Pu'u Maka'ala Natural Area Reserve NEON / PUUM

Pu‘u Maka‘ala Natural Area Reserve (PUUM) is a terrestrial NEON field site located in the South Hilo district on the Big Island of Hawai‘i. The 75.7 km² (18,700 acre) reserve is managed by the Hawaii Department of Natural Resources. NEON samples 47.2 km² (11,662.5 acres) at the reserve. Situated along an elevation gradient of 853 - 1899 m (2800 - 6230 ft.) on Mauna Loa, it features a range of habitat types, from shrubby grasslands to wet rainforest. The unique endemic diversity coupled with threats from invasive species makes Pu‘u Maka‘ala a compelling location to conduct long-term ecological research. The reserve is dedicated solely for the purpose of conservation, making the area extremely important for the protection of native species. PUUM is the only field site of the NEON Pacific Tropical Domain (D20), which includes all of the Hawaiian islands. [1] [2]

Rain is frequent, as is moisture from fog, as prevailing northeast trade winds bring regular precipitation. Located on the northeast side of Mauna Loa, the reserve receives an average rainfall of 2656.8mm (104.6 in.) per year. Occasionally, large weather systems, including hurricanes, bring extremely heavy rain events. Despite Hawaii's low latitude, PUUM's elevation leads to moderate daily temperatures, ranging from near freezing to hot at the extremes. The average annual temperature is 12.7°C (54.9°F). Hotter and wetter weather occur at lower elevation zones in the reserve. [2] [5] [12]

In Pu‘u Maka‘ala Natural Area Reserve, the lava flow substrate age can be as recent as 1942 to as old as 8000 BCE. Extreme geologic disturbance in the form of volcanic activity has occurred historically, the latest being in 1942, and part of the reserve is downslope of potential eruption sites on Mauna Loa. The 1984 Mauna Loa lava flow comes within 1.6 km (1 mi.) of the Reserve. The geology can be described as Pāhoehoe and ʻAʻā of the Kaʻū Basalt. [2] [10]

NRCS has classified the areas within the reserve to have over 25 different soil types, ranging from very deep at lower elevation to very shallow or nonexistent at higher elevation. Soils are well drained due to the abundant precipitation. [2]

Soils are well drained, and there are no bodies of water aside from sparse bogs in the reserve. [2]

Since the reserve spans across elevational gradients with varying substrate age, there are several plants considered to be dominant in different areas. Pu‘u Maka‘ala NAR is primarily ʻōhiʻa (Metrosideros polymorpha), with a dense understory of hapu‘u tree ferns (Cibotium glaucum and Cibotium menziesii). In areas with older substrate, koa (Acacia koa) can tower up to 36 meters. In areas with younger substrate, or where there was previous grazing, the ecosystem can be classified as montane grassland, with native and non-native grasses. In the lowlands, non-native Strawberry Guava (Psidium cattleianum) encroaches upon and can dominate native ʻōhiʻa forests. Across the entire site, there are more than 160 endemic plant and fern species. [2]

Pu‘u Maka‘ala Natural Area Reserve provides habitat for a dozen native bird species, including 6 honeycreepers (subfamily Drepanidinae). The reserve serves as an area of significant importance for bird protection from avian malaria, since it is partially above the elevation at which mosquitoes generally are found. Feral boars are found in lowland areas of the reserve, but because Hawaii DLNR management involves fencing, trapping, and other redirection mechanisms, they are generally not found at higher elevations. Notably, in 2017, San Diego Zoo Global began managing the re-introduction of a small population of the previously extinct-in-the-wild Hawaiian Crow (Corvus hawaiiensis) in Pu‘u Maka‘ala. Also present in the reserve is Hawaii's only endemic land mammal, the Hawaiian Hoary Bat (Lasiurus cinereus semotus). [1] [2] [6] [7]

Despite the lack of archaeological findings in Pu‘u Maka‘ala, cultural documents reveal a rich history of native Hawaiians using the land for bird hunting, timber harvest, and medicinal plant gathering. More recently, the reserve has been partially used for logging and ranching. In some lower elevation areas of the preserve, there is a history of military testing of chemical and biological weapons.

Various eruptions and lava flows from Mauna Loa have provided regular disturbance on the geological scale in Pu‘u Maka‘ala. Ungulate trampling, nest predation and noxious weed invasion underline the modern environmental disturbance history and ongoing threats to the reserve. Two invasive fungi pathogens, ROD canker disease (Ceratocystis huliohia) and ROD wilt disease (Ceratocystis lukuohia), have had devastating impacts to regional ʻōhiʻa forest communities, rapidly killing ʻōhiʻa trees (Metrosideros polymorpha). Yet, today most of the area in which NEON operates has been largely unimpacted by the fungi. [2] [3] [9]

In 2005, the entirety of Pu‘u Maka‘ala Natural Area Reserve was dedicated solely to conservation. To strengthen the forest connectivity, NARS staff also routinely conduct outplanting of koa and ʻōhiʻa trees in areas previously used for cattle ranching. Pu‘u Maka‘ala's native ecological resources have benefitted greatly from partnership with adjacent landowners, such as Three Mountain Alliance, Kamehameha Schools, and National Park Service. [2]

Plot establishment of PUUM began in 2017, and the site was reviewed for sampling readiness in 2018. Dry runs of observational sampling began in late 2018. Instrumentation systems went online and began producing data in May 2019.