桉树人工林树液流动密度随边材径向深度的变化

树液流动密度(SFD)随边材径向深度的变化对于准确估测流经边材的树液通量是非常重要的,后者又制约着Heat Pulse的应用精度.但迄今为止,只有很少的研究估计了由于SFD随径向的梯度变化而带来的误差,SFD沿树干径向分布规律的获得往往依靠对少数几棵树的观测资料.基于在广东雷州半岛对两块3～4年生桉树(Eucalyptus urophylla S.T. Blake)人工林1年的Heat Pulse观测,探讨了对来自39株立木大量观测资料的综合处理方法,发现这两个样地(纪家和河头)的林分中SFD随边材径向深度的变化可以用如下回归方程来描述:纪家: y=3.667 5x3-7.295 5x2+3.682 6x+0.567 4 (R2=0.939 1, n=80, P=0.01)河头: y=5.006 2x3-9.116 1x2+4.454 4x+0.463 4 (R2=0.806 9, n=72, P=0.01)式中:y--某一树液感应器所测得的SFD与不同深度的4个感应器所测得的SFD的平均值之比;x-某一树液感应器在边材中的深度与边材厚度之比.从形成层到心材,SFD最初有所增加,随后持续减小,但由于树木年龄很小,最大的SFD只比最小的SFD大0.33～0.36倍.     

华南桉树人工林树液流通量及蒸散作用

通过对广东省湛江市雷州半岛桉树(Eucalyptus urophylla S.T.Blake)人工林的树液流通量、环境因子、土壤蒸发、林冠截留和林分特性相关指标一年多的连续观测,以及通过一个理论公式对日蒸散量的计算,得出了如下结论:(1)土壤特性及由此决定的土壤水势对树液流通量,以及树液流通量密度(SFD)与气温的关系有一定影响;(2)林冠层的VPD(空气饱和差)对SFD有显著影响;(3)由测定和计算得来的蒸散量在河头和纪家分别有5.26%和6.14%的偏差,可以认为这两种方法有较好的一致性;(4)河头和纪家的林分蒸腾量占总蒸散量百分比分别为62.2%和51.3%;(5)树种单位叶面积水平上的SFD是评价该树种水分利用的重要指标.     

应用热脉冲系统对桉树人工林树液流通量的研究

应用热脉冲式树液流测定系统和自动气象站 1 999年 9月～ 2 0 0 0年 9月的观测资料 ,探讨了广东省湛江市雷州半岛两个桉树人工林树液流通量 (Sap flux density,SFD)的时空动态及其与环境因子的相关关系。河头和纪家两地桉树林的树液流变化具有明显的昼夜节律性 ,大约从清晨 7:0 0开始萌动 ,1 2 :0 0以后达到峰值 ,夏季连续 4 d中 (2 0 0 0年 6月 1 5日～ 6月 1 8日 )河头 SFD最大值 44.2 1± 4.5 ml/ (cm2 · h) ,纪家 2 9.2± 7.2 ml/ (cm2· h)。此后 ,SFD逐渐减小 ,一直到日落前后降至最低值。树液流在不同的季节具有不同的昼夜节律性变化规律。两地 SF D值的季节波动节律相似 ,湿季时相对较大。但是河头日平均 SFD值 (2 4 36± 1 1 92 .5 ml/ (cm2 · d) )要比纪家 (1 70 3± 82 4 .5 ml/ (cm2 · d) )高 ,这主要是由于两地土壤质地的差异所导致的。在所选时段内 ,SFD的最大值出现在河头的冬季和纪家的夏季 ,这是由于这两天的大气饱和水气压差 ,太阳辐射和土壤有效持水量都比较高的缘故。在空间上 ,从形成层到心材 ,SF D最初有所增加 ,随后持续减小。整个观测期间两地 SFD的极大值均出现在 6月中旬 ,河头为 51 .53ml/ (cm2· h) ,而纪家为 39.85ml/ (cm2 · h) ,显然 ,由于环境条件的限制 ,主要是土     

华南桉树人工林树液流通量及蒸散作用(英文)

通过对广东省湛江市雷州半岛桉树(Eucalyptus urophylla S.T.Blake)人工林的树液流通量、环境因子、土壤蒸发、林冠截留和林分特性相关指标一年多的连续观测,以及通过一个理论公式对日蒸散量的计算,得出了如下结论:(1)土壤特性及由此决定的土壤水势对树液流通量,以及树液流通量密度(SFD)与气温的关系有一定影响;(2)林冠层的VPD(空气饱和差)对SFD有显著影响;(3)由测定和计算得来的蒸散量在河头和纪家分别有5.26％和6.14％的偏差,可以认为这两种方法有较好的一致性;(4)河头和纪家的林分蒸腾量占总蒸散量百分比分别为62.2％和51.3％;(5)树种单位叶面积水平上的SFD是评价该树种水分利用的重要指标。     

