桉树人工林木材生长应变研究

以我国南方生长较好的4种人工林桉树为研究对象，测试并比较了4种桉树立木的纵向生长应变及其相关性,结果表明：不同桉树种间生长应变差异显著；相同树龄的尾园桉的生长应变与胸径成直线相关。以上结果可为桉树实体木材的加工利用提供借鉴。     

Microbial biomass in subtropical forest soils： effect of conversion of natural secondary broad-leaved forest to Cunninghamia lanceolata plantation

Conversion of natural secondary broad-leaved forest to Cunninghamia lanceolata plantation is a common management practice in subtropical China. In this study, we compared soil physico-chemical properties, microbial biomass in one natural secondary broad-leaved forest and two C. lanceolata plantation sites to estimate the effects of forest conversion on soil microbial biomass at the Huitong Experimental Station of Forestry Ecology, Chinese Academy of Sciences. Concentrations of soil organic carbon, total nitrogen, NH4^＋-N and microbial biomass carbon and nitrogen were much lower under C. lanceolata plantations as compared to natural secondary broad-leaved forest. Soil microbial biomass C in the first and second rotation of C. lanceolata plantations was only 53%, 46% of that in natural secondary broad-leaved forest, and microbial biomass N was 97% and 79%, respectively. The contribution of microbial biomass C to soil organic C was also lower in the plantation sites. However, the contribution of microbial N to total nitrogen and NH4^＋-N was greater in the C. lanceolata plantation sites. Therefore, conversion of natural secondary broad-leaved forest to C. lanceolata plantation and continuous planting of C. lanceolata led to the decline in soil microbial biomass and the degradation of forest soil in subtropical China.     

杉木和I-72杨人工林木材干缩性质的研究

通过对杉木和I-72杨人工林木材南北向、不同高度位置、不同径向位置横向干缩(弦、径向)的测量,研究上述3个因素对2种木材横向干缩(弦、径向)的影响规律。结果表明:南北向的不同对杉木和I-72杨人工林木材的干缩均无显著影响;高度位置的不同对杉木和I-72杨木的弦向干缩均有显著影响,而对径向干缩则无显著影响;径向位置的不同对杉木和I-72杨人工林木材的径、弦向干缩均有极显著影响:从树皮到髓心,木材径、弦向干缩逐渐减小,与其基本密度的变化趋势一致。     

速生人工林桉树木材材色处理初步研究

试验用漂白剂、酸性染料和其他化学药剂,采用单纯漂白、单纯染色、先漂白再染色和化学着色等4种不同的方案对人工林桉树木材进行材色改良处理研究.结果发现:单纯漂白可获得一定的材色改良效果;硫化物类、过硫酸铵类的药剂配方漂白效果不明显;硼氢化钠类的药剂配方可得到一定的漂白效果;双氧水类、次氯酸钠类的药剂配方可得到很好的漂白效果.单纯染色比较难获得好的材色处理效果.采用先漂白后染色的方法,获得的材色过于鲜艳.采用化学着色的方法,可获得较理想的材色改良效果;草酸类药剂配方着色效果明显,可消除材色缺陷,根据不同的配方和处理工艺可获得从浅粉红色到红棕色的色调;用双氧水做活性剂,引入带发色团的化学药剂,材色改良效果明显,通过调整配方药品的浓度和处理工艺可获得从浅黄色到橙黄色的不同色调和较佳的材质.     

Leaf-water potential and soil-water depletion of walnut mulched with polyethylene and intercropped with alfalfa in Central Italy

In Italy, new agroforestry cultural models could play an important role in the diffusion of plantation forestry timber species. We studied the stem growth rates and leaf water potentials () of common walnut (Juglans regia L.), and gravimetric soil moisture (_DW) depletion during the third and fourth growing seasons in an agroforestry trial in central Italy. Since the establishment of experimental plots in 1992, walnut was intercropped with alfalfa (Medicago sativa L.), with or without polyethylene (PE) mulching along tree rows. By the end of the study period, the unmulched-intercropped walnut was almost 68% smaller in stem diameter and height than the sole-unmulched control, demonstrating walnuts sensitivity to alfalfa competition. The competitive effect of alfalfa on walnut stem growth was effectively controlled/reduced by PE mulching. Stem growth rates of mulched-intercropped walnut were always lower than the control, but much higher (ca. 235% in stem diameter and height) than those of unmulched-intercropped walnut. The higher field performance of mulched-intercropped walnut compared to the un- mulched-intercropped treatment was associated with higher soil moisture and predawn and midday values during the summers driest periods. The presence of PE mulching was also associated with lower levels of soil moisture during the early and late growing season, but this did not negatively affect walnut and growth rates. These results suggest that in the climatic conditions of central Italy, competition for soil moisture between young common walnut trees and alfalfa can be substantially lowered, but not completely eliminated, by PE mulching.This revised version was published online in November 2005 with corrections to the Cover Date.     

洞庭湖滩地造林成活率的关键影响因子

用样行法对洞庭湖滩地新造速生丰产纸浆林的成活率进行调查,同时了解造林地连续4 a汛期的水文规律和海拔高程的演变过程,通过分析造林成活率与主要影响因子之间的关系,发现淹水时间为滩地造林的限制性因子,营造速生丰产林、一般用材林和短周期工业原料林时,造林地年淹水天数依次不能超过19、35和62 d;苗木等级对造林成活率有重大影响,特级苗、Ⅰ级苗、Ⅱ级苗、Ⅲ级苗的平均成活率在海拔低于32 m的造林地上分别为68.8%、49.3%、18.7%、2.4%,在海拔超过32 m的造林地上分别为98.8%、79.6%、36.4%、14.7%;采用开沟抬垄整地可减轻涝渍胁迫,从而大幅度提高造林成活率.     

NUTRIENT CYCLING IN THE DAHURIAN LARCH PLANTATION ECOSYSTEM

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田间供水与杨树生长关系的研究——Ⅰ.供水处理对杨树生长、树体结构和叶量的影响

在集约栽培的杨树人工林中作了小区灌溉试验,进行了林木生长指标、水分生理指标与供水量关系的研究。结果表明,供水大大促进了林木生长,其树高、胸径和材积的年增长量均随供水量的提高而增加。1983—1986年其树高、胸径、材积分别比对照增加 17.2—24.6％、10.7—22.1％和22.0—42.6％。供水还影响到树体的结构,有利于同化产物向枝条中运输与积累,促进了树干、枝条、叶数与叶面积的增长。     

极大值原理在确定人工林最优采伐年龄中的应用

人工林可看作一个离散系统,每个采伐分期中各龄级的林分面积定义为系统的状态变量,各龄级的采伐面积定义为控制变量。在控制变量的作用下,人工林从现状态经过N个采伐分期到达一个终端状态,可看作一个控制过程。寻求最优的控制过程的方法有多种,在国内外有关的研究中较为普遍的是多周期的线性规划(或非线性规划)和动态规划。但前者需为每个分期定义控制变量和状态变量,因而计算机计算时占用大量的存贮空间,后者在维数较高时因计算量太大难以求解。极大值原理是最优控制理论中的主要方法之     

落叶松人工林土壤因子变化规律的研究

从5个方面分析落叶松人工林土壤的变化,得出经营落叶松人工林有使土壤肥力递减趋势的结论。