Contour farming is usually employed in

Assertion : In tropical rain forests. $O-$ horizon and $A-$ Horizon of soil profile are shallow and nutrient-poor.
Reason : Excessive growth of micro-organisms in the soil depletes its organic content

$A$ : Biosphere reserves are also included under the ex-situ conservation strategies.

$R$ : Cropping and grazing are allowed in the transition zone of biosphere reserve.

In-situ conservation of one horned Rhino is being done in

Full forms : $MAB$