Factors influencing stump sprouting by pondcypress (Taxodium distichum var. nutans (Ait.) Sweet)

Sprouting can be an important mechanism of regeneration in harvested cypress (Taxodium sp.) wetlands; however, limited information exists on factors influencing sprouting. We examined the influence of harvesting practices, tree size, and site conditions on stump sprouting in eight pondcypress (Taxodium distichum var. nutans (Ait.) Sweet) wetlands in Florida, USA. Stumps were cut at three heights: 20 cm below high water level, at high water, and 40 cm above high water. Half of each site was harvested using a sawhead feller and the other half using shearhead. We monitored sprouting for 2 years post-harvest. Stump height affected first year sprouting, but the effect disappeared during year 2. Felling equipment did not affect sprouting; however, the shearhead caused greater stump damage. Sprouting declined with increasing parent tree size; percentage of stumps with sprouts after 2 years was 68% for trees 10–14 cm dbh and 28% for trees 20–24 cm dbh. Stump sprouting ranged among sites from 23 to 54% after 2 years. Results indicate that sprouting may be an important, but inadequate, form of regeneration. At sites with short hydroperiods, dense understories, and/or predominance of trees greater than 20 cm dbh, reduced sprouting may occur, and planting seedlings may be beneficial.     

南亚热带不同人工林对土壤理化性质的影响及土壤质量评价

目的 探讨相同立地条件下的不同人工林对土壤理化性质的影响,为实现人工林养分的精确调控和可持续经营提供科学依据。 方法 选取在柳州沙塘林场马尾松采伐迹地上同为1987年营造的木荷、米老排、蓝果树和杉木人工纯林为研究对象,以未造林灌草地为对照,分层（0～15、15～30、30～50、50～70、70～100 cm）测定14个土壤理化性质指标,结合KMO和Bartlett球形度检验,采用主成分分析法对土壤质量进行综合评价。 结果 同种林分内,随土层加深,土壤密度递增,孔隙度、土壤有机碳、全N、碱解N、有效P含量递减。不同林分间各土壤理化性质差异明显,5种林地的土壤pH值变幅为3.94～5.12;土壤有机碳、全N、碱解N、有效P含量以及化学计量特征C:N、C:P、N:P比值均表现为：阔叶林>针叶林>灌草地;杉木林土壤的全P含量在所有林分中最低,杉木林生长可能消耗更多的磷元素;与对照灌草地相比,营造这4种人工林后使土壤全K含量明显减少,速效K（除米老排林外）也有相似规律,这种变化规律暗示了人工林对K元素的消耗量大;木荷林和杉木林土壤的pH值、全K、速效K及阳离子交换量的含量明显低于其它林分和灌草地。土壤综合质量根据主成分得分依次为：米老排林 >蓝果树林 >木荷林 >灌草地 >杉木林。 结论 （1）人工阔叶林比针叶林能更有效地积累土壤有机碳、N和P等养分,并能明显地优化土壤密度和孔隙度,在今后的造林实践中应优先考虑阔叶林。（2）人工林营造33 a后,土壤全K含量明显地小于对照灌草地,且不同林分间具有差异,因此,在森林经营时应注重K元素调控管理。     

大兴安岭林区冻土与森林更新关系的探讨

本文探讨了大兴安岭林区与冻土与森林更新的关系，以及冻土更新森林的影响，并对大兴安岭林区如何进行采伐及造林的技术措施提出了见解，对大兴安岭林区恢复森林资源具有借鉴意义。     

次生阔叶林不同更新方式对林分组成及土壤肥力的影响

我国南方林区的采伐迹地大都采用人工造林方式更新 ,砍阔造针是营造杉木马尾松等速生丰产林的主要方法。随着大量采伐天然阔叶林 ,导致阔叶林面积锐减 ,原始阔叶林已极少 ,大部分阔叶林已被人工针叶林取代 ,而营造的人工林树种单一 ,针叶化明显 ,导致林分抗逆性差 ,林内野生动植物资源锐减 ,物种多样性降低 ,极易发生病虫害 ,并出现多氏经营导致林地退化 ,特别是杉木连栽造成的弊端已引起许多学者的极大关注4)～ 6 ) 。如何保护和发展阔叶树资源是当今林业面临的重大问题。本文根据作者1 6ａ的研究 ,探讨了次生阔叶林采伐迹地不同更新方式对…     

The North American long-term soil productivity experiment: Findings from the first decade of research

First decade findings on the impacts of organic matter removal and soil compaction are reported for the 26 oldest installations in the nation-wide network of long-term soil productivity sites. Complete removal of surface organic matter led to declines in soil C concentration to 20 cm depth and to reduced nutrient availability. The effect is attributed mainly to the loss of the forest floor. Soil C storage seemed undiminished, but could be explained by bulk density changes following disturbance and to decomposition inputs of organic C from roots remaining from the harvested forest. Biomass removal during harvesting had no influence on forest growth through 10 years. Soil compaction effects depended upon initial bulk density. Soils with densities greater than 1.4 Mg m⁻³ resisted compaction. Density recovery was slow, particularly on soils with frigid temperature regimes. Forest productivity response to soil compaction depended both on soil texture and the degree of understory competition. Production declined on compacted clay soils, increased on sands, and generally was unaffected if an understory was absent.     

毛竹生长与土壤环境

土壤是影响毛竹生长的重要因子,该文综述了土壤化学性质、物理性质及生物学性质对毛竹生长的影响,这对毛竹林地土壤管理、合理施肥具有一定意义.     

