Heartwood, sapwood and bark content of teak trees grown in Karnataka, India

We evaluated heartwood, sapwood and bark content in teak trees. A total of 27 sample plots were laid out in teak plantations raised by State Forest Department in Kamataka covering different age groups （11-36 years）, density （516-2061 trees/ha） and sites. From these planta- tions, a total of 130 trees were felled for estimating the yield and bark content in relation to diameter at breast height （DBH）, age and density. Bark content ranged from 22.2%-54.3%. Heartwood and sapwood con- tent were analyzed by sampling five trees each from two different planta- tions, one 30 years old at 553 trees.ha-1 and the other 32 years old at 911 trees.ha-1. The highest heartwood proportion of stem wood volume （over-bark） was 56.3% and the lowest was 37.1%.

Growth and mineral nutrient analysis of teak (Tectona grandis) grown on acidic soils in south China

Teak （Tectona grandis L.f.） is widely planted in the world due to its high market demand, economic, ecological and social value. Its plantations have mostly been established and expanded into sites that are acidic to severely acidic in southern China. But, there are no available and specific evidence-based nutrient management techniques. To better recognize and understand the relationship between teak tree growth and nutrient content in the foliage and soil and establish nutrient norms are critical to optimally manage these young plantations. We studied the foliar nutrient and soil chemistry in 19 representative teak plantations aged 5-8 years. Regression analysis indicated that the mean annual increment of teak volume was linearly and positively correlated with foliar N, Ca, Fe and B concentrations, with soil base saturation percentage, available P and Zn concentrations, and negatively correlated with soil Al concentration. Only if the Ca and Mg contents in soil were enhanced, could the increase in soil base saturation percentage benefit teak growth. A revised classification of low-and high-yielding stands was established by using a sorting method of principal components over 6 foliar macro and 8 micro elements in a Diagnosis and Recommendation Integrated System （DRIS）. Specific DRIS norms for teak plantations in acid soils were derived. The nutrient balance of N, P, K Ca, Mg, Zn, B with Fe or A1, Ca with Mg, and Fe with AI provided a key to promote the growth of teak in acid soils. Meanwhile, soil Zn was also found as a primary trace element that affected teak growth in this study.

Genetic and morphological variation in natural teak(Tectona grandis) populations of the Western Ghats in Southern India

Teak （Tectona grandis L.f.） is a popular hardwood species native to South and South-East Asia. The possible association of ampli- fied fragment length polymorphism （AFLP） marker with morphological variables of eleven important characters viz. girth at breast height （GBH）, height of tree, bole height, branch knots, presence of fluting, spiral stem, leaf hair, leaf length/breadth ratio, branching pattern, bark colour and petiole shape for nine natural populations comprising 180 genotypes of teak （9 populations x 20 trees）. The phenogram constructed using Euclidean distances for the eleven morphological characters showed that the populations were not grouped according to their geographical origin. The Mantel＇s test for pairwise correlation between Euclidean distances of different morphological variables and genetic distances from AFLP data revealed that only petiole character （r =0.269; p =0.046） and height of tree （r =0,200; p =0.001） were significantly correlated with that of AFLP data matrix. The nine populations in this study covered a geographic area of about 1000 km stretch along the Western Ghat of South India. A test of correlation between genetic and geographic distance matrices revealed a significant positive correlation （r =0.475; p =0.009）. The lack of perfect congruence between morphological and molecular data except for geo-graphic distance, tree height and petiole character suggested that the morphological system might be useful for the morphotypes management but not appropriate to study the genetic structure of the teak populations.

Effect of auxins on axillary and de novo shoot regeneration from in vitro shoot cultures derived from forced epicormic buds of teak (Tectona grandis L.)

