A Pantropical Overview of Soils across Tropical Dry Forest Ecoregions

Abstract

Pantropical variation in soils of the tropical dry forest (TDF) biome is enormously high but has been poorly characterized. To quantify variation in the global distribution of TDF soil physical and chemical properties in relation to climate and geology, we produced a synthesis using 7500 points of data with gridded fields representing lithologic, edaphic, and climatic characteristics. Our analyses reveal that 75 TDF ecoregions across five biogeographic domains (Afrotropical, Australasian, Indo-Malayan, Neotropical, and Oceanian) varied strongly with respect to parent material: sediment (57%), metamorphic (22%), volcanic (13%), and plutonic (7%). TDF ecoregions support remarkably high variability in soil suborders (32), with the Neotropical and Oceanian realms being especially diverse. As a whole, TDF soils trend strongly toward low fertility with strong variation across biogeographic domains. Similarly, the exhibited soil properties marked heterogeneity across biogeographic domains, with soil depth varying by an order of magnitude and total organic C, N, and P pools varying threefold. Organic C and N pool sizes were negatively correlated with mean annual temperature (MAT) and positively correlated with mean annual precipitation (MAP). By contrast, the distribution of soil P pools was positively influenced by both MAT and MAP and likely by soil geochemistry, due to high variations in soil parent material across the biogeographic domains. The results summarized here raise important questions as to how climate and parent material control soil biogeochemical processes in TDFs.

Tropical Dry Forest Restoration in an Era of Global Change: Ecological and Social Dimensions

“…Future restoration science and practice should build upon these findings in a number of ways. First, the variability in climates within the TDF biome [12] and the enormous range in soil conditions and large functional diversity documented by the studies of this Special Issue [13,27,31] suggest that future TDF restoration practices should be founded on the links between biodiversity, soil heterogeneity, and climate, as well as the needs, motivations, and overall wellbeing of local people. Second, in order for restoration efforts to effectively match plant performance with restoration sites under changing climate conditions, a careful evaluation of a selection of native tropical dry forest species with respect to their functional traits and distribution along environmental gradients may prove a fruitful approach.…”

“…For example, although it is often cited that TDFs have higher soil fertility than their humid counterparts [9,14,20], the limited available soil data examining how ecosystem function varies along environmental gradients suggests that TDFs are a nutrient-limited ecosystem [21,22]. The pantropical analysis in Rivero-Villar's paper [13] included in this Special Issue addresses an important soil fertility knowledge gap for TDFs. The results from the study do not corroborate the idea that TDFs grow on high fertility soils.…”

“…The considerable variation in total annual precipitation, length of the dry season, topographic features, and edaphic conditions in which these forests occur contribute to their high species richness, diversity of life forms, endemism, physiognomies, and the diversity of functional groups [6,11], as well as the range of ecosystem functions [12] (see Figure 1). Encompassing 80 ecoregions, TDFs 2 of 5 occur across the Americas, Africa, and Asia [12], typically on low soil fertility [13], where they are threatened by multiple anthropogenic stressors including land use change [14,15], fires [16,17], increases in atmospheric nitrogen deposition [18], climate change [19], and combinations thereof. Addressing these threats with TDF restoration programs will require science-based practices that engage the human dimensions of TDF stewardship.…”

Inner bark vs sapwood is the main driver of nitrogen and phosphorus allocation in stems and roots across three tropical woody plant communities

“…With a fire return interval of 3–10 yr, fire is one of the main selective factors in the savanna, but not in the tropical forests (return intervals > 100 yr). Soils in the TDF are < 0.5 m deep Entisols and Inceptisols with high P and cation exchange capacity (Campo et al ., 2000, 2001), fertile for this ecosystem type (Rivero‐Villar et al ., 2022). Soils in the TRF are mainly 0.5–1 m deep Andisols with high nutrient contents (Tobón, 2009).…”