Rehabilitation of Swamp Paperbark (<Emphasis Type="Italic">Melaleuca ericifolia</Emphasis>) wetlands in south-eastern Australia: effects of hydrology,microtopography, plant age and planting technique on the success of community-based revegetation trials

Wetlands dominated by Swamp Paperbarks (Melaleuca spp., Myrtaceae) are common in coastal regions across Australia. Many of these wetlands have been filled in for coastal development or otherwise degraded as a consequence of altered water regimes and increased salinity. Substantial resources, often involving community groups, are now being allocated to revegetating the remaining wetland sites, yet only rarely is the effectiveness of the rehabilitation strategies or on-ground procedures robustly assessed. As part of a larger project investigating the condition and rehabilitation of brackish-water wetlands of the Gippsland Lakes, we overlaid a scientifically informed experimental design on a set of community-based planting trials to test the effects of water depth, microtopography, plant age and planting method on the survival and growth of seedlings of Melaleuca ericifolia Sm. in Dowd Morass, a degraded, Ramsar-listed wetland in south-eastern Australia. Although previous laboratory and greenhouse studies have shown M. ericifolia seedlings to be salt tolerant, the strongly interactive effects of waterlogging and salinity resulted in high seedling mortality (>90%) in the field-based revegetation trials. Seedlings survived best if planted on naturally raised hummocks vegetated with Paspalum distichum L. (Gramineae), but their height was reduced compared with seedlings planted in shallowly flooded environments. Age of plants and depth of water were important factors in the survival and growth of M. ericifolia seedlings, whereas planting method seemed to have little effect on survival. Improved testing of revegetation methods and reporting of success or otherwise of revegetation trials will improve the effectiveness and accountability of projects aiming to rehabilitate degraded coastal wetlands.     

Photosynthesis and water relations of four oak species: impact of flooding and salinity

 As global climate changes, sea level rise and increased frequency of hurricanes will expose coastal forests to increased flooding and salinity. Quercus species are frequently dominant in these forest, yet little is known about their salinity tolerance, especially in combination with flooding. In this study, 1-year-old seedlings of Quercus lyrata Walt. (overcup oak), Q. michauxii Nutt. (swamp chestnut oak), Q. nigra L. (water oak), and Q. nuttallii Palmer (Nuttall oak) were chronically (simulating sea level rise) and acutely (simulating hurricane storm surge) exposed to increased flooding and salinity, individually and in combination. The four species demonstrated two response patterns of photosynthesis (A), conductance, and leaf water potential, apparently related to their relative flood tolerance. In Q. lyrata, Q. nuttallii, and Q. nigra (moderately flood-tolerant), A was not immediately reduced after the initiation of the freshwater flooding, but was reduced as the duration of flooding increased. In the second pattern, demonstrated by the weakly flood-tolerant Q. michauxii, A was immediately reduced by freshwater flooding with an increasing impact over time. Watering with 2 parts per thousand (ppt) saline water did not consistently reduce A, but flooding with 2 ppt reduced A of all species, similar to the response with freshwater flooding. Photosynthesis of all species was reduced by 6 ppt watering or flooding, with the latter treatment killing all species within 8 weeks. When acutely exposed to 30 ppt salinity, A was quickly and severely reduced regardless of whether the seedlings were watered or flooded. Acutely flooded seedlings exposed to high salinity died within 2 weeks, but seedlings watered with 30 ppt saline water recovered and A was not reduced the following spring. As saline flooding of coastal areas increases due to sea level rise, photosynthesis of these species will be differentially affected based primarily on their flood tolerance. This suggests that increased flooding associated with sea level rise will impact these tree species to a greater extent than small increases in soil salinity. High salinity accompanying storm surges will be very harmful to all of these species. Received: 20 October 1997 / Accepted: 2 December 1998     

Ectomycorrhizal fungi promote growth of <Emphasis Type="Italic">Shorea balangeran</Emphasis> in degraded peat swamp forests

Shorea balangeran is an important component of peat swamp forests in Southeast Asia and is an important source of timber. However, S. balangeran has been decreasing in number due to overexploitation. The objective of this study was to investigate the effect of inoculation of native ectomycorrhizal (ECM) fungi on growth of S. balangeran in degraded peat swamp forest. Spores of Boletus sp., Scleroderma sp., and Strobilomyces sp. were collected from natural peat swamp forest in Indonesia. Seedlings of S. balangeran were inoculated with or without (control) spores and grown in sterilized peat soil under nursery conditions for 6 months. Then, the seedlings were transplanted into a degraded peat swamp forest and grown for 40 months. ECM colonization was 59–67% under nursery conditions and increased shoot height and weight. Shoot height, stem diameter, and survival rates were higher in inoculated seedlings than in control 40 months after transplantation. The results suggest that inoculation of native ECM fungi onto native tree species is useful for reforestation of degraded peat swamp forests.     

