scholarly journals Peat depth as a control on moss water availability during drought

2020 ◽  
Author(s):  
Paul Moore ◽  
Benjamin Didemus ◽  
Alexander Furukawa ◽  
James Waddington
Keyword(s):  
Climate Change ◽  
Water Content ◽  
Soil Water ◽  
Water Table ◽  
Summer Drought ◽  
Drought Period ◽  
Near Surface ◽  
Soil Water Tension ◽  
Water Tension

Peatlands are globally important long-term sinks of carbon, however there is concern that enhanced moss moisture stress due to climate change mediated drought will reduce moss productivity making these ecosystems vulnerable to carbon loss and associated long-term degradation. Peatlands are resilient to summer drought moss stress because of negative ecohydrological feedbacks that generally maintain a wet peat surface, but where feedbacks may be contingent on peat depth. We tested this ‘survival of the deepest’ hypothesis by examining water table position, near-surface moisture content, and soil water tension in peatlands that differ in size, peat depth, and catchment area during a summer drought. All shallow sites lost their WT (i.e. the groundwater well was dry) for considerable time during the drought period. Near-surface soil water tension increased dramatically at shallow sites following water table loss, increasing ~5–7.5× greater at shallow sites compared to deep sites. During a mid-summer drought intensive field survey we found that 60%–67% of plots at shallow sites exceeded a 100 mb tension threshold used to infer moss water stress. Unlike the shallow sites, tension typically did not exceed this 100 mb threshold at the deep sites. Using species dependent water content - chlorophyll fluorescence thresholds and relations between volumetric water content and water table depth, Monte Carlo simulations suggest that moss had nearly twice the likelihood of being stressed at shallow sites (0.38 ± 0.24) compared to deep sites (0.22 ± 0.18). This study provides evidence that mosses in shallow peatland may be particularly vulnerable to warmer and drier climates in the future, but where species composition may play an important role. We argue that a critical ‘threshold’ peat depth specific for different hydrogeological and hydroclimatic regions can be used to assess what peatlands are especially vulnerable to climate change mediated drought.

scholarly journals Monitoring of Soil Water Content in Maize Rotated with Pigeonpea Fallows in South Africa

Water ◽  
2020 ◽  
Vol 12 (10) ◽  
pp. 2761
Author(s):  
Misheck Musokwa ◽  
Paramu L. Mafongoya ◽  
Paxie W. Chirwa
Keyword(s):  
South Africa ◽  
Water Content ◽  
Soil Water ◽  
Water Distribution ◽  
Smallholder Farmers ◽  
Block Design ◽  
Maize Production ◽  
Soil Water Tension ◽  
Continuous Maize ◽  
Water Tension

Maize production under smallholder systems in South Africa (RSA) depends on rainfall. Incidences of dry spells throughout the growing season have affected maize yields negatively. The study examined water distribution and water use efficiency (WUE) of maize rotated with two-year pigeonpea fallows as compared to continuous maize without fertilizer. A randomized complete block design, replicated three times, was used with four treatments, which included continuous unfertilized maize, natural fallow-maize, pigeonpea + grass-pigeonpea-maize, and two-year pigeonpea fallow-maize. Soil water mark sensors were installed 0.2; 0.5; and 1.2 m on each plot to monitor soil water tension (kPa). Soil samples were analyzed using pressure plates to determine water retention curves which were used to convert soil water tension to volumetric water content. Maize rotated with two-year pigeonpea fallows had higher dry matter yield (11,661 kg ha−1) and WUE (20.78 kg mm−1) than continuous maize (5314 kg ha−1 and 9.48 kg mm−1). In this era of water scarcity and drought incidences caused by climate change, maize rotated with pigeonpea fallows is recommended among smallholder farmers in RSA because of its higher WUE, hence food security will be guaranteed.

Soil water extraction by a mixed eucalypt forest during a drought period

Soil Research ◽  
1986 ◽  
Vol 24 (1) ◽  
pp. 25 ◽  
Author(s):  
T Talsma ◽  
EA Gardner
Keyword(s):  
Soil Water ◽  
Water Use ◽  
Water Table ◽  
Unsaturated Flow ◽  
Growth Ring ◽  
Soil Water Potential ◽  
Water Extraction ◽  
Depth Interval ◽  
Summer Drought ◽  
Drought Period

Eucalypt trees growing on deep soils, with a water table at about 8 m depth, showed no apparent drought effects during the 1982-83 dry period in south-east Australia when gross precipitation was only 388 mm. At the end of the drought, soil water to 4 m depth was depleted to a soil water potential of -0.5 MPa and under these conditions unsaturated flow from the water table to the lower root zone was calculated to be 0.17 mm day-1. Water extraction over the depth interval from 0 to 6 m in the drought year was 533 mm, some 200 mm in excess of that used during a year of average rainfall. The contribution to tree water use from unsaturated flow from the water table was calculated to be small (15 mm) even in a drought year, and in most years water movement would be towards the water table to yield a deep drainage term estimated between 40 and 100 mm. Growth ring studies indicated that the lower water use, estimated at 2.6 mm day-1 during the spring-summer drought, did not affect the slowly growing E. radiata species, but reduced stem diameter growth of the faster growing E. dalrympleana and E. pauciflora species.

