Effects of post-fire management practices and slope-aspect on medium-term Spanish black pine regeneration: implications of using a direct seeding strategy in burnt areas

The natural regeneration of non-serotinous Spanish black pine (Pinus nigra Arn. ssp. salzmannii) is known to be null or limited after severe wildfires. However, it remains challenging to define efficient management strategies within the burnt area, which can help to increase the post-fire resilience of this species. We conducted a direct seeding experiment during 2011–2015 to assess the effect of different post-fire management treatments (control, soil ripping, woodchips, and soil ripping?+?woodchips) performed in opposite slope-aspects (north- and south-facing) on pine emergence, seed predation, survival, growth, and biomass allocation during the early stages of seedling development (1–5 years) after a severe wildfire. Our results showed that the slope-aspect did not have an important effect in both the seedling emergence and seed predation rates. In contrast, the influence of slope-aspect was significant as both survival and growth of pine seedlings were reduced at the south-facing slope-aspect compared to the north-facing slope-aspect due to harsher environmental conditions. A variable and reduced impact on seedling emergence and seed predation rates was induced by both soil ripping and woodchips treatments. Overall, post-fire management treatments helped to enhance survival rates during early growth stages, although this effect was short-lasting. This knowledge can be used to define post-fire seeding management strategies oriented to enhance the resilience of severely burnt pine forest stands; therefore, while both the soil ripping and woodchips treatments might not be practices leading to increase their post-fire regeneration, direct seeding at north-facing slope-aspects could be a more appropriate management strategy.     

Influence of herbaceous ground cover on forest restoration of eastern US coal surface mines

Competitive effects of dense herbaceous vegetation (ground cover) can inhibit forest restoration on mine sites. Here we review the evidence of ground cover interactions with planted tree seedlings on coal surface mines of the eastern US, discuss recent research into these interactions, and draw conclusions concerning ground cover management when restoring forests on reclaimed coal mines. Reclaimed mine sites have a high potential to support productive forests, however forest establishment is inhibited by reclamation practices that included soil compaction, and the seeding of competitive ground covers. In the first few years after tree planting, a dense ground cover of grass and legume species commonly seeded on mine sites often affect growth and survival negatively. Herbaceous vegetation providing less extensive and competitive ground coverage may either facilitate or inhibit tree establishment, depending on site conditions. The use of quality planting stock promotes the competitive ability of seedlings by improving nutrient status and the ability to capture available resources. Herbaceous species have contrasting functional characteristics, and thus compete differently with trees for available resources. Negative interactions with trees are more frequently reported for non-native cool-season grasses than for native warm-season grasses, while the effects of legumes change over time. Further research is needed to fully understand the mechanisms of tree/ground cover interactions. The development of seeding mixes that can control erosion, facilitate survival and growth of planted trees, and allow establishment by unplanted native species would aid forest restoration on eastern US, coal mines.

     

Survival and growth responses of Populus nigra, Salix elaeagnos and Alnus incana cuttings to varying levels of hydric stress

The Salicaceae and Betulaceae are important plant families within riparian ecosystems throughout the Northern hemisphere, and cuttings of species within these families are often used in riparian restoration projects due to their capacity for vegetative (asexual) propagation and rapid growth. Riparian zones can experience a wide range of hydrological conditions and establishing cuttings may be subjected to substantially varying levels of hydric stress from inundation and drought. Tolerance to such stress can vary notably between species, and the absence of knowledge of species-specific responses to inundation and drought has resulted in high mortality in many riparian restoration projects. In this paper, the survival and growth responses of Salix elaeagnos (Salicaceae), Populus nigra (Salicaceae) and Alnus incana (Betulaceae) cuttings in relation to varying rates of water table decline and periods of inundation were investigated using rhizopods during a 69-day greenhouse experiment, in substrates of contrasting sediments (sand versus gravel).

