Family selection and evaluation of Larix gmelinii var.principis-rupprechtii(Mayr.)Pilger based on stem analysis data at multiple sites

Larix gmelinii var.principis-rupprechtii(Mayr.)Pilger is an important native tree species in North China with advantages of fast growth,straight trunk,and good wood properties.The multi-year and multi-site breeding research of families of the species has not been reported previously.Based on diameter at breast height(DBH),height and volume of 25 families on four experimental sites,we calculated variance components,genetic parameters,juvenile and mature trait correlations and made genotype main effect plus genotype×environment interaction effect(GGE)biplot based on the breeding values estimated using the method of best linear unbiased prediction(BLUP).Compared with height,DBH and volume had higher heritability and larger variation coefficients,making them the more suitable traits for family selection and evaluation.Based on these,GGE biplots containing 20 combinations of site×age were drawn using data at 13 to 17 years when the interactions between family and location were strong.Test sites classifications based on DBH,and volume were inconsistent,with two categories for DBH and one for volume.The Guyuan site was the most suitable with strong discriminating ability,high representativeness and stability among tree ages.Integrating the ranking results of DBH and volume,families 66,76,82 and 111 were high-yielding and stable,families 78 and96 were high-yielding with above average stability,families72 and 79 were high-yielding with below average stability,whereas stability of family 100 was inconsistent between DBH and volume.Early selection based on DBH was convenient and reliable,and can be made at seven years.This study provides support for the selection of Larix gmelinii var.principis-rupprechtii families in Hebei province and an example for the application of stem analysis data from multiple sites in tree breeding.

Phenological observations on Larix principis-rupprechtii Mayr. in primary seed orchard

Through 5 years of phenological observations on Larix principis-rupprechtii Mayr. in primary seed orchard and studies on population and individuals of clones, the annual periodic phenological laws were revealed and the annual phe-nological periodic table was drawn up. The correlation between various phenophases, the air temperature and active accumu-lated temperature were analyzed and expounded. The authors also analyzed the similarities and differences of phenophases among clonal individuals as well as the blooming properties of male and female flowers at the same time. This study could pro-vide theoretical reference for working out the production plan of improved varieties and other management measures in seed orchard of Larix principis-rupprechtii.

Age–age correlations and early selection for growth traits in 40 half-sib families of Larix principis-rupprechtii

Larix principis-rupprechtii Mayr is a dominant species in coniferous forests of North China.However,early selection of L.principis-rupprechtii for growth traits is poorly characterised.To explore the optimal selection age for this species,heights(HT)and diameters at breast(DBH)of 40 half-sib families were measured at ages 3,12,22,and 28 years in a progeny test population established in the town of Kangjiahui,Shanxi Province.Age trends in heritability,age–age genetic correlations,and early selection efficiency for height and DBH were analysed.The individual heritability of these growth traits varied over time,and maximized at different ages(0.55 at age 12 for HT and 0.48 at age 28 for DBH).The age–age genetic correlations were always positive,and the majority were high(0.790–0.953)between the juvenile and mature ages for HT and DBH.For the same pairs of measurements,HT demonstrated higher age–age genetic correlations than DBH,and both age–age genetic correlation data sets were described well by the linear relationship with the logarithm of the age ratio(r2[0.90).The regression slope for DBH was lower than that for HT.Based on the early selection efficiency estimates,the optimal selection age could be as early as age 6 for DBH and 8–9 years for HT.The results of this study provide information that can be used to assist early selection practices in L.principis-rupprechtii improvement programs in Shanxi Province.