Akram MUHAMMAD, Aftab FAHEEM＊Abstract In this presentation, we report on de novo and axillary shoot regeneration and rooting of shoots maintained over a long term, from cultures of Tectona grandis L. Shoot-tips of teak shoots forced from epicormic buds were used as the starting material for axenie shoot-culture establishment. Long term maintenance of such axenic shoot cultures was carried out by regular sub-culturing on MS media supplemented with N6-benzyleadenine （BA, 8.8 μmol·L^-1） and indole-3-butyric acid （IBA, 2 μmol·L ^1） for 24 months. Vigorously growing shoot tips （2-3 cm long） were inoculated on the MS basal medium supplemented with different concentrations （0, 1, 2, 4, 6, 8 or 10 p.mol-L-~） of either [BA or a-naphthaleneacetic acid （NAA） for rooting. Axillary and de novo shoots were de- veloped from axillary and cut basal ends of shoots, respectively. Shoots growing on auxins were further sub-cultured （every 15 days） and maintained for 45 days. The greatest number of de novo （5.06） as well as axillary shoots （2.85） was observed on the MS medium supplemented with 10 μmol-L^-1 NAA or 8 μmol·L^-1 IBA, respectively, after 45 days. The combinations of both IBA （μmol·L^-1） ＋ NAA （μmol·L^-1） were tested at different concentrations （4 ＋ 4, 6 ＋ 6, 8 ＋ 8） supplemented to a half strength MS basal medium with 0.1% activated charcoal for rooting of decapitated and non-decapitated de novo and axillary shoots. Rooting from non-decapitated de novo shoots was highest （93.33%） with a mean number of roots of 4.61 on this medium, supplemented with 6 μmol·L^-1 IBA ＋ 6 gmol.L l NAA, after 36 days of initial culture. Individual auxin, however, was not effective for root induction. Rooted shoots were acclimatized in a green house and after four weeks plantlets were transferred to the field.

Morphological parameters and genetic diversity of progenies from seed production areas and unimproved stands of teak(Tectona grandis L.f.)in India

We compared morphological and genetic attributes of prog- eny obtained from three seed production areas （SPAs） and three corre- sponding unimproved stands （UIS） of teak （Tectona grandis L.f） at three broad teak growing regions in the state of Karnataka, India. In general, seed morphological parameters such as seed weight, seed size and seed emptiness were significantly superior in SPAs compared to UISs. Seed germination percentage was also higher in seeds from SPAs. Seedling performance measured at two monthly intervals for six months was ob- served to be superior in SPAs at two of the three regions compared. Although the genetic diversity of progeny of SPAs was lower than UIS at all regions, the values were moderately high. Germination percent was positively correlated with fruit weight and kernel weight per seed, while diversity indices were negatively correlated with fruit weight, fruit di- ameter and kernel weight per seed. SPAs proved important as a source of moderately improved planting material with no severe threat to the ge- netic diversity of future plantations.

The effects of teak monoculture on forest soils: a case study in Bangladesh

Teak plantations date back to 1871 in Bangladesh. This study was designed to assess how teak monoculture has impacted the soil properties in Bangladesh. Multiple linear regression and correlation matrices were estimated to evaluate these impacts. The means of soil physicochemical properties were compared across various attributes of the plantations. Older plantations accumulated more organic carbon in the soils than the younger plantations. Excessive removal of litter from the forest floor resulted in reduced levels of N, P, K, and other nutrients in the soils. Since bulk density was continuously decreasing deeper into the soil, the penetration of mineral nutrients into the soil was low. Furthermore, moisture content in the topsoil was significantly lower than that in the bottom layers due to the exposed and dry condition of the forest floor under teak plantations. For improving depleted teak plantation soils, teak could be planted with other tree species rather than just in monocultures. In addition, the forest floor could be enriched with leguminous herbs and shrubs to improve soil health in these plantations.

Development of heartwood,sapwood,bark,pith and specific gravity of teak(Tectona grandis)in fast-growing plantations in Costa Rica

To elucidate the development of heartwood,bark,sapwood,pith and specific gravity of wood in fastgrowing teak(Tectona grandis)plantations in Costa Rica,we sampled three trees in each of 55 plantations and modelled each variable with age,site and different tree heights.Age and stand density of plantations were significant correlated with stem diameter at breast height and total height of the tree.Formation of heartwood was initiated at the age of 4-year-old and increased in direct proportion with age.The age of plantation had a significant relationship with stem diameter at breast height,heartwood percentage,sapwood thickness,sapwood percentage,percentage of bark,pith diameter and percentage,and specify gravity.The model for these tree parameters was model with these parameters as dependent variable and in relation to age as independent variable.

