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Our research on the herbaceous understory vegetation in the Kluane region, Yukon, has focused on the structure and function of natural forest understory and grassland communities. The research has involved two long-term projects. The first investigated fertilizer addition and mammalian herbivore exclosure in understory vegetation over a 20-year period and showed that nutrient availability, and not herbivory, controlled herbaceous biomass. Fertilization increased the amount and nutrient content of vegetation, but 13 species were lost, whereas natural levels of mammalian herbivory rarely affected this vegetation or its diversity. The second study investigated how removing plant functional groups from a grassland influences its functioning. Over a seven-year period, we determined that the identity of the functional group was important in determining ecosystem properties and that graminoids were more influential than expected from their proportional biomass. In both of these studies, short-term responses were transient and not indicative of longer-term responses of these communities. This finding reinforces the need for long-term experiments, especially in northern ecosystems. The long-term plots from both projects will continue to be valuable, and they may detect shifts in the plant community due to climate change or unique events in the area. [ABSTRACT FROM AUTHOR]

Background and Aims: Carbon and nutrient cycling are influenced by ectomycorrhizal (EM) fungi in forests. Factors altering carbon allocation in trees are likely to alter EM fungal community composition. We aimed to determine the effects of high fertilization, thinning, and their interaction on EM fungal communities and fine roots. Methods: Roots and EM fungi were sampled three years after establishment of fertilization and thinning plots in Pinus contorta forests of Canada. Ectomycorrhizas were identified using morphological and molecular techniques and changes to EM composition were detected by multivariate analyses. Results: We recovered 77 EM fungal taxa with colonization levels up to 99 % in untreated plots; a 30 % decrease in colonization levels and similar declines in EM richness and diversity was found after fertilization. Thinning interacted with fertilization by decreasing the magnitude of shifts in EM abundance. Thinning tended to alleviatiate the effects of fertilization, suggesting there was sustained allocation of carbon to EM communities and greater root exploration. The fertilization treatment highlights an intimate and mechanistic relationship between tree and soil fungi and suggests that a reduced carbon allocation controls fungal proliferation and alters community composition. Conclusions: Intensive forest management treatments shift soil communities to an altered state, possibly impacting nutrient cycling in the interim. [ABSTRACT FROM AUTHOR]

The influence of individual parentage on progeny responses to early developmental temperature stress was examined in a cross-fertilization experiment using sockeye salmon Oncorhynchus nerka. Differences in survival, hatch timing and size were examined among five paternally linked and five maternally linked offspring families (Weaver Creek population, British Columbia, Canada) incubated at 12, 14 and 16° C from just after fertilization to hatch. Mean embryonic survival was significantly lower at 14 and 16° C; however, offspring families had substantially different survival responses across the thermal gradient (crossing reaction norms). Within temperature treatments, substantial variation in embryonic survival, alevin mass, time-to-hatch and hatch duration were attributable to family identity; however, most traits were governed by significant temperature-family interactions. For embryonic survival, large differences between families at 16° C were due to both female and male spawner influence, whereas inter-family differences were obscured at 14° C (high intra-family variation), and minimal at 12° C (only maternal influence detected). Despite post-hatch rearing under a common cool thermal regime, persistent effects of both temperature and parentage were detected in alevin and 3 week-old fry. Collectively, these findings highlight the crucial role that parental influences on offspring may have in shaping future selection within salmonid populations exposed to elevated thermal regimes. An increased understanding of parental and temperature influences and their persistence in early development will be essential to developing a more comprehensive view of population spawning success and determining the adaptive capacity of O. nerka populations in the face of environmental change. [ABSTRACT FROM AUTHOR]

Field experiments were conducted at three different sites in Saskatchewan, Canada (Colonsay, Vanscoy and Rosthern) over two years (2005 and 2006) to determine the effects of dribble-banded and coulter-injected liquid fertilizer applied in the spring of 2005 at 56, 112 and 224 kg N ha−1 with and without P at 28 kg P2O5 ha−1. The three sites were unfertilized, 7- to 8-year old stands of mainly meadow bromegrass ( Bromus riparius)-dominated haylands. All fertilization treatments produced significantly ( P ≤ 0·05) higher dry matter yield than the control in the year of application at the three Saskatchewan sites. There was no significant difference between the two application methods (surface dribble band vs. coulter injected) for any fertilizer treatments. The addition of 28 kg P2O5 ha−1 P fertilizer along with the N fertilizer did not have a significant effect on yield in most cases. In the year of application, increasing N rates above 56 kg N ha−1 did not significantly increase yield over the 56 kg N ha−1 rate in most cases, but did increase N concentration, N uptake and protein concentration. A significant residual effect was found in the high N-rate treatments in 2006, with significantly higher yield and N uptake. In 2005, the forage N and P uptake in the fertilized treatments were significantly higher than the control in all cases. The N uptake at the three Saskatchewan sites increased with increasing N rate up to the high rate of 224 kg N ha−1, although the percent recovery of applied N decreased with increasing rate. The P fertilization with 28 kg P2O5 ha−1 also increased P uptake. Overall, rates of fertilizer of approximately 56 kg N ha−1 appear to be sufficient to produce nearly maximum forage yield and protein concentration of the grass in the year of application. [ABSTRACT FROM AUTHOR]

Brooders of Surubí ( Pseudoplatystoma fasciatum) were caught in the Ichillo River (Bolivian Amazon) and adapted to captivity conditions for 1 year in the facilities of the experimental aquaculture station of ‘El Prado’ (Santa Cruz de la Sierra) under natural temperature and photoperiod conditions. Induced reproduction was obtained by means of Ovaprim® (Syndel, Canada) injections and artificial fertilization. Sperm and ova were obtained by gentle stripping of male and female brooders. Fertilized eggs were incubated in 60 L Zug jars. A mean hatching rate of 73.7±19.0% was obtained after 24 h at 26.5 °C. For larval rearing, several protocols were tested with different settings of photoperiod, light intensity, food type and period of distribution, and stocking density. The best survival rates were obtained with Artemia nauplii feeding in total darkness. A high level of aggressiveness between larvae and precocious appearance of jumpers was observed, but these can be controlled with appropriate rearing conditions. [ABSTRACT FROM AUTHOR]

Focuses on a study which investigated the nature and functioning of dichogamy in eastern Ontario populations of Aquilegia canadensis or Ranunculaceae. Factors that affect the extent to which dichogamy reduces self-fertilization; Methodology; Results and discussion.

We tested the hypothesis that fertilisation increases community and ecosystem variability while reducing predictability using annual fossil records from fertilised Lake 227, Experimental Lakes Area, Ontario, Canada. Comparison of fossil pigments from unperturbed and eutrophied periods using a median-log Levene’s test demonstrated that variability increased significantly during enrichment for total algae (chlorophyll a, sum of carotenoids), cyanobacteria (aphanizophyll, lutein-zeaxanthin), chlorophytes (pheophytin b, lutein-zeaxanthin), and cryptophytes (alloxanthin), but not for other algal taxa (chrysophytes, dinoflagellates) or herbivory (pheophorbides). Dynamic linear models (DLMs) of individual time series showed that forecast accuracy declined during enrichment for taxa which showed increased variability, while forecast uncertainty increased for all fossil pigments. DLMs of simulated data identified a strong inverse relationship between variability and predictability, suggesting that predictability will decline whenever variability increases. These findings imply that anthropogenic eutrophication of ecosystems may destabilise lakes, obscure impacts of global change, and reduce the sensitivity of whole-ecosystem experiments. [ABSTRACT FROM AUTHOR]