Variations in stem radii of Larix principis-rupprechtii to environmental factors at two slope locations in the Liupan Mountains,northwest China

Relationships between stem growth and climatic and edaphic factors,notably air temperatures and soil moisture for different slopes,are not completely understood.Stem radial variations were monitored at the bottom and top slope positions in a Larix principis-rupprechtii plantation during the 2017 and 2018 growing seasons.Total precipitation during the growing season in 2017 and 2018 was 566 mm and 728 mm,respectively.Stem contractions typically occurred after mid-morning followed by swelling in the late afternoon in both plots,reflecting the diurnal cycle of water uptake and loss.Trees at the two locations showed the same growth initiation(mid-May)because of the small differences in air and soil temperatures.There were no significant differences in cumulative stem radial growth between the bottom plot(1.57±0.34 mm)and the top plot(1.55±0.26 mm)in 2018.However,in 2017,the main growth period of the bottom plot ceased 17 days earlier than in the top plot,while cumulative seasonal growth of the bottom plot(1.08±0.25 mm)was significantly less than the top plot(1.54±0.43 mm).Maximum daily stem shrinkage was positively correlated with air and soil temperatures,solar radiation,vapor pressure deficits,and negatively correlated with volumetric soil moisture content.The maximum daily shrinkage reflected transpiration rates as affected by environmental factors.Daily radial stem increment was correlated with precipitation and volumetric soil moisture in both years,but with air temperatures only in 2017.The seasonal growth of L.principis-rupprechtii Mayr thus shows interannual dynamics,while precipitation constitutes a key driving factor.

Estimation of leaf area index from high resolution ZY-3 satellite imagery in a catchment dominated by Larix principis-rupprechtii,northern China

Leaf area index(LAI) is a key factor that determines a forest ecosystem's net primary production and energy exchange between the atmosphere and land surfaces.LAI can be measured in many ways, but there has been little research to compare LAI estimated by different methods. In this study, we compared the LAI results from two different approaches, i.e., the dimidiate pixel model(DPM) and an empirical statistic model(ESM) using ZY-3 high-accuracy satellite images validated by field data. We explored the relationship of LAI of Larix principis-rupprechtii Mayr plantations with topographic conditions. The results show that DPM improves the simulation of LAI(r = 0.86,RMSE = 0.57) compared with ESM(r = 0.62, RMSE =0.79). We further concluded that elevation and slope significantly affect the distribution of LAI. The maximum peak of LAI appeared at an aspect of east and southeast at an elevation of 1700–2000 m. Our results suggest that ZY-3 can satisfy the needs of quantitative monitoring of leaf area indices in small-scale catchment areas. DPM provides a simple and accurate method to obtain forest vegetation parameters in the case of non-ground measurement points.

Rules of Changes in Soil Nutrients and Enzyme Activities of Larix principis-rupprechtii in Different Forest Ages

In this study,three different ages of Larix principis-rupprechtii forests in 5,10 and 20 years were selected as the research objects,and the changes in soil nutrient and soil enzyme activities in different growth stages were analyzed. The results showed that the contents of organic matter and available phosphorus in the soil of different growth stages showed a significant downward trend with the increase of soil depth.For different forest ages in the same soil layer,the soil available phosphorus content declined with the increase of the forest age. The organic matter content of 40-60 cm in 20 years of forest age was the lowest in July,which was 4. 17 g/kg,significantly lower than that in other soil layers. Besides,the soil available phosphorus content of 5 years of forest age reached the maximum in July,with an average of 4. 44 mg/kg,which was higher than the available phosphorus content in soil in May and September,but the difference between the three months was not significant. The changes in ammonium nitrogen and nitrate nitrogen content in soil with different forest ages were consistent with the changes in the soil depth,showing a downward trend. In the new leaf stage,the ammonium nitrogen content of the L. principis-rupprechtii forest land in5 years of age at 20-40 and 40-60 cm of the soil depth was 13. 47 and 9. 09 mg/kg,respectively,which was 46. 9% and 64. 2% lower than that at 0-20 cm( 25. 36 mg/kg) of the soil depth. The soil nitrate nitrogen content of 20 years of forest age was 19. 24 mg/kg,which was25. 8% lower than that of 10 years of forest age,showing significant difference( P < 0. 05). In addition,with the increase of the age of L. principis-rupprechtii,soil catalase( CAT),alkaline phosphatase( ALP) and urease( Ure) decreased,and the decline of ALP was slow,while CAT and Ure decreased significantly. In summary,it is concluded that the soil fertility of forest land declined with the increase of forest age on the basis of change trend of soil nutrient and soil enzyme activity in the surveyed forest age.

