Results 1 - 10 of 1016
Results 1 - 10 of 1016. Search took: 0.025 seconds
|Sort by: date | relevance|
[en] The relationship between diversity and productivity of plant community under plant invasion has been not well known up to now. Here, we investigated the relationship between diversity and productivity under plant invasion and studied the response of species level plant mass to species richness in native and invaded communities. A field experiment from 2008 to 2013 and a pot experiment in 2014 were conducted to study the effects of plant invasion on the relationship between diversity and productivity and the response of species level plant mass to species richness in native and invaded communities. The community level biomass was negatively correlated to plant species richness in invaded communities while the same relationship was positive in native communities. The species level plant mass of individual species responded differently to overall plant species richness in the native and invaded communities, namely, most of the species’ plant mass increased in native communities, but decreased in invaded communities with increasing species richness. The complementarity or selection effects might dominate in native communities while competition effects might dominate in invaded communities. Accordingly, the negative relationship between diversity and productivity under plant invasion is highlighted in our experiments.
[en] Reducing emissions from deforestation and forest degradation, and enhancing carbon stocks (REDD+) is a crucial component of global climate change mitigation. Remote sensing can provide continuous and spatially explicit above-ground biomass (AGB) estimates, which can be valuable for the quantification of carbon stocks and emission factors (EFs). Unfortunately, there is little information on the fate of the land following tropical deforestation and of the associated carbon stock. This study quantified post-deforestation land use across the tropics for the period 1990–2000. This dataset was then combined with a pan-tropical AGB map at 30 m resolution to refine EFs from forest conversion by matching deforestation areas with their carbon stock before and after clearing and to assess spatial dynamics of EFs by follow-up land use. In Latin America, pasture was the most common follow-up land use (72%), with large-scale cropland (11%) a distant second. In Africa deforestation was often followed by small-scale cropping (61%) with a smaller role for pasture (15%). In Asia, small-scale cropland was the dominant agricultural follow-up land use (35%), closely followed by tree crops (28%). Deforestation often occurred in forests with lower than average carbon stocks. EFs showed high spatial variation within eco-zones and countries. While our EFs are only representative for the studied time period, our results show that EFs are mainly determined by the initial forest carbon stock. The estimates of the fraction of carbon lost were less dependent on initial forest biomass, which offers opportunities for REDD+ countries to use these fractions in combination with recent good quality national forest biomass maps or inventory data to quantify emissions from specific forest conversions. Our study highlights that the co-location of data on forest loss, biomass and fate of the land provides more insight into the spatial dynamics of land-use change and can help in attributing carbon emissions to human activities. (letter)
[en] Exponential fertilization has been shown to be a useful technique for improving seedling quality during nursery production. In this study, we evaluated (i) the impact of exponential vs. conventional fertilization on trembling aspen (Populus tremuloides Michx.) and white spruce (Picea glauca (Moench) Voss) seedlings during nursery production and (ii) the growth performance and nitrogen (N) utilization of those seedlings in response to foxtail barley (Hordeum jubatum L.) competition after the transplantation of seedlings in a greenhouse experiment. Exponential fertilization with an application rate higher than the conventional fertilization increased the internal N reserve in trembling aspen and white spruce seedlings during nursery production and also increased new leaf, new stem, and old stem biomass and N retranslocation rates in trembling aspen seedlings but not in white spruce seedlings after transplantation. Foxtail barley competition decreased N concentrations in seedlings and soil N uptake by the seedlings; however, increased N retranslocation rates with foxtail barley competition were observed in white spruce seedlings but not in trembling aspen seedlings. Our results suggest that the growth performance of seedlings was improved by N loading, whereas the impact of vegetation management was species specific. (author)
[en] The utilization of agricultural residues may become one of the major sources for production of energy from biomass. The objective of this paper was to analyse the type and quantity of agricultural residues and to determine their energy potential. Area of study: The Međimurje County (north Croatia).The paper analyses three models of sustainable agricultural residues management applying the multi-criteria analysis. The assessment included potentially available quantities of residues in crops, fruit, viniculture and livestock production. For determining the most appropriate model of residues utilisation the multi-criteria analysis was applied.The results show that total quantities of agricultural biomass amount to 323,912 t with energy potential of 1,092 TJ annually. The largest sustainably available potential of agricultural biomass consists of biomass from arable crops production, with total quantity of 33,670 t followed by 281,233 t of manure from livestock production. The lowest share of potential biomass are pruning residues in fruit and grapevine production with total available residual quantity of 8,109 t. Also, it results from the multi-criteria analysis that a central large scale plant for biogas production is the most feasible facility for such production. The results of this paper provide ground for further development of the models for assessing the sustainability of using agricultural residues, and they can also serve as a basis for assessments of bioenergy projects in specific regions of the European Union.
