Differential Competitive Ability and Growth Habit of Pearl Millet and Clusterbean Cultivars in a Mixed Cropping System in the Arid Zone of India

Dryland sustainable agriculture in the arid zone of India depends upon the choice of suitable cultivars for pure and mixed crop stands. Field experiments were conducted for two years to examine the response of two contrasting cultivars each of pearl millet (Pennisetum glaucum) and clusterbean (Cyamopsis tetragonoloba) in pure stands and in mixed pearl millet‐clusterbean stands. The differential response of cultivars of both crops to pure and mixed stands resulted in a significant genotype × cropping system interaction. Reduction in seed yield of both clusterbean cultivars was greater in mixed stands with tall and long duration pearl millet MH 179 than with medium statured and early maturing HHB 67. The degree of reduction was greater in Naveen, the branched clusterbean cultivar, than in RGC 197, the single stemmed cultivar. Mixing of pearl millet HHB 67 with medium duration clusterbean cultivar Naveen produced maximum pearl millet equivalent total yield. Higher land equivalent ratios (LERs) were also observed when clusterbean cultivars were mixed with early maturing and short statured pearl millet HHB 67.     

湘西桤木人工林蓄积量模型及适宜经营密度研究

密度是表达林分结构的重要指标,立地条件、树种及林龄不同时,其林分最佳密度也不相同。笔者以湘西桤木人工林为研究对象,采用数量化方法I和非线性回归分析方法,对2009年和2010年调查的78块标准地数据进行数据分析处理与建模。结果表明：（1）平均高、公顷株数、土层厚度、龄组、坡向、坡位、自然灾害、海拔、树种组成8种因子中,平均高、公顷株数、土层厚度和龄组对湘西桤木人工林平均木材积和单位面积蓄积量均有显著性影响,而海拔和树种组成对湘西桤木人工林平均木材积和单位面积蓄积量均无显著性影响。这对建立桤木人工林蓄积量与密度、平均高收集数据时提供理论指导,同时既能节省外业调查费用,又能保证建模数据的科学性。（2）建立了湘西8~10年桤木人工林蓄积量与密度、平均高相关关系模型： ,建模精度为96.8458%,平均相对误差为1.1334%。模型适应性检验表明,残差值呈对称均匀分布,其平均相对误差为-1.2156%。（3）该地区8~10年桤木人林的最佳经营密度为800~1000株/hm2。这对于合理地经营和管理湘西桤木人工林具有重要的理论和实际指导意义。     

闽东山区不同密度突脉青冈人工林土壤肥力的分形研究

针对闽东山区造林树种针叶化且连栽引起生产力下降和地力退化问题,开展乡土阔叶树种突脉青冈密度选择试验。运用分形理论对造林密度分别为2400、3000、3600 和4050 株/hm2的突脉青冈人工林的土壤结构和理化性质进行研究,以荒山为对照。结果显示：突脉青冈土壤分形维数与土壤水稳性团聚体、团聚体含量、结构体破坏率及土壤理化性质呈显著回归关系,分形维数与＞0.25 mm土壤颗粒含量线性负相关,与结构体破坏率呈线性正相关;不同密度的突脉青冈土壤团粒结构的分形维数大小顺序表现为荒山＞4050 株/hm2＞3600 株/hm2＞2400 株/hm2＞3000 株/hm2。上述表明：分形维数可用于表征土壤肥力大小,突脉青冈造林密度为3000 株/hm2时的土壤结构、稳定性及肥力最好,是最佳造林密度;运用分形理论研究林地肥力状况为林地质量评价提供了一种新思路。     

不同树种林分造林经济效益评价研究

以柳杉(Cryptomeria fortunei)、杉木(Cunninghamia lanceolata)和福建柏(Fokienia hodginsii)3个不同人工林分为研究对象,首先对3个林分蓄积量和出材量进行了分析讨论,接着应用净现值、内部收益率、收益成本比、土地期望值和净效益投资比等动态经济指标对3个林分的造林经济效果进行评价。结果表明,在3个林分中,杉木林分平均单株材积、蓄积量和经济材出材量最高,杉木林的NPV、IRR、LEV、B/C、N/K最大。     

