scholarly journals Relationships between Structure, Composition, and Dynamics of the Pristine Northern Boreal Forest and Air Temperature, Precipitation, and Soil Texture in Quebec (Canada)

2009 ◽  
Vol 2009 ◽  
pp. 1-13 ◽  
Author(s):  
Louis Duchesne ◽  
Rock Ouimet
Keyword(s):  
Boreal Forest ◽  
Air Temperature ◽  
Tree Growth ◽  
Soil Texture ◽  
Forest Composition ◽  
Stand Age ◽  
Stand Dynamics ◽  
Precipitation Regime ◽  
Temperature And Precipitation ◽  
Precipitation Regimes

This study reports on the contemporary structure, composition, and dynamics of the pristine northern boreal forest in Quebec, Canada, associated with air temperature, precipitation, and soil texture, using 147 permanent sample plots located at the limit of continuous forest in Quebec. The results show that tree species composition of stands is associated with stand age, soil texture, air temperature, and precipitation regime. After establishment of the pioneer cohort, the postsuccessional stand dynamics differed among temperature and precipitation regimes, probably because of their influence on tree growth. Our results support the hypothesis that shifts in forest composition related to stand dynamics and the subsequent senescing phase associated with the old growth stage generally occur sooner and proceed faster on more fertile sites due to quicker growth and the subsequent earlier mortality of pioneer species. This study suggests that climate warming should accelerate the successional dynamics of these ecosystems through its positive influence on tree growth.

scholarly journals Climatic changes and their influence on air temperature and precipitation in Ukraine during transitional seasons

2020 ◽  
pp. 60-67
Author(s):  
V. M. Khokhlov ◽  
H. O. Borovska ◽  
M. S. Zamfirova
Keyword(s):  
Air Temperature ◽  
Meteorological Parameters ◽  
Regional Climate ◽  
Monitoring Network ◽  
Climatic Changes ◽  
Precipitation Regime ◽  
Runoff Water ◽  
The West ◽  
Temperature And Precipitation ◽  
Dynamic Methods

      Since modern research indicates climatic changes in all regions of our planet, including on the territory of Ukraine (in particular, the deviation of temperature and other meteorological parameters from the values of the climatic norm), their study is extremely important. After all, they can lead to changes in the nature of precipitation distribution, the length of the growing season, a decrease in the duration of the stable snow cover, local runoff water resources, etc. Most scientific works in recent years describe changes in the distribution of temperature characteristics and precipitation regime, because they are one of the main indicators of the state of the climate system. Therefore, the purpose of this article is to identify the features of changes in air temperature and precipitation for the entire territory of Ukraine from 2021 to 2050 based on the results of 16 simulations of the ensemble of CORDEX models based on the RCP4.5 scenario. The CORDEX project is a modern simulation of the future climate and has a resolution of ~ 12.5 km in the horizontal plane, which makes it possible to better simulate the characteristics under study. It integrates regional climate predictions that are generated using statistical and dynamic methods. The results obtained are presented for 177 cities of Ukraine, which currently form the basis of a modern monitoring network. It was found that the number of days with precipitation ≥ 5 mm in transitional seasons increases on average by 1-3 days per month, depending on the region. The maximum values of the frequency of occurrence of the number of days with precipitation ≥ 5 mm are observed in the west and gradually decrease in the south. Compared to 1961-1990, the most significant changes occur with the number of frosty days with an air temperature of ≤ 0°С, which noticeably decreases during the study period from north to south. In April and October, for the southern regions of Ukraine, the considered parameter is equal to 0, which means that in these months the air temperature for these regions will have positive values. From the above, there is a tendency towards warming in transitional seasons and a change in the nature of moisture supply to the territory of Ukraine in the next thirty years.

Growth trends and stand dynamics in natural loblolly pine in the southeastern United States

1992 ◽  
Vol 22 (5) ◽  
pp. 660-666 ◽  
Author(s):  
Paul C. Van Deusen
Keyword(s):  
United States ◽  
Loblolly Pine ◽  
Tree Growth ◽  
Southeastern United States ◽  
Tree Age ◽  
Stand Age ◽  
Stand Dynamics ◽  
Individual Tree ◽  
Growth Trends ◽  
Individual Tree Growth

A number of recent studies have shown reduced stand-level and individual-tree growth in natural loblolly pine (Pinustaeda L.) stands in the southeastern United States. This study uses increment cores from dominant and codominant trees to determine if individual-tree growth has changed from 1915 to 1985. The cores are grouped for comparison by first sorting on the basis of median stand age and then further sorting these groups of cores by individual-tree age. These trees experienced increasing basal area increments from the mid-1940s into the mid-1970s, after which growth rates returned to preincrease levels. These data support recent findings of growth reductions, but also indicate previously unreported growth increases preceding the growth decreases. These and supplemental permanent plot data suggest that stand dynamics is a viable hypothesis for explaining these growth trends.

