Objective: To study the growth, accumulation and soil nutrient content of each overseeded species under different interharvesting intensity treatments of Eucalyptus, and to explore the best re-cultivation method suitable for mixed overseeded species after Eucalyptus interharvesting. Methods: In Guangxi state-owned Qipo forest, Eucalyptus tailorii with different planting densities (DH32-29) were mixed with Castanopsis hystrix, Mytilaria laosensis and Michelia macclurei, and four different treatments (CK, LT, MT and HT) were established for re-cultivation of Eucalyptus near-mature forests with different logging intensities, and the differences in growth conditions and soil physicochemical properties of each species were analyzed. Results: (1) As the proportion of Eucalyptus allocation decreased, the growth of Eucalyptus diameter at breast height, tree height and individual wood volume could be promoted; the growth of the three parameters of HT and MT Eucalyptus were significantly different from LT and CK. (2) The average wood volume per plant of the set species in the CK and LT treatments was Mytilaria laosensis > Michelia macclurei > Castanopsis hystrix, while in the MT and HT treatments it was Mytilaria laosensis > Castanopsis hystrix > Michelia macclurei. (3) The differences in soil aeration, total saturated water holding capacity, capillary water holding capacity, and field water holding capacity in soil layers of different depth varied. In the same soil layer, soil aeration, total porosity and capillary porosity were HT > CK > LT > MT; saturated water holding capacity and capillary water holding capacity were HT > CK > LT > MT, while field water holding capacity was CK > HT > LT > MT. (4) Organic matter, pH, total nitrogen, total phosphorus, total potassium, fast-acting nitrogen, fast-acting phosphorus, and fast-acting potassium changed with varying soil depth in each treatment.

为建立枫香(Liquidambar formosana)景观优良无性系繁殖的技术体系,以枫香4年生播种苗为母树,开展枫香扦插繁殖技术研究.考虑4个因素,每因素设置3～6个处理,具体为因素A:4种基质,因素C:6种ABT1号生根促进剂浓度,因素H:5种插穗长度,因素L:3种插穗类型,每处理重复3次,每重复扦插45根插穗,采用随机区组试验设计.结果表明:扦插基质以A3最好,平均生根率可达85.93％;ABT1号生根促进剂浓度C3最适宜,平均生根率可达87.41％;插穗长度H3最好,平均生根率可达74.81％;插穗类型L2最好,平均生根率可达76.30％.上述研究结果表明,彩叶树种枫香扦插的最佳组合为采用珍珠岩∶泥炭土 ∶红壤土=1∶1∶1(体积比)的基质,用1 000 mg/L浓度ABT1号生根促进剂,选取15cm半木质化枝条,平均生根率可达80％左右.

The rapid growth and expansion ofCryptomeria japonica (Thunb. ex L. f.) D. Don in karst area strongly affects plant composition of native deciduous broad-leaved forest, which seriously threat ecosystem function and service. Given the importance of soil microorganisms in regulating nutrients cycling and plant species coexistence, understanding soil microbial attributes and their relationships with soil and vegetation features in forests harboring different C. japonica abundance will help understanding the drivers of ecosystem function changes. Here we examined the diversity and composition of soil bacterial and fungal communities and their correlations with plant diversity as well as soil physicochemical properties in karst broad-leaved forests with different relative abundances of C. japonica (i.e., a high, moderate, low and no proportion level with a stem density of 1,487, 538, 156 and 0 plant/hm2, respectively) in Mid-Subtropical China. We found that soil pH decreased while soil water content (SWC), total nitrogen (TN), total phosphorus (TP) and total potassium (TK) tended to increase with the increase in C. japonica abundance. In contrast, soil available nitrogen (AN), available phosphorus (AP) and available potassium (AK) content declined by 26.1%∼49.3% under the high level of C. japonica abundance. A gradual decrease in relative abundance of Acidobacteria and Chloroflexi while a pronounced increase in relative abundance of Ascomycota and Basidiomycota were observed with increase of C. japonica abundance. Alternations in bacterial composition were closely related to changes in AP and AK, while the change of fungal structure was mainly related to SWC, soil organic carbon (SOC) and pH, indicating that bacterial community was sensitive to declines in soil available nutrients and fungal structure was sensitive to changes in soil physicochemical properties (i.e., pH and SWC) and organic carbon resource. Understory plants had the highest α-diversity in forest containing moderate abundance of C. japonica, which might be related to the high bacterial diversity. Our findings suggest conservation of soil bacterial and fungal taxa that are responsible for nutrients availability and carbon sequestration is of great significance for improving the resistance of natural deciduous broad-leaved forests to the rapid spread of C. japonica in karst areas. Moreover, Acidobacteria, Chloroflexi, Ascomycota and Basidiomycota are potential indicators for soil properties changes, which should be taken into consideration in karst forest managements.

