TABLE OF CONTENTS. PART I. HISTORICAL THE DEVELOPMENT OF THE CONCEPT OF LIFE ZONES……………………………… 1 VALUE OF THE STUDY OF LIFE ZONES…………………………………………………. 2 BEGINNING OF THIS SYSTEMATIC STUDY OF ALTITUDINAL DISTRIBUTION ………………………………………………………….. 3 THE SAN FRANCISCO MOUNTAIN SURVEY………………………………………………… 4 ORIGIN OF THE BIOLOGICAL SURVEY………………………��………………………… 6 WORK OF THE BIOLOGICAL SURVEY IN IDAHO …………………………………………… 6 WORK OF THE BIOLOGICAL SURVEY IN DEATH VALLEY …………………………….. 7 CORRELATION OF THE LIFE ZONES …………………….. 9 THE NAMES OF THE LIFE ZONES AND THEIR SIGNIFICANCE ……………………. 9 SUMMARY OF THE ZONES ………………………………………………………………….. 11 EFFECT OF THE GLACIAL AGE ON THE PRESENT POPULATION OF THE BOREAL ZONES………………………………. 11 STATUS OF MT. MAZAMA DURING THE GLACIAL AGE ……………………………… 13 COMPARISON OF THE FLORA OF THE GLACIAL AGE WITH THAT OF TODAY ……………………………………….. 13 PART II. HOW THEY ARE DETERMINED, WITH SPECIAL REFERENCE TO CRATER LAKE NATIONAL PARK CHOICE Of INDICATORS IN MAPPING A LIFE ZONE ……………………………… 15 FACTORS AFFECTING DISTRIBUTION OF PRESENT DAY ……………………………….16 CALCULATING THE SUM OF POSITIVE TEMPERATURES……………………………….. 18 DISTRIBUTION AS AFFETED BY LENGTH OF DAY AND NIGHT .................................. 19 GOVERNING TEMPERATURES OF LIFE ZONES ……………………………………………………………………………………………. 19 PART III. ZONES AT CRATER LAKE NATIONAL PARK. ZONES AT CRATER LAKE ….......................................................................................................................................................................... 21 COMPARISION OF THE ZONES AT CRATER LAKE PARK WITH THOSE OF MT. RAINIER ………………………………………………………………………….. 21 HABITATS ……………………………………………………………………………………………………………��………………. 22 INDICATORS OF THE Z0NES AT CRATER LAKE PAKK …………………………………………………………23 HUDSONIAN ZONE ………………………………………………………………………………………………………………………..24 Indicators ………………………………………………………………………………………………………………………………..24 Elevations ………………………………………………………………………………………………………………………………….25 IrrcgnlaritieS •••••••• 25 Habitats •••••••••• 26 White Bark Pine Forest • • • 26 Pumice Slopes of the highest elevations • • • • • 28 a) Mountain Hemlock Forest • • 31 d) Stream Side •••••• 33 c) Pumice Slopes of the lower elevations • • • • ��� 36 f) Talus slopes, including all rocky exposures • • • 56 g) Swamp • • • • •?•• 41 CANADIAN ZONE • • • 43 Indicators •••?••••• 45 Elevations ••••••••• 44 Irregularities •••••••• 45 Habitats •••••«•••• 46 Lodge Pole Fine Forest • • • 46 Stream Sides •••••• 40 Desert »•»»••••« 50 Wizard Island •••••• 51 Phantom Ship ……………………………………. 56 TRANSITION ZONE • ? # 59 Indicators •••*•••••• 59 Elevations • « • • • 60 Irregularities ••••• 60 Habitats ••••••••••61 Yellow Pine Forest • • • . • 62 Moist Canyons •••••• 65 Open Slopes ••?•••• 68 REFERENCE CITED •••••• • 70