scholarly journals An individual-based forest model links canopy dynamics and shade tolerances along a soil moisture gradient

2016 ◽  
Vol 3 (2) ◽  
pp. 150589 ◽  
Author(s):  
Jean Liénard ◽  
Nikolay Strigul
Keyword(s):  
Soil Moisture ◽  
Multiple Scales ◽  
Environmental Gradients ◽  
Spatial Competition ◽  
Climatic Changes ◽  
Moisture Gradient ◽  
The North ◽  
Trade Offs ◽  
Shade Tolerant Species ◽  
Closed Canopy

Understanding how forested ecosystems respond to climatic changes is a challenging problem as forest self-organization occurs simultaneously across multiple scales. Here, we explore the hypothesis that soil water availability shapes above-ground competition and gap dynamics, and ultimately alters the dominance of shade tolerant and intolerant species along the moisture gradient. We adapt a spatially explicit individual-based model with simultaneous crown and root competitions. Simulations show that the transition from xeric to mesic soils is accompanied by an increase in shade-tolerant species similar to the patterns documented in the North American forests. This transition is accompanied by a change from water to sunlight competitions, and happens at three successive stages: (i) mostly water-limited parkland, (ii) simultaneously water- and sunlight-limited closed canopy forests featuring a very sparse understory, and (iii) mostly sunlight-limited forests with a populated understory. This pattern is caused by contrasting successional dynamics that favour either shade-tolerant or shade-intolerant species, depending on soil moisture and understory density. This work demonstrates that forest patterns along environmental gradients can emerge from spatial competition without physiological trade-offs between shade and growth tolerance. Mechanistic understanding of population processes involved in the forest–parkland–desert transition will improve our ability to explain species distributions and predict forest responses to climatic changes.

Effects of soil moisture and light intensity on the chasmogamous and cleistogamous components of reproductive effort of Dichanthelium clandestinum populations

1987 ◽  
Vol 65 (11) ◽  
pp. 2243-2249 ◽  
Author(s):  
Timothy J. Bell ◽  
James A. Quinn
Keyword(s):  
Soil Moisture ◽  
Biomass Allocation ◽  
Reproductive Effort ◽  
Environmental Gradients ◽  
Perennial Grass ◽  
Moisture Gradient ◽  
Sharp Drop ◽  
Population Responses ◽  
Steady Decrease ◽  
Significant Difference

Plants from six New Jersey populations of Dichanthelium clandestinum, a perennial grass with chasmogamous and cleistogamous flowers on the same individual, showed significant differences in their responses to decreasing light and soil moisture, but chasmogamous reproductive effort was always less than cleistogamous. In an experiment with three light treatments, populations were significantly different in biomass allocation to chasmogamous and cleistogamous reproduction and varied as to which light treatment produced the most significant difference between chasmogamous and cleistogamous allocation. In an experiment using soil moisture gradient boxes, chasmogamous reproductive effort remained relatively constant over the moisture gradient for all six populations; however, for five populations, percentage biomass allocation to cleistogamous reproduction was significantly lower at low soil moistures. The population responses formed a continuum from no difference in allocation to cleistogamy along the moisture gradient to a sharp drop in cleistogamous allocation at the lower end of the gradient to a relatively steady decrease in cleistogamous allocation with decreasing soil moisture. These results indicate genetically based differences in phenotypic plasticity and underscore the need to use more than one population of a species when research is conducted on variation in relative allocation to chasmogamous and cleistogamous reproduction along environmental gradients.

The influence of snow on subalpine meadow community pattern, North Cascades, Washington

1990 ◽  
Vol 68 (1) ◽  
pp. 212-220 ◽  
Author(s):  
R. D. Evans ◽  
R. W. Fonda
Keyword(s):  
Soil Moisture ◽  
Soil Temperature ◽  
Moisture Gradient ◽  
North Cascades ◽  
Community Pattern ◽  
The North ◽  
Subalpine Meadow ◽  
Soil Moisture Gradient

The relationships among community pattern, date of snowmelt, and microclimate were examined on Excelsior Ridge in the North Cascades. Nine communities were delineated and placed into three groups based on date of snowmelt and topographic location. The Veratrum viride, Valeriana sitchensis, Lupinus latifolius, and Carex spectabilis communities, all found on windward slopes, were released from snow from June to mid-July. The Phyllodoce empetriformis, Vaccinium deliciosum, and Saxifraga tolmiei communities were located on leeward slopes where snow melted in July. Sheltered basins, which retained snow until late July or early August, supported the Carex nigricans and Luetkea pectinata communities. The influence of time of snowmelt generally was reflected in soil temperature, so that earlier sites were warmer than later sites. A soil moisture gradient was not apparent among any of the communities.

scholarly journals Influence of Drought on Acacia senegal (L.) Willd: Gum Yield within a Soil Moisture Gradient in North Eastern Nigeria

2021 ◽  
Vol 25 (7) ◽  
pp. 1201-1206
Author(s):  
A.U. Jibo
Keyword(s):  
Soil Moisture ◽  
Gum Arabic ◽  
Moisture Gradient ◽  
Line Transect ◽  
Acacia Senegal ◽  
The North ◽  
Statistical Analysis System ◽  
North Eastern ◽  
Soil Moisture Gradient ◽  
Analysis System

