Effect of soil physical–chemical properties on the decay of standing Pinus koraiensis in Xiaoxing'an Mountains,northeast China

We selected 18 rotten and nine healthy post- mature live standing Korean pine （Pinus koraiensis） to study the correlation between the degree of tree decay and soil physical-chemical properties in the Dialing Forest District of the Xiaoxing＇an Mountains, China. One trans- verse section of each sample tree at 40-50 cm height above the ground was tested by Resistograph to determine the inner decay status. We collected soil samples around the root zones （6-20 cm depth） of each sample tree to test the soil physical-chemical indicators including moisture con- tent, bulk density, total porosity, pH, organic matter con- tent, total and hydrolyzed N contents, total and available P contents, total and available K contents, and C/N ratio. The degree of decay of postmature Korean pine live standing trees was significantly and positively correlated with the C/N ratio （R = 0.838, P 〈 0.05）, organic matter （R = 0.615, P = 0.007） and moisture content （R = 0.543, P = 0.020） of soil around the rodt. The contents of total N, hydrolyzed N and available P sample trees were significantly in the soil under healthy greater than those underdecayed sample trees, and larger N and P contents might inhibit the decay fungi breeding in soils of pH 4.4-6.29. The optimum multiple regression equation for degree of tree decay on soil physical-chemical indicators showed that the linear correlations between the degree of decay and soil C/N ratio and pH were significant （P 〈 0.01） and the correlation was high （R2 = 0.778）. Enhancement soil C/N ratio and pH could promote the decay of tree trunks.

Theoretical modeling of the effects of temperature and moisture content on the acoustic velocity of Pinus resinosa wood

To investigate the effects of temperature and moisture content(MC) on acoustic wave velocity(AWV)in wood,the relationships between wood temperature,MC,and AWV were theoretically analyzed.According to the theoretical propagation characteristics of the acoustic waves in the wood mixture and the differences in velocity among various media(including ice,water,pure wood or oven-dried wood),theoretical relationships of temperature,MC,and AWV were established,assuming that the samples in question were composed of a simple mixture of wood and water or of wood and ice.Using the theoretical model,the phase transition of AWV in green wood near the freezing point(as derived from previous experimental results) was plausibly described.By comparative analysis between theoretical and experimental models for American red pine(Pinus resinosa) samples,it was established that the theoretically predicted AWV values matched the experiment results when the temperature of the wood was below the freezing point of water,with an averageprediction error of 1.66%.The theoretically predicted AWV increased quickly in green wood as temperature decreased and changed suddenly near 0 °C,consistent with the experimental observations.The prediction error of the model was relatively large when the temperature of the wood was above the freezing point,probably due to an overestimation of the effect of the liquid water content on the acoustic velocity and the limited variables of the model.The high correlation between the predicted and measured acoustic velocity values in frozen wood samples revealed the mechanisms of temperature,MC,and water status and how these affected the wood(particularly its acoustic velocity below freezing point of water).This result also verified the reliability of a previous experimental model used to adjust for the effect of temperature during field testing of trees.

Effect of moisture content on the ultrasonic acoustic properties of wood

We determined the ultrasonic velocity and en- ergy attenuation value of three tree species （basswood, elm, and fir） 1 per tree in different moisture content levels, using RSM-SY5 ultrasonic testing instrument, and analyzed the regularity of ultrasonic velocity and energy attenuation values with moisture content, respectively. The ultrasonic velocity of the three species decreased as moisture content increased, with the turning point at 32 % of moisture content. When the moisture content was more than 32 %, the growth curve of ultrasonic wave velocity was flattened. The moisture contents of all three species increased under the any point moisture content of 1-60 %. The differen- tiation degrees of energy attenuation value of three species were higher than the corresponding ultrasonic wave ve- locity, when the moisture content was less than 15 %. The differentiation degrees of the energy attenuation value of three species was higher than the corresponding ultrasonic velocity, when the moisture content was more than 15 %.

Propagation behavior of acoustic wave in wood

We used acoustic tests on a quarter-sawn poplar timbers to study the effects of wood anisotropy and cavity defects on acoustic wave velocity and travel path, and we investigated acoustic wave propagation behavior in wood. The timber specimens were first tested in unmodified condition and then tested after introduction of cavity defects of varying sizes to quantify the transmitting time of acoustic waves in laboratory conditions. Two-dimensional acoustic wave contour maps on the radial section of specimens were then simulated and analyzed based on the experimental data. We tested the relationship between wood grain and acoustic wave velocity as waves passed in various directions through wood. Wood anisotropy has significant effects on both velocity and travel path of acoustic waves, and the velocity of waves passing longitudinally through timbers exceeded the radial velocity. Moreover, cavity defects altered acoustic wave time contours on radial sections of timbers. Acous-tic wave transits from an excitation point to the region behind a cavity in defective wood more slowly than in intact wood.

