3 and 8%, depending on the substrate. Water retention patterns in the two‐week periods following each water addition were similar between the simulation and rainfall, and among all substrate types as values returned to background (pre‐water) conditions. The abandoned road substrate had higher background water content (16.5%) than the overburden pile (6%) and heap leach (5%). The road also had three times higher organic matter and five times higher soil nitrogen than the other two sites. Soil water retention was improved on the overburden pile by the addition of just surface rock mulch or of straw‐plus‐rock mulch. On the heap leach, increases were found with rock mulch only or with growth medium‐plus‐rock mulch. Rock mulches did not improve soil water retention and straw additions decreased soil water on the abandoned road. Judicious use of soil amendments can improve soil water conditions and improve revegetation efforts on disturbed lands in desert environments.     

Invasive autumn olive performance varies in different reclamation conditions: implications for restoration

Surface mining has caused significant disturbance globally, and is responsible for the loss of more than 600,000 ha of the world's largest temperate deciduous forest in the Appalachian region of the United States alone. Due to the heavy disturbance on mine lands, invasive plants have become dominant on many former coalfields, some of which were intentionally planted with exotic species. The establishment of invasive plants on these disturbed lands has often led to reductions in establishment of desirable native species. Autumn olive (Elaeagnus umbellata), an exotic nitrogen‐fixing shrub, is a problematic invasive species on reclaimed sites in Appalachia. To better understand how reclamation conditions affect autumn olive, we assessed the effects of the mine‐soil substrate and vegetation seeding on autumn olive establishment and growth. In each experiment, we also manipulated the herbaceous plant community to further examine effects on autumn olive establishment and growth. In spring 2015, we transplanted 480 1‐year‐old autumn olive seedlings across both experiments. After 2 years of growth, autumn olive performed better in weathered‐rock than in unweathered‐rock substrates; in bare‐ground plots than in vegetated plots; and in tree‐compatible (low‐competition) seeding than in more‐competitive conventional seeding. No treatment precluded autumn olive establishment. However, our results show that strategic use of beginning substrates and planting mixes can have strong inhibitory effects on invasive plants, but also that substrate and herbaceous‐plant community conditions favorable to establishment of native trees are also favorable to autumn olive.     

Composted soil conditioner and mulch promote native plant establishment from seed in a constructed seasonal wetland complex

Three thicknesses of composted soil conditioner, and one combined with mulch, surface‐applied and then incorporated into the sandy topsoil, were tested against controls for promotion of native plant establishment by direct seeding in construction of a seasonal wetland complex. Located 50 km south of Perth, Western Australia in a Mediterranean climate, the site typically dries out in summer. In wetter seasons ponds intercept contaminants in freeway runoff and act as a buffer for peak flows. The 20 mm thickness of soil conditioner was the most effective. The 40 mm thick 40:60 blend of soil conditioner and mulch was also effective – the mulch can help reduce soil erosion. Composted soil conditioner, typically produced by recycling accumulated municipal waste, counteracts soil organic matter and nutrient depletion.     

The Restoration of Degraded Mountain Woodlands: Effects of Seed Provenance and Microsite Characteristics on Polylepis australis Seedling Survival and Growth in Central Argentina

South American high‐mountain ecosystems are greatly influenced by human disturbance. In the mountains of Córdoba, Argentina, Polylepis australis (Rosaceae) woodlands are currently highly fragmented and subject to extensive burning and livestock grazing, resulting in severe changes of habitat characteristics, which hamper natural regeneration. In order to find out how to achieve successful reforestation, we compared P. australis seedling survival and growth and the development of a shrubby habit for two seed provenances and different planting microsites. Survival of planted seedlings after 5 years was 70%, with most deaths (19%) in the first year and declining mortality with ongoing establishment. Survival did not show any relationship with seed provenance or microsite characteristics. Height growth averaged 34.6 ± 1.2 cm in 5 years. Seedlings produced from seeds collected in a well‐preserved woodland grew taller and showed a higher tendency for development of shrubby habit than those produced from seeds collected in a degraded woodland. Seedlings planted in more degraded microsites with exposed soil or rock due to past grazing pressure grew less and developed a more shrubby habit than those planted in better preserved microsites. Our results show that restoration of degraded areas with P. australis is possible and that there is potential to improve restoration success with a careful selection of seed provenance and planting microsites.     

