The impact of liana proliferation on recovery of biomass in secondary tropical forests

世界上的热带森林是重要的碳汇，也是大多数陆地生物多样性的家园。世界上剩余的森林有一半以上被归类为退化或次生林，森林砍伐仍在继续；1990至2015年间，森林净损失1.29亿公顷，其中最大的森林损失发生在热带地区[1]。东南亚的森林砍伐和木材采掘率超过了大多数其他热带地区[2，3]。仅婆罗洲的木材出口就超过了整个热带非洲和拉丁美洲的出口总和[4]。东南亚剩余的未受干扰的森林大部分被归类为生产林，因此可以进行选择性采伐。在东南亚的龙脑果林中，几乎所有的大树都具有很高的木材价值，直接影响到选择性采伐的影响。在第一次采伐轮伐期，通常所有可销售的树干都被移除，只留下小树干和不太理想的木材树种。在第一次伐木轮伐后，森林可能会再次被砍伐，通常不到20年后[6]。这一过程留下了高度退化的森林，其结构和组成发生了变化；伐木森林往往具有低矮、开阔的树冠，藤本植物密度高，演替后期树种的丰度降低[7]。人们普遍认为，选择性采伐的森林比其他退化的森林生境具有更大的保护价值[7]。最近的一项审查表明，选择性采伐的森林通常保留了它们的大部分生物多样性和相关的生态系统功能[8]。然而，大多数研究调查的是动物物种的多样性和组成，而不是树木，这可能比依赖它们的动物物种受到直接采伐和物理破坏的影响更严重。此外，选择性采伐可能对树木再生产生影响，从而限制这些森林的长期可持续性。首先，移除高价值用材树减少了潜在的种子来源，限制了高木材密度树种的苗木招募，并可能在长期内改变成年树木的未来组成[9]。其次，对残留林的物理破坏和采伐后森林结构的变化会导致藤本植物的繁殖。最近的研究表明，藤本植物的丰度可以显著影响森林动态和地上生物量[AGB；10，11]。然而，没有研究调查选择性采伐可能如何影响未来的森林组成，以及藤本植物在塑造选择性采伐后再生的森林群落中所起的作用。与未受干扰的森林相比，决定树木群落吸收的机制被选择性地记录下来。藤本植物在塑造群落动态中的作用3.东南亚伐木森林的长期可持续性。

The world's tropical forests are essential carbon sinks and home to the majority of terrestrial biodiversity. Over half of the world's remaining forests are categorised as degraded or secondary forests and deforestation continues; between 1990 and 2015 there was a net loss of 129 million ha of forest, with the largest forest losses occurring in the tropics [1]. The rate of deforestation and timber extraction in Southeast Asia exceeds that of most other tropical regions [2,3]. Timber exports from Borneo alone surpass those from all of tropical Africa and Latin America combined [4]. The majority of the remaining undisturbed forest in Southeast Asia is classified as production forest [5] and therefore is open to selective logging.In dipterocarp forests of Southeast Asia virtually all large trees have high timber value with direct implications for the impacts of selective logging. On the first logging rotation typically all marketable stems are removed, leaving only small stems and less desirable timber species. After the first logging rotation, the forest may be logged again, frequently less than 20 years later [6]. This process leaves behind a highly degraded forest with altered structure and composition; logged forests tend to have low, open canopies, high liana densities and reduced abundance of late-successional tree species [7].It is widely accepted that selectively logged forests have greater conservation value than other degraded forest habitats [7]. A recent review indicated that selectively logged forests typically retain most of their biodiversity and associated ecosystem functions [8].However, most studies have investigated the diversity and composition of animal species not trees, which may be more severely impacted by direct extraction and physical damage than the animal species that depend on them. In addition, selective logging may have, as yet unseen, impacts on tree regeneration that limits the sustainability of these forests in the long term. First, removal of high value timber trees reduces potential seed sources limiting seedling recruitment of high-wood density species and potentially shifting future composition of adult trees in the long term [9]. Second, physical damage to the residual forest stand and changes in forest structure post-logging can result in the proliferation of lianas. Recent studies have shown that liana abundance can significantly impact forest dynamics and aboveground biomass [AGB; 10,11]. However no studies have investigated how selective logging may impact future forest composition, and the role that lianas play in shaping the forest communities that regenerate after selective logging.This project aims to investigate1. The mechanisms that determine recruitment into the tree community in selectively logged compared to undisturbed forests2. The role of lianas in shaping community dynamics 3. The long-term sustainability of logged forests in Southeast Asia.