[目的]建立千年桐优株选择综合评价体系,进行千年桐优株的准确评价,为千年桐育种奠定理论基础.[方法]以湘南地区实生繁殖的进入盛果期的5 000 hm2千年桐为选优林分,根据单株结果数、单株产果量、树体大小、树形、果实聚集度等表型指标初步确定565株千年桐,通过复选确定40株备选优树,再从40株备选优树中筛选出优株.根据对单株结果量、单株产果量、冠高比、冠形指数、鲜果单果质量、鲜果出籽率、干籽出仁率、种仁含油率、病虫害程度、果熟一致性、果实聚集度11个性状指标,进行了聚类分析和综合评价,建立了千年桐优树综合评价体系.[结果]利用综合评价法,从40株备选优树选出了19株优树,然后对19株优树进行聚类分析,结果为三类,其中Ⅰ类4株、Ⅱ类5株、Ⅲ类10株;Ⅰ类优树的单株结果量、单株产果量的均值分别为1 181个、29.68 kg,是Ⅱ类优树均值的1.63、1.62倍,是Ⅲ类优树的1.65、1.71倍,是40株备选优树的1.87、1.85倍.Ⅰ类优树的鲜果单果质量、鲜果出籽率、干籽出仁率、种仁含油率的均值分别为41.63 g、51.20%、59.97%、59.75%,是Ⅱ类优树均值的1.14、1.03、1.01、1.11倍,是Ⅲ类优树均值的1.16、1.35、1.12、1.17倍,是40株备选优树均值的1.14、1.23、1.15、1.17倍.Ⅰ类优树4株可作为嫁接繁殖的采穗母树,可进一步作为目标优树.[结论]基于综合评价法筛选出的优树为千年桐优良无性系选育打下了基础.

[目的]研究抚育间伐对不同年龄杉木林分生长和林下植被多样性的影响,旨在明晰抚育效益,为杉木人工林提质改造提供理论依据.[方法]以8年生、13年生、18年生杉木人工林为研究对象,分别设置抚育(25％株数间伐强度)与对照(不间伐)两种处理,连续4年对林木生长和林下植被进行观测.[结果]抚育间伐促进了树高、胸径、单株材积和蓄积的增长,8年生、13年生杉木树高年生长量抚育间伐与对照之间均达到显著水平(P<0.05),18年生杉木无显著性差异.3种年龄杉木抚育间伐与对照之间胸径和单株材积年生长量均具有显著性差异(P<0.05).8年生、13年生杉木抚育间伐与对照之间蓄积年生长量有显著性差异(P<0.05),18年生杉木无显著性差异(P>0.05).抚育间伐改善了杉木干形,3种年龄杉木树干林分平均实验形数均为抚育大于对照,抚育间伐对8年生、13年生杉木树干实验形数的变动幅度有显著性影响(P<0.05),对18年生杉木无显著性影响(P>0.05).抚育间伐4年后,3种年龄杉木林下植物种类比对照分别增加了7、6、4种,林下植被Shannon-wiener、Simpson和Pielou指数均呈增加趋势,抚育间伐与对照之间Shannon-Wiener和Pielou的变化值有显著性差异(P<0.05),Simpson的变化值差异不显著(P>0.05).8年生、13年生、18年生杉木的抚育间伐效益分别为17.39％、56.06％和23.15％,3者之间差异显著.[结论]抚育间伐可以促进不同年龄杉木人工林生长,改善林木干形,提高林下植被多样性,缩短林木成材期,持续发挥其多功能效益.