Effect of thinning intensity on the stem CO_(2) efflux of Larix principis-rupprechtii Mayr

Background:Stem CO_(2) efflux(E_(S))plays a critical role in the carbon budget of forest ecosystems.Thinning is a core practice for sustainable management of plantations.It is therefore necessary and urgent to study the effect and mechanism of thinning intensity(TI)on E_(S).Methods:In this study,five TIs were applied in Larix principis-rupprechtii Mayr 21-,25-,and 41-year-old stands in North China in 2010.Portable infrared gas analyzer(Li-8100 A)was used to measure ES and its association with environmental factors at monthly intervals from May to October in 2013 to 2015.In addition,nutrients,wood structure and nonstructural carbon(NSC)data were measured in August 2016.Results:The results show that ES increased with increasing TI.The maximum ES values occurred at a TI of 35%(3.29,4.57 and 2.98μmol·m^(-2)·s^(-1))and were 1.54-,1.94-and 2.89-fold greater than the minimum E_(S) value in the CK stands(2.14,2.35 and 1.03μmol·m^(-2)·s^(-1))in July for the 21-,25-and 41-year-old forests,respectively.The E_(S) of the trees in low-density stands was more sensitive to temperature than that of the trees in high-density stands.Soluble sugars(SS)and temperature are the main factors affecting ES.When the stand density is low enough as 41-year-old L.principis-rupprechtii forests with TI 35%,bark thickness(BT)and humidity should be considered in addition to air temperature(T_(a)),wood temperature(T_(w)),sapwood width(SW),nitrogen concentration(N)and SS in the evaluation of ES.If a change in stand density is ignored,the CO_(2) released from individual 21-,25-and 41-year-old trees could be underestimated by 168.89%,101.94% and 200.49%,respectively.CO_(2) release was estimated based on the stem equation in combination with the factors influencing ES for reference.Conclusions:We suggest that it is not sufficient to conventional models which quantify ES only by temperature and that incorporating the associated drivers(e.g.density,SS,SW and N)based on stand density into conventional models can improve the accuracy of ES estimates.

Range-wide genetic diversity in natural populations of Larix principis-rupprechtii Mayr.

Prince Rupprecht’s larch(Larix principis-rupprechtii Mayr.),a deciduous conifer,widely grows in middle and high elevations of Northern China.Its natural distribution has sharply decreased and has become fragmented,which may have resulted in the loss of genetic variation.In this study,ten natural populations across the entire range of this species were analyzed using amplifi ed fragment length polymorphism markers.A total of 309 loci were detected from 225 individuals of these populations,of which 261(84.5%)were polymorphic.At the species level,the genetic diversity was high(average of the Nei’s genetic diversity H e=0.2602,and Shannon’s information index I=0.3967).The results of molecular variance analysis showed that 90.71%of the genetic diversity occurred within populations.The genetic diff erentiation among populations was moderate as a whole(F ST=0.0929,G ST=0.1510),which is consistent with the moderate level of gene fl ow among populations(N m=2.8116).Based on the unweighted pair group method with arithmetic mean and STRU CTU RE analysis,these populations were grouped into three genetically distinct clusters.The degree of inter-population diff erentiation(G ST=0.1338)for the south group was larger than that for the north group(G ST=0.0915).There was a signifi cant correlation between genetic distance and geographic distance across the species range(r=0.316,P<0.05).Genetic diversity was signifi-cantly associated with longitude but not elevation or climatic factors.The populations with high genetic diversity from each cluster are therefore recommended for future conservation and management of this species.