Dispersal and recruitment dynamics in the fleshy‐fruited Persoonia lanceolata (Proteaceae)

Question: What is the role of dispersal, persistent soil seed banks and seedling recruitment in population persistence of fleshy‐fruited obligate seeding plant species in fire‐prone habitats? Location: Southeastern Australia. Methods: We used a long‐term study of a shrubby, fleshy‐fruited Persoonia species (Proteaceae) to examine (1) seed removal from beneath the canopy of adult plants; (2) seedling recruitment after fire; (3) the magnitude and location of the residual soil seed bank; and (4) the implications for fire management of obligate seeding species. We used demographic sampling techniques combined with Generalised Linear Modelling and regression to quantify population changes over time. Results: Most of the mature fruits (90%) on the ground below the canopy of plants were removed by Wallabia bicolor (Swamp wallaby) with 88% of seeds extracted from W. bicolor scats viable and dormant. Wallabies play an important role in moving seeds away from parent plants. Their role in occasional long distance dispersal events remains unknown. We detected almost no seed predation in situ under canopies (< 1%). Seedling recruitment was cued to fire, with post‐fire seedling densities 6‐7 times pre‐fire adult densities. After fire, a residual soil seed bank was present, as many seeds (77‐100%) remained dormant and viable at a soil depth where successful future seedling emergence is possible (0‐5 cm). Seedling survival was high (> 80%) with most mortality within 2 years of emergence. Plant growth averaged 17 cm per year. The primary juvenile period of plants was 7–8 years, within the period of likely return fire intervals in the study area. We predicted that the study population increased some five‐fold after the wildfire at the site. Conclusions: Residual soil seed banks are important, especially in species with long primary juvenile periods, to buffer the populations against the impact of a second fire occurring before the seed bank is replenished.     

Soil seed bank in different vegetation types in the Loess Plateau region and its role in vegetation restoration

In the Loess Plateau region, soil erosion is a serious problem. Vegetation restoration is an effective approach to control soil erosion and improve ecosystems. The soil seed bank generally plays an important role in vegetation restoration after disturbance. Thus, we reviewed soil seed bank studies to reveal the soil seed bank characteristics and its role in vegetation restoration in three vegetation types (forest, forest‐steppe, and steppe). We selected 38 seed bank studies and analyzed several seed bank characteristics, such as seed density, species composition, and the relationship between seed size and seed bank. We also assessed the role of the soil seed bank in vegetation restoration. The soil seed bank density ranged from 2,331 ± 1,993 to 6,985 ± 4,047 seeds/m² among the different vegetation types. In the soil seed bank, perennial herbs and grasses accounted for 51.5% of the total species. Native species that were dominant or common in the standing vegetation usually had relatively high seed bank densities. Moreover, species with smaller seeds generally had higher soil seed bank densities. The present study indicates that the soil seed bank plays a significant role in spontaneous vegetation restoration, especially during the early successional stages in abandoned slope farmlands and grazing‐excluded grasslands. However, species with large seeds or transient soil seed banks should be reintroduced through seeding to accelerate target species restoration. More studies on soil seed banks need to be conducted to comprehensively reveal their characteristics.     

碎石覆盖对河流硬质护坡土壤抗侵蚀性及植物生长的影响

针对河流硬质护坡生态修复中的稳定性和水分平衡等技术难点,提出了一种碎石覆盖技术,并通过抗冲刷实验和盆栽实验分析了不同碎石覆盖对土壤抗冲刷能力、保水性能及植物生长的影响.结果表明：粒径为1.5～2 cm的碎石覆盖处理在增强土壤抗冲刷能力、提高土壤保水性能和植物生物量方面效果明显,但覆盖厚度为5 cm和8 cm的碎石覆盖处理在抗冲刷、保水和促进植物生长方面的作用均无明显差异.厚5 cm、粒径为1.5～2 cm的碎石覆盖技术是硬质护坡生态修复中一种经济有效的技术方法.     

