香草醛对杉木幼苗生长的影响

为了解杉木连栽土壤中有毒化感物质对杉木幼苗毒害作用 ,采用水培杉木幼苗方法 ,通过投加不同浓度香草醛 ,发现 1mg·kg- 1 香草醛显著抑制杉木种子胚根的伸长 (P<0 .0 5) ,只为对照的 70 % ;香草醛浓度达 1 0mg·kg- 1 时 ,叶绿素总量明显下降到对照的80 % ;超过 2 0mg·kg- 1 对杉木幼苗地径与高度生长产生明显抑制作用 ;50mg·kg- 1 以上将明显影响地上部分枝叶的正常生长发育 ,及至植株冠层的生长 ;超过 1 0 0mg·kg- 1 ,整个植株的生长受到显著抑制 .香草醛是连栽土壤中毒性较大的一种有毒化感物质 ,是杉木存活率低的重要原因之一 .     

Dynamic of polysaccharide and lipid in the developing microsporangiums of Chinese fir (Cunninghamia lanceolata)

Microsporongium development in Chinese fir (Cunninghamia lanceolata) was investigated using cytochemical methods with a special attention to the fluctuations (in amount and distribution) of polysaccharide and lipid reserves along the development of the microsporangium. Semi-thin sections of microsporangia at different developmental stages were stained with periodic acid–Schiff (PAS) reagent and Sudan Black B to detect insoluble polysaccharides and neutral lipids, respectively. In young microsporangia, microspore mother cells began to accumulate starch grains and lipids, which disappeared during microspore development. Following microspore division, the starch grains present in bicellular pollen disappeared and abundant lipid deposits were accumulated. In mature pollen, only abundant lipids accumulated as storage material. The pollen wall of C. lanceolata is predominantly composed of polysaccharidic intine, and the sporopollenin-containing exine is weakly developed and only forms a thin layer covering the intine.     

杉木人工林种子雨组成和季节动态

杉木人工林已成为亚热带森林的重要组成部分,它具有可持续的自然更新能力,是决定杉木林群落演替方向和维持杉木林大面积存在的基础.本文以杉阔混交林和杉木纯林为研究对象,分析其种子雨的物种组成、数量大小和季节动态,以及林分优势物种种子雨数量特征和季节变化,揭示种源条件是否是制约杉木人工林天然更新的主要因素.结果表明:杉阔混交林和杉木纯林分别收集到13科18属21种和12科16属19种的种子.混交林和纯林的所有物种种子雨强度分别为3797和3300粒·m^-2.乔木物种种子数量在种子雨中占绝对优势,混交林占89.1%,纯林占86.2%,其中杉木种子数量最多,其完整种子雨强度分别为825和345粒·m^-2.两林分种子雨各类型种子所占比例均为完整种子>干瘪或腐烂种子>被取食种子.两林分种子雨均具有明显的季节动态,均在秋季到达高峰,且在落种高峰期种子雨以完整种子为主.无论是杉阔混交林还是杉木纯林都有充足的种源,种源(种子雨)条件不是制约杉木林天然更新的主要因素.     

Carbon mineralization of Chinese fir (Cunninghamia lanceolata) soils under different temperature and humidity conditions

Burned and unburned mineral soils (0–10 cm) from a 40-year-old Chinese fir (Cunninghamia lanceolata) forest in Nanping, Fujian, China were incubated for 90 days at different temperatures (25 °C and 35 °C) and humidity [25%, 50%, and 75% of water holding capacity (WHC)] conditions. Carbon (C) mineralization of all soils was determined using CO₂ respiration method. The results showed that CO₂ evolution rates of the burned and control soils exhibited similar temporal patterns, and similar responses to temperature and moisture. CO₂ evolution rates for all soil samples decreased with incubation time. At different humidity conditions, average rate of C mineralization and cumulative mineralized C from burned and control soils were significantly higher at 35 °C than at 25 °C. This implied that C mineralization was less sensitive to soil moisture than to temperature. In both soils at 25 °C or 35 °C, the amount of soil evolved CO₂ over the 90 days incubation increased with increasing moisture content from 25% to 75% WHC. A temperature coefficient (Q₁₀) varied with soil moisture contents. The maximum values recorded for Q₁₀ were 1.7 in control soil and 1.6 in burned soil both at 25% WHC. However, there were no significant differences in Q₁₀ values between the control and burned soils over all moisture ranges (P > 0.05). The data of cumulative C–CO₂ released from control and burned soils were fitted to two different kinetic models. The two simultaneous reactions model described mineralization better than the first-order exponential model, which reflected the heterogeneity of substrate quality. Based on these results, it is possible to conclude that temperature and moisture are important in the controls of C mineralization, and the combined effects of these variables need to be considered to understand and predict the response of CO₂ release in subtropical ecosystems to climate change.     

