三江源东部祁连圆柏天然更新特征研究

天然更新是维持天然林可持续发展的重要途径,祁连圆柏天然林集中分布于青海三江源地区,了解该林分天然更新状况及影响机制,对于维护三江源水生态安全具有重要的战略意义。本研究以三江源东部麦秀林场祁连圆柏天然林为对象,采用系统调查、室内分析、相关与通径分析相结合的方法,探讨了天然更新状况及影响林分天然更新的关键因子。结果表明:1）林分天然更新不良,平均更新密度为220株·hm^-2,林下缺乏幼苗补充,更新幼树种群处于衰退状态;2）林龄、林分密度、平均树高、草本盖度、海拔对更新幼树密度的影响达到显著水平,其中林分密度起正向和负向促进作用;林龄、平均树高、草本盖度起间接阻碍作用;海拔起间接促进作用。3）林龄、林分密度、平均树高、海拔是影响更新幼树密度的主要因素。     

A new natural spiro heterocyclic compound and the cytotoxic activity of the secondary metabolites from Juniperus brevifolia leaves

A new natural spiro compound 3,4-dehydrotheaspirone and the known arctiol [1β,6α-dihydroxy-4(14)-eudesmene] were isolated from Juniperus brevifolia. Arctiol is reported for the first time in the Juniperus genus. Their structures were established by 1D, and 2D NMR and MS spectra. Antimicrobial and cytotoxic activities of 1 and several secondary metabolites ,,,,,,,,, previously isolated by our group from J. brevifolia were evaluated and some SAR has been established. The 18-hydroxydehydroabietane (4) displayed great antiproliferative activity against cancer cell lines tested, namely HeLa, A-549 and MCF-7. Compound 4 also presented a significant bactericidal effect against Bacillus cereus at different concentrations tested.     

Land-use legacy of historical tree harvesting for charcoal production in a semi-arid woodland

Historical processes may have longer lasting effects in arid forest and woodlands because of slow rates of succession. We investigated the influence of historical tree harvesting upon contemporary spatial dynamics of pinyon-juniper woodland in the western United States. Despite intensive and widespread harvesting of woodland by the charcoal industry during the late 19th century, the role of afforestation has seldom been addressed as a potential mechanism for the dramatic expansion of pinyon-juniper woodlands over the past century. Spatial models of disturbance processes are one way to ascertain effects of such historical influences. We developed a process-based spatial model to estimate the historical tree harvest pressure according to a parsimonious set of rules and constraints. The model used a convection-diffusion approach that incorporated the influences of topography, transportation, and mining production. We used a combination of field-surveyed, archaeological, historical, and GIS data sets to calibrate, validate, and compare the alternative mathematical models. Model results were consistent with the historical harvest evidence (AUC > 0.66), with high harvest intensity closer to the mining districts, quickly decreasing at the maximum distance of influence. Performance was improved by including the local terrain. Harvesting initially showed radial patterns emanating from the significant mining districts, and then gradually expanded northward with development of the railway system. Our spatial modeling approach provides a means to assess the pattern and magnitude of historical tree harvesting in semi-arid woodlands. The general approach can be applied to explore the importance of other historical disturbance and cultural processes, whose effects may no longer be evident, in forests and woodlands worldwide.     

Potential variation of nitrogen transformations in pinyon-juniper ecosystems resulting from burning

Summary Forest floor litter, duff, and underlying soils were assembled in laboratory microcosms representing pinyon, juniper, and interspace field conditions. Burning removed more than 95% of both N and C from the litter, with losses from the duff dependent on soil moisture conditions. No significant changes in total N or C were noted in the soil. Immediate increases were observed in soil NH _inf4 ^sup+ , decreasing with depth and related to soil heating. The greatest increases were noted in both the pinyon and juniper soils that were dry at the time of the burn, with interspace soils exhibiting the least changes. Soil NH _inf4 ^sup+ closely approximated the controls on day 90 after the burns in all treatments. Ninety days after the burn microbial biomass N was highest in the controls, followed by the wet and then the dry-burned soils, in both the pinyon and juniper microcosms. This was inversely related to the levels of accumulated NO _inf3 ^sup- . Nitrifying bacteria populations were indirectly correlated to soil temperatures during the burn. Population levels 90 days after the burn showed increases in both the wet- and the dry-burn treatments, with those in the pinyon treatments exceeding those found in the nitial controls of pinyon soils.The use of trade and company names in this paper is for the benefit of the reader; such use does not constitute an official endorsement or approval of any service or product by the U.S. Department of Agriculture to the exclusion of others that may be suitable     

侧柏毒蛾在萧山的发生与防治

对侧柏毒蛾在杭州市萧山区苗木基地的发生情况、生物学特性进行了观察,结果表明,侧柏毒蛾在萧山1 a发生2代,以卵越冬,4 ～ 5月和7 ～ 8月是幼虫为害期,幼虫为害侧柏、桧柏、刺柏等的嫩梢枝叶,造成枝叶枯死,树势减弱.并根据其生物学特性和初步防治试验结果提出了防治方法.     