scholarly journals 533 Monitoring Soil Water Content in Tropical Fruit Orchards in Southern Florida with Multi-sensor Capacitance Probes and Tensiometers

HortScience ◽  
2000 ◽  
Vol 35 (3) ◽  
pp. 487C-487 ◽  
Author(s):  
R. Nuñez-Elisea ◽  
B. Schaffer ◽  
M. Zekri ◽  
S.K. O'Hair ◽  
J.H. Crane
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Volumetric Soil Water Content ◽  
Tropical Fruit ◽  
Soil Water Tension ◽  
Scheduling Irrigation ◽  
Southern Florida ◽  
Fruit Orchards ◽  
Water Tension

Tropical fruit trees in southern Florida are grown in porous, oolitic limestone soil that has very low organic matter content and water-holding capacity. Thus, trees require frequent irrigation during dry periods. In these soils, a quantitative basis for monitoring soil water content to determine when and how much to irrigate has been lacking. Multi-sensor capacitance probes (EnviroSCAN™, Sentek, Australia) were installed in commercial carambola, lime, and avocado orchards to continuously monitor changes in soil water content at depths of 10, 20, 30, and 50 cm. Eight probes were installed per orchard. Volumetric soil water content was recorded at 15-min intervals with a solar-powered datalogger. Results were downloaded to a laptop computer twice a week. Monitoring the rate of soil water depletion (evapotranspiration) allowed irrigation before the onset of water stress. The time at which soil reached field capacity could be determined after each irrigation (or rain) event. Soil water tension was recorded periodically using low-tension (0–40 cbars) tensiometers placed adjacent to selected capacitance probes at 10- and 30-cm depths. Soil water tension was better correlated with volumetric soil water content at a 10-cm depth than at 30-cm depth. Using multi-sensor capacitance probes is a highly accurate, although relatively expensive, method of monitoring soil water content for scheduling irrigation in tropical fruit orchards. Whereas tensiometers require periodic maintenance, the multi-sensor capacitance probe system has been virtually maintenance free. The correlation between soil water content and soil water tension obtained in situ indicates that tensiometers are a less precise, but considerably cheaper, alternative for scheduling irrigation in tropical fruit orchards in southern Florida.

Variability of soil water tension and soil water content

1990 ◽  
Vol 18 (2) ◽  
pp. 135-148 ◽  
Author(s):  
J.M.H. Hendrickx ◽  
P.J. Wierenga ◽  
M.S. Nash
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Soil Water Tension ◽  
Water Tension

scholarly journals Water balance in soil covered by regenerating rainforest in the Paraíba Valley region, São Paulo, Brazil

2019 ◽  
Vol 14 (6) ◽  
pp. 1
Author(s):  
Marcelo Dos Santos Targa ◽  
Emilson Pohl ◽  
Ana Aparecida da Silva Almeida
Keyword(s):  
Soil Moisture ◽  
Water Balance ◽  
Water Content ◽  
Soil Water ◽  
Characteristic Curve ◽  
Residual Water ◽  
Deep Drainage ◽  
Soil Water Tension ◽  
Experimental Area ◽  
Water Tension

The objective of this study was to evaluate the water balance in a Red-Yellow Latosol covered by a regenerating rainforest for 30 years in the Una River Basin between April 2016 and March 2017. Field capacity (FC) and permanent wilting-point values (PWP) used to calculate the available water capacity (AWC) in the soil were determined by the soil moisture characteristic curve obtained in pots, which made it possible to determine the soil residual water content (g / g) from the measurement of water tension in 15 Watermark (TM) sensors installed at depths of 40, 60 and 120 cm. Precipitation during the period (1962 mm) was obtained from the automatic weather station located 300 m from the experimental area. Soil surface runoff was obtained from 5 collectors distributed in the experimental area. Precipitation was characterized by a maximum of 454 mm in January 2017 and no rain in July 2016. The actual evapotranspiration was 744 mm. There were 56 runoff events (SR) totaling 60 mm. The average soil water tension remained below 37 kPa in 67% of the studied period, a condition that kept the soil moisture content high. The soil water balance of the tropical forest area, up to 120 cm deep, kept soil water content near its maximum capacity (173 mm) 49% of the time and saturated 51% of the time, so that it generated deep drainage beyond 120 cm deep and 1023 mm deep.

scholarly journals Pigeonpea Yield and Water Use Efficiency: A Savior under Climate Change-Induced Water Stress

Agronomy ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 5
Author(s):  
Misheck Musokwa ◽  
Paramu Mafongoya
Keyword(s):  
Climate Change ◽  
Grain Yield ◽  
Water Use Efficiency ◽  
Soil Water ◽  
Water Use ◽  
Smallholder Farmers ◽  
Block Design ◽  
Soil Water Tension ◽  
Use Efficiency ◽  
Water Tension

