Vegetation of the Gwydir Wetlands 2022

This is a vegetation map of the Gwydir wetlands. It was produced using air photo interpretation from high resolution aerial imagery collected in August 2022 and January 2023.\r\n\r\nMap development began with the collection of high-resolution aerial colour (Red-Green-Blue) imagery. The imagery was provided as an orthographic mosaic (ie a straight down view) with a 40 cm ground sampling distance covering the whole study area at each wetland. This formed the primary input of information for vegetation extent mapping. This aerial imagery was acquired in August 2022 for the Gwydir Wetlands. In addition, 15 cm high-resolution colour imagery, collected in January 2023, was also sourced from another project and provided as an orthomosaic. This additional imagery helped inform the aerial interpretation of vegetation community extents for an eastern portion of the Gwydir Wetlands study area. \r\nSeveral interpreters were then trained in Aerial Photographic Interpretation (API) to visually analyse the imagery to identify and delineate different vegetation types. This was done based on their spectral characteristics, colour, texture, shape, spatial patterns and associations with predictive environmental layers (such as flood frequency categories, elevation and geomorphology type). Existing survey data was also used to help identify vegetation types from imagery. This included BioNet species data, floristic data and other grey literature. Oblique aerial handheld photos captured from a helicopter were also sourced from another project to inform the aerial imagery interpretation. A subset of the available oblique handheld photos was selected to correspond to the timing (within two years) of the 40cm aerial imagery acquired for vegetation map development. The subset of oblique handheld photos adopted to inform the air photo interpretation included photos collected between January-December 2022. \r\nA polygon layer divided into small regions was sourced to overlay on the 40cm aerial imagery. This spatial layer was produced using the Definiens eCognition software package. A computer-based image analysis tool known as segmentation was applied to a set of raster datasets with a 5m grid cell size. This produced a spatial layer of ‘segments’ or very small polygons based on the combined spectral and textural features of the input rasters (Roff et al., 2022). The segmented layer was overlayed on the 40cm aerial imagery. Interpreters then manually selected groups of segments and assigned classes (‘attributes’) to the polygons to delineate vegetation patterns. The use of the segmented spatial layer enabled more efficient mapping, as interpreters did not have to manually draw polygon linework with a mouse. \r\nVegetation patterns were interpreted from the high-resolution 40cm aerial imagery at a scale of 1:25 000 for non-flood dependent vegetation and at a scale of 1:10 000 for wetland communities. The minimum map unit (smallest polygon) was 2 ha.\r\nSelected polygons from the segmentation process were initially assigned to an artificial class referred to as a Vegetation Photo Pattern (VPP), analogous to NSW Vegetation Classes (for more information on NSW Vegetation Classes see https://www.environment.nsw.gov.au/topics/animals-and-plants/biodiversity/nsw-bionet/the-nsw-vegetation-classification-framework ). \r\nThe VVPs were aligned with plant community types (PCTs) as described in the NSW BioNet Vegetation Classification Database (see https://vegetation.bionet.nsw.gov.au/). \r\nEach PCT was also aligned to a vegetation functional group corresponding to the vegetation objectives in the Gwydir Wetlands and Macquarie Marshes LTWPs.\r\nThe accuracy of the map vegetation functional groups was assessed using 780 independently collected field validation points. The overall accuracy was 0.77 and the Kappa statistic was 0.7.\r\nAccuracies and 95% confidence intervals for map individual map classes were:\r\nNon woody wetland: 0.78 (0.73-0.87)\r\nFlood dependent woodland 0.81 (0.76-0.86)\r\nRiver red gum forest: 0.77 (0.68-0.86)\r\nRiver red gum woodland: no field data, not assessed. \r\nTerrestrial vegetation: 0.68 (0.62-0.75)\r\nNon-native or other (includes pasture, cropping, infrastructure, dams): 0.89 (0.81-0.98)\r\n\r\nThis mapping project was funded by the NSW Water for the Environment Program and the Gwydir Reconnecting Watercourse Country Program.\r\n\r\n\r\nThis mapping project was funded by the NSW Water for the Environment Program, and the Gwydir Reconnecting Watercourse Country Program.\r\n

