During the hike at the Lower Fire Trail at the Berkeley hills, I found these organisms to have niches that adapted to their environment.
Western Sword Fern and Bracken Fern were found along the trail where they mainly occupy the space around larger trees( or some dead tree trunk). These ferns generally have very large leaves that are broadly disposed. Due to the relatively high humidity in these moist evergreen forest, they are able to adapt to such niche by growing out large leaves without worrying of loosing too much water to the environment.
The Blewit mushrooms were found at the ground where there are moist layer of soil and dead leaves after the rain on Monday. Hence, these mushrooms grew very large. The biggest one I have found is almost larger than my hand. However, they seemed to have a short life as under the afternoon sun on Tuesday, some of the larger guys exposed to direct sunlight were already wilting and partially dried out. Whereas, those grown in the shades (such as the one I put in the observation) was still fresh as the shades from the above plants provide a room for moisture retention which can be seen as a niche these mushrooms were adapted to in this moist evergreen forest.
Some other shorter plants with large leaves were also found in this site. These plants also adapt themselves to this moist environment by growing out broad leaves to maximize their photosynthesis in places shadowed by larger and talker evergreen trees. With relatively less sunlight exposure due to taller trees, these short plants utilized their leaf size as a niche to better compete with other talker plants in this forest.
At the Chaparral side of the trail, I have found plants with strange shaped leaves that seems to develop their specialized niches for the relatively dry environment.
The plant with heart shaped leaves: This plant can be seen at multiple locations. They are having these heart shaped leaves that form a special curvature, which I suspect is easier for them to "collect" moisture/precipitation for the plant in this drier environment.
The Apoidea (Bee)** found on a leaf seems to have a niche adapted from the environment: its brownish yellow body color that is less visible (despite it being so visible here at this green leaf) at the Chaparral environment, which is dominate by dried up plant debris and small shrubs. And since it is spring now, lots of flowers available at this place makes plenty of food for it.
Lots of different plants with spiny leaves were found at this Chaparral region. They mainly develop their leaves to adapt to the dry environment by protecting moisture from evaporating too fast.
The pill-bugs found under a decaying tree trunk have developed such a thick shell as a niche for the dry environment. Also, they usually hide under the shade or decaying plant debris during the day and come out only at night. Such behavior can also be their niche developed for such a dry Chaparral environment.
** Update! I was fooled by this bee-mimicking hover fly~ Thanks for the help from @kueda's ! He taught me the easy way to distinguish them from bees is their eyes touching each other. Great lesson!