氮添加对三峡库区马尾松-栓皮栎混交林土壤微生物生物量和酶活性的影响

选择三峡库区的马尾松-栓皮栎混交林,分析不同浓度氮添加(0、30、60、90 kg N·hm-2·a-1)对土壤微生物生物量、酶活性和养分含量的影响,为在大气氮沉降持续增加的背景下预测该地区森林土壤碳动态提供科学依据.结果 表明:各氮添加处理下土壤有机碳、全氮和微生物生物量碳、氮、磷均显著提高,土壤pH值下降,全磷含量...     

云南热区几种阔叶人工林C储量的研究

为了研究云南热区几种主要阔叶人工林分的固碳能力,利用实际测定生物量的方法对西双版纳的几种阔叶人工林生态系统的C储量进行了研究。研究结果发现,山桂花纯林,西南桦纯林,高阿丁枫纯林,马尖相思纯林以及西南桦+山桂花混交林和西南桦+马尖相思混交林几种7年生人工林生态系统的C密度为109.37～136.97 t/hm2。几种人工林分的年固C量在3.97～7.03 t/hm2·a之间。表明:这些树种都是开展以固C为目标的生态造林项目的适合树种。     

亚热带常绿阔叶林和杉木人工林茎流与穿透雨的养分特征

亚热带常绿阔叶林和杉木人工林树干茎流和穿透雨养分含量均表现季节动态变化。养分含量中,K^ 、Ca^2 、NO3%-浓度高,Na^ 、Mg^2 居中,HPO4^2-含量低,相对于林外雨,养分均出现富集化,但树干茎流养分富集化高于穿透雨。树干茎流出现强烈的酸化,而穿透雨酸化现象不明显。树种之间的茎流养分特征表现不一样,樟树和枫香总的养分浓度较高,其次为刨花楠,最后为青冈和红栲。     

The importance of pre-thicket conifer plantations for nesting Hen Harriers Circus cyaneus in Ireland

Hen Harriers Circus cyaneus are threatened across much of their range and their conservation requires appropriate habitat management. The locations of 148 Hen Harrier nests found in the Republic of Ireland during national breeding surveys in 2000 and 2005 were used to assess nest-site selection. The distribution of these nests was compared to distributions of randomly located points to investigate selection at the scale of the nest-site and landscape. The main nesting habitats selected were pre-thicket stage of first and, particularly, second rotation plantations, mostly of exotic conifers. There was no evidence that the area of post-closure plantations negatively affected Hen Harrier nest distribution. There was a positive correlation across study areas between changes in numbers of Hen Harrier nests between 2000 and 2005 and changes in the area of pre-thicket second rotation plantations over the same period. The overall effect of plantation forests on breeding Hen Harriers in Ireland therefore appears to be positive. However, this study did not consider the effects of plantation habitats on breeding success. Improved grassland was strongly avoided as a nesting habitat. Furthermore, after controlling for the influence of nesting habitat on nest location, landscapes with a high percentage cover of improved grassland were also avoided. Further agricultural intensification of grassland in areas where Hen Harriers breed is likely to have a negative impact on this species. These results are required for the development of management strategies for the conservation of this species.     

Biological legacies soften pine plantation effects for bryophytes

Biological legacies are organic structures and patterns remaining after a disturbance that may contribute to the complexity of the recovering vegetation. Legacies may, in turn, reduce the impacts of human disturbances such as logging and habitat transformation on elements of biodiversity. To examine the effects of biological legacies on biotic responses after disturbance, we surveyed 32 sites for bryophytes in an area subject to large-scale conversion of native eucalypt forest to exotic Pinus radiata D. Don plantations in eastern Australia. We sampled bryophyte and substrate diversity (log, bare ground, upturned tree/log, and trees) in eight sites in each of four landscape context classes: pine plantation stands, elliptical-shaped remnants, strip-shaped remnants, and controls in a large area of contiguous, unmanaged eucalypt forest. We found a muted response by individual species of bryophyte to landscape context. We attribute this, in part, to the presence of logs in the intensively managed pine plantation sites. The boost in bryophyte diversity from species on logs meant that some pine sites supported similar species composition to the continuous eucalypt forest controls. Our findings also underline the importance of local controls and structural variation, including leaving logs and native trees in plantations, for enhancing bryophyte species richness in managed landscapes.     

福安三种不同茶园节肢动物群落的消长动态调查

根据对福建福安的3种不同茶园（天香有机茶园、北门高山茶园和溪柄平地茶园）的节肢动物群落消长动态调查。并经多样性分析,结果获知：福安3种茶园节肢动物群落的物种丰富度（s）和多样性指数（H）的大小顺序依次为：天香（S=19．64,H=2．537）〉北门（S=18．01,H=2．502）〉溪柄（S=17．59,H=2．297）;而均匀度指数的大小顺序是：北门（J=0．621）〉天香（J=0．595）〉溪柄（J=0．559）。表明植被比较丰富、人为干扰较少的茶园,节肢动物群落的物种丰富度、多样性指数和均匀度指数较高,害、益虫群落易于保持较好的平衡状态,有利于减少（或不使用）化学农药、发展绿色无公害茶叶生产。     

人工林对海南鹦哥岭鸟类多样性的影响

为了解在天然林中所种植的人工林对鹦哥岭鸟类多样性的影响,于2005年10月～2006年4月,分别采用样带法和雾网法,对海南鹦哥岭的原生林、次生林、人工林及其林缘的鸟类多样性进行了比较研究.野外记录到鸟类102种,其中栗腹矶鸫Monticola rufiventris、橙胸姬鹟Ficedula strophiata和黄雀Carduelis spinus 3种为海南鸟类新纪录.与原生林和次生林相比,人工林及其林缘的鸟类多样性很低,其中人工林最低.人工林不仅对鹦哥岭自然保护区的鸟类多样性具有非常大的负面影响,而且由于人工林的种植使天然林破碎化而产生的林缘与天然林林缘不同,鸟类多样性较低.     

