scholarly journals Environmental Drivers for Cambial Reactivation of Qilian Junipers (Juniperus przewalskii) in a Semi-Arid Region of Northwestern China

Atmosphere ◽  
2020 ◽  
Vol 11 (3) ◽  
pp. 232
Author(s):  
Qiao Zeng ◽  
Sergio Rossi ◽  
Bao Yang ◽  
Chun Qin ◽  
Gang Li
Keyword(s):  
Soil Moisture ◽  
Water Availability ◽  
Arid Regions ◽  
High Elevation ◽  
Northwestern China ◽  
Environmental Drivers ◽  
Limiting Factor ◽  
Severe Drought ◽  
Cambial Reactivation ◽  
Semi Arid

Although cambial reactivation is considered to be strongly dependent on temperature, the importance of water availability at the onset of xylogenesis in semi-arid regions still lacks sufficient evidences. In order to explore how environmental factors influence the initiation of cambial activity and wood formation, we monitored weekly cambial phenology in Qilian juniper (Juniperus przewalskii) from a semi-arid high-elevation region of northwestern China. We collected microcores from 12 trees at two elevations during the growing seasons in 2013 and 2014, testing the hypothesis that rainfall limits cambial reactivation in spring. Cambium was reactivated from late April to mid-May, and completed cell division from late July to early August, lasting 70–100 days. Both sites suffered from severe drought from January to April 2013, receiving < 1 mm of rain in April. In contrast, rainfall from January to April 2014 was 5–6 times higher than that in 2013. However, cambial reactivation in 2014 was delayed by 10 days. In spring, soil moisture gradually increased with warming temperatures, reaching 0.15 m3/m3 before the onset of xylogenesis, which may have ensured water availability for tree growth during the rainless period. We were unable to confirm the hypothesis that rainfall is a limiting factor of cambial reactivation. Our results highlight the importance of soil moisture in semi-arid regions, which better describe the environmental conditions that are favorable for cambial reactivation in water-limited ecosystems.

scholarly journals Suitability Evaluation of Typical Drought Index in Soil Moisture Retrieval and Monitoring Based on Optical Images

2020 ◽  
Vol 12 (16) ◽  
pp. 2587
Author(s):  
Yan Nie ◽  
Ying Tan ◽  
Yuqin Deng ◽  
Jing Yu
Keyword(s):  
Remote Sensing ◽  
Soil Moisture ◽  
Arid Regions ◽  
Drought Index ◽  
Dynamic Monitoring ◽  
Landsat 8 ◽  
Landsat 8 Oli ◽  
Rapid Acquisition ◽  
Semi Arid ◽  
Soil Moisture Inversion

As a basic agricultural parameter in the formation, transformation, and consumption of surface water resources, soil moisture has a very important influence on the vegetation growth, agricultural production, and healthy operation of regional ecosystems. The Aksu river basin is a typical semi-arid agricultural area which seasonally suffers from water shortage. Due to the lack of knowledge on soil moisture change, the water management and decision-making processes have been a difficult issue for local government. Therefore, soil moisture monitoring by remote sensing became a reasonable way to schedule crop irrigation and evaluate the irrigation efficiency. Compared to in situ measurements, the use of remote sensing for the monitoring of soil water content is convenient and can be repetitively applied over a large area. To verify the applicability of the typical drought index to the rapid acquisition of soil moisture in arid and semi-arid regions, this study simulated, compared, and validated the effectiveness of soil moisture inversion. GF-1 WFV images, Landsat 8 OLI images, and the measured soil moisture data were used to determine the Perpendicular Drought Index (PDI), the Modified Perpendicular Drought Index (MPDI), and the Vegetation Adjusted Perpendicular Drought Index (VAPDI). First, the determination coefficients of the correlation analyses on the PDI, MPDI, VAPDI, and measured soil moisture in the 0–10, 10–20, and 20–30 cm depth layers based on the GF-1 WFV and Landsat 8 OLI images were good. Notably, in the 0–10 cm depth layers, the average determination coefficient was 0.68; all models met the accuracy requirements of soil moisture inversion. Both indicated that the drought indices based on the Near Infrared (NIR)-Red spectral space derived from the optical remote sensing images are more sensitive to soil moisture near the surface layer; however, the accuracy of retrieving the soil moisture in deep layers was slightly lower in the study area. Second, in areas of vegetation coverage, MPDI and VAPDI had a higher inversion accuracy than PDI. To a certain extent, they overcame the influence of mixed pixels on the soil moisture spectral information. VAPDI modified by Perpendicular Vegetation Index (PVI) was not susceptible to vegetation saturation and, thus, had a higher inversion accuracy, which makes it performs better than MPDI’s in vegetated areas. Third, the spatial heterogeneity of the soil moisture retrieved by the GF-1 WFV and Landsat 8 OLI image were similar. However, the GF-1 WFV images were more sensitive to changes in the soil moisture, which reflected the actual soil moisture level covered by different vegetation. These results provide a practical reference for the dynamic monitoring of surface soil moisture, obtaining agricultural information and agricultural condition parameters in arid and semi-arid regions.

