Does Salinity Enhance Allelopathic Effects of Tribulus terrestris L. in Citrullus Vulgaris Schrad. Agroecosystems at Nobaria, Egypt? Experimental Investigation | Chapter 02 | Recent Progress in Plant and Soil Research Vol. 5

 Field investigations in the summer of 2013 revealed that some undiscovered stressful factors had a significant impact on Citrullus vulgaris growth and yield in the Nobaria district of Egypt. Presumably, the problem was confined to the two combined causes of soil salinity and Tribulus terrestris inhibitory effects (a common weed dominant in C. vulgaris fields in the study area). Weeds are seen to be an important part of natural and agroecosystems, and their allelopathic activity has been linked to their success. Experiments in the field and in the lab were conducted to back up the previous hypothesis. The plant C. vulgaris was found to be harmed by the interaction of the two variables. The phytomass and leaf area index (LAI) of the study plant were considerably lower in the proximity of T. terrestris (bad weed management) than in the vicinity of T. terrestris (excellent weed management). In a laboratory test, the interaction of salinity and allelochemicals watery derived from T. terrestris plants had a significant impact on germination efficiency, hypocotyl-radicle length, and germination index of C. vulgaris when compared to the influence of just one factor. Finally, T. terrestris showed a significant suppressive effect on C. vulgaris growth and yield, which increased with modest or moderate salinity. Importantly, in desert agro-ecosystems, weed control is a critical technique for avoiding a wide range of interactions between crop-weed on the one hand, and weed-external climatic and edaphic factors on the other.

Author(S) Details

S. M. EL-Darier
Department of Botany and Microbiology, Faculty of Science, Alexandria University, Alexandria 21511, Egypt.

R. S. Youssef
Department of Botany and Microbiology, Faculty of Science, Alexandria University, Alexandria 21511, Egypt.

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Models for Semideciduous Seasonal Forest Production of Leaves and Deciduousness: Recent Perspectives | Chapter 4 | International Research in Environment, Geography and Earth Science Vol.2

 The climate, mainly the water availability and temperature, drives the renewal of biomass in seasonal

forest ecosystem, and the greenness and leaf area of its canopy are responsive by climate variations.
The renewal of leaves indicated by deciduousness can be model to obtain the estimates of this
component as an additional compartment of the ecosystem carbon sink. In this study was investigated
the relationship between litterfall, climate variables, Leaf Area Index (LAI), and Normalized Difference
Vegetation Index (NDVI) in semideciduous forests, to test models to explain the leaf production and
deciduousness by time. The data were obtained in satellite images and in plots installed at forest
monitoring sites, visited monthly. The tests were conducted in eight semideciduous forest fragments.
Permanent plots were monitored monthly and LAI measurements and weighing of litterfall deposited
in nets. In this time, Landsat and IRS satellite images were obtained and processed for generation of
NDVI. The water balance was calculated for each day. The relationship among the variables “leaf dry
weight”, “LAI”, “NDVI” and climate variables were verified and regression models was build and
evaluated. With monitoring of the sites, the model was validated and reviewed with new variables and
data and three equations were compared. It is possible to estimate the fall and renew of leaves
biomass in semideciduous forests with reasonable precision. This study showed that only the leaf
component of the litterfall of a semideciduous forest in tropical climate can capture average 6.5
Mg.ha-1.yr-1 of CO2 and this amount can be estimated using climate, biophysics and vegetation index
variables.

Author(s) Details

Thomaz Correa e Castro da Costa
Embrapa Milho e Sorgo, Road MG 424, Km 45, 35701-970 Sete Lagoas, MG, Brazil.

João Herbert Moreira Viana
Embrapa Milho e Sorgo, Road MG 424, Km 45, 35701-970 Sete Lagoas, MG, Brazil.

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