Roadside revegetation with native plants: Experimental seeding and transplanting of stem cuttings

Questions: Can we use local native plants for roadside revegetation? What cultural methods help enhance the process? Location: Trans Canada Highway, Terra Nova National Park, Newfoundland. Objectives: To (1) test stratification requirements for seed ger‐mination, (2) determine if germination, survival and growth of seedlings and stem cuttings of selected plants can be increased by mulching treatments and (3) identify native plants and cultural treatments useful for revegetation. Methods: We tested seed germination of Kalmia angustifoliaIris versicolorJuncus effususEriophorum vaginatum, Clintonia borealis and Cornus canadensis in a greenhouse experiment. We conducted field experiments of roadside revegetation using seeds of K. angustifolia, I. versicolorJ. effusus and E. vaginatum, as well as seedlings of I. versicolor and rooted stem cuttings of Emptrum nigrum and Juniperus communis after hay‐mat mulch and organic matter mulch application. Results: Stratified seeds of K. angustifoliaI. versicolor, J. effusus and E. vaginatum germinated successfully in the greenhouse, whereas C. borealis and C. canadensis seeds did not. Along roadsides, only I. versicolor seeds germinated. Iris versicolor cover increased significantly in organic matter mulch compared to hay‐mat mulch and control. Transplanted I. versicolor seedlings had high survival in all treatments but growth was reduced in organic matter mulch. Survival and growth of stem cuttings of E. nigrum and J. communis were significantly increased on hay‐mat mulch. Application: Rooted stem cuttings of E. nigrum and J. communis planted on hay‐mat mulch can be used as a practical method of roadside revegetation. These shrubs have low structure, are evergreen, and exhibit stress‐tolerance properties, which make them ideal species for roadside revegetation. They are also non‐palatable to wildlife. Roadside ditches can be revegetated by seeds or seedlings of I. versicolor. Robust roots and rhizomes of this plant may provide soil stability and dark green leaves and attractive flowers create aesthetically pleasing vegetation cover.     

Accelerating the Restoration of Vegetation in a Southern California Salt Marsh

Re-establishing plant cover is essential for restoring ecosystem functions, but revegetation can be difficult in severe sites, such as salt marshes that experience hypersalinity and sedimentation. We tested three treatments (adding tidal creeks, planting seedlings in tight clusters, and rototilling kelp compost into the soil) in a site that was excavated to reinstate tidal flows and restore salt marsh. The magnitude of responses was the reverse of expectations, with tidal creeks having the least effect and kelp compost the most. On the marsh plain, kelp compost significantly increased soil organic matter (by 17% at 0–5 cm; p = 0.026 and 11.5% at 5–20 cm; p = 0.083), total Kjeldahl nitrogen (45% at 5–8 cm; p < 0.001) and inorganic nitrogen (35% at 5–8 cm; p < 0.006), and decreased bulk density (16% at 0–5 cm; p < 0.001 and 21% at 5–8 cm depth; p < 0.001) compared to control plots. Survivorship of kelp compost treated plantings increased, along with growth (> 50% increase in a growth index at 20 months after planting; p < 0.0001). In Spartina foliosa plots, kelp compost did not affect soil organic matter, but plants were taller (by ~11 cm; p = 0.003) and denser (47% more stems; p = 0.003). Planting seedlings 10-cm apart in tight clusters on the marsh plain increased survivorship by 18% (compared to 90-cm apart in loose clusters; p = 0.053), but not growth. Tidal creek networks increased survivorship of Batis maritima and Jaumea carnosa by ≥20% (p = 0.060 and 0.077, respectively). Kelp compost had a strong, positive influence on vegetation establishment by ameliorating some of the abiotic stress.     

