Canada's National Forest Inventory (NFI) sampling program is designed to support reporting on forests at the national scale. On the other hand, continuous maps of forest attributes are required to support strategic analyses of regional policy and management issues. We have therefore produced maps covering 4.03 × 10 6 km 2 of inventoried forest area for the 2001 base year using standardised observations from the NFI photo plots (PP) as reference data. We used the k nearest neighbours (kNN) method with 26 geospatial data layers including MODIS spectral data and climatic and topographic variables to produce maps of 127 forest attributes at a 250 × 250 m resolution. The stand-level attributes include land cover, structure, and tree species relative abundance. In this article, we report only on total live aboveground tree biomass, with all other attributes covered in the supplementary data (http://nrcresearchpress.com/doi/suppl/10.1139/cjfr-2013-0401). In general, deviations in predicted pixel-level values from those in a PP validation set are greater in mountainous regions and in areas with either low biomass or sparse PP sampling. Predicted pixel-level values are overestimated at small observed values and underestimated at large ones. Accuracy measures are improved through the spatial aggregation of pixels to 1 km 2 and beyond. Overall, these new products provide unique baseline information for strategic-level analyses of forests (https://nfi.nfis.org).
Considerable evidence exists that current global temperatures are higher than at any time during the past millennium. However, the long-term impacts of rising temperatures and associated shifts in the hydrological cycle on the productivity of ecosystems remain poorly understood for mid to high northern latitudes. Here, we quantify species-specific spatiotemporal variability in terrestrial aboveground biomass stem growth across Canada's boreal forests from 1950 to the present. We use 873 newly developed tree-ring chronologies from Canada's National Forest Inventory, representing an unprecedented degree of sampling standardization for a largescale dendrochronological study. We find significant regional-and species-related trends in growth, but the positive and negative trends compensate each other to yield no strong overall trend in forest growth when averaged across the Canadian boreal forest. The spatial patterns of growth trends identified in our analysis were to some extent coherent with trends estimated by remote sensing, but there are wide areas where remote-sensing information did not match the forest growth trends. Quantifications of tree growth variability as a function of climate factors and atmospheric CO 2 concentration reveal strong negative temperature and positive moisture controls on spatial patterns of tree growth rates, emphasizing the ecological sensitivity to regime shifts in the hydrological cycle. An enhanced dependence of forest growth on soil moisture during the late-20th century coincides with a rapid rise in summer temperatures and occurs despite potential compensating effects from increased atmospheric CO 2 concentration. drought impacts | climate change | dendrochronology | normalized difference vegetation index | ecology C ircumpolar boreal forests are estimated to store ∼53.9 Pg of carbon or ∼14% of terrestrial vegetation biomass (1). These regions are currently experiencing accelerated changes, including warmer and longer growing seasons, tree line expansion, species migration, increased frequency and severity of drought, and increases in the frequency and severity of disturbances (2-10). These changes create uncertainty about the boreal forests' future role in the global carbon cycle (11). Adding to this uncertainty is the discrepancy over recent changes in the productivity of boreal and other northern latitude forests. Some empirical evidence suggests increases in the forest productivity (12)(13)(14), whereas other studies suggest decreasing productivity over the last decades (7,8,(15)(16)(17). Furthermore, inversion and process-based ecosystem models indicate large carbon sinks (7,8), whereas field-based bottom-up approaches suggest smaller carbon sinks or small carbon sources (3, 18), or large sinks (19). Quantifying
Drought and high salinity are two major environmental factors that significantly limit the productivity of agricultural crops worldwide. WRKY transcription factors play essential roles in the adaptation of plants to abiotic stresses. However, WRKY genes involved in drought and salt tolerance in cotton (Gossypium hirsutum) are largely unknown. Here, a group IId WRKY gene, GhWRKY17, was isolated and characterized. GhWRKY17 was found to be induced after exposure to drought, salt, H2O2 and ABA. The constitutive expression of GhWRKY17 in Nicotiana benthamiana remarkably reduced plant tolerance to drought and salt stress, as determined through physiological analyses of the germination rate, root growth, survival rate, leaf water loss and Chl content. GhWRKY17 transgenic plants were observed to be more sensitive to ABA-mediated seed germination and root growth. However, overexpressing GhWRKY17 in N. benthamiana impaired ABA-induced stomatal closure. Furthermore, we found that GhWRKY17 modulated the increased sensitivity of plants to drought by reducing the level of ABA, and transcript levels of ABA-inducible genes, including AREB, DREB, NCED, ERD and LEA, were clearly repressed under drought and salt stress conditions. Consistent with the accumulation of reactive oxygen species (ROS), reduced proline contents and enzyme activities, elevated electrolyte leakage and malondialdehyde, and lower expression of ROS-scavenging genes, including APX, CAT and SOD, the GhWRKY17 transgenic plants exhibited reduced tolerance to oxidative stress compared with wild-type plants. These results therefore indicate that GhWRKY17 responds to drought and salt stress through ABA signaling and the regulation of cellular ROS production in plants.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.