The tolerance of newly emerged broadleaved tree seedlings to the herbicides clopyralid, cycloxydim and metazachlor

In direct-seeded woodlands and nursery seed-beds, weeds canrapidly invade newly sown areas, leading to death or suppressionof tree seedlings. Hand weeding is usually expensive, and thesafe use of broad-spectrum contact herbicides is seldom possible.Hence in the work reported here, the tolerance of young treeseedlings to the potentially more selective, post-emergenceherbicides clopyralid, cycloxydim and metazachlor, was tested.Seedlings of Fraxinus excelsior L. (ash) with two to four expandedtrue leaves (2–4 ETL), Fagus sylvatica L. (beech) (2–4ETL), Acer pseudoplatanus L. (sycamore) (4–6 ETL), Prunusavium L. (cherry) (6–8 ETL) and Quercus robur L. (oak)(6–8 ETL) appeared to tolerate applications of cycloxydimat a rate of 0.45 kg a.i. ha^–1. Applications of 0.2 kga.i. ha^–1 clopyralid or 1.25 kg a.i. ha^–1 metazachloralso appeared to be generally tolerated, but did cause somesuppression of annual growth increment in Q. robur, P. avium,F. sylvatica and A. pseudoplatanus, particularly where repeatapplications were made to the earliest growth stages. Seedlingsurvival was unaffected by any herbicide treatment. Mixturesof all three herbicides were no more damaging than the sameherbicides applied separately. Therefore, depending on treespecies and growth stage, it appears that clopyralid could potentiallybe safely used to control a range of herbaceous weed species,metazachlor a variety of seedling or germinating weeds and cycloxydima range of established grass weed species, in direct sown woodlandsor nursery seed-beds, although further research is advisableto confirm crop safety.     

Tolerance of Pinus caribaea var. hondurensis seedlings to five post-emergence herbicides

Five herbicides were evaluated for their potential to reduce reliance on directed white (mineral) spirits applications and hand weeding for grass control in P. caribaea var. hondurensis nurseries. Post-emergent applications of haloxyfop-methyl, fluazifop-P, fenoxaprop-ethyl and sethoxydim were identified as being selective to P. caribaea var. hondurensis seedlings whilst providing effective grass control. Ametryn was toxic to P. caribaea var. hondurensis seedlings at 1 kg ha^–1.     

The unstable fate of seedlings of the small-seeded pioneer tree species, Betula maximowicziana

The dynamics of the seedling population of the pioneer tree, Betula maximowicziana, were studied for 6 years under various site conditions, with special reference to mortality and mortality factors, in order to better understand their seedling bank formation process. We found that current year seedlings suffered high annual mortality of more than 80%, but that mortality fell with age. Canopy covers and cohorts maintained strong influences on seedling mortality during the first 3 years after emergence. The open site with disturbed soil surface was best suited for 3-year seedling survival. Since the seedlings of B. maximowicziana emerged regardless of canopy covers, high seedling mortality was thought to be the main factor that interrupted their regeneration under a canopy. The occurrence of various hazards together caused high seedling mortality. The major mortality factors, regardless of site conditions, were drought, cold hazard and debilitation, though occurrence of the three factors varied, dependent upon the climate of that particular year. Annual mortality and the occurrence of each mortality factor at a fine scale of 0.2 m² quadrate each showed certain spatio-temporal variations within the same site condition. The extremely high mortality of B. maximowicziana seedlings should be attributed to their inherently small, initial size. The poor root system of the small seedlings may be responsible for their low resistance to various hazards, such as drought and frost heaving.     

The natural regeneration pattern and process of Korean pine population under natural Poplar-birch forest in Xiaoxing’an Mountains

According to a great deal of field investigation and detailed indoor analysis, the natural regeneration pattern and process of Korean pine population under natural Poplar-birch forest has been uncovered. The results show that the regeneration quantity and quality of Korean pine population under mountainous Poplar-birch forest and mountainous white birch forest are better than those under valley moss-grass White Birch forest and virgin broad-leaved Korean pine forest. Korean pine population shows aggregated distribution, the mass-occurrence period of Korean pine population is behind the mass-occurrence period of Poplar-birch population. Various aged Korean pines growth is affected by different stand structure factors. Man-made lighting tending can accelerate the regeneration process and increase the regeneration quality of Korean pine population. It is feasible to set up regeneration recombination of upper layer White Birch and lower layer Korean pines.     