Models for the establishment and height development of naturally regenerated Pinus sylvestris in Finnish Lapland

Abstract

The study focused on constructing models for the establishment and seedling height development of naturally regenerated seedling stands in the natural regeneration of Scots pine by the seed-tree method in Lapland, northern Finland. Modelling was used to describe the dynamics of the regeneration process and to analyse the principal ecological factors and management activities influencing regeneration success. Models for the density of seedling stands were developed with the generalized linear mixed model method. The most significant variables affecting seedling establishment were elevation, time since the establishment cutting, the interaction of forest site type and site preparation, and stoniness. The results indicated that the average stocking level tends to remain unsatisfactory on moist, fertile site types without site preparation. Seedling height development was modelled as a function of age using the linear mixed model. Age explained 97% of the variance of seedling height. Other independent variables in the model were effective temperature sum, site preparation and the presence or absence of seed trees.     

Soil organic matter in European forest floors in relation to stand characteristics and environmental factors

Published data on the quantities of organic matter in the forest floor (SOM_fl) of European forest stands were collated. Studies of SOM_fl were included if the total sampled surface was at least 0.15 m², the surface of a single sample was at least 100 cm², live material was sorted out, and ash or carbon content was determined. Data from 59 forest stands were compared with regard to stand characteristics and environment. Using a single variable, tree genus was most important for the amount of SOM_fl (R ² _adj = 0.34). The amounts in spruce stands (41 × 10³ kg ha^?1) were significantly higher than those in larch, Douglas fir, oak and birch stands (4–11 × 10³ kg ha^?1). The best significant multiple model was genus combined with stand age and basal area (R ² _adj. = 0.72). The importance of litter quantity and quality for differentiating the tree genera is discussed.     

小叶锦鸡儿退耕还林地林分生长状况

小叶锦鸡儿是我国北方干旱地区主要造林树种之一。通过对乌兰察布市后山地区不同林龄小叶锦鸡儿灌木林进行林分生长状况的研究,结果表明:该区小叶锦鸡儿灌木林地均出现不同程度的衰退,随着造林年限的增加,植物个体死亡情况趋于严重;植物个体生物量随造林年限的增加而增加;10年后个体生长缓慢,年生物量呈先增大后减少的趋势;土壤含水量随造林年限增加呈降低趋势。因此,对衰弱的小叶锦鸡儿灌木林要进行人为干预,促进林分快速恢复。     

高效培育麻竹笋用林技术研究

通过对麻竹笋用林立竹密度、施肥量、截梢、灌溉等技术的试验研究,结果表明4种措施对竹笋产量有显著影响,前三者与竹笋产量呈抛物线型关系,竹笋产量随立竹密度、施肥量、截梢增加呈现先上升后下降的趋势;竹笋产量与灌溉次数呈直线相关,竹笋产量随灌水间隔时间增长而减少。4种因素的影响程度大小依次为：施肥量、立竹密度、灌溉、截梢。提出高效培育麻竹笋用林的优化模式为：施肥量为1800kg／hm^2,立竹密度为3600株／hm^2,灌溉为发笋期连晴10d浇水1次,截梢是保留竹秆高4m为宜。     

不同整地方式对造林质量的影响

在黑龙江省半干旱地区通过全面整地、开沟整地、穴状整地和不整地对樟子松、云杉、落叶松和银中杨的造林成活率、保存率以及树高和地径生长量影响的试验研究,结果表明:开沟整地可大大提高针叶树的造林成活率和保存率,同时可有效提高樟子松和云杉的林木生长量。     

尤溪县生态公益林林分改造的分析与对策

对尤溪县境内的闽江支流尤溪河两岸、道路两边及库区周边一重山的生态公益林现状及存在问题进行了分析,提出了对公益林部分林分进行改造的初步规划,探讨了公益林改造的对策,为尤溪县“两沿一环”（即沿高速公路、公路、铁路,沿河,环城区周边一重山）林分改造工程提供参考。