丘陵红壤不同人工林型土壤微生物类群、酶活性与土壤理化性状关系的研究

在中国科学院红壤生态试验站优化农业生态模式的长期定位试验地选取恢复14年的常绿针叶林地（马尾松）、落叶阔叶林地（小叶栎）、针阔混交林地（湿地松一小叶栎）和自然恢复地（受到人为干扰）为样地，并以附近疏草荒地作为对照，研究了不同人工林型对土壤微生物类群、酶活性以及土壤理化性质的影响。结果表明：与对照相比，不同林型下土壤细菌、真菌和放线菌总数均有很大程度的增加，依次为针阔混交林〉阔叶林〉针叶林〉自然恢复地〉疏草荒地。土壤蔗糖酶、脲酶和酸性磷酸酶活性表现为阔叶林〉针阔混交林〉针叶林〉自然恢复地〉疏草荒地。在剖面分布上，土壤微生物类群和酶活性也有明显的层次差异，即随土层的增加而减少。在0—10cm土层中，土壤细菌、真菌与脲酶、酸性磷酸酶之间具有显著或极显著相关性。土壤微生物类群和酶活性与土壤有机质、全氮和有效氮之间具有极显著相关性。

亚热带红壤丘陵区不同人工林型对土壤理化性质、微生物类群和酶活性的影响

为了探讨亚热带红壤丘陵区不同人工林对土壤理化性质、微生物类群和酶活性的影响.以亚热带红壤丘陵区的纯樟树林（CC）、纯杉木林（CL）、杉木樟树混交林（CLCC）、自然恢复地（受到人为干扰）（NR）作为研究对象,并以附近的疏草荒地（GD）作为对照（CK）,通过调查取样和实验分析相结合的方法,分析不同人工林型中不同土层（0~10、10~20 和20~40 cm）土壤的理化性质、微生物类群和酶活性的变化.结果表明,（1）与对照相比,不同林型下土壤细菌、真菌和放线菌总数均显著增加,依次为微生物总数（CLCC）〉微生物总数（CC）〉微生物总数（CL）〉微生物总数（NR）〉微生物总数（CK）（P〈0.05）.（2）土壤脲酶（URE）活性在不同林型下的大小顺序为脲酶（CC）〉脲酶（CLCC）〉脲酶（CL）〉脲酶（NR）〉脲酶（CK）（P〈0.05）;蔗糖酶（INV）活性的大小顺序为蔗糖酶（CC）〉蔗糖酶（NR）〉蔗糖酶（CLCC）〉蔗糖酶（CK）〉蔗糖酶（CL）（P〈0.05）;酸性磷酸酶（APE）活性的大小顺序为酸性磷酸酶（CC 和CLCC）〉酸性磷酸酶（NR）〉酸性磷酸酶（CL）〉酸性磷酸酶（CK）（P〈0.05）.（3）在剖面层次上,土壤微生物类群和酶活性也有明显的层次性,即随着土层的增加而减小.（4）相关分析表明：土壤细菌、真菌与脲酶、酸性磷酸酶之间具有显著或极显著的相关性（P〈0.05 或P〈0.01）;土壤微生物类群和酶活性与土壤有机质（SOM）、全氮（TN）和有效氮（AN）之间具有极显著的相关性（P〈0.01）.研究结果表明退耕还林（草）可增加土壤微生物类群的数量和土壤酶活性,促进土壤物理性状的改善和肥力的提高.

红壤丘陵不同人工林型对土壤理化性状的影响

在中国科学院红壤生态试验站的优化农业生态模式的长期定位试验地,以恢复14年的常绿针叶林地(马尾松林)、落叶阔叶林地(小叶栎)、针阔混交林地(湿地松-小叶栎)和自然恢复地(受到人为干扰)为样地,并且在附近选择疏草荒地作为对照,研究不同人工林型对土壤理化性状的影响。结果表明,不同人工林型对土壤的理化性状有不同程度的影响,阔叶林和针阔混交林在改善物理性状,增加有机质和养分含量等方面优于针叶林和自然恢复地,均优于疏草荒地。在剖面分布上,也有明显的层次差异,即随土层的增加理化性状有下降的趋势。

太行山低山丘陵区不同人工林型对土壤性质及酶活性的影响

为探明太行山干旱低山丘陵区不同人工林型对土壤酶活性及土壤质量修复的影响,以立地条件一致的3种典型32年生人工林为试验样地,对栓皮栎(Quercus variabilis)、侧柏(Platycladus orientalis)和刺槐(Robinia pseudoacacia)3种不同人工林型下土壤的脲酶(Urease)和蔗糖酶(Sucrase)活性进行了测定,并比较了不同林型下土壤的理化和生物学性质。研究结果表明:1)林分类型对土壤脲酶、蔗糖酶活性有明显的影响,不同林分类型下土壤脲酶、蔗糖酶活性均呈现侧柏>刺槐>栓皮栎的变化趋势;2)各林地土壤含水率较低,土壤呈弱碱性。3种林地类型中,侧柏林地对土壤的改良效果较好,土壤容重和土壤pH值都显著降低,且土壤总孔隙度、全氮(TN)和有机碳(TOC)含量均显著增加(P<0.05)。此外,侧柏人工林根长密度、根表面积密度和根体积密度均显著高于栓皮栎和刺槐林(P<0.05);3)土壤酶活性的高低与土壤性质有较强的相关性。线性回归分析表明,土壤碱解氮、含水率和速效磷是影响脲酶活性的主要因素,而蔗糖酶活性主要受土壤有机碳含量的影响。综合分析表明,太行山干旱低山丘陵区侧柏人工林的种植有利于提高土壤酶活性和土壤质量,在该区人工林培育及植被恢复过程中可适当扩大侧柏人工林的育林面积。