Relative importance of different secondary successional pathways in an Alaskan boreal forest

2008 ◽  
Vol 38 (7) ◽  
pp. 1911-1923 ◽  
Author(s):  
Thomas A. Kurkowski ◽  
Daniel H. Mann ◽  
T. Scott Rupp ◽  
David L. Verbyla
Keyword(s):  
Boreal Forest ◽  
Tree Species ◽  
Black Spruce ◽  
Fire Frequency ◽  
Forest Composition ◽  
Stand Age ◽  
Solar Insolation ◽  
Species Dominance ◽  
Complex Landscape ◽  
Successional Pathways

Postfire succession in the Alaskan boreal forest follows several different pathways, the most common being self-replacement and species-dominance relay. In self-replacement, canopy-dominant tree species replace themselves as the postfire dominants. It implies a relatively unchanging forest composition through time maintained by trees segregated within their respective, ecophysiological niches on an environmentally complex landscape. In contrast, species-dominance relay involves the simultaneous, postfire establishment of multiple tree species, followed by later shifts in canopy dominance. It implies that stand compositions vary with time since last fire. The relative frequencies of these and other successional pathways are poorly understood, despite their importance in determining the species mosaic of the present forest and their varying, potential responses to climate changes. Here we assess the relative frequencies of different successional pathways by modeling the relationship between stand type, solar insolation, and altitude; by describing how stand age relates to species composition; and by inferring successional trajectories from stand understories. Results suggest that >70% of the study forest is the product of self-replacement, and tree distributions are controlled mainly by the spatial distribution of solar insolation and altitude, not by time since last fire. As climate warms over the coming decades, deciduous trees will invade cold sites formerly dominated by black spruce, and increased fire frequency will make species-dominance relay even rarer.

scholarly journals Carbon, nitrogen, and phosphorus stoichiometry of organic matter in Swedish forest soils and its relationship with climate, tree species, and soil texture

2021 ◽  
Author(s):  
Marie Spohn ◽  
Johan Stendahl
Keyword(s):  
Organic Matter ◽  
Boreal Forest ◽  
Forest Soils ◽  
Soil Texture ◽  
Tree Species ◽  
Mineral Soil ◽  
Stand Age ◽  
Organic Layer ◽  
Mean Annual Temperature ◽  
P Concentration

Abstract. While the carbon (C) content of temperate and boreal forest soils is relatively well studied, much less is known about the ratios of C, nitrogen (N), and phosphorus (P) of the soil organic matter, and the abiotic and biotic factors that shape them. Therefore, the aim of this study was to explore carbon, nitrogen, and organic phosphorus (OP) contents and element ratios in temperate and boreal forest soils and their relationships with climate, dominant tree species, and soil texture. For this purpose, we studied 309 forest soils with a stand age >60 years located all over Sweden between 56° N and 68° N. The soils are a representative subsample of Swedish forest soils with a stand age >60 years that were sampled for the Swedish Forest Soil Inventory. We found that the N stock of the organic layer increased by a factor of 7.5 from −2 °C to 7.5 °C mean annual temperature (MAT), it increased almost twice as much as the organic layer stock along the MAT gradient. The increase in the N stock went along with an increase in the N : P ratio of the organic layer by a factor of 2.1 from −2 °C to 7.5 °C MAT (R2 = 0.36, p < 0.001). Forests dominated by pine had higher C : N ratios in the litter layer and mineral soil down to a depth of 65 cm than forests dominated by other tree species. Further, also the C : P ratio was increased in the pine-dominated forests compared to forests dominated by other tree species in the organic layer, but the C : OP ratio in the mineral soil was not elevated in pine forests. C, N and OP contents in the mineral soil were higher in fine-textured soils than in coarse-textured soils by a factor of 2.3, 3.5, and 4.6, respectively. Thus, the effect of texture was stronger on OP than on N and C, likely because OP adsorbs very rigidly to mineral surfaces. Further, we found, that the P and K concentrations of the organic layer were inversely related with the organic layer stock. The C and N concentrations of the mineral soil were best predicted by the combination of MAT, texture, and tree species, whereas the OP concentration was best predicted by the combination of MAT, texture and the P concentration of the parent material in the mineral soil. In the organic layer, the P concentration was best predicted by the organic layer stock. Taken together, the results show that the N : P ratio of the organic layer was most strongly related to MAT. Further, the C : N ratio was most strongly related to dominant tree species, even in the mineral subsoil. In contrast, the C : P ratio was only affected by dominant tree species in the organic layer, but the C : OP ratio in the mineral soil was hardly affected by tree species due to the strong effect of soil texture on the OP concentration.