Autoinhibition and soil allelochemical (cyclic dipeptide) levels in replanted Chinese fir (Cunninghamia lanceolata) plantations

Aims and background

Despite increasing knowledge of the role of allelochemicals in the productivity decline of replanted Chinese fir plantations, relatively little is known about the levels and sources of allelochemicals in relation to autoinhibition.

Methods

Allelopathic potential of litter, root exudates, and soils in successive rotations of Chinese fir plantations were detected. An allelochemical cyclic dipeptide (6-hydroxy-1,3-dimethyl-8-nonadecyl-[1,4]-diazocane-2,5-dione) from litter, root exudates, and soils in successive rotations was quantified.

Results

Extracts of leaf litter, fine root, and root exudates significantly inhibited the growth of Chinese fir germinants, and inhibition increased with successive rotations. Similar results were observed in the rhizosphere soil, basal soil, and bulk soil. The largest observed inhibition occurred in the rhizosphere soil. Furthermore, cyclic dipeptide was found in litter, root exudates, and soils, and the concentrations increased with successive rotations. The rhizosphere soil had the highest cyclic dipeptide level, followed by basal soil, while bulk soil contained the lowest concentration. There was a significant positive relationship between the inhibition of radicle growth of Chinese fir germinants and the concentration of cyclic dipeptide. Annual release of cyclic dipeptide through root exudation was 2.08–9.78 mol ha^?1 annum, but the annual release of cyclic dipeptide through leaf litter decomposition was lowered to 0.32–1.41 mol ha^?1 annum.

Conclusions

Cyclic dipeptide which caused autoinhibition of Chinese fir may be released into the soil through litter decomposition and root exudation. Root exudates provided more contributions to soil cyclic dipeptide levels than litter in Chinese fir plantations.     

阔叶和杉木人工林对土壤碳氮库的影响比较

通过比较我国亚热带地区19年生阔叶人工林和杉木人工林土壤碳氮储量,探讨树种对土壤碳氮库的影响.结果表明：阔叶人工林0～40 cm土层碳储量平均为99.41 Mg·hm^-2,比杉木人工林增加33.1%;土壤氮储量为6.18 Mg·hm^-2,比杉木人工林增加22.6%.阔叶人工林林地枯枝落叶层现存量、碳和氮储量分别是杉木人工林的1.60、1.49和1.52倍,两个树种的枯落叶生物量、碳和氮储量均有显著差异.枯枝落叶层碳氮比值与土壤碳、氮储量之间呈显著负相关.阔叶人工林细根生物量(0～80 cm)是杉木林的1.28倍,其中0～10 cm土壤层细根生物量占48.2%;阔叶人工林细根碳、氮储量均高于杉木人工林.在0～10 cm土层,细根碳储量与土壤碳储量具有显著正相关关系.阔叶树种比杉木的土壤有机碳储存能力更大.     