Effects of roe deer browsing and site preparation on performance of planted broadleaved and conifer seedlings when using temporary fences

Abstract

The effects of fencing and site preparation on performance of birch (Betula pendula Roth), oak (Quercus robur L.), pine (Pinus sylvestris L.) and spruce [Picea abies (L.) Karst.] seedlings were studied over four growing seasons in southern Sweden. The experiment was composed of four browsing treatments, from which roe deer (Capreolus capreolus L.) were excluded for 0, 12, 24 or 42 months, and four soil treatments. Natural browsing was combined with artificial browsing (clipping). It was demonstrated that browsing by roe deer could be isolated from browsing by moose (Alces alces L.) by selective fencing. Except for birch, browsing had little effect on seedling survival. Browsing reduced height growth by more than 100% for oak and pine, and more than 60% of pine seedling developed multiple stems. Except for oak, site preparation increased seedling survival. Inverting site preparation, in combination with or without fertilization, produced positive growth responses in seedlings, whereas patch scarification did not. There was no interaction between browsing and soil treatments on seedling performance. It was concluded that long-term protection against browsing by roe deer is needed for oak and pine, whereas short-term fences might be used for birch, and that spruce is relatively unaffected by browsing.     

Effects of management, environment and landscape conditions on establishment of hardwood seedlings and saplings in central Japanese coniferous plantations

There is an increasing need to restore natural hardwood forests in landscapes dominated by monocultural conifer plantations. A convenient restoration approach is to exploit natural regeneration processes. Natural regeneration, however, is affected by diverse interacting factors, for which better understanding is required, in order to optimize restoration programs. To identify optimal management practices for improving natural regeneration of hardwood trees in coniferous plantations, we examined the effects of multiple factors on the abundance of seedlings, small saplings and large saplings (height <0.3, 0.3-1.3 and ?1.3 m, respectively) of hardwood tree and shrub species in both line thinned (LT) and unthinned (UT) plantations of sugi (Cryptomeria japonica) and hardwood forests (HF) in central Japan. The effects of management practices (number of the times of weeding and cleaning, thinning method, years after thinning and forest age), environment (slope position, slope angle and canopy openness), and landscape conditions (distance from nearest hardwood forest, altitude and landuse before planting) on the number of hardwood individuals were examined by using the data obtained from the LT plantations. We also compared hardwood density between LT and UT plantations to examine the effect of line thinning. Finally, we examined species composition of LT plantations and HF to identify hardwood forest components in the thinned plantations. The effects on hardwood regeneration of environmental conditions, landscape factors and management practices applied in the plantations varied, depending on the size class and life form of the regenerating species. The abundance of large saplings of tall tree species was affected by several management factors, especially number of the times of weeding. Landscape conditions (distance from the nearest hardwood forest and altitude) affected the abundance of small saplings and seedlings of tall tree species, but not the other classes. Seedlings and small saplings of many tall tree species that contribute to hardwood forest canopies were less abundant in the LT plantations. The results show that numerous factors affect the establishment and abundance of naturally regenerating hardwood tree species, and suggest that successful establishment during early plantation stages can have long-lasting effects on natural regeneration of tall tree species.     

Improved recruitment and early growth of Scots pine (Pinus sylvestris L.) seedlings after fire and soil scarification

The success of seedling recruitment of Scots pine (Pinus sylvestris L.) is strongly dependent on soil surface properties, such as humus depth and moisture content. In an undisturbed forest floor, seedlings are seldom able to become established due to the high incidence of desiccation in the organic soil layer. Methods that remove the organic soil layer are often necessary to improve the availability for radicles to reach the more stable moisture regime in the mineral soil. In this study we investigated pine-seedling establishment after mechanical soil scarification, burning of litter (O_L) and burning of litter and humus (O_L and O_FH) in two mature pine stands in Germany. The herbaceous layer of the first stand was dominated by grasses (Molinia caerulea L. and Deschampsia flexuosa L.), whereas the herbaceous layer of the second stand was dominated by blueberry (Vaccinium myrtillus L.). Pine seeds were placed in experimental plots, and seedling numbers and heights were recorded at regular intervals. All treatments that removed organic soil resulted in higher seedling counts than did the undisturbed forest floor. The highest seedling counts were found on scarified and severely burnt plots, whereas seedling counts were lower on lightly burnt plots. Seedlings were significantly taller on burnt plots. This study shows that pine regeneration is stimulated by fire, not only in boreal forests, but also under central European conditions. With the expectation of higher fire frequency in the near future due to climatic changes, natural regeneration and succession on burnt sites should receive more focus in forest management and research.     

