Climate and weather must be considered for the interpretation of monitoring. In arid regions especially, timing and effectiveness of precipitation, which can vary by season and size of each precipitation event, is an important climatic factor that must be considered as changes are evaluated. The bottom line for plants is the soil moisture (and soil temperature) during their thermal growing season. Drought, along with fires and unusually wet conditions of flooding or prolonged rapid plant growth, are common reasons why flexibility in management is so important.
Drought is defined in a number of ways (NOAA 2012), but is often described as a series of years when low rainfall and moderate to high temperatures exceed some average. Drought may be considered as a period of abnormally dry weather sufficiently prolonged for the lack of water to cause a significant reduction in plant growing conditions and productivity or a serious hydrologic imbalance in the affected area. These two effects can happen simultaneously or, either can happen in the absence of the effects of the other. Each has different management implications. Extreme drought may or may not modify the structure of rangelands by changing vegetation composition. However, in a summer-dry climate such as most of Nevada, moisture limitations end the growing season for most rangeland plants every year. Plants express growth and phenology to reflect the limited amount and duration of soil moisture. No two droughts are the same, so the management response to drought should vary to reflect the unique conditions of the current drought.
The management of plants before, during and after drought influences the impact of drought and rate of plant recovery following relief from drought. Drought may or may not modify ecological processes by influencing species composition, biomass production, nutrient cycling and soil properties. Understanding how individual plant species respond to drought, and how ecological processes are affected by drought, informs flexibility in management and interpretation of monitoring data.
Monitoring helps managers detect, record and understand drought effects and separate the respective influences of drought and management. Plants that may have had time to recover after grazing may not have soil moisture to do so. Observations on growing conditions may lead to altered management within the season to minimize impact to range plants.