Effects of simulated nitrogen deposition on growth and photosynthesis of 1-year-old Chinese fir (Cunninghamia lanceolata) seedlings

To study the impact of nitrogen deposition on 1-year-old Chinese fir (Cunninghamia lanceolata) seedlings in pots, the dissolved NH₄NO₃ was sprayed on the seedlings every 3 days for 1 year. The simulated elevated N depositions were equivalent to N0(0), N1(6 gN/(m² a)), N2(12 gN/(m² a)), N3(24 gN/(m² a)) and N4(48 gN/(m² a)). The results indicated that medium N treatments (N2, N3) enhanced growth significantly. The height, stem base diameter and per-seedling biomass of Chinese fir seedlings increased with N loads and decreased in the high N treatments. Compared to N0, the height and per-seedling biomass were highest in N2 treatment and increased by 10.77% and 12.35%, respectively. The stem base diameter was highest in N3 treatment and increased by 8.81% compared to N0. The net photosynthetic rate (Pn) in treatments N1, N2, N3, N4 increased by 1.20%, 9.28%, 24.23% and 4.30%, and the highest photosynthetic rate by 67.09%, 125.32%, 148.10% and 51.90%, respectively. The N1–N3 treatments, especially N2, stimulated light compensation point (LCP) of the seedlings significantly, but N4 exhibited inhibitive effect. Compared with LCP, light saturation point (LSP) showed weaker response to N loads, positive to N2, but negative to all other N treatments. Low-to-medium N treatments (N1, N2) enhanced Chl (a + b) by 2.19% and 37.15%, while medium-to-high N treatments (N3, N4) reduced Chl (a + b) by 7.95% and 15.56%, respectively. Water use efficiency (WUE) and stomatal conductance (C) decreased slightly with N loads.     

杉木采伐迹地造林树种转变对土壤可溶性有机质的影响

以二代杉木林采伐迹地上营造的19年生米老排与杉木人工林为对象,采用冷水、热水和2 mol·L^-1 KCl溶液提取0～5、5～10和10～20 cm层土壤中的可溶性有机碳(DOC)和有机氮(DON),研究造林树种转变对土壤可溶性有机质的影响.结果表明: 造林树种转变对林地土壤DOC和DON库有显著影响.米老排人工林土壤中用冷水、热水和KCl溶液浸提的DOC含量均显著高于杉木人工林,0～5和5～10 cm层土壤中用冷水和热水浸提的DON含量显著高于杉木林.不同方法浸提的DOC和DON含量大小顺序均为KCl>热水>冷水.在0～5 cm土层,米老排人工林土壤微生物生物量碳(MBC)含量比杉木林高76.3%.相关分析结果显示,热水浸提的DOC和DON与土壤MBC之间均呈显著正相关.不同树种人工林间土壤可溶性有机质的差异主要与凋落物输入的数量和质量有关.在杉木采伐迹地上营造米老排,能够明显改善土壤肥力.     

氮沉降下杉木(Cunninghamia lanceolata)人工林凋落叶分解过程中C、N元素动态变化

在12年生的杉木(Cunninghamia lanceolata)人工林中开展模拟氮沉降试验,分N0(对照)、N1、N2、N3等4种处理,N沉降量依次为0、60、120、240 kg N hm-2 a-1,每处理重复3次.通过2 a的监测和分析发现,经N0、N1、N2、N3处理后,凋落物分解过程中C平均含量分别为46.47%、46.35%、46.79%、46.6%,各处理之间无显著差异,但均随着分解时间的增加呈下降趋势.氮沉降明显增加了凋落物中的N含量,且随着沉降水平的增加而增加.各处理凋落物C的分解系数依次为0.739、0.744、0.936、0.708,周转期为4.26 a、4.26 a、3.46 a、4.41 a;而N的分解系数分别为0.458、0.543、0.776、0.565,周转期为6.26 a、5.44 a、3.91 a、5.20 a.N1处理表现出促进N释放的作用,但对C释放影响不明显;N2处理促进了凋落物C、N元素的释放,而N3处理则表现出一定的抑制作用.氮沉降处理也明显降低了凋落物的C/N比,N1、N2、N3处理使C/N比分别比N0下降8.59%、14.20%和17.54%.     

