Contribution of fine roots to ecosystem biomass and net primary production in black spruce, aspen, and jack pine forests in Saskatchewan

Fine root (<2 mm) processes contribute to and exhibit control over a large pool of labile carbon (C) in boreal forest ecosystems because of the high proportion of C allocated to fine root net primary production (NPP), and the rapid decomposition of fine roots relative to aboveground counterparts. The objective of this study was to determine the contribution of fine roots to ecosystem biomass and NPP in a mature black spruce (Picea mariana Mill.) (OBS), aspen (Populus tremuloides Michx.) (OA), and jack pine (Pinus banksiana Lamb.) (OJP) stand, and an 11-year-old harvested jack pine (HJP) stand in Saskatchewan. Estimates of fine root biomass and NPP were obtained from nine minirhizotron (MR) tubes at each of the four Boreal Ecosystem Research and Monitoring Sites (BERMS). Fine root data were collected once a month for May–September in 2003 and 2004. Additional C biomass and NPP data for various components of the forest stands were obtained from Gower et al. (1997) and Howard et al. (2004). Annual fine root biomass averaged 3.10 ± 0.89, 1.71 ± 0.49, 1.62 ± 0.32, and 2.96 ± 0.67 Mg C ha⁻¹ (means ± S.D.) at OBS, OA, OJP, and HJP, respectively, comprising between 1 and 6% of total stand biomass. Annual fine root NPP averaged 2.66 ± 0.97, 2.03 ± 0.43, 1.44 ± 0.43, and 2.16 ± 0.81 Mg C ha⁻¹ year⁻¹ (means ± S.D.) at OBS, OA, OJP, and HJP, respectively, constituting between 41 and 71% of total stand NPP. Results of this study indicate that fine roots produce a large amount of C in boreal forests. It is speculated that fine root NPP may control a large amount of labile C-cycling in boreal forests and that fine root responses to environmental and anthropogenic stress may be an early indicator of impaired ecosystem functioning.     

Discrepancies between ergosterol and the phospholipid fatty acid 18:2ω6,9 as biomarkers for fungi in boreal forest soils

Ergosterol and the phospholipid fatty acid (PLFA) 18:2ω6,9 are frequently used as fungal biomarkers in studies on soils, and in accordance with the ideal for biomarkers of microorganisms they are thought to turn over rapidly after cell death and lysis. These biomarkers should also show the same patterns and responses to perturbations of the studied system. Here, I report strong correlations, in natural boreal forests of contrasting fertility, between free ergosterol and PLFA 18:2ω6,9 (r=0.821, P=0.007, n=9). Surprisingly, ergosterol, but not PLFA 18:2ω6,9, appears non-responsive to both large-scale tree girdling, which interrupts tree belowground C allocation to ectomycorrhizal fungi, and to long-term N-loading, which may have negative effects on both mycorrhizal and saprotrophic fungi. These results, therefore, question the use of ergosterol to monitor effects of soil perturbations on fungi in the field, but do not put into question the use of the biomarker in natural forest ecosystems.     

Ion mass balances for three small forested catchments in Sweden

Ion mass budget calculations were performed for three small, forested catchments. The study sites are situated along a deposition gradient fom high loads of sulphur and nitrogen in southwest Sweden to low deposition in the northern part of the country. The sites showed three different H⁺production/H⁺consumption patterns mainly featuring the catchment characteristics and to a lesser extent the atmospheric deposition. External proton production, with atmospheric deposition as the main source, accounted for 34–40% of the total H⁺production in southern Sweden and only for 12% in northern Sweden. This is low concidering that the two southern sites are within the most exposed area for acid deposition in Sweden. It is obvious that natural H⁺production processes can be very important also in such areas.     