广东省桉树人工林土壤有机碳密度及其影响因子

研究了广东省粤北、粤东、粤西和珠江三角洲4个地区桉树人工林土壤有机碳含量和有机碳密度,以及土壤有机碳密度的主要影响因子.结果表明:土壤A层和B层有机碳含量分别为(23.94±2.97)g·kg-1和(9.68±1.05)g·kg-1,二者差异显著;A层和B层有机碳密度分别为(27.64±7.72)t·hm-2和(108.36±9.37)t·hm-2,有显著差异;0～50 cm土层有机碳密度为(66.72±6.53)t·hm-2,略高于同一地区马尾松和杉木人工林.有机碳密度与海拔、A层和B层土壤总孔隙度、毛管孔隙度、毛管持水量和全氮含量呈显著正相关;土壤毛管孔隙度、毛管持水量和pH值是影响有机碳密度的主导因子.     

南宁市桉树人工林土壤有机碳密度与地形因子的关系

桉树人工林土壤有机碳密度与地形因子的关系还不明确,且当前的研究较少地关注复合地形因子,对两者的线性和非线性关系强度的对比研究也较少。以南宁市高峰林场中的桉树人工林地为研究区,采用条件拉丁超立方抽样法布设采样点,通过建立数字高程模型提取和计算得到地形因子的指标;采用线性回归和回归树分别建立桉树人工林土壤有机碳密度-地形因子的线性和非线性回归模型。结果表明:研究区土壤表层、0—50 cm和全剖面的土壤有机碳密度均值分别为2.8、7.7、10.9 kg/m2,属于中等水平;仅坡度在0.05显著性水平上与表层和全剖面土壤有机碳密度显著相关,总体而言,简单地形因子与土壤有机碳密度的相关性普遍好于复合地形因子;随着土壤层次厚度的增加,线性和非线性回归模型对土壤有机碳密度空间变异解释能力都提升;回归模型对土壤有机碳密度空间变异的解释能力大小顺序为:回归树全变量多元线性回归逐步线性回归,因此,桉树人工林土壤有机碳密度与地形因子之间的非线性关系比线性关系强。     

林分密度对桉树人工林群落结构和物种多样性的影响

采用典型样地法,以四川新津县普兴镇桉树(Eucalyptus robusta)人工林为研究对象,设置5种不同林分密度(A.625株·hm~(-2);B.750株·hm~(-2);C.875株·hm~(-2);D.1 000株·hm~(-2);E.1 125株·hm~(-2))样地各3个,对不同林分密度人工林群落结构和物种多样进行分析,探讨确定桉树人工林的合理栽植密度,为维持桉树人工林群落结构稳定、增加物种多样性提供依据。结果表明:(1)研究区桉树人工林群落共记录到96种植物,隶属于51科79属;在各个林分密度的群落中,植物科属种数量变化规律均为:草本层灌木层乔木层;当密度为1 000株·hm~(-2)时,乔木层物种数最高(6种);当密度为750、875株·hm~(-2)时,灌木层群落物种数最高(17种);在林分密度625株·hm~(-2)下,草本层物种数最高(32种)。(2)桉树人工林群落各层次的丰富度指数D值、Shannnon-Wiener指数H值、Simpson指数H′、Pielou均匀度指数Jsw)值均表现为:草本层灌木层乔木层;乔木层的D值和H′值在875株·hm~(-2)密度下最大,H值在625株·hm~(-2)密度下最大,Jsw)值在750株·hm~(-2)密度下最大;灌、草层各指数分别均在密度750、625株·hm~(-2)时有最大值。(3)从群落结构上看,5种林分密度的群落径级结构均呈单峰型分布,乔木个体多分布在中径级(7.0≤d23.0cm);高度级结构与径级结构对林分密度的响应不一致,密度A、B、C和D、E的个体分别集中在高度级Ⅱ~Ⅴ(6.0≤h18.0m)、Ⅲ~Ⅴ(9.0≤h18.0m)、Ⅱ~Ⅲ(6.0≤h12.0m)和Ⅳ~Ⅴ(12.0≤h18.0 m)。(4)各层次优势种不同,乔木层中桉树是绝对优势树种,各密度林分中构树(Broussonetia papyrifera)的重要值基本仅次于桉树;灌木层中,桉树幼苗只在密度E出现,构树在各密度下优势地位显著,在密度B~D中,均有八角枫(Alangium chinense)和女贞(Ligustrum lucidum)存在,并在密度B下八角枫(0.118 4)和女贞(0.183 2)长势较好,具有较大的更新潜力;青蒿(Artemisia carvifolia)和荩草(Arthraxon hispidus)作为草本层的优势种在5种林分密度下都有生长。研究认为,林分密度750株·hm~(-2)(密度B)是新津桉树人工林的最适林分密度,该密度更有利于该地区桉树人工林群落结构和物种多样性的稳定可持续发展。     

