Recruitment of ponderosa pine seedlings in the Cascade Range

Abiotic stresses on seedling regeneration in xeric ecosystems are great, hence recruitment processes can be facilitated by stand factors that ameliorate the germinant-scale microenvironment. An experiment was conducted on the eastern slope of the Cascade Range to test the effects of shrub cover, simulated seed caching, and substrate on the recruitment of Pacific ponderosa pine (Pinus ponderosa var. ponderosa Dougl. ex Laws.) seedlings. Failure rates of seeds sowed in exclosures were large, with less than 30% emerging as germinants in the spring following fall sowing. Simulated seed caching improved emergence rates by more than sevenfold and was responsible for 88% of all spring germinants. Emergence rates were lowest from uncached seeds on litter. Just 16% of the crop survived the summer and fall to the month of November, or less than 5 months after emergence. Shrub cover did not affect emergence rates, but establishment rates were higher: seedlings beneath shrubs succumbed to desiccation at a slower rate than unshaded seedlings. By August there were 2.3 times more survivors at shrub-shaded sites than unshaded sites, and by the end of fall, when seedlings were considered established, more than 78% existed beneath shrubs. This study provides evidence that the natural recruitment of ponderosa pine seedlings is facilitated by the occurrence of the species’ common shrub associates.     

Large mulches and manual release enhance growth of ponderosa pine seedlings

Woody and herbaceous vegetation that captures scarce soil moisture often kills or stunts the growth of conifer seedlings in young plantations in the Sierra Nevada of California. Two methods for excluding this vegetation are to apply large (3-m×3-m), long-lasting (at least 5 years) mulches around the seedlings soon after planting, or to repeatedly grub seedlings of competing vegetation in study plots. Both techniques were tested and proved to be effective, significantly increasing ponderosa pine diameter and height relative to the control and to seedlings surrounded by small paper mulches. The effective treatments were large enough to enable conifer seedlings to capture site resources unimpeded by competing plants. Eight species of shrubs, seventeen forbs, four grasses, and one fern grew naturally on the study site.Results suggest that the forester now has two biologically effective means for controlling unwanted vegetation and for attaining rapid early pine growth in environments similar to the study area. Although more expensive, the large heavy polyester mulches ($9.90 per seedling over 5 years) give the forester an alternative to manual release ($2.05 per seedling over 5 years).     

Frost hardiness of nutrient-loaded two-year-old <Emphasis Type="Italic">Picea abies</Emphasis> seedlings in autumn and at the end of freezer storage

The effects of nutrient loading (NLOAD) on the frost hardening and dehardening of Picea abies (L.) Karst. seedlings were investigated under nursery conditions. Before NLOAD, second-year container seedlings were either short-day (SD) treated for 3 weeks in July or left for the natural photoperiod (CO). By mid-September, after 5 weeks of NLOAD, the fertilization of three foliar nutrient concentration levels (low = L-SD, medium = M-SD, and high = H-SD) for the SD-treated seedlings and one (medium = M-CO) for the CO-seedlings was completed. The NLOAD resulted in foliar nitrogen concentration 10.6, 16.1, 22.3, and 17.5 g kg⁻¹ for L-SD, M-SD, H-SD and M-CO seedlings, respectively. The NLOAD had no effects on the morphology or dry mass variables of the seedlings, while SD-treatment reduced the dry mass of shoots, but not that of roots. The frost hardiness (FH) of different batches of the seedlings was assessed by the visual scoring of damage in their needles, stems and buds after their controlled exposure to freezing during frost hardening and dehardening. The low nutrient concentration in the SD-treated seedlings (L-SD seedlings) resulted in poor FH, to an even lower extent than that of the M-CO seedlings. The NLOAD did not affect the dehardening of the seedlings at the end of the freezer storage in the following spring.     

Predicting survival of planted Douglas-fir and ponderosa pine seedlings on dry,low-elevation sites in southwestern Oregon