Consequences of soil compaction for seedling establishment: Implications for natural regeneration and restoration

Abstract Soil compaction can affect seedling root development by decreasing oxygen availability and increasing soil strength. However, little quantitative information is available on the compaction tolerances of non‐crop native species. We investigated the effects of soil compaction on establishment and development of two New Zealand native species commonly used in restoration programmes; Cordyline australis (Agavaceae) (cabbage tree) a fleshy rooted species, and Leptospermum scoparium (Myrtaceae) (manuka) a very finely rooted species. Seedlings were grown in a range of soil compaction levels in growth cabinet experiments. Low levels of soil compaction (0.6 MPa) reduced both the number and speed of C. australis seedlings penetrating the soil surface. In contrast, L. scoparium seedlings showed improved establishment at an intermediate compaction level. Root and shoot growth of both species decreased with increasing soil strength, with L. scoparium seedlings tolerating higher soil strengths than did C. australis. Despite these results, soil strength accounted for only a small amount of variation in root length (R² < 0.25), due to greater variability in growth at low soil strengths. Soil strengths of 0.6 MPa are likely to pose a barrier to C. australis regeneration. This is consistent with adaptation to organic and/or soft, waterlogged soils. Active intervention may be necessary to establish C. australis from seed on many sites previously in farmland.     

Establishing Cool‐Season Grasses on a Degraded Arid Rangeland of the Colorado Plateau

Reestablishing cool‐season (C3) grass communities on low elevation rangelands of the Colorado Plateau is notoriously difficult, raising questions about the viability of restoring native species and continuing to actively graze these landscapes. We conducted a seeding experiment on an arid (15.4 cm rain/year), historically heavily‐grazed rangeland in Northern Arizona to test the effects of seeding technique and simulated seasonal climate scenarios on germination and recruitment of four species of native, cool‐season bunchgrasses: Achnatherum hymenoides, Hesperostipa comata, Poa secunda, and Elymus elymoides. Initial results indicated that C3 grasses germinated significantly more in drill‐seeded treatments under simulated high precipitation years than in other treatment types. Five years post‐treatment, P. secunda and E. elymoides were not observed but simulated drill‐seeded treatments, had significantly higher densities of A. hymenoides and H. comata recruits relative to most other treatment types. Simulated drill seeding also increased soil disturbance which increased the establishment of the invasive weed Salsola tragus in year 1, but not thereafter. Although it appears critical to coordinate effective seeding techniques with high winter–spring precipitation, predicting such events may not be possible at some sites, suggesting that seeding low elevation, arid rangelands of the Colorado Plateau may not always be realistic under a future climate that is drier and less predictable .     

Aphid suppression by natural enemies in mulched cereals

Large populations of natural enemies are the basis for natural pest control. Effects of mulch on predator–prey interactions in arable fields are poorly known, despite its potential to enhance ground‐dwelling predators and thereby reduce pest infestations. We studied the densities of predators and parasitoids, and their impact on cereal aphids in the presence and absence of mulch. Released populations of the bird cherry aphid, Rhopalosiphum padi (L.) (Homoptera: Aphididae), and two naturally occurring aphid species, were monitored under experimentally reduced densities of: (i) ground‐dwelling predators, (ii) flying predators and parasitoids, and (iii) with straw mulch. The three treatments were applied in a 2 × 2 × 2 factorial design in a field of spring wheat (Triticum aestivum L.). The exclusion of ground‐dwelling predators increased aphid populations by 55% in June and 40% in July, respectively. Mulched plots had 25% lower aphid densities in June. This was presumably due to enhanced densities of spiders (Araneida) in mulched plots. The exclusion of flying predators and parasitoids led to 94% higher aphid populations in late July (109 vs. 56 individuals per 100 shoots), irrespective of mulch or ground predator manipulation. This was attributed to the larvae of gall midges Aphidoletes cf. aphidimyza (Rondani) (Diptera: Cecidomyiidae) and hoverflies (Diptera: Syrphidae). The results indicate that a scarcity of predators and a bare soil surface renders crops more susceptible to arthropod pests. Farming schemes should aim at enhancing both ground‐dwelling and flying predators for elevated levels of natural pest control.     

