Lime-induced chlorosis inPinus radiata

Summary Addition of marl (CaCO₃) and/or manure to an acid soil in pots caused lime-induced chlorosis inPinus radiata seedlings, especially after excessive irrigation for 15 days. Chlorotic symptoms and their intensity were found to be related more to soil moisture and to the HCO₃ ^– concentrations, than to percentage of free CaCO₃, in the soil mixtures.Comparative chemical analysis showed lower total Fe and Mn concentrations and higher concentrations of cations and organic anions in the needles of seedlings with chlorotic symptoms than in the needles of healthy ones.     

巴山松天然林生物量和生产力的研究

 经测定分析陕西南部28—37年生巴山松天然林的生物量和净初级生产量,结果表明,林分乔木层生物量为81.28t／ha,草本下木生物量为1.45t／ha,林分凋落物量为11.16t／ha;乔木层净初级生产量为6.94t／ha·yr,约45%分配到树叶。巴山松林的消光系数平均为0.33。在地上部生产结构方面,枝重主要集中在树冠中、下部,叶龄愈大,叶重在树冠下部的比例愈高。巴山松林木的根系总长度约99.4km／ha,其中细根占58%。     

浙江省松阳县黄山松种群的密度与生物量动态

 本文研究了浙江省松阳县关山源地区黄山松种群的密度与生物量动态以及它们之间的相互关系。黄山松是该地区森林演替中的先锋种群之一。在演替过程中,黄山松种群的动态可分成三个阶段。大约在黄山松种群入侵次生裸地的最初10年期间,种群的密度和生物量迅速增长(阶段Ⅰ)。此后,种群密度达到饱和,由于自疏作用出现以及其他阔叶树种的入侵,种群密度开始急剧下降,个体平均重量和种群生物量迅速增长(阶段Ⅱ),–3/2自疏定律适用于种群动态的此阶段。随着阔叶树种进入林冠层,虽然个体平均重量仍缓慢增长,黄山松种群的密度和种群生物量逐渐下降直至退出群落(阶段Ⅲ)。但在一些特殊生境中(如裸岩陡坡或山脊),黄山松种群可形成稳定的地形顶极群落,其种群密度、个体平均重量和种群生物量可长期维持相对稳定的状态。     

Survival and Infectivity of Bursaphelenchus xylophilus in Wood Chip-Soil Mixtures

To determine the effect of soil environment on the life stages and total numbers of Bursaphelenchus xylophilus, nematode-infested wood chips alone and mixed with soil were incubated at 12 and 20 C. Nematodes were extracted at 2-week intervals for 12 weeks. Numbers of nematodes and percentage of third-stage dispersal larvae were greater at 12 C and in chips without soil. Percentage of juveniles of the propagative cycle was greater at 20 C and in chips with soil. Although B. xylophilus survived in chips with soil for 12 weeks, nematode numbers and life stage percentages changed little over time. To determine if B. xylophilus was capable of infecting wounded roots, infested and uninfested chips were mixed with soil in pots with white and Scots pine seedlings. Trees were maintained at 20 and 30 C and harvested at mortality or after 12 weeks. Only seedlings treated with infested chips contained nematodes. In field experiments, planted seedlings were mulched with infested chips to determine if nematodes would invade basal stem wounds. Among these trees, Scots pine was more susceptible than white or red pines to infection and mortality.     

Long-term needle litterfall of a Scots pine Pinus sylvestris stand: relation to temperature factors

Summary Needle litterfall of a Scots pine was caught over 24 years (1962–1986) with litter-traps in a Scots pine stand in southeastern Finland. The age of the trees averaged 111 years in 1962. The stand was naturally recruited and only minor silvicultural treatments occurred during its history. Litterfall showed great year-to-year variation, the minimum being 18 g/m² (in 1968) and maximum 213 g/m² (in 1973). There was no overall trend in the amount of litterfall, and the age of the stand was thus not important in determining the needle fall. We used time domain time series analysis (ARIMA) and standard climatic data (temperature, precipitation) to investigate the relationship of litterfall to climatic factors. Mean July temperature was clearly correlated with needle litterfall. High temperature in July coincided with enhanced litterfall in the same and the next year. Litterfall enhanced litterfall in the same and the next year. Litterfall increased also after high temperatures during March–April, but only in the same year. In addition to these the litterfall had a 4-year self-dependency. This is approximately the same as the mean longevity of needles in the study area. Altogether the time series model we propose covers about 90% of the variance of the original time series.     