Four equations were developed for predicting the probability of Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco] and ponderosa pine (Pinus ponderosa Dougl. ex Laws.) survival for the first (0–1) and first to third (1–3) growing seasons after applying mulching, scalping, or artificial shading (shade cards) treatments in plantations in southwestern Oregon, U.S.A. Variables describing conifer size, levels of competing vegetation, presence of silvicultural treatments, site factors, and climate factors were collected from 13 sites ranging from 0 to 6 years after planting and examined as potential predictors of survival. Age, stem diameter, a competition index for shrubs, severity of growing season at time of treatment, average annual precipitation, aspect, and slope angle were predictors of Douglas-fir survival during 0–1 and 1–3 growing seasons after treatment; the presence of silvicultural treatments was also a predictor only during the first growing season after treatment. Age, aspect, and slope angle were predictors of ponderosa pine survival over both 0–1 and 1–3 growing seasons after treatment; height-diameter ratio, competition indices for herbs, shrubs, and hardwoods, silvicultural treatment, severity of growing season at time of treatment, and average annual precipitation were also predictors only during the first growing season after treatment; crown width was a predictor of survival only during 1–3 growing seasons after treatment. When significant in the models, predicted probability of survival increases with treatments, less severe weather conditions, diameter, crown width, age, and precipitation; probability decreases with increasing height-diameter ratio and competition indices for herbs, shrubs, and hardwoods.     

The effect of sub-zero temperatures in the light and dark on cold-hardened,dehardened and newly flushed white spruce (Picea glauca [Moench.] Voss) seedlings

Cold hardened, dehardened, and newly flushed foliage of one year old white spruce (Picea glauca [Moench.] Voss) seedlings were exposed to various sub-zero temperatures (--2 to --22.5°C) either in the dark or light. The freezing treatment had no significant effect on the variable fluorescence to maximal fluorescence ratio (F_v/F_m) of hardened seedlings, either in the light or dark. Also, no visible damage or increase in electrolyte leakage were evident in either the light or the dark treated seedlings. Both dehardened and newly flushed foliage were significantly affected by the freezing treatment, and light enhanced the effect. A decline in F_v/F_mincreased electrolyte leakage and visible damage were observed at warmer temperatures in newly flushed needles than in dehardened needles. Seedlings exposed to sub-zero treatments in the light also had lower F_v/F_m, increased electrolyte leakage and showed more visible damage than seedlings exposed to the same sub-zero treatments in the dark. The temperature where 50% of the needles were damaged (LT₅₀) as estimated from visible damage data was --10.8°C in the light and --12.1°C in the dark for dehardened, one year old needles. The LT₅₀in newly flushed needles was --4.8°C in the light and --6.2°C in the dark. Recovery of F_v/F_mvalues 3 days after freezing exposure was only evident in treatments where little visible damage was present. Both F_v/F_mand electrolyte leakage were strongly correlated with visible damage.     

电导法在植物抗寒研究中的应用

本文综述了电导法不同计量单位在植物抗寒研究中的应用。电解质渗出率、相对抗性和回归系数“ｂ”更为有用     

Influence of different nursery container media on rooting of Scots pine and silver birch seedlings after transplanting

Scots pine (Pinus sylvestris L.) and silver birch (Betula pendula Roth.) seedlings were grown in containers filled with growth media based on medium-textured sphagnum peat, coarse perlite and fine sand. The seedlings were then planted into fine and coarse sandy soils in 2.2 l pots, which were subjected to two water-content treatments (only one for birch). After the seedlings had grown five weeks in a greenhouse, rooting into the surrounding soil and shoot growth were measured. Addition of perlite and sand to peat medium slightly affected rooting; thus suggesting minor effects on seedling establishment. However, nitrogen concentration of the seedlings varied between growth media and correlated positively with rooting into the soil. The particle size and water content of the soil affected considerably rooting of the seedlings. Seedling height at the time of planting did not affect rooting or shoot growth. The fact that the fewest out-grown roots occurred in the dry fine sandy soil, suggests that dry soil together with high strength and resistance to root penetration reduce rooting and water uptake by container seedlings most and may thus cause water and nutrient stresses to seedlings after outplanting.     

Shoot and root sensitivity of containerized black spruce,white spruce and jack pine seedlings to late fall freezing

Damage to containerized forest seedlings due to freezing can occur in the fall or early winter in Canadian forest nurseries. The following spring, damage to shoots and impairment of growth is observed. The objectives of this experiment were to measure the impact of late fall low temperatures (0° to --30°C) on whole seedlings of the three most common species used for reforestation in Quebec: black spruce (BS), white spruce (WS) and jack pine (JP). Impacts of freezing temperatures on (i) whole seedling and apical bud mortality, (ii) shoot growth and root mortality, (iii) stem electrical resistance, (iv) shoot and root water relations, (v) concentrations of N, P, K, Ca, Mg, and total sugars in shoots were assessed. JP showed the highest rate of whole seedling mortality while WS showed the highest rate of apical bud mortality. JP was the most severely affected: destruction of the root system at low temperatures as well as a reduction of shoot growth and stem diameter and a decrease (more negative) in shoot and root water potential. WS showed a reduction of shoot growth despite no apparent damage to the root system at low temperatures. BS was not affected by temperatures as low as --30°C. Nutrient and sugar concentrations were not affected by low temperature treatments.     