栽杉留阔模式群落区系特征研究

通过标准地调查 ,研究 2 9年生栽杉留阔模式及杉木纯林 (对照 )群落区系特征 ,结果表明 :栽杉留阔模式群落植物属和种组成数量 (10 2属、138种 )均大大超过杉木纯林群落 (87属、10 8种 ) ,具有生物多样性和更强的水土保持功能。其区系特征与杉木纯林相比有较大不同 ,群落间的相似性较小。栽杉留阔模式群落乔木层中落叶阔叶树种具有较大的重要值。栽杉留阔模式群落草本层以阳性种类为主 ,未发现观音座莲 ,而观音座莲是杉木纯林的指示植物。 2个群落种子植物属的分布区类型都是以热带成分为主 ,栽杉留阔模式群落属的热带分布比例小于杉木纯林     

Population structure and regeneration of multiple-use tree species in a semi-deciduous African tropical rainforest: Implications for primate conservation

The conservation of threatened frugivorous primates (e.g. chimpanzees) and birds in the Albertine Rift Ecoregion rainforests requires the conservation of food tree species aided by an understanding of their natural regeneration and population trends. However, little is known of the population structure and regeneration patterns of a wide range of multiple-use tree species in many of these forests.     

Estimation of taper curve using stand variables and sample tree measurements

The aim of the study was to develop methods for estimating the taper curves for trees tallied in a forest inventory. The average stem form in a stand was described by the principal components of the stand effects in the stem dimensions measured in the polar coordinate system. Measurements of diameter at breast height, diameter at a height of 6 meters, and height taken from trees on the sample tree plots were used for determining the first four principal components. Regression models were derived to predict the principal components from the site and growing stock variables. These models were used to estimate the taper curves of the tallied trees. Use of the principal components estimated by the regression models gave less reliable results than use of the principal component estimates based on measurement of the height of one randomly chosen tree on the sample plot. The best result was found with combined use of the principal component estimates and one height measurement per sample plot.     

Long-term growth response of black spruce advance regeneration (layers), natural seedlings and planted seedlings to scarification: 25th year update

Careful logging around advance growth and tree planting following site preparation or not (fill planting) have been widely used to regenerate black spruce (Picea mariana) stands in the boreal forest of Canada. An experiment was established in 1990 to compare these regeneration modes and natural seeding over a 25-year period following two types of scarification (cone- or disk-trenching) that were applied at two intensities (single- or double-pass). Without scarification, the three types of regeneration had slow height growth during the first 10 years (3.4–5.8?cm/year). Thereafter, planted seedlings (6.1–9.8?cm/year) and pre-established layers (5.8–8.5?cm/year) had 2–3 times higher growth than natural seedlings (2.6–3.1?cm/year). Scarification improved height growth of the three types of regeneration, but planted seedlings responded much earlier, and more strongly over the 25 years (+9.4?cm/year) than layers (+2.8?cm/year) and natural seedlings (+2.7?cm/year). A shift in the proportion of layers and natural seedlings was observed following treatment. Long-term monitoring revealed that double-pass scarification was beneficial to layer growth from years 15 to 20, while no positive effect was observed on natural or planted seedlings. Our results suggest that decades may be required for natural regeneration to respond to scarification in cold soils of the boreal forest.     

