RESULTS OF CUTTING IN THE SIERRA FORESTS. 19 
• 
reasons to which failure is attributed. On the poorer sites it is 
probably due primarily to drought and infrequent seed crops and on 
the better sites to infrequent seed crops, abundant brush and ground 
cover present before cutting, and light cuttings where the original 
stand was heavy. 
In what way could changes in marking affect these factors? On 
most of the older sales enough, and in some cases too many, seed 
trees were left on the poorer sites, but what effect a heavier cutting- 
would have on amount of seed borne is unknown. Apparently trees 
on the sale areas bear more seed than similar trees in adjoining 
virgin timber, and as on these poorer sites, particularly on the east 
slope of the Sierras, brush invasion is slow in the absence of fire, a 
heavier cutting leaving only well-distributed, well-formed, frequent 
seed trees, as at present, seems justified. Grouping of reserved trees 
should be avoided. (PI. IV.) As to modifying the effects of 
drought, there is doubtless a compromise between some method, 
such as the shelterwood. designed to prevent soil deterioration and 
loss of soil moisture by evaporation, and clear cutting, which makes 
more soil moisture available to seedlings by reducing root com- 
petition of the older trees but encourages heavier herbaceous and 
shrubby undergrowth. This matter is still an open question. On 
poor sites some cover doubtless favors the establishment of repro- 
duction. On the Plumas plot over 90 per cent of the seedlings are 
situated in patches of squaw carpet which covers only about 20 per 
cent of the area. This plant (Ceanothus prostratus) forms dense 
flattened mats which protect seed from rodents, act as fire barriers, 
probably reduce frost damage, and prevent excessive evaporation 
during the early season when seed is germinating, thus favoring 
establishment. Apparently root competition later results in slow 
growth of the seedlings until sufficient shade is provided to kill the 
shrub. 
On the better sites, in addition to the question of seed supply, the 
control of brush and ground cover assumes greater importance and 
offers a particularly difficult problem. Until recent years uncon- 
trolled fires, started by lightning, Indians, miners, stockmen, etc. 
have favored the spread of many species of Ceanothus, manzanita, 
bear clover (Chamcebatia folwlosa), and other shrubs whose vigor- 
ous sprouting and seeding capacities enable them to seize openings 
to the detriment of reproduction. The light requirement of some of 
these shrubs, notably Ceanothus cordulatus, Primus emarginata, 
Castanopsis chrysophylla, and Chamcebatm foliolosa is nearly the 
same, but lower than that necessary for yellow-pine reproduction. 
In many cases the crown canopy is already sufficiently open to permit 
the shrubs to gain a foothold before logging, so that no choice is left 
but to risk their extension by cutting the timber. That the brush 
does spread appreciably following cutting is evidenced by. photo- 
graphs taken at intervals from the same point. Under intensive 
management this underbrush might be grubbed out and the spare 
replanted with trees, a course not open at present because of exces- 
sive cost. Seedlings gradually become established in even the densest 
brush (especially is this true of white fir), and, after severe competi- 
tion for soil moisture for a time, overtop the brush and shade it out. 
(Pis. V and VI.) Several instances are known where this has hap- 
