Abiotic and vertebrate seed dispersal in the Brazilian Atlantic forest: implications for forest regeneration     

Marcelo Tabarelli 《Biological conservation》2002,106(2):165-176

This study documents the proportion of woody plant species having different modes of seed dispersal, and classes of seed and fruit size at 16 Atlantic montane forest plots of southeastern Brazil (23-24° S). These plots represent six chronosequences (from 5-year-old to old-growth forest) of forest regeneration following small-scale shifting agriculture. Our results indicate that there is a gradual but predictable increase in the number of woody plant species relying on vertebrate-mediated seed dispersal in increasingly older plots. Moreover, the percentage of plant species bearing small seeds and fruits (< 0.6 cm in length) was more than halved from earlier to older forest plots, while the percentage of plant species producing middle-sized seeds and fruits at least doubled. Plant species belonging to the Melastomataceae, Myrsinaceae, Rubiaceae and Flacourtiaceae comprised a large proportion of the small-seeded and fruit species (33-53%), and largely occurred in early successional forest plots (5-30 years old). In contrast, species belonging to the Myrtaceae and Lauraceae represented most of the species (51-72%) bearing medium-sized seeds and fruits (0.6-1.5 cm in length), and occurred primarily in the old-growth forests. Shifts in the relative importance of dispersal strategies during the regeneration process of Atlantic montane forest, as well as in diaspore size appear to be related to the balance between early successional and shade-tolerant species associated with particular life forms and plant families. Finally, we discuss the relationships between the species richness of Myrtaceae and Lauraceae trees, seed dispersal by medium to large vertebrates, and possible regeneration scenarios for the Atlantic forest.  相似文献   

Seasonal changes in microbial biomass and nutrient flush in forest soils   总被引：14，自引：0，他引：14  

M. Díaz-Raviña  M. J. Acea  T. Carballas 《Biology and Fertility of Soils》1995,19(2-3):220-226

Microbial biomass and N, P, K, and Mg flushes were estimated in spring, summer, autumn, and winter samples of different forest soils. The microbial biomass showed significant seasonal fluctuations with an average distribution of 880±270 g C g^-1 soil in spring, 787±356 g C g^-1 soil in winter, 589±295 g C g^-1 soil in summer, and 560±318 g C g^-1 soil in autumn. The average annual concentrations of C, N, P, K, and Ca in the microbial biomass were 704, 106, 82, 69 and 10 g g^-1 soil, respectively. Microbial C represented between 0.5 and 2% of the organic soil C whereas the percentage of microbial N with respect to the total soil N was two-to threefold higher than that of C; the annual fluctuations in these percentages followed a similar trend to that of the microbial biomass. Microbial biomass was positively correlated with soil pH, moisture, organic C, and total N. The mean nutrient flush was 31, 15, 7, and 4 g g^-1 soil for N, K, P, and Mg, respectively, and except for K, the seasonal distribution was autumn spring winter summer. The average increase in available nutrient due to the mineralization of dead microbial cells was 240% for N, and 30, 26, and 14% for P, K, and Mg, respectively. There was a positive relationship between microbial biomass and the N, P, K, and Mg flushes. All the variables studied were significantly affected by the season, the type of soil, and the interaction between type of soil and season, but soil type often explained most of the variance.  相似文献   

Biased seed rain in forest edges: Evidence from the Brazilian Atlantic forest     

Felipe Pimentel Lopes de Melo  Rodolfo Dirzo 《Biological conservation》2006,132(1):50-60

In this paper, we test the hypothesis that seed rain in forest edges differs from that in forest interior in terms of seed abundance, species richness, seed size, dispersal mode, and manipulation by vertebrates. The study was carried out in the Coimbra forest (3500 ha), the largest fragment currently found in the Atlantic forest of northeast Brazil. We assessed seed rain during a 1-year period by using a 1500-m long transect (with 100 sampling units) for each habitat. Seeds were categorized according to size, dispersal mode, and vertebrate manipulation. A total of 76,207 seeds belonging to 146 species were collected during the whole study and in average edge received more seeds and species per unit of area during particular periods of time. However, the analysis of all seeds and species recorded in both habitats during the 1-year period revealed that forest interior received a significant higher percentage of medium, large and very large seeds (21.8%) and species (82.6%) in comparison to edge (13.5% of seeds and 57.5% of species). The contribution of large and very large seed species dispersed by vertebrates was also lower in the edge forest as it represented 13.04% of all vertebrate-dispersed species recorded in this habitat vs. 31.5 % in the forest interior. Finally, seeds handled by vertebrates accounted for 5.9% of all seeds in forest edge, and reached 11% in the forest interior. The biased seed rain documented in the Coimbra forest raises the possibility that the creation of forest edges may alter some attributes of seed rain, particularly its content of large-seeded plants and of those dispersed by vertebrates.  相似文献   