More tree growth reduction due to consecutive drought and its legacy effect for a semiarid larch plantation in Northwest China

Extreme climate has increasingly led to negative impacts on forest ecosystems globally,especially in semiarid areas where forest ecosystems are more vulnerable.However,it is poorly understood how tree growth is affected by different drought events.In 2006–2009,the larch plantations in the semiarid areas of Northwest China were negatively affected by four consecutive dry years,which was a very rare phenomenon that may occur frequently under future climate warming.In this study,we analyzed the effect of these consecutive dry years on tree growth based on the data of the tree rings in the dominant layer of the forest canopy on a larch plantation.We found that the tree-ring width index(RWI)in dry years was lower than that in normal years,and it experienced a rapidly decreasing trend from 2006 to 2009(slope=-0.139 year^(-1),r=-0.94)due to water supply deficits in those dry years.Drought induced legacy effects of tree growth reduction,and consecutive dry years corresponded with greater growth reductions and legacy effects.Growth reductions and legacy effects were significantly stronger in the third and fourth consecutive dry years than that of single dry year(p<0.05),which might have been due to the cumulative stress caused by consecutive dry years.Our results showed that larch trees experienced greater tree growth reduction due to consecutive dry years and their legacy effect,and the trees had lower recovery rates after consecutive dry years.Our results highlight that consecutive dry years pose a new threat to plantations under climate warming,and thus,the effect of climate extremes on tree growth should be considered in growth models in semiarid areas.

Point pattern analysis of different age-classes of Larix principis-rupprechtii in Luya Mountain Reserve,Shanxi Province,China

Larix principis-rupprechtii forest is an important vegetation formation and has a large distribution area in Luya Mountain Reserve,China.Spatial pattern analysis on individual trees in different age-classes of Larix principis-rupprechtii was made in this paper.Here,we employed the technique of point pattern analysis,which could analyze pat-terns under all scales along a gradient.It was based on spatial mapped points of individual distribution.The results of this study showed that the densities of the five age-classes varied in the order:age-class 3>age-class 4>age-class 5>age-class 2>age-class 1.Although age-classes 1 and 2 have much fewer individuals than other three age-classes do,the popula-tion was stable at present.However,it would be necessary to take some measures for improving population regeneration for a long-time view.The individuals of all age-classes focused on clumping distribution in space;however,their distribution pattern varied with the change of scale.This mainly depended on biological features of Larix principis-rupprechtii and forest environments,but it also meant that the scale was an important factor in controlling spatial distribution pattern of tree individuals.The feature of clumping distribution became more significant with the increase of age.The relationships between individuals in different age-classes were almost all significantly correlated with each other.These associations became more significant within the older age-classes.This suggested that the individuals of different age-classes were interdistributed,by which the population could get benefits in resource utilization.The technique of point pattern analysis is effective and easy to be used in species pattern study.Its results are more closer to the reality,especially for community structure.

不同林龄华北落叶松人工林叶凋落物分解及养分动态比较

采用网袋法,对0～540 d内不同林龄华北落叶松(Larix principis-rupprechtii)人工林叶凋落物的分解特征及营养元素质量分数变化动态进行了比较分析。结果表明:经过540 d的分解,幼、中、近、成熟林4个龄组的叶质量损失率为48.47%～61.72%,并呈极显著差异,不同林龄的叶凋落物分解速率呈现出成熟林>近熟林>中龄林>幼龄林。用含哑变量的Olson指数衰减模型对叶凋落物的分解动态进行拟合,结果显示,幼龄林、中龄林、近熟林和成熟林叶凋落物的分解系数为0.028 30～0.036 19;半衰期和周转期分别为1.59～2.04 a和6.90～8.82 a。在整个分解过程中,4个龄组的养分质量分数变化一致,随着时间的延长,N质量分数不断升高;P质量分数呈现出先降低后上升的趋势;K、C质量分数和C/N呈下降的趋势。在分解过程中,4个龄组的N、P、K、C的释放率在总体上变化一致,C和K不断释放,且为净释放状态,呈现直接释放模式;N的释放率为富集-释放模式;P的释放率表现为淋溶-富集-释放模式。结果表明,成熟林和近熟林的叶凋落物比幼龄林和中龄林的叶凋落物易分解,且成熟林和近熟林中的营养元素也较易释放。