Each species responded differently to the experimental treatments. S. elaeagnos demonstrated an ability to establish in stable, declining and inundated conditions by the production of relatively substantial root and shoot biomass in all treatments, along with elongated roots when experiencing water table decline. P. nigra showed high mortality and poor root and shoot production in inundation treatments, suggesting that this species is intolerant to reduced oxygen conditions. A. incana displayed complete mortality in all gravel-based treatments and high mortality or poor growth in the sand-based inundation treatments. All species showed preferences for stable conditions without inundation, along with slow water table decline for S. elaeagnos. Fast rates of water table decline were detrimental to all species. Overall, sand was a much more effective substrate than gravel for supporting cutting establishment. These results suggest that riparian restoration schemes utilizing S. elaeagnos cuttings may experience greater success than those using the other species investigated. P. nigra cuttings may establish more easily if situated where inundation does not occur often or for prolonged periods, and A. incana cuttings should be planted only where very stable conditions dominate. The study highlights the inter-species variability in the survival and growth response of riparian trees to differing hydrological conditions.     

Nutrient dynamics of forested catchments in Southeastern Australia and changes in water quality and nutrient exports following clearing

Nutrient inputs in rainfall, and streamwater chemistry and quality, were measured from May 1976 to April 1982 at three forested catchments in Victoria. Streamwater chemistry was influenced by the strong seasonal fluctuations in streamflow. Yearly input-export balances for Na, K, Ca, Mg and Cl varied substantially and were highly correlated with runoff. This underlines the importance of sampling a wide range of climatic variation to derive meaningful balances.

Calibration relationships between catchments were used to evaluate the impact of clearing native eucalypt forest for the establishment of P. radiata on streamwater chemistry and quality and on nutrient exports. Clearing was found to have little effect on streamwater quality, thus demonstrating the effectiveness of a 30-m wide buffer strip retained on both sides of the stream channel. Only minor changes in streamwater chemistry were observed; however, exports of nutrients and suspended solids were significantly higher because of increased discharge following clearing.

Exports of most nutrients returned to pre-treatment levels within 18 months after clearing. Nutrient losses in streamwater were small when compared with losses due to burning the cleared vegetation. Balances for Na were used to estimate nutrient inputs from geological weathering. It was concluded that inputs of Ca are probably too low to ensure adequate supply of Ca for successive rotations of P. radiata, and future management practices should aim at conserving this nutrient.     

紫竹和灰金竹在西藏拉萨的引种栽培试验

紫竹（Phyllostachys nigra）和灰金竹（Ph.nigra var.henonis）是重要的观赏竹种，为丰富西藏的城市绿化树种种类，在拉萨市开展了紫竹和灰金竹引种栽培试验。试验采用3因素（基质、复合肥和生根粉）3水平的正交试验设计，分析不同因素和水平对引种竹种生长的影响。结果表明：引种自云南昆明的紫竹和灰金竹在西藏拉萨栽植2年后，2个竹种的成活率分别达到68.0%和47.0%，发笋率分别为36.8%和35.8%，显示出紫竹在拉萨的适应性要强于灰金竹；在各因素中，复合肥对于紫竹成活率影响最大，而生根粉对灰金竹成活率影响最大。各因素对于2个竹种生长指标影响程度的排序是一致的，即基质>生根粉浓度>复合肥施肥量；3因素最优水平组合均为：以牛粪为基质、复合肥施用量为10 g/丛、用0.02%的生根粉溶液浸泡竹篼。研究结果为紫竹和灰金竹在西藏拉萨市等高寒地区的引种及苗木繁育提供了重要的技术依据。     

Early recovery process and restoration planning of burned pine forests in central eastern Korea

In central eastern Korea, there has been a continued effort to sustain pine forests because of their value for wood and mushroom production, as well as for other resources. Through the analysis of previously burned areas,we clarified the effects of fire on vegetation dynamics of pine forests by measuring changes in species composition,population structure, and the growth rates of major tree species. Vegetation analysis was conducted on a series of 100 m^2 plots established in Korean red pine(Pinus densiflora Siebold. & Zucc.) and Mongolian oak(Quercus mongolica Fisch. Ex Ledeb.) forests situated in three different topographic positions on slopes where fire severity varied. We confirmed that most pine trees will succumb to even a surface fire, whereas oak may be killed following high intensity or infrequent fires but will sprout and become dominant. Complete protection from fire favors other, more shade-tolerant deciduous hardwoods. Different restoration plans apply, based on observed vegetation responses for each topographic zone. Near the ridge top,where pine seed sources are most limited, it may be necessary to restore pine forests by planting and to control competing shrubs and herbs. At the mountain foot, where exotic species and species modified by hybridization have invaded aggressively, restoration that involves the introduction of natural vegetation is required. Mid-slope sites,where pine has been replaced by natural vegetation dominated by Mongolian oak, do not require any form of restorative treatment.     