Effects of Silvicultural Alternatives on Model-Based Financial Evaluation of Teak (<i>Tectona grandis</i>L.) Farm Forestry Management for Small-Scale Farmers in Northeast Thailand

Teak (Tectona grandis L.) plantation management is said to be profitable, but small-scale farmers with teak plantations need to find appropriate and effective choices for plantation management because of their small plots. There have been few studies on how combinations of site quality, rotation and plant spacing affect financial evaluations of teak plantation management quantitatively. In this study, we introduced the yield table for teak plantations in Northeast Thailand, and investigated the effects of site quality with rotation (15-year and 20-year) and spacing (2 m × 4 m and 4 m × 4 m) on the financial evaluation of teak plantation management using discounted cash flow analysis. The equivalent annual incomes (EAI) and benefit/cost ratios (BCR) were negative and <1, respectively, at site indexes (SI) of 14 and 18, but increased ~2 - 3 times as SI rose from 22 (site of medium quality) to 26 and 26 to 30. The 20-year rotation was generally preferable to the 15-year one, especially at SI 22. At SI 30, 2 m × 4 m was more profitable than 4 m × 4 m for both rotations, but at SI 22, 20-year rotation with 4 m × 4 m was the most profitable, followed by 20-year with 2 m × 4 m.

Erratum to “Effects of Silvicultural Alternatives on Model-Based Financial Evaluation of Teak (Tectona grandis L.) Farm Forestry Management for Small-Scale Farmers in Northeast Thailand” [Open Journal of Forestry, 4 (2014) 558-569]

The original online version of this article (Noda, I. et al. (2014). Effects of Silvicultural Alternatives on Model-Based Financial Evaluation of Teak (Tectona grandis L.) Farm Forestry Management for Small-Scale Farmers in Northeast Thailand. Open Journal of Forestry, 4, 558-569. http://dx.doi.org/10.4236/ojf.2014.45060) was published in October. The author wishes to correct Table 5.

Effect of Climatic Factors on the Radial Growth of Teak （Tectona grandis L.F.） in Parakou and Tchaourou Districts in Northern Benin

Climatic factor＇s effect was studied on the radial growth of teak （Tectona grandis L.F.） by using the stem analysis of 36 trees distributed in 6 plantations in Parakou and Tchaourou districts in northern Benin. The results showed that the plantations of Parakou were in general more productive than those of Tchaourou. The annual average growth was estimated in the first five years at 0.86 cm/year for Parakou and 0.76 cm/year at Tchaourou. The analysis of the radial growth showed that a significant percentage of the variance was allotted to the growth model. It follows that a big part of the ring width was predetermined before the intervention of the other factors, in particular the climatic conditions. The percentage of the variance related to the climatic conditions was thus more reduced for the plantations of Tchaourou than those of Parakou. The radial growth was influenced by the conditions of humidity （evapotranspiration, humidity and rain） of February to May on the one hand and those from August to October on the other hand.

Simple Protocol for the Micropropagation of Teak(Tectona grandis Linn.)in Semi-Solid and Liquid Media in RITA^(█) Bioreactors and ex Vitro Rooting