落叶松种子超干贮藏含水量和引发条件的选择

采用硅胶干燥法处理华北落叶松(Larix gmelinii var.principis-rupprechtii)种子,获得含水量分别为9.11%、7.00%、5.09%、4.18%、3.21%、2.11%的种子。超干种子在室温下贮藏3个月后,进行回湿处理或PEG 6000引发处理后进行发芽试验,测定种子发芽率、发芽指数和活力指数。结果表明,超干处理的种子采用质量分数20%的PEG 6000引发有较高的种子活力。含水量为4.18%的种子发芽率、发芽指数以及活力指数均比其他含水量的超干种子高。

The effects of fall fertilization on the growth of Chinese pine and Prince Rupprecht’s larch seedlings

Nutrient loading in the fall is a practical way to improve seedling quality and has been proven to increase nutrient accumulation,translocation and utilization.Few studies have reported on the variation in free amino acids as a result of fall fertilization,especially for diff erent seasonal needle habits(evergreen,deciduous).Therefore,a balanced two-factor factorial design with one fall fertilization treatment(10 mg N/seedling)and Chinese pine(Pinus tabulaeformis Carr.)and Prince Rupprecht’s larch(Larix principis-rupprechtii Mayr.)seedlings was used to examine growth response over one nursery season.Associated changes between fall fertilization,N storage and free amino acids were analyzed.Results showed that:(1)stem height,diameter and biomass for both species were similar between controls and fall fertilization treatments;(2)compared to controls,fall fertilization increased Chinese pine needle and root N by 17.7%and 36.9%,respectively.For Prince Rupprecht’s larch,fall fertilization resulted in 26.3%and 34.54%more N in stem and roots,respectively,than controls;(3)the three main amino acids in control and fertilization treatments in Prince Rupprecht’s larch seedlings were glutamine,arginine and proline,and in Chinese pine seedlings were glutamine,arginine andγ-amino butyric acid;(4)total amino acid contents were not signifi cantly increased by fall fertilization,but glutamine in Chinese pine and Prince Rupprecht’s larch increased by 64.2%and 35.2%,respectively.Aboveground biomass of Prince Rupprecht’s larch had higher proline contents than Chinese pine,which suggests that the stress resistance of the aboveground tissue may be higher for Prince Rupprecht’s larch.The results indicate that diff erent plant organs with various response are well adapted to nitrogen loading for nutrient storage in evergreen and deciduous conifer seedlings.

不同经营模式下华北落叶松人工林土壤理化性质

为了研究不同经营模式下华北落叶松(Larix gmelinii var.principis-rupprechtii)人工林土壤理化性质的差异性,以河北省木兰围场国有林场燕格柏分场36年华北落叶松人工林为研究对象,选取目标树经营(S)、均质经营(N)以及对照(CK)样地,分析不同经营模式下华北落叶松人工林土壤理化性质的差异,以期对冀北地区华北落叶松人工林经营提供理论和实践依据。结果表明:1)从土壤物理性质指标上看,不同经营模式下华北落叶松林下土壤毛管孔隙度、总孔隙度、最大持水量均表现为目标树经营>均质经营>对照。2)从土壤化学性质指标来看,不同经营模式下华北落叶松林下土壤铵态氮、有效磷、速效钾、有机质以及pH值化学性质指标表现为目标树经营>均质经营>对照,其中速效钾含量目标树经营改善效果明显,与均质经营以及对照具有显著差异(P<0.05);土壤有机质含量目标树经营与对照差异显著(P<0.05),与均质经营差异不显著。总体来看,目标树经营下的华北落叶松人工林土壤理化性质指标相较于均质经营以及对照有明显改善。