Altitudinal genetic variation in Pinus hartwegii Lindl. I: Height growth,shoot phenology,and frost damage in seedlings

The altitudinal pattern of genetic variation in Pinus hartwegii Lindl. populations was explored for seedling height growth, frost damage, grass-stage, and phenological stage of the terminal shoot. A provenance test was conducted with open-pollinated seed from 13 populations collected along an altitudinal transect (3000–3600 m) at the National Park Pico de Tancítaro, Michoacán, center-west Mexico. Height growth of seedlings in a nursery was assessed at seven and 18 months of age. Frost damage at −15 °C was evaluated in laboratory at 18 months of age; proportion of plants that had left grass-stage and stage of shoot development was assessed at the age of 22 months. Significant differences among provenances (P < 0.0001) were detected for all of the evaluated characters. The variation among populations was structured as a moderate altitudinal cline, with populations from lower altitudes showing larger height growth in seedlings, larger proportion of frost damages, fewer seedlings in grass-stage and more seedlings with developed shoot, whereas in populations from higher altitudes, seedlings exhibiting shorter plant height, lower percentages of frost damage, more seedlings with unbroken grass-stage, and fewer seedlings with advanced shoot development were displayed. Options for seed and seedling movement along the altitudinal gradient are discussed under the scope of reforestation, aiming at ecological restoration, conservation of forest genetic resources, and assisted migration considering global warming. We suggest delineation of two altitudinal seed zones (Zone I: 3000–3350 m; Zone II: 3350–3700 m).     

Partial cutting in mixedwood stands: Effects of treatment configuration and intensity on stand structure,regeneration, and tree mortality

In temperate and boreal mixedwood forests of eastern North America, partial disturbances such as insect outbreaks and gap dynamics result in the development of irregular forest structures. From a forest ecosystem management perspective, management of these forests should therefore include silvicultural regimes that incorporate medium- to high-retention harvesting. We present 12-year results of a field experiment undertaken to evaluate the effects of variable retention harvesting on stand structure, recruitment, and mortality. Treatments were gap harvesting (GAP), diameter-limit harvesting (DL), careful logging (CL), and careful logging followed by scarification (CL + SCAR), and an unharvested control. Although post-harvest basal area in the GAP treatment was significantly lower than that of controls, it maintained a diameter distribution profile and densities of balsam fir regeneration similar to those of pre-harvest conditions. Lower retention treatments (DL, CL, and CL + SCAR) tended to favor regeneration of pioneer, shade-intolerant species. Except for black spruce (for which mortality was highest in DL), stem mortality was similar among harvesting treatments. From an ecosystem management perspective, this study suggests that gap harvesting can maintain, in the short term, forest stand composition and structure similar to unharvested forests, and could be used where management objectives include the maintenance of late successional forest conditions.     

Variation in seed and seedling traits among natural populations of <Emphasis Type="Italic">Trigonobalanus doichangensis</Emphasis> (A. Camus) Forman (Fagaceae), a rare and endangered plant in southwest China

The extent of genetic variation in seed and seedling traits of Trigonobalanus doichangensis, a rare and endangered tree in southwest China, was evaluated at the population level. Seeds were collected from four natural populations in the south and southwest Yunnan province, China. Significant differences (P < 0.05) between populations were observed in seed length, seed weight and seedling morphological characters. The analyses revealed that none of the seed and seedling traits had significant correlations with the geo-climatic variables of the populations. Among seed and seedling traits, significant correlations (P < 0.05) were discovered among seed length, seed weight and height of 30-day-old seedlings. Significant correlation (r = 1.00, P < 0.01) occurred also between the height and root collar diameter of 4-year-old seedlings. With the exception of seed width and seed germination percentage, 51–96% of total variation in other seed and seedling related traits was attributed to population effect, as determined by the broad sense heritability. In conclusion, these observations on variation in seed and seedling traits should be a reference point, when considering seed collection of this species for ex situ conservation and species restoration.     

大老岭林场次生林更新方式对林分组成和林地肥力的影响分析

利用湖北宜昌大老岭林场次生林采伐迹地3种不同更新方式林分的调查数据,对不同 的更新方式的林分组从树种组成、林下植被和林木生长三个方面分析了林分组成;从林地水分 物理性质和林地化学性质分析了林地肥力状况,得出如下结论:1.不同更新方式的林分组成和 林地肥力有明显不同;2.次生林采伐迹地更新所形成的人工林表现出不稳定性。     

Variations in electrical impedance and phase angle among seedlings of Pinus densata and parental species in Pinus tabuliformis habitat environment

Electrical impedance (EI) and phase angle (PHI) parameters in AC impedance spectroscopy are important electrical parameters in the study of medical pathology. However, little is known about their appli...     