杉木宿存叶片的分解及稳定性碳氮同位素和化学组成

杉木枯死枝叶由于长期宿存于树冠,不易脱落,且生物量大,其分解和养分释放对杉木人工林营养循环具有重要意义。用比叶质量法估算了我国亚热带地区福建南平17年生杉木树冠层不同高度宿存叶片的分解程度,测定了碳氮含量、碳氮稳定性同位素及有机碳化学组成。结果表明:杉木宿存叶片的比叶质量呈现出由上向下逐渐减小的趋势,树冠8~10 m处宿存叶片的比叶质量(26.02 mg·cm-2)显著大于刚死杉木叶片的比叶质量(23.12 mg·cm-2)和6~8 m处宿存叶片的比叶质量(15.39 mg·cm-2),而0~2、2~4和4~6 m这3层宿存叶片的比叶质量无显著差异。刚死杉木叶的碳含量(50.67%)和氮含量(0.75%)显著低于不同高度宿存叶片的碳氮含量,而不同高度宿存叶片的碳氮含量和碳氮比均无显著差异。刚死杉木叶片的碳氮比(67.58)显著高于不同高度宿存叶片的碳氮比。当杉木宿存叶片的C/N为45.91±0.45时开始净氮释放。刚死杉木叶片和8~10 m高度处宿存叶片δ15N值显著高于其他高度宿存叶片,而其他高度宿存叶片的δ15N含量无显著差异。不同高度杉木宿存叶片的δ13C无显著差异。杉木宿存叶片中多糖碳和乙缩醛碳首先被分解,而烷基碳、芳碳、酚碳和羧基碳的分解速度比多糖碳和乙缩醛碳的慢。     

Determination of reactive oxygen species generated in laccase catalyzed oxidation of wood fibers from Chinese fir (Cunninghamia lanceolata) by electron spin resonance spectrometry

The aim of the present study was to determine whether the radical reaction intermediates--reactive oxygen species (ROS) were formed during the laccase-catalyzed oxidation of wood fibers from Chinese fir (Cunninghamia lanceolata) and to quantify tentatively its production with electron spin resonance (ESR) spectrometry. To investigate the activation pathways triggered by laccase, ESR spin-trapping techniques using N-tert-butyl-alpha-phenylnitrone (PBN) as spin trap followed by ethyl acetate extraction were employed to identify and quantify the free radical intermediates. ROS such as the superoxide and hydroxyl radical was detected and quantified in the laccase catalyzed oxidation of wood fibers, suggesting that ROS is the main free radical intermediates for laccase reaction. Based on the findings of the presence of ROS and previous literature on the free radical reaction of laccase oxidation of wood fibers, a possible reaction mechanism involving ROS-mediated attack on the domains of lignin which is not directly accessible for the enzyme and solubilized low-molecular mass lignins which function as reactive compounds like adhesives and may cling back to the fiber surface, could accordingly describe laccase-catalyzed oxidation of Chinese fir wood fibers.     

外生菌根真菌对杉木的接种效应

对商南县2年生杉木苗木进行乳牛肝菌(Suillus bovines)、褐环乳牛肝菌(Suillus luteus)和褐黄牛肝菌(Boletus luridus)3种外生菌根真菌的接种试验.结果显示,外生菌根真菌对杉木苗木成活率、苗高和地径生长均有明显的促进作用,能明显提高苗木的菌根化水平,增加苗木体内叶绿素含量,促进其游离脯氨酸含量的累积,降低丙二醛含量.对不同坡向杉木苗木各项生长指标的分析显示,在杉木人工造林中,阳坡的综合效应明显优于阴坡.乳牛肝菌和褐黄牛肝菌可作为一种生物肥料,在杉木人工造林中应用.     

杉木-观光木人工混交林林木竞争效应研究

将人工混交林中林木竞争影响空间划分为内、外两圈,采用Hegyi提出的单木竞争指数模型对福建省建瓯东安林场杉木（Cunninghamia lanceolata）一观光木（Tsoongi odenodrum）混交林中林木的种内、种间竞争强度进行分析。结果表明,无论是内圈还是外圈,杉木种内、种间竞争强度均随林木径级的增大而减小;竞争强度顺序为：内圈杉木种内竞争〉内圈杉木观光木种间竞争〉外圈杉木种内竞争〉外圈杉木观光木种间竞争。用模型拟合预测杉木种内、种间的竞争强度,认为杉木在胸径达到36cm之前应采取适当的控制措施。