Posthurricane Seedling Structure in a Multi‐aged Tropical Dry Forest: Implications for Community Succession

Hurricane‐caused tree mortality in tropical dry forests occurs predominantly in early successional species. Consequently, hurricanes may accelerate succession in these forests. Forest regeneration, however, must be measured over an extended posthurricane time period to demonstrate this pattern. In this study, we recorded tree seedlings in 19 Florida Keys forests during May–August 1995, 3 years after Hurricane Andrew. For these forests—spanning a chronosequence from 14 to over 100 years since the most recent clearing—we used weighted averaging regression on relative abundances of pre‐hurricane trees to calculate a successional age optimum for each species; and used weighted averaging calibration to calculate inferred successional ages for stands based on pre‐hurricane trees and on posthurricane seedlings. To test the hypothesis that successional stage of seedlings exceeded successional stage of pre‐hurricane trees, we compared inferred stand ages based on posthurricane seedlings with those based on pre‐hurricane trees. Across the study area, inferred stand ages based on posthurricane seedlings were greater than those based on pre‐hurricane trees (P < 0.005); however, more seedlings in the youngest stands were early successional than in older stands. Of 29 species present both as pre‐hurricane trees and posthurricane seedlings, 23 had animal‐dispersed seeds. These results provide evidence that: (1) hurricanes do not ‘reset’ succession, and may accelerate succession; and (2) a strong legacy of stand successional age influences seedling assemblages in these forests.     

Habitat suitability and nest survival of white-headed woodpeckers in unburned forests of Oregon

We evaluated habitat suitability and nest survival of breeding white-headed woodpeckers (Picoides albolarvatus) in unburned forests of central Oregon, USA. Daily nest-survival rate was positively related to maximum daily temperature during the nest interval and to density of large-diameter trees surrounding the nest tree. We developed a niche-based habitat suitability model (partitioned Mahalanobis distance) for nesting white-headed woodpeckers using remotely sensed data. Along with low elevation, high density of large trees, and low slope, our habitat suitability model suggested that interspersion–juxtaposition of low- and high-canopy cover ponderosa pine (Pinus ponderosa) patches was important for nest-site suitability. Cross-validation suggested the model performed adequately for management planning at a scale >1 ha. Evaluation of mapped habitat suitability index (HSI) suggested that the maximum predictive gain (HSI = 0.36), where the number of nest locations are maximized in the smallest proportion of the modeled landscape, provided an objective initial threshold for identification of suitable habitat. However, managers can choose the threshold HSI most appropriate for their purposes (e.g., locating regions of low–moderate suitability that have potential for habitat restoration). Consequently, our habitat suitability model may be useful for managing dry coniferous forests for white-headed woodpeckers in central Oregon; however, model validation is necessary before our model could be applied to other locations. © 2011 The Wildlife Society.     

一株高含玫红品的红树林海洋紫色硫细菌分离鉴定及特性

摘要:【目的】挖掘我国海洋紫色硫细菌物种资源、深入理解紫色硫细菌在红树林生态系统中的作用。【方法】采用琼脂振荡稀释法、显微技术、紫外可见吸收光谱法、TLC、HPLC 和MS 法。【结果】从福建泉州洛阳桥红树林潮间带泥水样分离获得一株细胞内含多个硫粒的细菌菌株,光合内膜呈囊状、含细菌叶绿素a 和螺菌黄质系类胡萝卜素,结合16S rRNA 基因序列分析和系统发育分析,表明该菌株属于海洋着色菌属(Marichromatium)。该菌株细胞球杆状;最适pH 范围5.7－6.7;最适盐度范围2%－3.5%;温度范围20℃ －35℃;能耐受3.6 mmol/L 硫化物;主要积累玫红品类胡萝卜素,而不是螺菌黄质;3 种细菌叶绿素组分中,一种为BChl aP,另2 种未见报道;不需要生长因子;可光同化固定CO2、能很好利用多种有机酸盐、多价态氮化物和硫化物,尤其能利用柠檬酸、葡萄糖、蔗糖、果糖和丙醇;对氯霉素、头孢唑林、苯、对羟基联苯、恩诺沙星、啶虫脒、HgCl2 和CdCl2的IC50 值分别为70、100、20、20、3、170、5 mg /L和25 mg/L。【结论】该菌株是一株轻度耐酸、高含玫红品类胡萝卜素的紫色硫细菌,被鉴定为Marichromatium gracile 新菌株,编号YL28。该菌株具有广泛利用多种碳源、氮源和硫源物质的能力,对抗生素氯霉素和头孢唑啉、农药啶虫脒、重金属汞和镉具有较强耐受性,对抗生素恩诺沙星较敏感。     

浙江庆元槠栲林的群落学特征

利用样方法对浙江省庆元县槠栲林的群落学特征进行了分析.该槠栲林主要分为甜槠[Castanopsis eyrei (Champ. ex Benth.) Tutch.]林[含甜槠-木荷(Schima superba Gardn. et Champ.)林]、栲(C. fargesii Franch.)林、米槠[C. carlesii (Hemsl.) Hayata]林、罗浮栲(C. fabrii Hance)林、南岭栲(C. fordii Hance)林5个类型,并对各个群落类型的特征作了详细的描述.年龄结构分析表明:甜槠林和米槠林为金字塔形结构; 南岭栲林为纺锤形结构; 罗浮栲林和甜槠-木荷林部分年龄结构缺失; 栲林既有金字塔形,也有年龄结构缺失的类型.从幼苗和幼树数量分析,大多类型更新情况良好,罗浮栲林和南岭栲林更新情况较差.     

