STEP - Vegetation

Vegetation types within the STEP planning domain. The final vegetation map for the STEP planning domain comprised two sections: (i) Thicket vegetation (mapped in the field by the Biological Survey team , see Vlok, J.H.J. and Euston-Brown, D.I.W. 2002. The patterns within, and the ecological processes that sustain, the subtropical thicket vegetation in the planning domain for the Subtropical Thicket Ecosystem Planning (STEP) project. TERU Report 40: 142pp), and (ii) non-thicket vegetation (mapped as a desktop exercise from CAPE Project and the vegetation map produced by the National Botanical Institute). (i) Thicket vegetation - 112 thicket types were identified and mapped for the STEP project by in Vlok and Euston-Brown (2002). These included 34 solid thicket vegetation types, and 78 mosaic thicket vegetation types. This map covered the entire STEP planning domain, and therefore included non-thicket vegetation types, but these were very broadly (coarsely) defined. The 112 thicket types from this map remained unchanged in the final STEP vegetation map (with three exceptions, see Table 7 - coastal vegetation). The broad definitions of non-thicket vegetation types were used simply as a guide for the further delineation and coding of non-thicket types in the final vegetation map. (ii) Non-thicket vegetation - 55 non-thicket vegetation types were defined and delineated as a desktop exercise using two sources of information (see map below). In the west, the Broad Habitat Units (BHUs) defined by Cowling and Heijnis (2001) for the CAPE Project were used (1:250 000 scale). In the east, the vegetation types compiled by Dr M. Rutherford, National Botanical Institute (NBI - preliminary map) were used (mixed scales). Additional non-thicket vegetation boundaries mapped by the Biological Survey team were also used places where they were in sufficiently fine detail. The three water types mapped by the team remained unchanged and were incorporated directly in the final STEP vegetation map. The 58 non-thicket types referred to in this document refer to the 55 vegetation types and the three water types. Purpose: Created for the Subtropical Thicket Ecosystem Planning Project. Method of capture/Lineage: (See Lombard et al. 2003) Vegetation polygons were delineated in the field by the Biological Survey team onto fifty-five Landsat TM images which were plotted by the Institute for Soil, Climate and Water on paper at 1:100,000 scale, in Gauss Conform Projection, Central Meridian 20 - 29 East, Clarke 1880 Spheroid. To assist with the definition of the vegetation polygons, geology (1:1 000 000) and homogeneous climate zones (Dent et al. 1990) were plotted as clear overlays at 1:250 000 scale (by Lombard, Wolf and Cole), to enable the Biological Survey team to view them over the Surveyor General 1:250 000 topo-cadastral map sheets. A unique ID number was assigned to each vegetation polygon at the time of field delineation. The unique ID numbers were then entered into an Excel spread sheet along with the description for each vegetation polygon (Vlok and Euston-Brown 2002, Appendix 3). The vegetation polygons were digitized on a GTCO Super LII Plus- A0 digitizing tablet using ArcView GIS 3.2a (ESRI) at the same projection as each 1:100 000 satellite image. Unique ID numbers were captured as points and imported into the final vegetation polygon GIS map. Maps were registered for digitizing using existing tick points on the 1:100 000 images. Once the line digitizing was complete the final polygon file was built using ArcInfo 7.2.1 (ESRI) in Albers Equal Area projection (Appendix 1). Additional vegetation polygon descriptions were imported into the final polygon file from the Excel spread sheet using the unique ID as the link field. 