Factors affecting detection probability in plant distribution studies PDF下载：Chenguoke.pdf
Guoke Chen1, Marc Kéry2, Jinlong Zhang1 and Keping Ma1*
1State Key Laboratory of Vegetation and Environmental Change, Institute of
Botany, Chinese Academy of Sciences, Beijing 100093, China; and 2Swiss
Ornithological Institute, 6204 Sempach, Switzerland
中文摘要：
在生态学研究和生物多样性调查过程中，即使目标物种存在，我们往往也会见不到相应物种，这就是“不充分检测”(imperfect detection)造成的。“不充分检测”问题在动物生态学领域已经有了很深入的研究，相应的成果也得到了很好的应用。但是，由于大家一直认为植物相对于动物的移动性更小，因此，更容易被研究和调查。从而，在植物生态学研究和调查过程中，“不充分检测”的问题就一直没有得到足够的重视。
本文通过在古田山样地对6种木本植物进行调查实验，证实了“不充分检测”问题的确存在。不仅如此，我们还量化了本研究中“不充分检测”水平，本研究中对6种木本植物的“检测”水平在6－34%的范围内。更进一步，我们确定了造成“不充分检测”的一些因素、以及这些因素间的关系。
首先，不同物种的生活型以及形态特征有较大差异，从而造成它们被“检测”到的水平不一样；其次，目标物种被“检测”到的水平随着调查强度和目标物种在调查区域内的斑块大小的增加而增加。预测结果表明，当调查强度足够覆盖调查区域20％的面积、或者目标物种的斑块大小能覆盖调查区域19％的面积时，就能够达到对目标物种95％的“检测”水平。而且调查强度和斑块大小对“检测”水平的影响是交互的，也就是说，当目标物种的斑块比较小时，我们就需要较大的调查强度来保证一定的“检测”水平，反之亦然；最后，调查前的训练能够消除不同调查人之间“检测”水平的差异，这一点对于消除生物多样性调查过程中不同调查人之间的“检测”水平差异有应用价值。
最后，我们再一次强调“不充分检测”问题在植物生态学研究和调查过程中应该得到足够重视。否则，有关种群动态、群落物种丰富度以及物种分布的估计就会有较大的误差。
Summary
1. Plant ecologists have been rather slow to appreciate the existence and
the effects of imperfect detection probability in plants. Sources of
heterogeneous detectability include differences in morphology or life form,
patch size, observers and survey effort. Understanding the relationship
between such factors and detectability is crucial for the efficient design
of new plant distribution studies and for the interpretation of existing
ones.
2. We have studied the factors affecting detectability in a large permanent
plot (24 ha) in East China where the true distribution of six shrub and tree
species was known from a detailed earlier inventory. Two observers
independently resurveyed and recorded detection and non-detection of each
species in each 20 × 20 m sampling quadrat. A total of 288 quadrats were
resurveyed (218 by observer A, 211 by observer B, 141 by both). We used
generalized linear mixed modelling to study the relationships between
detection and species, observer, survey effort and patch size.
3. Detectability of an occupied quadrat was remarkably low and ranged from
0.09 to 0.34 on average for the six shrub and tree species. Differences of
detection among species were mainly due to distinctive morphology rather
than to life form. There was no significant difference of overall detection
probability between the two observers. Detectability increased to 0.95 as
the survey path approached 20% area of the sampling quadrat and as a plant
patch coverd c. 19% of the area of the sampling quadrat.
4. Synthesis. Our results suggest that imperfect detection is much more
widespread than currently acknowledged by most plant ecologists. We identify
several sources of heterogeneity in detectability (species, survey effort
and patch size) that ought to be considered when studying and modelling the
distribution of plant species. Detectability should be accounted for in
plant distribution studies to avoid spurious inferences.
Key-words: biodiversity, China, detection probability, forest dynamic plot,
generalized linear mixed model, monitoring, plant distribution |