There had been a discernible shift in climate affecting the Sahelian zone of northern Nigeria. This attribute of drought influenced the rate of gum Arabic production in the North eastern axis. Therefore, these called for the studied of the Influence of drought on Acacia senegal (L.) Willd. Gum yield within a Soil moisture gradient in north eastern Nigeria. Two studied areas were purposively selected based on the availability (Gujba and Nguru). Complete Randomised Design was employed with three (3) samples examined at six (6) levels in six different tapping periods. Also, systematic line transect of 1Km was laid at the middle of both plantations where 1m by 1m transect were further laid in four transect sample plots. The soil samples were collected with the aid of soil auger at different levels (0-25 cm, 25-50 cm, 50-75 cm, 75-100 cm, 100-150 cm, 150-200 cm). Data was subjected using analysis of variance with statistical analysis system and descriptive statistic was also employed. The results showed that mean yield of Gum Arabic is Gujba is higher than Nguru (45kg and 30kg) respectively. Furthermore, physiochemical properties showed that pH, aluminium calcium and magnesium in both plantations were very high which is harmful for plantation development. Therefore, there is need for proper conservation and silvicultural management for both study areas.

Microclimatic and soil moisture responses to gap formation in coastal Douglas-fir forests

2002 ◽  
Vol 32 (2) ◽  
pp. 332-343 ◽  
Author(s):  
Andrew N Gray ◽  
Thomas A Spies ◽  
Mark J Easter
Keyword(s):  
Soil Moisture ◽  
Solar Radiation ◽  
Pacific Northwest ◽  
Air Temperature ◽  
Douglas Fir ◽  
Organic Substrates ◽  
Gap Formation ◽  
The North ◽  
Soil Temperatures ◽  
Closed Canopy

The effects of gap formation on solar radiation, soil and air temperature, and soil moisture were studied in mature coniferous forests of the Pacific Northwest, U.S.A. Measurements were taken over a 6-year period in closed-canopy areas and recently created gaps in four stands of mature (90–140 years) and old-growth (>400 years) Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) forest in the western Cascade Range of central Oregon and southern Washington. Gap sizes ranged from 40 to 2000 m2. Summer solar radiation levels and soil temperatures differed significantly among gap sizes and positions within gaps and were driven primarily by patterns of direct radiation. Nevertheless, effects on air temperature were slight. Soil moisture was more abundant in gaps than in controls, was most abundant in intermediate gap sizes, and tended to decline during the growing season in single-tree gaps and on the north edges of large gaps. However, there was substantial variation in moisture availability within individual gaps, primarily related to the variety of organic substrates present. Moisture in gaps declined over multiple years, likely caused by encroachment of vegetation within and around gaps. Low light levels probably limit filling of natural gaps in these forests, but the variety of microenvironments in large gaps may facilitate diverse plant communities.

Vegetation controls on soil moisture distribution in the Valles Caldera, New Mexico, during the North American monsoon

Ecohydrology ◽  
2008 ◽  
Vol 1 (3) ◽  
pp. 225-238 ◽  
Author(s):  
Enrique R. Vivoni ◽  
Alex J. Rinehart ◽  
Luis A. Méndez-Barroso ◽  
Carlos A. Aragón ◽  
Gautam Bisht ◽  
...  
Keyword(s):  
Soil Moisture ◽  
New Mexico ◽  
North American ◽  
Moisture Distribution ◽  
North American Monsoon ◽  
Valles Caldera ◽  
The North ◽  
Soil Moisture Distribution

EFFECT OF DEFICIT IRRIGATION ON YIELD, RELATIVE LEAF WATER CONTENT, LEAF PROLINE ACCUMULATION AND CHLOROPHYLL STABILITY INDEX OF COTTON–MAIZE CROPPING SEQUENCE

2013 ◽  
Vol 50 (3) ◽  
pp. 407-425 ◽  
Author(s):  
T. SAMPATHKUMAR ◽  
B. J. PANDIAN ◽  
P. JEYAKUMAR ◽  
P. MANICKASUNDARAM
Keyword(s):  
Soil Moisture ◽  
Water Stress ◽  
Water Content ◽  
Deficit Irrigation ◽  
Stability Index ◽  
Moisture Gradient ◽  
Proline Content ◽  
Leaf Water Content ◽  
Chlorophyll Stability Index ◽  
Soil Moisture Gradient

SUMMARYWater stress induces some physiological changes in plants and has cumulative effects on crop growth and yield. Field experiments were conducted to study the effect of deficit irrigation (DI) on yield and some physiological parameters in cotton and maize in a sequential cropping system. Creation of soil moisture gradient is indispensable to explore the beneficial effects of partial root zone drying (PRD) irrigation and it could be possible only through alternate deficit irrigation (ADI) practice in paired row system of drip layout that is commonly practiced in India. In the present study, PRD and DI concepts (creation of soil moisture gradient) were implemented through ADI at two levels of irrigation using drip system. Maize was sown after cotton under no till condition without disturbing the raised bed and drip layout. Relative leaf water content (RLWC) and chlorophyll stability index (CSI) of cotton and maize were reduced under water stress. A higher level of leaf proline content was observed under severe water-stressed treatments in cotton and maize. RLWC and CSI were highest and leaf proline content was lowest in mild water deficit (ADI at 100% crop evapotranspiration once in three days) irrigation in cotton and maize. The same treatments registered higher values for crop yields, net income and benefit cost ratio for both the crops.

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