*2.1. Study Areas*

The semi-arid climate (Köppen's BSh) [34], where the Caatinga is located, presents accumulated precipitation below 600 mm and an average air temperature of 25 ◦C to 30 ◦C throughout the year [35]. However, seasonally, the average annual rainfall varies widely from 300 mm to 1000 mm annually, mainly concentrated in a period of 3 to 4 months, during summer and autumn, followed by a prolonged dry season lasting 8 to 9 months during winter and spring [36]. The Caatinga is characterised by high interannual precipitation variability, with droughts that can last for years and high potential evapotranspiration rates of between 1500 mm and 2000 mm annually [37]. The Caatinga region has different soil categories, ranging from shallow, rocky, and relatively fertile to deep with high natural fertility and sedimentary or sandy, deep, and non-fertile [35]. In the Caatinga, the typical vegetation comprises deciduous and thorny forests or small forests that grow mainly in exposed crystalline rocky terrains, such as the Depression Sertaneja [38]. The region's geomorphology ranges from lowlands of 300 m, mountains, plateaus, and plateaus with an altitude of up to 1000 m [35].

The study was carried out at three SDTF protected sites, each area being in a different ecoregion (Figure 1): (i) Meridional Sertaneja Depression (MSD) ecoregion experimental

site located Embrapa Semi-arid, Petrolina, Pernambuco; (ii) Sertanejas Depressions (SD) ecoregion experimental site located at Seridó Ecological Station, Serra Negra do Norte, Paraíba; (iii) Borborema Plateau (BP) ecoregion experimental site located at Semi-arid National Institute, Campina Grande, Paraíba. The MSD experimental site's geographic coordinates are 9◦0247 S, 40◦1916 W, 395 m altitude, and its vegetation is dry xerophilous forest, with trees and shrubs that average five metres in height [39]. The average annual temperature is 26.2 ◦C, and the rainfall is 387 mm [39], concentrated mainly from January to April. The predominant soil type in the experimental site is Red-Yellow Argisol, followed by Haplossol and Hydromorphic Vertisol [40]. The SD experimental site's geographic coordinates are 6◦3442 S, 37◦1505 W, and 203 m altitude. Its area is characterised by dry xerophilous forest with deciduous plant species and the predominance of small, widely dispersed trees and shrubs up to 10 metres high, which develop and grow only in the rainy season between January and May [41]. The average annual precipitation varies between 400 and 700 mm, and the average yearly temperature ranges from 28 to 30 ◦C. The dominant soil is Neosol Litolic, shallow (about 40 cm), stony, and low fertility [42]. The BP experimental site's geographic coordinates are 7◦1649 S, 35◦5834 W, and 492 m altitude. The vegetation present in the experimental site is composed of dense Caatinga, with tree heights between three and seven metres. The region experiences a rainy season starting in March/April and extending until August, while the dry season lasts for five to six months [43]. The average annual rainfall of Campina Grande is about 750 mm, and the average annual air temperature is 23.3 ◦C [44]. The soil is nitric planosol [45].

**Figure 1.** Map of the Caatinga with the physical boundaries of the ecoregions and the locations under study. Koppen's climate classification for Brazil from ALVARES et al. [34] emphasizes the semi-arid (BSh) climate of Caatinga SDTF in orange. Location of sites in ecoregions: 1. MSD (Meridional Sertaneja Depression ecoregion); 2. SD (Sertanejas Depressions ecoregion); 3. BP (Borborema Plateau ecoregion).
