## 3 Results
Cluster 2 (light green) starts to increase in biomass in the mid-1990s, reaching the levels of Clusters 3 and 4 around year 2000. Cluster 1 (dark green) remains fairly constant until the early 2000s and then increases to almost the level of the other clusters by 2013. Based on these trends, the diversity of grassland conditions could be considered to have decreased within the 25 years as described by the narrowing NDVI (biomass) range between clusters. Similar patterns can be observed in Wahnbachtal (Figure 6), with the two highest NDVI clusters (4 and 5, orange and purple) remaining fairly constant between 1989 and 2015. A trend that is not present in the Orbroich site is Cluster 3 (blue). This cluster has a constant high NDVI similar to Clusters 4 and 5 until about year 2000, but it has a period of decline to 2010 and then tracks closely with Cluster 1 (dark green). Parcels in Cluster 2 (light green) exhibit increasing biomass starting in the early 1990s and match the high-biomass clusters around 2005. Cluster 1 (dark green) remains relatively constant up to about 2005 and then increases to 2015. The time series plots for each site are comparable in their temporal patterns; however, caution should be used when comparing NDVI values across sites. Each of the two study sites used a different 1989 base image for normalization; therefore, these were independent analyses of the clusters' temporal trends. An additional analysis of all Wahnbachtal clusters was performed using a sub-clustering approach to explore further temporal trends within the main clusters. For example, the analysis of two highly separable clusters (TD = 2000) in Wahnbachtal (Clusters 2 and 3, light green and blue) revealed additional temporal patterns indicating that each of the resulting subclusters initiates changes in NDVI at different time periods (Figure 7). All subclusters followed the same increasing or decreasing trend as the primary cluster over the 25 years; however, the timing of the increase or decrease differed between the subclusters. Figure 5: Time series plots of annual biomass (NDVI) of Orbroich grassland parcels into four clusters from 1989 to 2013. An analysis of within-cluster variability over time was performed by plotting the standard deviation of the annual average NDVI for all grassland polygons within a cluster for each year. This demonstrated that cluster variability (i.e., standard deviation of individual grassland parcel NDVI values) was low and stayed consistent for Clusters 3 and 4, decreased for Cluster 2, and was high but somewhat variable for Cluster 1 for Orbroich (Figure S9). For Wahnbachtal, cluster variability was also low for Clusters 4 and 5, increasing for Clusters 1 and 3, and decreasing for Cluster 2 (Figure S10). An increase in total parcel biomass coupled with a decrease in biomass variability within a cluster over time (e.g., Cluster 2 in both Orbroich and Wahnbachtal) indicates lower spatial and temporal diversity. This could be the result of the increasing management intensification of grassland habitats in these areas, with possible related reductions in insect abundance. Figure 6: Time series plots of annual biomass (NDVI) of Wahnbachtal grassland parcels into four clusters from 1989 to 2015. Figure 7: Sub-clustering of Wahnbachtal Clusters 2 (light green) and 3 (blue) showing that overall trends are similar between subclusters and parent clusters, but the timing of the biomass changes differs within the subclusters.