Elevation difference of Ca2+ levels in young leaf cells of bromegrass and induced cold-tolerant enhancement under different controlled chilling temperatures

The changes of Ca2+ levels in young leaf cells of bromegrass under different controlled chilling temperatures were inves-tigated by an antimonite precipitation eytochemical method. The main results were as follows: under 25/20℃ (day/night) tempera-ture and 14 h photoperiod, electron-dense Ca2+ antimonite precipitates, indicators of Ca2+ localization, were mainly localized in the vacuoles, cell walls and intercellular spaces; few Ca2+ deposits were observed in the cytosol and nuclei. After a 3℃ chilling treatment for 3 h, many Ca2+ precipitates appeared in the cytosol and nuclei, indicating that Ca2+ influx had occurred in the cytosol and nuclei.When the 3℃ treatment was prolonged to 8 h, more Ca2+ deposits appeared in the nuclei and cytosol, but the amount of Ca2+ depos-its in both the cytosol and nuclei decreased markedly after a 24 h treatment and most Ca2+ deposits were returned to the vacuoles and intercellular spaces after an 8 d treatment. When bromegrass was exposed to 7℃ for 3 h, the Ca2+ distribution in the cells had no visible changes, compared with that of the 25/20℃ grown control plants. However, when the chilling treatment of 7℃ was pro-longed to 8 h, a Ca2+ influx occurred, where many Ca2+ deposits were observed in the nuclei and cytosol. More Ca2+ deposits ap-peared in the nuclei and cytosol after a 24 h treatment, but the amount of Ca2+ deposits in the cytosol and nuclei was reduced mark-edly after an 8 d treatment. After a 14 d treatment, the remaining low level of Ca2+ was recovered in both the cytosol and nuclei andthe Ca2+ deposits were again located in the vacuoles and the intercellular spaces. The dynamics of subcellular Ca2+ localization in young leaf cells of bromegrass during a 12℃ chilling treatment were similar to those of the 7℃ treatment. Besides, the results showed that the frost tolerance of bromegrass exposed to 3℃ for 8 d increased by 6℃, for 7℃ and 8 d by 4℃ and for 12℃ and 14 d by 3℃, compared with the controls. Finally, the relationship between different Ca2+ dynamics and induced frost tolerance was also explored.     

Photosynthesis,chilling acclimation and the response of antioxidant enzymes to chilling stress in mulberry seedlings

This study investigates the effects of cold-acclimation in conferring chilling tolerance in seedlings of the mulberry(Morus alba) variety ‘Qiuyu'. Changes in photosynthesis and antioxidant enzymes in chilling acclimatized(CA), and non-acclimatized(NA) seedlings were recorded during chilling stress(3 °C) and a recovery period(25 °C) each for 3 days. The results showed that CA plants had higher net photosynthetic rates(P_n), stomatal conductance(G_s), and maximum photochemical efficiency of photosystem Ⅱ(F_v/F_m) in response to chilling stress compared to NA. The seedlings maintained the same trends during the recovery stage. The responses of Q_A reduction degree (1-q_P) and prime electronic transfer rates(F_o) were lower in acclimatized than in non-acclimatized seedlings. Low-temperature acclimation and chilling stress also caused an increase in leaf proline and soluble sugar contents. Leaf malondialdehyde levels were significantly lower while ascorbate peroxidase(APX) activity was significantly higher in acclimatized seedlings, suggesting that elevated osmolytes and APX confer resistance to chilling temperatures. In this study on the response of mulberry seedlings to chilling stress, we also looked at the recovery process. The response to chilling determines whether mulberry leaves can survive under cold temperatures, while the recovery process determines whether photosynthesis can recover as soon as possible to avoid any secondary damage.     

