2011-08-29_REVISION - M1986015 (11)

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• • Relative Humidity Relative humidity is an important factor in reclamation programs. The higher the humidity the less moisture stress young plants experience. Low humidities (less than about 50% to 60 %) combined with high temperatures can result in drought kill of unadapted young vegetation. Pueblo is subject to this pattern. The most favorable growth humidities occur in winter when there is little or no growth occurring. In summer when growth is occurring, the humidity, especially during the hottest time of the day averages about 30 %. This low humidity, although comfortable for people, produces severe moisture stress in vegetation. Unless the soil contains high amounts of available moisture (irrigation or ground water) vegetation growth will require water conservation strategies on the part of the plants. Except where a steady supply of soil moisture is available, planted vegetation should be highly adapted to drought resistance. The low humidity also reduces the rate of development of vegetation. Because even drought resistant species may frequently be under severe moisture stress, reproduction tends to be low. This results in both low density vegetation and vegetation that takes a long time to achieve community closure. Even when closure is achieved plant cover may be sparse and may not exceed 25% to 50% in even very old, fully established vegetation communities. 6 Mean Relative Humidity at Four Times of the Day Pueblo eo 70 — GO I _ — Jen Feb ■ 1 MW 5:00 am Apr i Miry . 11:00 am Jun — ■ Jul 5:00 pm 1 Aup ■ Sp 11:00 pm Oct Nov Doc • • Relative Humidity Relative humidity is an important factor in reclamation programs. The higher the humidity the less moisture stress young plants experience. Low humidities (less than about 50% to 60 %) combined with high temperatures can result in drought kill of unadapted young vegetation. Pueblo is subject to this pattern. The most favorable growth humidities occur in winter when there is little or no growth occurring. In summer when growth is occurring, the humidity, especially during the hottest time of the day averages about 30 %. This low humidity, although comfortable for people, produces severe moisture stress in vegetation. Unless the soil contains high amounts of available moisture (irrigation or ground water) vegetation growth will require water conservation strategies on the part of the plants. Except where a steady supply of soil moisture is available, planted vegetation should be highly adapted to drought resistance. The low humidity also reduces the rate of development of vegetation. Because even drought resistant species may frequently be under severe moisture stress, reproduction tends to be low. This results in both low density vegetation and vegetation that takes a long time to achieve community closure. Even when closure is achieved plant cover may be sparse and may not exceed 25% to 50% in even very old, fully established vegetation communities. 6