不同强度间伐对长白山天然林林下植物多样性的影响

对吉林森工集团松江河林业局辖区内的阔叶红松林、杂木林和杨桦林采取30%～40%（T1）、20%（T2）株数强度的均匀间伐处理,以不间伐处理为对照（CK）,对间伐2 a后林下植物木本、草本植物进行调查,采用Simpson、Shannon-Wiener多样性指数和Pielou均匀度指数进行植物多样性分析,探讨不同强度间伐对3个林型林下植物多样性的影响。研究结果表明：T1间伐后3个林型的物种丰富度均有增加（杂木林木本植物例外）,T2间伐后杨桦林木本植物丰富度降低,草本植物丰富度增加。两种间伐处理均增加阔叶红松林木本植物多样性,T1处理尤为明显。T1处理增加杂木林和杨桦林木本植物多样性,而T2间伐处理有较弱的降低作用。两种间伐处理均降低阔叶红松林和杂木林草本植物多样性,与强度无明显关系。随着间伐强度的增加杨桦林草本植物多样性增大。在长白山天然林中,较大间伐强度T1（30%～40%）能够有效提高植物多样性。     

我国公益林生态效益补偿研究与实践综述

在理论基础和分析手段上,我国公益林生态效益补偿研究经历了从传统政治经济学向现代经济学的转变;在实践中,经历反复论证和试点实施后,公益林生态效益补偿制度已经建立、推行。文中综述了我国公益林生态效益补偿理论研究和实践历程,通过实例比较,分析、总结了当前我国不同尺度的公益林生态效益补偿制度的特点,并提出了今后的关注重点,以期为我国森林生态效益补偿理论研究和推行的进一步深化提供参考。     

Selective logging in public pine forests of the central Iberian Peninsula: Effects of the recovery process on ant assemblages

Pine forests on the northern plateau of the Iberian Peninsula have a long history of use, exploitation, and management. Current management practices consist of selective logging with relatively short periods of time between logging events. The main objective of this study is to detect changes in ant assemblages in the short time periods between selective logging activities. Ants were sampled at 44 sites considering three grouping categories of time periods after the last timber extraction: short (<4 years), medium (4-8 years) and long (>8 years). After selective logging the number of ant species increases as the forest recovers. A look at the differences between the assemblages when the analysis shifts from the species-specific level to functional groups showed differences between the short and long categories. This indicates that in certain circumstances the functional groups may be more informative of the functional restructuring of the ant assemblages in a disturbed habitat. Ant species from three functional groups display significant indicative values (Opportunist, Hot Climate Specialists and Subordinate Camponotini) in the medium- and long-time-after-logging categories: Messor capitatus (HCS) for medium-time category sites; and Aphaenogaster iberica (Op), Camponotus cruentatus (SC) and, Cataglyphis velox (HCS) for long-time category sites. No indicator species were found for the early stages of recovery. This information may also be of interest to managers because it reduces the number of data elements of the recovery status of these forests, and can be translated into monitoring protocols. The continued exploitation of these forests leads to an ant fauna that reflects this change. The results show that ant assemblages need at least 8 years to recover since only after that much time there is an emergence of Subordinate Camponotinae, a behaviorally dominant and low stress-tolerant functional group. This selective logging maintains the relative diversity and structure of ant assemblages.     

闽浙地区乡村庭院树种的结构特征比较

在闽浙两省各选择4个县(区)14个村庄,进行庭院树种的结构特征比较分析,结果表明:福建、浙江乡村庭院绿化以常绿、乡土树种为主;福建省庭院树种比浙江省的更为丰富,科、属、种数分别比浙江高出6.4%、18.8%、21.0%;两省5a前种植的乔木平均占82.5%,且浙江的比福建的高14.6%,近5a新植的灌木占79.3%,且浙江新植灌木比福建高出16.5%;两省乡村庭院树种栽植截干和管护截干的比例都很小;两省庭院乔木胸径平均为11.6cm、灌木地径平均为4.2cm;两省频度最高的前10个树种中,柿树、桃、枇杷、桂花4个树种同时出现。     

毛竹林内混交擦树效果好

毛竹林内混交擦树，相互之间能起到很好的促进作用，既有利于加快毛竹成材，又可改善立地条件，提高了生产力。     

广元市市中区退耕规模对粮食安全的影响

粮食安全是关系于国计民生的大事,退耕还林是改善我国生态环境的重要工程.本文以广元市市中区为例,利用最小人均耕地面积和耕地压力指数模型对该区11个乡镇进行了退耕前与退耕后粮食安全评价,得出退耕还林不影响该区粮食安全.