雷州半岛桉树生物质能源林生长的密度效应研究

以雷州半岛2年生桉树无性系DH201(Eucalyptus grandis  E. tereticornis)能源林为研究对象,对6种不同密度配置下的林分生长量、生物量以及热值等进行了分析,探讨密度对桉树生物质能源林生长的影响。结果表明,密度对桉树胸径和树高生长量影响极显著,在林分不同发育阶段对林分蓄积量的影响不同;单株生物量随密度增大而减小。1年生的林分蓄积量和生物量均以密度为10000 ind. hm-2的最大,分别为52.57 m3 hm-2和32.02 t hm-2;2年生的林分蓄积量和生物量均以密度为2500 ind. hm-2的最大,分别为75.85 m3 hm-2和45.66 t hm-2;密度对热值及灰分含量的影响不显著。因此,1年生和2年生的桉树能源林的最优密度分别为10000 ind. hm-2和2500 ind. hm-2。     

小兴安岭红松日径向变化及其对气象因子的响应

利用带状树干径向变化记录仪监测了小兴安岭凉水国家级自然保护区原始阔叶红松林中的红松树干径向生长,分别用两种数据处理方法(日最大值法与周期循环法)分析了红松径向生长与气象因子的关系。结果表明:红松径向生长于5月中旬开始,在7月末趋于结束,最大径向生长速率出现在6月中旬。使用Gompertz生长模型能很好的拟合红松的径向生长,可以解释红松92%以上的径向变化。对于日最大值法,偏相关分析表明日径向变化与空气相对湿度、土壤温度和降雨量显著相关;对于周期循环法,第一阶段(收缩阶段)收缩量主要受到相对湿度、土壤温度和水汽压亏缺的影响。第二阶段(膨胀阶段)影响树干径向恢复的主要因子是降雨量和最高气温。第三阶段(增长阶段)对树干径向生长影响最显著的是最低气温和降雨量。应用多元线性模型分析显示,周期循环法能更加细化的分析日气象因子对红松径向生长的影响,能够更为真实地解释红松径向生长动态变化特点与规律,其中第二和第三阶段的降雨和最低气温对红松径向生长的影响最大。     

辽宁省人工林樟子松径向生长对水热梯度变化的响应

基于树轮年代学的理论和方法,建立辽宁地区人工林樟子松年轮宽度年表网络,研究人工林樟子松树木年轮生长变化,探讨樟子松生长与气候变化的关系以及其对水热梯度变化的响应规律。结果表明,研究区各采样点人工林樟子松的径向生长变化呈现较为一致的显著下降趋势(P0.05),并且下降趋势由西北至东南降低。空间上水平上,研究区樟子松的径向生长与研究区降水和相对湿度的空间梯度变化吻合(P0.05),均呈西北至东南增加的特点;各采样点樟子松年轮宽度变化的平均敏感度与降水量、相对湿度显著负相关关系(P0.05),但与温度的正相关关系不显著。各样点樟子松径向生长与月降雨量和月平均相对湿度多呈正相关关系,与月平均温度多呈负相关关系,进一步表明区域水分因子对人工林樟子松生长的限制作用明显。     

Sap flow rates and sapwood density are critical factors in within- and between-tree variation in CO2 efflux from stems of mature Dacrydium cupressinum trees

Measurements of CO2 efflux from stems and branches, sap velocity, and respiratory activity of excised wood cores were conducted in Dacrydium cupressinum trees that differed in diameter, age, and canopy emergence. The objective of this study was to determine if consistent linkages exist among respiratory production of CO2 within stems, xylem transport of CO2, and the rate of CO2 diffusing from stem surfaces. Stem CO2 efflux was depressed during periods of sap flow compared with the efflux rate expected for a given stem temperature and was positively correlated with sapwood density. By contrast, no significant relationships were observed between CO2 efflux and the respiratory activity of wood tissues. Between 86 and 91% of woody tissue respiration diffused to the atmosphere over a 24-h period. However, at certain times of the day, xylem transport and internal storage of CO2 may account for up to 13-38% and 12-18%, respectively, of woody tissue respiration. These results demonstrate that differences in sap flow rates and xylem anatomy are critically important for explaining within- and between-tree variation in CO2 efflux from stems.     