scholarly journals VARIEDADES DE CANA-DE-AÇÚCAR SUBMETIDAS A DIFERENTES LÂMINAS DE REPOSIÇÃO HÍDRICA POR GOTEJAMENTO SUBSUPERFICIAL

2019 ◽  
Vol 34 (3) ◽  
pp. 350-363
Author(s):  
Anderson Ramos de Oliveira ◽  
Marcos Brandão Braga
Keyword(s):  
Water Availability ◽  
Arid Regions ◽  
Sugarcane Juice ◽  
Sugarcane Varieties ◽  
Raw Sugar ◽  
Technological Quality ◽  
Subsurface Drip ◽  
Semi Arid Region ◽  
Semi Arid

VARIEDADES DE CANA-DE-AÇÚCAR SUBMETIDAS A DIFERENTES LÂMINAS DE REPOSIÇÃO HÍDRICA POR GOTEJAMENTO SUBSUPERFICIAL   ANDERSON RAMOS DE OLIVEIRA1, MARCOS BRANDÃO BRAGA2   1 Embrapa Semiárido, Rodovia BR-428, Km 152, Zona Rural, 56302-970, Petrolina, PE, Brasil, [email protected] 2 Embrapa Hortaliças, Rodovia BR-060, Km 09, Fazenda Tamanduá, 70275-970, Brasília, DF, Brasil, [email protected]   RESUMO: A região semiárida brasileira apresenta grande potencial de produção de cana-de-açúcar. Contudo, verifica-se que existem oscilações na produção devido à baixa e irregular disponibilidade hídrica. O objetivo deste estudo foi avaliar o comportamento de variedades de cana-de-açúcar irrigadas por gotejamento subsuperficial submetidas a diferentes lâminas de irrigação. O experimento foi conduzido no Campo Experimental de Bebedouro, na Embrapa Semiárido, em Petrolina, PE. Foram realizadas análises de produtividade e de qualidade tecnológica do caldo. As variedades com maior tolerância ao déficit hídrico foram RB92579 e RB961003, pois alcançam máxima produtividade utilizando-se menor lâmina de reposição hídrica, em torno de 80% da ETc. A qualidade tecnológica do caldo apontou diferenças no °Brix e na porcentagem bruta de açúcares das variedades que reduziram em função do aumento da reposição hídrica. Contudo, estas diferenças não foram limitantes à qualidade tecnológica. Sendo assim, o cultivo das variedades RB92579 e RB961003 sob menor lâmina de reposição hídrica pode ser recomendado, pois as mesmas atingem alta produtividade e mantém a qualidade tecnológica do caldo.   Palavras-chave: biomassa, irrigação, estresse hídrico, regiões semiáridas.   SUGARCANE VARIETIES SUBMITTED TO DIFFERENT WATER REPLENISHMENT DEPTHS BY SUBSURFACE DRIP   ABSTRACT: Brazilian semi-arid region presents great potential for sugarcane production. However, due mainly to low and irregular water availability, there are fluctuations in production. This study proposed to evaluate the performance of sugarcane varieties irrigated by subsurface drip, submitted to different water replenishment depths. The experiment was carried out at Campo Experimental de Bebedouro, belonging to Embrapa Semiárido, Petrolina, PE, Brazil. Productivity and technological quality of sugarcane juice analysis were performed. The varieties with higher tolerance to water deficit were RB92579 and RB961003, which reached maximum productivity using lower water replenishment depths of ETc, around 80%. Technological quality of sugarcane juice showed differences in °Brix and raw sugar percentage of varieties that reduced due to water replacement depths increasing. However, these differences were not limiting to the technological quality of sugarcane juice. In summary, the cultivation of RB961003 and RB92579 cultivars under lower water replenishment depth can be recommended, because they maintain the technological quality of sugarcane juice.   Keywords: biomass, irrigation, water stress, semi-arid regions.

scholarly journals Relating surface backscatter response from TRMM Precipitation Radar to soil moisture: results over a semi-arid region

2009 ◽  
Vol 6 (5) ◽  
pp. 6425-6454
Author(s):  
H. Stephen ◽  
S. Ahmad ◽  
T. C. Piechota ◽  
C. Tang
Keyword(s):  
Soil Moisture ◽  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Arid Regions ◽  
Vegetation Index ◽  
Temporal Trends ◽  
Model Parameters ◽  
Precipitation Radar ◽  
Semi Arid