冬季太平洋与大西洋异常大气环流关系研究     

陈佳迪 《现代农业科技》2015,(11)

利用1958-2010年逐年的12月和1月的NCEP/NCAR格点资料,分别对北半球太平洋和大西洋、欧亚大陆和北美大陆这2组区域的500 hPa高度场进行了奇异值(SVD)分解。结果表明院所选的2组区域太平洋和大西洋、欧亚大陆和北美大陆500 hPa的位势高度场存在协同变化的关系。当太平洋地区位势高度场偏高时,大西洋地区的位势高度场偏低,反之亦然。冬季的1月上述现象最为明显。上述现象在陆地上比海洋上明显,大洋上高纬度比低纬度明显。  相似文献   

IBA浓度对马铃薯大西洋和Bora组培苗生根移栽的影响   总被引：4，自引：0，他引：4  

周晓燕  廉玉姬 《安徽农业科学》2006,34(21):5505-5505,5530

研究了不同浓度的IBA对马铃薯大西洋和Bora组培苗生根和移栽成活率的影响。结果表明:诱导大西洋生根的最低培养基为1/2 MS+0.4 mg/L IBA,诱导Bora生根的最低培养基为1/2 MS+0.6 mg/L IBA;两者的最高移栽成活率分别为87.61%和93.58%,诱导此成活率的IBA浓度均为0.6 mg/L。  相似文献   

Infectious pancreatic necrosis virus in Atlantic salmon, Salmo salar L., post-smolts in the Shetland Isles, Scotland: virus identification, histopathology, immunohistochemistry and genetic comparison with Scottish mainland isolates     

Smail DA  Bain N  Bruno DW  King JA  Thompson F  Pendrey DJ  Morrice S  Cunningham CO 《Journal of fish diseases》2006,29(1):31-41

During mid-June 1999 peak mortalities of 11% of the total stock per week were seen at a sea cage site of Atlantic salmon, Salmo salar L., post-smolts in the Shetland Isles, Scotland. Virus was isolated on chinook salmon embryo (CHSE) cells in a standard diagnostic test and infectious pancreatic necrosis virus (IPNV) identified by enzyme-linked immunosorbent assay. IPNV was confirmed as serogroup A by a cell immunofluorescent antibody test using the cross-reactive monoclonal antibody AS-1. Four weeks after the main outbreak, virus titres in surviving moribund fish were assayed at >10(10) TCID50 g(-1) kidney. Histopathology of moribund fish was characterized by pancreatic acinar cell necrosis and a marked catarrhal enteritis of the intestinal mucosa. In the liver, necrosis, leucocytic infiltration and a generalized cell vacuolation were noted. IPNV-specific immunostaining was demonstrated in pancreas, liver, heart, gill and kidney tissue. The nucleotide sequence of the coding region of segment A was determined from the Shetland isolate. A 1180 bp fragment of the VP2 gene of this isolate was compared with a 1979 reference isolate from mainland Scottish Atlantic salmon, La/79 and another more recent mainland isolate, 432/00. Both A2 isolates were derived from carrier fish without signs of IPN and serotyped by a plaque neutralization test. The Shetland isolate shows a different nucleotide and amino acid sequence compared with the two isolates from carrier fish. These latter isolates showed identical amino acid sequences in the fragment examined, despite the 21 years separating the isolations. Sequence comparisons with other A2 (Sp) isolates on the database confirm all three Scottish isolates are A2 (Sp).  相似文献   

