Response Breadths on Environmental Gradients of Germination and Seedling Growth in Two Dominant Forest Tree Species of Central Himalaya

Abstract

The responses of Pimis roxburghii (chir pine), an early successional species, andQuercus leucotrichophora(banj oak), a late successional species were compared in terms of seed germination and seedling growth. Seed germination was observed on single-factor gradients of temperature, water stress, seed desiccation and light, and seedling growth on gradients of shade and soil moisture. The suppression of germination caused by continuous dark and far-red was greater in Pinus than in Quercus. Pinus seed germination showed wider response breadth on gradients of water stress and seed desiccation, and narrower response breadth on the gradient of light quality, compared withQuercus. In terms of seedling growth, the response breadth of Pinus was wider on the gradient of soil moisture and narrower on the gradient of shade compared with Quercus. Under higher soil moisture stress, the seedlings of both species attained similar heights, butQuercus seedlings achieved higher dry weights, a higher root: shoot ratio and lower leaf weight ratio than Pinus.