Firn Jennifer, Erskine Peter D, Lamb David
School of Integrative Biology, The University of Queensland, Brisbane, QLD 4072, Australia.
Oecologia. 2007 Dec;154(3):521-33. doi: 10.1007/s00442-007-0850-8. Epub 2007 Sep 27.
We investigated the relationship between plant diversity and ecological function (production and nutrient cycling) in tropical tree plantations. Old plantations (65-72 years) of four different species, namely Araucaria cunninghamii, Agathis robusta, Toona ciliata and Flindersia brayleyana, as well as natural secondary forest were examined at Wongabel State Forest, in the wet tropics region of Queensland, Australia. Two young plantations (23 years) of Araucaria cunninghamii and Pinus caribaea were also examined. The close proximity of the older plantations and natural forests meant they had similar edaphic and climatic conditions. All plantations had been established as monocultures, but had been colonised by a range of native woody plants from the nearby rainforest. The extent to which this had occurred varied with the identity of the plantation species (from 2 to 17 species in 0.1 ha blocks). In many cases these additional species had grown up and joined the forest canopy. This study is one of the few to find a negative relationship between overstorey plant diversity and productivity. The conversion of natural forest with highly productive, low-diversity gymnosperm-dominated plantations (young and old Araucaria cunninghamii and Pinus caribaea) was found to be associated with lower soil nutrient availability (approximately five times less phosphorus and 2.5 times less nitrogen) and lower soil pH (mean=6.28) compared to the other, less productive plantations. The dominant effects of two species, Araucaria cunninghamii and Hodgkinsonia frutescens, indicate that ecosystem functions such as production and nutrient availability are not determined solely by the number of species, but are more likely to be determined by the characteristics of the species present. This suggests that monoculture plantations can be used to successfully restore some functions (e.g. nutrient cycling and production), but that the level to which such functions can be restored will depend upon the species chosen and site conditions.
我们研究了热带人工林中植物多样性与生态功能（生产和养分循环）之间的关系。在澳大利亚昆士兰州湿润热带地区的旺加贝尔州立森林，对四种不同树种（即南洋杉、大叶贝壳杉、红椿和布氏弗林德木）的老龄人工林（65 - 72年）以及天然次生林进行了调查。还对南洋杉和加勒比松的两片幼龄人工林（23年）进行了调查。老龄人工林与天然林距离相近，这意味着它们具有相似的土壤和气候条件。所有人工林最初都是单一栽培，但已被来自附近雨林的一系列本地木本植物所占据。这种情况发生的程度因人工林树种而异（在0.1公顷的区域内有2至17种植物）。在许多情况下，这些额外的物种已经长大并进入了林冠层。本研究是少数发现上层植物多样性与生产力之间存在负相关关系的研究之一。与其他生产力较低的人工林相比，将天然林转变为以高生产力、低多样性裸子植物为主的人工林（南洋杉和加勒比松的幼龄和老龄人工林）与土壤养分有效性降低（磷减少约五倍，氮减少2.5倍）以及土壤pH值降低（平均值 = 6.28）有关。南洋杉和弗氏霍奇金森木这两个物种的主导作用表明，诸如生产和养分有效性等生态系统功能并非仅由物种数量决定，而更可能由现存物种的特性决定。这表明单一栽培人工林可用于成功恢复某些功能（如养分循环和生产），但这些功能能够恢复的程度将取决于所选择的物种和立地条件。