Facilitation and herbivory during restoration of California coastal sage scrub

Using nurse plants to facilitate native plant recruitment in degraded habitats is a common restoration practice across various arid and semiarid environments. Living trees or shrubs are typically considered nurse plants, whereas dead shrubs left in the landscape from prolonged drought are understudied prospective facilitators for native plant recruitment. The interaction between nurse plants and biotic pressures, such as herbivory, on native recruitment is also not well understood in semiarid plant communities. We investigated the effects of facilitation and herbivory on native seedling germination, growth, and survival in the restoration of degraded coastal sage scrub (CSS) habitat. Native shrub seedlings (Artemisia californica and Salvia mellifera) were planted, and native annual species (Amsinckia intermedia, Deinandra fasciculata, Phacelia distans, and Pseudognaphalium californicum) were sown in three Shrub Type treatments (live shrub, dead shrub, and exposed areas), with a nested Cage treatment (no cage and cage) in each Shrub Type treatment. Annual species grew equally well in all Shrub Type treatments; shrub seedlings grew largest in exposed areas. While there was little evidence of facilitation for all species tested, there were strong positive effects of caging on growth and establishment of all species. Caging palatable native species or planting species with anti‐herbivory traits around target plants may be more strategic approaches compared to using nurse plants in restoring degraded CSS after extended drought.     

Effects of Stream Restoration on Woody Riparian Vegetation of Southern Appalachian Mountain Streams,North Carolina,U.S.A

Riparian revegetation, such as planting woody seedlings or live stakes, is a nearly ubiquitous component of stream restoration projects in the United States. Though evaluations of restoration success usually focus on in‐stream ecosystems, in order to understand the full impacts of restoration the effects on riparian ecosystems themselves must be considered. We examined the effects of stream restoration revegetation measures on riparian ecosystems of headwater mountain streams in forested watersheds by comparing riparian vegetation structure and composition at reference, restored, and degraded sites on nine streams. According to mixed model analysis of variance (ANOVA), there was a significant effect of site treatment on riparian species richness, basal area, and canopy cover, but no effect on stem density. Vegetation characteristics at restored sites differed from those of reference sites according to all metrics (i.e. basal area, canopy cover, and species composition) except species richness and stem density. Restored and degraded sites were structurally similar, with some overlap in species composition. Restored sites were dominated by Salix sericea and Cornus amomum (species commonly planted for revegetation) and a suite of disturbance‐adapted species also dominant at degraded sites. Differences between reference and restored sites might be due to the young age of restored sites (average 4 years since restoration), to reassembly of degraded site species composition at restored sites, or to the creation of a novel anthropogenic ecosystem on these headwater streams. Additional research is needed to determine if this anthropogenic riparian community type persists as a resilient novel ecosystem and provides valued riparian functions.     

Woody plant regeneration in three South Carolina Taxodium/Nyssa stands following Hurricane Hugo

Long-term monitoring began in 1990 to follow community changes resulting from hurricane disturbance. In addition, one-year-old Taxodium distichum seedlings were planted to determine if planting was feasible in saltwater-flooded areas. The canopy of the least impacted swamp recovered rapidly, but there were few seedlings growing in the understory. Planted seedlings survived well, but they grew very little. Both lack of seedlings and poor growth of planted seedlings were probably due to intense shading and flooding. Two impacted areas contained a greater number of seedlings, most of which were found growing on raised microsites like Taxodium knees. The majority of the seedlings in all areas were shrub species. Planted seedlings grew cell (30 cm/yr) where open canopy conditions allowed sunlight to reach the forest floor and no new saltwater has been introduced since the hurricane.     

Establishment of Carex stricta Lam. seedlings in experimental wetlands with implications for restoration

