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Southwest Season Trackers
Southwest Season Trackers was a partnership between researchers and volunteers to improve models that predict how plants in the southwest U.S. will respond to changing climate and also to enhance efficiency of landscape restoration and management efforts in the region. For example, phenology can tell us when to harvest fruits of native plants, when to apply herbicides to unwanted shrubs, and when allergy season will begin.
Phenology records in southwestern ecosystems are not as common as they are in other parts of the country. Southwest Season Trackers was created to engage the Southwest community to bolster efforts of USDA Agriculture Research Service (ARS) scientists to assess and improve performance of models that predict timing of seasonal activity in common shrub and grass species. Phenology observations help to increase our understanding of the environmental conditions that signal plants to start growing, to flourish, to flower, to produce fruit, and to shut down.
The observations contributed to Nature’s Notebook are being used to verify predicted dates of start and end of the growing season based on an ongoing six-year study of plant phenology on the Jornada Experimental Range in southern New Mexico. We can then better understand what transitions the models characterize well and where we can improve our predictions of plant phenology for Southwest species.
We have ended the phenology observation phase of the Southwest Season Trackers campaign. However, we still encourage observations of these species in Nature's Notebook!
See what we learned from this campaign in 2019
The campaign included observations of the following drought-deciduous shrubs:
American tarwort (Flourensia cernua)
broom snakeweed (Gutierrezia sarothrae)
mariola (Parthenium incanum)
honey mesquite (Prosopis glandulosa)
And evergreen shrubs and plants:
fourwing saltbush (Atriplex canescens)
creosote bush (Larrea tridentata)
soaptree yucca (Yucca elata)
And the following grasses:
purple threeawn (Aristida purpurea)
black grama (Bouteloua eriopoda)
bush muhly (Muhlenbergia porteri)
tobosa (Hilaria mutica)
alkali sacaton (Sporobolus airoides)
spike dropseed (Sporobolus contractus)
mesa dropseed (Sporobolus flexuosus)
For the drought-deciduous shrubs, we were especially interested in the following phenophases, though observers were welcome to report on all phenophases.
For the evergreen shrubs and plants, we were especially interested in the following phenophases, though observers were welcome to report on all phenophases.
(Click to enlarge)
|Young leaves||One or more young, unfolded leaves are visible on the plant. A leaf is considered "young" and "unfolded" once its entire length has emerged from a breaking bud, stem node or growing stem tip, so that the leaf stalk (petiole) or leaf base is visible at its point of attachment to the stem, but before the leaf has reached full size or turned the darker green color or tougher texture of mature leaves on the plant. Do not include fully dried or dead leaves.|
|Flowers or flower buds||One or more fresh open or unopened flowers or flower buds are visible on the plant. Include flower buds or inflorescences that are swelling or expanding, but do not include those that are tightly closed and not actively growing (dormant). Also do not include wilted or dried flowers.|
|Open flowers||One or more open, fresh flowers are visible on the plant. Flowers are considered "open" when the reproductive parts (male stamens or female pistils) are visible between or within unfolded or open flower parts (petals, floral tubes or sepals). Do not include wilted or dried flowers.|
|Fruits||One or more fruits are visible on the plant.|
For the grasses, we were especially interested in the following phenophases, though observers were welcome to report on all phenophases. See more photos for help with identification of the grass species on the Southwest Season Trackers list.
(Click to enlarge)
|Inititial growth||New growth of the plant is visible after a period of no growth (winter or drought), either as new green shoots sprouting from nodes on existing stems, or new green shoots breaking through the soil surface. For each shoot, growth is considered "initial" until the first leaf has unfolded.
Learn more about initial growth »
|Leaves||One or more live, green, unfolded leaves are visible on the plant. A leaf is considered "unfolded" once it unrolls slightly from around the stem and begins to fall away at an angle from the stem. Do not include fully dried or dead leaves.|
|Flower heads||One or more fresh flower heads (inflorescences) are visible on the plant. Flower heads, which include many small flowers arranged in spikelets, emerge from inside the stem and gradually grow taller. Include flower heads with unopened or open flowers, but do not include heads whose flowers have all wilted or dried or begun to develop into fruits (grains).|
|Open flowers||One or more open, fresh flowers are visible on the plant. A flower is considered "open" when reproductive parts (male anthers or female stigmata) can be seen protruding from the spikelet. Do not include flowers with wilted or dried reproductive parts.|
Grass species identification
(Click to enlarge)
|purple threeawn (Aristida purpurea): Mature leaves are revolute (rolled up like a burrito). Dried leaves have a purplish caste. The fruits have 3 slender appendages (awns) oriented like a propeller which aid in dispersal.|
|black grama (Bouteloua eriopoda): Easily and consistently identified by hairy internodes (stems). Dried leaves are gray, much like tobosa, but without the stout “troll hair” look to it. Can form dense colonies in sandy soils.|
|bush muhly (Muhlenbergia porteri): Overall shape is usually rounded, “fluffy,” and broad. Often dried leaves turn to a muted maroon. Flower head is an open panicle, with a single fruit at the end of each terminal panicle branch. It often prefers to grow in the shelter a nurse plant such as mesquite, creosote, tarbush, or even chollas.|
|tobosa (Hilaria mutica): Often found in large colonies on or near clay flats. Dried leaves are a gray hue with a characteristic unkempt “troll hair” look from afar. The flower head terminates in a dense, shaggy spike (more akin to wheat or barley) rather than an open panicle that is about 1-1.5 inches in length.|
|alkali sacaton (Sporobolus airoides): It can be difficult to distinguish spp. of Sporobolus without a flower head (inflorescence) but all have open leaves at maturity (in contrast to purple threeawn) and all have hairy ligules (the region where the leaf emerges from the sheath). The inflorescense is an erect, open panicle. Dried leaves have a straw color. Broadly distributed, but is common in Chihuahuan desert grasslands, the edges of playas or other drainages, and has an affinity for saline soils.|
|spike dropseed (Sporobolus contractus): Has a tight, narrow panicle, that looks more akin to a wheat flower head than to the other dropseeds of interest to SWST that can easily exceed 6 in. in length. Often grows in sandy soils, among creosote or mesquite dunes. Dried leaves are a straw color and have hairy ligules.|
|mesa dropseed (Sporobolus flexuosus): Has an open flower head (inflorescence) like alkali sacaton, but is usually nodding and ‘tangled’ due to tiny appendages in the inflorescence branches that render it clingy/sticky (alkali sacaton lacks these appendages and is not clingy). Has hairy ligules, like other dropseed spp. and dried leaves have a straw color. It is often found in sandy soils, and seems to have less of a water requirement than alkali sacaton.|