In Latin America the forestry of exotic species such as teak has been increasing in recent decades, due to their advantages in wood quality, rapid growth;and the relative ease of producing clones and their multiplication with respect to native species. Therefore, there is great interest in developing larger-scale propagation strategies that reduce costs and intensive manual labor. Culture in liquid media with temporary immersion and the semi-automation of the system has raised expectations for large-scale micropropagation. We report a protocol for teak, which reuses the primary explants in several culture cycles in semi-solid medium to produce nodal explants for the multiplication phase in temporary immersion bioreactors (RITA&reg;). The control of factors such as cytokinin concentration, explants density, immersion frequencies and culture duration was analyzed. The number of shoots increased with 0.5 mg&middot;l-1 of BA (6-Benzyladenine), alone or in combination with 0.5 mg&middot;l-1 of Kinetin, with 2 daily immersions of 1 minute each;however, these shoots showed a high degree of hyperhydricity. When 0.05 mg&middot;l-1 of BA was used with 1 immersion of 1 minute every 2 days, the hyperhydricity decreased. Although the number of shoots was lower, they showed good length to be used during multiplication and rooting ex vitro. Our results suggest that teak micropropagation can be simplified in two phases in vitro, the establishment and multiplication;followed by rooting ex vitro and acclimatization. This would imply a reduction in production costs, since most of the multiplication would take place in RITA&reg;containers.

Genetic transformation of cry1A(b) gene into teak

Teak (Tectona grandis) provides one of the most highly sought after timber in the world and is a widely recommended species for reforestation. As such teak is widely planted in Malaysia. Though no serious outbreaks have been recorded for teak in Malaysia, but insect attack remains the most important threat to the timber industry. Thus, in efforts to overcome the problem, an integrated pest management system needs to be developed. Spraying of commercial Bt has been a common practice in addressing minor outbreaks. However, one of the main limitations of the spraying technique is poor coverage, especially on plant surfaces. Poor coverage, however, could be overcome by planting insect resistant trees. In addition, the approach of using genetic engineering in addressing the above problem proves to be possible with the advancement made in genetic transformation of trees especially in the last decade. This, together with improved knowledge on gene function following improved DNA recombinant techniques promises the major advancement in pest management of forest species. This report demonstrates the possibility of transferring foreign gene into teak cells. In this study, nodal segments of teak were subjected to particle bombardment. Nodal segments bombarded with gold particles coated with plasmid DNA carrying hygromycin phosphotransferase (hpt), β glucuronidase (gus) and cry1A(b) genes were then transferred onto medium for shoot development. The shoots were than transferred onto the same medium supplemented with 10mg/L hygromycin for selection. Selection was repeated several times with six week subculture intervals on the same Hm containing media. The presence of the transgenes in the Hmr plants was confirmed using PCR.

配比施肥对柚木早期生长及叶片养分含量的影响

【目的】探究不同肥料配比对柚木幼树生长及叶片养分和叶绿素含量的影响,为确定适宜的柚木施肥方案提供参考。【方法】以柚木幼林为研究对象,采用随机区组试验设计,设置5种配比施肥处理(0.25 kg/株氮磷钾复合肥+0.25 kg/株钙镁磷肥(T1)、0.25 kg/株钙镁磷肥+2.50 kg/株有机肥(T2)、0.25 kg/株氮磷钾复合肥+0.25 kg/株氧化镁+10.00 g/株硼肥(T3)、0.25 kg/株氮磷钾复合肥(T4)、0.25 kg/株氮磷钾复合肥+1.50 kg/株钙镁磷肥(T5)),以不施肥处理为对照(CK),分析不同施肥处理柚木幼树生长量及叶片养分和叶绿素含量的变化,运用隶属函数法对不同处理的施肥效应进行综合评价。【结果】①与CK相比,不同配比施肥处理均可以提高柚木的树高、胸径和材积平均增量,其中均以T5处理柚木的树高、胸径和材积平均增量最高,较CK分别提高了44.81%,82.02%和108.72%。②与CK相比,不同配比施肥处理柚木叶片全N、全K、交换性Ca含量均无显著变化,但叶片全P、交换性Mg含量显著提升,叶片N/P值显著降低。③与CK相比,不同配比施肥处理均可以提高柚木叶片的叶绿素a、叶绿素b和总叶绿素含量,降低叶绿素a/b值,其中T5处理叶片叶绿素a和总叶绿素含量与CK差异达显著水平。④隶属函数法评价结果显示,5种配比施肥处理的肥料效应由大到小排序为T5>T3>T2>T1>T4。【结论】5种配比施肥处理均可促进柚木叶片对钙、镁、磷营养元素的吸收与累积,加快叶绿素的合成,促进柚木幼树生长量的增加,其中0.25 kg/株氮磷钾复合肥+1.5 kg/株钙镁磷肥为最佳肥料组合。

