长白落叶松人工林心材变化规律

依据黑龙江省孟家岗林场49株人工落叶松1179个圆盘和轮盘数据,分析了心材半径的纵向变化规律.结果表明: 心材半径随树高增高而逐渐减小,与树干外形基本一致,其中去皮半径(XR)、胸径(DBH)及形成层年龄(CA)与心材半径之间关系较显著,利用逐步回归分析建立落叶松心材半径(HR)和面积(HA)模型:HR=b₁+b₂XR²+b₃CA+b₄XR, HA=b₁+b₂DBH·XR+b₃CA+b₄DBH·XR².应用AIC、BIC、对数似然值以及似然比检验等模型评价指标,对利用样地、样木效应拟合的心材半径和面积模型进行比较.当考虑样木效应拟合心材半径和面积模型时,将b₁、b₂、b₃作为混合参数得出的模型最好.混合模型的预测精度高于基本模型.在应用上,总体心材半径和面积可以通过混合模型来预测.采用Beta回归模型模拟了心材比例,模型中各参数均显著,决定系数较高,模型模拟效果较好.     

Analysis of household's energy consumption,forest degradation and plantation requirements in Eastern Tigray,Northern Ethiopia

This study examines the link between household's energy consumption, forest degradation and plantation requirements in Eastern Tigray. Data on household's fuelwood, cow‐dung, kerosene and electricity consumption in the study sites were collected from 557 urban and 114 rural households. Deforestation rate was estimated following FAO and Woody Biomass Inventory Strategy Planning Project (WBISPP's) conversion factors. The study showed that household's fuelwood consumption in urban areas (mean = 2.5 kg/day) was about 52% lower as compared to the rural villages (mean = 3.8 kg/day). The estimated area abandoned annually in the vicinity of urban areas as the result of urban fuelwood consumption varies from 217 ha around Maichew town to 12047 ha around Mekelle City. The estimated area abandoned in rural areas annually as the result of tree cutting for fuelwood also varies from 6.5 ha around Sinkata to 127 ha around Dergajen village. It is therefore recommended that an estimated annual tree plantation of area ranging from 286 ha around Maichew town to 21,684 ha around Mekelle city is required. Moreover, an estimated annual tree plantation of area ranging from 16 ha around Sinkata village to 229 ha around the Dergajen village is required taking the existing population into account.     

Effects of patch size and basal area on avian taxonomic and functional diversity in pine forests: Implication for the influence of habitat quality on the species–area relationship

Relationships between avian diversity and habitat area are assumed to be positive; however, often little attention has given to how these relationships can be influenced by the habitat structure or quality. In addition, other components of biodiversity, such as functional diversity, are often overlooked in assessing habitat patch value. In the Sandhills Ecoregion of Georgia, USA, we investigated the relationship between avian species richness and functional diversity, forest basal area, and patch size in pine forests using basal area as a surrogate for overstory structure which in turn impacts vegetation structure and determines habitat quality within a patch. We conducted bird surveys in planted mature pine stands, during breeding season of 2011. We used three classes of stand basal area (BA): OS, overstocked (BA ≥ 23 m²/ha); FS, fully/densely stocked (13.8 m²/ha ≤ BA < 23 m²/ha); and MS, moderately stocked (2.3 m²/ha ≤ BA < 13.8 m²/ha). MS patches showed more structural diversity due to higher herbaceous vegetation cover than other two pine stocking classes of patches. Total species richness and functional richness increased with the size of MS patches, whereas functional divergence decreased with the size of OS patches (p < 0.05). Functional richness tended to be lower than expected as the size of OS patches increased. Greater richness of pine–grassland species was also found at MS patches. Percent cover of MS patches within a landscape influenced positively the richness of pine–grassland species (p < 0.05). Our results suggest that (a) avian species–habitat area relationship can be affected by habitat quality (structural diversity) and varies depending on diversity indices considered, and (b) it is important to maintain moderate or low levels of pine basal area and to preserve large‐sized patches of the level of basal area to enhance both taxonomic and functional diversity in managed pine forests.     