The loss of Carex dominated meadows due to agricultural drainage in the previously glaciated midcontinent of North America has been extensive. The lack of natural Carex recruitment in wetland restorations and the failures of revegetation attempts underscore the need for information on the establishment requirements of wetland sedges. In this study, seedlings of Carex stricta Lam. were planted in three experimental wetlands in east-central Minnesota, USA to investigate the biotic and abiotic environmental limitations to establishment. Seedlings were planted along an elevational water depth gradient to assess the effects of water depth and water level fluctuation on seedling survival and growth. A different water level fluctuation regime was assigned to each of the experimental wetlands to assess seedling tolerance for seasonal water level changes. The effects of seedling planting density and the presence or absence of non-sedge colonizers on seedling survival and growth were also studied. The experiment was followed for three growing seasons. The results of this study indicate that C. stricta seedlings were sensitive to the timing and duration of inundation during the first growing season. Once established, plants tolerated a broad range of seasonal drying and flooding conditions. Seedling and juvenile growth was slowed by non-sedge colonizers during the first two growing seasons, but by the third growing season, C. stricta was able to out-grow all annual and perennial weeds, except the aggressive perennial, Phalaris arundinacea L. The rapid growth of C. stricta plants, once established, indicates that the use of seedlings is a successful method for (re) introducing this tussock sedge into wetland restorations under a variety of environmental conditions. Comparison with other studies performed under similar conditions suggests that planting of seedlings is a more appropriate method of establishing this species than the use of transplanted rhizomes. This revised version was published online in June 2006 with corrections to the Cover Date.     

Survival and Growth of Tree Species under Two Direct Seedling Planting Systems

Direct tree planting restoration systems are frequently used for recovering degraded tropical landscapes. Although manual planting tends to be more viable economically and logistically over small areas, in large restorations the use of agricultural equipment that optimizes effort is preferable. The aim of this study was to investigate the efficiency of the two native tree species planting systems—manual and mechanized—used in the restoration of Atlantic Forest landscapes that have been converted to pasture. In recently abandoned grazing areas with abundant cover of the exotic grass Brachiaria humidicola, 393 seedlings of 6 species were planted in two treatments: a mechanized planting system (soil prepared with a rotary tiller attached to a tractor; seedlings in polypropylene tubes) and a manual planting system (holes dug with a manual excavator; seedlings wrapped in polyethylene bags). After 12 months, survival (manual: 85%; mechanized: 71%) and growth rates (RGR_height: manual = 0.88 ± 0.06 and mechanized = 0.98 ± 0.06 cm/cm; RGR_diameter: manual = 0.77 ± 0.05 and mechanized = 0.86 ± 0.05 cm/cm) were high in both treatments, but no differences were found between them. Both planting systems proved efficient for planting native tree seedlings in pastures. The excellent results demonstrated in this study by the mechanized planting system are important because this cheap and readily available technique provides a good, but less frequently used, alternative to the manual planting system.     

Application of composted urban residue enhanced the performance of afforested shrub species in a degraded semiarid land

Improvement of physical-chemical soil quality is a key step for carrying out revegetation programs of degraded lands in Mediterranean semiarid areas. Organic residue addition may restore the quality of these areas. A field experiment was conducted in a silt-loam soil (Typic Petrocalcid) from a degraded semiarid Mediterranean area to evaluate the effect of the addition of a composted urban residue on soil aggregate stability, bulk density and chemical properties and on the establishment of Pistacia lentiscus and Retama sphaerocarpa seedlings. The composted residue was applied at a rate of 6.7 kg m(-2) before planting. The nutrient content (NPK), total organic C and water soluble C were increased and bulk density was decreased, in the rhizosphere soil of both shrub species, by the composted residue. The addition of composted residue significantly increased the soil aggregate stability by about 22% for both shrub species. The beneficial effect of the composted residue on soil quality still persisted 18 months after addition. Eighteen months after planting, the addition of composted residue to soil had increased significantly the production of shoot biomass by P. lentiscus and R. sphaerocarpa, by about 160% and 320% respectively, compared to control values. Composted residue addition to soil can be considered an effective preparation method of a degraded area for carrying out successful revegetation programs with Mediterranean shrubs under semiarid conditions.     

Effect of flooding and draw‐down disturbance on germination from a seashore meadow seed bank

Abstract. The objective of this study was to investigate the effects of flooding and draw‐down on the germination from the coastal grassland seed banks and to determine whether the effect of flooding varies between the delta and the seashore. Seed bank samples were collected from three shore transects in SW Finland, two on the shore of the Baltic Sea and one on the delta of River Kokemäenjoki. Samples were germinated in non‐flooded and flooded conditions for over a month, after which both treatments were maintained in non‐flooded conditions. A total of 9267 seedlings of 47 species germinated and mean density of seeds in the soil was ca. 84 000/m². Most of the seedlings were monocots (98%) and perennials (98%). Ca. 30–40% of the species found in the above‐ground vegetation had a seed bank including the majority of the most abundant species. The number of seeds and species richness increased as the organic layer became thicker. The organic layer was thicker in the seashore samples and the seed bank was significantly larger than in the delta. The flooding and draw‐down treatment significantly increased the number of germinating seedlings in the seashore and also increased species richness in two transects, one in the delta and the other in the seashore. Two species, Schoenoplectus tabernaemontani and Typha latifolia, had significantly higher germination in the flooded treatment than in the non‐flooded. Apparently, many species in these coastal grasslands have adapted to flood disturbance and for seeds of some species flooding may work as a positive signal, possibly breaking dormancy.     