琼西南5年生柚木无性系生长性状遗传变异分析

【目的】研究柚木无性系生长性状遗传变异和年度相关性,早期选育速生优良无性系。【方法】采用6株单行小区、6次重复的完全随机区组设计,对海南省乐东县15个柚木无性系大田测定林造林后1~5 a的保存率和生长指标进行方差分析、邓肯多重比较、遗传参数估算和相关性分析,并通过主成分分析,计算综合得分,在此基础上选出速生优良无性系。【结果】造林后5 a,柚木无性系间保存率差异显著(P<0.05),无性系保存率为61.50%~83.33%,平均保存率为73.26%,无性系7509的保存率最高,为83.33%;造林后5 a,柚木无性系间树高、胸径和单株材积均呈极显著差异(P<0.001),其平均值分别为5.29 m、7.29 cm和16.34 dm^(3),以无性系74_12最高,其树高、胸径和单株材积的平均值分别为6.12 m、9.11 cm和27.45 dm^(3);造林后1~5 a柚木无性系的树高、胸径和单株材积的变异系数分别为15.02%~19.35%、13.65%~20.14%和31.04%~41.01%,重复力分别为0.697~0.858、0.819~0.847、0.751~0.854;柚木无性系生长性状的年度相关性呈显著水平(P<0.05)。【结论】柚木无性系生长性状间存在稳定的遗传变异,有较高的遗传改良潜力;为琼西南地区筛选出柚木速生无性系74_12、7114和7509,入选无性系的树高、胸径、单株材积和保存率的平均值分别为35.77 m、8.07 cm、21.27 dm和74.61%,分别比对照提高了19.21%、23.60%、75.60%和3.40%。选择后树高、胸径和单株材积的现实增益为9.07%、10.69%和30.20%,遗传增益为7.71%、9.09%和25.67%,入选的3个无性系可作为后续柚木育种和推广的优良材料。

柚木种源/家系种子表型变异及其与环境因子的相关性

通过研究柚木(Tectona grandis L.F.)不同种源、家系种子的表型性状,揭示柚木种子遗传变异规律及其对环境因子变化的响应机制,促进柚木种质资源保护和遗传改良。以广东、广西、海南和云南4个省(区)13个种源81个柚木家系种子为材料,测定种子长度、宽度、长宽比、长宽积和百粒重5个性状。结果显示:(1)柚木种子的5个表型性状在种源及家系间均存在极显著差异(P<0.01),不同家系各性状变异系数为10.27%~23.88%,不同种源各性状变异系数为4.21%~20.32%。(2)各表型性状间呈极显著相关关系,不同环境因子对种子性状的影响程度不同,经纬度、海拔、年降水量是影响柚木种子性状的主要因子,其次是年均温,年均相对湿度的影响相对较小。不同的种子性状对环境因子变化的响应也不相同,种长、种宽和长宽积对年降水量的响应最为敏感,而长宽比和百粒重则对纬度的响应最为敏感。(3)聚类分析将13个种源分为3类。柚木种子在种源和家系间均存在丰富的表型变异,种子性状受母本遗传和地理气候因子等多因素影响。研究结果为柚木多样性种质资源保护和利用提供理论基础和科学依据。

Establishment of Embryogenic Cultures and Efficient Plant Regeneration System from Explants of Forced Softwood Shoots of Teak (Tectona grandis L.)