112 Thicket vegetation units were defined using a concatenation of a number of database fields, and a unique name was assigned to each unit by the Biological Survey team (Vlok and Euston-Brown 2002, Appendix 3). (ii) Non-thicket vegetation Western Area Broad Habitat Units (BHUs) from the CAPE project The CAPE BHU map was delineated for the CAPE project and is fully described in Cowling and Heijnis (2001). It was used as the primary layer for delineating and coding the non-thicket vegetation types in the western half of the planning domain, where the STEP planning domain and the CAPE planning domain overlap. The decision to use the BHU map for the western planning domain, instead of using the NBI vegetation map, was made after careful consideration of the two options by R. Cowling, J. Vlok and A. Lombard. From a botanical perspective, the very fine subdivisions of non-thicket vegetation types in the preliminary NBI map were often based on underlying geology, and these subdivisions were not considered appropriate for the final STEP vegetation map. From a technical (GIS) perspective, the NBI map consisted of the 112 thicket types from the STEP thicket map overlaid on the underlying NBI vegetation base map, and this had created many sliver polygons along the edges of the 112 thicket polygons. The BHU definitions, however, seamed more neatly into the STEP thicket map and were considered more appropriate for the western part of the STEP planning domain. The integration of the BHU map into the STEP thicket map was performed as a desktop exercise by R. Cowling and A. Lombard. The problems encountered with the NBI vegetation map in this western part were less pronounced in the eastern part. Eastern Area National Botanical Institute (NBI) preliminary vegetation map This map was received from the NBI at the end of August 2002, and was in a preparation stage. It was used as the primary layer for delineating and coding the non-thicket vegetation types in the eastern half of the planning domain. The integration of this map into the STEP thicket map was performed as a desktop exercise by J. Vlok and A. Lombard. Forest patches A forest map was received from the National Botanical Institute, consisting of four forest types (extant areas only, Table 6). For the final STEP vegetation map, these forest boundaries were ignored where they fell under STEP thicket vegetation types (solid or mosaic). Where they fell outside of thicket, they were assigned to four final STEP forest types defined in Table 6. The final STEP vegetation map included the following four forest types: (i) Knysna Afromontane Forest and (ii) Alexandria Indian Ocean Forest (both names were derived from the BHU map) and (iii) Amatole Afromontane Forest and (iv) Zuurberg Afromontane Forest (both newly defined names for STEP). Completeness: The final STEP layer is as complete