Shorea balangeran and Dyera polyphylla (syn. Dyera lowii) as tropical peat swamp forest restoration transplant species: effects of mycorrhizae and level of disturbance

Tropical peat swamp forests (TPSF) are being rapidly deforested, leading to disturbed hydrology, wildfires and carbon loss. Cost-effective methods are needed to increase the scale of restoration activities. One method is to inoculate seedlings with their corresponding mycorrhizae species, thereby increasing performance during nursery cultivation, although the benefits post-transplantation are less well understood. This study considered two TPSF tree species, Shorea balangeran and Dyera polyphylla (syn. Dyera lowii), and their mycorrhiza; Scleroderma columnare (S. balangeran) and Glomus clarum and Gigaspora decipiens (D. polyphylla). The performance of non-inoculated and inoculated seedlings was compared following transplantation into five forest zones, representing a gradient from intact to degraded TPSF. In the degraded area, both inoculated seedling species supported higher colonization levels compared to non-inoculated seedlings. Both tree species showed high survival rates in all forest zones, and survival, growth and biomass production were not affected by mycorrhizal treatment. Both species grew faster and accumulated greater biomass in the more degraded forest zones. Nitrogen and phosphorus content reduced for both tree species in the more degraded forest zones, however, inoculated D. polyphylla seedlings had higher nutrient content across all forest zones, as did S. balangeran though less uniformly. Both these tree species are therefore suitable for reforesting degraded TPSF and mycorrhizal inoculation is recommended given a) inoculated seedlings in the degraded area permitted a higher mycorrhizal colonization level, and b) mycorrhizae increased nutrient uptake in the transplanted seedlings, although in this short-term study survival or growth improvement in the inoculated seedlings was not apparent.     

The response of forest floor vegetation and tree regeneration to deer exclusion and disturbance in a riparian deciduous forest,central Japan

The response of forest floor vegetation and regeneration of major treespecies to deer exclusion in a riparian forest were studied for 3 years withtheinteractive effects of natural disturbances. At the start of this study, deerdensity had quickly increased to a fairly high level (29–31 individualskm^–2) during the last decade and had severely reduced theamount of forest floor vegetation in the study area. Dwarf bamboos, which weredominant before, had almost diminished from the forest floor. During the studyperiod, aboveground biomass increased steadily but species diversity did notchange much in the exclosures. Outside the exclosures, the seedlings of alltreespecies were damaged greatly by deer browsing, especially the taller ones. Deerbrowsing had little effect on the emergence of tree seedlings, but deertrampling might have accelerated emergence indirectly by disturbing the soilsurface for some species. Differences in plant responses were also observed fordeer browsing and the presence of dwarf bamboo that strongly inhibits therecruitment of tree seedlings. The nine major species were classified intothreegroups according to the response of seedlings to deer browsing and disturbance.Group 1 consists of the species whose seedling survival is affected bybrowsing,but seldom by disturbances (Phellodendron amurense,Kalopanax pictus, Quercus crispulaandMalus toringo). Groups 2 and 3 consist of species adaptedto tree-fall disturbance (Betula spp.) and ripariandisturbance (Alnus hirsuta var.sibirica, Ulmus davidiana var.japonica, Populus maximowiczii andSalix sachalinensis), respectively, and seedling survivalof these two groups is principally affected by light conditions. The effect ofdeer browsing on seedling survival and growth was greater for Group 2 than forGroup 3.     