Intra-annual climatic signal in tree rings of Larix sp. based on the Vaganov-Shashkin model output

2021 ◽  
Author(s):  
Marina Fonti ◽  
Olga Churakova (Sidorova) ◽  
Ivan Tychkov
Keyword(s):  
Tree Ring ◽  
Tree Growth ◽  
Climatic Factors ◽  
Ring Width ◽  
Growing Season ◽  
Climatic Conditions ◽  
Limiting Factor ◽  
Precipitation Regime ◽  
The North ◽  
Temperature And Precipitation

&lt;p&gt;Air temperature increase and change in precipitation regime have a significant impact on northern forests leading to the ambiguous consequences due to the complex interaction between the ecosystem plant components and permafrost. One of the major interests in such circumstances is to understand how tree growth of the main forest species of the Siberian North will change under altering climatic conditions. In this work, we applied the process-based Vaganov-Shashkin model (VS - model) of tree growth in order to estimate the daily impact of climatic conditions on tree-ring width of larch trees in northeastern Yakutia (Larix cajanderi Mayr.) and eastern Taimyr (Larix gmelinii Rupr. (Rupr.) for the period 1956-2003, and to determine the extent to which the interaction of climatic factors (temperature and precipitation) is reflected in the tree-ring anatomical structure. Despite the location of the study sites in the harsh conditions of the north, and temperature as the main limiting factor, it was possible to identify a period during the growing season when tree growth was limited by lack of soil moisture. The application of the VS-model for the studied regions allowed establishing in which period of the growing season the water stress is most often manifest itself, and how phenological phases (beginning, cessation, and duration of larch growth) vary among the years.&lt;/p&gt;&lt;p&gt;The research was funded by RFBR, Krasnoyarsk Territory and Krasnoyarsk Regional Fund of Science, project number 20-44-240001 and by the Russian Ministry of Science and Higher Education (projects FSRZ-2020-0010).&lt;/p&gt;

Coarse woody debris in the southeastern Canadian boreal forest: composition and load variations in relation to stand replacement

2000 ◽  
Vol 30 (5) ◽  
pp. 674-687 ◽  
Author(s):  
C Hély ◽  
Y Bergeron ◽  
M D Flannigan
Keyword(s):  
Boreal Forest ◽  
Coarse Woody Debris ◽  
Structural Characteristics ◽  
Woody Debris ◽  
Decay Rates ◽  
Forest Composition ◽  
Stand Age ◽  
Time Since Fire ◽  
Clay Deposits ◽  
Canopy Composition

Quantities and structural characteristics of coarse woody debris (CWD) (logs and snags) were examined in relation to stand age and composition in the Canadian mixedwood boreal forest. Forty-eight stands originating after fire (from 32 to 236 years) were sampled on mesic clay deposits. The point-centered quadrant method was used to record canopy composition and structure (living trees and snags). The line-intersect method was used to sample logs of all diameters. Total log load, mean snag density, and volume per stand were similar to other boreal stands. Linear and nonlinear regressions showed that time since fire and canopy composition were significant descriptors for log load changes, whereas time since fire was the only significant factor for snag changes. Coarse woody debris accumulation models through time since fire were different from the U-shaped model because the first initial decrease from residual pre-disturbance debris was missing, the involved species had rapid decay rates with no long-term accumulation, and the succession occurred from species replacement through time.

scholarly journals Air temperature and precipitation regime in Ukraine in 2021-2050 by CORDEX model ensemble