我国邓恩桉抗寒性研究进展

邓恩桉具有生长快、材性好、耐寒的特点,成为我国桉树北移种植的优良树种。本文概述了国内有关邓恩桉抗寒性的研究动态,讨论了邓恩桉抗寒性与细胞膜系统、保护酶系统等方面的相关性,参考其他植物抗寒性研究方法与思路,对邓恩桉抗寒性的进一步研究提出了一些设想。     

Effects of length of seed chilling period and sowing date on family performance and genetic variances of Douglas-fir seedlings in the nursery

Seeds of four full-sibling Douglas-fir families (F) were moist chilled (C) for 14, 33, and 77 days and sown (S) March 29, April 26, and May 24 at two densities (D=111 and 200 seeds/m²), grown for 2 years in nursery beds and phenology and size traits recorded. The study was analyzed in two parts: part I evaluated seed treatment effects and their interactions with families; and part II investigated the effect of treatments on genetic variances, particularly among-family (_F ²) and within-plot ( ²) components and the intraclass correlation for families (t_{% MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGak0dh9WrFfpC0xh9vqqj-hEeeu0xXdbba9frFj0-OqFf% ea0dXdd9vqaq-JfrVkFHe9pgea0dXdar-Jb9hs0dXdbPYxe9vr0-vr% 0-vqpWqaaeaabaGaaiaacaqabeaadaqaaqaaaOqaaGqaa0Gaa8NKba% aa!3886!\[f\]}). In part I there were large and highly significant differences associated with C and S and among F for all traits. Early S combined with long C resulted in early emergence and gave large seedlings with little loss and damage. Many interactions between C and F, and S and F, were significant. Interactions involved rank changes for size but not for phenology traits, and were larger for C×F than for S×F. Seedling density affected seedling size but not phenology, did not interact with seed treatments, and interacted significantly but weakly with families. In part II, C and S, but not D, had significant effects on _F ², ², and t_{% MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGak0dh9WrFfpC0xh9vqqj-hEeeu0xXdbba9frFj0-OqFf% ea0dXdd9vqaq-JfrVkFHe9pgea0dXdar-Jb9hs0dXdbPYxe9vr0-vr% 0-vqpWqaaeaabaGaaiaacaqabeaadaqaaqaaaOqaaGqaa0Gaa8NKba% aa!3886!\[f\]}, but not in a predictable manner. Because of significant interactions, it is recommended that standardized seed treatments be used in family nursery tests. This should aid in keeping the results from these tests as repeatable as possible. Long chilling and sowing as early as practicable are recommended to minimize disease losses and winter damages and to provide good nursery stock.     

Guidelines for Managing Wildlife Habitats in Southwestern Ponderosa Pine Forests of the United States

IntroductionEcoledcalrelahonshipsanddePendenceofwildlifesPe-ciesonsouthwesternPOnderosapine(Pineponderosa)fOrestsarecloselyrelat6dtohabitatuse.Foraginghabits,seasOndfoodPreferences,anduseoftreesforfeedingarelawtydePendentuponthestrUctureandspahalar-rangme…     

Respiratory potential in sapwood of old versus young ponderosa pine trees in the Pacific Northwest

Our primary objective was to present and test a new technique for in vitro estimation of respiration of cores taken from old trees to determine respiratory trends in sapwood. Our secondary objective was to quantify effects of tree age and stem position on respiratory potential (rate of CO2 production of woody tissue under standardized laboratory conditions). We extracted cores from one to four vertical positions in boles of +200-, +50- and +15-year-old Pinus ponderosa Dougl. ex Laws. trees. Cores were divided into five segments corresponding to radial depths of inner bark; outer, middle and inner sapwood; and heartwood. Data suggested that core segment CO2 production was an indicator of its respiratory activity, and that potential artifacts caused by wounding and extraction were minimal. On a dry mass basis, respiratory potential of inner bark was 3-15 times greater than that of sapwood at all heights for all ages (P < 0.0001). Within sapwood at all heights and in all ages of trees, outer sapwood had a 30-60% higher respiratory potential than middle or inner sapwood (P < 0.005). Heartwood had only 2-10% of the respiratory potential of outer sapwood. For all ages of trees, sapwood rings produced in the same calendar year released over 50% more CO2 at treetops than at bases (P < 0.0001). When scaled to the whole-tree level on a sapwood volume basis, sapwood of younger trees had higher respiratory potential than sapwood of older trees. In contrast, the trend was reversed when using the outer-bark surface area of stems as a basis for comparing respiratory potential. The differences observed in respiratory potential calculated on a core dry mass, sapwood volume, or outer-bark surface area basis clearly demonstrate that the resulting trends within and among trees are determined by the way in which the data are expressed. Although these data are based on core segments rather than in vivo measurements, we conclude that the relative differences are probably valid even if the absolute differences are not.     

