The browning of leaves on your Buddhist pine (Podocarpus micro) could be due to several factors:
Underwatering: Buddhist pines prefer consistently moist soil. If the soil is too dry for extended periods, it can cause the leaves to turn brown and fall off. Check the moisture level of the soil and ensure it's kept evenly moist, but not waterlogged.
Overwatering: While they like moisture, overwatering can lead to root rot, which can also cause leaves to brown. Ensure that the pot has good drainage, and you're not letting the roots sit in water.
Light Conditions: Buddhist pines prefer bright, indirect light. If the tree is placed in too much direct sunlight, the leaves may burn, leading to browning. Conversely, too little light can stress the plant and cause browning leaves.
Nutrient Deficiency: If the soil lacks essential nutrients, the tree may start to show signs of stress, such as browning leaves. Fertilizing with a balanced fertilizer could help address this.
Temperature or Humidity: Sudden temperature changes or exposure to cold drafts can stress the tree, causing the leaves to turn brown. Similarly, if the indoor humidity is too low, it could cause leaf damage.