as is currently possible. Supplemental Information: Lombard, A.T., Wolf, T. and Cole, N. 2003. GIS coverages and spatial analyses for the Subtropical Thicket Ecosystem Planning (STEP) Project. TERU Report 42: 78 pp, Appendix 78 pp. Vlok, J.H.J. and Euston-Brown, D.I.W. 2002. The patterns within, and the ecological processes that sustain, the subtropical thicket vegetation in the planning domain for the Subtropical Thicket Ecosystem Planning (STEP) project. TERU Report 40: 142pp. http://zoo.upe.ac.za/step http://cpu.uwc.ac.zaSTEP规划区域内的植被类型 本亚热带灌丛生态系统规划（Subtropical Thicket Ecosystem Planning, STEP）项目的规划区域最终植被地图包含两个部分：(i) 灌丛植被（由生物调查团队野外实地测绘，详见Vlok, J.H.J.与Euston-Brown, D.I.W. 2002年发表的《STEP项目规划区域内亚热带灌丛植被的分布格局与维持生态过程》，TERU报告40：142页）；(ii) 非灌丛植被（通过室内办公解译自CAPE项目成果与国家植物研究所（National Botanical Institute, NBI）编制的植被地图）。 (i) 灌丛植被：Vlok与Euston-Brown（2002）为STEP项目识别并测绘了112种灌丛类型，其中包括34种纯灌丛植被类型与78种镶嵌状灌丛植被类型。该地图覆盖了整个STEP规划区域，因此也包含了非灌丛植被类型，但这些类型的定义非常宽泛（粗略）。该地图中的112种灌丛类型在最终STEP植被地图中基本保持不变（仅3处例外，详见表7——海岸植被）。非灌丛植被类型的宽泛定义仅作为最终植被地图中非灌丛类型进一步勾绘与编码的参考依据。 (ii) 非灌丛植被：通过室内办公解译，结合两类信息源（详见下文地图），共定义并勾绘了55种非灌丛植被类型。在规划区域西部，采用了Cowling与Heijnis（2001）为CAPE项目定义的宽生境单元（Broad Habitat Units, BHUs）（比例尺1:250 000）；在东部，则采用了国家植物研究所（NBI）Rutherford博士编制的植被类型（初步地图，混合比例尺）。当生物调查团队测绘的非灌丛植被边界具备足够精细的细节时，也被纳入其中。该团队测绘的3种水体类型未作修改，直接纳入最终STEP植被地图。本文中提及的58种非灌丛类型，即对应上述55种植被类型与3种水体类型。 ## 用途 专为亚热带灌丛生态系统规划（STEP）项目编制。 ## 采集/传承方法 详见Lombard等人2003年的研究。生物调查团队在55幅陆地卫星专题制图仪（Landsat TM）影像上进行野外植被多边形勾绘，这些影像由土壤、气候与水研究所按1:100 000比例尺打印，采用高斯-克吕格投影，中央经线为20°E-29°E，椭球体为克拉克1880椭球体。为辅助植被多边形的定义，Lombard、Wolf与Cole将地质图（比例尺1:1 000 000）与均质气候区（Dent等人1990年成果）按1:250 000比例尺制作成透明叠加层，以便生物调查团队在测量总局1:250 000地形地籍图幅上查看这些叠加层。野外勾绘阶段为每个植被多边形分配了唯一标识符（ID）。随后，将唯一标识符与每个植被多边形的描述信息一同录入Excel电子表格（详见Vlok与Euston-Brown 2002年附录3）。使用ArcView GIS 3.2a（ESRI）与GTCO Super LII Plus-A0数字化板，按照每幅1:100 000卫星影像的投影对植被多边形进行数字化。将唯一标识符以点要素形式录入，并导入最终植被多边形GIS地图。利用1:100 000影像上的现有格网控制点进行配准，以完成数字化。线要素数字化完成后，使用ArcInfo 7.2.1（ESRI）在阿尔伯斯等面积投影下构建最终多边形文件（详见附录1）。通过唯一标识符作为关联字段，将Excel电子表格中的额外植被多边形描述信息导入最终多边形文件。Vlok与Euston-Brown（2002年附录3）通过多个数据库字段的拼接定义了112个灌丛植被单元，并由生物调查团队为每个单元分配了唯一名称。 ### 非灌丛植被细分 #### 西部区域：CAPE项目宽生境单元（BHUs） CAPE宽生境单元地图为CAPE项目编制，详细描述见Cowling与Heijnis（2001）。在规划区域西部，即STEP规划区域与CAPE规划区域重叠的部分，该地图被用作非灌丛植被类型勾绘与编码的基础图层。R. Cowling、J. Vlok与A. Lombard经慎重考量后，决定在西部规划区域使用宽生境单元地图，而非NBI植被地图。从植物学视角来看，初步NBI地图中非灌丛植被类型的精细细分往往基于底层地质条件，这些细分并不适用于最终STEP植被地图。从地理信息系统（GIS）技术视角来看，NBI地图是将STEP灌丛地图的112种灌丛类型叠加在底层NBI植被底图上形成的，这在112个灌丛多边形的边缘产生了大量狭长多边形。而宽生境单元的定义与STEP灌丛地图的衔接更为自然，因此被认为更适用于STEP规划区域的西部部分。将宽生境单元地图整合至STEP灌丛地图的工作由R. Cowling与A. Lombard以室内办公解译的方式完成。西部区域遇到的NBI植被地图问题在东部区域并不明显。 #### 东部区域：国家植物研究所（NBI）初步植被地图 该地图于2002年8月底从NBI获取，处于编制阶段。它被用作规划区域东部非灌丛植被类型勾绘与编码的基础图层。将该地图整合至STEP灌丛地图的工作由J. Vlok与A. Lombard以室内办公解译的方式完成。 #### 森林斑块 从国家植物研究所获取的森林地图包含4种森林类型（仅包含现存分布区域，详见表6）。在最终STEP植被地图中，若森林边界位于STEP灌丛植被类型（纯灌丛或镶嵌灌丛）范围内，则忽略该边界；若位于灌丛范围外，则将其归为表6中定义的4种最终STEP森林类型。最终STEP植被地图包含以下4种森林类型：(i) 克尼斯纳山地森林（Knysna Afromontane Forest）与(ii) 亚历山大印度洋森林（Alexandria Indian Ocean Forest，两类名称均源自宽生境单元地图），以及(iii) 阿马托莱山地森林（Amatole Afromontane Forest）与(iv) 祖尔贝格山地森林（Zuurberg Afromontane Forest，两类为STEP项目新增定义的名称）。 ## 完整性 最终STEP图层已达到当前可行的最高完整度。 ## 补充信息 1. Lombard, A.T., Wolf, T. 与 Cole, N. 2003. 《STEP项目的GIS覆盖范围与空间分析》，TERU报告42：78页，附录78页。 2. Vlok, J.H.J. 与 Euston-Brown, D.I.W. 2002. 《STEP项目规划区域内亚热带灌丛植被的分布格局与维持生态过程》，TERU报告40：142页。 3. http://zoo.upe.ac.za/step 4. http://cpu.uwc.ac.za