Coarse pine bark mulch as open surface cover fails to improve establishment of sown native grasslands

This study was conducted across twelve agricultural locations in south-western Victoria, Australia, encompassing a range of soil types and climatic conditions. It investigated the addition of an open layer of coarse organic pine wood chip mulch (~70% surface cover) directly following direct seeding of native grassland species. The intent was to mimic positive effects of naturally occurring organic surface litter (which are typically depleted in such settings) on seedling emergence and establishment. Findings revealed negative results in that the use of an open layer of coarse pine chip mulch failed to improve native establishment at 12-months or to moderate soil temperature and moisture extremes in comparison to non-mulched plots. This outcome suggests the effectiveness of open surface mulches under the scenario of direct seeding may be highly site context, mulch-type, and application approach dependent. In situations where such mulch applications are not likely to be beneficial, significant costs relating to their purchase and application could be avoided.     

Seed bed treatment effects on vegetation and seedling establishment in a New Zealand pasture one year after seeding with native woody species

Summary Efforts to re‐establish indigenous forests in pastoral New Zealand have increased as the value of native biodiversity has been realized. Direct seeding of woody species is preferable to transplanting, as labour and material costs are less. However, the success rate of direct seeding in pasture has been variable due to intense competition from adventive species. We initiated an experiment in pasture plots adjacent to a forest fragment where seed bed treatments (increasing in degree of disturbance from herbicide application to turf removal and topsoil removal) in combination with mulch treatments (wood chip shavings with and without forest floor organic material) were seeded with a mixture of New Zealand lowland forest species. The objective of the study was to determine if early successional plant communities, and ultimately seedling establishment, differed as a result of seed bed preparation after 1 year. Coprosma robusta (Karamu) and Kunzea ericoides (Kanuka) seedlings established on plots in significant numbers: both species were most abundant on topsoil‐removed plots where bare substrate was greatest and plant cover least. Both seed bed treatments and mulching treatments led to measurable differences in overall composition of early successional plant communities. However, absence of plant cover and low soil fertility (both associated with the topsoil‐removed treatment) were the most important factors in seedling success.     

Establishment of Chamaecyparis thyoides on an Extremely Low-Nutrient Sandy Site on the Atlantic Coastal Plain, U.S.A.

Abstract Sustained‐release fertilizer and two kinds of mulch treatments were tested to determine their effects on survival and growth of planted Chamaecyparis thyoides (Atlantic white cedar) on a sandy extremely nutrient‐deficient site. Height, basal trunk diameter, dry weight, and concentrations of nitrogen (N), phosphorus (P), and potassium (K) were measured for each treatment. After two growing seasons, survival was very high in untreated controls (mean, 86%) and was not significantly increased by any treatment (significance was assessed at p = 0.05 throughout this work). Stem height and cross‐sectional area doubled in unamended plots during the course of the study. Fresh mulch alone caused no additional increase in growth, compared with unamended plots. Decomposed mulch caused a slight but significant increase. Sustained‐release fertilizer caused significant increases in height (threefold) and dry weight (approximately sixfold). Combined treatment with fertilizer and mulch gave significantly greater growth responses than did other treatments, increasing heights 4‐ to 5‐fold, trunk cross‐sectional areas 4‐fold, and dry weights 11‐ to 21‐fold over no‐treatment controls. Tissue concentrations of N and P correlated with growth trends, with combinations of mulch and timed‐release fertilizer providing the highest values. Though statistically different, the two mulch treatments were similar in their effects on tissue nutrient concentrations. When combined with fertilizer, undecomposed mulch stimulated increases in height and dry weight significantly more than did decomposed mulch. Thus, establishment of C. thyoides on low‐nutrient sandy soils is improved by combined soil amendment with sustained‐release nutrients and organic mulch.     