Effects of logging, liana tangles and pasture on seed fate of dry forest tree species in Central Brazil

We assessed seed fate of six tree species in a seasonally deciduous forest of Central Brazil. Seed germination, predation, removal and death caused by pathogens or dessication were followed in an undisturbed forest site, a logged forest site, and an active pasture. In both forest types we sowed seeds under patches of liana tangles (Low Forest habitat) and under patches of mature forest (High Forest habitat). Seeds were monitored weekly for up to 8 months. Overall, small-seeded species (Astronium fraxinifolium and Tabebuia impetiginosa) had high germination, although germination was lower in the pasture due to insect predation. The hard-coated seeds of Erythrina sp. had higher germination rates in the pasture. The large-seeded Cavanillesia arborea and Swartzia multijuga had high seed removal (ca. 90%) in the pasture and under High Forest, but only 23–34% under Low Forest in the logged site. Lower removal of large seeds in Low Forest suggests that this habitat conceals the seeds and constrains the movement of large mammals. Both species were favored in Low Forest, suggesting that caution should be used when managing lianas. When protected from predation, seeds with a soft coat and high water content, such as the seeds of Eugenia dysenterica and S. multijuga, died from desiccation in the pasture. Restoration efforts must take into consideration high mortality caused by desiccation or insect predation in abandoned pastures of dry forests.     

Growth and survival of Fagus sylvatica seedlings in relation to light intensity and soil water content

Previous investigations have shown different growth and root/shoot ratio increases of beech seedlings (Fagus sylvatica) with increased light intensity. In the present investigation both light intensity and soil water content were regulated on four levels in a factorial experiment. At the highest level of soil water content the seedling growth increased linearly with light intensity while the root/shoot ratio decreased with light intensity. At low levels of soil water content both the growth and root/shoot ratio slightly increased with increased light. The soil water content was also affected by the light intensity indicating that the soil water content may have caused unobserved effects in responding to increased light in previous investigations. It is concluded that both light intensity and soil water content should be quantified or manipulated even if only the effect of one of the two growth factors are investigated.     

From seedlings to trees: Using ontogenetic models of growth and survivorship to assess long-term (>100 years) dynamics of a neotropical dry forest

Long-term tree and seedling growth and survivorship data from permanent sample plots established in a neotropical dry forest in Jamaica from 1998 to 2008 were used to (1) model growth (periodic annual increment) and survivorship dynamics, (2) cluster structural and functional types, and (3) estimate the age of selected tropical dry forest tree species. A statistical comparison of parameter estimates derived from a generalized linear model (GLM) of each species to a reference species was used to group individuals based on size (DBH and height), and demographic dynamics (periodic annual increment and survivorship). We identified two groups of species based on structural types (canopy and sub-canopy species), three groups of species based on periodic annual increment (fast, intermediate, and slow growing) and four groups of species based on the probability of survivorship of seedlings and trees (very low probability of seedling survivorship but high tree survivorship (two groups); high survivorship throughout the DBH classes; very low survivorship, regardless of stem size). The composition of the groups was mixed, and included individuals of both structural types, and with different periodic annual increment and survival probabilities. The dichotomy of guilds found in tropical rainforests (pioneer and climax species) was not found in this forest. Individual and group GLMs incorporating empirical relationships between periodic annual increment and survivorship, across a spectrum of ontogenies and DBH’s, were also generated. The periodic annual increment models were then used to estimate the time taken by a newly germinated seedling to reach the largest recorded DBH. The fastest growing species was the hemi-cryptophyte Clusia flava which was estimated to take 74 years to reach its maximum recorded size (12.1 cm DBH), whereas the slowest growing species, Ziziphus sarcomphalus, was estimated to take 399 years to reach its maximum size (24.4 cm DBH). These dry forest trees were estimated to reach their maximum size (which was one-half or one-third of the largest DBH recorded for tropical rainforests) in a time similar to tropical rainforest trees. Some of the tree species are ubiquitous to other neotropical dry forests; therefore, our equations for periodic annual increment and survivorship can be applied elsewhere in the region.