Larrea Seedling Monitoring Study at the Sevilleta National Wildlife Refuge, New Mexico (1999-2018)

The germination rate of creosote (Larrea tridentata) on the
Sevilleta appears to be very low. During the early years of the LTER
project it was attempted to quantify such germination through the
use of seedling plots which were monitored on a bi-annual basis
(spring and fall). During the period from 1989 through 1992 there
were no creosote seedling that germinated on the monitoring plots.
In 1999 a rather sizeable population of small seedlings was observed
in one quite localized area in the vicinity of Five Points. This
rather large number of individuals in one very limited area raised
several questions:1. When did this small community of individuals
germinate- the supposition is that they had all germinated at the
same time.2. What conditions existed in this particular location
which allowed such prolific germination when there was no indication
of virtually any other germination in this vicinty.3. The most
immediate question was whether these seedlings would survive through
the impending La Nina winter, spring and summer as many of the
individuals did not appear to be very "healthy." To help
answer these questions it was decided to begin a "small"
monitoring project. All of the individuals in this small area that
appeared to be of the same age were marked with posts, located with
GPS, measured (height) and photographed. This initial survey
included 78 individuals. The population was resurveyed in August,
2000 and it was discovered that: 1. Many individuals were missed in
the initial survey; 2. Most of the individuals (72 of 78) had
survived the intervening 9 months; and 3. The average individual
growth during this period was 1.4 cm. It is planned that this
population will continue to be monitored (probably on an annual
basis) to track survival and growth rate of these individuals.

塞维利塔（Sevilleta）研究区内三齿拉瑞阿（creosote, Larrea tridentata）的萌发率似乎极低。在长效生态研究（Long Term Ecological Research, LTER）项目的早期阶段，研究人员曾尝试通过设置幼苗样地、每半年（春季与秋季）开展一次监测的方式，量化该物种的萌发情况。1989年至1992年期间，所有监测样地内均未发现三齿拉瑞阿的萌发幼苗。1999年，研究人员在“五点（Five Points）”附近一处极为局限的区域内，发现了数量可观的小型幼苗种群。在如此狭小的区域内出现如此大量的个体，引发了诸多疑问：1. 该小型幼苗群落何时萌发？研究推测它们应是同期萌发的。2. 该区域周边几乎未出现任何其他萌发迹象，那么此特定地点具备了何种条件，使得萌发如此旺盛？3. 最迫切的问题是：鉴于多数幼苗看起来长势不佳，这些幼苗能否挺过即将到来的拉尼娜（La Niña）冬季、春季与夏季？为解答上述疑问，研究团队决定启动一项“小型”监测项目。该区域内所有外观年龄一致的个体均被标记桩定位，并用全球定位系统（GPS）记录其位置，测量其高度并拍摄照片。本次初始调查共记录78株个体。研究团队于2000年8月对该种群进行了复访，结果显示：1. 初始调查漏测了大量个体；2. 初始调查的78株个体中，有72株在间隔的9个月内存活；3. 此期间单株平均生长量为1.4厘米。研究团队计划后续将持续对该种群进行监测（大概率每年一次），以跟踪这些个体的存活情况与生长速率。