[en] The distribution of tropical forest biomass across the landscape is poorly understood, particularly in increasingly common secondary tropical forests. We studied the landscape-scale distribution of edaphic properties, plant community characteristics, and aboveground biomass (AGB) in secondary tropical dry forests in northwest Costa Rica. We used structural equation modeling to examine conceptual models of relationships among these factors, with data from 84 0.1 ha plots. Stand age and soils explained 33%--60% of the variation in community-weighted mean values of foliar traits including specific leaf area, foliar nitrogen, phosphorus, and δ13C. Aboveground biomass ranged from 1.7 to 409 Mg·ha-1 among plots between 5 and >100 years old. Stand age alone explained 46% of the variation in AGB among plots, while a model including age, soil pH, traits, and forest type explained 58%. Stand age was the most important variable explaining the distribution of AGB and community characteristics in secondary forests. We speculate that plot size, landscape heterogeneity, disturbance history, and stand dynamics contribute to the unexplained variation in AGB across the landscape. (author)
[en] Various approaches can minimize biomass accumulation in biotricking filters (BTF), which can be classified as: (1) physical, (2) chemical and (3) biological. Other approaches include (4) improvement of the bioreactor design and (5) modification of the mode and operational parameters. All of these methods involve either reduction in biomass growth or removal of excess biomass and each method has unique advantages and disadvantages as far as biomass reduction capability, sustainability and ease of integration to the system are concerned, which are compared and contrasted in this review. A careful comparison and analysis of these methods is a requisite to an optimum operation of a BTF system.
[en] Quantification of long-term wind-speed variability is a critical component in wind resource assessment, and effective wind-farm operations require proper assessment of this variability. Yet, wind-speed variations differ across averaging temporal scales because hourly mean wind speeds fluctuate more than yearly averages. In this study, we quantify the influence of averaging timescale to the resultant variability. We assess three spread metrics (standard deviation, coefficient of variation, and robust coefficient of variation) and two distribution measures (skewness and kurtosis) based on 38 years of wind speeds from the National Aeronautics and Space Administration's MERRA-2 reanalysis data set over the contiguous United States. The spatial distributions of wind-speed variability differ with metrics and timescales: wind speeds of fine temporal resolution generate strong variabilities that dilute spatial contrasts; small sample size becomes a constraint in calculating interannual variabilities via annual means and leads to inaccurate results. Overall, we find that metrics based on monthly data portray the largest spatial differences of wind-speed variability. Although standard deviation yields consistent geographical projections, none of the wind-speed data of any time frame are perfectly Gaussian. Furthermore, the robust coefficient of variation, a statistically robust and resistant approach, appears to be the ideal metric for quantifying wind-speed variabilities based on monthly mean data.
[en] Water deficit is a serious threat to the global crop production. Marigold (Tagetes erecta L.), an economically important annual is resistant to drought stress, however, anatomical adaptations confirming drought tolerance are still unexplored. In this context, key growth and anatomical difference of two marigold (T. erecta L.) cultivars, Inca (drought resistant) and Bonanza (drought sensitive), to water deficit conditions were studied. Plants of both marigold cultivars were subjected to control (T0; 100% FC) and water deficit conditions (T1; 60 FC and T2; 40 FC) three weeks after transplantation. Drought stress caused a significant reduction in growth of cv. Bonanza while cv. Inca remained unaffected. However, drought stress significantly affected anatomical features in both marigold cultivars. Increasing drought stress levels enhanced the reduction in root vascular area of both cultivars. Under both levels of water stress, shoot cortex area decreased only in cv. Bonanza. Leaf thickness and cortex area decreased at 40% FC in both cultivars. The growth and biomass performance of cv. Inca was better than cv. Bonanza under water stress conditions. (author)
[en] Tropical forests ecosystems remain the most diverse on the planet, and store considerable amounts of biomass and carbon. Despite the importance of tropical forests, sizable knowledge gaps exist regarding species diversity, plant biomass and carbon. These knowledge gaps are particularly large in tropical systems, and even more so in the African tropics. This study provides baseline data on species composition and vegetation structure, and evaluate variation along elevational gradient transecting of four elevation-forest types: lowland, mid-elevation, sub-montane and montane forest in the Rumpi Hills Forest Reserve of Cameroon. We collected data on tree species diversity, above-ground biomass and carbon in 25 1-ha plots sampled in 500 m long x 20 m width transect. Results revealed high species diversity, particularly in lowland forest. Overall, the study enumerated 12,037 individuals (trees ≥ 10 cm dbh) of 441 species. The mean species per plot decreased with increasing elevation, 112 in lowland, 81 in mid-elevation, 60 in submontane and 38 in montane forest. Above-ground carbon averaged 162.88±50 t ha-1. We found the greatest carbon storage and tree and liana species diversity at low elevations. Our results indicate that high species diversity and occurrence of larger tree species are more important in carbon storage in lowland forest than at higher elevations. These findings are useful for management and land use planning of the forests in the Rumpi Hills Forest Reserve. (author)
[en] MAIDENiso is a new version of the process-based biogeochemical model MAIDEN of tree growth. Isotopic modules have been implemented to simulate stable oxygen and carbon isotopes in tree-ring cellulose (TRC). In addition to annual increment biomass, this new model version estimates δ18O and δ13C associated with the daily amount of carbon allocated to the stem. MAIDENiso only requires daily input data: minimal and maximal air temperatures, amount of precipitation, CO2 atmospheric concentration, and δ13C in CO2. MAIDENiso simulates tree-ring width, δ18O in precipitation (δ18OP), δ18O in soil water (δ18OSW), δ18O in xylem water (δ18OXW), δ18O in cellulose (δ18OTRC), and δ13C in cellulose (δ13CTRC). The model has been calibrated and validated with tree-ring series sampled in the Fontainebleau Forest (France) from 1953 to 2000. We first calibrated several parameters for the 1977-2000 period and then validated it for the independent 1953-1976 period. Over the complete interval (1953-2000), we obtained correlations between observations and simulations above 0.5 for both isotopic series and above 0.65 for tree growth series. An important feature of the model is its ability to simulate not only extreme values of tree growth, such as the effect of 1976 drought, but also its persistence over several years. (author)