Rodent impact on establishment of direct-seeded Fagus sylvatica,Quercus robur and Quercus petraea on forest land

Abstract

Seed predation by granivorous rodents constitutes a major problem during reforestation using direct seeding. Acorns or beech nuts were sown at 14 different sites in Denmark and southern Sweden, and seedling establishment was inventoried during the first three growing seasons. Around the time of sowing, rodents were either snap-trapped or live-trapped. At some sites, perches for raptors were installed, and at other sites, signs of predation were investigated or predation was monitored by camera surveillance. Granivorous rodents had a profound negative influence on sowings, and the removal of beech nuts occurred rapidly following sowing. Establishment of oak was better when surroundings consisted of mixed forests rather than broadleaved forests. Fewer rodents were caught, and establishment was better, in large reforestation areas. Rodent captures indicated that forest edges, slash piles and stone wall remains were suitable rodent microhabitats. Snap-trapping or raptor perches did not result in increased oak establishment. Neither sowing in summer nor increased seeding depth decreased predation by rodents on beech nuts. In conclusion, seeds need protection from rodents immediately at the time of sowing. Choosing large regeneration areas combined with removal of suitable rodent habitats seems to be a practical alternative for the development of successful strategies for direct seeding.     

Direct seeding of late-successional trees to restore tropical montane forest

Natural regeneration of large-seeded, late-successional trees in fragmented tropical landscapes can be strongly limited by a lack of seed dispersal resulting in the need for more intensive restoration approaches, such as enrichment planting, to include these species in future forests. Direct seeding may be an alternative low-cost approach to planting nursery-raised tree seedlings, but there is minimal information on its efficacy or when in the successional process this technique will be most successful. We tested directly seeding five native tree species into habitats representing passive and active restoration approaches: (1) recently abandoned pasture; (2) naturally establishing, young secondary forests; and (3) young, mixed-species (fast-growing N-fixers and commercially valuable species) tree plantations established to facilitate montane forest recovery in southern Costa Rica. We monitored germination, survival, growth, and above- and below-ground biomass over a 2-year period. Germination in pastures, secondary forests, and tree plantations was similar (∼43%). Seedling survival after one and two years was significantly higher under tree plantations (91% year 1, 75% year 2) compared to secondary forests (76, 44%) or pastures (74, 41%). Moreover, seedlings had greater total biomass and lower root:shoot ratios in the plantations, suggesting higher nutrient availability in that treatment. Costs for direct seeding were 10- to 30-fold less per 100 seedlings after 2-year compared to nursery-raised seedlings planted at the same sites; however, there are important trade-offs to the two restoration approaches. Planting nursery-raised seedling is a more effective but higher cost approach for rapidly establishing canopy cover and restoring large areas whereas direct seeding is a more efficient way to enrich an existing system. We particularly recommend using direct seeding as a complimentary measure to the more intensive restoration approach of planting fast-growing and N-fixing trees.     

Growth and physiological response of eastern white pine seedlings to partial cutting and site preparation