The role of germination microsite in the establishment of sugar pine and Jeffrey pine seedlings

Mature shrubs can provide microhabitats that are beneficial to tree seedling growth and development. Sugar pine trees (Pinus lambertiana) grow in a narrow zone on the eastern slope of the Carson Range in extreme western Nevada, whereas Jeffrey pine (Pinus jeffreyi) is the dominant tree species in the region, an area extensively disturbed by wild fire. This study compares seedling establishment of sugar pine and Jeffrey pine relative to mature shrubs. In the fall of 2002 (cohort 1) and 2003 (cohort 2), 13,600 seeds of both species were planted in wire mesh enclosures, at three sites, under a variety of microhabitat treatments: under shade and in the open, under two species of shrub cover, and with and without plant litter. Seedlings were monitored for survival through two growing seasons. Even though more sugar pine seedlings emerged, more Jeffrey pine seedlings survived, and Jeffrey pine was the more drought tolerant species, better suited for the xeric climate found in the Carson Range. Litter slightly hindered seedling emergence but had no effect on survival and there was no significant species × litter interaction. Supplemental water facilitated survival in all treatments with highest survival in shade treatments. Sugar pine seedlings showed a significant increase in survival over Jeffrey pine seedlings with the addition of water, particularly in open treatments and more of both species survived under manzanita shrubs with water. The highest seedling mortality occurred when shrub canopy was removed, and seedlings experienced the effect of full sun and competition for soil water. For either species, microhabitat is a significant factor in determining success or failure in rehabilitation efforts after disturbance.     

2013年滇西石斛寒害情况调查

报道2013年冬云南滇西7个县(市)人工栽培石斛寒害灾情和灾后恢复情况;调查发现,不同石斛种抗寒性有很大差异,尖刀唇石斛、报春石斛、铁皮石斛寒害率较低,抗寒性强,而晶帽石斛、兜唇石斛、齿瓣石斛寒害率较高,抗寒性明显较弱。     

低温胁迫对乐东拟单性木兰幼苗生理生化特性的影响

以盆栽乐东拟单性木兰幼苗为试材,研究其在人工模拟自然逐渐降温过程中细胞膜透性、膜脂过氧化（MDA）和细胞膜内源保护系统酶（SOD、POD、CAT）的变化规律。结果表明：低温胁迫下,细胞膜透性增大,丙二醛大量积累,膜脂过氧化增加,并随着温度的降低和时间的延长而加剧。过氧化物酶（POD）活性逐渐下降,超氧化物歧化酶（SOD）和过氧化氢酶（CAT）活性表现为先升后降。上述说明了乐东拟单性木兰通过调节内源保护酶活性来适应低温变化,从而提高耐寒能力。     

砧木对藤稔葡萄需冷量影响研究

连续2 a用3种模型分别对需冷量观察结果比较表明,犹他模型计算的需冷量较能客观地反映供试材料在扬州地区的萌芽表现,且不同砧木对藤稔葡萄需冷量的满足有重要影响。藤稔葡萄嫁接到高需冷量的砧木上其需冷量增高,嫁接到低需冷量的砧木上其需冷量降低。     

Response of antelope bitterbrush to repeated prescribed burning in Central Oregon ponderosa pine forests

Antelope bitterbrush is a dominant shrub in many interior ponderosa pine forests in the western United States. How it responds to prescribed fire is not well understood, yet is of considerable concern to wildlife and fire managers alike given its importance as a browse species and as a ladder fuel in these fire-prone forests. We quantified bitterbrush cover, density, and biomass in response to repeated burning in thinned ponderosa pine forests. Low- to moderate-intensity spring burning killed the majority of bitterbrush plants on replicate plots. Moderately rapid recovery of bitterbrush density and cover resulted from seedling recruitment plus limited basal sprouting. Repeated burning after 11 years impeded the recovery of the bitterbrush community. Post-fire seed germination following the repeated burns was 3–14-fold lower compared to the germination rate after the initial burns, while basal sprouting remained fairly minor. After 15 years, bitterbrush cover was 75–92% lower on repeated-burned compared to unburned plots. Only where localized tree mortality resulted in an open stand was bitterbrush recovery robust. By controlling bitterbrush abundance, repeated burning eliminated the potential for wildfire spread when simulated using a customized fire behavior model. The results suggest that repeated burning is a successful method to reduce the long-term fire risk imposed by bitterbrush as an understory ladder fuel in thinned pine stands. Balancing the need to limit fire risk yet provide adequate bitterbrush habitat for wildlife browse will likely require a mosaic pattern of burning at the landscape scale or a burning frequency well beyond 11 years to allow a bitterbrush seed crop to develop.