森林采伐方式对伐后迹地光照条件及更新质量的影响

本文应用野外观测方法,对森林采伐方式（皆伐、择伐、带状皆伐）对迹地光照条件和作业后天然更新质量进行了局部性研究。结果表明,更新树种不仅与种源有关,而且还与光照条件显著相关,即与森林采伐方式有关。     

Soil quality assessment across different stands in tropical moist deciduous forests of Nagaland,India

To analyze the relationship between the management of three forest stand plantations and soil quality in the Dimapur district of the Northeastern Himalayan region,India,three forest soil profiles,covered by different species stands,at three depths were tested for 13 physical and chemical variables.Only four of these variables(electric conductivity,bulk density exchangeable Mg and available P)were included in a minimum data set,after using a varimax rotation algorithm in a principal component analysis,and subsequently used to calculate a soil quality index(SQI).Results showed higher SQIs in the surface layers(0–20 cm depth)than in the deeper ones.Average weighed SQI varied significantly(P<0.05)through the three considered forest sites,with the lowest value at site FS3.These findings reveal that the approach used here is suitable for preliminary screening of the impact of a forestry species on soil,to aid in species selection and improve soil health for afforestation and reforestation projects.     

Natural regeneration of Pinus brutia Ten. in a recreational public forest in Zawita-Kurdistan region,Iraq

Zawita natural forest has recently has been subject to mass recreational activities during spring that have denuded large areas of the forest.It was thus essential to assess regeneration before designing optimizing strategies.To this end,we studied the overstory canopy and microhabitat conditions for recruitment of Pinus brutia Ten in 10 plots(20×25 m)on the southern aspects where the Zawita natural forest is still present.In total,1540 regenerating P.brutia were recorded,854 seedlings,597 saplings,and 89 trees.Seedlings and saplings were more frequent beyond the canopy than under the canopy of the parent trees.Regeneration requirements differed between seedlings and saplings.The probability of the occurrence of seedlings was negatively correlated with increasing litter depth and increasing soil compaction.The density of saplings only showed a positive significant correlation with increasing slope.The nearest neighbor index showed a trend toward a positive spatial association between understory shrubs with their neighboring seedlings at a mean distance of 1.6 m.Overall,the study highlighted the requirements for seedling regeneration as a relatively open canopy cover,a light understory litter layer,and noncompacted soils.These results are a step towards designing effective management and restoration programs.     

半边莲繁殖及采收技术

本文介绍了半边莲(LobeliaSchinensis)的生物特性、生长习性以及繁育采收技术,包括选地整地方法、种子繁殖方法、扦插繁殖方法、分株繁殖方法、组织培养繁殖方法、田间管理技术以及采收加工技术等。     

Initial responses of woody vegetation, water quality, and soils to harvesting intensity in a Texas bottomland hardwood ecosystem

Sustainable management of bottomland hardwood forest ecosystems requires a knowledge of responses to management impacts, including timber harvesting. The effects of clearcutting and partial cutting on woody vegetation regeneration dynamics, surface and groundwater quality, soil physical properties, and soil respiration were tested in a bottomland hardwood ecosystem in southeastern Texas, USA, through comparison with non-cut control areas. Overstory removal only slightly affected composition of woody vegetation regeneration 1 year after harvesting compared with pre-harvest composition. Initial composition in both cutting treatments appeared to be the strongest determinant of post-harvest composition, at least for the first year after harvesting. There were few significant differences in groundwater properties when harvesting treatments were compared with control areas during a 17-month period following harvest. Turbidity, temperature, electrical conductivity, dissolved O₂, NH₄-N, NO₃-N, and PO₄-P of streamwater did not vary significantly among treatments. Slight decreases in total and macroporosity were observed in association with higher bulk densities at 0–5 cm depth in the clearcut and partial cut treatments. Saturated hydraulic conductivity values did not decline significantly with treatment intensity. No significant differences among treatments in measured soil physical properties were observed at 5–10 cm depth. Although in situ soil respiration increased with harvest intensity, treatment had no significant effect on mineral soil respiration. In summary, most variables showed only slight response to harvesting, thereby indicating that harvesting practices can be conducted with minimal initial impacts on measured response variables.     

Effect of corylus clusters on the physicochemical properties of soil

IntroductionThe corylus is one of the important shrub speciesin the Northeast of China, which has a high economic value as oil material or food. The corylus isusually the dominant shrub species in some foresttypes and plays an important part in ameliorating thephysical and chemical properties of the soil in that itsroots are well developed in comparison with otherkinds of shrub species. Sometimes the soil under thecorylus clusters is applied to the nurseries to improvesoil f6rtility (Zhou 198…     

广西英罗港不同红树植物群落土壤理化性质与酶活性的研究

本文对广西英罗港自然保护区不同红树植物群落土壤主要性质进行了较系统的研究。结果表明 ,英罗港不同红树植物群落土壤理化性质和酶活性均存在明显差异 ,土壤粘粒粉粒含量和有机质、全氮、水解氮、全磷、速效磷及盐分含量为 :木榄群落 >红海榄群落 >秋茄群落 >桐花树群落 >白骨群落 ;土壤蔗糖酶、蛋白酶、脲酶、酸性磷酸酶 4种水解酶和过氧化氢酶的活性大小顺序为红海榄群落 >木榄群落 >秋茄群落 >桐花树群落 >白骨壤群落 ,多酚氧化酶则与此相反 ;土壤养分含量和土壤水解酶以及多酚氧化酶活性均随剖面深度而降低 ,过氧化氢酶则呈相反趋势。英罗港红树植物群落土壤酶活性与土壤肥力因素密切相关 ,各土壤酶活性之间也存在不同程度的相关性。因此 ,土壤酶活性可以作为该土壤肥力的指标之一。