We examined how white pine (Pinus strobus L.) seedlings planted under a mature cover of white and red (Pinus resinosa Ait.) pine in eastern Ontario (Canada) responded to treatments aimed at improving light and soil conditions for seedling growth. The treatments were: (a) three levels of partial cutting (no cut or CS0, cut to one-crown spacing between residual trees or CS1, cut to two-crown spacing or CS2); (b) two levels of vegetation control (without herbicide or H0, with herbicide or H1); and (c) two levels of soil scarification (S0 and S1). On the third growing season after planting, total growth of seedlings was lowest in CS0 treatment and similar in CS1 and CS2 treatments. The CS2 created better growing light conditions than the CS1, with and average of 50% of full light at seedling height, which corresponded to the maximum height and diameter growth rates of seedlings. However, CS2 also stimulated the growth of competing woody vegetation (both understory trees and shrubs), and resulted in greater microsite heterogeneity of light availability. Scarification warmed the soil (approximately 1–3 °C in the middle of the growing season), decreased the density of competing trees, but increased the shrub density, with no impact on white pine seedling growth. The treatments had no effect on light-saturated photosynthetic rate (A) of current-year foliage of seedlings, nor on their midday shoot water potential. Leaf N was higher in partial cuts and with vegetation control, but the relationship between N and A was weak to non-existent for the different foliage classes. Measures of the proportion of aboveground biomass allocated to foliage (leaf-mass ratio) suggest an acclimation response of young white pine that improves growth under moderate light availability and compensates for the lack of leaf-level photosynthetic plasticity. We suggest a combination of soil scarification under a one-crown spacing partial cut (corresponding to 14 m² ha⁻¹ of residual basal area, or an average of 32% of available light at seedling height) as an establishment cut. This should provide optimum growth conditions for planted understory white pine, while also favoring natural regeneration and providing some protection against damage from insects and disease.     

Direct seeding of Quercus robur L. for reforestation: The influence of mechanical site preparation and sowing date on early growth of seedlings

Compared with conventional planting, direct seeding of Quercus spp. is a method that can reduce the costs of reforestation considerably. However, interference from natural vegetation and predation on acorns contribute to regeneration failures. Mechanical site preparation has the potential to reduce both these problems. To study the influence of sowing date and of different mechanical site preparation treatments on early seedling growth, an experiment was carried out in storm-felled areas, formerly Norway spruce forests, in southern Sweden from May 2006 to September 2008. Five treatments were applied and acorns were planted in May and July 2006. The treatments were: disc trenching, patch scarification, topsoil removal, mounding and an undisturbed control. A delay of less than two months in seeding resulted in the equivalent of one year's growth reduction with respect to oak seedling's height and biomass. This could be explained by delayed emergence of seedlings, and by the dry conditions during summer seeding. The seedlings only exhibited a weak positive biomass growth response following disc trenching, patch scarification and top soil removal. In the latter case this might be explained by increased soil compaction and extensive removal of the humus layer. Site preparation by mounding resulted in good vegetation control, an increased biomass growth response and deeper seedling roots. In this treatment, we found high relative light levels near seedlings, reduced soil moisture and dry bulk density of the soil and higher soil temperatures. One or more of these environmental factors could have influenced the growth response. Whether this increased early growth rate persists throughout young stand development is, however, uncertain.     

Strategies for empowering the local people to participate in forest restoration

Within various parts of the tropics and temperate regions, there are increasingly more efforts towards reforestation or restoration. Interventions in the tropics however, have not adequately addressed the needs of local people compelling them to degrade forests. We conducted a study in and around Mabira Forest Reserve in Uganda with the aim of assessing locally proposed restoration techniques and conditions for empowering local people to raise their willingness to participate in forest restoration practices. We specifically set out to; (i) identify proposed techniques to restore the degraded forests, and (ii) determine the pre-conditions for supporting local people’s participation in restoration activities. Data were collected using individual semi-structured interviews, focus group discussions and participatory forest surveys. The findings show that the local people mainly engaged in practices that address their needs concurrently. The most reported practices include: planting trees on farm, enrichment tree planting in the forest, control of soil erosion, and control of invasive alien species. The main pre-conditions for their participation in forest restoration is assurance for more access to forest resources. The efficiency of local people in restoration will be enhanced by strengthening their capacity for collaborative forest management, raising their awareness on restoration, building their capacity, as well as continuous monitoring by forest managers.     