The mangrove-based coastal and nearshore fisheries of Bangladesh: ecology,exploitation and management

The mangrove forest of Bangladesh, the largest continuous mangrove forest of the world, is one of the most important coastal features of the country. The existence of the mangrove has increased the values of other coastal and marine resources such as the coastal and marine fisheries by increasing productivity and supporting a wide biological diversity. The artisanal fishery, which is highly influenced by mangroves, has been contributing 85–95% of the total coastal and marine catch of Bangladesh. The mangrove also supports offshore and deep sea fisheries by playing a significant role as nursery ground for many deep sea fishes and shrimps including the giant tiger shrimp (Penaeus monodon) which is the major species of the industrial bottom trawl fishery of Bangladesh. The mangrove also contributes significantly in shrimp farming which has been the most significant export-oriented industry since the 1970s. However, the mangrove fisheries have been under intensive pressure from deleterious fishing activities and deliberate aquaculture development by destructing mangrove habitats. The impacts of mangrove have been reflected in the contribution of artisanal fishery catch that has been in a continuous decline since the 1980s. Shrimp farming has been the most destructive contributor to mangrove destruction with a corresponding loss of biological resources particularly the wild shrimp fishery. This paper reviews different aspects of the mangrove fisheries of Bangladesh and discusses the impacts of different fisheries. The paper identifies the importance of reviewing, amending and/or replacing the traditional management approaches by the new management techniques such as habitat restoration and stock enhancement in the natural environment; the paper also identifies the need for research findings in formulating and implementing new management approaches.     

川西亚高山云杉人工林土壤质量性状演变

通过对川西亚高山云杉人工林不同演替阶段土壤肥力质量性状的研究 ,结果表明 ,人工云杉林土壤肥力退化与土壤有机质有关 ,在人工云杉林地中 ,随着抚育林龄的增加 ,土壤全 N、碱解 N、全 P、腐殖质、HA、FA、CEC、EB、微生物总数、细菌及真菌数量随有机质的减少而降低 ,土壤最大持水量、毛管持水量及总孔隙和毛管孔隙则先减少 ,之后随着云杉自疏而有上升的趋势 ,毛管持水量是决定林地自然含水量的主要因子。土壤 K素和酶活性变化较复杂 ,钾素主要与土壤母质有关 ,酶活性主要与林地微生态环境有关。土壤综合肥力评价表明 ,土壤综合肥力指标 (IFI)从人工云杉幼林向成熟林演替时 ,先迅速下降 ,之后随云杉自疏而缓慢上升 ,表现出非正“U”型的变化。解决当前人工成熟云杉林土壤退化的主要措施应因地制宜地进行间伐或轮伐 ,改善林地的微生态条件 ,尽量避免营造针叶纯林 ,建议营造针阔混交林。     

The above-ground coarse wood productivity of 104 Neotropical forest plots

The net primary production of tropical forests and its partitioning between long‐lived carbon pools (wood) and shorter‐lived pools (leaves, fine roots) are of considerable importance in the global carbon cycle. However, these terms have only been studied at a handful of field sites, and with no consistent calculation methodology. Here we calculate above‐ground coarse wood carbon productivity for 104 forest plots in lowland New World humid tropical forests, using a consistent calculation methodology that incorporates corrections for spatial variations in tree‐size distributions and wood density, and for census interval length. Mean wood density is found to be lower in more productive forests. We estimate that above‐ground coarse wood productivity varies by more than a factor of three (between 1.5 and 5.5 Mg C ha^?1 a^?1) across the Neotropical plots, with a mean value of 3.1 Mg C ha^?1 a^?1. There appear to be no obvious relationships between wood productivity and rainfall, dry season length or sunshine, but there is some hint of increased productivity at lower temperatures. There is, however, also strong evidence for a positive relationship between wood productivity and soil fertility. Fertile soils tend to become more common towards the Andes and at slightly higher than average elevations, so the apparent temperature/productivity relationship is probably not a direct one. Coarse wood productivity accounts for only a fraction of overall tropical forest net primary productivity, but the available data indicate that it is approximately proportional to total above‐ground productivity. We speculate that the large variation in wood productivity is unlikely to directly imply an equivalent variation in gross primary production. Instead a shifting balance in carbon allocation between respiration, wood carbon and fine root production seems the more likely explanation.     

Plant-mediated methane emission from an Indian mangrove

Mangroves have been considered for a long time to be a minor methane source, but recent reports have shown that polluted mangroves may emit substantial amounts of methane. In an unpolluted Indian mangrove, we measured annual methane emission rates of 10 g CH₄ yr^?1 from the stands of Avicennia marina. This rate is of the same order of magnitude as rates from Northern wetlands. Methane emission from a freshwater‐influenced area was higher, but was lower from a stunted mangrove growing on a hypersaline soil. Methane emission was mediated by the pneumatophores of Avicennia. This was consistent with the methane concentration in the aerenchyma, which decreased on average from 350 ppm_v in the cable roots to 10 ppm_v in the emergent part of the pneumatophores. However, the number of pneumatophores varied seasonally. The minimum number occurred during the monsoon season, which reduced methane emissions largely. Ebullition from unvegetated areas may also be important, at least during monsoon season when measured bubble fluxes were occasionally about five times as high as pneumatophore‐mediated emissions.