Amoebic gill disease (AGD)-affected Atlantic salmon, Salmo salar L., are resistant to subsequent AGD challenge     

Vincent BN  Morrison RN  Nowak BF 《Journal of fish diseases》2006,29(9):549-559

There is inconsistent evidence of resistance of Atlantic salmon, Salmo salar L., to amoebic gill disease (AGD). Here, evidence is presented that demonstrates that Atlantic salmon exposed and subsequently challenged with AGD are more resistant than naïve control fish. Seventy‐three per cent of Atlantic salmon previously exposed to AGD survived to day 35 post‐challenge compared with 26% exposed to Neoparamoeba sp. for the first time, yet the gill pathology of surviving naïve control or previously exposed fish was not significantly different. Development of resistance to AGD is associated with anti‐Neoparamoeba sp. antibodies that were detectable in serum of 50% of surviving Atlantic salmon previously exposed to AGD. However, anti‐Neoparamoeba sp. antibodies were not detectable in cutaneous mucus of resistant fish. Increased resistance of Atlantic salmon after secondary Neoparamoeba sp. infection and detection of specific serum antibodies provides support for the development of a vaccine for AGD.  相似文献   

A comparative study of susceptibility and induced pathology of cod, Gadus morhua (L.), and halibut, Hippoglossus hippoglossus (L.), following experimental infection with Moritella viscosa     

Gudmundsdóttir BK  Björnsdóttir B  Gudmundsdóttir S  Bambir SH 《Journal of fish diseases》2006,29(8):481-487

In this study experimental challenges with Moritella viscosa, the causative agent of winter ulcers in salmonids, were performed on juvenile Atlantic cod and Atlantic halibut. The challenges involved both intramuscular (i.m.) and intraperitoneal (i.p.) injections and bath with a strain originally isolated from Atlantic salmon. Cod was found to be significantly more sensitive than halibut to the infection. Both fish species were found to be more sensitive to i.m. than i.p. challenges. Both challenges induced a systemic disease in cod and halibut, but only cod was infected with an experimental bath challenge. Pathognomonic signs were found to be comparable with those described in M. viscosa-infected salmon and turbot. The main distinguishing pathological sign was that the cod showed host response to M. viscosa infection resulting in granuloma formation in infected tissues, which is a known response of cod to a infection with another Gram-negative bacterium, Aeromonas salmonicida. Re-isolation of M. viscosa from kidneys of cod and halibut with clear disease signs was problematic and optimization of isolation measures is needed. The results of this study indicate that M. viscosa infection may be a risk factor in cod farming, but that halibut is more resistant.  相似文献   

A survey of salmon gill poxvirus (SGPV) in wild salmonids in Norway          下载免费PDF全文

Å H Garseth  M C Gjessing  T Moldal  A G Gjevre 《Journal of fish diseases》2018,41(1):139-145

In 2016, the Norwegian health monitoring programme for wild salmonids conducted a real‐time PCR‐based screening for salmon gill poxvirus (SGPV) in anadromous Arctic char (Salvelinus alpinus L.), anadromous and non‐anadromous Atlantic salmon (Salmo salar L.) and trout (Salmo trutta L.). SGPV was widely distributed in wild Atlantic salmon returning from marine migration. In addition, characteristic gill lesions, including apoptosis, were detected in this species. A low amount of SGPV DNA, as indicated by high Ct‐values, was detected in anadromous trout, but only in fish cohabiting with SGPV‐positive salmon. SGPV was not detected in trout and salmon from non‐anadromous water courses, and thus seems to be primarily linked to the marine environment. This could indicate that trout are not a natural host for the virus. SGPV was not detected in Arctic char but, due to a low sample size, these results are inconclusive. The use of freshwater from anadromous water sources may constitute a risk of introducing SGPV to aquaculture facilities. Moreover, SGPV‐infected Atlantic salmon farms will hold considerable potential for virus propagation and spillback to wild populations. This interaction should therefore be further investigated.  相似文献   

Overview of infectious salmon anaemia virus (ISAV) in Atlantic Canada and first report of an ISAV North American‐HPR0 subtype          下载免费PDF全文

N Gagné  F LeBlanc 《Journal of fish diseases》2018,41(3):421-430

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