Establishment of the Woody Grass Arundinaria gigantea for Riparian Restoration

Canebrakes are dense stands of Arundinaria gigantea (Walt.) Muhl. that covered large areas of the southeastern North America. With agricultural development, canebrakes were quickly converted to crop and pastureland and now occur only in small, isolated patches. There is growing interest in the use of A. gigantea and other temperate bamboo species in riparian and floodplain revegetation in North America, but lack of detailed information on propagation and management of woody perennial grasses hinders reestablishment activities. Our study assesses the influence of nutrient and woodchip mulch amendments on survival and growth of A. gigantea transplanted as part of a riparian restoration project in central Kentucky. After two growing seasons, culm number (aboveground stems) increased 4‐fold and extent of transplanted clumps expanded 26‐fold. The survival rate of transplanted cane clumps was 98%. Hardwood chip mulch significantly increased the emergence of new culms, culm height growth, and clump area. Composted manure, applied at a rate that contributed a similar mass of organic matter as the hardwood mulch, also significantly increased new culm number and clump area. Our findings demonstrate that addition of manure or hardwood mulch can significantly enhance aboveground production of A. gigantea transplants. However, survival and initial growth of untreated clumps were also adequate in this study. It appears that careful site selection, transplantation, and site maintenance may be sufficient to ensure A. gigantea establishment on many sites. Practitioners should assess soil drainage, water stress, and fertility along with herbaceous competition and incidence of overbank flooding before determining the necessity of organic amendments to supplement establishment of A. gigantea or other woody grasses for riparian restoration.     

The Effects of Intermittent Flooding on Seedlings of Three Forest Species

Under greenhouse conditions, seedlings of three forest species, baldcypress (Taxodium distichum), nuttall oak (Quercus nuttallii), and swamp chestnut oak (Quercus michauxii) were subjected to an intermittent flooding and subsequent physiological and growth responses to such conditions were evaluated. Baldcypress showed no significant reductions in stomatal conductance (g _s) or net photosynthetic rate (P _N) in response to flood pulses. In nuttall oak seedlings g _s and P _N were significantly decreased during periods of inundation, but recovered rapidly following drainage. In contrast, in swamp chestnut oak g _s was reduced by 71.8 % while P _N was reduced by 57.2 % compared to controls. Baldcypress displayed no significant changes in total mass while oak species had significantly lower leaf and total mass compared to their respective controls. Thus baldcypress and nuttall oak showed superior performance under frequent intermittent flooding regimes due to several factors including the ability for rapid recovery of gas exchange soon after soil was drained. In contrast, swamp chestnut oak seedlings failed to resume gas exchange functions after the removal of flooding.     

Nutrient Mineralization and Leaf Litter Preference by the Earthworm Pontoscolex corethrurus on Iron Ore Mine Wastes

Abstract The effects of the earthworm Pontoscolex corethrurus (Muller) on the rate of mineralization of cattle dung‐amended iron (Fe^{2 +} ) ore mine wastes and its preference for partially decomposed leaf litter with contrasting chemical composition were studied in pot trials. The growth and survival rates of earthworms showed significant positive correlations with percent of organic matter. During 96 days of exposure, the earthworms significantly increased exchangeable Ca^{2 +} , Mg^{2 +} , PO₄^{3 ?} and NH₄‐N. Iron ore mine wastes amended with 5–10% organic matter supported earthworm fauna better than mine wastes amended with 0–3% organic matter. The leaf litter preference shown by the earthworm was, in descending order, Phyllanthus reticulatus, Tamarindus indica, Anacardium occidentale, Casuarina equisetifolia, Acacia auriculiformis, and Eucalyptus camaldulensis. A significant positive correlation was observed between the survival and growth rates of earthworms and the nutrient contents of partially decomposed leaf litter. The first three plant species were significantly richer in nutrients, mainly organic carbon, calcium, phosphorus, and nitrogen, than the other two plant species. Acacia auriculiformis and E. camaldulensis litter were preferred less because of their high lignin and polyphenolic compounds, despite being rich in other macronutrients like nitrogen and phosphorus. It is concluded that the introduction of P. corethrurus to cattle dung‐amended (5–10%) iron ore mine wastes or revegetation of the sites with P. reticulatus, T. indica, and A. occidentale plant species should be attempted before earthworm introduction. The litter from these species acts as a source of food for earthworms, thereby hastening the process of restoration of abandoned iron ore mines of Goa, India.     