Abstract. The Tropical Rainfall Measuring Mission (TRMM) carries aboard the Precipitation Radar (TRMMPR) that measures the backscatter (σ°) of the surface. σ° is sensitive to surface soil moisture and vegetation conditions. Due to sparse vegetation in arid and semi-arid regions, TRMMPR σ° primarily depends on the soil water content. In this study we relate TRMMPR σ° measurements to soil water content (ms) in Lower Colorado River Basin (LCRB). σ° dependence on ms is studied for different vegetation greenness values determined through Normalized Difference Vegetation Index (NDVI). A new model of σ° that couples incidence angle, ms, and NDVI is used to derive parameters and retrieve soil water content. The calibration and validation of this model are performed using simulated and measured ms data. Simulated ms is estimated using Variable Infiltration Capacity (VIC) model whereas measured ms is acquired from ground measuring stations in Walnut Gulch Experimental Watershed (WGEW). σ° model is calibrated using VIC and WGEW ms data during 1998 and the calibrated model is used to derive ms during later years. The temporal trends of derived ms are consistent with VIC and WGEW ms data with correlation coefficient (R) of 0.89 and 0.74, respectively. Derived ms is also consistent with the measured precipitation data with R=0.76. The gridded VIC data is used to calibrate the model at each grid point in LCRB and spatial maps of the model parameters are prepared. The model parameters are spatially coherent with the general regional topography in LCRB. TRMMPR σ° derived soil moisture maps during May (dry) and August (wet) 1999 are spatially similar to VIC estimates with correlation 0.67 and 0.76, respectively. This research provides new insights into Ku-band σ° dependence on soil water content in the arid regions.

scholarly journals Soil Water Balance and Vegetation Dynamics in a Semi-arid Mediterranean Ecosystem

Proceedings ◽  
2020 ◽  
Vol 30 (1) ◽  
pp. 76
Author(s):  
Ioannis N. Daliakopoulos ◽  
Ioanna Panagea ◽  
Luca Brocca ◽  
Erik van den Elsen
Keyword(s):  
Water Balance ◽  
Soil Water ◽  
Water Availability ◽  
Vegetation Dynamics ◽  
Soil Water Balance ◽  
Mediterranean Ecosystem ◽  
Limiting Factor ◽  
Arid Conditions ◽  
Water Balance Models ◽  
Semi Arid

Under arid conditions, where water availability is the limiting factor for plant survival, water balance models can be used to explain vegetation dynamics. [...]

scholarly journals Influence of climate variability on water partitioning and effective energy and mass transfer (EEMT) in a semi-arid critical zone

2015 ◽  
Vol 12 (8) ◽  
pp. 7933-7969 ◽  
Author(s):  
X. Zapata-Rios ◽  
P. D. Brooks ◽  
P. A. Troch ◽  
J. McIntosh ◽  
C. Rasmussen
Keyword(s):  
Climate Variability ◽  
Water Availability ◽  
Snow Water Equivalent ◽  
High Elevation ◽  
Critical Zone ◽  
Effective Energy ◽  
Near Surface ◽  
Basin Scale ◽  
Water Partitioning ◽  
Semi Arid

Abstract. The Critical Zone (CZ) is the heterogeneous, near-surface layer of the planet that regulates life-sustaining resources. Previous research has demonstrated that a quantification of the influxes of effective energy and mass (EEMT) to the CZ can predict its structure and function. In this study, we quantify how climate variability in the last three decades (1984–2012) has affected water availability and the temporal trends in EEMT. This study takes place in the 1200 km2 upper Jemez River Basin in northern New Mexico. The analysis of climate, water availability, and EEMT was based on records from two high elevation SNOTEL stations, PRISM data, catchment scale discharge, and satellite derived net primary productivity (MODIS). Records from the two SNOTEL stations showed clear increasing trends in winter and annual temperatures (+1.0–1.3 °C decade−1; +1.2–1.4 °C decade−1, respectively), decreasing trends in winter and annual precipitation (−41.6–51.4 mm decade−1; −69.8–73.2 mm decade−1, respectively) and maximum Snow Water Equivalent (SWE; −33.1–34.7 mm decade−1). The water partitioning fluxes at the basin scale showed statistically significant decreasing trends in precipitation (−61.7 mm decade−1), discharge (−17.6 mm decade−1) and vaporization (−45.7 mm decade−1). Similarly Q50, an indicator of snowmelt timing, is occurring 4.3 days decade−1 earlier. Results from this study indicated a decreasing trend in water availability, a reduction in forest productivity (4 g C m−2 per 10 mm of reduction in Precipitation) and EEMT (1.2–1.3 MJ m2 decade−1). These changes in EEMT point towards a hotter, drier and less productive ecosystem which may alter critical zone processes in high elevation semi-arid systems.

Sign in / Sign up

Export Citation Format

Share Document