应用Granier热消散探针(TDP)法测定树木的木质部液流:理论与实践

Granier热消散探针法是目前研究树木生理生态和森林水文最常用的测定整树水分利用的方法之一.然而,已有的相关综述文献中,还没有专门介绍利用Granier热消散探针研究木质部液流的综述文章.本文重点介绍了Granier热消散探针测定系统的理论基础,对有关该探针的校准和改进的最新研究进展进行了综述,并还深入探讨了零液流信号值的确定、自然热梯度、损伤效应、液流的逆格型和将木质部液流密度外推至整树蒸腾耗水量等重要的实际问题.     

Diagnosis of zinc deficiency in seedlings of a tropical eucalypt (Eucalyptus urophylla S. T. Blake)

A glasshouse experiment was undertaken to establish the internal Zn requirement for shoot growth of Eucalyptus urophylla, a fast-growing commercial plantation species widely planted in tropical regions of the world. A Zn-deficient sand was supplemented with ten rates of Zn and seedlings were harvested after three months. In Zn-deficient plants the new growth was dwarfed with small, necrotic leaves and short internodes. Foliar Zn concentrations declined markedly with leaf age in both Zn-deficient and Zn-adequate plants. The critical Zn concentration for the diagnosis of Zn deficiency also fell with leaf age. Zinc concentrations in the youngest fully expanded leaf ranged from 8–11 g Zn g^–1 dry weight in plants with severe symptoms to 30–37 g Zn g^–1 dry weight in non-deficient plants. The critical Zn concentration for the diagnosis of Zn deficiency at 90% of maximum shoot growth in the same leaf was 21 g Zn g^–1 dry weight. This value is nearly twice that reported for several other species of eucalypts and may indicate a higher internal demand for Zn in tropical than in temperate eucalypts.     

Impact of a eucalyptus (Eucalyptus globulus Labill.) plantation on the nutrient content and dynamics of coarse particulate organic matter (CPOM) in a small stream

Litterfall inputs, benthic storage and the transport of coarse particulate organic matter (CPOM) were studied in two headwater streams, one flowing through a mixed deciduous forest and one through a plantation of Eucalyptus globulus. Vertical and lateral traps, transported CPOM and benthic CPOM were sampled monthly to biweekly and sorted into four categories: leaves, twigs and bark, fruits and flowers and debris. The litterfall inputs were about 20% lower at the eucalyptus site but this reduction was unevenly distributed among the litter categories. The reduction of the nitrogen and phosphorus inputs was larger (50%) than that of CPOM because of the low nutrient concentration of the CPOM at the eucalyptus site. Transported CPOM was also lower at the eucalyptus site. Although total CPOM inputs to the stream were reduced in the eucalyptus plantation, benthic storage of CPOM was 50% higher due to (1) high inputs of CPOM and low discharge during summer, (2) more twig and bark inputs, (3) eucalyptus leaves being retained more efficiently in the stream than deciduous leaves (4) a lower discharge, which may in part be attributable to eucalyptus-induced changes in the hydrological cycle. Increased retention balanced lower nitrogen and phosphorus content of CPOM, so benthic storage of nitrogen and phosphorus was similar at both sites. This work demonstrates that the timing, quality and quantity of inputs and benthic storage of CPOM in streams changes substantially because of the substitution of natural deciduous forest with eucalyptus plantation. Maintenance of buffer strips of natural vegetation may be the best way to protect ecological functioning of small, forested streams.     

Function of Prolonged Copulation in Nysius huttoni White (Heteroptera: Lygaeidae) Under Male-Biased Sex Ratio and High Population Density

Prolonged copulation as a response to sex ratio and population density has been demonstrated for a number of species but the functions behind it remain controversial. It is difficult to determine the function of prolonged copulations without examining the mechanisms of sperm transfer and storage, and fertilization success–copulation duration relationships. Here, we report our work on a polygamous seed bug, Nysius huttoni White (Heteroptera: Lygaeidae), where we manipulated the population density and sex ratio for a series of mating trials, quantified the relationship between copulation duration and ejaculate amount as well as reproductive outputs, and examined the sperm transfer and storage mechanisms. Our results suggest that males prolong copulations to increase their fertilization success relative to their rivals in response to high sperm competition intensity under male-biased sex ratio and high population density. The mechanism behind the positive correlation between copulation duration and fertilization success may be attributed to the characteristic structures of aedeagus and spermatheca in this insect, which allow direct transfer of sperm to a storage site of fixed size during copulation.