不同混交比例华北落叶松和白桦混交林碳储量

以河北省承德市围场满族自治县塞罕坝机械林场华北落叶松[Larix gmelinii var.principis-rupprechtii(Mayr)]—白桦(Betula platyphylla Suk.)混交林为研究对象,采用标准地调查法,获取相应数据,通过FORECAST模型,模拟不同立地条件、不同混交比例(落桦比2∶1,1∶1,1∶2,1∶3,1∶4)混交林300年(6个轮伐期)碳储量时空变化,结果表明:落桦混交比例1∶2、1∶3和1∶4林分土壤碳储量在6个轮伐期内呈现上升趋势。落桦比为2∶1和1∶1混交林在6个轮伐期内土壤有机碳储量呈下降趋势,且华北落叶松比例越高,土壤退化程度越严重。落桦比为1∶2的混交林在1个生长周期内碳储量最大,并且这种营林方式也有利于土壤有机碳库的积累。无论是从经济价值的角度还是从改良土壤有机碳库的角度来讲落桦比为1∶2能够积累更多的碳储量。

Response of larch species to climate changes

Global warming has changed the distributions of forests of northeastern China.Larix are very important species in this area.Predicting the potential distributions of Larix species and their responses to climate change would attract more and more attention.This paper predicted the potential distributions of three Larix species based on‘climatic-topographic’relationships by logistic regression.The results showed that L.gmelinii is predicted to retreat northwestward by 220 km by 2050 and by 270 km more by 2100;L.olgensis var.changpaiensis is predicted to retreat northwestward by 200 km by 2050 and by 190 to 300 km more by 2100;L.principis-rupprechtii is predicted to retreat northeastward by 200 km by 2050 and by 250 to 400 km more by 2100.This indicated that L.gmelinii could have its optimum latitude moved into Russia,L.olgensis var.changpaiensis could move to the Small Xing’an Mountains and L.principisrupprechtii would move to the middle part of the Great Xing’an Mountains.

Quartered neighbor method: A new distance method for density estimation

Quantitative data are essential to an appro-priate characterization of vegetation.In the past few years,considerable attention has been paid to vegetation sampling techniques.A number of methods have been developed for plant density estimations that utilize spacing distances instead of fixed-area quadrats.In this paper,we review the main distance methods for estimating density and propose a new distance method denominated the quartered neighbor method.In this method,the sampling point is considered the center,and the area around it is divided into four quadrants.The distance from the closest individual in each quadrant to its closest neighbor in the same quadrant is measured,and the average of them is the distance we need.It is actually an integration of two old distance methods,the nearest neighbor method,and the point-centered quarter method.With our new method and an old distance method(the point-centered quarter method),we calculated the average spacing distances of the Larix principis-rupprechtii population in the larch forests of the Donglingshan Mountain.Comparing the two methods with the quadrat method,we found they were almost the same in accuracy,but the precision of the new one was better.Meanwhile,it is adequate in sampling intensity and adaptable for general use in rapid ecological survey work.

缓释肥对华北落叶松容器苗生长的影响

为探究缓释肥对华北落叶松（Larix principis-rupprechtii Mayr）容器苗生长的影响,设置3个处理,测定不同处理条件下容器苗的苗高、地径和生物量。结果表明,缓释肥能够有效地促进华北落叶松容器苗的生长,有助于苗木生物量的累积。当施氮量为100mg/株时,容器苗的苗高、地径和生物量累积均达到最大值,分别为12.14cm、2.51mm、0.51g,显著高于其他处理,施加量过高或者过低均不利于容器苗的生长。

关于中阳县造林树种多样化的探索

根据中阳县县域造林树种的选择历史和保存状况遴选出3个分布范围较广生长良好的树种：白皮松（Pinus bungeana）、华北落叶松（Larix principis-rupprechtii）和五角枫（Acer truncatum）,通过分析其分布区域的立地条件、生境特征,结合其生物学特性,总结了3个树种的适生环境和在中阳县适宜推广的区域,以利于中阳县造林树种的多样化发展,改善林分结构,发挥森林持续稳定的生态效能。