皖江滩地杨树抑螺防病林下植物多样性分析

以时空互代的方法,对皖江段滩地不同林龄的杨树人工林林下植物多样性进行了调查。结果表明:①杨树人工林林下以草本植物为主,居于前4位的优势科分别是菊科(9种)、禾本科(6种)、豆科(5种)、蓼科(5种),优势种以萝藦、菱叶鹿藿、无辣蓼、葎草为主。木本植物有桑科桑树、蔷薇科野蔷薇;②滩地造林后,林下植物的丰富度、多样性指数、均匀度指数均高于无林滩地上以芦苇为主的群落;③随着人工林林龄的增加,多样性指数表现出了先降低后上升的趋势,3年生的人工林丰富度(S)、多样性指数(D,H′)最高,20年生的人工林均匀度指数最高。滩地造林后植物多样性有一定程度增加,但成林后植物多样性又逐年减少。     

青藏高原东缘不同人工林替代乡土灌木对地被物水文特征的影响

尽管森林地被物在保水与养分循环中扮演重要角色,但我们仍然对由植被转换引起的森林地被物的变化缺乏了解。为评价不同人工林替代乡土灌丛对森林地被物水文特性的影响,我们选择了4种人工林（连香树Cercidiphyllum japonicum[Cj],油松Pinus tabulaeformis[Pt],华山松Pinus armandi[Pa],落叶松Larix kaempferi[Lk]）,以次生乡土灌丛（QC）（Quercus liaotungensis和Corylus heterophylla var.sutchuenensis为优势种）为对照。人工林种植于1987年,初始密度为2500株ha-1。我们发现针叶人工林地被物厚度和贮量明显大于次生灌丛地和阔叶人工林地。地被物最大持水量在各林地之间差异与厚度和贮量显示相同的趋势,我们认为其主要贡献因子为林地凋落物数量及单位重量凋落物的最大持水量差异。地被物吸水过程和吸水速率与浸泡时间分别呈对数与指数回归关系。吸水过程在各植被之间与地被物各层次之间明显不同,主要受各植被的凋落物叶结构与分解程度影响。我们的结果显示针叶林地被物储量明显高于阔叶林,这说明以针叶树种为优势的林地大量养分滞留在凋落物中,难于返还土壤被植物利用,同时,半分解层（F）和分解层（H）最大持水能力高于未分解层（L）,因此,改善林地微环境,促进L层地被物向F和H层转化,是改善人工林地被物水文功能的主要方法之一。     

不同更新方式对中亚热带森林土壤理化性质的影响

森林的不同更新方式对森林土壤理化性质有重要影响．本研究通过野外调查探讨中亚热带山区杉木人工林和米槠人促更新林2种不同更新方式下林地土壤理化性质的变化特征,并用土壤退化指数定量描述土壤质量变化．结果表明：杉木人工林土壤表层（0—10cm）容重显著高于米槠人促更新林（P〈0．05）;随土壤深度的增加,杉木人工林和米槠人促更...     

Effects of afforestation on soil carbon turnover in China’s subtropical region

Afforestation in China’s subtropics plays an important role in sequestering CO2 from the atmosphere and in storage of soil carbon (C). Compared with natural forests, plantation forests have lower soil organic carbon (SOC) content and great potential to store more C. To better evaluate the effects of afforestation on soil C turnover, we investigated SOC and its stable C isotope (δ13C) composition in three planted forests at Qianyanzhou Ecological Experimental Station in southern China. Litter and soil samples were collected and analyzed for total organic C, δ13C and total nitrogen. Similarly to the vertical distribution of SOC in natural forests, SOC concentrations decrease exponentially with depth. The land cover type (grassland) before plantation had a significant influence on the vertical distribution of SOC. The SOC δ13C composition of the upper soil layer of two plantation forests has been mainly affected by the grass biomass 13C composition. Soil profiles with a change in photosynthetic pathway had a more complex 13C isotope composition distribution. During the 20 years after plantation establishment, the soil organic matter sources influenced both the δ13C distribution with depth, and C replacement. The upper soil layer SOC turnover in masson pine (a mean 34% of replacement in the 10 cm after 20 years) was more than twice as fast as that of slash pine (16% of replacement) under subtropical conditions. The results demonstrate that masson pine and slash pine plantations cannot rapidly sequester SOC into long-term storage pools in subtropical China.     

杉木-观光木混交林不同经营模式土壤团粒结构的分形特征

利用分形理论、弹性分析及边际分析方法对四种不同经营模式的杉木人工林进行了研究。探讨了四种杉木人工林的土壤团粒结构分形维数对林地土壤性质变化影响的效应。结果表明:土壤>0 25nm的团聚体及水稳性团聚含量越大,团粒结构的分形维数越小,土壤肥力越高,在四种经营模式中以杉木同观光木行间混交的土壤壮况最好;土壤团粒结构的分形维数与土壤团聚体、水稳性团聚体之间存在显著回归关系。分形理论为林地土壤科学管理提供了理论依据。     

Relative contribution of evapotranspiration and soil compaction to the fluctuation of catchment discharge: case study from a plantation landscape

ABSTRACT

Over the last decade, monoculture plantations have rapidly developed in Jambi Province on Sumatra, Indonesia. Meanwhile, there has been intensification of discharge fluctuation in the study area. We examined the relative contribution of changes in evapotranspiration and soil compaction to the catchment discharge by using the Soil Water Assessment Tool model. Evapotranspiration values based on the catchment water balance analysis in intensively cultivated oil palm plantations, smallholder oil palm plantations, rubber plantations, and the secondary forest are 5.03 ± 0.30, 4.11 ± 0.38, 3.36 ± 0.32, and 4.50 ± 0.18 mm d^?1, respectively. Infiltration rate in active interrows of oil palm, rubber plantations, agroforest, oil palm frond pile is 2.6 ± 1.7, 16.3 ± 6.8, 28.0 ± 3.9, 58.2 ± 21.8 cm h^?1, respectively. We found that increased evapotranspiration and soil compaction increased the frequency of low discharge by 30%, with increased evapotranspiration contributing 10% and increased soil compaction contributing 20%.     