Relationship between severity of trunk decay of Pinus koraiensis and soil properties around roots

The decay rate of standing Korean pine(Pinus koraiensis)in natural forests can be as high as 50%and is likely infl uenced by the soil properties and nutrient and water status of the site.To clarify the relationship between the severity of tree decay and soil properties in order to prevent decay in a natural mixed forest in the Xiaoxing'an Mountains,wood strength of standing trees was nondestructively assessed,and the severity of decay of extracted wood cores was quantified based on differences in mass between two decayed increment cores extracted at breast height and an intact increment core near the decayed ones.Soil samples from the critical root zone(non-rhizosphere)of each tree were analyzed for chemical properties and microbial composition.The abundance of chemical elements(especially total N and K)and the species richness of soil microbes increased as decay severity increased.Fungal number(FN)and actinomycetes number(AN)were related to decay severity(R^(2)=0.504).Bacterial number(BN)was higher than FN or AN,but had a minor effect on tree decay.Path analysis showed BN might indirectly inhibit decay by affecting FN.Decay severity was not significantly correlated with either soil fungal or bacterial diversity.These results suggest that forest managers need to monitor levels of fungi and total N and total K levels to reduce the decay of Korean pine.

Mechanical properties,components and decay resistance of Populus davidiana bioincised by Coriolus versicolor

The experiment was conducted to improve the decay resistance of wood by increasing the wood preservatives uptake and penetration depth by bioincising with Coriolus versicolor.The mechanical properties of bioincised Populus davidiana sapwood were measured.The changes of wood components(lignin,cellulose and hemicellulose)were analyzed by FTIR.The staining treatment using potassium permanganate was to measure the preservatives uptake and penetration depth in wood specimens.The decay resistance of bioincised specimens impregnated with IPBC and CA was assessed against C.versicolor and Gloeophyllum trabeum using bioincised P.davidiana sapwood and untreated controls.The results showed that the mechanical properties of the bioincised specimens were changed with the incubation time and mass loss.The mechanical strength was decreased after 17 days compared to that of the specimens bioincised<13 days.The bioincised specimens demonstrated the deeper penetration depth than the un-bioincised specimens.It was significant correlation(P<0.01)between penetration depth and incubation time.The average value of the penetration depth of the bioincised specimens was deeper than the control groups by 158.7%.By FTIR analysis,the biodegradation ability of C.versicolor to decay cellulose and hemicellulose was weaker than that of lignin.The bioincising treatment significantly increased the wood uptake of IPBC and CA,and reached the maximum uptake value at 17 and 13 days,respectively.Summarily,the bioincising pretreatment can obviously improve the wood decay resistance against C.versicolor and G.trabeum following by introducing the IPBC and CA.

水稻穗部性状QTL定位及候选基因分析

水稻(Oryza sativa)穗部性状与产量直接相关,其相关基因的挖掘与功能解析对于保障国家粮食安全意义重大。以籼稻华占(HZ)和粳稻热研2号(Nekken2)及构建的120个重组自交系(RILs)为实验材料,测定了穗长、每穗粒数、结实率、柱头外露率及一次枝梗数等穗部性状。结合高密度分子遗传图谱进行QTL定位,结果共检测到31个QTLs,分别位于第1、2、3、4、5、6、10和11号染色体上,其中2个位点的LOD值分别高达5.45与5.28。通过分析筛选QTL区间内可能影响穗部性状的相关基因,并利用qRT-PCR进行基因表达检测,发现LOC_Os05g05490、LOC_Os05g06150、LOC_Os03g11700、LOC_Os03g12430、LOC_Os05g28720、LOC_Os05g30890、LOC_Os05g31740和LOC_Os02g17880在双亲间的表达水平差异显著。其中,前5个基因编码三角状五肽重复蛋白,而后3个基因编码糖基转移酶。研究挖掘到31个与穗部性状相关的QTLs,为进一步定位和克隆相关基因,从而选育高产水稻新品种奠定理论基础。