Soil‐dwelling insect pests of tree crops in Sub‐Saharan Africa,problems and management strategies—A review

This review aims to draw the attention of researchers, ecologists and farmers to the threats of soil‐dwelling insect pests on important tree crops in sub‐Saharan Africa, with a special focus on termites. It synthesizes the information on the effects of various factors affecting soil pest occurrence and damage, suggesting that the resultant undesirable effects of soil pests in this region are largely as a result of indiscriminate tree cutting, slash‐and‐burn agriculture and indiscriminate use of pesticides. Major insect orders, their host ranges and the nature of damage on selected tree crops are described. This study further critiques existing soil pest management practices, showing that majority of soil pest management practices are ineffective. Thus, management strategies like “attract and kill” approach based on entomopathogenic fungi need to be studied, developed and emphasized for the management of soil insect pests in sub‐Saharan Africa. A conclusion section attempts to offer suggestions for ways in which future work on soil pests in sub‐Saharan Africa could proceed.     

管理措施对人工林土壤质量的影响

可持续性生产力是人工林发展的一个关键问题。然而,人工林培育过程中常出现土壤质量退化和人工林生产力下降等问题。管理措施是人工林发展过程中土壤质量变化的一个重要因素,正确的管理措施能够维护和提高林地的土壤质量。管理措施主要包括整地、施肥、林地收获与凋落物管理和营造混交林等。不同的整地方式、整地强度、整地时间等能改变土壤物理、化学和生物学性状,进而对其土壤质量产生一定的影响;施肥措施能改善土壤质量、提高人工林生产力,而过量施肥能够导致林地养分的流失和地下水质的恶化;木材收获和林地凋落物焚烧导致人工林系统养分的大量流失,加强对人工林系统有机物质的保护有利于林地土壤质量的改善;营造混交林在一定程度上有利于土壤质量维护,由于物种间存在复杂的相互关系,其对混交树种、混交方式和立地条件的选择等管理措施均能影响土壤质量。最后,文章对今后人工林管理措施对土壤质量影响的重点研究方向作了展望。     

改变碳输入对亚热带人工林土壤微生物生物量和群落组成的影响

通过在亚热带杉木(Cunninghamia lanceolata)和米老排(Mytilaria laosensis)人工林中设置互换凋落物、去除凋落物、去除凋落物+去除根系和对照处理来分析改变地上、地下碳输入对人工林土壤微生物生物量和群落组成的影响。结果显示,改变地上、地下碳输入对土壤微生物生物量碳、氮的影响因树种而异。在米老排林中,土壤微生物生物量不受碳源的限制。而在杉木林中,加入米老排凋落物、去除凋落物和去除凋落物+去除根系3种处理中土壤微生物生物量碳、氮具有明显增加的趋势。磷脂脂肪酸分析结果显示,杉木林中,添加高质量的米老排凋落物后,革兰氏阳性细菌、阴性细菌、丛枝菌根真菌、放线菌和真菌群落生物量分别显著增加了24%、24%、53%、25%、28%,革兰氏阴性细菌和丛枝菌根真菌的相对丰度均有显著增加。与对照相比,杉木林中去除凋落物后革兰氏阳性细菌、阴性细菌、丛枝菌根真菌、放线菌和真菌群落生物量分别显著增加了22%、29%、44%、25%、52%,真菌与细菌比值显著增加了21%。但是,去除凋落物+去除根系处理对两个树种人工林土壤微生物群落组成均无显著影响。米老排和杉木林土壤微生物生物量碳、氮的季节变化格局不同,土壤养分有效性可能是驱动土壤微生物生物量季节变化的主要因子。未来研究需要关注凋落物和根系在不同树种人工林中对土壤微生物群落的相对贡献。     

