Analysis scripts for: Occurrence dataset of birds in Gansu Province (2011-2020)

This repository contains R scripts used to generate Figures 2 and 3 of the associated data paper: "Occurrence dataset of birds from multi-region avifaunal surveys in Gansu Province, China (2011–2020)".

**Purpose**
- Figure 2: Species accumulation curves for 12 study regions, showing cumulative species richness as a function of sampling events ordered by date.
- Figure 3: Annual trends in sampling effort (number of sampling events) and observed species richness from 2011 to 2020.

**Dependencies**
The scripts require R version 4.3.0 or higher and the following R packages:
- dplyr (for data manipulation)
- tidyr (for reshaping data)
- stringr (for extracting dates from Event_ID)
- ggplot2 (for plotting)

**How to run**
1. Place the raw data file "12个市县.csv" in the working directory (or modify the `input_file` path in the script).
2. Open and run the script `Figure2_species_accumulation.R` to generate the species accumulation curves.
3. Open and run the script `Figure3_annual_trend.R` to generate the annual sampling effort and species richness plot.
Both scripts will output figures as PNG and PDF files in the specified output directory (default: same as the input file location).

**Note**
The raw data file is available from the GBIF repository (DOI: xxx) and as Supplementary Table 2 of the paper. Please adjust file paths if necessary.