Estimation of suspended sediment sources using 137Cs and 210Pbex in unmanaged Japanese cypress plantation watersheds in southern Japan

To analyse suspended sediment sources in unmanaged Japanese cypress plantation watersheds, field measurements and fingerprinting of the suspended sediment was conducted in the Shimanto River basin in southern Japan. For sediment fingerprinting, ¹³⁷Cs and ²¹⁰Pb_ex were detected by means of gamma‐ray spectrometry in the surface soil of the forest floor, stream bank and truck trail and mobilized sediment by interrill erosion. The ¹³⁷Cs and ²¹⁰Pb_ex activities associated with the forest floor materials were considerably higher than those of the stream bank and truck trail. The ¹³⁷Cs and ²¹⁰Pb_ex activities associated with the suspended sediment were found to vary with the sampling period. Evidently, the suspended sediment can comprise materials generated from the forest floor by interrill erosion and those from the truck trail and/or stream bank. The multivariate sediment‐mixing model using ¹³⁷Cs and ²¹⁰Pb_ex showed that the contribution of the forest floor varied periodically, ranging from 23–56% in the Hinoki 156 subwatershed and from 18–85% in the Hinoki 155 subwatershed. The difference in the average contribution of the forest floor between Hinoki 156 (46%) and Hinoki 155 (69%) may relate to the presence of truck trail networks in the watershed. The truck trail network can play roles of sediment source and pathway for sediment from forest floor to stream channel due to the concentrated overland flow on the truck trail during heavy rainfall events. These results indicate that the forest floor should be recognized as a major source of suspended sediment in unmanaged Japanese cypress plantation watersheds. Copyright © 2008 John Wiley & Sons, Ltd.     

古尔班通古特沙漠人工林土壤水分及其影响因素

通过2004年2～12月对古尔班通古特沙漠南缘2年生人工梭梭和沙拐枣混交林内3条典型坡面土壤水分进行了系统监测与研究。结果表明:人工林土壤水分状况受季节性降水、人工林种植密度、地形因子的影响而出现明显的时空分异。在空间上将土壤水分变化划分为三层,0～30cm为活跃层,30～60 cm为次活跃层,60～120 cm为相对稳定层。通过主成分分析,得出地形因子、种植密度对0～30 cm土层土壤水分的影响次序为坡度>坡向>种植密度>高程,30～60 cm土层为坡向>种植密度>坡度>高程,60～120 cm土层为种植密度>高程>坡度>坡向。     

大孔径闪烁仪法测算低丘山地人工混交林显热通量的可行性分析

利用位于河南省济源市的华北低丘山地30年生栓皮栋-侧柏-刺槐人工混交林2009年主要生长季节(5-9月)湍流通量及空气结构参数等观测数据,确定迭代法为该下垫面条件下大孔径闪烁仪(LAS)测算显热通量的计算法,测算白天大气非稳定层结状况下的显热通量(HLAS).并采用通量印痕模型,对LAS法通量源区内由2台涡度相关系统观测得到的显热通量进行订正,得到源区内总显热通量值(HfEC).分析LAS法与涡度相关法的显热通量测算或测定值的相关性,结果表明:HLAS与HfEC的线性相关系数可达0.93.说明在分析通量印痕和通量源区的基础上,采用LAS法测算低丘山地人工混交林显热通量具有较好的可行性.     

Different times,same story: Native forest loss and landscape homogenization in three physiographical areas of south-central of Chile

Temperate forest represents the smallest area among the main world's forest biomes, but is one of those most threatened by forest loss. Chile contains most of the temperate forest in South America and more than half of the temperate forest in the southern hemisphere. Chilean temperate forest is considered to be one of the world's biodiversity hotspots. In this study we assessed the rate of land use and land cover (LULC) change over time, identified the main LULCs replacing native forest, and described how changes have evolved in contrasting physiographical conditions and through different historical phases of the landscape over the last 40 years. To achieve this, we analysed LULC change with particular focus on forest cover in three areas representing different physiographical conditions and histories of human occupation in the Araucanía Region of Chile, namely the Central Valley, the Coastal range, and the Andean range. We found substantial differences in temporal and intra-regional patterns of forest loss and LULC change. In the Central Valley, forest loss started long ago, and the area occupied by native forest nowadays is less than 5% of the landscape. In the Coastal range, rapid land cover change has taken place since 1973, with an increasing rate of forest loss over time. We detected a similar but less intense pattern in the forests of the Andean range. Overall, the general pattern points to a process of landscape homogenization in all three physiographical areas. Exotic tree plantations have spread over large geographical areas, becoming the dominant land cover. Land cover change in the Araucanía Region reflects a model of change in which areas with better environmental conditions and accessibility are occupied first for productive activities. As the availability of suitable areas for the expansion of productive activities diminishes, these activities start to move into physiographical areas which were previously “protected” by adverse environmental conditions or poor accessibility. This model of production growth could lead to the complete deforestation of areas outside national protected areas, and other areas which still remain inaccessible due to technological restrictions on exploitation.