Metal pollution in relation to mass outbreaks of Dendrolimus punctatus Walker on Pinus massoniana Lamb.in China

Insects with their ecological superpower have enormous capacity to transform small pollution damage in forests to full scale calamities. Acid rain resulting from extensive coal burning is the chief pollutant in China. Acid rain activates from soil deposits toxic metals, which are transferred to trees and further to insects eating them. We studied the levels of the toxic Cd, its antagonists Zn and Cu, and acid rain indicators Fe and Mn in the forest pest moth Dendrolimus punctatus Walker (Lepidoptera:Lasiocampidae) in variously polluted Pinus massoniana Lamb forests in China.\; The highest density of D. punctatus , as well as the highest Cd levels developed in the moderately polluted forests. Possibly Cd had there broken down the pest resistance of the pines. The paradoxical coexistence of high Cd level and elevated population density of the pest seems to result from the high accumulation of Cd in its ichneumonid parasitoid. In the most heavily polluted forests the Cd level in needles was low, possibly because the strong acid rain had washed away most of the Cd deposit in the soil. It existed there no D.punctatus population. Absence of pest insects from the most heavily polluted areas is a common phenomenon.

Microenvironmental effects on growth response of Pinus massoniana to climate at its northern boundary in the Tongbai Mountains,Central China

The Tongbai Mountains is an ecologically sensi-tive region and the northern boundary of Pinus massoniana Lamb.To analyze the effect of different microenvironments on tree growth response to climate factors,we developed standard chronologies for earlywood width(EWW),late-wood width(LWW),and total ring width(TRW)of P.massoniana at two sampling sites on slopes with different orientations,then analyzed characteristics of the chronolo-gies and their correlations with climate variables from five stations in the region and with a regional normalized differ-ence vegetation index(NDVI).Statistical results showed that the TRW/EWW/LWW chronology consistency and charac-teristics(mean sensitivity,signal to noise ratio,expressed population signal)for trees growing on the southeastern slope were much higher than for trees on the northeastern slope.Correlations indicated that temperature in current March and August has a significant positive effect on TRW/EWW/LWW formation,and the effect on the northeastern slope was weaker than on the southeastern slope.Compared to temperature,precipitation has more complicated effects on tree growth,but the effect on the northeastern slope was also generally weaker than on the southeastern slope.Step-wise linear regression analyses showed that temperature in August was the main limiting factor at the two sampling sites.Similarly,the response of tree growth on the southeast-ern slope as determined by the NDVI is better than on the northeastern slope,and the TRW/EWW/LWW chronologies for the southeastern slope explained over 50%of the total NDVI variances in June.Overall,the results indicate that the difference in the climate response of P.massoniana at two sampling sites is clearly caused by differences in the microenvironment,and such differences should be properly considered in future studies of forest dynamics and climate reconstructions.

Intratree Variation in Viscoelastic Properties of Cell Walls of Masson Pine (Pinus Massoniana Lamb)

In this study,Pinus massoniana Lamb at different heights,across the annual rings,and between earlywood and latewood was measured by X-ray diffraction and the chemical composition was analyzed by chemical treatment.Results indicated that the microfibril angle(MFA)decreased and the chemical composition changed little with the increase in height from 1 m to 9 m.In the radial direction,the MFA decreased and the chemical composition changed little with an increase in annual rings.The cellulose content of latewood was higher than that of early-wood.The viscoelastic changes of wood cell walls at different heights,across the annual rings by the method of quasi-static nanoindentation and dynamic modulus mapping techniques.Results indicated that the wood cell walls’elastic modulus increased,and the creep rate and creep compliance decreased with the increase in height;The elastic modulus and hardness increased with the annual rings.The cell walls’storage modulus increased and the loss modulus gradually decreased with an increase in height;the storage modulus gradually increased and the loss modulus decreased with the annual rings.

The essential oil components of Cinnamomum cassia: an analysis under different thinning models of plantation Pinus massoniana

Thinning is an important activity employed in forest management. To date, studies have mainly focused on the effects of thinning on the growth of trees during the same thinning period. In this study, plantation Pinus massoniana Lamb. near maturity were thinned at varying intensities and an economically important species, Cinnamomum cassia Presl., was planted beneath the thinned canopy. The aim of the study was to explore the effects of the extent of thinning on the essential oil content and its components of C. cassia in different parts of the plant, as well as the economic feasibility of the P. massoniana-C.cassia management model. Thinning significantly reduced the oil yield in the bark and branches of C. cassia, but hardly impacted the oil yield from C. cassia leaves compared with pure C. cassia forest（CK）. Among the different thinning treatments, both light（T.4） and extensive（T.1）thinning reduced the oil yield of C. cassia bark and new branches. The concentrations of the main aldehydes differed in different parts of the plant and were affected by the extent of thinning. The influence on cinnamaldehyde in the bark was minor, but was much greater in the branches and leaves. Both the oil yield and content of cinnamaldehyde showed that moderate（T.3） thinning was more favorable than other thinning models. These results not only provide a potentially promising model for the transformation of low-yield artificial pure forests of P. massoniana in the future, but also offer a reference for the management of artificial mixed stands.

Effects of sulfur dioxide on growth， gas exchange rate and leaf sulfur content of massion pine seedlings

The effects of sulfur dioxide(SO_2) on the dry weight growth gas exchange rate and leaf sulfur content of massion pine(Pinus massoniana Lamb. )were investigated. The results obtained in this study show that the dry weight growth and net photosynthetic rate of masson pine seedlings are reduced by exposure to SO_2 at ≥100 ppb. From these results,one of the main causes in the dieback of masson pine forest reported in Chongqing,China may be relatively high concentrations of atmospheric SO_2 in the relevant area.

生根剂和季节对马尾松嫩枝扦插生根率的影响

以马尾松组培苗为采穗母株,开展了生根剂类型及浓度、插穗浸泡时间和扦插季节等因子对扦插生根效果影响的研究,为马尾松(Pinus massoniana Lamb.)优良种质的高效利用提供技术支持。结果表明:不同浓度IAA、IBA、NAA和ABT1生根剂对马尾松组培苗插穗生根有一定的促进作用,生根率为12.4%~20.7%,总体效果较差,同一生根剂不同浓度处理间差异不明显;自制生根剂扦插生根率随生根剂浓度增大先上升后下降,各浓度间差异显著,其中,以100 mg/L浓度扦插效果最好,生根率达到86.8%。插穗生根率随浸泡时间延长先上升后下降,不同浸泡时长间生根率差异显著,其中,以浸泡4 h效果最好,生根率达到82.1%,与快蘸相比提高了191.1%。不同季节扦插生根率和生根时间差异明显,平均生根率以秋季最高(97.1%),春季次之(81.1%),夏季最低(32.3%);平均生根时间在春季、夏季、秋季和冬季分别为35、29、47、62 d。实际育苗生产中,可根据马尾松组培苗插穗生根特点,选择在夏季和冬季进行母株管护和更新,以提高生产效率。