The present study highlights an efficient plant regeneration system in teak(Tectona grandis L.) using forced softwood shoots as an initial plant material. Forced softwood shoots of teak were cut to prepare shoot tip, nodal and internodal explants and cultured on Murashige and Skoog(MS) medium + NAA(1, 3, 6, 10, and 15 μmol · L-1) or TDZ(0.001, 0.01, 0.1, 1, 4, 8, 10, 12 μmol · L-1) for callus induction. Such calluses were further grown on the same levels of TDZ or 0.4, 1, 4, 8, 10 μmol · L-1 BA + 1 μmol · L-1 IBA or GA3. Callus induction was the highest with4.55 cm3 callus volume and 5.75 g dry weight at 0.1 μmol · L-1 TDZ from shoot tips after 35 days. Embryogenic calluses were then shifted to 6, 8 or12 μmol · L-1 TDZ + 2 μmol · L-1 BA or IBA along with 5 mmol · L-1 ascorbic acid(AA) for shoot regeneration from embryogenic cultures. The highest embryogenesis(100%) with 36.4 globular and 5.5 heart-shaped embryo-like structures was obtained at 8 μmol · L-1 TDZ + 2 μmol · L-1 BA after 63 days. Such cultures when further maintained on the same medium up to 150 days resulted in 100% shoot regeneration with 16.4 mean shoots.Shoots were elongated up to 50 mm on agar medium + 8 μmol · L-1 BA + 1 μmol · L-1 GA3. An efficient rooting response(70%) was achieved having4.50 mean number and 49.10 mm root length at 8 μmol · L-1 IBA + 8 μmol · L-1 NAA + 0.1% activated charcoal after 36 days. Rooted shoots were acclimatized in glasshouse, achieving 56.6% plantlet survival.

11年生柚木无性系遗传变异与优良无性系选择

以从每个柚木(Tectona grandis L.f.)种源试验林、家系试验林的种源以及国内早期引种的人工林(片林)中各选出的3株以上最优单株,经组培繁殖的23个无性系为研究对象,以海南尖峰岭无性系种子园中选出1株优树采集种子培育的实生苗为对照,所有苗木以1年生营养袋苗经修剪后的裸根截干造林;以云南省普洱市景谷傣族彝族自治县益智乡的威远江干热河谷为试验地,采用完全随机区组设计,6株单行小区,6次重复;穴状整地,2010年6月9—10日种植,株行距2.5 m×4.0 m,种植后3 a抚育8次、追肥4次;11年生时,测定无性系的树高、胸径、冠幅、树干通直度,计算单株材积;采用统计分析软件(Genstat)以单株观测值为统计单元进行生长性状和形质性状方差分析、邓肯多重比较和主成分分析,采用ASReml-R软件计算表型相关性、遗传相关性等;依据各无性系主成分得分,按20%的入选率综合遴选优良无性系。结果表明:11年生6个性状柚木无性系间差异达极显著,其中,7029无性系的树高、胸径、单株材积、冠幅与对照差异显著,分别提高了9.21%、18.73%、45.36%、16.38%,分别是试验林平均值的1.22、1.32、1.93、1.34倍。不同性状表型变异系数范围为0~69.39%,单株材积变异系数最大(达34.26%~69.39%);无性系各性状主要受遗传影响,重复力较高(达0.8885~0.9419)。柚木无性系树高、胸径、单株材积、冠幅,相互间的表型相关和遗传相关达极显著正相关;无性系树干通直度,与树高、胸径、单株材积、冠幅的遗传相关显著,表型相关不显著。以各无性系在贡献率95.45%的第一主分得分值大小和20%的入选率,综合选出4个优良无性系(7029、7531、Z408、8301),树高、胸径、单株材积、树干通直度、冠幅的遗传增益,分别为12.82%、17.24%、45.58%、4.96%、17.50%;其中最优的7029无性系遗传增益极显著,分别达到20.35%、28.74%、82.53%、6.02%、31.82%。

珍贵柚木及其伪品的鉴别

柚木色泽美观,尺寸稳定性好,享有“万木之王”的美誉,市面上出现了众多伪品。为了保护消费者权益,规范市场秩序,使用木材宏观与微观构造识别的手段重点研究爱里古夷苏木、大美木豆、大绿柄桑、特斯金莲木、刺槐以及纤皮玉蕊6种伪柚木与真柚木的构造特征。结果表明,市面上明示“非洲柚木”“柚木王”“金丝柚木”“金丝柚”“金刚柚”“南美柚木”“巴西柚木”“墨西哥红柚木”“铁柚木”“婆罗洲柚木”都不是真柚木,都是柚木的伪品,并给出了其真实的木材名称。