Interference of bracken (Pteridium aquilinum L. Kuhn) with Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies L. Karst.) seedling establishment

The nature of interference of bracken with Scots pine and Norway spruce seedling establishment was considered in three field experiments. In a seeding experiment, it was found that Scots pine germination was highest on exposed mineral soil and lowest when intact bracken litter and humus were present, suggesting adverse effects of litter and humus on pine regeneration probably due to phytotoxicity. In a second experiment, smothering by bracken caused high mortality of Scots pine seedlings while Norway spruce seedlings were relatively unaffected. Mortality for both Scots pine and Norway spruce seedlings was low when planted in a adjacent Scots pine-bilberry stand with no bracken. Annual shoot growth of Norway spruce was higher in bracken than in Scots pine-bilberry vegetation while no differences in shoot growth between these two vegetation types occurred for Scots pine. In a third experiment, activated carbon was added to the ground under Norway spruce seedlings planted in bracken to adsorb possible phytotoxic compounds released by bracken. The addition of carbon had no effect on seedling mortality or growth rate, indicating that the seedlings were not susceptible to allelochemicals released by bracken. Since large Norway spruce seedlings were relatively unaffected by bracken interference in this study, artificial regeneration with containerized Norway spruce seedlings is suggested to achieve an acceptable conifer tree establishment on clear-cuts invaded by bracken.     

Factors influencing establishment by direct seeding of indigenous tree species in typical plantations and shrubland in South China

Seed limitation of desired indigenous species has constrained the succession of established plantations from an early successional stage, to more natural forests in South China. Because of its low cost and time-saving advantages, direct seeding has been considered a useful method in forest regeneration. To improve our understanding of whether and how direct seeding can lead to the establishment of indigenous tree species, we carried out an experiment in four typical plantations (eucalyptus, mixed-native, mixed-legume, mixed-conifer) and a shrubland in South China. We also tested the effect of understory vegetation and litter removal on seedling establishment and growth. Seeds of three indigenous tree species (Castanopsis chinensis, Cryptocarya chinensis, and Psychotria rubra) were sown with understory vegetation and litter either retained or removed. Seedling emergence, survival, and growth were recorded for 21 months. We found that conditions that favored seedling emergence often differed from those that favored seedling survival. While the removal of understory vegetation and litter did not influence the final seedling establishments for all the three introduced species, growth of Psychotria rubra was influenced at several sites. Seed mass was positively correlated with seedling emergence and subsequent growth. The large-seeded Castanopsis chinensis showed higher emergence and growth than the intermediate-seeded Cryptocarya chinensis or the small-seeded Psychotria rubra. Seedlings of Castanopsis chinensis grew better in plant communities with high understory light penetration and high soil exchangeable potassium. Growth of P. rubra seedlings decreased significantly with soil hydrolyzed nitrogen. In conclusion, direct seeding can be useful for the establishment of indigenous tree species into plantations and shrubland. Optimizing early seedling establishment and growth will require the selection of suitable native species for improving seedling establishment in different plantations. Additionally, understory vegetation and litter and fertilizer should be properly managed to enhance the establishment of certain indigenous tree species.     

Restoration of dry tropical forests in Central America: A review of pattern and process

Much information on restoration and management exists for wet tropical forests of Central America but comparatively little work has been done in the dry forests of this region. Such information is critical for reforestation efforts that are now occurring throughout Central America. This paper describes processes of degradation due to land use and provides a conceptual framework for the restoration of dry tropical forest. Most of this forest type was initially harvested for timber and then cleared for cattle in the last century (1930-1970). Only 1.7% remains largely restricted to infertile soils and remote areas on the Pacific coastal side of Panama, Costa Rica, Nicaragua and Mexico. These cleared areas are again in a state of transition due to a combination of decreasing land productivity, and land speculation for tourism development. Some farms have been sold to new landowners who are interested in reforesting to increase biodiversity and forest cover. Attempts have therefore been made to reforest by protecting the land from fire and cattle, by supplementing natural regrowth with enrichment planting, or through use of tree plantations. Experimental studies have demonstrated the ability of these lands to grow back to forests because of native species ability to sprout after cutting, and the capacity of remnant trees in field and riparian zones to provide seeds and to moderate edge environment for seed germination and seedling establishment. However, research also shows that on sites with long histories of land clearance, species diversity will remain low with functional groups missing unless some active management occurs. Under-planting with late-successional native tree species can add structure and diversity; enrichment planting with large-fruited shade-intolerant species can initiate new islands of more diverse regeneration beneath their canopies; and plantings of fast-growing, nitrogen-fixing trees that provide light canopy shade can moderate the environment below, promoting regeneration establishment of late-successional species. Plantations are the only option for lands that have lost almost all remnants of native forest, and where soils and vegetation have changed to new states of structure and function. Conversion of pastures to tree plantations that can facilitate natural regeneration beneath them is appropriate when pastures are prone to fire and/or lack immediate seed sources nearby. After the grasses have been shaded out, natural recruitment can slowly occur over a 10-15 years period. Under-planting of shade-tolerant late-successional species can supplement species composition and structure.     