2020 ◽  
pp. 17-27
Author(s):  
M. S. Zamfirova ◽  
V. M. Khokhlov
Keyword(s):  
Air Temperature ◽  
Climate Models ◽  
Regional Climate ◽  
Regional Climate Models ◽  
Monthly Precipitation ◽  
Precipitation Regime ◽  
Maximum Increase ◽  
Temperature And Precipitation ◽  
Maximum Temperatures ◽  
Southern Ukraine

Global temperatures over the period of 2081–2100 are expected to rise by 0.3–4.8 °C compared to the period of 1986–2005. According to the previous studies, the average annual air temperature in all regions of Ukraine will keep increasing in the near future and the maximum increase in precipitation is expected mainly in the western and northern regions during winter and spring, whereas the decrease in precipitation will be registered in the central, eastern and southern regions during summer and autumn. This article aims to identify the features of changes in air temperature and precipitation for different regions of Ukraine in 2021–2050 based on the modelling results of the ensemble of CORDEX models as per the RCP4.5 scenario. 16 simulation runs for 7 regional climate models were selected for the analysis and the results were presented for five regional centers of Ukraine: Kyiv, Lviv, Kropyvnytskyi, Kharkiv and Odesa. It is shown that future monthly precipitation in all regions tends to increase by an average of 20–40 mm during autumn, winter and spring, whereas the decrease is expected to occur in summer. According to some models, the monthly precipitation will be close to zero in the Southern Ukraine in July and August, which is typical for the Mediterranean climate. Compared to the period of 1961–1990, the average monthly temperature will undergo small changes (up to 1 °C) in spring and autumn, while the temperature in summer and winter will increase by 2.5–3.5 °C. In Odesa, in contrast to the present-day situation, a positive average monthly air temperature will be expected to be recorded throughout the whole year, and only 25% of the runs show negative average monthly minimum temperatures. In the Northern Ukraine, the average monthly minimum and maximum temperatures in winter will increase by 2.0–2.5 °C, and in summer only the maximum air temperature will increase significantly. Thus, we can assume a change in the regime of moisture supply in Ukraine over the next thirty years. One can also assume a high probability of snow cover absence throughout the whole winter in the Southern Ukraine as a result of positive temperatures.

scholarly journals The climatic imprint of bimodal distributions in vegetation cover for western Africa

2016 ◽  
Vol 13 (11) ◽  
pp. 3343-3357 ◽  
Author(s):  
Zun Yin ◽  
Stefan C. Dekker ◽  
Bart J. J. M. van den Hurk ◽  
Henk A. Dijkstra
Keyword(s):  
Land Cover ◽  
Congo Basin ◽  
Shortwave Radiation ◽  
Mean Annual Precipitation ◽  
Above Ground Biomass ◽  
Precipitation Regime ◽  
Ground Biomass ◽  
Western Africa ◽  
Precipitation Regimes ◽  
Woody Cover

Abstract. Observed bimodal distributions of woody cover in western Africa provide evidence that alternative ecosystem states may exist under the same precipitation regimes. In this study, we show that bimodality can also be observed in mean annual shortwave radiation and above-ground biomass, which might closely relate to woody cover due to vegetation–climate interactions. Thus we expect that use of radiation and above-ground biomass enables us to distinguish the two modes of woody cover. However, through conditional histogram analysis, we find that the bimodality of woody cover still can exist under conditions of low mean annual shortwave radiation and low above-ground biomass. It suggests that this specific condition might play a key role in critical transitions between the two modes, while under other conditions no bimodality was found. Based on a land cover map in which anthropogenic land use was removed, six climatic indicators that represent water, energy, climate seasonality and water–radiation coupling are analysed to investigate the coexistence of these indicators with specific land cover types. From this analysis we find that the mean annual precipitation is not sufficient to predict potential land cover change. Indicators of climate seasonality are strongly related to the observed land cover type. However, these indicators cannot predict a stable forest state under the observed climatic conditions, in contrast to observed forest states. A new indicator (the normalized difference of precipitation) successfully expresses the stability of the precipitation regime and can improve the prediction accuracy of forest states. Next we evaluate land cover predictions based on different combinations of climatic indicators. Regions with high potential of land cover transitions are revealed. The results suggest that the tropical forest in the Congo basin may be unstable and shows the possibility of decreasing significantly. An increase in the area covered by savanna and grass is possible, which coincides with the observed regreening of the Sahara.

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