Change in CO2 balance under a series of forestry activities in a cool-temperate mixed forest with dense undergrowth

To evaluate the effects on CO₂ exchange of clearcutting a mixed forest and replacing it with a plantation, 4.5 years of continuous eddy covariance measurements of CO₂ fluxes and soil respiration measurements were conducted in a conifer-broadleaf mixed forest in Hokkaido, Japan. The mixed forest was a weak carbon sink (net ecosystem exchange, −44 g C m⁻² yr⁻¹), and it became a large carbon source (569 g C m⁻² yr⁻¹) after clearcutting. However, the large emission in the harvest year rapidly decreased in the following 2 years (495 and 153 g C m⁻² yr⁻¹, respectively) as the gross primary production (GPP) increased, while the total ecosystem respiration (RE) remained relatively stable. The rapid increase in GPP was attributed to an increase in biomass and photosynthetic activity of Sasa dwarf bamboo, an understory species. Soil respiration increased in the 3 years following clearcutting, in the first year mainly owing to the change in the gap ratio of the forest, and in the following years because of increased root respiration by the bamboo. The ratio of soil respiration to RE increased from 44% in the forest to nearly 100% after clearcutting, and aboveground parts of the vegetation contributed little to the RE although the respiration chamber measurements showed heterogeneous soil condition after clearcutting.     

Increased Litter Build Up and Soil Organic Matter Stabilization in a Poplar Plantation After 6 Years of Atmospheric CO2 Enrichment (FACE): Final Results of POP-EuroFACE Compared to Other Forest FACE Experiments

Free air CO₂ enrichment (FACE) experiments in aggrading temperate forests and plantations have been initiated to test whether temperate forest ecosystems act as sinks for anthropogenic emissions of CO₂. These FACE experiments have demonstrated increases in net primary production and carbon (C) storage in forest vegetation due to increased atmospheric CO₂ concentrations. However, the fate of this extra biomass in the forest floor or mineral soil is less clear. After 6 years of FACE treatment in a short-rotation poplar plantation, we observed an additional sink of 32 g C m⁻² y⁻¹ in the forest floor. Mineral soil C content increased equally under ambient and increased CO₂ treatment during the 6-year experiment. However, during the first half of the experiment the increase in soil C was suppressed under FACE due to a priming effect, that is, the additional labile C increased the mineralization of older SOM, whereas during the second half of the experiment the increase in soil C was larger under FACE. An additional sink of 54 g C m⁻² y⁻¹ in the top 10 cm of the mineral soil was created under FACE during the second half of the experiment. Although, this FACE effect was not significant due to a combination of soil spatial variability and the low number of replicates that are inherent to the present generation of forest stand FACE experiments. Physical fractionation by wet sieving revealed an increase in the C and nitrogen (N) content of macro-aggregates due to FACE. Further fractionation by density showed that FACE increased C and N contents of the light iPOM and mineral associated intra-macro-aggregate fractions. Isolation of micro-aggregates from macro-aggregates and subsequent fractionation by density revealed that FACE increased C and N contents of the light iPOM, C content of the fine iPOM and C and N contents of the mineral associated intra-micro-aggregate fractions. From this we infer that the amount of stabilized C and N increased under FACE treatment. We compared our data with published results of other forest FACE experiments and infer that the type of vegetation and soil base saturation, as a proxy for bioturbation, are important factors related to the size of the additional C sinks of the forest floor–soil system under FACE. Author Contribution: MRH conceived of and designed the study, performed research, analyzed data, and wrote the paper; GES conceived of and designed the study and performed research.     

Trans‐Atlantic slavery: Isotopic evidence for forced migration to Barbados

The question of the ultimate origin of African slaves is one of the most perplexing in the history of trans‐Atlantic slavery. Here we present the results of a small, preliminary isotopic study that was conducted in order to determine the geographical origin of 25 enslaved Africans who were buried at the Newton plantation, Barbados, sometime between the late 17th and early 19th century. In order to gain a more nuanced understanding of the slaves' origin, we used a combination of carbon, nitrogen, oxygen, and strontium isotope analyses. Carbon and nitrogen isotope ratios were determined in bone and dentinal collagen; oxygen and strontium isotopes were measured in tooth enamel. Results suggest that the majority of individuals were born on the island, if not the estate itself. Seven individuals, however, yielded enamel oxygen and strontium ratios that are inconsistent with a Barbadian origin, which strongly suggests that we are dealing with first‐generation captives who were brought to the island with the slave trade. This idea is also supported by the fact that their carbon and nitrogen stable isotope values differ markedly between their teeth and bones. These intra‐skeletal shifts reflect major dietary changes that probably coincided with their enslavement and forced migration to Barbados. While it is impossible to determine their exact origins, the results clearly demonstrate that the slaves did not all grow up in the same part of Africa. Instead, the data seem to suggest that they originated from at least three different areas, possibly including the Gold Coast and the Senegambia. Am J Phys Anthropol, 2009. © 2009 Wiley‐Liss, Inc.