本数据集为吉德湿地（Gwydir wetlands）植被图，基于2022年8月与2023年1月采集的高分辨率航空影像，通过航空相片解译制作而成。

地图制作首先启动于高分辨率航空彩色（红-绿-蓝）影像的采集工作。该影像以正射镶嵌图（即垂直俯视视角）形式提供，地面采样距离为40厘米，覆盖每个研究湿地的全部研究区域，为植被范围制图提供核心基础信息。这套航空影像于2022年8月针对吉德湿地采集。此外，项目还获取了另一项目中2023年1月采集的15厘米高分辨率彩色正射镶嵌影像，该补充影像可辅助解译吉德湿地研究区东部区域的植被群落范围。

随后，多名解译员接受航空相片解译（Aerial Photographic Interpretation, API）培训，通过目视分析影像，依据光谱特征、色彩、纹理、形状、空间格局，以及与洪水频率分级、高程、地貌类型等预测性环境图层的关联关系，识别并勾勒不同植被类型。解译过程还参考了现有调查数据，包括BioNet物种数据、植物区系数据及其他灰色文献。此外，项目还从另一项目获取了直升机拍摄的倾斜航空手持照片，辅助航空影像解译。研究人员选取了与2022年8月采集的40厘米航空影像时间跨度在两年内的倾斜手持照片子集，该子集涵盖2022年1月至12月期间采集的照片，用于辅助航空相片解译。

研究人员获取了一套分割为小区域的面图层，将其叠加至40厘米航空影像上。该空间图层由Definiens eCognition软件生成，通过对5米栅格分辨率的多套栅格数据集应用图像分割这一计算机图像分析工具，基于输入栅格的光谱与纹理特征组合，生成了“分割块”（即极小面要素）的空间图层（Roff等，2022）。随后将分割图层叠加至40厘米航空影像上，解译员可手动选择分割块群组，并为面要素赋予类别（属性）以勾勒植被格局。使用分割空间图层可大幅提升制图效率，无需解译员再通过鼠标手动绘制面要素轮廓。

研究人员基于高分辨率40厘米航空影像开展植被格局解译：非淹水依赖植被的解译比例尺为1:25000，湿地群落解译比例尺为1:10000。最小制图单元（最小面要素）为2公顷。

分割流程中选取的部分面要素最初被归为一类人工类别，即植被照片模式（Vegetation Photo Pattern, VPP），该类别类比新南威尔士州（New South Wales, NSW）植被类别（如需了解新南威尔士州植被类别详情，请参阅：https://www.environment.nsw.gov.au/topics/animals-and-plants/biodiversity/nsw-bionet/the-nsw-vegetation-classification-framework）。

随后将VPP与新南威尔士州BioNet植被分类数据库中定义的植物群落类型（Plant Community Types, PCTs）进行匹配（详情请参阅：https://vegetation.bionet.nsw.gov.au/）。

每种植物群落类型还被对应至植被功能群，以匹配吉德湿地与麦考里沼泽（Macquarie Marshes）长期水规划（Long-Term Water Plans, LTWPs）中的植被管理目标。

本研究通过780个独立采集的野外验证点位，对地图植被功能群的制图精度进行评估。总体精度为0.77，Kappa统计量为0.7。

各单个制图类别的精度及95%置信区间如下：
- 非木本湿地植被：0.78（0.73-0.87）
- 淹水依赖林地：0.81（0.76-0.86）
- 河岸红桉林：0.77（0.68-0.86）
- 河岸红桉林地：无野外数据，未进行评估
- 陆地植被：0.68（0.62-0.75）
- 非本土植被或其他类型（涵盖牧场、农田、基础设施、水坝）：0.89（0.81-0.98）

本制图项目由新南威尔士州水环境计划（NSW Water for the Environment Program）与吉德水系连通乡村计划（Gwydir Reconnecting Watercourse Country Program）资助。

本制图项目由新南威尔士州水环境计划（NSW Water for the Environment Program）与吉德水系连通乡村计划（Gwydir Reconnecting Watercourse Country Program）资助。