Soil acidification as caused by the nitrogen uptake pattern of Scots pine (Pinus sylvestris)

Three-year-old Scots pine (Pinus sylvestris) trees were grown on a sandy forest soil in pots, with the objective to determine their NH₄/NO₃ uptake ratio and proton efflux. N was supplied in three NH₄-N/NO₃-N ratios, 3:1, 1:1 and 1:3, either as ¹⁵NH₄+¹⁴NO₃ or as ¹⁴NH₄+¹⁵NO₃. Total N and ¹⁵N acquisition of different plant parts were measured. Averaged over the whole tree, the NH₄/NO₃ uptake ratios throughout the growing season were found to be 4.2, 2.5, and 1.5 for the three application ratios, respectively. The excess cation-over-anion uptake value (C_a-A_a) appeared to be linearly related to the natural logarithm of the NH₄/NO₃ uptake ratio. Further, this uptake ratio was related to the NH₄/NO₃ ratio of the soil solution. From these relationship it was estimated that Scots pine exhibits an acidifying uptake pattern as long as the contribution of nitrate to the N nutrition is lower than 70%. Under field circumstances root uptake may cause soil acidification in the topsoil, containing the largest part of the root system, and soil alkalization in deeper soil layers.     

Characterization of cDNAs encoding CuZn-superoxide dismutases in Scots pine

A Scots pine (Pinus sylvestris L.) cDNA library was screened with two heterologous cDNA probes (P31 and T10) encoding cytosolic and chloroplastic superoxide dismutases (SOD) from tomato. Several positive clones for cytosolic and chloroplastic superoxide dismutases were isolated, subcloned, mapped and sequenced. One of the cDNA clones (PS3) had a full-length open reading frame of 465 bp corresponding to 154 amino acid residues and showed approximately 85% homology with the amino acid sequences of angiosperm cytosolic SOD counterparts. Another cDNA clone (PST13) was incomplete, but encoded a putative protein with 93% homology to pea and tomato chloroplastic superoxide dismutase. The derived amino acid sequence from both cDNA clones matched the corresponding N-terminal amino acid sequence of the purified mature SOD isozymes. Northern blot hybridizations showed that, cytosolic and chloroplastic CuZn-SOD are expressed at different levels in Scots pine organs. Sequence data and Southern blot hybridization confirm that CuZn-SODs in Scots pine belong to a multigene family. The results are discussed in relation to earlier observations of CuZn-SODs in plants.     

Tracheid production in response to indole-3-acetic acid varies with internode age in Pinus sylvestris stems

Summary Different concentrations of indole-3-acetic acid (IAA) in lanolin were applied to the cambial region of approximately 10- and 34-year-old internodes in the main stem of Pinus sylvestris (L.) trees during the tracheid production period. After 5 weeks of treatment, the radial width of xylem produced in both ages of internode was positively related to exogenous IAA concentration measured at 0, 1 and 3 cm directly below the application site. Tracheid production in response to exogenous IAA in the 34-year-old internode was approximately one-half of that in the 10-year-old internode. The endogenous IAA level in the 7-, 17- and approximately 34-year-old internodes of similar trees was measured by radioimmunoassay, using gas chromatography-selected ion monitoring-mass spectrometry for validation. No consistent relationship was found between xylem radial width and IAA concentration. The data indicate that the cambium's ability to respond to exogenous IAA is qualitatively the same in 1-year-old shoots and older internodes. However, as the internode ages, there is a decrease in the extent of the response and in the optimal IAA level for inducing tracheid production.