以川西9a生柳杉人工林为研究对象,设置对照（CK,0%）、轻度间伐（T1,21.1%）、中度间伐（T2,36.9%）、重度间伐（T3,49.0%）共4种处理,观测抚育间伐对林木生长和土壤有机碳的影响,结果表明:间伐4年后柳杉胸径、树高、蓄积量年平均生长量均为间伐＞CK,两者间均存在显著差异（P＜0.05）,胸径年平均生长量大小排序为T3＞T2＞T1＞CK,各处理间差异显著（P＜0.05）,间伐样地各处理间树高和蓄积量年平均生长量差异不显著（P＞0.05）;T2与T3林内径阶株数占比向更高径阶集中;0～40 cm土层有机碳含量与碳密度均值T2与T3显著大于CK（P＜0.05）;抚育间伐可显著降低土壤容重、提高毛管持水量,土壤全N均值T2和T3显著大于CK（P＜0.05）,间伐样地0～20 cm土层有机碳含量和碳密度与全N及全P之间存在极显著相关性（P＜0.01）。中等间伐强度（T2）能够获得较高的生态和经济效益。

为给千年桐无性系高效栽培繁育提供参考,以湘南地区千年桐8年生优树为采穗母树,以千年桐播种苗为砧木,研究嫁接方法、砧木苗龄和高度、套袋、接穗成熟度等5个因素对千年桐成活率的影响.结果表明:1年生砧木芽接、切接、劈接的成活率分别为65.00％、53.33％、36.67％,芽接的成活率与劈接有显著差异,与切接无显著差异.1年生砧木的平均嫁接成活率为47.9％,2年生砧木为23.33％,1年生砧木芽接、劈接、切接的成活率与2年生砧木均有显著差异.20、30、50 cm高1年生砧木的切接成活率分别为53.33％、65.00％、40.00％,30 cm砧木的嫁接成活率与50 cm砧木存在显著差异,20 cm砧木与30 cm砧木和50 cm砧木的切接成活率均无显著差异.1年生砧木套袋的平均嫁接成活率为51.67％,不套袋的为39.44％,1年生砧木套袋切接成活率与不套袋切接有显著差异.1年生砧木半木质化绿色枝、木质化绿色枝、褐色老枝的平均嫁接成活率分别为46.92％、29.83％、16.83％,芽接、切接、劈接时3种接穗间平均嫁接成活率均存在显著差异.因此,整套嫁接技术的最优组合为芽接+1年生砧木+套袋+半木质化绿色枝,嫁接成活率最高可达80％.

以江西省靖安县8a生湿地松人工林为研究对象,设置对照(C,0％)、轻度间伐(L,15％)、中度间伐(M,35％)、重度间伐(H,55％)4种处理,观测抚育间伐对林木生长和林下植被的影响,结果表明:与C相比,随着间伐强度的增加,林木的径阶分布向右偏移,径阶分布L和M符合正态分布、C和H不符合正态分布;抚育间伐对林木胸径和蓄积的生长有明显的促进作用,胸径年平均生长量C与H和M存在显著差异,蓄积年平均增长量C与H存在显著差异,树高年平均生长量各处理间差异不显著;抚育间伐对林下植被种数的增加和植被层Simpson,Shannon-Wiener和Pielou指数的提高总体上有促进作用,这种促进作用在间伐后的前两年比较明显,后随着时间的延迟逐渐减弱.