川南退耕丛生竹林枯落物持水特性研究

以四川省长宁县退耕梁山慈竹、撑绿杂交竹3号(以下简称撑绿竹)和硬头黄竹3种丛生竹林为对象,对其枯落物蓄积量及持水特性进行了研究。结果表明:不同种类丛生竹枯落物厚度为33～51 mm,蓄积量为6.88～9.46 t/hm²,其大小顺序为:梁山慈竹>硬头黄竹>撑绿竹;浸泡持水实验表明,不同枯落物持水量、吸水速率与浸水时间的动态变化具有相似的规律性:0～2 h变化最快,2～8 h逐渐减缓,8 h以后基本饱和,并分别得出其相关关系;不同枯落物最大持水量、最大拦蓄量和有效拦蓄量变化规律一致,最高为梁山慈竹,分别达到了36.52,32.53,27.05 t/hm²,其次为硬头黄竹,分别为30.33,28.33,23.83 t/hm²,最低的为撑绿竹,仅为28.35,25.89,21.63 t/hm²。     

贺兰山杜松种子萌发的影响因素研究

【目的】研究不同预处理及环境因素对贺兰山杜松种子萌发的影响,为提高杜松种子的萌发效率、促进杜松林实生更新及人工栽培奠定基础。【方法】在气候箱内模拟林间生境条件,研究不同温度(5,10,15,20,25,30,35℃)、光照时间(0,10,24h)、土壤含水量(10%,15%,20%,25%,30%,35%,40%,45%)、埋土深度(0,1,2,3,4,5cm)及超声波时间(0,5,10,15,20,25,30min)和不同质量分数(0%,10%,20%,30%)聚乙二醇(PEG)浸种2种预处理方法对贺兰山杜松种子萌发的影响。【结果】不同温度下杜松种子萌发率、萌发势和发芽指数差异显著,萌发的适宜温度为15~25℃;杜松种子在全光照(24h)条件下的萌发率高达71%,显著高于其他非全光照处理;杜松种子萌发的最适土壤含水量为20%,在此条件下的萌发率可达75%;埋土深度对杜松种子萌发有一定影响,以1~2cm浅层埋土更适宜于种子萌发;超声波和PEG预处理均能促进种子萌发,种子萌发率随超声波时间的延长与PEG溶液质量分数的增大而呈现先升高后降低的变化趋势,59kHz、500 W超声波处理10 min种子的萌发率最高,但仍低于经20%PEG溶液浸泡24h时的萌发率。【结论】在4种环境因素与2种预处理方法中,光照时间和PEG预处理是影响杜松种子萌发的重要因素。用20%的PEG溶液浸泡种子24h后,在25℃、全光照、土壤含水量20%、埋土深度1~2cm条件下,杜松种子萌发效果最佳,萌发率可达75%。     

施肥对硬头黄竹林地上部分生物量结构的影响

以赣县3种不同施肥处理及不施肥对照的硬头黄竹林为研究对象,调查和测定其单丛分株数、立竹年龄结构和生物量,研究施肥对硬头黄竹地上部分生物量结构的影响。结果表明,施肥能有效地提高硬头黄竹林的立竹数量和地上部分群体生物量。与对照相比,矿渣肥、毛竹专用肥和复合肥处理立竹数分别增加了26.33、20.50株·丛^-1和8.5株·丛^-1,地上生物量分别增加了109.24、22.92 g·株^-1和162.63 g·株^-1;不同处理单丛生物量表现为矿渣肥>毛竹专用肥>复合肥>CK。矿渣肥肥效时间较长,1 a竹所占比例比CK提高了5.31%,而毛竹专用肥和复合肥对竹林年龄组成的调节作用较弱。复合肥处理分别对3 a秆、2 a枝和1 a叶生物量提高的作用最强,矿渣肥分别对2 a秆和3 a枝、叶生物量提高的作用最强。地上生物量在不同施肥处理、不同年龄和不同构件间差异均显著（P<0.05）。随着年龄和竹高的增加,秆生物量的增加速率最大,其次分别为叶和枝。硬头黄竹地上部分的生物量中,秆生物量占的比例最大,叶的生物量次之,略大于枝生物量所占比例。因此,在硬头黄竹林的经营管理中,除了进行施肥外,还应合理采伐,使竹林保持合理密度。     

四川不同地区硬头黄竹RAPD和ISSR分析

以四川不同地区硬头黄竹为研究对象.通过随机扩增多态性DNA标记(RAPD)和简单序列重复区间(ISSR)标记进行扩增,探讨硬头黄竹的遗传多样性.研究表明,6个RAPD引物扩增出了42条条带,多态性高达69.05%;5个ISSR引物扩增出了47条条带,多态性为61.70%.利用Popgen32进行聚类分析,聚类结果可将不同地区的硬头黄竹类型区分开来.其遗传距离分别为0.182 3～0.602 2和0.043 5～0.672 1,说明RAPD和ISSR分子标记为硬头黄竹的遗传改良提供了理论依据.     

Ecological assessment of populations of Juniperus phoenicea L. in the Al-Akhdar mountainous landscape of Libya

The Phoenician juniper (Juniperus phoenicea L.) has long been common in the Al-Akhdar mountain range in NE Libya. Juniper trees in the region are showing signs of dieback, and minimal successful seedling recruitment has occurred. We investigate this effect at the level of individual trees, tree size classes, and populations. At ten sites, population size, growth and reproductive traits, and percentage dieback in different size classes were evaluated. Elevation, distance from the sea, and the interaction between these factors had a significant effect on tree volume, and number of branches, number of female cones per branch and number of female cones per tree. Two groups of populations were recognized: the first (Sites 2, 3, and 4) were near the coast. They appeared to be more recently established, with no individuals in the largest size class, and, at this point, less severe dieback. In contrast, in the rest of the sites there were no individuals (Sites 1, 5, 6, and 9) or very few individuals (Sites 7, 8, and 10) in the smallest size class, indicating widespread failure of recruitment in recent years. Mature female cones containing seeds were abundant at these sites (except for Site 8); therefore, this was not attributable to failure of sexual reproduction, but rather was associated with higher levels of intra- and inter-specific competition, combined with more variable rainfall in recent years. Smaller trees are particularly susceptible to dieback throughout the region. Conservation initiatives should include restrictions on clearing these natural forests for conversion to agriculture and, where harvesting is necessary, preferential harvesting of larger individuals.