Data presented in the paper: To Plant or Not to Plant: When can Planting Facilitate Mangrove Restoration?

We studied the natural and assisted processes of mangrove expansion in Demak Regency, Indonesia. We studied expansion in both landward direction (i.e. the aquaculture pond zone) and seaward direction (i.e. the coastal zone) from the current coastline in the project area (the old coastal road). The pond zone in the study area is characterized by active traditional aquaculture ponds, and drowning abandoned aquaculture ponds towards the coast. The coastal zone in the study is defined as the area ranging from MHW to MLW (the maximum depth at which the EMR-dams are placed), which ranges roughly 0 to 600 meters from the shoreline. In order to shed light on best practices for mangrove recovery, we aimed to answer four research questions: : 1) how has mangrove expansion occurred in seaward and landward direction in the past, mainly through planting or mainly through natural expansion?; 2) Can hydrological EMR measures (e.g. sluice gate management) induce natural mangrove recovery in the pond zone (i.e. would enough propagules be available at landward sites if hydrological connectivity to target ponds was increased)?; 3) Can wave-reducing and sediment-trapping measures (EMR-dams) induce natural mangrove recovery at challenging sites in the coastal zone by increasing the chances of a) new seedling establishment or b) survival of established seedlings? and; 4) Can mangrove planting in combination with EMR-dams accelerate mangrove recovery at challenging coastal sites?<br>We addressed research questions 1-4 in the manuscript, using the following correspondingly numbered methods. 1) GIS monitoring of natural and planted mangrove vegetation in the coastal zone and pond zone using time series of satellite images (Q1_GIS_data &amp; Q1_forest_structure). 2) A year-round propagule monitoring campaign seawards and landwards of the old coastal road (Q2_EMR-hydrology_propagules) to assess the potential for natural mangrove colonization in the active pond zone if maximal EMR-hydrology would be applied. 3) A field experiment at multiple coastal sites with different wave exposure conditions to understand the effect of EMR-dams on mangrove recruitment and seedling survival (Q3_EMR-dams_natural_seedling_establishment_mon &amp; Q3_EMR-dams_seedling_survival_exp). Finally, 4) a field experiment to study the effect of mangrove planting in combination with EMR-dams on seedling growth and survival (Q4_EMR-and-planting)

本研究以印度尼西亚德马克县（Demak Regency）为研究区，探究其内红树林的自然扩张与人工辅助扩张过程。研究覆盖项目区（旧沿海公路沿线）内，以当前海岸线为基准的向陆（养殖塘区域）与向海（海岸带区域）两个方向的红树林扩张情况。研究区内的养殖塘区域以活跃的传统养殖塘为主要特征，同时存在向海岸带逐渐被海水淹没的废弃养殖塘。本研究界定的海岸带区域为介于平均高潮位（MHW，Mean High Water）与平均低潮位（MLW，Mean Low Water）之间的范围（即布设EMR拦坝（EMR-dams）的最大水深区间），离岸距离大致为0至600米。为阐明红树林修复的最优实践路径，本研究旨在回答四项研究问题：
1. 过往向海与向陆方向的红树林扩张主要以人工种植为主，还是以自然扩张为主？
2. 水文调控类EMR措施（如水闸管理）能否促使养殖塘区域实现红树林自然修复？具体而言，若提升目标养殖塘的水文连通性，向陆区域是否能够获得充足的繁殖体供给？
3. 减浪滞沙类EMR拦坝（EMR-dams）能否通过提升以下两方面的概率，促使海岸带困难立地实现红树林自然修复：a) 新苗定植；b) 定植幼苗的存活？
4. 将红树林种植与EMR拦坝相结合，能否加速海岸带困难立地的红树林修复进程？

本研究采用以下对应编号的研究方法，系统解答了上述1至4项研究问题：
1. 借助卫星影像时序数据，对海岸带与养殖塘区域内的天然及人工种植红树林植被开展GIS监测（对应数据集：Q1_GIS_data与Q1_forest_structure）。
2. 在旧沿海公路的向海与向陆两侧开展为期一年的繁殖体监测工作（对应数据集：Q2_EMR-hydrology_propagules），以评估当实施最大化EMR水文调控措施时，活跃养殖塘区域实现红树林自然定植的潜力。
3. 在不同波浪暴露条件的多个海岸带站点开展野外试验，以解析EMR拦坝对红树林种苗定植及幼苗存活的影响（对应数据集：Q3_EMR-dams_natural_seedling_establishment_mon与Q3_EMR-dams_seedling_survival_exp）。
4. 开展野外试验以探究红树林种植结合EMR拦坝措施对幼苗生长与存活的影响（对应数据集：Q4_EMR-and-planting）