Question

1-Explain why some plants are winter deciduous others are summer deciduous?

2-Why soil develops faster in warm, moist environments and slowest in cold or arid ones?

3-Comment on the fertility of a soil that is characterized by high CEC and an acidic pH.

4-Why some desert plants have deep roots others have shallow ones?

Answer 1

1. Tropical deciduous trees shed their leaves in summer because the climate becomes hot and the leaves automatically becomes dry and shed off. Also, they need to conserve water in order to sustain in winters and so they shed their leaves. Temperate deciduous trees become dormant in winters in order to prevent water in the leaves from freezing. This freezing can lead to fungal or bacterial attack and thus they shed their leaves in winters.

2. The formation of soil is called weathering. Weathering typically increases as temperatures rise and rain falls, which means rocks in hot and wet climates experience faster rates of chemical weathering than do rocks in cold, dry climates. Moist climates accelerate the rates of chemical weathering, caused when C02 in dirt mixes with air and water to form a weak acid. The weak acid breaks down rocks more rapidly in wet climates compared with arid ones.

3. Cation exchange capacity or CEC is the ability of the soil to hold or store cations. When soil particles are negatively charged they attract and hold on to cations (positively charged ions) stopping them from being leached down the soil profile. CEC measures a soils ability to hold nutrients and is a key determinant of soil fertility. Soils with high CEC have the ability to hold more cations making them sufficient in calcium, magnesium and other cations. CEC is influenced by pH of the soil and thus higher the pH of soil, more is the CEC and better is the fertility of the soil.

4. Desert trees have deeper roots because of lack of water on the surface. These roots can go deeper near the water table and aquifers where they can absorb water and transport to the trees. These deep roots allow desert trees to grow by getting the water and nutrients from deep earth.