不同密度柚木人工林林下植被及土壤理化性质的研究

研究不同密度柚木人工林对林下植被及土壤理化性质的影响,为柚木人工林营建与可持续经营提供理论依据。以广东揭阳14~16年生不同林分密度(650、900、1 050、1 200和1 450株·hm^(-2))柚木人工林为研究对象,通过样方调查植被的种名、株数、高度及盖度等,并采集0~20和20~40 cm土样进行理化性质分析,对林下植被物种多样性指数及其土壤理化性质进行主成分分析评价,来评价不同林分密度下柚木人工林的立地质量。结果表明:随着林分密度增加,柚木人工林林下植被盖度整体表现出降低趋势,草本优势物种由阳生性到中生性,逐渐向阴生性的过渡,林下植被Shannon-Wiener指数、Simpson优势度指数、丰富度指数和均匀度指数表现出先增加后减少的趋势;相同密度下,表层土土壤理化性质优于下层土,随着林分密度增大,土壤理化性质整体呈现出先改善后退化的变化过程,不同林分密度间柚木人工林土壤毛管孔隙度、非毛管孔隙度、速效K、速效P、全P、交换性酸和交换性Al等指标差异性显著(P<0.05);基于林下植被物种多样性和土壤理化性质主成分分析,不同林分密度柚木人工林物种多样性和土壤理化性质综合得分由大到小依次是:1 050株·hm^(-2)(4.82)、900株·hm^(-2)(1.58)、650株·hm^(-2)(-1.30)、1 200株·hm^(-2)(-1.81)、1 450株·hm^(-2)(-3.29)。因此,说明适宜的林分密度(1 050株·hm^(-2))有利于保持较好的林下植被物种多样性和土壤理化性质,在柚木人工林经营的过程中,可以根据实际情况合理调整林分的密度。

云南西双版纳柚木人工林立地类型划分及评价

【目的】探讨西双版纳柚木人工林立地类型,为西双版纳及其他类似地区的柚木人工林立地选择提供科学依据。【方法】对12~26年生的柚木人工林,采用典型抽样方法,设置51块样地,测定样地内柚木生长指标,记录地形因子,分析土壤理化性质;采用逐步回归方法筛选土壤主要化学因子,以主成分分析划分土壤养分等级。运用数量化理论Ⅰ,分析立地因子与样地林木生长量的关系。【结果】土壤养分等级、土壤质地、坡向、坡位、坡度、土壤密度和海拔等立地因子与优势木高生长拟合的数量化模型复相关系数为0.865,达极显著相关(P<0.01);土壤密度、土壤质地、坡度以及8个土壤养分因子(pH值、交换酸含量、全K含量、全P含量、有效P含量、交换性Ca^(2+)含量、交换性Al^(3+)含量和有效Fe含量)组成的土壤养分等级与生长均极显著相关(P<0.01);在数量化模型中,土壤因子(土壤养分、土壤密度和土壤质地)对柚木优势木高生长贡献率达58.3%,且影响均极显著(P<0.01);根据数量化回归模型中各样地立地因子得分,划分4组生产力等级,并以土壤密度、土壤质地及土壤养分3个立地因子划分11个立地类型,且对各生产力等级生长情况及立地因子特点进行评述,4组生产力等级由高产到劣产,柚木优势木年均高生长量分别为1.70~1.81,1.22~1.31,1.08~1.12和0.51 m。【结论】柚木生长在通气透水性较好的粉砂质壤土上好于在砂壤土、重壤土上;对土壤密度敏感,喜欢较高土壤密度;在盐基饱和度、全K含量、有效P含量和交换Mg^(2+)含量均高的立地上最佳;在强酸性、土壤交换性Al^(3+)和有效Fe含量高时生长极差。在本区选择合适的立地发展柚木时,应着重考虑土壤密度、质地以及酸度等,选取较高肥力的立地;对因立地差而生长不良的现有林分应及时改造,以尽量降低损失。