Wyoming Big Sagebrush Density: Effects of Seeding Rates and Grass Competition

The mining industry commonly seeds shrubs and grasses concurrently on coal‐mined lands of northeastern Wyoming, but ecological interactions between seeded shrubs and grasses are not well documented. Artemisia tridentata Nutt. ssp. wyomingensis (Beetle and Young) (Wyoming big sagebrush) is the dominant pre‐mining shrub on many Wyoming mine sites. Despite past failures to establish Wyoming big sagebrush, the Wyoming Department of Environmental Quality, Land Quality Division's rules and regulations require establishment of 1 shrub per m² on 20% of post‐mined land in Wyoming. A study was established at the Belle Ayr Coal Mine south of Gillette, Wyoming to evaluate the effects of sagebrush seeding rates and grass competition on Wyoming big sagebrush seedling density. Three sagebrush seeding rates (1, 2, and 4 kg pure live seed [pls]/ha; 350, 700, and 1,400 pls/m², respectively) and seven cool‐season perennial grass mixture seeding rates (0, 2, 4, 6, 8, 10, and 14 kg pls/ha; 0, 187, 374, 561, 750, 935, and 1,309 pls/m², respectively) were applied during winter 1998–1999. Pascopyrum smithii (Rydb.) A. Love (western wheatgrass), Elymus lanceolatus (Scribner & J.G. Smith) Gould (thickspike wheatgrass), and Elymus trachycaulus (Link) Gould ex Shinners (slender wheatgrass) comprised the grass seed mix (equal seed numbers of each species). Sagebrush seedling density differed among sagebrush seeding rates but not among grass seeding rates. On all sampling dates in 1999 and 2000, sagebrush seedling density differed among sagebrush rates and was greatest at the 4 kg pls/ha sagebrush seeding rate. All sagebrush seeding rates provided densities of at least 1 shrub per m² after two growing seasons. Grass density and production in 2000 suggest that adequate grass production (75 g/m²) was achieved by seeding at 6 to 8 kg pls/ha. Within these grass seeding rates, four or more sagebrush seedlings per m² were attained when sagebrush was seeded at 2 to 4 kg pls/ha. Use of these seeding rate combinations in mine reclamation can achieve Wyoming big sagebrush standards and reduce reseeding costs.     

Use of Shallow Basins to Restore Cutover Peatlands: Hydrology

Basins 20‐, 10‐, and 4‐m wide were excavated 15 to 20 cm into cutover peat fields near Lac Saint Jean, Québec, Canada to facilitate the establishment of Sphagnum mosses. Sphagnum diaspores (fragments) and straw mulch were spread over the excavated surfaces, a control peat field, and a mulch‐protected site without basins. Mean water tables in the 20‐, 10‐, and 4‐m wide basins and the mulch‐protected site were 27.2, 8.3, 11.4, and 9.7 cm higher, respectively, than in the control peat field in May to August 1996. Similar improvements were observed in 1997 (a drier summer). The higher water table was due to lowering of the peat surface with respect to the local water table, retention of meltwater and stormwater by the peripheral ridges formed during excavation, retention of water during drier periods by the groundwater mound beneath the ridges, and mulch. Soil moisture was always higher in the experimental basins than in the control peat field or in the mulch‐protected site, demonstrating the superior soil wetness characteristic of sites with basins and straw mulch. Water tension data signaled the absence of the capillary fringe (i.e., capillary drainage) near the surface for some finite period, thus possibly limiting water for best Sphagnum growth. At the experimental basins and mulch‐protected site, 100% of these periods lasted four or fewer days. In the control peat field, 20% of the periods when capillary drainage had occurred lasted more than four days, with one period of 17 days. The mulch protection alone provided considerable improvement in hydrological conditions compared with the control peat field, but the additional water retained in the experimental basins protected against Sphagnum desiccation and loss during more extreme dry periods.