Glossary - Afforestation, Reforestation and Forest Restoration in Arid and Semi-arid Tropics - page 274

Seed bank The quantity of seeds found naturally scattered in the soil of a given
area.

Seeding time Time of the year when a particular species of plant bears seeds. Often,
seeding takes place over an extended period of time, whereas in case of certain
species, seeding may be a continuous process throughout the year.

Seedling A young plant grown from seed.

Selection Marking out plants in a given group of plants produced in a nursery, for
their quality, and retaining these for specific use, especially for outplanting.

Semi-arid Climate marked by inadequate rain and atmospheric moisture. Places
with an annual rainfall in the range of 500-800 mm and the number of rainy days in
the range of 20-35 can be said to be semi-arid. In terms of the Thorntwaite aridity
index, a climate with an index of 0.2 to 0.50 is classified as semi-arid.

Shelterbelt A vegetative barrier of substantial length and height to protect an area
from adverse effects of winds. An effective shelterbelt slows down wind speed in
an area extending to fifty times its height on the leeward side. A shelterbelt should
include trees of different heights to obstruct wind at different levels. One or two rows
of ground-hugging shrubs should also be included in its design.
Shipment losses Losses in plant materials or plants in the process of transportation.

Shockproofing Pre-handling of plants in a nursery by shifting or shaking to ensure
that these develop resistance to shock, in order to avoid higher mortality in the process
of transportation.

SI Units ⇒ International System of Units.

siemens Unit of conductance in the SI system of units. One siemens is equal to one
ampere per volt, which is also called one mho.

Silvicultural management Management of a plantation or a natural forest so that
steady amount of produce is drawn from it without damaging the resource itself.

Silvipastoral plantation A type of plantation in which both trees and forage grasses
are established so that the area acts as a pasture and also as a forest.

Singling A silvicultural operation wherein the multiple shoots of a tree or sapling
are removed, leaving behind only one stem, in order to encourage vertical growth
and well-formed stem and canopy.

Site nursery ⇒ Field nursery.

Skeletal soils Soils found only in patches on rocky surfaces. Usually, such soils are
poor in organic matter and in finer particles, and hence unsuitable for plant growth.

Slack In network analysis, the difference between the early start and the late start
times of an activity. This is the period by which an activity may be delayed without
affecting the overall schedule of the project.