As forest fragmentation continues in many parts of the tropics, the conservation value of forest remnants remains controversial. Our study aimed to assess the structure and tree species diversity of mixed dipterocarp forest remnants from the Planted Forest Zone (PFZ) located in the Bintulu Division, Sarawak, compared with a forest considered relatively undisturbed (i.e. that has experienced no recent logging activities). We also compared three plot methods (50 × 50 m, 20 × 50 m and 10 × 50 m plots) in order to evaluate which could be used for time- and cost-effective inventories of structure and tree species diversity in fragmented forests. No significant differences were found between the fragmented forests and the relatively undisturbed forest for stem density, species richness and diversity indices (Shannon and Simpson). Dissimilarities in species, genus and family composition were observed between fragmented and relatively undisturbed forest, as well as between forest remnants themselves. These dissimilarities were likely to be related to intrinsic variation in these highly diverse tropical forests. However, an unusually high abundance of pioneer species (i.e. Macaranga) was found in plots from forest remnants. The forest remnants also had significantly lower basal areas due to a lack of trees in large diameter classes, which is likely a result of impacts from past logging activities. Otherwise, our results highlight the current high conservation value of the forest remnants—although the studied communities are likely to experience time-delayed shifts in species composition and/or extinctions in the future, with the effect of fragmentation on biodiversity being currently underestimated. Finally, for further studies of fragmented forests we recommend the use of 10 × 50 m plots which are faster and easier to implement in the field while providing estimates of structure and tree species diversity that are consistent with those from larger plots.

随着热带地区许多地区森林破碎化的继续，森林残留物的保护价值仍然引起争议。我们的研究旨在评估砂拉越民都鲁分区的人工林区（PFZ）中混合的二香果林残余物的结构和树种多样性，与之相比，该林被认为相对未受干扰（即最近没有进行过伐木活动）。我们还比较了三种绘图方法（50×50 m，20×50 m和10×50 m绘图），以评估可用于时间和成本效益的零散森林结构和树木物种多样性清单。在零散的森林和相对未受干扰的森林之间，在茎密度，物种丰富度和多样性指数（Shannon和Simpson）上没有发现显着差异。在零散的和相对未受干扰的森林之间以及森林残留物本身之间，观察到物种，属和家庭组成的差异。这些差异可能与这些高度多样化的热带森林的内在变化有关。但是，先锋物种异常丰富（即马卡兰加（Macaranga）在森林残留物中被发现。由于缺乏大直径树木，森林残留物的基础面积也大大降低，这很可能是过去伐木活动造成的影响。否则，我们的结果将凸显当前森林残余物的高保护价值-尽管被研究的社区将来可能会经历物种组成和/或灭绝的时滞变化，而目前零碎对生物多样性的影响却被低估了。最后，为进一步研究零散的森林，我们建议使用10×50 m的样地，该样地在田间实施起来更快，更容易，同时提供与较大样地一致的结构和树种多样性的估计值。