青藏高原东缘不同树种人工林对土壤酶活性及养分的影响

为评价不同树种人工林对土壤酶及养分的影响,选择立地条件和营林方式相同的4种人工林(连香树[CJ]、油松[PT]、落叶松[LK]和华山松[PA])为研究对象,以落叶灌丛(QC)为对照,比较不同树种人工林地土壤酶活性和土壤养分的变化。结果显示:(1)造林降低了土壤酸性磷酸酶、脱氢酶、β-葡萄糖苷酶和过氧化氢酶活性,但人工造林后土壤脲酶活性增加;(2)造林也明显影响了土壤养分,与对照林地相比,除CJ人工林土壤中磷(P)略高外,造林地土壤有机碳(TOC)、氮(N)、水可提取有机碳(WEOC)和氮(WEON)、铵态氮(NH+4-N)和硝态氮(NO-3-N)均降低;(3)不同的人工林树种之间土壤养分及酶活性也存在一定的差异性,CJ和LK人工林土壤C、N、P及相关酶活性明显不同于PT和PA人工林;(4)土壤酶与养分变化有一定的相关性,除转化酶和多酚氧化酶反应较迟钝外,其它酶对环境反应较敏感。综合分析表明,在川西地区选择高密度单一树种造林并没有改善土壤养分和酶活性,在该地区选择落叶或阔叶树种造林可使土壤肥力恢复。     

不同林龄油松(Pinus tabulaeformis)人工林植物、凋落物与土壤C、N、P化学计量特征

在陕西省北部延安市境内子午岭林区,采用时空互代的方法选取9、23、33、47年生油松(Pinus tabuliformis)人工林为研究对象,比较油松不同器官(叶、枝、干、根)、凋落物及土壤C、N、P含量及其比值的差异,探讨它们随林龄的变化及其相互间的关系,以期为油松人工林的生产、改善和林木生长环境的调节提供参考。结果表明:除根中C含量在林龄间差异不显著外,其它器官C、N、P含量及其比值在林龄间均差异显著且随林龄增加变化趋势不尽相同。9、23、33、47年生油松林C、N、P含量及N∶P比值均在叶中最高;C∶N比值均在干中最高,根中次之;C∶P比值均在干中最高,其它器官大小次序不一。除33年生油松林叶中N∶P比值大于14外,其它各器官各林龄N∶P比值均小于14,且N∶P比值随林龄先增加后减少,故可判断油松在该区域受N限制较为严重,且随林龄的增加受N限制的情况有所缓解。不同林龄土壤和凋落物C、N、P含量及其比值差异显著,且后者均大于前者。土壤与凋落物C、P含量及C∶N、C∶P、N∶P比值随林龄增加变化趋势完全一致,表明土壤与凋落物之间有着密切的关系。叶片与凋落物N、P含量及C∶N、C∶P、N∶P比值之间显著相关,表明凋落物的养分承自植物叶片,二者之间关系紧密;植物和土壤的C、N、P含量之间均不存在显著相关性,说明土壤C、N、P供应量对乔木叶片C、N、P含量影响不大。     

浅层地下水对华北地区河岸杨树林树干液流的影响

华北地区河岸杨树林生长季的用水特征对杨树人工林经营管理具有重要意义.本文以北京市潮白河畔的杨树人工林为研究对象,采用热扩散式探针(TDP)测定树干液流、管式TDR土壤含水量法测定土壤体积含水量、开路涡度相关系统测定环境因子数据,对2014年6—7月的杨树树干液流及其影响因素进行系统研究,以探究浅层地下水对树干液流的可能影响.结果表明: 杨树树干液流日变化随太阳辐射呈现单峰或双峰变化,在土壤水分相对亏缺时,杨树树干液流密度明显减小,达到峰值的时间从14:00提前到12:30,但树干液流对太阳辐射的时滞效应没有明显变化.在表层土壤水分相对充足时,太阳辐射和空气饱和水汽压差是杨树树干液流变化的主导因子,但在表层土壤水分亏缺时,土壤水会成为杨树树干液流的限制因子;当表层土壤水分相对亏缺时,杨树单株耗水与100 cm土层土壤体积含水量呈显著负相关,与其余各土层体积含水量呈显著正相关.浅层地下水(相对稳定的150 cm及更深处)在土壤表层土壤水分含量相对亏缺时,可在毛管力作用下对上层土壤水进行补充,供给杨树生长需要.