Arbuscular mycorrhizal fungi increased early growth of two nontimber forest product species Dyera polyphylla and Aquilaria filaria under greenhouse conditions

Nontimber forest products (NTFPs) represent an important source of income to millions of people in tropical forest regions, but some NTFP species have decreased in number and become endangered due to overexploitation. There is increasing concern that the planting stocks of Dyera polyphylla and Aquilaria filaria are not sufficient to sustain the yield of NTFPs and promote forest conservation. The objective of this study was to determine the effect of two arbuscular mycorrhizal (AM) fungi, Glomus clarum and Gigaspora decipiens, on the early growth of two NTFP species, D. polyphylla and A. filaria, under greenhouse conditions. The seedlings of both species were inoculated with G. clarum or G. decipiens, or uninoculated (control) under greenhouse conditions. Percentage of AM colonization, plant growth, survival rate, and nitrogen (N) and phosphorus (P) concentrations were measured after 180 days of growth. The percentage of AM colonization of D. polyphylla and A. filaria ranged from 87 to 93% and from 22 to 39%, respectively. Colonization by G. clarum and G. decipiens increased plant height, diameter, and shoot and root dry weights. Shoot N and P concentrations of the seedlings were increased by AM colonization by as much as 70–153% and 135–360%, respectively. Survival rates were higher in the AM-colonized seedlings at 180 days after transplantation than in the control seedlings. The results suggest that AM fungi can accelerate the establishment of the planting stocks of D. polyphylla and A. filaria, thereby promoting their conservation ecologically and sustaining the production of these NTFPs economically.     

Survival and growth responses of Myricaria laxiflora seedlings to summer flooding

Myricaria laxiflora, an endangered shrub species distributed along the banks of the Yangtze River in the Three Gorges area, is completely submerged from June to October every year. It is generally assumed that summer flooding has a strong impact on the survival and growth of seedlings. We designed an outdoor randomized block experiment on the responses of seedling survival and growth to different flooding depth and flooding duration treatments during the flood season in the Three Gorges area. Seedling survival rate, aboveground biomass, belowground biomass, total biomass, root depth, length of primary branch and the number of primary and secondary branches were examined.M. laxiflora was found to acclimate to summer flooding by becoming dormant and losing biomass. Seedlings of M. laxiflora ceased growing during the summer flooding season, regardless of the flooding depth and flooding duration they were subjected to. The number of primary and secondary branches, aboveground biomass and total biomass of seedlings was reduced with prolonged flooding. The length of primary branches and aboveground biomass were more sensitive to flooding than other measured parameters and differed significantly between the onset and the end of flooding.In each flooding treatment most seedlings of M. laxiflora survived a flooding period of 2 months and recovered rapidly after the flooding was terminated in September. After 3 months of recovery, aboveground biomass, total biomass and the number of the primary branches increased significantly. Furthermore, seedling survival and growth in the flooding treatments were not significantly different from the controls both during the summer flooding stage and in the recovery stage. All of these results suggest that summer flooding does not affect seedling survival and growth in this species. On the contrary, flooding released seedlings from the stress of drought during summer and facilitated seedling establishment. M. laxiflora appears to cope adaptively with the flooding cycle by going into a state of dormancy during the flood season.     

RESPONSE OF WOODY SWAMP SEEDLINGS TO FLOODING AND INCREASED WATER TEMPERATURES. I. GROWTH,BIOMASS, AND SURVIVORSHIP

Growth, biomass, and survival of bald cypress (Taxodium distichum [L.] Richard), water tupelo (Nyssa aquatica L.), black willow (Salix nigra Marshall), and button bush (Cephalanthus occidentalis L.) were examined in a 3 times 3 factorial experiment varying water temperatures (AMBIENT, MID, and HIGH [~40 C]) and water levels (DRAINED, SATURATED, and FLOODED). Stem diameter and height, biomass, and survivorship for water tupelo and bald cypress were all reduced by the HIGH/FLOODED treatment. Black willow growth had the greatest variability among nonlethal flooding and temperature treatments, and achieved the greatest biomass of the four species. In the HIGH/FLOODED treatment, however, only 47% of the black willow seedlings survived and stem diameter, height, and biomass of survivors were greatly reduced. Button bush had intermediate variability of growth to the nonlethal treatments as compared to the other study species. Survival of button bush seedlings in the HIGH/FLOODED treatment was high (87%), but root biomass of the survivors was reduced. Interspecific differences in growth, biomass, survivorship, and morphological characteristics existed among these swamp species to experimental conditions. These responses may help explain vegetation patterns in a thermally impacted swamp.