Anatomical adaptations of three species of Chinese xerophytes （Zygophyllaceae）

Secondary xylem characteristics and horizontal variations were described in three xerophytic species, Zygophyllum xanthoxylon, Nitraria tangutorum, Tetraena mongolica of Zygophyllaceae native to western China. All the species have obvious growth ring boundaries except sometimes discontinuous in T. mongolica and Z xanthoxylum ring to semi-ring-porosity; simple perforation plate; alternate intervessel pitting; non-septate fibres; paratracheal confluent axial parenchyrna; helical thickenings and heterocellular rays. However the vessel arrangement and quantitative features of vessels were different. Vessel elements tend to be shorter and narrower and more frequent in T. mongolica than in other two species that are hardly different could lead to greater conductive safety. The variation of vessel element length and fibre length along radial direction showed irregular tendency. There was significant difference in both fibre length and vessel element length among-tree and within-tree. Furthermore, the relationships between anatomical features and adaptability to desert environments were also discussed.

Study on the Growth Law of 23-year-old Castanopsis fissa Plantation

This paper studies the growth law of 23-year-old Castanopsis fissa planta- tion in Haiming forest farm （Pingguo County, Baise City, Guangxi Province） with the method of stem analysis. The results show that the average DBH, tree height and volume of the 23-year-old C. fissa plantation are 19.4 cm, 20.4 m and 0.326 1 m3 respectively. The fast growing periods of DBH, tree height and volume are the 2^nd- 8^th, 6^th-11^th, 6^th-23^nd year. Annual increment curve and average increment curve of volume haven＇t intersected in the 23 years, which means the 23-year-old C. fissais plantation has not reached the quantitative mature age. The growth equations of DBH, tree height and volume are D=1.713 3T-0.050 6T2＋0.000 7T2-1.942 2, H= 1.925 7T-0.039 8T2-2.489 0, V=-0.010 4T-0.002 4T2-4.084 8e^-0.005 T2＋0.012 7. Ac- cording to the volume regression equation of Castanopsis fissa, it will reach quanti- tative maturity in the 24~ year.

Collapse-type shrinkage characteristics in plantation-grown eucalypts： I . Correlations of basic density and some structural indices with shrinkage and collapse properties

Collapse-type shrinkage is one of highly refractory drying defects inlow-medium density plantation-grown eucalypt wood used as solid wood products. Basic density (BD),microfibril angle (MFA), double fibre cell wall thickness (DWT), proportion of ray parenchyma (RP),unit cell wall shrinkage, total shrinkage and residual collapse, which are associated withcollapse-type shrinkage characteristics, were investigated by using simple regression method forthree species of collapse-susceptible Eucalyptus urophyll,, E. grandis and E. urophyllaxE.grandis,planted at Dong-Men Forest Farm in Guangxi autonomous region, China. The results indicated that:unit cell wall shrinkage had a extremely strong positive correlation with BD, moderately strongpositive correlation with DWT, and a weakly or moderately negative correlation with RP and MFA;total shrinkage was positively correlated with BD, DWT and RP and negatively related to MFA, but notable to be predicted ideally by any examined factors alone owing to lower R^2 value (R^2≤0.5712);residual collapse was negatively correlated with BD and DWT, linearly positively correlated withMFA, and had strongly positive linear correlation with RP. It is concluded that BD can be used assingle factor (R^2≥ 0.9412) to predicate unit cell wall shrinkage and RP is the relatively soundindicator for predicting residual collapse

Are There Differences in the Response of Natural Stand and Plantation Biomass to Changes in Temperature and Precipitation?A Case for Two-needled Pines in Eurasia

A comparative discussion of the advantages and disadvantages of natural stands and plantations,including in terms of their productivity and stability,began from the moment of the first forest plantings and continues to this day.In the context of the progressive replacement of natural forests by plantations due to deforestation,the question of how will change the carbon storage capacity of forest cover when replacing natural forests with artificial ones in a changing climate becomes extremely relevant.This article presents the first attempt to answer this question at the transcontinental level on a special case for two-needled pine trees(subgenus Pinus L.).The research was carried out using the database compiled by the authors on the single-tree biomass structure of forest-forming species of Eurasia,in particular,data of 1880 and 1967 of natural and plantation trees,respectively.Multi-factor regression models are calculated after combining the matrix of initial data on the structure of tree biomass with the mean January temperature and mean annual precipitation,and their adequacy indices allow us to consider them reproducible.It is found that the aboveground and stem biomass of equal-sized and equal-aged natural and plantation trees increases as the January temperature and precipitation rise.This pattern is only partially valid for the branches biomass,and it has a specific character for the foliage one.The biomass of all components of plantation trees is higher than that of natural trees,but the percent of this excess varies among different components and depends on the level of January temperatures,but does not depend at all on the level of annual precipitation.A number of uncertainties that arose during the modeling process,as well as the preliminary nature of the obtained regularities,are noted.