agronomy Article Tree Canopy Management Affects Dynamics of Herbaceous Vegetation and Soil Moisture in Silvopasture Systems Using Arboreal Legumes Izabela A. Gomes da Silva 1 , José C. B. Dubeux, Jr. 2, * ,Mércia Virginia Ferreira Santos 1 , Alexandre Carneiro Leão de Mello 1 ,Márcio Vieira Cunha 1 , Valéria X. O. Apolinário 3 and Erinaldo Viana de Freitas 4   Citation: Silva, I.A.G.d.; Dubeux, J.C.B.,Jr.; Santos, M.V.F.; Mello, A.C.L.d.; Cunha, M.V.; Apolinário, V.X.O.; Freitas, E.V.d. Tree Canopy Management Affects Dynamics of Herbaceous Vegetation and Soil Moisture in Silvopasture Systems Using Arboreal Legumes. Agronomy 2021, 11, 1509. https://doi.org/ 10.3390/agronomy11081509 Academic Editors: Juan J. Villalba and Jennifer MacAdam Received: 29 June 2021 Accepted: 27 July 2021 Published: 29 July 2021 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). 1 Animal Science Department, Federal Rural University of Pernambuco, Recife 52171030, Brazil; izabelagomesz@gmail.com (I.A.G.d.S.); mercia.vfsantos@ufrpe.br (M.V.F.S.); alexandre.lmello@ufrpe.br (A.C.L.d.M.); marcio.cunha@ufrpe.br (M.V.C.) 2 North Florida Research and Education Center, Institute of Food and Agricultural Sciences, University of Florida, 3925 Highway 71, Marianna, FL 32446, USA 3 Animal Science Department, State University of Maranhão, São Luis 65055970, Brazil; valeriaapolinario@cca.uema.br 4 Agronomic Institute of Pernambuco, Recife 50761000, Brazil; erinaldo.viana@ipa.br * Correspondence: dubeux@ufl.edu Abstract: Understanding ecological interactions between the arboreal and the herbaceous compo- nents is key to get the full benefits from silvopastoral systems. The objective of this 2-yr research was to evaluate productivity and nutritive value of signalgrass (Urochloa decumbens (Stapf.) R. Webster) subjected to shading from the tree legumes Gliricidia (Gliricidia sepium (Jacq.) Steud) or Mimosa (Mimosa caesalpiniifolia Benth.) under different tree canopy management. Trees were planted in double rows and were either unharvested or harvested only one row, leaving the other row unharvested. Response variables for the herbaceous vegetation included canopy height, herbage mass (green leaf blade, green stem, senescent leaves, and senescent stem), herbage accumulation rate, canopy bulk density, and soil moisture. Total herbage mass, green herbage mass, and green leaf mass were affected by treatment × month and harvest management × month interactions. Herbage accumulation rate in Gliricidia was greater (55 kg DM ha −1 d −1 ) than Mimosa (32 kg DM ha −1 d −1 ). Soil moisture was lesser at the Mimosa sites (16.2%) compared with the Gliricidia ones (17.2%), and it was greater between tree rows (21.9%) compared with full sun (11.5%), varying across the season. Harvesting management had a short-term transient effect on herbage responses. Tree canopy management can affect forage quantity and quality; however, these effects are transient and vary with tree spacing. Signalgrass grew faster and had better nutritive value when growing with Gliricidia. Keywords: nutrient cycling; shade; tree spacing 1. Introduction Shade affects the productive, nutritional, and morphological traits of tropical for- ages [1]. Warm-climate C4 grasses growing under shade must self-adapt through pheno- typic plasticity, such as increased leaf area and shoot-to-root ratio, as well as decreased tiller population density, and canopy bulk density [2]. Moreover, shade might increase chlorophyll [3] and crude protein (CP) concentrations [4] of herbaceous vegetation in silvopastoral systems. Silvopastoral systems with tree legumes have added benefits such as the potential biological N 2 fixation and nutrient cycling [5]. There have been reports that Gliricidia and Mimosa root systems are able to take advantage of the association with rhizobia symbionts, affecting soil Nitrogen (N) cycling [6]. Agronomy 2021, 11, 1509. https://doi.org/10.3390/agronomy11081509 https://www.mdpi.com/journal/agronomy