Silviculture & Agroforestry

Shorea robusta (Sal) seeds are recalcitrant with an extremely short period of viability (only about 7 to 10 days).
Sal seeds mature and fall during late May to June, precisely coinciding with the onset of the South-West Monsoon.
If the monsoon rains are delayed and do not arrive within a few days of seed fall, the seeds rapidly lose their viability due to desiccation and high summer temperatures, resulting in complete failure of natural regeneration.

Detailed Analysis of Silvicultural Regeneration Terms:

• Rab (Option 1): In Indian silviculture (traditionally in dry deciduous forests of Maharashtra and Gujarat), 'Rab' refers to a patch (commonly $20\text{ m} \times 20\text{ m}$) where slash and dry brushwood are heaped and burnt intensely to sterilize the soil, kill weed seeds, and release nutrient-rich ash, followed by sowing or planting valuable timber species to supplement natural regeneration. Hence, Option 1 is correct.
• Block (Option 2): A large territorial management unit of a forest comprising several compartments.
• Compartment (Option 3): The permanent basic territorial unit of forest management and silvicultural treatment.
• Coupe (Option 4): A felling area prescribed to be harvested in a single year or period.

In forest nursery management, wrenching involves cutting or breaking tap roots beneath the seedling bed using a spade or mechanical undercutter, which halts shoot elongation and stimulates abundant lateral fibrous root growth. Option analysis: (A) Root modification refers to anatomical adaptation. (B) Wrenching is the standard silvicultural term for root pruning. (C) Rooting refers to root formation from cuttings. (D) Pricking out is transplanting young germinated seedlings into nursery containers or beds.

Topping in forest nurseries is the physical clipping or trimming of the terminal apical shoot tip of overgrown seedlings to restrict excessive height growth, reduce transpiration, and improve the root-to-shoot ratio before field planting. Option analysis: (A) Root growth is controlled by root pruning or wrenching. (B) Height growth is restricted by topping. (C) Collar diameter growth is encouraged by topping, not restricted. (D) Diameter is not restricted.