Frequent droughts have threatened the crop yields and livelihoods of many smallholder farmers in South Africa. Pigeonpea can be grown by farmers to mitigate the impacts of droughts caused by climate change. An experiment was conducted at Fountainhill Farm from January 2016 to December 2017. The trial examined grain yield in addition to water use efficiency (WUE) of pigeonpea intercropped with maize versus sole pigeonpea and maize. A randomized complete block design, replicated three times, was used. Soil water tension was measured at 20, 50, and 120 cm within plots. The highest and lowest soil water tension was recorded at 20 m and 120 m respectively. Combined biomass and grain yield were significantly different: pigeonpea + maize (5513 kg ha−1) > pigeonpea (3368 kg ha−1) > maize (2425 kg ha−1). A similar trend was observed for WUE and land equivalent ratio (LER), where pigeonpea + maize outperformed all sole cropping systems. The inclusion of pigeonpea in a traditional mono-cropping system is recommended for smallholder farmers due to greater WUE, LER and other associated benefits such as food, feed and soil fertility amelioration, and it can reduce the effects of droughts induced by climate change.

Citrus Carbohydrate Levels were Related to Irrigation Frequency but Not Arbuscular Mycorrhizal Fungal (AMF) Inoculum

HortScience ◽  
1998 ◽  
Vol 33 (3) ◽  
pp. 498a-498
Author(s):  
Matthew W. Fidelibus ◽  
Chris A. Martin
Keyword(s):  
Soil Water ◽  
Arbuscular Mycorrhizal ◽  
Irrigation Frequency ◽  
Soil Water Tension ◽  
Root Starch ◽  
Carbohydrate Levels ◽  
Amf Communities ◽  
Sugar Levels ◽  
Shoot Mass ◽  
Water Tension

Sugar and starch concentrations in leaves and roots of Citrus volkameriana Tan and Pasq were measured in response to irrigation frequency and AMF inoculum. Non-mycorrhizal seedlings were treated with a soil inoculum from one of five different communities of AMF; two AMF communities from Arizona citrus orchard soils, and three communities from undisturbed desert soils. Plants were assigned to frequent (soil water tension > –0.01 MPa) or infrequent (soil water tension > –0.06 MPa) irrigation cycles and were container-grown in a glasshouse for 4 months before tissues were analyzed. Fungal inoculum source did not affect shoot or root carbohydrate levels. Plants grown under high irrigation frequency had increased leaf and root starch levels and increased root sugar levels compared with those under low irrigation frequencies. High irrigation frequency also increased shoot mass.

scholarly journals Multimodel assessment of climate change-induced hydrologic impacts for a Mediterranean catchment

2018 ◽  
Vol 22 (7) ◽  
pp. 4125-4143 ◽  
Author(s):  
Enrica Perra ◽  
Monica Piras ◽  
Roberto Deidda ◽  
Claudio Paniconi ◽  
Giuseppe Mascaro ◽  
...  
Keyword(s):  
Climate Change ◽  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Climate Models ◽  
Actual Evapotranspiration ◽  
Soil Conditions ◽  
Hydrologic Models ◽  
The Future ◽  
The Mediterranean

Abstract. This work addresses the impact of climate change on the hydrology of a catchment in the Mediterranean, a region that is highly susceptible to variations in rainfall and other components of the water budget. The assessment is based on a comparison of responses obtained from five hydrologic models implemented for the Rio Mannu catchment in southern Sardinia (Italy). The examined models – CATchment HYdrology (CATHY), Soil and Water Assessment Tool (SWAT), TOPographic Kinematic APproximation and Integration (TOPKAPI), TIN-based Real time Integrated Basin Simulator (tRIBS), and WAter balance SImulation Model (WASIM) – are all distributed hydrologic models but differ greatly in their representation of terrain features and physical processes and in their numerical complexity. After calibration and validation, the models were forced with bias-corrected, downscaled outputs of four combinations of global and regional climate models in a reference (1971–2000) and future (2041–2070) period under a single emission scenario. Climate forcing variations and the structure of the hydrologic models influence the different components of the catchment response. Three water availability response variables – discharge, soil water content, and actual evapotranspiration – are analyzed. Simulation results from all five hydrologic models show for the future period decreasing mean annual streamflow and soil water content at 1 m depth. Actual evapotranspiration in the future will diminish according to four of the five models due to drier soil conditions. Despite their significant differences, the five hydrologic models responded similarly to the reduced precipitation and increased temperatures predicted by the climate models, and lend strong support to a future scenario of increased water shortages for this region of the Mediterranean basin. The multimodel framework adopted for this study allows estimation of the agreement between the five hydrologic models and between the four climate models. Pairwise comparison of the climate and hydrologic models is shown for the reference and future periods using a recently proposed metric that scales the Pearson correlation coefficient with a factor that accounts for systematic differences between datasets. The results from this analysis reflect the key structural differences between the hydrologic models, such as a representation of both vertical and lateral subsurface flow (CATHY, TOPKAPI, and tRIBS) and a detailed treatment of vegetation processes (SWAT and WASIM).

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