Restoration genetics of degraded forest landscapes: Land management and evolution of reproductive strategies in keystone tree species

Brigalow森林群落以一种金合欢树acacia harpophyla （Brigalow）为主导，曾经在澳大利亚东北部昆士兰州的Brigalow带地区占据约8 M公顷的面积，但通过将土地转为牧场的清理已经减少到原来的8%。布里加洛森林只在世界上的这个地区发现，并支持着独特的动植物群，作为一个生态群落，它现在被澳大利亚环境保护和生物多样性保护法（EPBC）列为濒危物种。Brigalow生态群落恢复计划指出，缺乏对Brigalow生态学的了解是对其恢复的威胁，并建议进一步研究Brigalow以及如何恢复退化的森林。在本研究中，我们将推进对布里加洛生态学的认识。特别是，我们将提供经验证据，以进一步了解布里加罗如何应对人类活动造成的栖息地干扰。具体地说，我们将使用遗传标记比较种子（有性繁殖）和根系（无性系繁殖）在残余林和受干扰次生林（再生林）中的扩散。这是一个独特的机会来了解这个物种的生殖生物学，因为brigalow很少产生种子。这种罕见的种子招募事件发生在2008年初，这是60年来的第一次，并且幼苗在残柳和再生柳中都建立起来了。我们期望发现，由于再生柳的广泛吸根，再生柳成虫和幼苗的遗传多样性低于残柳。事实上，在再生过程中，人们预计扩散主要是通过无性繁殖发生的，因为无性繁殖使物种能够迅速在开阔的土地上定居，但实际上从未对其进行过评估。由于遗传多样性使一个物种能够对环境条件的变化作出反应和适应，因此再生布里加洛缺乏遗传多样性可能最终对其生存能力产生有害的遗传影响。帮助维持再生Brigalow遗传多样性的一种方法是设计优化遗传多样性的主动管理策略，例如通过去除吸盘（变薄）。由于我们将记录树木和幼苗的空间位置，以及确定它们的遗传特性，我们将能够制作出无性克隆位置和种子传播距离的地理地图，我们将能够在模型中使用这些信息来预测哪种间伐管理策略最能优化恢复的杨柳林的遗传多样性。以及将森林结构和碳固存（即树木中储存的碳量）恢复到成熟残余森林的水平。这对碳市场和矿区恢复具有经济意义。该研究将大大提高我们对金合欢在自然环境中的生物学认识，并有助于填补EPBC关于如何成功恢复退化的金合欢群落的知识空白。我们将提出切实可行的建议，为布里加洛森林的可持续恢复管理提供信息。总的来说，该项目将进一步加深我们对树种如何响应栖息地干扰的理解，特别是对于没有经验数据的部分无性系物种。这一点很重要，因为退化的再生森林现在在世界范围内占主导地位，我们需要了解树种如何应对人类活动造成的广泛干扰，以便以环境可持续的方式开展经济活动。最后，本项目将提出一个在恢复生态学中新颖的疏林管理遗传模型。如果在其他地方采用这种方法，将改善生态恢复方案的长期可持续性。

Brigalow forest communities, are dominated by an acacia tree, Acacia harpophylla (brigalow), and once occupied ~8 M ha across the Brigalow Belt region of northeastern Australia in Queensland, but have been reduced to 8% of their former range through clearing for conversion of the land to pasture. Brigalow forests are only found in this region of the world and support a unique flora and fauna which as an ecological community is now listed as endangered under the Australian Environmental Protection and Biodiversity Conservation Act (EPBC). The recovery plan for Brigalow ecological communities identifies lack of knowledge on the ecology of brigalow as a threat to their recovery and recommends that further research on brigalow and how to restore degraded forests should be carried out. In the proposed research, we will advance the knowledge on the ecology of Brigalow. In particular we will provide empirical evidence that will further our understanding of how brigalow respond to habitat disturbance caused by human activities. Specifically, we will compare dispersal by seed (sexual reproduction) and dispersal by root suckering (clonal reproduction) in remnant and disturbed secondary brigalow (regrowth) forests using genetic markers. This is a unique opportunity to find out about the reproductive biology of the species because brigalow only produces seeds very rarely. Such a rare seed recruitment event occurred early in 2008, for the first time in 60 years, and seedlings established in both remnant and regrowth brigalow. We expect to find that the genetic diversity in adults and seedlings of regrowth brigalow is lower than in remnant brigalow because of extensive root suckering in regrowth Brigalow. Indeed, in regrowth, it is expected that dispersal occurs primarily by clonal reproduction because it allows the species to rapidly colonise open land, but it has never actually been assessed. The lack of genetic diversity in regrowth Brigalow may ultimately have detrimental genetic effects for its viability because genetic diversity enables a species to respond and adapt to change in environmental conditions. One way to help maintain genetic diversity in regrowth Brigalow is to design active management strategies that optimize genetic diversity, for instance by removing suckers (thinning). As we will record the spatial location of trees and seedlings, as well as identify their genetic identity, we will be able to produce a geographic map of the location of clones and the distance of dispersal of seeds and we will be able to use this information in a model to predict which thinning management strategy best optimises genetic diversity in restored brigalow stands, as well as restore forest structure and carbon sequestration (which is how much carbon is stored in the trees) to the levels of mature remnant forests. This has economic implications for carbon markets and mined-land rehabilitation.The proposed research will considerably advance our knowledge of the biology of brigalow acacia in its natural environment, and will contribute to fill the gap of knowledge identified by the EPBC on how to successfully restore degraded Brigalow communities. We will make practical recommendations to inform sustainable restoration management of Brigalow forests. Generally, the project will further our understanding of how tree species respond to habitat disturbance, especially for partially clonal species for which no empirical data are available. This is important because degraded regrowth forests are now predominant worldwide, and we need to understand how tree species respond to widespread disturbance as a result of human activities in order to carry out economic activities in an environmentally sustainable way. Finally, this project will present a genetic model of thinning management, which is novel in restoration ecology. The approach, when adopted elsewhere, will improve the long-term sustainability of ecological restoration programmes.