马尾松不同苗木类型与整地方式造林早期效果的研究

通过对不同苗木类型和整地方式的马尾松幼林的造林成活率、生长状况、生物量和根系特征进行测定，结果表明：容器苗可明显提高造林成活率、当年抽梢高和生物量；整地方式对造林当年的马尾松幼林有一定影响，而在第３年则对幼林树高和抽梢高起着明显促进作用。     

水源涵养林火烧迹地造林更新试验初报

在福州市马尾区亭江镇白眉村白眉水库西侧山场90 hm2的水源涵养林火灾迹地,选择木荷、山杜英、枫香、台湾相思等阔叶树树种,采用不同整地方式和不同造林方式营造水源涵养林试验,2 a的试验结果初步表明,造林更新效果比较理想,选用的树种是合适的,采用带状整地并以营造混交林的方式效果更佳。     

Regeneration result of excavator-mounted rototiller in direct seeding of Scots pine on forestry-drained peatland

The need to regenerate peatland forests is expected to increase in the near future in Finland due to harvest of large amounts of peatlands drained during the 1950s and 1960s. In anticipation of this, a new type of excavator-mounted rototiller for soil scarification in peatlands has been developed in Finland to improve the moisture conditions of the seedbed by mixing the ground vegetation, raw humus layer, and peat. The regeneration result of the new rototiller was compared with traditional patch scarification (i.e. scalping) in direct seeding of Scots pine in three forestry-drained peatland sites in eastern Finland. After two growing seasons, rototilling offered no advantage over scalping in terms of the number of established seedlings, probability of empty patches, or seedling height. Seedling establishment was on average higher on scalping (10%) than on rototilling (8%). The main problem in rototilling may have been the loose and porous structure of the seedbed resulting in drought and frost damages.     

豫北斑竹笋用林改造技术

斑竹为豫北地区主要栽培竹种,曾经为当地经济发展作出了巨大贡献。随着传统手工业的衰落,竹材价格逐年走低,竹林从材用林向笋用林转变已是大势所趋。文章在总结多年实践经验的基础上,提出了通过封园清杂、林地垦复、水肥管理、结构调整、合理采笋等将斑竹林改造为笋用林的关键技术措施。实践证明,改造后的斑竹林生长良好,经济效益显著提高。该技术可在豫北地区推广应用,为豫北地区竹林可持续发展提供技术支撑。     

Why seedlings survive: influence of plant attributes

Seedling survival and successful forest restoration involves many silvicultural practices. One important aspect of a successful forest restoration program is planting quality seedlings with high survival capability. Thus the nursery needs to create seedlings with plant attributes that allow for the best chance of success once a seedling is field planted. Since the mid-twentieth century, research foresters have critically examined plant attributes that confer improved seedling survival to field site conditions. This review describes the value of commonly measured seedling quality material (i.e. shoot height, stem diameter, root mass, shoot to root ratio, drought resistance, mineral nutrient status) and performance (i.e. freezing tolerance and root growth) plant attributes defined as important in answering the question of why seedlings survive after planting. Desirable levels of these plant attributes can increase the speed with which seedlings overcome planting stress, become ‘coupled’ to the forest restoration site, thereby ensuring successful seedling establishment. Although planting seedlings with these desirable plant attributes does not guarantee high survival rates; planting seedlings with desirable plant attributes increases chances for survival after field planting.     

毛乌素沙地植被恢复措施

毛乌素是我国较大的沙区之一.针对毛乌素沙区不同沙地类型及特点,提出了采取封育、固沙造林、飞播、营建防风阻沙林等几种植被恢复技术措施.